The Role Of Schwann Cell Pannexin 1-Mediated Inflammatory Response In Neuropathic Pain

Objective Neuropathic pain is still a challenge for clinical treatment due to the complicated pathogenesis.Accumulating evidence suggests that non-neuronal cells,especially glial cells(astrocytes and microglia),play a non-neglectful role in regulating neuropathic pain.Although Schwann cells are the most prevalent glial cells in the PNS,the role and underlying mechanisms of Schwan cells in the regulation of neuropathic pain remains little known.Pannexin 1(Panx 1)forms hexameric channels in the cellular membrane,and has an access to great many molecules,especially for ATP.Panx 1 is widely expressed in the neurons and glial cells,and the opening of Panx 1 regulates the release of inflammatory cytokines and pain-related molecules(such as ATP),which results in glial cells activation and neuronal hyperactivity,and all of them play a key role in the development and maintenance of neuropathic pain.In our previous study,we demonstrated that inhibition of Panx 1 profoundly attenuated hypotonicity-induced ATP release in cultured Schwann cells.Therefore,we boldly hypothesized that Schwann cell Panx 1 participates in the regulation of neuropathic pain.Methods 1.The characterization of Panx 1 localization and expression in DRG and sciatic nerve in chronic constriction injury(CCI)by q PCR,WB and IHC.2.After the injection of Panx 1 blockers,CBX and probenecid,and Panx 1 polypeptide(10Panx),Von Frey and a hot plate assay were applied to evaluate mechanical and thermal sensitivity in CCI-induced neuropathic pain;and Panx 1 expression both in the sciatic nerve and DRG were detected by IHC.3.Cytokine production and the changes were assessed in LPS-treated Schwann cells by q PCR,ELISA and Array under the conditions of the treatment with si RNA and CBX.4.Panx 1 channel activity was detected by ethidium bromide(EB)uptake under the condition of different treatment.Result 1.CCI induced persistent neuroinflammatory response and up-regulation of Panx 1 in Schwann cells.2.Perineural injection of Panx 1 blockers,carbenoxolone(CBX),probenecid,and Panx 1 peptides(10Panx)effectively reduced mechanical and thermal allodynia.3.Probenecid significantly reduced Panx 1 expression in Schwann cells,but not in dorsal root ganglion(DRG)in CCI-induced mice.4.Inhibition of Panx 1 with CBX and Panx 1-si RNA effectively attenuated the production of selected cytokines in LPS-treated Schwann cells.5.Neuroinflammatory response in LPS-treated Schwann cells depend on both the expression and its activity.Conclusion This study illustrated that Panx 1 is primarily distributed in Schwann cells and inhibition of Panx 1 ameliorates CCI-induced neuropathic pain.In LPS-treated Schwann cells,Panx 1 participated in regulating the production of pro-inflammatory factors,which is dependent on both the channel activity and the expression levels of Panx 1.