Wang Chia-Yu, Core Amanda B, Canali Susanna, Zumbrennen-Bullough Kimberly B, Ozer Sinan, Umans Lieve, Zwijsen An, Babitt Jodie L
Program in Anemia Signaling Research, Division of Nephrology, and.
Program in Membrane Biology, Center for Systems Biology, Massachusetts General Hospital, Harvard Medical School, Boston, MA.
Blood. 2017 Jul 6;130(1):73-83. doi: 10.1182/blood-2016-12-759423. Epub 2017 Apr 24.
Anemia suppresses liver hepcidin expression to supply adequate iron for erythropoiesis. Erythroferrone mediates hepcidin suppression by anemia, but its mechanism of action remains uncertain. The bone morphogenetic protein (BMP)-SMAD signaling pathway has a central role in hepcidin transcriptional regulation. Here, we explored the contribution of individual receptor-activated SMADs in hepcidin regulation and their involvement in erythroferrone suppression of hepcidin. In Hep3B cells, or but not knockdown inhibited hepcidin () messenger RNA (mRNA) expression. Hepatocyte-specific double-knockout mice exhibited ∼90% transferrin saturation and massive liver iron overload, whereas mice or female mice with 1 functional or allele had modestly increased serum and liver iron, and single-knockout or mice had minimal to no iron loading, suggesting a gene dosage effect. mRNA was reduced in all Cre mouse livers at 12 days and in all Cre primary hepatocytes. However, only double-knockout mice continued to exhibit low liver at 8 weeks and failed to induce in response to Bmp6 in primary hepatocyte cultures. Epoetin alfa (EPO) robustly induced bone marrow erythroferrone () mRNA in control and mice but suppressed hepcidin only in control mice. Likewise, erythroferrone failed to decrease mRNA in primary hepatocytes and / knockdown Hep3B cells. EPO and erythroferrone reduced liver Smad1/5 phosphorylation in parallel with mRNA in control mice and Hep3B cells. Thus, and have overlapping functions to govern hepcidin transcription. Moreover, erythropoietin and erythroferrone target Smad1/5 signaling and require Smad1/5 to suppress hepcidin expression.
贫血会抑制肝脏铁调素的表达，以提供足够的铁用于红细胞生成。红细胞生成素介导贫血对铁调素的抑制作用，但其作用机制仍不明确。骨形态发生蛋白（BMP）-SMAD信号通路在铁调素转录调控中起核心作用。在此，我们探讨了单个受体激活的SMAD在铁调素调控中的作用及其在红细胞生成素对铁调素抑制中的参与情况。在Hep3B细胞中，敲低 或 而非 可抑制铁调素（ ）信使核糖核酸（mRNA）的表达。肝细胞特异性双敲除 小鼠表现出约90%的转铁蛋白饱和度和大量肝脏铁过载，而 小鼠或具有1个功能性 或 等位基因的雌性小鼠血清和肝脏铁含量适度增加，单敲除 或 小鼠的铁负荷最小或无铁负荷，提示存在基因剂量效应。在所有12天龄的Cre小鼠肝脏和所有Cre原代肝细胞中， mRNA均减少。然而，只有双敲除小鼠在8周龄时肝脏 仍持续处于低水平，并且在原代肝细胞培养中对Bmp6无反应而无法诱导 。促红细胞生成素α（EPO）在对照小鼠和 小鼠中均强烈诱导骨髓红细胞生成素（ ）mRNA，但仅在对照小鼠中抑制铁调素。同样，红细胞生成素在 原代肝细胞和 / 敲低的Hep3B细胞中未能降低 mRNA。EPO和红细胞生成素与对照小鼠和Hep3B细胞中的 mRNA平行降低肝脏Smad1/5磷酸化。因此， 和 在调控铁调素转录方面具有重叠功能。此外，促红细胞生成素和红细胞生成素靶向Smad1/5信号通路，并且需要Smad1/5来抑制铁调素表达。
