Adenosine prevents activation of transcription factor NF-kappa B and enhances activator protein-1 binding activity in ischemic rat heart.
BACKGROUND
Adenosine prevents myocardial TNF-alpha production induced by ischemia/reperfusion, but the mechanisms are poorly understood. Transcription factors NF-kappa B and AP-1 have been implicated in the regulation of a variety of inducible gene expressions in response to oxidative stress and cellular defense. The effects of adenosine on NF-kappa B and AP-1 activation have not been clearly defined. This study demonstrated differential effects of adenosine on NF-kappa B and AP-1 nuclear binding activity in ischemic myocardium.


METHODS
Isolated working rat hearts were subjected to 0, 1, 2, 3, 4, 5, 7.5, 10, 15, and 30 minutes of ischemia, with 4 to 6 hearts for each time point with and without adenosine (100 mumol/L). NF-kappa B and AP-1 binding activity in the nucleus were analyzed by electrophoretic mobility shift assay (EMSA). I kappa B alpha levels in the cytoplasm were measured by Western blot analysis. TNF-alpha mRNA levels were determined by RT-PCR.


RESULTS
NF-kappa B binding activity in the nucleus significantly increased after 4 minutes of ischemia and remained to 30 minutes. The levels of I kappa B alpha protein in the cytoplasm markedly decreased after 4, 5, 7.5, and 10 minutes of ischemia. TNF-alpha mRNA levels peaked after 10 minutes of ischemia. AP-1 DNA binding activity was induced and persisted during all ischemic periods. Adenosine significantly inhibited NK-kappa B binding activity in the nucleus, markedly prevented the loss of I kappa B alpha proteins from the cytoplasm, and concomitantly down-regulated TNF-alpha mRNA expression, but enhanced AP-1 binding activity in the nucleus of ischemic myocardium.


CONCLUSIONS
Adenosine modulation of NF-kappa B activation may be the cellular molecular mechanism of down-regulation of TNF-alpha mRNA expression. The cardioprotective properties of adenosine may be involved in the differential modulation of NF-kappa B and AP-1 activation during myocardial ischemia.
Li
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C
Department of Surgery, James H. Quillen College of Medicine, Mountain Home VA Center, East Tennessee State University, Johnson City 37614-0575, USA.
Ha
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Liu
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Browder
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Kao
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D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D001667:Binding, Competitive; D015153:Blotting, Western; D002467:Cell Nucleus / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D015536:Down-Regulation; D004586:Electrophoresis; D066298:In Vitro Techniques; D008297:Male; D017202:Myocardial Ischemia / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D016328:NF-kappa B / Q000378:metabolism*; D012313:RNA / Q000032:analysis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018808:Transcription Factor AP-1 / Q000378:metabolism*; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D016328:NF-kappa B; D018808:Transcription Factor AP-1; D014409:Tumor Necrosis Factor-alpha; D012313:RNA; D000241:Adenosine