Expression of NF-κB in Schwann cells and its effect on motor neuron apoptosis in spinal cord following sciatic nerves injury in rats

Abstract

Objective To explore the expression of nuclear factor-kappa B (NF- kB) in Schwann cells (SCs) and its effect on motor neuron apoptosis in spinal cord following sciatic nerves injury in adult rats. Methods Thirty-six adult Sprague-Dawley (SD) rats were divided randomly into normal control group ( n = 6), and sciatic nerves crushing group ( n = 30), and the later was further equally randomized into 5 subgroups: 1, 3, 7, 14, and 21 d post-injury groups. The expression of NF- kB of normal and injured nerves were examined by immunohistochemistry staining, and the apoptosis of motor neurons in spinal cord of lumbar 4 to lumbar 6 (L 4-L 6) was investigated by terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) assay. Both were quantitated by image analysis. Results In crushing group, except 21 d post-injury group, the expression of NF- kB was markedly higher than that in the normal control group ( P<0.05, P<0.01). At 1 d after sciatic nerves crushing, the expression of NF- kB was obviously up-regulated, reached peak at 3 d, and recovered at 21 d. The same trend was observed in the time-course on motor neuron apoptosis after sciatic nerves injury. Correlation analyses revealed that motor neuron apoptosis was significantly and positively correlated with the expression of NF- kB following sciatic nerves injury ( r = 0.976 0, P<0.01). Conclusion After injury of sciatic nerves, the presence and up-regulation of NF-κB in SCs may be involved in motor neuron apoptosis in L 4-L 6 spinal cord.