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中起到重要作用[17]。另一方面，细胞内pH 稳态在髓系造血中亦有很大作用，作为调节细胞 内pH 值的重要膜蛋白，NHE1 在造血细胞分化中贡献及其与C/EBPα 的相互关系受到越来 越多的关注[18]。根据我们的研究结果，低氧诱导K562 细胞分化过程中伴随C/EBPα 表达增 高，提示其为重要的下游效应因子；值得注意的是，pHi 值也发生改变，在24 小时增高，到 165 48 小时恢复至对照组，说明NHE1 可能在低氧诱导K562 细胞分化中起到一定作用。在加入 NHE1 特异性抑制剂Cariporide 抑制NHE1 表达及活性后，分化程度的进一步增强。据此看 似矛盾的结果，我们推测低氧环境下pHi 为代偿性的增高，抑制NHE1 表达及活性后，可能 通过某些信号通路促进低氧诱导的细胞分化。因此我们继而考察MAPK 信号通路在该过程 中的变化。MAPK 家族是细胞中广泛表达并介导重要调节信号的丝氨酸-苏氨酸激酶家族。 170 其活化后，磷酸化其下游底物一转录因子、蛋白激酶、结构蛋白等，以此调控细胞的生长、 增殖、分化、凋亡和黏附、迁移等过程，继而影响肿瘤的发生、 侵袭、转移以及耐药。结 果显示NHE1 抑制剂Cariporide 能够显著提高p38MAPK 及ERK5 磷酸化水平，而ERK1/2， JNK 磷酸化水平未见明显改变。因此我们推测MAPK 信号通路可能介导了NHE1 与C/EBPα 的相互作用，但相关具体机制仍未阐明，需进一步深入研究。 175 4 结论 本文给出了低氧微环境能够诱导K562 细胞向粒系分化，其中NHE1 可能通过MAPK 信号通路参与该分化过程。这一结果显示低氧诱导K562 白血病细胞分化的机制，以及NHE1 在该过程中的关键作用，进一步揭示低氧与NHE1 抑制剂联合应用治疗白血病的潜能。 180 [参考文献] (References) [1] ROSENBAUER F, TENEN DG. Transcription factors in myeloid development: balancing differentiation with transformation [J]. Nat Rev Immunol, 2007, 7(2): 105-117. [2] ZHANG J, SONG LP, HUANG Y, et al. Accumulation of hypoxia-inducible factor-1 alpha protein and its role in the differentiation of myeloid leukemic cells induced by all-trans retinoic acid [J]. Haematologica, 2008, 93(10): 185 1480-1487. [3] JIANG Y, XUE ZH. SHEN WZ, et a1. Desferrioxamine induces leukemic cell differentiation potentially by hypoxia-inducible factor-1 alpha that augments transcriptional activity of CCAAT ／ enhancer-binding protein-alpha [J]. Leukemia, 2005, 19(7): 1239-1247. [4] LIU W, GUO M, XU YB, et a1. Induction of tumor arrest and differentiation with prolonged survival by 190 intermittent hypoxia in a mouse model of acute myeloid leukemia [J]. Blood, 2006, 107(2): 698-907. [5] SONG LP, ZHANG J, WU SF, et al. Hypoxia-inducible factor-1a-induced differentiation of myeloid leukemic cells is its transcriptional activity independent [J]. Oncogene, 2008, 27(4): 519-527. [6] KEMP G, YOUNG H, FLIEGEL L. Structure and function of the human Na(+)/H(+) exchanger isoform 1 [J]. Channels (Austin), 2008, 2(5): 329-336. 195 [7] KOLIAKOS G, PALETAS K, KALOYIANNI M. NHE-1: a molecular target for signalling and cell matrix interactions [J]. Connect Tissue Res, 2008, 49(3): 157-161. [8] 芦颖, 李庆华, 马丽, 等. 细胞酸化对K562/A02 耐药细胞株中P-gp 糖蛋白的影响[J]. 中国实验血液学杂 志, 2009, 17(3): 568-573. [9] XIE H, YE M, FENG R, et al. Stepwise reprogramming of B cell into macrophages. Cell, 2004, l17(5): 200 663-676. [10] AKASHIK I. Myeloid lineage commitment from the hematopoietic stem cell [J]. Immunity, 2007, 26(6): 726-740. [11] ZHANG J, CHEN GQ. Hypoxia-HIF-1alpha-C/EBPalpha/Runx1 signaling in leukemic cell differentiation [J]. Pathophysiology, 2009, 16(4): 297-303. 205 [12] SAUNTHARARAJAH Y, BOCCUNI P, NUCIFORA G. Combinatorial action of RUNX1 and PU. 1 in the regulation of hematopoiesis [J]. Crit Rev Eukaryot, Gene Expr, 2006, 16(2): 183-192. [13] DING Y, HARADA Y, KIMURA A, et al. AML1/RUNX1 point mutation possibly promotes leukemic transformation in myeloproliferative neoplasms [J]. Blood, 2009, 114(25): 5201-5205. [14] RAMJI DP, FOKA P. CCAAT/enhancer-binding proteins: structure, function and regulation [J]. Biochem J, 210 2002, 365(3), 561-575. [15] DHAWAN P, WIEDER R, CHRISTAKOS S, et al. CCAAT enhancer-binding protein alpha is a molecular target of 1,25-dihydroxyvitamin D3 in MCF-7 breast cancer cells [J]. J Biol Chem, 2009, 284(5): 3086-3095. [16] SUH HC, GOOYA J, RENN K, et al. C/EBP alpha determines hematopoietic cell fate in multipotential progenitor cells by inhibiting erythroid differentiation and inducing myeloid differentiation [J]. Blood, 2006, 215 107(11): 4308-4316. [17] IIDA S, WATANABE-FUKUNNAGA R, NAGATA S, et al. Essential role of C/EBP alpha in G-CSF-induced transcriptional activation and chromatin modification of myeloid-specific genes [J]. Genes Cells, 2008, 13(4): 313-327. [18] FACANH AL, DOS-REIS MC, Montero-Lomeli M. Structural study of the porcine Na+/H+ exchanger NHE1 220 gene and its 5'-flanking region [J]. Mol Cell Biochem, 2000, 210(1-2): 91-99. 学术论文网Tag： |
