Regulation of Iron Metabolism Unit, Division of Genetics and Cell Biology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ospedale San Raffaele, Milan, Italy; Vita-Salute San Raffaele University, Milan, Italy.
Regulation of Iron Metabolism Unit, Division of Genetics and Cell Biology, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS) Ospedale San Raffaele, Milan, Italy.
Kidney Int. 2023 Jul;104(1):61-73. doi: 10.1016/j.kint.2023.03.012. Epub 2023 Mar 27.
Anemia is a common complication of systemic inflammation. Proinflammatory cytokines both decrease erythroblast sensitivity to erythropoietin (EPO) and increase the levels of the hepatic hormone hepcidin, sequestering iron in stores and causing functional iron deficiency. Anemia of chronic kidney disease (CKD) is a peculiar form of anemia of inflammation, characterized by impaired EPO production paralleling progressive kidney damage. Traditional therapy based on increased EPO (often in combination with iron) may have off-target effects due to EPO interaction with its non-erythroid receptors. Transferrin Receptor 2 (Tfr2) is a mediator of the iron-erythropoiesis crosstalk. Its deletion in the liver hampers hepcidin production, increasing iron absorption, whereas its deletion in the hematopoietic compartment increases erythroid EPO sensitivity and red blood cell production. Here, we show that selective hematopoietic Tfr2 deletion ameliorates anemia in mice with sterile inflammation in the presence of normal kidney function, promoting EPO responsiveness and erythropoiesis without increasing serum EPO levels. In mice with CKD, characterized by absolute rather than functional iron deficiency, Tfr2 hematopoietic deletion had a similar effect on erythropoiesis but anemia improvement was transient because of limited iron availability. Also, increasing iron levels by downregulating only hepatic Tfr2 had a minor effect on anemia. However, simultaneous deletion of hematopoietic and hepatic Tfr2, stimulating erythropoiesis and increased iron supply, was sufficient to ameliorate anemia for the entire protocol. Thus, our results suggest that combined targeting of hematopoietic and hepatic Tfr2 may be a therapeutic option to balance erythropoiesis stimulation and iron increase, without affecting EPO levels.
贫血是全身炎症的常见并发症。促炎细胞因子既能降低红系祖细胞对促红细胞生成素(EPO)的敏感性,又能增加肝脏激素铁调素的水平,从而将铁储存在体内并导致功能性缺铁。慢性肾脏病(CKD)贫血是一种特殊形式的炎症性贫血,其特征是随着肾功能的进行性损害,EPO 的产生受损。基于增加 EPO(通常与铁联合使用)的传统治疗可能会由于 EPO 与其非红细胞受体的相互作用而产生脱靶效应。转铁蛋白受体 2(Tfr2)是铁-红细胞生成相互作用的介质。其在肝脏中的缺失会阻碍铁调素的产生,增加铁的吸收,而其在造血细胞中的缺失会增加红细胞对 EPO 的敏感性和红细胞的生成。在这里,我们表明,选择性造血 Tfr2 缺失可改善无菌性炎症小鼠的贫血,而肾功能正常,促进 EPO 反应性和红细胞生成,而不增加血清 EPO 水平。在以绝对而非功能性缺铁为特征的 CKD 小鼠中,Tfr2 造血缺失对红细胞生成有类似的影响,但由于铁的可用性有限,贫血的改善是短暂的。此外,通过下调仅肝脏 Tfr2 来增加铁水平对贫血的影响较小。然而,同时缺失造血和肝脏 Tfr2,刺激红细胞生成和增加铁供应,足以改善整个方案的贫血。因此,我们的结果表明,联合靶向造血和肝脏 Tfr2 可能是一种治疗选择,以平衡红细胞生成刺激和铁增加,而不影响 EPO 水平。
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