Ischemia-reperfusion activates the nuclear transcription factor NF-κB and upregulates messenger RNA synthesis of adhesion molecules in the liver in vivo

Abstract

Hepatic ischemia-reperfusion induces a neutrophil-induced injury, which is dependent on adhesion molecules. The transcription factor NF-κB plays a key role in the activation of adhesion molecule gene expression in vitro. To investigate activation of NF-κB and initiation of adhesion molecule gene transcription in the liver in vivo, Fischer rats were subjected to 30 min of hepatic ischemia and up to 24 h of reperfusion. A moderate baseline activation of NF-κB was found in the liver in sham-operated controls and during ischemia, however, at 1 h and 5 h reperfusion, nuclear NF-κB DNA-binding activity increased by 270–300% as determined by densitometric analysis of electrophoretic mobility shift assays. At 24 h, NF-κB was still activated by 140% above sham control levels. NF-κB complexes consisted of subunits p50 and p65 (RelA). In addition, nuclear translocation of the transcription factor C/EBPβ was increased during reperfusion. Northern blot analysis of RNA isolated from the intact liver showed minor intercellular adhesion molecule-1 (ICAM-1) mRNA expression in sham controls, a moderate but significant increase during ischemia and a further significant increase during reperfusion. Isolation of hepatic endothelial cells demonstrated transiently increased gene transcription for ICAM-1, vascular adhesion molecule-1 (VCAM-1), E-and P-selectin at 1 h reperfusion. In the nonischemic lobes a similar time course of NF-κB activation and ICAM-1 mRNA formation was observed during reperfusion suggesting the involvement of circulating mediators. The data support the conclusion that hepatic ischemia-reperfusion induces NF-κB and C/EBPβ activation and enhances transcription of cellular adhesion molecule genes in the liver.