Immunotoxic responses of chronic exposure to cypermethrin in common carp

Novel protective aspects of dietary polyphenols against pesticidal toxicity and its prospective application in rice-fish mode: A Review

The rice fish system represents an innovative and sustainable approach to integrated farming, combining rice cultivation with fish rearing in the same ecosystem. However, one of the major challenges in this system is the pesticidal pollution resulting from various sources, which poses risks to fish health and overall ecosystem balance. In recent years, dietary polyphenols have emerged as promising bioactive compounds with potential chemo-preventive and therapeutic properties. These polyphenols, derived from various plant sources, have shown great potential in reducing the toxicity of pesticides and improving the health of fish within the rice fish system. This review aims to explore the novel aspects of using dietary polyphenols to mitigate pesticidal toxicity and enhance fish health in the rice fish system. It provides comprehensive insights into the mechanisms of action of dietary polyphenols and their beneficial effects on fish health, including antioxidant, anti-inflammatory, and detoxification properties. Furthermore, the review discusses the potential application methods of dietary polyphenols, such as direct supplementation in fish diets or through incorporation into the rice fields. By understanding the interplay between dietary polyphenols and pesticides in the rice fish system, researchers can develop innovative and sustainable strategies to promote fish health, minimize pesticide impacts, and ensure the long-term viability of this integrated farming approach. The information presented in this review will be valuable for scientists, aqua-culturists, and policymakers aiming to implement eco-friendly and health-enhancing practices in the rice fish system.

Assessment of deltamethrin-induced DNA damage, neurotoxic and neuroimmune effects in the brain tissue of brown trout (Salmo trutta fario)

This study investigated the impact of deltamethrin (DM) toxicity on brown trout (Salmo trutta fario), examining its effects on the immune system, including the white blood cell (WBC), lymphocyte (Lym), total immunoglobulin (T. Ig), and lysozyme levels, as well as its neurotoxic consequences on the brain tissue. The neurotoxic effects encompassed oxidative stress, the activity of the antioxidant enzymes, such as the superoxide dismutase (SOD) and catalase (CAT), acetylcholinesterase (AChE) activity, and DNA damage using 8-hydroxy-2-deoxyguanosine (8-OHdG). The DM exposure led to elevated levels of malondialdehyde (MDA), and 8-OHdG, while concurrently causing a reduction in the AChE activity, protein and lipid content, WBC count, Lym, lysozyme activity, T. Ig levels, as well as the SOD and CAT levels in the brain tissues of groups 2 and 3 when compared to those in group 1. In summary, the findings of this study strongly indicate that DM induces DNA damage, immunotoxicity, and neurotoxicity in the brain tissue of brown trout, primarily due to the excessive production of reactive oxygen species (ROS). Moreover, the observed dose-dependent responses of DM to the environmental concentrations on all the investigated parameters suggest its potential utility in aquaculture risk assessment.

Physiological and histopathological effects of polystyrene nanoparticles on the filter-feeding fish Hypophthalmichthys molitrix

Excessive use of plastics in daily life is causing plastic pollution in aquatic environment and threatening the aquatic life. Therefore, research on the plastic pollution in aquatic environment is crucial to understand its impact and develop effective solution for safeguarding aquatic life and ecosystem. The current study investigated the effects of water borne polystyrene nanoparticles (PS-NPs) on hemato-immunological indices, serum metabolic enzymes, gills, and liver antioxidant parameters, plasma cortisol level and histopathological changes in liver and gill tissues of the widely distributed fish Hypophthalmichthys molitrix. The fingerlings of H. molitrix were exposed to different concentrations (T1-0.5, T2-1.0, and T3-2.0 mg/L) of PS-NPs respectively for 15 days consecutively. Our results indicated the dose dependent negative effects of PS-NPs on the physiology and histopathology of H. molitrix. Immuno-hematological indices showed significant increase in WBCs count, phagocytic activity, and lysozyme activity, while decreased RBC count, Hct%, Hb level, total proteins, IgM, and respiratory burst activity were observed. The levels of antioxidant enzymes like SOD, CAT and POD showed the decreasing trends while metabolic enzymes (AST, ALT, ALP and LDH), LPO, ROS activities and relative expressions of SOD1, CAT, HIF1-α and HSP-70 genes increased with increased concentrations of PS-NPs. Moreover, blood glucose and cortisol levels also showed significant increasing trends with dose dependent manner. Histopathological examination indicated moderate to severe changes in the gills and liver tissues of the group treated with 2.0 mg/L of PS-NPs. Overall, the results showed the deleterious effects of PS-NPs on physiology, immunity, metabolism, and gene expressions of H. molitrix. It is concluded that particulate plastic pollution has deleterious effects on filter feeding fish, which might affect human health through food chain and particulate chemical toxicity.

Alpha-lipoic acid suppresses gibberellic acid nephrotoxicity in Nile tilapia (Oreochromis niloticus) via modulating oxidative stress, inflammation, cytokine production, and apoptosis

Globally, gibberellic acid (GA) is one of the extensively used plant growth regulators in agriculture. Yet, there is limited information about their toxicity to fish. Recently, alpha lipoic acid (ALA) has drawn much interest due to its antioxidant properties. This study was planned to determine whether ALA might protect Nile tilapia's kidneys from the toxic effects of GA and the probable underlying mechanisms. Thus, 240 Oreochromis niloticus fish (average initial weight 30.67 ± 0.57) were allocated into four groups received a basal diet or a basal diet supplemented with 600 mg/kg ALA or a basal diet but exposed to a GA (150 mg/L), or ALA-fortified diet and concurrently exposed to GA as previously described. After 60 days, hematological, oxidative stress, lipid peroxidation, stress indices, selected kidney toxic byproducts, histological investigations, and associated gene expression were assessed. Anemia, leukopenia, hypoproteinemia, and elevated kidney function indicators were noticed in the GA-treated group. Additionally, there were detectable cortisol, glucose, 8-OHdG, and MDA increases. However, there was a considerable drop in Cat, Sod, Gpx, GSH, and AChE levels. Structural damage to the kidneys was also identified. In the kidney of fish treated with GA, pro-inflammatory cytokines (tnfα, il-1β), stress, and apoptotic genes (hsp70, pcna, caspase-3, and p53) genes were markedly up-regulated, while anti-oxidative (cat, sod) gene expression was downregulated. Conversely, adding ALA to the diet abolished the GA-induced changes in most of the markers mentioned above. Conclusively, ALA protects against GA-induced hematotoxicity, oxidative damage, and nephrotoxic effects in Nile tilapia fish.

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.

Cypermethrin induces apoptosis, autophagy and inflammation via ERS-ROS-NF-κB axis in hepatocytes of carp (Cyprinus carpio)

Cypermethrin (CYP, IUPAC name: [cyano-(3-phenoxyphenyl)methyl] 3-(2,2-dichloroethenyl)-2,2-dimethylcyclopropane-1-carboxylate) is a pyrethroid insecticide that poses a threat to the health of humans and aquatic animals due to its widespread use and environmental contamination. However, the mechanism of CYP on apoptosis, autophagy and inflammation in hepatocytes of carp (Cyprinus carpio) is unknown. We hypothesized that CYP caused damage to hepatocytes through the endoplasmic reticulum stress (ERS) pathway, CCK-8 was used to detect the toxic effects of different doses of CYP on hepatocytes, and finally low (L, 10 μM), medium (M, 40 μM), and high (H, 80 μM) doses of CYP was selected to construct the model. ROS staining, oxidative stress-related indices (MDA, CAT, T-AOC, SOD), AO/EB staining, MDC staining, and the expression levels of related genes were detected using qRT-PCR and western blot. Our results showed that CYP exposure resulted in an increase in ROS production, an increase in MDA content, and a decrease in the activity of CAT, SOD, and T-AOC in hepatocytes; the proportion of apoptotic, necrotic, and autophagic cells increased significantly in a dose-dependent manner. We also found that CYP exposure increased the expression levels of endoplasmic reticulum-related genes (GRP78, PERK, IRE-1, ATF-6 and CHOP), apoptosis (Bcl-2, Bax, Caspase-3, Caspase-9 and Cyt-c) and autophagy-related genes (LC3b, Beclin1 and P62) also showed dose-dependent changes, and the expression levels of inflammation-related genes (NF-κB, TNF-α, IL-1β, IL-6) were also significantly elevated. Thus, we demonstrated that CYP exposure caused apoptosis, autophagy and inflammation in hepatocytes via ERS-ROS-NF-κB axis. This research contributes to our understanding of the molecular mechanisms underlying CYP-induced damage in hepatocytes of carp (Cyprinus carpio).

Modulatory effect of thymol on the immune response and susceptibility to Aeromonas hydrophila infection in Nile tilapia fish exposed to zinc oxide nanoparticles

Zinc oxide nanoparticles (ZnO-NPs) have many exciting properties that make their use in a continuous increase in various biomedical, industrial, and agricultural applications. This is associated with accumulation in the aquatic ecosystems and fish exposure with consequent deleterious effects. To determine the potential of thymol to counteract the immunotoxic effects of ZnO-NPs, Oreochromis niloticus was exposed to ZnO-NPs (⅕ LC₅₀ =1.14 mg/L, for 28 days) with or without feeding a thymol-incorporated diet (1 or 2 g/kg diet). Our data demonstrated a reduction of aquaria water quality, leukopenia, and lymphopenia with a decrease in serum total protein, albumin, and globulin levels in exposed fish. At the same time, the stress indices (cortisol and glucose) were elevated in response to ZnO-NPs exposure. The exposed fish also revealed a decline in serum immunoglobulins, nitric oxide, and the activities of lysozyme and myeloperoxidase, in addition to reduced resistance to the Aeromonas hydrophila challenge. The RT-PCR analysis showed downregulation of antioxidant (SOD) superoxide dismutase and (CAT) catalase gene expression in the liver tissue with overexpression of the immune-related genes (TNF-α and IL-1β). Importantly, we found that thymol markedly protected against ZnO-NPs-induced immunotoxicity in fish co-supplemented with thymol (1 or 2 g/kg diet) in a dose-dependent manner. Our data confirm the immunoprotective and antibacterial effects of thymol in ZnO-NPs exposed fish, supporting the potential utility of thymol as a possible immunostimulant agent.

Integrative time series of cellular, humoral and molecular response revealed immunotoxicity of bifenthrin to Chinese rare minnow (Gobiocypris rarus) following Pseudomonas fluorescens challenge

Bifenthrin is a common pesticide that is widespread in aquatic environments. Although it has been shown to be toxic to aquatic organisms, its immunotoxicity and mechanism are unclear. Herein, we reported the immunotoxicity of bifenthrin on adult Chinese rare minnow (Gobiocypris rarus) after 28 days of exposure to different concentrations of bifenthrin (0.1, 0.3, and 1.0 μg/L) and 36-h Pseudomonas fluorescens challenge. Bifenthrin inhibited the fish humoral immune response to bacteria by altering the lymphocyte and neutrophil ratios and decreasing the production of lysozyme, complement component 3, immunoglobulin M, and C-reactive protein, particularly were 1.0 μg/L. Bifenthrin caused intestinal damage and significantly reduced the volume of intestinal mucus at 12 and 36 hours postinjection (hpi) (p < 0.05). Moreover, 1.0 μg/L bifenthrin significantly increased the fish mortality and bacterial loads at 12 and 36 hpi (p < 0.05). RNA-seq analysis revealed several enriched genes involved in pathogen attachment and recognition, inflammatory responses, and complement system at the early-to-mid stage of infection (4-12 hpi). Overall, our results corroborated that bifenthrin induced immunotoxicity in Gobiocypris rarus, resulting in immune dysfunction of fish and increasing their sensitivity to bacterial infection and accelerating mortality. Moreover, 4-12 hpi was better than 36 hpi for analyzing immune responses against pathogen infection in fish exposed to bifenthrin.

Evaluation of Taraxacum mongolicum flavonoids in diets for Channa argus based on growth performance, immune responses, apoptosis and antioxidant defense system under lipopolysaccharide stress

To ascertain the effects of Taraxacum mongolicum flavonoids (TMF) on the growth performance, digestive enzyme activity, immune indices, inflammatory response and antioxidant capacity of Channa argus, 400 C. argus with an average body weight of (8.08 ± 0.21) g were selected and divided randomly into four groups. They were fed with four experimental diets supplemented with TMF of 0 (control), 25, 50 and 100 mg/kg for 56 d, and then challenged with lipopolysaccharide (LPS) for 96 h, afterwards indices were detected. The results manifested that the addition of TMF above 50 mg/kg in the dietary could significantly improve the final body weight, WGR, SGR and PER of C. argus, while decreased FCR (P < 0.05). Similarly, the 50 mg/kg group had the highest activity of digestive enzymes (protease, lipase, amylase) in intestine and hepatopancreas, which were notably higher than those in the control group (P < 0.05). Nevertheless, 100 mg/kg group could effectively inhibit the liver and gut injury caused by LPS and reduce the contents of ALT and AST, LPS and LBP in serum. In the immune (LY, AKP, ACP, IgM, C3) and antioxidant (T-AOC, SOD, CAT, GSH-PX, GR, ASA, MDA) systems, 100 mg/kg groups were the optimal group, which were remarkably higher than those of the control group (P < 0.05). Additionally, the expression of genes revealed that 100 mg/kg group could noteworthy restrain the expression of pro-inflammatory factors (tnf-α, il-1β, il-8) and pro-apoptosis (cas-3,8,9, p53, bax, bcl-2) related genes, up-regulate the expression of anti-inflammatory (il-10, tgf-β) factors, antioxidant-related (nrf2, gpx, gst, cat) genes and heat shock proteins (hsp70, hsp90). Simultaneously, the survival rate of C. argus in the 100 mg/kg TMF-supplemented group was the highest after LPS challenge. Our results elucidate that dietary supplementation TMF protects C. argus from LPS-induced inflammatory injury, to ameliorate digestion, immune response, antioxidant status and apoptosis, implying that TMF could be regarded as an anti-inflammatory and antioxidant agent adding to aquatic animal feed.

Toxic effects of pesticides on cellular and humoral immunity: an overview

People are exposed to pesticides through food, drinking water, and the environment. These compounds are associated with several disorders, such as inflammatory diseases, rheumatoid arthritis, cancer, and a condition related to metabolic syndrome. The immunotoxicants or immunotoxic compounds can cause a wide variety of effects on immune function, altering humoral immunity and cell-mediated immunity, resulting in adverse effects to the body. Here, immune system disorders are highlighted because they are closely linked to multiple organs, including the nervous, endocrine, reproductive, cardiovascular, and respiratory systems, leading to transient or permanent changes. Therefore, this study reviewed the mechanisms involved in the immunotoxicity of fungicides, herbicides, and insecticides in cells, animals, and humans in the past 11 years. According to the studies analyzed, the pesticides interfere with innate and adaptive immune functions, but the effects observed mainly on cellular and humoral immunity were highlighted. These compounds affected specific immune cells, causing apoptosis, changes in factor nuclear kappa B (NF-κB) expression, pro-inflammatory factors interleukin 6 (IL-6), interleukin 8 (IL-8), interferon-gamma (IFN-γ), chemokines (CXCL-c1c), and anti-inflammatory factor, such as interleukin 10 (IL-10). To verify the threats of these compounds, new evaluations with immunotoxicological biomarkers are necessary. HighlightsPesticides interfere with the innate and adaptive immune response.Cells, animals and human studies demonstrate the immunotoxicity of pesticides in the cellular and humoral immune response.Fungicides, herbicides, and insecticides alter the immune system by various mechanisms, such as pro-inflammatory and anti-inflammatory factors.

Environmentally relevant concentrations of fenvalerate induces immunotoxicity and reduces pathogen resistance in Chinese rare minnow (Gobiocypris rarus)

Fenvalerate is a broadly used type II pyrethroid with a potential toxic effect in fish. However, information on the immunotoxicity of fenvalerate in fish is scarce. Here, to discover the immunotoxicity of fenvalerate and its underlying mechanism in fish, adult Chinese rare minnow was exposed to fenvalerate at 0, 0.3, 1, and 3 μg/L for 28 days and then subjected to Pseudomonas fluorescens (P. fluorescens) challenge. Fenvalerate induced significant pathological changes, with disintegration of cell boundaries in the intestine, epithelial hyperplasia in gills, and vacuolation of hepatocytes at 3 μg/L treatment. Additionally, the pathological characteristics were more serious during P. fluorescens infection after fenvalerate exposure. A significant increase in neutrophil counts was observed after 3 μg/L fenvalerate exposure for 28 days (p < 0.05), whereas significantly increased monocyte and neutrophil counts and greatly decreased lymphocyte counts were detected at 24 h post-injection (hpi) with P. fluorescens (p < 0.05). Furthermore, obvious decreases in LYS, IgM, ALP, and C3 levels were detected in plasma after 3 μg/L fenvalerate exposure for 28 days, which was consistent with the results at 24 and 48 hpi. Notably, fish exposed to fenvalerate suppressed the transcription of TLR-NF-κB signaling pathway-relevant genes in response to P. fluorescens, accompanied by high mortalities and bacterial loads. Therefore, our results demonstrate that fenvalerate at environmentally relevant concentrations caused immunotoxicity in fish. This study highlights the importance of considering the combined effects of chemicals and pathogens to refine our ability to predict the effects of environmental contaminants on aquatic organisms.

Dietary α-lipoic acid alleviates deltamethrin-induced immunosuppression and oxidative stress in northern snakehead (Channa argus) via Nrf2/NF-κB signaling pathway

The goal of the study was to determine the ameliorative effects of dietary alpha-lipoic acid (α-LA) on deltamethrin (DEL)-induced immunosuppression and oxidative stress in northern snakehead (Channa argus). The northern snakeheads (15.38 ± 0.09 g) were exposed to DEL (0.242 μg/L) and fed with diets supplemented α-LA at 300, 600, and 900 mg/kg. After the 28-day exposure test, we obtained the following results: i) α-LA alleviates DEL-induced liver injury by reversing the increase of the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels and liver cytochrome P450 enzymes (Cytochrome P450 (cyp)1a and cyp1b) expression levels. ii) α-LA can reverse the DEL-induced reduction of serum complement 4 (C4), C3, immunoglobulin M (IgM), and lysozyme (LYS) levels and the increase of liver and intestine nuclear factor kappa B (nf-κb) p65, tumor necrosis factor (tnf)-α, interleukin (il)-1β, il-8, and il-6 gene expressions, while il-10 expression levels showed the opposite result. iii) α-LA reversed the reduction of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), glutathione-S-transferase (GST) and glutathione peroxidase (GSH-Px) levels in the liver and intestine induced by DEL, while malondialdehyde (MDA) showed the opposite result. iv) α-LA reversed the reduction of Cu/Zn sod, nuclear factor erythroid 2-related factor 2 (nrf2), NAD (P)H: quinone oxidoreductase (nqo)1, and heme oxygenase (ho)-1 antioxidant gene expression levels in the liver and intestine induced by DEL. Therefore, our study indicated that optimal α-LA (600 mg/kg) could attenuate DEL-induced toxicity (including liver damage, immunotoxicity, and oxidative stress) in northern snakehead via Nrf2/NF-κB signaling pathway. This is the first research that explores the alleviated effects of α-LA on DEL-induced toxicity damage in fish. This study provides a positive measure to reduce the toxicity damage caused by DEL to aquatic animals, and provides a theoretical basis for exploring the regulation mechanism of α-LA in toxic substances.

Multi-biomarkers approach to assess the toxicity of novel insecticide (Voliam flexi®) on Clarias gariepinus: From behavior to immunotoxicity

This study was conducted to determine for the first time the immunological, histopathological, histochemical, and ultrastructural changes; hematological and biochemical alterations; and poikilocytosis induced in Clarias gariepinus by Voliam flexi® 40% WG (thiamethoxam + chlorantraniliprole). Beside control fish, juvenile C. gariepinus were subjected to three sublethal concentrations of Voliam flexi® (43.5, 87.5, and 175 mg/L) for 15 days. Voliam flexi® induced immunotoxic impairments in C. gariepinus, such as a decrease in some immunity variables (lysozyme and phagocyte activity, immunoglobulin concentration, and nitro blue tetrazolium level). It also caused an extreme increase in the levels of primary cytokines (interleukin-1β and IL-6), compared with the control. The toxic effects of Voliam flexi® increased gradually with the increasing concentrations tested. Histological examination of the liver demonstrated necrosis, vacuolated hepatocytes (fatty deposition), melanomacrophage centers, foci of inflammatory cells, congested and dilated blood sinusoids, hepatic degeneration, fibrosis increment (Sirius Red stain), and glycogen depletion, as well as cytopathological alterations. We conclude that the toxic effects of Voliam flexi® must be restricted or prevented by using control mechanisms in aquatic systems.

Oxidative stress is involved in the activation of NF-κB signal pathway and immune inflammatory response in grass carp gill induced by cypermethrin and/or sulfamethoxazole

At present, the concentration of environmental pollutants, such as pesticides and antibiotics exposed in environment, especially in aquatic environment is increasing. Research on environmental pollutants has exploded in the last few years. However, studies on the combined effects of pesticides and antibiotics on fish are rare, especially the toxic damage to gill tissue is vague. In this paper, cypermethrin (CMN) and sulfamethoxazole (SMZ) were analyzed and found that there was a strong correlation between the pathways affected by the first 30 genes regulated by CMN and SMZ, respectively. Therefore, the toxic effects of CMN (0.651 μg L^-1) and/or SMZ (0.3 μg L^-1) on grass carp gill were studied in this paper. Histopathology, quantitative real-time PCR, and other methods were used to detect the tissue morphology, oxidative stress level, inflammation, and apoptosis-related indicators of the fish gills after exposure of 42 days. It was found that compared with the single exposure (CMN/SMZ) group, the combined exposure (MIX) group had a more pronounced oxidative stress index imbalance. At the same time, nuclear factor-κB (NF-κB) signal pathway was activated and immuno-inflammatory reaction appeared in MIX group. The expression of tumor necrosis factor (TNF-α) in the rising range is 2.94 times that of the C group, while the expression of interleukin 8 (IL-8) is as high as 32.67 times. This study reveals the harm of CMN and SMZ to fish, and provides a reference and basis for the rational use of pesticides and antibiotics.

Immunotoxicological effects of insecticides in exposed fishes

Biologically active compounds used in agriculture that develop near aquatic environments easily spill into rivers or lakes. As a result, insecticides, herbicides and fungicides are observed worldwide in aquatic environments and accumulated in aquatic organism. Many insecticides, including organochlorine and organophosphate, have long been banned long ago because of their high persistence and non-target toxicity. However, previous studies have shown that persistent pesticides remain in aquatic organisms. The immune system is the first defense mechanism against exposure to persistent organic pollutants or pesticides that have been released into the aquatic environment. Many insecticides have been reported to cause immunotoxicity, which is represented by alteration of phagocytic and lysozyme activity. Recent studies show that immunotoxicity by insecticides exerts a more complex mechanism in fish. Insecticides induce immunotoxic effects, such as the release of inflammatory cytokines from head kidney macrophages and inhibition of immune cell proliferation in fish, which can lead to death in severe cases. Even currently used pesticides, such as pyrethroid, with low bioaccumulation have been shown to induce immunotoxicological effects in fish when exposed continuously. Therefore, this review describes the types and bioaccumulation of insecticides that cause immunotoxicity and detailed immunotoxicological mechanisms in fish tissues.

An Overview on the Potential Hazards of Pyrethroid Insecticides in Fish, with Special Emphasis on Cypermethrin Toxicity

Simple Summary

Pyrethroid insecticides are extensively used in controlling agricultural insects and treatment of ectoparasitic infestation in farm animals. However, the unhygienic disposable and seepage of pyrethroids from the agricultural runoff will lead to contamination of the aquatic ecosystems, which will, in turn, induce harmful toxic effects in the exposed living aquatic organisms, including fish. Cypermethrin (CYP) is a commonly and widely used type II pyrethroid insecticide with known dangerous toxic effects on the exposed organisms. Serious hazardous effects of these toxicants have been reported in several fish species leading to high mortalities and economic losses of the exposed fish.

Abstract

Pesticides are chemicals used to control pests, such as aquatic weeds, insects, aquatic snails, and plant diseases. They are extensively used in forestry, agriculture, veterinary practices, and of great public health importance. Pesticides can be categorized according to their use into three major types (namely insecticides, herbicides, and fungicides). Water contamination by pesticides is known to induce harmful impacts on the production, reproduction, and survivability of living aquatic organisms, such as algae, aquatic plants, and fish (shellfish and finfish species). The literature and information present in this review article facilitate evaluating the toxic effects from exposure to various fish species to different concentrations of pesticides. Moreover, a brief overview of sources, classification, mechanisms of action, and toxicity signs of pyrethroid insecticides in several fish species will be illustrated with special emphasis on Cypermethrin toxicity.

Immune response and susceptibility of Nile tilapia fish to Aeromonas hydrophila infection following the exposure to Bifenthrin and/or supplementation with Petroselinum crispum essential oil

Bifenthrin (BF) is a widely used 3rd generation type I pyrethroid with a potential toxic effect in fish. Nevertheless, its effect on the immune system remains unclear. In the present study, Oreochromis niloticus was exposed to BF at 0.68 μg/L for 60 days, followed by evaluating the hematological, biochemical, and immunological responses. Additionally, the potential of parsley (Petroselinum crispum) essential oil (PEO) to ameliorate the BF-induced toxic insults was explored. Our data have shown reductions in the growth performance with alterations observed in the hematological variables, protein profile and serum biomarkers of stress. DNA oxidative damage was evidenced by elevation of serum 8-hydroxy-2-deoxyguanosine (8-OHdG) content. BF-exposed fish presented also decline in serum lysozyme activity and levels of immunoglobulins (IgG and IgM) and nitric oxide (NO), with diminished resistance to Aeromonas hydrophila challenge. Furthermore, the RT-PCR analysis showed an upregulated expression pattern of immune -related genes including interleukin 1β (IL-1β), interferon - γ (IFN-γ) and tumor necrosis factor - α (TNF-α) genes in the liver tissue. Dietary co-supplementation of PEO at 1 or 2 mL/kg diet with concomitant BF exposure, alleviated the adverse effects of the insecticide in a dose-dependent manner. The observations from this study demonstrate the immunomodulation by BF and provide further insight into the protective properties of PEO and strengthen its applicability as a promising feed supplement to fish.

PKCα mediated by the PI3K/Akt-FOXA1 cascade facilitates cypermethrin-induced hyperthyroidism

Cypermethrin (CYP), a broad-spectrum pyrethroid insecticide is extensively used. CYP is also considered as a potential endocrine disruptor with the thyroid-disturbing property. Protein kinase C alpha (PKCα) is a pleiotropic signal transduction molecule that functions crucially in thyroid hormone (TH) homeostasis and thyroid functions. To explore underlying roles of PKCα in CYP-mediated disturbance of TH homeostasis, Sprague-Dawley rats and rat thyroid cells were used in this study. Results showed that β-CYP stimulated TH biosynthesis, as shown by the increase in plasma levels of TT4, FT4, TT3, FT3, and TSH. After β-CYP treatment, expressions of PKCα, three miRNAs (miR-17-5p, miR-330-3p, and miR-331-3p), thyroid transcription factor TTF-1, and thyroid-specific proteins (TSHr, TPO, and Tg) were significantly increased, while expressions of PI3K p110α, p-Akt, FOXA1, and thyroid transcription factors (TTF-2 and Pax8) were decreased. Further studies found that β-CYP induced PKCα translation by the miR-330-3p-targeted PI3K/Akt-FOXA1 cascade and then PKCα positively regulated TTF-1 to promote TPO and Tg expressions, which in turn facilitated TH biosynthesis. Likewise, PKCα positively modulated TSHr expressions to strengthen the TSH/TSHr signal in the HPT axis, thereby synergistically contributing to TH biosynthesis. Moreover, β-CYP also disturbed TH biotransformation and biotransport by inducing DIO1 and inhibiting DIO3 in thyroids and TTR expressions in livers. Taken together, β-CYP has the thyroid-disturbing effect and could promote TH biosynthesis, and PKCα plays vital roles in β-CYP-caused hyperthyroidism.

Effects of deltamethrin subacute exposure in snakehead fish, Channa argus: Biochemicals, antioxidants and immune responses

To evaluate the effects on biochemicals, antioxidants, immune responses and disease resistance of the snakehead fish, following exposure to deltamethrin at 0.061, 0.121, 0.242, 0.485 and 0.970 μg/L. After 28 d, the biochemical, the levels of antioxidant enzymes and immune enzymes in liver, spleen, kidney and intestine were negatively related to the concentrations of deltamethrin exposure. Likewise, the survival rates of the fish after 7 d challenge with Aeromonas veronii were negatively related. The levels of IL-1β, IL-8, TNF-α, Hsp70 and malondialdehyde in liver, spleen, kidney and intestine were positively connected to the concentrations of deltamethrin exposure. Results demonstrated that environmentally relevant concentrations (0.121, 0.242, 0.485 and 0.970 μg/L) inhibited the biochemicals, antioxidants and immune responses and disease resistance of snakehead fish.

Effect of Lambdacyhalothrin on Locomotor Activity, Memory, Selected Biochemical Parameters, Tumor Necrosis Factor α, and Interleukin 1ß in a Mouse Model

Background: Pyrethroids are synthetic insecticides used for plant protection. They are synthetic analogues of pyrethrins. Lambdacyhalothrin (LCH) is a type II pyrethroid used for wheat, potato, corn farming, and malaria control. There are data that pyrethroids may cause neurotoxicity, nephrotoxicity, hepatotoxicity, and immunotoxicity in non-target organisms. Methods: The experiment was carried on 32 Albino Swiss mice (16 females and 16 males). The animals were divided into four groups. Controls received canola oil; the rest received LCH orally in oil at a dose of 2 mg/kg bw for 7 days. Memory retention was assessed in a passive avoidance task on day 2 and 7, and spatial memory and motor activity in a Y-maze on day 1 and 7. Blood morphology, biochemical tests, tumor necrosis factor α, and interleukin 1ß were measured. Results: Decreased white blood cell count and red blood cell count, increased creatinine, and increased kidney and liver mass were observed in groups exposed to LCH. In LCH-exposed males’ kidneys and livers, interleukin 1ß was significantly elevated, and it was correlated with creatinine concentration. Conclusions: Subacute poisoning with a low dose of LCH does not significantly affect memory nor locomotor activity but increases proinflammatory interleukin 1ß in male livers and kidneys and reduces white and red blood cell counts.

Grass carps co-exposed to environmentally relevant concentrations of cypermethrin and sulfamethoxazole bear immunodeficiency and are vulnerable to subsequent Aeromonas hydrophila infection

The aquatic ecosystem is seriously damaged because of the heavy use of pesticides and antibiotics. Fish is the indispensable link between environmental pollution and human health. However, the toxic effects of environment-related concentrations of pesticides and antibiotics in fish have not been thoroughly studied. In this study, grass carps exposed to cypermethrin (CMN, 0.651 μg/L) or/and sulfamethoxazole (SMZ, 0.3 μg/L) for 42 days caused oxidative stress, apoptosis and immunodeficiency in the spleen of grass carps. CMN or/and SMZ exposure led to oxidative damage (consumption of antioxidant enzymes (superoxide dismutase and catalase)) and lipid peroxidation (accumulation of malondialdehyde), induced apoptosis (increases in TUNEL index, Bax/bcl-2, p53, puma and Caspase family expression). In addition, the levels of immunoglobulin M (IgM), complement 3 (C3) were significantly decreased in all treatment groups, which trend was also found in C-reactive protein in CMN and MIX group, and lysozyme in MIX group. Transcription of almost all genes involved in the Toll-like receptors (TLR) signaling pathway was up-regulated under CMN or/and SMZ exposure. However, when subsequently attacked by Aeromonas hydrophila for 2 days, the TLR pathway was inhibited in spleens of all treatment groups accompanied by higher mortality. Overall, the environmentally relevant concentration of CMN and SMZ damages the immune system, triggering oxidative stress and apoptosis in carps. And by affecting the conduction of TLR signaling pathway, CMN or/and SMZ exposure inhibits the innate immune response of fish and reducing their disease resistance. This study highlights the importance of rational and regulated use of these pesticides and antibiotics.

Dietary Origanum vulgare essential oil attenuates cypermethrin-induced biochemical changes, oxidative stress, histopathological alterations, apoptosis, and reduces DNA damage in Common carp (Cyprinus carpio)

The study was designed to evaluate the possible protective roles of dietary Origanum vulgare essential oil (OVEO) against cypermethrin (CP)-induced serum biochemical changes and oxidative stress of common carp (Cyprinus carpio). Moreover, histopathological alterations, apoptosis, cell proliferation, and DNA damage in the gills and hepatic tissues were also assessed. Briefly, fish were allotted into six groups with three triplicates whereas a group fed on basal diet and did not exposed to CP and served as control (CTR), two groups were fed on diets supplemented with two levels of OVEO (0.5 % and 1.0 %), a group exposed to sub-lethal concentration of CP (1/10 of 96 h-LC₅₀ = 0.4134 μg/L), and two other groups exposed to the same concentration of CP and fed on diets supplemented with both levels of OVEO (CP + 0.5 % OVEO, and CP + 1.0 % OVEO), respectively, for 30 days. CP induced significant elevation of serum alanine transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), urea, and creatinine levels indicating hepato-renal toxicity (P < 0.05). Besides, there was a significant decrease in serum catalase (CAT) and superoxide dismutase (SOD) activities (P < 0.05). Moreover, CP induced significant histopathologic alterations in gills, anterior kidneys, and hepatic tissues with activation of apoptosis (Caspase-3) and proliferating cell nuclear antigen (PCNA). Comet assay demonstrated significant DNA damage in gills and liver tissues of the CP-exposed group. Interestingly, a significant attenuation of serum ALT, AST, ALP, urea, creatinine, CAT, and SOD levels (P < 0.05) was noticed in CP-exposed fish and concurrently fed diets supplemented with either 0.5 % or 1.0 % OVEO. Moreover, histopathologic alterations and apoptosis were significantly reduced along with a concomitant significant decrease in DNA damage (P < 0.05) which indicated the mitigation of DNA damage. Conclusively, the study showed that OVEO is an effective counteractive treatment against CP-induced damage in exposed common carp and is recommended during the formulation of fish rations.

Triclosan induces immunosuppression and reduces survivability of striped catfish Pangasianodon hypophthalmus during the challenge to a fish pathogenic bacterium Edwardsiella tarda

Toxicological studies on the emergent pollutant, triclosan (TCS) have established the wide-ranging effects of the compound on fish and other aquatic organisms. Although the available literature describes the standalone effects of TCS on growth and metabolism of fish yet, reports about the combined effects of TCS with microbial pathogens are scarce. In a real environment, a combined exposure to TCS and pathogens is of common occurrence, therefore, such investigation facilitates in developing a better understanding about the gross effects of pollutants and microbial pathogens on aquatic organisms including fish. In this context, the experimental fish (striped catfish, Pangasianodon hypophthalmus) were exposed to three different concentrations of TCS viz. 10, 20 and 30% of 96 h LC₅₀ (1177 μg L^-1) for 45 days including two control group firstly solvent control (without TCS) group and another one (without solvent and TCS) group in triplicate. Sampling was performed fortnightly and blood, serum and tissues (liver, and gills) samples were collected for evaluating immunological and biochemical parameters. Following 45 days of the experiments, the experimental fish in each treatment group including controls were challenged with a fish pathogenic bacterium Edwardsiella tarda (LD₅₀ dose) and fish mortality was daily monitored for calculating cumulative mortality till 7 days and further, relative per cent survivable was estimated. A significant reduction in cellular immune responses i.e. respiratory burst activity (RBA), myeloperoxidase activity (MPO), phagocytic activity (PA) and humoral immune components viz. serum lysozyme activity, total immunoglobulin in serum, ceruloplasmin level, serum total protein, albumin and globulin level was evident in TCS exposed groups in comparison to control during the experimental periods. Further, oxidative stress parameters viz. superoxide dismutase (SOD), catalase (CAT), glutathione-s-transferase (GST) activity in liver and gill tissue exhibited a dose-dependent increase in activity with related to TCS concentration during the experimental periods. A significant reduction in relative percentage survival was observed with increasing TCS concentration. The present study reveals that TCS can inhibit the cellular and humoral components of the innate immune system of the fish and can elevate the mortality due to TCS mediated immunosuppression in fish during the bacterial infection.

Exposure to environmentally relevant concentrations of deltamethrin renders the Chinese rare minnow (Gobiocypris rarus) vulnerable to Pseudomonas fluorescens infection

In this study, to assess the immunotoxicity of deltamethrin on fish, adult Chinese rare minnows (Gobiocypris rarus) were exposed to 0.1, 0.3, and 1 μg/L deltamethrin for 28 d. Many immunological parameters and histopathological alterations were determined. The results showed that lymphocyte number was markedly decreased at 0.3 and 1 μg/L treatments, whereas the neutrophil number was strongly increased at 1 μg/L treatments (p < 0.05). Furthermore, lysozyme (LYS), immunoglobulin M (IgM), and complement component 3 (C3) levels at 0.3 and 1 μg/L treatments were markedly reduced, whereas alkaline phosphatase (ALP) activity were marked increased at 1 μg/L treatments (p < 0.05). The transcripts of almost all TLR (Toll-like receptor) signaling pathway-related genes were up-regulated. Histological lesions in the livers, intestines, and gills were observed at all treatments. Then, all remaining fish from controls and deltamethrin-exposed groups were injected with Pseudomonas fluorescens (P. fluorescens) for 48 h. At 24 and 48 h post-injection with P. fluorescens (hpi), the lymphocyte numbers were strongly reduced at 0.3 and 1 μg/L deltamethrin-exposed groups, whereas LYS and C3 levels were strongly reduced at 0.3 and 1 μg/L deltamethrin-exposed groups (p < 0.05). Obvious reduces in IgM levels were also detected at 0.3 and 1 μg/L deltamethrin-exposed groups at 48 hpi (p < 0.05). The transcripts of almost all TLR signaling pathway-related genes were significantly down-regulated, whereas the levels of related microRNAs (miRNAs) were markedly increased at all deltamethrin-exposed groups at 24 and 48 hpi. Moreover, the bacterial load in the liver and the mortality of fish were significantly increased at 1 μg/L deltamethrin-exposed groups at 24 and 48 hpi (p < 0.05). Furthermore, obvious histological damage in the livers, intestines, and gills were observed at all deltamethrin-exposed fish at 48 hpi. Overall, our results demonstrated that environmentally relevant concentration deltamethrin suppressed immunity and rendered the fish vulnerable to P. fluorescens infection, subsequently inducing mortality.

Immunomodulatory effect of mancozeb, chlorothalonil, and thiophanate methyl pesticides on macrophage cells

Mancozeb (MZ), chlorothalonil (CT), and thiophanate methyl (TM) are pesticides commonly used in agriculture due to their efficacy, low acute toxicity to mammals, and short environmental persistence. Although the toxic effects of these pesticides have been previously reported, studies regarding their influence on the immune system are limited. As such, this study focused on the immunomodulatory effect of MZ, CT, and TM pesticides on macrophage cells. RAW 264.7 cells were exposed to a range of concentrations (0.1-100 μg/mL) of these pesticides. CT exposure promoted an increase in reactive oxygen species (ROS) and nitric oxide (NO) levels. The MTT and ds-DNA assay results demonstrated that MZ, CT, and TM exposure induced macrophage proliferation. Moreover, MZ, CT, and TM promoted cell cycle arrest at S phase, strongly suggesting macrophage proliferation. The levels of pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, and IFN-γ) and caspases (caspase 1, 3, and 8) in macrophages exposed to MZ, CT, and TM pesticides increased, whereas the anti-inflammatory cytokine levels decreased. These results suggest that MZ, CT, and TM exert an immunomodulatory effect on the immune system, inducing macrophage activation and enhancing the inflammatory response.

The immune responses of the Chinese rare minnow (Gobiocypris rarus) exposed to environmentally relevant concentrations of cypermethrin and subsequently infected by the bacteria Pseudomonas fluorescens

In the present study, to assess the immunotoxicity of cypermethrin (CYP) in fish, Chinese rare minnows (Gobiocypris rarus) were exposed to environmentally relevant concentrations (0.15, 0.5, and 1.5 μg/L) of CYP for 28 d and subjected to pathogen challenge trials for 2 d. After 28 d of CYP exposure, the levels of Immunoglobulin M (IgM), Alkaline phosphatase (ALP), and C-reactive protein (CRP) were significantly decreased (p < 0.05) after treatment with 1.5 μg/L CYP. Moreover, an induction of inflammatory cytokine transcripts (tnfa, il-6, il-8, and il-12) was observed (p < 0.05) after treatment with 1.5 μg/L CYP. After challenge with Pseudomonas fluorescens (P. fluorescens), plasma lysozyme (LYS) activity at 24 and 48 hours post-injection (hpi) was significantly decreased in the 0.5 and 1.5 μg/L CYP treatment groups (p < 0.05). Moreover, liver Complement component 3 (C3) and CRP contents at 24 hpi were significantly decreased in the 1.5 μg/L CYP treatment group (p < 0.05), whereas significant decreases in liver C3 and IgM contents were observed at 48 hpi (p < 0.05). Inhibition of expression of Toll-like receptor-nuclear factor kappa B (TLR-NF-kB) signaling pathway-related genes was observed in the CYP treatment groups and resulted in significant down-regulation of inflammatory cytokines (il-1β and il-12) in the 1.5 μg/L CYP treatment group at 48 hpi (p < 0.05). Interestingly, the mortality in the 0.5 and 1.5 μg/L CYP treatments was significantly increased at 48 hpi (p < 0.05). These results indicated that environmentally relevant concentrations of CYP suppressed the Chinese rare minnow immune system and reduced immune defense against bacterial infection, thereby causing subsequent mortality. Meanwhile, our results demonstrated that a subsequent host resistance challenge is an effective method for determining the immunotoxicity of chemicals (e.g., CYP).