Laboratory of Neurobiology, Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
Glia. 2020 Sep;68(9):1810-1823. doi: 10.1002/glia.23806. Epub 2020 Feb 20.
Neurodegeneration is associated with inflammation and mismanaged iron homeostasis, leading to increased concentration of non-transferrin-bound iron (NTBI) in the brain. NTBI can be taken up by cells expressing Zrt-, Irt-like protein-14 (ZIP14), which is regulated by iron overload and pro-inflammatory cytokines, for example, interleukin-1β (IL-1β) and IL-6. Here, we focus on the astrocytic involvement and regulation of ZIP14 in an experimental model of chronic neurodegeneration with inflammation and iron overload. Rats were unilaterally injected with ibotenic acid in striatum resulting in excitotoxicity-induced neuronal loss in substantia nigra pars reticulata (SNpr). ZIP14 expression was measured in SNpr using immunohistochemistry, western blotting, and RT-qPCR. Cultures of primary astrocytes were examined for Zip14 mRNA expression after stimulation with ferric ammonium citrate (FAC), IL-6, or IL-1β. To study the involvement of ZIP14 in astrocytic iron uptake, uptake of Fe was investigated after treatment with IL-1β and siRNA-mediated ZIP14 knockdown. In the lesioned SNpr, reactive astrocytes, but not microglia, revealed increased ZIP14 expression with a main confinement to cell bodies and cellular processes. In astrocyte cultures, FAC and IL-1β stimulation increased Zip14 expression and IL-1β stimulation increased uptake of Fe. Increased Fe uptake was also observed after siRNA-mediated ZIP14 knockdown suggesting that lowering of ZIP14 impaired the balance between astrocytic uptake and export of iron. We conclude that astrocytes increase ZIP14 expression in response to inflammation and iron exposure and that ZIP14 seems pertinent for iron uptake in astrocytes and plays a role for a balanced astrocytic iron homeostasis.
神经退行性变与炎症和铁代谢失调有关，导致大脑中未结合转铁蛋白的铁（NTBI）浓度增加。能够表达 Zrt-、Irt-样蛋白 14（ZIP14）的细胞可以摄取 NTBI，而 ZIP14 受到铁过载和促炎细胞因子（如白细胞介素-1β（IL-1β）和 IL-6）的调节。在这里，我们专注于星形胶质细胞在炎症和铁过载引起的慢性神经退行性变的实验模型中的作用和 ZIP14 的调节。大鼠单侧纹状体注射鹅膏蕈氨酸导致黑质网状部（SNpr）中兴奋性毒性诱导的神经元丧失。使用免疫组织化学、western blot 和 RT-qPCR 测量 SNpr 中的 ZIP14 表达。用三氯化铁铵（FAC）、IL-6 或 IL-1β 刺激原代星形胶质细胞后，检查 Zip14 mRNA 表达。为了研究 ZIP14 在星形胶质细胞铁摄取中的作用，在经过 IL-1β 处理和 siRNA 介导的 ZIP14 敲低后，研究了 Fe 的摄取。在损伤的 SNpr 中，反应性星形胶质细胞（而不是小胶质细胞）显示出 ZIP14 表达增加，主要局限于细胞体和细胞突起。在星形胶质细胞培养物中，FAC 和 IL-1β 刺激增加了 Zip14 表达，IL-1β 刺激增加了 Fe 的摄取。siRNA 介导的 ZIP14 敲低后也观察到 Fe 摄取增加，表明 ZIP14 降低会损害星形胶质细胞摄取和铁输出之间的平衡。我们得出结论，星形胶质细胞在炎症和铁暴露下增加 ZIP14 表达，并且 ZIP14 似乎与星形胶质细胞中铁摄取有关，并在平衡星形胶质细胞铁稳态中发挥作用。
