Zn2+and mPTP Mediate Endoplasmic Reticulum Stress Inhibition-Induced Cardioprotection Against Myocardial Ischemia/Reperfusion Injury.
The purpose of this study was to determine whether Zn2+is involved in endoplasmic reticulum (ER) stress inhibition-induced cardioprotection against ischemia/reperfusion (I/R) injury by modulation of the mitochondrial permeability transition pore (mPTP) opening. Isolated rat hearts were subjected to 30-min regional ischemia followed by 2 h of reperfusion. Expression of glucose regulated protein 78 (GRP 78 or BIP), an ER homeostasis marker, was not increased during ischemia but was increased upon reperfusion, indicating that ER stress was initiated upon reperfusion but not during ischemia. The ER stress inhibitor tauroursodeoxycholic acid (TUDCA) given at reperfusion resulted in a significant reduction of GRP78 expression 30 and 60 min after the onset of reperfusion, an effect that was reversed by the zinc chelator N,N,N',N'-tetrakis-(2-pyridylmethyl) ethylenediamine (TPEN). The immunofluorescence study also showed that the effect of TUDCA on GRP78 expression was reversed by TPEN. TUDCA reduced infarct size and this was reversed by the mPTP opener atractyloside, indicating that ER stress inhibition may induce cardioprotection by modulating the mPTP opening. Experiments with transmission electron microscopy and hematoxylin-eosin staining also revealed that TUDCA prevented endoplasmic reticulum and mitochondrial damages at reperfusion, which was blocked by TPEN. Exposure of cardiac H9c2 cells to H2O2increased GRP 78 and GRP 94 expressions, suggesting that oxidative stress can induce ER stress. Cells treated with H2O2showed a significant decrease in tetramethylrhodamine ethyl ester (TMRE) fluorescence, indicating that H2O2triggers the mPTP opening. In contrast, TUDCA prevented the loss of TMRE fluorescence, the effect that was blocked by TPEN, indicating a role of Zn in the preventive effect of ER stress inhibition on the mPTP opening. In support, TUDCA significantly increased intracellular free zinc. These data suggest that reperfusion but not ischemia initiates ER stress and inhibition of ER stress protects the heart from reperfusion injury through prevention of the mPTP opening. Increased intracellular free Zn accounts for the cardioprotective effect of ER stress inhibition.
Department of Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050017, China.|Heart Institute, North China University of Science and Technology, Tangshan, 063000, China.
Guochen
G
Wang
Department of Internal Medicine, Linyi People's Hospital, Linyi, Shandong, 276034, China.
Hongping
H
Huang
Heart Institute, North China University of Science and Technology, Tangshan, 063000, China.
Huan
H
Zheng
Heart Institute, North China University of Science and Technology, Tangshan, 063000, China.
Yonggui
Y
He
Heart Institute, North China University of Science and Technology, Tangshan, 063000, China.
Yidong
Y
Zhang
Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, 300070, China.
Zhelong
Z
Xu
Department of Surgery, Third Hospital of Hebei Medical University, Shijiazhuang, 050017, China. zhliu130@sohu.com.|Heart Institute, North China University of Science and Technology, Tangshan, 063000, China. zhliu130@sohu.com.
Liu
L
Zhang
Heart Institute, North China University of Science and Technology, Tangshan, 063000, China. jinkunxi@126.com.|Department of Physiology and Pathophysiology, Tianjin Medical University, Tianjin, 300070, China. jinkunxi@126.com.
Jinkun
J
Xi
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006360:Heat-Shock Proteins / Q000378:metabolism; D008297:Male; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D015428:Myocardial Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D051381:Rats; D017208:Rats, Wistar; D013655:Taurochenodeoxycholic Acid / Q000494:pharmacology*; D015032:Zinc / Q000378:metabolism*; D000091342:Endoplasmic Reticulum Chaperone BiP
D002316:Cardiotonic Agents; D006360:Heat-Shock Proteins; D033681:Mitochondrial Membrane Transport Proteins; D000083162:Mitochondrial Permeability Transition Pore; D013655:Taurochenodeoxycholic Acid; D015032:Zinc; C051684:GRP78 protein, rat; D000091342:Endoplasmic Reticulum Chaperone BiP; C031655:ursodoxicoltaurine
Cardioprotection; Endoplasmic reticulum stress; Ischemia/reperfusion injury; Mitochondrial permeability transition pore; Zn2+