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.

项目摘要 吗啡的脊柱给药，一种潜在的阿片类药物，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副作用 瘙痒，导致已经苦恼的患者瘙痒。第一行治疗是阿片类药物拮抗剂， 但这可能会与初始阿片类药物治疗竞争，并导致患者在不必要的疼痛之间进行选择 或瘙痒。两种感觉都是密切相关的，但是阿片类药物如何引起瘙痒和 镇痛仍然不清楚。 ？ Mor是一个 G蛋白偶联受体（GPCR）与抑制性GI肠系膜异三聚元素蛋白（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 发生的是Gβγ直接抑制瞬态受体电势曲霉素3（TRPM3）离子通道A 在神经元上表达的热敏感和伤害感受阳离子通道。最近，一种天然发生的剪接 鉴定出不与Gβγ结合的TRPM3的变体。有了这些知识，一条新颖的鼠标线是 生成的（TRPM3DEX17），其中所有TRPM3通道表达这同工型。利用TRPM3DEX17 小鼠线我们对吗啡诱导的瘙痒和镇痛进行了初步行为研究。 数据表明，鞘内注射时TRPM3DEX17小鼠的瘙痒症明显较小 吗啡与WT相比。在足底切口模型中，TRPM3DEX17小鼠的吗啡没有变化 静脉内注射热和机械伤害感受时，镇痛。吗啡发生镇痛 通过抑制兴奋性（VGLU2+）神经元，而瘙痒是通过抑制性（VGAT+）而发生的 脊髓中的神经元或抑制作用。有趣的是，TRPM3和MOR更常见 与疼痛激发性vglut2+神经元相比，在瘙痒抑制性VGAT+神经元上 行为发现。该提案的目标1将通过原位杂交探索，共同表达 trpm3和MOR中的VGLU2+和VGAT+神经元中的TRPM3DEX17小鼠脊髓中的TRPM3和MOR，并使用两个记者 带有GFP标记兴奋和抑制性神经元的小鼠线，以执行脊柱的全细胞斑块夹紧 脐带切片比较每个神经元种群中吗啡抑制。 AIM 2将尝试克服 通过将TRPM3激动剂硫酸盐抑制TrPM3抑制在智能小鼠中 使用吗啡，并观察是否可以在保持镇痛时减轻阿片类药物诱导的瘙痒。这些 结果可能表明TRPM3是负责抑制的主要去极化离子通道 瘙痒，可能是减轻接受OID患者的吗啡诱导瘙痒的潜在靶标 治疗而不会影响所需的镇痛。