Contemporary trends in toxicological research on arsenic

Arsenic and cancer: Evidence and mechanisms

Arsenic is a potent carcinogen and poses a significant health concern worldwide. Exposure occurs through ingestion of drinking water and contaminated foods and through inhalation due to pollution. Epidemiological evidence shows arsenic induces cancers of the skin, lung, liver, and bladder among other tissues. While studies in animal and cell culture models support arsenic as a carcinogen, the mechanisms of arsenic carcinogenesis are not fully understood. Arsenic carcinogenesis is a complex process due its ability to be metabolized and because of the many cellular pathways it targets in the cell. Arsenic metabolism and the multiple forms of arsenic play distinct roles in its toxicity and contribute differently to carcinogenic endpoints, and thus must be considered. Arsenic generates reactive oxygen species increasing oxidative stress and damaging DNA and other macromolecules. Concurrently, arsenic inhibits DNA repair, modifies epigenetic regulation of gene expression, and targets protein function due its ability to replace zinc in select proteins. While these mechanisms contribute to arsenic carcinogenesis, there remain significant gaps in understanding the complex nature of arsenic cancers. In the future improving models available for arsenic cancer research and the use of arsenic induced human tumors will bridge some of these gaps in understanding arsenic driven cancers.

Protein nanofibrils as versatile and sustainable adsorbents for an effective removal of heavy metals from wastewater: A review

Water is a valuable natural resource, which plays a crucial role in ecological survival as well as economic progress. However, the water quality has deteriorated in recent years as a result of urbanization, industrialization and human activities due to the uncontrolled release of industrial wastes, which can be extremely carcinogenic and non-degradable, in air, water and soil bodies. Such wastes showed the presence of organic and inorganic pollutants in high dosages. Heavy metals are the most obstinate contaminants, and they can be harmful because of having a variety of detrimental consequences to the ecosystem. The existing water treatment methods in many situations may not be sustainable or effective because of their high energy requirements and ecological impacts. In this review, state-of-the-art water treatment methods for the elimination of heavy metals with the help of protein nanofibrils are covered featuring a discussion on the strategies and possibilities of developing protein nanofibrils for the active elimination of heavy metals using kitchen waste as well as residues from the cattle, agriculture, and dairy industries. Further, the emphasis has been given to their environmental sustainability and economical aspects are also discussed.

Deregulation of autophagy is involved in nephrotoxicity of arsenite and fluoride exposure during gestation to puberty in rat offspring

Exposure to fluoride (F) or arsenite (As) through contaminated drinking water has been associated with chronic nephrotoxicity in humans. Autophagy is a regulated mechanism ubiquitous for the body in a toxic environment with F and As, but the underlying mechanisms of autophagy in the single or combined nephrotoxicity of F and As are unclear. In the present study, we established a rat model of prenatal and postnatal exposure to F and As with the aim of investigating the mechanism underlying nephrotoxicity of these pollutants in offspring. Rats were randomly divided into four groups that received NaF (100 mg/L), NaAsO₂ (50 mg/L), or NaF (100 mg/L) with NaAsO₂ (50 mg/L) in drinking water or clean water during pregnancy and lactation; after weaning, pups were exposed to the same treatment as their mothers until puberty. The results revealed that F and As exposure (alone or combined) led to significant increases of arsenic and fluoride levels in blood and bone, respectively. In this context, F and/or As disrupted histopathology and ultrastructure in the kidney, and also altered creatinine (CRE), urea nitrogen (BUN) and uric acid (UA) levels. Intriguingly, F and/or As uptake induced the formation of autophagosomes in kidney tissue and resulted in the upregulation of genes encoding autophagy-related proteins. Collectively, these results suggest that nephrotoxicity of F and As for offspring exposed to the pollutants from in utero to puberty is associated with deregulation of autophagy and there is an antagonism between F and As in the toxicity autophagy process.

Subchronic exposure to arsenite and fluoride from gestation to puberty induces oxidative stress and disrupts ultrastructure in the kidneys of rat offspring

Underground drinking water is commonly contaminated with arsenite (As) and fluoride (F) associated with chronic kidney diseases in humans; however, the combined renal toxicity of these pollutants and the underlying mechanisms are still unclear. The aim of the present study was to investigate the interaction between As and F regarding toxic effects on the kidney of rat offspring exposed to pollutants during prenatal and postnatal development. Pregnant rats were randomly divided into four groups that received NaAsO₂ (50 mg/L), NaF (100 mg/L), NaAsO₂ (50 mg/L) and NaF (100 mg/L) in drinking water, or clean water, respectively, during gestation and lactation. After weaning, six male pups were randomly selected from each group and continued on the same treatment as their mothers for up to three months. The results revealed that subchronic exposure to high-dose As and/or F decreased the organ coefficient of the kidneys and disrupted kidney ultrastructure, moreover inhibited the activity of antioxidant enzymes and increased the generation of malondialdehyde in the kidney. As exposure alone or combined with F led to an upregulation of nuclear factor erythroid 2-related factor-2 (Nrf2) and its regulatory targets (Ho-1, Gclc, and Nqo1), whereas the effect of F alone was not significant. These results suggest that the renal toxicity of As and F is associated with the induction of mitochondrial damage and oxidative stress, and alters the expression of Nrf2 and its regulatory targets. Furthermore, variance analysis results showed that an interaction between As and F in the toxicity process.