Disruption of Nrf2 exacerbated the damage after spinal cord injury in mice.

ABSTRACT

BACKGROUND: Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key transcriptional factor for antioxidant response element-regulated genes. After spinal cord injury (SCI), the Nrf2-antioxidant response element pathway is activated in the spinal cord. However, the function of Nrf2 after SCI has not yet been studied. METHODS: Spinal cord compression injury of Nrf2 knockout (KO) and wild-type (WT) mice was induced by the application of vascular clips (force of 10 g) to the dura. Neurologic function was assayed by the Basso open-field motor score, footprint analysis, and spinal motor-evoked potentials. Degenerating neuronal cells were stained with Fluoro Jade C and observed by a confocal microscopy. Nrf2 DNA-binding activity was assessed by electrophoretic mobility shift assay. The mRNA levels of interleukin (IL)-6, IL-1ß, NAD(P)H quinone oxidoreductase (NQO)-1, and glutathione S-transferase (GST)-α1 were detected by reverse transcriptase-polymerase chain reaction. Enzyme-linked immunosorbent assay was used to detect IL-6 and IL-1ß protein expression, and colorimetric method was used to detect the enzyme activity of NQO1 and GST-α1. RESULTS: Nrf2 KO mice developed severer hindlimb motor dysfunction and neuronal death after SCI compared with WT mice. In correlation with neurologic deficits, the release of IL-6 and IL-1ß in the spinal cord of KO mice was higher than that in WT mice, whereas the Nrf2 banding activity, the expression and activity of NQO1 and GST-α1 were all lesser in KO mice 24 hours after SCI compared with WT mice. CONCLUSION: Genetic ablation of Nrf2 exacerbated the neurologic deficit and inflammation after SCI in mice. These findings raise the possibility that Nrf2 could be relevant in improving outcome after SCI.