Methods: Using our isolated, ventilated, ex vivo blood perfused rabbit lung model, all groups (n=6/group) underwent 2 hours of reperfusion after 18 hours of cold ischemia (4° C). ATL-313, a specific and potent agonist of the A2AR, was administered one hour prior to ischemia intravenously (100nM), with the preservation solution (100nM), and/or during reperfusion (100nM).

Results: Pretreatment of donor lungs with ATL-313 and the concomitant administration of ATL-313 during reperfusion most significantly increased lung compliance and oxygenation compared to control (all P < 0.05) (Table 1). Myeloperoxidase (MPO) levels, bronchoalveolar lavage tumor necrosis factor-alpha (TNF) levels, and pulmonary edema quantified by wet to dry ratios were all decreased in the aforementioned group compared to control (all P < 0.05). The inclusion of ATL-313 in the preservation solution failed to diminish lung injury. The administration of equimolar amounts of the highly selective A2AR antagonist, ZM241385, with ATL-313 resulted in the loss of protection conferred by A2AR agonism.

Conclusion: A2AR agonism with ATL-313 resulted in the greatest protection against LIRI when given prior to cold ischemia and during reperfusion. A2AR agonism and the associated decrease in TNF-alpha and neutrophil sequestration (decreased MPO) ultimately translated into substantial improvements in lung function. The loss of protection seen with the concurrent administration of the A2A antagonist, ZM241385, with ATL-313 supports that the mechanism of ATL-313 protection is specifically mediated via A2AR activation.

Table 1. Results

Values are expressed as the mean ± standard error of the mean. * MPO - myeloperoxidase, TNF - tumor necrosis factor, LC - lung compliance, & PAP - pulmonary artery pressure # P < 0.05 compared to control.