Gabbianelli Marco, Testa Ugo, Massa Adriana, Morsilli Ornella, Saulle Ernestina, Sposi Nadia Maria, Petrucci Eleonora, Mariani Gualtiero, Peschle Cesare
Department of Hematology and Oncology, Istituto Superiore di Sanità, Rome, Italy.
Blood. 2003 Apr 1;101(7):2826-32. doi: 10.1182/blood-2002-05-1477. Epub 2002 Nov 7.
Mechanisms underlying fetal hemoglobin (HbF) reactivation in stress erythropoiesis have not been fully elucidated. We suggested that a key role is played by kit ligand (KL). Because glucocorticoids (GCs) mediate stress erythropoiesis, we explored their capacity to potentiate the stimulatory effect of KL on HbF reactivation, as evaluated in unilineage erythropoietic culture of purified adult progenitors (erythroid burst-forming units [BFU-Es]). The GC derivative dexamethasone (Dex) was tested in minibulk cultures at graded dosages within the therapeutical range (10(-6) to 10(-9) M). Dex did not exert significant effects alone, but synergistically it potentiated the action of KL in a dose-dependent fashion. Specifically, Dex induced delayed erythroid maturation coupled with a 2-log increased number of generated erythroblasts and enhanced HbF synthesis up to 85% F cells and 55% gamma-globin content at terminal maturation (ie, in more than 80%-90% mature erythroblasts). Equivalent results were obtained in unicellular erythroid cultures of sibling BFU-Es treated with KL alone or combined with graded amounts of Dex. These results indicate that the stimulatory effect of KL + Dex is related to the modulation of gamma-globin expression rather than to recruitment of BFU-Es with elevated HbF synthetic potential. At the molecular level, Id2 expression is totally suppressed in control erythroid culture but is sustained in KL + Dex culture. Hypothetically, Id2 may mediate the expansion of early erythroid cells, which correlates with HbF reactivation. These studies indicate that GCs play an important role in HbF reactivation. Because Dex acts at dosages used in immunologic disease therapy, KL + Dex administration may be considered to develop preclinical models for beta-hemoglobinopathy treatment.
应激性红细胞生成过程中胎儿血红蛋白（HbF）重新激活的潜在机制尚未完全阐明。我们认为干细胞因子（KL）起着关键作用。由于糖皮质激素（GCs）介导应激性红细胞生成，我们研究了它们增强KL对HbF重新激活刺激作用的能力，这一作用在纯化的成人祖细胞（红细胞爆式集落形成单位[BFU-Es]）的单系红细胞生成培养中进行评估。在微型批量培养中测试了糖皮质激素衍生物地塞米松（Dex）在治疗范围内的分级剂量（10⁻⁶至10⁻⁹M）。Dex单独作用时未产生显著影响，但它以剂量依赖的方式协同增强了KL的作用。具体而言，Dex诱导红细胞成熟延迟，同时生成的成红细胞数量增加2个对数级，并在终末成熟时（即超过80%-90%的成熟成红细胞）将HbF合成增强至85%的F细胞和55%的γ-珠蛋白含量。在用KL单独处理或与分级量的Dex联合处理的同胞BFU-Es的单细胞红细胞培养中也获得了相同的结果。这些结果表明，KL + Dex的刺激作用与γ-珠蛋白表达的调节有关，而不是与募集具有高HbF合成潜力的BFU-Es有关。在分子水平上，Id2表达在对照红细胞培养中完全被抑制，但在KL + Dex培养中持续存在。据推测，Id2可能介导早期红细胞的扩增，这与HbF重新激活相关。这些研究表明，糖皮质激素在HbF重新激活中起重要作用。由于Dex在免疫疾病治疗中使用的剂量下起作用，给予KL + Dex可能被认为是开发β-血红蛋白病治疗临床前模型的一种方法。
