Non-target toxic effects of avermectin on carp spleen involve oxidative stress, inflammation, and apoptosis

Silybin prevented avermectin-induced cardiotoxicity in carp by modulating oxidative stress, inflammation, endoplasmic reticulum stress, mitochondrial apoptosis, and autophagy

Avermectin is one of the widely used anthelmintics in aquaculture and exhibits substantial toxicity to aquatic organisms. Silybin is extensively used for its anti-inflammatory, antioxidant and anti-apoptotic biological properties. Heart is essential for the survival of fish and plays a vital role in pumping blood oxygen and nutrients. Residual avermectin in water poses harm to carp. However, there is still insufficient research on whether silybin can mitigate the toxicity of avermectin to carp heart tissues. In this research, we established a model involving carp subjected to acute avermectin exposure and administered diets containing silybin to explore the potential protective effects of silybin against avermectin-induced cardiotoxicity. The results revealed that avermectin induced oxidative stress, inflammation, endoplasmic reticulum (ER) stress, mitochondrial pathway apoptosis and autophagy in the cardiac tissues of carp. Compared with the avermectin group, silybin significantly reduced ROS accumulation in cardiac tissues, restored antioxidant enzyme activity, inhibited mRNA transcript levels of pro-inflammatory-related factors, and attenuated ER stress, mitochondrial pathway apoptosis and autophagy. Protein-protein interaction (PPI) analysis demonstrated that silybin mitigated avermectin-induced cardiac oxidative stress, inflammation, ER stress, mitochondrial pathway apoptosis and autophagy. Silybin exerted anti-inflammatory effects through the Nuclear Factor kappa B (NF-κB) pathway, antioxidant effects through the Nuclear factor erythroid 2-related factor 2 (Nrf2) - Kelch-like ECH-associated protein 1 (Keap1) pathway, alleviated cardiac ER stress through the Glucose-regulated protein 78 (GRP78)/Activating Transcription Factor 6 (ATF6)/C/EBP homologous protein (CHOP) axis, suppressed apoptosis through the mitochondrial pathway, and inhibited excessive autophagy initiation through the PTEN-induced putative kinase 1 (PINK1)/Parkin RBR E3 ubiquitin protein ligase (PARKIN) signaling pathway. This study provided evidence supporting the protective effect of silybin against avermectin-induced cardiotoxicity in carp, highlighting its potential as a dietary additive to protect fish from adverse effects caused by avermectin exposure.

Dietary additive ferulic acid alleviated oxidative stress, inflammation, and apoptosis induced by chronic exposure to avermectin in the liver of common carp (Cyprinus carpio)

Avermectin (AVM) has been utilized extensively in agricultural production since it is a low-toxicity pesticide. However, the pollution caused by its residues to fisheries aquaculture has been neglected. As an abundant polyphenolic substance in plants, ferulic acid (FA) possesses anti-inflammatory and antioxidant effects. The goal of the study is to assess the FA's ability to reduce liver damage in carp brought on by AVM exposure. Four groups of carp were created at random: the control group; the AVM group; the FA group; and the FA + AVM group. On day 30, and the liver tissues of carp were collected and examined for the detection of four items of blood lipid as well as the activity of the antioxidant enzymes catalase (CAT), glutathione (GSH) and malondialdehyde (MDA) in carp liver tissues by biochemical kits, and the transcript levels of indicators of oxidative stress, inflammation and apoptosis by qPCR. The results showed that liver injury, inflammation, oxidative stress, and apoptosis were attenuated in the FA + AVM group compared to the AVM group. In summary, dietary addition of FA could ameliorate the hepatotoxicity caused by AVM in carp by alleviating oxidative stress, inflammation, apoptosis in liver tissues.

Silybin mitigates chronic Avermectin exposure-induced intestinal damage and growth inhibition in carp

Avermectins, as a new type of environmental pollutant, have received significant attention in recent years. Previous research has shown that acute exposure to avermectins can induce oxidative stress and inflammation in non-target fish species, such as carp. Flavonoid lignans, particularly Silybin, have demonstrated promising biological activities, including regulation of non-alcoholic fatty liver and cerebral ischemia-reperfusion injury. This study aims to investigate the impact of dietary supplementation with Silybin on the intestinal damage in carp caused by chronic exposure to avermectins and to improve the health status and production of carp in aquaculture. Silybin was used as a dietary supplement by adding it to the experimental feed, and an animal experimental model was utilized to assess its effects on oxidative stress, inflammation, and cell apoptosis in carp intestine. Additionally, intestinal barrier integrity, digestive capacity, and fish growth were evaluated. The results indicated that dietary supplementation with Silybin effectively alleviated the oxidative stress induced by chronic exposure to avermectins in carp intestine. Furthermore, Silybin improved intestinal barrier integrity and digestive capacity by modulating the Nrf2/Keap1 pathway. This study demonstrates that dietary supplementation with Silybin can effectively mitigate the intestinal damage caused by chronic exposure to avermectins in carp, providing a sustainable solution for the aquaculture industry to enhance the overall health and production of cultured fish. The research expands our understanding of avermectin environmental pollution and offers a potential remediation approach.

Immunoprotective effect of silybin through blocking p53-driven caspase-9-Apaf-1-Cyt c complex formation and immune dysfunction after difenoconazole exposure in carp spleen

As a broad-spectrum and efficient triazole fungicide, difenoconazole is widely used, which not only pollutes the environment but also exerts toxic effects on non-target organisms. The spleen plays an important role in immune protection as an important secondary lymphoid organ in carp. In this study, we assessed the protective impact of silybin as a dietary additive on spleen tissues of carp during exposure to difenoconazole. Sixty carp were separated into four groups for this investigation including control group, difenoconazole group, silybin group, and silybin and difenoconazole group. By hematoxylin-eosin staining, dihydroethidium staining, immunohistochemical staining, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, quantitative real-time PCR assay, Western blot analysis, biochemical assays, and immune function indicator assays, we found that silybin could prevent difenoconazole-induced spleen tissue damage, oxidative stress, and immune dysfunction, and inhibited apoptosis of carp spleen tissue cells by suppressing the formation of p53-driven caspase-9-apoptotic protease activating factor-1-cytochrome C complex. The results suggested that silybin as a dietary additive could improve spleen tissue damage and immune dysfunction induced by difenoconazole in aquaculture carp.

Gypenoside XLIX attenuates sepsis-induced splenic injury through inhibiting inflammation and oxidative stress

BACKGROUND

To investigate the effect of Gypenoside XLIX (Gyp-XLIX) on acute splenic injury (ASI) induced by cecal ligation and puncture (CLP) in septic mice, a study was conducted.

METHODS

Sixty healthy mice were randomly divided into six groups: the NC group, the Sham group, the Sham + Gyp-XLIX group, the CLP group, the CLP + Gyp-XLIX group, and the CLP + Dexamethasone (DEX) group. The NC group did not undergo any operation, while the rest of the groups underwent CLP to establish the sepsis model. The Sham group only underwent open-abdominal suture surgery without cecum puncture. After the operation, the groups were immediately administered the drug for a total of 5 days. Various methods such as hematoxylin and eosin (HE) staining, biochemical kits, qRT-PCR, and reactive oxygen species (ROS) were used for analysis.

RESULTS

The results demonstrated that Gyp-XLIX effectively mitigated the splenic histopathological damage, while reducing the malondialdehyde (MDA) lipid peroxidation index and enhancing the antioxidant activities of catalase (CAT), glutathione (GSH) and total antioxidant capacity (T-AOC). The utilization of Dihydroethidium (DHE) fluorescent probe revealed that Gyp-XLIX inhibited the acute splenic accumulation of ROS induced by CLP in septic mice. Further investigations revealed that Gyp-XLIX exhibited a down-regulatory effect on the protein levels of inflammatory mediators iNOS and COX-2, consequently leading to the suppression of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-1β. Additionally, it up-regulated the expression of anti-inflammatory factor IL-10.

CONCLUSION

In conclusion, Gyp-XLIX was significantly effective in attenuating CLP-induced acute splenic inflammation and oxidative stress in septic mice.

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.

Quercetin attenuates environmental Avermectin-induced ROS accumulation and alleviates gill damage in carp through activation of the Nrf2 pathway

Avermectin (AVM) is one of the most often used insecticides which is toxic to aquatic organisms, and cause oxidative-induced damages to the fish respiratory organ, the "gills". To better understand the mechanism by which an antioxidant reduces AVM-induced gill damage, we investigated the effects of Quercetin (Que) on AVM induction of oxidative stress to inhibit damages to the gills using common carp as a model organism. The Que is a fruit and vegetable rich flavonoid with antioxidant activity. In this study, four groups were created: the Control group, the Que group (400 mg/kg), the AVM group (2.404 μg/L), and the Que plus AVM group. The analytical methods were pathological structure examination, qPCR, Reactive Oxygen Species (ROS) and Western blot. The results showed that Que alleviated AVM-induced oxidative stress, inflammatory damage and apoptosis in the carp gills by activating the Nrf2 pathway. The mechanism was that Que alleviated the accumulation of ROS, reduced the balance between oxidation and antioxidant disrupted by AVM exposure, lowered the content of lipid peroxidation produced malondialdehyde (MDA), and increased the content of antioxidant enzymes including glutathione (GSH) and catalase (CAT). Nrf2 pathway was activated. Meanwhile, Que inhibited gill apoptosis in carp by decreasing the levels of Bax, Cytochrome C, Caspase9, Cleaved-Caspase3 and reduced Bcl2. This has important implications for future studies on Que and AVM. New suggestions are provided to reduce the threat of aquatic environmental pollution.

Ferulic acid alleviates carp brain damage and growth inhibition caused by avermectin by modulating the Nrf2/Keap1 and NF-κB signaling pathways

The increasing concern over environmental pollution caused by the pesticide avermectin used in aquaculture has attracted significant attention. The use of avermectin, a neurotoxic pesticide, in aquatic environments leads to toxic effects on non-target organisms, particularly causing harm to fish. The phenolic compound ferulic acid possesses excellent anti-inflammatory and antioxidant capabilities. This study was conducted by establishing a chronic exposure experiment to avermectin, proposes the use of ferulic acid as a dietary additive to protect the carp brain from damage caused by exposure to avermectin. Furthermore, it investigates the anti-inflammatory and antioxidant effects of ferulic acid in the carp brain under chronic exposure to avermectin. The experimental results demonstrate that ferulic acid can alleviate brain tissue inflammation and oxidative stress by modulating the Nrf2/Keap1 and NF-κB signaling pathways. It protects the carp brain from chronic avermectin-induced damage, preserves the integrity of the carp blood-brain barrier, enhances the levels of feeding factors, and thereby alleviates carp growth inhibition. These findings provide new therapeutic strategies and a theoretical foundation for the sustainable development of carp aquaculture.

A review on aquatic toxins - Do we really know it all regarding the environmental risk posed by phytoplankton neurotoxins?

Aquatic toxins are potent natural toxins produced by certain cyanobacteria and marine algae species during harmful cyanobacterial and algal blooms (CyanoHABs and HABs, respectively). These harmful bloom events and the toxins produced during these events are a human and environmental health concern worldwide, with occurrence, frequency and severity of CyanoHABs and HABs being predicted to keep increasing due to ongoing climate change scenarios. These contexts, as well as human health consequences of some toxins produced during bloom events have been thoroughly reviewed before. Conversely, the wider picture that includes the non-human biota in the assessment of noxious effects of toxins is much less covered in the literature and barely covered by review works. Despite direct human exposure to aquatic toxins and related deleterious effects being responsible for the majority of the public attention to the blooms' problematic, it constitutes a very limited fraction of the real environmental risk posed by these toxins. The disruption of ecological and trophic interactions caused by these toxins in the aquatic biota building on deleterious effects they may induce in different species is paramount as a modulator of the overall magnitude of the environmental risk potentially involved, thus necessarily constraining the quality and efficiency of the management strategies that should be placed. In this way, this review aims at updating and consolidating current knowledge regarding the adverse effects of aquatic toxins, attempting to going beyond their main toxicity pathways in human and related models' health, i.e., also focusing on ecologically relevant model organisms. For conciseness and considering the severity in terms of documented human health risks as a reference, we restricted the detailed revision work to neurotoxic cyanotoxins and marine toxins. This comprehensive revision of the systemic effects of aquatic neurotoxins provides a broad overview of the exposure and the hazard that these compounds pose to human and environmental health. Regulatory approaches they are given worldwide, as well as (eco)toxicity data available were hence thoroughly reviewed. Critical research gaps were identified particularly regarding (i) the toxic effects other than those typical of the recognized disease/disorder each toxin causes following acute exposure in humans and also in other biota; and (ii) alternative detection tools capable of being early-warning signals for aquatic toxins occurrence and therefore provide better human and environmental safety insurance. Future directions on aquatic toxins research are discussed in face of the existent knowledge, with particular emphasis on the much-needed development and implementation of effective alternative (eco)toxicological biomarkers for these toxins. The wide-spanning approach followed herein will hopefully stimulate future research more broadly addressing the environmental hazardous potential of aquatic toxins.

Abamectin induced brain and liver toxicity in carp: The healing potential of silybin and potential molecular mechanisms

Abamectin (ABM) abuse contaminated aquatic environment and posed a potential threat to fish health as well as public safety. Silybin (SIL), a flavonoid, has been widely used as a novel feed additive to promote fish health. This research was to explore the potential antagonistic mechanism between ABM and SIL on brain and liver toxicity was investigated in common carp. Sixty carp were divided into four groups at random: the Control group, the SIL group, the ABM group, and ABM + SIL group. This experiment lasted for 30 d. According to behavioral observation, the detection of levels of acetylcholinesterase (AchE), iron, and mRNA expression levels of blood-brain barrier (BBB) related tight junction proteins (ZO-1, Claudin7, Occludin, MMP2, MMP9, and MMP13) in brain tissues, it was found that SIL relieved neurobehavioral disorders caused by ABM-induced BBB destruction in carp. H&E staining showed SIL mitigated nerve injury and liver injury caused by ABM. Oil Red O staining and liver-related parameters showed that SIL alleviated hepatotoxicity and lipid metabolism disorder caused by ABM exposure. Furthermore, this work also explored the specific molecular mechanism of SIL in liver protection and neuroprotection. It was shown that SIL lowered ROS levels in liver and brain tissues via the GSK-3β/TSC2/TOR pathway. Simultaneously, SIL inhibited NF-κB signaling pathway and played an anti-inflammatory role. In conclusion, we believed that SIL supplementation has a protective effect on the brain and liver by regulating oxidative stress and inflammation.

Quercetin attenuates avermectin-induced cardiac injury in carp through inflammation, oxidative stress, apoptosis and autophagy

As an important antibiotic, avermectin (AVM) has been widely used in China, but its unreasonable application has caused serious harm to the water environment. In view of the various pharmacological effects of quercetin (QUE), such as anti-inflammatory and antioxidant, the scientific hypothesis that "QUE may cause carp poisoning by inhibiting AVM" was proposed in this study. However, its protective effect in AVM -induced heart damage has not been reported. QUE reduced the symptoms of AVM toxicity and decreased the levels of creatine kinase, lactate dehydrogenase, and creatine kinase in the serum of carp. By histological observation, QUE was found to significantly reduce cardiac fiber swelling in carp. A DHE fluorescence probe study showed that QUE was able to inhibit AVM -induced accumulation of reactive oxygen species (ROS) in carp myocardium. We found that QUE significantly increased the intracellular antioxidant enzymes CAT, T-AOC and GSH enzyme activity and reduced intracellular MDA content. In addition, QUE significantly increased il-10 and tgf-β1 expression, and significantly down-regulated tnf-α, il-6, il-1β and inos expression. Tunel assay showed that QUE attenuated AVM -induced apoptosis, significantly decreased the transcript levels of pro-apoptosis-related genes, and increased the expression of anti-apoptosis-related genes. We also detected the protein expression of LC3 in the AVM group and QUE + AVM group, and found that the expression of LC3 was significantly increased in both groups compared with the Control group, but after adding QUE, the expression of LC3 was significantly decreased compared with the AVM group. In addition, the transcript levels of p62 and atg5 were also detected by qPCR. QUE significantly increased the expression of p62 and decreased the expression of atg5, suggesting that QUE could attenuate AVM -induced cardiac autophagy in carp. This study will provide preliminary evidence of the principle of QUE attenuating AVM -induced myocardial injury in carp from four aspects, including oxidative stress, inflammatory response, apoptosis and autophagy, and provide a theoretical basis for its prevention and treatment.

Disruption of the intestinal barrier by avermectin in carp involves oxidative stress and apoptosis and leads to intestinal inflammation

Avermectin (AVM) is a widely used insecticide. Due to its sensitive toxicity to aquatic organisms, the toxicology of AVM on fish intestines remains unclear. Here, we established a 96 h AVM acute toxicity model to explore the effects of AVM on the intestinal tract of carp. The 96 h LC50 of carps exposed to AVM was 24.04 μg/L, 12.02 μg/L was selected as the high-dose group and 3.005 μg/L was selected as the low-dose group. After 96 h of exposure, intestinal tissues were collected and subsequently analyzed for histopathology, the activities of antioxidant oxidases (CAT, SOD, GSH-Px), and the expression of mRNA associated with oxidative stress, inflammation, and apoptosis. Our study showed that AVM exposure caused intestinal damage in carp, decreased the expression of the tight junction protein gene, activated oxidative stress, induced apoptosis, and induced intestinal inflammation in carp. Therefore, we demonstrated that AVM exposure compromised the integrity of the intestinal barrier in carp, activated oxidative stress, induced endogenous apoptosis, and induced intestinal inflammatory responses. These results indicate that AVM, as a drug-sensitive to aquatic organisms, has a much more complex toxic effect on the fish intestinal tract, which provides a new perspective for studying the toxicology of AVM on the fish intestinal tract.

Ferulic acid attenuated difenoconazole-induced immunotoxicity in carp by inhibiting TRAF/TAK1/NF-κB, Nrf2 and p53 pathways

Difenoconazole (DFZ) is a classical triazole fungicide that causes immunosuppression in non-target organisms. Ferulic acid (FA) is a polyphenolic molecule found in nature that has antioxidant and anti-inflammatory activities. The purpose of this investigation was to see if FA could prevent DFZ-induced immunosuppression and to identify the potential mechanisms. Carp were exposed to 1/10 LC50 of DFZ as well as fed normal feed or feed containing dietary additive FA for 30 d. It was found that DFZ-induced immunosuppression could be improved by FA, as evidenced by upregulation of Hb, C3 and IgM and downregulation of LDH. It was then investigated that FA could ameliorate DFZ-induced splenic injury through p53-mediated apoptosis. At the same time, enhancing the levels of CAT, GSH and T-AOC in spleen and transcription levels Nrf2 signaling pathway related genes indicated that FA reduced oxidative damage caused by DFZ by blocking the Nrf2 signaling pathway. In addition, FA inhibited the inflammatory response triggered by TRAF/TAK1/NF-κB signaling pathway, downregulated the transcript levels of pro-inflammatory factors (il-1β, tnf-α, il-6) and the level of NLRP3 inflammasome (NRLP3, ASC, Caspase 1), and upregulated the transcript levels of anti-inflammatory factors (tgf-β1, il-10). In conclusion, the above results suggested that FA mediated TRAF/TAK1/NF-κB, Nrf2, and p53 pathways to attenuate DFZ-induced inflammation, oxidative stress, and apoptosis thereby enhancing the immune capacity of carp.

Molecular mechanism of kidney damage caused by abamectin in carp: Oxidative stress, inflammation, mitochondrial damage, and apoptosis

Indiscriminate use of pesticides not only leads to environmental pollution problems, but also causes poisoning of non-target organisms. Abamectin (ABM), a widely used insecticide worldwide, is of wide concern due to its persistence in the environment and its high toxicity to fish. The kidney, as a key organ for detoxification, is more susceptible to the effects of ABM. Unfortunately, few studies investigated the mechanisms behind this connection. In this study, carp was used as an indicator organism for toxicological studies to investigate renal damage caused by ABM residues in carp. In this work, carp were exposed to ABM (0, 3.005, and 12.02 μg/L) for 4 d and the nephrotoxicity was assessed. Histopathological findings revealed that ABM exposure induced kidney damage in carp, as well as an increase Creatinine and BUN levels. Meanwhile, ABM as a reactive oxygen species (ROS) stimulator, boosted ROS bursts and lowered antioxidant enzyme activity while activating the body's antioxidant system, the Nrf2-Keap1 signaling pathway. The accumulation of ROS can also lead to the imbalance of the body's oxidation system, leading to oxidative stress. At the same time, NF-κB signaling pathway associated with inflammation was activated, which regulated expression levels of inflammatory cytokines (TNF-α, IL-6, IL-1β, and iNOS increased, while IL-10 and TGF-β1 decreased). In addition, ABM exposure caused structural damage to kidney mitochondria of carp, resulting in decreased mitochondrial membrane potential and ATP production capacity, and mediated apoptosis through endogenous pathways Bax/Bcl-2/Caspase-9/Caspase-3. In conclusion, ABM caused kidney damage in carp by inducing oxidative stress, inflammation, and apoptosis through mitochondrial pathway. These findings will be useful for future research into molecular mechanisms of ABM-induced nephrotoxicity in aquatic organisms.

Difenoconazole disrupts carp intestinal physical barrier and causes inflammatory response via triggering oxidative stress and apoptosis

As a common fungicide, difenoconazole (DFZ) is widespread in the natural environment and poses many potential threats. Carp makes up a significant proportion of China's freshwater aquaculture population and are vulnerable to the DFZ. Therefore, this study investigated the effects of DFZ (0.488 mg/L and 1.953 mg/L) exposure for 4 d on the intestinal tissues of carp and explored the mechanisms. Specifically, DFZ exposure caused pathological damage to the intestinal tissues of carp, reducing the expression levels of intestinal tight junction proteins, and leading to damage to the intestinal barrier. In addition, DFZ exposure activated the NF-κB signaling pathway, increasing the levels of pro-inflammatory factors (TNF-α, IL-1β, IL-6) and decreasing the levels of anti-inflammatory factors (IL-10, TGF-β1). As disruption of the intestinal barrier is closely linked to oxidative stress and apoptosis, we have conducted research in both areas for this reason. The results showed that DFZ exposure elevated reactive oxygen species in carp intestines, decreased antioxidant enzyme activity, and suppressed the expression of oxidative stress-related genes. TUNEL results showed that DFZ induced the onset of apoptosis. In addition, the expression levels of apoptosis-related genes and proteins were examined. Western blotting results showed that DFZ could upregulate the protein expression levels of Bax, Cytochrome C and downregulate the protein levels of Bcl-2. qPCR results showed that DFZ could upregulate the transcript levels of Bax, Caspase-3, Caspase-8 and Caspase-9 and downregulate the transcript levels of Bcl-2 transcript levels. This suggests that DFZ can induce apoptosis of mitochondrial pathway in carp intestine. In conclusion, DFZ can induce oxidative stress and apoptosis in carp intestine, leading to the destruction of intestinal physical barrier and the occurrence of inflammation. Our data support the idea that oxidative stress and apoptosis are important triggers of pesticide-induced inflammatory bowel illness.

Protective effect of quercetin on avermectin induced splenic toxicity in carp: Resistance to inflammatory response and oxidative damage

Avermectin pollution is an important problem that cannot be ignored in aquatic system in recent years. It has brought great trouble to freshwater aquaculture, especially fishery aquaculture. Plant-derived quercetin has anti-inflammatory and antioxidant properties and is widely used as a dietary additive, but its protective effect on immune damage induced by avermectin in freshwater carp remains unclear. This study evaluated the role of dietary additive quercetin supplementation in chronic avermectin exposure of carp spleen. Sixty carp were divided into 4 groups (n = 15/ group), including control group, avermectin treatment group, quercetin treatment group, quercetin and avermectin co-treatment group. Carp were exposed to a 1/10 96 h LC₅₀ dose of avermectin for 30 d and fed a carp diet containing 400 mg/kg quercetin twice a day (3% body weigh/ carp). The results showed that chronic avermectin exposure caused the loose parenchymal structure of carp spleen tissue and the increase of inflammatory cells, accompanied by increased transcription levels of pro-inflammatory il-1β, il-6, tnf-α and decreased levels of anti-inflammatory factors il-10 and tgf-β1, ROS accumulation in spleen tissue. MDA content increased and T-AOC, CAT and GSH levels decreased. Quercetin down-regulates the NF-κB pathway by inhibiting the expression of iNOS and activating p38 MAPK, blocking the transcription of inflammatory factors, and alleviating the inflammation of carp spleen caused by chronic avermectin exposure. In addition, quercetin inhibits the over-activation of Nrf2/Keap-1 signaling axis, blocks ROS accumulation, and restores the spleen REDOX homeostasis. In conclusion, quercetin, as a dietary additive for carp feed, can effectively improve the immune damage caused by avermectin pollution in aquatic environment, resist spleen inflammation and oxidative stress, and provide a theoretical basis for clinical development of freshwater carp feed.

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.

A review on the ecotoxicity of macrocyclic lactones and benzimidazoles on aquatic organisms

Despite its wide production and several applications, veterinary antiparasitics from macrocyclic lactones and benzimidazole classes have not received much scientific attention concerning their environmental risks. Thus, we aimed to provide insights into the state of the environmental research on macrocyclic lactone and benzimidazole parasiticides, emphasizing their toxicity to non-target aquatic organisms. We searched for relevant information on these pharmaceutical classes on PubMed and Web of Science. Our search yielded a total of 45 research articles. Most articles corresponded to toxicity testing (n = 29), followed by environmental fate (n = 14) and other issues (n = 2) of selected parasiticides. Macrocyclic lactones were the most studied chemical group (65% of studies). Studies were conducted mainly with invertebrate taxa (70%), with crustaceans being the most predominant group (n = 27; 51%). Daphnia magna was the most used species (n = 8; 15%). Besides, it also proved to be the most sensitive organism, yielding the lowest toxicity measure (EC₅₀ 0.25 μg/L for decreased mobility after 48 h-abamectin exposure) reported. Moreover, most studies were performed in laboratory settings, tracking a limited number of endpoints (acute mortality, immobility, and community disturbance). We posit that macrocyclic lactones and benzimidazoles warrant coordinated action to understand their environmental risks.

Crosstalk of oxidative stress, inflammation, apoptosis, and autophagy under reactive oxygen stress involved in difenoconazole-induced kidney damage in carp

Difenoconazole is a commonly used triazole fungicide in agricultural production. Because of its slow degradation and easy accumulation in the environment, it seriously endangers both animal health and the ecological environment. Therefore, it is hoped that the effects on carp kidneys can be studied by simulating difenoconazole residues in the environment. The experiment was designed with two doses (0.488 mg/L, 1.953 mg/L) as exposure concentrations of difenoconazole for 4 d. Histopathological results showed that difenoconazole could cause severe damage to the kidney structure and extensive inflammatory cell infiltration in carp. Elevated levels of Creatinine, and BUN suggested the development of kidney damage. The DHE fluorescence probe's result suggested that difenoconazole might cause reactive oxygen species (ROS) to accumulate in the kidney of carp. Difenoconazole was found to increase MDA levels while decreasing the activities of CAT, SOD, and GSH-PX, according to biochemical indicators. In addition, difenoconazole could up-regulate the transcription levels of inflammatory factors tnf-α, il-6, il-1β, and inos. At the same time, it inhibited the transcription level of il-10 and tgf-β1. The TUNEL test clearly showed that difenoconazole induced apoptosis in the kidney and vastly raised the transcript levels of apoptosis-related genes p53, caspase9, caspase3, and bax while inhibiting the expression of Bcl-2, fas, capsase8. Additionally, TEM imaging showed that clearly autophagic lysosomes and autophagosomes were formed. Elevated levels of LC3II protein expression, increased transcript levels of the autophagy-related gene atg5 as well as decreased transcript levels of p62 represented the generation of autophagy. In conclusion, the study illustrated that oxidative stress, inflammation, apoptosis, and autophagy all played roles in difenoconazole-induced kidney injury in carp, which was closely linked to ROS production. This work provides a valuable reference for studying the toxicity of difenoconazole to aquatic organisms.