Aquaporin-9 facilitates liver regeneration following hepatectomy

Aquaporin-9 (AQP9) is an aquaglyceroporin strongly expressed in the basolateral membrane of hepatocytes facing the sinusoids. AQP9 is permeable to hydrogen peroxide (H2O2) and glycerol as well as to water. Here, we report impaired liver regeneration in AQP9−/− mice which involves altered steady-state H2O2 concentration and glucose metabolism in hepatocytes. AQP9−/− mice showed remarkably delayed liver regeneration and increased mortality following 70% or 90% partial hepatectomy. Compared to AQP9+/+ littermates, AQP9−/− mice showed significantly greater hepatic H2O2 concentration and more severe liver injury. Fluorescence measurements indicated impaired H2O2 transport across plasma membrane of primary cultured hepatocytes from AQP9−/− mice, supporting the hypothesis that AQP9 deficiency results in H2O2 accumulation and oxidative injury in regenerating liver because of reduced export of intracellular H2O2 from hepatocytes. The H2O2 overload in AQP9−/− hepatocytes reduced PI3K-Akt and insulin signaling, inhibited autophagy and promoted apoptosis, resulting in impaired proliferation and increased cell death. In addition, hepatocytes from AQP9−/− mice had low liver glycerol and high blood glycerol levels, suggesting decreased glycerol uptake and gluconeogenesis in AQP9−/− hepatocytes. Adeno-associated virus (AAV)-mediated expression of hepatic expression of aquaglyceroporins AQP9 and AQP3 in AQP9−/− mice, but not water-selective channel AQP4, fully rescued the impaired liver regeneration phenotype as well as the oxidative injury and abnormal glucose metabolism. Our data revealed a pivotal role of AQP9 in liver regeneration by regulating hepatocyte H2O2 homeostasis and glucose metabolism, suggesting AQP9 as a novel target to enhance liver regeneration following injury, surgical resection or transplantation.