Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030.
Center for Neuroscience and Pain Research, Department of Anesthesiology and Perioperative Medicine, University of Texas M. D. Anderson Cancer Center, Houston, Texas 77030
J Neurosci. 2020 May 6;40(19):3707-3719. doi: 10.1523/JNEUROSCI.0282-20.2020. Epub 2020 Apr 8.
Calcineurin inhibitors, such as tacrolimus (FK506) and cyclosporine, are widely used as standard immunosuppressants in organ transplantation recipients. However, these drugs can cause severe pain in patients, commonly referred to as calcineurin inhibitor-induced pain syndrome (CIPS). Although calcineurin inhibition increases NMDAR activity in the spinal cord, the underlying mechanism remains enigmatic. Using an animal model of CIPS, we found that systemic administration of FK506 in male and female mice significantly increased the amount of α2δ-1-GluN1 complexes in the spinal cord and the level of α2δ-1-bound GluN1 proteins in spinal synaptosomes. Treatment with FK506 significantly increased the frequency of mEPSCs and the amplitudes of monosynaptic EPSCs evoked from the dorsal root and puff NMDAR currents in spinal dorsal horn neurons. Inhibiting α2δ-1 with gabapentin or disrupting the α2δ-1-NMDAR interaction with α2δ-1Tat peptide completely reversed the effects of FK506. In α2δ-1 gene KO mice, treatment with FK506 failed to increase the frequency of NMDAR-mediated mEPSCs and the amplitudes of evoked EPSCs and puff NMDAR currents in spinal dorsal horn neurons. Furthermore, systemic administration of gabapentin or intrathecal injection of α2δ-1Tat peptide reversed thermal and mechanical hypersensitivity in FK506-treated mice. In addition, genetically deleting GluN1 in dorsal root ganglion neurons or α2δ-1 genetic KO similarly attenuated FK506-induced thermal and mechanical hypersensitivity. Together, our findings indicate that α2δ-1-bound NMDARs mediate calcineurin inhibitor-induced tonic activation of presynaptic and postsynaptic NMDARs at the spinal cord level and that presynaptic NMDARs play a prominent role in the development of CIPS. Calcineurin inhibitors are immunosuppressants used to prevent rejection of transplanted organs and tissues. However, these drugs can cause severe, unexplained pain. We showed that calcineurin inhibition enhances physical interaction between α2δ-1 and NMDARs and their synaptic trafficking in the spinal cord. α2δ-1 is essential for calcineurin inhibitor-induced aberrant activation of presynaptic and postsynaptic NMDARs in the spinal cord. Furthermore, inhibiting α2δ-1 or disrupting α2δ-1-NMDAR interaction reduces calcineurin inhibitor-induced pain hypersensitivity. Eliminating NMDARs in primary sensory neurons or α2δ-1 KO also attenuates calcineurin inhibitor-induced pain hypersensitivity. This new information extends our mechanistic understanding of the role of endogenous calcineurin in regulating synaptic plasticity and nociceptive transmission and suggests new strategies for treating this painful condition.
钙调神经磷酸酶抑制剂，如他克莫司（FK506）和环孢素，广泛用作器官移植受者的标准免疫抑制剂。然而，这些药物会导致患者出现严重疼痛，通常称为钙调神经磷酸酶抑制剂诱导的疼痛综合征（CIPS）。虽然钙调神经磷酸酶抑制可增加脊髓中 NMDAR 的活性，但潜在机制仍不清楚。在 CIPS 的动物模型中，我们发现，FK506 全身性给药可显著增加雄性和雌性小鼠脊髓中α2δ-1-GluN1 复合物的数量和脊髓突触小体中α2δ-1 结合的 GluN1 蛋白的水平。FK506 处理可显著增加背根和吹气 NMDAR 电流诱发的背角神经元中 mEPSC 的频率和单突触 EPSC 的幅度。用加巴喷丁抑制α2δ-1 或用α2δ-1Tat 肽破坏α2δ-1-NMDAR 相互作用可完全逆转 FK506 的作用。在α2δ-1 基因敲除小鼠中，FK506 处理未能增加脊髓背角神经元中 NMDAR 介导的 mEPSC 的频率和诱发 EPSC 的幅度以及吹气 NMDAR 电流。此外，全身性给予加巴喷丁或鞘内注射α2δ-1Tat 肽可逆转 FK506 处理小鼠的热和机械性痛敏。此外，在背根神经节神经元中敲除 GluN1 或α2δ-1 基因敲除同样减弱 FK506 诱导的热和机械性痛敏。总之，我们的研究结果表明，α2δ-1 结合的 NMDAR 介导钙调神经磷酸酶抑制剂在脊髓水平诱导突触前和突触后 NMDAR 的持续激活，并且突触前 NMDAR 在 CIPS 的发展中起重要作用。钙调神经磷酸酶抑制剂是用于预防移植器官和组织排斥的免疫抑制剂。然而，这些药物会导致严重的、无法解释的疼痛。我们表明，钙调神经磷酸酶抑制增强了α2δ-1 与 NMDAR 之间的物理相互作用及其在脊髓中的突触运输。α2δ-1 对于钙调神经磷酸酶抑制剂在脊髓中诱导的突触前和突触后 NMDAR 的异常激活是必需的。此外，抑制α2δ-1 或破坏α2δ-1-NMDAR 相互作用可减少钙调神经磷酸酶抑制剂诱导的痛觉过敏。在初级感觉神经元中消除 NMDAR 或α2δ-1 敲除也可减弱钙调神经磷酸酶抑制剂诱导的痛觉过敏。这些新信息扩展了我们对钙调神经磷酸酶在调节突触可塑性和伤害性传递中的内源性作用的机制理解，并为治疗这种疼痛状态提供了新的策略。
