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Background/aims: Our previous work suggested an important role for the peptidyl-prolyl isomerase, Pin1, in hepatic NF-kappaB activation and liver injury during ischemia/reperfusion (I/R). In this study, we sought to determine the function of Pin1 in the injury response to hepatic I/R., Methods: Wild-type and Pin1(-/-) mice were subjected to partial hepatic I/R. In addition, hepatocytes and Kupffer cells were isolated from these mice., Results: Pin1(-/-) mice had reduced hepatic NF-kappaB activation and more liver injury after I/R than wild-type mice. The increased injury was not a result of enhanced inflammation as Pin1(-/-) mice had the same level of proinflammatory cytokine production and less neutrophil accumulation in the liver. The reduced NF-kappaB activation was not a result of a defect in nuclear translocation of NF-kappaB. In fact, hepatic nuclear p65 protein expression was higher in Pin1(-/-) mice than wild-type mice. This suggests that Pin1 is important for NF-kappaB-DNA binding. This effect was specific to hepatocytes as isolated Kupffer cells from wild-type and Pin1(-/-) mice were identical in their activation of NF-kappaB and production of cytokines after stimulation. In contrast, hepatocytes stimulated with TNFalpha had greatly reduced NF-kappaB activation, reduced production of the CXC chemokine, MIP-2, and increased cell death., Conclusions: These data suggest that Pin1 is a critical regulator of NF-kappaB activation in hepatocytes and its role in these cells appears to confer direct protective effects.

Background/aims: Nuclear factor kappa B (NF-kappa B) is a primary regulator of gene expression and is activated during hepatic ischemia/reperfusion injury. The objective of the present study was to determine whether activation of NF-kappa B is causally related to the induction of the acute inflammatory response induced by hepatic ischemia/reperfusion., Methods: Wild-type (p50(+/+)) and NF-kappa B p50-deficient (p50(-/-)) mice underwent hepatic ischemia/reperfusion. NF-kappa B activation was determined by electrophoretic mobility shift assay. Hepatic neutrophil accumulation was measured by liver myeloperoxidase content. Hepatocellular injury was assessed by serum level of alanine aminotransferase and liver histology., Results: In p50(+/+) mice, ischemia/reperfusion induced marked activation of NF-kappa B consisting of p50/p65 heterodimers. In contrast, NF-kappa B activation in livers from p50(-/-) mice was abrogated, but p65 was observed in nuclear extracts. Despite amelioration of NF-kappa B activation there was no significant difference between p50(+/+) and p50(-/-) mice in expression of TNF alpha and MIP-2, liver accumulation of neutrophils or hepatocellular injury., Conclusions: Gene deletion of NF-kappa B p50 does not alter the hepatic inflammatory response to ischemia/reperfusion. Despite abrogation of DNA-binding by the NF-kappa B p50/p65 complex, p65 was still observed in nuclear extracts suggesting that there may be functional redundancy amongst members of the Rel protein family in order to preserve the inflammatory response.