Chronic exposure to lead and cadmium pollution results in genomic instability in a model biomonitor species (Apodemus flavicollis Melchior, 1834)

Water contamination by delorazepam induces epigenetic defects in the embryos of the clawed frog Xenopus laevis

Delorazepam, a derivative of diazepam, is a psychotropic drug belonging to the benzodiazepine class. Used as a nervous-system inhibitor, it treats anxiety, insomnia, and epilepsy, but is also associated with misuse and abuse. Nowadays benzodiazepines are considered emerging pollutants: conventional wastewater treatment plants indeed are unable to eliminate these compounds. Consequently, they persist in the environment and bioaccumulate in non-target aquatic organisms with consequences still not fully clear. To collect more information, we investigated the possible epigenetic activity of delorazepam, at three concentrations (1, 5 and 10 μg/L) using Xenopus laevis embryos as a model. Analyses demonstrated a significant increase in genomic DNA methylation and differential methylation of the promoters of some early developmental genes (otx2, sox3, sox9, pax6, rax1, foxf1, and myod1). Moreover, studies on gene expression highlighted an unbalancing in apoptosis/proliferation pathways and an aberrant expression of DNA-repair genes. Results are alarming considering the growing trend of benzodiazepine concentrations in superficial waters, especially after the peak occurred as a consequence of the pandemic COVID-19, and the fact that benzodiazepine GABA-A receptors are highly conserved and present in all aquatic organisms.

Effects of lead and cadmium co-exposure on liver function in residents near a mining and smelting area in northwestern China

Chronic exposure to environmental cadmium (Cd) and lead (Pb) may have adverse effects on the human health. In this study, we aimed to determine the primary and interactive effects of Cd and Pb exposure on liver function in residents near a mining and smelting area in northwestern China. A total of 451 subjects were recruited, from which blood samples were collected to determine the levels of Cd, Pb, and liver function indices. Additionally, the association between the levels of exposure markers and liver function indices was analysed. Cd and Pb levels were significantly higher in subjects living in the polluted area than in those living in the non-polluted reference area. The liver function levels of subjects in the polluted area were poor compared with those in the reference area. In addition, Cd and Pb levels in the blood were positively associated with gamma glutamyl transpeptidase (GGT) levels and negatively associated with direct bilirubin (DBil) levels. Cd and Pb may be risk factors for abnormal liver function. The risk of abnormal liver function was higher in subjects with moderate Cd and Pb levels, high Cd levels, high Pb levels, and high Cd and Pb levels than in those with low Cd and Pb levels. Our data show that exposure to Cd and/or Pb can cause abnormal liver function. Cd and Pb may have an antagonistic effect on liver function, and high Cd exposure alone has a more profound effect on abnormal liver function compared with co-exposure to Pb and Cd.

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.

Lead content in soil, plants, rodents, and amphibians in the vicinity of a heating plant's ash waste

This study supplements previous research focused on environmental condition in the vicinity of waste ash material. The main aim of our study was the comparative analysis of lead levels in soil, plant, and animal organisms in the area of the tailings pond and surroundings, using x-ray. Findings confirm that the level of Pb in the top layer of soil is in the range of 20-135 ppm. Lead content in Calamagrostis plant tissues was confirmed only at the tailings pond area, with the highest lead concentrations measured in above-ground components; stems with blooms followed by roots and ground floor sheats. The livers, kidneys, and hearts of Apodemus flavicollis were examined, with findings of higher values in the tailings pond area than in the reference site, and average values of 14.5 ppm for livers, 16.0 ppm for kidneys, and 16.6 ppm for hearts. No significant differences were discovered based on sex and body length/body weight of A. flavicollis individuals. Values for Bombina variegata liver tissue reached an average of 12.3 ppm for individuals caught in a water reservoir without ash sediments, versus 15.7 ppm in those trapped by the edge of then tailings pond area. Females had lower concentrations of lead than males, but with no statistically significant differences found. Despite lower lead levels in soil and ash than expected, concentrations in mammalian and amphibian organs suggest a possible transition of this element into the food chain, and therefore further research in this area is recommended.

How Divalent Cations Interact with the Internal Channel Site of Guanine Quadruplexes

The formation of guanine quadruplexes (GQ) in DNA is crucial in telomere homeostasis and regulation of gene expression. Pollution metals can interfere with these DNA superstructures upon coordination. In this work, we study the affinity of the internal GQ channel site towards alkaline earth metal (Mg²⁺, Ca²⁺, Sr²⁺, and Ba²⁺), and (post‐)transition metal (Zn²⁺, Cd²⁺, Hg²⁺, and Pb²⁺) cations using density functional theory computations. We find that divalent cations generally bind to the GQ cavity with a higher affinity than conventional monovalent cations (e. g. K⁺). Importantly, we establish the nature of the cation‐GQ interaction and highlight the relationship between ionic and nuclear charge, and the electrostatic and covalent interactions. The covalent interaction strength plays an important role in the cation affinity and can be traced back to the relative stabilization of cations’ unoccupied atomic orbitals. Overall, our findings contribute to a deeper understanding of how pollution metals could induce genomic instability.

Novel insights into cytochrome P450 enzyme and solute carrier families in cadmium-induced liver injury of pigs

Cadmium (Cd) is a typical pollutant and carcinogen in environment. Exposure assessment of contaminants is an important component of occupational and environmental epidemiological studies. Early studies of Cd have focused on aquatic animals, chickens and rats. However, toxicological evaluation of Cd in pigs has not been reported. Therefore, twelve pigs were randomly divided into two groups (n = 6): the control group and the Cd group (Cd content: 15 ± 0.242 mg/kg feed) in this study, the experimental period was 30 d, and the toxic effects of Cd on the liver of weanling piglets were examined by antioxidant function, liver function, Cd content, histological examination and transcriptomics. The results showed that the changes of antioxidant function, liver function and Cd content were significant in the liver. Transcriptional profiling results showed that 399 differentially expressed genes (DEGs) were significantly up-regulated while 369 DEGs were remarkably down-regulated in Cd group, and which were concentrated in three ontologies: molecular function, cellular component and biological processes. Interestingly, significant changes in some genes of the cytochrome P450 enzyme (CYP450) and solute carrier (SLC) families have been observed and were consistent with qRT-PCR results. In conclusion, Cd could cause liver injury in weanling piglets and change the transcriptomic characteristics of liver. CYP450 and SLC families play an indispensable role in Cd-mediated hepatotoxicity. Importantly, changes in mRNA levels of CYP2B22, CYP7A1, CYP8B1, SLC26A8, SLC11A1, SLC27A2 and SLC22A7 induced by Cd have been reported for the first time. Our findings will provide a new insight for better assessing the mechanism of Cd toxicity to the liver.