Mechanism Of VEGFA Invovled In Neuropathic Pain Induced By Nerve Injury

Background and objectionNeuropathic pain is caused by a lesion or disease of the somatosensory nervous system.A review of epidemiological studies estimates the prevalence of neuropathic pain is about 6.9 to 10%.Since the pathomechanism of neuropathic pain still be unclear,the treatment of neuropathic pain is mainly through stabilize neuromembrane potential,reduce synaptic excitability,inhibit ectopic discharge from the damaged nerve,or given symptomatic treatment.The opioid analgesic drugs are the strongest pain killer in clinical practice,but it can not effectively control the neuropathic pain,and show stronger tolerance and addiction,making it an urgent problem to find other drug targets to relieve neuropathic pain.Current studies have shown that neuroinflammation is closely related to the onset and progression of neuropathic pain.Vascular endothelial growth factor A(VEGFA)has been demonstrated to be widely involved in the nerve inflammatory process.This study aims to explore the possible mechanism of the involvement of VEGFA in neuropathic pain in the spinal cord,so as to provide a target and treatment idea for the treatment of neuropathic pain.Methods1.C57BL/6J mice were used to establish SNI model and sham operation group.On day 14,the spinal cord of L4-6 segment was taken and the expression of VEGFA protein in the spinal cord was detected by Western Blot(WB).2.Test the mechanical pain threshold and thermal pain threshold of C57BL/6J mice after intrathecal injection or plantar injection of VEGFA recombinant protein(rp VEGFA).3.C57BL/6J mice were randomly divided into seven groups: the SHAM group,the SNI group,the sFlt1 plus SNI group,the rp VEGF plus sFlt1 plus SNI group,the rp VEGF plus SNI group,the 740 Y-P plus sFlt1 plus SNI group,the 740 Y-P plus SNI group.Then(1)Mechanical pain threshold and thermal pain threshold were recorded before the procedure and at the 1st,3rd,5th,7th,10 th,and 14 th day after SNI model.(2)The expressions of vascular endothelial growth factor A(VEGFA),vascular endothelial growth factor 2(VEGFR2),phosphorylated protein kinase B(p-Akt),transient receptor potential vanilloid type 1(TRPV1),and inflammatory factors in the spinal cords in each group were detected by Western blot(WB).(3)The expressions of VEGFA,p-AKT,and TRPV1 in the spinal dorsal horn of mice were detected by the double-immunofluorescence.4.SNI model was established to observe whether Akt agonist 740 Y-P could inhibit the neuropathic pain relief effect of sFlt1.Results1.The SNI model was established successfully.Compared with the sham operation group,the expression of VEGFA in the spinal cord of mice in the SNI group was significantly increased.2.The VEGFA recombinant protein i.t.or i.pl.Injection can reduce the mechanical pain threshold and thermal pain threshold in C57BL/6J mice.3.The spared nerve injury(SNI)model was established successfully.In the SNI model,C57BL/6J mice developed noticeable mechanical pain sensitivity,but the thermal pain threshold did not change significantly.(1)sFLT1 can relieve SNI-induced mechanical hyperalgesia and increased the expression of IL-1β、IL-6、TNF-α in spinal cord.Compared with the SNI group,PWMT of sFLT1 group mice was significantly increased(P < 0.05).PWMT of the rp VEGFA plus sFlt1 plus SNI group mice was decreased compared with sFlt1 plus SNI group mice,and the expression of inflammatory factors in VEGFA mice showed significant increase compared to the sFlt1 plus SNI group.(2)WB results showed that the elevated levels of VEGFA,VEGFR2,p-AKT,and TRPV1 in SNI mice were significantly decreased after sFLT1 treatment,and the molecules in VEGFA group shows increased compared to sFlt1 plus SNI group,P < 0.05.(3)The results of double immunofluorescence showed that the expressions of VEGFA,p-AKT,and TRPV1 in SDH in mice were significantly decreased after sFLT1 treatment.VEGFA is co-expressed with p-AKT and TRPV1,and the co-expression was reduced after sFLT1 treatment.(4)VEGFA recombinant protein can reverse the above impacts of sFlt1.4.Akt agonist 740 Y-P inhibited mechanical hyperalgesia alleviated by sFlt1.Conclusion:1.VEGFA is involved in SNI-induced neuropathic pain in the spinal cord.2.VEGFA is involved in the pain deveopment and transmission.3.sFLT1 may reduce mechanical pain sensitivity and spinal cord inflammation in SNI mice by inhibiting VEGFA and affecting p-Akt /TRPV1 pathway.