Inflammatory response and oxidative stress attenuated by sulfiredoxin-1 in neuron-like cells depends on nuclear factor erythroid-2-related factor 2

Sulfiredoxin-1 (SRX1) is a conserved endogenous antioxidative protein, which is involved in the response to cellular damage caused by oxidative stress. Oxidative stress and inflammation are the primary pathological changes in spinal cord injuries (SCI). The aim of present study was to explore the roles of SRX1 in SCI. Using reverse transcription-quantitative PCR and western blotting, the present study discovered that the expression levels of SRX1 were downregulated in the spinal cord tissues of SCI model rats. Massive irregular cavities and decreased Nissl bodies were observed in the model group compared with the sham group. Thus, to determine the underlying mechanisms, neuron-like PC12 cells were cultured in vitro. Western blotting analysis indicated that SRX1 expression levels were downregulated following the exposure of cells to lipopolysaccharide (LPS). Following the transfection with the SRX1 overexpression plasmid and stimulation with LPS, the results of the Cell Counting Kit-8 assay indicated that the cell viability was increased compared with LPS stimulation alone. Furthermore, the expression levels of proinflammatory cytokines secreted by LPS-treated PC12 cells were downregulated following SRX1 overexpression. Increased malondialdehyde content, decreased superoxide dismutase activity and reactive oxygen species production were also identified in PC12 cells treated with LPS using commercial detection kits, whereas the overexpression of SRX1 partially reversed the effects caused by LPS stimulation. The aforementioned results were further verified by determining the expression levels of antioxidative proteins using western blotting analysis. In addition, nuclear factor erythroid-2-related factor 2 (NRF2), a transcription factor known to regulate SRX1, was indicated to participate in the protective effect of SRX1 against oxidative stress. Inhibition of NRF2 further downregulated the expression levels of SRX1, NAD(P)H dehydrogenase quinone 1 and heme oxygenase-1 in the presence of LPS, while activation of NRF2 reversed the effects of LPS on the expression levels of these proteins. In conclusion, the results of the present study indicated that the anti-inflammatory and antioxidative effects of SRX1 may depend on NRF2, providing evidence that SRX1 may serve as a novel molecular target to exert a neuroprotective effect in SCI.