IN VIVO EFFECTS OF CO-RELEASING MOLECULES: PRELIMINARY DATA IN A LARGE ANIMAL MODEL

Abstract

P85 Introduction: Carbon monoxide (CO) administration has been shown to protect from ischemia reperfusion (IR) injury associated with organ transplantation. However, CO administration by gas inhalation, as currently done in experimental transplantation, offers the disadvantage of being complicated and unpractical particularly with regard to its possible future clinical application. Therefore, we have studied the potential therapeutic effects of a recently generated CO-releasing molecule (CO-RM) as a new mode of administering CO for clinical use. Methods: In a preliminary pharmacodynamic study in the pig, tricarbonylchloro(glycinato) ruthenium(II) (CORM-3) was administered as a single dose of 4 mg/kg i.v. into two Large White pigs. PBMC isolated at 2, 6, 12, 24, 48, 72 and 168 hrs after CORM-3 administration, were stimulated in vitro with 1-10 μg/ml LPS and the production of TNF-α, one of the key initiators of apoptosis in IR injury, was evaluated by ELISA. Subsequently, four immunosuppressed Large White pigs were induced with 4 mg/kg of CORM-3 one day before renal transplantation and received the drug at 1 mg/kg or 4 mg/kg every second day until the end of the experiment. In these allograft recipients, the efficacy of CORM-3 on the in vitro production of TNF-α was evaluated on the day of transplantation and at the time of euthanasia. All the routine haematological and biochemical parameters were monitored throughout the experiments. Results: A single dose of 4 mg/kg of CORM-3 was able to significantly reduce TNF-α production by PBMC starting from 24 hrs after administration. This effect was maintained for 48 hrs. 72 hrs after a single dose treatment, the levels of TNF-α were back to the control pre-dose values or even higher. The efficacy of CORM-3 as an inhibitor of TNF-α production has also been observed in allotransplanted pigs where PBMC isolated after 24 hr treatment with CORM-3 were unable to release TNF-α after LPS stimulation. In these animals, CORM-3 administration was not associated with any noticeable side-effects. Conclusion: At the doses used in this study, in vivo administration of CORM-3 in a large animal model is well-tolerated and is able to interfere with TNF-α production by PBMC. As TNF-α is a key initiator of the apoptotic events in IR injury, it is expected that this approach may prove useful for the long term survival of transplanted organs.