FGF 10 Inhibited Spinal Microglial Activation in Neuropathic Pain via PPAR-γ/NF-κB Signaling

Overactivated microglia in the spinal cord leads to neuropathic pain sensitivity. The FGF 10, a Fibroblast Growth Factor (FGFs) that is prevalent in neurons, has been demonstrated to suppress microglial polarization. The objective of this study was to investigate the role of FGF 10 in neuropathic pain and the underlying regulatory mechanisms. Immunofluorescence staining and western blot detection revealed that FGF 10 expression was upregulated in the ipsilateral spinal dorsal horn of Spared Nerve Injury (SNI) rat models and was mainly detected in neurons and microglia. To test the anti-microgliosis actions of FGF 10, SNI rats were intrathecally administered with different concentrations of recombinant FGF 10. Behavioral tests and immunostaining results showed that FGF 10 relieved hyperalgesia in SNI rats and inhibited microglial activity in the ipsilateral spinal dorsal horn in a dose-dependent manner. Besides, BV2 cells were cultured and treated with LPS to activate microglia to explore the underlying mechanisms of FGF 10-induced analgesic effects in vitro. As a result, FGF 10 administration suppressed the LPS-induced microglial augmentation in a dose-dependent manner, followed by increased PPAR-γ and decreased NFκB phosphorylation (p-NFκB) levels. Moreover, PPAR-γ agonist (pioglitazone) and antagonist (GW9662) were administrated into spinal cords of SNI rats, revealing that pioglitazone had similar anti-nociceptive and anti-microglial effects to FGF 10. Conversely, GW9662 reversed all beneficial effects of FGF 10 on SNI rats. In addition, phosphorylated levels of NFκB were reduced by pioglitazone or FGF 10 treatment but raised by GW9662 administration in FGF 10-treated SNI rats. Our findings show that FGF 10 has analgesic effects in rats after peripheral nerve injury and justify the role of PPAR-γ/NFκB signaling in FGF 10-regulated anti-microgliosis.