Abstract 20115: Cross-Class Serine Protease Inhibitor Serp-2 Blocks Liver Ischemia Reperfusion Injury in Mice After Inflammasome Blockade
Introduction: Ischemia reperfusion injury (IRI) causes approximately 10% of transplant failure, contributing to a higher incidence of acute and chronic rejection and to a shortage of donor organs. Inflammasome activation through caspase-1 drives LIRI. Myxomaviral protein Serp-2 is a cross-class inhibitor of both serine (granzymeB) mediated apoptosis and cysteine proteases (caspase-1) mediated inflammasome activation reducing inflammation after aortic transplant.
Method: Ischemia (70%) was induced by clamping the hepatic artery and portal vein for 90 min in caspase-1-/-, IFNγR-/- and wild-type (WT) C57Bl/6 mice. Survival and LIRI were assessed after treatments with Serp-2, a broad spectrum chemokine inhibitor, M-T7 or M-T7 R171E mutant protein with comparison to saline controls. PMA stimulation of cellular invasion into ascites was also tested in WT, Casp1-/- and GzmB-/- mice for the effects of Serp-2 and control cowpox cross-class serpin, CrmA which does not reduce inflammation.
Results: Serp-2 significantly increased survival (P<0.046) and decreased vacuolization (3.0 ± 0.58, P< 0.006), congestion (3.0 ± 0.54, P< 0.006) and necrosis (3.14 ± 0.14, P<0.0001), as well as overall hepatic damage (Suzuki score 3.04 ± 0.381, P<0.0006) compared to controls. Serp-2 treatment also significantly reduced infarct scar thickness at 24 hr follow-up and F4/80+ macrophage counts while caspase-1-/- mice had only a decrease in macrophage invasion. Caspase-1 deficiency improved survival compared to controls, but with borderline significance (P=0.174). IFNγR-/- transplant and M-T7 and M-T7mutant treatment did not improve survival. Gene expression in LIRI sections with Serp-2 or Casp1-/- demonstrated trends toward increased apoptosis gene expression (P ≤ 0.05). In peritoneal exudates, both GzmB-/- and Casp1-/- showed increased numbers of Ly6Clo (M2 macrophage) cells. With GzmB-/- mice CrmA increased the neutrophil count compared to saline treatment significantly while Serp-2 did not.
Conclusion: Serp-2 treatment is more effective than caspase-1 deficiency alone in reducing LIRI and improving survival. Combining blockade of apoptotic and inflammasome pathways has potential for greater protective benefit, preventing LIRI in transplanted donor organs.
Author Disclosures: S. Ambadapadi: None. D. Wakefield: None. H. Chen: None. J. Fuentes: None. J. Davids: None. B. Marques: None. L. Dixon: None. W. Clapp: None.
- © 2016 by American Heart Association, Inc.