Effects of nerve graft on nitric oxide synthase, NAD(P)H oxidase, and antioxidant enzymes in chronic spinal cord injury

Oxidative stress and nitrosative stress play important roles in the pathogenesis of secondary spinal cord injury. Recently, we demonstrated that peripheral nerve grafts (PNG) with acidic fibroblast growth factor (aFGF) partially restore hind limb locomotion in adult rats with completely transected spinal cords. This study investigated the protein abundances of the superoxide (O2 )-generating enzyme nicotinamide adenine dinucleotide (phosphate) oxidase (NAD(P)H oxidase; gp91phox subunit), nitric oxide synthases (NOS), antioxidant enzymes, superoxide dismutases (Cu Zn SOD, Mn SOD), catalase, and glutathione peroxidase (GPX) as well as nitrotyrosine in the spinal cord tissue 4 months after spinal cord transection in rats with and without PNG and aFGF. The protein abundances of the gp91phox subunit of NAD(P)H oxidase, Mn SOD, catalase, GPX, eNOS, and nitrotyrosine were significantly upregulated, whereas Cu Zn SOD and nNOS were unchanged in the injury group compared to the sham controls. The nerve graft with aFGF treated group showed significantly better hind limb locomotion recovery than the injury group. Although the protein abundances of gp91phox, nitrotyrosine, and Cu Zn SOD were similar in the treated group (nerve graft with aFGF) compared to the injury group, Mn SOD, GPX, catalase, and eNOS protein abundances were significantly higher, whereas nNOS was markedly lower in the treated group. We conclude that the combination of nerve graft and aFGF enhances the local antioxidant defense system after spinal cord transection in rats.