P 037 - Effect of Neutral Sphingomyelinase Inhibition on ER Stress and Apoptosis in Liver Ischemia–Reperfusion Injury

Abstract

This study determined the role of selective neutral sphingomyelinase (N-SMase) inhibition on endoplasmic reticulum (ER) stress and apoptotic markers in a rat model of liver ischemia reperfusion (IR) injury. Liver IR injury was created by clamping blood vessels supplying the median and left lateral hepatic lobes for 60 min, followed by 60 min reperfusion. Sphingmyelin and ceramide levels in liver tissue were determined by tandem mass spectrometry. Spingomyelin levels were significantly increased in all IR groups compared to controls. Treatment with a specific N-SMase inhibitor significantly decreased all measured ceramides in IR injury. A significant increase was observed in ER stress markers C/EBP-homologous protein (CHOP) and 78 kDa glucose-regulated protein (GRP78) in IR injury, which was not significantly altered by N-SMase inhibition. Inhibition of N-SMase caused a significant reduction in phospho-NF-kB levels, hepatic TUNEL staining, cytosolic cytochrome c and caspase-3, -8 and -9 activities which were significantly increased in IR injury. Data herein confirm the role of ceramide in increased apoptotic cell death and highlight the protective effect of N-SMase inhibition in down-regulation of apoptotic stimuli responses occurring in hepatic IR injury.