Developmental neurotoxic effects of bisphenol A and its derivatives in Drosophila melanogaster

Clearing the path: Unraveling bisphenol a removal and degradation mechanisms for a cleaner future

Bisphenol A (BPA) is a prevalent chemical found in a range of consumer goods, which has raised worries about its possible health hazards. Comprehending the breakdown pathways of BPA is essential for evaluating its environmental consequences and addressing associated concerns. This review emphasizes the significance of studying the degradation/removal of BPA, with a specific focus on both natural and artificial routes. It explores natural processes such as photolysis, hydrolysis, and biodegradation, as well as manmade methods including advanced oxidation processes (AOPs) and enzymatic degradation. Examining the decomposition of BPA helps to understand how it behaves in the environment, providing valuable information for managing risks and addressing pollution. Furthermore, comprehending degradation mechanisms aids in the creation of more secure substitutes and regulatory actions to reduce BPA exposure and safeguard human health. This review emphasizes the need of promptly addressing this environmental and public health concern through the research of BPA degradation.

BPAP induces autism-like behavior by affecting the expression of neurodevelopmental genes in Drosophila melanogaster

Bisphenol AP (BPAP), an environmental endocrine disruptor, may cause neurodevelopmental disorders affecting human health. Studies have shown that BPAP impacts hormone synthesis and metabolism, causes social behavior abnormalities, and induces anxiety-like behavioral impairments in mice. However, evidence for the neurobehavioral effects of BPAP is still lacking. Here, we examined the toxic effects of BPAP on neurodevelopment using a Drosophila model. We assessed the role of BPAP exposure in autism-like behavior and explored the underlying mechanisms. Our findings indicated that BPAP exposure reduced pupation and eclosion rates and delayed growth in Drosophila. Furthermore, BPAP exposure caused autism-like behaviors, characterized by increased grooming times and aberrant social interactions, along with abnormalities in locomotor activity, as well as learning and memory ability. Mechanistically, we found that BPAP decreases the number of neuroblasts (NBs) and mature intermediate neural progenitors (INPs) in the 3rd larval brain, impairing axon guidance in the mushroom body of the adult Drosophila brain. Additionally, our transcriptome analysis revealed that BPAP exposure alters the expression of neurodevelopment-related genes (Nplp3, sand, lush, and orco) and affects the estrogen signaling pathway (Hsp70Ab, Hsp70Bc, Hsp70Ba, and Hsp70Bb). These changes potentially explain the BPAP-induced autism-like behavior in Drosophila.

Bisphenol A induces lipid metabolism disorder and impairs hepatopancreas of Sesarmops sinensis

Bisphenol A (BPA) is a chemical that disrupts the endocrine system and may have negative implications on the lipid metabolism of organisms. To ascertain BPA implications on lipid metabolism in the hepatopancreas of Sesarmops sinensis, we exposed S. sinensis to different concentrations of BPA for 14 days. The outcomes manifested that BPA may stimulate hepatopancreas injury and lipid deposition in the hepatopancreas of S. sinensis and lead to the increase of hepatosomatic index (HSI). Transcriptome analysis showed that lipid metabolism-related pathways were significantly enriched in KEGG pathways. BPA exposure also caused disorders in lipid metabolism by altering fatty acid composition and lipid metabolites. The up-regulation of lipid synthesis genes and the alteration of lipid transport genes may be important reasons for the disorder of lipid metabolism. Furthermore, these outcomes provide a fresh point of reference for comprehending the ecotoxicological impacts of BPA on aquatic organisms.

Ancestral lineages of dietary exposure to an endocrine disrupting chemical drive distinct forms of transgenerational subfertility in an insect model

Across the globe, many species of insects are facing population decline. This is largely driven by anthropogenic changes to the environment, including the widespread exposure of invertebrates to endocrine disrupting chemicals (EDCs), which impair fertility. To test whether generations of Drosophila melanogaster born from parents exposed to a common dietary EDC, equol, could recover reproductive function, we quantified the reproductive capacity of the two subsequent generations. Using a novel suite of flow cytometry assays to assess sperm functionality in real time, we find that sperm function is compromised across three generations, even after non-exposed in individuals contribute to the breeding population. Though the sex ratio alters in response to EDC exposure, favouring the survival of female offspring, most lineages with ancestral EDC exposure exhibit persistent subfertility in both the male and female. Male offspring with ancestral EDC exposure present with reduced fertility and dysfunctional spermatozoa, whereby spermatozoa are metabolically stressed, lack DNA integrity and present with permanent epigenetic alterations. Across generations, male and female offspring demonstrate distinct patterns of reproductive characteristics, depending upon the specific lineage of EDC exposure. Our results illustrate how dietary EDCs present in agricultural plants could promote transgenerational subfertility and contribute to declining insect populations.

Sexual dimorphism in neurobehavioural phenotype and gut microbial composition upon long-term exposure to structural analogues of bisphenol-A

Bisphenol S (BPS) and Bisphenol F (BPF), the analogues of the legacy endocrine disrupting chemical, Bisphenol A (BPA) are ubiquitous in the environment and present in various consumer goods, and potentially neurotoxic. Here, we studied sex-specific responses of bisphenols on behavioural phenotypes, including their association with pro-inflammatory biomarkers and altered neurotransmitters levels, and the key gut microbial abundances. Neurobehavioural changes, using standard test battery, biochemical and molecular estimations for inflammatory cytokines, neurotransmitters, and oxido-nitrosative stress markers, gene expression analysis using qRT-PCR, H&E based histological investigations, gut permeability assays and Oxford Nanopore-based 16S-rRNA metagenomics sequencing for the gut microbial abundance estimations were performed. Bisphenol(s) exposure induces anxiety and depression-like behaviours, particularly in the male mice, with heightened pro-inflammatory cytokines levels and systemic endotoxemia, altered monoamine neurotransmitters levels/turnovers and hippocampal neuronal degeneration and inflammatory responses in the brain. They also increased gut permeability and altered microbial diversity, particularly in males. Present study provides evidence for sex-specific discrepancies in neurobehavioural phenotypes and gut microbiota, which necessitate a nuanced understanding of sex-dependent responses to bisphenols. The study contributes to ongoing discussions on the multifaceted implications of bisphenols exposure and underscores the need for tailored regulatory measures to mitigate potential health risks associated with them.

Regrettable Substitutes and the Brain: What Animal Models and Human Studies Tell Us about the Neurodevelopmental Effects of Bisphenol, Per- and Polyfluoroalkyl Substances, and Phthalate Replacements

In recent decades, emerging evidence has identified endocrine and neurologic health concerns related to exposure to endocrine-disrupting chemicals (EDCs), including bisphenol A (BPA), certain per- and polyfluoroalkyl compounds (PFASs), and phthalates. This has resulted in consumer pressure to remove these chemicals from the market, especially in food-contact materials and personal care products, driving their replacement with structurally or functionally similar substitutes. However, these "new-generation" chemicals may be just as or more harmful than their predecessors and some have not received adequate testing. This review discusses the research on early-life exposures to new-generation bisphenols, PFASs, and phthalates and their links to neurodevelopmental and behavioral alterations in zebrafish, rodents, and humans. As a whole, the evidence suggests that BPA alternatives, especially BPAF, and newer PFASs, such as GenX, can have significant effects on neurodevelopment. The need for further research, especially regarding phthalate replacements and bio-based alternatives, is briefly discussed.

Exposure to Bisphenol F and Bisphenol S during development induces autism-like endophenotypes in adult Drosophila melanogaster

Bisphenol F (BPF) and Bisphenol S (BPS) are being widely used by the industry with the claim of "safer substances", even with the scarcity of toxicological studies. Given the etiological gap of autism spectrum disorder (ASD), the environment may be a causal factor, so we investigated whether exposure to BPF and BPS during the developmental period can induce ASD-like modeling in adult flies. Drosophila melanogaster flies were exposed during development (embryonic and larval period) to concentrations of 0.25, 0.5, and 1 mM of BPF and BPS, separately inserted into the food. When they transformed into pupae were transferred to a standard diet, ensuring that the flies (adult stage) did not have contact with bisphenols. Thus, after hatching, consolidated behavioral tests were carried out for studies with ASD-type models in flies. It was observed that 1 mM BPF and BPS caused hyperactivity (evidenced by open-field test, negative geotaxis, increased aggressiveness and reproduction of repetitive behaviors). The flies belonging to the 1 mM groups of BPF and BPS also showed reduced cognitive capacity, elucidated by the learning behavior through aversive stimulus. Within the population dynamics that flies exposed to 1 mM BPF and 0.5 and 1 mM BPS showed a change in social interaction, remaining more distant from each other. Exposure to 1 mM BPF, 0.5 and 1 mM BPS increased brain size and reduced Shank immunoreactivity of adult flies. These findings complement each other and show that exposure to BPF and BPS during the development period can elucidate a model with endophenotypes similar to ASD in adult flies. Furthermore, when analyzing comparatively, BPS demonstrated a greater potential for damage when compared to BPF. Therefore, in general these data sets contradict the idea that these substances can be used freely.

Bisphenol Z exposure inhibits oocyte meiotic maturation by rupturing mitochondrial function

The use of bisphenol A (BPA) has been restricted due to its endocrine-disrupting effects. As a widely used alternative to BPA today, environmental levels of bisphenol Z (BPZ) continue to rise and accumulate in humans. Oocyte quality is critical for a successful pregnancy. Nevertheless, the toxic impacts of BPZ on the maturation of mammalian oocytes remain unexplored. Therefore, the impacts of BPZ and BPA on oocyte meiotic maturation were compared in an in vitro mouse oocyte culture model. Exposure to 150 μM of both BPZ and BPA disrupted the assembly of the meiotic spindle and the alignment of chromosomes, and BPZ exerted stronger toxicological effects than BPA. Furthermore, BPZ resulted in aberrant expression of F-actin, preventing the formation of the actin cap. Mechanistically, BPZ exposure disrupted the mitochondrial localization pattern, reduced mitochondrial membrane potential and ATP content, leading to impaired mitochondrial function. Further studies revealed that BPZ exposure resulted in oxidative stress and altered expression of genes associated with anti-oxidative stress. Moreover, BPZ induced severe DNA damage and triggered early apoptosis in oocytes, accompanied by impaired lysosomal function. Overall, the data in this study suggest that BPZ is not a safe alternative to BPA. BPZ can trigger early apoptosis by affecting mitochondrial function and causing oxidative stress and DNA damage in oocytes. These processes disrupt cytoskeletal assembly, arrest the cell cycle, and ultimately inhibit oocyte meiotic maturation.

Bisphenol F affects neurodevelopmental gene expression, mushroom body development, and behavior in Drosophila melanogaster

Bisphenol F (BPF) is a potential neurotoxicant used as a replacement for bisphenol A (BPA) in polycarbonate plastics and epoxy resins. We investigated the neurodevelopmental impacts of BPF exposure using Drosophila melanogaster as a model. Our transcriptomic analysis indicated that developmental exposure to BPF caused the downregulation of neurodevelopmentally relevant genes, including those associated with synapse formation and neuronal projection. To investigate the functional outcome of BPF exposure, we evaluated neurodevelopmental impacts across two genetic strains of Drosophila- w1118 (control) and the Fragile X Syndrome (FXS) model-by examining both behavioral and neuronal phenotypes. We found that BPF exposure in w1118 Drosophila caused hypoactive larval locomotor activity, decreased time spent grooming by adults, reduced courtship activity, and increased the severity but not frequency of β-lobe midline crossing defects by axons in the mushroom body. In contrast, although BPF reduced peristaltic contractions in FXS larvae, it had no impact on other larval locomotor phenotypes, grooming activity, or courtship activity. Strikingly, BPF exposure reduced both the severity and frequency of β-lobe midline crossing defects in the mushroom body of FXS flies, a phenotype previously observed in FXS flies exposed to BPA. This data indicates that BPF can affect neurodevelopment and its impacts vary depending on genetic background. Further, BPF may elicit a gene-environment interaction with Drosophila fragile X messenger ribonucleoprotein 1 (dFmr1)-the ortholog of human FMR1, which causes fragile X syndrome and is the most common monogenetic cause of intellectual disability and autism spectrum disorder.

Bisphenol F and Bisphenol S exposure during development reduce neuronal ganglia integrity and change behavioral profile of Drosophila melanogaster larvae

The behavior and neuronal ganglia integrity of Drosophila melanogaster larvae exposed to Bisphenol F (BPF) and Bisphenol S (BPS) (0.25, 0.5 and 1 mM) was evaluated. Larvae exposed to BPF and BPS (0.5 and 1 mM) showed hyperactivity, reduced decision-making capacity and were not responsive to touch (no sensitivity to physical stimuli). There was also a reduction in the tunneling capacity induced by 1 mM of BPF and BPS (innate behaviors for survival). Behaviors resulting from changes in neuronal functioning, thermotaxis and phototaxis showed that BPS was more harmful compared to BPF. Furthermore, the concentration of 1 mM BPS generated greater damage to neuronal ganglia when compared to BPF. This difference may be related to the LC50 of the 10.04 mM BPS and 15.07 mM BPF. However, these behavioral changes presented by the larvae here are characteristic of those presented in neurodevelopmental disorders. Our findings are novel and refute the possibility that BPF and BPS are safer alternatives.

Lead exposure induced transgenerational developmental neurotoxicity by altering genome methylation in Drosophila melanogaster

Heavy metal toxicity is a significant global health concern, with particular attention given to lead (Pb) exposure due to its adverse effects on cognitive development, especially in children exposed to low concentrations. While Pb neurotoxicity has been extensively studied, the analysis and molecular mechanisms underlying the transgenerational effects of Pb exposure-induced neurotoxicity remain poorly understood. In this study, we utilized Drosophila, a powerful developmental animal model, to investigate this phenomenon. Our findings demonstrated that Pb exposure during the developmental stage had a profound effect on the neurodevelopment of F0 fruit flies. Specifically, we observed a loss of correlation between the terminal motor area and muscle fiber area, along with an increased frequency of the β-lobe midline crossing phenotype in mushroom bodies. Western blot analysis indicated altered expression levels of synaptic vesicle proteins, with a decrease in Synapsin (SYN) and an increase in Bruchpilot (BRP) expression, suggesting changes in synaptic vesicle release sites. These findings were corroborated by electrophysiological data, showing an increase in the amplitude of evoked excitatory junctional potential (EJP) and an increase in the frequency of spontaneous excitatory junctional potential (mEJP) following Pb exposure. Importantly, our results further confirmed that the developmental neurotoxicity resulting from grandparental Pb exposure exhibited a transgenerational effect. The F3 offspring displayed neurodevelopmental defects, synaptic function abnormalities, and repetitive behavior despite lacking direct Pb exposure. Our MeDIP-seq analysis further revealed significant alterations in DNA methylation levels in several neurodevelopmental associated genes (eagle, happyhour, neuroglian, bazooka, and spinophilin) in the F3 offspring exposed to Pb. These findings suggest that DNA methylation modifications may underlie the inheritance of acquired phenotypic traits resulting from environmental Pb exposure.

Exposure to the Natural Compound Climacostol Induces Cell Damage and Oxidative Stress in the Fruit Fly Drosophila melanogaster

The ciliate Climacostomum virens produces the metabolite climacostol that displays antimicrobial activity and cytotoxicity on human and rodent tumor cells. Given its potential as a backbone in pharmacological studies, we used the fruit fly Drosophila melanogaster to evaluate how the xenobiotic climacostol affects biological systems in vivo at the organismal level. Food administration with climacostol demonstrated its harmful role during larvae developmental stages but not pupation. The midgut of eclosed larvae showed apoptosis and increased generation of reactive oxygen species (ROS), thus demonstrating gastrointestinal toxicity. Climacostol did not affect enteroendocrine cell proliferation, suggesting moderate damage that does not initiate the repairing program. The fact that climacostol increased brain ROS and inhibited the proliferation of neural cells revealed a systemic (neurotoxic) role of this harmful substance. In this line, we found lower expression of relevant antioxidant enzymes in the larvae and impaired mitochondrial activity. Adult offsprings presented no major alterations in survival and mobility, as well the absence of abnormal phenotypes. However, mitochondrial activity and oviposition behavior was somewhat affected, indicating the chronic toxicity of climacostol, which continues moderately until adult stages. These results revealed for the first time the detrimental role of ingested climacostol in a non-target multicellular organism.

Associations of exposure to bisphenol A and its substitutes with neurodevelopmental outcomes among infants at 12 months of age: A cross-sectional study

BACKGROUND

Bisphenol A (BPA) exposure has been linked to adverse childhood neurodevelopment, but little is known about whether BPA substitutes exposures are also related to childhood neurodevelopment.

OBJECTIVES

To investigate the associations of exposure to BPA and its substitutes with infant neurodevelopment at 12 months.

METHODS

A total of 420 infants at 12 months were included from the Laizhou Wan (Bay) Birth Cohort in Shandong, China. Urinary concentrations of BPA and its substitutes including bisphenol S (BPS), bisphenol B (BPB), bisphenol AF (BPAF), bisphenol AP (BPAP), bisphenol P (BPP) and bisphenol Z (BPZ) were measured. Developmental quotient (DQ) scores based on the Gesell Development Schedules (GDS) were used to evaluate infant neurodevelopment. The multivariable linear regression and weighted quantile sum (WQS) regression were applied to estimate the associations of exposure to individual bisphenols and their mixtures with DQ scores, respectively. Sex-stratified analyses were also performed.

RESULTS

BPA was detected in most infants (89.05%) and had the highest median concentration (0.709 ng/mL) among all bisphenols. BPA substitutes except BPZ were ubiquitous in infants' urine samples (>70%), and BPS showed the highest median concentration (0.064 ng/mL) followed by BPAP (0.036 ng/mL), BPAF (0.028 ng/mL), BPP (0.015 ng/mL) and BPB (0.013 ng/mL). In multivariable linear regression, only BPAF exposure was inversely associated with social DQ scores among all infants (β = -0.334; 95% CI: -0.650, -0.019). After sex stratification, this inverse association was significant in girls (β = -0.605; 95% CI: -1.030, -0.180). Besides, BPA exposure was negatively related to gross motor DQ scores in boys (β = -1.061; 95% CI: -2.078, -0.045). WQS analyses confirmed these results.

CONCLUSIONS

Our study suggests that bisphenol exposure during infancy may be associated with poor infant neurodevelopment, and BPAF as a commonly used BPA substitute contributing the most to this adverse association deserves more attention.