Relevance of proteolysis and proteasome activation in fatty liver graft preservation: An Institut Georges Lopez-1 vs University of Wisconsin appraisal

摘要

AIM To compare liver proteolysis and proteasome activation in steatotic liver grafts conserved in University of Wisconsin(UW) and Institut Georges Lopez-1(IGL-1)solutions.METHODS Fatty liver grafts from male obese Zücker rats were conserved in UW and IGL-1 solutions for 24 h at 4 ℃and subjected to "ex vivo " normo-thermic perfusion(2 h; 37 ℃). Liver proteolysis in tissue specimens and perfusate was measured by reverse-phase high performance liquid chromatography. Total free amino acid release was correlated with the activation of the ubiquitin proteasome system(UPS: measured as chymotryptic-like activity and 20 S and 19 S proteasome), the prevention of liver injury(transaminases), mitochondrial injury(confocal microscopy) and inflammation markers(TNF 1 alpha, high mobility group box-1(HGMB-1) and PPAR gamma), and liver apoptosis(TUNEL assay, cytochrome c and caspase 3).RESULTS Profiles of free AA(alanine, proline, leucine, isoleucine, methionine, lysine, ornithine, and threonine, among others) were similar for tissue and reperfusion effluent. In all cases, the IGL-1 solution showed a significantly higher prevention of proteolysis than UW(P < 0.05) after cold ischemia reperfusion. Livers conserved in IGL-1 presented more effective prevention of ATP-breakdown and more inhibition of UPS activity(measured as chymotryptic-like activity). In addition, the prevention of liver proteolysis and UPS activation correlated with the prevention of liver injury(AST/ALT) and mitochondrial damage(revealed by confocal microscopy findings) as well as with the prevention of inflammatory markers(TNF1alpha and HMGB) after reperfusion. In addition, the liver grafts preserved in IGL-1 showed a significant decrease in liver apoptosis, as shown by TUNEL assay and the reduction of cytochrome c, caspase 3 and P62 levels. CONCLUSION Our comparison of these two preservation solutions suggests that IGL-1 helps to prevent ATP breakdown more effectively than UW and subsequently achieves a higher UPS inhibition and reduced liver proteolysis.