Background and Aims:Mammalian target of rapamycin (mTOR) signaling controls many essential cellular functions. However, the role and its underlying mechanism of Rictor/mTOR complex 2 (mTORC2) in regulating liver ischemia and reperfusion (IR) injury remains largely unknown.

Methods: In a murine liver partial warm IR model, we selectively knockdown Rictor signaling in liver parenchymal and non-parenchymal cells. Hepatocellular injury and Kupffer cell (KC) pro-inflammatory activation were studied. Rictor signaling in human liver tissues post ischemia was also analyzed.

Results: Liver ischemia triggered a transient inactivation followed by a rapid reactivation during reperfusion. Abrogation of mTORC2 signaling in hepatocytes by Rictor-shRNA-AAV8 resulted in significantly increased liver IR injury. In vitro, knockdown of Rictor in hepatocyte inhibited hepatocellular autophagy, enhanced CHOP and pro-apoptosis signaling pathway activation, leading to increased TNF-a induced cell death. Furthermore, Rictor siRNA with mannose-conjugated polymers was used to specifically block Rictor signaling in KC. KCs post IR were isolated and inflammatory cytokine secretion was evaluated. Specific Rictor knockdown in KC resulted in significant increase in TNF-α and IL-6 secretion but dramatically decreased anti-inflammatory IL-10 secretion. Interestingly, autophagy in KC was inhibited by Rictor knockdown as well. We further analyzed the role of Rictor in KC M1/M2 polarization. Rictor knockdown inhibited IL-10-secreting M2-like macrophage polarization, as revealed by decreased Arg1 and Mrc1 gene induction accompanied by a decrease in STAT6 signaling pathway activation. In vivo Rictor knockdown decreased intrahepatic anti-inflammatory IL-10 gene induction, leading to aggravated liver IR injury. Finally, human liver tissues were collected in patients undergoing liver partial resection with blockade of hepatic portal. Western blot analysis revealed that Rictor activation was inhibited by liver ischemia.

Conclusion: Our findings defined a critical role of mTORC2 signaling in protecting livers against IR injury by promoting hepatocellular autophagy and facilitating KC M2 polarization. Targeting Rictor signaling pathway may shine light on ways to protect against liver ischemic injury in patients.

CITATION INFORMATION: Zhou H., Rao Z., Liu R., Zhou S., Rao J., Gu J., Lu H., Xia Y., Wang X., Zhai Y., Lu L. Rictor mTORC2 Signaling Protects Ischemic Liver Injury by Targeting Both Liver Parenchymal and Non-Parenchymal Cells Am J Transplant. 2017;17 (suppl 3).

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