Attenuation of myocardial injury by postconditioning: role of hypoxia inducible factor-1alpha.
Postconditioning (PostC) has regenerated interest as a mechanical intervention against myocardial ischemia/reperfusion injury, but its molecular mechanisms remain elusive. This study tested the hypothesis that hypoxia inducible factor-1alpha (HIF-1alpha) plays a role in PostC-induced cardioprotection. Male Wistar rats were subjected to 30 min ischemia followed by 3 h of reperfusion (Control). PostC with 3 cycles of 10 s reperfusion and 10 s re-occlusion was applied at the onset of reperfusion. Relative to the Sham group, HIF-1alpha protein level was increased by 2.9-fold in the Control group, but its level was enhanced by 5.8-fold with PostC (P < 0.01 vs. Control). However, HIF-1alpha protein level was further augmented by 2.0-fold and 3.3-fold, respectively, when the prolyl hydroxylase inhibitor, dimethyloxalylglycine (DMOG, 40 mg/kg, i.p.) was given at 24 h before ischemia in both Control and PostC groups. PostC reduced infarct size by 24% compared with the Control (27 +/- 4.2% vs. 36 +/- 5.2%, P < 0.01), consistent with significant lower levels of plasma creatine kinase activity, index of cardiomyocyte apoptosis and caspase-3 activity. Although pretreatment with DMOG significantly reduced infarct size relative to the Control, the infarct-sparing effect of PostC was remarkably enhanced when DMOG was given before PostC (18 +/- 2.0% vs. 27 +/- 4.2% in PostC alone, P < 0.05). There was a significant linear inverse relationship between HIF-1alpha protein level and infarct size (r = -0.799, P < 0.01) among all groups. Furthermore, along with up-regulated HIF-1alpha expression, the levels of iNOS mRNA and protein were significantly increased in the PostC alone and DMOG plus PostC groups. In conclusion, these data suggest that HIF-1alpha is involved in cardioprotection by PostC and pharmacological augmentation of HIF-1alpha expression that enhances the infarct-sparing effect of PostC; iNOS, the downstream gene of HIF-1alpha, may participate in signaling pathways in mediating PostC's protection.
Zhao
Huan-Xin
HX
Department of Physiology, Shanxi Medical University, 56 South Xinjian Road, 030001, Taiyuan, Shanxi, People's Republic of China.
Wang
Xiao-Liang
XL
Wang
Ye-Hong
YH
Wu
Ye
Y
Li
Xiao-Yu
XY
Lv
Xiao-Ping
XP
Zhao
Zhi-Qing
ZQ
Zhao
Rong-Rui
RR
Liu
Hui-Rong
HR
D000600:Amino Acids, Dicarboxylic; D000818:Animals; D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D003402:Creatine Kinase / Q000097:blood; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D008297:Male; D015428:Myocardial Reperfusion Injury / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D009206:Myocardium / Q000473:pathology; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism*; D011393:Procollagen-Proline Dioxygenase / Q000037:antagonists & inhibitors; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D015854:Up-Regulation
D000600:Amino Acids, Dicarboxylic; C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D011393:Procollagen-Proline Dioxygenase; D052247:Nitric Oxide Synthase Type II; D003402:Creatine Kinase; D053148:Caspase 3; C040947:oxalylglycine