Abstract 3784: Apoptosis Signal-Regulating Kinase 1 Regulates Mitochondrial Permeability Transition in Necrotic Cell Death
Introduction: Cardiomyocyte death is a critical process in the pathogenesis of heart failure. Although apoptotic cardiomyocyte death has been thought to be a major cause of cardiomyocyte injury in the disease, a recent report implies the possible involvement of necrotic cell death in the pathogenesis. Cyclophilin D-dependent mitochondrial permeability transition (MPT) mediates necrotic cell death. However, intracellular signaling pathways connecting necrotic stimuli, such as oxidative stress and Ca2+, with MPT have yet to be clarified. We have been reported that reactive oxygen species-sensitive apoptosis signal-regulating kinase 1 (ASK1) plays a pivotal role in the signal transduction pathway mediating not only apoptotic myocardial cell death but necrotic cell death as well.
Hypothesis: ASK1 may regulate cyclophilin D-dependent MPT in necrotic cell death.
Method and Results: Cyclophilin D-deficient mice showed significantly better cardiac function 4 weeks after treatment with pressure overload when compared with wild-type control mice. H2O2 treatment induced MPT in wild-type cardiomyocytes, but did not in cyclophilin D- or ASK1-deficient cardiomyocytes. Overexpression of a constitutively active mutant of ASK1 (ASKΔN) resulted in a loss of mitochondrial membrane potential in wild-type cardiomyocytes, but not in cyclophilin D-deficient cells. H2O2 treatment led to the recruitment of GFP-tagged ASK1 to mitochondria. The expression level of endogenous ASK1 in mitochondria was increased after H2O2 treatment. Immunoprecipitation analysis revealed the interaction of ASK1 with cyclophilin D and activation of ASK1 by H2O2 enhanced the protein interactions. Furthermore, cyclophilin D ablation attenuated left ventricular contractile dysfunction in transgenic mice expressing ASKΔN in the heart.
Conclusion: ASK1 is a key signaling molecule connecting necrotic stimuli with cyclophilin D-dependent MPT, which leads to necrotic cell death and cardiac injury.