Expression and Function of ABC Proteins in Fish Intestine

Toxicity of parental co-exposure of microplastic and bisphenol compounds on adult zebrafish: Multi-omics investigations on offspring

In recent years, the widespread use of bisphenol compounds and microplastics (MP) have attracted attention due to their harmful effects. Here, individual and combined effects of MP and bisphenol compounds, were assessed on adult zebrafish after co-exposure of bisphenol A (BPA) or bisphenol S (BPS) and 25 μm polyethylene MP. Impacts on their offspring (the F1 generation) were also investigated. The reproductive toxicity in adult zebrafish impacted exerted by bisphenol compounds were aggravated by the co-presence of MP. Transcriptomics and metabolomics further showed single or co-exposure of bisphenol compounds and MP could together regulate apoptosis, calcium signaling pathway and glycerophospholipid signaling pathways. Our results also showed the different toxicity mechanisms on transcriptional and metabolic profiles in the combination effects of bisphenol compounds and MP. The co-exposure of BPA and MP predominantly influenced neurotoxicity via the MAPK signaling pathway and voltage-dependent calcium channels, whereas the co-exposure of BPS and MP principally affected visual development through phototransduction and retinol metabolism. The co-exposure of BPA and MP, as well as BPS and MP, specifically regulate lipid metabolism and carbohydrate metabolism in zebrafish offspring, respectively. Overall, this study provided a deep understanding of the toxicity differences between co-exposure and single exposure of bisphenol compound and MP in zebrafish, as well as the transgenerational effects and potential molecular mechanisms of bisphenol compounds and MP in zebrafish offspring.

Potency and mechanism of p-glycoprotein chemosensitizers in rainbow trout (Oncorhynchus mykiss) hepatocytes

The membrane efflux transporter P-glycoprotein (P-gp, [ABCB1, MDR1]) exports a wide range of xenobiotic compounds, resulting in a continuous first line of defense against toxicant accumulation at basal expression levels, and contributing to the multixenobiotic resistance (MXR) phenotype at elevated expression levels. Relatively little information exists on P-gp inhibition in fish by chemosensitizers, compounds which lower toxicity thresholds for harmful P-gp substrates in complex mixtures. The effects of four known mammalian chemosensitizers (cyclosporin A [CsA], quinidine, valspodar [PSC833], and verapamil) on the P-gp-mediated transport of rhodamine 123 (R123) and cortisol in primary cultures of rainbow trout (Oncorhynchus mykiss) hepatocytes were examined. Competitive accumulation assays using 25 µM R123 or cortisol and varying concentrations of chemosensitizers (0-500 µM) were used. CsA, quinidine, and verapamil inhibited R123 export (IC50 values ± SE: 132 ± 60, 83.3 ± 27.2, and 43.2 ± 13.6 µM, respectively). CsA and valspodar inhibited cortisol export (IC50 values: 294 ± 106 and 92.2 ± 34.9 µM, respectively). In an ATP depletion assay, hepatocytes incubated with all four chemosensitizers resulted in lower free ATP concentrations, suggesting that they act via competitive inhibition. Chemosensitizers that inhibit MXR transporters are an important class of environmental pollutant, and these results show that rainbow trout transporters are inhibited by similar chemosensitizers (and mostly at similar concentrations) as seen in mammals and other fish species.

Ivermectin toxicokinetics in rainbow trout (Oncorhynchus mykiss) following P-glycoprotein inhibition

Changes to ivermectin (IVM [22,23-dihydro avermectin B1a + 22,23-dihydro avermectin B1b]) toxicokinetics (TK) with and without P-glycoprotein (P-gp) inhibition by cyclosporin A (CsA) were examined in rainbow trout (Oncorhynchus mykiss). Rainbow trout were injected with 175 μg/kg 3H-IVM (8.6 μCi/mg IVM) with or without co-administration of 480 μg/kg CsA into the caudal vasculature. Fish were sacrificed at various time points (0.25, 0.5, 1, 3, 24, 48, 96, and 168 h) for organ and tissue sampling (blood, liver, kidney, gill, intestines, brain [5 regions], eye, gonad, and fat) which were analyzed for IVM-derived radioactivity. The IVM concentration decreased over time in blood, liver, kidney, and gill, while concentrations in other tissues remained constant. The highest maximum IVM concentration (Cmax) was found in kidney, followed by liver; the lowest Cmax was found in eye, followed by brain and adipose tissue. The highest % of the administered dose was found in the blood 15 min post-IVM administration, followed by the intestine at 60 min post-IVM administration. P-gp inhibition by CsA did not significantly affect calculated TK parameters (AUC [7.33 ± 0.73 - 11.5 ± 2.5 mg•h/kg], mean residence time [84.7 ± 21 - 125 ± 55 h], T1/2 [58.7 ± 15 - 86.8 ± 38 h], clearance rate [0.0152 ± 0.0033 - 0.0239 ± 0.0024 L/kg•h], or volume of distribution [1.91 ± 0.47 - 2.02 ± 0.33 L/kg]), but resulted in small but significant changes in the % administered dose found in blood and medulla. These results suggest that P-gp plays a limited role in overall IVM TK, and that its role in xenobiotic protection may be much less robust in fish than it is in mammals.

Exploration of Response Mechanisms in the Gills of Pacific Oyster (Crassostrea gigas) to Cadmium Exposure through Integrative Metabolomic and Transcriptomic Analyses

Marine mollusks, including oysters, are highly tolerant to high levels of cadmium (Cd), but the molecular mechanisms underlying their molecular response to acute Cd exposure remain unclear. In this study, the Pacific oyster Crassostrea gigas was used as a biological model, exposed to acute Cd stress for 96 h. Transcriptomic analyses of their gills were performed, and metabolomic analyses further validated these results. In our study, a total of 111 differentially expressed metabolites (DEMs) and 2108 differentially expressed genes (DEGs) were identified under acute Cd exposure. Further analyses revealed alterations in key genes and metabolic pathways associated with heavy metal stress response. Cd exposure triggered physiological and metabolic responses in oysters, including enhanced oxidative stress and disturbances in energy metabolism, and these changes revealed the biological response of oysters to acute Cd stress. Moreover, oysters could effectively enhance the tolerance and detoxification ability to acute Cd exposure through activating ABC transporters, enhancing glutathione metabolism and sulfur relay system in gill cells, and regulating energy metabolism. This study reveals the molecular mechanism of acute Cd stress in oysters and explores the molecular mechanism of high tolerance to Cd in oysters by using combined metabolomics and transcriptome analysis.

Effects of cold acclimation on serum biochemical parameters and metabolite profiles in Schizothorax prenanti

BACKGROUND

Environmental temperature is critical in regulating biological functions in fish. S. prenanti is a kind of cold-water fish, but of which we have little knowledge about the metabolic adaptation and physiological responses to long-term cold acclimation.

RESULTS

In this study, we determined the physiological responses of S. prenanti serum after 30 days of exposure to 6℃. Compared with the control group, the levels of TC, TG, and LDL-C in the serum were significantly (P < 0.05) increased, and the level of glucose was significantly (P < 0.05) decreased under cold acclimation. Cold acclimation had no effect on the gene expression of pro-inflammatory factors and anti-inflammatory factors of S. prenanti. Metabolomics analysis by LC-MS showed that a total of 60 differential expressed metabolites were identified after cold acclimation, which involved in biosynthesis of amino acids, biosynthesis of unsaturated fatty acids, steroid degradation, purine metabolism, and citrate cycle pathways.

CONCLUSION

The results indicate that cold acclimation can alter serum metabolites and metabolic pathways to alter energy metabolism and provide insights for the physiological regulation of cold-water fish in response to cold acclimation.

Toxic heavy metals in a landfill environment (Vientiane, Laos): Fish species and associated health risk assessment

Leachates from municipal landfills introduce toxic heavy metals into water, causing bioaccumulation. This study assesses metal levels and potential human health risks associated with consuming Anabas testudineus and Channa striata. Inductively coupled plasma mass spectrometry detected Cd, Cu, Cr, Ni, Pb, and Zn in both fish species. Leachate metal concentrations meet international discharge standards, Cd, Cr, and Pb in the fish exceed the international accepted values. Gastrointestinal tract+liver samples show significant variation between species, particularly in Cd and Pb. EDI, THQ/HI, and TR for the both species fall below TDIs, lower than the limit of 1, and within the acceptable range of the US-EPA permissible limit, respectively. Fish consumption appears safe regarding carcinogenic risk, but exceeding metal limits could impact heavy metals accumulation in the local food chain. Raising public awareness is crucial, and governmental agencies and environmental organizations should enhance waste treatment technologies and enact relevant health legislation.

The roles of ABCB1/P-glycoprotein drug transporters in regulating gut microbes and inflammation: insights from animal models, old and new

Commensal enteric bacteria have evolved systems that enable growth in the ecologic niche of the host gastrointestinal tract. Animals evolved parallel mechanisms to survive the constant exposure to bacteria and their metabolic by-products. We propose that drug transporters encompass a crucial system to managing the gut microbiome. Drug transporters are present in the apical surface of gut epithelia. They detoxify cells from small molecules and toxins (xenobiotics) in the lumen. Here, we review what is known about commensal structure in the absence of the transporter ABCB1/P-glycoprotein in mammalian models. Knockout or low-activity alleles of ABCB1 lead to dysbiosis, Crohn's disease and ulcerative colitis in mammals. However, the exact function of ABCB1 in these contexts remain unclear. We highlight emerging models-the zebrafish Danio rerio and sea urchin Lytechinus pictus-that are poised to help dissect the fundamental mechanisms of ATP-binding cassette (ABC) transporters in the tolerance of commensal and pathogenic communities in the gut. We and others hypothesize that ABCB1 plays a direct role in exporting inflammatory bacterial products from host epithelia. Interdisciplinary work in this research area will lend novel insight to the transporter-mediated pathways that impact microbiome community structure and accelerate the pathogenesis of inflammatory bowel disease when perturbed. This article is part of the theme issue 'Sculpting the microbiome: how host factors determine and respond to microbial colonization'.

Effects of Commercial Probiotics on the Growth Performance, Intestinal Microbiota and Intestinal Histomorphology of Nile Tilapia (Oreochromis niloticus) Reared in Biofloc Technology (BFT)

Though different types of commercial probiotics are supplemented in biofloc technology (BFT), very little information is available on their effects on the farmed fish. Therefore, this study focused on evaluating the effects of three most commonly used commercial probiotics on the growth performance, intestinal histomorphology, and intestinal microbiota of Nile tilapia (Oreochromis niloticus) reared in BFT. Tilapia fry, with an average weight of 3.02 ± 0.50 g, were stocked at a density of 60 fry/0.2 m3, and cultured for 90 days. Three commercial probiotics were administered, with three replications for each: a single-genus multi-species probiotic (Bacillus spp.) (T1), a multi-genus multi-species probiotic (Bacillus sp., Lactobacillus sp., Nitrosomonas sp., Nitrobacter sp.) (T2), and a multi-species probiotic (Bacillus spp.) combined with enzymes including amylase, protease, cellulase, and xylanase (T3). The results showed significant variations in growth and feed utilization, with T3 outperforming other treatments in terms of weight gain, liver weight, and intestine weight. Adding Bacillus spp. with enzymes (T3) to water significantly increased the histomorphological parameters (villi length, villi depth, crypt depth, muscle thickness, intestinal thickness) as well as microbes (total viable count and total lactic acid bacteria) of intestine of fish compared to T1 and T2, leading to improved digestion and absorption responses. It is concluded that the supplementation of commercial probiotics has potential benefits on farmed fish species in BFT.

Microcystin-LR sensitizes the Oncorhynchus mykiss intestinal epithelium and interacts with paralytic shellfish toxins to alter oxidative balance

In the context of harmful algal blooms, fish can be exposed to the combined effects of more than one toxin. We studied the effects of consecutive exposure to Microcystin-LR (MCLR) in vivo and paralytic shellfish toxins (PST) ex vivo/in vitro (MCLR+PST) in the rainbow trout Oncorhynchus mykiss's middle intestine. We fed juvenile fish with MCLR incorporated in the feed every 12 h and euthanized them 48 h after the first feeding. Immediately, we removed the middle intestine to make ex vivo and in vitro preparations and exposed them to PST for one hour. We analyzed glutathione (GSH) and glutathione disulfide (GSSG) contents, glutathione S-transferase (GST), glutathione reductase (GR), catalase (CAT), and protein phosphatase 1 (PP1) activities in ex vivo intestinal strips; apical and basolateral ATP-biding cassette subfamily C (Abcc)-mediated transport in ex vivo everted and non- everted sacs; and reactive oxygen species (ROS) production in isolated enterocytes in vitro. MCLR+PST treatment decreased the GSH content, GSH/GSSG ratio, GST activity, and increased ROS production. GR activity remained unchanged, while CAT activity only increased in response to PST. MCLR inhibited PP1 activity and activated Abcc-mediated transport only at the basolateral side of the intestine. Our results show a combined effect of MCLR+PST on the oxidative balance in the O. mykiss middle intestine, which is not affected by the two toxins groups when applied individually. Basolateral Abcc transporters activation by MCLR treatment could lead to an increase in the absorption of toxicants (including MCLR) into the organism. Therefore, MCLR makes the O. mykiss middle intestine more sensitive to possibly co-occurring cyanotoxins like PST.

Ivermectin Toxicokinetics in Rainbow Trout (Oncorhynchus mykiss) following P-glycoprotein Induction

Alterations in ivermectin (IVM, 22,23-dihydro avermectin B1a+22,23-dihydro avermectin B1b) toxicokinetics following P-glycoprotein (P-gp) induction by clotrimazole (CTZ) were examined in rainbow trout (Oncorhynchus mykiss) to assess the potential importance of P-gp activity levels in xenobiotic distribution and kinetics in fish. Control and fish pretreated with CTZ (30 µmol/kg) were administered 175 µg/kg 3H-IVM into the caudal vasculature. At various time points (0.25, 0.5, 1, 3, 24, 48, 96, and 168 h) following injection, tissues (blood, liver, kidney, gill, intestines, brain [5 regions], eye, gonad and fat) were removed analyzed for IVM-derived radioactivity. IVM concentration declined in blood, liver, kidney and gill, and concentrations in other tissues remained constant over the sampling period. The highest measured concentrations were found in kidney, followed by liver, with the lowest values found in brain, eye and gonad. The highest % of the administered dose was found in the liver and kidney in the immediate hours post-administration, and in the intestines and fat at 24 h post-administration. P-gp induction by CTZ did not alter IVM distribution or any calculated toxicokinetic parameter (AUC, mean residence time, T1/2, clearance rate, volume of distribution), suggesting that P-gp induction may be limited or that P-gp plays a lesser role in xenobiotic kinetics in fish compared to mammals.

Profiling the Physiological Roles in Fish Primary Cell Culture

Fish primary cell culture has emerged as a valuable tool for investigating the physiological roles and responses of various cell types found in fish species. This review aims to provide an overview of the advancements and applications of fish primary cell culture techniques, focusing on the profiling of physiological roles exhibited by fish cells in vitro. Fish primary cell culture involves the isolation and cultivation of cells directly derived from fish tissues, maintaining their functional characteristics and enabling researchers to study their behavior and responses under controlled conditions. Over the years, significant progress has been made in optimizing the culture conditions, establishing standardized protocols, and improving the characterization techniques for fish primary cell cultures. The review highlights the diverse cell types that have been successfully cultured from different fish species, including gonad cells, pituitary cells, muscle cells, hepatocytes, kidney and immune cells, adipocyte cells and myeloid cells, brain cells, primary fin cells, gill cells, and other cells. Each cell type exhibits distinct physiological functions, contributing to vital processes such as metabolism, tissue regeneration, immune response, and toxin metabolism. Furthermore, this paper explores the pivotal role of fish primary cell culture in elucidating the mechanisms underlying various physiological processes. Researchers have utilized fish primary cell cultures to study the effects of environmental factors, toxins, pathogens, and pharmaceutical compounds on cellular functions, providing valuable insights into fish health, disease pathogenesis, and drug development. The paper also discusses the application of fish primary cell cultures in aquaculture research, particularly in investigating fish growth, nutrition, reproduction, and stress responses. By mimicking the in vivo conditions in vitro, primary cell culture has proven instrumental in identifying key factors influencing fish health and performance, thereby contributing to the development of sustainable aquaculture practices.

ABC transporter-mediated MXR mechanism in fish embryos and its potential role in the efflux of nanoparticles

ATP-binding cassette (ABC) transporters are believed to protect aquatic organisms by pumping xenobiotics out, and recent investigation has suggested their involvement in the detoxification and efflux of nanoparticles (NPs), but their roles in fish embryos are poorly understood. In this regard, this paper summarizes the recent advances in research pertaining to the development of ABC transporter-mediated multi-xenobiotic resistance (MXR) mechanism in fish embryos and the potential interaction between ABC transporters and NPs. The paper focuses on: (1) Expression, function, and modulation mechanism of ABC proteins in fish embryos; (2) Potential interaction between ABC transporters and NPs in cell models and fish embryos. ABC transporters could be maternally transferred to fish embryos and thus play an important role in the detoxification of various chemical pollutants and NPs. There is a need to understand the specific mechanism to benefit the protection of aquatic resources.

Factors Determining the Susceptibility of Fish to Effects of Human Pharmaceuticals

The increasing levels and frequencies at which active pharmaceutical ingredients (APIs) are being detected in the environment are of significant concern, especially considering the potential adverse effects they may have on nontarget species such as fish. With many pharmaceuticals lacking environmental risk assessments, there is a need to better define and understand the potential risks that APIs and their biotransformation products pose to fish, while still minimizing the use of experimental animals. There are both extrinsic (environment- and drug-related) and intrinsic (fish-related) factors that make fish potentially vulnerable to the effects of human drugs, but which are not necessarily captured in nonfish tests. This critical review explores these factors, particularly focusing on the distinctive physiological processes in fish that underlie drug absorption, distribution, metabolism, excretion and toxicity (ADMET). Focal points include the impact of fish life stage and species on drug absorption (A) via multiple routes; the potential implications of fish's unique blood pH and plasma composition on the distribution (D) of drug molecules throughout the body; how fish's endothermic nature and the varied expression and activity of drug-metabolizing enzymes in their tissues may affect drug metabolism (M); and how their distinctive physiologies may impact the relative contribution of different excretory organs to the excretion (E) of APIs and metabolites. These discussions give insight into where existing data on drug properties, pharmacokinetics and pharmacodynamics from mammalian and clinical studies may or may not help to inform on environmental risks of APIs in fish.

Physiological Benefits of Dietary Lysophospholipid Supplementation in a Marine Fish Model: Deep Analyses of Modes of Action

Given the hydrophilic structure of lysophospholipids (LPLs), their dietary inclusion translates into a better emulsifying capacity of the dietary components. The present study aimed to understand the mechanisms underlying the growth-promoting effect of LPL supplementation by undertaking deep analyses of the proximal intestine and liver interactomes. The Atlantic salmon (Salmo salar) was selected as the main aquaculture species model. The animals were divided into two groups: one was fed a control diet (C-diet) and the other a feed (LPL-diet) supplemented with an LPL-based digestive enhancer (0.1% AQUALYSO^®, Adisseo). The LPL-diet had a positive effect on the fish by increasing the final weight by 5% and reducing total serum lipids, mainly due to a decrease in the plasma phospholipid (p < 0.05). In the intestine, the upregulated interactome suggests a more robust digestive capacity, improving vesicle-trafficking-related proteins, complex sugar hydrolysis, and lipid metabolism. In the liver, the LPL-diet promotes better nutrients, increasing several metabolic pathways. The downregulation of the responses to stress and stimuli could be related to a reduced proinflammatory state. This study on the benefits and modes of action of dietary LPLs opens a new window into fish nutrition and could be extended to other productive species.

Impact of Pesticide Residues on the Gut-Microbiota–Blood–Brain Barrier Axis: A Narrative Review

Accumulating evidence indicates that chronic exposure to a low level of pesticides found in diet affects the human gut-microbiota–blood–brain barrier (BBB) axis. This axis describes the physiological and bidirectional connection between the microbiota, the intestinal barrier (IB), and the BBB. Preclinical observations reported a gut microbial alteration induced by pesticides, also known as dysbiosis, a condition associated not only with gastrointestinal disorders but also with diseases affecting other distal organs, such as the BBB. However, the interplay between pesticides, microbiota, the IB, and the BBB is still not fully explored. In this review, we first consider the similarities/differences between these two physiological barriers and the different pathways that link the gut microbiota and the BBB to better understand the dialogue between bacteria and the brain. We then discuss the effects of chronic oral pesticide exposure on the gut-microbiota-BBB axis and raise awareness of the danger of chronic exposure, especially during the perinatal period (pregnant women and offspring).

Microcystin-LR modulates multixenobiotic resistance proteins in the middle intestine of rainbow trout, Oncorhynchus mykiss

Global climate change favors explosive population growth events (blooms) of phytoplanktonic species, often producing toxic products, e.g., several genera of cyanobacteria synthesize a family of cyanotoxins called microcystins (MCs). Freshwater fish such as the rainbow trout Oncorhynchus mykiss can uptake MCs accumulated in the food chain. We studied the toxic effects and modulation of the activity and expression of multixenobiotic resistance proteins (ABCC transporters and the enzyme glutathione S-transferase (GST) in the O. mykiss middle intestine by microcystin-LR (MCLR). Juvenile fish were fed with MCLR incorporated in the food every 12 h and euthanized at 12, 24, or 48 h. We estimated the ABCC-mediated transport in ex vivo intestinal strips to estimate ABCC-mediated transport activity. We measured total and reduced (GSH) glutathione contents and GST and glutathione reductase (GR) activities. We studied MCLR cytotoxicity by measuring protein phosphatase 1 (PP1) activity and lysosomal membrane stability. Finally, we examined the relationship between ROS production and lysosomal membrane stability through in vitro experiments. Dietary MCLR had a time-dependent effect on ABCC-mediated transport, from inhibition at 12 h to a significant increase after 48 h. GST activity decreased only at 12 h, and GR activity only increased at 48 h. There were no effects on GSH or total glutathione contents. MCLR inhibited PP1 activity and diminished the lysosomal membrane stability at the three experimental times. In the in vitro study, the lysosomal membrane stability decreased in a concentration-dependent fashion from 0 to 5 µmol L ^- 1 MCLR, while ROS production increased only at 5 µmol L ^- 1 MCLR. MCLR did not affect mRNA expression of abcc2 or gst-π. We conclude that MCLR modulates ABCC-mediated transport activity in O. mykiss's middle intestine in a time-dependent manner. The transport rate increase does not impair MCLR cytotoxic effects.