Behavioral and general effects of subacute oral arsenic exposure in rats with and without fluoride

Co-exposure to arsenic and fluoride to explore the interactive effect on oxidative stress and autophagy in myocardial tissue and cell

Co-contamination of arsenic and fluoride is widely distributed in groundwater. However, little is known about the interactively influence of arsenic and fluoride, especially the combined mechanism in cardiotoxicity. Cellular and animal models exposure to arsenic and fluoride were established to assess the oxidative stress and autophagy mechanism of cardiotoxic damage using the factorial design, a widely used statistical method for assessing two factor interventions. In vivo, combined exposure to high arsenic (50 mg/L) and high fluoride (100 mg/L) induced myocardial injury. The damage is accompanied by accumulation of myocardial enzyme, mitochondrial disorder, and excessive oxidative stress. Further experiment identified that arsenic and fluoride induced the accumulation of autophagosome and increased expression level of autophagy related genes during the cardiotoxicity process. These findings were further demonstrated through the in vitro model of arsenic and fluoride-treated the H9c2 cells. Additionally, combined of arsenic-fluoride exposure possesses the interactively influence on oxidative stress and autophagy, contributing to the myocardial cell toxicity. In conclusion, our data suggest that oxidative stress and autophagy are involved in the process of cardiotoxic injury, and that these indicators showed interaction effect in response to the combined exposure of arsenic and fluoride.

Effects of neuron autophagy induced by arsenic and fluoride on spatial learning and memory in offspring rats

There are numerous studies showing that exposure to arsenic (As) or fluoride (F) damages the nervous system, but there is no literature investigating the effects of combined As and F exposure to induce autophagy on neurotoxicity in the offspring. In this study, we developed a rat model of As and/or F exposure through drinking water from before pregnancy to 90 days postnatal. The offspring rats were randomly divided into nine groups. Sodium arsenite (NaAsO₂) (0, 35, 70 mg/L) and Sodium fluoride (NaF) (0, 50, 100 mg/L) were designed according to 3 × 3 factorial design. Our results suggested that the presence of F might antagonize the excretion of total As in urine, and As-F co-exposure led to severe pathological damage in brain tissue and reduced spatial learning and memory ability. At the same time, the experiments showed that As and F increased Beclin1 expression and LC3B ratio to activate autophagy; both P62 and Lamp2 expression were increased, suggesting that autophagy lysosomal degradation was blocked; SYN and JIP1 expression were significantly decreased, disrupting synaptic structure and function. Axonal autophagosome reverse transport regulation might be affected by combined As-F exposure, exacerbating neuronal synaptic damage and inducing neurotoxicity. Further analysis showed that there was an interaction between As and F exposure-induced changes in autolysosome-related proteins in the hippocampus, which showed antagonism, and the antagonism of the high As combined exposure groups were stronger than that of the low As combined exposure groups. In conclusion, our study showed that combined As and F exposure might induce reverse transport impairment of autophagy on axons, leading to autophagy defects, which in turn led to disruption of synaptic morphology and function, induced neurotoxicity, and there was an interaction between As and F, the type of its combined effect was antagonism.

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.

Molecular mechanism of brain impairment caused by drinking-acquired fluorosis and selenium intervention

This study investigated the molecular mechanism of brain impairment induced by drinking fluoridated water and selenium intervention. Results showed that the learning and memory of rats in NaF group significantly decreased. Moreover, the number of apoptotic cells, the expression levels of Cytc mRNA and protein, and the expression levels of Caspase-9 and Caspase-3 mRNA significantly increased; by contrast, Caspase-9 and Caspase-3 protein levels significantly decreased. Compared with the NaF group, the mRNA levels of Cytc and Caspase-9, as well as the protein levels of Cytc in NaF+Se group, significantly decreased. Conversely, the protein levels of Caspase-3 and Caspase-9, as well as the mRNA levels of Caspase-3, significantly increased. Thus, the mitochondrial CytC-Caspase-9-Caspase-3 apoptosis pathway in the hippocampus was one of the mechanisms leading to fluorosis-induced brain damage. Furthermore, the Cytc signaling molecules were possibly the key target molecules in fluorosis-induced apoptosis, and selenium could alleviate fluorosis-induced brain injury.