PDF(Pubmed)
Abstract：
Prostaglandin E2 (PGE2) is a major contributor to inflammatory pain hyperalgesia, however, the extent to which it modulates the activity of nociceptive axons is incompletely understood. We developed and characterized a microfluidic cell culture model to investigate sensitisation of the axons of dorsal root ganglia neurons. We show that application of PGE2 to fluidically isolated axons leads to sensitisation of their responses to depolarising stimuli. Interestingly the application of PGE2 to the DRG axons elicited a direct and persistent spiking activity propagated to the soma. Both the persistent activity and the membrane depolarisation in the axons are abolished by the EP4 receptor inhibitor and a blocker of cAMP synthesis. Further investigated into the mechanisms of the spiking activity showed that the PGE2 evoked depolarisation was inhibited by Nav1.8 sodium channel blockers but was refractory to the application of TTX or zatebradine. Interestingly, the depolarisation of axons was blocked by blocking ANO1 channels with T16Ainh-A01. We further show that PGE2-elicited axonal responses are altered by the changes in chloride gradient within the axons following treatment with bumetanide a Na-K-2Cl cotransporter NKCC1 inhibitor, but not by VU01240551 an inhibitor of potassium-chloride transporter KCC2. Our data demonstrate a novel role for PGE2/EP4/cAMP pathway which culminates in a sustained depolarisation of sensory axons mediated by a chloride current through ANO1 channels. Therefore, using a microfluidic culture model, we provide evidence for a potential dual function of PGE2 in inflammatory pain: it sensitises depolarisation-evoked responses in nociceptive axons and directly triggers action potentials by activating ANO1 and Nav1.8 channels.
摘要：
前列腺素E2（PGE2）是炎性痛觉过敏的主要贡献者，然而,它调节伤害性轴突活动的程度尚不完全清楚。我们开发并表征了微流体细胞培养模型，以研究背根神经节神经元轴突的敏化。我们表明，将PGE2应用于流体分离的轴突会导致其对去极化刺激的反应敏感。有趣的是，将PGE2应用于DRG轴突会引起直接和持续的尖峰活动，传播到体细胞。EP4受体抑制剂和cAMP合成阻断剂消除了轴突的持续活性和膜去极化。对加标活性机制的进一步研究表明，Nav1.8钠通道阻滞剂抑制了PGE2诱发的去极化，但对TTX或扎特拉定的应用是难以反应的。有趣的是,通过用T16Ainh-A01阻断ANO1通道来阻断轴突的去极化。我们进一步表明，用Na-K-2Cl协同转运蛋白NKCC1抑制剂布美他尼治疗后，由于轴突内氯化物梯度的变化，PGE2引起的轴突反应发生了变化，但不是VU01240551氯化钾转运蛋白KCC2的抑制剂。我们的数据证明了PGE2/EP4/cAMP途径的新作用，该途径最终导致了通过ANO1通道的氯化物电流介导的感觉轴突的持续去极化。因此,使用微流体培养模型，我们为PGE2在炎性疼痛中的潜在双重功能提供了证据:它使痛觉轴突的去极化诱发反应敏感,并通过激活ANO1和Nav1.8通道直接触发动作电位.
