Nascimento Merielen G, Suzuki Shugo, Wei Min, Tiwari Ashish, Arnold Lora L, Lu Xiufen, Le X Chris, Cohen Samuel M
Department of Pathology and Microbiology and the Eppley Institute for Cancer Research, University of Nebraska Medical Center, Omaha, NE 68198-3135, USA.
Toxicology. 2008 Jul 10;249(1):69-74. doi: 10.1016/j.tox.2008.04.007. Epub 2008 Apr 22.
Based on epidemiological data, chronic exposure to high levels of inorganic arsenic in the drinking water is carcinogenic to the urinary bladder of humans. The highly reactive trivalent organic arsenicals dimethylarsinous acid (DMA(III)) and monomethylarsonous acid (MMA(III)) are formed during the metabolism of inorganic arsenic in vivo in addition to the corresponding mono-, di- and trimethylated pentavalent arsenicals. The objective of this study was to determine if combining arsenicals was additive or synergistic toward inducing cytotoxicity in a rat urothelial cell line. The MYP3 cell line, an immortalized but not transformed rat urinary bladder epithelial cell line, was seeded into appropriate culture wells. Treatment with the arsenicals was begun 24 h after seeding and continued for 3 days. Combinations of arsenicals used were DMA(III) with arsenite, dimethylarsinic acid (DMA(V)) or trimethylarsine oxide (TMAO). Combinations of concentrations used were the LC50, one-quarter or one-half the LC50 of one arsenical with one-half or one-quarter the LC50 of the other arsenical. To determine if MYP3 cells metabolize arsenicals, cells were treated with arsenate, arsenite and MMA(V) as described above and the medium was analyzed by HPLC-ICPMS to determine species and quantity of arsenicals present. When cells were treated with one-quarter or one-half the LC50 concentration of both arsenicals, the cytotoxicity was approximately the same as when cells were treated with half the LC50 concentration or the LC50 concentration, respectively, of either arsenical. Treatment with one-quarter the LC50 concentration of one arsenical plus the LC50 concentration of a second arsenical had similar cytotoxicity as treatment with the LC50 concentration of either of the arsenicals. Quantitation and speciation of arsenicals in the cell culture medium showed that MYP3 cells have some reductase activity but the cells do not methylate arsenicals. The effect on the cytotoxicity of arsenicals in combination was additive rather than synergistic toward a rat urothelial cell line.
基于流行病学数据，长期饮用含有高浓度无机砷的水会导致人类膀胱癌。除了相应的一甲基、二甲基和三甲基五价砷化合物外，无机砷在体内代谢过程中还会形成高反应性的三价有机砷化合物——二甲基亚砷酸（DMA(III)）和一甲基亚砷酸（MMA(III)）。本研究的目的是确定砷化合物组合对大鼠尿道上皮细胞系诱导细胞毒性的作用是相加还是协同。将永生化但未转化的大鼠膀胱上皮细胞系MYP3接种到合适的培养孔中。接种24小时后开始用砷化合物处理，并持续3天。所用的砷化合物组合为DMA(III)与亚砷酸盐、二甲基砷酸（DMA(V)）或三甲基氧化砷（TMAO）。所用的浓度组合为一种砷化合物的半数致死浓度（LC50）、其四分之一或二分之一与另一种砷化合物的二分之一或四分之一LC50。为了确定MYP3细胞是否代谢砷化合物，按照上述方法用砷酸盐、亚砷酸盐和MMA(V)处理细胞，并通过高效液相色谱-电感耦合等离子体质谱法（HPLC-ICPMS）分析培养基，以确定砷化合物的种类和数量。当用两种砷化合物的四分之一或二分之一LC50浓度处理细胞时，细胞毒性分别与用其中一种砷化合物的二分之一LC50浓度或LC50浓度处理时大致相同。用一种砷化合物的四分之一LC50浓度加另一种砷化合物的LC50浓度处理，其细胞毒性与用其中任何一种砷化合物的LC50浓度处理相似。细胞培养基中砷化合物的定量和形态分析表明，MYP3细胞具有一定的还原酶活性，但细胞不会使砷化合物甲基化。砷化合物组合对大鼠尿道上皮细胞系的细胞毒性作用是相加的，而非协同的。
