A Novel Approach for Chronic Pain Treatment Using Resiniferatoxin

描述（由申请人提供）：瞬时受体电位香草素1（TRPV 1）的强效激动剂，具有独特的特性，可用于治疗慢性疼痛。TRPV 1是一种Ca 2+可渗透的非选择性阳离子通道，可被物理和化学刺激激活，并介导炎性热感觉。目前，通过评价不同的拮抗剂，该受体被认为是镇痛药的靶点。该提议将评估利用RTX的激动活性来抑制伤害性神经传递的方法。在这个建议中，使用脊髓切片制备，我们将测试的假设，在短期内，RTX的管理抑制突触传递激活突触前TRPV 1和引起去极化阻滞，从而减少伤害性传递。然后，使用行为研究，我们将测试的假设，在长期的，鞘内注射RTX减轻伤害性炎症疼痛和效果可能是由于消融TRPV 1表达神经末梢作为过度的Ca 2+内流的结果。鞘内给予RTX选择性地影响脊髓感觉神经元的TRPV 1表达神经末梢，而不影响背根神经节（DRG）神经元。由于表达TRPV 1的DRG神经元履行其他传出功能，因此炎性和神经/血管活性物质的释放可以由完整的DRG保存。初步/已发表的结果表明，RTX引起TRPV 1的缓慢和持续激活，导致神经末梢去极化和突触传递的抑制。此外，鞘内施用RTX促进在背角（DH）中的注射部位处的感觉神经元的TRPV 1表达中枢末梢的选择性和局部消融，并导致行为模型中的持续疼痛缓解。这些研究将加强我们对中枢TRPV 1在伤害性传递中的作用的理解。RTX对含有伤害性神经末梢的TRPV 1的选择性作用是一种可能的策略，可考虑用于治疗由于内脏和骨骼恶性肿瘤而引起的大面积和不可接近区域的慢性、衰弱性和终末疼痛病症。公共卫生相关性：难治性慢性疼痛是一个主要问题，特别是在绝症患者中。吗啡治疗是目前唯一可用的选择，它会引起严重的副作用，从镇静到呼吸抑制，导致过早死亡。树脂毒素（RTX）是瞬时受体电位香草酸1（TRPV 1）的强效激动剂，具有独特的特性，可用于治疗慢性疼痛。鞘内注射RTX可有效地选择性激活TRPV 1，短期内引起中枢神经末梢的去极化阻滞，长期内在脊髓水平消融含有TRPV 1的感觉神经元的中枢神经末梢。由于RTX的作用对中枢神经末梢具有选择性，因此可以保留其他神经元功能。这些包括DRG神经元的外周传出功能，例如通过TRPV 1介导的炎症和神经/血管活性剂的释放来调节微血管循环。最后，使用RTX防止脊髓水平的伤害性传递将是一种有用的策略，用于治疗由大面积和难以接近的区域引起的慢性、衰弱性和顽固性疼痛，例如内脏和骨骼的恶性肿瘤。

Description (provided by applicant): A potent agonist of Transient Receptor Potential Vanilloid 1 (TRPV1), exhibits unique properties that can be utilized to treat chronic pain conditions. TRPV1, a Ca2+ permeable, nonselective cation channel, is activated by physical and chemical stimuli and mediates inflammatory thermal sensation. Presently, this receptor is being considered as a target for analgesics through the evaluation of different antagonists. This proposal will evaluate an approach utilizing agonistic activity of RTX to inhibit nociceptive neurotransmission. In this proposal, using spinal cord slice preparation, we will test the hypothesis that in the short-term, administration of RTX inhibits synaptic transmission by activating presynaptic TRPV1 and causing a depolarization block, thus reducing nociceptive transmission. Then, using behavioral studies, we will test the hypothesis that in the long-term, intrathecal administration of RTX alleviates nociceptive inflammatory pain and the effect is likely to be due to ablation of TRPV1 expressing nerve terminals as a result of the excessive Ca2+ influx. The intrathecal administration of RTX selectively affects TRPV1 expressing nerve terminals of the sensory neurons at the spinal cord without affecting the dorsal root ganglion (DRG) neurons. Since TRPV1 expressing DRG neurons fulfill other efferent functions, the release of inflammatory and neuro/vasoactive substances can be preserved by the intact DRG. Preliminary/published results indicate that RTX causes a slow and sustained activation of TRPV1 leading to nerve terminal depolarization and depression of synaptic transmission. Further, intrathecal administration of RTX promotes a selective and localized ablation of TRPV1 expressing central terminals of sensory neurons at the injection site in the dorsal horn (DH), and leads to sustained pain relief in behavioral models. These studies will enhance our understanding of the role of central TRPV1 in nociceptive transmission. The selective action of RTX on TRPV1 containing nociceptive nerve terminals is a possible strategy to consider for treating chronic, debilitating and terminal pain conditions arising from large and inaccessible areas, due to malignancies of internal organs and bone. PUBLIC HEALTH RELEVANCE: Refractory chronic pain is a major problem especially in terminally ill patients. Treatment with morphine is currently the only available option, which causes significant side effects, ranging from sedation to respiratory depression leading to premature death. Resiniferatoxin (RTX), a potent agonist of Transient Receptor Potential Vanilloid 1 (TRPV1) exhibits unique properties that can be utilized to treat chronic pain conditions. Intrathecal administration of RTX potently and selectively activates TRPV1 causing a depolarization block of the central nerve terminals in the short-term, and ablating TRPV1 containing central nerve terminals of the sensory neuron in the long-term at the level of the spinal cord. Since RTX action is selective to the central nerve terminals, other neuronal functions can be preserved. These include the peripheral efferent functions of DRG neurons, such as the regulation of microvascular circulation by TRPV1-mediated release of inflammatory and neuro/vasoactive agents. Finally, preventing nociceptive transmission at the level of the spinal cord using RTX will be a useful strategy in chronic, debilitating and intractable pain arising from large and inaccessible areas, such as malignancies of internal organs and bone.