Gazitt Y, Reddy S V, Alcantara O, Yang J, Boldt D H
Division of Hematology, Department of Medicine, University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Drive, San Antonio, TX78229-3900, USA.
J Cell Physiol. 2001 Apr;187(1):124-35. doi: 10.1002/1097-4652(2001)9999:9999<::AID-JCP1061>3.0.CO;2-E.
To investigate the role of iron in hematopoiesis, we studied effects of iron deprivation on PMA-induced monocyte/macrophage differentiation in HL-60 cells. Iron deprivation induced by desferrioxamine (DF) blocked PMA-induced differentiation and induced S-phase arrest and apoptosis in up to 60% of cells. Apoptosis was not related to a decrease of bcl-2 or to c-myc overexpression. In the presence of DF, PMA-induced upregulation of the cyclin dependent kinase inhibitor (CDKI), p21(WAF1/CIP1), was blocked and its expression could be restored in the presence of DF by supplementation with ferric citrate. Furthermore, ferrioxamine (iron saturated DF) did not block induction of p21(WAF1/CIP1) indicating that the changes were not due to a nonspecific toxic effect of DF. Similarly, hydroxyurea, an inhibitor of ribonucleotide reductase, did not block p21 expression. p21(WAF1/CIP1) antisense oligonucleotides caused cell cycle alterations similar to DF and p21 overexpression overcame effects of iron deprivation on both cell cycling and differentiation. Therefore, p21 is a key target for the effects of iron deprivation on HL-60 cell cycling and differentiation. Nuclear run-on transcription assays and p21 mRNA half-life studies indicated that iron was required to support transcriptional activation of p21(WAF1/CIP1) after a PMA stimulus. By contrast, iron deprivation did not inhibit expression of a second CDKI, p27(KIP1). These data demonstrate a new role for iron during monocyte/macrophage differentiation. A key role of iron is to allow induction of p21(WAF1/CIP1) in response to a differentiation stimulus subsequently blocking cells at the G(1)/S cell cycle interface and preventing premature apoptosis. This effect of iron is independent of its requirement in supporting the activity of the enzyme, ribonucleotide reductase. Because of the central role of p21(WAF1/CIP1) as regulator of the G(1)/S cell cycle checkpoint this requirement for iron to support p21 expression represents an important mechanism by which iron may modulate hematopoietic cell growth and differentiation. Published 2001 Wiley-Liss, Inc.
为研究铁在造血过程中的作用，我们研究了铁缺乏对HL - 60细胞中佛波酯（PMA）诱导的单核细胞/巨噬细胞分化的影响。去铁胺（DF）诱导的铁缺乏阻断了PMA诱导的分化，并诱导高达60%的细胞进入S期停滞和凋亡。凋亡与bcl - 2的减少或c - myc的过表达无关。在DF存在的情况下，PMA诱导的细胞周期蛋白依赖性激酶抑制剂（CDKI）p21（WAF1/CIP1）的上调被阻断，并且通过补充柠檬酸铁，其表达在DF存在时可以恢复。此外，铁饱和的去铁胺（ferrioxamine）并不阻断p21（WAF1/CIP1）的诱导，表明这些变化不是由于DF的非特异性毒性作用。同样，核糖核苷酸还原酶抑制剂羟基脲也不阻断p21的表达。p21（WAF1/CIP1）反义寡核苷酸引起的细胞周期改变类似于DF，并且p21的过表达克服了铁缺乏对细胞周期和分化的影响。因此，p21是铁缺乏对HL - 60细胞周期和分化影响的关键靶点。细胞核连续转录分析和p21 mRNA半衰期研究表明，在PMA刺激后，需要铁来支持p21（WAF1/CIP1）的转录激活。相比之下，铁缺乏并不抑制第二种CDKI p27（KIP1）的表达。这些数据证明了铁在单核细胞/巨噬细胞分化过程中的新作用。铁的关键作用是允许在分化刺激下诱导p21（WAF1/CIP1），随后在G(1)/S细胞周期界面阻断细胞并防止过早凋亡。铁的这种作用独立于其对支持核糖核苷酸还原酶活性的需求。由于p21（WAF1/CIP1）作为G(1)/S细胞周期检查点调节因子的核心作用，铁对支持p21表达的这种需求代表了铁调节造血细胞生长和分化的重要机制。2001年由Wiley - Liss公司出版。
