Sato T, Selleri C, Young N S, Maciejewski J P
Hematology Branch, National Heart, Lung and Blood Institute, Bethesda, MD 20892-1652, USA.
Blood. 1995 Nov 1;86(9):3373-80.
Biologic responses to cytokines are mediated by intracellular pathways involving induction of signaling and metabolic cascades. Interferon (IFN) regulatory factor-1 (IRF-1) is a major transcription factor induced not only by IFN-gamma but also by other cytokines including tumor necrosis factor-alpha (TNF-alpha). Possible IRF-1 binding sequence elements have been located in the promoter regions of several genes, including p53, inducible nitric oxide synthase, and cyclin D1. IFN-gamma and TNF-alpha can inhibit hematopoiesis in vitro and have been implicated in the pathophysiology of bone marrow (BM) failure. We investigated whether the inhibitory effects of these cytokines were intracellularly mediated through the expression of IRF-1 or -2 in target cells. In total BM cells, IRF-1 mRNA expression increased after stimulation with IFN-gamma and TNF-alpha; the stronger effect was observed with IFN-gamma. In contrast, IRF-2 mRNA expression was constitutive and not altered by cytokine stimulation. By gene amplification, low levels of IRF-1 mRNA were present in unstimulated, highly purified CD34+ cells; on exposure to IFN-gamma and TNF-alpha, amplified IRF-1 mRNA showed a much stronger signal than control. When CD34+ cells were treated with IFN-gamma and TNF-alpha, IRF-1 antisense oligodeoxynucleotide (ODN) partially reversed the suppressive effects on CD34+ cell-derived colony formation by IFN-gamma but not those by TNF-alpha. In parallel experiments, IRF-1 antisense ODN decreased both IRF-1 protein and mRNA expression. The effects of ODN were sequence-specific and concentration-dependent. These results suggest that the inhibitory hematopoietic effects of IFN-gamma and TNF-alpha are mediated by different pathways. For IFN-gamma, IRF-1 is involved in the activation of cellular genes responsible for IFN-gamma suppressive effects.
细胞因子的生物学反应是由涉及信号传导和代谢级联反应诱导的细胞内途径介导的。干扰素（IFN）调节因子-1（IRF-1）是一种主要的转录因子，不仅由IFN-γ诱导，还可由包括肿瘤坏死因子-α（TNF-α）在内的其他细胞因子诱导。可能的IRF-1结合序列元件已定位在几个基因的启动子区域，包括p53、诱导型一氧化氮合酶和细胞周期蛋白D1。IFN-γ和TNF-α可在体外抑制造血，并与骨髓（BM）衰竭的病理生理学有关。我们研究了这些细胞因子的抑制作用是否通过靶细胞中IRF-1或-2的表达在细胞内介导。在全骨髓细胞中，用IFN-γ和TNF-α刺激后，IRF-1 mRNA表达增加；IFN-γ的作用更强。相反，IRF-2 mRNA表达是组成性的，不受细胞因子刺激的影响。通过基因扩增，未刺激的、高度纯化的CD34+细胞中存在低水平的IRF-1 mRNA；暴露于IFN-γ和TNF-α后，扩增的IRF-1 mRNA显示出比对照更强的信号。当CD34+细胞用IFN-γ和TNF-α处理时，IRF-1反义寡脱氧核苷酸（ODN）部分逆转了IFN-γ对CD34+细胞衍生集落形成的抑制作用，但不能逆转TNF-α的抑制作用。在平行实验中，IRF-1反义ODN降低了IRF-1蛋白和mRNA表达。ODN的作用具有序列特异性和浓度依赖性。这些结果表明，IFN-γ和TNF-α的造血抑制作用是由不同途径介导的。对于IFN-γ，IRF-1参与负责IFN-γ抑制作用的细胞基因的激活。
