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

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.

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-1β, 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-1β protein expression, and colorimetric method was used to detect the enzyme activity of NQO1 and GST-α1.

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-1β 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.

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.