Hydroxyurea exerts bi-modal dose-dependent effects on erythropoiesis in human cultured erythroid cells via distinct pathways.
Hydroxyurea (HU) has been shown to increase the proportion of fetal haemoglobin (HbF) in most sickle cell patients. A low-dosage regimen increased total haemoglobin (Hb) levels in some thalassaemia intermedia patients by preferentially increasing beta-globin biosynthesis. To further characterize these apparent dose-dependent effects of HU, we examined erythroid cells exposed to HU (5-100 micro mol/l) in two-phase liquid culture. Low doses (from 5 to 25 micro mol/l) increased Hb levels by up to 2.7-fold, and a high dose (100 micro mol/l) increased Hb levels when added at d 3-6 of phase II, with no significant changes in response to HU during the late stage of phase II culture (> or = 9 d). HU exposure during d 0-3 of phase II culture increased the number of erythroid colonies to a maximum of fivefold at 5 micro mol/l HU. GATA-1 mRNA was downregulated at a high dose and GATA-2 was dose dependently upregulated over a lower dosage range. Treatment with 100 micro mol/l HU dramatically upregulated the death receptor DR-5, caspase 3, as determined by cDNA microarray analysis. In contrast, 10 micro mol/l HU modestly upregulated mRNA levels of the early growth response gene. Our results suggest that HU exerts concentration-dependent effects on HbF production and erythropoiesis and that these two effects are mediated by distinct molecular mechanisms.
Wang
Min
M
The Molecular and Clinical Hematology Branch, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
Tang
Delia C
DC
Liu
Wenli
W
Chin
Kyung
K
Zhu
Jianqion G
JG
Fibach
Eitan
E
Rodgers
Griffin P
GP
D000328:Adult; D018929:Cell Culture Techniques / Q000379:methods; D002454:Cell Differentiation / Q000187:drug effects; D002851:Chromatography, High Pressure Liquid; D003114:Colony-Forming Units Assay; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D015672:Erythroid Precursor Cells / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D050981:Erythroid-Specific DNA-Binding Factors; D004920:Erythropoiesis / Q000187:drug effects*; D050982:GATA1 Transcription Factor; D050989:GATA2 Transcription Factor; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation / Q000187:drug effects; D005914:Globins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006918:Hydroxyurea / Q000494:pharmacology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology*; D012333:RNA, Messenger / Q000235:genetics; D014157:Transcription Factors / Q000378:metabolism
D004268:DNA-Binding Proteins; D050981:Erythroid-Specific DNA-Binding Factors; D050982:GATA1 Transcription Factor; C494688:GATA1 protein, human; D050989:GATA2 Transcription Factor; C494711:GATA2 protein, human; D019384:Nucleic Acid Synthesis Inhibitors; D012333:RNA, Messenger; D014157:Transcription Factors; D005914:Globins; D006918:Hydroxyurea