The Role And Mechanism Of Spinal Microglial Fgr In Neuropathic Pain

Objectives: To observe the dynamic trend and spatial distribution of the non-receptor tyrosine kinase Fgr in the spinal cord of neuropathic pain rats and to further study the underlying mechanism of neuropathic pain.Methods: Firstly,we observed the pain behaviors of rats at 1,3,7and 14 days after chronic sciatic nerve constriction injury(CCI).The dynamic changes and spatial distribution of Fgr and the transcription factor STAT3 in spinal cord were detected by q RT-PCR,Western blot and immunofluorescence staining tests.We futher verified their spatial distribution through magnetic activated cell sorting.In vitro test,the rat microglia cell line HAPI was cultured and the cells were respectively transfected with Fgr overexpression virus(AAV-Fgr)and knockdown virus(AAV-sh Fgr).We conducted Western blot and q RT-PCR to examine the levels of Fgr,IL6,IL1β and the phosphorylation of STAT3 at tyrosine residue 705(p-STAT3(Tyr705)).Furthermore,after intrathecal injections of AAV-Fgr and AAV-sh Fgr in rats respectively,we investigated the pain behaviors in these rats and the changes of STAT3.Finally,we assayed the pain behaviors in CCI rats injected intrathecally with the Fgr selective inhibitor TL02-59.Results:1.CCI operation decreased the PWMT and PWTL significantly compared with sham operated rats(p < 0.001).Fgr,p-STAT3(Tyr705)and nuclear translocation of STAT3 were found increased in the spinal dorsal horn of CCI rats(p < 0.05).Besides,the increased Fgr and p-STAT3(Tyr705)were mainly located in microglia(p < 0.05).2.Overexpression of Fgr in vitro promoted the phosphorylation of STAT3(Tyr705)(p < 0.05)and up-regulated the expression of inflammatory mediators,IL6 and IL1β(p < 0.05),while knockdown of Fgr inhibited the phosphorylation of STAT3(Tyr705)and suppressed the expression of IL6 and IL1β induced by lipopolysaccharides(p < 0.05).3.In vivo test,overexpression of Fgr evoked neuropathic pain,promoted STAT3(Tyr705)phosphorylation and nuclear translocation of STAT3(p < 0.05),whereas Fgr knockdown alleviated these symptoms of CCI rats.4.TL02-59 can effectively relieve CCI-induced neuropathic pain(p< 0.05).Conclusion: Fgr plays an important role in the occurrence and development of neuropathic pain.Inhibition of Fgr could effectively alleviate neuropathic pain.The underlying mechanisms may involve STAT3-dependent regulation of inflammatory gene expression in microglia.Targeting Fgr has therapeutic potential for neuropathic pain.