NO-cGMP-PKG信号通路介导BKCa改善前庭内侧核缺氧损伤的机制及丹参酮IIA作用研究

The medial vestibular nucleus (MVN) plays an important role in the pathogenesis of vertigo, which is very sensitive to hypoxia. Our previous studies indicated that Hypoxia induced abnormal firing and decreased the activity of BKCa in MVN, which was allievated by pre-treatment with a selective agonist. Tanshinone IIA, an active component of Traditional Chinese Medicine, can effectively improve the symptoms of vestibular vertigo, and up-regulate the expression of BKCa in hypoxic MVN. Studies had reported that NO could activate BKCa through the cGMP-PKG signaling pathway, but the underlying mechanism in hypoxic MVN remained unclear. Therefore, we hypothesize that “Tanshinone IIA activates BKCa through NO-cGMP-PKG signaling pathway in MVN, thus inhibiting anoxic-induced neuronal abnormal discharge and exerting neuroprotective effect on hypoxic injury”. In this study, we conduct hypoxia animal model and primary MVN cells as the research object, meanwhile set up BKCa agonists and antagonists as controls. The techniques of patch clamp, FLIPR and molecular biology are used to investigate the neuroprotective mechanism of BKCa and its upstream key sites and the intervention effect of tanshinone IIA in hypoxic MVN. This study will elucidate the biological mechanism and target of tanshinone IIA in the treatment of vertigo, and provide important scientific basis for Traditional Chinese Medicine with promoting blood circulation and removing blood stasis in prevention and treatment of vertigo.

前庭内侧核（MVN）是研究眩晕的重要核团，对缺氧极敏感。课题组前期发现：缺氧能诱发MVN神经兴奋性异常，激活BKCa对缺氧MVN起着神经保护作用。活血化瘀中药丹参的活性成分丹参酮IIA能有效改善前庭性眩晕症状，上调缺氧MVN中BKCa表达。研究报道，NO能通过cGMP-PKG信号通路激活BKCa，但在缺氧MVN中的确切作用机制尚不清楚。由此，我们提出“丹参酮IIA通过MVN中NO-cGMP-PKG信号通路激活BKCa，从而抑制缺氧诱发的神经异常放电活动，对缺氧损伤发挥神经保护作用”的假说。本项目以动物模型、原代MVN细胞为研究对象，并设BKCa激动剂及拮抗剂对照，采用膜片钳、FLIPR、分子生物学等技术，探讨BKCa及其上游关键位点对缺氧MVN的神经保护作用机制，以及丹参酮IIA对其干预作用。该研究将阐释丹参酮IIA治疗眩晕的生物学机制及作用靶点，为活血化瘀中药防治眩晕提供重要的科学依据。

前庭内侧核（MVN）是研究前庭系统疾病的重要核团，对缺氧极敏感并可诱发眩晕，课题组前期研究发现：激活BKCa对缺氧MVN起着神经保护作用。活血化瘀中药丹参的活性成分丹参酮IIA已在我们临床应用治疗眩晕疗效良好，其作用机理与BKCa调控信号密切相关，上调缺氧MVN中BKCa表达。但丹参酮IIA是否通过直接作用于MVN而发挥防治缺氧损伤的作用尚无报道。研究报道，NO能通过cGMP-PKG信号通路激活BKCa，但在缺氧MVN中是否通过MVN中NO-cGMP-PKG信号通路激活BKCa对缺氧损伤发挥神经保护作用尚不清楚。由此，本项目以缺氧动物模型、原代MVN细胞为研究对象，从药理效应、机制研究评价两方面探讨BKCa及其上游关键位点对缺氧MVN的神经保护作用机制，以及丹参酮IIA对其干预作用。.课题组研究发现，丹参酮IIA可以改善缺氧诱发的大鼠的运动平衡能力、MVN神经形态和功能损伤、细胞活性及细胞凋亡，尤其是丹参酮IIA高剂量组，提示丹参酮IIA对MVN缺氧损伤神经元的细胞修复的积极作用。经丹参酮IIA治疗后能不同程度地增加缺氧所致的MVN中NO-cGMP-PKG和BKCa的减少，并呈一定的量效关系。丹参酮IIA可以有效调控NO-cGMP-PKG-BKCa信号通路从而改善缺氧MVN神经损伤，以及发挥抗凋亡、抗氧化作用，对缺氧诱导的MVN神经损伤具有保护作用，提示丹参酮IIA有可能成为治疗缺氧所致神经疾病的潜在药物。.该研究从现代分子和神经电生理角度深入发掘丹参酮 IIA 的生物学作用机制，将进一步丰富丹参酮IIA的作用机理和改善MVN缺氧损伤的部分机制，为用于临床活血化瘀中药改善缺氧神经损伤作用提供理论与临床实践依据，从而指导临床开发出以特定条件下的作用于前庭系统的高选择性药物，更加有效地促进缺氧修复，进而为临床开发新的抗组织器官缺氧药物提供新的途径，能产生良好的社会和经济效应。