tretinoin and retinol-palmitate

A wide range of cosmeceutical products are available on the market currently, but evidence to support their use is often lacking in the literature. Specifically, there is a substantial amount of evidence supporting the efficacy of tretinoin in photoaging, but the evidence supporting retinoid-based cosmeceuticals remains sparse. The authors review the current data in the literature related to vitamin A-derived cosmeceutical products and conclude that cosmeceuticals containing retinaldehyde have been shown in large randomized, controlled trials to have the most beneficial effect on aging skin.

Topics: Administration, Topical; Antioxidants; Cosmetics; Dermatologic Agents; Diterpenes; Humans; Keratolytic Agents; Randomized Controlled Trials as Topic; Retinaldehyde; Retinoids; Retinyl Esters; Skin Aging; Tretinoin; Vitamin A

All-trans and 13-cis-retinoic acids are normal constituents of human blood. Blood levels of both compounds increase upon oral ingestion of all-trans-retinyl palmitate, to a greater extent with higher amounts of ingested retinyl palmitate. These data suggest a mechanism whereby levels of dietary vitamin A could influence blood levels of the known cancer chemopreventive retinoic acids.

Topics: Diterpenes; Humans; Neoplasms; Retinyl Esters; Tretinoin; Vitamin A

Topics: Adjuvants, Immunologic; Animals; Breast Neoplasms; Carcinogens; Cricetinae; Diterpenes; Female; Humans; Keratoacanthoma; Lung Neoplasms; Male; Mice; Neoplasms; Prostatic Neoplasms; Rats; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

Animal liver is a rich source of vitamin A. Due to retinoic acid (RA) metabolites, vitamin A has a teratogenic potential and women are generally advised to avoid or to limit the consumption of liver during pregnancy. In a recent study in non-pregnant female volunteers following single and repeated doses of up to 30,000 IU/day of vitamin A as a supplement, the plasma concentration time curve of all-trans RA acid showed a diurnal-like profile. But, the overall exposure (AUC24h) remained essentially unaltered whereas AUC24h increased linearly with dose for 13-cis and 13-cis-4-oxo RA. The current study in non-pregnant female volunteers showed that a single high vitamin A intake with a liver meal (up to 120,000 IU) exhibited a similar diurnal-like plasma concentration time curve for all-trans RA and its overall exposure remained also unaltered, despite a temporary two-fold increase in peak plasma concentration. Concentrations of 13-cis and 13-cis-4-oxo RA increased several-fold after a liver meal, and exposure (AUC24h) increased three- to five-fold. Pooling our results with data in the literature revealed a linear relation between the mean AUC24h of 13-cis and 13-cis-4-oxo RA and vitamin A intake with liver. Metabolism to all-trans RA of vitamin A with liver seems not to be of safety concern. However, the observed increase of plasma concentrations and the dose-dependent increase in exposure to 13-cis and 13-cis-4-oxo RA support the current safety recommendations on vitamin A intake and suggest that women should be cautious regarding their consumption of liver-containing meals during pregnancy.

Topics: Adolescent; Adult; Animals; Cattle; Diterpenes; Female; Humans; Kinetics; Liver; Meat; Retinyl Esters; Tretinoin; Vitamin A

Retinyl palmitate (RP), the most stable vitamin A derivative, is used to treat photoaging and other skin disorders. The need to minimize the adverse effects of topical drug administration has led to an enhanced interest in loading RP on ethosomes for topical drug delivery. The aim of the current study was to prepare and compare the performance of RP decorated ethosomal hydrogel with tretinoin cream in the treatment of acne vulgaris as an approach to improve drug efficacy and decrease its side effects.. RP-loaded ethosomes were prepared using the injection sonication technique. A Box-Behnken design using Design Expert. The optimized ethosomal RP showed particle size of 195.8±5.45 nm, ZP of -62.1±2.85 mV, EE% of 92.63±4.33%, drug release % of 96.63±6.81%, and drug permeation % of 85.98 ±4.79%. Both the optimized RP ethosomal hydrogel and tretinoin effectively reduced all types of acne lesions (inflammatory, non-inflammatory, and total lesions). However, RP resulted in significantly lower non-inflammatory and total acne lesion count than the marketed tretinoin formulation. Besides, RP-loaded ethosomes showed significantly improved tolerability compared to marketed tretinoin with no or minimal skin irritation symptoms.. RP ethosomal hydrogel is considerably effective in controlling acne vulgaris with excellent skin tolerability. Therefore, it represents an interesting alternative to conventional marketed tretinoin formulation for topical acne treatment.

Topics: Acne Vulgaris; Administration, Cutaneous; Adult; Animals; Diterpenes; Drug Delivery Systems; Drug Liberation; Female; Humans; Hydrogels; Male; Particle Size; Prospective Studies; Rats, Wistar; Retinyl Esters; Skin Absorption; Skin Irritancy Tests; Tretinoin

Vitamin A is an essential nutrient that is obtained from the daily diet. The major forms of vitamin A in the body consist of retinol, retinal, retinoic acid (RA), and retinyl esters. Retinal is fundamental for vision and RA is used in clinical therapy of human acute promyelocytic leukemia. The actions of retinol and retinyl palmitate (RP) are not known well. Recently, we found that retinol is a potent anti-proliferative agent against human refractory cancers, including gallbladder cancer, being more effective than RA, while RP was inactive. In the current study, we determined serum retinol concentrations in xenograft mice bearing tumors derived from four refractory cancer cell lines. We also examined the effects of vitamin A on proliferation of human gallbladder cancer cells in vivo. Serum retinol concentrations were significantly lower in xenograft mice with tumors derived from various refractory cancer cell lines as compared with control mice. The growth of tumors was inhibited with increasing serum retinol concentrations obtained post-administration of RP. In addition, pre-administration of RP increased serum retinol concentrations and suppressed tumor growth. These results indicate that administration of RP can maintain retinol concentrations in the body and that this might suppress cancer cell growth and attachment. The regulation of vitamin A concentration in the body, which is critical biomarker of health, could be beneficial for cancer prevention and therapy.

Topics: Animals; Carcinogenesis; Cell Line, Tumor; Diet, Healthy; Diterpenes; Drug Resistance, Neoplasm; Humans; Male; Mice; Mice, Nude; Neoplasms; Retinyl Esters; Specific Pathogen-Free Organisms; Tretinoin; Vitamin A; Vitamins; Xenograft Model Antitumor Assays

Topics: Aged; Anthracenes; Antioxidants; Benzoates; Bronchi; Diterpenes; Epithelial Cells; Female; Humans; In Vitro Techniques; Male; Middle Aged; Naphthols; Pulmonary Disease, Chronic Obstructive; Randomized Controlled Trials as Topic; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoic Acid Receptor gamma; Retinyl Esters; Skin Diseases; Smoking; Tetrahydronaphthalenes; Thiophenes; Tretinoin; Uteroglobin; Vitamin A

Vitamin A constituents include retinal, which plays a role in vision, and retinoic acid (RA), which has been used in the therapy of human acute promyelocytic leukemia. However, the effects on cancer of retinol (Rol) and its ester, retinyl palmitate (RP) are not known well. In the current study, we examined the effects of these agents on proliferation and adhesion of various cancer cells. Rol exhibited dose-dependent inhibition of the proliferation of human refractory and prostate cancer cells, while RA and RP showed little or no effect. In contrast, RA inhibited the growth of human breast cancer cells to a greater extent than Rol at low concentrations, but not at high concentrations. Rol suppressed adhesion of refractory and prostate cancer cells to a greater extent than RA, while it suppressed adhesion of breast cancer cells as well as RA and of JHP-1 cells less effectively than RA. These results indicate that Rol is a potent suppressor of cancer cell growth and adhesion, which are both linked to metastasis and tumor progression. Rol might be useful for the clinical treatment of cancer.

Topics: Antineoplastic Agents; Cell Adhesion; Cell Line, Tumor; Cell Proliferation; Diterpenes; Drug Resistance, Neoplasm; Humans; Neoplasms; Retinyl Esters; Tretinoin; Vitamin A

Vitamin A deficiency (VAD) is a leading cause of pediatric morbidity and mortality due to infectious diseases. Recent pre-clinical studies have revealed that VAD impairs mucosal IgA-producing antibody forming cell (AFC) responses toward a paramyxovirus vaccine in the upper respiratory tract (URT), thus impeding a first line of defense at the pathogen's point-of-entry. The studies described here tested the hypothesis that VAD may also impair immune responses after FluMist vaccinations. Results show that (i) IgA-producing antibody forming cells (AFCs) are significantly reduced following FluMist vaccination in VAD mice, and (ii) oral doses of either retinyl palmitate or retinoic acid administered on days 0, 3, and 7 relative to vaccination rescue the response. Data encourage the conduct of clinical studies to determine if there are FluMist vaccine weaknesses in human VAD populations and to test corrective supplementation strategies. Improvements in vaccine efficacy may ultimately reduce the morbidity and mortality caused by influenza virus worldwide.

Topics: Administration, Intranasal; Animals; Antibody-Producing Cells; Diterpenes; Female; Immunity, Mucosal; Immunoglobulin A; Influenza Vaccines; Mice; Mice, Inbred C57BL; Pregnancy; Retinyl Esters; Tretinoin; Vaccination; Vitamin A; Vitamin A Deficiency

We studied β-carotene (BC) absorption and metabolism and compared BC and retinyl palmitate (RE) for their impact on white adipose tissue (WAT) development in suckling rats.. Rat pups received daily orally from days 1-20 of life either the vehicle or vitamin A (approx. ×3 that ingested daily from maternal milk) in the form of BC or RE. Intact BC was found in serum and liver of BC-supplemented rats. Both BC and RE supplementation increased retinoic acid mediated transcriptional responses in intestine (on Isx and Bco1) and the liver (on Cyp26a1 and Cpt1a). In contrast, responses in WAT were dependent on the vitamin A source: WAT of BC-supplemented rats, like WAT of control rats, was enriched in larger adipocytes with increased adipogenic markers (peroxisome proliferator-activated receptor γ and downstream genes) and reduced markers of proliferative status (proliferating cell nuclear antigen) compared to WAT of RE-supplemented rats.. BC is partly absorbed intact by suckling rats, which resembles the situation in humans and suggests that suckling rats may be an appropriate animal model to study BC uptake, metabolism and biological activity, particularly in infants. Vitamin A supplementation with BC or RE in early life differentially affects WAT and may thus entail different outcomes regarding adiposity programming.

Topics: Adiponectin; Adipose Tissue, White; Administration, Oral; Animals; beta Carotene; Blood Glucose; Cell Proliferation; Diterpenes; Female; Insulin; Intestinal Mucosa; Intestines; Leptin; Liver; Male; PPAR gamma; Rats; Rats, Wistar; Retinyl Esters; Tretinoin; Vitamin A

Calcific aortic valve disease (CAVD) is a major public health problem with no effective treatment available other than surgery. We previously showed that mature heart valves calcify in response to retinoic acid (RA) treatment through downregulation of the SRY transcription factor Sox9. In this study, we investigated the effects of excess vitamin A and its metabolite RA on heart valve structure and function in vivo and examined the molecular mechanisms of RA signaling during the calcification process in vitro.. Using a combination of approaches, we defined calcific aortic valve disease pathogenesis in mice fed 200 IU/g and 20 IU/g of retinyl palmitate for 12 months at molecular, cellular, and functional levels. We show that mice fed excess vitamin A develop aortic valve stenosis and leaflet calcification associated with increased expression of osteogenic genes and decreased expression of cartilaginous markers. Using a pharmacological approach, we show that RA-mediated Sox9 repression and calcification is regulated by classical RA signaling and requires both RA and retinoid X receptors.. Our studies demonstrate that excess vitamin A dietary intake promotes heart valve calcification in vivo. Therefore suggesting that hypervitaminosis A could serve as a new risk factor of calcific aortic valve disease in the human population.

Topics: Animals; Aortic Valve; Calcinosis; Cell Line; Chick Embryo; Collagen Type II; Dietary Supplements; Disease Models, Animal; Diterpenes; Gene Expression Profiling; Gene Expression Regulation; Heart Valve Diseases; Hypervitaminosis A; Mice; Mice, Inbred C57BL; Oligonucleotide Array Sequence Analysis; Osteogenesis; Osteopontin; Receptors, Retinoic Acid; Retinoid X Receptors; Retinyl Esters; RNA Interference; Signal Transduction; SOX9 Transcription Factor; Time Factors; Tissue Culture Techniques; Transfection; Tretinoin; Vitamin A; Vitamins

Although retinoids have been reported to be present and active in vertebrates and invertebrates, the presence of mechanisms for retinoid storage in the form of retinyl esters, a key feature to maintain whole-organism retinoid homeostasis, have been considered to date a vertebrate innovation. Here we demonstrate for the first time the presence of retinol and retinyl esters in an invertebrate lophotrochozoan species, the gastropod mollusk Osilinus lineatus. Furthermore, through a pharmacological approach consisting of intramuscular injections of different retinoid precursors, we also demonstrate that the retinol esterification pathway is active in vivo in this species. Interestingly, retinol and retinyl esters were only detected in males, suggesting a gender-specific role for these compounds in the testis. Females, although lacking detectable levels of retinol or retinyl esters, also have the biochemical capacity to esterify retinol, but at a lower rate than males. The occurrence of retinyl ester storage capacity, together with the presence in males and females of active retinoids, i.e., retinoic acid isomers, indicates that O. lineatus has a well developed retinoid system. Hence, the present data strongly suggest that the capacity to maintain retinoid homeostasis has arisen earlier in Bilateria evolution than previously thought.

Topics: Animals; Biological Evolution; Chromatography, High Pressure Liquid; Diterpenes; Esterification; Female; Homeostasis; Male; Microinjections; Mollusca; Muscles; Retinaldehyde; Retinyl Esters; Testis; Tretinoin; Vitamin A

Iron bioavailability seems to be regulated by vitamin A (VA) but the molecular events involved in this mechanism are not well understood. It is also known that retinoids mediate most of their function via interaction with retinoid receptors, which act as ligand-activated transcription factors controlling the expression of a number of target genes. Here, we evaluated the VA effects on the modulation of the levels of mRNA encoding proteins involved in the iron bioavailability, whether in the intestinal absorption process or in the liver iron metabolism. The expression of genes involved in iron intestinal absorption (divalent metal transporter 1, duodenal cytochrome B, ferroportin 1 FPN1, and ferritin) were evaluated in vitro by treating Caco-2 cells with retinoic acid or in vivo by observing the effects of vitamin A deficiency (VAD) in BALB/C mice. Liver hepcidin and ferritin mRNA levels were upregulated by VAD; however, this condition did not promote any change on the expression of those genes that participate in the iron absorption. Moreover, data from the in vitro analysis showed that VA induced FPN1 gene expression by a hepcidin-independent manner. Therefore, the in vivo results support the idea that VAD may not affect iron absorption but would rather affect iron mobilization mechanisms. On the other hand, our results using Caco-2 cells raises the possibility that VA addition to intestinal epithelium may improve iron absorption through the induction of FPN1 gene expression.

Topics: Animals; Antimicrobial Cationic Peptides; Blotting, Western; Caco-2 Cells; Cation Transport Proteins; Dietary Supplements; Diterpenes; Drug Evaluation, Preclinical; Duodenum; Ferritins; Gene Expression Regulation; Hepcidins; Humans; Intestinal Absorption; Intestinal Mucosa; Iron; Liver; Male; Mice; Mice, Inbred BALB C; Retinyl Esters; RNA, Messenger; Tretinoin; Vitamin A; Vitamin A Deficiency

Previous research in our laboratory showed that retinol inhibited all-trans retinoic acid (ATRA)-resistant human colon cancer cell invasion via a retinoic acid receptor-independent mechanism in vitro. The objective of the current study was to determine if dietary vitamin A supplementation inhibited metastasis of ATRA-resistant colon cancer cells in a nude mouse xenograft model. Female nude mice (BALB/cAnNCr-nu/nu, n = 14 per group) consumed a control diet (2,400 IU retinyl palmitate/kg diet) or a vitamin A supplemented diet (200,000 IU retinyl palmitate/kg diet) for 1 mo prior to tumor cell injection to preload the liver with vitamin A. HCT-116, ATRA-resistant, human colon cancer cells were intrasplenically injected. Mice continued to consume their respective diets for 5 wk following surgery. Consumption of supplemental vitamin A decreased hepatic metastatic multiplicity to 17% of control. Hepatic and splenic retinol and retinyl ester concentrations were significantly higher in the mice supplemented with vitamin A when compared to mice consuming the control diet. Supplemental vitamin A did not decrease body weight, feed intake, or cause toxicity. Thus, supplemental dietary vitamin A may decrease the overall number of hepatic metastasis resulting from colon cancer.

Topics: Animals; Antineoplastic Agents; Biotransformation; Carcinoma; Colorectal Neoplasms; Dietary Supplements; Diterpenes; Drug Resistance, Neoplasm; Female; HCT116 Cells; Humans; Liver; Liver Neoplasms, Experimental; Mice; Mice, Nude; Random Allocation; Retinyl Esters; Spleen; Tissue Distribution; Tretinoin; Vitamin A; Xenograft Model Antitumor Assays

Topical retinoids, compounds that are metabolites, analogues, or derivatives of retinol and possess biological vitamin A activity, are among the most used adjunctive agents for the mitigation of fine wrinkles, mottled hyperpigmentation, and tactile roughness of photodamaged and chronically aged skin. Retinoic acid (RA) is the most active biological form of vitamin A and remains the medical treatment of choice for photoaged skin. Retinyl palmitate (RP) is the major storage form of vitamin A in the skin and, because RP is also the most stable of available vitamin A esters, it is readily incorporated into the oil phase of cosmetic creams or lotions. Therefore, the topical application of RP is a practical strategy for increasing the levels of vitamin A in the skin. Usual cosmetic product concentrations of RA range from 0.025% to 0.1% and those of RP range from 0.1% to 5%. With a maximum absorbance around 325 nm, RA and RP absorb both ultraviolet A and B radiation (UVA and UVB) in incident sunlight. A 1-year study was conducted in mice to determine whether RA and RP would alter the photocarcinogenicity of broad-UV spectrum light generated by xenon arc lamps, termed simulated solar light (SSL), or narrow spectrum UV light generated by UVA and UVB lamps.

Topics: Administration, Topical; Animals; Antineoplastic Agents; Carcinogenicity Tests; Carcinoma, Squamous Cell; Diterpenes; Dose-Response Relationship, Drug; Female; Male; Mice; Mice, Inbred Strains; Mice, Nude; Retinyl Esters; Skin; Skin Neoplasms; Sunlight; Tretinoin; Vitamin A

A role of vitamin A in the synthesis of hyaluronic acid by skin cells is well known. Hyaluronic acid is produced by corneal epithelial cells and keratocytes in the eye. We investigated whether rabbit corneal epithelial cells and keratocytes release hyaluronic acid after exposure to vitamin A compounds. Rabbit corneal epithelial cells and keratocytes were inoculated with RCGM2 medium and incubated at 37ºC under 5% CO(2) in air for 24 h. The medium was then replaced with medium containing 0.1, 1, 10, or 100 μM retinoic acid or retinol palmitate (VApal) and incubated for another 48 h. Hyaluronic acid release from both corneal epithelial cells and keratocytes during culture was increased by retinoic acid at the lower concentration of 0.1 μM and 1 μM determined with a sandwich binding protein assay kit. However, it was significantly decreased at the higher concentrations of 10 μM and 100 μM, and the cell count determined with a Neutral Red assay kit was also decreased at these concentrations. On the other hand, hyaluronic acid release from corneal epithelial cells during culture was increased by VApal at the lower concentration of 0.1 μM and 1 μM, but there was no significant difference in the cell count for either corneal epithelial cells or keratocytes in the presence of VApal at any concentration. In conclusion, it is suggested that vitamin A stimulates the release of hyaluronic acid from cultured rabbit corneal epithelial cells and keratocytes.

Topics: Animals; Cell Count; Cells, Cultured; Cornea; Corneal Keratocytes; Diterpenes; Epithelial Cells; Hyaluronic Acid; Rabbits; Retinyl Esters; Tretinoin; Vitamin A

Topics: Adipocytes; Animals; Chromatography, High Pressure Liquid; Dimerization; Diterpenes; Gene Expression Regulation; Lipids; Liver; Mice; Models, Chemical; Oxidoreductases Acting on CH-CH Group Donors; Retinoids; Retinyl Esters; Stereoisomerism; Tretinoin; Vitamin A; Zebrafish; Zebrafish Proteins

Retinoic acid (RA) is a signaling molecule in the morphogenesis of the mammary gland, modulating the expression of matrix metalloproteinases (MMPs). The aim of this paper was to study the role of RA during weaning, which consists of three events: apoptosis of the secretory cells, degradation of the extracellular matrix, and adipogenesis. CRABP II and CRBP-1 carrier proteins increased significantly during weaning compared with lactating glands but reverted to control values after the litter resuckled. The effects of RA are mediated by the nuclear receptors RARalpha, RARbeta, RARgamma, and RXRalpha, which underwent an increase in protein levels during weaning. In an attempt to elucidate the RARalpha-dependent signaling pathway, ChIP assays were performed. The results showed the binding of RARalpha to the MMP-9 promoter after 24- and 72-h weaning together with its coactivator p300; this fact could be responsible for the increase found in MMP-9 mRNA and protein levels in these conditions. Expression of related MMPs (MMP-2 and MMP-3) was also increased during weaning. Using gelatine zymography, we observed a time-dependent increase in active forms of MMP-9 and MMP-2. On the other hand, the inhibitor of MMPs, TIMP-1, was almost undetectable at 24- and 72-h weaning by Western blot. The role of retinoids in matrix remodeling is reinforced by the fact that administration of an acute dose of retinol palmitate to control lactating rats also induces MMP-9 expression. This emphasizes the importance of retinoids in vivo to regulate mammary gland involution.

Topics: Adipogenesis; Animals; Apoptosis; Diterpenes; Extracellular Matrix; Female; Lactation; Mammary Glands, Animal; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Matrix Metalloproteinases; Pregnancy; Rats; Rats, Wistar; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoids; Retinol-Binding Proteins; Retinol-Binding Proteins, Cellular; Retinyl Esters; RNA, Messenger; Signal Transduction; Time Factors; Tretinoin; Vitamin A; Weaning

The relation between vitamin A (VA) nutritional status and the metabolism of all-trans-retinoic acid (RA) is not well understood. In this study, we determined the tissue distribution and metabolism of a test dose of [(3)H]-RA in rats with graded, diet-dependent, differences in VA status. The design included 3 groups, designated VA-deficient, VA-marginal, and VA-adequate, with liver total retinol concentrations of 9.7, 35.7 and 359 nmol/g, respectively, (P < 0.05), and an additional group of VA-deficient rats treated with a single oral dose of retinyl palmitate (RP) 20 h before the injection of [(3)H]-RA. Plasma, liver, lung, and small intestines, collected 30 min after [(3)H]-RA, were analyzed for total (3)H, unmetabolized [(3)H]-RA, polar organic-phase metabolites of [(3)H]-RA, and aqueous phase [(3)H]-labeled metabolites. In all groups, [(3)H]-RA was rapidly removed from plasma and concentrated in the liver. VA deficiency did not prevent the oxidative metabolism of RA. Nevertheless, the quantity of [(3)H]-RA metabolites in plasma and the ratio of total [(3)H]-polar metabolites to unmetabolized [(3)H]-RA in liver varied directly with VA status (VA-adequate > VA-marginal > VA-deficient, P < 0.05). Moreover, supplementation of VA-deficient rats with RP reduced the metabolism of [(3)H]-RA, similar to that in VA-adequate or VA-marginal rats. Liver retinol concentration, considered a proxy for VA status, was correlated (P < 0.05) with [(3)H]-RA metabolites in liver (R(2) = 0.54), plasma (R(2) = 0.44), lung (R(2) = 0.40), intestine (R(2) = 0.62), and all combined (R(2) = 0.655). Overall, the results demonstrate close linkage between dietary VA intake, hepatic storage of VA, and the degradation of RA and suggest that measuring plasma retinoid metabolites after a dose of RA may provide insight into the metabolism of this bioactive retinoid by visceral organs.

Topics: Animals; Body Weight; Cytochrome P-450 Enzyme System; Diterpenes; Female; Organ Size; Rats; Rats, Sprague-Dawley; Retinoic Acid 4-Hydroxylase; Retinyl Esters; RNA, Messenger; Tretinoin; Vitamin A

Epidemiological studies have shown an inverse relationship between dietary vitamin A intake and the risk of developing lung cancer. The aim of this study was to investigate the vitamin A status in patients with lung cancer, by determining the serum levels of retinoic acid, retinol and retinyl palmitate.. In total, 36 patients with lung cancer and 27 controls were assessed. Of the patients 14 had squamous cell carcinoma, 3 adenocarcinoma, 15 non-small cell lung cancer and 4 small cell lung cancer. Serum retinoic acid, retinol and retinyl palmitate levels were determined with HPLC and UV detection, after liquid extraction.. Serum retinol levels did not differ between patients (733.5 +/- 326.4 ng/mL) and controls (734.5 +/- 337.1 ng/mL). The retinyl palmitate concentration tended to be lower in patients (14.3 +/- 9.7 ng/mL) than in controls (16.7 +/- 13.7 ng/mL). The serum retinoic acid levels were significantly lower in patients (1.9 +/- 0.6 ng/mL) than in controls (2.5 +/- 1.1 ng/mL, P < 0.05). A positive correlation was observed between the retinol and retinoic acid levels and retinyl palmitate and retinoic acid levels.. The lower levels of retinoic acid in patients with lung cancer suggest there may be a deficiency or impairment in retinol metabolism in these patients. Further studies with larger numbers of patients are needed to evaluate the possible relationship between serum retinoid levels and lung cancer.

Topics: Adenocarcinoma; Aged; Biomarkers, Tumor; Carcinoma, Non-Small-Cell Lung; Carcinoma, Small Cell; Carcinoma, Squamous Cell; Chromatography, High Pressure Liquid; Disease Progression; Diterpenes; Female; Humans; Lung Neoplasms; Male; Prognosis; Retinyl Esters; Risk Factors; Tretinoin; Vitamin A

Vitamin A (VA) is stored in tissues predominantly as retinyl esters (REs), which provide substrate for the production of bioactive retinoids. Retinoic acid (RA), a principal metabolite, has been shown to induce postnatal lung development. To better understand lung RE storage, we compared VA (given as retinyl palmitate), RA, and a nutrient-metabolite combination, VARA, given orally on postnatal days 5-7, for their ability to increase lung RE in neonatal rats. VARA increased lung RE significantly [ approximately 14, 2.4, 2.1, and <1 nmol/g for VARA, VA, RA, and control (C), respectively; P < 0.001]; the increase by VARA was more than additive compared with the effects of VA and RA alone. Lung histology and morphometry were unchanged. In a 6 h metabolic study, providing [(3)H]retinol with VARA, compared with VA or C, increased the uptake of newly absorbed (3)H by 3-fold, indicating that VARA stimulated the uptake of [(3)H]retinol and its retention as [(3)H]RE in neonatal lungs. After cessation of VARA, lung RE remained increased for 9 d afterward, through the period of alveolar development. In conclusion, VARA, a 10:1 nutrient-metabolite combination, increased lung RE significantly compared with VA alone and could be a promising therapeutic option for enhancing the delivery of VA to the lungs.

Topics: Animals; Animals, Newborn; Diterpenes; Drug Synergism; Esters; Liver; Lung; Pulmonary Alveoli; Random Allocation; Rats; Rats, Sprague-Dawley; Retinoids; Retinyl Esters; Time Factors; Tretinoin; Vitamin A; Vitamins

The free radical scavenging properties of retinyl ascorbate (RA-AsA) were determined by monitoring the decomposition of 2,2-diphenyl-1-picrylhydrazyl (DPPH) as a function of time and in comparison with ascorbic acid (AsA), ascorbic acid palmitate (AsA-Pal), retinoic acid (RA), retinol (ROL) and retinol palmitate (Rol-Pal). The rate constant of RA-AsA (mean3+/-SD) was 4.9+/-0.3 M(-1) s(-1), and indicated greater potency as an antioxidant compared to the rest of the test compounds (AsA 3.4+/-0.4 M(-1) s(-1), AsA-Pal, 2.9+/-0.2 M(-1) s(-1), RA 1.4+/-0.3 M(-1) s(-1), ROL 1.3+/-0.1 M(-1) s(-1), Rol-Pal exhibited insignificant activity). The decomposition rate constant of DPPH, 5+/-0.6 x 10(-8) M(-1) s(-1), in ethanol and BHA, 154+/-3 M(-1) s(-1) were both used as control. The compound RA-2-carboxy-2-hydroxy-ethanoate was isolated by prep-TLC and was identified, by 13C and 1HNMR spectroscopy, as the major by-product from the reaction of RA-AsA with DPPH, which was also found to be potent antioxidant, 2.1+/-0.2 M(-1) s(-1). This suggests that oxidation of AsA moiety did not lead to the production of erythrulose species, which could cause deleterious modifications of cellular proteins.

Topics: Administration, Topical; Ascorbic Acid; Biphenyl Compounds; Diterpenes; Free Radical Scavengers; Hydrazines; Picrates; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

RPE65 is essential in the operation of the visual cycle and functions as a chaperone for all-trans-retinyl esters, the substrates for isomerization in the visual cycle. RPE65 stereospecifically binds all-trans-retinyl esters with a K(D) of 47 nM. It is shown here by using a quantitative fluorescence technique, that Accutane (13-cis-retinoic acid), a drug used in the treatment of acne but that causes night blindness, binds to RPE65 with a K(D) of 195 nM. All-trans-retinoic acid binds with a K(D) of 109 nM. The binding of the retinoic acids to RPE65 is competitive with all-trans-retinyl ester binding, and this competition inhibits visual cycle function. A retinoic acid analog that binds weakly to RPE65 is not inhibitory. These data suggest that RPE65 function is rate-limiting in visual cycle function. They also reveal the target through which the retinoic acids induce night blindness. Finally, certain forms of retinal and macular degeneration are caused by the accumulation of vitamin A-based retinotoxic products, called the retinyl pigment epithelium-lipofuscin. These retinotoxic products accumulate during the normal course of rhodopsin bleaching and regeneration after the operation of the visual cycle. Drugs such as Accutane may represent an important approach to reducing the accumulation of the retinotoxic lipofuscin by inhibiting visual cycle function. The identification of RPE65 as the visual cycle target for the retinoic acids makes it feasible to develop useful drugs to treat retinal and macular degeneration while avoiding the substantial side effects of the retinoic acids.

Topics: Animals; Cattle; Diterpenes; Eye Proteins; Macular Degeneration; Proteins; Retinyl Esters; Tretinoin; Vitamin A

Retinoids have been studied extensively for their chemopreventive properties. The biological activity of retinoids is acquired through their conversion to retinoic acid (RA). Characterization of endogenous circulating RA concentrations after supplementation with vitamin A over longer time periods has not been done previously. Our investigation was conducted to determine whether vitamin A (retinyl palmitate) supplementation significantly increases circulating RA concentrations of all-trans-, 9-cis-, and 13-cis-RA. Using plasma samples from 41 participants enrolled in a randomized clinical trial of placebo, 25,000, 50,000, or 75,000 IU supplemental retinyl palmitate daily, high-performance liquid chromatography analyses were conducted for concentrations of three RA isomers. Seven plasma samples were analyzed for each participant over a 16-month period. Based on an intention-to-treat analysis, results obtained using linear mixed models showed that supplementation with retinyl palmitate statistically significantly increased concentrations of all three RA isomers from baseline levels. This study suggests that supplementation with retinyl palmitate is an effective means to increase circulating all-trans, 9-cis-, and 13-cis-RA concentrations among humans.

Topics: Aged; Anticarcinogenic Agents; Chromatography, High Pressure Liquid; Diterpenes; Dose-Response Relationship, Drug; Female; Humans; Male; Middle Aged; Randomized Controlled Trials as Topic; Retinyl Esters; Skin Neoplasms; Stereoisomerism; Tretinoin; Vitamin A

Recent studies have revealed that retinoids play an important role in the adult central nervous system and cognitive functions. Previous investigations in mice have shown that vitamin A deficiency (VAD) generates a hypo-expression of retinoic acid (RA, the active metabolite of vitamin A) receptors and of neurogranin (RC3, a neuronal protein involved in synaptic plasticity) and a concomitant selective behavioural impairment. Knowing that RC3 is both a triiodothyronine (T3) and a RA target gene, and in consideration of the relationships between the signalling pathways of retinoids and thyroid hormones, the involvement of T3 on RA signalling functionality in VAD was investigated. Thus, the effects of vitamin A depletion and subsequent administration with RA and/or T3 on the expression of RA nuclear receptors (RAR, RXR), T3 nuclear receptor (TR) and on RC3 in the brain were examined. Rats fed a vitamin A-deficient diet for 10 weeks exhibited a decreased expression of RAR, RXR and TR mRNA and of RC3 mRNA and proteins. RA administration to these vitamin A-deficient rats reversed only the RA hypo-signalling in the brain. Interestingly, T3 is able to restore its own brain signalling simultaneously with that of vitamin A and the hypo-expression of RC3. These results obtained in vivo revealed that one of the consequences of VAD is a dysfunction in the thyroid signalling pathway in the brain. This seems of crucial importance since the down regulation of RC3 observed in the depleted rats was corrected only by T3.

Topics: Animals; Blotting, Western; Brain Chemistry; Calmodulin-Binding Proteins; Diterpenes; GTP-Binding Proteins; Liver; Male; Nerve Tissue Proteins; Neurogranin; Protein Glutamine gamma Glutamyltransferase 2; Rats; Rats, Wistar; Receptors, Retinoic Acid; Receptors, Thyroid Hormone; Retinoid X Receptors; Retinyl Esters; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Transcription Factors; Transglutaminases; Tretinoin; Triiodothyronine; Vitamin A; Vitamin A Deficiency

The construction of transgenic FVB/N mice targeting the PMLRARA fusion gene under the control of a human MRP8 promoter recapitulated the phenotype of acute promyelocytic leukemia but had the unexpected result of multiple squamous papillomas of the skin (Brown et al., PROC: Natl. Acad. Sci. USA, 94:2551-2556, 1997). In addition, transgenic MRP8-PMLRARA mice exhibited a skin phenotype characteristic of vitamin A deficiency. The severity of the skin phenotype and spontaneous papilloma development correlated with the level of transgene expression. Papilloma formation was preceded by follicular hyperplasia and the expression of epidermal differentiation markers in the follicular epithelium. Mutations in the Ha or Ki alleles of ras were not detected in papillomas that developed on transgenic skin, and papilloma formation was accentuated on the C57/Bl6 background, unlike the usual resistance of this strain to skin tumor induction. Analysis of liver extracts from transgenic mice indicated a deficiency in the production of retinoic acid. Furthermore, affected transgenic epidermis had reduced levels of retinoic acid receptoralpha (RARalpha) and retinoic X receptor (RXRalpha), and supplementation with exogenous retinoic acid prevented the skin phenotype. When transgenic keratinocytes were grafted to nude mice, the resulting integument was normal, and conversely, when transgenic bone marrow was grafted to normal mice, a skin phenotype did not develop. Together these results suggest that local interruption of PML and RARalpha signaling in the skin, together with a systemic retinoid deficiency, initiates a tumor induction pathway that is independent of ras activation.

Topics: Animals; Calgranulin A; Cell Differentiation; Diterpenes; Genes, ras; Genetic Predisposition to Disease; Hair Follicle; Humans; Liver; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Neoplasm Proteins; Oncogene Proteins, Fusion; Papilloma; Promoter Regions, Genetic; Receptors, Retinoic Acid; Retinoic Acid Receptor alpha; Retinoid X Receptors; Retinoids; Retinyl Esters; Skin Neoplasms; Transcription Factors; Transgenes; Tretinoin; Vitamin A

Vitamin A (VA) and insulin-like growth factors (IGF) are important regulators of a wide range of physiological processes. To investigate the IGF system's involvement in the physiological actions of VA, we examined the effects of VA status on components of the IGF system in rats. Male rats (3-wk-old) fed a VA-deficient diet for 11 wk developed VA deficiency, as confirmed by the depletion of serum retinol and hepatic retinyl palmitate. Rats fed the VA-deficient diet had significantly lower body weight (p < 0.05) and lower serum IGF-I concentrations than the rats fed the control diet. The decreases in serum IGF-I levels were accompanied by approximately 40% lower levels of the IGF-I mRNA in the liver and lungs. With respect to the gene expression of other IGF system components, VA deficiency caused a twofold induction of IGF-I receptor (IGF-IR) mRNA in the heart and a twofold reduction in IGFBP-6 mRNA in the lungs, but did not alter the expression of IGF-II, IGFBP-1, IGFBP-3, IGFBP-4 or IGFBP-5 in all tissues examined. When VA-deficient rats received a single injection of retinoic acid (2 mg/rat), tissue IGF-I and IGF-IR gene expression did not change after 4 or 8 h, while the expression of IGF-II, IGFBP-4, and IGFBP-6 mRNAs in some tissues increased rapidly. These results suggest a possible involvement of the IGF system in mediating the physiological actions of VA, including VA-supported growth, in the rat.

Topics: Animals; Blotting, Northern; Diterpenes; Gene Expression Regulation; Insulin-Like Growth Factor Binding Proteins; Male; Random Allocation; Rats; Rats, Wistar; Retinyl Esters; RNA, Messenger; Somatomedins; Tissue Distribution; Tretinoin; Vitamin A; Vitamin A Deficiency

Regulation of S-adenosylmethionine (SAM) and the SAM/S-adenosylhomocysteine (SAH) ratio by the key cytosolic enzyme glycine N-methyltransferase (GNMT) is essential in optimizing methyl group supply and subsequent functioning of methyltransferase enzymes. Therefore, inappropriate activation of GNMT may lead to the loss of methyl groups vital for many SAM-dependent transmethylation reactions. Previously, we demonstrated that the retinoid derivatives 13-cis- (CRA) and all-trans-retinoic acid (ATRA) mediated both the activity of GNMT and its abundance. The present study was conducted to determine whether vitamin A had a similar ability to up-regulate GNMT and to assess the biological importance of GNMT modulation by examining both the transmethylation and transsulfuration pathways after retinoid treatment. Rats were fed a control (10% casein + 0.3% L-methionine) diet and orally given retinyl palmitate (RP), CRA, ATRA or vehicle daily for 10 d. RP, CRA and ATRA elevated hepatic GNMT activity 32, 74 and 124%, respectively, compared with the control group. Moreover, the retinoid-mediated changes in GNMT activity were reflected in GNMT abundance (38, 89 and 107% increases for RP-, CRA-, and ATRA-treated rats, respectively). In addition, hepatic DNA, a substrate for SAM-dependent transmethylation, was hypomethylated (approximately 100%) after ATRA treatment compared with the control group. In contrast, the transsulfuration product glutathione was unaffected by retinoid treatment. These results provide evidence of the following: 1) vitamin A, like its retinoic acid derivatives, can induce enzymatically active GNMT; and 2) inappropriate induction of GNMT can lead to a biologically important loss of methyl groups and the subsequent impairment of essential transmethylation processes.

Topics: Animals; Diterpenes; DNA Methylation; Enzyme Activation; Glutathione; Glycine N-Methyltransferase; Isotretinoin; Liver; Male; Methyltransferases; Rats; Rats, Sprague-Dawley; Retinyl Esters; Tretinoin; Vitamin A

Glycine N-methyltransferase (GNMT) is a key protein in the liver that functions to regulate S-adenosylmethionine (SAM) and the SAM/S-adenosylhomocysteine ratio. Significant GNMT expression is also present in the kidney and pancreas. Inappropriate regulation of GNMT may have negative consequences on methyl group and folate metabolism. We have demonstrated that retinoid compounds significantly elevated hepatic GNMT activity and abundance (approximately 2-fold) in male rats. However, pancreatic GNMT activity and abundance were not altered by retinoid treatment. Likewise, retinoid administration was without effect on renal GNMT activity. Hepatic GNMT activity was also elevated in female rats treated with all-trans-retinoic acid, but to a lesser extent compared to males. Collectively, these results indicate that the modulation of methyl group metabolism by retinoids is tissue- and gender-specific, and may compromise the availability of methyl groups for SAM-dependent transmethylation reactions. In support of this, SAM-dependent synthesis of creatinine was significantly reduced 21% following all-trans-retinoic acid treatment.

Topics: Animals; Diterpenes; Enzyme Activation; Enzyme Induction; Female; Glycine N-Methyltransferase; Isotretinoin; Kidney; Liver; Male; Methyltransferases; Pancreas; Rats; Rats, Sprague-Dawley; Retinoids; Retinyl Esters; S-Adenosylmethionine; Sex Characteristics; Tissue Distribution; Tretinoin; Vitamin A

Sertoli cells, the somatic epithelial cells of the seminiferous tubules, provide both structural and biochemical support for developing male germ cells. The Sertoli cells are targets of retinoid action in the testis. We have found that FSH, (Bu)(2)cAMP, and leukemia inhibitory factor elicit substantial changes in the metabolism of [(3)H]retinol (vitamin A) in primary cultures of purified rat Sertoli cells. Addition of (Bu)(2)cAMP for 2 h or FSH for 6 h results in a 3-fold increase in the metabolism of [(3)H]retinol to [(3)H]retinoic acid ([(3)H]RA); the esterification of [(3)H]retinol to [(3)H]retinyl esters, especially [(3)H]retinyl palmitate, is also increased by approximately 5-fold. The addition of 1 microM all-trans-RA also elicits changes in [(3)H]retinol metabolism, but in this case the metabolism of [(3)H]retinol to [(3)H]RA is inhibited, whereas the metabolism of [(3)H]retinol to [(3)H]retinyl esters is increased by over 50-fold. Leukemia inhibitory factor increases the esterification of [(3)H]retinol by 2- to 3-fold. FSH leads to a reduction in the level of cellular retinol binding protein I transcripts, whereas RA increases the cellular retinol binding protein I messenger RNA level by about 2-fold at approximately 24 h. Levels of AHD-2 (aldehyde dehydrogenase-2) and RALDH-2 (retinaldehyde dehydrogenase-2) messenger RNAs, which encode enzymes that convert [(3)H]retinaldehyde to [(3)H]RA, are increased by about 2-fold by FSH, whereas no change in CYP26 (RA hydroxylase) expression is seen. Our results suggest that one function of FSH (and/or (Bu)(2)cAMP) in Sertoli cells is to increase the metabolism of retinol to the biologically active metabolite RA and to retinyl esters.

Topics: Animals; Bucladesine; Cells, Cultured; Cyclic AMP; Diazomethane; Diterpenes; Esterification; Follicle Stimulating Hormone; Gene Expression; Growth Inhibitors; Interleukin-6; Leukemia Inhibitory Factor; Lymphokines; Male; Rats; Rats, Wistar; Retinyl Esters; Sertoli Cells; Tretinoin; Vitamin A

Normal embryonic development and survival in utero is dependent on an adequate supply of vitamin A. Embryos from vitamin A-deficient (VAD) pregnant rats fed an inadequate amount of all-trans retinoic acid (atRA; 12 microg per g of diet or approximately 230 microg per rat per day) exhibit severe developmental abnormalities of the anterior cardinal vein and hindbrain by embryonic day (E) 12.5 and die shortly thereafter.. In the present study, we sought to determine whether supplementation of VAD-RA supported (12 microg per g of diet) pregnant rats with retinol (ROL) at the late-gastrula (presomite or rat E9.5) or early somite stages (E10.5), or provision of higher levels of atRA throughout this period could prevent abnormalities in the developing cardiovascular and nervous systems.. A newly described defect in the sinuatrial venus valve along with enlarged anterior cardinal veins and nervous system abnormalities and the later death of embryos are prevented by supplementing pregnant animals with ROL on the morning of E9.5. If ROL supplementation is delayed by 1 day (E10.5), most embryos are abnormal and die by E18.5. Supplementation of VAD rats with atRA (250 microg per g of diet) between E8.5 and E10.5 also prevents the cardiovascular and nervous system abnormalities and a significant number of these embryos survive to parturition. Thus, high levels of atRA can obviate the need for ROL between E9.5 and E10.5.. These results support an essential role for retinoid signaling between the late gastrula and early somite stages in the rat embryo for normal morphogenesis of the primitive heart tube and the posterior hindbrain. Further, these results suggest that embryonic death occurring at midgestation in the VAD rat may be linked to the abnormal development of one or both of these embryonic structures.

Topics: Abnormalities, Multiple; Animal Feed; Animals; Cranial Nerves; Diterpenes; Dose-Response Relationship, Drug; Embryonic and Fetal Development; Female; Fetal Death; Fetal Heart; Fetal Resorption; Gastrula; Genes, Homeobox; Gestational Age; Morphogenesis; Pregnancy; Pregnancy Complications; Rats; Retinyl Esters; Rhombencephalon; Transcription Factors; Tretinoin; Veins; Vitamin A; Vitamin A Deficiency

There remains a remarkable discordance between the results of observational epidemiological studies and intervention trials using beta-carotene as a potential chemopreventive agent. One question that needs to be examined is whether the adverse outcomes of human beta-carotene trials are related to the large doses of beta-carotene that were administered. In the present study, ferrets were given a physiological (low) dose or a pharmacological (high) dose of beta-carotene supplementation (0.43 mg versus 2.4 mg/kg body wt/day, which is equivalent to 6 mg versus 30 mg/day in humans) and exposed to cigarette smoke for 6 months. We investigated the effects of these doses of beta-carotene on retinoid concentrations, expression of retinoic acid receptors (RARs), activator protein 1 (AP-1; c-Jun and c-Fos), cyclin D1, proliferating cellular nuclear antigen (PCNA), and histopathological changes in the lungs of both normal and cigarette smoke-exposed ferrets. Thirty-six male ferrets were treated in six groups-control, smoke-exposed (SM), low-dose beta-carotene (LBC), high-dose beta-carotene (HBC), low-dose beta-carotene plus smoke exposure (LBC+SM) or high-dose beta-carotene plus smoke exposure (HBC+SM)-for 6 months. Retinoic acid concentration and RAR beta gene expression, but not expression of RAR alpha and RAR gamma, was reduced in the lung tissue of HBC+SM, HBC, SM and LBC+SM ferrets, but not in that of LBC ferrets, as compared with the control group. Expression of AP-1 and PCNA was greater in HBC+SM, HBC, SM and LBC+SM ferrets, but not in the LBC ferrets, as compared with the control group. Increased amounts of cyclin D1 and keratinized squamous metaplasia were observed in the lung tissue of HBC+SM, HBC and SM groups but not in that of the LBC+SM, LBC or control groups. These data suggest that, in contrast with a pharmacological dose of beta-carotene, a physiological dose of beta-carotene in smoke-exposed ferrets has no potentially detrimental effects and may afford weak protection against lung damage induced by cigarette smoke.

Topics: Animals; beta Carotene; Cell Division; Cyclin D1; Dietary Supplements; Diterpenes; Dose-Response Relationship, Drug; Ferrets; Humans; Lung; Male; Proliferating Cell Nuclear Antigen; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Retinyl Esters; Tobacco Smoke Pollution; Tretinoin; Vitamin A

Epidemiologic studies have demonstrated that individuals who eat more fruits and vegetables and/or have high levels of serum beta-carotene have a lower risk of cancer, especially lung cancer. However, recent human intervention studies using beta-carotene supplements have shown an increase in the risk of lung cancer among smokers and asbestos workers. In this study, we used an animal model system to evaluate the hazard associated with a combination of high-dose beta-carotene supplementation and tobacco smoking.. Ferrets were given a beta-carotene supplement, exposed to cigarette smoke, or both for 6 months. Cell proliferation and squamous metaplasia in lung tissue were assessed by examination of proliferating-cell nuclear antigen expression and histopathologic examination, respectively. beta-Carotene and retinoid concentrations in lung tissue and plasma samples were analyzed by high-performance liquid chromatography. Expression of genes for retinoic acid receptors (RARs) and activator protein-1 (encoded by the c-Jun and c-Fos genes) in lung tissue specimens was examined by western blotting.. A strong proliferative response in lung tissue and squamous metaplasia was observed in all beta-carotene-supplemented animals, and this response was enhanced by exposure to tobacco smoke. When compared with control groups, all three treatment groups had statistically significantly lower concentrations of retinoic acid in lung tissue, and they exhibited 18%-73% reductions in RARbeta gene expression; however, RARalpha and RARgamma gene expression was not reduced. Ferrets given a beta-carotene supplement and exposed to tobacco smoke had threefold to fourfold elevated expression of the c-Jun and c-Fos genes.. Diminished retinoid signaling, resulting from the suppression of RARbeta gene expression and overexpression of activator protein-1, could be a mechanism to enhance lung tumorigenesis after high-dose beta-carotene supplementation and exposure to tobacco smoke.

Topics: Animals; beta Carotene; Cell Division; Cocarcinogenesis; Diterpenes; Down-Regulation; Environmental Exposure; Ferrets; Gene Expression Regulation; Genes, fos; Genes, jun; Humans; Lung; Lung Neoplasms; Male; Metaplasia; Nicotiana; Plants, Toxic; Precancerous Conditions; Proliferating Cell Nuclear Antigen; Receptors, Retinoic Acid; Retinyl Esters; Signal Transduction; Smoke; Transcription Factor AP-1; Tretinoin; Vitamin A

HaCaT keratinocytes differ from normal human epidermal keratinocytes (HEK) by constitutive expression of differentiation markers which are normally suppressed by vitamin A. In search of an explanation for this discrepancy we compared the vitamin A content, the expression of retinoid-binding proteins, and the vitamin A metabolism in the two cell types. The concentrations of retinol and 3,4-didehydroretinol in cultured HaCaT cells were less than one-fifth those in HEK, and the content of fatty acyl esters was even lower. Similarly, the concentrations of cellular retinol-binding protein and cellular retinoic acid-binding protein (CRBPI and CRABPII, respectively) were 10-30 times lower in HaCaT cells than in HEK corresponding to a reduced mRNA expression of these proteins. Unexpectedly, HaCaT cells expressed RARbeta in addition to RARalpha, RARgamma and RXRalpha, which are nuclear receptors normally found in HEK. Radioactive retinol added to the culture medium appeared only transiently in HaCaT cells, and pulse labeling confirmed a defective cellular retention of retinyl esters. After 24 h of incubation with [3H]retinol, cell-associated radioactivity corresponding to retinol, 3,4-didehydroretinol, all-trans-retinoic acid and 3,4-didehydroretinoic acid was found in both HaCaT cells and HEK. [3H]Retinoic acid showed a more rapid metabolism to 4-hydroxy/4-keto-retinoic acid in HaCaT cells than in HEK, which could be explained by a higher expression of cytochrome p450RAI in the former cells. In conclusion, the abnormal uptake of vitamin A and low levels of retinoid binding proteins in HaCaT cells, linked with an aberrant metabolism of retinol, may help to explain why these cells differentiate also in the presence of retinoids.

Topics: Biomarkers; Carrier Proteins; Cell Differentiation; Cell Line; Cytochrome P-450 Enzyme System; Diterpenes; Humans; Keratinocytes; Receptors, Retinoic Acid; Reference Values; Retinoic Acid 4-Hydroxylase; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

The inhibitory effects of vitamins A and K toward P4501A1-dependent 7-ethoxycoumarin O-deethylation were examined in the reconstituted system containing the microsomal fraction prepared from the recombinant Saccharomyces cerevisiae cells producing rat P4501A1 and yeast NADPH-P450 reductase. On vitamins A, all-trans-retinol, all-trans-retinal, all-trans-retinoic acid and retinol-palmitate showed competitive inhibition with K(i) values of 0.068, 0.079, 2.6 and 2.0 microM, respectively. Judging from the K(i) values, the inhibitory effects of those vitamins A appear to have physiological significance on the basis of their contents in liver, lung and kidney. On vitamins K, vitamin K(1) showed competitive inhibition with K(i) value of 24 microM, while vitamin K(2) showed noncompetitive inhibition with K(i) value of 60 microM. Judging from these K(i) values together with the contents of these vitamins K in liver, the inhibitory effects of the vitamins K are not as significant as those of vitamins A. These results suggest that the ingestion of enough amounts of vitamins A from foods might lead to the inhibition of the activity of P4501A1 which is known to be induced by smoking, drugs such as omeprazole and lansoprazole, and environmental pollutants like dioxins.

Topics: Animals; Coumarins; Cytochrome P-450 CYP1A1; Diterpenes; Kinetics; Microsomes; NADP; Oxygenases; Rats; Recombinant Proteins; Retinyl Esters; Saccharomyces cerevisiae; Tretinoin; Vitamin A; Vitamin K

Maturation of fetal ductus arteriosus is associated with increased constriction in response to maternally administered indomethacin. Recently retinoic acid has been shown to be important in development of the fetal ductus arteriosus. To determine whether retinoid might be of value in the treatment of patent ductus arteriosus in premature infants, we studied the response of fetal ductus arteriosus to indomethacin with and without pretreatment with vitamin A (1 mg (3000 IU)/kg, intramuscular injection) in near-term and preterm rats. Maturation of the ductus arteriosus was studied by measuring the inner diameters of the ductus arteriosus (D) and main pulmonary artery (P) to get D/P ratio 4 h after orogastric administration of 1 mg/kg indomethacin. D/P was 1.0 in the fetus before administration of indomethacin. In near-term fetuses on the 21st d without vitamin A, D/P decreased to 0.54 with indomethacin, whereas it decreased to 0.27 (p < 0.05) in those with pretreatment with vitamin A on the 19th and 20th d. In preterm fetuses on the 20th d without pretreatment with vitamin A, D/P decreased to 0.82 with indomethacin, whereas it decreased to 0.66 (p < 0.05) in those with pretreatment with vitamin A on the 19th d. It is concluded that maternally administered vitamin A accelerates maturation of the ductus arteriosus in fetal rats.

Topics: Analysis of Variance; Animals; Diterpenes; Ductus Arteriosus; Embryonic and Fetal Development; Gestational Age; Indomethacin; Rats; Rats, Wistar; Retinyl Esters; Tretinoin; Vasoconstriction; Vasodilation; Vitamin A

The formation of all-trans retinoic acid is an oxidative process whereby retinol is converted to retinaldehyde and then to retinoic acid. Because retinol causes qualitative molecular changes similar to those produced by retinoic acid, we compared potency of retinol, retinaldehyde, and retinyl palmitate to retinoic acid and assessed the effects of occlusion. Retinoids were prepared in an experimental vehicle of 95% ethanol:propylene glycol (7:3) with anti-oxidant. Induction of retinoic acid 4-hydroxylase activity was the end point for comparison. Retinoic acid concentrations from 0.001% to 0.05% under occlusion produced a linear dose-response induction of 4-hydroxylase activity. The concentrations of the other retinoids under occlusion required to achieve significant induction of enzyme activity were 0.6% retinyl palmitate, 0.025% retinol, and 0.01% retinaldehyde. The linear dose-response was lost with retinoid concentrations in excess of 0.25% retinol or 0.5% retinaldehyde. Statistical analyses showed no difference in 4-hydroxylase activity between unoccluded and occluded retinol treated sites. By contrast, however, unoccluded sites treated with retinoic acid or retinyl palmitate had less induction of 4-hydroxylase activity than occluded sites. Retinol, retinaldehyde, and retinyl palmitate did not produce erythema but did increase epidermal thickness. Although retinol is a weaker retinoid than retinoic acid, the increased penetration of unoccluded retinol in comparison to unoccluded retinoic acid with this prototypic vehicle confers on retinol a more effective delivery of a retinoidal effect than unoccluded retinoic acid. Retinol at 0.25% may be a useful retinoid for application without occlusion because it does not irritate but does induce cellular and molecular changes similar to those observed with application of 0.025% retinoic acid.

Topics: Administration, Topical; Adult; Anticarcinogenic Agents; Antioxidants; Cell Membrane Permeability; Cytochrome P-450 Enzyme System; Diterpenes; Dose-Response Relationship, Drug; Enzyme Activation; Erythema; Humans; Hyperplasia; Retinoic Acid 4-Hydroxylase; Retinyl Esters; Skin; Tretinoin; Vitamin A

Mice homozygous for the vitiligo mutation of the microphthalmia (Mitf) gene have a retinal degeneration characterized by slow loss of photoreceptor cells and compromised retinal pigment epithelial (RPE) structure and function. The levels of retinyl esters, which are essential for generation of 11-cis-retinaldehyde for the formation of rhodopsin, were reported previously to be elevated by 6 weeks postnatally in the RPE of vitiligo mutant mice. The purpose of the present study was to determine whether this elevation was due to increased activity of lecithin:retinol acyl transferase (LRAT) the enzyme that converts all-trans-retinol to retinyl esters.. Retinoids extracted from the RPE and neural retina of mutant and normal mice ages 2, 4, 6 and 8 weeks were analyzed by reversed-phase HPLC. The esterification capacity of the RPE to convert 3H-retinol to 3H-retinyl ester was determined by HPLC in mutant and normal mice at 3 and 9 weeks.. Retinyl ester levels were elevated significantly in the mutant RPE as early as postnatal week 2 and were four-fold greater by 8 weeks. The esterification assay indicated no significant differences between mutants and controls at 3 weeks. At 9 weeks, the esterification activity of the mutant RPE was significantly reduced compared to controls rather than elevated.. The data suggest that the accumulation of retinyl esters is not due to increased LRAT activity. Alternative explanations for the retinyl ester accumulation are discussed.

Topics: Acyltransferases; Aging; Animals; Chromatography, High Pressure Liquid; Diterpenes; DNA-Binding Proteins; Esterification; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microphthalmia-Associated Transcription Factor; Microscopy, Electron, Scanning; Microsomes, Liver; Mutation; Pigment Epithelium of Eye; Retinyl Esters; Time Factors; Transcription Factors; Tretinoin; Vitamin A; Vitiligo

The expression of nuclear receptors of retinoic acid (RAR) and triiodothyronine (TR) was analyzed in the liver of rats aged 2.5 (young), 6 (adult) and 24 (aged) months. In aged rats, decreased binding properties, binding capacity (Cmax) and affinity (Ka), of nuclear receptors were observed. This resulted, at least in part, from decreased transcription of receptor genes in that the amount of their mRNA also decreased. Moreover, the activity of malic enzyme (ME) and tissue transglutaminase (tTG), whose genes are TR and RAR responsive, respectively, was reduced in aged rats. These results are in agreement with the decreased binding capacity of these receptors. An inducer-related increase of RAR and TR expression was observed 24 h after a single dose of retinoic acid administration (5 mg/kg), while retinol administration (retinyl palmitate, 13 mg/kg) was without incidence on nuclear receptor expression in aged rats.

Topics: Aging; Animals; Cell Nucleus; Diterpenes; Liver; Male; Rats; Rats, Wistar; Receptors, Retinoic Acid; Receptors, Thyroid Hormone; Retinyl Esters; Tretinoin; Vitamin A

Retinoid pharmacokinetics were examined in plasma, placenta and embryos of gestational d 12 rabbits following application of an embryotoxic dosing regimen (10 mg retinyl palmitate/kg body wt per day from gestational d 7 to 12). Vehicle-treated or untreated rabbits served as controls. Physiological concentrations of all-trans-retinoic acid (all-trans-RA) and 13-cis-RA in rabbit plasma (5-8.33 nmol/L) were very close to the endogenous levels in human plasma. In addition, we identified endogenous all-trans-RA, 3,4-didehydroretinol and 3,4-didehydroretinoic acid in rabbit embryo. Following the last retinyl palmitate administration, apparent steady-state concentrations of all retinoids were reached in the examined compartments of rabbits. The major polar retinoid in plasma was 9, 13-di-cis-RA, but its embryonic concentrations were only about 6% of those in plasma. In the embryo, retinol and its esters were found at high concentrations; lower amounts of all-trans-4-oxo-RA and the newly identified 14-hydroxy-4, 14-retro-retinol could also be measured. Embryonic concentrations of all-trans-RA were about 100% higher than endogenous levels. The overall exposure of the embryo to this retinoid was, however, substantial. Embryonic area under the concentration time curve values strongly suggest that the embryotoxicity of the applied dosing regimen is mainly due to the action of all-trans-RA. A very remarkable finding of this study is the marginal increase of plasma concentrations of all-trans-RA over their endogenous levels, which is comparable to the human situation after vitamin A intake. This analogy indicates that high vitamin A intake may be associated with a higher risk for teratogenic effects in humans even in the absence of high elevation of plasma all-trans-RA levels.

Topics: Animals; Diterpenes; Dose-Response Relationship, Drug; Embryo, Mammalian; Embryonic and Fetal Development; Female; Humans; Male; Maternal-Fetal Exchange; Placenta; Pregnancy; Rabbits; Retinoids; Retinyl Esters; Time Factors; Tretinoin; Vitamin A

Patients with retinitis pigmentosa have been suggested to benefit from treatment with moderate doses of retinyl palmitate. Retinyl palmitate is not an active retinoid in itself but is metabolised to active components in the body. To find out which metabolites of retinyl palmitate were formed and at which concentrations, we measured the concentrations of retinol, retinyl palmitate, retinoic acids and tocopherol in serum of patients treated with oral retinyl palmitate for retinitis pigmentosa.. Nine male patients and one female diagnosed as having retinitis pigmentosa after a complete ophthalmological examination including a full-field electroretinogram were given vitamin A at their own request as one daily morning dose of 16600 IU vitamin A. Blood samples were obtained before and after > 2 weeks of treatment. The concentrations of retinoids and tocopherol were measured with established methods.. The patients were not deficient in vitamin A or vitamin E as judged from the serum vitamin concentrations. Treatment with retinyl palmitate significantly increased the serum concentration of retinyl palmitate and of 13-cis-retinoic acid but not of retinol, tocopherol or all-trans-retinoic acid.. Neither retinyl palmitate nor 13-cis-retinoic acid, are known to be biologically active. However, 13-cis-retinoic acid can isomerise to the active vitamin A derivative, all-trans-retinoic acid. It is suggested that patients may be treated with a small dose of 13-cis-retinoic acid instead, to avoid the relatively long metabolic detour from retinyl palmitate.

Topics: Administration, Oral; Adult; Aged; Anticarcinogenic Agents; Chromatography, High Pressure Liquid; Diterpenes; Electroretinography; Female; Humans; Male; Middle Aged; Retinitis Pigmentosa; Retinoids; Retinyl Esters; Tretinoin; Vitamin A; Vitamin E

The vitamin A derivative retinoic acid (RA) is a powerful teratogen which can induce severe craniofacial and limb malformations if administered at certain stages of gestation. In addition this compound has been shown to affect patterning in regenerating systems. A classical example is the induction of supernumerary structures along the proximodistal axis of the regenerating amphibian limb. We have investigated the effect of RA on other regenerating systems, the amphibian lower and upper jaws, both in developing and adult animals. We report here that RA does not induce formation of extra structures either in the lower or in the upper jaw of adult newts under experimental conditions where duplications of the regenerating limb occur. However, RA selectively induces severe malformations in the upper jaw regenerate that resemble those induced in avian and mammalian embryos. Analysis of the expression of the newt retinoic acid receptors RAR alpha and delta in upper and lower jaws showed that RAR alpha was expressed at a significant level in the wound epidermis, but not in blastemal cells, whereas no RAR delta could be detected in the regenerate either by in situ hybridization or by using an anti-RAR delta antibody. Therefore, unlike in the limb, in jaws RAR delta is not up-regulated following amputation, and this difference in expression may be causally related to the different effects induced by RA on jaws and limbs. In order to establish whether retinoids affected regeneration of developing jaws in a similar fashion, their effects were studied in animals whose jaws had been amputated at different developmental stages. Under the experimental conditions used overall growth retardation and head defects were observed in the majority of embryos which had been amputated and treated with retinol palmitate (RP) between stages 26-28 and 38-39. In contrast, patterning of upper jaw regenerates in larvae amputated at stage 26-28 and 38-39. In contrast, patterning of upper jaw regenerates in larvae amputated at stage 45 was not significantly affected by the treatment, although the early phase of regeneration was slower than in controls. The different responses to retinoids of regenerating facial structures in embryos, larvae and adults will be discussed.

Topics: Abnormalities, Drug-Induced; Animals; Diterpenes; Gene Expression; In Situ Hybridization; Jaw; Mandible; Maxilla; Notophthalmus; Receptors, Retinoic Acid; Regeneration; Retinyl Esters; Teratogens; Tretinoin; Vitamin A

Retinol deficiency in animal models results in histopathologic airway changes that appear similar to those found in human premature infants with bronchopulmonary dysplasia (BPD). Dexamethasone (DEX), a steroid now often used in the treatment of BPD, might potentially affect lung vitamin A homeostasis since it alters serum and liver retinoid stores in certain models. Our objective was to determine the effect of DEX on neonatal rat lung retinoid status and the binding of retinoic acid (RA) to cytosolic and nuclear receptor proteins. We examined this effect both in room air and when the animals breathed 95% oxygen (O2). Twenty-four 1-day-old rat pups received either 1 microgram/g DEX subcutaneously, an equal volume of normal saline (NS) subcutaneously at 0 (start experiment time), 24, and 48 hours, or no injection at all, and were sacrificed at 72 hours. Twelve rats in each treatment group were housed in room air and 12 in each group were exposed to > 95% O2 for the 3 day period. Lung and liver were analyzed for retinyl palmitate (RP). Nuclear retinoic acid receptor (RAR) and cellular retinoic acid binding protein (CRABP) were measured by specific binding assays. DEX decreased liver RP by 33-55% and rat pup lung RP by over 60%; it also decreased lung RAR binding (mean dpm/microgram protein +/- SEM) in both room air and oxygen groups: Air (11.2 +/- 1.0) vs. Air/DEX (4.6 +/- 1.3, n = 6; P < 0.01), and O2 (18.2 +/- 0.6) vs. O2/DEX (3.2 +/- 0.6, n = 6; P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Animals, Newborn; Dexamethasone; Diterpenes; Liver; Lung; Models, Biological; Oxygen; Protein Binding; Rats; Rats, Sprague-Dawley; Receptors, Retinoic Acid; Retinyl Esters; Time Factors; Tretinoin; Vitamin A

Biological functions of retinoids in the vertebrate retina include the role of 11-cis retinaldehyde as visual pigment chromophore, and possible effects of retinoic acid in histogenesis and cell survival. Qualitative and quantitative regulation of retinoid availability for these complex processes could involve several cell types, including retinal pigment epithelium, Müller glia and retinal photoreceptors and non-photoreceptor neurons; their relative contributions, however, have not been fully elucidated. Using purified cultures, we have carried out a study of cell-type-specific metabolism and storage of retinoids in chick embryo retinal photoreceptors and other neuronal cells, as compared to those of retinal glia. Retinal glia were found to synthesize both retinoic acid and retinyl esters, and to hydrolyse the latter; they also displayed retinol dehydrogenase activities. Cultured neurons and photoreceptors also synthesized and hydrolysed retinyl esters; their capacity for retinaldehyde synthesis from a retinol or retinyl ester substrate suggested the presence of retinol dehydrogenase activity. Retinoic acid was not synthesized in differentiated neuronal cultures, although some synthesis was detectable at early culture stages when the cells were still morphologically undifferentiated. These findings indicate that cell-type-specific metabolic activities are expressed during retinal cell differentiation in vitro, and that embryonic retinal photoreceptors and nonphotoreceptor neurons are active participants in the metabolism and storage of retinoids.

Topics: Animals; Cells, Cultured; Chick Embryo; Diterpenes; Neuroglia; Neurons; Photoreceptor Cells; Retina; Retinaldehyde; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

To determine whether vitamin A is involved in pancreatic alpha cell function, we tested for (a) effects of vitamin A deficiency on glucagon release from perifused islets and perfused pancreases, and (b) the presence of cytosolic retinol-binding proteins (CRBP) and retinoic acid-binding proteins (CRABP), in the glucagon-secreting alpha cell line, ln-R1-G9. Arginine 19 mM plus glucose 2.8 mM-stimulated glucagon secretion was markedly impaired in islets and pancreases of vitamin A-deficient rats or rats that had at some time been cycled through vitamin A deficiency (ever A-def) despite repletion with retinoids for 2-4 weeks. Insulin secretion was impaired likewise. Repletion starting early in the development of vitamin A deficiency and for a longer period of time (18 or 60 days) did not restore glucagon secretion, but did normalize insulin secretion. CRBP and CRABP were present in ln-R1-G9 cells. We conclude that (a) vitamin A deficiency is associated with a defect in glucagon secretion; (b) The defect in secretion occurs early in the course of vitamin A deficiency; (c) The defect persists despite repletion; and (d) The requirement of vitamin A for secretion and the presence of CRBP and CRABP in glucagon-secreting cells support a physiologic role for vitamin A at the alpha cell level.

Topics: Animals; Arginine; Cell Line; Diterpenes; Female; Glucagon; Glucose; Insulin; Insulin Secretion; Islets of Langerhans; Pregnancy; Radioimmunoassay; Rats; Rats, Sprague-Dawley; Receptors, Retinoic Acid; Retinoids; Retinol-Binding Proteins; Retinol-Binding Proteins, Cellular; Retinyl Esters; Tretinoin; Vitamin A; Vitamin A Deficiency

The retinoids are teratogenic in a wide variety of species. In the rat, 13-cis-retinoic acid and retinyl palmitate are significantly less potent teratogens than all-trans-retinoic acid. This investigation questioned whether differing teratogenic potencies of these moieties can be correlated with the concentrations of these drugs and/or metabolites in the embryonic compartment. Approximately equipotent teratogenic doses of these three retinoids were administered and the pharmacokinetics in maternal plasma and embryo of the most prevalent vitamin A metabolites were measured. The glucuronides of the respective retinoids were the predominant metabolites in the maternal plasma, but were not detected in the embryo. Also, the transport of 13-cis-retinoic acid across the placenta occurred to a much lesser extent than the transport of all-trans-retinoic acid. Administration of either all-trans- or 13-cis-retinoic acid causes a depression in the endogenous retinol concentration. This depression is more pronounced in the maternal plasma than in the embryo. The depression of the retinol level in both plasma and embryo after 13-cis-retinoic acid administration (75 mg/kg/day) was greater than the depression after all-trans-retinoic acid (6 mg/kg/day), corroborating the inferential teratological data that the 13-cis-retinoic acid dose was more embryotoxic than the all-trans-retinoic acid dose. Although the dose of all-trans-retinoic acid was less embryotoxic than that of either 13-cis-retinoic acid or retinyl palmitate, the embryonic exposure to all-trans-retinoic acid was considerably larger, as determined by maximum concentration or area under the concentration-versus-time curve, after administration of all-trans-retinoic acid than after either retinyl palmitate or 13-cis-retinoic acid application. These results suggest that embryonic retinoids other than all-trans-retinoic acid--including the administered substances themselves--are important in the teratogenic process induced by 13-cis-retinoic acid and retinyl palmitate.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Embryonic and Fetal Development; Female; Isotretinoin; Male; Placenta; Rats; Rats, Sprague-Dawley; Rats, Wistar; Retinyl Esters; Teratogens; Tretinoin; Vitamin A

Ten healthy female volunteers were given 5 doses of retinol as the palmitate; 50 and 150 mg retinol as an oral supplement, 50 and 150 mg as fried calf liver (50 and 150 g) and 3, 9 or 30 mg by intra-muscular injection. Plasma concentrations of retinyl palmitate were higher after 50 mg retinol given as an oral supplement compared with 50 mg as liver; there was no significant difference between the 150 mg doses. Plasma concentrations of retinol showed only small increases. The peak plasma concentrations (Cmax) of all-transretinoic acid, the principal teratogenic metabolite of retinol, and the area under the concentration-time curve (AUC) were up to 20-times higher after supplements compared to the same dose as liver. Plasma concentrations of all-trans-4-oxo-retinoic acid, 13-cis-retinoic acid and 13-cis-4-oxo-retinoic acid showed smaller differences between supplements and liver. Intra-muscular administration of 30 mg retinol gave retinyl palmitate concentrations similar to those found after the oral doses but did not increase circulating concentrations of the acid metabolites. Based on the formation of all-trans-retinoic acid, liver and supplements are not of equivalent teratogenic potential. Advice to pregnant women on the consumption of liver based on the reported teratogenicity of vitamin A supplements should be reconsidered.

Topics: Administration, Oral; Adult; Diterpenes; Female; Food; Humans; Injections, Intramuscular; Retinyl Esters; Teratogens; Tretinoin; Vitamin A

A retinoid-binding protein has been identified in the extracellular space that separates the photoreceptor cells and the retinal pigment epithelium (RPE) of the mammalian retina. This protein (interphotoreceptor retinoid-binding protein, IRBP) appears to be involved in the transport of visual cycle retinoids between the photoreceptors and the RPE. Experiments were conducted to evaluate the possibility that the amount of IRBP in the retina is regulated by the availability of retinoids in the retina. Rats were fed diets containing vitamin A either in the form of retinyl palmitate (+A), which can be metabolically converted into the retinoids involved in vision, or retinoic acid (-A), which does not support visual function. After 23 weeks, when rhodopsin levels had declined by over 90% in the -A rats, some animals in the latter group were given a single intramuscular injection of all-trans retinol. Both 1 day and 1 week later, the IRBP immunoreactivities in the retinas from the treated rats were determined with quantitative immunocytochemistry. IRBP immunolabeling densities were also determined in the +A and -A groups. Retinas of animals that had consumed the -A diet for 23 weeks bound an average of 50% less anti-IRBP antibody in the retina than rats that had been fed the +A diet for the same period. One day after retinol administration, the mean IRBP immunolabeling density had returned to that observed in the +A rats. The restored level of IRBP immunoreactivity was maintained 1 week after injection. The immunocytochemical findings were confirmed by immunoblot analysis of eyecup homogenates.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Diterpenes; Eye Proteins; Light; Male; Microscopy, Immunoelectron; Pigment Epithelium of Eye; Rats; Rats, Inbred F344; Retina; Retinol-Binding Proteins; Retinyl Esters; Tretinoin; Vitamin A

In conditions of chronic liver inflammation, liver fat-storing cells (FSC) differentiate into 'myofibroblast-like cells'. This transition is characterized by a gradual loss of vitamin A stores, and previous studies suggest a possible relationship between the intracellular retinoid content and the proliferative potential of this cell type. In the present study, we further characterized this aspect of FSC biology by monitoring ultrastructural changes and growth characteristics during several serial passages in culture. Our observations suggest that the complete transition to the 'myofibroblast-like phenotype' is paralleled by a sudden and remarkable increase in the growth rate. At this stage, cell growth appears rather independent from the presence of mitogens in the culture medium, suggesting cell transformation. Accordingly, the mitogenic effects of platelet-derived growth factor and epidermal growth factor appears reduced when compared to those observed in FSC retaining the original 'storing' phenotype. Incubation of vitamin A-depleted FSC with retinol and retinoic acid resulted in the partial recovery of intracellular retinoid stores and in a significant reduction of basal growth rate and basal and growth factor-induced DNA synthesis. In summary, these in vitro observations suggest that intracellular retinoids play a central role in the control of unstimulated and growth factor-induced FSC proliferation and may help understand in vivo mechanisms leading to liver fibrosis.

Topics: Analysis of Variance; Animals; Autoradiography; Cell Division; Cells, Cultured; Diterpenes; DNA Replication; Epidermal Growth Factor; Kinetics; Liver; Male; Phenotype; Platelet-Derived Growth Factor; Rats; Rats, Inbred Strains; Recombinant Proteins; Retinoids; Retinyl Esters; Thymidine; Tretinoin; Vitamin A

Using a sensitive HPLC method, plasma concentrations of vitamin A and metabolites were measured from 6 female volunteers who had taken once daily 0.46 mg/kg BW retinol palmitate (Vitadral) for 10 days. The metabolites all-trans- and 13-cis-retinoic acid were increased significantly (2- and 5-fold, resp.) 6 h after the ist intake. 13-cis-4-oxo retinoic acid the 10th intake in the morning of the 10th day (9.22 +/- 2.77 ng/ml, 4-fold increase). The results show continuous increase of retinoic acids, which have to be considered as potential teratogens, after administration of vitamin A. The plasma concentration of retinol itself did not change, whereas only short-term increases were observed for retinol esters.

Topics: Adolescent; Adult; Chromatography, High Pressure Liquid; Diterpenes; Female; Humans; Isotretinoin; Retinyl Esters; Tretinoin; Vitamin A

Retinoids are known to enhance macrophage function and enhance bacterial clearance during experimental infection. The purpose of these experiments was to determine if one indicator of macrophage activation, chemiluminescence (CL), was enhanced by retinoids. Peritoneal exudate cells (PEC) harvested from mice injected intraperitoneally for 5 days with retinol palmitate (25, 125, or 250 U/g body wt./d) showed significantly enhanced chemiluminescence (CL) when exposed to opsonized zymosan. A direct dose-response effect was observed, in that the more retinol palmitate was injected, the more CL was observed. The same dose of retinol palmitate injected subcutaneously did not result in enhanced CL. In vitro incubation of murine PEC with physiological concentrations of retinol palmitate or retinoic acid for 1, 6 or 24 h did not result in enhanced CL. The reasons for the effect of the route of administration of retinol palmitate are unknown, but may include poor absorption from the site of subcutaneous injection or an adjuvant effect when injected intraperitoneally due to the particulate nature of the water-dispersible retinol palmitate preparation.

Topics: Animals; Antibody Formation; Diterpenes; Dose-Response Relationship, Drug; Female; Injections, Intraperitoneal; Injections, Subcutaneous; Luminescent Measurements; Macrophage Activation; Macrophages; Mice; Peritoneal Cavity; Retinyl Esters; Tretinoin; Vitamin A

The synthesis of plasminogen activators and inhibitors in endothelial cells is highly regulated by hormones, drugs and growth factors. The present study evaluates the effect of retinoic acid on the synthesis of tissue-type plasminogen activator (t-PA) and of plasminogen activator inhibitor-1 (PAI-1) by cultured human umbilical vein endothelial cells (HUVEC). Retinoic acid produced a time- and concentration-dependent increase in the secretion of t-PA-related antigen but not of PAI-1 related antigen into the culture medium. A maximal sevenfold increase of t-PA antigen after 24 h was observed with 10 microM and a half-maximal increase with 0.1 microM retinoic acid. Retinoic acid induced a time-dependent increase of the t-PA mRNA, with a maximum at 8 h and returning to normal at 24 h. The protein kinase inhibitor H7 decreased the t-PA antigen induced by both retinoic acid and phorbol 12-myristate 13-acetate. These results suggest that treatment of HUVEC with retinoic acid increases t-PA production by a pathway which, at some level, involves protein kinases. Thus, retinoic acid induces t-PA synthesis in the absence of altered PAI-1 synthesis, which may enhance the fibrinolytic potential of the endothelium.

Topics: 1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; Cells, Cultured; Diterpenes; Endothelium, Vascular; Enzyme Inhibitors; Gene Expression Regulation; Humans; Isoquinolines; Molecular Probe Techniques; Piperazines; Plasminogen Inactivators; Protein Kinase Inhibitors; Retinyl Esters; RNA, Messenger; Tissue Plasminogen Activator; Tretinoin; Vitamin A

Plasma concentrations of retinyl esters, retinol, retinol-binding protein and the polar retinol metabolites all-trans-retinoic acid, 13-cis-retinoic acid, all-trans-4-oxoretinoic acid and 13-cis-4-oxoretinoic acid were measured for six male volunteers who received 0.46 mg retinyl palmitate per kilogram body weight as oily drops (equivalent to 0.25 mg retinol per kilogram body weight) once daily over a 20-d period. Retinol and retinol-binding protein levels remained virtually constant throughout the study. Following absorption of vitamin A, retinyl esters as well as all-trans-retinoic acid and 13-cis-retinoic acid were transiently increased in plasma. 13-cis-4-Oxoretinoic acid increased gradually to a steady state level present on d 10 or 20. All-trans-4-oxoretinoic acid was not detected in plasma of the volunteers, with the exception of one on d 10 of the study. Plasma pharmacokinetic profiles of retinyl esters and polar metabolites of retinol displayed great interindividual differences (peak concentrations, time to peak, area-under-the-concentration-time curve values) among the volunteers. Because of the relatively high and consistent steady state concentrations of plasma 13-cis-4-oxoretinoic acid, we suggest that this compound be further investigated as a biochemical marker of vitamin A uptake in humans.

Topics: Administration, Oral; Adult; Chromatography, High Pressure Liquid; Diterpenes; Humans; Male; Retinol-Binding Proteins; Retinol-Binding Proteins, Plasma; Retinyl Esters; Stereoisomerism; Tretinoin; Vitamin A

Subunit vaccines require potent adjuvants to induce effective immunity. Currently, most known adjuvants have not been approved for human and veterinary use, mainly because of adverse effects resulting from local injections. A material with adjuvant properties proven to be safe for the host would be of importance, particularly if it had a constructive physiological role. A possible candidate is vitamin A and its analogues. The objectives herein were to re-evaluate adjuvant properties of vitamin A by employing water-miscible vitamin A (WMVA) derivatives (retinol palmitate and retinoic acid), and to determine their ability to induce effective immune responses to protein antigens. Injection of WMVA in an aqueous solution prevented adverse effects of local injection, hypervitaminosis and oil depot damage. Other results show that WMVA derivatives behave as extrinsic adjuvants, and increase immune responses to protein antigens without causing hypervitaminosis or significant elevation of liver vitamin A. Primary immune responses were of short duration, but were increased and maintained by booster immunizations. The responses induced by WMVA derivatives were of similar magnitude to those induced by water soluble murmyl-dipeptide and Salmonella typhimurium mitogen. Hence, WMVA derivatives have potential as both efficient and safe adjuvants.

Topics: Adjuvants, Immunologic; Animals; Antibody Formation; Diterpenes; Female; Injections, Subcutaneous; Liver; Lymphocyte Activation; Male; Mice; Retinyl Esters; Solutions; Tretinoin; Vaccines, Synthetic; Vitamin A; Water

In view of the clinical trials of retinoids as therapeutic agents for premalignant skin lesions, a radiographic study was undertaken to measure skeletal toxicities after chronic dietary administration of retinoids in mice exposed to tumor initiation and promotion. CD-1 mice were initiated with 0.15 moles of 7,12-dimethylbenz[a]anthracene and promoted twice daily with 8 nmoles of 12-0-tetradecanoylphorbol-13-acetate for 23 weeks. Diets were supplemented with 60 IU, 200 IU, or 700 IU of retinyl palmitate (RP) per g diet. After 5 weeks, the 700 IU of RP /g diet was lowered to 350 IU/g diet. Administration of these diets to mice during the 23 weeks of tumor promotion resulted in a 0-fold, 2-fold, or 10-fold increase in bone fractures, respectively. Osteoporotic bone lesions identified on radiographs rose 0-fold, 0-fold, and 10-fold at the respective doses, whereas metaphyseal flares increased 0-fold, 1.4-fold, and 3.6-fold. Bone deformities were augmented 0-fold, 1.8-fold and 2.9-fold at the respective doses. Addition of selenium (2 ppm in the drinking water) did not alter the bone toxicity of RP. 13-cis-retinoic acid (CRA) was less toxic at 700 IU/g diet than was RP at that dose, as evidenced by the death of 12 of 70 mice by the 6th week of dietary RP and no deaths in the 35 mice fed 700 IU CRA/g diet for 23 weeks. CRA at 700 IU/g diet resulted in 3/4 as many osteoporotic bones, 1/3 as many bone fractures, 4/5 as many metaphyseal flares, and a similar number of bone deformities as mice fed 700/350 IU/g diet. At the dose of 200 IU/g food, osteotoxicities were similar in the mice fed diets supplemented with RP and CRA. Thus, the light dose of CRA (700 IU/g diet) was less toxic than the high dose of, RP but at a lower dose (200 IU/g), CRA was as osteotoxic as was RP. Bone fractures in mice exposed to prolonged dietary administration of retinoids was a more sensitive index of retinoid toxicity than was body weight. We have detected osteotoxicity in mice at a total dose of CRA which was about twice the total dose used clinically.

Topics: Administration, Oral; Animals; Bone and Bones; Bone Diseases; Carcinogens; Diterpenes; Dose-Response Relationship, Drug; Female; Mice; Mice, Inbred Strains; Osteoporosis; Retinyl Esters; Selenium; Skin Neoplasms; Tretinoin; Vitamin A

Drugs which affect the processing of vitamin A in the retina or pigment epithelium can cause ocular toxicity. It is shown here that the retinoic acids, which are used in the treatment of skin disorders and which cause night blindness, inhibit the ocular retinol dehydrogenases in an in vitro system. This is shown to lead to a decrease in the formation of the visual chromophore 11-cis-retinal, thus explaining why night blindness might occur.

Topics: Alcohol Oxidoreductases; Animals; Diterpenes; Night Blindness; Pigment Epithelium of Eye; Rana pipiens; Retina; Retinaldehyde; Retinyl Esters; Tretinoin; Vitamin A

Nude mice are deficient in thymus gland development and hence lacking functional, mature T-lymphocytes. Weanling nude mice were given various deficient and high retinyl palmitate (RP) or 13-cis retinoic acid (CRA) diets. The high RP (vitamin A) diets stimulated phagocytosis in the absence of mature T-helper cells. However, T-cell dependent mitogens did not cause significant mitogenesis in any group, while LPS, a B-cell mitogen, did. RP had no effect on mitogenesis. NK cell activity was increased only at a very high level of RP, as has been reported with conventional mice. Macrophage production of cytotoxic factors was unaffected by high levels of RP or CRA. Direct cytotoxicity in vitro of tumor cells was increased only at very high RP levels. Thus, mature T cells may be needed for RP to produce normal activation of macrophage, except at very high RP levels.

Topics: Animals; B-Lymphocytes; Cytotoxicity, Immunologic; Diterpenes; Female; Immunologic Deficiency Syndromes; Killer Cells, Natural; Macrophages; Melanoma; Mice; Mice, Nude; Mitogens; Phagocytosis; Retinyl Esters; T-Lymphocytes; Tretinoin; Vitamin A

The aim of the present work was to determine the effect of giving increasing doses of supplements of beta-carotene on serum retinoic acid levels in rabbits. Four groups of 7-week-old female rabbits were fed for 9 weeks on a pelleted diet containing 1.72 mg vitamin A as retinyl acetate/kg and including control gelatin beadlets devoid of beta-carotene or 1, 2 or 4 mg beta-carotene/kg body-weight per d. Serum was collected at 3, 6 and 9 weeks after the beginning of the experiment and the concentration of all-trans retinoic acid was determined by a gradient reverse-phase high-performance liquid chromatography system following a double-phase extraction. The average concentration of retinoic acid in serum of the combined control and 1 mg beta-carotene/kg groups was 3.80, 3.06 and 2.40 nM at 3, 6 and 9 weeks respectively. The concentrations of retinoic acid in serum of the combined 2 and 4 mg beta-carotene/kg groups were 4.80 nM (P less than 0.05), 3.76 nM (not significant) and 4.90 nM (P less than 0.005) at 3, 6 and 9 weeks respectively. A SAS (SAS Institute Inc., 1985) general linear model repeated-measures analysis of variance revealed that the effects of treatment (P less than 0.01), time (P less than 0.05) and treatment x time interaction (P less than 0.05) were statistically significant. It is concluded that giving beta-carotene is associated with higher concentrations of all-trans retinoic acid in the serum of rabbits than in those receiving no beta-carotene.

Topics: Animals; beta Carotene; Carotenoids; Diterpenes; Drug Administration Schedule; Female; Liver; Rabbits; Retinyl Esters; Tretinoin; Vitamin A

The transfer of retinoic acid, retinyl acetate, and retinyl palmitate between single unilamellar vesicles was studied by resonance energy transfer. The retinoic acid transfers spontaneously between single unilamellar vesicles with a first order rate constant of 9.6 s-1 at 15 degrees C and pH 7.4. At 30 degrees C, the transfer rate was 3.5 times faster than that at 10 degrees C. At pH 7.4, the transfer rate was almost 2 orders of magnitude faster than that observed at pH 1.6. Increasing the concentration of NaCl decreased the retinoic acid transfer rate significantly. Retinyl acetate transfers with a rate constant of 0.15 s-1, but no spontaneous transfer of retinyl palmitate was observed over 60 min. The evidence supports the proposal that retinoic acid and retinyl acetate transfer between single unilamellar vesicles occur via the aqueous phase. In contrast, no spontaneous transfer of retinyl palmitate was observed. However, linear free energy relationships and the thermodynamic parameters for retinyl acetate transfer permit the calculation of rate constant for retinyl palmitate transfer.

Topics: Diterpenes; Energy Transfer; Kinetics; Liposomes; Osmolar Concentration; Phosphatidylcholines; Phosphatidylethanolamines; Retinyl Esters; Spectrometry, Fluorescence; Thermodynamics; Tretinoin; Vitamin A

Vitamin A (retinol) and some of its analogs exhibited varying degrees of inhibition on induced iron and ascorbic acid lipid peroxidation of rat brain mitochondria. Malonyldialdehyde production was used as an index of the extent of in vitro lipid peroxidation. The fat-soluble vitamins retinol, retinol acetate, retinoic acid, retinol palmitate, and retinal at concentrations between 0.1 and 10.0 mmol/L inhibited brain lipid peroxidation. Retinol and retinol acetate were the most effective inhibitors. It is concluded from this study that retinol and its analogs can be considered as potential antioxidant factors, more potent than some of the well-known antioxidants such as alpha-tocopherol and butylated hydroxytoluene.

Topics: Animals; Ascorbic Acid; Brain; Diterpenes; Ferrous Compounds; Free Radicals; Lipid Peroxidation; Male; Malondialdehyde; Mitochondria; Rats; Rats, Inbred Strains; Retinaldehyde; Retinyl Esters; Tretinoin; Vitamin A

Young male Wistar rats received single i.p. injections of 3,3',4,4',5,5'-hexabromobiphenyl. In rats dosed with 40 mg/kg, food consumption and growth as well as liver retinol and retinyl palmitate concentrations decreased, while serum retinol and liver weight increased within 28 days following the injection. In rats receiving a 20-mg/kg dose, food consumption, growth, liver weight, and serum retinol were not affect, although liver retinol and retinyl palmitate concentrations declined to 23 and 21% of their respective control values. Vitamin A metabolism was studied in liver microsomes prepared from rats sacrificed 7 days after the 20-mg/kg injection. The rate of retinoic acid hydroxylation via the cytochrome P-450 system to 4-hydroxyretinoic acid plus the subsequent oxidation to 4-ketoretinoic acid was significantly elevated. Retinoic acid conjugation by UDP-glucuronyl transferase was also significantly increased. These changes corresponded with increased activities of cytochrome P-450-dependent aryl hydrocarbon hydroxylase and UDP-glucuronyltransferase conjugation of p-nitrophenol. These results provide a direct link between enzyme induction due to xenobiotics and specific steps in the vitamin A metabolic pathway.

Topics: Animals; Cytochrome P-450 Enzyme System; Diterpenes; Glucuronosyltransferase; Hydroxylation; Liver; Male; Nitrophenols; Polybrominated Biphenyls; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Vitamin A

The present study was designed to investigate the embryo-fetotoxicity of vitamin A in protein-energy malnourished animals. Retinyl palmitate (66, 99 and 132 mg/kg) suspended in corn oil was given by gavage to well-nourished and malnourished rats from gestational days 8 to 10 and cesarean sections were performed on day 20. All fetuses were weighed and examined for malformations before being prepared for skeletal evaluation. The proportion of malformed fetuses was higher in the malnourished group at each one of the three dose levels. The data indicate that malnourished animals are more susceptible to the toxic effects of retinyl esters.

Topics: Animals; Body Weight; Congenital Abnormalities; Diterpenes; Female; Hypervitaminosis A; Pregnancy; Protein-Energy Malnutrition; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Vitamin A

These studies were performed to follow a spectrum of relevant parameters in male Syrian golden hamsters fed either a vitamin A-deficient diet or the same diet supplemented with retinoic acid at 3 micrograms/g diet. Body weight and life span were not affected by the vitamin A-deficient diet until after 6-7 wk. Squamous metaplastic lesions of the Formalin-fixed tracheas were not generally observed in the hamsters fed the deficient diet until 6-7 wk, at which time blood retinol and liver retinyl palmitate levels had also decreased. Blood glucose levels remained normal (90 mg/dl) until about 7 wk but declined to about 40% of normal at 9 and 10 wk. Dietary retinoic acid supplementation of the vitamin-deficient diet (3 micrograms/g diet) inhibited the loss of retinol from blood and of retinyl palmitate from the liver so that these compounds were still present at 10 wk, but were not detectable in hamsters fed the vitamin A-deficient diet without retinoic acid.

Topics: Animals; Blood Glucose; Cricetinae; Diet; Diterpenes; Epithelium; Growth; Life Expectancy; Liver; Male; Mesocricetus; Metaplasia; Retinyl Esters; Trachea; Tretinoin; Vitamin A; Vitamin A Deficiency

Topics: Animals; Antigen-Presenting Cells; Diterpenes; Female; Male; Mice; Retinyl Esters; T-Lymphocytes, Cytotoxic; Tretinoin; Vitamin A

The present study was designed to determine the effects of dietary 13-cis-retinoic acid and retinyl palmitate on mouse skin tumor promotion by 12-O-tetradecanoylphorbol-13-acetate (TPA). Female CD-1 mice were initiated with 150 nmol of 7,12-dimethylbenz(a)anthracene and promoted twice weekly with 8 nmol of TPA. Diets supplemented with retinyl palmitate to yield 60,000 or 200,000 IU or 700,000 for 5 wk followed by 350,000 IU per kg of diet (700,000/350,000) fed to mice during tumor promotion resulted in 9%, 37%, and 65% inhibition of the papilloma yield, respectively, at 21 wk of promotion. Although topical applications of 13-cis-retinoic acid have been almost as effective as retinoic acid in preventing the appearance of mouse skin tumors, dietary 13-cis-retinoic acid at 200,000 or 700,000 IU per kg of diet resulted in no reduction in papilloma yield but did result in a dose-dependent decrease in the tumor burden (weight of tumors per mouse). Therefore, dietary retinyl palmitate yielded a dose-dependent inhibition of the number and weight of tumors promoted by TPA, whereas dietary 13-cis-retinoic acid resulted in a decrease in weight but not in number of tumors promoted by TPA.

Topics: Administration, Cutaneous; Animals; Cell Transformation, Neoplastic; Diet; Diterpenes; Dose-Response Relationship, Drug; Female; Isotretinoin; Mice; Papilloma; Retinyl Esters; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate; Time Factors; Tretinoin; Vitamin A

The effects of two vitamin A analogues, retinol palmitate and retinoic acid, on pattern formation during limb regeneration in larvae of two European newts, P. waltl and T. vulgaris are described. The response of the regenerating limb to retinoid treatment differed according to the larval stage of development for P. waltl. Young larval limbs, which were anterior limb buds at the time of amputation, duplicated transversely while limbs of older larvae duplicated proximodistally. Proximodistal duplications were usually limited to the production of supernumerary carpals or a second zeugopod. Complete limbs regenerating from a distal amputation plane were rarely seen. T. vulgaris larvae regenerated limbs with either one or the other type of duplication, but never both on the same limb, at all larval stages tested. When larval P. waltl were kept in normal laboratory light during the treatment with retinol palmitate suspended in the rearing water the percentage of limbs which duplicated was very small for young larvae and increased with the age of the larvae used. Keeping the animals in the dark during the treatment period greatly increased the percentage of duplicate limbs obtained on the young larvae but not on the older larvae. This result is discussed in terms of the photodegradation of the retinoid and the length of the sensitive period for the regenerating limb. A dose-response relationship between the dose of retinol palmitate and either the percentage of limbs duplicated or the degree of duplication was not found. Such a relationship, however, was observed when retinoic acid was injected intraperitoneally into stage-54+ P. waltl larvae. Additionally, this technique revealed a peak of sensitivity to retinoic acid on the 6th day after amputation. Limb regeneration in older larvae was temporarily blocked by retinoid treatment. The limbs showed little or no regression and began blastemal development shortly after the treatment ended. Limbs of young larvae, however, often regressed. Such regressions were followed by blastemal formation and middle- to late-bud blastemas were found at the end of 11 or 14 days treatments with retinol palmitate.

Topics: Animals; Diterpenes; Dose-Response Relationship, Drug; Extremities; Larva; Light; Pleurodeles; Regeneration; Retinoids; Retinyl Esters; Tretinoin; Triturus; Vitamin A

The temporal effects of retinoic acid supplementation on hepatic cytochrome P-450-dependent enzymes were studied on the rat. Four groups of male weanling rats were fed semi synthetic diets: two groups containing 0 or 4.4 mg retinol equivalents per kg diet as retinyl palmitate (A- RA- and A+ RA- groups) and two similar groups supplemented with all trans retinoic acid (12 mg/kg diet) (A- RA+ and A+ RA+ groups). After five or ten weeks of feeding, the rats were killed, liver microsomes were prepared and assayed for aniline hydroxylase, aminopyrine N demethylase activities and cytochrome P-450 levels. Whereas no change was observed between the four groups after 5 weeks, the following modifications appeared after 10 weeks: Vitamin A deficiency decreased hepatic drug metabolism by phase I enzymes (hydroxylase and N demethylase) but only when liver storage pool was not detectable. Vitamin A concentration as low as 4 micrograms/g is sufficient to avoid any perturbation of these enzymes. Parallel to a sparing effect on liver reserves of vitamin A, retinoic acid maintained a normal activity of enzymes of xenobiotic metabolism. However, retinoic acid treatment produced an alteration of phase I enzymes in vitamin A supplemented group (A+ RA+). As this was accompanied by a doubling of vitamin A liver reserves, compared to A+ RA- group, it is suggested that this might result from a liver vitamin A overloading, leading to membrane damage perturbing microsomal enzymes. These results indicate the need for a more careful use of retinoids as a therapeutic agent.

Topics: Aminopyrine N-Demethylase; Aniline Hydroxylase; Animals; Cytochrome P-450 Enzyme System; Diterpenes; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Vitamin A; Vitamin A Deficiency

The vitamin A analogs retinoic acid and retinol caused a significant increase in concanavalin A-induced agglutination of human erythrocytes, while its esters, retinyl acetate and retinyl palmitate, were found to be ineffective. The effect of membrane labilizers and stabilizers on the enhancement of agglutination as well as the properties of the model system employed showed that the action of vitamin A is due to a direct action on cell membrane and is not mediated by the release of lysosomal proteases into the medium, a hypothesis proposed by earlier workers.

Topics: Concanavalin A; Diterpenes; Erythrocytes; Hemagglutination; Humans; Retinyl Esters; Tretinoin; Vitamin A

All-trans-[11-3H]retinyl acetate was injected directly into the testes of young rats and testicular and liver metabolites were analyzed by HPLC at 6, 24 and 72 h post injection. All-trans-retinyl acetate was hydrolyzed to retinol and further metabolized to polar compounds and a trace of retinoic acid, or reesterified to various retinyl esters including retinyl palmitate and retinyl stearate. Thus, retinyl ester hydrolyzing and esterifying enzymes are present in the testes of young rats. Eleven, twelve and ten radioactive peaks were observed at 6, 24 and 72 h, respectively. The amount of radioactivity in retinyl palmitate and retinyl stearate increased with time and reached 24 and 4%, respectively, by 72 h. Although retinol predominated, retinyl palmitate was the major esterified form in testis. The amount of radioactivity in retinol and retinyl acetate decreased with time and increased in unidentified metabolites and retinyl esters. An insignificant amount of radioactivity was found in liver. We conclude from these results that some vitamin A is stored/accumulated in the testes as retinyl esters in order to support the process of spermatogenesis and other physiological functions and that the retinol esterifying enzyme is quite active in the testes of young rats.

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Injections; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Testis; Time Factors; Tretinoin; Vitamin A

The influence of all-trans- and 13-cys-methylretinoate on antibacterial and antiviral immunity was studied in experiments on noninbred C57Bl/6 and (CBA X C57Bl/6) F1 mice. All-trans-methylretinoate was shown to stimulate the production of antibodies to E. coli antigens, with the effect being dose-dependent. At the same time both compounds inhibited the production of inhibitors, interferon and antibodies to influenza virus.

Topics: Animals; Antibodies, Bacterial; Antibodies, Viral; Antibody Formation; Antiviral Agents; Diterpenes; Escherichia coli; Female; Interferons; Male; Mice; Orthomyxoviridae; Retinyl Esters; Tretinoin; Vitamin A

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Female; Fenretinide; Liver; Mice; Rats; Rats, Inbred Strains; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

Invasion of chick chorioallantoic membrane (CAM) organ cultures by rat 3Y1 cells transformed by the highly oncogenic human adenovirus type 12 (3Y1/12-10 cells) was inhibited by several retinoids tested. The anti-invasive activity of the retinoids was dependent on retinoid concentration and continuous (4 d) exposure of the CAM. The 50% retinoid dose (dose effective in achieving a response in half of the organ cultures) that inhibited invasion was 0.85 micrograms/ml of retinol palmitate, 0.39 micrograms/ml of retinoic acid, or 0.16 micrograms/ml of retinol acetate. This dose was of the same order of magnitude as that which induced CAM differentiation, and was three- to fourfold less than the dose that caused cytotoxic damage of CAM. In addition, the retinoids inhibited 3Y1/12-10 cell growth by approximately 40% at levels over 10-fold higher than those needed for anti-invasion activity. The findings suggest that the anti-invasive activity of retinoids was at least partly due to direct induction of cell differentiation of the CAM host tissue.

Topics: Adenoviruses, Human; Allantois; Animals; Cell Differentiation; Cell Division; Cell Transformation, Neoplastic; Cell Transformation, Viral; Chick Embryo; Chorion; Diterpenes; Extraembryonic Membranes; Neoplasm Invasiveness; Organ Culture Techniques; Rats; Retinoids; Retinyl Esters; Tretinoin; Vitamin A

Topics: Animals; Antibody-Producing Cells; Diterpenes; Leukocyte Count; Lymphocyte Activation; Lymphocytes; Male; Rats; Retinyl Esters; Tretinoin; Vitamin A; Vitamin A Deficiency

Regulation of the biosynthesis of alpha-fetoprotein and albumin was studied in a temperature-sensitive fetal rat hepatocyte line (RLA209-15) which exhibits a differentiated phenotype when grown at 40 degrees C. Retinoic acid inhibited alpha-fetoprotein production but increased albumin production. This retinoid also changed the proportion of three forms of alpha-fetoprotein; the biosynthesis of the 73,000- and 69,000-dalton variants, which are indistinguishable from authentic rat alpha-fetoprotein, was inhibited and an additional 65,000-dalton variant was induced. It has previously been shown that alpha-fetoprotein production decreases during maturation whereas albumin production increases. Our data suggest that retinoic acid induces maturation of fetal liver cells in vitro. Further, the 65,000-dalton alpha-fetoprotein variant may be characteristic of liver maturation.

Topics: alpha-Fetoproteins; Animals; Cell Line; Diterpenes; Fetus; Kinetics; Liver; Rats; Retinyl Esters; Serum Albumin; Tretinoin; Vitamin A

The chemopreventive effects of beta-carotene and 13-cis-retinoic acid (RA) on chemically induced salivary gland tumors were studied in rats. Young male Sprague-Dawley rats were injected in one of the submandibular salivary glands with 1 mg of dimethylbenzanthracene (DMBA) dissolved in olive oil. The contralateral gland was injected with the vehicle alone. Rats were divided into four groups and were fed ad libitum a semisynthetic diet supplemented with 0 or 100 mg beta-carotene/kg diet, or 20 or 100 mg RA/kg diet. Rats were killed at 22 weeks after the DMBA treatment, and tumors were examined histologically. Tumors were generally found to be squamous cell carcinomas or poorly differentiated neoplasms resembling squamous cell carcinomas. The tumor incidence was slightly lower in rats fed the diet supplemented with beta-carotene. RA had no appreciable effect on tumor incidence. A high activity of gamma-glutamyl transpeptidase was histochemically demonstrated in the tumors. There were some mortalities in the beta-carotene and RA supplemented groups, especially in the group fed high levels of RA. This mortality appeared to be related to vitamin K becoming somewhat limited.

Topics: 9,10-Dimethyl-1,2-benzanthracene; Animals; beta Carotene; Butylated Hydroxytoluene; Carotenoids; Diterpenes; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Salivary Gland Neoplasms; Submandibular Gland Neoplasms; Time Factors; Tretinoin; Vitamin A

Two retinoids (13-cis-retinoic acid and retinyl palmitate ) have been shown to exert a good preventive effect in chemically induced papillomas and carcinomas of the skin in female Swiss mice; this effect was investigated over a period of 23 weeks. The tumors were induced by repeated topical application of 3-methylcholanthrene (0.3% MCA, dissolved in acetone; 14 applications). Retinyl palmitate (RP; 6 mg in 0.1 ml acetone/mouse; 10 applications) and 13-cis-retinoic acid (RA; 3 mg in 0.1 ml acetone/mouse; 10 applications) were also administered topically for the 3rd to 9th week from the start of the experiment. This investigation gave evidence for the fact that both the retinoids did not only inhibit the development of skin papillomas but had also a marked effect on skin carcinomas.

Topics: Animals; Diterpenes; Isotretinoin; Methylcholanthrene; Mice; Papilloma; Retinyl Esters; Skin Neoplasms; Tretinoin; Vitamin A

F344 rats were given saline, vitamin A placebo or vitamin A analogues orally for 4 consecutive days. The following day they were killed and their alveolar macrophages (AM phi) were harvested by lavage. The functional integrity of the AM phi was determined by their capacity to phagocytize opsonized SRBC and to kill syngeneic adenocarcinoma cell lines nonspecifically. Results showed that 4 days treatment with greater than 100 IU of vitamin A as retinyl palmitate per gram body weight rendered the AM phi tumoricidal against syngeneic mammary adenocarcinoma cell lines (MADB-100 and MADB-200) and that AM phi activated with retinyl palmitate showed increased ability to phagocytize opsonized SRBC. Other retinoids, such as retinoic acid and retinol, had the same effect of inducing tumoricidal activity in rat AM phi. AM phi harvested from normal rats were also rendered tumoricidal by direct interaction with greater than 10(3) IU ml-1 of retinyl palmitate for 24 h in vitro. Thus, vitamin A at high doses can increase the phagocytic and tumoricidal activities of rat AM phi.

Topics: Adenocarcinoma; Animals; Cells, Cultured; Cytotoxicity, Immunologic; Diterpenes; Dose-Response Relationship, Immunologic; Macrophage Activation; Macrophages; Male; Mammary Neoplasms, Experimental; Phagocytosis; Pulmonary Alveoli; Rats; Rats, Inbred F344; Retinyl Esters; Tretinoin; Vitamin A

Retinol esterification in the small intestine, liver and kidney of rats given a normal diet or a vitamin-A-free diet and of rats given large doses of vitamin A was studied. The active enzyme is a microsomal acyl CoA:retinol acyl transferase (ARAT). In the small intestine ARAT activity was 0.37 nmol ester/mg microsomal protein per min. Large doses of vitamin A increased the activity significantly, while the enzyme activity in the vitamin-A-deficient rats was in the range of that of the controls. Retinoic acid in physiological doses (0.064 mg three times per week) had no influence on ARAT activity. In the liver, ARAT activity of the controls was 0.58 nmol ester/mg microsomal protein per min. The activity was increased after large doses of vitamin A. It was not significantly reduced in vitamin-A-deficient animals. The kidney had a low, but significant ARAT activity, both in normal and vitamin-A-deficient animals and after large doses of vitamin A (range 0.08-0.14 nmol ester/mg microsomal protein per min). The vitamin-A-esterifying enzyme in the small intestine and liver of the rat seems to be influenced by the amount of retinol in the diet.

Topics: Acyltransferases; Animals; Diterpenes; Intestinal Mucosa; Jejunum; Kidney; Liver; Male; Microsomes; Microsomes, Liver; Rats; Rats, Inbred Strains; Retinol O-Fatty-Acyltransferase; Retinyl Esters; Tretinoin; Vitamin A

Topics: Animals; Chromatography, High Pressure Liquid; Diterpenes; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Testis; Tretinoin; Vitamin A

The effect of retinoids (Rds) on cell proliferation was studied in serum-free culture condition, using non-transformed and transformed derivatives of BALB 3T3. Cell proliferation of an SV40-transformed line was inhibited significantly by Rd treatment. However, proliferation of two cell lines that were transformed by a Kirsten and Moloney strain of murine sarcoma virus (MSV) and produced growth factor into culture medium, was remarkably stimulated by Rds. Addition of serum masked both the inhibitory and stimulatory effects of Rds.

Topics: Animals; Blood; Cell Line; Cell Transformation, Viral; Culture Media; Diterpenes; Dose-Response Relationship, Drug; Growth Substances; Kirsten murine sarcoma virus; Mice; Retinaldehyde; Retinyl Esters; Sarcoma Viruses, Murine; Simian virus 40; Tretinoin; Vitamin A

20-Methylcholanthrene induced the encystment of Opalina ranarum when injected into its host, Rana ridibunda. Also, urine of frogs injected with this hydrocarbon induced encystment of the parasites. It is speculated that methylcholanthrene or its metabolites reach the parasites in the recta of the frogs and stimulate the parasites to encyst. Injections of frogs with methylcholanthrene and 13-cis-retinoic acid failed to induce cyst formation in the opalinids. Moreover, encystment of the parasite was lessened when the host was injected with methylcholanthrene and retinyl palmitate. Urine of frogs injected with methylcholanthrene and 13-cis-retinoic acid failed to induce cyst formation in the parasites. Moreover, urine of frogs injected with this hydrocarbon and retinyl palmitate lessened the induction of cyst formation in the parasites in vitro. It is suggested that 13-cis-retinoic acid as well as retinyl palmitate inhibits methylcholanthrene-induced cyst formation of the opalinids.

Topics: Animals; Ciliophora; Diterpenes; Female; Isotretinoin; Male; Methylcholanthrene; Ranidae; Retinyl Esters; Tretinoin; Urine; Vitamin A

The effect of feeding large amounts of beta-carotene and 13-cis-retinoic acid (RA) on plasma and liver levels of alpha-tocopherol, lipid peroxides and retinoids was studied. Groups of young male rats were fed semipurified diets supplemented with 0, 100 mg/kg beta-carotene, 20 and 100 mg/kg 13-cis-RA. After feeding the various diets for 11 weeks, rats were killed and the concentrations of lipid peroxides, alpha-tocopherol, and retinoids were measured in blood plasma and liver. Peroxide levels were increased and alpha-tocopherol levels were decreased in plasma as well as liver of rats fed diets containing 13-cis-RA; this effect seems to be dose dependent, beta-Carotene had no significant effect on either of the above parameters. There was a decrease in the liver and plasma concentrations of retinol in rats fed 13-cis-RA; the levels of RA were generally higher in these two groups. The results suggest that the mechanism whereby 13-cis-RA increases the tissue peroxide levels may be related to its ability to decrease alpha-tocopherol levels.

Topics: Animals; beta Carotene; Carotenoids; Chromatography, High Pressure Liquid; Diet; Diterpenes; Isotretinoin; Lipid Peroxides; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Vitamin A; Vitamin E; Weaning

These experiments describe further investigations into the effects of vitamin A on regenerating limbs. The effects of different retinoids, the time of administration, concentration of vitamin A and histological, autoradiographic and histochemical studies are reported. The most obvious result of vitamin A treatment is to cause proximal elements to regenerate from distal amputation levels, that is to cause serial reduplication of pattern in the proximodistal axis. Retinoic acid was the most potent of the analogues tested and longer times of administration or higher concentrations cause a greater amount of serial reduplication. Various tissue changes have been found which include the inhibition of cell division, loss of cartilage metachromasia, changes in the mucous-secreting properties of the epidermis and an increased packing in the blastemal cells. The significance of these cellular effects in relation to the pattern-formation changes is discussed.

Topics: Ambystoma mexicanum; Animals; Connective Tissue; Diterpenes; Dose-Response Relationship, Drug; Forelimb; Mitotic Index; Morphogenesis; Regeneration; Retinyl Esters; Time Factors; Tretinoin; Vitamin A

Topics: Animals; Cell Differentiation; Chick Embryo; Diterpenes; Embryonic Induction; Extremities; Pharmaceutical Vehicles; Regeneration; Retinyl Esters; Time Factors; Tretinoin; Vitamin A

We treated experimental corneal epithelial wounds in rabbits with topical retinoids. Treatment with 0.1% all-trans-retinoic acid three times per day resulted in a 21% increase in the healing rate compared to the control eyes. Treatment five times a day resulted in a 35% increase in healing rate. Treatment with topical retinoic acid also promoted corneal deturgescence. Retinyl palmitate, retinyl acetate, retinol, and 13-cis-retinoic acid had no effect on corneal wound healing. These data suggested that topically applied all-trans-retinoic acid may be effective in promoting corneal healing after surgery and in the treatment of persistent and recurring corneal epithelial defects.

Topics: Administration, Topical; Animals; Cornea; Corneal Injuries; Diterpenes; Rabbits; Retinyl Esters; Tretinoin; Vitamin A; Wound Healing

A study has been made of the effects of retinoic acid, retinal, retinol, retinyl palmitate and retinyl acetate on HeLa cell viability. The results obtained show that (i) these cells seem to be more resistant to vitamin A than other cell cultures; (ii) the various vitamin A compounds differ in their inhibitory action on HeLa cells; (iii) the effects of retinoic acid, retinal, retinol and retinyl acetate are cytotoxic, those of retinyl palmitate are always cytolytic.

Topics: Cell Survival; Diterpenes; HeLa Cells; Humans; Retinaldehyde; Retinyl Esters; Tretinoin; Vitamin A

Investigation of retinoids for anticancer activity in humans, either in the chemopreventive or treatment mode, has been little studied. We summarize here our ongoing investigations in four different areas: (1) secondary prevention of cervical dysplasia with topical application of all-trans-retinoic acid; (2) adjuvant treatment of resected high-risk stage I and II malignant melanoma with bacille Calmette Guérin (BCG) plus or minus oral vitamin A; (3) topical vitamin A acid therapy for cutaneous metastatic melanoma; an (4) oral isotretinoin as an anticancer agent.

Topics: Diterpenes; Female; Humans; Isomerism; Isotretinoin; Melanoma; Neoplasms; Palmitates; Retinyl Esters; Skin Neoplasms; Tretinoin; Uterine Cervical Dysplasia; Vitamin A

Topics: Animals; Chemical and Drug Induced Liver Injury; Diterpenes; Etretinate; Hematologic Diseases; Liver; Male; Rats; Rats, Inbred Strains; Retinyl Esters; Tretinoin; Vitamin A

Retinoids are known to inhibit the substrate mediated enzyme induction of benzo[a]pyrene metabolizing enzymes. Consequently, the effect of two retinoids on the induction of benzo[a]pyrene metabolizing enzymes by the more potent inductor 2,3,7,8-tetrachlorodibenzo-p-dioxine (TCDD) was investigated. The studies were performed with human diploid fibroblasts in culture. Vitamin A palmitate and all-trans-retinoic-acid were found to prevent the TCDD induced increase of benzo[a]pyrene metabolism in a dose-dependent manner. The fact that this effect was immediately reversible makes it unlikely that it was due to non-specific toxic effects. The data suggest that retinoids cause a preferential inhibition of the de novo synthesis of benzo[a]pyrene metabolizing enzymes.

Topics: Anticarcinogenic Agents; Benzo(a)pyrene; Cells, Cultured; Dioxins; Diploidy; Diterpenes; Dose-Response Relationship, Drug; Drug Interactions; Enzyme Induction; Fibroblasts; Humans; Retinyl Esters; Skin; Solubility; Tretinoin; Tritium; Vitamin A