280 SURGERY APOPTOSIS, KNOWN AS PROGRAMMED CELL DEATH, is vital to many normal processes such as develop- ment. However, apoptosis also contributes to the pathogenesis of a wide range of disorders including certain cancers and organ ischemia/reperfusion injury. In the liver, apoptosis plays a role in the pathogenesis of fulminant hepatic failure, hepati- tis, organ dysfunction after liver transplantation, and liver ischemia/reperfusion injury. 1–3 Apoptot- ic signaling can be initiated by ligand binding to 1 of a series of death receptors including Fas, tumor necrosis factor (TNF)-α, TNF-related apoptosis- inducing ligand, or direct genotoxic agents such as ultraviolet (UV) light. 4 In addition, other biologic molecules relevant in liver disease can activate these receptors, such as the bile salt glycochen- odeoxycholic acid (GCDC), which can cause apop- tosis by activating the Fas receptor. 5 In response to death-ligand binding, a cascade of cysteine pro- teases known as caspases are cleaved into their active forms, culminating in the apoptotic death of the cell. 6 Because of the importance of apoptosis in liver disease, understanding the signaling pathways that alter its effects are of great significance. c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinases family, which represents a group of signaling cascades that regu- late cellular responses to stimuli. 7 The JNK path- way is activated by such diverse stimuli as cytokines (TNF-α and IL-1) and environmental stress (UV radiation and oxidative stress of ischemia/reperfu- sion injury). 8 A series of phosphorylation events from upstream kinases leads to phosphorylation of JNK, which in turn phosphorylates c-Jun. c-Jun, once phosphorylated, is able to dimerize and bind to recognition sites in the promoter elements of a broad array of genes with a variety of cellular effects. 9 Although JNK activation and apoptosis are both common to certain phenomena, such as ischemia/reperfusion and cytokine binding events, the link between these 2 pathways is not well under- Protection of rat hepatocytes from apop- tosis by inhibition of c-Jun N-terminal kinase Eric L. Marderstein, MD, Brian Bucher, BS, Zhong Guo, MD, Xuesheng Feng, MD, Kaye Reid, MD, and David A. Geller, MD, Pittsburgh, Pa Background. Apoptotic cell death and c-Jun N-terminal kinase (JNK) activation occur after hepatic ischemia/reperfusion injury. In other cell types, JNK activation was shown to be required for apoptosis. This study tested the hypotheses that JNK contributes to hepatocellular apoptosis, and that inhibition of JNK activity improves cell viability. Methods. Rat hepatocytes were harvested from Sprague-Dawley rats and pretreated with SP600125, a JNK inhibitor. Subsequently, they were exposed to apoptotic stimuli consisting of either the bile salt gly- cochenodeoxycholic acid (GCDC) or tumor necrosis factor (TNF)-α and actinomycin D. Results. Western blotting demonstrated specific inhibition of JNK by SP600125. Inhibition of JNK resulted in improved viability measured with crystal violet, decreased in situ DNA nick end labeling pos- itivity, and decreased cleavage of poly (ADP-ribose) polymerase and caspase-3. TNF-α and actinomycin D induced apoptosis, upregulated p53, and downregulated expression of the anti-apoptotic protein X- linked inhibitor of apoptosis protein. These effects were abrogated by JNK inhibition. Conclusion. These data show that pharmacologic inhibition of JNK activity reduces bile salt or TNF- α–induced apoptosis by maintaining expression of anti-apoptotic proteins. The results indicate that JNK is an important component of the apoptosis signaling cascade and suggest a possible therapeutic strategy in certain liver disorders. (Surgery 2003;134:280-4.) From the Department of Surgery, University of Pittsburgh Medical Center, Pittsburgh, Pa Presented at the 64th Annual Meeting of the Society of Univer- sity Surgeons, Houston, Texas, February 12-15, 2003. Research supported by the American Society of Transplant Sur- geons-Roche Laboratories Surgical Scientist Scholarship. Reprint requests: Eric L. Marderstein, MD, PO Box 7533, Pitts- burgh, PA 15213. © 2003 Mosby, Inc. All rights reserved. 0039-6060/2003/$30.00 + 0 doi:10.1067/msy.2003.237