Neuroprotective and neuroregenerative effects of new TSPO ligands in the peripheral nervous system

TSPO已被认为是保护神经元和提高周围神经系统轴突再生速度的有效药理靶点。因此，TSPO的激动型配体为促进创伤后或周围神经病患者的周围神经再生提供了有前景的治疗前景。作为大型线粒体膜蛋白复合体的一部分，TSPO调节着许多线粒体的活动。它最典型的功能是胆固醇在线粒体内的运输，这是类固醇合成的限速步骤。然而，类固醇在介导TSPO配体再生效应中的确切作用仍有待确定。Grünenthal开发了新的有效的TSPO激动剂，可以改善感觉神经元和运动神经元的功能再生，并防止严重周围神经损伤后神经病理性疼痛的发展。这些特别有效的化合物实际上是双靶标配体，因为它们激活了KV7家族的TSPO和电压门控延迟整流钾通道。这些离子通道参与神经元兴奋性的调节，并在神经病理性疼痛的发生发展中发挥作用。这导致了一种假说，即TSPO和KV7通道的共同激活可能是相加的，甚至加强了单独机制的药理效应。我们的目标是通过实验验证这一双激活假说，并阐明类固醇在TSPO激活的神经保护和神经再生功效中的作用。为了达到这些目的，我们建立了颈椎神经和坐骨神经严重挤压伤大鼠模型。此外，我们将使用转基因、药理和生化工具。由于TSPO基因敲除大鼠的出现以及选择性TSPO和KV7配体的出现，可以研究TSPO和KV7通道激活在Grünenthal化合物治疗潜力中的各自贡献。TSPO刺激的类固醇合成的重要性将通过使用类固醇生成酶和类固醇受体的选择性和有效的抑制剂来研究。周围神经类固醇水平的变化将用气相色谱-串联质谱仪(GC-MS/MS)进行分析。该技术已成为分析小生物样品中类固醇的一种特异、灵敏和可靠的参考方法。因此，我们的GC-MS/MS平台将成为整个研究单位类固醇分析的集中设施。促进神经保护和神经再生对应着一个未得到满足的医疗需求。TSPO结合KV7通道激活可能构成一种新的治疗方法，用于周围神经病变和周围轴索病变，包括糖尿病和中毒性神经病变，这些疾病的特征都是再生能力降低。

TSPO has been identified as an effective pharmacological target for protecting neurons and for increasing the speed of axonal regrowth in the peripheral nervous system. Agonistic ligands of TSPO therefore offer promising therapeutic perspectives for promoting peripheral nerve regeneration after traumatic injury or in patients with peripheral neuropathies. As part of a large mitochondrial membrane protein complex TSPO regulates many mitochondrial activities. Its best characterized function is the intramitochondrial transport of cholesterol, a rate-limiting step in steroid synthesis. However, the precise role of steroids in mediating the regenerative effects of TSPO ligands remains to be determined.Grünenthal has developed new potent TSPO activators, which improve functional regeneration of both sensory neurons and motoneurons and prevent the development of neuropathic pain after severe peripheral nerve injury. These particularly efficient compounds are in fact dual-target ligands, as they activate both TSPO and voltage-gated delayed-rectifier potassium channels of the Kv7 family. These ion channels are involved in the regulation of neuronal excitability and play a role in the development of neuropathic pain. This has led to the hypothesis that the co-activation of both TSPO and Kv7 channels may be additive, or even reinforce the pharmacological effects of the individual mechanisms.Our objectives are to experimentally test this dual-activation hypothesis and to clarify the role of steroids in the neuroprotective and neuroregenerative efficacy of TSPO activation. To reach these aims we have set up experimental rat models of severe crush injury of cervical spine nerves and of the sciatic nerve. Moreover, we will use transgenic, pharmacological and biochemical tools. The respective contribution of TSPO and Kv7 channel activation in the curative potential of the Grünenthal compounds can be investigated due to the advent of TSPO knockout rats and the availability of selective TSPO and Kv7 ligands. The importance of TSPO-stimulated steroid synthesis will be studied by using selective and potent inhibitors of steroidogenic enzymes and steroid receptors. Changes in peripheral nerve steroid levels will be analyzed by gas chromatography-tandem mass spectrometry (GC-MS/MS). This technology has become a reference method for the specific, sensitive and robust analysis of steroids in small biological samples. Our GC-MS/MS platform will therefore become a centralized facility for steroid analysis for the whole research unit.Promoting neuroprotection and neuroregeneration corresponds to an unmet medial need. The delineation of TSPO in combination with Kv7 channel activation may constitute a novel therapeutic approach for peripheral nerve lesions and for peripheral axonopathies, including diabetic and toxic neuropathies, which all are characterized by a reduced regenerative capacity.