HSP90 and pCREB alterations are linked to mancozeb-dependent behavioral and neurodegenerative effects in a marine teleost

Assessing the Influence of Low Doses of Sucrose on Memory Deficits in Fish Exposed to Common Insecticide Based on Fipronil and Pyriproxyfen

Although pesticides have been a constant concern for decades, in the last ten years, public discussions and scientific research have emphasized their impact on human health and the environment, drawing increased attention to the problems associated with their use. The association of environmental stressors such as pesticides with a sugar-rich diet can contribute to the growing global metabolic disease epidemic through overlapping mechanisms of insulin resistance, inflammation, and metabolic dysregulation. The main aim of this study was to evaluate the behavioral effects of the exposure of Silver crucian carp (Carassius auratus gibelio) to a commercial insecticide formulation containing fipronil, pyriproxyfen, and other additives, as well as sucrose and their mixtures. The behavioral responses in the T-test showed significant abnormalities in the exploratory activity evocative of memory deficits and an increased degree of anxiety in the groups of fish treated with the insecticide formulation and the mixture of the insecticide with sucrose. Aggression, quantified in the mirror-biting test, as biting and the frequency of approaches to the mirror contact zone, was significantly decreased only in the insecticide and sucrose group. All three groups showed behavioral changes reflective of toxicity, but only the combination of the two stress factors, environmental (insecticide) and metabolic (sucrose intake), resulted in pronounced memory alterations.

Potential role of dietary Boswellia serrata resin against mancozeb fungicide-induced immune-antioxidant suppression, histopathological alterations, and genotoxicity in Nile tilapia, Oreochromis niloticus

This study was established to look into the toxicological consequences of chronic exposure to a fungicide (mancozeb; MAZ) on the immune-antioxidant response, gene expressions, hepato-renal functions, and histological pictures of Nile tilapia (Oreochromis niloticus). Additionally, the effectiveness of Indian frankincense resin extract (IFRE) to mitigate their toxicity was taken into account. Fish (n =240; average body weight: 22.45 ± 2.21 g) were randomized into four groups for eight weeks in six replicates (control, IFRE, MAZ, and IFRE + MAZ), where ten fish were kept per replicate. The control and IFRE groups received basal diets that included 0.0 and 5 g/kg of IFRE without MAZ exposure. The MAZ and IFRE+MAZ groups received the same diets and were exposed to 1/10 of the 96-h of LC50 of MAZ (1.15 mg/L). The outcomes displayed that MAZ exposure resulted in a lower survival rate (56.67 %) and significantly decreased levels of immune-antioxidant variables (antiprotease, complement3, phagocytic activity, lysozyme, glutathione peroxidase, superoxide dismutase, and total antioxidant capacity) compared to the control group. The MAZ-exposed fish showed the greatest levels of lipid peroxide (malondialdehyde), alkaline phosphatase, alanine amino-transferase, and stress indicators (cortisol and glucose). Additionally, histopathological alterations, including vacuolation, severe necrosis, degeneration, and mononuclear cell infiltrations in the hepatic, renal, and splenic tissues resulted, besides a reduction in the melanomacrophage center in the spleen. A down-regulation of immune-antioxidant-associated genes [toll-like receptors (TLR-2 and TLR-7), nuclear factor kappa beta (NF-κβ), transforming growth factor-beta (TGF-β), phosphoinositide-3-kinase regulatory subunit 3 gamma b (pik3r3b), interleukins (IL-1β and IL-8), glutathione synthetase (GSS), glutathione peroxidase (GPx), and superoxide dismutase (SOD)] were the consequences of the MAZ exposure. Remarkably, the dietary inclusion of IFRE in MAZ-exposed fish augmented the immune-antioxidant parameters, including their associated genes, decreased stress response, and increased survival rate (85 %) compared with the MAZ-exposed fish. Moreover, dietary IFRE improved hepato-renal function indices by preserving the histological architecture of the hepatic, renal, and splenic tissues. The insights of this study advocate the use of an IFRE-dietary addition to protect Nile tilapia from MAZ toxicity, which provides perspectives for future implementations in enhancing fish health for sustainable aquaculture.

Teleosts as behaviour test models for social stress

Stress is an important aspect of our everyday life and exposure to it is an unavoidable occurrence. In humans, this can come in the form of social stress or physical stress from an injury. Studies in animal models have helped researchers to understand the body's adaptive response to stress in human. Notably, the use of behavioural tests in animal models plays a pivotal role in understanding the neural, endocrine and behavioural changes induced by social stress. Under socially stressed conditions, behavioural parameters are often measured physiological and molecular parameters as changes in behaviour are direct responses to stress and are easily assessed by behavioural tests. Throughout the past few decades, the rodent model has been used as a well-established animal model for stress and behavioural changes. Recently, more attention has been drawn towards using fish as an animal model. Common fish models such as zebrafish, medaka, and African cichlids have the advantage of a higher rate of reproduction, easier handling techniques, sociability and most importantly, share evolutionary conserved genetic make-up, neural circuitry, neuropeptide molecular structure and function with mammalian species. In fact, some fish species exhibit a clear diurnal or seasonal rhythmicity in their stress response, similar to humans, as opposed to rodents. Various social stress models have been established in fish including but not limited to chronic social defeat stress, social stress avoidance, and social stress-related decision-making. The huge variety of behavioural patterns in teleost also aids in the study of more behavioural phenotypes than the mammalian species. In this review, we focus on the use of fish models as alternative models to study the effects of stress on different types of behaviours. Finally, fish behavioural tests against the typical mammalian model-based behavioural test are compared and discussed for their viability.

Acute mancozeb-fungicide exposure induces neuro-ethology disruption, health disorders, and immune-oxidative dysfunction in Nile tilapia (Oreochromis niloticus)

An acute exposure study of mancozeb (MAZ) fungicide was applied on Oreochromis niloticus for 96-h duration. Three hundred fish (20.50 ± 1.60 g) were assigned into six groups (50 fish/ group; 10 fish/replicate) and exposed to different six concentrations (0, 4, 8, 12, 16, and 20 mg L^-1) of MAZ for 96-h. The Probit analysis program was used to compute the 96-h lethal concentration 50 (96-h LC₅₀) of MAZ. During the exposure duration, the fish's behavior, clinical symptoms, and mortalities were recorded daily. After the exposure period was ended, the hematological, biochemical, immunological, and oxidant/antioxidant parameters were evaluated. The results of this study recorded the 96-h LC₅₀ of MAZ for O. niloticus to be 11.49 mg L^-1. Acute MAZ exposure badly affected the fish's behavior in the form of increased the breath gasping and swimming activity with aggressive mode. The exposed fish showed excessive body hemorrhages and fin rot. The survival rate of the exposed fish to MAZ was 100, 80, 66, 50, 38, and 30% in 0, 4, 8, 12, 16, and 20 mg L^-1 MAZ, respectively. The hematological indices (red blood cell count, hemoglobin, packed cell volume%, and white blood cell count) were significantly decreased by increasing the MAZ exposure concentration (8-20 mg L^-1). The acetylcholine esterase activity and immune indices (lysozyme, nitric oxide, immunoglobulin M, complement 3) were decreased by MAZ exposure (4-20 mg L^-1). Acute MAZ exposure induced hepato-renal dysfunction and elevated stress-related parameter (cortisol) by increasing the MAZ concentration. A significant reduction in the antioxidant parameters (total antioxidant activity, catalase, and superoxide dismutase) with increasing the lipid peroxidation marker (malondialdehyde) was noticed by acute MAZ exposure (4 -20 mg L^-1) in O. niloticus. Based on these outcomes, the MAZ exposure induced toxicity to the fish evident in changes in fish behavior, neurological activity, hepato-renal functioning, and immune-antioxidant responses which suggest physiological disruption.

Interactive effects of venlafaxine and thermal stress on zebrafish (Danio rerio) inflammatory and heat shock responses

Venlafaxine (VFX), a commonly prescribed antidepressant often detected in wastewater effluent, and acute temperature elevations from climate change and increased urbanization, are two environmental stressors currently placing freshwater ecosystems at risk. This study focused on understanding if exposure to VFX impacts the agitation temperature (T_ag) and critical thermal maximum (CT_max) of zebrafish (Danio rerio). Additionally, we examined the interactive effects of VFX and acute thermal stress on zebrafish heat shock and inflammatory immune responses. A 96 h 1.0 μg/L VFX exposure experiment was conducted, followed by assessment of thermal tolerance via CT_max challenge. Heat shock proteins and pro-inflammatory immune cytokines were quantified through gene expression analysis by quantitative PCR (qPCR) on hsp 70, hsp 90, hsp 47, il-8, tnfα, and il-1β within gill and liver tissue. No significant changes in agitation temperature between control and exposed fish were observed, nor were there any differences in CT_max based on treatment. Unsurprisingly, hsp 47, 70, and 90 were all upregulated in groups exposed solely to CT_max, while only hsp 47 within gill tissue showed signs of interactive effects, which was significantly decreased in fish exposed to both VFX and CT_max. No induction of an inflammatory response occurred. This study demonstrated that environmentally relevant concentrations of VFX have no impact on thermal tolerance performance in zebrafish. However, VFX can cause diminished function of protective heat shock mechanisms, which could be detrimental to freshwater fish populations and aquatic ecosystems as temperature spikes become more frequent from climate change and urbanization near watersheds.

L-carnitine attenuates acoustic startle reflex dysfunction in adult male rats exposed to mancozeb

The fungicide mancozeb increases oxygen-free radicals in the central nervous system. As an antioxidant, L-carnitine protects DNA and cell membranes from damage caused by oxygen-free radicals. The present study investigated how L-carnitine affected the acoustic startle response (ASR) in rats exposed to mancozeb. In this experimental study, male Wistar rats were gavaged orally with mancozeb (500, 1000, and 2000 mg/kg), L-carnitine (100, 200, and 400 mg/kg), or L-carnitine (200 mg/kg) + mancozeb (500 mg/kg) three times in 1 week. In the sham group, saline (0.9%, 10 mL/kg) was gavaged at a volume equivalent to that of the drugs. The control group did not receive any treatment. The results showed that locomotor activity and the percentage of prepulse inhibition in the mancozeb groups decreased compared to the sham group while these parameters increased in the L-carnitine group (200 mg/kg) compared to sham rats. In conclusion, mancozeb may increase the risk factor for cognitive diseases such as schizophrenia in people exposed to it while pretreatment with L-carnitine can attenuate the toxic effect.

Modulation of CREB and its associated upstream signaling pathways in pesticide-induced neurotoxicity

Human beings are exposed to various environmental xenobiotics throughout their life consisting of a broad range of physical and chemical agents that impart bodily harm. Among these, pesticide exposure that destroys insects mainly by damaging their central nervous system also exerts neurotoxic effects on humans and is implicated in the etiology of several degenerative disorders. The connectivity between CREB (cAMP Response Element Binding Protein) signaling activation and neuronal activity is of broad interest and has been thoroughly studied in various diseased states. Several genes, as well as protein kinases, are involved in the phosphorylation of CREB, including BDNF (Brain-derived neurotrophic factor), Pi3K (phosphoinositide 3-kinase), AKT (Protein kinase B), RAS (Rat Sarcoma), MEK (Mitogen-activated protein kinase), PLC (Phospholipase C), and PKC (Protein kinase C) that play an essential role in neuronal plasticity, long-term potentiation, neuronal survival, learning, and memory formation, cognitive function, synaptic transmission, and suppressing apoptosis. These elements, either singularly or in a cascade, can result in the modulation of CREB, making it a vulnerable target for various neurotoxic agents, including pesticides. This review provides insight into how these various intracellular signaling pathways converge to bring about CREB activation and how the activated or deactivated CREB levels can affect the gene expression of the upstream molecules. We also discuss the various target genes within the cascade vulnerable to different types of pesticides. Thus, this review will facilitate future investigations associated with pesticide neurotoxicity and identify valuable therapeutic targets.

OctylPhenol (OP) Alone and in Combination with NonylPhenol (NP) Alters the Structure and the Function of Thyroid Gland of the Lizard Podarcis siculus

Different environmental contaminants disturb the thyroid system at many levels. AlkylPhenols (APs), by-products of microbial degradation of AlkylPhenol Polyethoxylates (APEOs), constitute an important class of Endocrine Disrupting Chemicals (EDCs), the two most often used environmental APs being 4-nonylphenol (4-NP) and 4-tert-octylphenol (4-t-OP). The purpose of the present study was to investigate the effects on the thyroid gland of the bioindicator Podarcis siculus of OP alone and in combination with NP. We used radioimmunoassay to determine their effects on plasma 3,3',5-triiodo-L-thyronine (T₃), 3,3',5,5'-L-thyroxine (T₄), thyroid-stimulating hormone (TSH), and thyrotropin-releasing hormone (TRH) levels in adult male lizards. We also investigated the impacts of AP treatments on hepatic 5'ORD (type II) deiodinase and hepatic content of T₃ and T₄. After OP and OP + NP administration, TRH levels increased, whereas TSH, T₃, and T₄ levels decreased. Lizards treated with OP and OP + NP had a higher concentration of T₃ in the liver and 5'ORD (type II) activity, whereas T₄ concentrations were lower than that observed in the control group. Moreover, histological examination showed that the volume of the thyroid follicles became smaller in treated lizards suggesting that that thyroid follicular epithelial cells were not functionally active following treatment. This data collectively suggest a severe interference with hypothalamus-pituitary-thyroid axis and a systemic imbalance of thyroid hormones.

Daidzein Pro-cognitive Effects Coincided with Changes of Brain Neurotensin1 Receptor and Interleukin-10 Expression Levels in Obese Hamsters

At present, concerns are pointing to "tasteful" high-fat diets as a cause of conditioning physical-social states that through alterations of some key emotional- and nutritional-related limbic circuits such as hypothalamic and amygdalar areas lead to obesity states. Feeding and energetic homeostatic molecular mechanisms are part of a complex neuronal circuit accounting for this metabolic disorder. In an attempt to exclude conventional drugs for treating obesity, daidzein, a natural glycosidic isoflavone, which mimics estrogenic neuroprotective properties against increased body weight, is beginning to be preferred. In this study, evident anxiolytic-like behaviors were detected following treatment of high-fat diet hamsters with daidzein as shown by extremely evident (p < 0.001) exploration tendencies in novel object recognition test and a notably greater amount of time spent (p < 0.01) in open arms of elevated plus maze. Moreover, the isoflavone promoted a protective role against neurodegeneration processes as shown by few, if any, amino cupric silver granules in amygdalar, hypothalamic and hippocampal neuronal fields when compared with obese hamsters. Interestingly, elevated expression levels of the anorexic neuropeptide receptor neurotensin1 in the above limbic areas of obese hamsters were extremely reduced by daidzein, especially during recovery of cognitive events. Contextually, such effects were strongly paralleled by increased levels of the anti-neuroinflammatory cytokine, interleukin-10. Our results corroborate a neuroprotective ability of this natural glycosidic isoflavone, which through its interaction with the receptor neurotensin1 and interleukin-10 pathways is correlated not only to improved feeding states, and subsequently obesity conditions, but above all to cognitive performances.

Environmental level of the antidepressant venlafaxine induces behavioral disorders through cortisol in zebrafish larvae (Danio rerio)

Psychoactive drugs discharged into the environment have different effects on the behavior of vertebrates. The objective of this study was to evaluate the effect of venlafaxine on the behavior of zebrafish, and whether melatonin could reverse the induction of venlafaxine. In this study, a series of venlafaxine concentrations (1 μg/L, 10 μg/L, 100 μg/L) was used to treat zebrafish embryos from 2 hours post-fertilization (hpf) to 5dpf. We found that venlafaxine (1 μg/L) can stimulate the growth of the head area, eye area, and body length of zebrafish. The light-dark test showed that venlafaxine (1 μg/L) could increase the activity of zebrafish larvae. What's more, venlafaxine (1 μg/L) upregulated the expression of steroid regulatory factors including steroidogenic acute regulatory protein (star), cytochrome P450 family member 11A1 (cyp11a1) and 11 β hydroxylase (cyp11b1) by cAMP-pCREB pathway, affecting the function of the steroidogenic cells, which might be involved in the increased cortisol levels in zebrafish larvae. Whereas, melatonin (230 μg/L) restored the altered locomotion behavior induced by venlafaxine and recovered the altered gene expression. Our results demonstrate that venlafaxine at levels detected in the aquatic environment impacts behavior and may compromise the adaptive responses to the environment in zebrafish larvae.

Adrenal gland response to endocrine disrupting chemicals in fishes, amphibians and reptiles: A comparative overview

The adrenal gland is an essential component of the body stress response; it is formed by two portions: a steroidogenic and a chromaffin tissue. Despite the anatomy of adrenal gland is different among classes of vertebrates, the hormones produced are almost the same. During stress, these hormones contribute to body homeostasis and maintenance of ion balance. The adrenal gland is very sensitive to toxic compounds, many of which behave like endocrine-disruptor chemicals (EDCs). They contribute to alter the endocrine system in wildlife and humans and are considered as possible responsible of the decline of several vertebrate ectotherms. Considering that EDCs regularly can be found in all environmental matrices, the aim of this review is to collect information about the impact of these chemical compounds on the adrenal gland of fishes, amphibians and reptiles. In particular, this review shows the different behavior of these "sentinel species" when they are exposed to stress condition. The data supplied in this review can help to further elucidate the role of EDCs and their harmful impact on the survival of these vertebrates.

Toxic effects of a mancozeb-containing commercial formulation at environmental relevant concentrations on zebrafish embryonic development

The toxicological knowledge of mancozeb (MZ)-containing commercial formulations on non-target species is scarce and limited. Therefore, the objective of this work was to represent a realistic application scenario by evaluating the toxicity of environmental relevant and higher concentrations of a commercial formulation of MZ using zebrafish embryos. Following determination of the 96-h LC₅₀ value, the embryos at the blastula stage (~ 2 h post-fertilisation, hpf) were exposed to 0.5, 5, and 50 μg L^-1 of the active ingredient (~ 40× lower than the 96-h LC₅₀). During the exposure period (96 h), lethal, sublethal, and teratogenic parameters, as well as behaviour analysis, at 120 hpf, were assayed. Biochemical parameters such as oxidative stress-linked enzymes (superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR)), reactive oxygen species (ROS) levels, and glutathione levels (GSH and GSSG), as well as the activity of degradation (glutathione S-transferase (GST) and carboxylesterase (CarE)), neurotransmission (acetylcholinesterase (AChE)), and anaerobic respiration (lactate dehydrogenase (LDH))-related enzymes, were analysed at the end of the exposure period. Exposed embryos showed a marked decrease in the hatching rate and many malformations (cardiac and yolk sac oedema and spinal torsions), with a higher prevalence at the highest concentration. A dose-dependent decreased locomotor activity and a response to an aversive stimulus, as well as a light-dark transition decline, were observed at environmental relevant concentrations. Furthermore, the activities of SOD and GR increased while the activity of GST, AChE, and MDA contents decreased. Taken together, the involvement of mancozeb metabolites and the generation of ROS are suggested as responsible for the developmental phenotypes. While further studies are needed to fully support the hypothesis presented, the potential cumulative effects of mancozeb-containing formulations and its metabolites could represent an environmental risk which should not be disregarded.

Developmental exposure to mancozeb induced neurochemical and morphological alterations in adult male mouse hypothalamus

Mancozeb, a dithiocarbamate widely used in agriculture, is considered a developmental hazard in humans; however, more evidences are still needed concerning the consequences of chronic exposure to this pesticide. Mancozeb neurotoxicity in developing mouse hypothalamus was evaluated by subchronic exposure of male Mus musculus mice to low and high doses of mancozeb (30 and 90 mg/kg body weight, respectively) from late neonatal until adolescence. Variations in hypothalamic amino acid neurotransmitter levels and changes in histological as well as cytological characteristics were analyzed in young adult experimental mice and compared with control. A dose-dependent increase in excitation/ inhibition ratio was observed in mancozeb-exposed hypothalamus, indicating an overall state of excitoxicity. Histopathological and ultrastructural studies showed increased apoptosis, neuroinflammation and demyelination, demonstrating mancozeb-induced cytotoxicity in hypothalamic neurosecretory cells. In summary, both neurochemical and morphological data revealed mancozeb-induced alterations during development of hypothalamic circuitry that are critical for maturation of the neuroendocrine system.

Mancozeb exposure results in manganese accumulation and Nrf2-related antioxidant responses in the brain of common carp Cyprinus carpio

Manganese (Mn)-containing dithiocarbamates such as Mancozeb (MZ) have been shown to induce oxidative stress-related toxicity in rodents and humans. However, little is known about the neurotoxic effects induced by MZ in fish. In this study, carp (Cyprinus carpio) were exposed to non-lethal waterborne concentrations of MZ, and oxidative stress parameters as well as metal accumulation in fish brains were evaluated. The experimental groups were as follows: control, MZ 5 mg/L, and MZ 10 mg/L. Fish were exposed for 7 days, and then brain was removed and prepared for subsequent analysis of antioxidant enzymes, reactive oxygen species (ROS), and expression of Nrf2 and phosphoNrf2. In parallel, manganese (Mn) levels were evaluated in blood and brain tissues. Mn levels were significantly increased in blood and brain of MZ-exposed carps. In addition, a concentration-dependent increase (p < 0.05) in ROS levels was observed in parallel to increments (p < 0.05) in the activity of major antioxidant enzymes, such as GPx, GR, and GST. On the other hand, significant decreases (p < 0.05) in CAT and SOD activities were observed. The expression of total and phosphorylated forms of Nrf2 was significantly (p < 0.05) upregulated in the brain of carps exposed to Mz when compared to the control, indicating an activation of the Nrf2 antioxidant pathway. Our study showed for the first time the activation of the Nrf2/ARE pathway and bioaccumulation of Mn induced by MZ exposure in fish species, highlighting important mechanisms of action and its toxicological impacts to aquatic organisms.

Orexin receptor expression is increased during mancozeb-induced feeding impairments and neurodegenerative events in a marine fish

Food intake ensures energy resources sufficient for basic metabolism, immune system and reproductive investment. It is already known that food-seeking performances, which are crucially controlled by orexins (ORXs), may be under the influence of environmental factors including pollutants. Among these, mancozeb (mz) is becoming an environmental risk for neurodegenerative diseases. Due to few studies on marine fish exposed to mz, it was our intention to correlate feeding latency, food intake and feeding duration to potential neurodegenerative processes in key diencephalic sites and expression changes of the ORX neuroreceptor (ORXR) in the ornate wrasses (Thalassoma pavo). Hence, fish exposed for 4 days (d) to mz 0.2 mg/l (deriving from a 0.07, 0.14, 0.2, 0.3 mg/l screening test) displayed a significant reduction (p < 0.05) of food intake compared to controls as early as 1d that became more evident (p < 0.01) after 3d. Moreover, significant enhancements of feeding latency were reported after 1d up to 3d (p < 0.001) and even feeding duration was enhanced up to 3d (p < 0.001), which instead moderately increased after 4d (p < 0.05). A reduction (-120%; p < 0.001) of mean body weight was also detected at the end of exposure. Likewise, a notable (p < 0.001) activation of ORXR protein occurred together with mRNA up-regulations in diencephalic areas such as the diffuse nucleus of the inferior lobe (+48%) that also exhibited evident degenerative neuronal fields. Overall, these results highlight an ORX role as a vital component of the neuroprotective program under environmental conditions that interfere with feeding behaviors.

Interference of dibutylphthalate on human prostate cell viability

Dibutylphthalate (DBP) is an environmental pollutant widely used as plasticizer in a variety of industrial applications worldwide. This agent can be found in personal-care products, children's toy, pharmaceuticals, food products. Exposure to DBP can occur via ingestion and inhalation as well as intravenous or skin contact. DBP belongs to the family of endocrine disrupting chemicals (EDCs) and its effects on reproductive system were demonstrated both in vivo and in vitro. In the present study we evaluated the effects of DBP on human prostate adenocarcinoma epithelial cells (LNCaP) in order to highlight xenoestrogens influence on human prostate. Moreover, we have compared DBP effects with 17β-estradiol action in order to investigate possible mimetical behaviour. We have assessed the effects of both compounds on the cell viability. After then, we have evaluated the expression of genes and proteins involved in cell cycle regulation. Furthermore, we have observed the expression and the cell localization of estrogen (ERs) and androgen (AR) receptors. In conclusion, we have demonstrated that DBP interacts with estrogen hormonal receptor pathway but differently from E2. DBP alters the normal gland physiology and it is involved in the deregulation of prostate cell cycle.