Shibata Noriyuki, Kataoka Ikuko, Okamura Yukinori, Murakami Kumiko, Kato Yoichiro, Yamamoto Tomoko, Masui Kenta
Department of Neurology and Internal Medicine, Sayama Shojukai Hospital, Sayama, Japan.
Faculty of Medicine, Tokyo Women's Medical University, Tokyo, Japan.
Neuropathology. 2025 Jun;45(3):177-201. doi: 10.1111/neup.13033. Epub 2025 Mar 10.
Oxidative stress in sporadic amyotrophic lateral sclerosis (ALS) has been evidenced by accumulation of oxidatively modified products of nucleic acids, lipids, sugars, and proteins in the motor neuron system of brains and spinal cords obtained at autopsy from the patients. We recently demonstrated soluble iron accumulation in activated microglia of sporadic ALS spinal cords. This finding could indicate that iron-mediated Fenton reaction is most likely to be responsible for oxidative stress associated with this disease. The excitatory amino acid neurotoxicity hypothesis for sporadic ALS has been proposed based on increased glutamate and aspartate concentrations in cerebrospinal fluid from the patients. Initially, the increase in extracellular excitatory amino acid levels was considered to reflect excessive release from the axon terminal of upper motor neurons. However, it is a question of whether the damaged upper motor neurons continue releasing glutamate even in advanced stage of this disease. To address this issue, we hypothesized that glial cells might be a glutamate release source. Our immunohistochemical analysis on autopsied human spinal cords revealed that ferritin, hepcidin, ferroportin, aconitase 1, tumor necrosis factor-α (TNF-α), TNF-α-converting enzyme (TACE), and glutaminase-C (GAC) were expressed mainly in microglia and that cystine/glutamate antiporter (xCT) was expressed mainly in astrocytes. We next performed cell culture experiments. Cultured microglia treated with soluble iron over-released glutamate and TNF-α via aconitase 1 and TACE, respectively. Cultured microglia treated with TNF-α over-released glutamate via GAC. Cultured microglia treated with hepcidin, of which expression is known to be upregulated by TNF-α, showed downregulated expression of ferroportin. Cultured astrocytes treated with hydrogen peroxide over-released glutamate via xCT. These observations provide in vivo and in vitro evidence that microglia and astrocytes are glutamate suppliers in response to soluble iron overload and oxidative stress, respectively, in sporadic ALS.
散发性肌萎缩侧索硬化症（ALS）中的氧化应激已通过对死于ALS的患者进行尸检，发现其脑和脊髓运动神经元系统中核酸、脂质、糖和蛋白质的氧化修饰产物积累得以证实。我们最近证明散发性ALS脊髓中活化的小胶质细胞存在可溶性铁积累。这一发现表明铁介导的芬顿反应很可能是该疾病相关氧化应激的原因。散发性ALS的兴奋性氨基酸神经毒性假说基于患者脑脊液中谷氨酸和天冬氨酸浓度升高而提出。最初，细胞外兴奋性氨基酸水平的升高被认为反映了上运动神经元轴突末端的过度释放。然而，受损的上运动神经元在该疾病晚期是否仍继续释放谷氨酸仍是个问题。为解决这个问题，我们推测神经胶质细胞可能是谷氨酸的释放源。我们对尸检后的人类脊髓进行的免疫组织化学分析显示，铁蛋白、铁调素、铁转运蛋白、顺乌头酸酶1、肿瘤坏死因子-α（TNF-α）、TNF-α转换酶（TACE）和谷氨酰胺酶-C（GAC）主要在小胶质细胞中表达，而胱氨酸/谷氨酸反向转运体（xCT）主要在星形胶质细胞中表达。接下来我们进行了细胞培养实验。用可溶性铁处理的培养小胶质细胞分别通过顺乌头酸酶1和TACE过度释放谷氨酸和TNF-α。用TNF-α处理的培养小胶质细胞通过GAC过度释放谷氨酸。用铁调素处理的培养小胶质细胞（已知其表达受TNF-α上调）显示铁转运蛋白表达下调。用过氧化氢处理的培养星形胶质细胞通过xCT过度释放谷氨酸。这些观察结果提供了体内和体外证据，表明在散发性ALS中，小胶质细胞和星形胶质细胞分别是对可溶性铁过载和氧化应激作出反应的谷氨酸供应者。
