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Open Access Publications from the University of California

Macrophage heme oxygenase-1-SIRT1-p53 axis regulates sterile inflammation in liver ischemia-reperfusion injury.

  • Author(s): Nakamura, Kojiro
  • Zhang, Min
  • Kageyama, Shoichi
  • Ke, Bibo
  • Fujii, Takehiro
  • Sosa, Rebecca A
  • Reed, Elaine F
  • Datta, Nakul
  • Zarrinpar, Ali
  • Busuttil, Ronald W
  • Araujo, Jesus A
  • Kupiec-Weglinski, Jerzy W
  • et al.

BACKGROUND & AIMS:Hepatic ischemia-reperfusion injury (IRI), characterized by exogenous antigen-independent local inflammation and hepatocellular death, represents a risk factor for acute and chronic rejection in liver transplantation. We aimed to investigate the molecular communication involved in the mechanism of liver IRI. METHODS:We analyzed human liver transplants, primary murine macrophage cell cultures and IR-stressed livers in myeloid-specific heme oxygenase-1 (HO-1) gene mutant mice, for anti-inflammatory and cytoprotective functions of macrophage-specific HO-1/SIRT1 (sirtuin 1)/p53 (tumor suppressor protein) signaling. RESULTS:Decreased HO-1 expression in human post-reperfusion liver transplant biopsies correlated with a deterioration in hepatocellular function (serum ALT; p<0.05) and inferior patient survival (p<0.05). In the low HO-1 liver transplant biopsy group, SIRT1/Arf (alternative reading frame)/p53/MDM2 (murine double minute 2) expression levels decreased (p<0.05) while cleaved caspase 3 and frequency of TUNEL+cells simultaneously increased (p<0.05). Immunofluorescence showed macrophages were the principal source of HO-1 in human and mouse IR-stressed livers. In vitro macrophage cultures revealed that HO-1 induction positively regulated SIRT1 signaling, whereas SIRT1-induced Arf inhibited ubiquitinating activity of MDM2 against p53, which in turn attenuated macrophage activation. In a murine model of hepatic warm IRI, myeloid-specific HO-1 deletion lacked SIRT1/p53, exacerbated liver inflammation and IR-hepatocellular death, whereas adjunctive SIRT1 activation restored p53 signaling and rescued livers from IR-damage. CONCLUSION:This bench-to-bedside study identifies a new class of macrophages activated via the HO-1-SIRT1-p53 signaling axis in the mechanism of hepatic sterile inflammation. This mechanism could be a target for novel therapeutic strategies in liver transplant recipients. LAY SUMMARY:Post-transplant low macrophage HO-1 expression in human liver transplants correlates with reduced hepatocellular function and survival. HO-1 regulates macrophage activation via the SIRT1-p53 signaling network and regulates hepatocellular death in liver ischemia-reperfusion injury. Thus targeting this pathway in liver transplant recipients could be of therapeutic benefit.

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