Serp-2, a virus-derived apoptosis and inflammasome inhibitor, attenuates liver ischemia-reperfusion injury in mice

Abstract

Background Ischemia-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 ser ine p rotease in hibitor ( 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. Methods Wildtype (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. Results Serp-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). Conclusions Treatment with Serp-2, a virus-derived inflammasome and apoptotic pathway inhibitor, improves sur...

Deriving Immune Modulating Drugs from Viruses—A New Class of Biologics

“…Continuous infusion of vMIP-II decreased infiltrating hematogenous cells at the site of injury in a spinal cord contusion injury in rats, with associated reductions in neuronal loss and gliosis [150]. However, this study did not include an assessment of locomotor function, thus it remains to be seen whether chemokine antagonism with vMIP-II improves functional recovery, as seen with the poxvirus chemokine modulator M-T7 [61]. Gene transfer of vMIP-II by direct injection of plasmid DNA improved cardiac allograft survival when hearts were placed in the subcutaneous position of the ear pinnae of CBA/J recipients [151].…”

“…In mouse models of aortic allograft transplants, Serp-2 significantly reduced inflammation and intimal hyperplasia, again with no detected side effects [50,51]. In a model of partial 70% warm ischemia-reperfusion injury in the liver (LIRI), Serp-2 treatment given systemically also improved survival over 10 days, reduced necrotic damage of the liver and lowered acute markers of liver damage [61]. Surprisingly, caspase-1, caspase-3 and caspase-8 activation were not suppressed, suggesting an alternative mechanism of protection potentially by inhibition of circulating inflammatory proteases.…”

Inflammasome-Mediated Inflammation in Liver Ischemia-Reperfusion Injury

“…Moreover, specific inhibitors of inflammasome need to be examined under conditions of different warm ischemia times and percentages. A recent study shows that treatment with Serp-2, a virus-derived inhibitor of apoptosis and inflammasome, regulates the levels of caspase-1, 8 and 10, improving the survival of mice submitted to 90 min of partial (70%) warm ischemia [128]. Interestingly, a study by Yang et al, using an experimental model of hepatic I/R based on 45 min of 70% warm ischemia, showed that Z-VD-fmk, a pan-caspase inhibitor (including caspase-1), had no effect on I/R injury or on the number of TUNEL-positive cells and staining pattern (nucleus and cytosol) [129].…”

“…Interestingly, a study by Yang et al, using an experimental model of hepatic I/R based on 45 min of 70% warm ischemia, showed that Z-VD-fmk, a pan-caspase inhibitor (including caspase-1), had no effect on I/R injury or on the number of TUNEL-positive cells and staining pattern (nucleus and cytosol) [129]. The authors noted the minor role of apoptosis, thus contesting a relevant role for inflammasome or pyroptosis in hepatic I/R, at least in conditions of 90 min of partial (70%) warm ischemia [128] or 30 min of total warm I/R injury [126]. Data suggest that future research should be focused on detailing the type of cell death (necrosis, apoptosis and/or pyroptosis) and the signaling mechanisms of cell death, to identify specific targets for attenuating hepatic I/R injury.…”

Recombinant Myxoma Virus-Derived Immune Modulator M-T7 Accelerates Cutaneous Wound Healing and Improves Tissue Remodeling

“…Myxoma virus (MYXV) is a leporipoxvirus with well-known strict species-specificity and host-tropism to the European rabbit ( Oryctolagus cuniculus ) [ 16 ]. We have demonstrated the safety and immunotherapeutic efficacy of several MYXV immune modulators in a wide array of preclinical models [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ]. M-T7 is an MYXV-derived immune modulator with broad chemokine-binding activity and proven therapeutic potential in inflammation-related diseases.…”