Role of astrocytes and astrocytic CD38 in spinal opioid signaling

项目摘要 阿片类药物通常用于治疗疼痛，也是阿片类药物信号传导的经典机制 涉及神经机制。慢性阿片类药物给药会导致负面影响，如 痛觉过敏和阿片耐受性，并可导致依赖和成瘾。这些负面影响不是 仅由神经机制来解释。了解非神经元细胞在阿片信号传导中的作用 在正常和病理条件下，对于开发新的疼痛干预措施是重要的。 星形胶质细胞，传统上被认为是支持性细胞，现在已知在调节神经元的功能中具有重要作用。 突触传递和突触外谷氨酸是疼痛和阿片类镇痛的关键神经递质。在 脑桥核是成瘾途径的重要脑区，已显示星形胶质细胞表达 μ-阿片受体（莫尔），并通过钙升高和谷氨酸释放对阿片类药物作出反应。尽管 它们在调节突触传递和突触外谷氨酸中的关键作用， 星形胶质细胞是否在脊髓（疼痛处理的重要区域）中的μ-阿片样物质信号传导中发挥作用 和阿片类镇痛药。我们的初步行为实验表明，蛋白质CD 38，一个重要的 负责钙稳态的蛋白质，仅在脊髓中的星形胶质细胞中表达， 缺乏CD 38的动物对吗啡的抗伤害效应显著降低 鞘内注射，指出星形胶质细胞CD 38在脊髓阿片机制中的作用。因此，我们目前 目的是在突触水平上定义：i）脊髓星形胶质细胞在μ-阿片信号传导中的作用; ii） 脊髓星形胶质细胞蛋白CD 38，在μ-阿片信号和抗伤害感受。我们假设星形胶质细胞 通过星形胶质细胞钙蛋白CD 38及其受体参与脊髓阿片样物质信号传导。 代谢产物cADPR。为了验证这一假设，我们将进行离体脊髓星形胶质细胞钙成像 使用新开发的遗传编码钙指标和电生理读数来测量 阿片刺激后星形胶质细胞释放谷氨酸。为了检测星形胶质细胞CD 38在 在突触水平的抗伤害感受中，我们将测量阿片样物质抑制光遗传神经元的能力。 Nav1.8伤害感受器的突触刺激。将在我们的野生型和CD 38之间进行比较 缺陷小鼠我们的研究结果将描述星形胶质细胞和星形胶质细胞CD 38参与μ-阿片样物质 信号在脊髓水平，并将定义为新的有前途的未开发的潜力星形胶质细胞 目标的发展疼痛干预减少成瘾倾向。

Project Summary Opioids are commonly prescribed for the treatment of pain, and the classic mechanism of opioid signaling involves neuronal mechanisms. Chronic opioid administration results in negative effects like paradoxical hyperalgesia and opioid tolerance and can lead to dependence and addiction. These negative effects are not explained by neuronal mechanisms alone. Understanding the role of non-neuronal cells in opioid signaling during normal and pathological conditions is important for the development of novel pain interventions. Astrocytes, classically considered supportive cells, are now known to have important roles in modulating synaptic transmission and extrasynaptic glutamate a key neurotransmitter in pain and opioid analgesia. In the nucleus accumbens, an important brain region for addiction pathways, astrocytes have been shown to express µ-opioid receptors (MOR) and to respond to opioids with calcium elevations and glutamate release. Despite their critical role in modulating synaptic transmission and extrasynaptic glutamate, no studies have determined whether astrocytes play a role in µ-opioid signaling in the spinal cord, an important region for pain processing and opioid antinociception. Our preliminary behavioral experiments show that the protein CD38, an important protein responsible for calcium homeostasis, is expressed exclusively in astrocytes in the spinal cord, and animals deficient in CD38 had markedly reduced antinociceptive efficacy to morphine administered intrathecally, pointing to a role of astrocytic CD38 in spinal opioid mechanisms. Therefore, our current objectives are to define at the synaptic level: i) the role of spinal astrocytes in µ-opioid signaling and ii) the role of spinal astrocytic protein CD38, in µ-opioid signaling and antinociception. We hypothesize that astrocytes are involved in spinal opioid signaling via mechanisms that engage the astrocytic calcium protein CD38 and its metabolite cADPR. To test this hypothesis, we will perform ex vivo calcium imaging of spinal cord astrocytes using newly developed genetically encoded calcium indicators and electrophysiological readouts to measure the release of glutamate by astrocytes following opioid stimulation. To test the role of astrocytic CD38 in antinociception at the synaptic level, we will measure the ability of the opioid to inhibit optogenetic neuronal synaptic stimulation of Nav 1.8 nociceptors. Comparisons will be made between our wild type and CD38 deficient mice. Our results will characterize the involvement of astrocytes and astrocytic CD38 in µ-opioid signaling at the spinal level and would define the promising underexplored potential of astrocytes as novel targets for the development of pain interventions with reduced addiction liability.