Multigenerational effects and mutagenicity of three flame retardants on germ cells in Caenorhabditis elegans.

Flame retardants (FRs) have raised public concerns because of their environmental persistence and negative impacts on human health. Recent evidence has revealed that many FRs exhibit reproductive toxicities and transgenerational impacts, whereas the toxic effects of FRs on germ cells remain barely explored. Here we investigated the multigenerational effects of three flame retardants (TBBPA, TCEP and TCPP) on germ cell development in Caenorhabditis elegans, and examined the germ cell mutagenicity of these FRs by using whole genome sequencing. Parental exposure to three FRs markedly increased germ cell apoptosis, and impeded oogenesis in F1-F6 offspring. In addition, the double-increased mutation frequencies observed in progeny genomes uncover the mutagenic actions of FRs on germ cells. Analysis of mutation spectra revealed that these FRs predominantly induced point mutations at A:T base pairs, whereas both small and large indels were almost unaffected. These results revealed the long-term effects of FRs on development and genomic stability of germ cells, which may pose risks to environmental organisms and human reproductive health. Taken together, our findings suggest that germ cell mutagenicity should be carefully examined for the environmental risk assessment of FRs and other emerging pollutants.

Microplastics released from disposable medical devices and their toxic responses in Caenorhabditis elegans.

Owing to accelerated urbanization and industrialization, many plastic products have been manufactured and discharged into the environment, causing environmental and public health problems. Plastics in environmental media are further degraded by prolonged exposure to light, heat, mechanical friction, and other factors to form new pollutants called microplastics (MPs). Medical plastics have become a crucial source of plastics in environmental media. However, the release profiles of MPs from medical plastics and their potential ecological and health risks remain unclear. We used optical photothermal infrared spectroscopy to explore the release profiles of eight typical disposable medical devices under high-temperature steam disinfection (HSD). We also evaluated the toxicity of disposable medical devices-derived MPs in Caenorhabditis elegans (C. elegans). Our results showed that the changes in the surface morphology and modification of the disposable medical devices were mainly associated with the material. Polypropylene (PP) and polystyrene (PS) materials exhibited high aging phenomena (e.g., bumps, depressions, bulges and cracks), and HSD broke their oxygen-containing functional groups and carbon chains. By contrast, minor changes in the chemical and physical properties were observed in the polyvinyl chloride (PVC)-prepared disposable medical devices under the same conditions. Further physicochemical characterization indicated that the amount of MPs released from PP-prepared disposable medical devices (P4: 1.27 ± 0.34 × 106) was greater than that from PVC-prepared disposable medical devices (P7: 1.08 ± 0.14 × 105). The particle size of the released MPs was the opposite, PVC-prepared disposable medical devices (P7: 11.45 ± 1.79 µm) > PP-prepared disposable medical devices (P4: 7.18 ± 0.52 µm). Toxicity assessment revealed that disposable medical devices-released MPs significantly increased germ cell apoptosisin C. elegans. Moreover, MPs from PP-prepared disposable medical devices disrupted the intestinal barrier of worms, decreasing their lifespan. Our findings provided novel information regarding the profiles and mechanisms of MP release from disposable medical devices and revealed their potential risks to ecological environment.

Evaluation of toxicity and mutagenicity of oxaliplatin on germ cells in an alternative in vivo model Caenorhabditis elegans.

The platinum compound oxaliplatin is a widely used chemotherapeutic drug that shows a broad spectrum of activity in various human tumors. While the treatment-related side effects of oxaliplatin on directly treated individuals have been well-documented, little is known about the influence of oxaliplatin on germ cells and non-exposed progenies. Here we investigated the reproductive toxicity of oxaliplatin in a 3R-compliant in vivo model Caenorhabditis elegans, and evaluated the germ cell mutagenicity of oxaliplatin by using whole genome sequencing. Our results indicated that oxaliplatin treatment significantly disrupts development of spermatids and oocytes. By treating parental worms with oxaliplatin for three successive generations, sequencing data unveiled the mutagenic effects of oxaliplatin on germ cells. Analysis of genome-wide mutation spectra showed the preferentially induction of indels by oxaliplatin. In addition, we uncovered the involvement of translesion synthesis polymerase ζ in modulating mutagenic effects of oxaliplatin. These findings suggest that germ cell mutagenicity is worthy of consideration for the health risk assessment of chemotherapeutic drugs, while the combined use of alternative in vivo models and next generation sequencing technology appears to be a promising way for the preliminary safety assessment of various drugs.

Effects of moderate static magnetic fields on the lipogenesis and lipolysis in different genders of Caenorhabditis elegans.

With the rapid development of magnetic technology, the biological effects of moderate static magnetic fields (SMFs) have attracted increasing research interest due to their potential medical diagnosis and treatment application. The present study explored the effects of moderate SMFs on the lipid metabolism of Caenorhabditis elegans (C. elegans) in different genders including male, female, and hermaphrodite. We found that the fat content was significantly decreased by moderate SMFs in wild-type N2 worms, which was associated with their development stages. The diameters of lipid droplets in N2 worms, him-5 worms, and fog-2 worms were greatly decreased by 19.23%, 15.38%, and 23.07% at young adult stage under 0.5 T SMF, respectively. The mRNA levels of lipolysis related genes atgl-1 and nhr-76 were significantly up-regulated by SMF exposure, while the mRNA levels of the lipogenesis related genes fat-6, fat-7, and sbp-1 were down-regulated by SMF, whereas the concentration of ß-oxidase was increased. There was a slight effect of SMF on the mRNA levels of ß-oxidation related genes. Moreover, the insulin and serotonin pathway were regulated by SMF, instead of the TOR pathway. In wild-type worms, we found that their lifespan was prolonged by exposure to 0.5 T SMF. Our data suggested that moderate SMFs could significantly modify the lipogenesis and lipolysis process in C. elegans in a gender and development stage-dependent manner, which could provide a novel insight into understanding the function of moderate SMFs in living organisms.

Multiple generation exposure to ZnO nanoparticles induces loss of genomic integrity in Caenorhabditis elegans.

Zinc oxide nanoparticles (ZnO NPs) are commonly used in industrial and household applications, prompting the assessment of their associated health risks. Previous studies indicated that ZnO NPs can induce somatic cell mutations, while the aging process appears to increase the mutagenicity of ZnO NPs. However, little is known about the influence of ZnO NPs on genome stability of germ cells, and non-exposed progeny. Here we show that 20 nm ZnO NPs exposure disrupts germ cell development, and elevates the overall mutation frequency of germ cells in Caenorhabditis elegans (C. elegans). We observed that pristine ZnO NPs elicit germ cell apoptosis to a greater extent than the 60-day aged ZnO NPs. By treating parental worms with ZnO NPs for seven successive generations, whole-genome sequencing data revealed that, although the frequency of point mutations is kept unchanged, large deletions are significantly increased in F8 worms. Furthermore, we found that the mutagenicity of ZnO NPs might be partially attributed to the release of Zn2+ ions. Together, our results demonstrate the genotoxic effects of ZnO NPs on germ cells, and the possible underlying mechanism. These findings suggest that germ cell mutagenicity is worthy of consideration for the health risk assessment of engineered NPs.

Whole-Genome Sequencing Reveals Germ Cell Mutagenicity of α-Endosulfan in Caenorhabditis elegans.

Endosulfan is an extensively used organochlorine pesticide around the world, which was classified as a persistent organic pollutant (POP) in 2009. Although previous studies have documented the reproductive toxicity of endosulfan in a variety of organisms, little is known about the influence of endosulfan on the genome stability of germ cells and nonexposed progeny. Here we applied whole-genome sequencing to explore the germ cell mutagenicity of α-endosulfan in Caenorhabditis elegans (C. elegans). We found that, although low doses of α-endosulfan exhibited a minor effect on the reproductive capacity of C. elegans, chronic exposure to 1 µM α-endosulfan significantly increased the mutation frequencies of nonexposed progeny. Further analysis of genome-wide mutation spectra demonstrated that α-endosulfan preferentially elicited A:T → G:C substitutions and clustered mutations. By using worms deficient in DNA damage response genes, our results suggest the involvement of translesion synthesis polymerase η in modulating α-endosulfan-induced mutations in germ cells. Together, these observations reveal the germ cell mutagenicity of α-endosulfan in C. elegans and the possible underlying mechanism. In addition, our findings implicate that germ cell mutagenicity might be a necessary consideration for the health risk assessment of environmental chemicals such as POPs.

Moderate intensity of static magnetic fields can alter the avoidance behavior and fat storage of Caenorhabditis elegans via serotonin.

Man-made static magnetic fields (SMFs) widely exist in human life as a physical environmental factor. However, the biological responses to moderate SMFs exposure and their underlying mechanisms are largely unknown. The present study was focused on exploring the nervous responses to moderate-intensity SMFs at 0.5 T and 1 T in Caenorhabditis elegans (C. elegans). We found that SMFs at either 0.5 T or 1 T had no statistically significant effects on the locomotor behaviors, while the 1 T magnetic field increased pharyngeal pumping. The avoidance behavior of the pathogenic Pseudomonas aeruginosa was greatly decreased in either 0.5 T or 1 T SMFs exposed nematodes, and the learning index was reducede from 0.52 ± 0.11 to 0.23 ± 0.17 and 0.16 ± 0.11, respectively. The total serotonin level was increased by 17.08% and 16.45% with the treatment of 0.5 T and 1 T SMF, compared to the control group; however, there were minimal effects of SMFs on other three neurotransmitters including choline, γ-aminobutyric acid (GABA), dopamine. RT-qPCR was used to further investigate the expression of serotonin-related genes, including rate-limiting enzymes, transcription factors and transport receptors. The expression levels of tph-1 and unc-86 genes were increased by SMF exposure, while those of ocr-2, osm-9, ser-1 and mod-1 genes were decreased. With the staining of lipid in either wild-type N2 or tph-1 mutants, we found that 0.5 T and 1 T SMFs decreased fat storage in C. elegans via serotonin pathway. Our study demonstrated that moderate-intensity SMFs induced neurobehavioral disorder and the reduction of fat storage by disturbing the secretion of serotonin in C. elegans, which provided new insights into elucidating nervous responses of C. elegans to moderate-intensity SMFs.