Neurodevelopmental and behavioral effects of nonylphenol exposure during gestational and breastfeeding period on F1 rats

Developmental exposure to nonylphenol leads to depletion of the neural precursor cell pool in the hippocampal dentate gyrus

Developmental exposure to nonylphenol (NP) results in irreversible impairments of the central nervous system (CNS). The neural precursor cell (NPC) pool located in the subgranular zone (SGZ), a substructure of the hippocampal dentate gyrus, is critical for the development of hippocampal circuits and some hippocampal functions such as learning and memory. However, the effects of developmental exposure to NP on this pool remain unclear. Thus, our aim was to clarify the impacts of developmental exposure to NP on this pool and to explore the potential mechanisms. Animal models of developmental exposure to NP were created by treating Wistar rats with NP during pregnancy and lactation. Our data showed that developmental exposure to NP decreased Sox2-and Ki67-positive cells in the SGZ of offspring. Inhibited activation of Shh signaling and decreased levels of its downstream mediators, E2F1 and cyclins, were also observed in pups developmentally exposed to NP. Moreover, we established the in vitro model in the NE-4C cells, a neural precursor cell line, to further investigate the effect of NP exposure on NPCs and the underlying mechanisms. Purmorphamine, a small purine-derived hedgehog agonist, was used to specifically modulate the Shh signaling. Consistent with the in vivo results, exposure to NP reduced cell proliferation by inhibiting the Shh signaling in NE-4C cells, and purmorphamine alleviated this reduction in cell proliferation by restoring this signaling. Altogether, our findings support the idea that developmental exposure to NP leads to inhibition of the NPC proliferation and the NPC pool depletion in the SGZ located in the dentate gyrus. Furthermore, we also provided the evidence that suppressed activation of Shh signaling may contribute to the effects of developmental exposure to NP on the NPC pool.

Association between prenatal exposure to alkylphenols and intelligence quotient among preschool children: sex-specific effects

BACKGROUND

While prenatal exposure to alkylphenols (APs) has been demonstrated to be associated with neurodevelopmental impairments in animals, the evidence from epidemiological studies remains limited and inconclusive. This study aimed to explore the link between AP exposure during pregnancy and the intelligence quotient (IQ) of preschool children.

METHODS

A total of 221 mother-child pairs from the Guangxi Zhuang Birth Cohort were recruited. Nonylphenol (NP), 4-tert-octylphenol (4-T-OP), 4-n-nonylphenol (4-N-NP), and 4-n-octylphenol were measured in maternal serum in early pregnancy. Childhood IQ was evaluated by the Fourth Edition of Wechsler Preschool and Primary Scale of the Intelligence at 3 to 6 years of age. The impact of APs on childhood IQ were evaluated by generalized linear models (GLMs), restricted cubic spline (RCS), and Bayesian kernel machine regression (BKMR).

RESULTS

In GLMs, prenatal exposure to NP and the second tertile of 4-T-OP exhibited an inverse association with full-scale IQ (FSIQ) (β = -2.38; 95% CI: -4.59, -0.16) and working memory index (WMI) (β = -5.24; 95% CI: -9.58, -0.89), respectively. Prenatal exposure to the third tertile of 4-N-NP showed a positive association with the fluid reasoning index (β = 4.95; 95% CI: 1.14, 8.77) in total children, as well as in girls when stratified by sex. A U-shaped relationship between maternal 4-T-OP and WMI was noted in total children and girls by RCS (all P nonlinear < 0.05). The combined effect primarily driven by NP, of maternal AP mixtures at concentrations above the 50th percentile exhibited an inverse trend on FSIQ in total children and girls in BKMR.

CONCLUSIONS

Prenatal exposure to various APs affects IQ in preschool children, and there may be nonmonotonic and sex-specific effects. Further investigation across the population is required to elucidate the potential neurotoxic effects of APs.

Exposure to nonylphenol in early life causes behavioural deficits related with autism spectrum disorders in rats

Early-life exposure to environmental endocrine disruptors (EDCs) is a potential risk factor for autism spectrum disorder (ASD). Exposure to nonylphenol (NP), a typical EDC, is known to cause some long-term behavioural abnormalities. Moreover, these abnormal behaviours are the most frequent psychiatric co-morbidities in ASD. However, the direct evidence for the link between NP exposure in early life and ASD-like behavioural phenotypes is still missing. In the present study, typical ASD-like behaviours induced by valproic acid treatment were considered as a positive behavioural control. We investigated impacts on social behaviours following early-life exposure to NP, and explored effects of this exposure on neuronal dendritic spines, mitochondria function, oxidative stress, and endoplasmic reticulum (ER) stress. Furthermore, primary cultured rat neurons were employed as in vitro model to evaluate changes in dendritic spine caused by exposure to NP, and oxidative stress and ER stress were specifically modulated to further explore their roles in these changes. Our results indicated rats exposed to NP in early life showed mild ASD-like behaviours. Moreover, we also found the activation of ER stress triggered by oxidative stress may contribute to dendritic spine decrease and synaptic dysfunction, which may underlie neurobehavioural abnormalities induced by early-life exposure to NP.

The mechanisms of learning and memory impairment caused by nonylphenol: a narrative review based on in vivo and in vitro studies

Learning and memory play a fundamental role on brain cognitive functions which are crucial for human life. Nonylphenol (NP), a serious environmental pollutant over the world, is proven to be harmful for learning and memory mainly via diet exposure. Currently, besides the administrative restrictions for the use of NP, there are rarely other effective approaches against learning and memory impairment caused by NP. This review summarized the mechanisms underlying NP-induced learning and memory impairment according to in vivo and in vitro experiments. Based on the studies involved in behavior tests, these mechanisms were classified as oxidative stress, neurotransmitter disorder, synaptic plasticity impairment, and neuron injury. In addition, according to the studies which did not conduct behavior tests, the possible mechanisms underlying NP-induced learning and memory impairment were proposed as chronic inflammation and gut permeability increment. Furthermore, this review also revealed the demanding questions for the mechanism investigations and therapeutic methods. Notably, the summarized mechanisms might accelerate the prevention and remediation of NP-induced learning and memory impairment.

Hazards of Chronic Exposure to Nonylphenol: Concomitant Effect on Non-alcoholic Fatty Liver Disease in Male Albino Rats

BACKGROUND: Chronic exposure to environmental endocrine disruptors like nonylphenol (NP), has been shown in previous studies to predispose to non-alcoholic fatty liver disease. METHODS: In this work, forty adult male albino rats were divided into four groups, a high sucrose-high-fat diet (HSHFD) group, a group receiving 20 μg/kg/day of NP, an NP + HSHFD group, and a control group. The rats were sacrificed on day 60 after anesthetization. RESULTS: Biochemical tests indicated that serum transaminases (alanine aminotransferase, aspartate aminotransferase) were significantly increased in the NP + HSHFD group. Lipid metabolism was most disrupted in the NP + HSHFD with a highly significant increase (p < 0.001) of serum cholesterol, triglyceride, and low-density lipoprotein cholesterol compared to other groups. Heme oxygenase 1 showed the highest expression in the NP + HSHFD group, with a highly significant difference in comparison with the other groups (p < 0.001). Histopathological studies revealed fatty changes and dilatation in the central vein in the HSHFD group. Lymphoid cell aggregates were detected in the NP group. Massive inflammation and degeneration were revealed in the NP + HSHFD group. There was also marked expression of the apoptotic protein caspase-3 in the NP + HSHFD group. CONCLUSION: In conclusion, exposure to a 20 μg/kg/day of NP induced oxidative stress leading to non-alcoholic steatohepatitis.

Endocrine disruptors also function as nervous disruptors and can be renamed endocrine and nervous disruptors (ENDs)

Endocrine disruption (ED) and endocrine disruptors (EDs) emerged as scientific concepts in 1995, after numerous chemical pollutants were found to be responsible for reproductive dysfunction. The World Health Organization established in the United Nations Environment Programme a list of materials, plasticizers, pesticides, and various pollutants synthesized from petrochemistry that impact not only reproduction, but also hormonal functions, directly or indirectly. Cells communicate via either chemical or electrical signals transmitted within the endocrine or nervous systems. To investigate whether hormone disruptors may also interfere directly or indirectly with the development or functioning of the nervous system through either a neuroendocrine or a more general mechanism, we examined the scientific literature to ascertain the effects of EDs on the nervous system, specifically in the categories of neurotoxicity, cognition, and behaviour. To date, we demonstrated that all of the 177 EDs identified internationally by WHO are known to have an impact on the nervous system. Furthermore, the precise mechanisms underlying this neurodisruption have also been established. It was previously believed that EDs primarily function via the thyroid. However, this study presents substantial evidence that approximately 80 % of EDs operate via other mechanisms. It thus outlines a novel concept: EDs are also neurodisruptors (NDs) and can be collectively termed endocrine and nervous disruptors (ENDs). Most of ENDs are derived from petroleum residues, and their various mechanisms of action are similar to those of "spam" in electronic communications technologies. Therefore, ENDs can be considered as an instance of spam in a biological context.

The protective role of curcumin against toxic effect of nonylphenol on bone development

INTRODUCTION

In the study, it was aimed to investigate the possible protective effects of curcumin, a potent antioxidant, against the toxic effect of nonylphenol on bone development.

METHODS

Thirty pregnant female Wistar albino rats were used. The rats were randomly divided into the following five groups; the control group, corn oil group (150 µl/kg/day), nonylphenol group (50 µl/kg/day), curcumin group (100 mg/kg/day) and curcumin + nonylphenol group (100 mg/kg/day + 50 µl/kg/day). The doses were given by gavage from the 5th day to the 20th day of gestation. The fetuses were removed out on the 20th day of pregnancy by cesarean at the end of the study. After the sacrifice of the animals, double skeletal staining in front extremity (clavicula, scapula, humerus, radius, ulna) and hind extremity (femur, tibia, fibula), additionally histological and immunohistochemical examinations in femur bone were performed.

RESULTS

The nonylphenol group offspring have the lowest weights of fetuses and placenta, head-to-hip lengths, biparietal and occipitofrontal length, and also, bone length percentage and percentage of the ossification area in all measurements of the front extremity and hind extremity Interestingly, the groups treated with curcumin showed close to the control group in terms of double skeletal staining, histological, and immunohistochemical examinations.

CONCLUSIONS

Our findings demonstrated an association between bone development and exposure to nonylphenol. The findings suggest that curcumin treatments may be effective in accelerating bone formation.

Behavioral disorders caused by nonylphenol and strategies for protection

Nonylphenol (NP) is widely used in daily production and life due to its good emulsification. In this review, we discuss toxicology studies that examined behavioral disorders caused by NP, the corresponding toxicological mechanisms in the central nervous system (CNS), and strategies for protection. Available in vitro and in vivo evidence suggests that exposure to NP during adulthood or early childhood is associated with cognitive dysfunction, including depression-like behaviors, anxiety-like behaviors, and impaired learning and memory. The main mechanisms underlying NP-related cognitive disorders include inflammation, destruction of synaptic plasticity, and destruction of important signaling pathways that affect the synthesis and secretion of neurotransmitters. The effects and mechanisms of NP exposure on CNS-mediated reproductive function, including interference with the expression of hormones, proteins, and enzymes, are discussed. Other abnormal behaviors such as locomotor activity and swimming behavior are also described. Several measures to prevent NP neurotoxicity are summarized. These measures are based on the toxicological mechanisms underlying NP exposure and include external protection and internal self-regulation of the nervous system. Finally, a new treatment idea is proposed based on the gut-brain axis. Characterizing the behavioral changes and underlying toxicity mechanisms associated with NP exposure and investigating the possible methods of treatment will help to expand the understanding of these mechanisms and could lead to more effective treatments.

Nonylphenol induced individual and population fluctuation of Caenorhabditis elegans: Disturbances on developmental and reproductive system

The environmental risks that have arisen from endocrine disruption compounds (EDCs) have become global challenges, especially for persistent bio-accumulated xenobiotic chemicals, such as nonylphenol (NP). In the present study, the population dynamics of Caenorhabditis elegans (C. elegans) were systemically investigated by conducting developmental and reproductive bioassays under the exposure of NP, which has been widely detected in actual aquatic environments. The results revealed that under NP exposure (400 μg L^-1 NP), developmental indictors of C. elegans, including the body length and width were significantly inhibited at different life stages of L1 and L4 larva, and the growth curves were further adversely affected. In addition, abnormalities in reproductive systems were also observed under NP exposure. Such abnormalities obeyed a dose-dependent relationship with NP levels, which were closely related to the delayed spawning time and decreased reproductive rates. Moreover, the results from global genome expression analysis for nematodes revealed that the most significant enriched GO terms could be predominantly responsible for the dysregulation of growth and reproductive system. The population's parameters, including age composition and intrinsic growth rate (r_m d^-1), displayed significant changes, with a suppressed potentiality of population growth. Those data elucidated that NP exhibited a profound impact on the dynamic stability of the population, even with no obvious effect on certain biochemical markers.

Exposure to nonylphenol in early life increases pro-inflammatory cytokines in the prefrontal cortex: Involvement of gut-brain communication

A growing body of evidence indicates that exposure to nonylphenol (NP), a typical persistent organic pollutant (POP), in early life results in the impairment of the central nervous system (CNS), but the underlying mechanism still remains to be elucidated. High levels of pro-inflammatory cytokines in the brain have been implicated in the CNS damages. The animal model of exposure to NP in early life was established by maternal gavage during the pregnancy and lactation in the present study. We found that exposure to NP in early life increased the levels of pro-inflammatory cytokines in the rat prefrontal cortex. Interestingly, the levels of pro-inflammatory cytokines in the intestine as well as in the serum were also increased by NP exposure. Furthermore, the increased permeability of intestinal barrier and blood-brain barrier (BBB), two critical barriers in the gut to brain communication, was observed in the rats exposed to NP in early lives. The decreased expression of zonula occludens-1 (ZO-1) and claudin-1 (CLDN-1), tight junction proteins (TJs) that responsible for maintaining the permeability of intestinal barrier and BBB, was found, which may underlie these increases in permeability. Taken together, these results suggested that the disturbed gut-brain communication may contribute to the increased levels of pro-inflammatory cytokines in the prefrontal cortex caused by NP exposure in early life.

Depressive behavior induced by nonylphenol and its effect on the expression of ER-α and ER-β in nerve cells of rats

OBJECTIVE

To investigate the effects of nonylphenol (NP) exposure on the depressive behavior in rats, and the effects of the expressions of estrogen receptor-α (ER-α) and estrogen receptor-β (ER-β) in nerve cells in vivo and vitro.

METHODS

Forty male SD rats were randomly divided into 4 groups: blank control group (0 mg/kg), low dose group (0.4 mg/kg), middle dose group (4 mg/kg) and high dose group (40 mg/kg), which were exposed to NP for 180 days. The exposure dose of NP in HT22 was 20μM, which was divided into4 groups: blank control group, NP group, ICI182780 group and ICI182780+NP group.

RESULTS

In vivo, in the open field experiment, the number of entries in the central area and duration of attention in central square decreased gradually in the NP high dose group compared with the control (F = 3.561, p = .029). In forced swimming experiment, with the increase of NP dose, the immobility time increased, and the increasing degree of middle dose group and high dose group was higher than that of the low dose group (F = 3.047, p = .048). The concentrations of serum dopamine (DA) in the middle dose and high dose groups decreased greatly compared with the control (F = 3.967, p = .023). NP exposure at the doses of 4 mg/kg and 40 mg/kg induced an increase in the level of serum corticosterone compared to the control (F = 11.536, p<.001). Compared with the control group, the expression of ER-β decreased gradually with an increase of NP dose in the NP treatment groups (F = 4.513, p = .014). In vitro, the activity of HT22 cells decreased with an increase of NP dose (F = 316.6, p<.001). When the dose of NP was 200 μM, the growth inhibition rate of HT22 cells was (0.54±0.11)%. The expression levels of ER-α and ER-β in ICI182780+NP group was lower than those in the control and ICI182780 groups, but higher than those in the NP group (F = 1.592, p=.266; F = 10.166, p=.004).

CONCLUSION

Long-term exposure to NP could induce the alterations in depressive behavior, and the levels of neurotransmitters as well as the expression of ER in the hippocampus of rats. Moreover, NP could reduce the activity of HT22 cells and decrease the expression levels of ER-α and ER-β in vitro.

Influence of nonylphenol exposure on basic growth, development, and thyroid tissue structure in F1 male rats

Objective

Environmental endocrine disruptors (EEDs) with a weak ability to mimic estrogen have been associated with thyroid dysfunction. However, little is known about the effect of nonylphenol (NP), a well-known EED, on thyroid structure. The present study evaluates whether gestational and lactational exposure to NP impacts growth and thyroid structure in F1 male rats.

Methods

A total of 60 rats were gavaged with NP (25, 50, and 100 mg/kg), estradiol (E₂, 30 μg/kg/day), and corn oil alone (vehicle control) from gestational day 6 to postnatal day (PND) 21. Serum thyroid hormones free triiodothyronine (FT3), free thyroxine (FT4) and thyroid stimulating hormone levels were detected by automated chemiluminescence immunoassay analyzer. The NP level in the thyroid was measured using high-performance liquid chromatography. The ultrastructure of follicular epithelial cells was examined using transmission electron microscopy. Histopathology was conducted using hematoxylin and eosin staining.

Results

On PND 0, exposure to 50 and 100 mg/kg/day NP led to a significant decrease in the average litter size, litter weight and number of live pups per litter compared to the control group (P < 0.05). Dams exposed to NP during perinatal period demonstrated decreased serum levels of FT3 and FT4 in F1 male rats, when compared to the control group (P < 0.05). The NP level in the control group was 3.39 ± 0.08 ng/mg, while NP levels in the low, middle, and high dose groups ranged from 5.20 to 11.00 ng/mg. Exposure caused a dose-related increase in NP level in the thyroid of male pups (P < 0.01). The thicknesses of the thyroid follicular epithelium were 2.06 ± 0.37 μm in the control group and 3.97 ± 1.61 μm in the high-dose group. The thickness of the thyroid follicular epithelium increased with an increase in treatment dose in a dose-dependent manner (P < 0.05). The sizes of the thyroid follicles were 1,405.53 ± 866.62 μm² in the control group and 317.49 ± 231.15 μm² in the high-dose group. With increasing NP dosages, animals showed a decreased size of the thyroid follicle (P < 0.01). Thyroid follicular cells of NP-treated rats showed mildly swollen mitochondria and dilated rough endoplasmic reticulum in the cytoplasm.

Conclusion

Nonylphenol can cross the placental barrier and accumulate in the thyroid of F1 male rats. Gestational and lactational exposure to NP in dams impacted both development and growth of pups and damaged the ultrastructure of their thyroid tissue, which may further negatively influence normal thyroid function.

Perinatal exposure to nonylphenol impairs dendritic outgrowth of cerebellar Purkinje cells in progeny

Nonylphenol (NP) is a commercially produced nonionic surfactant that has become a global environmental pollutant due to poor biodegradability. Many studies have confirmed that NP has detrimental effects on the central nervous system. However, the damaging roles of NP on the cerebellum and the underlying mechanisms remain unclear. Therefore, we investigated the effects of perinatal exposure to NP on cerebellar Purkinje cell (PC) dendrites and explored the potential mechanism involved. The animal model of perinatal exposure to NP was established by orally administering dams with either corn oil or NP (10, 50, or 100 mg/kg) during pregnancy and lactation. Offspring subjected to NP exposure during pregnancy and lactation had shorter and fewer cerebellar PC dendritic branches in childhood (postnatal day (PND)21) and adulthood (PND80). Contrary to expectations, perinatal NP treatment increased phosphorylation of protein kinase C gamma on PND21, but not on PND80. However, perinatal exposure to NP decreased phosphorylation of stathmin and tropomyosin-related kinase B (TrkB), as well as the expression of brain derived neurotrophic factor (BDNF) in cerebellar PCs on PND21 and PND80. These results indicate that perinatal exposure to NP irreversibly inhibited dendritic growth of PCs in the cerebella of offspring. Furthermore, the irreversible damage to PC dendrites in the cerebella of offspring subjected to perinatal NP exposure may be due to increased stathmin activity mediated by BDNF-TrkB signaling.

Endocrine-disrupting metabolites of alkylphenol ethoxylates - A critical review of analytical methods, environmental occurrences, toxicity, and regulation

Despite the fact that metabolites of alkylphenol ethoxylates (APEO) are classified as hazardous substances, they continue to be released into the environment from a variety of sources and are not usually monitored. Their wide use has led to an increase in the possible exposure pathways for humans, which is cause for alarm. Moreover, there is a lack of knowledge about the behaviour of these metabolites with respect to the environment and toxicity, and their biological effects on human health. The aim of this work is to give an overview of the APEO metabolites and their analysis, occurrences and toxicity in various environmental and human samples. APEO metabolites have adverse effects on humans, wildlife, and the environment through their release into the environment. Currently, there are some reviews available on the behaviour of alkylphenols in soil, sediments, groundwater, surface water and food. However, none of these articles consider their toxicity in humans and especially their effect on the nervous and immune system. This work summarises the environmental occurrences of metabolites of APEOs in matrices, e.g. water, food and biological matrices, their effect on the immune and nervous systems, and isomer-specific issues. With that emphasis we are able to cover most common occurrences of human exposure, whether direct or indirect.

Nonylphenol aggravates non-alcoholic fatty liver disease in high sucrose-high fat diet-treated rats

Exposure to environmental endocrine disruptors (EEDs) contributes to the pathogenesis of many metabolic disorders. Here, we have analyzed the effect of the EED-nonylphenol (NP) on the promotion of non-alcoholic fatty liver disease (NAFLD) in rats fed high sucrose-high fat diet (HSHFD). Fifty Sprague-Dawley rats were divided into five groups: controls fed a normal diet (C-ND); HSHFD-fed controls (C-HSHFD); and rats fed a HSHFD combined with NP at doses of 0.02 μg/kg/day (NP-L-HSHFD), 0.2 μg/kg/day (NP-M-HSHFD), and 2 μg/kg/day (NP-H-HSHFD). Subchronic exposure to NP coupled with HSHFD increased daily water and food intake (p < 0.05), hepatic echogenicity and oblique liver diameter (p < 0.05), and plasma levels of alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglycerides, and low density lipoprotein cholesterol (p < 0.05). Combined exposure to NP and HSHFD induced macrovesicular steatosis with dilation and congestion of the central vein, liver inflammatory cell infiltration, and expression of genes regulating lipid metabolism, SREBP-1C, FAS, and Ucp2. These results demonstrate that NP aggravates NAFLD in HSHFD-treated rats by up-regulating lipogenic genes, and that HSHFD increases the toxic effects of NP. Thus subchronic NP exposure may lead to NAFLD, especially when combined with a high-sucrose/high-fat diet.

Histopathology and Histomorphometric Investigation of Bisphenol A and Nonylphenol on the Male Rat Reproductive System

Background:

Bisphenol A (BPA) and nonylphenol (NP) have harmful effects on the endocrine system of humans and animals.

Aim:

We sought to investigate the effect of three doses of BPA and NP on the reproductive parameters of rats.

Materials and Methods:

Adult Wistar male rats weighing 150–200 g were used for a consecutive 35-day study. BPA and NP were given as gavage in three doses (5, 25, and 125 μg/kg). At the end of the study, the rats were anesthetized and 2 ml blood sample was obtained from the auxiliary venous plexus for the assessment of sex hormone levels. The testes were removed and kept in 10% formalin for the histomorphometric and histopathologic analyses.

Results:

BPA and NP significantly decreased the body weight of the animals compared to the controls (P < 0.05). The seminiferous tubule diameter and thickness of the seminiferous epithelium were significantly decreased in the groups receiving BPA and NP compared to the control (P < 0.05). The number of seminiferous tubules in every experimental group increased, except for the highest dose of NP (125 μg/kg), which showed a significant difference compared to the controls (P < 0.05). The number of spermatocytes and spermatogonia (54.97 ± 5.824, 35.78 ± 3.956, respectively) in the group receiving NP (125 μg/kg) was significantly decreased compared to the other groups. Serum levels of luteinizing hormone, Follicle stimulating hormone, and testosterone did not show any significant change compared to the controls.

Conclusion:

Based on the results, all three doses of BPA and NP significantly produced weight loss, as well as destruction of the testis tissue and impairment of the spermatogenesis.