Somji Seema, Zhou Xu Dong, Garrett Scott H, Sens Mary Ann, Sens Donald A
Department of Pathology, School of Medicine and Health Sciences, University of North Dakota, Grand Forks, North Dakota 58202, USA.
Toxicol Sci. 2006 Dec;94(2):293-301. doi: 10.1093/toxsci/kfl108. Epub 2006 Sep 15.
This laboratory has shown that both Cd(+2) and As(+3) can malignantly transform human urothelial cells. The present study examined metal resistance and the mechanism of cell death when the parental and malignantly transformed UROtsa cells were exposed to Cd(+2) and As(+3). It was shown that the malignantly transformed UROtsa cells were more resistant to the toxic effects of both metals. The assessment of the mode of cell death demonstrated that the parental UROtsa cells died by both apoptosis and necrosis when exposed to either metal. It was shown that apoptosis was the more prominent mechanism of cell death, accounting for over 50% of cell death. Apoptotic cell death was determined by the observation of fragmented nuclei using 4',6-diamidino-2-phenylindole staining, the formation of a DNA ladder, and the detection of cleaved caspase-3 and caspase-9 products in the cell lysates. Necrotic cell death was determined by measuring the release of lactate dehydrogenase into the growth medium. It was determined that the extent of apoptosis of the malignantly transformed UROtsa cells was decreased and that the extent of necrosis was increased compared to the parental UROtsa cells. These observations are consistent with in vivo studies which suggest that As(+3) can act as a tumor promoter during the regeneration of the bladder urothelium. The present in vitro studies suggest that As(+3)-induced cytotoxicity could set the stage for tissue repair due to its own inherent toxicity to normal urothelium, and then subsequently act as a tumor promoter during the regeneration process through the stimulation of the regrowth of cells that have gained increased resistance to As(+3).
本实验室已表明，Cd(+2) 和 As(+3) 均可使人类尿道上皮细胞发生恶性转化。本研究检测了亲本及恶性转化的UROtsa细胞暴露于Cd(+2) 和 As(+3) 时的金属抗性及细胞死亡机制。结果表明，恶性转化的UROtsa细胞对这两种金属的毒性作用更具抗性。对细胞死亡方式的评估表明，亲本UROtsa细胞在暴露于任何一种金属时均通过凋亡和坏死两种方式死亡。结果表明，凋亡是更主要的细胞死亡机制，占细胞死亡的50% 以上。通过使用4',6-二脒基-2-苯基吲哚染色观察细胞核碎片化、DNA梯形条带的形成以及检测细胞裂解物中裂解的caspase-3和caspase-9产物来确定凋亡性细胞死亡。通过测量乳酸脱氢酶释放到生长培养基中的量来确定坏死性细胞死亡。已确定，与亲本UROtsa细胞相比，恶性转化的UROtsa细胞的凋亡程度降低，坏死程度增加。这些观察结果与体内研究一致，体内研究表明As(+3) 在膀胱尿道上皮再生过程中可作为肿瘤促进剂。目前这项体外研究表明，As(+3) 诱导的细胞毒性因其对正常尿道上皮的固有毒性可为组织修复奠定基础，随后在再生过程中通过刺激已获得对As(+3) 抗性增强的细胞再生长而作为肿瘤促进剂发挥作用。
