Modulation of acrylonitrile-induced embryotoxicity in vitro by glutathione depletion

The association between exposure to volatile organic chemicals and serum α-Klotho in USA middle to old aged population: A cross-sectional study from NHANES 2011-2016

BACKGROUND

Volatile Organic Compounds (VOCs) constitute an omnipresent category of environmental contaminants. Numerous studies have identified associations between various VOCs and human diseases. The anti-aging protein α-Klotho has been shown to exert protective influences across a variety of disease origins and progressions. This study aims to explore the relationship between serum α-Klotho levels and exposure to VOCs in humans.

METHODS

This analysis utilized data from 1672 participants aged from 40 to 79 years in 2011-2016 NHANES. Exposure to VOCs was assessed through measurements of urinary VOC metabolites (mVOCs), with 16 mVOCs selected for analysis. Multivariate generalized linear models (GLM), restricted cubic splines (RCS), weighted quantile sum (WQS) regression models, and Bayesian kernel machine regression (BKMR) models were employed to examine the connection between serum α-Klotho and individual mVOCs and mVOCs mixtures, as well as to identify the primary monomeric mVOCs responsible for these associations.

RESULTS

Our research revealed that 8 mVOCs exhibited inverse associations with serum α-Klotho levels in GLM and RCS models. Particularly noteworthy, N-Acetyl-S-(2-cyanoethyl)-L-cysteine (CYMA), a metabolite of acrylonitrile, emerged as the most influential mVOC in both WQS and BKMR models. Furthermore, the mVOCs mixture was found to be negatively correlated with serum α-Klotho. The detrimental effects of mVOCs on serum α-Klotho were observed to significantly diminish in individuals with elevated serum vitamin D levels.

CONCLUSION

Our study highlights a significant inverse relationship between serum α-Klotho and the mixture of mVOCs, indicating that exposure to VOCs may impact the molecular pathways of aging and related diseases by influencing α-Klotho concentrations. Remarkably, the attenuation of this association by high serum vitamin D levels implies potential therapeutic strategies. Our study underscores the importance of minimizing VOCs exposure to mitigate the adverse effects on α-Klotho. Further research is warranted to elucidate the underlying mechanisms of these relationships.

Acute and chronic toxicity effects of acrylonitrile to the juvenile marine flounder Paralichthys olivaceus

Acrylonitrile (ACN) spills in marine environment have the potential to cause ecological hazards and consequences, but currently little is known about the disruptive effects of ACN on marine organisms. In the present study, we investigated the lethal and sublethal effects of ACN on juvenile flounder Paralichthys olivaceus. The results showed that the 96-h LC50 of ACN to P. olivaceus juveniles was 6.07 mg/L. The fish were then exposed to different sublethal concentrations (0.1, 0.2, and 0.4 mg/L) of ACN for 28 days and then transferred to clean seawater and keep in clean seawater for 14 days to simulate the conditions of a spill incident. Biomarkers (EROD, GST, SOD, AChE activity, and levels of LPO and DNA alkaline unwinding) were tested in liver and brain. The weight gain rates and specific growth rate of juvenile marine flounder exposed to ACN (≥ 0.1 mg/L) for 28 days decreased significantly, indicating that ACN had an inhibitory effect on juvenile growth. Deformity of fish tails was observed on individuals exposed to the highest concentration (0.4 mg/L ACN) for 14 days, and the malformation rate was 38% after 28-day exposure. The present study provides the first evidence that ACN causes inhibition of AChE activity in fish brain. Furthermore, the results showed that ACN can significantly inhibit SOD activity and cause lipid peroxidation and DNA damage in fish brain. The results indicated that brain is more sensitive to ACN toxicity compared to liver and provides a suitable tissue for biomonitoring. The biomarkers measured during the depuration period showed that the effects caused by ACN were reversible when the exposure concentration was lower than 0.4 mg/L. These results highlight the adverse effects of ACN in brain of fish, which should be considered in environmental risk assessment. Biomarkers including AChE activity, LPO, and DNA damage of brain tissue should be included in fish bioassays for toxic effect assessment of ACN spills.

Acrylonitrile-induced gastric toxicity in rats: the role of xanthine oxidase

BACKGROUND

Acrylonitrile (ACN) is an extensively produced aliphatic nitrile. The gastrointestinal tract is an important target organ for ACN toxicity. The objective of the present study was to investigate the role of xanthine oxidase (XO) in ACN-induced gastric toxicity in rats.

MATERIAL/METHODS

We assessed the effect of ACN on oxidative stress parameters as xanthine oxidase (XO) and total xanthine dehydrogenase (XD)/ XO activity, superoxide anion (O(2)(.-)) production, reduced glutathione (GSH) levels and lipid peroxidation in gastric tissues.

RESULTS

A single oral dose of ACN (25 mg/kg) caused a significant enhancement in XO activity. ACN also caused a significant depletion of GSH levels, enhanced O(2)(.-) production and increased lipid peroxidation in the time-course experiment. In the dose-response experiment, ACN accelerated the conversion of XD to XO, with a significant depletion of gastric GSH in a dose-related manner. A strong negative correlation existed between the levels of GSH and the percentage enhancement in XO activity (r =-0.997). (O(2)(.-)) production and malondialdehyde (MDA) formation were significantly elevated in a dose-related manner. Pretreatment with allopurinol (50 mg/kg) significantly protected against ACN-induced rise in XO activity, depletion of GSH, and elevated production of (O(2)(.-)). However, pretreatment with diethyl maleate (DEM; 100 mg/kg) significantly aggravated the ACN-induced GSH depletion and rise in XO activity. Furthermore, DEM significantly enhanced (O(2)(.-)) and MDA production.

CONCLUSIONS

The present study indicates that enhancement of XO activity could be implicated in ACN-induced gastric damage in rats.

Facing the key workplace challenge: assessing and preventing exposure to nanoparticles at source

Nanomaterials present new challenges to understanding, predicting, and managing potential health risks in occupational environments. In this study, we characterize the key physical processes related to formation and growth of nanoparticles. The main focus is on various occupational environments, as these are known to be major environments with nanoparticles in indoor air. The protection of people potentially to be exposed to nanoparticles is one of the key issues in terms of risk assessment and prevention. Two of the main protection techniques that are discussed and characterized are ventilation and filtration, which are widely used in practical applications.

Weight-of-the-evidence review of acrylonitrile reproductive and developmental toxicity studies

Risk assessment of acrylonitrile (AN) toxicity to humans has focused on potential carcinogenicity and acute toxicity. Epidemiological studies from China reported reproductive and developmental effects in AN workers, including infertility, birth defects, and spontaneous abortions. A weight-of-the-evidence (WoE) evaluation of the AN database assessed study strength, characterized toxicity, and identified no-observed-adverse-effect levels (NOAELs). The epidemiological studies do not demonstrate causality and are not sufficiently robust to be used for risk assessment. Rodent developmental studies showed fetotoxicity and malformations at maternally toxic levels; there was no unique developmental susceptibility. NOAELs for oral and inhalation exposures were 10 mg/kg/day and 12 ppm (6 h/day), respectively. Drinking-water and inhalation reproductive toxicity studies showed no clear effects on reproductive performance or fertility. Maternally toxic concentrations caused decreased pup growth. The drinking-water reproductive NOAEL was 100 ppm (moderate confidence due to study limitations). The inhalation exposure reproductive and neonatal toxicity high confidence NOAEL was 45 ppm (first generation 90 ppm) (6 h/day). The inhalation reproductive toxicity study provides the most robust data for risk assessment. Based on the WoE evaluation, AN is not expected to be a developmental or reproductive toxicant in the absence of significant maternal toxicity.

Sensitivity of mouse lung fibroblasts heterozygous for GPx4 to oxidative stress

Phospholipid hydroperoxide glutathione peroxidase (GPx4) is a member of the family of selenium-dependent enzymes that catalyze the reduction of cell membrane-bound phospholipid hydroperoxides in situ and thus protects against membrane damage. Overexpression of GPx4 protects cultured cells from phosphatidylcholine hydroperoxide (PCOOH)-induced loss of mitochondrial membrane potential and blocks cell death induced by treatment with various apoptotic agents. We have generated mice that are heterozygous for a GPx4 null allele (GPx4 +/-); the homozygous null genotype is embryonic lethal. We report that cultured lung fibroblasts (LFs) isolated from adult GPx4 +/- mice had approximately 50% of the GPx4 activity of LFs from GPx4 +/+ mice and were significantly more susceptible to H2O2, cadmium, and cumene hydroperoxide-induced cytotoxicity, as measured by neutral red assay. Both GPx4 +/+ and GPx4 +/- LFs were susceptible to PCOOH-induced cytotoxicity at a high PCOOH concentration. We also found that GPx4 +/- LFs have lower mitochondrial membrane potential, greater cardiolipin oxidation, and lower amounts of reduced thiols relative to GPx4 +/+ LFs, but are more resistant than GPx4 +/+ LFs to further decrements in these endpoints following PCOOH treatment. These results suggest that adult lung fibroblasts deficient in GPx4 may have upregulated compensatory mechanisms to deal with the highly oxidized environment in which they developed.

Comparative developmental toxicities of aliphatic nitriles: in vivo and in vitro observations

The effects on embryonic development of a series of eight saturated (acetonitrile, propionitrile, and n-butyronitrile) and unsaturated (acrylonitrile, methacrylonitrile, allylnitrile, cis-2-pentenenitrile, and 2-chloroacrylonitrile) nitriles were compared in vitro using the whole embryo culture system. Day 10 rat embryos were cultured for 46 h in rat serum in the presence of either of these chemicals. All the tested chemicals produced concentration-dependent decreases in growth and differentiation and increases in the incidences of morphologically abnormal embryos. A wide range of embryotoxic potency was observed, with 2-chloroacrylonitrile and acetonitrile at the extremes (lowest effect levels of 50 microM and 40 mM, respectively). No common pattern could be drawn for all the eight nitriles tested in vitro, although there were some similarities between the malformations elicited by propionitrile and n-butyronitrile or between those elicited by the five unsaturated nitriles. Presence of a rat hepatic microsomal fraction and NADPH in the culture medium enhanced the embryotoxic effects of the five unsaturated nitriles tested but had no effects on saturated nitriles embryotoxicity. In addition to these in vitro experiments, pregnant rats were given a single oral dose of each compound on Day 10 of gestation and the embryos were evaluated on Day 12 of gestation, i.e., at a time of development corresponding to the developmental stage at the end of the whole embryo culture. All the nitriles investigated produced the characteristic defects developed by embryos exposed to sodium cyanide in utero or in culture. Our results provide further evidence that maternal production of cyanide may contribute to the developmental toxicity of saturated and unsaturated nitriles and suggest that distinct metabolites derived from microsomal metabolism of unsaturated nitriles may also play a role.

Mutagenicity, carcinogenicity, and teratogenicity of acrylonitrile

Acrylonitrile (AN) is an important intermediary for the synthesis of a variety of organic products, such as artificial fibres, household articles and resins. Although acute effects are the primary concern for an exposure to AN, potential genotoxic, carcinogenic and teratogenic risks of AN have to be taken seriously in view of the large number of workers employed in such industries and the world-wide population using products containing and possibly liberating AN. An understanding of the effect of acrylonitrile must be based on a characterization of its metabolism as well as of the resulting products and their genotoxic properties. Tests for mutagenicity in bacteria have in general been positive, those in plants and on unscheduled DNA synthesis doubtful, and those on chromosome aberrations in vivo negative. Wherever positive results had been obtained, metabolic activation of AN appeared to be a prerequisite. The extent to which such mutagenic effects are significant in man depends, however, also on the conditions of exposure. It appears from the limited data that the ultimate mutagenic factor(s), such as 2-cyanoethylene oxide, may have little opportunity to act under conditions where people are exposed because it is formed only in small amounts and is rapidly degraded. The carcinogenic action of AN has been evaluated by various agencies and ranged from 'reasonably be anticipated to be a human carcinogen' to 'cannot be excluded', the most recent evaluation being 'possibly carcinogenic to humans'. Animal data that confirm the carcinogenic potential of AN have certain limitations with respect to the choice of species, type of tumors and length of follow up. Epidemiological studies which sometimes, but not always, yielded positive results, encounter the usual difficulties of confounding factors in chemical industries. Exposure of workers to AN should continue to be carefully monitored, but AN would not have to be considered a cancer risk to the population provided limitations on releases from consumer products and guidelines on AN in water and air are enforced. AN is teratogenic in laboratory animals (rat, hamster) at high doses when foetal/embryonic (and maternal) toxicity already is manifest. Pregnant workers should not be exposed to AN. In view of the small concentrations generally encountered outside plants, women not professionally exposed would appear not to be at risk of teratogenic effects due to AN. Future research should concentrate on the elucidation of the different degradation pathways in man and on epidemiological studies in workers including pregnant women, assessing also, if possible, individual exposure by bio-monitoring.

Biochemical toxicology of chemical teratogenesis

Although exposure during pregnancy to many drugs and environmental chemicals is known to cause in utero death of the embryo of fetus, or initiate birth defects (teratogenesis) in the surviving offspring, surprisingly, little is known about the underlying biochemical and molecular mechanisms, or the determinants of teratological susceptibility, particularly in humans. In vitro and in vivo studies based primarily on rodent models suggest that many potential embryotoxic xenobiotics are actually proteratogens that must be bioactivated by enzymes such as the cytochromes P450 and peroxidases such as prostaglandin H synthase to teratogenic reactive intermediary metabolites. These reactive intermediates generally are electrophiles or free radicals that bind covalently (irreversibly) to, or directly of indirectly oxidize, embryonic cellular macromolecules such as DNA, protein, and lipid, irreversibly altering cellular function. Target oxidation, known as oxidase stress, often appears to be mediated by reactive oxygen species (ROS) such as hydroxyl radicals. The precise nature of the teratologically relevant molecular targets remains to be established, as do the relative conditions of the various types of macromolecular lesions. Teratological suseptibility appears to be determined in part by a balance among pathways of maternal xenobiotic elimination, embryonic xenobiotic bioactivation and detoxification of the xenobiotic reactive intermediate, direct and indirect pathways for the detoxification of ROS (cytoprotection), and repair of macromolecular lesions. Due largely to immature or otherwise compromised embryonic pathways for detoxification, Cytoprotection, and repair, the embryo is relatively susceptible to reactive intermediates, and teratogenesis via this mechanism can occur from exposure to therapeutic concentrations of drugs, or supposedly safe concentrations of environmental chemicals. Greater insight into the mechanisms involved in human reactive intermediate-mediated teratogenicity, and the determinants of individual teratological susceptibility, will be necessary to reduce the unwarranted embryonic attrition from xenobiotic exposure.