Stigmasterol regulates microglial M1/M2 polarization via the TLR4/NF‐κB pathway to alleviate neuropathic pain

Abstract

Abstract(Switching from the microglial M1 phenotype to the M2 phenotype is a promising therapeutic strategy for neuropathic pain (NP). This study aimed to investigate the potential use of stigmasterol for treating NP. In animal experiments, 32 male Sprague–Dawley rats were randomly divided into the sham operation group, chronic constriction injury (CCI) group, CCI + ibuprofen group, and CCI + stigmasterol group. We performed behavioral tests, enzyme‐linked immunosorbent assay, hematoxylin‐esoin staining (H&E) staining and immunohistochemistry, immunofluorescence, and Western blotting. In cell experiments, we performed flow cytometry, immunofluorescence, Western blotting, and qRT‐PCR. Stigmasterol reduced thermal and mechanical hyperalgesia and serum IL‐1β and IL‐8 levels and increased serum IL‐4 and TGF‐β levels in CCI rats. Stigmasterol reduced IL‐1β, COX‐2, and TLR4 expression in the right sciatic nerve and IL‐1β expression in the spinal cord. Stigmasterol reduced the expression of Iba‐1, TLR4, MyD88, pNF‐κB, pP38 MAPK, pJNK, pERK, COX‐2, IL‐1β, and CD32 in the spinal cord of CCI rats while increasing the expression of IL‐10 and CD206. Stigmasterol decreased M1 polarization markers and increased M2 polarization markers in lipopolysaccharide (LPS)‐induced microglia and decreased the expression of Iba‐1, TLR4, MyD88, pNF‐κB, pP38 MAPK, pJNK, pERK, iNOS, COX‐2, and IL‐1β in LPS‐treated microglia while increasing the expression of Arg‐1 and IL‐10. Stigmasterol regulates microglial M1/M2 polarization via the TLR4/NF‐κB pathway to alleviate NP.

Biological role of mitochondrial TLR4‐mediated NF‐κB signaling pathway in central nervous system injury

“…Recent research suggests that modulating TLR4 activity may effectively regulate neuroinflammation in these diseases 69 . Specifically, targeting the TLR4/NF‐κB pathway in microglia and astrocytes has shown promise in attenuating neuroinflammation, preventing neuronal apoptosis, and promoting neural regeneration in inflammatory conditions affecting the CNS 70,72,74 . In PD, the suppression of the TLR4/MyD88/NF‐κB pathway in microglia and astrocytes has been shown to ameliorate dopaminergic neuronal degeneration and mitigate motor impairments in patients 80–82 .…”

“…Inhibition of the TLR4/MyD88/NF‐κB pathway in LPS‐induced microglia has been shown to decrease the expression of pro‐inflammatory cytokines such as TNF‐α, iNOS, and IL‐6 while increasing the expression of anti‐inflammatory markers including arginase‐1 (Arg‐1) and IL‐10. This modulation ultimately leads to the alleviation of neuroinflammation and the facilitation of nerve regeneration 70,71 . Through the inhibition of neuronal apoptosis and the upregulation of neuronal process growth, nerve growth factor (NGF), and other neuronutrients within astrocytes, neuronal cells may be shielded from neuroinflammatory harm facilitated by TLR4/NF‐κB pathway in LPS‐activated microglia.…”