Dexmedetomidine Protects against Hepatic Ischemia-Reperfusion Injury by inhibiting Endoplasmic Reticulum Stress and Cell Apoptosis in Rats

Background: Hepatic ischemia-reperfusion injury (IRI) remains a major complication of liver surgery, dexmedetomidine (DEX) has a certain protective effect on liver during ischemia-reperfusion, but the underlying mechanisms are not fully understood. This study explored the protective effects of DEX and investigated whether DEX protects against hepatic IRI by inhibiting endoplasmic reticulum stress (ERS) and its downstream apoptotic pathway in a rat model. Methods: Thirty-six male Sprague-Dawley (SD) rats were divided into six groups: S, IR, DL, DM1, DH and DM2 group. Group S was subjected to laparotomy, and exposure of the portal triad without occlusion. I-R injury model was induced by clamping the portal vessels supplying the middle and left hepatic lobes for 30 min in IR, DL, DM1, DH and DM2 group. Then DL, DM1, DH group received DEX of 25 μg/kg, 50 μg/kg and 100 μg/kg intraperitoneally at 30 min before ischemia, respectively, DM2 group received 50 μg/kg DEX intraperitoneally 30 min after reperfusion, and IR group received normal saline. After 6 h of reperfusion, assessment of liver function, histopathology, oxidative stress was performed. The liver cell microstructure was detected by transmission electron microscopy. Hepatocyte apoptosis was determined by TUNEL assay. Real-time PCR, Western blotting were performed to analyze various ERS molecules. Results: We observed that DEX protected the liver by alleviating hepatocytes damage, reducing the content of ALT and MDA, increasing the activity of SOD, reducing the number of TUNEL-positive cells, down-regulating the expression of GRP-78, PERK, ATF-6, Caspase-12 mRNA, and p-PERK, p-IRE-1 α, CHOP proteins, up-regulating Bcl-2 protein. The effect of 50 μg/kg DEX is superior to 25 μg/kg DEX, but not significantly different from 100μg/kg DEX. There was no significant difference in the above monitoring indexes between DM1 and DM2 group. Conclusions: DEX protects the liver from IRI by inhibiting ERS and cell apoptosis. The protective effect of DEX was dose-dependent in a certain dose range, both DEX administered prior to ischemia and following reperfusion markedly reduced liver injury induced by hepatic IRI in mice.