Abstract: Objective To explore the regulatory mechanism of inducible nitric oxide synthetase (iNOS) expression in lesional skin of psoriasis. Methods The expression of tumor necrosis factor α(TNFα), nuclear factor κB (NF κB) and iNOS was detected by immunohistochemical technique. Results Fifteen skin samples of healthy controls did not express NF κB, 5 of them expressed TNFαin hair follicles, sweat glands, sebaceous glands or arrectores pilorum, 9 of them slightly and evenly expressed iNOS in all layers of epidermis, 5 of them also slightly expressed iNOS on mononuclear cells (MNCs) in dermis. The TNFα, NF κB and iNOS were expressed on epidermal keratinocytes and dermal MNCs, and strongly expressed in Munro's microabscess in lesional skin of 26 cases of psoriasis vulgaris. The intensity of expression of TNFαand iNOS was significantly correlated between keratinocytes and dermal MNCs (r_s'were 0.526 and 0.665, respectively, P<0.01 and 0.001, respectively), and the intensity of expression of NF κB was not correlated to TNFα or iNOS between two kinds of cells in psoriasis vulgaris. Conclusion TNFα induces iNOS expression on keratinocytes and MNCs in lesional skin of psoriasis vulgaris through NF κB-independent mechanism, and on neutrophils in Munro's microabscess through NF κB-dependent mechanism.

Key words: Psoriasis, Inducible nitric oxide synthetase, NF-kappa B, Tumor necrosis factor