Isoglycyrrhizinate Magnesium Enhances Hepatoprotective Effect of FK506 on Ischemia-Reperfusion Injury Through HMGB1 Inhibition in a Rat Model of Liver Transplantation.

BACKGROUND: Ischemia-reperfusion injury after liver transplantation (LT) impairs graft function and affects prognosis of recipients. Isoglycyrrhizinate magnesium (Iso) is a hepatoprotective drug usually used after liver injury. In this study, we intended to explore whether Iso alone have protective effect after ischemia-reperfusion injury in a rat model of liver transplantation. We also aimed to study whether Iso could enhance the hepatoprotective effect of FK506 (tacrolimus) and underlying mechanism.

METHODS: Rats after LT were treated with different concentration of FK506 with or without, Iso or lower-dose FK506 plus Iso. Alanine transaminase, aspartate transaminase, and albumin level were measured after 48 hours, 72 hours, and 7 days. A cell ischemic/reperfusion model was established to further study the mechanism of hepatoprotective effect of FK506 and Iso.

RESULTS: Iso treatment alone had no effect on liver grafts after LT, but lower-dose FK506 + Iso was better for maintenance of liver function than lower-dose FK506 alone at 48 hours, 72 hours, and 7 days after LT. In terms of mechanism, FK506 induced autophagy which resulted in significantly reduced apoptosis and maintained proliferative potential. However, autophagy induced by FK506 also lead to high-mobility group box (HMGB) 1 release from nuclei, resulting in hepatocyte injury through triggering of p38 phosphorylation and chemokine release. Iso effectively inhibited the release of HMGB1 and downstream inflammatory cytokines.

CONCLUSIONS: Iso could inhibit release of HMGB1 by FK506 and enhance the hepatoprotective effect of FK506 in rat LT. Combining Iso with FK506 would be promising for the patients after LT.