Titus Family Department of Clinical Pharmacy, School of Pharmacy, University of Southern California, Los Angeles, CA 90033, United States.
Center for Learning and Memory, University of Texas at Austin, Austin, TX 78712, United States.
Neuropharmacology. 2018 Jan;128:11-21. doi: 10.1016/j.neuropharm.2017.09.030. Epub 2017 Sep 22.
Neuroinflammation is one of the mechanisms leading to neurodegenerative brain damage induced by chronic alcohol (ethanol) exposure. Microglia play a major role in the development of innate immune responses to environmental injuries including ethanol. Adenosine 5″-triphosphate (ATP)-activated purinergic P2X receptor (P2XR) subtypes, P2X4Rs and P2X7Rs, are endogenously expressed in microglia and can modulate their activity. These 2 P2XR subtypes differ pharmacologically and functionally: 1) P2X4Rs are activated at lower (≤0.1 mM) whereas P2X7Rs - at higher (≥1.0 mM) ATP concentrations; 2) P2X4R activation contributes to the release of brain derived neurotrophic factor and its role in tactile allodynia and neuropathic pain is demonstrated; 3) Due to its role in the secretion of pro-inflammatory IL-1β, P2X7Rs have been implicated in the development of neurodegenerative pathologies, pain and morphine tolerance. To date, the roles of individual P2XR subtypes in ethanol effects on microglia and the functional consequences are not completely understood. Based on the existing knowledge on the pharmacological and functional differences between P2X4Rs and P2X7Rs, the present work tested the hypothesis that P2X4Rs and P2X7Rs play differential roles in ethanol action in microglia. Effects of ethanol on P2X4R and P2X7R activity, expression and functional consequences were determined using murine BV2 microglial cells. Ethanol (≥100 mM) inhibited P2X4Rs but was inactive on P2X7 channel activity. Ethanol (25, 100 mM) inhibited P2X4R-mediated microglia migration whereas it potentiated pore formation in P2X7Rs. Furthermore, ethanol (25, 100 mM) potentiated P2X7R-mediated IL-1β secretion from BV2 microglia. Ethanol also induced protein expression for both P2XR subtypes. Overall, the findings identify differential roles for P2X4Rs and P2X7Rs in regards to ethanol effects on microglia which may be linked to different stages of ethanol exposure.
神经炎症是慢性酒精（乙醇）暴露导致神经退行性脑损伤的机制之一。小胶质细胞在环境损伤引起的固有免疫反应的发展中起主要作用，包括乙醇。三磷酸腺苷（ATP）激活的嘌呤能 P2X 受体（P2XR）亚型 P2X4R 和 P2X7R 在小胶质细胞中内源性表达，并可以调节其活性。这 2 种 P2XR 亚型在药理学和功能上有所不同：1）P2X4R 在较低（≤0.1 mM）而 P2X7R - 在较高（≥1.0 mM）ATP 浓度下被激活；2）P2X4R 的激活有助于脑源性神经营养因子的释放，其在触觉过敏和神经病理性疼痛中的作用已得到证实；3）由于其在促炎 IL-1β分泌中的作用，P2X7R 被牵连到神经退行性病变、疼痛和吗啡耐受的发展中。迄今为止，单个 P2XR 亚型在乙醇对小胶质细胞的影响及其功能后果中的作用尚不完全清楚。基于 P2X4R 和 P2X7R 之间药理学和功能差异的现有知识，本工作测试了以下假设，即 P2X4R 和 P2X7R 在小胶质细胞中的乙醇作用中发挥不同的作用。使用小鼠 BV2 小胶质细胞确定了乙醇对 P2X4R 和 P2X7R 活性、表达和功能后果的影响。乙醇（≥100 mM）抑制 P2X4R，但对 P2X7 通道活性无作用。乙醇（25、100 mM）抑制 P2X4R 介导的小胶质细胞迁移，而增强 P2X7R 中的孔形成。此外，乙醇（25、100 mM）增强了 BV2 小胶质细胞中 P2X7R 介导的 IL-1β 分泌。乙醇还诱导了这两种 P2XR 亚型的蛋白表达。总的来说，这些发现确定了 P2X4R 和 P2X7R 在乙醇对小胶质细胞的影响方面的不同作用，这可能与乙醇暴露的不同阶段有关。
