Background: In experimental liver transplantation, endogenous protease inhibitors alleviate ischemia-reperfusion (I/R) injury by inhibiting proteolysis and by direct anti-inflammatory actions. We described the kinetics of endogenous protease inhibitors and explored their anti-inflammatory potential during reperfusion and their effects on graft function in human liver transplantation.
Methods: We measured circulating levels of protease inhibitors (secretory leukocyte proteinase inhibitor, SLPI; tissue inhibitor of metalloproteinases-1, TIMP-1) and proteolytic enzymes (elastase; matrix metalloproteinase-9, MMP-9) with ELISA, and neutrophil and monocyte CD11b and L-selectin expression with flow cytometry during liver transplantation in ten patients. To assess changes within the graft during reperfusion, blood samples from portal and hepatic veins were obtained simultaneously.
Results: Circulating SLPI and TIMP-1 levels decreased during surgery. During initial reperfusion, the transhepatic SLPI gradient was -27 (-35 to -22) ng/ml, P = 0.005, and TIMP-1 -510 (-636 to -362) ng/ml, P = 0.005, indicating graft protease inhibitor uptake. Concomitantly, hepatic phagocyte activation and sequestration as well as elastase and MMP-9 release into the circulation occurred. The transhepatic SLPI gradient correlated with postoperative liver enzymes (ALT R = -0.648, P = 0.043; ALP R = -0.661, P = 0.038; bilirubin R = -0.821, P = 0.004; GGT R = -0.648, P = 0.043).
Conclusions: The results suggest a relative shortage of protease inhibitors within the liver during reperfusion, which may contribute to the development of graft injury.