Inhibition of Nitric Oxide Mediated Protein Nitration Therapeutic Implications in Experimental Radiculopathy

Study Design. Experimental animal study. Objective. This study investigated whether nitric oxide (NO) mediated protein nitration is involved in the pathogenesis of radiculopathy and whether the symptoms can be relieved by its suppression. Summary of Background Data. It has been reported that nitration of protein mediated by NO is involved in the degenerative neurological disorders, but its involvement is not clear in the radiculopathy. Methods. Two kinds of rat models of radiculopathy were used. Radiculopathy was induced either by ligation of spinal nerve roots or transplantation of autologous nucleus pulposus. In separate groups of rats, aminoguanidine, a potent nitric oxide synthetase inhibitor, was administered just before induction of radiculopathy, to suppress NO production and resultant nitration of protein. Sensation of the hind limb was evaluated by plantar stimulation test, and motor weakness was assessed by observation of gait pattern. Nitrotyrosine, product of protein nitration, was assayed quantitatively by Western immunoblotting. Results. Mechanical allodynia was observed in both compression and nucleus pulposus groups, but motor weakness was observed only in the compression group. Preoperative administration of aminoguanidine attenuated mechanical allodynia and motor weakness. Optical densities of nitrotyrosine bands increased signifi cantly in radiculopathy groups, but they were lowered by administration of aminoguanidine. Conclusion. NO mediated protein nitration contributes to the development of both types of radiculopathies. Suppression of NO production can decrease protein nitration and relieve neural dysfunctions of radiculopathy.