Upregulation Of Nav1.7 Voltage-gated Sodium Channels By Endogenous Hydrogen Sulfide Mediate Neuropathic Pain

Object:The aim of the present study was to investigate the the mechanism by which the endogenous hydrogen sulfide?H₂S?regulates the voltage-gated sodium channel 1.7?Nav1.7?in rat dorsal root ganglion?DRG?neurons,and to clarify its role in the development of neuropathic pain.Methods:In this study,Sprague-Dawley?SD?rats were used to establish a SNI model.Immunofluorescence and Western blot were used to detect the expression of endogenous H2S synthase Cystathionine?-Synthetase?CBS?and Nav1.7 protein in L4-L6 DRG neurons before and after modeling.The effects of blocking agents on the expression of CBS,MEK/ERK,pMEK/pERK and Nav1.7 in L4-L6 DRG neurons were detected by Western blot.Whole-cell patch clamp technique was used to detect changes in the excitability index of L4-L6 DRG neurons before and after modeling and administration of blockers.Behavioral experiment were used to detect changes in nociceptive behavior in rats before and after administration of blockers.Results:?1?Immunofluorescence results showed that compared with the Sham group,the expression of CBS and Nav1.7 in SNI+Vehicle group increased on the day 7,day 14 and day 21?p<0.05,n=6?.?2?Western blot results showed that compared with the Sham group,the expression of CBS and Nav1.7 in the DRG neurons on the day 7,day 14 and day 21 was increased in the SNI+Vehicle group?p<0.05,n=6?,and the most pronounced is on the day 21.?3?AOAA?CBS blocker?can inhibit the increase of CBS,pMEK1/2,pERK1/2 and Nav1.7 induced by SNI surgery?p<0.05,n=6?,while PF-04856264?Nav1.7specific blocker?cannot?p<0.05,n=6?.In addition,U0126?MEK blocker?can inhibit the increase of pMEK1/2,pERK1/2 and Nav1.7 induced by SNI surgery?p<0.05,n=6?,but it cannot inhibit the increase of CBS induced by SNI.?4?The patch clamp experiment results show that the reheobase of action potential decreased and the frequency of action potential increased on DRG neurons after the SNI modeling?p<0.001,n=8?.?5?AOAA,U0126 and PF-04856264 can suppress the change of the reheobase and the frequency of action potential caused by SNI?p<0.001,n=8 neurons?.?6?Behavioral experiment results revealed that there were not significantly different in thermal withdrawal latency?TWL?among each group?F=0.130,p=0.941>0.05,n=6?.However,seconds with the paw lifted values in SNI+Vehicle group were increased significantly?F=924.429,p<0.001,n=6?compared with that in the Sham group.And seconds with the paw lifted values were decreased significantly after the administration of AOAA?F=64.280,p<0.001,n=6?,U0126?F=46.196,p<0.001,n=6?and PF-04856264?F=24.021,p=0.001<0.01,n=6?.Conclusion:Endogenous H₂S activates MEK/ERK pathway to upregulate Nav1.7 involved in neuropathic pain,and Nav1.7 channel is expected to be a therapeutic target for neuropathic pain.