REDUCTION OF HEPATIC ISCHEMIA REPERFUSION INJURY BY A SOLUBLE P-SELECTIN GLYCOPROTEIN LIGAND-1/

Objective The authors' goal was to determine the effects of specific b inding and blockade of P-and E-selectins by a soluble P-selectin glyco protein ligand-1 (PSGL-1) in rat models of hepatic in vivo warm ischem ia and ex vivo cold ischemia. The authors also sought to determine the effect of selectin blockade on isograft survival in a syngeneic rat o rthotopic liver transplant model. Summary Background Data Ischemia/rep erfusion (I/R) injury is a major factor in poor graft function after l iver transplantation, which may profoundly influence early graft funct ion and late changes. it is hypothesized that I/R injury leads to the upregulation of P-selectin, which is then rapidly translocated to endo thelial cell surfaces within 5 minutes of reperfusion of the liver, in itiating steps leading to tethering of polymorphonuclear neutrophil le ukocytes to the vascular intima. Local production by leukocytes of int erleukin-1, tumor necrosis factor-alpha or both induces P-selectin exp ression on the endothelium and continues the cascade of events, which increases cell adherence and infiltration of the organ. Methods To exa mine directly the effects of selectins in a warm hepatic I/R injury mo del, 100 mu g of PSGL-1 or saline was given through the portal vein at the time of total hepatic inflow occlusion. The effects of PSGL-1 in cold ischemia were assessed using an isolated perfused rat liver after 6 hours of 4 degrees C storage in University of Wisconsin (UW) soluti on, with or without the instillation of PSGL-1 before the storage. To evaluate the effect of selectin blockade on liver transplant survival, syngeneic orthotopic liver transplants were performed between inbred male Sprague-Dawley rats after 24 hours of cold ischemic storage in UW solution. A separate group of animals received two doses of 100 mu g of PSGL-1 through the portal vein before storage and before reperfusio n of the transplanted liver. Recipient survival was assessed at 7 days , and the Kaplan-Meier product limit estimate method was used for univ ariate calculations of time-dependent recipient survival events. Resul ts In an in vivo warm rat liver ischemia model, perfusion with PSGL-1 afforded considerable protection from I/R injury, as demonstrated by d ecreased transaminase release, reduced histologic hepatocyte damage, a nd suppressed neutrophil infiltration, versus controls (p < 0.05). Whe n cold stored livers were reperfused, PSGL-1 reduced the degree of hep atocyte transaminase release, reduced neutrophil infiltration, and dec reased histologic hepatocyte damage (p < 0.05 vs. UW-only controls). O n reperfusion, livers treated with PSGL-1 demonstrated increased porta l vein blood flow and bile production (p < 0.05 vs. UW-only controls). in addition, 90% of the rats receiving liver isografts stored in UW s olution supplemented with PSGL-1 survived 7 days versus 50% of those w hose transplanted syngeneic livers had been stored in UW alone (p < 0. 05). Conclusions Selectins play an important role in I/R injury of the liver. Early modulation of the interaction between P-selectin and its ligand decreases hepatocyte injury, neutrophil adhesion, and subseque nt migration in both warm and cold rat liver ischemia models. In addit ion, the use of PSGL-1 before ischemic storage and before transplantat ion prevents hepatic injury, as documented by a significant increase i n liver isograft survival. These findings have important clinical rami fications: early inhibition of alloantigen-independent mechanisms duri ng the I/R damage may influence both short-and long-term survival of l iver allografts.