454: Biliverdin-Supplementation into the Preservation Solution Prevents Lung Cold Ischemia/Reperfusion Injury

Abstract

Purpose: Biliverdin (BV), one of the byproducts of heme catalysis through the heme oxygenase system, is known to be a scavenger of reactive oxygen species. We hypothesized that the addition of BV to the perfusate and cold storage solution could protect rat lung grafts from oxidative injury via its anti-oxidant properties. Methods and Materials: Orthotopic left lung transplantation was performed in a syngeneic Lewis to Lewis rat combination under 100% oxygen mixed with isoflurane. Grafts were preserved in low potassium dextran solution at 4C for 6 hrs. The lung graft function was assessed by graft pulmonary vein (PV) blood gas analysis. Results: Prolonged cold storage and reperfusion impaired graft function and resulted in a decrease of graft PV PaO2 to 195 mmHg at 2 hrs after reperfusion from 297 mmHg in sham operated animals. BV treatment significantly improved lung graft function (graft PV PaO2 of 244.8 mmHg). Graft MDA level, a marker of lipid peroxidation, increased to 0.38 M 2 hrs after reperfusion compared to those of sham controls (0.25 M). BV reduced MDA levels to 0.28 M, demonstrating that BV attenuated graft oxidative injury. The effect of BV on proinflammatory cytokine production was also evaluated. Realtime RT-PCR revealed that intragraft mRNA for IL-6 and TNFwere rapidly upregulated within 2 hrs after reperfusion and elevated to 693 fold and 12 fold from base line of sham-operated controls. BV markedly inhibited the increase of these inflammatory mediators to 417 fold and 8.4 fold. IRI resulted in recruitment of polymorphonuclear cells (PMN) into the grafts, but BV-treatment did not reduce the number of infiltrating PMN cells (control 47/0.1mm vs BV 44/ 0.1mm). Conclusions: This study demonstrates that exposure of the lung grafts to BV during cold storage can impart potent cytoprotective effects in lung I/R injury and significantly improve function of lung grafts following extended cold preservation and transplantation by a mechanism involving amelioration of oxidative injury and subsequent inflammatory events.