Abstract: BACKGROUND: The inflammatory response of microglia is closely related to neuronal survival, regeneration, and functional recovery after spinal cord injury. Peroxiredoxin 1 is not only involved in the regulation of oxidative stress, but also has an important effect on cell proliferation, apoptosis, and inflammatory response.
OBJECTIVE: To investigate the role and mechanism of peroxiredoxin 1 in the inflammatory response of microglia following spinal cord injury.
METHODS: (1) Twelve female C57BL/6 mice were randomly divided into sham-operated (n=6) and spinal cord injury (n=6) groups. The sham-operated group was not modeled and acute spinal cord injury models were constructed in the spinal cord injury group using the modified Allen’s method. Spinal cord tissue at the injured site was taken at 7 days after modeling and transcriptome sequencing was performed to identify differentially expressed genes. The expression of peroxiredoxin 1 in spinal cord tissues was verified using western blot and RT-qPCR. (2) Mouse microglia BV2 were divided into two groups: the control group was stimulated with lipopolysaccharide for 6 hours, and in the knockout group, lipopolysaccharide stimulation was applied for 6 hours at 24 hours after peroxiredoxin 1 was knocked down in the cells. RT-qPCR was performed to detect mRNA expression of peroxiredoxin 1, inflammatory factors (interleukin 1β, interleukin 6, inducible nitric oxide synthase, tumor necrosis factor α, C-C motif chemokine ligand 2, and C-X-C motif chemokine ligand 2), and western blot was performed to detect the expression of peroxiredoxin 1, inducible nitric oxide synthase, and reactive oxygen/ mitogen-activated protein kinase signaling pathway proteins. Mouse microglia BV2 were treated in two groups: the control group was stimulated by hydrogen peroxide for 4 hours, and the knockout group was stimulated by hydrogen peroxide for 4 hours at 24 hours after knockdown of peroxiredoxin 1. The level of reactive oxygen species was detected by 2,7-dichlorodihydrofluorescein diacetate probe.
RESULTS AND CONCLUSION: (1) Results from transcriptome sequencing, western blot and RT-qPCR confirmed that peroxiredoxin 1 expression levels in mouse spinal cord tissues were significantly higher in the spinal cord injury group than the sham-operated group (P < 0.05). (2) Peroxiredoxin 1 knockdown in microglial cells led to decreased expression of peroxiredoxin 1 mRNA and protein (P < 0.05), increased mRNA expression of interleukin 1β, interleukin 6, inducible nitric oxide synthase, tumor necrosis factor α, C-C motif chemokine ligand 2, and C-X-C motif chemokine ligand 2 (P < 0.05), increased protein expression of inducible nitric oxide synthase, P-P38, P-JNK and P-ERK proteins (P < 0.05), and increased level of reactive oxygen species (P < 0.05). To conclude, peroxiredoxin 1 regulates microglial inflammation by targeting the reactive oxygen species/mitogen-activated protein kinase signaling pathway.

Key words: spinal cord injury, peroxiredoxin 1, microglia, reactive oxygen species, inflammation, mitogen-activated protein kinase, engineered tissue construction