Amoyal Ilana, Prus Eugenia, Fibach Eitan
Department of Hematology, Hadassah-Hebrew University Medical Center, Jerusalem, Israel.
Exp Biol Med (Maywood). 2007 May;232(5):654-61.
Increased fetal hemoglobin (HbF) in erythroid precursors of patients with beta-hemoglobinopathies (sickle cell anemia and beta-thalassemia), in which adult hemoglobin synthesis is defective, ameliorates the clinical symptoms of the underlying diseases. The production of erythroid precursors depends on the action of erythropoietin (EPO), which prevents their apoptosis and stimulates their proliferation. EPO binds to its surface receptor, induces its homodimerization, and initiates a cascade of phosphorylation and dephosphorylation of a series of proteins by kinases and phosphatases, respectively. Vanadate inhibits various phosphatases, including those that are involved in the EPO pathway, thereby intensifying the signal. In this study, we investigated the effect of vanadate on the proliferation and maturation of human erythroid precursors in culture. When vanadate was added to cells derived from normal donors, cell maturation was delayed, as indicated by cell morphology, cell growth kinetics, the rate of appearance of hemoglobin-containing cells, and the expression of surface antigens (CD117, CD71, and glycophorin A). Analysis by high-performance liquid chromatography and flow cytometry of the hemoglobin profile of vanadate-treated normal cells revealed a higher proportion of HbF than was found in untreated cells. When vanadate was added to cells derived from patients with beta-thalassemia, a significant increase in HbF was observed. The results suggest that intensification of the EPO signal by vanadate results in maturation arrest and increased HbF production. Thus, inhibitors that are more specific and less toxic than vanadate may present a novel option for elevating HbF in patients with beta-hemoglobinopathies, as well as for intensifying the EPO response in other forms of anemia.
在成人血红蛋白合成存在缺陷的β-血红蛋白病（镰状细胞贫血和β-地中海贫血）患者的红系前体细胞中，胎儿血红蛋白（HbF）增加可改善潜在疾病的临床症状。红系前体细胞的产生取决于促红细胞生成素（EPO）的作用，EPO可防止其凋亡并刺激其增殖。EPO与其表面受体结合，诱导其同源二聚化，并分别通过激酶和磷酸酶引发一系列蛋白质的磷酸化和去磷酸化级联反应。钒酸盐可抑制各种磷酸酶，包括那些参与EPO信号通路的磷酸酶，从而增强信号。在本研究中，我们调查了钒酸盐对培养的人红系前体细胞增殖和成熟的影响。当向来自正常供体的细胞中添加钒酸盐时，细胞成熟被延迟，这通过细胞形态、细胞生长动力学、含血红蛋白细胞的出现率以及表面抗原（CD117、CD71和血型糖蛋白A）的表达得以体现。通过高效液相色谱法和流式细胞术对钒酸盐处理的正常细胞的血红蛋白谱进行分析，结果显示HbF的比例高于未处理细胞。当向来自β-地中海贫血患者的细胞中添加钒酸盐时，观察到HbF显著增加。结果表明，钒酸盐增强EPO信号会导致成熟停滞并增加HbF的产生。因此，比钒酸盐更具特异性且毒性更小的抑制剂可能为提高β-血红蛋白病患者的HbF水平以及增强其他形式贫血中的EPO反应提供一种新的选择。
