Induction of nuclear factor kappa B and activation protein 1 in postischemic myocardium

Ischemia/reperfusion induces nuclear factor kappa B (NF-kappa B) and AP-1 in rat hearts after 15 min of ischemia followed by reperfusion (R) for various periods of time (15 and 30 min, 1, 2, 3, 6, 12, and 24 h). Low levels of NF-kappa B and no signal for AP-1 were detected in shams and in non-ischemic tissue distant from the ischemic zone, In postischemic tissue, NF-kappa B levels increased biphasically with peak levels at 15 min and again at 3 h R, Immunoblotting showed minimal NF-kappa B p50 subunit at all times, with changes in p65 similar to EMSA results. Northern blots showed low p50 and increased p65 expression levels at both 2 and 3 h R, By contrast, AP-1 increased monophasically, with peak levels at 15 min R, which dropped steadily thereafter. These results indicate that NF-kappa B and AP-1 are differentially regulated during reperfusion, which may be a control mechanism for gene expression in reperfused myocardium.