Effects of baicalin on expression of inducible nitric oxide synthase in cultured fibroblasts stimulated by cytokines

Objective : To investigate the effects of baicalin on expression of inducible nitric oxide synthase (iNOS) in fibroblasts and its mechanisms in treating psoriasis. Methods : Fibroblasts cultured in vitro were stimulated with tumor necrosis factor-α (TNF-α), interferon-γ (IFN-γ), interleukin-8 (IL-8) in different groups. iNOS was detected by western blot and immunocytochemistry assay, and in addition, the effects of baicalin on its expression were investigated. Results : Fibroblasts did not express iNOS without cytokine stimulation. When treated for 24 h with 1.0 × 10 6 U/L TNF-α , 0.2 × 10 6 U/L IFN-γ , 0.2 × 10 6 pg/L IL-8 alone or in combinations indicated, fibroblasts produced iNOS when stimulated by TNF-α alone while neither IFN-γ nor IL-8 could induce the production of iNOS. The combination of TNF-α and IL-8 induced a strong expression of iNOS, the combined exposure of three kinds of cytokines showed an even stronger effects. The strongly stained area was in the cytoplasm near the nuclei. Expression of iNOS induced by TNF-α and IL-8 was inhibited by 50 μg/ ml of baicalin. Conclusion : Fibroblasts might express iNOS when stimulated by certain cytokines. Baicalin decreased production of nitric oxide through inhibiting the expression of iNOS, furthermore it reduced inflammation, which might be part of its mechanisms in treating psoriasis.