A Soluble Form of P Selectin Glycoprotein Ligand 1 Requires Signaling by Nuclear Factor Erythroid 2–Related Factor 2 to Protect Liver Transplant Endothelial Cells Against Ischemia–Reperfusion Injury

Liver endothelial cell ( LEC ) damage is essential in the pathogenesis of ischemia–reperfusion injury ( IRI ) in transplant recipients. We analyzed the mechanism of LEC resistance against IRI by using a novel recombinant soluble form of P selectin glycoprotein ligand 1, tandem P selectin glycoprotein ligand immunoglobulin ( TSGL ‐Ig), in a mouse model of hepatic cold preservation (4°C in University of Wisconsin solution for 20 h) and syngeneic orthotopic liver transplantation ( OLT ). Unlike controls, TSGL ‐Ig protected orthotopic liver transplants against ischemia–reperfusion ( IR ) stress, shown by depressed serum alanine aminotransferase levels, well‐preserved hepatic architecture, and improved survival (42% vs. 92%). TSGL ‐Ig suppressed neutrophil/macrophage sequestration and proinflammatory cytokine/chemokine programs in OLT . Treatment with TSGL ‐Ig mitigated LEC activation (P and E selectin, VCAM ‐1 and intercellular adhesion molecule 1 expression). In parallel in vitro studies, TSGL ‐Ig diminished cellular damage in H 2 O 2 ‐stressed LEC cultures (lactic acid dehydrogenase and alanine aminotransferase levels). Increased thioredoxin, glutamate‐cysteine ligase , NAD(P)H quinone dehydrogenase 1, and hypoxia‐inducible factor 1α expression, along with transcription factor nuclear factor erythroid 2–related factor 2 (Nrf2), implied that TSGL ‐Ig exerts antioxidant functions in IR ‐stressed OLT and H 2 O 2 ‐stressed LEC s. Indeed, Nrf2‐deficient livers suffered fulminant IRI compared with WT despite concomitant TSGL ‐Ig therapy. Thus, TSGL ‐Ig is not only acting as a competitive antagonist blocking leukocyte migration into IR ‐stressed liver, but it may also act directly as an agonist stimulating Nrf2‐mediated cytoprotection in LEC s. This study supports the role of P selectin signaling in hepatic homeostasis in OLT , with broad implications for tissue damage conditions.