Hepatic expression of S32A/S36A IkappaBalpha does not reduce postischemic liver injury

Activation of the transcription factor, NF-kappaB, during hepatic ischemia/reperfusion injury is associated with proinflammatory mediator expression and is thought to be one of the initial triggers for the inflammatory response after reperfusion. In the current study, we sought to determine whether in vivo adenoviral transfection of a mutant inhibitor of kappaB-alpha (IkappaBalpha), which cannot be serine phosphorylated or degraded (IkappaBalphaSR), would inhibit NF-kappaB and ameliorate the hepatic inflammatory response to ischemia/reperfusion.

Male C57BL/6 mice were subjected to sham surgery or partial hepatic ischemia (90 min) and reperfusion (up to 8 h). Mice were infected with 1 x 10(9) PFU of adenovirus containing either beta-galactosidase (LacZ) or IkappaBalphaSR 3 days prior to induction of ischemia. Serum and tissues were obtained at various times for analysis.

In unmanipulated mice, degradation of IkappaBalpha, as occurs after serine phosphorylation, was evident in liver by the end of ischemia and during early reperfusion. Mice transfected with IkappaBalphaSR displayed the same degree of inflammation and hepatocellular injury as LacZ-transfected mice. There was no difference between LacZ- and IkappaBalphaSR-transfected livers in terms of NF-kappaB activation or proinflammatory cytokine production.

The data demonstrate that the pathway of NF-kappaB activation involving serine phosphorylation of IkappaBalpha is not the primary mechanism for induction of liver inflammation after ischemia/reperfusion and suggest that alternative pathways, such as tyrosine phosphorylation of IkappaBalpha, may be essential for the postischemic response in liver.