Department of Clinical and Biological Sciences, University of Turin, 10126 Turin, Italy.
Department of Neuroscience Rita Levi Montalcini, Neuroscience Institute Cavalieri Ottolenghi, University of Turin, 10126 Turin, Italy.
Int J Mol Sci. 2024 Aug 23;25(17):9142. doi: 10.3390/ijms25179142.
Iron is a vital element involved in a plethora of metabolic activities. Mammalian systemic iron homeostasis is mainly modulated by hepcidin, the synthesis of which is regulated by a number of proteins, including the hemochromatosis-associated proteins Hfe and Transferrin Receptor 2 (TfR2). Macrophages play versatile functions in iron homeostasis by storing iron derived from the catabolism of erythrocytes and supplying iron required for erythropoiesis. The absence of Hfe in macrophages causes a mild iron deficiency in aged mice and leads to an overproduction of the iron exporter Ferroportin 1 (Fpn1). Conversely, gene silencing in macrophages does not influence systemic iron metabolism but decreases transcription of the macrophage Fpn1 in adult mice and modulates their immune response. This study investigated cellular and systemic iron metabolism in adult and aged male mice with macrophage-specific Hfe and TfR2 silencing (double knock-out, DKO). Serum iron parameters were significantly modified in aged animals, and significant differences were found in hepatic hepcidin transcription at both ages. Interestingly, splenic iron content was low in adult DKOs and splenic Fpn1 transcription was significantly increased in DKO animals at both ages, while the protein amount does not reflect the transcriptional trend. Additionally, DKO macrophages were isolated from mice bone marrow (BMDMs) and showed significant variations in the transcription of iron genes and protein amounts in targeted mice compared to controls. Specifically, Tranferrin Receptor 1 (TfR1) increased in DKO adult mice BMDMs, while the opposite is observed in the cells of aged DKO mice. transcript was significantly decreased in the BMDMs of adult DKO mice, while the protein was reduced at both ages. Lastly, a significant increase in Erythropoietin production was evidenced in aged DKO mice. Overall, our study reveals that Hfe and TfR2 in macrophages regulate hepatic Hepc production and affect iron homeostasis in the spleen and BMDMs, leading to an iron deficiency in aged animals that impairs their erythropoiesis.
铁是参与多种代谢活动的重要元素。哺乳动物的系统性铁稳态主要由铁调素调节，其合成受许多蛋白质的调节，包括血色病相关蛋白 Hfe 和转铁蛋白受体 2 (TfR2)。巨噬细胞通过储存来自红细胞分解的铁并提供造血所需的铁，在铁稳态中发挥多种功能。巨噬细胞中 Hfe 的缺失会导致老年小鼠出现轻度缺铁，并导致铁输出蛋白 Ferroportin 1 (Fpn1) 的过度产生。相反，巨噬细胞中的基因沉默不会影响系统性铁代谢，但会降低成年小鼠中巨噬细胞 Fpn1 的转录，并调节其免疫反应。本研究调查了巨噬细胞特异性 Hfe 和 TfR2 沉默（双敲除，DKO）的成年和老年雄性小鼠的细胞和系统性铁代谢。血清铁参数在老年动物中发生显著改变，并且在两个年龄段均发现肝内 hepcidin 转录存在显著差异。有趣的是，成年 DKO 动物的脾脏铁含量较低，两个年龄段的 DKO 动物的脾脏 Fpn1 转录均显著增加，而蛋白质含量并不反映转录趋势。此外，从骨髓中分离出 DKO 巨噬细胞（BMDMs），与对照组相比，目标小鼠的铁基因转录和蛋白含量发生了显著变化。具体而言，在成年 DKO 小鼠的 BMDMs 中，转铁蛋白受体 1 (TfR1) 增加，而在老年 DKO 小鼠的细胞中则相反。在成年 DKO 小鼠的 BMDMs 中，转录显著减少，而在两个年龄段蛋白均减少。最后，在老年 DKO 小鼠中证实了促红细胞生成素的产生显著增加。总体而言，我们的研究表明，巨噬细胞中的 Hfe 和 TfR2 调节肝脏 Hepc 的产生，并影响脾脏和 BMDMs 中的铁稳态，导致老年动物出现缺铁，从而损害其造血功能。
