Cytokines produced by immune cells infiltrating pancreatic islets are important mediators of β-cell destruction in insulin-dependent diabetes mellitus. Cytokines stimulate an inducible form of nitric oxide synthase (iNOS) expression and nitric oxide (NO) production, leading to insulin insufficiency. In the present study, the effects of Artemisia capillaris extract (ACE) on cytokine-induced β-cell damage were examined. Treatment of RINm5F (RIN) rat insulinoma cells with interleukin-1β (IL-1β) and interferon-γ (IFN-γ) induced cell damage. ACE completely protected IL-1β and IFN-γ-mediated cytotoxicity in a concentration-dependent manner. Incubation with ACE resulted in a significant reduction in IL-1β and IFN-γ-induced NO production, a finding that correlated well with reduced levels of the iNOS mRNA and protein. The molecular mechanism by which ACE inhibited iNOS gene expression appeared to involve the inhibition of NF-κB activation. The IL-1β and IFN-γ-stimulated RIN cells showed increases in NF-κB binding activity and p65 subunit levels in the nucleus, and IκBα degradation in cytosol compared to unstimulated cells. Furthermore, ACE restored the cytokine-induced inhibition of insulin release from isolated islets. These results suggest that ACE protects β-cells by suppressing NF-κB activation.

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