Juvenile Toxicity Rodent Model to Study Toxicological Effects of Bisphenol A (BPA) at Dose Levels Derived From Italian Children Biomonitoring Study

Effects of Endocrine-Disrupting Chemicals on Adrenal Function

The adrenal glands play crucial roles in regulating metabolism, blood pressure, immune system function, and response to stress through the secretion of hormones. Despite their critical functions, the adrenal glands are often overlooked in studies on the effects of potential toxicants. Research across human, animal, and in vitro studies has identified more than 60 compounds that can induce adrenocortical toxicity. These compounds, known as endocrine-disrupting chemicals (EDCs), are natural or synthetic substances that interfere with the endocrine system. This review aims to provide an overview of the effects of 4 major families of EDCs-flame retardants, bisphenols, phthalates, and microplastics-on the function of the adrenal glands. The PubMed database was searched for studies reporting the effects of the chemicals in these 4 families on the adrenal glands. There is clear evidence that the morphology and function of the adrenal gland are affected, particularly through disrupting the steroidogenic pathway. Additionally, some EDCs have been shown to exert transgenerational effects, raising further concerns about their long-term effect. However, most EDCs have not been thoroughly evaluated for their effects on the function of the adrenal glands, especially in human studies. Thus, developing regulatory testing guideline to include the adrenal glands in the screening of EDCs is urgently needed.

Influence of nano-polystyrene on cyfluthrin toxicity in honeybee Apis cerana cerana Fabricius

Plastics and pesticides are commonly used and often coexist in the environment. As pollinating insects, honeybees are simultaneously exposed to both these toxins. However, there has been no study on the toxic effects of nano-polystyrene plastics (nanoPS) and cyfluthrin (Cy) on the Apis cerana cerana Fabricius until now. This study found that nanoPS did not significantly impact the mortality of Apis cerana cerana but could reduce cyfluthrin-induced mortality. Additionally, nanoPS caused damage to the honeybee gut and hindered the development of the hypopharyngeal glands, whereas cyfluthrin did not produce these pathological changes. Concerning the detoxification-related genes, the two toxins alone and in combination significantly promoted the expression of P450 9E2 and Cyp9Q3 genes, and the upregulation trend was found more significant for the combination. Regarding immune gene expression, exposure to a single toxin or both toxins significantly down-regulated the abaecin gene, but only exposure to nanoPS significantly decreased apidaecin expression. The changes in metabolites and metabolic pathways in honeybees after ingesting nanoPS were also studied. This study highlights the toxicity of nano-microplastics and Cy alone and in combination to Apis cerana cerana Fabricius and provides new insights into the potential ecological risks of nanoPS.

Bisphenol analogues induce thyroid dysfunction via the disruption of the thyroid hormone synthesis pathway

Bisphenol analogues are widely used in industrial and daily-use consumer products having imperfect thyroid hormones (THs) structures. Widespread exposure interferes with thyroid-related health outcomes in human. The mechanisms of disruption on TH synthesis and subsequent thyroid dysfunction by different bisphenol analogues remain unclear. Here, we evaluated bisphenol-induced thyroid endocrine disruption in C57BL/6 mice at doses of 0.002, 0.02, 2, and 20 mg/kg body weight/day (BW/d) for five consecutive weeks. Administration of 20 mg/kg BW/d bisphenol S (BPS) and 2 mg/kg BW/d tetrabromobisphenol S (TBBPS) significantly increased serum thyrotropin (TSH) levels to 1.21-fold and 1.20-fold of control group, respectively, indicating that bisphenols induced thyroid dysfunction in mice. Height of the thyroid follicle epithelium significantly increased to 1.27-, 1.24-, 1.26-, and 1.36-fold compared to control group with BPA, BPS, TBBPA, and TBBPS at 20 mg/kg BW/d, respectively, indicating impairment of the thyroid gland structure, and TBBPS showed potent effect. Exposure to bisphenol analogues of 0.02 mg/kg BW/d downregulated the protein expression levels of thyrotropin receptor, the sodium/iodide symporter, thyroperoxidase. The TH-dependent effects were further determined using the T-Screen assay at 10-11 M to 10-5 M concentrations. Bisphenol analogues significantly decreased TH-dependent GH3 cell proliferation, indicating the antagonistic activity of bisphenol analogues. The gene responsible for THs synthesis of thyrotropin releasing hormone receptor and TSH were upregulated, but downregulation of thyroid receptor β was observed. Our results suggest that bisphenol analogues distinctly induce thyroid dysfunction via TH synthesis, implying adverse effect of bisphenol analogues on TH homeostasis and subsequent physiological processes.

Sex-Specific Effects of Short-Term Oral Administration of Food-Grade Titanium Dioxide Nanoparticles in the Liver and Kidneys of Adult Rats

Titanium dioxide (TiO2) nanomaterial is used in several items (implant materials, pills composition, cosmetics, etc.). Although TiO2 is no longer considered safe as a food additive, the general population is exposed daily through different routes, and information is lacking on some aspects of animal and human health. This study evaluated liver and kidney toxicity of food-grade TiO2 nanoparticles (NPs) (primary size < 25 nm) in male and female rats that were orally exposed for 5 days to 0, 1, and 2 mg/kg body weight per day (comparable with daily E171 consumption). Selected liver and kidney toxicity endpoints included serum biomarkers, histopathological analysis and expression of osteopontin (SPP1), vascular endothelial growth factor (VEGF), interleukin 6 (IL-6), and neuropeptide Y (NPY). Although TiO2 NPs are known to affect the gastric mucosa, short-term exposure induced sex-specific effects: general toxicity parameters were predominantly altered in female rats, whereas the liver appeared to be more affected than the kidneys in male rats, which also showed overexpression of NPY and SPP1. In the kidneys, the TiO2 NP effects were quantitatively similar but qualitatively different in the two sexes. In conclusion, careful consideration should be paid to the presence of TiO2 NPs in other items that can lead to human exposure.

Impact of combined chronic exposure to low-dose bisphenol A and fructose on serum adipocytokines and the energy target metabolome in white adipose tissue

Background: Adipose tissue is a dynamic endocrine organ that plays a key role in regulating metabolic homeostasis. Previous studies confirmed that bisphenol A (BPA) or fructose can interfere with the function of adipose tissue. Nonetheless, knowledge on how exposure to BPA and fructose impacts energy metabolism in adipose tissue remains limited.Purpose: To determine impact of combined chronic exposure to low-dose bisphenol A and fructose on serum adipocytokines and the energy target metabolome in white adipose tissue.Method: 57 energy metabolic intermediates in adipose tissue and 7 adipocytokines in serum from Sprague Dawley rats were examined after combined exposure to two levels of BPA (lower dose: 0.25, and higher dose: 25 μg/kg every other day) and 5% fructose for 6 months.Results: combined exposure to lower-dose BPA and fructose significantly increased omentin-1, pyruvic acid, adenosine triphosphate (ATP), adenosine monophosphate (AMP), inosine monophosphate (IMP), inosine, and l-lactate; however, these parameters were not significantly affected by higher-dose BPA combined with fructose. Interestingly, the level of succinate (an intermediate of the citric acid cycle) increased dose-dependently in adipose tissue, and the level of apelin 13 (a versatile adipocytokine) decreased dose-dependently in serum after combined exposure to BPA and fructose. Phosphoenolpyruvic acid, phenyl-lactate, and ornithine were significantly correlated with asprosin, omentin-1, apelin, apelin 13, and adiponectin, while l-tyrosine was significantly correlated with irisin and a-FABP under combined exposure to BPA and fructose.Conclusions: these findings indicated that lower-dose BPA combined with fructose could amplify the impact on glycolysis, energy storage, and purine nucleotide biosynthesis in adipose tissue, and adipocytokines, such as omentin-1 and apelin 13, may be related to metabolic interference induced by BPA and fructose exposure.

Endocrine disruptor chemicals, adipokines and reproductive functions

The prevalence of adult obesity has risen markedly in recent decades. The endocrine system precisely regulates energy balance, fat abundance and fat deposition. Interestingly, white adipose tissue is an endocrine gland producing adipokines, which regulate whole-body physiology, including energy balance and reproduction. Endocrine disruptor chemicals (EDCs) include natural substances or chemicals that affect the endocrine system by multiple mechanisms and increase the risk of adverse health outcomes. Numerous studies have associated exposure to EDCs with obesity, classifying them as obesogens by their ability to activate different mechanisms, including the differentiation of adipocytes, increasing the storage of triglycerides, or elevating the number of adipocytes. Moreover, in recent years, not only industrial deception and obesity have intensified but also the problem of human infertility. Reproductive functions depend on hormone interactions, the balance of which may be disrupted by various EDCs or obesity. This review gives a brief summary of common EDCs linked with obesity, the mechanisms of their action, and the effect on adipokine levels, reproduction and connected disorders, such as polycystic ovarian syndrome, decrease in sperm motility, preeclampsia, intrauterine growth restriction in females and decrease of sperm motility in males.

Italian Children Exposure to Bisphenol A: Biomonitoring Data from the LIFE PERSUADED Project

A human biomonitoring (HBM) study on bisphenol A (BPA) in Italian children and adolescents was performed within the LIFE PERSUADED project, considering the residing areas, sex and age. The median urinary BPA level was 7.02 µg/L, with children living in the South of Italy or in urban areas having higher levels than those residing in the North or in rural areas. Children aged 4–6 years had higher BPA levels than those aged 7–10 and 11–14 years, but no differences were detected between sexes. The exposure in Italian children was higher compared to children from other countries, but lower than the HBM guidance value (135 µg/L). The estimated daily intake was 0.17 μg/kg body weight (bw) per day, about 24-fold below the temporary Tolerable Daily Intake of 4 μg/kg bw per day established by the European Food Safety Authority. However, this threshold was exceeded in 1.44% of the enrolled children, raising concern about the overall exposure of Italian young population.

Toxicological Assessment of Oral Co-Exposure to Bisphenol A (BPA) and Bis(2-ethylhexyl) Phthalate (DEHP) in Juvenile Rats at Environmentally Relevant Dose Levels: Evaluation of the Synergic, Additive or Antagonistic Effects

BACKGROUND

The general population (including children) is exposed to chemical mixtures. Plasticizers such as Bisphenol A (BPA) and Phthalates (mainly Bis(2-ethylhexyl) phthalate-DEHP) are widespread contaminants classified as endocrine disrupters which share some toxicological profiles and coexist in food and environment.

METHODS

To identify hazards of DEHP and BPA mixtures, the juvenile toxicity test-where rodents are in peripubertal phase of development, resembling childhood-was selected using exposure data from biomonitoring study in children. Biological activity and potential enhanced and/or reduced toxicological effects of mixtures due to common mechanisms were studied, considering endpoints of metabolic, endocrine and reproductive systems. The degree of synergy or antagonism was evaluated by synergy score calculation, using present data and results from the single compound individually administered.

RESULTS

In metabolic system, synergic interaction predominates in female and additive in male rats; in the reproductive and endocrine systems, the co-exposure of BPA and DEHP showed interactions mainly of antagonism type.

CONCLUSIONS

The present approach allows to evaluate, for all the endpoints considered, the type of interaction between contaminants relevant for human health. Although the mode of action and biological activities of the mixtures are not completely addressed, it can be of paramount usefulness to support a more reliable risk assessment.

Hazard identification of pyrogenic synthetic amorphous silica (NM-203) after sub-chronic oral exposure in rat: A multitarget approach

Food additive E551 consists of synthetic amorphous silica (SAS), comprising agglomerates and aggregates of primary particles in the nanorange (<100 nm), which potential nanospecific risks for humans associated to dietary exposure are not yet completely assessed. In NANoREG project, aim of the study was to identify potential hazards of pyrogenic SAS nanomaterial NM-203 by a 90-day oral toxicity study (OECD test guideline 408). Adult Sprague-Dawley rats of both sexes were orally treated with 0, 2, 5, 10, 20 and 50 mg SAS/kg bw per day; dose levels were selected to be as close as possible to E551 dietary exposure. Several endpoints were investigated, the whole integrative study is presented here along with the results of dispersion characterization, tissue distribution, general toxicity, blood/serum biomarkers, histopathological and immunotoxicity endpoints. No mortality, general toxicity and limited deposition in target tissues were observed. NM-203 affected liver and spleen in both sexes. Proposed NOAEL 5 mg/kg bw per day in male rats for enlarged sinusoids in liver. In female rats, TSH and creatinine levels were affected, proposed LOAEL 2 mg/kg bw per day. Overall, these data provide new insight for a comprehensive risk assessment of SAS exposure by the oral route.