Background: Hepatic steatosis presents a major challenge in liver transplantation. Steatotic livers show an increased susceptibility to cold ischemia and reperfusion (CIR) injury. The mechanisms responsible for the vulnerability of this liver are not fully understood. Recently it has been reported that ubiquitin proteasome system (UPS), the main non lysosomal proteolytic system, is activated during cold storage which enhances graft injury. In this communication we evaluated the addition of reversible proteasome inhibitor Bortezomib (BRZ) at non toxic low dose (100 nM) to the IGL-1 solution. Protective mechanisms were investigated

Experimental: Steatotic livers were preserved for 24h (4ºC) in IGL-1 solution with and without BRZ (100 nM) or pretreated with AMPK inhibitor Adenine 9-Β-D-arabinofuranoside (Ara) and preserved in IGL+BRZ. Livers were then perfused for 2 hours at 37 C. Liver injury (ALT/AST) and function (bile production and vascular resistane) were measured. AKT/ mTOR, pAMPK and reticulum stress were determined by western blot. Proteasome activity was assessed after ischemia / reperfusion. Results: We show that activation of UPS during cold storage was much higher for steatotic livers compared to lean. Addition of BRZ to IGL-1 solution significantly reduces steatotic liver injury; ameliorates graft function and decreases endoplasmic reticulum stress (GRP78, CHOP).These benefits were abolished by the pretreatment of obese rats with AMPK inhibitor Ara. Western blot analyses show a significant increase in pAMPK after reperfusion but not after cold storage. We also observed in IGL+BRZ group, a significant phosphorylation of Akt, which in turn induces the phosphorylation of mTOR. Conclusion: BRZ at low non toxic concentration is a promising additive to IGL-1 solution for steatotic liver preservation. Its protective effect is due, in part, to the inhibition of AMPK degradation during the early phase of reperfusion and the activation of Akt and mTOR pathways.

« Back to 2013 American Transplant Congress