Viral interleukin-10 gene transfer prevents liver ischemia-reperfusion injury: Toll-like receptor-4 and heme oxygenase-1 signaling in innate and adaptive immunity

Ischemia-reperfusion injury (IRI) contributes to early and late dysfunction of liver transplants. We have shown that sentinel Toll-like receptor-4 (TLR4) plays a key role in the activation of T cell immune responses during hepatic IRI. We have also documented that overexpression of heme oxygenase-1 (HO-1) exerts potent cytoprotective effects. This study analyzes how adenovirus (Ad)-based viral interleukin-10 (vIL-10) gene transfer affects TLR4 and HO-1 signaling in host innate and adaptive immunity during liver IRI. Using a partial lobar warm IRI model, groups of wild-type and HO-1^+/- knockout (KO) mice were assessed for severity of hepatocellular damage after 90 min of warm ischemia followed by 6 hr of reperfusion. Both wild-type and HO-1^+/- KO mice treated with Ad-vIL-10 have shown improved hepatic function (serum glutamic-oxaloacetic transaminase levels), ameliorated histological signs of IRI (Suzuki's score), decreased neutrophil accumulation (myeloperoxidase activity), and depressed tumor necrosis factor-α/IL-1β, IL-2/interferon- γ, E-selectin, and macrophage inflammatory protein-2 expression. These effects were IL-10 dependent as treatment with neutralizing antibody re-created liver IRI. In contrast, untreated wild-type and HO-1^+/- KO mice, as well as wild-type and HO-1^+/- KO mice treated with Ad-β-Gal, showed severe hepatocellular damage due to IRI. Unlike in controls, wild-type and HO-1^+/- KO mice treated with Ad-vIL-10 revealed markedly depressed TLR4 and NF-κB expression, along with increased HO-1 and Bcl-2/Bcl-x_L expression, as compared with respective controls. Thus, vIL-10 gene transfer prevents hepatic IRI in association with depressed expression of innate TLR4, and adaptive Th1 cytokine/chemokine programs. The induction of antioxidant HO-1 and anti-apoptotic Bcl-2/Bcl-x_L by vIL-10 exerts synergistic cytoprotective function against antigen-independent hepatic inflammatory response triggered by IRI.