EGR2 Facilitates LPS-Elicited Microglial Inflammation and Inflammatory Pain by Transcriptionally Activating MRTO4

Abstract

This study discovers the high expression of EGR2 in neuropathic pain (NP) and further explores the molecular mechanism of EGR2-mediated inflammatory response of spinal microglia. GSE92718 was obtained from the GEO database to screen differentially expressed genes in NP. A chronic constriction injury (CCI) model was established in male C57BL/6J mice. EGR2 shRNA was intrathecally injected into CCI mice, followed by RT-qPCR, Western blot, ELISA, and immunofluorescence to detect inflammatory response and microglial activation. An in vitro inflammatory cell model was established by inducing BV-2 cells with 100 ng/mL LPS. The binding between EGR2 and MRTO4 was predicted through bioinformatics and verified by dual luciferase and ChIP assays. EGR2 was the most significantly differentially expressed gene in NP. EGR2 expression was upregulated in spinal cord tissues of male CCI mice, mainly in microglia and neurons. EGR2 shRNA alleviated CCI-induced mechanical allodynia and thermal hyperalgesia, inhibited pro-inflammatory cytokines and microglial activation. EGR2 transcriptionally activated MRTO4 expression. LPS induced BV-2 cell activation and inflammatory response. Overexpression of EGR2 increased pro-inflammatory cytokines and Iba-1 + positive cells in LPS-stimulated BV2 cells, while the addition of sh-MRTO4 rescued the trend. In conclusion, EGR2 gene is significantly upregulated in the spinal cord tissues of male CCI mice. EGR2 facilitates LPS-induced inflammatory responses in microglia by transcriptionally activating MRTO4 expression, suggesting that this signaling pathway may participate in NP-associated spinal inflammation.