Cannabinoid-2 receptor mediates protection against hepatic ischemia/reperfusion injury

Hepatic ischemia-reperfusion (I/R) injury continues to be a fatal complication that can follow liver surgery or transplantation. We have investigated the involvement of the endocannabinoid system in hepatic I/R injury using an in vivo mouse model. Here we report that I/R triggers several-fold increases in the hepatic levels of the endocannabinoids anandamide and 2-arachidonoylglycerol, which originate from hepatocytes, Kupffer, and endothelial cells. The I/R-induced increased tissue endocannabinoid levels positively correlate with the degree of hepatic damage and serum TNF- alpha, MIP- 1 alpha, and MIP- 2 levels. Furthermore, a brief exposure of hepatocytes to various oxidants (H2O2 and peroxynitrite) or inflammatory stimuli (endotoxin and TNF-alpha) also increases endocannabinoid levels. Activation of CB2 cannabinoid receptors by JWH133 protects against I/R damage by decreasing inflammatory cell infiltration, tissue and serum TNF-alpha, MIP-1 alpha and MIP- 2 levels, tissue lipid peroxidation, and expression of adhesion molecule ICAM- 1 in vivo. JWH133 also attenuates the TNF-alpha-induced ICAM-1 and VCAM- 1 expression in human liver sinusoidal endothelial cells (HLSECs) and the adhesion of human neutrophils to HLSECs in vitro. Consistent with the protective role of CB2 receptor activation, CB2-/- mice develop increased I/R-induced tissue damage and proinflammatory phenotype. These findings suggest that oxidative/nitrosative stress and inflammatory stimuli may trigger endocannabinoid production, and indicate that targeting CB2 cannabinoid receptors may represent a novel protective strategy against I/R injury. We also demonstrate that CB2-/- mice have a normal hemodynamic profile.-Batkai, S., Osei-Hyiaman, D., Pan, H., El-Assal, O., Rajesh, M., Mukhopadhyay, P., Hong, F., Harvey-White, J., Jafri, A., Hasko, G., Huffman, J. W., Gao, B., Kunos, G., Pacher, P. Cannabinoid-2 receptor mediates protection against hepatic ischemia/ reperfusion injury.