Department of Pharmacology and Physiology, Drexel University College of Medicine, Philadelphia, Pennsylvania 19102.
Department of Anesthesiology, Rutgers New Jersey Medical School Newark, Newark, New Jersey 07103.
J Neurosci. 2024 Jan 3;44(1):e0329232023. doi: 10.1523/JNEUROSCI.0329-23.2023.
Peripheral sensitization is one of the primary mechanisms underlying the pathogenesis of chronic pain. However, candidate molecules involved in peripheral sensitization remain incompletely understood. We have shown that store-operated calcium channels (SOCs) are expressed in the dorsal root ganglion (DRG) neurons. Whether SOCs contribute to peripheral sensitization associated with chronic inflammatory pain is elusive. Here we report that global or conditional deletion of Orai1 attenuates Complete Freund's adjuvant (CFA)-induced pain hypersensitivity in both male and female mice. To further establish the role of Orai1 in inflammatory pain, we performed calcium imaging and patch-clamp recordings in wild-type (WT) and Orai1 knockout (KO) DRG neurons. We found that SOC function was significantly enhanced in WT but not in Orai1 KO DRG neurons from CFA- and carrageenan-injected mice. Interestingly, the Orai1 protein level in L3/4 DRGs was not altered under inflammatory conditions. To understand how Orai1 is modulated under inflammatory pain conditions, prostaglandin E2 (PGE2) was used to sensitize DRG neurons. PGE2-induced increase in neuronal excitability and pain hypersensitivity was significantly reduced in Orai1 KO mice. PGE2-induced potentiation of SOC entry (SOCE) was observed in WT, but not in Orai1 KO DRG neurons. This effect was attenuated by a PGE2 receptor 1 (EP1) antagonist and mimicked by an EP1 agonist. Inhibition of Gq/11, PKC, or ERK abolished PGE2-induced SOCE increase, indicating PGE2-induced SOCE enhancement is mediated by EP1-mediated downstream cascade. These findings demonstrate that Orai1 plays an important role in peripheral sensitization. Our study also provides new insight into molecular mechanisms underlying PGE2-induced modulation of inflammatory pain. Store-operated calcium channel (SOC) Orai1 is expressed and functional in dorsal root ganglion (DRG) neurons. Whether Orai1 contributes to peripheral sensitization is unclear. The present study demonstrates that Orai1-mediated SOC function is enhanced in DRG neurons under inflammatory conditions. Global and conditional deletion of Orai1 attenuates complete Freund's adjuvant (CFA)-induced pain hypersensitivity. We also demonstrate that prostaglandin E2 (PGE2) potentiates SOC function in DRG neurons through EP1-mediated signaling pathway. Importantly, we have found that Orai1 deficiency diminishes PGE2-induced SOC function increase and reduces PGE2-induced increase in neuronal excitability and pain hypersensitivity. These findings suggest that Orai1 plays an important role in peripheral sensitization associated with inflammatory pain. Our study reveals a novel mechanism underlying PGE2/EP1-induced peripheral sensitization. Orai1 may serve as a potential target for pathological pain.
外周敏化是慢性疼痛发病机制的主要机制之一。然而，涉及外周敏化的候选分子仍不完全了解。我们已经表明，储存操作的钙通道（SOCs）在背根神经节（DRG）神经元中表达。SOCs 是否有助于与慢性炎症性疼痛相关的外周敏化尚不清楚。在这里，我们报告说，全局或条件性敲除 Orai1 可减轻雄性和雌性小鼠完全弗氏佐剂（CFA）诱导的痛觉过敏。为了进一步确定 Orai1 在炎症性疼痛中的作用，我们在野生型（WT）和 Orai1 敲除（KO）DRG 神经元中进行了钙成像和膜片钳记录。我们发现，SOC 功能在 CFA 和角叉菜胶注射的 WT 但不在 Orai1 KO DRG 神经元中显著增强。有趣的是，炎症条件下 L3/4 DRGs 中的 Orai1 蛋白水平没有改变。为了了解 Orai1 在炎症性疼痛条件下是如何被调节的，我们使用前列腺素 E2（PGE2）使 DRG 神经元敏化。在 Orai1 KO 小鼠中，PGE2 诱导的神经元兴奋性增加和痛觉过敏明显降低。在 WT，但不在 Orai1 KO DRG 神经元中观察到 PGE2 诱导的 SOC 进入（SOCE）增强。该效应被 PGE2 受体 1（EP1）拮抗剂减弱，并被 EP1 激动剂模拟。抑制 Gq/11、PKC 或 ERK 可消除 PGE2 诱导的 SOCE 增加，表明 PGE2 诱导的 SOCE 增强是由 EP1 介导的下游级联介导的。这些发现表明 Orai1 在周围敏化中起重要作用。我们的研究还为 PGE2 诱导的炎症性疼痛调节的分子机制提供了新的见解。储存操作的钙通道（SOC）Orai1 在背根神经节（DRG）神经元中表达和功能。Orai1 是否有助于周围敏化尚不清楚。本研究表明，在炎症条件下，Orai1 介导的 SOC 功能在 DRG 神经元中增强。全局和条件性敲除 Orai1 可减轻完全弗氏佐剂（CFA）诱导的痛觉过敏。我们还表明，前列腺素 E2（PGE2）通过 EP1 介导的信号通路增强 DRG 神经元中的 SOC 功能。重要的是，我们发现 Orai1 缺乏可减少 PGE2 诱导的 SOC 功能增加，并降低 PGE2 诱导的神经元兴奋性增加和痛觉过敏。这些发现表明 Orai1 在与炎症性疼痛相关的外周敏化中起重要作用。我们的研究揭示了 PGE2/EP1 诱导的外周敏化的新机制。Orai1 可能是病理性疼痛的潜在靶点。
