Semaphorin3a Promotes Phosphorylation Of Cofilin1 And Contributes To Bone Cancer Pain

Bone cancer pain(BCP)is a kind of complex spontaneous or evoked chronic pain caused by primary carcinoma growth or metastasis to bone tissue.With high transfer rate and mortality,the bone metastases frequently result in severe pain and significantly lower the overall quality of late-stage cancer patients’ life.However,the mechanism that skeletal cancer caused hypersensitive pain remains unclear.Therefore,it is a serious worldwide health issue.Recently,increasing reviews show that synaptic plasticity at spinal dorsal horn level plays a fundamental and important role in the pain perception and regulation mechanisms.Synaptic plasticity represents structure and function of synapses regulate in an activity-dependent manner in the nervous system.Actin is highly enriched in the pre-and postsynaptic terminals,and synaptic regulation is performed by the actin to function as stable cytoskeleton or dynamic filaments.Semaphorin3a(Sema3a)is well known as the secreted axon chemorepulsive guidance molecule.Sema3a induce the collapse and restoration of growth cone to find the correct cue to form the presynaptic terminals.And it also control actin-based arborization and shrinkage of dendrite to regulate the postsynaptic membrane.As the specific actin depolymerizing factor,Cofilinl binds to actin and severs actin filaments as it is activated by dephosphorylation at conserved serine residue 3(Ser3).Synapsin I highly expresses in the development of synapses and anchor synaptic vesicles to actin filaments in the presynaptic membrane.Metabotropic AMPARs are excitatory neurotransmitter and crucially involved in nociceptive inputs with plasticity-dependent changes in postsynaptic membrane.GluRl subunits of AMPARs mainly express in the laminae of dorsal horn and are determinants of spinal hyperalgesia.Our results of pre-experiment showed that Sema3a was abundantly distributed in the dorsal horn of lumbar enlargement and well co-located with specific markers of synaptic membrane.The quantitative results showed that levels of Sema3a and Cofilinl were significantly decreased,suggested that Sema3a and Cofilinl may be involved in the maintenance of BCP.Based on these results,we made a hypothesis that Sema3a may regulate phosphorylation of Cofilinl and further influence the expression of synapsin I and GluRl subunits.The progress may enhance the excitatory synaptic transmission at spinal dorsal horn level,so as to maintain the pain of bone carcinoma.In this study,we used technologies of immunofluorescence,Western blot and PT-PCR and constructed overexpression lentivirus of Sema3a and CofilinlL We further explored the role of phosphorylated Cofilinl(P-cofilin),synapsin I,G1uR1 and the interaction between them.Our results showed that the expression of P-cofilin was significantly decreased and the levels of P-cofilin/Cofilinl was also decreased in the BCP rats.The co-localization ratio of P-cofilin and synapsin I was 3 times higher than the Sham group.The GluRl subunits in the postsynaptic membrane was increased.After giving the overexpression lentivirus of Sema3a to the rats with BCP,Cofilinl was efficiently phosphorylated and the ratio of P-cofilin and synapsin I was up-regulated.The G1uR1 subunits were also recovered to the normal.At last,the pain of bone cancer rats was relieved.Therefore,the bone carcinoma induced deficiency of Sema3a and activated Cofilinl.The reassembly of actin influenced activity of synapsin I in the presynaptic membrane and enhanced trafficking of GluRl to postsynaptic membrane.Sema3a overexpression can reverse the enhancement of excitatory synaptic transmission and relieve BCP.To summary,this study supports a new role of Sema3 a to relieve chronic bone pain by regulating phosphorylation Cofilinl.The mechanism may represent an important contribution to the treatment of bone cancer pain.