Published online Jun 21, 2017. doi: 10.3748/wjg.v23.i23.4211
Peer-review started: February 1, 2017
First decision: March 16, 2017
Revised: April 8, 2017
Accepted: June 1, 2017
Article in press: June 1, 2017
Published online: June 21, 2017
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.
Fatty liver grafts from male obese Zücker rats were conserved in UW and IGL-1 solutions for 24 h at 4 °Cand subjected to “ex vivo” normo-thermic perfusion (2 h; 37 °C). 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 20S and 19S 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).
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.
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.
Core tip: Although several reports have confirmed that proteolytic activity during cold storage determines graft outcome after transplantation, the effect of preservation solution on steatotic liver graft proteolysis and on the activation of ATP-dependent proteasome during cold ischemia injury has not been fully investigated. Here, we compared the effect of two preservation solutions Institut Georges Lopez-1(IGL-1) and University of Wisconsin on liver proteolysis and ubiquitin-proteasome activation when steatotic liver grafts were subjected to cold storage. We provide evidence for a protective role of proteasome and proteolysis inhibition using IGL-1 during steatotic liver graft preservation.