A role of TRPC3/6 in Myocardial Ischemia and Reperfusion (I/R) Injury

BIRNBAUMER, LUTZ; HE, XIJU; LI, SHOUTIAN; LIU, BENJU; FORMOSO, KARINA; SUSPERREGUY, SEBASTIAN; LIAO, YANHONG

Congreso; The 42nd Symposium on Hormones and Cell Regulation Ion Channels in Hormonal Homeostasis: Transient Receptor Potential Channels and Calcium Signaling; 2017

Calcium overload plays an important role in myocardiac ischemia and reperfusion injury. But the detailed mechanism by which excessive calcium ions enters cardiac myocytes has not been fully elucidated. Here we identify TRPC3 and TRPC6 as primary channels via which excessive calcium ions are accumulated in the cytosol of cardiomyocytes, leading to cell death in IR process. In In vivo experiments with TRPC3/6/7 KO mice and WT counterparts, animals were subjected to a 30-min/24-h I/R protocol. We observed: (1) the infarct size (IS) in TRPC3/6/7 KO mice is clearly smaller than in WT age-matched controls (Evans/TTC staining); (2) cardiac functionality of TRPC3/6/7 KO mice is better than that in WT controls (echocardiograph recording); (3) myocardial fibers and mitochondaria are less disrupted in AAR tissue of TRPC3/6/7 KO mice, compared to that in WT controls (LM, EM); (4) apopotic cells are less in AAR tissue of TRPC3/6/7 KO mice, compared to WT contros (TUNEL staining). In in vitro experiments, H9c2 cardiomyoblasts were subjected to a 9-h/6-h H/R protocol. We observed that: (1) H/R increases mitochondria?s permeability transition which is attenuated by the non-Orai inhibiting, 5 uM TRPC pan-blocker SKF96365; (2) H/R enhances proapoptotic the process (Bcl2/Bax ratio decrease); (3) H/R decreases p-NFAT (S240) and increases the expression of TRPC3, TRPC6 and Bax. We noticed a discrepancy in the expressions of p-AKT and p-GSK3b between I/R-treated AAR tissue (increase), and in H/R-treated H9c2 myoblast cells (decrease). We conclude that the positive-feedback loop which elevates cytosolic calcium via TRPC3 and TRPC6 in I/R activates calcineurin-mediated NFATc3 directed TRPC3 and 6 transcription, yielding more TRPC3 and 6, leading to pathological calcium overload, and triggering I/R injuries