Early developmental nanoplastics exposure disturbs circadian rhythms associated with stress resistance decline and modulated by DAF-16 and PRDX-2 in C. elegans

Enzymatic Stress Responses of Coreius guichenoti to Microplastics with Different Particle Sizes

The wild population resources of Coreius guichenoti have sharply declined in recent decades, and any negative factors may have a significant impact on their survival. In this study, the enzymatic stress responses of C. guichenoti to 25 and 48 μm polyethylene fragments were explored for the first time. This was achieved by evaluating the changes in physiological and biochemical indicators of the species in response to the environmental stimuli of microplastics. In this study, we observed an early stress response in the external tissues of C. guichenoti following exposure to microplastics. The TP content in skin and muscle and the MDA content in skin, gill and muscle initially showed a significant increase. The skin, gill, and muscle exhibited greater stress responses to M5 particles, whereas M3 particles caused a greater response in the intestine and especially the liver. After the removal of microplastic exposure, the stress state of the C. guichenoti would be alleviated in a short period, but it could not fully recover to the pre-exposure level. In summary, microplastics pose a significant threat to C. guichenoti. While their negative effects can be alleviated by the removal of microplastics exposure, full recovery does not occur in a short period. Continuous monitoring of microplastics in natural waters and targeted aquatic ecological restoration are essential to ensure the normal growth and reproduction of the wild population of C. guichenoti.

Methanol Extracts from Cirsium japonicum DC. var. australe Kitam. and Their Active Components Reduce Intracellular Oxidative Stress in Caenorhabditis elegans

Cirsium japonicum DC. var. australe Kitam. has been used as an herbal remedy and often involves using the whole plant or roots. However, the bioactivities of different parts of the plant have been far less explored. This study aimed to evaluate the antioxidative ability of methanol extracts from the flowers, leaves, stems, and roots of the Cirsium plant and their possible active components against juglone-induced oxidative stress in the nematode Caenorhabditis elegans. The results showed that the highest dry weight (12.3 g per plant) was observed in leaves, which was followed by stems (8.0 g). The methanol extract yields from the flowers, leaves, and roots were all similar (13.0-13.8%), while the yield from stems was the lowest (8.6%). The analysis of the silymarin contents in the extracts indicated that the flowers, leaves, stems, and roots contained silychristin and taxifolin; however, silydianin was only found in the leaves, stems, and roots. The flower, leaf, and stem extracts, at a concentration of 10 mg/L, significantly reduced juglone-induced oxidative stress in C. elegans, which was potentially due to the presence of silychristin and taxifolin. Overall, C. japonicum DC. var. australe Kitam. contains a significant amount of silymarin and exhibits in vivo antioxidative activity, suggesting that the prospects for the plant in terms of health supplements or as a source of silymarin are promising.

The gut-brain axis involved in polystyrene nanoplastics-induced neurotoxicity via reprogramming the circadian rhythm-related pathways

The production of plastic is still increasing globally, which has led to an increasing number of plastic particles in the environment. Nanoplastics (NPs) can penetrate the blood-brain barrier and induce neurotoxicity, but in-depth mechanism and effective protection strategies are lacking. Here, C57BL/6 J mice were treated with 60 μg polystyrene NPs (PS-NPs, 80 nm) by intragastric administration for 42 days to establish NPs exposure model. We found that 80 nm PS-NPs could reach and cause neuronal damage in the hippocampus, and alter the expression of neuroplasticity-related molecules (5-HT, AChE, GABA, BDNF and CREB), and even affect the learning and memory ability of mice. Mechanistically, combined with the results of hippocampus transcriptome, gut microbiota 16 s ribosomal RNA and plasma metabolomics, we found that the gut-brain axis mediated circadian rhythm related pathways were involved in the neurotoxicity of NPs, especially Camk2g, Adcyap1 and Per1 may be the key genes. Both melatonin and probiotic can significantly reduce intestinal injury and restore the expression of circadian rhythm-related genes and neuroplasticity molecules, and the intervention effect of melatonin is more effective. Collectively, the results strongly suggest the gut-brain axis mediated hippocampal circadian rhythm changes involved in the neurotoxicity of PS-NPs. Melatonin or probiotics supplementation may have the application value in the prevention of neurotoxicity of PS-NPs.

Nanoplastics exposure disrupts circadian rhythm associated with dysfunction of the endolysosomal pathway and autophagy in Caenorhabditis elegans

Nanoplastics (NPs), an emerging pollutant, have raised great safety concerns due to their widespread applications and continuous release into the environment, which lead to potential human and environmental risks. Recently, polystyrene NPs (100 nm; 100 mg/L) exposure has been reported to disrupt circadian rhythms under five days temperature entrainment and be associated with stress resistance decline in Caenorhabditis elegans. This study explored the possible relationship between circadian rhythm disruption and endocytosis and autophagy under polystyrene NPs exposure in C. elegans. We show that the disrupted circadian rhythm induced by NPs exposure reduced stress resistance via endocytosis and autophagy impairment. Furthermore, we found that most NPs taken up by intestinal cells were localized to early endosomes, late endosomes, and lysosomes and delivered to autophagosomes. In addition, the disruption of circadian rhythm inhibited NPs localization to these organelles. These findings indicate that NPs exposure disrupts circadian rhythm and alters its subcellular trafficking, leading to enhanced toxicity in C. elegans. Our results shed light on the prominent role of NPs exposure in circadian rhythm disruption associated with endocytosis and autophagy impairments, which may be conserved in higher animals such as humans.

Effects of microplastic exposure on the early developmental period and circadian rhythm of zebrafish (Danio rerio): A comparative study of polylactic acid and polyglycolic acid

Polyglycolic acid (PGA) is an emerging biodegradable plastic material. Together with polylactic acid (PLA), PGA is considered a suitable alternative to conventional plastics and has been widely used in biomedical and food packaging industries. However, degradable plastics continue to face the drawbacks of harsh degradation environment and long degradation time, and may harm the environment and the human body. Therefore, our study focused on assessing the effects of degradable microplastics PGA and PLA on the development and neurobehavior of zebrafish. The results showed that PGA and PLA had little effect on 3-10 hpf embryos. However, developmental stunting was observed in a100 mg/L PGA and PLA-exposed group at 24 hpf. In addition, PGA and PLA exposure decreased the survival and hatching rates, increased wakefulness, and reduced sleep in zebrafish. This indicates that PGA and PLA may affect the circadian behavior of zebrafish by affecting the brain-derived neurotrophic factor (BDNF). Therefore, our results suggest that PGA and PLA exposure induces developmental toxicity, reduces voluntary locomotion, induces of anxiety-like behaviors, and impairs sleep/wake behaviors in zebrafish larvae. This also suggests that the potentially toxic effects of degradable plastics cannot be ignored and that the biological effects of PGA require further research.

Chronic exposure to di(2-ethylhexyl) phthalate (DEHP) weakens innate immunity and leads to immunosenescence in C. elegans

Di(2-ethylhexyl) phthalate (DEHP), a widespread contaminant, has numerous adverse impacts on human health and ecosystems. Chronic DEHP exposure has been found to accelerate aging; however, its potential threat to age-dependent innate immune decline remains unknown. This study aims to evaluate the effects of chronic DEHP exposure on innate immunosenescence in Caenorhabditis elegans. We show that the length of the exposure period significantly impacts DEHP-induced age-related declines, which is linked to immunosenescence and oxidative stress. We found that the DEHP-caused immunosenescence is accompanied with downregulation of an antimicrobial gene lys-7 as well as an enhancement of the nuclear translocation of HLH-30, an orthologue of mammalian transcription factor EB (TFEB). Moreover, DEHP exposure increases the expression of riok-1, a human RIO kinase homolog, which is associated with DEHP-induced HLH-30/TFEB translocation. Our findings suggest that early-life and chronic exposure to DEHP, mostly due to parent compound rather than its metabolite mono(2-ethylhexyl) phthalate (MEHP), may weaken the innate immunity in C. elegans and may enhance susceptibility to infections or promote immunosenescence in aged populations.

Caenorhabditis elegans as a Prediction Platform for Nanotechnology-Based Strategies: Insights on Analytical Challenges

Nanotechnology-based strategies have played a pivotal role in innovative products in different technological fields, including medicine, agriculture, and engineering. The redesign of the nanometric scale has improved drug targeting and delivery, diagnosis, water treatment, and analytical methods. Although efficiency brings benefits, toxicity in organisms and the environment is a concern, particularly in light of global climate change and plastic disposal in the environment. Therefore, to measure such effects, alternative models enable the assessment of impacts on both functional properties and toxicity. Caenorhabditis elegans is a nematode model that poses valuable advantages such as transparency, sensibility in responding to exogenous compounds, fast response to perturbations besides the possibility to replicate human disease through transgenics. Herein, we discuss the applications of C. elegans to nanomaterial safety and efficacy evaluations from one health perspective. We also highlight the directions for developing appropriate techniques to safely adopt magnetic and organic nanoparticles, and carbon nanosystems. A description was given of the specifics of targeting and treatment, especially for health purposes. Finally, we discuss C. elegans potential for studying the impacts caused by nanopesticides and nanoplastics as emerging contaminants, pointing out gaps in environmental studies related to toxicity, analytical methods, and future directions.

Induction of transgenerational toxicity is associated with the activated germline insulin signals in nematodes exposed to nanoplastic at predicted environmental concentrations

Exposure to nanoplastics can induce toxicity on organisms at both parental generation (P0-G) and the offspring. However, the underlying mechanism remains unknown. Using Caenorhabditis elegans as a model organism, exposure to 20-nm polystyrene nanoparticle (PS-NP) (1-100 μg/L) upregulated the expressions of insulin ligands (INS-39, INS-3, and DAF-28), and this increase could be further detected in the offspring after PS-NP exposure. Germline ins-39, ins-3, and daf-28 RNAi induced resistance to transgenerational toxicity of PS-NP, indicating that increase in expression of these three insulin ligands mediated induction of transgenerational toxicity. These three insulin ligands transgenerationally activated function of insulin receptor DAF-2 to control transgenerational toxicity of PS-NP. Exposure to 1-100 μg/L PS-NP further upregulated DAF-2, AGE-1, and AKT-1 expressions and downregulated DAF-16 expression. During transgenerational toxicity control, DAF-16/AKT-1/AGE-1 was identified as downstream signaling cascade of DAF-2. Moreover, transcriptional factor DAF-16 activated two downstream targets of HSP-6 (a mitochondrial UPR marker) and SOD-3 (a mitochondrial SOD) to modulate transgenerational toxicity of PS-NP. Our findings indicate a crucial link between activation of insulin signaling and induction of transgenerational toxicity of nanoplastics at low concentrations in organisms.

Nanoplastics cause transgenerational toxicity through inhibiting germline microRNA mir-38 in C. elegans

Nanoplastic exposure potentially caused the induction of transgenerational toxicity. Nevertheless, the molecular basis for nanoplastic exposure-induced transgenerational toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the role of germline microRNA (miRNA) mir-38 in regulating the transgenerational toxicity of polystyrene nanoparticles (PS-NPs). After the exposure, 1-100 μg/L PS-NP decreased expression of germline mir-38. Meanwhile, germline mir-38 overexpression conferred a resistance to transgenerational PS-NP toxicity, which suggested that the decrease in germline mir-38 mediated the induction of transgenerational PS-NP toxicity. In the germline, mir-38 regulated transgenerational PS-NP toxicity by inhibiting activity of downstream targets (NDK-1, NHL-2, and WRT-3). Among these three downstream targets, germline NDK-1 further controlled transgenerational PS-NP toxicity by suppressing the function of KSR-1/2, two kinase suppressors of Ras. Therefore, in the germline, the decrease in mir-38 mediated induction of transgenerational PS-NP toxicity by at least inhibiting signaling cascade of NDK-1-KSR-1/2 in nematodes. The findings in this study are helpful for providing relevantly molecular endpoints to assess potential transgenerational toxicity of nanoplastics.