Tacrolimus preconditioning of rat liver allografts impacts glutathione homeostasis and early reperfusion injury.

Objective: To characterize the immunosuppressant tacrolimus as a protective antioxidant in rat liver transplantation.

Methods: Livers 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).

Results: Administration 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.

Conclusion: Hepatocellular 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.