Regulation of oxidant-induced cell death in cardiac myocytes

Date of Award




Degree Name

Doctor of Philosophy (Ph.D.)



First Committee Member

Nanette H. Bishopric - Committee Chair


The temporal contribution of varying cell death pathways induced by oxidative stress and the mechanisms underlying the cytoprotective effects of c-Jun N-terminal kinase (JNK) were evaluated. We found that hydrogen peroxide (in chronological order) induced cytochrome c release and the loss of mitochondria membrane potential, compromised sarcolemma integrity, and enhanced caspase activation and internucleosomal DNA fragmentation. Inhibition of JNK activity by adenovirus expressing a dominant negative JNK mutant (DNJ) accelerated and enhanced caspase-9 activation induced by either GSNO (1 mM) or H 2O2 (200 muM). JNK inhibition had no effect on the rate or extent of cytochrome c release from mitochondria. Caspase-9 and caspase-3 activities were significantly increased in cell-free extracts in which basal JNK activity was inhibited. Reciprocal co-immunoprecipitation revealed that endogenous cardiac myocyte JNK is physically associated with Apaf-1. In a cell-free system, addition of cytochrome c enhanced JNK-Apaf-1 interaction. In intact myocytes, JNK inhibition accelerated the rate of oxidant stress induced apoptosome formation. We conclude that active JNK inhibits caspase-9 through a novel post-mitochondrial mechanism that involves binding to Apaf-1 in the presence of cytochrome c and delaying apoptosome formation.


Health Sciences, Pharmacology

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