NTPDase8 Protects Against Liver Ischemia-Reperfusion Injury in Mice

CD39 or NTPDase1 and other nucleoside triphosphate diphosphohydrolases (NTPDases), including NTPDase2, NTPDase3, and NTPDase8, regulate purinergic signaling through tuning the extracellular levels of purine nucleotides and nucleosides. Purinergic signaling regulates liver ischemia-reperfusion (I/R) injury, and CD39 is protective. However, the role of other NTPDases is unknown. In this study, we investigated the role of NTPDase2, NTPDase3, and NTPDase8. Global Entpd2^-/-, Entpd3^-/-, and Entpd8^-/- and control wild type (WT) mice were subjected to liver I/R. In addition, WT and Entpd8^-/- mice underwent global ischemia induced by hemorrhagic shock and resuscitation and injury evaluated. Bone marrow chimeric mice were generated to understand the role of NTPDase expression on hematopoietic cells in regulating liver injury. Although WT, Entpd2^-/- and Entpd3^-/- mice exhibited comparable levels of liver injury following local IR, Entpd8^-/- mice had increased liver injury compared to WT mice. Studies with bone marrow chimeric mice indicated that NTPDase8 on parenchymal liver cells protected against hepatic injury. This was confirmed by single-nucleus RNAseq showing hepatocytes are the dominant cell type expressing NTPDase8 in the liver. Entpd8^-/- mice after I/R injury were noted to have higher ATP concentrations in the liver and plasma. The P2 receptor antagonist suramin decreased liver injury in Entpd8^-/- mice indicating P2 signaling contributes to liver injury in these mice. Finally, Entpd8^-/- mice had increased liver injury compared to WT mice also after hemorrhagic shock and resuscitation. These findings highlight the differential roles of NTPDase family members in the liver, with parenchymal/hepatocyte expression of NTPDase8 emerging as a critical suppressor of the inflammatory and metabolic responses to hepatic I/R insult, even in the presence of vascular NTPDase1 expression.