Hepatic ischemia/reperfusion in rats induces iNOS gene transcription by activation of NF-kappa B

It has been known that many immediately early genes are expressed during is chemia/reperfusion (I/R) injury. Here, employing a model of hepatic IIR, we show that inducible nitric oxide synthase (iNOS)is induced via the activat ion of nuclear factor kappaB (NF-kappa B) after I/R in rat liver. When live r was subjected to ischemia followed by reperfusion, but not ischemia alone , an NF-kappa B complex composed of p50/p65 heterodimer and p50 homodimer w as rapidly activated within 1 h and remained elevated for up to 3 h, and th en tended to decline after 5 h of reperfusion. Also, the expression of iNOS mRNA was initiated after 1 h and continued to increase after 5 h of reperf usion during the time course studied. This upregulated iNOS mRNA expression coincides with increased iNOS enzyme activity and NF-kappa B binding activ ity after hepatic I/R. Administration of N-acetylcysteine (NAC, 20 mg/kg i. v. 10 min before reperfusion), an antioxidant, not only significantly inhib ited the expression of iNOS mRNA but also blocked upregulated NF-kappa B bi nding activity after reperfused liver. These results suggest that NF-kappa B is activated by oxidative stress during hepatic I/R and may play a signif icant role in the induction of the iNOS gene. (C) 1999 Academic Press.