Department of Anatomy, Inha University School of Medicine, Incheon, 22212, Korea.
Department of Biomedical Sciences, Inha University School of Medicine, Inchon, 22212, Korea.
Exp Mol Med. 2023 Nov;55(11):2402-2416. doi: 10.1038/s12276-023-01111-z. Epub 2023 Nov 1.
Dysregulation of brain iron levels causes functional disturbances and damages neurons. Hepcidin (a peptide hormone) plays a principal role in regulating intracellular iron levels by modulating ferroportin (FPN, the only known iron exporter) through triggering its internalization and lysosomal degradation. We observed a significant and rapid iron surge in the cortices of ischemic hemispheres at 3 h after cerebral ischemia (middle cerebral artery occlusion, MCAO) that was maintained until 4 d post-MCAO. We showed upregulation of hepcidin expression in the brain as early as 3 h post-MCAO, mainly in astrocytes, and significant hepcidin accumulation in serum from 6 h post-MCAO, and these inductions were maintained for 1 day and 7 days, respectively. High mobility group box 1 (HMGB1), a prototypic danger-associated molecular pattern, accumulates markedly after transient MCAO and plays critical roles in damage aggravation via its proinflammatory effects. Here, we demonstrated that treatment with recombinant HMGB1 stimulated astrocytes to induce hepcidin expression in a TLR4- and CXCR4-dependent manner. Furthermore, hepcidin-mediated intracellular iron accumulation in neurons was confirmed by an experiment using N-methyl-D-aspartate (NMDA)-conditioned medium-treated primary astrocytes and fresh primary cortical neurons treated with hepcidin-containing astrocyte-conditioned medium. Moreover, HMGB1-mediated local hepcidin upregulation and subsequent local iron surge were found to cause ferroptosis in the postischemic brain, which was suppressed by the functional blocking of HMGB1 using intranasally administered HMGB1 A box or anti-HMGB1 antibody. These findings show that HMGB1 serves as a ferroptosis inducer by upregulating hepcidin in astrocytes and thus aggravates acute damage in the postischemic brain.
脑铁水平失调会导致功能紊乱和神经元损伤。铁调素（一种肽激素）通过触发其内化和溶酶体降解来调节铁蛋白（FPN，已知唯一的铁输出蛋白），从而在调节细胞内铁水平方面发挥主要作用。我们观察到，脑缺血（大脑中动脉闭塞，MCAO）后 3 小时缺血半球皮质中的铁含量显著快速增加，直到 MCAO 后 4 天仍保持不变。我们发现，脑缺血后 3 小时铁调素表达上调，主要在星形胶质细胞中，MCAO 后 6 小时血清中显著积累铁调素，这些诱导分别持续 1 天和 7 天。高迁移率族蛋白 B1（HMGB1）是一种典型的危险相关分子模式，在短暂性 MCAO 后明显积累，并通过其促炎作用在损伤加重中发挥关键作用。在这里，我们证明了用重组 HMGB1 处理可刺激星形胶质细胞以 TLR4 和 CXCR4 依赖的方式诱导铁调素表达。此外，通过用 N-甲基-D-天冬氨酸（NMDA）条件培养基处理原代星形胶质细胞和用含有铁调素的星形胶质细胞条件培养基处理新鲜原代皮质神经元的实验证实了铁调素介导的神经元内铁积累。此外，发现 HMGB1 介导的局部铁调素上调和随后的局部铁激增导致缺血后脑中的铁死亡，这可以通过用鼻内给予 HMGB1 A 盒或抗 HMGB1 抗体对 HMGB1 进行功能阻断来抑制。这些发现表明，HMGB1 通过在星形胶质细胞中上调铁调素来充当铁死亡诱导剂，从而加重缺血后大脑的急性损伤。
