The Effects Of PARP On Neuropathic Pain Induced By Lumbar 5 Spinal Nerve Ligation In Rats

ObjectivePrevious studies have demonstrated that neurological damage and inflammation induced DRG and spinal dorsal horn DNA methylation and histone acetylation,the so-called epigenetics,by regulating the transcription of related genes plays an important role in the occurrence and development of pathological pain.Poly(ADP-ribose)polymerase,PARP was identified as a group of enzyme proteins widely found in eukaryotic cells,which are involved in the regulation of gene transcription levels by the modification of ADP-ribosylation of related nucleoprotein.Howevr the role and expression changes of PARP in neuropathic pain are still unclear.In this study,PARP inhibitors were injected intrathecally to explore the effect of PARP activation on neuropathic pain induced by Lumbar 5 spinal nerve ligation(L5 SNL),and then the rats were treated with Western Blot to discover the effects of different time on spinal dorsal horn PARP-1 expression changes.Experimental methodsThe male SD rats were prepared to set up the neuropathic pain model the neuropathic pain model by L5 SNL.The sham operation group only exposed the spinal dorsal spinal nerve and closed the incision.A small amount of PARP inhibitor PJ34 was injected into the preemptive catheter and the control group was injectedwith an equal volume of solvent.The effect of PJ34 on pain behavior in rats was assessed by measuring rat Paw withdrawal threshold(PWT)and Puma withdrawal latency(PWL).The rat pain behavior test was divided into 6 groups:(1)L5 SNL sham operation;(2)L5 SNL +saline group;(3)L5 SNL + PJ34 1 ?g;(4)L5 SNL + PJ34 5 ?g;(5)L5 SNL + PJ34 10?g;(6)PJ34 10 ?g.Intrathecal injection of PJ34 or saline begin at a moment before L5 SNL,once a day for 7 days.In order to observe the effect of PJ34 on established neuropathic pain,intrathecal injection begin on day 7 after L5 SNL,once a day for 3days.The experiment was divided into two groups.(1)L5 SNL + saline group;(2)L5SNL + PJ34 10 ?g.To record the expression of PARP-1 in spinal dorsal horn after L5 SNL in rats,18 SD rats were randomly divided into six groups,each group of three.Samples were collected after 1,5,7,10,14 days of the surgery,took the left lumbar enlargement,measured protein concentration,and subjected to Western blot to detect the expression of PARP-1.Results1 Changes of PARP-1 expression in spinal dorsal horn after L5 SNL in rats.In this study,the protein expression of PARP-1 in spinal dorsal horn was observed by Western Blot after 1,5,7,10 and 14 days after L5 SNL.The results confirmed that L5 SNL could up-regulate the expression of PARP-1 protein in the spinal cord.Compared with the sham operation group,the difference was significant at the first day(P <0.05),peaked at day 7(P <0.01)and maintained until the 14 th day after surgery.2 Effects of precutaneous intrathecal injection(i.t.)PARP inhibitor PJ34 on neuropathic pain formation after L5 SNL in rats.Compared with sham operation group and preoperative baseline value,the difference of PWT and PWL was significant on the first day after L5 SNL(P <0.05),and reached the lowest value on the 7th day after L5 SNL(P < 0.001).Pretreatment with PJ34 could prevent the decrease of PWT and PWL in rats after L5 SNL.Compared with intrathecal injection group,the significant difference appeared on day3 after PJ34 application and continued on day 10 after L5 SNL.The dose and time ofPJ34 showed a dependency.Intrathecal injection of PJ34 alone did not affect the basal PWT and PWL in normal rats.3 Intrathecal injection of PJ34 on the neuropathic pain conducted after L5 SNL.In order to observe the effect of PARP inhibitor PJ34 on established neuropathic pain,PJ34 was injected intrathecally 1 day for 3 days on day 7 after L5 SNL.The results showed that PJ34 could reverse the L5 SNL-induced PWT And the decline of PWL.Compared with the injection solvent group,the significant difference occurred on the first day after treatment(P <0.05),and remained until the end of the experiment 1 days.ConclusionL5 SNL in rats can cause elevated expression of PARP1 in dorsal horn of spinal cord.PARP inhibitor PJ34 can significantly reduce the neuropathic pain induced by L5 SNL.