Department of Pharmacology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
J Pain. 2012 Aug;13(8):742-54. doi: 10.1016/j.jpain.2012.05.011.
Human and animal studies suggest that estrogens are involved in the processing of nociceptive sensory information and analgesic responses in the central nervous system. Rapid pronociceptive estrogenic effects have been reported, some of which likely involve G protein-coupled estrogen receptor (GPER) activation. Membrane depolarization and increases in cytosolic calcium and reactive oxygen species (ROS) levels are markers of neuronal activation, underlying pain sensitization in the spinal cord. Using behavioral, electrophysiological, and fluorescent imaging studies, we evaluated GPER involvement in spinal nociceptive processing. Intrathecal challenging of mice with the GPER agonist G-1 results in pain-related behaviors. GPER antagonism with G15 reduces the G-1-induced response. Electrophysiological recordings from superficial dorsal horn neurons indicate neuronal membrane depolarization with G-1 application, which is G15 sensitive. In cultured spinal sensory neurons, G-1 increases intracellular calcium concentration and induces mitochondrial and cytosolic ROS accumulation. In the presence of G15, G-1 does not elicit the calcium and ROS responses, confirming specific GPER involvement in this process. Cytosolic calcium concentration elevates faster and with higher amplitude following G-1 intracellular microinjections compared to extracellular exposure, suggesting subcellular GPER functionality. Thus, GPER activation results in spinal nociception, and the downstream mechanisms involve cytosolic calcium increase, ROS accumulation, and neuronal membrane depolarization.
Our results suggest that GPER modulates pain processing in spinal sensory neurons via cytosolic calcium increase and ROS accumulation. These findings extend the current knowledge on GPER involvement in physiology and disease, providing the first evidence of its pronociceptive effects at central levels and characterizing some of the underlying mechanisms.
人体和动物研究表明，雌激素参与中枢神经系统中伤害感受性感觉信息和镇痛反应的处理。已经报道了快速的致伤害性雌激素作用，其中一些可能涉及 G 蛋白偶联雌激素受体（GPER）的激活。膜去极化以及细胞溶质钙和活性氧（ROS）水平的增加是神经元激活的标志物，是脊髓中疼痛敏化的基础。使用行为、电生理和荧光成像研究，我们评估了 GPER 参与脊髓伤害感受处理。鞘内给予 GPER 激动剂 G-1 会导致与疼痛相关的行为。用 G15 拮抗 GPER 会减少 G-1 诱导的反应。来自浅层背角神经元的电生理记录表明，神经元膜去极化与 G-1 的应用有关，而 G15 对此敏感。在培养的脊髓感觉神经元中，G-1 增加细胞内钙浓度并诱导线粒体和细胞质 ROS 积累。在 G15 存在下，G-1 不会引起钙和 ROS 反应，从而证实了该过程中 GPER 的特异性参与。与细胞外暴露相比，G-1 细胞内微注射后细胞质钙浓度升高更快且幅度更大，表明亚细胞 GPER 功能。因此，GPER 的激活导致脊髓疼痛，下游机制涉及细胞质钙增加、ROS 积累和神经元膜去极化。
我们的结果表明，GPER 通过细胞质钙增加和 ROS 积累来调节脊髓感觉神经元中的疼痛处理。这些发现扩展了当前关于 GPER 在生理学和疾病中参与的知识，提供了其在中枢水平致伤害性作用的第一个证据，并描述了一些潜在的机制。
