Piccialli Ilaria, Ciccone Roselia, Secondo Agnese, Boscia Francesca, Tedeschi Valentina, de Rosa Valeria, Cepparulo Pasquale, Annunziato Lucio, Pannaccione Anna
Division of Pharmacology, Department of Neuroscience, Reproductive and Dentistry Sciences, School of Medicine, Federico II University of Naples, Naples, Italy.
IRCSS SDN, Naples, Italy.
Front Pharmacol. 2021 Dec 8;12:775271. doi: 10.3389/fphar.2021.775271. eCollection 2021.
The remodelling of neuronal ionic homeostasis by altered channels and transporters is a critical feature of the Alzheimer's disease (AD) pathogenesis. Different reports converge on the concept that the Na/Ca exchanger (NCX), as one of the main regulators of Na and Ca concentrations and signalling, could exert a neuroprotective role in AD. The activity of NCX has been found to be increased in AD brains, where it seemed to correlate with an increased neuronal survival. Moreover, the enhancement of the NCX3 currents (I) in primary neurons treated with the neurotoxic amyloid 1-42 (Aβ) oligomers prevented the endoplasmic reticulum (ER) stress and neuronal death. The present study has been designed to investigate any possible modulation of the I, the functional interaction between NCX and the Na1.6 channel, and their impact on the Ca homeostasis in a transgenic model of AD, the primary hippocampal neurons from the Tg2576 mouse, which overproduce the Aβ peptide. Electrophysiological studies, carried in the presence of siRNA and the isoform-selective NCX inhibitor KB-R7943, showed that the activity of a specific NCX isoform, NCX3, was upregulated in its reverse, Ca influx mode of operation in the Tg2576 neurons. The enhanced NCX activity contributed, in turn, to increase the ER Ca content, without affecting the cytosolic Ca concentrations of the Tg2576 neurons. Interestingly, our experiments have also uncovered a functional coupling between NCX3 and the voltage-gated Na1.6 channels. In particular, the increased Na1.6 currents appeared to be responsible for the upregulation of the reverse mode of NCX3, since both TTX and the antibiotic anisomycin, by reducing the Na1.6 currents, counteracted the increase of the I in the Tg2576 neurons. In agreement, our immunofluorescence analyses revealed that the NCX3/Na1.6 co-expression was increased in the Tg2576 hippocampal neurons in comparison with the WT neurons. Collectively, these findings indicate that NCX3 might intervene in the Ca remodelling occurring in the Tg2576 primary neurons thus emerging as a molecular target with a neuroprotective potential, and provide a new outcome of the Na1.6 upregulation related to the modulation of the intracellular Ca concentrations in AD neurons.
通道和转运体改变所引起的神经元离子稳态重塑是阿尔茨海默病（AD）发病机制的一个关键特征。不同的报道都聚焦于这样一个概念，即钠钙交换体（NCX）作为钠和钙浓度及信号的主要调节因子之一，可能在AD中发挥神经保护作用。已发现AD大脑中NCX的活性增加，这似乎与神经元存活率增加相关。此外，在用神经毒性淀粉样蛋白1-42（Aβ）寡聚体处理的原代神经元中，NCX3电流（I）的增强可预防内质网（ER）应激和神经元死亡。本研究旨在调查AD转基因模型（Tg2576小鼠的原代海马神经元，其过量产生Aβ肽）中I的任何可能调节、NCX与Na1.6通道之间的功能相互作用及其对钙稳态的影响。在存在小干扰RNA（siRNA）和亚型选择性NCX抑制剂KB-R7943的情况下进行的电生理研究表明，特定的NCX亚型NCX3在Tg2576神经元中以其反向的钙内流操作模式上调。增强的NCX活性反过来有助于增加内质网钙含量，而不影响Tg2576神经元的胞质钙浓度。有趣的是，我们的实验还揭示了NCX3与电压门控Na1.6通道之间的功能偶联。特别是，Na1.6电流增加似乎是NCX3反向模式上调的原因，因为河豚毒素（TTX）和抗生素茴香霉素通过降低Na1.6电流，抵消了Tg2576神经元中I的增加。与此一致，我们的免疫荧光分析显示，与野生型（WT）神经元相比，Tg2576海马神经元中NCX3/Na1.6共表达增加。总的来说，这些发现表明NCX3可能干预Tg2576原代神经元中发生的钙重塑，从而成为具有神经保护潜力的分子靶点，并提供了与AD神经元细胞内钙浓度调节相关的Na1.6上调的新结果。
