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)-1beta in the presence or absence of
rebamipide. Pretreatment of cells with
rebamipide resulted in up-regulation of iNOS induction by IL-1beta, followed by increased NO production.
Rebamipide enhanced the degradation of
IkappaBalpha and the activation of
NF-kappaB. 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 IkappaB/
NF-kappaB 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-kappaB, 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.