Reperfusion causes significant activation of heat shock transcription factor 1 in ischemic rat heart.
BACKGROUND
The myocardial protective role of heat shock protein (HSP) has been demonstrated, and there has been increasing interest in stress response in the heart. We examined the DNA-binding activity of heat shock transcription factor (HSF), by which the transcription of heat shock genes is mainly regulated, during heat shock or ischemia/reperfusion in isolated rat heart.


RESULTS
Rat hearts were isolated and perfused with Krebs-Henseleit buffer by the Langendorff method. Whole-cell extracts were prepared for gel mobility shift assay using oligonucleotides containing the heat shock element, which is present upstream of all heat shock genes. Induction of mRNAs for HSP70, HSP90, and GRP78 (glucose-regulated protein) was examined by Northern blot analysis. Although the activation of HSF during global ischemia was weak and rapidly attenuated, postischemic reperfusion induced a significant activation of HSF. In addition, although HSP70 mRNA was hardly induced during ischemia, its burst induction was detected during postischemic reperfusion. Supershift assays using specific antisera for HSF1 and HSF2 revealed that ischemia/reperfusion as well as heat shock induced the activation of HSF1 in hearts. Although the expression of HSP70 mRNA during heat shock was more vigorous than the expression during ischemia/reperfusion, the induction of HSP90 mRNA in postischemic reperfusion was significantly greater than that in heat shock.


CONCLUSIONS
Our findings demonstrated that reperfusion causes a significant activation of HSF1 in ischemia-reperfused heart. The striking contrast between the induction of HSP70 mRNA and that of HSP90 mRNA suggests the presence of regulatory mechanisms other than HSF.
Department of Cardiovascular Surgery, Faculty of Medicine, Kyoto University, Japan.
J
J
Nishizawa
A
A
Nakai
T
T
Higashi
M
M
Tanabe
S
S
Nomoto
K
K
Matsuda
T
T
Ban
K
K
Nagata
D000818:Animals; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism; D002461:Cell Line, Transformed / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D005786:Gene Expression Regulation / Q000502:physiology; D018840:HSP70 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D018841:HSP90 Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; D066298:In Vitro Techniques; D008297:Male; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D017202:Myocardial Ischemia / Q000235:genetics / Q000378:metabolism; D015428:Myocardial Reperfusion Injury / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013312:Stress, Physiological / Q000235:genetics / Q000378:metabolism; D014157:Transcription Factors
D002352:Carrier Proteins; D004268:DNA-Binding Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D018841:HSP90 Heat-Shock Proteins; D000076249:Heat Shock Transcription Factors; D006360:Heat-Shock Proteins; C000619709:Hsf1 protein, rat; D018832:Molecular Chaperones; D012333:RNA, Messenger; D014157:Transcription Factors