Effects of environmentally relevant cypermethrin and sulfamethoxazole on intestinal health, microbiome, and liver metabolism in grass carp

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.

Evaluating the combined toxicity of broflanilide and myclobutanil on honeybees (Apis mellifera L.): Molecular mechanisms and protective effects of curcumin

Pesticide toxicity to honeybees has become a pressing ecological issue, yet the effects of pesticide co-exposure are still not fully understood. This research investigates the toxicological implications of concurrent exposure to broflanilide (BFL), a novel diamide insecticide, and myclobutanil (MYC), a commonly used triazole fungicide, on honeybees (Apis mellifera L.), while exploring potential preventive strategies. Acute toxicity tests revealed a significantly lower 96-hour lethal concentration 50 (LC50) for BFL (0.34 mg a.i. L-1) compared to MYC (82.3 mg a.i. L-1), and their co-exposure resulted in pronounced synergistic toxicity. Worker bees were exposed to environmentally relevant doses of BFL and MYC for 7 days, and midgut toxicity was assessed. The co-exposure caused severe midgut damage, including G-layer deterioration, loss of columnar epithelium integrity, and downregulation of the tight junction protein ZO-2. Additionally, oxidative stress-related genes (Sod1, Catalase, SelK, GstD1) were upregulated, accompanied by higher MDA levels and increased CAT and SOD activities. Furthermore, a greater number of TUNEL-positive cells were detected, along with elevated expression of apoptosis-related genes (Caspase-3-like, Caspase-8-like, Caspase-9-like) and higher caspase enzyme activities. Curcumin (Cur) was tested for its protective effects, and it significantly alleviated midgut damage, oxidative stress, and apoptosis. This study reveals the synergistic ecotoxicological effects of pesticide combinations and suggests Cur as a potential prevention strategy for mitigating their harmful impact on honeybees.

Long-term chronic exposure to benzo[a]pyrene and catechol induced multidrug resistance in lung cancer cells

Multiple studies have raised concerns about the impact of long-term exposure to environmental pollutants on the occurrence and progression of cancer, but little is known about how these compounds affect the treatment of cancer patients. In this work, two common pollutants including benzo [a]pyrene (B [a]P) and catechol (CL) were tested for their chronic effects on the efficacy of common chemotherapeutic drug in lung cancer (A549) cells. Both pollutants were unlikely to be the substrates of ABC transporters, as their toxicity was unaffected by ABC transporter inhibitors. However, their repeated exposure led to the generation of chemoresistance to doxorubicin (DOX) and cisplatin (CDDP), indicating the formation of multidrug-resistance (MDR) cells. Compared with DOX-resistant cells, decreased expression of ABC transporters but increased responses were found in pollutants-resistant cells. In addition, pollutants-resistant cells were more potent in up-regulating anti-apoptosis, proliferation, and migration pathways, which were confirmed by the wound-healing and apoptosis assays. Overall, these results indicated a distinct MDR mechanism induced by non-substrate pollutants, and could be beneficial for understanding the environmental risk of pollutants in their "safe" concentrations.

Emerging antibiotic pollution and its remedy by waste based biochar adsorbents: a review

One of the pollutants of emerging concern, antibiotics, have been reported in soil, water, sediment, animal manure, food, and even drinking water. Their partially metabolized forms reach wastewater treatment plants (WWTPs) and natural waters wherein the development of antibiotic resistant bacteria (ARB) and dissemination of antibiotic resistance genes (ARGs) have been reported to occur. Antimicrobial resistance (AMR) is projected to cause 10 million deaths annually across the world by 2050 in case stringent measures are not taken. In this study, various methods of adsorptive removal of antibiotics with their critical analysis and emphasis on the application of biochar (BC) and modified biochar derived from waste biomass have been comprehensively reviewed. Also, the antibiotic toxicity, preparation of biomass waste-derived BC adsorbents from cost-effective precursors to ensure sustainability, the adsorption kinetics, isotherm models and thermodynamic parameters have been discussed. It was inferred that biochars are quite efficient in terms of antibiotic removal in water owing to their large surface area, excellent surface characteristics and functionality, facile synthesis and the potential to be regenerated, while being cost-effective and sustainable in nature. This review aims to guide the expansion of research in the aforementioned area of interest and to provide a progressive push towards the development of a circular economy.

Vitamin E alleviates zebrafish intestinal damage and microbial disturbances caused by pyraclostrobin

Pyraclostrobin (PY) is highly toxic to aquatic organisms, and its increased residues in aquatic environments may have harmful effects on the intestine of aquatic creatures. Previous research demonstrated that vitamin E (VE) alleviated the acute toxicity of PY to zebrafish. This study further explored the mitigation effect of VE on PY-induced intestinal toxicity in fish and the underlying mechanisms by exposing adult zebrafish to PY (10, 20 μg/L) with or without 4 μM VE supplementation for 21 days. The results showed that VE alleviated the gut histopathological lesions caused by PY. VE co-exposure also improved PY-induced intestinal inflammation and restored the expression level of genes encoding intestinal tight junction protein. Furthermore, VE restored the anti-oxidation level inhibited by PY and reduced pro-apoptotic cytokine level and apoptotic enzyme activity increased by PY. 16S rRNA high-throughput sequencing showed that VE improved the zebrafish intestinal flora imbalance caused by 20 μg/L PY, increased the relative abundance of beneficial bacterium Cetobacterium, and reduced the relative abundance of pathogenic bacteria. In conclusion, VE alleviated PY-induced intestinal toxicity via repairing the damaged intestinal mucosal barrier, inhibiting inflammation, reducing oxidative stress and apoptosis, and improving the intestinal microbial disorder in zebrafish.

TBBPA caused multiple intestinal injuries via ROS/NF-κB signal in common carp

Tetrabromobisphenol A (TBBPA) is an aquatic environment's prevalent pollutant, posing a great threat to the health of aquatic animals. The intestine is a key organ for nutrient absorption as well as an important barrier to prevent pollutants from invading the body of fish. Exploring the effects of pollutants on the intestine is of great significance for maintaining fish health. Therefore, the purpose of this study was to assess the toxic effects of TBBPA on the intestine of Cyprinus carpio L. (common carp) by establishing models of common carp and primary intestinal epithelial cells exposed to TBBPA. Histological observation revealed that TBBPA exposure led to damage in the intestinal mucosa and breakage of intestinal villi. Detection of oxidative stress levels showed that TBBPA increased the levels of ROS and MDA, and decreased the activity of SOD, CAT, GSH-PX, and T-AOC in intestinal tissue and cells. Observation of inflammatory factor levels revealed that TBBPA upregulated the mRNA levels of inflammatory factors (IL-6, TNF-α, IL-1β, NF-κB p65 and IκBα). ELISA and western blotting results were consistent with the mRNA results. Moreover, TBBPA induced cell death, as evidenced by TUNEL staining and flow cytometry and confirmed by increasing levels of Bax, Cas-3, Cyt C, RIP1, RIP3, and MLKL, together with decreasing the levels of Bcl-2. TBBPA also destroyed the intestinal tight junction by reducing the mRNA and protein levels of claudin-1, ZO-1, and occludin. In summary, this study reveals that TBBPA caused intestinal injuries, inducing oxidative stress, inflammation, cell death, and tight junction disruption via ROS/NF-κB signal in common carp.

Autophagy and PPARs/NF-κB-associated inflammation are involved in hepatotoxicity induced by the synthetic phenolic antioxidant 2,4-di-tert-butylphenol in common carp (Cyprinus carpio)

The synthetic phenolic antioxidant 2,4-di-tert-butylphenol (2,4-DTBP) is an emergent contaminant and can disrupt the delicate balance of aquatic ecosystems. This study aimed to investigate 2,4-DTBP-induced hepatotoxicity in common carp and the underlying mechanisms involved. Sixty common carp were divided into four groups and exposed to 0 mg/L, 0.01 mg/L, 0.1 mg/L or 1 mg/L 2,4-DTBP for 30 days. Here, we first demonstrated that 2,4-DTBP exposure caused liver damage, manifested as hepatocyte nuclear pyknosis, inflammatory cell infiltration and apoptosis. Moreover, 2,4-DTBP exposure induced hepatic reactive oxygen species (ROS) overload and disrupted antioxidant capacity, as indicated by the reduced activity of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px). In addition, transmission electron microscopy revealed that 2,4-DTBP exposure induced autophagosome accumulation in the liver of common carp. Western blot analysis further revealed that 2,4-DTBP exposure significantly decreased the protein levels of mTOR and increased the LC3II/LC3I ratio. Furthermore, 2,4-DTBP exposure inhibited lysozyme (LZM) and alkaline phosphatase (AKP) activity; decreased immunoglobulin M (IgM), complement 3 (C3), and complement 4 (C4) levels in the serum; increased the mRNA levels of proinflammatory cytokines (NF-κB, TNF-α, IL-1β and IL-6); and increased the mRNA levels of three types of proliferator-activated receptors (PPARs) (α, β/δ and γ). Molecular docking revealed that 2,4-DTBP directly binds to the internal active pocket of PPARs. Overall, we concluded that 2,4-DTBP exposure in aquatic systems could induce hepatotoxicity in common carp by regulating autophagy and controlling inflammatory responses. The present study provides new insights into the hepatotoxicity mechanism induced by 2,4-DTBP in aquatic organisms and furthers our understanding of the effects of 2,4-DTBP on public health and ecotoxicology.

Effect of emerging pollutants on the gut microbiota of freshwater animals: Focusing on microplastics and pesticides

In recent years, emerging environmental pollutants have increasingly endangered the health of freshwater organisms. The gut microbiota exhibits sensitivity to medications, dietary factors and environmental pollutants, rendering it a novel target for toxicological studies. The gut microbiota can be a potential exposure route affecting the host's health. Herein, we review the current knowledge on two different but concurrent pollutants, microplastics and pesticides, regarding their impact on the gut microbiota, which includes alterations in microbial composition, gene expression, function, and health effects in the hosts. Moreover, synergetic interactions between microplastics and pesticides can exacerbate dysbiosis and health risks. We discuss health-related implications of gut microbial changes based on the consequences in metabolism, immunity, and physiology function. Further research is needed to discover the mechanisms underlying these effects and develop strategies for mitigating their harmful impacts on freshwater animals.

Toxicological insight of metiram: immuno-oxidative, neuro-behavioral, and hemato-biochemical changes during acute exposure of Nile tilapia (Oreochromis niloticus)

BACKGROUND

The inappropriate use of pesticides including fungicides creates severe biological hazards that can endanger fish health and impede sustainable aquaculture.

OBJECTIVE

This study investigated the negative impacts of metiram (MET), a fungicide on the health status of Nile tilapia (Oreochromis niloticus) for a 96-hour duration as an acute exposure in a static renewal system.

METHODS

Three hundred fish (average body weight: 37.50 ± 0.22 g) were assigned into six groups (50 fish/group) with five replicates (10 fish/replicate). Fish were exposed to various six concentrations (0, 1.5, 3, 4.5, 6, and 7.5 mg/L) of MET as a water exposure to for 96-hour without water exchange. The fish's behavior, clinical signs, and mortalities were documented every day of the exposure period. Additionally, MET's impact on blood profile, stress biomarkers, hepato-renal functions, immune-antioxidant status, and brain biomarker were closely monitored.

RESULTS

The lethal concentration (LC50) of MET estimated using Finney's probit technique was 3.77 mg/L. The fish's behavior was severely impacted by acute MET exposure, as clear by an increase in surfacing, loss of equilibrium, unusual swimming, laterality, abnormal movement, and a decline in aggressive behaviors. The survivability and hematological indices (white and red blood cell count, differential white blood cell count, hematocrit value, and hemoglobin) were significantly reduced in a concentration-dependent manner following MET exposure. Acute exposure to MET (1.5-7.5 mg/L) incrementally increased stress biomarkers (nor-epinephrine, cortisol, and glucose), lipid peroxides (malondialdehyde), and brain oxidative DNA damage biomarker (8-hydroxy-2-deoxyguanosine). A hepato-renal dysfunction by MET exposure (4.5-7.5 mg/L) was evidenced by the significant increase in the alanine and aspartate aminotransferases and creatinine values. Moreover, a substantial decline in the immune parameters (lysozyme, complement 3, serum bactericidal activity, and antiprotease activity) and antioxidant variables (total antioxidant capacity, superoxide dismutase, and glutathione peroxidase) resulted from acute MET exposure.

CONCLUSION

According to these findings, the 96-hour LC50 of MET in Nile tilapia was 3.77 mg/L. MET exposure triggered toxicity in Nile tilapia, as seen by alterations in fish neuro-behaviors, immune-antioxidant status, hepato-renal functioning, and signifying physiological disturbances. This study emphasizes the potential ecological dangers provoked by MET as an environmental contaminant to aquatic systems. However, the long-term MET exposure is still needed to be investigated.

Integrated microbiome and metabolome analyses reveal the effects of low pH on intestinal health and homeostasis of crayfish (Procambarus clarkii)

Low pH (LpH) poses a significant challenge to the health, immune response, and growth of aquatic animals worldwide. Crayfish (Procambarus clarkii) is a globally farmed freshwater species with a remarkable adaptability to various environmental stressors. However, the effects of LpH stress on the microbiota and host metabolism in crayfish intestines remain poorly understood. In this study, integrated analyses of antioxidant enzyme activity, histopathological damage, 16S rRNA gene sequencing, and liquid chromatography-mass spectrometry (LC-MS) were performed to investigate the physiology, histopathology, microbiota, and metabolite changes in crayfish intestines exposed to LpH treatment. The results showed that LpH stress induced obvious changes in superoxide dismutase and catalase activities and histopathological alterations in crayfish intestines. Furthermore, 16S rRNA gene sequencing analysis revealed that exposure to LpH caused significant alterations in the diversity and composition of the crayfish intestinal microbiota at the phylum and genus levels. At the genus level, 14 genera including Bacilloplasma, Citrobacter, Shewanella, Vibrio, RsaHf231, Erysipelatoclostridium, Anaerorhabdus, Dysgonomonas, Flavobacterium, Tyzzerella, Brachymonas, Muribaculaceae, Propionivibrio, and Comamonas, exhibited significant differences in their relative abundances. The LC-MS analysis revealed 859 differentially expressed metabolites in crayfish intestines in response to LpH, including 363 and 496 upregulated and downregulated metabolites, respectively. These identified metabolites exhibited significant enrichment in 24 Kyoto Encyclopedia of Genes and Genomes pathways (p < 0.05), including seven and 17 upregulated and downregulated pathways, respectively. These pathways are mainly associated with energy and amino acid metabolism. Correlation analysis revealed a strong correlation between the metabolites and intestinal microbiota of crayfish during LpH treatment. These findings suggest that LpH may induce significant oxidative stress, intestinal tissue damage, disruption of intestinal microbiota homeostasis, and alterations in the metabolism in crayfish. These findings provide valuable insights into how the microbial and metabolic processes of crayfish intestines respond to LpH stress.