抑制外周神经元PAR2-PKA/PKCε通路对痛转化模型大鼠痛阈的影响

摘要

Objective To detect the role of PAR2-PKA/PKCε signaling pathway in periphery neurons in the tran-sition from acute to chronic pain,and investigate the possible approach to prevent both acute and chronic pain simultane-ously. Methods SD rats were randomly divided into control group,sham model group,model group,iPAR2-1 group and iPAR2-2 group. The hyperalgesia priming model was established by injection of carrageenan and PGE2 into the left hind-paw except control and sham model group. PGE2 was administrated at 7 days after carrageenan injection. The PAR2 inhibi-tor was administrated before and after PGE2 injection separately in the iPAR2-1 group and iPAR2-2 group. The paw with-drawal thresholds(PWTs)of rats in each group was detected before and at 5 h,3 d,6 d,7 d 0.5 h,7 d 4 h,7 d 24 h after carrageenan injection. The expression level of PAR2, PKA and PKCε proteins in the dorsal root ganglion(DRG) were detected at 24 h after carrageenan injection. Results The hyperalgesia priming model was successfully generated. When PGE2 was administrated at 7 days after carrageenan injection, the hyperalgesia induced by PGE2 was significantly prolonged. The PWTs of rats in the model group were significantly lower than that of the control and sham model groups(P<0.01),though the PWTs of sham model group had no significant difference with the control on 7 d 24 h after carrageenan injection(P>0.05). The expression level of PAR2 and PKCε in the ipsilateral DRG neurons were significantly increased on 7 d 24 h after carrageenan injection,when compared with the control and sham model groups(P<0.05). PAR2 inhibi-tor prevented the prolonged hyperalgesia induced by PGE2(P<0.05)and decreased the PKCε expression in DRG neurons whenever it was given(P<0.05). However,PAR2 inhibitor did not regulate the acute inflammatory pain of PGE2 and the expression of PKA in DRG neurons(P>0.05). Conclusions Inhibition of the expression of PAR2 can prevent the tran-sition from acute to chronic pain. This effect may be related with the inhibitory effect on the activation of PAR2-PKCε sig-naling pathway in DRG neurons. However,inhibition of PAR2 can not regulate the acute pain. These may because of that the PAR2-PKA signaling pathway does not play a role in acute pain.%目的 探讨外周神经元蛋白酶激活受体2-蛋白激酶A/蛋白激酶Cε(PAR2-PKA/PKCε)通路在痛转化中的作用,寻找同时干预急性痛和慢性痛的可能方案.方法 SD大鼠随机分为空白组、假诱发组、诱发组、抑制剂1组和抑制剂2组.除空白组和假诱发组,所有大鼠均通过先后足部注射角叉菜胶和前列腺素E2(PGE2)建立痛觉敏化诱发模型.PGE2于角叉菜胶注射后7 d进行足部注射.抑制剂1组和抑制剂2组大鼠于PGE2注射前/后,分别给予PAR2抑制剂.观察角叉菜胶/生理盐水,注射前、注射后5h、3d、6d、7d0.5h、7d4h和7d24h大鼠机械痛阈(PWTs)的变化,检测角叉菜胶注射后7 d 24 h造模侧背根神经节(DRG)中PAR2、蛋白激酶A(PKA)和蛋白激酶(PKCε)表达.结果 痛觉敏化诱发模型建立成功.角叉菜胶注射后7 d给予PGE2,显著延长了PGE2诱发疼痛的存在时间,角叉菜胶注射后7 d 24 h假诱发组大鼠PWTs与同期空白组相比差异无显著性(P>0.05),而诱发组大鼠PWTs明显低于同期空白组和假诱发组大鼠(P<0.01).诱发组大鼠造模侧DRG中PAR2和PKCε表达在角叉菜胶注射后7 d 24 h明显提升,高于同期假诱发组和空白组(P<0.05).给予PAR2抑制,不论时间均能显著翻转角叉菜胶注射后7 d 24 h,诱发组大鼠由PGE2诱发的疼痛(P<0.05),并抑制DRG中PKCε表达.但,给予PAR2抑制剂不能影响PGE2诱发的急性疼痛和调制DRG中PKA含量.结论 抑制PAR2表达能阻断急性痛向慢性痛转化,这可能与其抑制DRG中PAR2-PKCε通路激活有关.但抑制PAR2并不能干预急性痛,这可能是因为DRG中PAR2相关通路未参与急性痛的产生.