Regulation of Neurotrophin-3 and Interleukin-1β and Inhibition of Spinal Glial Activation Contribute to the Analgesic Effect of Electroacupuncture in Chronic Neuropathic Pain States of Rats

Growing evidence indicates that neurotrophin-3, interleukin-1β, and spinal glia are involved in neuropathic pain derived from dorsal root ganglia to spinal cord. Electroacupuncture is widely accepted to treat chronic pain, but the precise mechanism underlying the analgesic effect of EA has not been fully demonstrated. In this study, the mechanical withdrawal threshold and thermal withdrawal latency were recorded. We used immunofluorescence and western blots methods to investigate the effect of EA on the expression of NT-3 and IL-1β in DRG and spinal cord of CCI rats; we also examined the expression of spinal GFAP and OX-42 in spinal cord. In present study, the MWT and TWL of CCI group rats were lower than those in the Sham CCI group rats, but EA treatment increased the pain thresholds. Furtherly, we found that EA upregulates the expression of NT-3 in DRG and spinal cord of CCI rats, while EA downregulates the expression of IL-1β. Additionally, immunofluorescence exhibited that CCI-induced activation of microglia and astrocytes was inhibited significantly by EA treatment. These results demonstrated that the analgesic effect of EA may be achieved through promoting the neural protection of NT-3 as well as the inhibition of IL-1β production and spinal glial activity

Electroacupuncture inhibits dendritic spine remodeling through the srGAP3-Rac1 signaling pathway in rats with SNL

Abstract Previous studies have shown that peripheral nerve injury can lead to abnormal dendritic spine remodeling in spinal dorsal horn neurons. Inhibition of abnormal dendritic spine remodeling can relieve neuropathic pain. Electroacupuncture (EA) has a beneficial effect on the treatment of neuropathic pain, but the specific mechanism remains unclear. Evidence has shown that slit-robo GTPase activating protein 3 (srGAP3) and Rho GTPase (Rac1) play very important roles in dendritic spine remodeling. Here, we used srGAP3 siRNA and Rac1 activator CN04 to confirm the relationship between SrGAP3 and Rac1 and their roles in improving neuropathic pain with EA. Spinal nerve ligation (SNL) was used as the experimental model, and thermal withdrawal latency (TWL), mechanical withdrawal threshold (MWT), Western blotting, immunohistochemistry and Golgi-Cox staining were used to examine changes in behavioral performance, protein expression and dendritic spines. More dendritic spines and higher expression levels of srGAP3 were found in the initial phase of neuropathic pain. During the maintenance phase, dendritic spines were more mature, which was consistent with lower expression levels of srGAP3 and higher expression levels of Rac1-GTP. EA during the maintenance phase reduced the density and maturity of dendritic spines of rats with SNL, increased the levels of srGAP3 and reduced the levels of Rac1-GTP, while srGAP3 siRNA and CN04 reversed the therapeutic effects of EA. These results suggest that dendritic spines have different manifestations in different stages of neuropathic pain and that EA may inhibit the abnormal dendritic spine remodeling by regulating the srGAP3/Rac1 signaling pathway to alleviate neuropathic pain

Schaftoside ameliorates oxygen glucose deprivation-induced inflammation associated with the TLR4/Myd88/Drp1-related mitochondrial fission in BV2 microglia cells

Background: Neuroinflammation plays a major role in the development of ischemic stroke, and regulation of the proinflammatory TLR4 signaling pathway in microglia stands to be a promising therapeutic strategy for stroke intervention. Recently, the homeostasis of mitochondrial dynamics has also been raised as a vital component in maintaining neuronal health, but its relevance in microglia hasn't been investigated. Schaftoside, a natural flavonoid compound and a promising treatment for inflammation, has demonstrated potency against LPS-induced lung inflammation in mice; however, its action on TLR4-induced neuroinflammation and mitochondrial dynamics in microglia is still unknown. Methods: The effects of schaftoside in regulating inflammation and mitochondrial dynamics were investigated in vitro in oxygen glucose deprivation (OGD)-stimulated BV2 microglia cells. Results: Schaftoside inhibited mRNA and protein expressions of proinflammatory cytokines (IL-1β, TNF-α, and IL-6) after 4 h in OGD-stimulated BV2 microglia cells, similar to the effect of TAK242, an inhibitor of TLR4. TLR4/Myd88 signaling pathway was effectively suppressed by schaftoside. In addition, both schaftoside and TAK242 treatments significantly decreased Drp1 expression, phosphorylation, translocation and mitochondrial fission in OGD-stimulated BV2 cells. Conclusions: Our study suggested that schaftoside was able to reduce neuroinflammation, which is mediated in part by reducing TLR4/Myd88/Drp1-related mitochondrial fission in BV2 microglia cells. Keywords: Mitochondrial fission, Microglia, TLR4, Stroke, Schaftosid