Intergenerational reproductive toxicity of chlordecone in male Caenorhabditis elegans

Early-life long-term ibuprofen exposure reduces reproductive capacity involved in spermatogenesis impairment and associated with the transcription factor DAF-5 in Caenorhabditis elegans

Pharmaceuticals and personal care products (PPCPs) are emerging environmental contaminants and have raised significant concern due to their potential adverse impact on the environment. Ibuprofen is one of the most extensively used non-steroidal anti-inflammatory drugs (NSAIDs) and is also considered an environmental contaminant. The negative impact of ibuprofen on non-target organisms has been documented; however, the molecular mechanisms behind its reproductive toxicity remain unclear. We investigated the impact of early-life long-term ibuprofen exposure on reproductive capacity and its involvement of spermiogenesis in the non-target model organism Caenorhabditis elegans. Hermaphrodites were exposed to various ibuprofen concentrations (0.1, 1, 10, and 100 mg/L), resulting in a dose-dependent inhibition of reproduction. In addition, the lowest observed adverse effect concentration (LOAEC) for ibuprofen exposure on the total brood size of C. elegans was 0.1 mg/L, a concentration that falls within the environmentally relevant range for ibuprofen. Outcross progeny assays revealed a significant 47% reduction in total brood size for larval males (him-5) exposed to ibuprofen, while females (fog-2) exhibited only a minor effect. We found that early-life long-term ibuprofen exposure impairs spermatogenesis. The number of mitotic cells significantly reduced by 31%. The rate of sperm malformation in exposed males was 63%, much higher than in unexposed males (11%). Additionally, the percentage of sperm activation decreased from 89% to 39% in ibuprofen-exposed worms. Mechanistic insights indicated that ibuprofen downregulated mRNA levels of genes related to spermatogenesis and DAF-7/TGF-β signaling. RNAi assays provided evidence for the crucial role of the transcription factor DAF-5 in mediating the spermatogenesis impairment by ibuprofen. Our study provides insight into the environmental impacts of pharmaceutical contaminants, such as ibuprofen, on both male and female reproductive systems to safeguard environmental health.

Cadmium-induced reproductive toxicity combined with a correlation to the oogenesis process and competing endogenous RNA networks based on a Caenorhabditis elegans model

Accumulation of the heavy metal Cadmium (Cd) in the ovaries and placenta can affect the structure and function of these organs and induce female reproductive toxicity. This toxicity may be due to Cd's similarity to estrogen and its ability to disrupt endocrine systems. However, the exact molecular mechanism by which Cd causes reproductive toxicity at the transcriptome level remains poorly understood. Hence, this study aimed to observe Cd-induced reproductive damage at the gene level, scrutinize the repercussions of Cd exposure on oogenesis, and explicate the putative pathogenesis of Cd-induced oogenesis based on Caenorhabditis elegans (C. elegans) as an in vivo model. The results showed that Cd exposure significantly decreased the number of offspring and prolonged the reproductive span of C. elegans. Cd exposure also reduced the number of cells in mitosis and the pachytene and diakinesis stages of meiosis, thereby disrupting oogenesis. Combined with transcriptional sequencing and bioinformatics analysis, a total of 3167 DEmRNAs were identified. Regarding gene expression, cul-6, mum-2, and vang-1 were found to be related to Cd-induced reproductive toxicity, and their competing endogenous RNA networks were constructed. We observed that mutations of mom-2 and vang-1 in the Wnt pathway could induce susceptibility to Cd-caused meiosis injury. In conclusion, the results indicated that Cd could impair the oogenesis of C. elegans and the Wnt pathway might serve as a protective mechanism against Cd reproductive toxicity. These findings contribute to a better understanding of the damaging effects and molecular biological mechanisms of Cd on the human reproductive system.

Oxidative stress and mitochondrial damage induced by a novel pesticide fluopimomide in Caenorhabditis elegans

Fluopimomide is a novel pesticide intensively used in agricultural pest control; however, its excessive use may have toxicological effects on non-target organisms. In this study, Caenorhabditis elegans was used to evaluate the toxic effects of fluopimomide and its possible mechanisms. The effects of fluopimomide on the growth, pharyngeal pumping, and antioxidant systems of C. elegans were determined. Furthermore, the gene expression levels associated with mitochondria in the nematodes were also investigated. Results indicated that fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.001) decreased body length, pharyngeal pumping, and body bends in the nematodes compared to the untreated control. Additionally, fluopimomide at 0.2, 1.0, and 5.0 mg/L notably (p < 0.05) increased the content of malondialdehyde by 3.30-, 21.24-, and 33.57-fold, respectively, while fluopimomide at 1.0 and 5.0 mg/L significantly (p < 0.001) increased the levels of reactive oxygen species (ROS) by 49.14% and 77.06% compared to the untreated control. In contrast, fluopimomide at 1.0 and 5.0 mg/L notably reduced the activities of target enzyme succinate dehydrogenase and at 5.0 mg/L reduced the activities of antioxidant enzyme superoxide dismutase. Further evidence revealed that fluopimomide at 1.0 and 5.0 mg/L significantly inhibited oxygen consumption and at 0.2, 1.0, and 5.0 mg/L significantly inhibited ATP level in comparison to the untreated control. The expression of genes related to the mitochondrial electron transport chain mev-1 and isp-1 was significantly downregulated. ROS levels in the mev-1 and isp-1 mutants after fluopimomide treatments did not change significantly compared with the untreated mutants, suggesting that mev-1 and isp-1 may play critical roles in the toxicity induced by fluopimomide. Overall, the results demonstrate that oxidative stress and mitochondrial damage may be involved in toxicity of fluopimomide in C. elegans.

Modeling, optimization and understanding of adsorption process for pollutant removal via machine learning: Recent progress and future perspectives

It is crucial to reduce the concentration of pollutants in water environment to below safe levels. Some cost-effective pollutant removal technologies have been developed, among which adsorption technology is considered as a promising solution. However, the batch experiments and adsorption isotherms widely employed at present are inefficient and time-consuming to some extent, which limits the development of adsorption technology. As a new research paradigm, machine learning (ML) is expected to innovate traditional adsorption models. This reviews summarized the general workflow of ML and commonly employed ML algorithms for pollutant adsorption. Then, the latest progress of ML for pollutant adsorption was reviewed from the perspective of all-round regulation of adsorption process, including adsorption efficiency, operating conditions and adsorption mechanism. General guidelines of ML for pollutant adsorption were presented. Finally, the existing problems and future perspectives of ML for pollutant adsorption were put forward. We highly expect that this review will promote the application of ML in pollutant adsorption and improve the interpretability of ML.

SAHmap: Synergistic-antagonistic heatmap to evaluate the combined synergistic effect of mixtures of three pesticides on multiple endpoints of Caenorhabditis elegans

The environmental pollution caused by toxic chemicals such as pesticides has become a global problem. The mixture of dichlorvos (DIC), dimethoate (DIM), aldicarb (ALD) poses potential risks to the environment and human health. To fully explore the interaction of complex mixtures on Caenorhabditis elegans behavioral toxicity endpoint. This study created a synergistic-antagonistic heatmap (SAHmap) based on the combination index to systematically describe the toxicological interaction prospect of the mixture system. It was shown that the three pesticides and their binary as well as ternary mixture rays have significant concentration-response relationship on three behavioral endpoints of nematodes, From the perspective of synergistic-antagonistic heatmaps, all the mixture rays in the DIC-DIM mixture system showed strong synergism on the three behavioral and lethal endpoints. In the ternary mixture system, the five mixture rays showed different interaction between the behavioral endpoint and the lethal endpoint, and showed slight synergism to two behavioral endpoints as a whole. The emergence of synergism should arouse our attention to these hazardous chemicals. In addition, the use of SAHmap and the significant linear correlation among three behavioral endpoints further improved the efficiency of the study on the behavioral toxicity of pesticide mixtures to Caenorhabditis elegans.

Review of the toxicity and potential molecular mechanisms of parental or successive exposure to environmental pollutants in the model organism Caenorhabditis elegans

Environmental pollutants such as heavy metals, nano/microparticles, and organic compounds have been detected in a wide range of environmental media, causing long-term exposure in various organisms and even humans through breathing, contacting, ingestion, and other routes. Long-term exposure to environmental pollutants in organisms or humans promotes exposure of offspring to parental and environmental pollutants, and subsequently results in multiple biological defects in the offspring. This review dialectically summarizes and discusses the existing studies using Caenorhabditis elegans (C. elegans) as a model organism to explore the multi/transgenerational toxicity and potential underlying molecular mechanisms induced by environmental pollutants following parental or successive exposure patterns. Parental and successive exposure to environmental pollutants induces various biological defects in C. elegans across multiple generations, including multi/transgenerational developmental toxicity, neurotoxicity, reproductive toxicity, and metabolic disturbances, which may be transmitted to progeny through reactive oxygen species-induced damage, epigenetic mechanisms, insulin/insulin-like growth factor-1 signaling pathway. This review aims to arouse researchers' interest in the multi/transgenerational toxicity of pollutants and hopes to explore the possible long-term effects of environmental pollutants on organisms and even humans, as well as to provide constructive suggestions for the safety and management of emerging alternatives.

Alternative animal models in predictive toxicology

Toxicity testing relies heavily on animals, especially rodents as part of the non-clinical laboratory testing of substances. However, the use of mammalians and the number of animals employed in research has become a concern for institutional ethics committees. Toxicity testing involving rodents and other mammals is laborious and costly. Alternatively, non-rodent models are used as replacement, as they have less ethical considerations and are cost-effective. Of the many alternative models that can be used as replacement models, which ones can be used in predictive toxicology? What is the correlation between these models and rodents? Are there standardized protocols governing the toxicity testing of these commonly used predictive models? This review outlines the common alternative animal models for predictive toxicology to address the importance of these models, the challenges, and their standard testing protocols.

Intergenerational toxicity of nonylphenol ethoxylate (NP-9) in Caenorhabditis elegans

The ethoxylated isomers of nonylphenol (NPEs, NP-9) are one of the main active ingredients present in nonionic surfactants employed as herbicides, cosmetics, paints, plastics, disinfectants and detergents. These chemicals and their metabolites are commonly found in environmental matrices. The aim of this work was to evaluate the intergenerational toxicity of NP-9 in Caenorhabditis elegans. The lethality, length, width, locomotion and lifespan were investigated in the larval stage L4 of the wild strain N2. Transgenic green fluorescent protein (GFP) strains were employed to estimate changes in relative gene expression. RT-qPCR was utilized to measure mRNA expression for neurotoxicity-related genes (unc-30, unc-25, dop-3, dat-1, mgl-1, and eat-4). Data were obtained from parent worms (P0) and the first generation (F1). Lethality of the nematode was concentration-dependent, with 48 h-LC₅₀ values of 3215 and 1983 μM in P0 and F1, respectively. Non-lethal concentrations of NP-9 reduced locomotion. Lifespan was also decreased by the xenobiotic, but the negative effect was greater in P0 than in F1. Non-monotonic concentration-response curves were observed for body length and width in both generations. The gene expression profile in P0 was different from that registered in F1, although the expression of sod-4, hsp-70, gpx-6 and mtl-2 increased with the surfactant concentration in both generations. None of the tested genes followed a classical concentration-neurotoxicity relationship. In P0, dopamine presented an inverted-U curve, while GABA and glutamate displayed a bimodal type. However, in F1, inverted U-shaped curves were revealed for these genes. In summary, NP-9 induced intergenerational responses in C. elegans through mechanisms involving ROS, and alterations of the GABA, glutamate, and dopamine pathways.

piRNAs Regulated by Mitochondria Variation Linked With Reproduction and Aging in Caenorhabditis elegans

In Caenorhabditis elegans, the binding of Piwi protein to a non-coding RNA form, called piRNA, has been found to be important to both reproductive and aging processes. As the biosynthesis of piRNA is modulated by mitochondrial function, it is likely that the interaction between mitochondrial function and piRNA expression plays an unknown, yet important, role in reproductive and aging processes because both processes are known to be affected by declines in mitochondrial quality and activity. While the relationship between reproduction and longevity is not characterized in full, the optimality theory of aging and the disposable soma theory suggest that a trade-off between energy and resources is needed for reproductive and aging maintenance. In this study, the influence of mitochondrial variations, via a respiratory chain complex IV (COX1) polymorphism, on piRNA expression was examined in relation to the reproductive and aging outcomes of C. elegans. The COX1 polymorphism in mitochondria was found to affect the number of piRNAs expressed, the development of germ cells, and the length of the lifespan of the nematodes. Interestingly, more than two-thirds of the piRNA expression changes associated with the mitochondrial variation were found to also be affected by age. A gene ontology analysis of the altered piRNA species found that the piRNAs affected by mitochondrial variation and age were linked to genes known to have roles in reproductive and developmental function. Moreover, a piRNA-lncRNA-mRNA regulatory network based on the differential expression patterns of piRNA related to the mitochondrial variation was constructed to further identify potential gene targets with functional interactions. Similarly, this network identified genes involved in reproduction, development, and aging processes. These findings provide new insight into understanding how mitochondrial variations may regulate piRNA expression and may influence the underlying molecular mechanisms that affect reproduction and aging.