Intrathecal injection of siRNA targeting Toll-like receptor 4 reduces neuropathic pain in rat model of chronic constriction injury

Abstract

Objective To observe the effect of intrathecal injection of siRNA targeting Toll-like receptor 4(TLR4) on neuropathic pain and spinal cord levels of TLR4,IL-1β,and TNF-α in rat model of chronic constriction injury(CCI).Methods Male Sprague-Dawley rats were randomly divided into four groups(n=10): the sham group(intrathecal normal saline,IT NS),CCI group(CCI+IT NS),mismatch siRNA group(CCI+IT mismatch siRNA), and siRNA-TLR4 group(CCI+IT siRNA-TLR4).The lumbar intrathecal catheters were implanted in rats and CCI models were established as previously described.The TLR4 siRNA were administered intrathecally for 7 days starting from 1 day before surgery.The spinal cord expression of TLR4 mRNA was assessed by real-time PCR.Levels of TNF-α and IL-1β in spinal cord were detected by ELISA.The thermal and mechanical nociceptive thresholds were assessed by paw withdrawal latency(PWL) to radiant heat and von Frey filaments.Results Compared with the sham group,animals in CCI group had significantly lower mechanical and thermal pain thresholds,higher expression of TLR4 mRNA and levels of IL1β,TNF-α in the spinal cord(P0.05).Rats in the siRNA-TLR4 group had significantly higher mechanical and thermal pain thresholds(at 1,3,and 7 days after ligation,P0.05) and significantly lower expression of TLR4 mRNA and levels of IL-1β,TNF-α in the spinal cord compared with those in the CCI group and mismatch siRNA group(P0/05).Conclusion Intrathecal injection of siRNA-TLR4 can decrease the levels of inflammatory factors by silencing the TLR4 in the spinal cord of rats,and subsequently relieve the neuropathic pain induced by CCI.