Early activation of IKKβ during in vivo myocardial ischemia

We have demonstrated that in vitro brief ischemia activates nuclear factor (NF)-kappaB in rat myocardium. We report in vivo ischemia-reperfusion (I/R)-induced NF-kappaB activation, I kappaB kinase -beta (IKK beta) activity, and I kappaB alpha phosphorylation and degradation in rat myocardium. Rat hearts were subjected to occlusion of the coronary artery for up to 45 min or occlusion for 15 min followed by reperfusion for up to 3 h. Cytoplasmic and nuclear proteins were isolated from ischemic and nonischemic areas of each heart. NF-kappaB activation was increased in the ischemic area (680%) after 10 min of ischemia and in the nonischemic area (350%) after 15 min of ischemia and remained elevated during prolonged ischemia and reperfusion. IKK beta activity was markedly increased in ischemic (1,800%) and nonischemic (860%) areas, and phosphorylated I kappaB alpha levels were significantly elevated in ischemic (180%) and nonischemic (280%) areas at 5 min of ischemia and further increased after reperfusion. I kappaB alpha levels were decreased in the ischemic (45%) and nonischemic (36%) areas after 10 min of ischemia and remained low in the ischemic area during prolonged ischemia and reperfusion. The results suggest that in vivo I/R rapidly induces IKK beta activity and increases I kappaB alpha phosphorylation and degradation, resulting in NF-kappaB activation in the myocardium.