Topical steroid treatment reduces arachidonic acid and leukotriene B4 in lesional skin of psoriasis

Cytochrome p450: a target for drug development for skin diseases

Enzymes of the cytochrome P450 (P450 or CYP) super family are the most versatile and important class of drug-metabolizing enzymes that are induced in mammalian skin in response to xenobiotic exposure. At the same time, CYP have numerous important roles in endogenous and exogenous substrate metabolism in the skin. For example, they participate in the metabolism of therapeutic drugs, fatty acids, eicosonoids, sterols, steroids, vitamin A, and vitamin D, to name a few. In addition, in some skin diseases, for example in psoriasis, many CYP are elevated. CYP are the target of special interest in the development of drugs for skin diseases because most, if not all, drugs available in the armamentarium of the dermatologists are either substrate, inducer, or inhibitor of this enzyme family. The functional significance of drug metabolism in skin and the implication of CYP in skin pathology and therapy is an area for future investigation. A detailed insight into the mechanism of action of various cutaneous CYP, being capable of modulating the drug bioavailability, will be helpful in the development of better strategies for novel therapy against constantly increasing skin disorders. This brief review discusses some of these perspectives and suggests additional work in this research area with regard to the expression and modulation of CYP in mammalian skin as well as their implication in dermatological disorders and the therapy of skin diseases.

Increased serum leukotriene B4 level in the active stage of rheumatoid arthritis in children

The possible association of leukotriene B4 (LTB4)-like activity with the development of active rheumatoid arthritis was studied in 25 children with the disease and in 15 normal subjects. Serum LTB4-like activity was found to be significantly higher in the active stage of the disease when compared with the values obtained from patients during the inactive stage and from healthy children. No correlation was found between LTB4-activity and other laboratory parameters, e.g. haemoglobin level, white cell count and erythrocyte sedimentation rate.

Dibenzoxepinone hydroxylamines and hydroxamic acids: dual inhibitors of cyclooxygenase and 5-lipoxygenase with potent topical antiinflammatory activity

Hydroxylamine and hydroxamic acid derivatives of a known nonsteroidal antiinflammatory dibenzoxepine series display both cyclooxygenase (CO) and 5-lipoxygenase (5-LO) inhibitory properties. Many of these new dual CO/5-LO inhibitors also exhibit potent topical antiinflammatory activity in the arachidonic acid-induced murine ear edema model. On the basis of their promising profile of in vitro and in vivo activities, hydroxamic acids 24h, 3-(6,11-dihydro-11-oxodibenz[b,e]oxepin-2-yl)-N-hydroxy-N-++ +methylpropanamide (HP 977), and 25, 3-(6,11-dihydrodibenz[b,e]oxepin-2-yl)-N-hydroxy-N- methylpropanamide (P10294), were selected as developmental candidates for the topical treatment of inflammatory skin disorders.

Platelet activating factor, lyso-platelet activating factor and arachidonic acid release in normal human skin and the influence of topical steroid treatment

1. Previous, in vitro, studies have established the synthesis of platelet activating factor (PAF) by the 're-modelling' pathways in which the activation of a phospholipase A2 (PLA2) enzyme catalyses the hydrolysis of an ether-acyl-phosphocholine to give concomitant release of lyso-PAF, the immediate precursor of PAF, and arachidonic acid, the precursor of the icosanoids. The aim of this study was to investigate the relationship between PAF and eicosanoid release in human skin, and to study the effect of treatment of skin with a topical steroid, on the release of PAF, lyso-PAF and arachidonic acid. 2. A novel assay procedure was developed for the simultaneous assay of PAF and lyso-PAF in skin exudates from abrasions and suction blisters in normal human skin. In addition we assayed arachidonic acid and prostaglandin E2 (PGE2), a representative eicosanoid. 3. The mean amounts of mediator recovered in the first 30 min period following abrasion were PAF 0.43, lyso-PAF 11.9, PGE2 25.7 and arachidonic acid 760 pmol/sample. The molar ratio of PAF:lyso-PAF:arachidonic acid in skin exudates from abrasions was 1:30:1800 and in suction blister exudates was 1:90:3660. 4. Time course studies showed a decline in the recoveries of arachidonic acid and lyso-PAF, of about 50% in 2 h. In contrast, PAF was recovered in exudates at a constant rate over 2 h but PGE2 release decreased by more than 90% after the initial 30 min period. 5. Topical application under occlusion, of 0.05% clobetasol propionate, a potent corticosteroid, significantly reduced lyso-PAF by 30% in suction blister exudates but did not significantly alter the concentrations of PAF or arachidonic acid.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of eicosanoid biosynthesis by glucocorticoids in humans

Therapeutic doses of glucocorticoids are thought to inhibit prostaglandin and leukotriene formation in humans. Several studies in animals, however, have failed to demonstrate modulation of eicosanoid biosynthesis by steroids in vivo. We administered prednisone (60 mg/day) to eight healthy volunteers and measured eicosanoid formation by a variety of cell types in vivo and ex vivo, using sensitive and specific physicochemical assays. We found that the in vivo course of prednisone failed to inhibit the synthesis of thromboxane A2, prostaglandin I2 (prostacyclin), prostaglandin E2, and leukotriene E4 in vivo and of leukotriene B4 ex vivo. Biosynthesis of leukotriene B4, thromboxane B2, and prostaglandins F2 and E2 by macrophage-rich bronchoalveolar lavage cells was strongly suppressed. These findings indicate that therapeutic regimens of glucocorticoids suppress eicosanoid biosynthesis in human macrophages but not in a number of other cell types with steroid receptors, the capacity for eicosanoid formation, and lipocortin-like material.

Potent and selective inhibition of in vitro lymphocyte migration by cyclosporine and dexamethasone

We have studied the in vitro effects of cyclosporine A (CsA) and dexamethasone on lymphocyte migration, which is considered to play an important role in the pathogenesis of inflammatory and auto-immune disorders. Using a 48-well microchemotaxis assay, dose-related migratory responses of mixed peripheral blood lymphocytes (PBL) to recombinant interleukin (rIL)-1 alpha, rIL-2, leukotriene B4 (LTB4) and zymosan activated plasma (ZAP) were demonstrated. When preincubated with PBL under plasma free conditions and in the presence of undiluted autologous plasma, CsA in the dose range 4 x 10(-13)-1.6 x 10(-7) M caused concentration related inhibition of lymphocyte migration in response to fixed concentrations of rIL-1 alpha and rIL-2. CsA in the same dose range had no effect on the migration of PBL in response to ZAP and LTB4. Under plasma-free conditions dexamethasone (1 x 10(-11)-4 x 10(-6) M) caused concentration related inhibition of PBL migration in response to rIL-1 alpha and LTB4, but had no effect on the responses to rIL-2 and ZAP. These data provide evidence that CsA and dexamethasone are potent and selective inhibitors of in vitro lymphocyte migration, effects which may contribute to their therapeutic efficacy in vivo.

Effect of dithranol treatment on arachidonic acid and its lipoxygenase products in psoriasis

The concentrations of arachidonic acid and its lipoxygenase metabolites were measured in exudates from lesional psoriatic skin during treatment with 0.25% dithranol (anthralin) applied topically for 10 days. Dithranol caused a reduction in the concentration of arachidonic acid at 10 days (167 +/- 42 and 358 +/- 55 ng ml-1 treated and control sites respectively, p less than 0.05) concurrent with clinical improvement of the lesions. Neither 12-hydroxyeicosatetraenoic acid nor leukotriene B4 concentrations were significantly affected. These results do not support the view that lipoxygenase products are of major importance in the pathogenesis of psoriasis.