JNK mediates hepatic ischemia reperfusion injury.
OBJECTIVE
Hepatic ischemia followed by reperfusion (I/R) is a major clinical problem during transplantation, liver resection for tumor, and circulatory shock, producing apoptosis and necrosis. Although several intracellular signal molecules are induced following I/R including NF-kappaB and c-Jun N terminal kinase (JNK), their roles in I/R injury are largely unknown. The aim of this study is to assess the role of JNK during warm I/R injury using novel selective JNK inhibitors.


METHODS
Male Wistar rats (200+/-25 g) are pretreated with vehicle or with one of three compounds (CC0209766, CC0223105, and CC-401), which are reversible, highly selective, ATP-competitive inhibitors of JNK. In the first study, rats are assessed for survival using a model of ischemia to 70% of the liver for 90 min followed by 30% hepatectomy of the non-ischemic lobes and then reperfusion. In the second study, rats are assessed for liver injury resulting from 60 or 90 min of ischemia followed by reperfusion with analysis over time of hepatic histology, serum ALT, hepatic caspase-3 activation, cytochrome c release, and lipid peroxidation.


RESULTS
In the I/R survival model, vehicle-treated rats have a 7-day survival of 20-40%, while rats treated with the three different JNK inhibitors have survival rates of 60-100% (P<0.05). The decrease in mortality correlates with improved hepatic histology and serum ALT levels. Vehicle treated rats have pericentral necrosis, neutrophil infiltration, and some apoptosis in both hepatocytes and sinusoidal endothelial cells, while JNK inhibitors significantly decrease both types of cell death. JNK inhibitors decrease caspase-3 activation, cytochrome c release from mitochondria, and lipid peroxidation. JNK inhibition transiently blocks phosphorylation of c-Jun at an early time point after reperfusion, and AP-1 activation is also substantially blocked. JNK inhibition blocks the upregulation of the pro-apoptotic Bak protein and the degradation of Bid.


CONCLUSIONS
Thus, JNK inhibitors decrease both necrosis and apoptosis, suggesting that JNK activity induces cell death by both pathways.
Uehara
Tetsuya
T
Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
Bennett
Brydon
B
Sakata
Steve T
ST
Satoh
Yoshitaka
Y
Bilter
Graham K
GK
Westwick
John K
JK
Brenner
David A
DA
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism; D003593:Cytoplasm / Q000378:metabolism; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000494:pharmacology; D048031:JNK Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects; D008099:Liver / Q000201:enzymology* / Q000473:pathology; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D009336:Necrosis; D051381:Rats; D017208:Rats, Wistar; D015427:Reperfusion Injury / Q000188:drug therapy / Q000378:metabolism* / Q000401:mortality; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
D004791:Enzyme Inhibitors; D014409:Tumor Necrosis Factor-alpha; D045304:Cytochromes c; D048031:JNK Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases