Quantification of steroids and endocrine disrupting chemicals in rat ovaries by LC-MS/MS for reproductive toxicology assessment

Occurrence and removal of drugs and endocrine disruptors in the Bolonha Water Treatment Plant in Belém/PA (Brazil)

This study aimed to investigate the occurrence of drugs and endocrine disrupters in water supplies and in water for human consumption. Twelve sampling campaigns were carried out during the rainy and dry season at four sampling points in the Bolonha Complex, in the city of Belém, northern region of Brazil: Bolonha reservoir (catchment) and Water Treatment Plant (WTP) Bolonha (filtered water chamber, treated water tank, and washing water from the filters). The determination of the compounds was performed by solid phase extraction followed by gas and liquid chromatography coupled to mass spectrometry. The results confirmed the anthropic influence that the reservoir and WTP-Bolonha have been suffering, as consequence of the discharge of domestic sewage in natura. Among 25 microcontaminants analyzed, 12 were quantified in raw water and 10 in treated water. The antiallergic Loratadine (LRT) was the contaminant that occurred most frequently in all sample points, having been poorly removed (median 12%) in the conventional treatment used. Losartana (LST), 4-octylphenol (4-OP), and Bisphenol A (BPA) also occurred very frequently in raw water with concentrations ranging from 3.7 to 194 ng L^-1. Although such contaminants occurred in treated water in concentrations varying from 4.0 to 135 ng L^-1, the estimated margin of exposure ranged from 55 to 3333 times which indicates low risk of human exposure to such contaminants through ingestion of treated water.

Prediction, docking study and molecular simulation of 3D DNA aptamers to their targets of endocrine disrupting chemicals

Typical endocrine disrupting chemicals, including BPA (Bisphenol A), E₂ (17-β-Estradiol) and PCB 72 (polychlorinated biphenyl 72), are commonly and widely present in the environment with good chemical stability that are difficult to decompose in vitro and in vivo. Most of the high-qualified antibodies are required as the key biomaterials to fabricate the immunosensor for capturing and detecting. As an ideal alternative, the short-chain oligonucleotides (aptamer) are essentially and effectively employed with the advantages of small size, chemical stability and high effectiveness for monitoring these environmental contaminants. However, the molecular interaction, acting site and mode are still not well understood. In this work, we explored the binding features of the aptamers with their targeting ligands. The molecular dynamics simulations were performed on the aptamer-ligand complex systems. The stability of each simulation system was evaluated based on its root-mean-square deviation. The affinities of these proposed ligands and the predicted binding sites are analyzed. According to the binding energy analysis, the affinities between ligands and aptamers and the stability of the systems are BPA > PCB 72 >E₂. Trajectory analysis for these three complexes indicated that these three ligands were able to steadily bind with aptamers at docking site from 0 to 50 ns and contributed to alteration of conformation of aptamers.

Lack of immunotoxic effects of repeated exposure to atrazine associated with the adaptation of adrenal gland activation

T cell-dependent IgM antibody production and natural killer cell (NKC) activity were assessed in SD rats orally administered atrazine for 28 days to males (0, 6.5, 25, or 100 mg/kg/day) or females (0, 3, 6, or 50 mg/kg/day), or 30 or 500 ppm in diet (3 or 51 mg/kg/day). Anti-asialo GM1 antibodies (NKC) and cyclophosphamide (antibody-forming cell assay [AFC]) served as positive controls. Pituitary (ACTH, prolactin), adrenal (corticosterone, progesterone, aldosterone), and gonadal (androgens, estrogens) hormones were assessed after 1, 7, and/or 28 days of treatment. Food intake and body weights were significantly reduced in the highest dosed males, and transiently affected in females. Urinary corticosterone levels were not increased in atrazine-treated groups in either sex at any time point measured (10, 22, or 24 days). Corticosterone and progesterone were elevated in males after a single atrazine dose ≥6.5 mg/kg/day, but not after 7, 14, or 28 doses. There were no effects on adrenal, pituitary, or gonadal hormones in females. Atrazine did not suppress the AFC response or decrease NKC function after 28 days in males or females. Atrazine had no effect on spleen weights or spleen cell numbers in males or females, although thymus weights were elevated in males receiving the highest dose. The lack of immunotoxic effect of atrazine was associated with diminished adrenal activation over time in males, and no effects on adrenal hormones in females.

Atrazine triggers developmental abnormality of ovary and oviduct in quails (Coturnix Coturnix coturnix) via disruption of hypothalamo-pituitary-ovarian axis

There has been a gradual increase in production and consumption of atrazine (ATR) in agriculture to meet the population rising demands. Female reproduction is necessary for growth and maintenance of population. However, ATR impact on females and particularly ovarian developmental toxicity is less clear. The aim of this study was to define the pathways by which ATR exerted toxic effects on ovarian development of ovary and hypothalamo-pituitary-ovarian (HPO) axis. Female quails were dosed by oral gavage from sexual immaturity to maturity with 0, 50, 250 and 500 mg ATR/kg/d for 45 days. ATR had no effect on mortality but depressed feed intake and growth and influenced the biochemical parameters. Notably, the arrested development of ovaries and oviducts were observed in ATR-exposed quails. The circulating concentrations of E2, P, LH and PRL were unregulated and FSH and T was downregulated in ATR-treated quails. The mRNA expression of GnRH in hypothalamo and LH in pituitary and FSH in ovary was downregulated significantly by ATR exposure and FSH and PRL in pituitary were upregulated. ATR exposure upregulated the level of P450scc, P450arom, 3β-HSD and 17β-HSD in ovary and downregulated ERβ expression in female quails. However, ATR did not change ERα expression in ovary. This study provides new insights regarding female productive toxicology of ATR exposure. Ovary and oviduct in sexually maturing females were target organs of ATR-induced developmental toxicity. We propose that ATR-induced developmental abnormality of ovary and oviduct is associated with disruption of gonadal hormone balance and HPO axis in female quails.

Atrazine Exposure and Reproductive Dysfunction through the Hypothalamus-Pituitary-Gonadal (HPG) Axis

Endocrine disrupting chemicals (EDC) are exogenous agents that alter endogenous hormone signaling pathways. These chemicals target the neuroendocrine system which is composed of organs throughout the body that work alongside the central nervous system to regulate biological processes. Of primary importance is the hypothalamic-pituitary-gonadal (HPG) axis which is vital for maintaining proper reproductive function. Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a pre-emergent herbicide used to prevent the growth of weeds on various crops. This herbicide is reported to widely contaminate potable water supplies everywhere it is applied. As such, the European Union banned the use of atrazine in 2004. Currently the United States Environmental Protection Agency regulates atrazine at 3 parts per billion (ppb; μg/L) in drinking water, while the World Health Organization recently changed their drinking water guideline to 100 ppb. Atrazine is implicated to be an EDC that alters reproductive dysfunction by targeting the HPG axis. However, questions remain as to the human health risks associated with atrazine exposure with studies reporting mixed results on the ability of atrazine to alter the HPG axis. In this review, the current findings for atrazine’s effects on the HPG axis are examined in mammalian, anuran, and fish models and in epidemiological studies.

A computational model to predict rat ovarian steroid secretion from in vitro experiments with endocrine disruptors

A finely tuned balance between estrogens and androgens controls reproductive functions, and the last step of steroidogenesis plays a key role in maintaining that balance. Environmental toxicants are a serious health concern, and numerous studies have been devoted to studying the effects of endocrine disrupting chemicals (EDCs). The effects of EDCs on steroidogenic enzymes may influence steroid secretion and thus lead to reproductive toxicity. To predict hormonal balance disruption on the basis of data on aromatase activity and mRNA level modulation obtained in vitro on granulosa cells, we developed a mathematical model for the last gonadal steps of the sex steroid synthesis pathway. The model can simulate the ovarian synthesis and secretion of estrone, estradiol, androstenedione, and testosterone, and their response to endocrine disruption. The model is able to predict ovarian sex steroid concentrations under normal estrous cycle in female rat, and ovarian estradiol concentrations in adult female rats exposed to atrazine, bisphenol A, metabolites of methoxychlor or vinclozolin, and letrozole.