Wnek S M, Medeiros M K, Eblin K E, Gandolfi A J
Department of Pharmacology and Toxicology, University of Arizona, 1703 E. Mabel St., Tucson, AZ 85721, USA.
Toxicol Appl Pharmacol. 2009 Dec 1;241(2):202-9. doi: 10.1016/j.taap.2009.08.016. Epub 2009 Aug 20.
Malignant transformation was demonstrated in UROtsa cells following 52-weeks of exposure to 50 nM monomethylarsonous acid (MMA(III)); the result was the malignantly transformed cell line, URO-MSC. URO-MSC cells were used to study the induction of DNA damage and the alteration of DNA repair enzymes in both the presence of MMA(III) [URO-MSC(+)] and after subsequent removal of MMA(III) [URO-MSC(-)] following chronic, low-level exposure. In the presence of MMA(III), URO-MSC(+) cells demonstrated a sustained increase in DNA damage following 12-weeks of exposure; in particular, a significant increase in DNA single-strand breaks at 12-weeks of exposure consistently elevated through 52 weeks. The persistence of DNA damage in URO-MSC cells was assessed after a 2-week removal of MMA(III). URO-MSC(-) cells demonstrated a decrease in DNA damage compared to URO-MSC(+); however, DNA damage in URO-MSC(-) remained significantly elevated when compared to untreated UROtsa and increased in a time-dependent manner. Reactive oxygen species (ROS) were demonstrated to be a critical component in the generation of DNA damage determined through the incubation of ROS scavengers with URO-MSC cells. Poly (ADP-ribose) polymerase (PARP) is a key repair enzyme in DNA single-strand break repair. URO-MSC(+) resulted in a slight increase in PARP activity after 36-weeks of MMA(III) exposure, suggesting the presence of MMA(III) is inhibiting the increase in PARP activity. In support, PARP activity in URO-MSC(-) increased significantly, coinciding with a subsequent decrease in DNA damage demonstrated in URO-MSC(-) compared to URO-MSC(+). These data demonstrate that chronic, low-level exposure of UROtsa cells to 50 nM MMA(III) results in: the induction of DNA damage that remains elevated upon removal of MMA(III); increased levels of ROS that play a role in MMA(III) induced-DNA damage; and decreased PARP activity in the presence of MMA(III).
在将UROtsa细胞暴露于50 nM一甲基胂酸（MMA(III)）52周后，证实发生了恶性转化；结果产生了恶性转化细胞系URO-MSC。URO-MSC细胞用于研究在长期低水平暴露后，在存在MMA(III) [URO-MSC(+)] 以及随后去除MMA(III) [URO-MSC(-)] 的情况下DNA损伤的诱导和DNA修复酶的改变。在存在MMA(III) 的情况下，URO-MSC(+) 细胞在暴露12周后DNA损伤持续增加；特别是，在暴露12周时DNA单链断裂显著增加，并一直持续升高至52周。在去除MMA(III) 2周后评估URO-MSC细胞中DNA损伤的持续性。与URO-MSC(+) 相比，URO-MSC(-) 细胞的DNA损伤有所减少；然而，与未处理的UROtsa相比，URO-MSC(-) 中的DNA损伤仍显著升高，并呈时间依赖性增加。通过将ROS清除剂与URO-MSC细胞孵育，证实活性氧（ROS）是DNA损伤产生的关键成分。聚（ADP-核糖）聚合酶（PARP）是DNA单链断裂修复中的关键修复酶。在暴露于MMA(III) 36周后，URO-MSC(+) 导致PARP活性略有增加，表明MMA(III) 的存在抑制了PARP活性的增加。作为佐证，URO-MSC(-) 中的PARP活性显著增加，这与URO-MSC(-) 中与URO-MSC(+) 相比随后DNA损伤的减少相一致。这些数据表明，UROtsa细胞长期低水平暴露于50 nM MMA(III) 会导致：去除MMA(III) 后DNA损伤的诱导仍会升高；在MMA(III) 诱导的DNA损伤中起作用的ROS水平增加；以及在存在MMA(III) 的情况下PARP活性降低。
