Department de Farmacología y Terapéutica, ITH, Facultad de Medicina, Universidad Autónoma de Madrid, IRYCIS, Madrid, Spain.
Servicio de Neurobiología-Investigación, Hospital Universitario Ramón y Cajal, IRYCIS, Madrid, Spain.
Glia. 2022 Nov;70(11):2108-2130. doi: 10.1002/glia.24241. Epub 2022 Jul 8.
In ischemic stroke and post-traumatic brain injury (TBI), blood-brain barrier disruption leads to leaking plasma amino acids (AA) into cerebral parenchyma. Bleeding in hemorrhagic stroke and TBI also release plasma AA. Although excitotoxic AA were extensively studied, little is known about non-excitatory AA during hypoxic injury. Hypoxia-induced synaptic depression in hippocampal slices becomes irreversible with non-excitatory AA, alongside their intracellular accumulation and increased tissue electrical resistance. Four non-excitatory AA (l-alanine, glycine, l-glutamine, l-serine: AGQS) at plasmatic concentrations were applied to slices from mice expressing EGFP in pyramidal neurons or astrocytes during normoxia or hypoxia. Two-photon imaging, light transmittance (LT) changes, and electrophysiological field recordings followed by electron microscopy in hippocampal CA1 st. radiatum were used to monitor synaptic function concurrently with cellular swelling and injury. During normoxia, AGQS-induced increase in LT was due to astroglial but not neuronal swelling. LT raise during hypoxia and AGQS manifested astroglial and neuronal swelling accompanied by a permanent loss of synaptic transmission and irreversible dendritic beading, signifying acute damage. Neuronal injury was not triggered by spreading depolarization which did not occur in our experiments. Hypoxia without AGQS did not cause cell swelling, leaving dendrites intact. Inhibition of NMDA receptors prevented neuronal damage and irreversible loss of synaptic function. Deleterious effects of AGQS during hypoxia were prevented by alanine-serine-cysteine transporters (ASCT2) and volume-regulated anion channels (VRAC) blockers. Our findings suggest that astroglial swelling induced by accumulation of non-excitatory AA and release of excitotoxins through antiporters and VRAC may exacerbate the hypoxia-induced neuronal injury.
在缺血性中风和创伤性脑损伤（TBI）中，血脑屏障的破坏导致血浆氨基酸（AA）渗漏到脑实质中。出血性中风和 TBI 中的出血也会释放血浆 AA。尽管兴奋性 AA 受到了广泛的研究，但在缺氧损伤期间，关于非兴奋性 AA 知之甚少。缺氧诱导的海马切片突触抑制在非兴奋性 AA 存在的情况下变得不可逆转，同时伴随着它们的细胞内积累和组织电阻增加。在正常氧或缺氧条件下，将四种非兴奋性 AA（l-丙氨酸、甘氨酸、l-谷氨酰胺、l-丝氨酸：AGQS）应用于表达 EGFP 的神经元或星形胶质细胞的小鼠切片中。双光子成像、光透射（LT）变化以及海马 CA1 st 的电生理场记录和随后的电子显微镜检查。放射状用于同时监测突触功能、细胞肿胀和损伤。在正常氧条件下，AGQS 诱导的 LT 增加是由于星形胶质细胞而不是神经元肿胀。缺氧期间 LT 升高和 AGQS 表现为星形胶质细胞和神经元肿胀，伴随着突触传递的永久丧失和不可逆的树突珠化，表明急性损伤。神经元损伤不是由在我们的实验中没有发生的扩散去极化引发的。没有 AGQS 的缺氧不会引起细胞肿胀，使树突保持完整。NMDA 受体的抑制可防止神经元损伤和突触功能的不可逆丧失。AGQS 在缺氧期间的有害作用可以通过丙氨酸-丝氨酸-半胱氨酸转运体（ASCT2）和体积调节阴离子通道（VRAC）阻滞剂来预防。我们的研究结果表明，非兴奋性 AA 的积累引起的星形胶质细胞肿胀以及通过反向转运体和 VRAC 释放的兴奋性毒素可能会加剧缺氧引起的神经元损伤。
