Shaqura Mohammed, Li Xiongjuan, Al-Khrasani Mahmoud, Shakibaei Mehdi, Tafelski Sascha, Fürst Susanna, Beyer Antje, Kawata Mitsuhiro, Schäfer Michael, Mousa Shaaban A
Department of Anaesthesiology and Intensive Care Medicine, Charité University Berlin, Campus Virchow Klinikum and Campus Charité Mitte, Berlin, Germany.
Department of Pharmacology and Pharmacotherapy, Semmelweis University, Budapest, Hungary.
Neuropharmacology. 2016 Dec;111:1-13. doi: 10.1016/j.neuropharm.2016.08.019. Epub 2016 Aug 21.
Glucocorticoids were long believed to primarily function through cytosolic glucocorticoid receptor (GR) activation and subsequent classical genomic pathways. Recently, however, evidence has emerged that suggests the presence of rapid non-genomic GR-dependent signaling pathways within the brain, though their existence in spinal and peripheral nociceptive neurons remains elusive. In this paper, we aim to systemically identify GR within the spinal cord and periphery, to verify their putative membrane location and to characterize possible G protein coupling and pain modulating properties. Double immunofluorescence confocal microscopy revealed that GR predominantly localized in peripheral peptidergic and non-peptidergic nociceptive C- and Aδ-neurons and existed only marginally in myelinated mechanoreceptive and proprioreceptive neurons. Within the spinal cord, GR predominantly localized in incoming presynaptic nociceptive neurons, in pre- and postsynaptic structures of the dorsal horn, as well as in microglia. GR saturation binding revealed that these receptors are linked to the cell membrane of sensory neurons and, upon activation, they trigger membrane targeted [S]GTPγS binding, indicating G protein coupling to a putative receptor. Importantly, subcutaneous dexamethasone immediately and dose-dependently attenuated acute nociceptive behavior elicited in an animal model of formalin-induced pain hypersensitivity compared to naive rats. Overall, this study provides firm evidence for a novel neuronal mechanism of GR agonists that is rapid, non-genomic, dependent on membrane binding and G protein coupling, and acutely modulates nociceptive behavior, thus unraveling a yet unconsidered mechanism of pain relief.
长期以来，人们一直认为糖皮质激素主要通过激活胞质糖皮质激素受体（GR）以及随后的经典基因组途径发挥作用。然而，最近有证据表明，大脑中存在快速的非基因组GR依赖性信号通路，尽管它们在脊髓和外周伤害性神经元中的存在仍不明确。在本文中，我们旨在系统地鉴定脊髓和外周中的GR，验证其假定的膜定位，并表征可能的G蛋白偶联和疼痛调节特性。双免疫荧光共聚焦显微镜显示，GR主要定位于外周肽能和非肽能伤害性C神经元和Aδ神经元，在有髓机械感受和本体感受神经元中仅少量存在。在脊髓内，GR主要定位于传入的突触前伤害性神经元、背角的突触前和突触后结构以及小胶质细胞中。GR饱和结合显示，这些受体与感觉神经元的细胞膜相连，激活后，它们触发膜靶向的[S]GTPγS结合，表明G蛋白与假定的受体偶联。重要的是，与未处理的大鼠相比，皮下注射地塞米松能立即且剂量依赖性地减轻福尔马林诱导的疼痛超敏反应动物模型中引发的急性伤害性行为。总体而言，本研究为GR激动剂的一种新的神经元机制提供了确凿证据，该机制快速、非基因组、依赖膜结合和G蛋白偶联，并能急性调节伤害性行为，从而揭示了一种尚未被考虑的疼痛缓解机制。
