International audience | Telomeres are non-coding DNA repeats located at the termini of eukaryotic chromosomes, regulated by dynamic processes balancing shortening and maintenance. Despite a mechanism to slow-down telomere shortening, cell division leads to progressive attrition of chromosomes, leading to the onset of cellular senescence or apoptosis. However, telomere restoration based on telomerase activity is the primary mechanism for telomere maintenance. Telomere length is associated to health and survival and can be impacted by a broad panel of environmental factors. However, the effect of contaminants on telomeres is poorly known for living organisms. The aim of this study was to investigate relationships between some poly- and perfluoroalkyl substances (PFASs), body condition and telomere length by using both a cross-sectional and longitudinal approach in adult breeding Black-legged kittiwakes (Rissa tridactyla) from Svalbard. First, we examined the associations between absolute telomere length and PFASs contamination in a given year (cross-sectional approach). Second, we investigated the relationships between telomere dynamics and PFASs contamination within a two years’ time frame (longitudinal approach). Our results did not show any significant relationships of PFASs and body condition with absolute telomere length in a given year. Surprisingly, we found a positive and significant relationship between PFASs and telomere dynamics in both sexes with elongated telomere in birds bearing the highest concentrations of PFASs. Our study underlines (i) the need to investigate PFAS effects on telomere dynamics with a longitudinal approach and (ii) a potential positive effect of these contaminants on telomere length, with the most contaminated birds showing the slowest rate of telomere shortening or even displaying elongated ones. Our study is the first to report a relationship between PFASs and telomere length in free-living vertebrates. A possible underlying mechanism and other potential confounding factors are discussed.

International audience | Cephalopod beaks found in the diet of predators have been amajor source of scientific information. In this study,we evaluated the usefulness of DNA and contaminants analysis (total mercury — T-Hg) in cephalopod beaks inorder to assess their applicability as tools in marine ecology studies. We concluded that, when applying DNAtechniques to cephalopod beaks from Antarctic squid species, when using flesh attached to those beaks, it waspossible to obtain DNA and to successfully identify cephalopod species; DNA was not found on the beaks themselves.This study also showed that it is possible to obtain information on T-Hg concentrations in beaks: the T-Hgconcentrations found in the beaks were 6 to 46 times lower than in the flesh of the same cephalopod species.More research on the relationships of mercury concentrations in cephalopod beaks (and other tissues), intraandinter-specifically, are needed in the future.

Lead (Pb) exposure can induce DNA damage and alter DNA methylation but their inter-relationships have not been adequately determined. Our overall aims were to explore such relationships and to evaluate underlying epigenetic mechanisms of Pb-induced genotoxicity in Chinese workers. Blood Pb levels (BLLs) were determined and used as individual's Pb-exposure dose and the Comet assay (i.e., % tail DNA) was conducted to evaluate DNA damage. In the screening assay, 850 K BeadChip sequencing was performed on peripheral blood from 10 controls (BLLs ≤100 μg/L) and 20 exposed workers (i.e., 10 DNA-damaged and 10 DNA-undamaged workers). Using the technique, differentially methylated positions (DMPs) between the controls and the exposed workers were identified. In addition, DMPs were identified between the DNA-undamaged and DNA-damaged workers (% tail DNA >2.14%). In our validation assay, methylation levels of four candidate genes were measured by pyrosequencing in an independent sample set (n = 305), including RRAGC (Ras related GTP binding C), USP1 (Ubiquitin specific protease 1), COPS7B (COP9 signalosome subunit 7 B) and CHEK1 (Checkpoint kinase 1). The result of comparisons between the controls and the Pb-exposed workers show that DMPs were significantly enriched in genes related to nerve conduction and cell cycle. Between DNA-damaged group and DNA-undamaged group, differentially methylated genes were enriched in the pathways related to cell cycle and DNA integrity checkpoints. Additionally, methylation levels of RRAGC and USP1 were negatively associated with BLLs (P < 0.05), and the former mediated 19.40% of the effect of Pb on the % tail DNA. These findings collectively indicated that Pb-induced DNA damage was closely related to methylation of genes in cell cycle regulation, and methylation levels of RRAGC were involved in Pb-induced genotoxicity.

We investigated the biological response of soluble organic fraction (SOF) and water-soluble fraction (WSF) extracted from particulate matter (PM) emitted by an automotive diesel engine operating in a representative urban driving condition. The engine was fueled with ultra-low sulfur diesel (ULSD), and its binary blends by volume with 13% of butanol (Bu13), and with hydrotreated vegetable oil (HVO) at 13% (HVO13) and 20% (HVO20). Cytotoxicity, genotoxicity, oxidative DNA damage and ecotoxicity tests were carried out, and 16 polycyclic aromatic hydrocarbons (PAH) expressed as tbenzo(a)pyrene total toxicity equivalent (BaP-TEQ) were also analyzed. The Hepatocarcinoma epithelial cell line (HepG2) was exposed to SOF for 24 h and analyzed using comet assay, with the inclusion of formamidopyrimidine DNA glycosylase (FPG) and endonuclease III (Endo III) to recognize oxidized DNA bases. The WSF was evaluated through acute ecotoxicity tests with the aquatic microcrustacean Daphnia pulex (D. Pulex). Results showed that there was no cytotoxic activity for all tested SOF concentrations. Genotoxic responses by all the SOF samples were at same level, except for the HVO13 which was weaker in the absence of the enzymes. The addition of the FPG and Endo III enzymes resulted in a significant increase in the comet tail, indicating that the DNA damage from SOF for all tested fuel blends involves oxidative damage including a higher level of oxidized purines for ULSD and Bu13 in comparison with HVO blends, but the oxidized pyrimidines for HVO blends were slightly higher compared to Bu13. The WSF did not show acute ecotoxicity for any of the fuels. Unlike other samples, Bu13-derived particles significantly increase the BaP-TEQ. The contribution to the genotoxic activity and oxidative DNA from SOF was not correlated to BaP-TEQ, which means that the biological activity of PM might be affected also by other toxic compounds present in particulate phase.

Tetrabromobisphenol A (TBBPA), which is the most widely employed brominated flame retardant, and its alternative tetrachlorobisphenol A (TCBPA) are widely distributed in aquatic environments. In the present study, the hepatotoxicity induced by TBBPA and TCBPA was investigated in Rana nigromaculata, and the potential mechanisms were investigated with a particular focus on ROS (reactive oxygen species) -dependent mitochondria-mediated apoptosis. Healthy adult frogs were exposed to 0, 0.001, 0.01, 0.1, and 1 mg/L waterborne TBBPA and TCBPA for 14 days. The results showed that liver weight was significantly increased by 51.52%–98.99% in the 0.01, 0.1, and 1 mg/L TBBPA and TCBPA groups relative to the control. Histological examination revealed that the structure of the liver, to some extent, was influenced by TBBPA and TCBPA with nuclear shrinkage and mitochondrial swelling. Meanwhile, TBBPA and TCBPA have significantly increased the alanine transaminase level in serum and the content of ROS, while inhibiting the activity of superoxide dismutase in the liver. In addition, DNA fragments were observed in the TBBPA and TCBPA groups relative to the control. Expression of Cytochrome C was significantly increased by 1.13-, 1.38-, 1.60-, and 2.46-fold in 0.001, 0.01, 0.1, and 1 mg/L TBBPA, and by 1.26-, 1.51-, 2.14-, and 2.98- fold in 0.001, 0.01, 0.1, and 1 mg/L TCBPA, respectively, which indicated that TCBPA may be more toxic than TBBPA. Similarly, the ratio of Bax/Bcl-2 was increased in a dose-dependent manner. These results indicated that apoptosis in the ROS-dependent mitochondrial pathway mediates hepatotoxicity caused by TBBPA and TCBPA. The present study will facilitate an understanding of the toxicity mechanism of flame retardants.

Exposure to outdoor fine particulate matter (PM₂.₅)-bound polycyclic aromatic hydrocarbons (PAHs) is linked to reproductive dysfunction. However, it is unclear which component of PAHs is responsible for the adverse outcomes. In the Male Reproductive Health in Chongqing College Students (MARHCS) cohort study, we measured the exposure levels of 16 PAHs by collecting air PM₂.₅ particles and assessed eight PAHs metabolites from four parent PAHs, including naphthalene, fluorene, phenanthrene, and pyrene in urine samples. We investigated compositional profiles and variation characteristics for 16 PAHs in PM₂.₅, and then assessed the association between PAHs exposure and semen routine parameters, sperm chromatin structure, and serum hormone levels in 1452 samples. The results showed that naphthalene (95% CI: −17.989, −8.101), chrysene (95% CI: −64.894, −47.575), benzo[a]anthracene (95% CI: −63.227, −45.936) and all the high molecular weight (HMW) PAHs in PM₂.₅ were negatively associated with sperm normal morphology. Most of the low molecular weight (LMW) PAHs, such as acenaphthylene, fluorene, phenanthrene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, ∑LMW PAHs and ∑16 PAHs, were correlated with increased sperm motility (all corrected P < 0.05). On the other hand, sperm normal morphology was all negatively associated with urinary metabolites of ∑OH-Nap (95% CI: −5.611, −0.536), ∑OH-Phe (95% CI: −5.741, −0.957), and ∑OH-PAHs (95% CI: −5.274, −0.361). Urinary concentrations of ∑OH-PAHs were found to be negatively associated with sperm high DNA stainability (HDS) (P = 0.023), while ∑OH-Phe were negatively associated with serum testosterone level and sperm HDS (P = 0.004). Spearman correlation analysis showed that except for the urinary OH-Nap metabolites, the rest of the urinary OH-PAHs metabolites were negatively correlated with their parent PAHs in air. The results of this study suggest that various PAHs’ components may affect reproductive parameters differently. Inhalation of PAHs in air, especially HMW PAHs, may be a potential risk factor for male reproductive health.

The number of deaths from air pollution worldwide is estimated at 8.8 million per year, more than the number of deaths from smoking. Air pollutants, such as PM₂.₅, are known to induce respiratory and cardiovascular diseases by inducing oxidative stress. Thioredoxin (Trx) is a 12-kDa endogenous protein that exerts antioxidant activity by promoting dithiol disulfide exchange reactions. We previously synthesized human serum albumin-fused thioredoxin (HSA-Trx), which has a longer half-life in plasma compared with Trx, and demonstrated its efficacy against various diseases including respiratory diseases. Here, we examined the effect of HSA-Trx on urban aerosol-induced lung injury in mice. Urban aerosols induced lung injury and inflammatory responses in ICR mice, but intravenous administration of HSA-Trx markedly inhibited these responses. We next analyzed reactive oxygen species (ROS) production in murine lungs using an in vivo imaging system. The results show that intratracheal administration of urban aerosols induced ROS production that was inhibited by intravenously administered HSA-Trx. Finally, we found that HSA-Trx inhibited the urban aerosol-induced increase in levels of neutrophilic extracellular trap (NET) indicators (i.e., double-stranded DNA, citrullinated histone H3, and neutrophil elastase) in bronchoalveolar lavage fluid (BALF). Together, these findings suggest that HSA-Trx prevents urban aerosol-induced acute lung injury by suppressing ROS production and neutrophilic inflammation. Thus, HSA-Trx may be a potential candidate drug for preventing the onset or exacerbation of lung injury caused by air pollutants.

The overnight stagnation of tap water in plumbing systems can lead to water quality deterioration. Meanwhile, the indoor heating can improve the indoor temperature in cold areas during winter, which may affect the quality of tap water during stagnation. However, indoor heating drives bacterial ecological links with tap water stagnation during winter are not well understood. The results indicated that the water temperature increased significantly after stagnation during indoor heating periods. Moreover, the average intact cell number and total adenosine triphosphate (ATP) concentration increased 1.53-fold and 1.35-fold after stagnation, respectively (P < 0.01). In addition, the increase in the ATP per cell number indicated that the combined effects of stagnation and indoor heating could enhance the bacterial activity. Biolog data showed that the bacterial community metabolic capacity was significantly higher in stagnant water than that of fresh water. Co-occurrence networks suggested that the bacterial metabolic profile changed after stagnation during the heating periods. DNA analysis indicated that the composition of the bacterial community changed dramatically after stagnation. The abundances of potential pathogens such as Mycobacterium sp. and Pseudomonas sp. also increased after stagnation. These results will give novel insights on comprehensive understanding the combined effects of indoor heating and overnight stagnation on the water bacterial community ecology of plumbing systems, and provide a scientific basis for tap water quality management after overnight stagnation during the indoor heating periods.

General population are concurrently and extensively exposed to many volatile organic compounds (VOCs), including some Group 1 human carcinogens, such as 1,3-butadiene. However, only a few studies assessed internal exposure levels of VOCs; particularly, very limited studies have examined associations between the urinary concentrations of multiple VOC metabolites (mVOCs) and oxidative stress biomarkers (OSBs) among the general population. In this study, 21 mVOCs and three OSBs including 8-hydroxy-2′-deoxyguanosine (8-OHdG; for DNA), 8-hydroxyguanosine (8-OHG; for RNA), and 4-hydroxy nonenal mercapturic acid (HNEMA; for lipid) were measured in 406 urine samples collected from 128 healthy adults during autumn and winter of 2018 in Wuhan, central China, including repeated samples taken in 3 d from 75 volunteers. Inter-day reproducibility for most mVOCs was good to excellent; urinary concentrations of mVOCs in winter were generally higher than those in autumn. Risk assessment was conducted by calculating hazard quotients for the parent compounds, and the results suggested that acrolein, 1,3-butadiene, and cyanide should be considered as high-priority hazardous ones for management. After false-discovery adjustment, 16 of the studied mVOCs were positively associated with 8-OHdG and 8-OHG (β values ranged from 0.04 to 0.48), and four mVOCs were positively associated with HNEMA (β values ranged from 0.21 to 0.78). Weighted quantile sum regression analyses were used to assess associations of mVOC mixture and OSBs, and we found significantly positive associations between the mixture index and OSBs, among which the strongest mVOC contributors for the associations were 2-methylhippuric acid for both DNA (20%) and RNA (17%) oxidative damage, and trans,trans-muconic acid (50%) for lipid peroxidation. This study firstly reported good to excellent short-term reproducibility, seasonal difference in autumn and winter, and possible health risk in urinary concentrations of multiple mVOCs among the general population.

Dichlorodiphenyltrichloroethane (DDT) poses a significant health risk to humans which is associated with genomic DNA hypomethylation. However, the mechanism and biological consequences remain poorly understood. In vitro assays confirmed that the DDT metabolites 2,2-bis(p-chlorophenyl)-acetic acid (DDA) and 1-chloro-2,2-bis-(p-chlorophenyl)ethylene (DDMU), but not other DDT metabolites, significantly inhibited DNA methyltransferase 1 (DNMT1) activity, leading to genomic hypomethylation in cell culture assays. DNMT1 as a target for DNA hypomethylation induced by DDT metabolites was also confirmed using cell cultures in which DNMT1 was silenced or highly expressed. DDA and DDMU can modify methylation markers in the promoter regions of sexual development-related genes, and change the expression of Sox9 and Oct4 in embryonic stem cells. Molecular docking indicated that DDA and DDMU bound to DNMT1 with high binding affinity. Molecular dynamic simulation revealed that DDA and DDMU acted as allosteric modulators that reshaped the conformation of the catalytic domain of DNMT1. These findings provide a new insight into DDT-induced abnormalities in sexual development and demonstrate that selective binding to DNMT1 by DDA and DDMU can interfere with human DNMT1 activity and regulate the expression of the Sox9 and Oct4 genes.