calcimycin and Psoriasis

The purpose of the present study was to develop an ex vivo skin model to determine the capacity of lesional skin of psoriasis to form leukotriene B4 and other eicosanoids. Keratomed skin samples were incubated in the presence of the calcium ionophore A23187 and arachidonic acid for 45 min at 37 degrees C. After extraction of lipids, eicosanoids were determined by quantitative reversed-phase high-performance liquid chromatography in combination with specific radioimmunoassays. We found that stimulation of skin samples with A23187 and arachidonic acid increased the amount of leukotriene B4 4.0-fold. The 12-lipoxygenase product, 12-hydroxy-eicosatetraenoic acid, and the 15-lipoxygenase product, 15-hydroxy-eicosatetraenoic acid, were both increased 2.7-fold. The cyclooxygenase product, prostaglandin E2, was increased 8.0-fold. Similar incubations using psoriatic scales did not result in formation of eicosanoids. Incubations with the 5-lipoxygenase inhibitor RS43179 inhibited the formation of leukotriene B4 and prostaglandin E2 without significantly affecting the formation of 12-hydroxy-eicosatetraenoic acid and 15-hydroxy-eicosatetraenoic acid. These results reveal that lesional psoriatic skin ex vivo has the enzymatic capacity to increase the levels of eicosanoids. This provides an ex vivo skin model to determine whether putative lipoxygenase inhibitors are able to modulate the formation of eicosanoids in psoriatic skin.

Topics: 12-Hydroxy-5,8,10,14-eicosatetraenoic Acid; Arachidonic Acid; Calcimycin; Chromatography, High Pressure Liquid; Dinoprostone; Eicosanoids; Humans; Hydroxyeicosatetraenoic Acids; In Vitro Techniques; Leukotriene B4; Lipoxygenase Inhibitors; Naphthalenes; Psoriasis; Radioimmunoassay; Skin

Insulin-like growth factor I (IGF-I)/somatomedin C is an important mediator of keratinocyte growth in vitro, and the expression of IGF-I receptors in the basal layer of normal epidermis suggests that this growth pathway may function in the regulation of keratinocyte growth in vivo as well. The pattern of IGF-I receptor expression in normal skin is distinct from that of the epidermal growth factor (EGF) receptor, suggesting that these receptors might be differentially regulated. The purpose of this study was to obtain a better understanding of IGF-I receptor function in the skin by examining IGF-I receptor expression in psoriatic epidermis and in cultured human keratinocytes. Our findings indicate that IGF-I receptor expression is increased in psoriasis as measured by protein tyrosine kinase assays of biopsy extracts and by immunohistochemical staining with an IGF-I receptor-specific monoclonal antibody. Unlike EGF receptor expression, which is also increased in psoriatic epidermis, the pattern of IGF-I receptor expression corresponds closely with the increased size of the keratinocyte proliferative compartment in psoriasis. Biochemical agents that diminish EGF receptor ligand binding (phorbol ester or calcium ionophore treatment) produce opposite effects on the IGF-I receptor. These results suggest that cellular expression and differential regulation of both growth factor receptor systems may control critical aspects of epidermal proliferation or function.

Topics: Antibodies, Monoclonal; Calcimycin; Epidermal Growth Factor; Epidermis; ErbB Receptors; Humans; Insulin-Like Growth Factor I; Keratinocytes; Precipitin Tests; Protein Kinases; Psoriasis; Receptors, Cell Surface; Receptors, Somatomedin; Tetradecanoylphorbol Acetate

Topics: Calcimycin; Dinoprostone; HEPES; Humans; Inflammation; Leukotriene B4; Luminescent Measurements; Neutrophils; Psoriasis; Reference Values; Skin Diseases; Taurine

We evaluated the metabolism of exogenous arachidonic acid in polymorphonuclear leukocytes from psoriatic patients in comparison with those from normal subjects. The leukocytes were incubated with 10 microM labelled arachidonic acid and 5 microM A23187 for varying periods of time. We evaluated all the compounds derived from the 5-lipoxygenase activity, including the products of non-enzymatic transformation of leukotriene A4 and w-oxidized leukotriene B4. In the experimental conditions used, there was no significant difference in the formation of any compound at any time of incubation. These results indicate that there is no intrinsic alteration either in 5-lipoxygenase activity or in w-oxidation ability of circulating polymorphonuclear leukocytes in psoriatic patients.

Topics: Adult; Arachidonic Acids; Calcimycin; Female; Humans; Leukotrienes; Male; Middle Aged; Neutrophils; Psoriasis

Neutrophil (PMNL) infiltration is a prominent feature of human psoriasis. Psoriatic skin lesions contain abnormally high amounts of leukotriene B4 (LTB4), itself a potent PMNL chemoattractant both in vivo and in vitro. SC-41930 (7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)-propoxy]-3,4-dihydro-8- propyl-2H-1-benzopyran-2-carboxylic acid), an orally active LTB4 receptor antagonist, was tested topically in models of skin inflammation induced by 200 nmol of the calcium ionophore A23187 or 200 micrograms phorbol-12-myristate-13-acetate (PMA) applied topically to the guinea pig ear as assessed by ear weight, levels of the PMNL marker enzyme myeloperoxidase (MPO), and histological examination (PMA model) at 4 and 18 h respectively. When coapplied topically with A23187 or PMA, SC-41930 significantly inhibited epidermal inflammation with ED50 values of 0.6 and 4 mg, respectively. SC-41930 treatment also was associated with lowered dermal LTB4 levels in both models. The PMA-induced skin inflammation model also was assessed histologically and revealed acanthosis, edema, PMNL infiltration, and rete ridge prominence as long as 96 h after a single application that was completely inhibited by SC-41930 topical coapplication. Furthermore, oral treatment (40 mg/kg) significantly reduced edema and inflammatory cell infiltration in both models. These models possess many of the characteristics of human psoriasis, and agents such as SC-41930 that demonstrate activity in these models may well have therapeutic utility in the treatment of human psoriasis.

Topics: Administration, Cutaneous; Animals; Benzopyrans; Calcimycin; Disease Models, Animal; Guinea Pigs; Inflammation; Male; Psoriasis; Receptors, Immunologic; Receptors, Leukotriene B4; Skin; Tetradecanoylphorbol Acetate

Topics: Adult; Aged; Arachidonate 5-Lipoxygenase; Calcimycin; Eicosapentaenoic Acid; Erythema; Female; Glucuronidase; Humans; In Vitro Techniques; Kinetics; Leukotriene B4; Male; Middle Aged; Neutrophils; Psoriasis; Skin

The formation of leukotriene B4 and its omega-oxidised metabolites has been compared in calcium ionophore-stimulated polymorphonuclear leukocytes, in the absence of exogenous substrate, from fourteen psoriatic subjects and thirteen healthy controls. Although there was no significant difference in the levels of leukotriene B4, the psoriatic cells synthesised significantly greater amounts of omega-oxidation products than control cells. This difference was confirmed in an experiment comparing the time course of formation of the omega-oxidation products of leukotriene B4, under similar conditions, in polymorphonuclear leukocytes from four psoriatic subjects and three healthy controls. The kinetic constants for the metabolism of exogenous leukotriene B4 by 20-hydroxylase were determined by a radiochromatographic enzyme assay in polymorphonuclear leukocytes from three patients with psoriasis and three healthy controls. No significant differences were found in the apparent Km and Vmax values. It is concluded that the increased formation of omega-oxidation products in psoriatic cells may be secondary to increased synthesis of leukotriene B4 by these cells, with consequent increased metabolism, rather than to an inherent abnormality of the 20-hydroxylase system. Further work is needed to determine the kinetics of the enzymes involved in leukotriene B4 synthesis in the psoriatic polymorphonuclear leukocyte, and also to assess the contribution of the leukotriene B4 and omega-oxidation products from polymorphonuclear leukocytes infiltrating the skin to the pathogenesis of the psoriatic lesion.

Topics: Adult; Calcimycin; Cytochrome P-450 Enzyme System; Cytochrome P450 Family 4; Female; Humans; Kinetics; Leukotriene B4; Male; Mixed Function Oxygenases; Neutrophils; Oxidation-Reduction; Psoriasis

The metabolism of endogenous arachidonic acid by human polymorphonuclear leukocytes (PMNL) isolated from peripheral blood has been studied in 19 patients with chronic plaque psoriasis and 19 healthy controls. Using calcium ionophore A23187 as a stimulus, the PMNL synthesized leukotriene B4 (LTB4), 6-trans-leukotriene B4, 12-epi-6-trans-LTB4, and 5-hydroxy-6,8,11,14-eicosatetraenoic acid. There was no significant difference in the amounts of the products formed between the psoriatic and control groups. The elevated levels of LTB4 that have been described in psoriatic skin may therefore be due to the PMNL infiltrate or to enhanced synthesis by another cell type. The reported increase in activity of the circulating PMNL in psoriasis does not appear to be due to increased 5-lipoxygenase activity in these cells.

Topics: Adult; Arachidonate Lipoxygenases; Arachidonic Acid; Arachidonic Acids; Calcimycin; Chromatography, High Pressure Liquid; Chronic Disease; Female; Humans; Leukotriene B4; Lipoxygenase; Male; Middle Aged; Neutrophils; Psoriasis