TLR7 Is Involved In Rat Trigeminal Neuralgia Through NF-κB Inflammatory Pathway

Objective Trigeminal neuralgia(TN)is a clinical disease with limited treatment options at present,and its pathogenesis has not been fully elucidated.It is reported that Toll-like receptor 7(TLR7)is expressed in the spinal cord,dorsal root ganglion(DRG)and trigeminal ganglion(TG),and is involved in neuropathic pain.In this study,Infraorbital nerve-chronic constriction injury(ION-CCI)was used to establish a rat model of trigeminal neuralgia,and behavioral detection was used to observe the changes of mechanical pain threshold in rats,and then combined with molecular biology experiments to explore the mechanism of TLR7 in trigeminal nerve pain in SD rats.Methods In order to determine the effectiveness of the trigeminal neuralgia model,SD rats weighing between 180 g and 200 g were selected and trained for three days to ensure their stable response to stimuli.The rat model of trigeminal neuralgia was established by chronic constrictive injury of infraorbital nerve(ION-CCI).The first phase of the experiment:The rats were randomly divided into two groups:ION-CCI group and Sham group.Von Frey hair cilia stimulation wire was used to measure and record the mechanical pain threshold of whisker pad in different periods before and after the establishment of the model.On the 14 th day after operation,the experimental rats were killed and the ipsilateral trigeminal ganglion was removed.The expressions of Toll-like receptor 7(TLR7)and nuclear factor kappa-B(NF-κB)subunits p65,Phospho-p65(p-p65),tumor necrosis factor-α(TNF-α)and interleukin-1 β(IL-1β)m RNA and protein in TG of two groups were detected by real-time fluorescence quantitative polymerase chain reaction(RT-PCR)and Western blot.The second phase of the experiment: Hydroxychloroquine(HCQ),an inhibitor of TLR7,was administered intragastrically on the day of operation in experimental rats,and the daily dose of HCQ was 100mg/kg.According to the principle of random grouping,they were divided into ION-CCI group,ION-CCI+ NS group(ION-CCI+ saline group)and ION-CCI+ HCQ group.The mechanical pain threshold changes of the three groups were monitored during administration,and On the 14 th day after operation,the experimental rats were killed and the ipsilateral trigeminal ganglion was removed.and on the 14 th day after the establishment of the model,the rats were killed,and the ipsilateral trigeminal ganglion was removed.The expression levels of TLR7,p65,p-p65,TNF-α and IL-1βm RNA and protein in TG of experimental rats were detected by RT-PCR and Western blot techniques.Finally,the data are analyzed statistically.Results1.After the establishment of trigeminal neuralgia model rats,the mechanical pain threshold in the whisker pad area of ION-CCI group was significantly lower than that of Sham group,and reached the lowest value on the 14 th day.2.After the trigeminal nerve injury induced by ligation of infraorbital nerve,the results of RT-PCR and Western blot molecular biology showed that the expression of TLR7,p-p65,TNF-α and IL-1β m RNA and protein in ION-CCI group was significantly higher than that in Sham group.3.After administration of TLR7 inhibitor HCQ,the behavioral test of rats in different groups showed that the mechanical pain threshold in ION-CCI+HCQ group was significantly higher than that in ION-CCI group from the 7th day after administration and lasted to the 14 th day,but there was no significant change in mechanical pain threshold in ION-CCI+NS group compared with ION-CCI group.4.After administration of TLR7 inhibitor HCQ,the results of RT-PCR and Western blot molecular biology showed that the expression of TLR7 and inflammatory cytokines(TNF-α,IL-1β)in TG of ION-CCI+HCQ group decreased,and the translocation and phosphorylation of p65 nucleus decreased.Conculsion TLR7 may be involved in the pathogenesis of trigeminal neuralgia.Inhibition of TLR7 can improve trigeminal neuralgia induced by ION-CCI and reduce the expression of related inflammatory factors(TNF-α,IL-1 β).The mechanism may be related to the activation of NF-κB pathway in primary sensory neurons.