Abstract
BackgroundIschemia-reperfusion injury (IRI) is an antigen-independent, innate immune response to arterial occlusion and ischemia with subsequent paradoxical exacerbation after reperfusion. IRI remains a critical problem after vessel occlusion and infarction or during harvest and surgery in transplants. After transplant, liver IRI (LIRI) contributes to increased acute and chronic rejection and graft loss. Tissue loss during LIRI has been attributed to local macrophage activation and invasion with excessive inflammation together with hepatocyte apoptosis and necrosis. Inflammatory and apoptotic signaling are key targets for reducing post-ischemic liver injury.Myxomavirus is a rabbit-specific leporipoxvirus that encodes a suite of immune suppressing proteins, often with extensive function in other mammalian species. Serp-2 is a cross-class serine protease inhibitor (serpin) which inhibits the inflammasome effector protease caspase-1 as well as the apoptotic proteases granzyme B and caspases 8 and 10. In prior work, Serp-2 reduced inflammatory cell invasion after angioplasty injury and after aortic transplantation in rodents. In this report, we explore the potential for therapeutic treatment with Serp-2 in a mouse model of LIRI.MethodsWildtype (C57BL/6 J) mice were subjected to warm, partial (70%) hepatic ischemia for 90 min followed by treatment with saline or Serp-2 or M-T7, 100 ng/g/day given by intraperitoneal injection on alternate days for 5 days. M-T7 is a Myxomavirus-derived inhibitor of chemokine-GAG interactions and was used in this study for comparative analysis of an unrelated viral protein with an alternative immunomodulating mechanism of action. Survival, serum ALT levels and histopathology were assessed 24 h and 10 days post-LIRI.ResultsSerp-2 treatment significantly improved survival to 85.7% percent versus saline-treated wildtype mice (p = 0.0135), while M-T7 treatment did not significantly improve survival (p = 0.2584). Liver viability was preserved by Serp-2 treatment with a significant reduction in serum ALT levels (p = 0.0343) and infarct scar thickness (p = 0.0016), but with no significant improvement with M-T7 treatment. Suzuki scoring by pathologists blinded with respect to treatment group indicated that Serp-2 significantly reduced hepatocyte necrosis (p = 0.0057) and improved overall pathology score (p = 0.0046) compared to saline. Immunohistochemistry revealed that Serp-2 treatment reduced macrophage infiltration into the infarcted liver tissue (p = 0.0197).ConclusionsTreatment with Serp-2, a virus-derived inflammasome and apoptotic pathway inhibitor, improves survival after liver ischemia-reperfusion injury in mouse models. Treatment with a cross-class immune modulator provides a promising new approach designed to reduce ischemia-reperfusion injury, improving survival and reducing chronic transplant damage.
Highlights
Ischemia-reperfusion injury (IRI) is a two-step process characterized by an initial transient blockade of blood flow and oxygen delivery
We have demonstrated that treatment with Serp-1, a member of the serpin superfamily of proteins, as well as peptides derived from the Serp-1 reactive center loop (RCL), reduce severity and prolong survival in a lethal, herpesvirus-induced model of large vessel vasculitis [23,24,25]
Mouse liver ischemia reperfusion injury (LIRI) All animal protocols were approved by the University of Florida Institutional Animal Care and Use Committee (IACUC) and conform to national guidelines
Summary
Ischemia-reperfusion injury (IRI) is a two-step process characterized by an initial transient blockade of blood flow and oxygen delivery. IRI is a primary cause of early graft failure after transplant and can lead to a higher incidence of early acute and long term chronic rejection. Other approaches include inhibition of the mammalian target of rapamycin (mTOR) with drugs such as rapamycin and Everolimus [5], or generalized immune suppression with cyclosporine A or steroids [6]. While these treatments have significantly improved outcomes following liver transplantation in the past three decades, many adverse effects persist. Liver IRI (LIRI) contributes to increased acute and chronic rejection and graft loss. We explore the potential for therapeutic treatment with Serp-2 in a mouse model of LIRI
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