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.

项目总结 脊髓注射吗啡是一种有效的阿片类药物，通常用于治疗术后疼痛。 然而，理想的阿片类药物诱导的镇痛总是有阿片类药物诱导的副作用。 瘙痒，使本已痛苦的病人感到虚弱的瘙痒。一线治疗是阿片类拮抗剂， 但这可能会与最初的阿片类药物治疗产生竞争，导致患者在不想要的疼痛之间做出选择 或者发痒。这两种感觉都是密切相关的，但阿片类药物如何导致瘙痒和 止痛作用仍不清楚。 吗啡作用于单位阿片受体(MOR)，抑制痛觉神经元的活动。MOR是一种 G蛋白偶联受体与抑制性胃肠道异源三聚体蛋白(GαI和Gβγ)偶联 引起下游作用，以抑制神经元的去极化。这种抑制的一种机制 发生是通过G-βγ直接抑制瞬时受体电位-3(TRPM3)离子通道，a 温敏和伤害性阳离子通道在神经元上表达。最近，一种自然发生的剪接 发现了不与G-βγ结合的TRPM3的变异体。有了这个知识，一种新的老鼠品系是 产生的(TRPM3DEx17)，其中所有TRPM3通道都表达该异构体。利用TRPM3DEx17 我们对吗啡引起的瘙痒和镇痛作用进行了初步的行为学研究。 数据显示，鞘内注射TRPM3DEx17小鼠的瘙痒症状明显减少 吗啡与西药相比。在足底切开模型中，TRPM3DEx17小鼠的吗啡含量没有变化 鞘内注射时的热痛和机械性伤害性痛。吗啡的止痛作用 通过抑制兴奋性(Vlu2+)神经元，而通过抑制抑制性(Vgat+)发生瘙痒 脊髓中的神经元，或去抑制。有趣的是，TRPM3和MOR更频繁地共表达 对瘙痒抑制的Vgat+神经元和疼痛兴奋的Vgat+神经元的比较，支持我们的 行为发现。因此，该提案的目标1将通过原位杂交来探索 TRPM3和MOR在TRPM3DEx17小鼠脊髓Vlu2+和Vgat+神经元中的表达，并使用两个报告 GFP标记兴奋性和抑制性神经元的小鼠脊髓全细胞膜片钳实验 脊髓切片比较每个神经元群体中吗啡的抑制情况。目标2将试图克服 鞘内联合注射TRPM3激动剂硫酸孕烯醇酮对TRPM3的MOR抑制作用 应用吗啡，观察阿片类药物引起的瘙痒是否能在维持镇痛的同时减轻。这些 结果提示，TRPM3是去极化的主要离子通道，负责去抑制 瘙痒，并可作为减轻阿片类药物患者吗啡引起的瘙痒的潜在靶点 在不影响所需止痛的情况下进行治疗。