P1 Hydrogen sulfide improves renal graft function and survival in a model of allogeneic renal transplantation

Abstract

Organ procurement is inherently associated with ischemia–reperfusion injury (IRI), resulting from loss and subsequent restoration of blood flow and leading to increased rates of delayed graft function, acute graft rejection and early graft loss. Additionally, genetically dissimilar grafts are targeted by the recipient immune system causing rejection of the donor organ. Treatment of donor organs with endogenously produced gasotransmitters such as hydrogen sulfide (H 2 S) during preservation is a novel method for improving early graft function and survival, as has been previously illustrated in a model of murine syngeneic renal transplantation (RTx). The protective effects of H 2 S against IRI in renal allografts have not yet been studied. We aimed to characterize the protective role of H 2 S in a clinically applicable murine model of allogeneic RTx involving immunosuppressive therapy. Following bilateral native nephrectomy, recipient Lewis rats underwent RTx with left kidneys obtained from Brown Norway donor rats that were flushed, at the time of procurement, with 15 mL of either cold (4 °C) University of Wisconsin (UW group) or cold UW + H 2 S donor molecule (150 μM NaHS) (H 2 S group) solution and stored for 6 h at 4 °C in 50 mL of the same solution. Rats were monitored for 14 days or until time of sacrifice. Post-operatively, a subset of animals from the UW group were treated with the immunosuppressant Tacrolimus (Prograf®, 0.3 mg/kg; UW + TAC) daily. Blood was analyzed periodically for serum creatinine and blood urea nitrogen (BUN) concentrations as markers of kidney function, as well as serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) concentration as markers of systemic inflammation. Post-operative survival of rats was markedly improved in H 2 S treated animals compared to animals treated with UW alone ( Fig. 1 ). Treatment with tacrolimus further enhanced survival, with UW + TAC and H 2 S + TAC exhibiting 50% and 100% survival, respectively, at day 14. Whereas UW treated animals exhibited high serum creatinine and BUN levels that remained elevated until time of death, H 2 S treated animals initially exhibited reduced serum creatinine and BUN levels compared to UW that gradually increased until death later in the time course ( Fig. 2 ). H 2 S + TAC treatment and UW + TAC groups both showed a reduction in serum creatinine and BUN to normal levels by day 7, though this reduction occurred sooner in the H 2 S + TAC group. Serum levels of ALT and AST were initially elevated in all treatment groups. However, whereas these levels were decreased in both tacrolimus treated groups by day 4 until the end of the time course, H 2 S treated animals exhibited a surge of serum ALT and AST near the time of death (day 8.5). These findings are the first to report that H 2 S protects kidney allograft survival and function. H 2 S treatment appears to delay the onset of graft rejection associated with allogeneic transplantation, most likely mediated by anti-inflammatory actions of H 2 S. Further investigation into the effect of H 2 S on the innate and adaptive immune system may elucidate potential mechanisms behind these protective effects.