Abstract: Objective To investigate the internal relationship between the exp ression of inducible nitric oxide synthase (iNOS) and the activation of NF-κBp65 in the skin of patients with psoriasis vulgaris(PV) and their roles in the p athogenesis of PV. Methods The expression and distribution of iNOS and NF-κBp65 were studied by in situ hybridization and immunohistochemistry in 20 patients with PV and 12 healthy controls. The severity of PV was assessed by Psoriasis a nd Severity Index(PASI) score. Results① The expression of both iNOS mRNA and pr otein was significantly higher in lesional epidermis than those in non.lesiona l epidermis and epidermis of the controls (P<0.01). Weak exprssion of iNOS mRNA was found in basal cell layer in a small number of healthy controls, however, s trong expression was observed in entire basal cell layer and focal parts of pric kle cell layer in all PV epidermis.② There was significantly positive correlati on between iNOS and NF-κ Bp65 protein expression in lesional epidermis (P<0.0 1).③ There was significantly positive correlation between the level of expressi on of iNOS mRNA in lesional epidermis and PASI score of patients (P<0.01). Conclusions The expression of iNOS and NF-κBp65 is markedly increased in lesional epidermis of patient with PV. The activation of NF-κB probably takes part in the pathogenesis of PV. High-level expression of iNOS may be due to the activ ation of NF-κB.

Key words: NF-kappa B, Psoriasis, Nitric oxide synthase