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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