Sex-specific transgenerational effects of preconception exposure to arsenite: metabolic phenotypes of C57BL/6 offspring.

Chronic exposure to inorganic arsenic (iAs) has been linked to diabetes in both humans and mice, but the role of iAs exposure prior to conception and its transgenerational effects are understudied. The present study investigated transgenerational effects of preconception iAs exposure in C57BL/6J mice, focusing on metabolic phenotypes of G1 and G2 offspring. Body composition and diabetes indicators, including fasting blood glucose, fasting plasma insulin, glucose tolerance, and indicators of insulin resistance and beta cell function, were examined in both generations. The results suggest that the preconception iAs exposure in the parental (G0) generation induced diabetic phenotypes in G1 and G2 offspring in a sex-dependent manner. G1 females from iAs-exposed parents developed insulin resistance while no significant effects were found in G1 males. In the G2 generation, insulin resistance was observed only in males from iAs-exposed grandparents and was associated with higher bodyweights and adiposity. Similar trends were observed in G2 females from iAs-exposed grandparents, but these did not reach statistical significance. Thus, preconception iAs exposure altered metabolic phenotype across two generations of mouse offspring. Future research will investigate the molecular mechanisms underlying these transgenerational effects, including epigenomic and transcriptomic profiles of germ cells and tissues from G0, G1 and G2 generations.

Pyrolysis temperature and biochar redox activity on arsenic availability and speciation in a sediment.

Biochar is widely used for water and soil remediation in part because of its local availability and low production cost. However, its effectiveness depends on physicochemical properties related to its feedstock and pyrolysis temperature, as well as the environmental conditions of its use site. Furthermore, biochar is susceptible to natural aging caused by changes in soil or sediment moisture, which can alter its redox properties and interactions with contaminants such as arsenic (As). In this study, we investigated the effect of pyrolysis temperature and biochar application on the release and transformations of As in contaminated sediments subjected to redox fluctuations. Biochar application and pyrolysis temperature played an important role in As species availability, As methylation, and dissolved organic carbon concentration. Furthermore, successive flooding cycles that induced reductive conditions in sediments increased the As content in the solution by up to seven times. In the solid phase, the application of biochar and the flooding cycle altered the spatial distribution and speciation of carbon, iron (Fe) and As. In general, the application of biochar decreased the reduction of Fe(III) and As(V) after the first cycle of flooding. Our results demonstrate that the flooding cycle plays an important role in the reoxidation of biochar to the point of enhancing the immobilization of As.

Fate of arsenicals in mice carrying the human AS3MT gene exposed to environmentally relevant levels of arsenite in drinking water.

Although mice are widely used to study adverse effects of inorganic arsenic (iAs), higher rates of iAs methylation in mice than in humans may limit their utility as a model organism. A recently created 129S6 mouse strain in which the Borcs7/As3mt locus replaces the human BORCS7/AS3MT locus exhibits a human-like pattern of iAs metabolism. Here, we evaluate dosage dependency of iAs metabolism in humanized (Hs) mice. We determined tissue and urinary concentrations and proportions of iAs, methylarsenic (MAs), and dimethylarsenic (DMAs) in male and female Hs and wild-type (WT) mice that received 25- or 400-ppb iAs in drinking water. At both exposure levels, Hs mice excrete less total arsenic (tAs) in urine and retain more tAs in tissues than WT mice. Tissue tAs levels are higher in Hs females than in Hs males, particularly after exposure to 400-ppb iAs. Tissue and urinary fractions of tAs present as iAs and MAs are significantly greater in Hs mice than in WT mice. Notably, tissue tAs dosimetry in Hs mice resembles human tissue dosimetry predicted by a physiologically based pharmacokinetic model. These data provide additional support for use of Hs mice in laboratory studies examining effects of iAs exposure in target tissues or cells.

Ex vivo exposures to arsenite and its methylated trivalent metabolites alter gene transcription in mouse sperm cells.

We have previously reported that preconception exposure to iAs may contribute to the development of diabetes in mouse offspring by altering gene expressions in paternal sperm. However, the individual contributions of iAs and its methylated metabolites, monomethylated arsenic (MAs) and dimethylated arsenic (DMAs), to changes in the sperm transcriptome could not be determined because all three As species are present in sperm after in vivo iAs exposure. The goal of the present study was to assess As species-specific effects using an ex vivo model. We exposed freshly isolated mouse sperm to either 0.1 or 1 µM arsenite (iAsIII) or the methylated trivalent arsenicals, MAsIII and DMAsIII, and used RNA-sequencing to identify differentially expressed genes, enriched pathways, and associated protein networks. For all arsenicals tested, the exposures to 0.1 µM concentrations had greater effects on gene expression than 1 µM exposures. Transcription factor AP-1 and B cell receptor complexes were the most significantly enriched pathways in sperm exposed to 0.1 µM iAsIII. The Mre11 complex and Antigen processing were top pathways targeted by exposure to 0.1 µM MAsIII and DMAsIII, respectively. While there was no overlap between gene transcripts altered by ex vivo exposures in the present study and those altered by in vivo exposure in our prior work, several pathways were shared, including PI3K-Akt signaling, Focal adhesion, and Extracellular matrix receptor interaction pathways. Notably, the protein networks associated with these pathways included those with known roles in diabetes. This study is the first to assess the As species-specific effects on sperm transcriptome, linking these effects to the diabetogenic effects of iAs exposure.

Examining the effects of cigarette smoke on mouse lens through a multi OMIC approach.

Here, we report a multi OMIC (transcriptome, proteome, and metabolome) approach to investigate molecular changes in lens fiber cells (FC) of mice exposed to cigarette smoke (CS). Pregnant mice were placed in a whole-body smoke chamber and a few days later pups were born, which were exposed to CS for 5 hours/day, 5 days/week for a total of 3½ months. We examined the mice exposed to CS for CS-related cataractogenesis after completion of the CS exposure but no cataracts were observed. Lenses of CS-exposed and age-matched, untreated control mice were extracted and lens FC were subjected to multi OMIC profiling. We identified 348 genes, 130 proteins, and 14 metabolites exhibiting significant (p < 0.05) differential levels in lens FC of mice exposed to CS, corresponding to 3.6%, 4.3%, and 5.0% of the total genes, protein, and metabolites, respectively identified in this study. Our multi OMIC approach confirmed that only a small fraction of the transcriptome, the proteome, and the metabolome was perturbed in the lens FC of mice exposed to CS, which suggests that exposure of CS had a minimal effect on the mouse lens. It is worth noting that while our results confirm that CS exposure does not have a substantial impact on the molecular landscape of the mouse lens FC, we cannot rule out that CS exposure for longer durations and/or in combination with other morbidities or environmental factors would have a more robust effect and/or result in cataractogenesis.

Assessment of inorganic contamination of private wells and demonstration of effective filter-based reduction: A pilot-study in Stokes County, North Carolina.

Well water is the primary drinking source for nearly a quarter of North Carolina residents. Many communities across the state have been concerned about their well water quality and inorganic contamination. The "Well Empowered" study worked alongside a community in Stokes County, North Carolina to measure toxic metals in their well water as well as provide and test ZeroWater® filter pitchers in homes with arsenic (As) or lead (Pb) contamination. Multiple water samples, including a First Draw sample from the kitchen tap and a sample taken directly from the well, were collected from 39 homes in Stokes County. The samples were analyzed for 17 different inorganic contaminants, including As, boron (B), Pb, and manganese (Mn), using inductively coupled plasma mass spectrometry (ICP-MS). High concentrations of Pb along with copper (Cu), cadmium (Cd), and zinc (Zn) were only found in the First Draw sample and therefore likely originate in the home plumbing system while As, iron (Fe), and Mn were consistent across all samples and therefore are present in the groundwater. The low concentrations of B (<100 parts per billion (ppb)) make it unlikely that the source of As and Mn contamination was coal ash-derived. Out of the 39 homes, four had As levels exceeding the federal standard of 10 ppb and an additional two exceeded the Pb standard of 15 ppb. These homes were provided with a ZeroWater® filter pitcher and a water sample was taken pre- and post-filtration. The ZeroWater® filter removed 99% of As and Pb from the water, dropping the levels well below the drinking water standard levels. These ZeroWater® filter pitchers, while not a permanent solution, are a low-cost option for homeowners experiencing As or Pb contamination.

Placental Cadmium Levels Are Associated with Increased Preeclampsia Risk.

Environmental exposure to heavy metals is a potentially modifiable risk factor for preeclampsia (PE). Toxicologically, there are known interactions between the toxic metal cadmium (Cd) and essential metals such as selenium (Se) and zinc (Zn), as these metals can protect against the toxicity of Cd. As they relate to preeclampsia, the interaction between Cd and these essential metals is unknown. The aims of the present study were to measure placental levels of Cd, Se, and Zn in a cohort of 172 pregnant women from across the southeast US and to examine associations of metals levels with the odds of PE in a nested case-control design. Logistic regressions were performed to assess odds ratios (OR) for PE with exposure to Cd controlling for confounders, as well as interactive models with Se or Zn. The mean placental Cd level was 3.6 ng/g, ranging from 0.52 to 14.5 ng/g. There was an increased odds ratio for PE in relationship to placental levels of Cd (OR = 1.5; 95% CI: 1.1-2.2). The Cd-associated OR for PE increased when analyzed in relationship to lower placental Se levels (OR = 2.0; 95% CI: 1.1-3.5) and decreased with higher placental Se levels (OR = 0.98; 95% CI: 0.5-1.9). Similarly, under conditions of lower placental Zn, the Cd-associated OR for PE was elevated (OR = 1.8; 95% CI: 0.8-3.9), whereas with higher placental Zn it was reduced (OR = 1.3; 95% CI: 0.8-2.0). Data from this pilot study suggest that essential metals may play an important role in reducing the odds of Cd-associated preeclampsia and that replication in a larger cohort is warranted.

Gut microbiome phenotypes driven by host genetics affect arsenic metabolism.

Large individual differences in susceptibility to arsenic-induced diseases are well-documented and frequently associated with different patterns of arsenic metabolism. In this context, the role of the gut microbiome in directly metabolizing arsenic and triggering systemic responses in diverse organs raises the possibility that gut microbiome phenotypes affect the spectrum of metabolized arsenic species. However, it remains unclear how host genetics and the gut microbiome interact to affect the biotransformation of arsenic. Using an integrated approach combining 16S rRNA gene sequencing and HPLC-ICP-MS arsenic speciation, we demonstrate that IL-10 gene knockout leads to a significant taxonomic change of the gut microbiome, which in turn substantially affects arsenic metabolism.

Gut microbiome perturbations induced by bacterial infection affect arsenic biotransformation.

Exposure to arsenic affects large human populations worldwide and has been associated with a long list of human diseases, including skin, bladder, lung, and liver cancers, diabetes, and cardiovascular disorders. In addition, there are large individual differences in susceptibility to arsenic-induced diseases, which are frequently associated with different patterns of arsenic metabolism. Several underlying mechanisms, such as genetic polymorphisms and epigenetics, have been proposed, as these factors closely impact the individuals' capacity to metabolize arsenic. In this context, the role of the gut microbiome in directly metabolizing arsenic and triggering systemic responses in diverse organs raises the possibility that perturbations of the gut microbial communities affect the spectrum of metabolized arsenic species and subsequent toxicological effects. In this study, we used an animal model with an altered gut microbiome induced by bacterial infection, 16S rRNA gene sequencing, and inductively coupled plasma mass spectrometry-based arsenic speciation to examine the effect of gut microbiome perturbations on the biotransformation of arsenic. Metagenomics sequencing revealed that bacterial infection significantly perturbed the gut microbiome composition in C57BL/6 mice, which in turn resulted in altered spectra of arsenic metabolites in urine, with inorganic arsenic species and methylated and thiolated arsenic being perturbed. These data clearly illustrated that gut microbiome phenotypes significantly affected arsenic metabolic reactions, including reduction, methylation, and thiolation. These findings improve our understanding of how infectious diseases and environmental exposure interact and may also provide novel insight regarding the gut microbiome composition as a new risk factor of individual susceptibility to environmental chemicals.

Comparative oxidation state specific analysis of arsenic species by high-performance liquid chromatography-inductively coupled plasma-mass spectrometry and hydride generation-cryotrapping-atomic absorption spectrometry.

The formation of methylarsonous acid (MAsIII) and dimethylarsinous acid (DMAsIII) in the course of inorganic arsenic (iAs) metabolism plays an important role in the adverse effects of chronic exposure to iAs. High-performance liquid chromatography-inductively coupled plasma-mass spectrometry (HPLC-ICP-MS) and hydride generation-cryotrapping-atomic absorption spectrometry (HG-CT-AAS) have been frequently used for the analysis of MAsIII and DMAsIII in biological samples. While HG-CT-AAS has consistently detected MAsIII and DMAsIII, HPLC-ICP-MS analyses have provided inconsistent and contradictory results. This study compares the capacities of both methods to detect and quantify MAsIII and DMAsIII in an in vitro methylation system consisting of recombinant human arsenic (+3 oxidation state) methyltransferase (AS3MT), S-adenosylmethionine as a methyl donor, a non-thiol reductant tris(2-carboxyethyl)phosphine, and arsenite (iAsIII) or MAsIII as substrate. The results show that reversed-phase HPLC-ICP-MS can identify and quantify MAsIII and DMAsIII in aqueous mixtures of biologically relevant arsenical standards. However, HPLC separation of the in vitro methylation mixture resulted in significant losses of MAsIII, and particularly DMAsIII with total arsenic recoveries below 25%. Further analyses showed that MAsIII and DMAsIII bind to AS3MT or interact with other components of the methylation mixture, forming complexes that do not elute from the column. Oxidation of the mixture with H2O2 which converted trivalent arsenicals to their pentavalent analogs prior to HPLC separation increased total arsenic recoveries to ~95%. In contrast, HG-CT-AAS analysis found large quantities of methylated trivalent arsenicals in mixtures incubated with either iAsIII or MAsIII and provided high (>72%) arsenic recoveries. These data suggest that an HPLC-based analysis of biological samples can underestimate MAsIII and DMAsIII concentrations and that controlling for arsenic species recovery is essential to avoid artifacts.

Lead-210 and Beryllium-7 fallout rates on the southeastern coast of Brazil.

Total ²¹°Pb and 7Be fallout rates were measured on the coastal region of Niteroi, Brazil. The monthly depositional flux of ²¹°Pb and 7Be varied by a factor of 26, from 1.7 to 43.3 mBq cm⁻² year⁻¹ and ∼27, from 7.5 to 203.5 mBq cm⁻² year⁻¹, respectively. The relatively large oscillations in the depositional flux of ²¹°Pb at this study site were likely due to variations in air mass sources, while the 7Be fluctuations may be driven by a combination of weather conditions. Local geology could support the periodic high fluxes of ²¹°Pb from continental air masses, as shifting oceanic wind sources were affirmed by the uncorrelated ²¹°Pb and 7Be fallout activities and 7Be/²¹°Pb ratios. The ²¹°Pb atmospheric deposition was found to be in agreement with local sediment inventories, an important consideration in geochemical studies that estimate sedimentation processes.