Background: Little is known about neuronal death mechanisms following spinal cord ischemia. The present study aimed to investigate the protective effect of pentoxifylline (PTX) against spinal cord ischemia/reperfusion (I/R) injury.
Methods: Rabbits sustained spinal cord ischemia following 45 minutes cross-clamping of the infrarenal aorta. Experimental groups were as follows: the first group of animals (sham, n = 8) underwent laparotomy alone and served as the sham group; the second group (I/R, n = 20) received carrier (3 ml saline solution) and served as the control group; the third group (PTX-A, n = 20) received PTX intravenously 10 minutes prior to ischemia; and the fourth group (PTX-B, n = 20) received PTX intravenously at the onset of reperfusion. Rabbits were evaluated for hind-limb motor function with the Tarlov scoring system at 48 hours. Serum was assayed with enzyme-linked immunosorbent assay for tumor necrosis factor alpha (TNF-alpha) and spinal cords were harvested for myeloperoxidase (MPO) activity, histopathological analysis, terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling staining, platelet/endothelial cell adhesion molecule-1 (PECAM-1) and caspase-3 immunohistochemistry, and the number of necrotic and apoptotic neuron were counted and data analyzed at 12, 24, 48 and 72 hours of reperfusion. Spinal cords were studied by electron microscopy.
Results: Improved Tarlov scores were seen in PTX-treated rabbits as compared with ischemic control rabbits at 48 hours. A significant reduction was found in TNF-alpha in serum, activity of MPO and immunoreactivity of the PECAM-1 and caspase-3 in PTX-treated rabbits. There were fewer apoptotic neurons than necrotic neurons (P < 0.05). A significant decrease in both necrotic and apoptotic neurons was observed in the PTX-treated groups (PTX-A and PTX-B) compared with the I/R group (P < 0.05). Both necrotic and apoptotic neurons were found with the electron microscope.
Conclusions: PTX may induce protection against ischemia injury in the spinal cord, thereby preventing both necrosis and apoptosis. A major mode of cell death in spinal cord ischemia/reperfusion injury is necrosis while apoptosis is not dominant.