The Role of TRPM3 Ion Channels in Opioid-Induced Analgesia and Pruritus

TRPM3 离子通道在阿片类药物引起的镇痛和瘙痒中的作用

• 批准号: 10612804
• 负责人: Nawoo Kim
• 金额: --
• 依托单位: RUTGERS BIOMEDICAL AND HEALTH SCIENCES
• 依托单位国家: 美国
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-13 至 2023-04-13
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/10612804
• 关键词: Absence of pain sensation; Accounting; Affect; Agonist; Analgesics; Attenuated; Behavioral; Binding; Biological Assay; Cations; Cells; Coupled; Data; Disinhibition; Distress; Esthesia; Exhibits; Exons; G-Protein-Coupled Receptors; Goals; Image; In Situ Hybridization; Inhibitory G-Protein Gi; Intrathecal Injections; Ion Channel; Knowledge; Mechanics; Mediating; Modality; Modeling; Molecular; Morphine; Mus; Neurons; Nociception; Nociceptors; Opioid; Opioid Analgesics; Opioid Antagonist; Opioid Receptor Binding; Outcome; Pain; Pain management; Pathway interactions; Patients; Pattern; Perioperative; Peripheral; Physiological; Population; Postoperative Pain; Preparation; Protein Isoforms; Proteins; Pruritus; RNA Splicing; Receptor Activation; Receptor Inhibition; Reporter; Research; Role; Sensory; Slice; Spinal; Spinal Cord; Surgical incisions; Testing; Variant; Vertebral column; Work; antinociception; behavioral study; effective therapy; excitatory neuron; experience; experimental study; improved; inhibitory neuron; insight; morphine administration; mu opioid receptors; nociceptive response; novel; opioid therapy; pain relief; patch clamp; pregnenolone sulfate; preservation; receptor; receptor expression; receptor function; response; side effect; transcriptome sequencing

PROJECT SUMMARY Spinal administration of morphine, a potent opioid, is commonly used to treat post-operative pain. However, the desired opioid-induced analgesia consistently has a negative side effect of opioid-induced pruritus, causing debilitating itch in the already distressed patient. The first line treatment is opioid antagonists, but this may compete with the initial opioid treatment and cause the patient to choose between unwanted pain or itch. Both sensations are closely related, but the mechanism of how opioids can cause both pruritus and analgesia remains unclear. Morphine acts on mu-opioid receptors (MOR) to inhibit the activity of pain-sensing neurons. MOR is a G-protein coupled receptor (GPCR) coupled to the inhibitory Gi-heterotrimeric proteins (Gαi and Gβγ) which cause downstream actions to inhibit depolarization of the neuron. One mechanism by which this inhibition occurs is by direct inhibition by Gβγ on the Transient Receptor Potential melastatin 3 (TRPM3) ion channel, a thermosensitive and nociceptive cation channel expressed on neurons. Recently, a naturally occurring splice variant of TRPM3 that does not bind to Gβγ was identified. With this knowledge, a novel mouse line was generated (TRPM3DEx17) in which all the TRPM3 channels express this isoform. Utilizing the TRPM3DEx17 mouse line we performed preliminary behavioral studies on morphine induced pruritus and analgesia. Data showed that the TRPM3DEx17 mice experienced significantly less pruritus upon intrathecal injection of morphine compared to WT. In the plantar incision model, TRPM3DEx17 mice had no change in morphine analgesia when injected intrathecally in heat and mechanical nociception. Analgesia by morphine occurs through inhibition of excitatory (Vglu2+) neurons, while pruritus occurs by inhibition of inhibitory (Vgat+) neurons, or disinhibition, in the spinal cord. Interestingly, TRPM3 and MOR are more frequently coexpressed on the itch-inhibitory Vgat+ neurons compared to the pain-excitatory Vglut2+ neurons, supporting our behavioral findings. Thus, Aim 1 of the proposal will explore via in-situ hybridization, the co-expression of TRPM3 and MOR in Vglu2+ and Vgat+ neurons in the TRPM3DEx17 mouse spinal cord, and use two reporter mouse lines with GFP tagged excitatory and inhibitory neurons to perform whole-cell patch clamping of spinal cord slices to compare morphine inhibition in each neuronal population. Aim 2 will attempt to overcome the MOR inhibition of TRPM3 by co-injecting a TRPM3 agonist, pregnenolone sulfate, in the WT mice intrathecally with morphine, and observe if opioid-induced pruritus can be alleviated while analgesia is maintained. These results may suggest that TRPM3 is the main depolarizing ion channel responsible for the disinhibition of pruritus and can be a potential target for alleviating morphine induced pruritus in patients undergoing opioid therapy without affecting the desired analgesia.

项目概要 吗啡（一种强效阿片类药物）的脊髓给药通常用于治疗术后疼痛。 然而，所需的阿片类药物诱导的镇痛始终具有阿片类药物诱导的负面副作用 瘙痒，导致本已痛苦的患者出现令人衰弱的瘙痒。一线治疗是阿片类拮抗剂， 但这可能与最初的阿片类药物治疗相竞争，并导致患者在不必要的疼痛之间做出选择 两种感觉密切相关，但阿片类药物如何引起瘙痒和瘙痒的机制。 镇痛作用仍不清楚。 吗啡作用于μ阿片受体（MOR），抑制痛觉神经元的活性。 G 蛋白偶联受体 (GPCR) 与抑制性 Gi 异三聚体蛋白（Gαi 和 Gβγ）偶联， 引起下游作用以抑制神经元去极化，这是这种抑制的一种机制。 发生的原因是 Gβγ 对瞬时受体电位 melastatin 3 (TRPM3) 离子通道的直接抑制， 最近，神经元上表达的热敏和伤害性阳离子通道自然发生的剪接。 鉴定出不与 Gβγ 结合的​​ TRPM3 变体，从而开发出一种新的小鼠品系。 生成 (TRPM3DEx17)，其中所有 TRPM3 通道都利用 TRPM3DEx17 表达该亚型。 我们对小鼠系进行了吗啡引起的瘙痒和镇痛的初步行为研究。 数据显示，TRPM3DEx17 小鼠鞘内注射后瘙痒明显减轻 与 WT 相比，TRPM3DEx17 小鼠的吗啡含量没有变化。 鞘内注射时会出现热镇痛和机械性伤害感受吗啡会发生镇痛。 通过抑制兴奋性 (Vglu2+) 神经元，而瘙痒是通过抑制抑制性 (Vgat+) 神经元发生的 脊髓中的神经元或去抑制表明，TRPM3 和 MOR 更频繁地共表达。 与疼痛兴奋性 Vglut2+ 神经元相比，抑制瘙痒的 Vgat+ 神经元的作用，支持我们的研究 因此，该提案的目标 1 将通过原位杂交探索行为的共表达。 TRPM3DEx17 小鼠脊髓中 Vglu2+ 和 Vgat+ 神经元中的 TRPM3 和 MOR，并使用两个报告基因 带有 GFP 标记的兴奋性和抑制性神经元的小鼠品系，可对脊髓进行全细胞膜片钳 目标 2 将尝试克服每个神经群中的吗啡抑制。 通过在 WT 小鼠鞘内共同注射 TRPM3 激动剂孕烯醇酮硫酸盐来抑制 TRPM3 的 MOR 给予吗啡，观察在维持镇痛的同时能否缓解阿片类药物引起的瘙痒。 结果可能表明 TRPM3 是负责去抑制的主要去极化离子通道 瘙痒，可以成为减轻吗啡引起的阿片类药物患者瘙痒的潜在目标 治疗而不影响所需的镇痛效果。