8-hydroxy-2--deoxyguanosine and Hyperplasia

We aimed at investigating the antioxidant, antiinflamatory, antiapoptotic and antigenotoxic effects of a Romanian Propolis (RP) extract in two concentrations (RP1 3 mg, respectively RP2 1.5 mg polyphenols/cm(2)), topically administered, either prior to or after UVB exposure, in a Swiss mouse model. Our results showed that both concentrations of RP extract, independent of the time of administration, significantly attenuated the malondialdehyde (MDA) formation and restored glutathione peroxidase (GPx) activity. However, the 8-hydroxy-2-deoxy-guanosine (8-oxo-dG), nitric oxide (NO) and glutathione (GSH) levels were not influenced by UVB exposure and RP treatment. Interleukin (IL)-6 levels were significantly decreased by RP treatment, both before and after UVB-exposure. RP2 extract, in both regimens, significantly reduced the epidermal hyperplasia and dermal inflammation, whereas RP1 pre-treatment diminished only the dermal inflammation. The effect of our RP extract in terms of reduction of sunburn cell formation and of activated caspase-3 and TUNEL-positive cells was observed in both subsets of the experiment, RP2 having a slightly better protective effect as compared to RP1. The antigenotoxic effect of RP was demonstrated by significantly reduced cyclobutane pyrimidine dimers (CPDs) formation. Our results suggest that RP extract might be a potential chemopreventive candidate by modulation of multiple UVB-induced signaling pathways in skin.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Administration, Topical; Animals; Antioxidants; Caspase 3; Deoxyguanosine; Female; Glutathione; Hyperplasia; Interleukin-6; Mice; Nitric Oxide; Oxidative Stress; Polyphenols; Propolis; Pyrimidine Dimers; Radiation-Protective Agents; Radiodermatitis; Romania; Skin; Ultraviolet Rays

We previously reported that 8-oxo-2'-deoxyguanosine (8-oxo-dG) suppressed airway hyperresponsiveness and allergy-associated immune responses in ovalbumin-induced allergic mice by inactivating Rac. In the present study, 8-oxo-dG was investigated for its suppression of inflammation and remodeling in lung tissues induced by allergic reaction in mice. Mice were sensitized and challenged with ovalbumin without or with oral administration of 8-oxo-dG. The mice without 8-oxo-dG administration showed the following inflammatory and airway remodeling signs: infiltration of inflammatory cells into peribronchial area, hyperplasia of mucus-secreting goblet cells in bronchial walls, increase of expressions of Muc5ac and vascular cell adhesion molecule (VCAM)-1, collagen deposition and protein expression, and matrix metalloproteinase (MMP)-2/-9 expressions. We also observed an increase of various inflammation-mediating proteins, namely IL-4, IL-5, IL-8, IL-13, TNF-α and IFN-γ, and activation of STAT1 and NF-κB. Production of reactive oxygen species and nitric oxide (NO(.)) was increased as indicated by a dramatic increase in formation of nitro-tyrosine. Importantly, Rac1 and 2 were also markedly activated. However, 8-oxo-dG suppressed all these inflammatory and tissue remodeling signs as well as activation of Rac1 and 2. These results indicate that 8-oxo-dG can inhibit allergy-induced inflammation and remodeling in airway and lung tissues through Rac inactivation.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Airway Remodeling; Animals; Collagen; Cytokines; Deoxyguanosine; Enzyme Activation; Female; Gene Expression Regulation; Goblet Cells; Hyperplasia; Hypersensitivity; Immunosuppressive Agents; Inflammation; Lung; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Mice; Mice, Inbred BALB C; Mucin 5AC; NF-kappa B; rac GTP-Binding Proteins; RNA, Messenger; STAT1 Transcription Factor; Tyrosine; Vascular Cell Adhesion Molecule-1

To clarify the role of oxidative stress during breast carcinogenesis by studying the expression of 8-hydroxydeoxyguanosine (8-OHdG) (a marker of oxidative DNA damage) and 4-hydroxy-2-nonenal (HNE) (a marker of lipid peroxidation) during the different phases of breast carcinogenesis.. The study material consisted of a total of 219 patients: 31 with usual ductal hyperplasia (UDH), 25 with atypical ductal hyperplasia (ADH), 30 with ductal carcinoma in situ (DCIS) and 133 with invasive carcinoma. The expression of 8-OHdG and HNE were evaluated immunohistochemically. Both 8-OHdG (77.4%) and HNE (45.8%) expression was already seen in UDH lesions. Interestingly, the trend of these two immunostainings during breast carcinogenesis was diverse. 8-OHdG expression diminished significantly in invasive breast carcinomas compared to non-invasive lesions (P < 0.005 when set against non-invasive cohorts). Also within the same lesions, 8-OHdG expression was the most intensive in benign cells. Conversely, HNE immunostaining was strongest in invasive breast carcinomas (UDH versus invasive cohort, P = 0.015).. 4-hydroxy-2-nonenal as a marker of lipid peroxidation increases during breast carcinogenesis, reflecting the role of oxidative stress in the pathogenesis of breast cancer. However, 8-OHdG shows diminished levels in carcinomas, possibly resulting from the induction of DNA repair in these invasive lesions.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adult; Aged; Aged, 80 and over; Aldehydes; Biomarkers, Tumor; Breast Neoplasms; Carcinoma, Ductal, Breast; Carcinoma, Intraductal, Noninfiltrating; Cell Transformation, Neoplastic; Deoxyguanosine; DNA Repair Enzymes; Female; Humans; Hyperplasia; Lipid Peroxidation; Middle Aged; Oxidative Stress; Retrospective Studies

Carcinogen-mediated labilization of lysosomal enzymes such as β-glucuronidase (βG) is often associated with the general process of inflammation. Therefore, the primary goal of this study was to demonstrate that exposing the skin of SENCAR mice to the natural βG inhibitor D-glucaro-1,4-lactone (1,4-GL) and its precursor D-glucuronic acid-γ-lactone (GUL), prior to and during 7,12-dimethylbenz[α]anthracene (DMBA) treatment inhibits not only epidermal hyperplasia but also inflammation in the mouse skin complete carcinogenesis model, i.e., the 4-week inflammatory-hyperplasia assay. Topical administration of 1,4-GL or GUL prior to repetitive, high-dose DMBA treatment markedly and in a dose-related manner inhibited DMBA-induced epidermal hyperplasia (i.e., up to 57%). DMBA-mediated Ha-ras mutations in codon 61 were reduced by up to 78% by 1,4-GL. DMBA-induced inflammation, as measured by dermal leukocyte counts and immunologically, was inhibited by up to 37% by topical 1,4-GL but not by GUL. The inhibition of cellular proliferation and inflammation coincided with the inhibition of βG expression. Thus, the present study suggests that in the DMBA-induced complete skin carcinogenesis model, 1,4-GL when applied topically had both anti-proliferative properties as well as anti-inflammatory properties, whereas GUL had only anti-proliferative when applied topically. However, the number of inflammatory cells in the dermal portion of the skin of mice was significantly reduced by dietary treatment of GUL, whereas both topical and dietary treatments with 1,4-GL were very effective.

Topics: 8-Hydroxy-2'-Deoxyguanosine; 9,10-Dimethyl-1,2-benzanthracene; Administration, Oral; Administration, Topical; Animals; Anticarcinogenic Agents; Biomarkers; Carcinogens; Deoxyguanosine; Dermatitis, Contact; Female; Glucaric Acid; Glucuronates; Glucuronidase; HSP90 Heat-Shock Proteins; Hyperplasia; Inflammation Mediators; Interleukin-1alpha; Leukocyte Count; Mice; Mice, Inbred SENCAR; Neoplasms; Skin

Arsenite (As(III)), an inorganic arsenical, is a known human carcinogen, inducing tumors of the skin, urinary bladder and lung. It is metabolized to organic methylated arsenicals. Oxidative stress has been suggested as a mechanism for arsenic-induced carcinogenesis. Reactive oxygen species (ROS) can be important factors for carcinogenesis and tumor progression. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is known to produce intracellular ROS, therefore, we investigated the ability of apocynin (acetovanillone), an NADPH oxidase inhibitor, to inhibit the cytotoxicity and regenerative cell proliferation of arsenic in vitro and in vivo. Apocynin had similar effects in reducing the cytotoxicity of As(III) and dimethylarsinous acid (DMA(III)) in rat urothelial cells in vitro. When tested at the same concentrations as apocynin, other antioxidants, such as l-ascorbate and N-acetylcysteine, did not inhibit As(III)-induced cytotoxicity but they were more effective at inhibiting DMA(III)-induced cytotoxicity compared with apocynin. In vivo, female rats were treated for 3 weeks with 100ppm As(III). Immunohistochemical staining for 8-hydroxy-2'-deoxyguanosine (8-OHdG) showed that apocynin reduced oxidative stress partially induced by As(III) treatment on rat urothelium, and significantly reduced the cytotoxicity of superficial cells detected by scanning electron microscopy (SEM). However, based on the incidence of simple hyperplasia and the bromodeoxyuridine (BrdU) labeling index, apocynin did not inhibit As(III)-induced urothelial cell proliferation. These data suggest that the NADPH oxidase inhibitor, apocynin, may have the ability to partially inhibit arsenic-induced oxidative stress and cytotoxicity of the rat bladder epithelium in vitro and in vivo. However, apocynin did not inhibit the regenerative cell proliferation induced by arsenite in a short-term study.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Acetophenones; Acetylcysteine; Animals; Antioxidants; Arsenites; Ascorbic Acid; Cacodylic Acid; Carcinogens; Cell Line; Cell Proliferation; Cytoprotection; Deoxyguanosine; Diet; Dose-Response Relationship, Drug; Enzyme Inhibitors; Female; Hyperplasia; NADPH Oxidases; Oxidative Stress; Rats; Rats, Inbred F344; Sodium Compounds; Urinary Bladder; Urothelium

Combined treatment with several phenolic antioxidants and sodium nitrite (NaNO(2)) has already shown to enhance rat forestomach carcinogenesis. In the present experiment, effects of green tea catechins (GTC) alone or in combination with NaNO(2) on gastric carcinogenesis were investigated in a rat two-stage carcinogenesis model. Groups of eight, 6-week-old F344 male rats were given 0.01%N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in their drinking water and 5% NaCl in the diet for 10 weeks for glandular stomach initiation and a single intragastric administration of 100 mg/kg/bodyweight of MNNG at week 9 for forestomach initiation. From week 11, they received either drinking water containing 0.2% NaNO(2) and a diet supplemented with 1% GTC in combination, each individual chemical alone or a basal diet until the end of week 42. In the forestomach, incidences and multiplicities of neoplastic lesions were clearly increased by the combined treatment, in spite of GTC alone suppressing the occurrence of papillomas. In a short-term experiment with similar protocol without MNNG pretreatment, a significant increase of 8-hydroxydeoxyguanosine (8-OHdG) levels in forestomach DNA occurred 24 h after the combined treatment, concomitant with erosion and inflammatory cell infiltration. In an in vitro study, electron spin resonance demonstrated hydroxyl radical formation after incubation of epigallocatechin gallate or epicatechin gallate with the NO generator, NOC-7. Thus, GTC alone showed a weak chemopreventive effect on forestomach carcinogenesis, but in the presence of NaNO(2) it exerted a promotive effect which might involve hydroxyl-radical-associated oxidative DNA damage. However, no influence was exerted in the glandular stomach.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Catechin; Deoxyguanosine; Disease Models, Animal; Epithelial Cells; Hyperplasia; Male; Methylnitronitrosoguanidine; Rats; Rats, Inbred F344; Stomach Neoplasms; Tea

Matrix metalloproteinase (MMP) is critical to the progression of atherosclerosis and neointima hyperplasia after vascular injury. We investigated the effects of carvedilol, a pharmacological antioxidant with alpha- and beta-adrenergic blocking activity, on MMP-2 and MMP-9 expression. Vascular injury was induced with the balloon catheters on abdominal aortas of high-cholesterol-fed rabbits. On Day 21, there was significant aortic neointima formation with increased oxidative DNA damage by immunostaining with 8-hydroxy-2'-deoxyguanosine and enhanced MMP-2 and MMP-9 expressions by Western blotting, which were significantly reduced by oral administration of carvedilol (20 mg/kg/day) or probucol (100 mg/kg/day). Vascular expression (by Western blot), activity (by gelatin zymography), and mRNA levels of MMP-2 and MMP-9 were also reduced by carvedilol or probucol. Besides, pretreatment with carvedilol or probucol but not propranolol, a beta-blocker, or prazocin, an alpha-blocker, inhibited tumor necrosis factor-alpha-stimulated expressions and activities of MMP-2 and MMP-9 in human aortic smooth muscle cells. On electrophoretic mobility-shift assay, carvedilol inhibited the binding activities of activator protein-1 and specific protein-1, two major transcription factors for MMP promoter regions. Accordingly, carvedilol, a pharmacological antioxidant, inhibited in vivo and in vitro expression of MMP-2 and MMP-9 properly by modulating the redox-related pathways, suggesting its potential clinical implications.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Antioxidants; Aorta, Abdominal; Atherosclerosis; Carbazoles; Carvedilol; Cells, Cultured; Deoxyguanosine; Diet, Atherogenic; Humans; Hyperplasia; Male; Matrix Metalloproteinase Inhibitors; Probucol; Propanolamines; Rabbits; RNA, Messenger; Tumor Necrosis Factor-alpha; Tunica Intima

Vulvar cancer represents an important medical problem worldwide whose incidence is increasing at an alarming rate in young females. Several factors have been linked to vulvar cancer development, but its exact pathogenesis remains to be determined. Vulvar tumorigenesis proceeds through intermediate dysplastic lesions, known as vulvar intraepithelial neoplasias, frequently associated with non-neoplastic epithelial disorders of the vulva, such as lichen sclerosus and squamous cell hyperplasia. In this study, the expression of the CDK inhibitor p27Kip1 and the extent of endogenous oxidative DNA damage were evaluated in vulvar specimens, including normal tissues, lichen sclerosus, squamous cell hyperplasia, vulvar intraepithelial neoplasias and invasive squamous cell carcinomas. We found that p27Kip1 was constantly expressed in normal vulvar epithelium cells while a progressive significant reduction in the percentage of p27Kip1-positive cells was observed in vulvar intraepithelial neoplasias (77%) and in invasive carcinomas (64%). Mean percentage of positive cells in invasive carcinomas, but not in vulvar intraepithelial neoplasias, was also significantly lower than squamous cell hyperplasia lesions (78%) while lichen sclerosus displayed a percentage of positive cells (45%) significantly lower than both vulvar intraepithelial neoplasias and invasive carcinomas. 8-hydroxydeoxyguanosine (8-OHdG) is considered a sensitive biomarker for oxidative stress. We observed a progressive significant increase in the levels of 8-OHdG and in the percentage of positive cells from normal vulvar epithelium to vulvar intraepithelial neoplasias (25%) and to invasive carcinomas (64%). Squamous cell hyperplasia displayed an intermediate percentage of positive cells comparable to vulvar intraepithelial neoplasias 2 but significantly higher than vulvar intraepithelial neoplasias 1 and lower than invasive carcinomas. Lichen sclerosus staining was significantly lower than carcinomas but higher than vulvar intraepithelial neoplasias and squamous cell hyperplasia. These results demonstrate that expression of p27Kip1 is downregulated while oxidative DNA damage increases from early non-neoplastic epithelial alterations through vulvar intraepithelial neoplasias to invasive vulvar carcinomas. Thus, both parameters might play an important role in the development of this cancer and their study might contribute to our understanding of human vulvar carcinogenesis.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Aged; Aged, 80 and over; Carcinoma, Squamous Cell; Cell Line, Tumor; Cyclin-Dependent Kinase Inhibitor p27; Deoxyguanosine; DNA Damage; Female; Humans; Hyperplasia; Immunohistochemistry; Lichen Sclerosus et Atrophicus; Middle Aged; Oxidative Stress; Vulva; Vulvar Neoplasms

To clarify the in vivo genotoxic potential of kojic acid (KA), formation of DNA adducts and 8-hydroxy-deoxyguanosine (8-OHdG) in the thyroids of male rats subjected to dietary administration of 2% KA for 2 weeks were assessed by 32P-postlabeling analysis and with a high-performance liquid chromatography system coupled to an electrochemical detector (ECD), respectively. In addition, to investigate possible tumor initiation activity, male F344 rats were given diet containing 0, 0.02, 0.2 or 2% kojic acid for 8 weeks followed by administration of 0.1% sulfadimethoxine (SDM), a thyroid tumor promoter, in the drinking water for 23 weeks with a subsequent 13-week recovery period (two-stage thyroid tumorigenesis model). Rats given four times by s.c. injection of N-bis(2-hydroxypropyl)nitrosamine (DHPN; 700 mg/kg bw) during the initiation period followed by administration of 0.1% SDM and rats given diet containing 2% KA for the initial 8 weeks or for the entire 31 weeks of the experiment, or basal diet alone were provided as controls. DNA adducts were not formed, and the 8-OHdG level was not increased in the thyroids of rats given 2% KA for 2 weeks. In the two-stage thyroid tumorigenesis model, neither adenomas nor carcinomas were induced in the groups given 0, 0.02, 0.2 or 2% KA followed by 0.1% SDM administration, and incidences and multiplicities of focal follicular cell hyperplasias did not demonstrate any significant intergroup differences at the end of administration and recovery periods. In contrast, incidences and multiplicities of focal follicular cell hyperplasias, adenomas and carcinomas were all significantly increased in the DHPN + 0.1% SDM group. Although the incidences and multiplicities of focal follicular cell hyperplasias in the group given 2% KA for 31 weeks were greater than those in the 2% KA + 0.1% SDM group and an adenoma was observed in a rat at the end of the recovery period, no development of carcinomas was evident at either time point. No thyroid proliferative lesions were induced in the group given 2% KA for the initial 8 weeks only. The results of the present studies indicate that KA has neither in vivo genotoxic potential nor tumor initiation activity in the thyroid, and strongly suggest that the earlier observed thyroid tumorigenic activity of KA is attributable to a non-genotoxic mechanism.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adenoma; Animals; Carcinogens; Carcinoma; Deoxyguanosine; DNA Adducts; Hyperplasia; Male; Pyrones; Rats; Rats, Inbred F344; Thyroid Gland; Thyroid Neoplasms

Heme oxygenase (HO) is a microsomal enzyme that catalyzes the degradation of heme into biliverdin, which is subsequently reduced to bilirubin, free iron and carbon monoxide (CO), and induction of heme oxygenase-1 (HO-1) is potentially associated with cellular protection, especially against oxidative insults. Using transgenic mice that overexpress HO-1 (HO-1 Tg) specifically in vascular smooth muscle cells, we investigated the organ-protective effects of HO-1 against angiotensin II (Ang II). Following administration of Ang II and a high- salt diet for 14 days, marked intimal hyperplasia as well as inflammatory changes were observed in coronary arteries of Ang II/salt-treated wild type (Wt) mice. In Wt mice, Ang II/salt loading increased urinary excretion of 8- hydroxydeoxyguanosine (8-OHdG) and 8-lso-Prostaglandin F2 alpha. Cardiac levels of MDA and 4-HAE, markers of lipid peroxidation, and GSSG/GSH were also increased in Wt. mice after Ang II/salt loading, but not in HO-1 Tg mice. Consistently, immunostaining for both 8-0HdG, a marker of oxidative DNA damage, and 3-nitrotyrosine, the metabolites of reactive oxygen species, were apparently increased in the Ang II/salt-treated heart of Wt. mice; however, no significant changes in these responses were detected in HO-1 Tg mice after Ang II/salt loading. These data suggest that increased oxidative stress might be involved in the coronary artery changes induced by Ang II/salt loading. The evidence presented in the current study indicates that vascular HO-1 exerts its protective effect against cardiovascular damage, possibly through the inhibition of oxidative stress.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Angiotensin II; Animals; Blood Pressure; Cardiovascular System; Coronary Vessels; Deoxyguanosine; Dose-Response Relationship, Drug; Heme Oxygenase (Decyclizing); Heme Oxygenase-1; Hyperplasia; Isoprostanes; Membrane Proteins; Mice; Mice, Transgenic; Muscle, Smooth, Vascular; Myocardium; Myocytes, Cardiac; Myocytes, Smooth Muscle; Oxidative Stress; Sodium Chloride, Dietary; Transduction, Genetic; Tunica Intima; Vasculitis

p-Dichlorobenzene (pDCB) is a male rat kidney carcinogen believed to act through alpha2u-globulin nephropathy. Recent data on metabolism, however, suggest a potential for generating oxidative stress. To examine possible mechanisms of kidney carcinogenesis, pDCB was studied for ability to produce 8-oxodeoxyguanosine (8-oxodG) in kidney nuclear DNA and for initiating activity in a two-stage renal carcinogenesis model. F344 male rats were given pDCB by intragastric instillation, 5 days/week for 13 weeks at 300 mg/kg per day, which is a carcinogenic dose with chronic administration. To assess initiation after exposure, trisodium nitrilotriacetic acid (NTA), a kidney tumor promoter was given in the drinking water at 1,000 ppm for 39 weeks. At the end of the exposure segment, pDCB did not produce an increase of 8-oxodG levels in the kidney nuclear DNA in contrast to potassium bromate (KBrO3). Following NTA promotion, no neoplastic lesions occurred in rats given pDCB, although diethylnitrosamine carcinogenesis was enhanced. Thus, pDCB did not produce oxidative DNA damage in the rat kidney or effect initiation of kidney carcinogenesis. These data suggest that oxidative stress is not involved in pDCB-induced renal carcinogenesis. The alpha2u-globulin-mediated chronic nephropathy probably acts as a promoter, not an initiation of renal carcinogenesis. Accordingly, pDCB is assessed to have no cancer hazard to humans who are not susceptible to the alpha2u-globulin nephropathy.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Adenocarcinoma; Animals; Body Weight; Carcinogens; Cell Division; Cell Nucleus; Chlorobenzenes; Cystadenoma; Deoxyguanosine; DNA Damage; DNA, Neoplasm; Hyperplasia; Immunohistochemistry; Kidney Neoplasms; Male; Organ Size; Oxidation-Reduction; Rats; Rats, Inbred F344

The effect of metabolic activation of the food additive 3-tert-butyl-4-hydroxyanisole (BHA) by prostaglandin H synthase on the gastro-intestinal cell proliferation was determined by studies of the nature and the time dependency of early lesions in the forestomach, glandular stomach and colon/rectum of rats given BHA with and without co-administration of acetylsalicyclic acid (ASA: an inhibitor of prostaglandin H synthase), in combination with the formation of oxidative DNA damage in the epithelial cells of glandular stomach and colon/rectum as well as in the liver. BHA appeared to be a strong inducer of oxidative DNA damage in the epithelial cells of the glandular stomach, increasing the level of 7-hydro-8-oxo-2'deoxyguanosine (8-oxodG) with increasing duration of BHA administration. Similar observations were made in colorectal DNA although levels of oxidative DNA damage tend to be smaller. In liver DNA, BHA appeared to be capable of increasing background 8-oxodG levels only after 14 days of treatment. This relatively slow response may be related to very low prostaglandin H synthase activity of liver cells. The severity of hyperplasia and inflammation in both forestomach and glandular stomach appeared to increase gradually with continued BHA administration. The hyperplasia induced by BHA was paralleled by inflammatory changes. In colorectal tissue, however, no tissue abnormalities were observed. This indicates that oxidative DNA damage induced by BHA is not a consequence of early lesions in gastro-intestinal epithelium, but might be the initial step in the stimulation of gastro-intestinal cell proliferation which, as shown previously, also occurs in colon epithelium. Co-administration of the prostaglandin H synthase inhibitor ASA resulted in a significant decrease of both epithelial oxidative DNA damage and the incidence of lesions, which indicates that this enzyme system is involved in the enhancement of cellular proliferation induced by BHA. Co-oxidation by prostaglandin H synthase of the BHA-metabolite tert-butylhydroquinone into tert-butylquinone, yielding active oxygen species, might therefore be responsible for the carcinogenic effects of this food antioxidant.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Aspirin; Biotransformation; Butylated Hydroxyanisole; Cell Division; Colon; Cyclooxygenase Inhibitors; Deoxyguanosine; Digestive System; DNA Damage; Dose-Response Relationship, Drug; Drug Interactions; Epithelium; Food Additives; Hyperplasia; Inflammation; Liver; Male; Oxidation-Reduction; Prostaglandin-Endoperoxide Synthases; Rats; Rats, Wistar; Reactive Oxygen Species; Rectum; Stomach

Elevations of oxidatively modified DNA bases have been associated with a variety of carcinogens and tumor promoters, and implicated in causation of cancer. Since carcinogen exposure can induce cell proliferation, the relationship between induction of cell proliferation and levels of DNA base oxidation was examined. Cell proliferation was induced in livers of male F344 rats by stimuli of either regeneration or hyperplasia. Levels of DNA base oxidation were evaluated by measuring 8-OH-deoxyguanosine/deoxyguanosine (8-OHdG/dG) ratios by HPLC in enzymatic digests of DNA isolates. Despite induction of cell proliferation, hepatic levels of 8-OHdG/dG were not increased at 1, 2, 3 or 5 days after any of these treatments. Results of the present work suggest that the mechanism of elevated levels of DNA base oxidation is not directly related to induction of cell proliferation.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Carbon Tetrachloride; Cell Division; Deoxyguanosine; Hyperplasia; Liver; Liver Regeneration; Male; Oxidation-Reduction; Phenobarbital; Pyrimidines; Rats; Rats, Inbred F344

Significant differences in sensitivity to multistage carcinogenesis have been noted between mice that are sensitive (SENCAR) and resistant (C57BL/6J) to 12-O-tetradecanoylphorbol-13-acetate (TPA). However, the mechanism of this sensitivity has not yet been established. Recent studies from this laboratory have shown that TPA significantly enhances formation of hydrogen peroxide (H2O2) and oxidized DNA bases in SENCAR mouse skin, as it increases the infiltration of polymorphonuclear leukocytes (PMNs), as quantitated by myeloperoxidase (MPO). In the studies reported here, we compared SENCAR and C57BL/6J mice with respect to TPA-mediated edema, hyperplasia, PMN infiltration, oxidant formation and oxidative DNA damage in mouse skin. Topical application of two TPA doses (2x2-40 micrograms, 20 h apart) dose-dependently increased PMN infiltration and oxidant formation in both mouse strains, which was consistent with TPA-induced morphological alterations (edema and hyperplasia). However, at low TPA doses (2-4 micrograms), the increases over controls in the SENCAR mice were significantly greater (P < 0.01) than those in C57BL/6J mice. Comparison of the net values indicated that 4 micrograms TPA enhanced PMN infiltration (MPO units/cm2) and oxidant formation (nmol H2O2/cm2) in SENCAR mice by 7.7- and 11-fold respectively over those present in TPA-treated C57BL/6J mouse skin. At the same dose, TPA also significantly increased formation of thymidine glycol (dTG; 5.5-fold), 5-hydroxymethyl-2'-deoxyuridine (HMdU; 4.9-fold) and 8-hydroxyl-2-deoxyguanosine (8-OHdG; 11.4-fold) in SENCAR mouse epidermis. Then, the levels of all three declined. In C57BL/6J mice, there were virtually no increases at 4 micrograms TPA, but their levels gradually increased with higher TPA doses and reached maxima at 10 micrograms TPA for dTG (1.9-fold increase), at 20 micrograms TPA for 8-OHdG (6.0-fold), and at 30 micrograms TPA for HMdU (1.8-fold). We conclude that the TPA-mediated oxidative events and oxidative DNA modification by different doses of TPA correlate with the promoting potencies of those doses in both mouse strains. Therefore, they could be, at least in part, responsible for the strain-dependent sensitivity to tumor promotion.

Topics: 8-Hydroxy-2'-Deoxyguanosine; Animals; Carcinogens; Deoxyguanosine; DNA Damage; Hydrogen Peroxide; Hyperplasia; Mice; Mice, Inbred C57BL; Mice, Inbred Strains; Neutrophils; Peroxidase; Skin; Skin Neoplasms; Tetradecanoylphorbol Acetate; Thymidine