leukotriene-b4 and Dermatitis

Acute inflammatory reactions are characterized by leukocyte infiltration associated with increases in vascular permeability and in local blood flow. Leukocyte infiltration can be induced by chemotactic factors such as leukotriene B4 (LTB4) and paf-acether (formerly known as platelet-activating factor) that can be generated within inflammatory lesions. Vascular permeability and increase in blood flow are also affected by LTB4 and paf-acether, as well as by several other substances, including histamine and prostaglandins. Derived from arachidonic acid via the 5 lipo-oxygenase pathway, LTB4 is one of the most potent leukocyte chemotactic substances known. Intradermal injections of LTB4 induce dermal neutrophil infiltration in animal models and in humans. Topical application of LTB4 to human skin induces intraepidermal micro-abscesses containing numerous intact neutrophils. LTB4 has been found to be increased in psoriatic lesions, but its synthesis by epidermal cells remains undecided. Like other leukotrienes, LTB4 can stimulate DNA synthesis in cultured human epidermal keratinocytes. However, receptors for LTC4 but not for LTB4 have been found on human keratinocytes in culture. Paf-acether is an ether-linked phospholipid identified as 1-O-alkyl-2-O-acetyl-sn-glycero-3-phosphocholine and is considered to be one of the most potent mediators of acute allergic and inflammatory reactions. For instance, intradermal injection of paf-acether induces inflammatory events such as neutrophil infiltration and increase in vascular permeability. Recent data suggest that cutaneous cells, such as fibroblasts and keratinocytes, are capable of producing paf and that paf is released during the development of allergic cutaneous reactions.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Dermatitis; Humans; Leukotriene B4; Platelet Activating Factor; Psoriasis; Skin Physiological Phenomena

The purpose of this review is to underline the interactions between eicosanoids, platelet activating factor and IL-1. While the evidence for arachidonate metabolites, especially 12-HETE and the leukotrienes, as major mediators of skin inflammation is persuasive, we wish to draw attention to the potential importance of leukotrienes and prostaglandins as modulators of PAF and IL-1 activity. Phospholipase A2 emerges as a key enzyme in relation to the three above-mentioned mediator classes of human skin. Activation of phospholipase A2 leads to synthesis of both eicosanoids and PAF. Leukotriene products in addition to being pro-inflammatory per se also enhance IL-1 formation whilst cyclo-oxygenase products inhibit IL-1. Prostaglandin E2 also potentiates the actions of PAF. In this scheme it appears improbable that selective inhibition of one component (e.g. a PAF antagonist) or one enzyme (e.g. a 5-lipoxygenase inhibitor) would do more than create an imbalance in this closely integrated network of mediators which might not necessarily be beneficial. On the other hand phospholipase A2 inhibitors including lipocortin would seem to have a greater chance of clinical usefulness because of the central role this enzyme appears to play in the formation or modulation of all these classes of mediator.

Topics: Annexins; Arachidonic Acid; Arachidonic Acids; Dermatitis; Glycoproteins; Humans; Interleukin-1; Leukotriene B4; Lipoxygenase; Phospholipases; Platelet Activating Factor; Prostaglandins; Psoriasis

Topics: Dermatitis; Humans; Interleukin-1; Leukotriene B4; Prostaglandins; SRS-A

Topics: Chemical Phenomena; Chemistry; Dermatitis; Fatty Acids, Essential; Humans; Leukotriene B4; Lipid Metabolism; Lipoxygenase; Phospholipases A; Prostaglandin-Endoperoxide Synthases; Prostaglandins; Psoriasis

Prostaglandins appear to play an important role as mediators of inflammation since they fulfill the major criteria. They possess powerful proinflammatory properties; they are present in increased concentrations in a wide range of proinflammatory lesions, and anti-inflammatory drugs inhibit their formation. The role of leukotrienes and other hydroxy fatty acid products is far less clear although their participation in cellular events seems probable. Steroid and nonsteroid anti-inflammatory drugs owe their activity at least in part to inhibition of biosynthesis of prostaglandins, although these two drug classes appear to act at different points in the pathways. It becomes increasingly clear that the oxygenation of arachidonic acid leads to the formation of a multiplicity of pharmacologically active fatty acids of which only a few have so far been identified.

Topics: Animals; Anti-Inflammatory Agents; Arachidonic Acid; Arachidonic Acids; Dermatitis; Drug Interactions; Humans; Indomethacin; Leukotriene A4; Leukotriene B4; Prostaglandins; Skin; SRS-A

Clinical trials successfully using antibodies targeting IL-17 in psoriasis support the importance of IL-17 in the pathophysiology of this disease. However, there is a debate concerning the source and dynamics of IL-17 production in inflamed skin. Here we characterized IL-17-producing immune cells over time, using two established in vivo models of human skin inflammation that share many histological features with psoriasis, i.e., leukotriene B4 application and tape-stripping. Both treatments revealed a clear influx of neutrophils and T cells. Staining for IL-17 revealed that the majority of IL-17 was expressed by neutrophils and mast cells, in both models. Neutrophils, but not mast cells, coexpressed the IL-17-associated transcription factor RORγt and were able to form extracellular traps. While the presence of mast cells remained steady during the skin inflammatory process, the presence of neutrophils was clearly dynamic in time. Therefore, it is attractive to hypothesize that IL-17+/RORγt+ neutrophils contribute to human skin inflammation in vivo and possibly to the pathogenesis of skin diseases such as psoriasis. Surprisingly, T cells represented a minority of the IL-17-expressing cell population. These observations challenge the classical opinion that IL-17 is predominantly associated with T cells in skin inflammation.

Topics: Adaptive Immunity; Adolescent; Adult; Biopsy; Dermatitis; Female; Healthy Volunteers; Humans; Immunity, Innate; Interleukin-17; Leukotriene B4; Male; Mast Cells; Middle Aged; Neutrophils; Nuclear Receptor Subfamily 1, Group F, Member 3; Psoriasis; Skin; Surgical Tape; T-Lymphocytes, Regulatory; Young Adult

Antipsoriatic agents have been shown to decrease skin levels of arachidonic acid and its metabolites including 12-monohydroxy-eicosatetranoic acid (12-HETE), and leukotriene B4 (LTB4). In addition, specific systemic and topical lipoxygenase inhibitors have been reported to be effective in the treatment of psoriasis. The objective of this study was to investigate the effect of a potent oral leukotriene biosynthesis inhibitor (MK886) in patients with chronic plaque psoriasis. Clinical response together with the changes of LTB4 levels in lesional skin biopsy specimens, and urinary leukotriene E4 (LTE4) excretion were evaluated. In addition, markers of inflammation, proliferation and keratinization were studied immunohistochemically. No change in clinical scores or lesional LTB4 levels were observed with a 10 1/3-day course of MK886. A statistically significant reduction in urinary LTE4 excretion was observed: mean LTE4 (ng/h) were 5.14 before treatment and 1.51 on day 11 with MK886; and 7.55 before treatment and 6.57 on day 11 with placebo treatment. Epidermal accumulation of polymorphonuclear leukocytes (PMN) tended to diminish in the MK886 treatment group. These results indicate that although a reduction (greater than 70%) in urinary LTE4 excretion was found, and a slight decrease of epidermal PMN accumulation was observed, no correlative changes in clinical scores or LTB4 levels in skin lesion were found with a short course of MK886.

Topics: Administration, Oral; Adult; Aged; Biomarkers; Biopsy; Dermatitis; Double-Blind Method; Female; Humans; Immunohistochemistry; Indoles; Keratins; Leukotriene Antagonists; Leukotriene B4; Male; Middle Aged; Psoriasis; Skin

The time-course of cutaneous inflammatory responses to LTB4 and PGE2 both alone and in combination has been studied in 10 healthy volunteers. LTB4 induced a transient wheal and flare response in some subjects, maximal at 15 minutes and succeeded by an erythematous, indurated lesion at 2-4 hours. PGE2 elicited a wheal and erythema response which resolved within 1-2 hours. Combination of LTB4 and PGE2 produced acute wheal and erythema responses which did not differ significantly from the summation of responses to the individual constituents of the mixture or from responses to a two-fold increase in the concentration of either component. Wheal and erythema responses persisted, however, with significant potentiation of responses 4 hours after injection. As both leukotrienes and prostaglandins are generated in acute allergic reactions, the effects of these mediators in combination could contribute to persisting and late-onset responses to allergen, in both the skin and lung. In particular, sustained responses to the combination of LTB4 and PGE2 might be important in the pathogenesis of inflammatory skin diseases such as psoriasis.

Topics: Adult; Dermatitis; Dinoprostone; Drug Synergism; Female; Humans; Kinetics; Leukotriene B4; Male; Prostaglandins E; Skin

The potential of omega-3 poly-unsaturated fatty acids (PUFAs) as a therapeutic target for psoriasis, a chronic inflammatory skin disease of IL-23/IL-17 axis, is a long-disputed question, since various epidemiological studies have suggested the association between high-intake of omega-3 PUFAs and the reduced frequency and severity of psoriasis. However, their actual significance and the molecular mechanisms remain largely unknown. To address these issues, we focused on resolvin E1 (RvE1), an omega-3 PUFAs-derived metabolite, and examined its effects on psoriatic dermatitis, using an imiquimod-induced mouse psoriasis model. RvE1 potently suppressed the inflammatory cell infiltration and epidermal hyperplasia in the psoriatic skin. RvE1 decreased the mRNA expression of IL-23 in the skin. Consistently, RvE1 inhibited IL-23 production by dendritic cells (DCs) in vitro. Furthermore, RvE1 exerted inhibitory effects on migration of cutaneous DCs and γδ T cells, a major IL-17-producing cell population in mouse, both in vivo and in vitro. These suppressive effects of RvE1 were mediated by its antagonistic function on BLT1, a receptor of leukotriene B4, and were also observed in human DCs, Th17 and Tc17 cells. Our results indicate a novel mechanism of omega-3 PUFA-mediated amelioration of psoriasis, and suggest a potential of RvE1 as a therapeutic target for psoriasis.

Topics: Animals; Cell Movement; Dendritic Cells; Dermatitis; Disease Models, Animal; Eicosapentaenoic Acid; Fatty Acids, Omega-3; Female; Humans; Inflammation; Interleukin-17; Leukotriene B4; Mice; Mice, Inbred C57BL; Psoriasis; RNA, Messenger; Skin; Th17 Cells

Application of leukotriene B4 (LTB4) is an established in vivo model that locally induces skin inflammation. Currently in this model, a biopsy is inevitable. In vivo reflectance confocal microscopy (RCM), a noninvasive imaging technique, could overcome this limitation. To find out to what extent RCM may be an in vivo investigative and diagnostic tool in neutrophilic conditions, we studied the dynamics of polymorphonuclear leukocytes (PMN) migration from dermis to stratum corneum using an established LTB4 model.. Leukotriene B4 was topically applied on the skin of the lower back of seven volunteers. The skin sites were evaluated by RCM for three consecutive days with a 24 h time interval. For histological correlation, 3-mm punch biopsies were obtained. The tissue sections were hematoxylin-eosin and immunohistochemical stained. Minimal and average epidermal thickness was measured.. Reflectance confocal microscopy imaging showed highly reflective ill-defined particles with a granular content throughout the epidermis 24 h after application of LTB4. Over time, the appearance of these cells changed throughout the epidermis. Epidermal thickness increased over time, and the measurements based on the RCM images corresponded very well with the histological images.. Reflectance confocal microscopy was able to visualize PMN migration, accumulation, and degeneration over time in the used LTB4 model. The noninvasive character and the possibility to obtain multiple in vivo images from the same location over time make that RCM in combination with this model a useful tool to study the dynamics and function of PMN in inflammatory processes in the skin.

Topics: Adult; Animals; Dermatitis; Dermoscopy; Female; Humans; Leukotriene B4; Male; Microscopy, Confocal; Neutrophils; Reproducibility of Results; Sensitivity and Specificity; Young Adult

Scratching triggers skin flares in atopic dermatitis. We demonstrate that scratching of human skin and tape stripping of mouse skin cause neutrophil influx. In mice, this influx was largely dependent on the generation of leukotriene B4 (LTB4) by neutrophils and their expression of the LTB4 receptor BLT1. Allergic skin inflammation in response to epicutaneous (EC) application of ovalbumin to tape-stripped skin was severely impaired in Ltb4r1(-/-) mice and required expression of BLT1 on both T cells and non-T cells. Cotransfer of wild-type (WT) neutrophils, but not neutrophils deficient in BLT1 or the LTB4-synthesizing enzyme LTA4H, restored the ability of WT CD4(+) effector T cells to transfer allergic skin inflammation to Ltb4r1(-/-) recipients. Pharmacologic blockade of LTB4 synthesis inhibited allergic skin inflammation elicited by cutaneous antigen challenge in previously EC-sensitized mice. Our results demonstrate that a neutrophil-T cell axis reliant on LTB4-BLT1 interaction is required for allergic skin inflammation.

Topics: Animals; Biopsy; Dermatitis; Disease Models, Animal; Humans; Leukotriene B4; Mice; Mice, Inbred C57BL; Neutrophil Infiltration; Neutrophils; Receptors, Leukotriene B4

A critical role for leukotriene B(4) (LTB(4)) and/or platelet-activating factor (PAF) in regulating polymorphonuclear cell (PMN) trafficking to inflammatory sites has been reported in a number of experimental inflammatory models. In vitro, newly synthesized LTB(4) and PAF were shown to act in an autocrine/paracrine or intracrine fashion to enhance intracellular arachidonic acid availability and leukotriene biosynthesis. This suggested potentially cooperative effects of these lipid mediators in regulating PMN extravasation. The present study aimed to elucidate whether endogenous LTB(4) and PAF may both act to regulate plasma extravasation and PMN trafficking to inflammatory sites in experimental inflammation. With this aim, we have used selective and potent PAF and LTB(4) receptor antagonist pretreatments in dermal and pulmonary inflammation models in rats. Our results show additive inhibitory effects of dual LTB(4) and PAF receptor blockade in either PAF- or LTB(4)-elicited cutaneous PMN accumulation compared to single-drug administration. Furthermore, the combined administration of the drugs inhibited the PMN accumulation induced by the chemically unrelated soluble agonists tumour necrosis factor-alpha and C5a. Finally, in a model of pulmonary inflammation induced by the intravenous injection of Sephadex beads, lung neutrophilia was reduced by 63% following the administration of LTB(4) and PAF antagonists, in contrast with the lack of effect of single drug administration. Our results strongly support a role of both endogenous LTB(4) and PAF in regulating PMN trafficking to inflammatory sites in various experimental conditions.

Topics: Animals; Benzopyrans; Carboxylic Acids; Dermatitis; Dihydropyridines; Imidazoles; Leukotriene B4; Male; Neutrophil Infiltration; Neutrophils; Platelet Activating Factor; Platelet Membrane Glycoproteins; Pneumonia; Rats; Rats, Sprague-Dawley; Receptors, G-Protein-Coupled; Receptors, Leukotriene B4; Skin; Thiazoles

Sesquiterpene acids are natural products that, in contrast with the thoroughly studied sesquiterpene lactones, have received little pharmacological attention. A good source of this class of compounds is Inula viscosa (Asteraceae), a plant with documented anti-inflammatory effects. The present paper gives the results of our investigations on the biochemical mechanisms involved in the anti-inflammatory activity of one such compound, dehydrocostic acid. The most salient findings were that in vitro dehydrocostic acid inhibits leukotriene B(4) production (IC(50)=22 microM), elastase activity (IC(50)=43 microM) and bee venom phospholipase A(2) activity (IC(50)=17 microM). Furthermore, this sesquiterpenoid was effective on some models of acute edema induced by PLA(2) and 12-O-tetradecanoylphorbol 13-acetate (TPA) Comparison of these data with that known for ilicic acid firmly suggests that the presence of a semiplanar ring A is essential for an improved inhibitory activity on inflammatory mediators.

Topics: Animals; Anti-Inflammatory Agents; Cells, Cultured; Cyclooxygenase Inhibitors; Dermatitis; Dose-Response Relationship, Drug; Edema; Female; Inhibitory Concentration 50; Inula; Leukotriene B4; Mice; Neutrophils; Pancreatic Elastase; Phospholipases A; Plant Components, Aerial; Rats; Rats, Wistar; Sesquiterpenes; Tetradecanoylphorbol Acetate; Time Factors

Nociceptin, the endogenous peptide ligand for opioid receptor like-1 (ORL1) receptor, has been implicated in the inflammation and pain in the skin. We examined whether nociceptin is a pruritogen in mice. Intradermal injections of nociceptin (1-100 nmol per site) concentration dependently increased scratching in ICR mice; the effect started within 1 min, peaked at 10-20 min, and almost subsided by 30 min. The nociceptin action was absent in ORL1 receptor-deficient (ORL1(-/-)) mice. Systemic, but not local, treatment with naloxone significantly inhibited scratching induced by nociceptin. The action of nociceptin was inhibited by the leukotriene B(4) receptor antagonist ONO-4057 and azelastine, which inhibits the action and production of leukotriene B(4) in the skin. Prepronociceptin and ORL1 receptor mRNAs were substantially expressed in the skin, whereas their expression levels were very low in the dorsal root ganglia. In the skin, nociceptin- and ORL1 receptor-like immunoreactivities were localized in the epidermis. Administration of nociceptin to primary cultures of keratinocytes from ICR and C57BL/6 (ORL1(+/+)) mice, but not ORL1(-/-) mice, produced leukotriene B(4). The results suggest that nociceptin acts on ORL1 receptor on the keratinocytes to produce leukotriene B(4), which induces itch-associated responses in mice.

Topics: Animals; Anti-Allergic Agents; Dermatitis; Immunosuppressive Agents; Injections, Intradermal; Keratinocytes; Leukotriene B4; Male; Mice; Mice, Inbred C57BL; Mice, Inbred ICR; Mice, Mutant Strains; Naloxone; Narcotic Antagonists; Nociceptin; Nociceptin Receptor; Opioid Peptides; Phenylpropionates; Phthalazines; Protein Precursors; Pruritus; Receptors, Opioid; Terfenadine; Vasodilator Agents

Chronic granulomatous disease is the manifestation of genetic defects of the leukocyte NADPH oxidase resulting in the absence of a respiratory burst. Patients with chronic granulomatous disease can develop chronic granulomas in many locations of the body, including the skin. Using an established murine model of X-linked chronic granulomatous disease (X-CGD) created by homologous recombinant disruption of the gene encoding the gp91phox component of the NADPH oxidase, in this study we examined cutaneous reactivity to sterile Aspergillus fumigatus hyphae. Injection of Aspergillus fumigatus into the dorsal ears of X-CGD mice resulted in an enhanced inflammatory response by 24 h, consisting of neutrophils, which developed into suppurative granulomas by 10 d. Intradermal injection of Aspergillus fumigatus into wild-type mice only resulted in a transient inflammatory response that resolved by 10 d. Injection of Aspergillus fumigatus into female carrier mice resulted in an acute inflammatory response that was similar to that of wild-type mice, but, at higher doses of Aspergillus fumigatus, many carriers subsequently developed granulomatous lesions that were qualitatively similar but smaller than those seen in X-CGD mice by 30 d. Consistent with the ability of X-CGD mice to mount an enhanced neutrophil-rich inflammatory response to Aspergillus fumigatus, significant levels of the potent neutrophil activator/chemoattractant leukotriene B4 were measured by mass spectrometry in skin biopsies at 24 and 72 h. In contrast to the exaggerated inflammatory response to intradermal Aspergillus fumigatus in X-CGD mice compared to their wild-type counterparts, similar levels of inflammation were seen in a model of delayed-type hypersensitivity using 2,4-dinitrofluorobenzene. This study represents the first report of a cutaneous granuloma model in mice with X-CGD, which may also prove useful as a functional test to evaluate the efficacy of gene therapy protocols being developed for chronic granulomatous disease.

Topics: Animals; Aspergillosis; Aspergillus fumigatus; Dermatitis; Female; Granulomatous Disease, Chronic; Heterozygote; Hypersensitivity, Delayed; Leukotriene B4; Mice; Mice, Inbred C57BL; Reference Values

Studies were undertaken to define the role of 5-lipoxygenase (5-LO) products and, in particular, of leukotriene (LT) B4 in the polymorphonuclear leukocyte (PMN) emigration process using a rabbit model of dermal inflammation. Our results show that i.v. administration to rabbits of MK-0591, a compound that inhibits LT biosynthesis in blood and tissues when administered in vivo, significantly reduced 51Cr-labeled PMN accumulation in response to intradermally injected chemotactic agonists, including IL-8, FMLP, C5a, and LTB4 itself. In addition, pretreatment of the labeled PMN with MK-0591 ex vivo before their injection in recipient animals was equally effective in reducing 51Cr-labeled PMN emigration to dermal inflammatory sites. These results support a role for de novo synthesis of 5-LO metabolites by PMN for their chemotactic response to inflammatory mediators. Other studies demonstrated that elevated intravascular concentration of LTB4 interferes with PMN extravasation inasmuch as a continuous i.v. infusion of LTB4, in the range of 5-300 ng/min/kg, dose-dependently inhibited extravascular PMN accumulation to acute inflammatory skin sites elicited by the chemoattractants LTB4, FMLP, C5a, and IL-8 and by TNF-alpha, IL-1beta, and LPS; such phenomena may constitute a natural protective mechanism from massive tissue invasion by activated PMN in specific pathologic conditions such as ischemia (and reperfusion). These studies demonstrate additional functions of 5-LO products in the regulation of PMN trafficking, distinct from the well-characterized chemotactic activity of LTB4 present in the extravascular compartment.

Topics: Animals; Arachidonate 5-Lipoxygenase; Cell Movement; Chemotactic Factors; Chromium Radioisotopes; Complement C5a; Dermatitis; Indoles; Inflammation Mediators; Infusions, Intravenous; Injections, Intravenous; Leukotriene B4; Lipoxygenase Inhibitors; Male; N-Formylmethionine Leucyl-Phenylalanine; Neutrophils; Quinolines; Rabbits; Skin

Leukotriene B4 (LTB4) is a product of the 5-lipoxygenase pathway of arachidonic acid (AA) metabolism. LTB4 is a potent chemotactic factor for neutrophils and has been postulated to play an important role in a variety of pathological conditions including rheumatoid arthritis, psoriasis, and inflammatory bowel disease. To investigate the role of LTB4 in dermatitis, we used S-(4-dimethylaminobenzyl)-N-[(2S)-3-mercapto-2-methylpropionyl]-L- cysteine (SA6541), a potent leukotriene A4 (LTA4) hydrolase inhibitor. SA6541 inhibited LTB4 production with an IC50 value of 270 nM in vitro. 5-Hydroperoxyeicosatetraenoic acid (5-HPETE) or AA injection induced LTB4 production and neutrophil influx in mouse ear. SA6541 inhibited 5-HPETE- and AA-induced LTB4 production and neutrophil influx in mouse ear when administered orally at a dose of 50 mg/kg. SA6541 also inhibited 5-HPETE-induced prostaglandin E2 (PGE2) production, probably by an indirect effect through the inhibition of LTB4 production. These results suggest that LTB4 may be important in the pathogenesis of dermatitides such as psoriasis.

Topics: Aniline Compounds; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acid; Cysteine; Dermatitis; Enzyme Inhibitors; Epoxide Hydrolases; Leukotriene B4; Leukotrienes; Male; Mice; Mice, Inbred ICR

Laboratory animal models and clinical studies suggest that dietary n-3 fatty acids are beneficial in diseases with an inflammatory component such as rheumatoid arthritis or psoriasis. In the present study we investigated the effect of purified docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) on phorbol ester (TPA)-induced acute inflammation. Mice were fed for 6 weeks a diet containing 5% corn oil enriched with either 1% DHA or 1% EPA and compared with a group receiving 6% corn oil only. The dietary treatment with DHA or EPA elevated the n-3 polyunsaturated fatty acids as expected in the spleen and ear phospholipids, associated with a reduction in arachidonic acid levels. The degree of ear inflammation was quantified by measuring the four parameters including (1) edema as the increase in ear biopsy weight, (2) polymorphonuclear cell infiltration as myeloperoxidase activity (MPO) at the site of inflammation, (3) prostaglandin E2 (PGE2) and (4) leukotriene B4 (LTB4) concentrations in ear edema. The addition of DHA to the diet reduced significantly the edema formation and the MPO activity 24 h after TPA challenge. Both DHA and EPA significantly reduced the PGE2 and LTB4 levels compared with animals fed corn oil. This result suggests that DHA rather than EPA may be useful in the adjuvant treatment of diseases where acute inflammatory processes play a role.

Topics: Acute Disease; Animals; Anti-Inflammatory Agents; Dermatitis; Dinoprostone; Disease Models, Animal; Docosahexaenoic Acids; Ear, External; Edema; Eicosapentaenoic Acid; Leukotriene B4; Male; Mice; Mice, Inbred BALB C; Neutrophils; Peroxidase; Steroids; Tetradecanoylphorbol Acetate

SC-41930, 7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)propoxy]-3,4- dihydro-8-propyl-2H-1-benzopyran-2-carboxylic acid, is a selective, orally active, LTB4 receptor antagonist currently in clinical trials for psoriasis and ulcerative colitis. Exhaustive SAR studies found a potential backup compound, SC-50605, which was 7-16 times more potent than SC-41930 in LTB4 receptor binding, chemotaxis and degranulation assays. SC-50605 also inhibited LTB4-induced intradermal chemotaxis in cavine skin at an oral dose of 0.10 mg/kg and displayed good activity in animal models of colitis and epidermal inflammation both orally and topically.

Topics: Animals; Benzopyrans; Binding Sites; Cell Degranulation; Chemotaxis, Leukocyte; Colitis; Dermatitis; Disease Models, Animal; Drug Design; Guinea Pigs; In Vitro Techniques; Leukotriene B4; Mice; Receptors, Leukotriene B4; Thiazoles

ETH615 (4-[2-quinolylmethoxy]-N-[3-fluorobenzyl]-phenylaminometh yl-4-benzoic acid) is a potent inhibitor of leukotriene biosynthesis in A23187-stimulated leukocytes, and of IL-8 gene expression in LPS-stimulated PBMC. It shows anti-inflammatory activity in a canine model of dermal inflammation. A topical formulation is present in phase II clinical trials. In the present study the effect of ETH615 on oxazolone-induced acute inflammation and phorbol ester-induced chronic inflammation in the mouse ear was investigated. Betamethasone (0.04 mg/ear) and ETH615 (1-1.5 mg/ear) significantly inhibited both the oedema formation and the PMN infiltration. The cream and ointment formulations of ETH615 developed for clinical studies were equally active. ETH615 is thus an anti-inflammatory agent in these murine models of dermatosis.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Betamethasone; Dermatitis; Disease Models, Animal; Ear; Edema; Gene Expression; Interleukin-8; Leukotriene B4; Mice; Oxazolone; Peroxidase; Quinolines; T-Lymphocytes; Tetradecanoylphorbol Acetate

Vasodilatory prostaglandins (PG), contributing to the inflammatory reaction, have gained considerable attention. It is becoming apparent that PG have pharmacological effects traceable to biological activities distinct from smooth muscle relaxation. The data from pharmacological experiments presented here indicate the diverse action of vasodilatory PG analogues in the skin of laboratory animals. Nocloprost, a stable PGE2 analogue, induced erythema in intact skin of rats when applied topically and inhibited in the same dose range an irritant-induced inflammatory reaction in the ears of mice. Iloprost, a stable PGI2 analogue, showed proinflammatory activity after local application by enhancing the leukotriene B4 induced cell infiltration in the skin of mice. The attenuation of the spreading of ear necrosis in mice, on the other hand, indicates an anti-ischemic therapeutic potential of iloprost. Research in the past has elucidated the influence of PG on the vascular component of inflammation, but the role of PG on the cellular component of inflammation is less clear. The diverse effects of PG in skin indicate the need for a better understanding of their local actions.

Topics: Animals; Dermatitis; Female; Iloprost; Leukotriene B4; Male; Mice; Prostaglandins; Prostaglandins F, Synthetic; Rats; Rats, Wistar; Skin

Topical application of leukotriene-B4 (LTB4) on normal skin has been used as an in-vivo model to investigate cutaneous inflammation and epidermal proliferation, which are important phenomena in the pathogenesis of psoriasis. The aim of the present investigation is to further elucidate the interrelation between inflammation and epidermal proliferation, using specific monoclonal antibodies as markers for the different cell types involved. Aliquots of LTB4 were applied on the upperarms of eight healthy volunteers. After LTB4-application, biopsies were taken at consecutive time intervals. On frozen sections, epidermal proliferation was assessed by Ks8.12-(keratin 16) and Ki-67-binding (cycling cells), inflammation was characterized using anti-elastase (PMN), T11 (T-lymphocytes), pan-B (B-lymphocytes), WT 14 (CD14-positive cells) and OKT 6 (Langerhans cells). New observations were that the density of CD14-positive cells was increased even at 8 h and decreased slightly at 72 h. A striking rearrangement of Langerhans cells was seen in close vicinity to intra-epidermal accumulations of PMN. Remarkably an increased density of these cells in the dermis at 72 h was seen and a decrease in the epidermis. In line with previous studies, the accumulation of PMN reached a maximum 24 h after LTB4-challenge. The identity of the mononuclear infiltrate cells which have been reported 48-72 h after LTB4 proved to be T-lymphocytes. No B-lymphocytes were observed. Ki-67-positive nuclei were maximally increased 72 h after LTB4-application, which implies that recruitment of cycling cells is of relevance for the LTB4-induced proliferation in vivo. The hyperproliferation-related keratin 16 was expressed inconsistently in the suprabasal compartment.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Adult; Cell Division; Dermatitis; Female; Humans; Immunohistochemistry; Langerhans Cells; Leukotriene B4; Male; Neutrophils; Skin; T-Lymphocytes

Ammonium bituminosulphonate (Ichthyol) inhibits 5-lipoxygenase activity in human polymorphonuclear neutrophils. The inhibition is dose-dependent and occurs at non-cytotoxic concentrations of the drug. This results in a decreased release of Leukotriene B4 from polymorphonuclear neutrophils. Furthermore, when applied to the ear skin of AB/Bln mice pretreated with croton oil, Ichthyol reduces the inflammatory reaction.

Topics: Animals; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Croton Oil; Dermatitis; Dermatologic Agents; Leukotriene B4; Lipoxygenase Inhibitors; Male; Mice; Mice, Inbred Strains; Neutrophils

Topics: Animals; Cell Movement; Dermatitis; Guinea Pigs; Leukotriene B4; Mice; Molecular Structure; Peroxidase; Rats; Receptors, Immunologic; Receptors, Leukotriene B4

To estimate the pathogenesis of magnesium deficiency dermatitis (MDD) in the hairless rats fed with a hypomagnesic diet, plasma concentrations of leukotrienes (LTB4, LTC4, LTD4) were measured. Inhibitory effect of azelastine hydrochloride (AZ), which is known as an inhibitor of 5-lipoxygenase, on MDD was also evaluated. In the hairless rats with magnesium deficiency condition, plasma level of leukotriene B4 was increased, whereas LTC4 and LTD4 showed no changes. In AZ-administered rats, MDD was depressed with the dose-dependent tendency. However, the decrease of LTB4 level did not follow therapeutic effect of AZ for gross appearance of dermatitis. These results indicated that development of MDD associates with increase of LTB4, but its pathogenetic role still remains unknown, and inhibitory effect of AZ against MDD not based on reduction of LTB4 production.

Topics: Animals; Dermatitis; Female; Histamine H1 Antagonists; Leukotriene B4; Leukotrienes; Magnesium Deficiency; Phthalazines; Rats; Rats, Nude

The mode of extravasation of neutrophils (PMNs) in cutaneous inflammation was studied in sequential biopsy specimens taken from human skin. Inflammatory skin reactions were produced by intracutaneous injection of endogeneous mediators of inflammation--C5ades arg, LTB4, neutrophil-activating peptide (NAP) and interleukin-1 (IL-1). Within 30 min after injection neutrophils were observed in close contact with endothelial cells of postcapillary venules and, following cytoplasmic engulfment, the cells were found to be transported transcellulary through the endothelial layer. In a total of 20 biopsy specimens taken at various times, cell migration via interendothelial gaps was absent. Instead, the transcellular pathway appeared to be the first and foremost mode of diapedesis. During this migratory process PMNs lacked signs of degranulation and numerous electron-lucent vesicles and secondary lysosomes were found. In addition, coated pits present on leukocyte as well as endothelial-cell membranes were indicative of receptor-mediated endocytotic processes.

Topics: Cell Movement; Complement C5a, des-Arginine; Dermatitis; Endothelium, Vascular; Humans; Interleukin-1; Interleukin-8; Leukotriene B4; Neutrophils; Peptides; Skin

Intensive studies of the molecular pathways involved in common inflammatory skin disorders, coupled with detailed pharmacologic evaluation of the responses of skin to the end products of these pathways, have resulted in a much clearer understanding of the mode of action of nonsteroidal anti-inflammatory drugs. In particular the development of lipoxygenase inhibitors is prompting intense interest in their possible role as anti-inflammatory agents in psoriasis and other dermatoses. Because of the potency of these and other classes of new anti-inflammatory drugs, careful monitoring of their pharmacokinetics in individual patients, especially those at risk for adverse reactions, will prove necessary, especially in the early stages of treatment. Meanwhile, currently available nonsteroidal anti-inflammatory drugs have a limited but significant place in the treatment of certain dermatoses. Current experience of the high incidence of adverse reactions to existing nonsteroidal anti-inflammatory drugs suggests that this will be no less a problem with new agents under development. The skin is frequently involved in adverse reactions to this class of drug, and past experience suggests that cutaneous reactions are among the earliest unwanted side effects reported in a new drug of this type. The dermatologist, therefore, has an important responsibility to observe, document, and report such "early warning signs" to the appropriate licensing authority and the manufacturer.

Topics: Anti-Inflammatory Agents, Non-Steroidal; Arachidonic Acids; Aspirin; Cyclooxygenase Inhibitors; Dermatitis; Eicosanoic Acids; Humans; Ibuprofen; Leukotriene B4; Lipoxygenase Inhibitors; Propionates; Prostaglandins; Skin; Skin Diseases

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Arachidonic Acid; Arachidonic Acids; Dermatitis; Drug Tolerance; Forearm; Humans; Hydroxyeicosatetraenoic Acids; Leukotriene B4; Lipoxygenase; Psoriasis; Skin; Skin Tests; SRS-A; Time Factors

The effect of synthetic leukotriene B4 (LTB4) on chemotaxis in vivo (51Cr-polymorphonuclear leukocyte [PMN] accumulation) was examined and its potency compared with that of C5a des Arg-containing zymosan-activated plasma (ZAP). On a molar basis the amount of C5a des Arg calculated to be in our preparation of ZAP was found to be up to approximately 80 times more potent than LTB4, although in vitro the two chemotaxins have been reported to be about equipotent. ZAP is more representative of what may happen in vivo than its principal constituent C5a des Arg, but for a more precise comparison the purified and isolated peptide will have to be compared with synthetic LTB4. Whereas ZAP induced severe PMN-dependent microvascular injury (increase in vessel permeability [125I-albumin] and hemorrhage [59Fe-erythrocytes]), LTB4 only induced an increase in vascular permeability, and this occurred only in the presence of simultaneously injected prostaglandin E2 (PGE2). PGE2 also enhanced substantially the number of PMNs and the amount of exuded plasma at injection sites of the chemotaxins. However, unlike in two other reports, LTB4 did not cause an immediate transient increase in vessel permeability, nor did it enhance the permeability-increasing effect of bradykinin. Furthermore, unlike PGE2 LTB4 did not induce an increase in blood flow, but a decrease (57Co-microspheres). It is concluded that LTB4 may act as a host-derived chemoattractant in vivo, but, compared with that of ZAP (primarily activated complement), its role in acute inflammation is probably less significant than that of the complement-derived chemotaxin(s).

Topics: Animals; Capillary Permeability; Cell Movement; Chemotactic Factors; Complement C5; Complement C5a, des-Arginine; Dermatitis; Dinoprostone; Female; Hemorrhage; Leukotriene B4; Microcirculation; Neutrophils; Prostaglandins E; Rabbits; Regional Blood Flow; Scintillation Counting; Zymosan

Topics: Animals; Capillary Permeability; Dermatitis; Dinoprostone; Dose-Response Relationship, Drug; Female; Guinea Pigs; Leukotriene B4; Leukotriene E4; Male; Prostaglandins E; Rabbits; Skin; SRS-A

In vitro monocyte chemotaxis towards leukotriene B4(LTB4) and platelet activating factor (PAF) was studied with cells from 51 patients with various inflammatory dermatoses and 12 normal volunteers. Monocytes from normal subjects responded poorly to LTB4 (10(-8)-10(-12) M) and PAF (10(-6)-10(-10) M), and cells from patients with urticaria pigmentosa and vericella were even less responsive, while monocytes from patients with severe psoriasis and atopic eczema exhibited markedly enhanced chemotaxis. These changes persisted during high dose therapy with oral steroids, but returned to normal with healing of the skin lesions. Pre-incubation of monocytes with histamine, LTB4, PAF, lymphokines or sera from patients and normal controls did not result in enhanced chemotaxis of the cells. The chemotactic activity of monocytes did not correlate with that of neutrophils in the same patients (r = 0.08). Altered monocyte chemotaxis in patients with inflammatory dermatoses is therefore a reversible process that is related to the severity of the cutaneous inflammation but is not limited to a specific disease.

Topics: Adolescent; Adult; Cells, Cultured; Chemotaxis, Leukocyte; Child; Dermatitis; Dermatitis, Atopic; Dose-Response Relationship, Immunologic; Female; Humans; Leukotriene B4; Male; Monocytes; Platelet Activating Factor; Psoriasis; Urticaria