Rebamipide, anti-gastric ulcer drug, up-regulates the induction of iNOS in proinflammatory cytokine-stimulated hepatocytes

Nitric oxide (NO) generated from inducible NO synthase (iNOS) during hepatic injury has been reported to contribute to cytoprotection or cellular damage. Rebamipide, anti-gastric ulcer drug, has protective effects in a variety of tissue and organ injury. However, it remains unknown whether rebamipide is involved in the regulation of iNOS gene expression under pathological conditions. We examined whether rebamipide influences the induction of iNOS in hepatocytes exposed to pro-inflammatory cytokine. Primary cultured rat hepatocytes were treated with interleukin (IL)-1β in the presence or absence of rebamipide. Pretreatment of cells with rebamipide resulted in up-regulation of iNOS induction by IL-1β, followed by increased NO production. Rebamipide enhanced the degradation of IκBα and the activation of NF-κB. Further, rebamipide super-induced the up-regulation of type I IL-1 receptor (IL-1RI), which is essential for iNOS induction in addition to the IκB/NF-κB pathway. Transfection experiments revealed that rebamipide increased the transactivation of iNOS promoter and the stability of iNOS mRNA. In the latter, rebamipide increased the antisense-transcript corresponding to the 3′-UTR of iNOS mRNA, which stabilizes iNOS mRNA by interacting with the 3′-UTR and RNA-binding proteins. These findings demonstrate that rebamipide up-regulates iNOS by iNOS promoter activation through NF-κB, and by its mRNA stabilization presumably through the super-induction of IL-1RI and antisense-transcript. Rebamipide may contribute to a novel potentiated treatment in liver injuries.