Resatorvid Alleviates Oxaliplatin Induced Neuropathic Pain Through Inhibition Of TLR4 Signal

Background:Oxaliplatin（OXA）is an ideal chemotherapeutic agent for the treatment of advanced colorectal cancer.More and more studies have shown that oxaliplatin can induce neuropathic pain in the treatment of tumors.Based on some literatures,there is a close relationship between TLR4 and neuropathic pain induced by OXA.However,its mechanism is still unclear.In this paper,we investigated the effect of TLR4knockout on OXA-induced neuropathic pain in mice.We also studied TAK-242,an inhibitor of TLR4,in terms of its effects on the neuropathic pain induced by OXA in rates.Our data revealed that oxaliplatin made high expression of TLR4 and MyD88in lumbar L4-5 dorsal root ganglion,and TAK-242 alleviated neuropathic pain induced by oxaliplatin.The results of this study will have great significance for the clinical treatment of neuropathic pain induced by OXA.Methods:1.Ten-week-old male TLR4 knockout（genetic background C57B1/6J）and wild-type mice were divided into 4 groups:wild-type mice（WT）;TLR4 knockout mice(TLR4^-/-Group);wild-type mice+oxaliplatin group（WT+OXA group）and TLR4 knockout mice+oxaliplatin group(TLR4^-/-+OXA group),with 10 mice in each group.The WT+OXA group and the TLR4^-/-+OXA group were intraperitoneally injected with OXA at a dose of 10 mg/kg on days d0 and d2.The WT and TLR4^-/-groups were intraperitoneally injected with 5%dextrose solution.Mechanical withdrawal threshold（MWT）and tail-twitch reflex latency（TWL）were measured every 3 days.On d15 days,the mice were anesthetized with ether and the blood was taken off.The spinal cord and dorsal root ganglion were removed simultaneously.Real-time quantitative PCR was used to detect the expression of TLR4 m RNA in L4-5 DRG.Western Blot and immunohistochemistry were used to detect the expression of TLR4 and MyD88 protein in L4-5 dorsal root ganglion.2.Rats were randomly divided into 2 groups,the vehicle group and the OXA experimental group,with 8 rats in each group.The rats in the OXA group were treated with 10 mg/kg OXA intraperitoneally on days d0 and d2,while the vehicle group was administrated with 5%glucose solution intraperitoneally.On d0,d2,d4,d6 and d8 days,the mechanical withdrawal threshold（MWT）and tail withdrawal latency（TWL）were measured in two groups.On d8,rats were anesthetized with ether and the blood was taken off.The spinal cord（SC）and the dorsal root ganglia（DRG）were removed simultaneously.Real-time quantitative PCR was used to detect the expression of TLR4、MyD88、NF-κb P65 and IL-1βm RNA in L4-5 spinal cord and dorsal root ganglia.Western Blot and immunohistochemistry were used to detect the expression of TLR4、MyD88、NF-κb P65 and IL-1βprotein in L4-5 spinal cord and the dorsal root ganglia.3.SD rats were randomly divided into 4 groups,the vehicle group,the OXA group（OXA intraperitoneal injection of 10mg/kg）,the TAK-242 low dose treatment group（OXA 10mg/kg+TAK-242 100μg/kg/day）and the TAK-242 high dose treatment group（OXA 10mg/kg+TAK-242 100μg/kg/day）,with 8 rats in each group.Corresponding concentration of TAK-242 was injected intraperitoneally at d0after OXA intraperitoneal injection.On d0,d2,d4,d6 and d8 days,the MWT and TWL were measured in each group.On d8,rats were anesthetized with ether and the blood was taken off.The spinal cord（SC）and the dorsal root ganglia（DRG）were removed simultaneously.Real-time quantitative PCR was used to detect the expression of TLR4、MyD88、NF-κb P65 and IL-1βm RNA in L4-5 segment spinal cord and root ganglion.Western Blot and immunohistochemistry were used to detect the expression of TLR4、MyD88、NF-κb P65 and IL-1βprotein in L4-5 segment spinal cord and the root ganglion.Result:1.TLR4 knockout alleviates oxaliplatin-induced neuropathic pain in mice.2.oxaliplatin could increase the expression of TLR4、MyD88、NF-κb P65 and IL-1βin the spinal cord and the dorsal root ganglia.3.TAK-242,the inhibitor of TLR4,can alleviate oxaliplatin induced neuropathic pain in rats.4.TAK-242 could downregulate the expression of TLR4、MyD88、NF-κb P65and IL-1βin L4-5 SC and DRG of OXA-treated rats).Conclusion:The TLR4/MyD88 signaling pathway in the spinal cord and the dorsal root ganglia is involved in oxaliplatin induced neuropathic pain.TAK-242 can alleviate the OXA-induced neuropathic pain by inhibiting the TLR4/MyD88 signaling pathway.