DNA methylation 6 mA and histone methylation involved in multi-/trans-generational reproductive effects in Caenorhabditis elegans induced by Atrazine

Mycotoxin zearalenone induces multi-/trans-generational toxic effects and germline toxicity transmission via histone methyltransferase MES-4 in Caenorhabditis elegans

Zearalenone (ZEN), an endocrine-disrupting mycotoxin, is prevalent and persists in the environment. ZEN has the potential to cause adverse health impacts extending over generations, yet there is a lack of relevant research. Therefore, we explored the ZEN-induced multi-/trans-generational locomotive and reproductive toxicities, as well as the underlying epigenetic mechanisms in Caenorhabditis elegans. In multi-generational analysis, the evolution tendency and toxicity latency were observed under sustained exposure to 0.1 and 1 μM ZEN across five generations (P0-F4). The toxic effects were found in filial generations even if the initial parental exposure showed no apparent effects. Trans-generational results indicated the toxic inheritance phenomenon of 10 and 50 μM ZEN, where a single generation of ZEN exposure was sufficient to affect subsequent generations (F1-F3). Additionally, the pattern of locomotion was relatively sensitive in both generational studies, indicating varying sensitivity between indicators. Regarding epigenetic mechanism of toxicity transmission, ZEN significantly decreased the parental expression of histone methyltransferase encoded genes set-2, mes-2, and mes-4. Notably, the downregulation of mes-4 persisted in the unexposed F1 and F2 generations under trans-generational exposure. Furthermore, the mes-4 binding and reproduction-related rme-2 also decreased across generations. Moreover, parental germline specific knockdown of mes-4 eliminated the inherited locomotive and reproductive toxic effects in offspring, showing that mes-4 acted as transmitter in ZEN-induced generational toxicities. These findings suggest that ZEN is an epigenetic environmental pollutant, with a possible genetic biomarker mes-4 mediating the germline dependent transmission of ZEN-triggered toxicity over generations. This study provides significant insights into ZEN-induced epigenotoxicity.

Transgenerational reproductive toxicity induced by carboxyl and amino charged microplastics at environmental concentrations in Caenorhabditis elegans: Involvement of histone methylation

Microplastics, recognized as emerging contaminants, are commonly observed to be charged in the environment, potentially exerting toxic effects on various organisms. However, the transgenerational reproductive toxicity and underlying mechanisms of polystyrene (PS), particularly carboxyl-modified PS (PS-COOH) and amino-modified PS (PS-NH2), remain largely unexplored. In this study, the parental generation (P0) of Caenorhabditis elegans was subjected to environmental concentrations (0.1-100 μg/L) of PS, PS-COOH, and PS-NH2, with subsequent generations (F1-F4) cultured under normal conditions. Exposure to PS-NH2 at concentrations of 10-100 μg/L exhibited more pronounced reproductive toxicity compared to PS or PS-COOH, resulting in decreased brood size, egg ejection rate, number of fertilized eggs, and cell corpses per gonad. Similarly, maternal exposure to 100 μg/L of PS-NH2 induced more severe transgenerational reproductive effects in C. elegans. Significant increases in H3 on lysine 4 dimethylation (H3K4me2) and H3 on lysine 9 trimethylation (H3K9me3) levels were observed in the subsequent generation, concurrent with the transgenerational upregulation of set-30 and met-2 following parental exposure to PS, PS-COOH, and PS-NH2. Correlation analyses revealed significant associations between the expression of these genes with the reproductive ability. Molecular docking studies suggested that PS-NH2 exhibited higher affinity for SET-30 and MET-2. Further analysis demonstrated that transgenerational effects on reproduction were absent in set-30(gk315) and met-2(n4256) mutants, highlighting the pivotal role of set-30 and met-2 in mediating the transgenerational effect. This study provides novel insights into the environmental risks associated with negatively and positively charged microplastics.

Endocrine toxicity of atrazine and its underlying mechanisms

Atrazine (ATR) is one of the most widely utilized herbicides globally and is prevalent in the environment due to its extensive use and long half-life. It can infiltrate the human body through drinking water, ingestion, and dermal contact, and has been recognized as an environmental endocrine disruptor. This study aims to comprehensively outline the detrimental impacts of ATR on the endocrine system. Previous research indicates that ATR is harmful to various bodily systems, including the reproductive system, nervous system, adrenal glands, and thyroi d gland. The toxic effects of ATR on the endocrine system and its underlying molecular mechanisms are summarized as follows: influencing the expression of kisspeptin in the HPG axis, consequently affecting steroid synthesis; disrupting DNA synthesis and meiosis, as well as modifying DNA methylation levels, leading to reproductive and developmental toxicity; impacting dopamine by altering Nurr1, VMAT2, and DAT expression, consequently affecting dopamine synthesis and transporter expression, and influencing other neurotransmitters, resulting in neurotoxicity; and changing adipose tissue synthesis and metabolism by reducing basal metabolism, impairing cellular oxidative phosphorylation, and inducing insulin resistance. Additionally, a compilation of natural products used to mitigate the toxic effects of ATR has been provided, encompassing melatonin, curcumin, quercetin, lycopene, flavonoids, vitamin C, vitamin E, and other natural remedies. It is important to note that existing research predominantly relies on in vitro and ex vivo experiments, with limited population-based empirical evidence available.

Photoaged Polystyrene Nanoplastics Result in Transgenerational Reproductive Toxicity Associated with the Methylation of Histone H3K4 and H3K9 in Caenorhabditis elegans

Polystyrene nanoplastics (PS-NPs) are emerging environmental contaminants that are ubiquitously detected in various environments and have toxic effects on various organisms. Nevertheless, the transgenerational reproductive toxicity and underlying mechanisms of PS-NPs remain largely unknown, especially for photoaged PS-NPs under ultraviolet irradiation. In this study, only the parental generation (P0) was exposed to virgin and aged PS-NPs at environmentally relevant concentrations (0.1-100 μg/L), and subsequent generations (F1-F4) were cultured under normal conditions. Ultraviolet irradiation induced the generation of environmentally persistent free radicals and reactive oxygen species, which altered the physical and chemical characteristics of PS-NPs. The results of toxicity testing suggested that exposure to aged PS-NPs caused a more severe decrease in brood size, egg ejection rate, number of fertilized eggs, and hatchability than did the virgin PS-NPs in the P0, F1, and F2 generations. Additionally, a single maternal exposure to aged PS-NPs resulted in transgenerational effects on fertility in the F1 and F2 generations. Increased levels of H3K4 and H3K9 methylation were observed in the F1 and F2 generations, which were concomitant with the transgenerational downregulation of the expression of associated genes, such as spr-5, set-17, and met-2. On the basis of correlation analyses, the levels of histone methylation and the expression of these genes were significantly correlated to transgenerational reproductive effects. Further research showed that transgenerational effects on fertility were not observed in spr-5(by134), met-2(n4256), and set-17(n5017) mutants. Overall, maternal exposure to aged PS-NPs induced transgenerational reproductive effects via H3K4 and H3K9 methylation, and the spr-5, met-2, and set-17 genes were involved in the regulation of transgenerational toxicity. This study provides new insights into the potential risks of photoaging PS-NPs in the environment.

Polylactic acid microparticles in the range of μg/L reduce reproductive capacity by affecting the gonad development and the germline apoptosis in Caenorhabditis elegans

Polylactic acid (PLA) accounts for approximately 45% of the global market of biodegradable plastics. Using Caenorhabditis elegans as an animal model, we examined the effect of long-term exposure to PLA microplastic (MP) on reproductive capacity and the underlying mechanism. Brood size, number of fertilized eggs in uterus, and number of hatched eggs were significantly reduced by exposure to 10 and 100 μg/L PLA MP. Number of mitotic cells per gonad, area of gonad arm, and length of gonad arm were further significantly decreased by exposure to 10 and 100 μg/L PLA MP. In addition, exposure to 10 and 100 μg/L PLA MP enhanced germline apoptosis in the gonad. Accompanied with the enhancement in germline apoptosis, exposure to 10 and 100 μg/L PLA MP decreased expression of ced-9 and increased expressions of ced-3, ced-4, and egl-1. Moreover, the induction of germline apoptosis in PLA MP exposed nematodes was suppressed by RNAi of ced-3, ced-4, and egl-1, and strengthened by RNAi of ced-9. Meanwhile, we did not detect the obvious effect of leachate of 10 and 100 μg/L PLA MPs on reproductive capacity, gonad development, germline apoptosis, and expression of apoptosis related genes. Therefore, exposure to 10 and 100 μg/L PLA MPs potentially reduces the reproductive capacity by influencing the gonad development and enhancing the germline apoptosis in nematodes.

Activation of FGF signal in germline mediates transgenerational toxicity of polystyrene nanoparticles at predicted environmental concentrations in Caenorhabditis elegans

Nanoplastics in the environment could cause the ecological and health risks. Recently, the transgenerational toxicity of nanoplastic has been observed in different animal models. In this study, using Caenorhabditis elegans as an animal model, we aimed to examine the role of alteration in germline fibroblast growth factor (FGF) signal in mediating the transgenerational toxicity of polystyrene nanoparticle (PS-NP). Exposure to 1-100 μg/L PS-NP (20 nm) induced transgenerational increase in expressions of germline FGF ligand/EGL-17 and LRP-1 governing FGF secretion. Germline RNAi of egl-17 and lrp-1 resulted in resistance to transgenerational PS-NP toxicity, indicating the requirement of FGF ligand activation and secretion in formation of transgenerational PS-NP toxicity. Germline overexpression of EGL-17 increased expression of FGF receptor/EGL-15 in the offspring, and RNAi of egl-15 at F1 generation (F1-G) inhibited transgenerational toxicity of PS-NP exposed animals overexpressing germline EGL-17. EGL-15 functions in both the intestine and the neurons to control transgenerational PS-NP toxicity. Intestinal EGL-15 acted upstream of DAF-16 and BAR-1, and neuronal EGL-15 functioned upstream of MPK-1 to control PS-NP toxicity. Our results suggested the important role of activation in germline FGF signal in mediating the induction of transgenerational toxicity in organisms exposed to nanoplastics in the range of μg/L.

Paeoniflorin attenuates polystyrene nanoparticle-induced reduction in reproductive capacity and increase in germline apoptosis through suppressing DNA damage checkpoints in Caenorhabditis elegans

Due to high sensitivity to environmental exposures, Caenorhabditis elegans is helpful for toxicity evaluation and toxicological study of pollutants. Using this animal model, we investigated the reproductive toxicity of 20 nm polystyrene nanoparticle (PS-NP) in the range of μg/L and the following pharmacological intervention of paeoniflorin. After exposure from L1-larvae to young adults, 10-100 μg/L PS-NP could cause the reduction in reproductive capacity reflected by the endpoints of brood size and number of fertilized eggs in uterus. Meanwhile, the enhancements in germline apoptosis analyzed by AO staining and germline DNA damage as shown by alteration in HUS-1::GFP signals were detected in 10-100 μg/L PS-NP exposed nematodes, suggesting the role of DNA damage-induced germline apoptosis in mediating PS-NP toxicity on reproductive capacity. Following the exposure to 100 μg/L PS-NP, posttreatment with 25-100 mg/L paeoniflorin increased the reproductive capacity and inhibited both germline apoptosis and DNA damage. In addition, in 100 μg/L PS-NP exposed nematodes, treatment with 100 mg/L paeoniflorin modulated the expressions of genes governing germline apoptosis as indicated by the decrease in ced-3, ced-4, an egl-1 expressions and the increase in ced-9 expression. After exposure to 100 μg/L PS-NP, treatment with 100 mg/L paeoniflorin also decreased expressions of genes (cep-1, clk-2, hus-1, and mrt-2) governing germline DNA damage. Molecular docking analysis further demonstrated the binding potential of paeoniflorin with three DNA damage checkpoints (CLK-2, HUS-1, and MRT-2). Therefore, our data suggested the toxicity of PS-NP in the range of μg/L on reproductive capacity after exposure from L1-larvae to young adults, which was associated with the enhancement in DNA damage-induced germline apoptosis. More importantly, the PS-NP-induced reproductive toxicity on nematodes could be inhibited by the following paeoniflorin treatment.

Exposure to multi-walled carbon nanotubes causes suppression in octopamine signal associated with transgenerational toxicity induction in C.elegans

Multi-walled carbon nanotube (MWCNT), a kind of carbon-based nanomaterials, has been extensively utilized in a variety of fields. In Caenorhabditis elegans, MWCNT exposure can result in toxicity not only at parental generation (P0-G) but also in the offspring. However, the underlying mechanisms remain still largely unknown. DAF-12, a transcriptional factor (TF), was previously found to be activated and involved in transgenerational toxicity control after MWCNT exposure. In this study, we observed that exposure to 0.1-10 μg/L MWCNTs caused the significant decrease in expression of tbh-1 encoding a tyramine beta-hydroxylase with the function to govern the octopamine synthesis, suggesting the inhibition in octopamine signal. After exposure to 0.1 μg/L MWCNT, the decrease in tbh-1 expression could be also detected in F1-G and F2-G. Moreover, in germline cells, the TF DAF-12 regulated transgenerational MWCNT toxicity by suppressing expression and function of TBH-1. Meanwhile, exposure to 0.1-10 μg/L MWCNTs induced the increase in octr-1 expression and the decrease in ser-6 expression. After exposure to 0.1 μg/L MWCNT, the increased octr-1 expression and the decreased ser-6 expression were further observed in F1-G and F2-G. Germline TBH-1 controlled transgenerational MWCNT toxicity by regulating the activity of octopamine receptors (SER-6 and OCTR-1) in offspring. Furthermore, in the offspring, SER-6 and OCTR-1 affected the induction of MWCNT toxicity by upregulating or downregulating the level of ELT-2, a GATA TF. Taken together, these findings suggested possible link between alteration in octopamine related signals and MWCNT toxicity induction in offspring in organisms.