Environmentally relevant concentration of cypermethrin or/and sulfamethoxazole induce neurotoxicity of grass carp: Involvement of blood-brain barrier, oxidative stress and apoptosis

Ferulic acid alleviates long-term avermectin-induced damage to the spleen of carp and restores its inflammatory response and oxidative balance

Extensive use of avermectin (AVM) in agriculture can seriously contaminate fish in aquaculture. Ferulic acid (FA) is a strong antioxidant sourced from plants and is widely applied in food and medicine, but its protective function on the immunological damage caused by AVM is still lacking. In this study, carp were chronically exposed to (1/10 96 hr LC50) AVM for 30 day(s), with a dietary supplement of FA (400 mg/kg) to assess its effects on carp spleen. The experimental groups (n = 10) included: control, AVM-exposed (2.404 µg/L), FA + AVM co-treated, and FA alone. Long-term AVM exposure altered spleen tissue, reducing serum complement C3 (p < 0.01) and immunoglobulin M levels (p < 0.001), and increasing pro-inflammatory tnf-α (p < 0.001), il-6 (p < 0.001), il-1β (p < 0.001), and inos mRNA levels, whilst down-regulating the anti-inflammatory tgf-β (p < 0.05). Additionally, it disrupted the balance of oxidative stress indicators such as MDA (p < 0.001), T-AOC, GSH, and CAT, leading to spleen tissue apoptosis (42.4%). However, the addition of FA reversed these conditions, elevated the anti-inflammatory factor, and improved spleen immune function following chronic exposure to AVM in carp. Moreover, the ability to restore oxidative homeostasis in carp by adjusting the Nrf2/NQO-1 axis protected the health of spleen tissues. This discovery also supports the development of fish feed for aquaculture.

Fluoroquinolone and sulfonamide antibiotics (single and mixtures) impair the motor function of zebrafish larvae at environmentally relevant concentrations

The occurrence of antibiotics in freshwater is a global concern, with evidence pointing to potential neurotoxic effects after prolonged exposure. However, data on their impact on behavior, particularly at environmentally relevant concentrations, remain limited. This study examined the motor function of zebrafish larvae exposed to single and mixture of antibiotics from the sulfonamide and fluoroquinolone classes. Ten antibiotics were assessed, namely, fluoroquinolones: ciprofloxacin (CIP), norfloxacin (NOR), pefloxacin (PEF), ofloxacin (OFL), and enrofloxacin (ENR) and sulfonamides: sulfamethoxazole (SMX), sulfadiazine (SDZ), sulfamethazine (SMZ), sulfamerazine (SMR), and sulfadimethoxine (SDM). After 24 h of exposure, single exposures revealed that all antibiotics disrupted at least one typical larval behavior at environmentally relevant concentrations. Larvae showed similarities in the escape response provoked by a vibrating acoustic stimulus (startle) according to the antibiotic class, despite the significantly more severe effects of SDM on startle and SMX on habituation to repetitive acoustic stimulation. Exposures to sulfonamide mixtures caused a non-monotonic effect on the startle response and significantly increased the distance traveled over the visual motor response. On the other hand, fluoroquinolone mixtures at 0.1 and 10 μg L-1 reduced the habituation of zebrafish larvae. Biochemical markers suggest sulfonamide mixtures can potentially decrease catalase activity, whereas reduced glutathione levels are increased in fluoroquinolone mixtures at 10 μg L-1. Such findings support recent discussions on the potential of antibiotics to impair motor function in aquatic species, whether in isolated or combined forms. Regulatory mechanisms focused on discharging those substances into freshwater are pivotal to preventing adverse effects and ensuring biota safety.

Comparative toxicotranscriptomics of longterm cypermethrin exposure to aquacultured fish Labeo catla (Catla)

Cypermethrin (CYP), a persistent synthetic pyrethroid, poses a significant threat to aquatic life. The present work aims to identify the effect of CYP on the brain and liver transcriptome profile of fish Labeo catla. CYP (0.7 µg/L) was long-term exposed to L catla, and differentially expressed genes (DEGs) were investigated using RNA-sequencing (Illumina HiSeq2500). A total of 2665 and 18,020 unigenes and 333 and 454 DEGs were identified in the brain and liver transcriptome, respectively. DEGs associated with MAPK signaling and apoptosis pathways were co-expressed in both brain and liver transcriptome, according to pathway enrichment analysis. Concurrently, steroid and terpenoid backbone biosynthesis were overexpressed in liver, suggesting induction of apoptosis and steroid production, respectively. Among the identified DEGs, fosab, nr4a1, dhcr24 and tm7sf2 were significantly enriched and molecular docking studies further supported our findings. Long-term CYP exposure also altered the levels of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), and malondialdehyde (MDA) content in L. catla. The present study provides significant insights into the consequences of CYP-induced toxicity in fish and identified functional genes that could be screened for estimating the toxic load of CYP in future ecotoxicological risk assessment studies.

Benzimidazole Fungicide Carbendazim Induces Gut Inflammation through the TLR5/NF-κB Pathway in Grass Carp

Fungicides have been increasingly used across various sectors, including agriculture and textiles. The biocidal properties of fungicides may negatively impact the stability of intestinal microbiota, thereby posing a threat to intestinal health. In this study, we investigated the mechanisms of intestinal damage and functional abnormalities in grass carp following a 42-day exposure to the widely used fungicide carbendazim at environmentally relevant concentrations (0.2 to 20 μg/L). Histopathological observations, mRNA and protein expression analyses, biochemical analysis, quantification of short-chain fatty acids (SCFAs), cytokines, lipopolysaccharide (LPS), and 16S ribosomal ribonucleic acid (rRNA), as well as internal transcribed spacer (ITS) sequencing, were performed. At environmentally relevant concentrations, carbendazim strongly induced intestinal inflammation, leading to increased transcriptional and translational levels of genes involved in the toll-like receptor five (TLR5)/nuclear factor kappa B (NF-κB) pathway, including TLR5, NF-κB, interleukin-1 beta (IL-1β), and tumor necrosis factor-alpha (TNFα). Additionally, carbendazim damaged intestinal barriers and reduced the expression of tight junction proteins (e.g., occludin and zonula occludens-1/2), goblet cells, and immunoglobulin M levels, while also disrupting the gut microbiome, leading to intestinal metabolic disorders, particularly decreases in SCFAs and increases in LPS. Treatment with the TLR5 antagonist TH1020 mitigated intestinal inflammation caused by carbendazim, subsequently improving mechanical barrier function. Overall, our findings provide new insights into the toxicological mechanisms underlying intestinal damage caused by carbendazim in grass carp, indicating that carbendazim poses a significant threat to nontarget organisms. Given its widespread detection in the environment, these results underscore the substantial ecological risks to the gut health of fish living in carbendazim-contaminated water bodies.

Association between exposure to 35 environmental pollutants and mortality from cerebrovascular diseases: A long-term prospective study

Environmental pollutants have been implicated in various detrimental health effects. However, the specific relationship between environmental pollutant exposure and the risk of cerebrovascular disease mortality remains uncertain. This study aimed to comprehensively explore the potential relationship between environmental pollutant exposure and risk of cerebrovascular disease mortality in the U.S. population. Data on 35 types of environmental pollutant exposure were extracted from the National Health and Nutrition Examination Survey (NHANES). Cerebrovascular disease-related deaths were ascertained from the National Center for Health Statistics, with mortality follow-up data available until December 31, 2019. Weighted univariable and multivariable Cox regression analyses were employed to evaluate the association between environmental pollutants and mortality from cerebrovascular diseases. A total of 11,643 participants were included for organochlorine pesticides, 11,912 for brominated flame retardants, 13,797 for per- and polyfluoroalkyl substances, and 14,560 for phthalates, with a median follow-up of 8.6 years. The average age of participants was approximately 46 years, with male participants comprising around 48 % of the cohort. Four types of organochlorine pesticides (hexachlorobenzene, oxychlordane, 2,2-Bis(4-chlorophenyl)-1,1-dichloroethene, and trans-nonachlor), perfluorooctanoic acid, and mono-n-butyl phthalate were found to be associated with an increased risk of cerebrovascular disease mortality. Furthermore, the composite environmental index derived from these six pollutants also demonstrated a significant correlation with elevated cerebrovascular disease mortality risk. This prospective study provides evidence of an association between certain environmental pollutant exposure (especially for organochlorine pesticides) and risk of cerebrovascular disease mortality. These findings provide new insights into potential prevention strategies for this disease mortality from the perspective of environmental pollutant exposure.

Degradation mechanism and decomposition of sulfamethoxazole aqueous solution with persulfate activated by dielectric barrier discharge

The present study focused on the degradation of sulfamethoxazole (SMX) aqueous solution and the toxicity of processing aqueous by the dielectric barrier discharge (DBD) activated persulfate (PS). The effects of input voltage, input frequency, duty cycle, and PS dosage ratio on the SMX degradation efficiency were measured. Based on the results of the Response Surface Methodology (RSM), SMX degradation efficiency reached 83.21% which is 10.54% higher than that without PS, and the kinetic constant was 0.067 min-1 in 30 min when the input voltage at 204 V (input power at 110.6 W), the input frequency at 186 Hz, the duty cycle at 63%, and the PS dosage ratio at 5.1:1. The addition of PS can produce more active particles reached 1.756 mg/L (O3), 0.118 mg/L (H2O2), 0.154 mmol/L (·OH) in 30 min. Furthermore, the DBD plasma system effectively activated an optimal amount of PS, leading to improved removal efficiency of COD, and TOC to 30.21% and 47.21%, respectively. Subsequently, eight primary by-products were pinpointed, alongside the observation of three distinct pathways of transformation. Predictions from the ECOSAR software indicated that most of the degradation intermediates were less toxic than SMX. The biological toxicity experiments elucidated that the treatment with the DBD/PS system effectively reduced the mortality of zebrafish larvae caused by SMX from 100% to 20.13% and improved the hatching rate from 55.69% to 80.86%. In particular, it is important to note that the degradation intermediates exhibit teratogenic effects on zebrafish larvae.

Temporal and dosage impact of magnesium oxide nanoparticles on grass carp: unveiling oxidative stress, DNA damage, and antioxidant suppression

Magnesium oxide nanoparticles (MgO NPs) have gained significant importance in biomedicine and variety of nanotechnology-based materials used in the agriculture and biomedical industries. However, the release of different nanowastes in the water ecosystem becomes a serious concern. Therefore, this study was executed to evaluate the toxic impacts of MgO NPs on grass carp. A total of 60 grass carp were randomly divided in three groups (G0, G1, and G2). Fish reared in group G0 were kept as control while fish of groups G1 and G2 were exposed to 0.5 mg/L and 0.7 mg/L MgO NPs, respectively, mixed in water for 21 days. The 96h median lethal concentration (LC50) of MgO NPs was found to be 4.5 mg/L. Evaluation of oxidative stress biomarkers, antioxidant enzymes, DNA damage in different visceral organs and the presence of micronuclei in erythrocytes were determined on days 7, 14, and 21 of the trial. Results revealed dose- and time-dependent significantly increased values of reactive oxygen species, lipid peroxidation product, DNA damage in multiple visceral organs and formation of micronuclei in the erythrocytes of treated fish (0.7 mg/L). The results on antioxidant profile exhibited significantly lower amounts of total proteins, catalase, superoxide dismutase, and peroxidase in visceral organs of the fish exposed to MgO NPs (0.5 and 0.7 mg/L) at day 21 of trial compared to control group. In conclusion, it has been recorded that MgO NPs severely influence the normal physiological functions of the grass carp even at low doses.

The phototoxicity of sulfamethoxazole stress on pakchoi cabbage (Brassica rapa var. chinensis) seedlings: From the perspective of photoreaction and omics analysis

The increasing use of antibiotics has attracted widespread attention to their environmental risks. However, the phototoxicity of sulfonamide antibiotics to plants remain unclear. In this study, the mechanism of the effect of sulfamethoxazole on photosynthesis of pakchoi cabbage (Brassica rapa var. chinensis) was investigated. The results showed that sulfamethoxazole inhibited the growth of pakchoi cabbage and produced photosynthetic toxicity. The growth inhibition rates increased with concentration, the root and shoot weight were 76.02 % and 47.04 % of the control, respectively, with stay-greens phenomenon in 4 mg·L-1 sulfamethoxazole treatment. Chlorophyll precursors (protoporphyrin IX (Proto IX), Mg-proto IX, and protochlorophyllide (Pchlide), 5-aminolevulinic acid (ALA), and porphobilinogen (PBG)) were 1.38-, 1.26-, 1.12-, 1.71-, and 0.96-fold of the control, respectively; photosynthetic pigments (chlorophyll a, chlorophyll b, and carotenoids) were 1.26-, 1.39-, and 1.03-fold of the control, respectively. Respiration rate was 271.42 % of the control, whereas the net photosynthetic rate was 50.50 % of the control. The maximum photochemical quantum yield of PSII (Fv/Fm), the actual photosynthetic efficiency (Y(II)), the quantum yield of non-regulated energy dissipation (Y(NO)), the apparent electron transfer efficiency of PSII (ETR) under actual light intensity were affected, and chloroplast swelling was observed. Proteomic analysis showed that photosynthesis-related pathways were significantly up-regulated, biological processes such as light response, carbohydrates, and reactive oxygen species were activated. Metabolomic analysis revealed that the tricarboxylic acid cycle (TCA cycle) and carbohydrate catabolism were stimulated significantly (p < 0.05), sugars and amino acids were increased to regulate and enhance the resilience of photosynthesis. While folate biosynthesis and ribosomal pathways were significantly down-regulated, the synthesis and translation processes of amino acids and nucleotides were inhibited.

Testing the detoxification power of black cumin oil (Nigella sativa) over cypermethrin insecticide effects in rainbow trout (Oncorhynchus mykiss) at multiple scales

This study investigated the curative effect of black cumin oil (Nigella sativa, NS), which is a phytotherapeutic agent against to cypermethrin (CYP), which is known to have adverse effects on rainbow trout (Oncorhynchus mykiss)'s behavioral changes, oxidative stress-mediated neurotoxicity, hematotoxicity and hepatotoxicity parameters.At the end of the trial period; (i) evaluation of critical swimming speed (Ucrit) (ii) hematology indices [white blood cell (WBC), red blood cell (RBC), hemoglobin (Hgb), hematocrit (Hct), mean cell volume (MCV), mean cell hemoglobin) (MCH), mean cell hemoglobin concentration (MCHC)] (iii) Elucidation of the mechanism of functional damage in brain tissue of O. mykiss by neurological parameter [acetylcholinesterase (AChE)] (iv) Evaluation of oxidative damage in oxidative stress-mediated neurotoxicity and hepatotoxicity in liver, gill and brain tissue of O. mykiss with antioxidant enzymes [(Superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), Glutathione (GSH)] and [(detection by means of malondialdehyde (MDA)] (v) Obtaining applicable data in the toxicological field using a multi-biomarker approach to investigate the modulation of NS administration via target markers in the physiological pathway of O. mykiss were aimed.As a result of CYP application, it was determined that the Ucrit value of O. mykiss decreased significantly. It was determined that the changes in the values of RBC, Hgb and Hct, which are among the hematology parameters examined in the blood tissue, were statistically significant (p < 0.05). It was determined that WBC value was inhibited by CYP application and NS tried to make a positive contribution to WBC. It was determined that the AChE activity of O. mykiss in the brain tissue had a statistically significant inhibition in the CYP-treated group (p < 0.05). SOD, CAT, GPx, enzyme activities were found to be inhibited by CYP application and were statistically significant (p < 0.05). Acute toxicity of CYP was determined by antioxidant enzyme biomarkers in gill tissue. In the results obtained; While inhibitions were determined in SOD, CAT, GPx activities compared to the control group, an induction occurred in MDA value.NS administration was noted to be an important modulator of the SOD-CAT system against CYP exposure at both concentrations. Thus, it can be said that it indirectly functions as an effective antioxidant through the NS receptor protein and structurally stimulates the synthesis and activity of antioxidative enzymes under oxidative stress.

Deltamethrin increased susceptibility to Aeromonas hydrophila in crucian carp through compromising gill barrier

Pyrethroids serve as a significant method for managing and preventing parasitic diseases in fish. Among these, deltamethrin (DEL) is used extensively in aquatic environments. Our previous work has been confirmed that DEL exposure can induce oxidative stress and immunosuppression on the gill mucosal barrier of crucian carp (Carassius auratus). However, it is not clear whether DEL affects the susceptibility of farmed fish to bacterial infection. In this study, fish was pre-exposed to different DEL concentration (0, 0.3 and 0.6 μg L-1) and then challenged by immersion with Aeromonas hydrophila (1.0 × 10^8 CFU mL-1). After immersion challenge, fish pre-exposed to DEL developed prominent lipopolysaccharides level in gill and serum and had a significantly lower survival rate compared to the control group. In DEL pre-exposure fish after immersion, the gill apoptosis levels were significantly higher and disrupted the tight junction barrier by downregulating the zo1 and claudin12. Furthermore, fish pre-exposed to DEL exhibited increased activities of superoxide dismutase (SOD), total antioxidant capacity (T-AOC), and malonaldehyde (MDA) levels in the early stage after immersion but experiencing decreased activities of glutathione peroxidase (GPx) and lysozyme (LZM) in the later stage after immersion. And this process was regulated by the NRF2 pathway. Additionally, fish pre-exposed to DEL after immersion had significantly lower mRNA levels of immune-related genes tlr4, myd88, tnfα, and il-1β. Overall, these findings indicate that DEL damaged the gill barrier, weakened the immune response, raised LPS levels, and heightened vulnerability to A. hydrophila infection in crucian carp, resulting in mortality. Thus, this work will help social groups and aquaculture workers to understand the potential risk of DEL exposure for bacterial secondary infection in cultured fish.

Parental exposure to Cypermethrin causes intergenerational toxicity in zebrafish offspring

Cypermethrin (CYP), a synthetic pyrethroid pesticide, has been detected in agriculture and aquaculture. However, there is limited knowledge about the transgenerational impacts. This study aimed to investigate the developmental toxicity of CYP on F1 larvae offspring of adult zebrafish exposed to various CYP concentrations (5, 10, and 20 μg/L) for 28 days. The results indicated that CYP accumulated in parental zebrafish, and CYP was below the limit of quantification in offspring. Paternal exposure impacted the hatching rate and heart rate of the F1 generation. Furthermore, CYP significantly impacted the development of swim bladders in progeny and dysregulated the genes relevant to swim bladder development. The neutrophil migrated to the swim bladder. The mRNA levels of the inflammatory factors were also significantly elevated. According to network toxicology, PI3-AKT may be the signaling pathway for CYP-influenced bladder development. Subsequent molecular docking and Western blot analysis showed CYP affected the PI3-AKT signaling pathway. Notably, MK-2206, a specific Akt inhibitor, rescued the CYP-induced damage of swim bladder development in offspring. The present study highlights the potential risks of CYP on the development of offspring and lasting impact in aquatic environments.

Metabolic perturbations in zebrafish (Danio rerio) larvae exposed to sulfentrazone and imidacloprid

The intensive and widespread application of pesticides in agroecosystems can lead to the simultaneous exposure of non-target aquatic organisms to insecticides and herbicides. However, the underlying mechanisms through which aquatic organisms undergo metabolic reprogramming to withstand the combined effects of the insecticide imidacloprid (IMI) and herbicide sulfentrazone (SUL) remain poorly elucidated. This study employs metabolomics to investigate the effects of individual and combined exposures to IMI and SUL on zebrafish (Danio rerio), aiming to simulate complex environmental conditions. Metabolomics analysis revealed extensive metabolic reprogramming in larvae induced by the selected agrochemicals. Both individual and combined exposures disrupted nucleotide metabolism, inhibited glycolysis, and led to the accumulation of acetylcholine through the shared modulation of differential metabolites. Notably, individual exposure exhibited a unique mode of action. Larvae exposed to IMI alone showed mitochondrial dysfunction, potentially stemming from interference with the electron transport chain, while SUL-induced disruptions were associated with glycerophospholipid accumulation, marking it as a critical target. Additionally, calculations of the metabolic effect level index indicated antagonistic interactions between SUL and IMI mixtures at an overall metabolic level. The results obtained through investigating the lethal and sub-lethal effects also revealed that the simultaneous application of SUL and IMI may have the potential to diminish acute and developmental toxicity in zebrafish. This study underscores the significance of metabolomics as a valuable and effective strategy for deciphering the toxicity and interactions of agrochemical mixtures.

The azole biocide climbazole induces oxidative stress, inflammation, and apoptosis in fish gut

Climbazole is an azole biocide that has been widely used in formulations of personal care products. Climbazole can cause developmental toxicity and endocrine disruption as well as gut disturbance in aquatic organisms. However, the mechanisms behind gut toxicity induced by climbazole still remain largely unclear in fish. Here, we evaluate the gut effects by exposing grass carp (Ctenopharyngodon idella) to climbazole at levels ranging from 0.2 to 20 μg/L for 42 days by evaluating gene transcription and expression, biochemical analyses, correlation network analysis, and molecular docking. Results showed that climbazole exposure increased cyp1a mRNA expression and ROS level in the three treatment groups. Climbazole also inhibited Nrf2 and Keap1 transcripts as well as proteins, and suppressed the transcript levels of their subordinate antioxidant molecules (cat, sod, and ho-1), increasing oxidative stress. Additionally, climbazole enhanced NF-κB and iκBα transcripts and proteins, and the transcripts of NF-κB downstream pro-inflammatory factors (tnfα, and il-1β/6/8), leading to inflammation. Climbazole increased pro-apoptosis-related genes (fadd, bad1, and caspase3), and decreased anti-apoptosis-associated genes (bcl2, and bcl-xl), suggesting a direct reaction to apoptosis. The molecular docking data showed that climbazole could form stable hydrogen bonds with CYP1A. Mechanistically, our findings suggested that climbazole can induce inflammation and oxidative stress through CYP450s/ROS/Nrf2/NF-κB pathways, resulting in cell apoptosis in the gut of grass carp.

Ecological assessment of stream water polluted by phosphorus chemical plant: Physiological, biochemical, and molecular effects on zebrafish (Danio rerio) embryos

The rapid development of the phosphorus chemical industry has caused serious pollution problems in the regional eco-environment. However, understanding of their ecotoxic effects remains limited. This study aimed to investigate the developmental toxicity of a stream polluted by a phosphorus chemical plant (PCP) on zebrafish embryos. For this, zebrafish embryos were exposed to stream water (0, 25, 50, and 100% v/v) for 96 h, and developmental toxicity, oxidative stress, apoptosis, and DNA damage were assessed. Stream water-treated embryos exhibited decreased hatching rates, heart rates, and body lengths, as well as increased mortality and malformation rates. The general morphology score system indicated that the swim bladder and pigmentation were the main abnormal morphological endpoints. Stream water promoted antioxidant enzymes (superoxide dismutase (SOD), peroxidase (POD), and glutathione peroxidase (GPx)), lipid peroxidation, and DNA damage. It also triggered apoptosis in the embryos' heads, hearts, and spines by activating apoptotic enzymes (Caspase-3 and Caspase-9). Additionally, stream water influenced growth, oxidative stress, and apoptosis-related 19 gene expression. Notably, tyr, sod (Mn), and caspase9 were the most sensitive indicators of growth, oxidative stress, and apoptosis, respectively. The current trial concluded that PCP-polluted stream water exhibited significant developmental toxicity to zebrafish embryos, which was regulated by the oxidative stress-mediated activation of endogenous apoptotic signaling pathways.

A comparative study on targeted gene expression in zebrafish and its gill cell line exposed to chlorpyrifos

Chlorpyrifos (CPF) is an organophosphorus-based insecticide, which is known to pose a serious risk to aquatic animals. However, the mechanisms of CPF toxicity in animals still remain unclear. The present investigation aimed to compare the potential effects of CPF in zebrafish (Danio rerio) and its gill cell line (DrG cells). Based on the in vivo study, the LC50 was calculated as 18.03 µg/L and the chronic toxic effect of CPF was studied by exposing the fish to 1/10th (1.8 µg/L) and 1/5th (3.6 µg/L) of the LC50 value. Morphological changes were observed in fish and DrG cells which were exposed to sublethal concentrations of CPF. The results of MTT and NR assays showed significant decline in the survival of cells exposed to CPF at 96 h. The production of reactive oxygen species in DrG cells and expression levels of antioxidant markers, inflammatory response genes (cox2a and cox2b), cyp1a, proapoptotic genes (bax), antiapoptotic gene (bcl2), apoptotic genes (cas3 and p53), and neuroprotective gene (ache) were determined in vivo using zebrafish and in vitro using DrG cells after exposure to CPF. Significant changes were found in the ROS production (DrG cells) and in the expression of inflammatory, proapoptotic, and apoptotic genes. This study showed that DrG cells are potential alternative tools to replace the use of whole fish for toxicological studies.

Neurotoxic effects induced by flunitrazepam and its metabolites in zebrafish: Oxidative stress, apoptosis, and histone hypoacetylation

Benzodiazepines (BZDs) have been widely detected in aquatic environments, but their neurotoxic effects and potential mechanisms are still unclear. This study focuses on flunitrazepam (FLZ) and its metabolite, 7-aminoflunitrazepam (7-FLZ), as representative psychotropic BZD. We investigated their neurotoxic effects on adult zebrafish following a 30-day exposure to environmentally relevant concentrations. The findings reveal that exposure to these drugs induces anxiety-like and aggressive behaviors in zebrafish. Additionally, notable morphological damage to brain tissue and mitochondrial structures was observed. Through TUNEL staining, an increase in apoptotic cells was detected in the brain tissue of the exposed group, accompanied by marked elevations in ROS and caspase-3/9 levels. The upregulation of apoptosis-related genes Bax, p53, and Bcl-2 confirmed the occurrence of apoptosis. Furthermore, exposure to the drugs resulted in decreased acetylation levels of brain histones H3 and H4. The upregulation of histone deacetylation enzyme genes (HDAC1, HDAC3, HDAC4, and HDAC6) supported this result. Molecular docking results suggest that compared to 7-FLZ, FLZ has a higher binding affinity with HDAC3 and HDAC4, explaining why it causes lower histone acetylation levels. This study in zebrafish elucidates the neurotoxicity and molecular mechanisms induced by FLZ and 7-FLZ, which is significant for further understanding the impact of BZDs on human health and assessing their ecological risks.

An azole fungicide climbazole damages the gut-brain axis in the grass carp

Azole antifungal climbazole has frequently been detected in aquatic environments and shows various effects in fish. However, the underlying mechanism of toxicity through the gut-brain axis of climbazole is unclear. Here, we investigated the effects of climbazole at environmental concentrations on the microbiota-intestine-brain axis in grass carp via histopathological observation, gene expression and biochemical analyses, and high-throughput sequencing of the 16 S rRNA. Results showed that exposure to 0.2 to 20 μg/L climbazole for 42 days significantly disrupted gut microbiota and caused brain neurotoxicity in grass carp. In this study, there was an alteration in the phylum and genus compositions in the gut microbiota following climbazole treatment, including reducing Fusobacteria (e.g., Cetobacterium) and increasing Actinobacteria (e.g., Nocardia). Climbazole disrupted intestinal microbial abundance, leading to increased levels of lipopolysaccharide and tumor necrosis factor-alpha in the gut, serum, and brain. They passed through the impaired intestinal barrier into the circulation and caused the destruction of the blood-brain barrier through the gut-brain axis, allowing them into the brain. In the brain, climbazole activated the nuclear factor kappaB pathway to increase inflammation, and suppressed the E2-related factor 2 pathway to produce oxidative damage, resulting in apoptosis, which promoted neuroinflammation and neuronal death. Besides, our results suggested that this neurotoxicity was caused by the breakdown of the microbiota-gut-brain axis, mediated by reduced concentrations of dopamine, short chain fatty acids, and intestinal microbial activity induced by climbazole.

Effect of chronic deltamethrin exposure on brain transcriptome and metabolome of juvenile crucian carp

Deltamethrin (Del), a widely administered pyrethroid insecticide, has been established as a common contaminant of the freshwater environment and detected in many freshwater ecosystems. In this study, we investigated the changes in brain transcriptome and metabolome of crucian carp after exposure to 0.6 μg/L Del for 28 days. Elevated MDA levels and inhibition of SOD activity indicate damage to the antioxidant system. Moreover, a total of 70 differential metabolites (DMs) were identified using the liquid chromatography-mass spectrometry, including 32 upregulated and 38 downregulated DMs in the Del-exposed group. The DMs associated with chronic Del exposure were enriched in steroid hormone biosynthesis, fatty acid metabolism, and glycerophospholipid metabolism for prostaglandin G2, 5-oxoeicosatetraenoic acid, progesterone, androsterone, etiocholanolone, and hydrocortisone. Transcriptomics analysis revealed that chronic Del exposure caused lipid metabolism disorder, endocrine disruption, and proinflammatory immune response by upregulating the pla2g4, cox2, log5, ptgis, lcn, and cbr expression. Importantly, the integrative analysis of transcriptomics and metabolomics indicated that the arachidonic acid metabolism pathway and steroid hormone biosynthesis were decisive processes in the brain tissue of crucian carp after Del exposure. Furthermore, Del exposure perturbed the tight junction, HIF-1 signaling pathway, and thyroid hormone signaling pathway. Overall, transcriptome and metabolome data of our study offer a new insight to assess the risk of chronic Del exposure in fish brains.

Assessing the ecotoxicity of florfenicol exposure at environmental levels: A case study of histology, apoptosis and microbiota in hepatopancreas of Eriocheir sinensis

The intensification of production practices in the aquaculture industry has led to the indiscriminate use of antibiotics to combat diseases and reduce costs, which has resulted in environmental pollution, posing serious threats to aquaculture sustainability and food safety. However, the toxic effect of florfenicol (FF) exposure on the hepatopancreas of crustaceans remains unclear. Herein, by employing Chinese mitten crab (Eriocheir sinensis) as subjects to investigate the toxic effects on histopathology, oxidative stress, apoptosis and microbiota of hepatopancreas under environment-relevant (0.5 and 5 μg/L), and extreme concentrations (50 μg/L) of FF. Our results revealed that the damage of hepatopancreas tissue structure caused by FF exposure in a dose-and time-dependent manner. Combined with the increased expression of apoptosis-related genes (Caspase 3, Caspase 8, p53, Bax and Bcl-2) at mRNA and protein levels, activation of catalase (CAT) and superoxide dismutase (SOD), and malondialdehyde (MDA) accumulation, FF exposure also induced oxidative stress, and apoptosis in hepatopancreas. Interestingly, 7 days exposure triggered more pronounced toxic effect in crabs than 14 days under environment-relevant FF concentration. Integrated biomarker response version 2 (IBRv2) index indicated that 14 days FF exposure under extreme concentration has serious toxicity effect on crabs. Furthermore, 14 days exposure to FF changed the diversity and composition of hepatopancreas microbiota leading remarkable increase of pathogenic microorganism Spirochaetes following exposure to 50 μg/L of FF. Taken together, our study explained potential mechanism of FF toxicity on hepatopancreas of crustaceans, and provided a reference for the concentration of FF to be used in culture of Chinese mitten crab.

Influence of time-dependent sampling on the plasma metabolome and exposome of fish collected from an effluent-dependent pond

Metabolomics is increasingly recognized as a useful approach to characterize environmental pollution gradients. While the performance of analytical procedures must be validated and documented, many studies only briefly describe sampling and sample storage. Here we advance our recent study on the influences of sampling delay and holding media on contaminants of emerging concern in fish plasma by targeted analysis. We specifically examined the metabolome and exposome of common carp under three conditions: plasma sampled immediately after field collection (t = 0 h) and then after 3 h (t = 3 h) or 20 h (t = 20 h) of holding fish in lab water. Plasma samples were analyzed using reversed-phase and HILIC chromatography with mass spectrometric detection. 6143 of the 12,904 compounds (after clustering features) varied among the groups. We observed different metabolite variation patterns depending on the sample collection time. We also identified several xenobiotics (2-Ethylhexyl sulfate, 6-Chloro-5-methyl-1H-benzotriazole) at concentrations generally found at the highest levels in plasma sampled immediately after field collection (t = 0 h). Both the metabolome and the exposome changed rapidly in fish plasma with a time lag, which indicates that obtaining relevant results is complicated by fish-holding conditions. We further identified that non-lethal, relatively low-volume blood sample collection was sufficient with this species, which presents ethical and practical advantages.

Gross yield driving the mass fluxes of fishery drugs: Evidence of occurrence from full aquaculture cycle in lower Yangtze River Basin

Expanding aquaculture has generated pollutants like fishery drugs in wastewater, which affects the aquatic environments and hinders sustainable development of aquaculture. To evaluate the occurrence, mass fluxes and production factors of fishery drugs in aquaculture, full-aquaculture-cycle monitoring in finfish and crustacean wastewater was conducted in the lower Yangtze River Basin, and 28 pesticides and 15 antibiotics were detected. The results showed that individual fishery drugs varied from ppt to ppb levels. Among them, sulfonamides were dominant with a mean concentration of 105.95 ± 4.13 ng·L-1 in finfish aquacultural wastewater, and insecticides were prevailing in crustacean aquacultural wastewater with a content of 146.56 ± 0.66 ng·L-1. Since the susceptibility to finfish disease determined the aquaculture practice, there were significant differences between two types of aquacultural wastewater. Finfish aquacultural wastewater contained more drugs and reached peak earlier in rapid-growth period, yet crustacean aquacultural wastewater peaked at the harvest period, to prevent against disease. Meanwhile, higher ecological risk, especially for florfenicol, were found in finfish wastewater. With 6 production factors from Good Aquaculture Practice, the gross yield was the most influential factor of drug mass flux, explaining 98 % variance by stepwise regression. Apart from increasing concentrations of fishery drugs in wastewater, regional high-yield aquaculture also significantly impacted the corresponding mass flux. As estimated by linear regression, 1.63 tons of target drugs would be discharged by 1 Mt. aquatic products, and 7.77 tons were discharged from aquaculture in the lower Yangtze River Basin in 2021. This is the first report to quantify mass fluxes of fishery drugs and to highlight gross yield as the most influential factor, which provides guidance for the supervision and regulation of sustainable aquaculture.

Mitigation of avermectin exposure-induced brain tissue damage in carp by quercetin

Avermectin is widely used as an important insecticide in agricultural production, but it also shows strong toxicity to non-target organisms. Quercetin is a natural flavonoid that is widely used due to its good anti-inflammatory and antioxidant effects. We believe that quercetin may have a potential therapeutic effect on avermectin poisoning. This experiment was proposed to observe the effect of quercetin on the toxic response to avermectin by observing the toxic response caused by avermectin in the brain of carp. In this project, 60 carp were studied as control group (Control), quercetin administration group (QUE), avermectin exposure group (AVM) and quercetin treatment avermectin exposure group (QUE + AVM) with different interventions to study the effect of quercetin on avermectin. The carp brain tissues were stained and simultaneously analyzed for blood-brain barrier (BBB), oxidative stress indicators, inflammatory factors, and apoptosis using qPCR technique. The results of the study indicate that avermectin exhibits a neurotoxic mechanism of action in fish by decreasing the transcript levels of tight junction protein-related genes, which in turn leads to the rupture of the BBB in the carp brain tissue. Avermectin induced apoptosis in carp brain tissue by increasing oxidative stress response and promoting inflammatory cell infiltration. Quercetin could reduce the accumulation of reactive oxygen species (ROS) in the brain tissue of carp caused by avermectin exposure toxicity, maintain redox homeostasis, reduce inflammatory response, and protect brain tissue cells from apoptosis. The present study confirmed the therapeutic and protective effects of quercetin on neurotoxicity in carp caused by avermectin exposure.

Endocrine disruptive toxicity of cypermethrin in Labeo catla: Involvement of genes and proteins related to the HPG axis

Cypermethrin (CYP) is a synthetic pyrethroid abundantly used in agriculture and aquaculture. It is an established potent endocrine disruptor to fish, yet the molecular mechanism behind its reproductive toxicity remains unclear. In this study, fish Labeo catla (Catla) was exposed to environmentally relevant concentration of CYP (0.7 μg/L) and 0.14 μg/L for 30 days. The changes in circulating sex steroids, genes, and hormones linked to the hypothalamic-pituitary-gonadal (HPG) axis, stress response and associated histological alterations were studied. Significant decline (P < 0.05) in serum 17 beta (β) estradiol (E2), 11 ketotestosterone (11-KT), and brain (FSH and GnRH) were observed in 0.7 μg/L dose of CYP. These effects may be due to the down-regulated expression of the upstream genes of the HPG axis i.e. Kiss 1 and Kiss 2, which further downregulates the expression of the GnRH gene. The decreased level of E2 and 11-KT also affects the vitellogenin (Vtg) gene expression, reducing the production of Vtg, a crucial protein for ovarian development. Principal component analysis (PCA) revealed the relationship between CYP and the biosynthesis of sex steroids. The toxic effect of CYP was also visible in antioxidant enzyme assay and related histological alterations. Overall, the study elucidated that long-term exposure to CYP, even at an environmentally relevant dose, may affect reproductive potential and fish recruitment. The study provides important insights into molecular mechanisms underlying CYP-induced endocrine disruption in fish, and it also raises questions about CYP's potential toxicity at environmentally relevant concentration in terms of understanding ecological risk.

Pyrethroids toxicity in vertebrates and invertebrates and amelioration by bioactive compounds: A review

Generations of different synthetic pesticides have been launched over time to maintain balance between production and consumption of the agricultural yield, control various disease programmes, store grains, etc. Pyrethroids, which are supposed to be non-toxic, have been excessively implemented and have contaminated soil and water bodies. Thus, pyrethroids cause severe and dreadful pernicious effects on various life forms residing in soil, air, and water. Various obnoxious effects of pyrethroids have been analyzed in the vertebrate and invertebrate systems of the animal kingdom. Pyrethroids, namely, Cypermethrin, Deltamethrin, Beta-cyfluthrin, Esfenvalerate, Fenvalerate, and Bifenthrin, have set out various types of degenerative and toxic impacts that include oxidative stress, hepatotoxicity, immunotoxicity involving thymic and splenic toxicity, neurotoxicity, nephrotoxicity, foetal toxicity, alterations in serum calcium and phosphate levels, cerebral and bone marrow degeneration, degeneration of the reproductive system, histological alteration, and DNA damage. Bioactive compounds like Diosmin, Curcumin, Rutin, Spirulina platensis, sesame oil, Naringin, Allicin, Piperine, alpha-lipoic acid, alpha-tocopherol, Cyperus rotundus L. tuber extract, herbal syrup from chicory and artichoke leaves, green tea extract, Quercetin, Trans-ferulic acid, Ascorbic acid, Propolis, ethanolic extract of grape pomace, and Melatonin have been reported to sublime the toxic effects of these pesticides. The expanding harmfulness of pesticides is a real and demanding issue that needs to be overcome, and bioactive compounds have been shown to reduce the toxicity in vivo as well as in vitro.

The neurobehavioral impacts of typical antibiotics toward zebrafish larvae

Due to the widely usage in livestock, aquaculture and clinics, antibiotic residues are existed in aqueous environments and their potential toxicity to aquatic organisms is concerning. Here, we used zebrafish as the model to investigate the neurotoxicity and involved mechanism of seven antibiotics that were frequently detected in surface waters. The results revealed that the short-term exposure to clarithromycin (CLA), chlortetracycline (CTC) and roxithromycin (ROX) induced behavioral effects, with effective concentration of 1 μg/L (CTC and ROX) and 100 μg/L (CLA, CTC and ROX) respectively. A significant decrease in the travel distance and velocity as well as an increase in turn angle was measured. TUNEL assay identified increased cell apoptosis in brain sections of larvae exposed to three neurotoxic antibiotics, which raised the possibility that the behavioral symptoms were associated with neural damage. Transcriptome sequencing showed that the three antibiotics could affect the nervous system of zebrafish including the alteration of synaptogenesis and neurotransmission. Additionally, ROX and CTC affected pathways involved in mitochondrial stress response and endocrine system in zebrafish larvae. Besides, BDNF, ASCL1, and CREBBP are potential upstream regulatory factors that mediated these impacts. These findings indicated that exposure of CTC, ROX and CLA may cause abnormal behavior toward zebrafish larvae under environmental relevant concentration and revealed the potential role of neural cell apoptosis and synaptogenesis signaling in mediating this effect.

The induction of tau aggregation is restricted by sulfamethoxazole and provides new information regarding the use of the drug

The aggregation of tau protein in the form of paired helical filament (PHF) leads to the breakdown of microtubule structure and the development of neurodegenerative disorders, such as Alzheimer's disease. Therefore, inhibiting tau protein aggregation is a potential strategy for preventing the progression of these disorders. In this study, sulfamethoxazole (SMZ), an antibiotic that easily crosses the blood-brain barrier and interacts with tau protein, was tested for its ability to inhibit tau aggregation in vitro. Various multi-spectroscopic techniques including XRD, LDH cytotoxicity colorimetric assay, and microscopic imaging were employed. The results showed that SMZ effectively interacts with tau protein through hydrogen and van der Waals interactions. It also effectively inhibited tau protein aggregation in vitro and significantly reduced toxicity in the SH-SY5Y neuroblastoma cell line. Molecular docking and MD simulation results suggested that SMZ may reduce tau protein aggregation by interacting with the PHF6 motif. Overall, these findings indicate that SMZ has therapeutic potential as a tau protein aggregation inhibitor, at least under in vitro conditions. These findings suggest that SMZ has potential as a treatment for neurodegenerative disorders involving tau protein aggregation. However, further research is needed to confirm these results and assess the effectiveness of SMZ in animal models and clinical trials.Communicated by Ramaswamy H. Sarma.

Climbazole causes cell apoptosis and lipidosis in the liver of grass carp

Climbazole, an azole, is widely used in personal care products, pharmaceuticals, and pesticides and is frequently detected in surface water. Climbazole has showed endocrine-disrupting effects. However, the effects of climbazole in fish are still largely unclear. In this study, grass carp (Ctenopharyngodon idella) and liver cell lines (L8824 cells) were treated with climbazole at concentrations ranging from 0.2 to 20 μg/L for 42 days in vivo and 24 h in vitro to evaluate the effects on the liver, respectively. Pathological, biochemical, and gene transcription and expression analyses were conducted to examine the hepatotoxicity. Our results showed that climbazole significantly decreased the hepatosomatic index, caused cell apoptosis in vivo and in vitro, and finally accumulated lipids in the liver. Beside, climbazole increased ROS levels, reduced Nrf2 and Keap1 mRNA and protein levels, and further decreased transcription of Nrf2-dependent downstream antioxidant enzyme genes, causing oxidative stress. Moreover, climbazole increased transcription and protein levels of apoptosis-related genes. Finally, climbazole damaged mitochondrial function and structure, disrupted liver lipid metabolism. Overall, climbazole caused hepatotoxicity, leading to a high ecological risk for aquatic organisms.

Metabolic engineering of Paracoccus denitrificans for dual degradation of sulfamethoxazole and ammonia nitrogen

Sulfamethoxazole (SMX), as one of the most widely used sulfonamide antibiotics, has been frequently detected in the aqueous environment, posing potential risks to the environment and human health. Although microbial degradation methods have been widely applied, some issues remain, including low degradation efficiency and poor environmental adaptability. In this regard, constructing efficient degrading bacteria by metabolic engineering is an ideal solution to these challenges. In this study, we used Paracoccus denitrificans DYTN-1, a superior nitrogen removal environment strain, as chassis to construct an SMX degradation pathway, obtaining a new bacteria for simultaneous degradation of SMX and removal of ammonia nitrogen. In doing this, we first identified and characterized four native promoters of P. denitrificans DYTN-1 with gradient strength to control the expression of the SMX degradation pathway. After degradation pathway expression level optimization and FMN reductase optimization, SMX degradation efficiency was significantly improved. The constructed P. d-pIAB4-PCS-sutR strain exhibited superior co-degradation of SMX and ammonia nitrogen contaminants with degradation rates of 44% and 71%, respectively. This study could pave the way for SMX degradation engineered strain design and evolution of environmental bioremediation. IMPORTANCE The abuse of sulfamethoxazole (SMX) had led to an increased accumulation in the environment, resulting in the disruption of the structure of microbial communities, further disrupting the bio-degradation process of other pollutants, such as ammonia nitrogen. To solve this challenge, we first identified and characterized four native promoters of Paracoccus denitrificans DYTN-1 with gradient strength to control the expression of the SMX degradation pathway. Then SMX degradation efficiency was significantly improved with degradation pathway expression level optimization and FMN reductase optimization. Finally, the superior nitrogen removal environment strain, P. denitrificans DYTN-1, obtained an SMX degradation function. This pioneering study of metabolic engineering to enhance the SMX degradation in microorganisms could pave the way for designing the engineered strains of SMX and nitrogen co-degradation and the environmental bioremediation.

Conventional Anthelmintic Concentration of Deltamethrin Immersion Disorder in the Gill Immune Responses of Crucian Carp

Current treatment strategies for parasitic infectious diseases in crucian carp primarily rely on chemotherapy. As a commonly used antiparasitic agent, deltamethrin (DEL) may have the potential adverse effects on external mucosa of fish such as gills. In this study, 180 healthy juvenile crucian carp (Carassius auratus) (average weight: 8.8 ± 1.0 g) were randomly divided into three groups for 28 days, which were immersed in 0 μg/L, 0.3 μg/L, and 0.6 μg/L of DEL, respectively. The results of histological analysis revealed that severe hyperplasia in the secondary lamellae of gills was observed, and the number of goblet (mucus-secreting) cells increased significantly after DEL immersion. TUNEL staining indicated that the number of apoptotic cells increased in crucian carp gill. At the molecular level, the mRNA expression analysis revealed significant upregulation of apoptosis (caspase 3, caspase 8, and bax), autophagy (atg5 and beclin-1), and immune response (lzm, muc5, il-6, il-8, il-10, tnfα, ifnγ, tgfβ, tlr4, myd88, and nf-kb), whereas tight junction-related genes (occludin and claudin12) were downregulated after DEL immersion, suggesting that DEL immersion altered innate immunity responses and promoted mucus secretion. Moreover, tandem mass tag (TMT)-based proteomics revealed that a total of 428 differentially expressed proteins (DEPs) contained 341 upregulated DEPs and 87 downregulated DEPs with function annotation were identified between the control and DEL groups. Functional analyses revealed that the DEPs were enriched in apoptotic process, phagosome, and lysosome pathways. Additionally, DEL immersion also drove gill microbiota to dysbiosis and an increase in potentially harmful bacteria such as Flavobacterium. Overall, this study showed that DEL elicited shifts in the immune response and changes in the surface microbiota of fish. These results provide new perspectives on the conventional anthelmintic concentration of DEL immersion disorder of the gill immune microenvironment in crucian carp and theoretical support for future optimization of their practical application.

Cadmium exposure induces necroptosis of porcine spleen via ROS-mediated activation of STAT1/RIPK3 signaling pathway

Cadmium (Cd), a heavy metal, is used in a wide range of applications, such as plastics, electroplating process, electronics, and so forth. Due to its bioaccumulation ability, Cd can contaminate soil, water, air and food. To determine the effect of Cd exposure on the necroptosis in pig spleen and its mechanistic investigation, we constructed a model in pigs by feeding them food containing 20 mg/kg Cd. In this study, we analyzed the effects of Cd exposure on pig spleen through HE staining, Quantitative real-time PCR (qRT-PCR), Western blot (WB), and principal component analysis (PCA). Results show that Cd exposure can destroy the structure and function of pig spleen, which is closely related to necroptosis. Further results show that Cd exposure can induce necroptosis through ROS-mediated activation of Signal transducer and activator of transcription 1/Receptor-Interacting Serine/Threonine-Protein Kinase 3 (STAT1/RIPK3) signaling pathway in pig spleen. Additionally, Cd exposure also can affect the stability of mitochondrial-associated endoplasmic reticulum membrane (MAMs) structure, which also contributes to the process of necroptosis. Our study provides insights into the physiological toxicity caused by Cd exposure.

Pesticides at brain borders: Impact on the blood-brain barrier, neuroinflammation, and neurological risk trajectories

Pesticides are omnipresent, and they pose significant environmental and health risks. Translational studies indicate that acute exposure to high pesticide levels is detrimental, and prolonged contact with low concentrations of pesticides, as single and cocktail, could represent a risk factor for multi-organ pathophysiology, including the brain. Within this research template, we focus on pesticides' impact on the blood-brain barrier (BBB) and neuroinflammation, physical and immunological borders for the homeostatic control of the central nervous system (CNS) neuronal networks. We examine the evidence supporting a link between pre- and postnatal pesticide exposure, neuroinflammatory responses, and time-depend vulnerability footprints in the brain. Because of the pathological influence of BBB damage and inflammation on neuronal transmission from early development, varying exposures to pesticides could represent a danger, perhaps accelerating adverse neurological trajectories during aging. Refining our understanding of how pesticides influence brain barriers and borders could enable the implementation of pesticide-specific regulatory measures directly relevant to environmental neuroethics, the exposome, and one-health frameworks.

Abamectin causes toxicity to the carp respiratory system by triggering oxidative stress, inflammation, and apoptosis and inhibiting autophagy

Abamectin is a commonly used pesticide in agriculture and fisheries and poses a risk to aquatic species. However, the mechanism of its toxic effects on fish remains to be discovered. In this study, we explored the effects of abamectin exposure at different concentrations on the respiratory system of carp. Carp were divided into three groups, namely the control group, low-dose abamectin treatment group, and high-dose abamectin treatment group. Gill tissue was collected after abamectin exposure for histopathological, biochemical, tunnel, mRNA, and protein expression analysis. Histopathological analysis indicated that abamectin damaged the gill structure. Biochemical analysis showed that abamectin triggered oxidative stress with lowered antioxidant enzyme activities and increased MDA content. Moreover, abamectin led to enhanced INOS levels and pro-inflammatory transcription, activating inflammation. Tunnel results demonstrated that exposure to abamectin induced gill cell apoptosis through an exogenous pathway. In addition, exposure to abamectin activated the PI3K/AKT/mTOR pathway, leading to inhibition of autophagy. Overall, abamectin caused respiratory system toxicity in carp via triggering oxidative stress, inflammation, and apoptosis and inhibiting autophagy. The study suggests that abamectin has a profound toxicity mechanism in the respiratory system of carp, contributing to a better understanding of pesticide risk assessment in aquatic systems.

Mechanisms regarding respiratory toxicity triggered by accumulation of ROS in carp exposed to difenoconazole

Difenoconazole is a widely used but difficult-to-degrade fungicide that can directly affect aquatic ecosystems. Here, two doses (0.488 mg/L, 1.953 mg/L) of difenoconazole were used to study the toxicity to the respiratory system of carp at an exposure time of 96 h. The results showed that difenoconazole exposure resulted in severe structural damage to carp gill tissue with extensive inflammatory cell infiltration. Mechanistically, difenoconazole exposure led to excessive accumulation of ROS in carp gill tissue, which induced an inflammatory response in the gill tissue. Meanwhile, the activities of SOD and CAT were reduced and the NRF2 signaling pathway was activated to regulate the imbalance between oxidation and antioxidation. In addition, difenoconazole exposure further activated the mitochondrial pathway of apoptosis by upregulating cytochrome C, BAX, cleaved-caspase 9, and downregulating Bcl-2. More interestingly, exposure to difenoconazole increased autophagosomes, but lysosomal dysfunction prevented the late stages of autophagy from proceeding smoothly, resulting in a protective autophagic response that is not properly initiated. In summary, difenoconazole exposure caused respiratory toxicity including inflammation response, oxidative stress, apoptosis, and autophagy in carp through the accumulation of ROS. The present study expanded our understanding of the toxic effects of difenoconazole on organisms and its possible threat to the aquatic environment.

Effects of Sulfamethoxazole and Florfenicol on Growth, Antioxidant Capacity, Immune Responses and Intestinal Microbiota in Pacific White Shrimp Litopenaeus vannamei at Low Salinity

Antibiotic residue may pose a serious risk to aquaculture, and the culture of Litopenaeus vannamei in a low-salinity environment is a growing trend over the world. Here, we aimed to understand the combined effect of low salinity and sulfamethoxazole (SMZ) and florfenicol (FLO) antibiotics on L. vannamei. The growth performance, immune functions, antioxidant capacity and intestinal microbiota were investigated. Compared with the control group, the weight gain and survival rate significantly decreased (p < 0.05) in shrimp after they were exposed to low-salinity (salinity 3) water and the mixture of antibiotics and low-salt conditions for 28 days. The antioxidant activities of SOD and T-AOC, shown at low salinity and in the higher concentration of the SMZ treatment group (SMZH), were significantly decreased, while the GST activity was significantly increased in each treatment group in comparison with the control group. The expression of immune-related genes, including TOLL, LvIMD, PPO and HSP, in the low concentration of the SMZ treatment group (SMZL) was higher than that in the other groups. The diversity of intestine microbiota was disturbed with a lower Shannon index in the low-salinity and SMZH groups, and a higher Simpson index in the SMZH group. Proteobacteria, Actinobacteria and Bacteroidetes were the dominant phyla in the gut of L. vannamei. At the genus level, Microbacterium, Shewanella, Aeromonas, Acinetobacter, Gemmobacter, Paracoccus and Lysobacter were significantly decreased in the low-salinity group. However, the abundance of opportunistic pathogens belonging to the genus Aeromonas in the FLO group was increased. The predicted microbe-mediated functions showed that the pathway for “amino acid metabolism” and “replication and repair” was significantly inhibited in both the low-salinity and antibiotic-exposed groups. All the findings in this study indicate that the combined effect of antibiotics and low salinity on L. vannamei negatively impacted the physiological and intestinal microbiota functions.

Cypermethrin and/or sulfamethoxazole exposure effect on apoptosis and endoplasmic reticulum of grass carp cardiomyocyte

With the soar use range of pesticides and antibiotics in agricultural production, the pollution of surrounding runoff has become more severe; thus, the health and safety of non-target species such as fish are at risk. Excessive amounts of cypermethrin (CMN, 0.651 mg/l) and sulfamethoxazole (SMZ, 0.3 mg/l) are known to trigger oxidative stress and endoplasmic reticulum stress, resulting in toxic effects on cells. The damage degree of poisons on grass carp and the effect of the corresponding axis pathway PERK/eif2α/CHOP are still unknown. Therefore, our study set up two single poison groups (CMN/SMZ) and a combined poison group (CMN&SMZ) to detect this pathway and related indicators. After detection, the content of MDA both in CMN and SMZ group myocardium tissue was increased, while the SOD, CAT activity and GSH levels were decreased. Apoptosis-related genes (Bax, PUMA, P53 and Caspase-3/9), inflammation-related genes (TNF-α, iNOS and IL-1β/6/8), ER stress pathway PERK/eif2α/CHOP and related genes (ATF6, IRE1a and GRP78) were all increased; in contrast, the anti-apoptotic gene Bcl-2 was down-regulated. From the overall trend observation, the apoptosis proportion of cardiomyocytes in the combined poison group was higher than that of the single poison. In summary, this study shows that CMZ and SMZ can induce oxidative stress and subsequent ER stress in grass carp cardiomyocytes by regulating the PERK/eif2α/CHOP signaling axle, thereby inducing apoptosis, and followed by inflammatory responses. The combined effect of the CMZ and SMZ mixture was severer than that of a single poison (CMZ or SMZ), so it can be inferred that the damage degree of grass carp myocardium tissue would be aggravated with the appearance of CMZ or/and SMZ. The experimental results of this study have suggestions and warnings for the toxicological research of CMZ and SMZ and the management of industrial and ecological balance.

Kaempferol counteracts toxicity induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine in D. melanogaster: An implication of its mitoprotective activity

The current study aimed to investigate whether kaempferol (KMP), the major bioactive component of green leafy vegetables, could counteract the toxicity elicited by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) in Drosophila melanogaster or not. First, we performed a dose-response curve, where adult wild-type flies were fed on diet-containing different concentrations of KMP throughout their lifespan. Afterward, flies were fed on a diet containing MPTP (500 μM) and KMP (20 and 40 μM) for 7 days. The MPTP- fed flies presented a higher mortality rate, lower emergence rate, locomotor deficits, and disruption in circadian rhythm when compared to the control. MPTP exposure induced severe oxidative stress, which was marked by reduction in thiol content, overproduction of reactive species, lipid and protein oxidation, and disruption of enzymes of antioxidant and neurotransmission pathways. MPTP also compromised the mitochondrial dynamics and respiration of flies, affecting the electron transport chain, oxidative phosphorylation, and fusion/fission processes. Besides extending per se the lifespan of flies, KMP counteracted the toxic effects of MPTP on the circadian cycle, survival, climbing, and hatching rates. KMP was also effective in restoring the activities of acetylcholinesterase (AChE) and monoamine oxidase (MAO) enzymes, as well as in normalizing the levels of all oxidant/antioxidant markers disrupted in MPTP-fed flies. Indeed, KMP reestablished the mitochondrial functionality in MPTP- fed flies, restoring the electron transport system linked to mitochondrial complex I and II, and rescuing the mRNA transcription of genes associated with mitochondrial fusion and fission, namely OPA-1 (Optic atrophy 1) and DRP-1 (Dynamin related protein 1). Our results showed the efficacy of KMP in hindering the toxicity induced by MPTP in D. melanogaster and suggest that the mitoprotective action of flavonoid may be boosting its anti-parkinsonism activity in the model. Besides, the study showed that wild-type strains of D. melanogaster proved to be reproducible in vivo model to mimic parkinsonian phenotypes through exposure to the neurotoxin MPTP.

Ecological risk assessment of environmentally relevant concentrations of propofol on zebrafish (Danio rerio) at early life stage: Insight into physiological, biochemical, and molecular aspects

Propofol is an intravenous anesthetic injection extensively used in clinic, which has been proved to be neurotoxic in humans. Improper use and disposal of propofol may lead to its release into the aquatic environment, but the potential ecological risk of propofol to aquatic organisms remains poorly understood. For this study, we comprehensively explored the ecotoxicological effects and potential mechanisms of propofol (0.04, 0.2 and 2 mg L^-1) on 120 hpf zebrafish (Danio rerio) embryos from physiological, biochemical, and molecular perspectives. The results showed that propofol has moderate toxicity on zebrafish embryos (96 h LC₅₀ = 4.260 mg L^-1), which could significantly reduce the hatchability and delay the development. Propofol can trigger reactive oxygen species (ROS) generation, lipid peroxidation (Malondialdehyde, MDA) and DNA damage (8-hydroxy-2-deoxyguanosine, 8-OHdG). The glutathione peroxidase (GPX) activity of zebrafish embryos in 0.04 and 0.2 mg L^-1 propofol treatment group was activated in response to oxidative damage, while activities of superoxide dismutase (SOD), catalase (CAT) and GPX in zebrafish treated with 2 mg L^-1 was significant inhibited compared with the control group (p＜0.05). Moreover, the expression of antioxidant genes and related pathways was inhibited. Apoptosis was investigated at genes level and histochemistry. Molecular docking confirmed that propofol could change in the secondary structure of acetylcholinesterase (AChE) and competitively inhibited acetylcholine (ACh) binding to AChE, which may disturb the nervous system. These results described toxic response and molecular mechanism in zebrafish embryos, providing multiple aspects about ecological risk assessment of propofol in water environment.

Sulfamethoxazole (SMX) Alters Immune and Apoptotic Endpoints in Developing Zebrafish (Danio rerio)

Sulfamethoxazole (SMX) is a broad-range bacteriostatic antibiotic widely used in animal and fish farming and is also employed in human medicine. These antibiotics can ultimately end up in the aquatic ecosystem and affect non-target organisms such as fish. To discern the effect of SMX on developing zebrafish embryos and larvae, we investigated a broad range of sub-lethal toxicity endpoints. Higher concentrations of SMX affected survivability, caused hatch delay, and induced malformations including edema of the yolk sac, pericardial effusion, bent tail, and curved spine in developing embryos. Lower levels of SMX provoked an inflammatory response in larvae at seven days post fertilization (dpf), as noted by up-regulation of interferon (ifn-γ) and interleukin 1β (il-1β). SMX also increased the expression of genes related to apoptosis, including BCL2-Associated Agonist of Cell Death (bad) and BCL2 Associated X, Apoptosis Regulator (bax) at 50 µg/L and decreased caspase 3 (casp3) expression in a dose-dependent manner. SMX induced hyperactivity in larval fish at 500 and 2500 µg/L based upon the light/dark preference test. Collectively, this study revealed that exposure to SMX can disrupt the immune system by altering host defense mechanisms as well as transcripts related to apoptosis. These data improve understanding of antibiotic chemical toxicity in aquatic organisms and serves as a baseline for in-depth environmental risk assessment of SMX and antibiotics.

Impact on the antioxidant system, histology, and cell death of zebrafish liver after exposure to industrial sludge leachate

The improper disposal of sludge is a still-present phenomenon in China. The leachate formed at the bottom of the sludge pile would cause toxicological effects on aquatic organisms and affect the health of humans by entering the surrounding rivers and groundwater. In this study, the hepatotoxicity of zebrafish induced by sludge leachate was assessed by antioxidant enzyme activities, semi-quantitative histopathological assessment, and TUNEL apoptosis assay. The results indicated that the leachate would induce oxidative stress and eventually lead to an increase in lipid peroxide after a 7-day exposure. The histopathological indexes demonstrated that exposure to leachate would cause histological damage by circulatory disturbances, regressive changes, progressive changes, and inflammatory responses. According to the TUNEL results, it could be inferred that apoptotic hepatocytes increased after exposure for 7 days due to oxidative stress and histological damage. Overall, this study provided a valuable approach to assessing the toxic effects of sludge leachate and described the underlying mechanism of leachate-induced hepatotoxicity in zebrafish. This work will generate new insights into the ecological toxicity of leachate and promote the development of sludge disposal in China.

The toxicity of 4-tert-butylphenol in early development of zebrafish: morphological abnormality, cardiotoxicity, and hypopigmentation

Endocrine disrupting effects of 4-tert-butylphenol (4-t-BP) are well described in literature. However, the evidence regarding developmental toxic effect of 4-t-BP is still vague. The present study used zebrafish as a model organism to investigate the toxic effect of 4-t-BP. The results showed that 4-t-BP exposure at 3, 6, and 12 μM induced developmental toxicity in zebrafish, such as reduced embryo hatchability and abnormality morphological. Flow cytometry analysis showed that 4-t-BP also induced intracellular ROS production. 4-t-BP induced changes in the expression of genes related to cardiac development and melanin synthesis, resulting in cardiotoxicity and hypopigmentation. 4-t-BP also caused oxidative stress, and initiated apoptosis through p53-bcl-2/bax-capase3 pathway. Integrative biomarker response analysis showed time- and dose-dependent effects of 4-t-BP on oxidative damage and developmental toxicity in zebrafish embryos. Overall, this study contributed to a comprehensive evaluation of the toxicity of 4-t-BP, and the findings provided new evidence for early warning of residues in aquatic environments.

The distinct resistance mechanisms of cyanobacteria and green algae to sulfamethoxazole and its implications for environmental risk assessment

Cyanobacteria and green algae are the OECD recommended test organisms for environmental toxicity assessments of chemicals. Whether the differences in these two species' responses to the identical chemical affect the assessment outcomes is a question worth investigating. Firstly, we investigated the distinct resistance mechanisms of Synechococcus sp. (cyanobacteria) and R. subcapitata (green algae) to sulfamethoxazole (SMX). The antioxidant system analysis demonstrated that R. subcapitata mainly relies on enhancing the activity of first line defense antioxidants, including superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx), which is the most powerful and efficient response to get rid of ROS, whereas Synechococcus sp. depends upon increasing the activity of glutathione-S-transferase (GST) and GPx to resist oxidative stress. Besides, a total 7 transformation products (TPs) of SMX were identified in R. subcapitata culture medium. The analysis of conjectural transformation pathways and the predicted toxicity indicates that R. subcapitata could relieve SMX toxicity by degrading it to low eco-toxic TPs. Additionally, we summarized numerous exposure data and assessed the environmental risk of various antibiotics, revealing an inconsistent result for the same type of antibiotic by using cyanobacteria and green algae, which is most likely due to the different resistance mechanisms. In the future, modified indicators or comprehensive assessment methods should be considered to improve the rationality of environmental toxicity assessments.

Acute deltamethrin exposure induces oxidative stress, triggers endoplasmic reticulum stress, and impairs hypoxic resistance of crucian carp

Deltamethrin (Del) has been widely used for effectively controlling ectoparasites of crucian carp and was also strictly prohibited in a hypoxic environment. A previous study indicated that Del exposure causes gill injury in Carassius auratus, which is associated with oxidative stress and endoplasmic reticulum stress (ER stress), but the precise mechanism is not well understood. Here, crucian carp were exposed to Del (0.61, 1.22, 2.44, 4.88 μg/L) for 24 h and then subjected to acute hypoxia challenge (1.0 mg/L) for 24 h. The results revealed that acute exposure to Del notably increased MDA content but markedly decreased CAT activities. Moreover, the T-AOC and SOD activities first increased and then decreased in the 4.88 μg/L Del group. Likewise, the mRNA levels of Nrf2 signaling and its target genes (ho-1, mt, sod, cat, and gpx1) were significantly downregulated in the high concentration exposure groups, while the mRNA levels of keap1 showed the opposite change trend. Meanwhile, Del exposure evoked the PERK-ATF4-CHOP and IRE1 signaling pathways and triggered ER stress in a dose-dependent manner in crucian carp. Importantly, we found that Del exposure significantly decreased the survival rate of crucian carp after hypoxia challenge by reducing oxygen uptake, modifying energy metabolism, and promoting lactate accumulation. Additionally, Del exposure aggravated gill damage and apoptosis under hypoxic stress, which was confirmed by histological assays. Collectively, we inferred that acute exposure to deltamethrin induces oxidative stress and ER stress and impairs hypoxic resistance of crucian carp.

Integrative assessment of biomarker responses in Mytilus galloprovincialis exposed to seawater acidification and copper ions

The interactive effects of ocean acidification (OA) and copper (Cu) ions on the mussel Mytilus galloprovincialis are not well understood. The underlying mechanisms also remain obscure. In this study, individuals of M. galloprovincialis were exposed for 28 days to 25 μg/L and 50 μg/L Cu ions at two pH levels (ambient level - pH 8.1; acidified level - pH 7.6). The mussels were then monitored for 56 days to determine their recovery ability. Physiological parameters (clearance rate and respiration rate), oxidative stress and neurotoxicity biomarkers (activities of superoxide dismutase, lipid peroxidation, catalase, and acetylcholinesterase), as well as the recovery ability of these parameters, were investigated in two typical tissues (i.e., gills and digestive glands). Results showed that (1) OA affected the bioconcentration of Cu in the gills and digestive glands of the mussels; (2) both OA and Cu can lead to physiological disturbance, oxidative stress, cellular damage, energy metabolism disturbance, and neurotoxicity on M. galloprovincialis; (3) gill is more sensitive to OA and Cu than digestive gland; (4) Most of the biochemical and physiological alternations caused by Cu and OA exposures in M. galloprovincialis can be repaired by the recovery experiments; (5) integrated biomarker response (IBR) analysis demonstrated that both OA and Cu ions exposure caused survival stresses to the mussels, with the highest effect shown in the co-exposure treatment. This study highlights the necessity to include OA along with pollutants in future studies to better elucidate the risks of ecological perturbations. The work also sheds light on the recovery of marine animals after short-term environmental stresses when the natural environment has recovered.

Evaluation of L-Selenomethionine on Ameliorating Cardiac Injury Induced by Environmental Ammonia

L-Selenomethionine is one of the important organic selenium sources. The supplementation of L-selenomethionine in diets is significant to improve the health of pigs. Ammonia is a major pollutant in the atmosphere and piggery, posing a threat to human and animal health. Although ammonia exposure can damage the heart, the mechanism of cardiac toxicity by ammonia is still unknown. In this study, we investigated the mechanism of cardiac injury induced by ammonia exposure in pigs and the protective effect of L-selenomethionine on its cardiotoxicity. The results showed that the blood ammonia content of pig increased significantly in ammonia group, the expressions of energy metabolism-related genes (LDHA, PDK4, HK2, and CPTIB) and the oxidative stress indexes were significantly changed (P < 0.05), the AMPK/PPAR-γ/NF-κB signaling pathways were activated, the chromatin edge aggregation and nuclear pyknosis were observed in ultrastructure, the apoptotic cells were significantly increased (P < 0.05), and the mRNA and protein expressions of apoptosis-related genes (Bcl-2, Bax, Cyt-c, caspase-3, and caspase-9) were significantly affected (P < 0.05). The above changes were significantly alleviated in ammonia + L-selenomethionine group, but there were still significant differences compared with the C group (P < 0.05). Our results indicated that ammonia exposure could cause energy metabolism disorder and oxidative stress and induce apoptosis of cardiomyocytes through AMPK/PPAR-γ/NF-κB pathways, which could lead to cardiac injury and affect cardiac function. L-Selenomethionine could effectively alleviate the cardiac damage caused by ammonia and antagonize the cardiotoxicity of ammonia.

Endoplasmic reticulum stress-controlled autophagic pathway promotes polystyrene microplastics-induced myocardial dysplasia in birds

In complex ecosystems, birds are generally long-lived and occupy high trophic positions, making them good bioindicators for monitoring environmental contaminants. The effects of microplastics (MPs) on myocardial development in bird is currently unknown. Chicks, as a high trophic level terrestrial bird, may be more affected by MPs exposure and. Therefore, we established an in vivo model of chicks exposed to different concentrations of polystyrene microplastics (PS-MPs) and selected 12-day-old chicken embryos in vitro to extract primary cardiomyocytes to further investigate the potential molecular mechanisms of the effect of PS-MPs on myocardial development in birds. Histopathological observations revealed that the PS-MPs treated exhibited loose and irregular myocardial arrangement, large cell gaps and broken myocardial fiber bundles. More mechanistically, TnnT2, Nkx2-5, Gata4, TBX5 and ACTN2 were down-regulated, endoplasmic reticulum (ER) stress markers GRP78, PERK, eIF2α, IRE1, ATF4, ATF6 and CHOP were overexpressed, autophagy-related genes LC3, ATG5, Beclin1 and P62 were down-expressed after PS-MPs exposure, and the addition of 4PBA effectively deregulated the above aberrant expression. Hence, our report indicated that PS-MPs induced myocardial dysplasia in birds is mainly attributed to the ER stress-mediated autophagic pathway. This provided data supporting the protection of birds from the health risks of MPs pollution. More critically, the study of cardiac developmental toxicity in birds may help to better explain or solve the problem of MPs pollution in complex ecosystems.

Difenoconazole disrupts the blood-brain barrier and results in neurotoxicity in carp by inhibiting the Nrf2 pathway mediated ROS accumulation

Excessive use of hard-to-degrade pesticides threatens the ecological health of aquatic systems. This study aimed to investigate difenoconazole (DFZ) residues in the environment induced neurotoxicity in carp and the underlying mechanisms. A total of thirty-six carps were divided into three groups and exposed to 0, 0.5, and 2.0 mg/L DFZ for 96 h, respectively. The alterations in behavior and blood-brain barrier (BBB) were examined, and potential mechanisms were explored using immunological assays and biochemical methods. The results showed that DFZ exposure caused behavioral freezing, reduced feeding, and neuronal necrosis in carp. Mechanistically, DFZ triggered ROS accumulation and destroyed the balance between oxidation and antioxidation with increased lipid peroxidation product MDA contents and reduced antioxidant enzymes SOD and CAT activities in the carp brain by inhibiting the NF-E2-related factor 2 (Nrf2) pathway. The activation of oxidative stress further reduced tight junction proteins and MMP levels, thereby destroying BBB and leading to DFZ leakage into the brain. Increased BBB permeability additionally led to DFZ activation of nuclear factor kappa-B signaling-mediated inflammatory cytokine storm, exacerbating neuroinflammation. Meanwhile, DFZ exposure activated mitochondria-associated apoptosis in the carp's brain by up-regulating Bcl-2 associated X protein, cleaved-caspase3, and cytochrome C and decreasing B-cell lymphoma-2 levels. Interestingly, the carp's brain initiated a protective autophagic response via the PI3K/AKT/TOR pathway intending to counteract the neurotoxicity of DFZ. Overall, we concluded that accumulation of DFZ at high concentrations in the aquatic systems disrupted the BBB and resulted in neurotoxicity in carp through inhibition of Nrf2 pathway-mediated ROS accumulation. This study provides a reference for monitoring DFZ residues in the environment and a new target for the treatment of DFZ-induced neurotoxicity in carp.

Cadmium induces apoptosis by miR-9-5p targeting PTEN and regulates the PI3K/AKT pathway in the piglet adrenal gland

Cadmium (Cd) is an environmental pollutant that can cause endocrine organ damage. To explore the effect of subacute CdCl₂ exposure on piglet adrenal gland tissue and its mechanism based on the establishment of this model, bioinformatics, TUNEL assay, western blot (WB), and qRT-PCR methods were used to detect related indicators. The results showed that after Cd exposure, antioxidant enzymes decreased, heat shock protein increased, and miR-9-5p-gene of phosphatase and tensin homolog (PTEN) upregulates the phosphatidylinositol-3-kinase (PI3K/AKT) pathway. After this pathway was activated, the expression of the apoptosis-related factors cysteinyl aspartate-specific proteinase 3 and 9 (caspase 3 and 9), B-cell lymphoma-2-associated X (BAX) was increased sharply, and the expression of B-cell lymphoma-2 (BCL2) was significantly decreased. The changes in these indicators indicate that Cd exposure induces apoptosis and causes tissue damage in the adrenal gland of piglets. This study aims to reveal the toxic effects of CdCl₂ in animals and will provide new ideas for the toxicology of Cd.

Avermectin induces carp neurotoxicity by mediating blood-brain barrier dysfunction, oxidative stress, inflammation, and apoptosis through PI3K/Akt and NF-κB pathways

Avermectin, a "low toxicity insecticide", has been widely used in recent years, but its non-target toxicity, especially to aquatic organisms, has been neglected. In this study, we evaluated the neurotoxic effects of avermectin on carp by establishing a 96 h avermectin acute toxicity test, and its possible mechanism was discussed. The 96 h LC₅₀ of avermectin in carp was found to be 24.04 μg/L. Therefore, 3.005 μg/L and 12.02 μg/L were used as the low-dose and high-dose groups, respectively, to investigate the neurotoxic effects of avermectin on carp. The results of high-performance liquid chromatography (HPLC) analysis showed that avermectin accumulated in the carp brain. Histopathological observation and immunohistochemical analysis (IHC) of TNF-α and Bax showed that avermectin exposure led to inflammatory cell infiltration and neuronal necrosis. The mRNA levels of tight junction genes and the IHC results of ZO-1 and Occludin showed that the structure of the blood-brain barrier (BBB) was destroyed. Biochemical analysis showed that avermectin induced the accumulation of MDA in the brain and decreased the activity of antioxidant enzymes CAT and SOD, leading to oxidative stress. In addition, avermectin induces brain inflammation by activating NF-κB pathway and releasing inflammatory factors IL-1β, IL-6, TNF-α and iNOS. TEM and TUNEL assays showed that exposure to avermectin induced apoptosis in brain. what is more, the expression of apoptosis-related genes and proteins suggested that avermectin-induced apoptosis may be associated with inhibition of the PI3K/Akt signaling pathway. This study also showed that avermectin-induced NF-κB signaling activation was partially dependent on its upstream PI3K/Akt signaling pathway. Therefore, this study concludes that avermectin can induce neurotoxicity in carp by disrupting the blood-brain barrier structure and generating oxidative stress, inflammation, and apoptosis and that NF-κB and PI3K/Akt signaling pathways are involved in this process.

Toxic effects of glyphosate on the intestine, liver, brain of carp and on epithelioma papulosum cyprinid cells: Evidence from in vivo and in vitro research

Glyphosate (GLY) is the most widely used organophosphorus herbicide in agriculture. The present study aimed to analyze the comprehensive toxicological effects of GLY on juvenile common carp and an epithelioma papulosum cyprinid (EPC) cell line. In the in vivo experiments, exposure to GLY (5 and 15 mg/L) for 30 days induced liver inflammation and oxidative damage in common carp and changed the physical barrier of the intestine. Histopathological analysis of the intestine, liver, brain, and changes in oxidative stress biomarkers provided evidence of damage and immune system responses to GLY. Moreover, an inhibitory effect of 15 mg/L GLY on acetylcholinesterase (AChE) activity was found in the brain, which may be an important reason for the significant decrease in both swimming distance and average acceleration of common carp. Cell experiments showed that 0.65 and 3.25 mg/L GLY inhibited the viability of EPCs. Furthermore, oxidative DNA damage, mitochondrial dysfunction, and reactive oxygen species (ROS) production were observed in EPC cells following GLY exposure. Taken together, this study not only highlights the negative effects of GLY on common carp but also enriches the knowledge of the cytotoxicity mechanism to further clarify the comprehensive toxicity of GLY in common carp.