The transcription factor nuclear factor kappa B (NF-kappa B) regulates mult
iple immediate-early gene expressions involved in immune and inflammatory r
esponses and cellular defenses. Ischemia-reperfusion induces many immediate
-early gene expressions, but little is known about the NF-kappa B activatio
n in myocardium during ischemia and reperfusion. This study demonstrated th
at ischemia alone rapidly induced NF-kappa B activation in the myocardium o
f isolated working rat hearts. Electrophoretic mobility shift assay showed
that NF-kappa B binding activity significantly increased in the nucleus aft
er 5 min of ischemia and remained elevated for up to 30 min. Western blot a
nalysis 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 ischemi
a 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 t
ranslocation to the nucleus. Northern blot hybridization showed that I kapp
a B alpha mRNA levels were not significantly elevated during myocardial isc
hemia. Pyrrolidine dithiocarbamate, an antioxidant, significantly inhibited
the loss of I kappa B alpha protein from the cytoplasm and prevented NF-ka
ppa 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 a
nd regulating immediate-early gene expression during ischemia-reperfusion.