Cardioprotection involves activation of NF-κB via PKC-dependent tyrosine and serine phosphorylation of IκB-α

Previous studies indicated that activation of PKC and Src tyrosine kinases by ischemic preconditioning ( PC) may participate in the activation of NF-kappaB. However, the molecular mechanisms underlying activation of NF-kappaB during ischemic PC remain unknown. In the hearts of conscious rabbits, it was found that ischemic PC ( 6 cycles of 4-min coronary occlusion and 4-min reperfusion) significantly induced both tyrosine ( + 226.9 +/- 42%) and serine ( + 137.0 +/- 36%) phosphorylation of the NF-kappaB inhibitory protein IkappaB-alpha, concomitant with increased activation of the IkappaB-alpha kinases IKKalpha ( + 255.0 +/- 46%) and IKKbeta ( + 173.1 +/- 35%). Furthermore, both tyrosine and serine phosphorylation of IkappaB-alpha were blocked by pretreatment with either the nonreceptor tyrosine kinase inhibitor lavendustin-A (LD-A) or the PKC inhibitor chelerythrine (Che) ( both given at doses previously shown to block ischemic PC). Interestingly, Che completely abolished PC-induced activation of IKKalpha/beta, whereas LD-A had no effect. In addition, IkappaB-alpha protein level did not change during ischemic PC. Together, these data indicate that ischemic PC-induced activation of NF-kappaB occurs through both tyrosine and serine phosphorylation of IkappaB-alpha and is regulated by nonreceptor tyrosine kinases and PKC.