Adenosine A_2A analogue ATL-146e reduces systemic tumor necrosing factor-α and spinal cord capillary platelet-endothelial cell adhesion molecule-1 expression after spinal cord ischemia

Objective: Inflammation is likely a major contributor to spinal cord reperfusion injury after aortic reconstruction. Systemic 4-(3-[6-amino-9-(5- ethylcarbamoyl-3,4-dihydroxy-tetrahydro-furan-2-yl)-9H-purin-2-yl]-prop-2-ynyl) -cyclohexane-carboxylic acid methyl ester ( ATL-146e), a selective adenosine A^2A agonist, has been shown to reduce paralysis after spinal cord ischemia. We hypothesized that ATL-146e reduces cytokine production during spinal cord reperfusion, curtailing inflammation and decreasing spinal cord capillary platelet-endothelial cell adhesion molecule-1 (PECAM-1) expression. Study design: New Zealand White rabbits sustained spinal cord ischemia with 45-minute cross-clamping of the infrarenal aorta. One group of animals received intravenous ATL-146e at 0.06 μg/kg/min for 3 hours during reperfusion, beginning after 30 minutes of ischemia. A second group received saline solution vehicle alone for 3 hours, serving as an ischemic control. A third group served as sham-operated animals, undergoing laparotomy with anesthesia. Serum was assayed with enzyme-linked immunosorbent assay for tumor necrosing factor-α (TNF-α). Animals were allowed to recover for 48 hours and were evaluated for hind-limb motor function with the Tarlov (0 to 5) scoring system. At necropsy, animals from each group yielded spinal cords for immunohistochemical staining for PECAM-1. Data are expressed as mean ± standard error of the mean, with statistical analysis with Student t test and Kruskal-Wallis nonparametric test. Results: Markedly improved Tarlov scores were seen in rabbits with ATL-146e (P < .001) during spinal cord reperfusion as compared with ischemic control animals. A significant reduction was found in TNF-α in the sera of rabbits with ATL-146e infusion (P < .01) as compared with ischemic control animals. Significantly reduced endothelial PECAM-1 staining intensity (P < .05) was seen in microscopic spinal cord sections from rabbits with ATL-146e. Conclusion: ATL-146e, an adenosine A _2A agonist, reduces spinal cord reperfusion injury. The mechanism of the protection may involve a reduction in circulating TNF-α during a critical 3-hour reperfusion interval and reduction in spinal cord endothelial PECAM-1 upregulation.