Abstract 22: Transient Receptor Potential M2 is Involved in Secondary Myocardial Injury Induced by Nonlethal Mechanical Trauma in Rats

Background: It is an imperative task to identify the mechanisms responsible for post-traumatic secondary myocardial injury. Our previous experiments showed that mechanical trauma (MT) could induce secondary myocardial injury via oxidative stress. The transient potential receptor M2 (TRPM2) channel has emerged as an important Ca2+ signaling mechanism in a variety of cells, contributing to cellular functions that include cytokine production, cell motility and cell death. However, the role of TRPM2 channel in nonlethal mechanical traumatic cardiac damage remains unclear. The aim of the present study was to investigate whether TRPM2 channel is involved in myocardial injury in rats subjected to nonlethal MT. Methods and results: Western blot was used to quantify TRPM2 protein levels in Ventricular myocytes of adult male Sprague Dawley rats. Up-regulation of TRPM2 channel protein was observed in the following 12h after MT. It was observed that plasma harvested from MT rats increased cytosolic Ca2+ concentration dose-dependently in H9c2 cells. To verify the role of TRPM2 further, we administered TRPM2 blockers flufenamic acid (FFA, 100uM) and clotrimazole (CLZ, 30uM) respectively to inhibit Ca2+ influx, which leads to attenuated intracelluar Ca2+ overload and apoptosis induced by MT plasma in H9c2 cells. Those two TRPM2 blockers also improved cardiac dysfunction induced MT in rats. When we used TMB-8 (inhibitor of sarcoplasmic reticulum Ca2+ store) to inhibit calcium store mobilization, intracellular Ca2+ level, apoptosis and cardiac dysfunction were also ameliorated. However, the administration of KBR-7943 (inhibitor of Na/Ca exchanger) did not reverse the pathological process following MT. Conclusion: These results demonstrate that post-trauma pathological phenomena is associated with TRPM2 closely via a redox-sensitive signal transduction pathway (mainly via MT-initiated Ca2+ influx, even calcium overload pathway) .We propose that treatments like blockage of TRPM2 channel-associated Ca2+ influx and mobilization, may shed light on the novel therapeutic strategy in reducing cardiac injury and post-trauma multiple organ failure.