Abstract 17281: Programmed Necrosis of Ventricular Myocytes During Ischemic Stress Involves a Mitochondrial Regulated Bnip3- RIP-1- Cyclophilin D Signaling Pathway
Recent animal studies suggest that programmed necrosis plays a critical role in ischemia/reperfusion induced cardiac cell death and in the progression to heart failure. This caspase-independent form of programmed cell death involves RIP1/RIP3 phosphorylation and activation, as well as the formation of the cyclophilin D (CypD)-dependent mitochondrial permeability transition pore (PTP). Our previous work, along with the work of others, suggests that the hypoxia-inducible death gene, Bnip3, may promote a caspase-independent form of cell demise. Therefore, we hypothesized that Bnip3 was capable of triggering programmed necrosis in ventricular myocytes. We demonstrate for the first time that Bnip3-dependent mitochondrial perturbations involving the inner mitochondrial membrane, and cell death, are blocked by the RIP1 inhibitor, necrostatin-1. Furthermore, forced expression of Bnip3 in post-natal cardiac myocytes increased the mitochondrial localization of phospho-RIP3, which was attenuated by deletion of the mitochondrial-targeting transmembrane domain of Bnip3 or in Bnip3-/- cells. In addition, a physical association between Bnip3, RIP1, and CypD by co-immunoprecipitation, was observed in hypoxic myocytes but not normoxic cells, while inhibition of CypD, by cyclosporine A, was sufficient to block Bnip3-induced necrotic-like death. Furthermore, Bnip3 was incapable of inducing PTP opening or cell death in CypD-/- MEFs, despite its ability to interact with RIP1. Thus, our findings implicate CypD as a critical regulator of Bnip3-induced mitochondrial regulated programmed necrosis, and highlight a novel relationship between RIP1- CypD and Bnip3 for programmed necrosis of ventricular myocytes during ischemic injury.
- © 2011 by American Heart Association, Inc.