Protection by Glycyrrhizin against Warm Ischemia‐Reperfusion–Induced Cellular Injury and Derangement of the Microcirculatory Blood Flow in the Rat Liver

BACKGROUND/AIM: The mechanism by which ischemia-reperfusion (I/R)-induced derangement of the hepatic microcirculation leads to tissue injury is not fully understood. We postulated that alterations to the hepatic microcirculation, including hemodynamic derangement and increased leukocyte-endothelium interaction, play a role, and that glycyrrhizin exerts its hepatoprotective effects, in part, by reducing these microcirculatory changes. MATERIALS AND METHODS: Wistar rats were subjected to 30-60 minutes segmental hepatic ischemia, followed by 120 minutes of reperfusion. Glycyrrhizin was administered prior to ischemia. Using intravital fluorescence microscopy, the administration of fluorescein isothiocyanate-conjugated erythrocytes allowed the measurement of erythrocyte-velocity (RBC(vel)), lobular, and sinusoidal perfusion. Bleb formation was observed by electron microscopy. Blood and tissue were taken for the assessment of liver injury. RESULTS: Glycyrrhizin reduced I/R-induced liver injury (histology, liver enzymes) and reduced hepatocyte apoptosis (TUNEL, caspase-3 activity). Glycyrrhizin inhibited hepatocyte bleb formation and reversed the I/R-induced reductions in lobular perfusion and RBC(vel). Leukocyte rolling and adherence in postsinusoidal venules and neutrophil infiltration were reduced by glycyrrhizin. I/R-induced elevation in HMGB1 was prevented by glycyrrhizin. CONCLUSIONS: Early bleb formation with deranged microcirculatory flow and leukocyte-endothelium interaction would appear to contribute to I/R-induced hepatocellular injury. Glycyrrhizin exerts its hepatoprotective effect by preventing these changes, in addition to a direct cellular effect.