In vitro and in vivo effects of the carbon monoxide-releasing molecule, CORM-3, in the xenogeneic pig-to-primate context

Abstract: Background: Carbon monoxide (CO) interferes with inflammatory and apoptotic processes associated with ischemia–reperfusion injury and graft rejection. Here, the in vitro effects of carbon monoxide releasing molecule-3 (CORM-3), a novel water-soluble carbonyl CO carrier, have been investigated on porcine aortic endothelial cells (PAEC) and primate peripheral blood mononuclear cells (PBMC). Furthermore, the pharmacodynamics and pharmacotolerance of CORM-3 after administration of single and multiple doses in the primate have been assessed in view of its potential application in pig-to-primate xenotransplantation models.

Methods: For in vitro studies, PAEC and primate PBMC were exposed for 24, 48 and 72 h to CORM-3 (20 to 1000 μm) and viability was measured using an MTS assay. PAEC and primate PBMC proliferation after exposure to CORM-3 was assessed by CFSE labelling. Proliferation of primate PBMC against irradiated pig lymphocytes was also assessed. Tumor necrosis factor alpha (TNF-α) production and Caspase-3 and -7 activity in Concanavalin A (conA)-stimulated primate PBMC were measured following treatment with CORM-3. In vivo, CORM-3 was administered i.v. to cynomolgus monkeys at 4 mg/kg, as single or multiple doses for up to 30 days. The effect of CORM-3 was evaluated by the assessment of production of TNF-α and interleukin 1β following PBMC stimulation with LPS by species-specific ELISA. Complete hematologic and biochemical analyses were routinely performed in treated primates.

Results: At concentrations <500 μm, CORM-3 did not alter the viability of PAEC or primate PBMC cultures in vitro, nor did it induce significant levels of apoptosis or necrosis. Interestingly, at concentrations of 300 and 500 μm, significant PAEC proliferation was observed, whilst concentrations ≥50 μm inhibited conA-activated primate lymphocyte proliferation (IC₅₀ of 345.8 ± 51.9 μm) and the primate xenogeneic response against pig PBMC. Such responses were demonstrated to be CO-dependent. In addition, CORM-3 significantly inhibited caspase-3 and -7 activity at concentrations between 200 and 500 μm and caused a significant reduction in TNF-α production (IC₅₀ 332.8 ± 33.9 μm). In vivo, following the administration of multiple doses, TNF-α production was significantly reduced in comparison to pre-treatment responses, with decreased levels maintained throughout the study. Moreover, a slight and transient increase in transaminases and bilirubin was observed in animals exposed to multiple doses of CORM-3.

Conclusions: These studies suggest that CORM-3 has anti-inflammatory and immunomodulatory properties in primates that may result in clinical benefit to allo- and xenografted organs.