Effects of microplastics and phenanthrene on gut microbiome and metabolome alterations in the marine medaka Oryzias melastigma

Unraveling individual and combined toxicity of microplastics and tetracycline at environment-related concentrations to coral holobionts

Coral holobionts constitute the foundational organisms of coral reef ecosystems. As an emerging pollutant, the projected accumulated levels of microplastics (MPs) are expected to continue increasing. Meanwhile, due to their properties, MPs can absorb multiple other marine pollutants, such as antibiotics (ATs). However, the co-toxicity mechanism of MPs and ATs to coral holobionts remains to be explored. Here, using Zoanthus sociatus as a model organism, we investigate the individual and combined toxicity of MPs and tetracycline (TC) at environment-related concentrations to coral holobionts. Microbiomics indicate that MPs and TC increase coral holobionts bacterial species richness while concurrently reducing the microbial community structure stability. The key metabolites and enzyme activity results demonstrated that the impacts of MPs and TC on corals encompassed antioxidant capacity, detoxification capability, immune function, and lipid metabolism. Transcriptomics shows that MPs and TC disrupt coral-algae relationships mainly through host nutrition limitation and inhibition of symbiotic algae carbon/nitrogen metabolism, respectively. A synergistic effect between MPs and TC has also been observed. In contrast, coral holobionts have shown adaptability through activating coral-symbiodiniaceae-bacteria interactions, mainly including: 1) enhancing the abundance of BMCs (beneficial microorganisms for corals); 2) enhancing host lipid accumulation; 3) immunoregulation; 4) symbiotic regulation. Overall, our findings provide new insights into the co-toxicity of MPs and TC, and highlight those MPs and TC at current environment concentration and predicted for most oceans in the coming decades, can ultimately cause coral bleaching.

Toxic effects of emerging pollutants on mucosal organs of teleost fish: A review focusing on mucosal microbiota, physical barrier and immune barrier

The urgency of emerging pollutants driven by human activities presents an increasing threat to the health of fish. The mucosal system, serving as a primary barrier against environmental pollutants, has emerged as a central focus in toxicological research. Alterations in the mucosal microbiota can impact health at both local and systemic levels. This review explores the toxic effects of emerging pollutants on the mucosal immunity of teleost fish, reflects on the reasons behind the limited focus on adaptive immunity studies, and highlights changes in microbial composition, gene expression, histology, and overall mucosal organ function. Furthermore, we summarize the mechanisms through which these pollutants disrupt the mucosal barriers of teleosts, emphasizing interactions between the mucosal microbiota, physical barriers, and immune defenses. The relevant methodologies and potential solutions to the current challenges have been summarized. While current research predominantly centers on the intestines and gills, further studies are needed to investigate the toxic effects of emerging pollutants on other mucosal organs and to elucidate how microbiota influence host health through neuro-immune communication. This review aims to provide a comprehensive overview of mucosal immunity, serving as a theoretical foundation for the assessment of related ecological risks.

A critical review of the ecotoxic effects of microplastics on aquatic, soil and atmospheric ecosystems and current research challenges

The extensive use of plastics has brought unparalleled convenience to human social development. However, this has also led to severe environmental and health challenges, with microplastic (MP) pollution emerging as one of the most pressing issues. As ubiquitous environmental pollutants, MPs persist in ecosystems and pose potential risks to both ecological and human health. Studies reveal that MPs impact aquatic, soil, and atmospheric ecosystems by altering their physicochemical properties and causing toxicological harm to resident organisms. Despite these findings, a comprehensive assessment and analysis of MP impacts, especially on atmospheric ecosystems, remains lacking. Similarly, the environmental biotoxicity mechanisms associated with MPs are yet to be systematically described. This review provides an in-depth discussion of the sources and characteristics of MPs, laying the background for elaborating their ecological effects. Current knowledge on MP ecotoxicity in aquatic, soil, and atmospheric ecosystems is then synthesized. Potential molecular mechanisms of biotoxicity are explored. Oxidative stress, inflammatory responses, and metabolic signaling pathway impairment are considered important pathways through which MPs induce toxic injury in environmental animals and have received widespread attention. Additionally, this review emphasizes the challenges faced in studying ecotoxic effects and mechanisms of MPs, such as the lack of reliable detection of environmental MPs and in-depth mining of relevant data, and suggests possible directions for future research. Although progress has been made, significant knowledge gaps remain. Addressing these gaps is critical if effective strategies are to be developed to reduce the environmental and health risks posed by MPs.

Sex-specific effects of triphenyltin on gut microbiota and intergenerational effects in marine medaka (Oryzias melastigma)

In this study, a mixed model was applied to the marine medaka to investigate the intergenerational effects of parental exposure to Triphenyltin (TPT) and the subsequent perturbations in parental gut microbiota on the gut microbiota of offspring. In addition, "microgenderome" has been focused on elucidating the different responses of males and females to environmental stress. The results indicated that TPT exhibited androgenic effects and long-term toxicological consequences, influencing the internal steroid hormone levels of the offspring and leading to their abnormal growth and development. Furthermore, the "microgenderome" has been observed in fish, which resulted in sex-specific responses among females and males when exposed to TPT. The effects of parental TPT exposure on offspring also varied by sex; specifically, it disrupted the intestinal microenvironment in female offspring, creating selective pressure on gut microbiota. In contrast, the male gut microbiota exhibited greater sensitivity to environmental perturbations, allowing rapid community interactions to achieve a relatively stable state. These findings suggest that TPT poses significant long-term toxicological effects that warrant further attention and management. Moreover, the identification of the "microgenderome" phenomenon in fish may provide new insights into gut microbiota disruption and its functional implications.

Effect of microcystin-LR on intestinal microbiota, metabolism, and health of zebrafish (Danio rerio)

Microcystin-LR (MC-LR) is typically produced along with the occurrence of cyanobacterial blooms, potentially exerting deleterious effects on intestinal microbiota and health in aquatic animals. To date, the underlying mechanism by which MC-LR affects intestinal health remains elusive. In this study, adult male zebrafish were exposed to MC-LR to assess its impact on the microbiome and metabolome. Histopathological and biochemical results indicated that MC-LR damaged intestinal villi and epithelial cells, induced intestinal barrier injury and inflammatory response. Metabolomics results revealed that MC-LR induced amino acid, carbohydrate, lipid, energy metabolisms dysbiosis, and specifically promoted glycine, serine and threonine metabolism. Metagenomics results demonstrated that MC-LR altered the composition of intestinal microbiota, and microbial function prediction suggested that MC-LR promoted the functions associated with amino acid, lipid, carbohydrate and energy metabolisms. Multiomics and Metorigin analyses jointly confirmed that glycine, serine and threonine metabolism was predominantly regulated by dominant Proteobacteria, Firmicutes, Fusobacteriota and Bacteroidota under MC-LR stress. This study offers a comprehensive perspective on the toxicity of microbiota and microbiota-derived metabolism in fish intestines induced by MC-LR and deepens our comprehension of the disruptive influence of MC-LR on intestinal homeostasis in organisms.

Phenanthrene-induced hyperuricemia with intestinal barrier damage and the protective role of theabrownin: Modulation by gut microbiota-mediated bile acid metabolism

Hyperuricemia is prevalent globally and potentially linked to environmental pollution. As a typical persistent organic pollutant, phenanthrene (Phe) poses threats to human health through biomagnification. Although studies have reported Phe-induced toxicities to multiple organs, its impact on uric acid (UA) metabolism remains unclear. In this study, data mining on NHANES 2001-2016 indicated a positive correlation between Phe exposure and the occurrence of hyperuricemia in population. Subsequently, adolescent Balb/c male mice were orally exposed to Phe at a dosage of 10 mg/kg bw every second day for 7 weeks, resulting in dysfunction of intestinal UA excretion and disruption of the intestinal barrier. Utilizing intestinal organoids, 16S rRNA sequencing of gut microbiota, and targeted metabolomic analysis, we further revealed that an imbalance in bile acid metabolism derived from gut microbiota might mediate the intestinal barrier damage. Additionally, the tea extract theabrownin (TB) effectively improved Phe-induced hyperuricemia and intestinal dysfunction at a dose of 320 mg/kg bw per day. In conclusion, this study demonstrates that Phe exposure is positively associated with hyperuricemia and intestinal damage, which provides new insights into the toxic effects induced by Phe. Furthermore, the present study proposes that supplementation with TB would be a healthy and effective improvement strategy for patients with hyperuricemia and intestinal injury caused by environmental factors.

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Understanding the links between micro/nanoplastics-induced gut microbes dysbiosis and potential diseases in fish: A review

At present, the quantity of micro/nano plastics in the environment is steadily rising, and their pollution has emerged as a global environmental issue. The tendency of their bioaccumulation in aquatic organisms (especially fish) has intensified people's attention to their persistent ecotoxicology. This review critically studies the accumulation of fish in the intestines of fish through active or passive intake of micro/nano plastics, resulting in their accumulation in intestinal organs and subsequent disturbance of intestinal microflora. The key lies in the complex toxic effect on the host after the disturbance of fish intestinal microflora. In addition, this review pointed out the characteristics of micro/nano plastics and the effects of their combined toxicity with adsorbed pollutants on fish intestinal microorganisms, in order to fully understand the characteristics of micro/nano plastics and emphasize the complex interaction between MNPs and other pollutants. We have an in-depth understanding of MNPs-induced intestinal flora disorders and intestinal dysfunction, affecting the host's systemic system, including immune system, nervous system, and reproductive system. The review also underscores the imperative for future research to investigate the toxic effects of prolonged exposure to MNPs, which are crucial for evaluating the ecological risks posed by MNPs and devising strategies to safeguard aquatic organisms.

Chronic exposure to tris(1,3-dichloro-2-propyl) phosphate: Effects on intestinal microbiota and serum metabolism in rats

Tris(1,3-dichloro-2-propyl) phosphate (TDCIPP) is a widely used organophosphate ester that can adversely affect animal or human health. The intestinal microbiota is critical to human health. High-dose exposure to TDCIPP can markedly affect the intestinal ecosystem of mice, but the effects of long-term exposure to lower concentrations of TDCIPP on the intestinal flora and body metabolism remain unclear. In this study, TDCIPP was administered to Sprague-Dawley rats by gavage at a dose of 13.3 mg/kg bw/day for 90 days. TDCIPP increased the relative weight of the kidneys (P = 0.017), but had no effect on the relative weight of the heart, liver, spleen, lungs, testes, and ovaries (P > 0.05). 16 S rRNA gene sequencing revealed that long-term TDCIPP exposure affected the diversity, relative abundance, and functions of rat gut microbes. The serum metabolomics of the rats showed that TDCIPP can disrupt the serum metabolic profiles, result in the up-regulation of 26 metabolites and down-regulation of 3 metabolites, and affect multiple metabolic pathways in rat sera. In addition, the disturbed genera and metabolites were correlated. The functions of some disturbed gut microbes were consistent with the affected metabolic pathways in the sera, and these metabolic pathways were all associated with kidney disease, suggesting that TDCIPP may cause kidney injury in rats by affecting the intestinal flora and serum metabolism.

Global analysis of the adverse effects of micro- and nanoplastics on intestinal health and microbiota of fish

The wide occurrence of micro- and nanoplastics (MPs/NPs) within aquatic ecosystems has raised increasing concerns regarding their potential effects on aquatic organisms. However, the effects of MPs/NPs on intestinal health and microbiota of fish remain controversial, and there is a lack of comprehensive understanding regarding how the impact of MPs/NPs is influenced by MPs/NPs characteristics and experimental designs. Here, we conducted a global analysis to synthesize the effects of MPs/NPs on 47 variables associated with fish intestinal health and microbiota from 118 studies. We found that MPs/NPs generally exerted obvious adverse effects on intestinal histological structure, permeability, digestive function, immune and oxidative-antioxidative systems. By contrast, MPs/NPs showed slight effects on intestinal microbial variables. Further, we observed that the responses of intestinal variables to MPs/NPs were significantly regulated by MPs/NPs characteristics and experimental designs. For instance, polyvinyl chloride plastics showed higher toxicity to fish gut than polyethylene and polystyrene did. Additionally, larval fish appeared to be more sensitive to MPs/NPs than juvenile fish. Collectively, this study highlights the potential impacts of MPs/NPs on intestinal health and microbiota of fish, and underscores the determinant role of MPs/NPs characteristics and experimental designs in MPs/NPs toxicity.

Combined exposure with microplastics increases the toxic effects of PFOS and its alternative F-53B in adult zebrafish

Microplastics (MPs) can adsorb and desorb organic pollutants, which may alter their biotoxicities. Although the toxicity of perfluorooctane sulfonate (PFOS) and its alternative 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) to organisms has been reported, the comparative study of their combined toxic effects with MPs on aquatic organisms is limited. In this study, adult female zebrafish were exposed to 10 μg/L PFOS/F-53B and 50 μg/L MPs alone or in combination for 14 days to investigate their single and combined toxicities. The results showed that the presence of MPs reduced the concentration of freely dissolved PFOS and F-53B in the exposure solution but did not affect their bioaccumulation in the zebrafish liver and gut. The combined exposure to PFOS and MPs had the greatest impact on liver oxidative stress, immunoinflammatory, and energy metabolism disorders. 16S rRNA gene sequencing analysis revealed that the combined exposure to F-53B and MPs had the greatest impact on gut microbiota. Functional enrichment analysis predicted that the alternations in the gut microbiome could interfere with signaling pathways related to immune and energy metabolic processes. Moreover, significant correlations were observed between changes in gut microbiota and immune and energy metabolism indicators, highlighting the role of gut microbiota in host health. Together, our findings demonstrate that combined exposure to PFOS/F-53B and MPs exacerbates liver immunotoxicity and disturbances in energy metabolism in adult zebrafish compared to single exposure, potentially through dysregulation of gut microbiota.

The Exploration of Joint Toxicity and Associated Mechanisms of Primary Microplastics and Methamphetamine in Zebrafish Larvae

The co-existence of microplastics (MPs) and methamphetamine (METH) in aquatic ecosystems has been widely reported; however, the joint toxicity and associated mechanisms remain unclear. Here, zebrafish larvae were exposed individually or jointly to polystyrene (PS) and polyvinyl chloride (PVC) MPs (20 mg/L) and METH (1 and 5 mg/L) for 10 days. The mortality, behavioral functions, and histopathology of fish from different groups were determined. PS MPs posed a stronger lethal risk to fish than PVC MPs, while the addition of METH at 5 mg/L significantly increased mortality. Obvious deposition of MPs was observed in the larvae's intestinal tract in the exposure groups. Meanwhile, treatment with MPs induced intestinal deposits and intestinal hydrops in the fish, and this effect was enhanced with the addition of METH. Furthermore, MPs significantly suppressed the locomotor activation of zebrafish larvae, showing extended immobility duration and lower velocity. METH stimulated the outcome of PS but had no effect on the fish exposed to PVC. However, combined exposure to MPs and METH significantly increased the turn angle, which declined in individual MP exposure groups. RNA sequencing and gene quantitative analysis demonstrated that exposure to PS MPs and METH activated the MAPK signaling pathway and the C-type lectin signaling pathway of fish, while joint exposure to PVC MPs and METH stimulated steroid hormone synthesis pathways and the C-type lectin signaling pathway in zebrafish, contributing to cellular apoptosis and immune responses. This study contributes to the understanding of the joint toxicity of microplastics and pharmaceuticals to zebrafish, highlighting the significance of mitigating microplastic pollution to preserve the health of aquatic organisms and human beings.