Danelon Víctor, Montroull Laura E, Unsain Nicolás, Barker Philip A, Mascó Daniel H
Laboratorio de Neurobiología, Instituto de Investigaciones Biológicas y Tecnológicas, IIByT-CONICET-FCEFyN, Universidad Nacional de Córdoba, Av. Vélez Sarsfield 1611, Córdoba, Argentina.
Departments of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, 3801 University Street, Montreal, Quebec H3A 2B4, Canada.
Mol Cell Neurosci. 2016 Sep;75:81-92. doi: 10.1016/j.mcn.2016.07.002. Epub 2016 Jul 20.
Recent findings indicate that the mechanisms that drive reshaping of the nervous system are aberrantly activated in epilepsy and several neurodegenerative diseases. The recurrent seizures in epilepsy, particularly in the condition called status epilepticus, can cause permanent neurological damage, resulting in cognitive dysfunction and other serious neurological conditions. In this study, we used an in vitro model of status epilepticus to examine the role of calpain in the degeneration of hippocampal neurons. We grew neurons on a culture system that allowed studying the dendritic and axonal domains separately from the cell bodies. We found that a recently characterized calpain substrate, the neurotrophin receptor TrkB, is cleaved in the dendritic and axonal domain of neurons committed to die, and this constitutes an early step in the neuronal degeneration process. While the full-length TrkB (TrkB-FL) levels decreased, the truncated form of TrkB (Tc TrkB-FL) concurrently increased, leading to a TrkB-FL/Tc TrkB-FL imbalance, which is thought to be causally linked to neurodegeneration. We further show that the treatment with N-acetyl-Leu-Leu-norleucinal, a specific calpain activity blocker, fully protects the neuronal processes from degeneration, prevents the TrkB-FL/Tc TrkB-FL imbalance, and provides full neuroprotection. Moreover, the use of the TrkB antagonist ANA 12 at the time when the levels of TrkB-FL were significantly decreased, totally blocked neuronal death, suggesting that Tc TrkB-FL may have a role in neuronal death. These results indicate that the imbalance of these neurotrophins receptors plays a key role in neurite degeneration induced by seizures.
最近的研究结果表明，驱动神经系统重塑的机制在癫痫和几种神经退行性疾病中被异常激活。癫痫中的反复发作，尤其是在癫痫持续状态这种情况下，可导致永久性神经损伤，进而导致认知功能障碍和其他严重的神经疾病。在本研究中，我们使用癫痫持续状态的体外模型来研究钙蛋白酶在海马神经元退化中的作用。我们在一种培养系统上培养神经元，该系统允许分别从细胞体研究树突和轴突区域。我们发现，一种最近被鉴定的钙蛋白酶底物——神经营养因子受体TrkB，在注定死亡的神经元的树突和轴突区域被切割，这构成了神经元退化过程的早期步骤。虽然全长TrkB（TrkB-FL）水平下降，但TrkB的截短形式（Tc TrkB-FL）同时增加，导致TrkB-FL/Tc TrkB-FL失衡，这被认为与神经退行性变有因果关系。我们进一步表明，用特异性钙蛋白酶活性阻断剂N-乙酰-Leu-Leu-正亮氨酸处理，可完全保护神经元突起免于退化，防止TrkB-FL/Tc TrkB-FL失衡，并提供完全的神经保护作用。此外，在TrkB-FL水平显著下降时使用TrkB拮抗剂ANA 12，可完全阻断神经元死亡，这表明Tc TrkB-FL可能在神经元死亡中起作用。这些结果表明，这些神经营养因子受体的失衡在癫痫发作诱导的神经突退化中起关键作用。
