Early activation of transcription factor NF-κB during ischemia in perfused rat heart

The transcription factor nuclear factor kappa B (NF-kappa B) regulates multiple immediate-early gene expressions involved in immune and inflammatory responses and cellular defenses. Ischemia-reperfusion induces many immediate-early gene expressions, but little is known about the NF-kappa B activation in myocardium during ischemia and reperfusion. This study demonstrated that ischemia alone rapidly induced NF-kappa B activation in the myocardium of isolated working rat hearts. Electrophoretic mobility shift assay showed that NF-kappa B binding activity significantly increased in the nucleus after 5 min of ischemia and remained elevated for up to 30 min. Western blot analysis suggested that the levels of inhibitory I kappa B alpha protein in the cytoplasm became markedly decreased at 4, 5, 7.5, and 10 min of ischemia but were gradually restored following 10 min of ischemia. Reduction of I kappa B alpha protein in the cytoplasm by ischemia resulted in NF-kappa B translocation to the nucleus. Northern blot hybridization showed that I kappa B alpha mRNA levels were not significantly elevated during myocardial ischemia. Pyrrolidine dithiocarbamate, an antioxidant, significantly inhibited the loss of I kappa B alpha protein from the cytoplasm and prevented NF-kappa B binding activity in the nucleus. Reperfusion following short periods of ischemia augmented NF-kappa B binding activity in the nucleus induced by ischemia. The results suggest that early activation of NF-kappa B induced by ischemia in the myocardium could be a signal mechanism for controlling and regulating immediate-early gene expression during ischemia-reperfusion.