Anti-inflammatory effects of curcumin in experimental spinal cord injury in rats

Antioxidant transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) has been shown in our previous studies to play an important role in protection against spinal cord injury (SCI) induced inflammatory response. The objective of this study was to test whether curcumin, a novel Nrf2 activator, can protect the spinal cord against SCI-induced inflammatory damage. Adult male Sprague-Dawley rats were subjected to laminectomy at T8-T9 and compression with a vascular clip. The spinal cords spanning the injury site about 0.8 cm were collected for testing. There were three groups: (a) sham group; (b) SCI group; and (c) SCI + curcumin group. We measured Nrf2 and nuclear factor kappa B (NF-kappa B) binding activities by electrophoretic mobility shift assay, concentrations of tumor necrosis factor-alpha, interleukin-1 beta and interleukin-6 by enzyme-linked immunosorbent assay, hindlimb locomotion function by Basso, Beattie, and Bresnahan rating, spinal cord edema by the wet/dry weight method, and apoptosis by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling analysis. Induction of the Nrf2 activity by curcumin markedly decreased NF-kappa B activation and inflammatory cytokines production in the injured spinal cord. Administration of curcumin also significantly ameliorated the secondary spinal cord damage, as shown by decreased severity of locomotion deficit, spinal cord edema, and apoptosis. Post-SCI curcumin administration attenuates the inflammatory response in the injured spinal cord, and this may be a mechanism whereby curcumin improves the outcome following SCI.