A novel role of interleukin-1-converting enzyme in cytokine-mediated inducible nitric oxide synthase gene expression: Implications for neuroinflammatory diseases

Inducible nitric oxide synthase (iNOS)-derived NO plays an important role in several neurological disorders. Understanding of mechanisms involved in the regulation of iNOS induction is of particular interest. Here, we investigated mechanisms of iNOS induction in rat astrocytes (AC) and in brain endothelial cells (BEC). We find that activation of AC or BEC with pro-inflammatory cytokines reveals a different cell-specific activation pattern for iNOS expression. Despite these differences, in both cell types iNOS expression and activity exclusively depends on the endogenous availability of bioactive IL-1β as inhibition of ICE activity significantly decreases iNOS promoter activity, iNOS expression and enzyme activity. In summary, we here provide evidence that ICE represents a target for modulating iNOS expression and high-output NO formation in AC and BEC, to our knowledge the first report of a role of ICE in iNOS expression and the advantage of ICE inhibition in attenuating NO mediated inflammation and pathology.