Non-genomic effects of endocrine disrupters: inhibition of estrogen sulfotransferase by phenols and chlorinated phenols

Pesticide-derived bright chlorine-doped carbon dots for selective determination and intracellular imaging of Fe(III)

Inspired by the conversion from organics or biomass to fluorescent carbon dots (C-dots), the use of pesticide 4-chlorophenol (4-CP) as a precursor to prepare C-dots has been reported. The as-prepared chlorine-doped C-dots display a brightly blue emission at ∼445 nm with ∼22.8% quantum yield. Also, the surface of C-dots enriches functional groups, such as phenolic hydroxyl and carboxylic acid, etc., which can capture ferric ion (Fe(III)), resulting in the quenching of blue fluorescence of C-dots through an inner filter effect. The quantitative assay for Fe(III) was therefore realized by this probe with a 0.36 μM detection limit in the 0.6-25 μM concentration range. Most significantly, the cytotoxicity on Hela cells indicates the 4-CP-derived C-dots have a negligible cytotoxicity. The C-dots were applied in detection in environmental samples and imaging in Hela cells of Fe(III), demonstrating their good applicability, low toxicity and good biocompatibility, and providing an alterative approach to totally eliminate the harm of chlorophenols (CPs).

Sensitive 3-chlorophenol sensor development based on facile Er2O3/CuO nanomaterials for environmental safety

Low-dimensional Er₂O₃/CuO nanomaterials were synthesized by wet-chemical process and totally characterized with various conventional methods. The electrochemical approach could be a pioneer development in selective 3-CP sensor development using doped nano-structural materials by an electrochemical method for the various phenolic sensor applications for environmental safety in broad scales.

The toxic effects of chlorophenols and associated mechanisms in fish

Chlorophenols (CPs) are ubiquitous contaminants in the environment primarily released from agricultural and industrial wastewater. These compounds are not readily degraded naturally, and easily accumulate in organs, tissues and cells via food chains, further leading to acute and chronic toxic effects on aquatic organisms. Herein, we review the available literature regarding CP toxicity in fish, with special emphasis on the potential toxic mechanisms. CPs cause oxidative stress via generation of reactive oxygen species, induction of lipid peroxidation and/or oxidative DNA damage along with inhibition of antioxidant systems. CPs affect immune system by altering the number of mature B cells and macrophages, while suppressing phagocytosis and down-regulating the expression of immune factors. CPs also disrupt endocrine function by affecting hormone levels, or inducing abnormal gene expression and interference with hormone receptors. CPs at relatively higher concentrations induce apoptosis via mitochondria-mediated pathway, cell death receptor-mediated pathway, and/or DNA damage-mediated pathway. CPs at relatively lower concentrations promote cell proliferation, and foster cancers-prone environment by increasing the rate of point mutations and oxidative DNA lesions. These toxic effects in fish are induced directly by CPs per se or indirectly by their metabolic products. In addition, recent studies on the alteration of DNA methylation by CPs through high-throughput DNA sequencing analysis provide new insights into our understanding of the epigenetic mechanisms underlying CPs toxicity.

Interactions of cytosolic sulfotransferases with xenobiotics

Cytosolic sulfotransferases are a superfamily of enzymes that catalyze the transfer of the sulfonic group from 3'-phosphoadenosine-5'-phosphosulfate to hydroxy or amine groups in substrate molecules. The human cytosolic sulfotransferases that have been most studied, namely SULT1A1, SULT1A3, SULT1B1, SULT1E1 and SULT2A1, are expressed in different tissues of the body, including liver, intestine, adrenal, brain and skin. These sulfotransferases play important roles in the sulfonation of endogenous molecules such as steroid hormones and neurotransmitters, and in the elimination of xenobiotic molecules such as drugs, environmental chemicals and natural products. There is often overlapping substrate selectivity among the sulfotransferases, although one isoform may exhibit greater enzyme efficiency than other isoforms. Similarly, inhibitors or enhancers of one isoform often affect other isoforms, but typically with different potency. This means that if the activity of one form of sulfotransferase is altered (either inhibited or enhanced) by the presence of a xenobiotic, the sulfonation of endogenous and xenobiotic substrates for other isoforms may well be affected. There are more examples of inhibitors than enhancers of sulfonation. Modulators of sulfotransferase enzymes include natural products ingested as part of the human diet as well as environmental chemicals and drugs. This review will discuss recent work on such interactions.

Biomarkers of endocrine disruption: cluster analysis of effects of plasticisers on Phase 1 and Phase 2 metabolism of steroids

Although some endocrine disruptors (EDs) act at steroid receptors, it is now apparent that compounds may have ED potential if they alter steroid synthesis or metabolism, particularly if they affect Phase 1 or Phase 2 pathways. In the ENDOMET project (EU-funded 5th Framework programme), 23 different assays were used on a wide range of EDs. Cluster analysis of the matrix results enabled identification of four integrated test systems that can be used to pinpoint compounds that are able to alter steroid metabolism or function. Critical pathways were shown to include oestrogen synthesis and sulphonation, synthesis of sulphate/PAPS and thyroid hormone regulation so that the activity profiles of some Phase 1 and Phase 2 reactions can be used as biomarkers for detection of compounds with ED potential.

Calponin gene expression in Chironomus riparius exposed to di(2-ethylhexyl) phthalate

Di(2-ethylhexyl) phthalate, which is a ubiquitous environmental contaminant because of its extensive use as a plasticizer, is a potential nongenotoxic carcinogen. To assess the effects of DEHP exposure on the cytoskeleton of Chironomus, we characterized full-length cDNA sequences of the calponin gene from Chironomus riparius. The expression of the calponin gene was analyzed during different life-history stages and under various DEHP concentrations for short and long periods. A phylogenetic investigation was then conducted to compare different orders of insects using sequence database analysis. The complete cDNA sequence of the calponin gene was found to be 555 bp in length. The results of phylogenetic analysis revealed that C. riparius calponin is most closely related to that of beetles. The basal level of calponin mRNA was highly expressed during different life-history stages. In addition, calponin gene expression decreased within 1 h of short-term exposure to DEHP, regardless of the concentration. We also investigated expression of the calponin gene following long-term exposure (10 days). Calponin gene expression was found to decrease significantly in C. riparius that were exposed to a low dose of DEHP, and this response was found to occur in a dose-dependent manner. Taken together, these results suggest that DEHP affects the functions of Ca(2+) binding muscle proteins such as calponin in Chironomus species.

Hepatic transcriptomic and metabolomic responses in the stickleback (Gasterosteus aculeatus) exposed to environmentally relevant concentrations of dibenzanthracene

A three-spined stickleback (Gasterosteus aculeatus) cDNA array and one-dimensional 1H nuclear magnetic resonance (NMR) spectroscopy-based metabolomics approach, together with individual biomarkers,were employed to investigate the responses of male sticklebacks to polycyclic aromatic hydrocarbon exposure. Fish were exposed to 1,2:5,6-dibenzanthracene (DbA) at concentrations between 0.01 and 50 microg per liter dissolved in the ambient water for four days, and hepatic transcript and metabolite profiles were determined in comparison with those of solvent-exposed controls. Induction of gene expression was apparent for cytochrome P450 1A (CYP1A) and CYP2-family monooxygenases and these responses were strongly correlated with DbA exposure concentrations (for CYP1A r > 0.996). Expression of suites of genes related to bile acid biosynthesis, steroid metabolism, and endocrine function were also affected, as demonstrated by gene ontology analyses. Expression changes in selected genes were confirmed by real-time PCR. Metabolomics highlighted notable changes in concentrations of taurine, malonate, glutamate, and alanine. These statistically significant responses to environmentally relevant concentrations of DbA at the transcriptomic and metabolomic levels provided sensitive markers characteristic of environmentally relevant low-level DbA exposure. Metabolic pathways were identified where both gene expression and metabolite concentrations were altered in response to DbA.

Characterization of heat shock protein 40 and 90 in Chironomus riparius larvae: effects of di(2-ethylhexyl) phthalate exposure on gene expressions and mouthpart deformities

Di(2-ethylhexyl) phthalate (DEHP) is a widely distributed phthalate that organisms are frequently exposed to due to its wide range of commercial and manufacturing uses as a plasticizer. Indeed, DEHP is often found in freshwater systems that receive domestic waste water discharges. Therefore, we evaluated the effects of DEHP on the mRNA levels of heat shock protein (HSP) 40 and 90 in chironomids. In addition, we evaluated the effects of exposure to DEHP on the induction of morphological deformities in chironomids. To accomplish this, partial sequences of HSP 40 and 90 from Chironomus riparius larvae were amplified and sequenced. The inferred amino acid sequences were then aligned with those of other insect HSP 40 and 90 genes. The results of this alignment revealed that there was a high degree of similarity among the homologues. In addition, the HSP 40 and 90 mRNA expressions were significantly upregulated in response to short and long-term exposure to DEHP at concentrations of 1, 10, and 30 microgL(-1). Furthermore, the occurrence of mouthpart deformities was significantly higher in chironomids that were treated with DEHP (12-20%) than in controls (3-5%). Taken together, these results indicate that HSP 40 and 90 play important roles in the physiological changes related to metabolism and cell protection that occur in C. riparius larvae that have been exposed to DEHP.

Expression of Chironomus riparius serine-type endopeptidase gene under di-(2-ethylhexyl)-phthalate (DEHP) exposure

Environmental stressors can induce changes in gene expression that can be useful as biomarkers. To identify potential biomarkers of water quality, we characterized full-length cDNA sequences of the serine-type endopeptidase (SP) gene from Chironomus riparius. Their expression was analyzed during different life-history stages and in response to treatment with various concentrations of di(2-ethylhexyl) phthalate (DEHP) for short and long periods of time. A comparative molecular and phylogenetic investigation was then conducted among different orders of insects using sequence database analysis. The sequence of the C. riparius SP gene was found to be most closely related to the sequence of SPs isolated from Aedes aegypti. In addition, the basal level of C. riparius SP mRNA was more highly expressed in larvae than in other life-history stages. However, the expression of C. riparius SP was primarily limited to the gut in larvae. When the effects of short-term exposure to DEHP were evaluated, C. riparius SP gene expression decreased within 1 h of treatment, regardless of dose. We also investigated expression of the C. riparius SP gene following long-term DEHP exposure (10 days) and found that it decreased significantly across all DEHP dosages. Finally, the response of the SP gene was more sensitive in C. riparius that were exposed to low concentrations of DEHP than in those that were exposed to high concentrations. These results show that suppression of the C. riparius SP gene by DEHP is as a potential biomarker that could be useful for monitoring aquatic quality.

Pentachlorophenol and other chlorinated phenols are substrates for human hydroxysteroid sulfotransferase hSULT2A1

Pentachlorophenol (PCP) is a persistent chemical contaminant that has been extensively investigated in terms of its toxicology and metabolism. Similar to PCP, other chlorinated phenol derivatives are also widely present in the environment from various sources. Even though some of the chlorine-substituted phenols, and particularly PCP, are well-known inhibitors of phenol sulfotransferases (SULTs), these compounds have been shown to undergo sulfation in humans. To investigate the enzymatic basis for sulfation of PCP in humans, we have studied the potential for PCP as well as the mono-, di-, tri-, and tetra-chlorinated phenols to serve as substrates for human hydroxysteroid sulfotransferase, hSULT2A1. Our results show that all of these compounds are substrates for this isoform of sulfotransferase, and the highest rates of sulfation are obtained with PCP, trichlorophenols, and tetrachlorophenols. Much lower rates of sulfation were obtained with isomers of monochlorophenol and dichlorophenol as substrates for hSULT2A1. Thus, the sulfation of polychlorinated phenols catalyzed by hSULT2A1 may be a significant component of their metabolism in humans.

Phytoestrogens and xenoestrogens: the contribution of diet and environment to endocrine disruption

Some endocrine disrupting compounds such as phthalates and phenols act non-genomically by inhibiting the sulfotransferase (SULT 1E1 and SULT 1A1) isoforms which inactivate estrogens by sulfonation. A range of environmental phenolic contaminants and dietary flavonoids was tested for inhibition of the human SULT 1A1, 1E1 and 2A1 isoforms. In particular, the plasticisers 4-n-octyl- and 4-n-nonyl-phenol inhibit SULT 1E1 with IC(50) values of 0.16 microM vs. 10nM estradiol while the 2-substituted chlorophenols show similar values. Flavonoids are also SULT inhibitors; tricin is a competitive inhibitor of SULT 1E1 with a K(i) of 1.5+/-0.8 nM. In a small pilot study to determine whether ingestion of soy flavonoids would affect SULT1A1 activity in vivo as well as in vitro, sulfonation of daidzein was reduced in a group of women 'at risk' of breast cancer, as compared with controls, although the SULT 1A1*1/SULT 1A1*2 allele ratio was not different. Endocrine disrupting effects in man may be multifactorial when components from both the diet and the environment act at the same point in steroid metabolism.

Endocrine disrupters: a human risk?

Endocrine disrupters (EDs) alter normal hormonal regulation and may be naturally occurring or environmental contaminants. Classically, EDs act genomically, with agonistic or antagonistic effects on steroid receptors and may alter reproductive function and/or cause feminisation by binding to oestrogen or androgen receptors; their binding to the thyroid receptor may dysregulate the neuroendocrine system. Recently, it has been shown that EDs can also act by non-genomic mechanisms, altering steroid synthesis (inhibition of cytochrome P450 isoforms) or steroid metabolism. The alkylphenol and phthalate plasticisers inhibit the inactivation of oestrogens by sulphation (via SULT 1A1 and 1E1 isoforms) and so cause a rise in levels of the free active endogenous oestrogens. A range of ED effects have been shown in mammals, fish, birds, reptiles, amphibia and aquatic invertebrates but it is not yet clear whether these processes also occur in human beings. It is evident that EDs, as well as altering reproduction, can cause changes in neurosteroid levels and so have the potential to affect immune function, behaviour and memory. This may be of long-term concern since traces of EDs such as plasticisers, brominated fire retardants, sunscreen agents and cosmetic ingredients are widely distributed in the environment and in human biofluids.