Effect of chronic exposure to inorganic arsenic on intestinal cells

The impact of toxic metal bioaccumulation on colorectal cancer: Unravelling the unexplored connection

Colorectal cancer is a major public health concern, with increasing incidence and mortality rates worldwide. Environmental factors, including exposure to toxic metals, such as lead, chromium, cadmium, aluminium, copper, arsenic and mercury, have been suggested to play a significant role in the development and progression of this neoplasia. In particular, the bioaccumulation of toxic metals can play a significant role in colorectal cancer by regulating biological phenomenon associated to both cancer occurrence and progression, such as cell death and proliferation. Also, frequently these metals can induce DNA mutations in well-known oncogenes. This review provides a critical analysis of the current evidence, highlighting the need for further research to fully grasp the complex interplay between toxic metal bioaccumulation and colorectal cancer. Understanding the contribution of toxic metals to colorectal cancer occurrence and progression is essential for the development of targeted preventive strategies and social interventions, with the ultimate goal of reducing the burden of this disease.

Constructing interactive networks of functional genes and metabolites to uncover the cellular events related to colorectal cancer cell migration induced by arsenite

Tumor cell migration induced by arsenite (iAs^III) is closely associated with cancer progression. However, transcriptomic and metabolic traits of migrative human cells exposed to iAs^III remain to be well characterized. Here, the combination of transcriptomics and metabolomics approaches were employed to construct interactive networks of functional genes and metabolites in human colorectal cancer (DLD-1) cells exposed to iAs^III. The number of DLD-1 cells passing through the Transwell membrane was at least 6 times greater in the iAs^III-treated groups than in controls. Following iAs^III treatment, the expression of ZEB1 and SLUG protein was significantly upregulated while the expression of CRB2 was downregulated (p < 0.05), indicating the onset of epithelial to mesenchymal transition (EMT). Meanwhile, integrin- and collagen-mediated biological adhesion were enhanced by SLUG under iAs^III treatment. The expression of matrix metallopeptidase (MMP) genes was fostered by iAs^III, which have the functions to degrade extracellular matrix. Glutamine metabolism could be considerably interfered by iAs^III, and in turn glutamine supplementation could effectively enhance DLD-1 cell movement. Overall, our results suggested that DLD-1 cell migration could be promoted by iAs^III via a series of cellular events, including EMT activation, altered cell adhesion, MMP-dependent matrix degradation, accompanying with a metabolic focus on glutamine.

Intestinal homeostasis disruption in mice chronically exposed to arsenite-contaminated drinking water

Chronic exposure to inorganic arsenic [As(III) and As(V)] affects about 200 million people, and is linked to a greater incidence of certain types of cancer. Drinking water is the main route of exposure, so, in endemic areas, the intestinal mucosa is constantly exposed to the metalloid. However, studies on the intestinal toxicity of inorganic As are scarce. The objective of this study was to evaluate the toxicity of a chronic exposure to As(III) on the intestinal mucosa and its associated microbiota. For this purpose, BALB/c mice were exposed during 6 months through drinking water to As(III) (15 and 30 mg/L). Treatment with As(III) increased reactive oxygen species (43-64%) and lipid peroxidation (8-51%). A pro-inflammatory response was also observed, evidenced by an increase in fecal lactoferrin (23-29%) and mucosal neutrophil infiltration. As(III) also induced an increase in the colonic levels of pro-inflammatory cytokines (24-201%) and the activation of some pro-inflammatory signaling pathways. Reductions in the number of goblet cells and mucus production were also observed. Moreover, As(III) exposure resulted in changes in gut microbial alpha diversity but no differences in beta diversity. This suggested that the abundance of some taxa was significantly affected by As(III), although the composition of the population did not show significant alterations. Analysis of differential taxa agreed with this, 21 ASVs were affected in abundance or variability, especially ASVs from the family Muribaculaceae. Intestinal microbiota metabolism was also affected, as reductions in fecal concentration of short-chain fatty acids were observed. The effects observed on different components of the intestinal barrier may be responsible of the increased permeability in As(III) treated mice, evidenced by an increase in fecal albumin (48-66%). Moreover, serum levels of Lipopolysaccharide binding proteins and TNF-α were increased in animals treated with 30 mg/L of As(III), suggesting a low-level systemic inflammation.

Tocopherol Enhances the Antioxidant Defense System and Histomorphometric Parameters in The Gastrointestinal Tract of Rats Treated with Sodium Arsenite

Arsenic compromises the gastrointestinal integrity and function via the body's anti-oxidative system breakdown.  Hence, this study aimed to investigate the effects of tocopherol on redox imbalance and histoarchitectural alterations in rats' gastrointestinal tract exposed to sodium arsenite. Sodium arsenite and graded doses of tocopherol were administered orally into experimental rats assigned to different groups for four weeks concurrently. Redox status assay was done in homogenized samples by spectrophotometry. Parietal cell mass and mucous cell density (stomach), villus height and crypt depth (ileum), goblet cells count, and crypt depth (colon) were evaluated by histomorphometry. Inflammatory cells infiltration was also assessed using a semi-quantitative procedure. Sodium arsenite caused a significant increase in Malondialdehyde and Myeloperoxidase but, decreased Superoxide dismutase, Catalase, Nitric oxide, Glutathione peroxidase, Glutathione, and Glutathione-S-Transferase. Tocopherol treatment reversed the changes (p<0.05) though not largely dose-dependent. Furthermore, tocopherol annulled sodium arsenite-induced increase in parietal cell mass and decrease in mucous cell density in the stomach, decrease in villus height and villus height/crypt depth ratio in the ileum, and decrease in goblets cells and increase in crypt depth in the colon. Moreover, activated inflammatory cell infiltration by sodium arsenite was mitigated by tocopherol. Sodium arsenite provokes not only marked inflammatory cellular infiltration but a focal loss of glands, hyperplasia of crypts, atrophic villi, and hypertrophy of Peyer's patches in the intestines, which are all lessened with tocopherol treatment.  These findings underscore the anti-oxidative properties of tocopherol as a potent dietary factor against sodium arsenite toxicity in the gastrointestinal tract. Keywords: Tocopherol, arsenic, stomach, ileum, colon.

Effects of Selenium on the Immunotoxicity of Subacute Arsenic Poisoning in Chickens

This study aimed to determine the effects of selenium on the immune toxicity of subacute arsenic poisoning in chickens. Two hundred 8-day-old broilers were randomly divided into 5 groups: the control group (0.1 mg/kg As + 0.2 mg/kg Se), the As group (3 mg/kg As + 0.2 mg/kg Se), As + Se group I (3 mg/kg As + 5 mg/kg Se), As + Se group II (3 mg/kg As + 10 mg/kg Se), and As + Se group III (3 mg/kg As + 15 mg/kg Se). The conclusions were drawn based on the following measurements: 3.0 mg/kg added to feed led to a decrease in the growth performance of the broilers, reduced the level and conversion rate of ANAE, reduced the blood protein content of the broilers but had no effect on the albumin/globulin ratio, and had an inhibitory effect on erythrocyte immunity. Selenium-added of 5 and 10 mg/kg in daily feed leads to increased growth performance, increases the positive rate and conversion rate of ANAE, increases the hemoglobin content of broilers, and promotes erythrocyte immunity, which indicates that the selenium-added reduces the toxic effects of arsenic; 3.0 mg/kg arsenic with 15 mg/kg selenium had the most severe toxic effects. Fifteen milligrams per kilogram of selenium added in daily feed increases the toxicity of arsenic to broilers. The dose of 10 mg/kg selenium showed the best inhibitory effect on subacute arsenic poisoning in the broilers.

Ethanol extract of Vitellaria paradoxa (Gaertn, F) leaves protects against sodium arsenite - induced toxicity in male wistar rats

The inadvertent exposure to arsenic has been associated with diverse diseases such as cancers. Vitellaria paradoxa is a medicinal plant with antidiabetic and antiproliferative properties. Here, we assessed the ameliorative role of Ethanol Leaf extract of Vitellaria paradoxa (ELVp) in Sodium Arsenite (SA) - induced toxicity in rats after oral treatment for two weeks as follows: Group 1 (Control, distilled water), Group 2 (Vitamin E, 100 mg/kg), Groups 3 and 4 (ELVp, 100 & 200 mg/kg respectively), Group 5 (SA, 2.5 mg/kg), Group 6 (SA + Vit E) and Group 7 (SA + ELVp (100 mg/kg) and Group 8 (SA + ELVp (200 mg/kg). The results indicated that SA significantly increased liver and kidney function markers and elevated platelet, white blood cell (WBC) count and malondialdehyde levels in rats. Additionally, SA decreased Red Blood Cell (RBC), Hemoglobin (HGB) and Hematocrit (HCT) levels in rats (p < 0.05). Sodium arsenite caused mild expression of BCL-2 protein> NF-Kb = p53 in the kidney of rats. However, ELVp ameliorated SA-induced toxicity in the liver and kidney of rats with respect to these markers. Overall, ELVp has hepatoprotective, nephroprotective and apoptotic properties against sodium arsenite-induced toxicity.