title: TRPV1 activation exacerbates hypoxia/reoxygenation-induced apoptosis in H9C2 cells via calcium overload and mitochondrial dysfunction.
abstract: Transient potential receptor vanilloid 1 (TRPV1) channels, which are expressed on sensory neurons, elicit cardioprotective effects during ischemia reperfusion injury by stimulating the release of neuropeptides, namely calcitonin gene-related peptide (CGRP) and substance P (SP). Recent studies show that TRPV1 channels are also expressed on cardiomyocytes and can exacerbate air pollutant-induced apoptosis. However, whether these channels present on cardiomyocytes directly modulate cell death and survival pathways during hypoxia/reoxygenation (H/R) injury remains unclear. In the present study, we investigated the role of TRPV1 in H/R induced apoptosis of H9C2 cardiomyocytes. We demonstrated that TRPV1 was indeed expressed in H9C2 cells, and activated by H/R injury. Although neuropeptide release caused by TRPV1 activation on sensory neurons elicits a cardioprotective effect, we found that capsaicin (CAP; a TRPV1 agonist) treatment of H9C2 cells paradoxically enhanced the level of apoptosis by increasing intracellular calcium and mitochondrial superoxide levels, attenuating mitochondrial membrane potential, and inhibiting mitochondrial biogenesis (measured by the expression of ATP synthase β). In contrast, treatment of cells with capsazepine (CPZ; a TRPV1 antagonist) or TRPV1 siRNA attenuated H/R induced-apoptosis. Furthermore, CAP and CPZ treatment revealed a similar effect on cell viability and mitochondrial superoxide production in primary cardiomyocytes. Finally, using both CGRP(8-37) (a CGRP receptor antagonist) and RP67580 (a SP receptor antagonist) to exclude the confounding effects of neuropeptides, we confirmed aforementioned detrimental effects as TRPV1(-/-) mouse hearts exhibited improved cardiac function during ischemia/reperfusion. In summary, direct activation of TRPV1 in myocytes exacerbates H/R-induced apoptosis, likely through calcium overload and associated mitochondrial dysfunction. Our study provides a novel understanding of the role of myocyte TRPV1 channels in ischemia/reperfusion injury that sharply contrasts with its known extracardiac neuronal effects.
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. sns2006@zju.edu.cn.
authors.forename: Zewei
authors.initials: Z
authors.lastname: Sun
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. hanjie200641@163.com.
authors.forename: Jie
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. zhaowentingting@126.com.
authors.forename: Wenting
authors.initials: W
authors.lastname: Zhao
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. pizza_zyy@126.com.
authors.forename: Yuanyuan
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. wmmkao2@163.com.
authors.forename: Shuai
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. a7451840@126.com.
authors.forename: Lifang
authors.initials: L
authors.lastname: Ye
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. tingtingliu12345@163.com.
authors.forename: Tingting
authors.initials: T
authors.lastname: Liu
authors.affiliation: Department of Cardiology, the First Affiliated Hospital, College of Medicine, Zhejiang University, No. 79 Qingchun Road, Hangzhou 310003, China. zlrylnn@126.com.
authors.forename: Liangrong
authors.initials: L
authors.lastname: Zheng
mesh_terms: D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D015687:Cell Hypoxia; D002460:Cell Line; D017353:Gene Deletion; D015870:Gene Expression; D006321:Heart / Q000503:physiopathology; D008297:Male; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008810:Mice, Inbred C57BL; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology*; D015428:Myocardial Reperfusion Injury / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology; D032383:Myocytes, Cardiac / Q000378:metabolism / Q000473:pathology*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D050916:TRPV Cation Channels / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D015854:Up-Regulation
chemical_list: D034741:RNA, Small Interfering; D050916:TRPV Cation Channels; C493921:TRPV1 protein, mouse; C493922:Trpv1 protein, rat; D002118:Calcium