leukotriene-b4 and Dermatitis--Contact

Coconut oil is used as a dietary oil worldwide, and its healthy effects are recognized by the fact that coconut oil is easy to digest, helps in weight management, increases healthy cholesterol, and provides instant energy. Although topical application of coconut oil is known to reduce skin infection and inflammation, whether dietary coconut oil has any role in decreasing skin inflammation is unknown. In this study, we showed the impact of dietary coconut oil in allergic skin inflammation by using a mouse model of contact hypersensitivity (CHS). Mice maintained on coconut oil showed amelioration of skin inflammation and increased levels of cis-5, 8, 11-eicosatrienoic acid (mead acid) in serum. Intraperitoneal injection of mead acid inhibited CHS and reduced the number of neutrophils infiltrating to the skin. Detailed mechanistic studies unveiled that mead acid inhibited the directional migration of neutrophils by inhibiting the filamentous actin polymerization and leukotriene B

Topics: 8,11,14-Eicosatrienoic Acid; Actins; Animals; Biomarkers; Capillary Permeability; Chemotaxis; Coconut Oil; Dermatitis, Atopic; Dermatitis, Contact; Dietary Fats, Unsaturated; Disease Models, Animal; Female; Immunohistochemistry; Immunophenotyping; Leukotriene B4; Lipid Metabolism; Mice; Neutrophils; Skin

Leukotriene B4 (LTB4 ) is a lipid mediator that is rapidly generated in inflammatory sites, and its functional receptor, BLT1, is mostly expressed on immune cells. Contact dermatitis is a common inflammatory skin disease characterized by skin oedema and abundant inflammatory infiltrates, primarily including neutrophils and CD8(+) T cells. The role of the LTB4 -BLT1 axis in contact dermatitis remains largely unknown. In this study, we found up-regulated gene expression of 5-lipoxygenase and leukotriene A4 hydrolase, two critical enzymes for LTB4 synthesis, BLT1 and elevated LTB4 levels in skin lesions of oxazolone (OXA)-induced contact dermatitis. BLT1 deficiency or blockade of LTB4 and BLT1 by the antagonists, bestatin and U-75302, respectively, in the elicitation phase caused significant decreases in ear swelling and skin-infiltrating neutrophils and CD8(+) T cells, which was accompanied by significantly reduced skin expression of CXCL1, CXCL2, interferon-γ and interleukin-1β. Furthermore, neutrophil depletion during the elicitation phase of OXA-induced contact dermatitis also caused significant decreases in ear swelling and CD8(+) T-cell infiltration accompanied by significantly decreased LTB4 synthesis and gene expression of CXCL2, interferon-γ and interleukin-1β. Importantly, subcutaneous injection of exogenous LTB4 restored the skin infiltration of CD8(+) T cells in neutrophil-depleted mice following OXA challenge. Collectively, our results demonstrate that the LTB4 -BLT1 axis contributes to OXA-induced contact dermatitis by mediating skin recruitment of neutrophils, which are a major source of LTB4 that sequentially direct CD8(+) T-cell homing to OXA-challenged skin. Hence, LTB4 and BLT1 could be potential therapeutic targets for the treatment of contact dermatitis.

Topics: Animals; Arachidonate 5-Lipoxygenase; CD8-Positive T-Lymphocytes; Chemokine CXCL1; Chemokine CXCL2; Dermatitis, Contact; Epoxide Hydrolases; Fatty Alcohols; Female; Glycols; Inflammation; Interferon-gamma; Interleukin-1beta; Leucine; Leukotriene B4; Mice; Mice, Inbred C57BL; Mice, Knockout; Neutrophils; Oxazolone; Receptors, Leukotriene B4; Skin

Resolvin E1 (RvE1) is a lipid mediator derived from ω3 polyunsaturated fatty acids that exerts potent antiinflammatory roles in several murine models. The antiinflammatory mechanism of RvE1 in acquired immune responses has been attributed to attenuation of cytokine production by dendritic cells (DCs). In this study, we newly investigated the effect of RvE1 on DC motility using two-photon microscopy in a contact hypersensitivity (CHS) model and found that RvE1 impaired DC motility in the skin. In addition, RvE1 attenuated T cell priming in the draining lymph nodes and effector T cell activation in the skin, which led to the reduced skin inflammation in CHS. In contrast, leukotriene B4 (LTB4) induced actin filament reorganization in DCs and increased DC motility by activating Cdc42 and Rac1 via BLT1, which was abrogated by RvE1. Collectively, our results suggest that RvE1 attenuates cutaneous acquired immune responses by inhibiting cutaneous DC motility, possibly through LTB4-BLT1 signaling blockade.

Topics: Actins; Animals; Cell Movement; Cells, Cultured; Dendritic Cells; Dermatitis, Contact; Eicosapentaenoic Acid; Female; Interferon-gamma; Leukotriene B4; Mice; Mice, Inbred C57BL; Receptors, Leukotriene B4; Skin

Contact sensitivity (CS) is one of the primary in vivo models of T cell-mediated inflammation. The presence of CS-initiating CD4 T lymphocytes at the time of challenge is essential for transfer and full development of the late phase CS inflammatory response. From this observation investigators have speculated that early recruitment of CD4 T cells to the site of challenge must occur. Moreover, there must be rapid synthesis/release and disappearance of an important mediator during the first hours after hapten challenge. Using spinning disk confocal microscopy, we observed the very early effector events of the immune response. Simultaneous, real-time visualization of predominant neutrophil and extremely rare CD4 T cell trafficking in the challenged skin vasculature was noted (one rolling CD4 T cell for every 10-18 rolling and adherent neutrophils). We demonstrate that neutrophil adhesion during the early CS response was reduced in C5a receptor-deficient (C5aR-/-) mice or leukotriene B4 receptor antagonist-treated mice, whereas CD4 T cell recruitment was only inhibited in C5aR-/- mice. In line with these observations, leukocyte infiltration and the associated tissue damage were significantly reduced in C5aR-/- mice but not in leukotriene B4 receptor antagonist-treated wild-type mice 24 h after challenge. C5a receptor expression on T cells and not on tissue resident cells was important for the development of a CS response. Thus, by using spinning disk confocal microscopy we visualized the early events of an adaptive immune response and identified the rare but essential recruitment of CD4 T cells via the complement pathway.

Topics: Animals; Blood Vessels; CD4-Positive T-Lymphocytes; Cell Adhesion; Cell Movement; Complement C5a; Dermatitis, Contact; Leukotriene B4; Mice; Mice, Mutant Strains; Microscopy, Fluorescence; Neutrophils; Receptor, Anaphylatoxin C5a; Skin

Arachidonic acid metabolism by 5-lipoxygenase leads to production of the potent inflammatory mediators, leukotriene (LT) B4 and the cysteinyl LT. Relative synthesis of these subclasses of LT, each with different proinflammatory properties, depends on the expression and subsequent activity of LTA4 hydrolase and LTC4 synthase, respectively. LTA4 hydrolase differs from other proteins required for LT synthesis because it is expressed ubiquitously. Also, in vitro studies indicate that it possesses an aminopeptidase activity. Introduction of cysteinyl LT and LTB4 into animals has shown LTB4 is a potent chemoattractant, while the cysteinyl LT alter vascular permeability and smooth muscle tone. It has been impossible to determine the relative contributions of these two classes of LT to inflammatory responses in vivo or to define possible synergy resulting from the synthesis of both classes of mediators. To address this question, we have generated LTA4 hydrolase-deficient mice. These mice develop normally and are healthy. Using these animals, we show that LTA4 hydrolase is required for the production of LTB4 in an in vivo inflammatory response. We show that LTB4 is responsible for the characteristic influx of neutrophils accompanying topical arachidonic acid and that it contributes to the vascular changes seen in this model. In contrast, LTB4 influences only the cellular component of zymosan A-induced peritonitis. Furthermore, LTA4 hydrolase-deficient mice are resistant to platelet-activating factor, identifying LTB4 as one mediator of the physiological changes seen in systemic shock. We do not identify an in vivo role for the aminopeptidase activity of LTA4 hydrolase.

Topics: Acute Disease; Anaphylaxis; Animals; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Cell Movement; Crosses, Genetic; Cysteine; Dermatitis, Contact; Ear; Epoxide Hydrolases; Fluorescein-5-isothiocyanate; Immunoglobulin E; Inflammation Mediators; Leukotriene B4; Leukotrienes; Lipopolysaccharides; Mice; Mice, Knockout; Neutrophils; Peritonitis; Platelet Activating Factor

The ability of azaspiranes to modulate the acute inflammatory response in models of skin inflammation was examined.. The in vivo experiments involved the use of 5-6 age-matched male Balb/c inbred mice (22-25 g) per treatment group and a control group of 8-10 animals. In vitro mechanistic studies used RBL-1 and U937 cells lines and freshly isolated human monocytes.. Arachidonic acid (AA) (2 mg/20 microl in acetone) or PMA (phorbol myristate acetate) (4 microg/20 microl) were applied topically. SK&F 106615 and SK&F 106610 were administered topically either dissolved in acetone or dimethylacetamide just after the application of the irritant. Isolated cells were treated with the compounds dissolved in DMSO.. The thickness and influx of neutrophils into the treated ears was measured as was the effects of the azaspiranes on 5-lipoxygenase activity, cyclooxygenase activity, prostaglandin and leukotriene synthesis, and the activation of the transcription factor NF-kappaB.. SK&F 106615 and SK&F 106610 significantly reduced inflammation in the AA- and PMA-induced inflammation models (p < 0.05) with ED50's of 179 and 120 mg/ear for edema and myeloperoxidase, respectively. The compounds did not inhibit eicosanoid biosynthesis, have a direct effect on 5-lipoxygenase or cyclooxygenase enzymes, or inhibit NF-kappaB.. The potent anti-inflammatory and immunomodulatory activities of the azaspiranes observed in these and other studies appear to be mediated by a novel mechanism.

Topics: Administration, Topical; Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonate 5-Lipoxygenase; Arachidonic Acid; Cell Line; Cyclooxygenase 1; Dermatitis, Contact; Dinoprostone; Ear; Edema; Humans; Immunosuppressive Agents; Isoenzymes; Leukotriene B4; Male; Membrane Proteins; Mice; Mice, Inbred BALB C; Monocytes; NF-kappa B; Peroxidase; Piperidines; Prostaglandin-Endoperoxide Synthases; Spiro Compounds; Tetradecanoylphorbol Acetate

We investigated the effects of S-(4-dimethylaminobenzyl)-N-[(2S)-3-mercapto-2-methylpropionyl]-L- cysteine (SA6541), a potent leukotriene A4 hydrolase inhibitor. on early phase of carrageenan-induced dermatitis model. Carrageenan injection induced edema and neutrophil influx in the mouse ear. SA6541 inhibited edema formation and neutrophil influx. SA6541 also inhibited leukotriene B4 production but not prostaglandin E2 production in the mouse ear. On the other hand, indomethacin inhibited edema formation but not neutrophil influx. Indomethacin also inhibited prostaglandin E2 production but not leukotriene B4 production. Combination therapy with SA6541 and indomethacin strongly inhibited edema formation in comparison with treatment with either agent alone. These results suggest that leukotriene B4 may be important in the pathogenesis of dermatitis.

Topics: Aniline Compounds; Animals; Carrageenan; Cysteine; Dermatitis, Contact; Edema; Enzyme Inhibitors; Epoxide Hydrolases; Indomethacin; Leukotriene B4; Male; Mice; Mice, Inbred ICR

In the present investigation, the effects of selective inhibitors of 5-lipoxygenase (5-LO), zileuton and TZI-41127, E-6080, AA-861 and antagonists of leukotriene B4 (LTB4) receptors, SC-41930, and SC-51146 and a selective cyclooxygenase inhibitor, indomethacin, were examined in TPA-induced acute mouse dermal inflammation. Topical application of all these agents, except indomethacin, resulted in marked attenuation of TPA-induced edema and influx of neutrophils reflected in myeloperoxidase measurements. Topically applied SC-41930 attenuated TPA-induced edema and neutrophil influx in a dose-related manner. Oral administration of LTB4 receptor antagonists either as a pre-treatment or post-treatment attenuated TPA-induced edema and influx of neutrophils. The O-demethyl analog of SC-41930, SC-37920, which was nearly 1000-fold less active than SC-41930 in LTB4 receptor binding assays, was inactive in inflammation assays, suggesting a role for LTB4 in this response. Zileuton and TZI-41127 were more effective as anti-inflammatory agents following oral administration than after i.p. administration. Intraperitoneally administered indomethacin attenuated edema response but not influx of neutrophils. Taken together, these results suggest a role for leukotrienes in acute inflammation induced by TPA and possible utility of this model to test in vivo 5-LO inhibitors and LTB4 receptor antagonists.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Arachidonate 5-Lipoxygenase; Benzamides; Benzopyrans; Dermatitis, Contact; Disease Models, Animal; Drug Evaluation, Preclinical; Female; Indomethacin; Leukotriene B4; Lipoxygenase Inhibitors; Male; Mice; Mice, Inbred BALB C; Receptors, Leukotriene B4; Tetradecanoylphorbol Acetate

A topical application of 12-O-tetradecanoylphorbol-13-acetate (TPA) to mouse ear surface induces nonallergic inflammation, i.e. ear edema. Oral administration of 3-30 mg/kg of 1-([5'-(3"-methoxy-4"-ethoxycarbonyloxyphenyl)-2',4'-pentadieno yl]-aminoethyl)-4-diphenylmethoxypiperidine (TMK 688), a potent 5-lipoxygenase inhibitor with antihistamine activity, inhibited TPA-induced ear edema in a dose-dependent manner. TMK688 inhibited not only 5-lipoxygenase activity but also epidermal cyclooxygenase activity. 1-([5'-(3"-methoxy-4"-hydroxyphenyl)-2',4'-pentadienoyl]-aminoe thy l)- 4-diphenylmethoxypiperidine (TMK777), an active metabolite of TMK688, had more potent 5-lipoxygenase inhibitory activity but less potent cyclooxygenase inhibitory activity than TMK688. Oral administration of TMK688 (30 mg/kg) markedly inhibited TPA-stimulated LTB4 formation in mouse skin but TPA-stimulated PGE2 formation only slightly. Our experimental results suggest that both cyclooxygenase inhibitory activity and antihistamine activity of TMK688 are not essential to its anti-inflammatory action. The anti-inflammatory effect of orally administered TMK688 is due most probably to the anti-5-lipoxygenase activity of TMK688 and its active metabolite TMK777.

Topics: Administration, Oral; Animals; Anti-Inflammatory Agents, Non-Steroidal; Cells, Cultured; Cyclooxygenase Inhibitors; Dermatitis, Contact; Dinoprostone; Dose-Response Relationship, Drug; Female; Leukotriene B4; Lipoxygenase Inhibitors; Mice; Piperidines; Tetradecanoylphorbol Acetate

Systemic pretreatment of rabbits with dexamethasone results in a time-dependent inhibition of oedema responses caused by intradermal injection of both 'direct-acting' and 'neutrophil-dependent' stimuli. Local injection of actinomycin D, an inhibitor of RNA synthesis, inhibits this effect. Our studies suggest that a major action of dexamethasone in this model may be a local inhibition of increased permeability of the vascular endothelium.

Topics: Animals; Bradykinin; Dactinomycin; Dermatitis, Contact; Dexamethasone; Dinoprostone; Female; Histamine; Leukotriene B4; Male; N-Formylmethionine Leucyl-Phenylalanine; Platelet Activating Factor; Protein Biosynthesis; Rabbits; RNA; Skin; Zymosan

Topics: Acne Vulgaris; Arachidonic Acid; Arachidonic Acids; Capillary Permeability; Dermatitis, Atopic; Dermatitis, Contact; Humans; Leukotriene B4; Lipoxygenase; Lymphocytes; Phagocytes; Psoriasis; Skin; Skin Diseases; SRS-A; Urticaria

A new method is described allowing the quantitative and kinetic analysis, in vivo in human skin, of the chemotaxis of inflammatory cells, of the modifications of vascular permeability and of the histological and cytological events induced by certain mediators of inflammation. In order to illustrate the usefulness of the method, the effects of chronic contact to human skin of two potent mediators of inflammation, LTB4 and Paf-acether, are described.

Topics: Capillary Permeability; Chemotaxis, Leukocyte; Dermatitis, Contact; Humans; Leukotriene B4; Methods; Platelet Activating Factor; Skin

Increased concentrations of arachidonic acid and prostaglandin E2, but not 12-hydroxy-eicosatetraenoic acid, were found in the skin in human contact dermatitis due to nickel and chromate allergens. Significant levels of neutrophil chemokinetic activity, with similar properties to leukotriene B4, were found in a high proportion of exudates from inflamed skin treated with allergen but not in exudates from untreated skin. Neither arachidonic acid nor its metabolites were increased in primary irritant dermatitis due to benzylalkonium chloride.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Adolescent; Adult; Arachidonic Acid; Arachidonic Acids; Benzalkonium Compounds; Dermatitis, Contact; Dinoprostone; Exudates and Transudates; Female; Humans; Irritants; Leukotriene B4; Male; Nickel; Potassium Dichromate; Prostaglandins E; Skin