Departamento de Fisiología, Pontificia Universidad Católica de Chile, Santiago 6513677, Chile.
J Neurosci. 2011 Mar 30;31(13):4962-77. doi: 10.1523/JNEUROSCI.6417-10.2011.
The mechanisms involved in Alzheimer's disease are not completely understood and how glial cells contribute to this neurodegenerative disease remains to be elucidated. Because inflammatory treatments and products released from activated microglia increase glial hemichannel activity, we investigated whether amyloid-β peptide (Aβ) could regulate these channels in glial cells and affect neuronal viability. Microglia, astrocytes, or neuronal cultures as well as acute hippocampal slices made from GFAP-eGFP transgenic mice were treated with the active fragment of Aβ. Hemichannel activity was monitored by single-channel recordings and by time-lapse ethidium uptake, whereas neuronal death was assessed by Fluoro-Jade C staining. We report that low concentrations of Aβ(25-35) increased hemichannel activity in all three cell types and microglia initiate these effects triggered by Aβ. Finally, neuronal damage occurs by activation of neuronal hemichannels induced by ATP and glutamate released from Aβ(25-35)-activated glia. These responses were observed in the presence of external calcium and were differently inhibited by hemichannel blockers, whereas the Aβ(25-35)-induced neuronal damage was importantly reduced in acute slices made from Cx43 knock-out mice. Thus, Aβ leads to a cascade of hemichannel activation in which microglia promote the release of glutamate and ATP through glial (microglia and astrocytes) hemichannels that induces neuronal death by triggering hemichannels in neurons. Consequently, this work opens novel avenues for alternative treatments that target glial cells and neurons to maintain neuronal survival in the presence of Aβ.
阿尔茨海默病的发病机制尚不完全清楚，胶质细胞如何促进这种神经退行性疾病的发生仍有待阐明。由于炎症治疗和小胶质细胞激活释放的产物增加了小胶质细胞半通道的活性，我们研究了淀粉样β肽（Aβ）是否可以调节胶质细胞中的这些通道，并影响神经元的活力。用 Aβ的活性片段处理小胶质细胞、星形胶质细胞或神经元培养物以及来自 GFAP-eGFP 转基因小鼠的急性海马切片。通过单通道记录和荧光素摄取的延时拍摄来监测半通道活性，而通过氟罗-杰德 C 染色来评估神经元死亡。我们报告说，低浓度的 Aβ（25-35）增加了所有三种细胞类型的半通道活性，并且小胶质细胞启动了由 Aβ触发的这些效应。最后，通过由 Aβ（25-35）激活的胶质细胞释放的 ATP 和谷氨酸激活神经元半通道，导致神经元损伤。这些反应在存在外部钙的情况下观察到，并且被半通道阻滞剂以不同的方式抑制，而 Aβ（25-35）诱导的神经元损伤在来自 Cx43 敲除小鼠的急性切片中显著减少。因此，Aβ导致半通道激活级联反应，其中小胶质细胞通过胶质细胞（小胶质细胞和星形胶质细胞）半通道促进谷氨酸和 ATP 的释放，通过触发神经元中的半通道导致神经元死亡。因此，这项工作为靶向胶质细胞和神经元的替代治疗开辟了新途径，以在存在 Aβ的情况下维持神经元的存活。
