Cardioprotective role of Transient Receptor Potential Vanilloid 1 (TRPV1) channels in H9C2 cell line

During myocardial infarction, both ischemia and reperfusion (I/R) cause irreversible myocardial injuries. Among the cellular damages, calcium (Ca 2+ ) dysregulation occurs leading to cell death. To improve the recovery from I/R episodes, remote, pre- and post-conditioning are recognized to be cardioprotective. In particular, some strategies based on molecules acting on the TRPV1 channels have been used. The aim of our work is to better understand TRPV1 role in cardioprotection. We have recently demonstrated that TRPV1 is expressed and functional in adult mouse cardiomyocytes. In order to perform live imaging with genetic probes, an alternative model to cardiomyocytes was used in the present work: H9C2 cell line. Thanks to Western blot and confocal microscopy, we first showed that TRPV1 is expressed in H9C2 and seems to be localized at endoplasmic reticular (ER) plasma membrane. Secondly, we demonstrated that TRPV1 is a functional ER Ca 2+ leak channel via cytoplasmic and reticular Ca 2+ imaging (respectively with Fura-2 and ErGAP1). As ATP synthesis and cell fate are dependent of Ca 2+ exchanges between ER and mitochondria, we have analyzed the role of TRPV1 in the mitochondrial [Ca 2+ ] using R-GECO probe. We observed that pharmacological TRPV1 modulation increases both cytosolic and mitochondrial Ca 2+ contents by at least 20%. Finally, we performed hypoxia-reoxygenation sequences and we evaluated cell death by flow cytometry. We showed that TRPV1 activation has heterogeneous effects on cell viability, whereas TRPV1 inhibition always improves cell survival (at least by 22%). Precise and spatiotemporal Ca 2+ release events from ER to mitochondria are required to initiate or to regulate many processes like the balance between cell death/cell survival. In the present study, we show that TRPV1 could be one of the channels involved in Ca 2+ exchanges between ER and mitochondria, and that H9C2 is a valuable model to evaluate the role of TRPV1 in Ca 2+ fluxes during I/R.