Effects Of Hydroxyurea On Fetal Hemoglobin Synthesis Bet

羟基脲（HU）已被证明可以增加大多数镰状细胞患者胎儿血红蛋白（Hb F）的比例。低剂量HU方案通过优先增加b-球蛋白的生物合成来增加一些地中海贫血中间患者的总血红蛋白（Hb）水平。我们研究了剂量、暴露时间和HU给药的发育阶段对各种血液学参数和信号通路的影响。将两相液体培养的红系细胞脉冲暴露于5 ~ 100 mM的HU中3天或连续暴露12天。低剂量的HU（从0到25 mM）使Hb水平增加了2.7倍，高剂量的HU （100 mM）在II期的第3-6天增加了Hb水平。在II期培养后期（>=9-12天），虽然Hb F水平有明显的剂量依赖性增加，但Hb水平没有明显变化。II期培养0-3天暴露于HU，在5 mM HU下，红系菌落数量最多可增加5倍。GATA-1 mRNA在高剂量HU下下调，GATA-2 mRNA在较低剂量范围内呈剂量依赖性上调。通过cDNA芯片分析发现，100 mM HU显著上调死亡受体DR-5、caspase 3和其他与细胞周期控制和凋亡相关的基因。相比之下，10 mM HU适度上调早期生长反应基因（egr-1）的mRNA水平。我们的研究结果表明，HU对Hb F的产生和红细胞生成具有浓度依赖性，这两种作用是由不同的分子机制介导的。我们目前的重点是通过对Egr-1信号通路的研究，进一步阐明低剂量HU对红细胞生成的作用机制。

Hydroxyurea (HU) has been shown to increase the proportion of fetal hemoglobin (Hb F) in most sickle cell patients. A low dosage regimen of HU increased total hemoglobin (Hb) levels in some thalassemia intermedia patients by preferentially increasing b-globin biosynthesis. We examined the effect of dosage, duration of exposure, and developmental stage at which HU was given on various hematological parameters and signaling pathways. Erythroid cells in two-phase liquid culture were exposed to HU (5 to 100 mM) either as a pulse for 3 days or continuously for 12 days. Low doses of HU (from 0 to 25 mM) increased Hb levels by up to 2.7-fold, and a high dose of HU (100 mM) increased Hb levels when added at days 3-6 of phase II. No significant changes in Hb levels were observed in response to HU during the late stage of phase II culture (>=9-12 days), although there was a significant dose-dependent increase in Hb F levels. HU exposure during days 0-3 of phase II culture increased the number of erythroid colonies to a maximum of 5-fold at 5 mM HU. GATA-1 mRNA was down-regulated at a high dose of HU and GATA-2 was dose-dependently up-regulated over a lower dosage range. Treatment with 100 mM HU dramatically upregulated the death receptor DR-5, caspase 3, and various other genes related to cell cycle control and apoptosis, as determined by cDNA microarray analysis. In contrast, 10 mM HU modestly up-regulated mRNA levels of the early growth response gene (egr-1). Our results suggest that HU exerts concentration-dependent effects on Hb F production and erythropoiesis and that these two effects are mediated by distinct molecular mechanisms. We are currently focusing further clarifying the mechanism of low dose HU on erythropoiesis by studying the Egr-1 signal pathways.