Regulation of Iron Metabolism Unit, Division of Genetics and Cell Biology, Ospedale San Raffaele, Milan, Italy.
Vita Salute San Raffaele University, Milan, Italy.
Am J Hematol. 2022 Oct;97(10):1324-1336. doi: 10.1002/ajh.26673. Epub 2022 Aug 10.
β-thalassemia is a genetic disorder caused by mutations in the β-globin gene, and characterized by anemia, ineffective erythropoiesis and iron overload. Patients affected by the most severe transfusion-dependent form of the disease (TDT) require lifelong blood transfusions and iron chelation therapy, a symptomatic treatment associated with several complications. Other therapeutic opportunities are available, but none is fully effective and/or applicable to all patients, calling for the identification of novel strategies. Transferrin receptor 2 (TFR2) balances red blood cells production according to iron availability, being an activator of the iron-regulatory hormone hepcidin in the liver and a modulator of erythropoietin signaling in erythroid cells. Selective Tfr2 deletion in the BM improves anemia and iron-overload in non-TDT mice, both as a monotherapy and, even more strikingly, in combination with iron-restricting approaches. However, whether Tfr2 targeting might represent a therapeutic option for TDT has never been investigated so far. Here, we prove that BM Tfr2 deletion improves anemia, erythrocytes morphology and ineffective erythropoiesis in the Hbb murine model of TDT. This effect is associated with a decrease in the expression of α-globin, which partially corrects the unbalance with β-globin chains and limits the precipitation of misfolded hemoglobin, and with a decrease in the activation of unfolded protein response. Remarkably, BM Tfr2 deletion is also sufficient to avoid long-term blood transfusions required for survival of Hbb animals, preventing mortality due to chronic anemia and reducing transfusion-associated complications, such as progressive iron-loading. Altogether, TFR2 targeting might represent a promising therapeutic option also for TDT.
β-地中海贫血是一种由β-珠蛋白基因突变引起的遗传性疾病,其特征为贫血、无效红细胞生成和铁过载。患有最严重的输血依赖性疾病(TDT)的患者需要终生输血和铁螯合治疗,这种对症治疗与多种并发症相关。还有其他治疗机会,但没有一种是完全有效的和/或适用于所有患者,因此需要寻找新的策略。转铁蛋白受体 2(TFR2)根据铁的可用性来平衡红细胞的生成,它是肝脏中铁调节激素铁调素的激活剂,也是红系细胞中促红细胞生成素信号的调节剂。在 BM 中选择性地敲除 Tfr2 可改善非 TDT 小鼠的贫血和铁过载,无论是作为单一疗法,甚至更显著的是,与限制铁摄入的方法联合使用。然而,迄今为止,尚未研究过靶向 Tfr2 是否可能成为 TDT 的治疗选择。在这里,我们证明了 BM 中 Tfr2 的缺失可改善 TDT 的 Hbb 小鼠模型中的贫血、红细胞形态和无效红细胞生成。这种作用与α-珠蛋白表达的减少有关,它部分纠正了与β-珠蛋白链的不平衡,并限制了错误折叠的血红蛋白的沉淀,同时还降低了未折叠蛋白反应的激活。值得注意的是,BM 中 Tfr2 的缺失也足以避免 Hbb 动物生存所需的长期输血,从而防止因慢性贫血导致的死亡,并减少输血相关的并发症,如逐渐增加的铁负荷。总之,靶向 TFR2 可能也是 TDT 的一种有前途的治疗选择。