Tacrolimus Preconditioning of Rat Liver Allografts Impacts Glutathione Homeostasis and Early Reperfusion Injury

ObjectiveTo characterize the immunosuppressant tacrolimus as a protective antioxidant in rat liver transplantation.MethodsLivers of male Lewis rats underwent 24 h of hypothermic preservation in UW solution and were rinsed with tacrolimus or placebo directly before transplantation. Markers of liver injury, such as enzymes and bile flow, were determined during a 2 h reperfusion period. Concentrations of reduced (GSH) and oxidized (GSSG) glutathione were analyzed in plasma, bile, and liver tissue for estimation of oxidant stress caused by reactive oxygen species (ROS).ResultsAdministration of tacrolimus (10 ng/mL) resulted in decreased ALT plasma levels (1740 ± 1169 U/l versus 3691 ± 1144 U/l; P < 0.05) at 2 h of reperfusion. While endogenous intracellular GSH concentrations remained unchanged, GSSG, the oxidation product of GSH, was markedly decreased at 2 h of reperfusion in preconditioned livers (47.0 ± 10.4 nm/g versus 71.8 ± 30.6 nm/g; P < 0.05). Correspondingly, GSSG bile concentrations (0.19 ± 0.04 mM versus 0.13 ± 0.04 mM; P < 0.05) as well as plasma GSSG levels (2.4 ± 0.3 mM versus 1.4 ± 0.2 mM; P < 0.05) were significantly increased upon reperfusion. These findings suggest that tacrolimus impacts post-ischemic GSH metabolism when administered as a rinse solution for liver allografts through an unknown pathway.ConclusionHepatocellular injury following transplantation was significantly decreased by preconditioning with tacrolimus. One possible mechanism of action is the detoxification of ROS through the preservation of cytosolic and extracellular GSH/GSSG ratios.