Fecal microbiota transplantation attenuates nano-plastics induced toxicity in Caenorhabditis elegans

Innovative mechanisms of micro- and nanoplastic-induced brain injury: Emphasis on the microbiota-gut-brain axis

Micro- and nanoplastics (MNPs), emerging environmental pollutants, infiltrate marine, terrestrial, and freshwater systems via diverse pathways, culminating in their accumulation in the human body through food chain transmission, posing potential health risks. Researches have demonstrated that MNPs disrupt gut microbiota equilibrium and compromise intestinal barrier integrity, as well as traverse the blood-brain barrier, leading to brain damage. Moreover, the complex interaction between the gut and the nervous system, facilitated by the "gut-brain axis," indicates an additional pathway for MNPs-induced brain damage. This has intensified scientific interest in the intercommunication between MNPs and the gut-brain axis. While existing studies have documented microbial imbalances and metabolic disruptions subsequent to MNPs exposure, the precise mechanisms by which the microbiota-gut-brain axis contributes to MNPs-induced central nervous system damage remain unclear. This review synthesizes current knowledge on the microbiota-gut-brain axis, elucidating the pathogenesis of MNPs-induced gut microbiota dysbiosis and its consequent brain injury. It emphasizes the complex interrelation between MNPs and the microbiota-gut-brain axis, advocating for the gut microbiota as a novel therapeutic target to alleviate MNP-induced brain harm.

Advances on micro/nanoplastics and their effects on the living organisms: A review

Micro/nanoplastics (MPs) are attracting increasing attention owing to the potential threats they pose to the sustainability of the environment and the health of living organisms. Thus, a comprehensive understanding of the influence of MPs on living organisms is vital for developing countermeasures. We conducted an extensive literature search to retrieve the articles related to MPs via the Web of Science. Accordingly, 152 articles published in the last decade and in influential journals were selected to analyze the effects of MPs on plants, animals, microorganisms, and humans as well as the current status, hotspots, and trends of studies on MPs. The results showed that owing to the special characteristics of MPs and anthropogenic activities, MPs have become ubiquitous worldwide. MPs are ingested by plants and animals and enter the human body through various pathways, resulting in numerous adverse effects, such as growth inhibition, oxidative stress, inflammation, organ damage, and germ cell lesions. Moreover, they affect microorganisms by reshaping the structure and function of microbial communities and changing the spread pathway. However, microorganisms can also contribute to the degradation of MPs. With increasing evidence of the adverse effects of MPs on biota, coping with MP pollution and mitigating harmful outcomes have emerged as major challenges. This review focuses on (1) the main effects of MPs on living organisms, ranging from microorganisms to humans, (2) the current status and hotspots of studies related to MPs, and (3) the challenges and prospects of further studies on MPs.

Cloning and expression of the phenazine-1-carboxamide hydrolysis gene pzcH and the identification of the key amino acids necessary for its activity

Phenazine-1-carboxamide (PCN), a phenazine derivative, can cause toxicity risks to non target organisms. In this study, the Gram-positive bacteria Rhodococcus equi WH99 was found to have the ability to degrade PCN. PzcH, a novel amidase belonging to amidase signature (AS) family, responsible for hydrolyzing PCN to PCA was identified from strain WH99. PzcH shared no similarity with amidase PcnH which can also hydrolyze PCN and belong to the isochorismatase superfamily from Gram-negative bacteria Sphingomonas histidinilytica DS-9. PzcH also showed low similarity (˂ 39%) with other reported amidases. The optimal catalysis temperature and pH of PzcH was 30 °C and 9.0, respectively. The K_m and k_cat values of PzcH for PCN were 43.52 ± 4.82 μM and 17.028 ± 0.57 s^-1, respectively. The molecular docking and point mutation experiment demonstrated that catalytic triad Lys80-Ser155-Ser179 are essential for PzcH to hydrolyze PCN. Strain WH99 can degrade PCN and PCA to reduce their toxicity against the sensitive organisms. This study enhances our understanding of the molecular mechanism of PCN degradation, presents the first report on the key amino acids in PzcH from the Gram-positive bacteria and provides an effective strain in the bioremediation PCN and PCA contaminated environments.

Are Microplastics Toxic? A Review from Eco-Toxicity to Effects on the Gut Microbiota

Emerging studies have presented an initial picture of the toxic effects of exposure to environmental micro- and nanoplastics. They have indicated that micro- and nanoplastics may induce toxicity by leading to oxidative stress, energy metabolism disorders, gene damage, and so forth in environmental organisms, marine invertebrates and vertebrates, and laboratory mouse models. In recent years, micro- and nanoplastics have been discovered in human fecal samples, placentas, lung tissue, and even blood; thus, micro- and nanoplastics pose an alarming and ever-increasing threat to global public health. However, current research on the health effects of micro- and nanoplastics and the possible adverse outcomes in humans has only presented the tip of the iceberg. More robust clinical data and basic experiments are still warranted to elucidate the specific relationships and mechanisms. In this paper, we review studies on micro- and nanoplastic toxicity from the perspectives of eco-toxicity, the adverse effects on invertebrates and vertebrates, and the impact of micro- and nanoplastics on the gut microbiota and its metabolites. In addition, we evaluate the toxicological role of micro- and nanoplastic exposure and its potential implications in respect to human health. We also summarize studies regarding preventive strategies. Overall, this review provides insights on micro- and nanoplastic toxicity and its underlying mechanisms, opening up scientific avenues for future in-depth studies.

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.

Toxicity of transition metal nanoparticles: A review of different experimental models in the gastrointestinal tract

The development of nanotechnology is becoming a major trend nowadays. Nanoparticles (NPs) have been widely used in fields including food, biomedicine, and cosmetics, endowing NPs more opportunities to enter the human body. It is well-known that the gut microbiome plays a key role in human health, and the exposure of intestines to NPs is unavoidable. Accordingly, the toxicity of NPs has attracted more attention than before. This review mainly highlights recent advances in the evaluation of NPs' toxicity in the gastrointestinal system from the existing cell-based experimental models, such as the original mono-culture models, co-culture models, three-dimensional (3D) culture models, and the models established on microfluidic chips, to those in vivo experiments, such as mice models, Caenorhabditis elegans models, zebrafish models, human volunteers, as well as computer-simulated toxicity models. Owing to these models, especially those more biomimetic models, the outcome of the toxicity of NPs acting in the gastrointestinal tract can get results closer to what happened inside the real human microenvironment.

The gut microbiota, a key to understanding the health implications of micro(nano)plastics and their biodegradation

The effects of plastic debris on the environment and plant, animal, and human health are a global challenge, with micro(nano)plastics (MNPs) being the main focus. MNPs are found so often in the food chain that they are provoking an increase in human intake. They have been detected in most categories of consumed foods, drinking water, and even human feces. Therefore, oral ingestion becomes the main source of exposure to MNPs, and the gastrointestinal tract, primarily the gut, constantly interacts with these small particles. The consequences of human exposure to MNPs remain unclear. However, current in vivo studies and in vitro gastrointestinal tract models have shown that MNPs of several types and sizes impact gut intestinal bacteria, affecting gut homeostasis. The typical microbiome signature of MNP ingestion is often associated with dysbiosis and loss of resilience, leads to frequent pathogen outbreaks, and local and systemic metabolic disorders. Moreover, the small micro- and nano-plastic particles found in animal tissues with accumulated evidence of microbial degradation of plastics/MNPs by bacteria and insect gut microbiota raise the issue of whether human gut bacteria make key contributions to the bio-transformation of ingested MNPs. Here, we discuss these issues and unveil the complex interplay between MNPs and the human gut microbiome. Therefore, the elucidation of the biological consequences of this interaction on both host and microbiota is undoubtedly challenging. It is expected that microbial biotechnology and microbiome research could help decipher the extent to which gut microorganisms diversify and MNP-determinant species, mechanisms, and enzymatic systems, as well as become important to understand our response to MNP exposure and provide background information to inspire future holistic studies.

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.

A Lactobacilli diet that confers MRSA resistance causes amino acid depletion and increased antioxidant levels in the C. elegans host

Probiotic bacteria are increasingly popular as dietary supplements and have the potential as alternatives to traditional antibiotics. We have recently shown that pretreatment with Lactobacillus spp. Lb21 increases the life span of C. elegans and results in resistance toward pathogenic methicillin-resistant Staphylococcus aureus (MRSA). The Lb21-mediated MRSA resistance is dependent on the DBL-1 ligand of the TGF-β signaling pathway. However, the underlying changes at the metabolite level are not understood which limits the application of probiotic bacteria as timely alternatives to traditional antibiotics. In this study, we have performed untargeted nuclear magnetic resonance-based metabolic profiling. We report the metabolomes of Lactobacillus spp. Lb21 and control E. coli OP50 bacteria as well as the nematode-host metabolomes after feeding with these diets. We identify 48 metabolites in the bacteria samples and 51 metabolites in the nematode samples and 63 across all samples. Compared to the control diet, the Lactobacilli pretreatment significantly alters the metabolic profile of the worms. Through sparse Partial Least Squares discriminant analyses, we identify the 20 most important metabolites distinguishing probiotics from the regular OP50 food and worms fed the two different bacterial diets, respectively. Among the changed metabolites, we find lower levels of essential amino acids as well as increased levels of the antioxidants, ascorbate, and glutathione. Since the probiotic diet offers significant protection against MRSA, these metabolites could provide novel ways of combatting MRSA infections.

Microplastics and Their Impact on Reproduction-Can we Learn From the C. elegans Model?

Biologically active environmental pollutants have significant impact on ecosystems, wildlife, and human health. Microplastic (MP) and nanoplastic (NP) particles are pollutants that are present in the terrestrial and aquatic ecosystems at virtually every level of the food chain. Moreover, recently, airborne microplastic particles have been shown to reach and potentially damage respiratory systems. Microplastics and nanoplastics have been shown to cause increased oxidative stress, inflammation, altered metabolism leading to cellular damage, which ultimately affects tissue and organismal homeostasis in numerous animal species and human cells. However, the full impact of these plastic particles on living organisms is not completely understood. The ability of MPs/NPs to carry contaminants, toxic chemicals, pesticides, and bioactive compounds, such as endocrine disrupting chemicals, present an additional risk to animal and human health. This review will discusses the current knowledge on pathways by which microplastic and nanoplastic particles impact reproduction and reproductive behaviors from the level of the whole organism down to plastics-induced cellular defects, while also identifying gaps in current knowledge regarding mechanisms of action. Furthermore, we suggest that the nematode Caenorhabditis elegans provides an advantageous high-throughput model system for determining the effect of plastic particles on animal reproduction, using reproductive behavioral end points and cellular readouts.