Distinct functions of JNK and c-Jun in oxidant-induced hepatocyte death.
Overactivation of c-Jun N-terminal kinase (JNK)/c-Jun signaling is a central mechanism of hepatocyte injury and death including that from oxidative stress. However, the functions of JNK and c-Jun are still unclear, and this pathway also inhibits hepatocyte death. Previous studies of menadione-induced oxidant stress demonstrated that toxicity resulted from sustained JNK/c-Jun activation as death was blocked by the c-Jun dominant negative TAM67. To further delineate the function of JNK/c-Jun signaling in hepatocyte injury from oxidant stress, the effects of direct JNK inhibition on menadione-induced death were examined. In contrast to the inhibitory effect of TAM67, pharmacological JNK inhibition by SP600125 sensitized the rat hepatocyte cell line RALA255-10G to death from menadione. SP600125 similarly sensitized mouse primary hepatocytes to menadione toxicity. Death from SP600125/menadione was c-Jun dependent as it was blocked by TAM67, but independent of c-Jun phosphorylation. Death occurred by apoptosis and necrosis and activation of the mitochondrial death pathway. Short hairpin RNA knockdowns of total JNK or JNK2 sensitized to death from menadione, whereas a jnk1 knockdown was protective. Jnk2 null mouse primary hepatocytes were also sensitized to menadione death. JNK inhibition magnified decreases in cellular ATP content and β-oxidation induced by menadione. This effect mediated cell death as chemical inhibition of β-oxidation also sensitized cells to death from menadione, and supplementation with the β-oxidation substrate oleate blocked death. Components of the JNK/c-Jun signaling pathway have opposing functions in hepatocyte oxidant stress with JNK2 mediating resistance to cell death and c-Jun promoting death.
Department of Medicine, Marion Bessin Liver Research Center, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Muhammad
M
Amir
Kun
K
Liu
Enpeng
E
Zhao
Mark J
MJ
Czaja
D000255:Adenosine Triphosphate / Q000378:metabolism; D000256:Adenoviridae / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000873:Anthracenes / Q000494:pharmacology; D016923:Cell Death; D002461:Cell Line, Transformed; D004351:Drug Resistance; D055785:Gene Knockdown Techniques; D022781:Hepatocytes / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D020935:MAP Kinase Signaling System; D051379:Mice; D008810:Mice, Inbred C57BL; D048056:Mitogen-Activated Protein Kinase 9 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D019301:Oleic Acid / Q000494:pharmacology; D010084:Oxidation-Reduction; D018384:Oxidative Stress; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism; D010766:Phosphorylation; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D024483:Vitamin K 3 / Q000633:toxicity*
D000873:Anthracenes; D010446:Peptide Fragments; D016755:Proto-Oncogene Proteins c-jun; D034741:RNA, Small Interfering; D017382:Reactive Oxygen Species; C439528:TAM67 peptide; C432165:pyrazolanthrone; D019301:Oleic Acid; D024483:Vitamin K 3; D000255:Adenosine Triphosphate; D048056:Mitogen-Activated Protein Kinase 9