Spatiotemporal expression of inducible nitric oxide synthase and cyclooxygenase 2 in the spinal cord during early stage sciatic nerve crush injury

BACKGROUND: Previous studies have shown that inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2) participate in inflammatory immune responses and neuropathic pain following peripheral nerve injury However, few reports have addressed time-dependent expression of iNOS and COX-2 following peripheral nerve injury OBJECTIVE: To investigate spatiotemporal expression of iNOS and COX-2 during early stage sciatic nerve crush injury. DESIGN, TIME AND SETTING: The randomized, controlled, animal experiment was performed at the Laboratory of Applied Anatomy, Department of Human Anatomy and Neurobiology, Central South University, China from September 2006 to September 2007 MATERIALS: Mouse anti-rat iNOS monoclonal antibody and goat anti-rat COX-2 monoclonal antibody (Transduction Laboratory, USA), as well as biotinylated rabbit anti-mouse IgG and biotinylated rabbit anti-goat IgG (Santa Cruz Biotechnology, USA) were used in the present study METHODS: A total of 48 healthy, adult, Sprague Dawley rats were randomly assigned to three groups In the model group (n = 32), crush injury to the right sciatic nerve was established using an artery clamp. The model group was further assigned to four subgroups according to survival time (6, 12, 24, and 72 hours), respectively (n = 8). Sham surgery (n = 8) and normal control (n = 8) groups were also established MAIN OUTCOME MEASURES: iNOS and COX-2 expression was detected in the L4-6 spinal cord with immunohistochemistry Gray values of iNOS- and COX-2-postive cells in the anterior horn and posterior horn of spinal cord, as well as quantification of iNOS- and COX-2-positive cells in the anterior horn of spinal cord. were measured. RESULTS: iNOS and COX-2 expression gradually increased in the anterior horn and posterior horn of the spinal cord on the damaged side over time from 6 hours following sciatic nerve injury (P < 0 05) and peaked at 72 hours Simultaneously, the number of iNOS- and COX-2-positive cells similarly increased in the anterior horn of spinal cord on the damaged side (P < 0 05). CONCLUSION: iNOS and COX-2 expression increased in the spinal cord during early stage sciatic nerve crush, which suggested that iNOS and COX-2 participate in occurrence and development of inflammatory immune responses following peripheral nerve injury