Division of Pharmacology and Toxicology, Defence Research and Development Establishment, Jhansi Road, Gwalior-474 002, India.
Metallomics. 2012 Jan;4(1):78-90. doi: 10.1039/c1mt00118c. Epub 2011 Oct 10.
Arsenic and fluoride are major contaminants of drinking water. Mechanisms of toxicity following individual exposure to arsenic or fluoride are well known. However, it is not explicit how combined exposure to arsenic and fluoride leads to cellular and/or DNA damage. The present study was planned to assess (i) oxidative stress during combined chronic exposure to arsenic and fluoride in drinking water, (ii) correlation of oxidative stress with cellular and DNA damage and (iii) mechanism of cellular damage using IR spectroscopy. Mice were exposed to arsenic and fluoride (50 ppm) either individually or in combination for 28 weeks. Arsenic or fluoride exposure individually led to a significant increase in reactive oxygen species (ROS) generation and associated oxidative stress in blood, liver and brain. Individual exposure to the two toxicants showed significant depletion of blood glutathione (GSH) and glucose 6-phosphate dehydrogenase (G6PD) activity, and single-stranded DNA damage using a comet assay in lymphocytes. We also observed an increase in the activity of ATPase, thiobarbituric acid reactive substance (TBARS) and a decreased, reduced and oxidized glutathione (GSH : GSSG) ratio in the liver and brain. Antioxidant enzymes like superoxide dismutase (SOD), catalase and glutathione peroxidase (GPx) were decreased and increased in liver and brain respectively. The changes were more pronounced in liver compared to brain suggesting liver to be more susceptible to the toxic effects of arsenic and fluoride. Interestingly, combined exposure to arsenic and fluoride resulted in less pronounced toxic effects compared to their individual effects based on biochemical variables, IR spectra, DNA damage (TUNEL and comet assays) and histopathological observations. IR spectra suggested that arsenic or fluoride perturbs the strength of protein and amide groups; however, the shifts in peaks were not pronounced during combined exposure. These results thus highlight the role of arsenic- or fluoride-induced oxidative stress, DNA damage and protein interaction as the major determinants of toxicity, along with the differential toxic effects during arsenic-fluoride interaction during co-exposure. The study further corroborates our earlier observations that at the higher concentration co-exposures to these toxicants do not elicit synergistic toxicity.
砷和氟化物是饮用水中的主要污染物。单独暴露于砷或氟化物后的毒性机制是众所周知的。然而，目前尚不清楚砷和氟化物联合暴露如何导致细胞和/或 DNA 损伤。本研究旨在评估：（i）在饮用水中联合慢性暴露于砷和氟化物时的氧化应激；（ii）氧化应激与细胞和 DNA 损伤的相关性；（iii）使用红外光谱评估细胞损伤的机制。将小鼠单独或联合暴露于砷和氟化物（50ppm）28 周。单独暴露于砷或氟化物会导致血液、肝脏和大脑中活性氧（ROS）的产生和相关氧化应激显著增加。两种有毒物质的单独暴露导致血液谷胱甘肽（GSH）和葡萄糖 6-磷酸脱氢酶（G6PD）活性显著耗竭，以及淋巴细胞中的彗星试验中出现单链 DNA 损伤。我们还观察到肝脏和大脑中 ATP 酶、硫代巴比妥酸反应物质（TBARS）活性增加，还原型和氧化型谷胱甘肽（GSH：GSSG）比值降低。肝脏和大脑中的抗氧化酶如超氧化物歧化酶（SOD）、过氧化氢酶和谷胱甘肽过氧化物酶（GPx）减少和增加。与大脑相比，肝脏中的变化更为明显，表明肝脏对砷和氟化物的毒性作用更为敏感。有趣的是，与单独暴露于砷和氟化物相比，联合暴露于砷和氟化物在生化变量、IR 光谱、DNA 损伤（TUNEL 和彗星试验）和组织病理学观察方面导致的毒性作用不那么明显。IR 光谱表明，砷或氟化物会扰乱蛋白质和酰胺基团的强度；然而，在联合暴露期间，峰的移动并不明显。这些结果突出了砷或氟化物诱导的氧化应激、DNA 损伤和蛋白质相互作用作为毒性的主要决定因素的作用，以及在联合暴露期间砷-氟化物相互作用时的差异毒性作用。该研究进一步证实了我们之前的观察结果，即在较高浓度下，这些有毒物质的共暴露不会引起协同毒性。
