Imposex assessment and tributyltin levels in sediments along the Atlantic coast of South Africa

Subacute tributyltin exposure alters the development and morphology of mammary glands in association with CYP19A1 expression in female rats

Tributyltin (TBT) is an endocrine-disrupting chemical (EDC) related to reproductive dysfunctions. However, few studies have investigated the effects of TBT exposure on mammary gland development. Thus, we assessed whether subacute TBT exposure causes irregularities in mammary gland development. We administered TBT (100 and 1,000 ng/kg/day for 30 days) to female rats from postnatal day (PND) 25 to PND 55, and mammary gland development, morphology, inflammation, collagen deposition, and protein expression were evaluated. Abnormal mammary gland development was observed in both TBT groups. Specifically, TBT exposure reduced the number of terminal end buds (TEBs), type 1 (AB1) alveolar buds, and type 2 (AB2) alveolar buds. An increase in the lobule and differentiation (DF) 2 score was found in the mammary glands of TBT rats. TBT exposure increased mammary gland blood vessels, mast cell numbers, and collagen deposition. Additionally, both TBT rats exhibited intraductal hyperplasia and TEB-like structures. An increase in estrogen receptor alpha (ERα), progesterone receptor (PR), and cytochrome P450 family 19 subfamily A member 1 (CYP19A1) - positive cells was observed in the mammary glands of TBT rats. A strong negative correlation was observed between CYP19A1- positive cells and TEB number. In addition, CYP19A1 - positive cells were positively correlated with mammary gland TEB-like structure, ductal hyperplasia, inflammation, and collagen deposition. Thus, these data suggest that TBT exposure impairs mammary gland development through the modulation of CYP19A1 signaling pathways in female rats.

MCF-7 cell - derived exosomes were involved in protecting source cells from the damage caused by tributyltin chloride via transport function

Tributyltin chloride (TBTC) is a ubiquitous environmental pollutant with various adverse effects on human health. Exosomes are cell - derived signaling and substance transport vesicles. This investigation aimed to explore whether exosomes could impact the toxic effects caused by TBTC via their transport function. Cytotoxicity, DNA and chromosome damage caused by TBTC on MCF-7 cells were analyzed with CCK-8, flow cytometry, comet assay and micronucleus tests, respectively. Exosomal characterization and quantitative analysis were performed with ultracentrifugation, transmission electron microscope (TEM) and bicinchoninic acid (BCA) methods. TBTC content in exosomes was detected with Liquid Chromatography-Mass Spectrometry (LC-MS). The impacts of exosomal secretion on the toxic effects of TBTC were analyzed. Our data indicated that TBTC caused significant cytotoxicity, DNA and chromosome damage effects on MCF-7 cells, and a significantly increased exosomal secretion. Importantly, TBTC could be transported out of MCF-7 cells by exosomes. Further, when exosomal secretion was blocked with GW4869, the toxic effects of TBTC were significantly exacerbated. We concluded that TBTC promoted exosomal secretion, which in turn transported TBTC out of the source cells to alleviate its toxic effects. This investigation provided a novel insight into the role and mechanism of exosomal release under TBTC stress.

Contaminant occurrence, water quality criteria and tiered ecological risk assessment in water: A case study of antifouling biocides in the Qiantang River and its estuary, Eastern China

Antifouling biocides may cause adverse effects on non-target species. This study aims to determine the distribution, sources, and ecological risks of antifouling biocides in the surface waters of the Qiantang River and its estuary in eastern China. The concentrations of total antifouling biocides were ranged from 12.9 to 215 ng/L for all water samples. Atrazine, diuron and tributyltin were the major compounds in the water bodies of the study area. The acute and chronic toxicity criteria for tributyltin, diuron and atrazine were derived for freshwater and saltwater, respectively, based on the species sensitivity distribution approach. The freshwater and saltwater criteria were slightly different, and the toxicity to aquatic organisms could be summarized as tributyltin > diuron > atrazine. The graded ecological risk rating showed that the long-term risk of TBT was significant in coastal waters. The pollution of TBT in the Qiantang River deserves further attention.

Toxicity of antifouling biocides on planktonic and benthic neotropical species

Organotin-based (OTs: TBT and TPT) antifouling paints have been banned worldwide, but recent inputs have been detected in tropical coastal areas. However, there is a lack of studies evaluating the toxicity of both legacy and their substitute antifouling booster biocides (e.g., Irgarol and diuron) on neotropical species. Therefore, the acute toxicity of four antifouling biocides (TBT, TPT, Irgarol, and diuron) was investigated using the marine planktonic organisms Acartia tonsa and Mysidopsis juniae, the estuarine tanaid Monokalliapseudes schubarti (water exposure), and the burrowing amphipod Tiburonella viscana (spiked sediment exposure). Results confirmed the high toxicity of the OTs, especially to planktonic species, being about two orders of magnitude higher than Irgarol and diuron. Toxic effects of antifouling compounds were observed at levels currently found in tropical coastal zones, representing a threat to planktonic and benthic invertebrates. Furthermore, deterministic PNEC_{marine sediment} values suggest that environmental hazards in tropical regions may be higher due to the higher sensitivity of tropical organisms. Since regulations on antifouling biocides are still restricted to a few countries, more ecotoxicological studies are needed to derivate environmental quality standards based on realistic scenarios. The present study brings essential contributions regarding the ecological risks of these substances in tropical and subtropical zones.

Subacute and low dose of tributyltin exposure leads to brown adipose abnormalities in male rats

Tributyltin (TBT) is an obesogenic endocrine disrupting chemical (EDC) linked with several metabolic complications. Brown adipose tissue (BAT) is the principal site for thermogenesis, making it a potential target for obesity management and metabolic disease. However, few studies have evaluated TBT effect on BAT function. In this investigation, we assessed whether subacute (15 days) and low dose of TBT exposure (100 ng/kg/day) results in abnormal BAT morphophysiology in adult male rats. Body temperature, BAT morphology, inflammation, oxidative stress, collagen deposition and BAT metabolic gene expression markers were assessed in room temperature (Room, ∼24 ºC) and after cold tolerance test (Cold, ∼4 ºC) conditions. A reduction in body temperature was observed in both Room and Cold conditions in TBT rats, suggesting abnormal BAT thermogenic function. Changes in BAT morphology were observed in TBT rats, with an increase in BAT lipid accumulation, an increase in BAT unilocular adipocyte number and a decrease in BAT multilocular adipocyte number in Room condition. All these parameters were opposite in Cold condition TBT rats, leading to a borderline increase in BAT UCP1 protein expression. An increase in BAT mast cell number was observed in TBT rats in Room condition. An increase in ED1 protein expression (macrophage marker) was observed in TBT rats in Cold condition. Oxidative stress and collagen deposition increased in both Room and Cold conditions in TBT rats. TBT exposure caused a borderline increase in BAT COL1A1 protein expression in Cold condition. Further, strong negative correlations were observed between body temperature and BAT lipid accumulation, and BAT lipid accumulation and multilocular adipocyte number. Thus, these data suggest that TBT exposure impaired BAT morphophysiology through impacts on lipid accumulation, inflammation, fibrosis and oxidative stress in male rats.

Water quality criteria derivation and tiered ecological risk evaluation of antifouling biocides in marine environment

This study provides a comprehensive compilation of published toxicological and environmental data further used to assess the ecological risks of six antifouling biocides, including tributyltin (TBT), Irgarol 1051, Diuron, Chlorothalonil, 4,5-Dichloro-N-octyl-3(2H)-isothiazolone (DCOIT), and Dichlofluanid. The standard maximum concentration and standard continuous concentration of antifouling biocides were derived by the species susceptibility distribution method. Following that, the ecological risk assessment of antifouling biocides in the aquatic environment was conducted using the hazard quotient, margin of safety, joint probability curve, and Monte Carlo random sampling method. The following is a concise list of the antifouling biocide dangers associated with acute and chronic risks: Irgarol 1051 > TBT > Diuron > DCOIT > Chlorothalonil > Dichlofluanid. It is strongly advised that systematic and ongoing monitoring of these biocides in coastal areas take place, as well as the creation of acceptable and efficient environmental protection measures, to safeguard the coastal environment's services and functions.

Metals and co-presence of other pollutants in mussels (Perna perna) around Algoa Bay: Human consumption safety concerns

Elevated metal concentrations can become harmful to marine organisms and to humans that consume them. Metal concentrations at multiple sites around Algoa Bay, South Africa, were last investigated in the 1980s. We collected wild brown mussels (Perna perna) from seven sites around Algoa Bay, and quantified metallic elements using ICPMS. Metallic element concentrations differed significantly among the sampling sites and correlated with pollution sources at specific sites. The concentration of Pb in mussels at one site slightly exceeded South African limits. Based on the South African estimated daily intake, the target hazard quotient, and South African metal limits, mussels from Algoa Bay are safe for human consumption, except possibly from one site. However, combined with data on bisphenols and benzophenone UV filters in P. perna from the same sites, we suggest a possible health concern to consumers.

Tributyltin and the female hypothalamic-pituitary-gonadal disruption

The hypothalamic-pituitary-gonadal (HPG) axis is the principal modulator of reproductive function. Proper control of this system relies on several hormonal pathways, which make the female reproductive components susceptible to disruption by endocrine-disrupting chemicals such as tributyltin (TBT). Here, we review the relevant research on the associations between TBT exposure and dysfunction of the female HPG axis components. Specifically, TBT reduced hypothalamic gonadotropin-releasing hormone (GnRH) expression and gonadotropin release, and impaired ovarian folliculogenesis, steroidogenesis, and ovulation, at least in part, by causing abnormal sensitivity to steroid feedback mechanisms and deleterious ovarian effects. This review covers studies using environmentally relevant doses of TBT in vitro (1 ng-20 ng/mL) and in vivo (10 ng-20 mg/Kg) in mammals. The review also includes discussion of important gaps in the literature and suggests new avenue of research to evaluate the possible mechanisms underlying TBT-induced toxicity in the HPG axis. Overall, the evidence indicates that TBT exposure is associated with toxicity to the components of the female reproductive axis. Further studies are needed to better elucidate the mechanisms through which TBT impairs the ability of the HPG axis to control reproduction.

Distribution of Butyltin Compounds in the Coastal Environment of the Bahía Blanca Estuary, Argentina

This study evaluates for the first time the distribution and accumulation of butyltin compounds (BTs) in different compartments such as seawater, sediments, suspended particulate matter (SPM), and mussels (Brachidontes rodriguezii) in the Bahía Blanca estuary. The samples were collected from six sampling sites with different anthropogenic impacts. A better visualization and interpretation of data was achieved using chemometric tools (Tucker4 model), which made it possible to reveal the main relationships among the variables. This analysis showed the presence of BTs in all the estuarine environmental compartments, even in sites with low human intervention. The relationships found among BTs levels, seasons, and environmental matrices show the importance of biological processes such as phytoplankton blooms and remobilization of sediments (by tidal dynamics and/or periodic dredging) in BTs distribution and degradation. In addition, partition coefficients showed that mussels mainly bioaccumulate tributyltin from sediment, water and, to a lesser extent, SPM.

Tributyltin and high-refined carbohydrate diet lead to metabolic and reproductive abnormalities, exacerbating premature ovary failure features in the female rats

Exposure to the obesogen tributyltin (TBT) alone or high carbohydrate diet (HCD) alone leads to obesity and reproductive complications, such as premature ovary failure (POF) features. However, little is known about interactions between TBT and nutrition and their combined impact on reproduction. In this study, we assessed whether acute TBT and HCD exposure results in reproductive and metabolic irregularities. Female rats were treated with TBT (100 ng/kg/day) and fed with HCD for 15 days and metabolic and reproductive outcomes were assessed. TBT and HCD rats displayed metabolic impairments, such as increased adiposity, abnormal lipid profile and triglyceride and glucose (TYG) index, worsening adipocyte hypertrophy in HCD-TBT rats. These metabolic consequences were linked with reproductive disorders. Specifically, HCD-TBT rats displayed irregular estrous cyclicity, high follicle-stimulating hormone (FSH) levels, low anti-Müllerian hormone (AMH) levels, reduction in ovarian reserve, and corpora lutea (CL) number, with increases in atretic follicles, suggesting that HCD-TBT exposure exacerbated POF features. Further, strong negative correlations were observed between adipocyte hypertrophy and ovarian reserve, CL number and AMH levels. HCD-TBT exposure resulted in reproductive tract inflammation and fibrosis. Collectively, these data suggest that TBT plus HCD exposure leads to metabolic and reproductive abnormalities, exacerbating POF features in female rats.

Are antifouling residues a matter of concern in the largest South American port?

In the present study, levels of booster biocides (diuron, Irgarol, chlorothalonil, dichlofluanid and DCOIT), butyltin compounds (TBT, DBT and MBT) and antifouling paint particles (APPs) were assessed in sediments of areas under the influence of the largest Latin American port, marinas, boat traffic and ship/boat maintenance facilities located within Santos-São Vicente Estuarine System (SSES). Contamination profile was directly related to local maritime activities, where sediments from the main navigation channel (MNC) presented low levels of antifouling residues while adjacent areas (AA), characterized by the presence of boats and boatyards, showed higher contamination considering all analyzed residues. Moreover, areas under the influence of fishing boats/yards presented relevant levels of butyltins (ΣBTs > 300 ng g^-1) and APPs (>100 μg g^-1), while marinas dominated by recreational boats showed higher booster biocides occurrence. Sites located nearby shipyards in the MNC and boatyards in the AA presented expressive amounts of APPs (>200 μg g^-1). These APPs represent an important long-term source of biocides to the SSES. Thus, the profile of maritime activities in association to local oceanographic conditions drive the spatial distribution of antifouling residues within SESS, which in some case presented levels above sediment guidelines for TBT, DCOIT and diuron.

A mass spectrometry-based approach gives new insight into organotin-protein interactions

In this study, the combination of speciation analysis and native mass spectrometry is presented as a powerful tool to gain new insight into the diverse interactions of environmentally relevant organotin compounds (OTCs) with proteins. Analytical standards of model proteins, such as β-lactoglobulin A (LGA), were thereby incubated with different phenyl- and butyltins. For adduct identification and characterization, the incubated samples were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and electrospray ionization-mass spectrometry (ESI-MS) in combination with size exclusion chromatography (SEC). It allowed for a mild separation, which was most crucial to preserve the acid-labile organotin-protein adducts during their analyses. The binding of triorganotin compounds, such as triphenyltin, was shown to be sulfhydryl-directed by using cysteine-specific protein labeling. However, the sole availability of reduced cysteine residues in proteins did not automatically enable adduct formation. This observation complements previous studies and indicates the necessity of a highly specific binding pocket, which was identified for the model protein LGA via enzymatic digestion experiments. In contrast to triorganotins, their natural di- and mono-substituted degradation products, such as dibutyltin, revealed to be less specific regarding their binding to several proteins. Further, it also did not depend on reduced cysteine residues within the protein. In this context, they can probably act as linker molecules, interconnecting proteins, and leading to dimers and probably to higher oligomers. Furthermore, dibutyltin was observed to induce hydrolysis of the protein's peptide backbone at a specific site. Concerning unknown long-term toxic effects, our studies emphasize the importance of future studies on di- and mono-substituted OTCs.

Survey of imposex in Nucella lapillus as an indicator of tributyltin pollution in Northern Irish coastal waters, 2004 to 2017

Tributyltin (TBT) was a commonly used biocide in anti-fouling paints for marine vessels, however, it had negative impacts on non-target species, including causing imposex in dogwhelks (Nucella lapillus). Since the 1980s, legislation has been introduced to curtail its usage, culminating in a ban by the International Maritime Organisation (IMO) in 2008. In 2004 a national imposex monitoring network was established in Northern Ireland to determine the level and extent of TBT pollution. The level of imposex in N. lapillus was assessed according to the degree of male sexual development in the female using three measures: percentage of imposex-affected females (%I), the relative penis size index (RPSI), and the vas deferens sequence index (VDSI). All sites showed improvement since the initial survey with a reduction in imposex and an improvement in ecological quality under the classification of the Convention for the Protection of the Marine Environment of the North-East Atlantic (OSPAR).

RXR Expression in Marine Gastropods with Different Sensitivity to Imposex Development

The superposition of male sexual characteristics in female marine gastropods (imposex) represents one of the clearest ecological examples of organotin-mediated endocrine disruption. Recent evidences suggest that signaling pathways mediated by members of the nuclear receptor superfamily, RXR and PPARγ, are involved in the development of this pseudohermaphroditic condition. Here, we identified significant differences in RXR expression in two caenogastropod species from Nuevo Gulf, Argentina, Buccinanops globulosus and Trophon geversianus, which present clear contrast in imposex incidence. In addition, B. globulosus males from a polluted and an unpolluted area showed differences in RXR expression. Conversely, PPARγ levels were similar between both analyzed species. These findings indicate specie-specific RXR and PPARγ expression, suggesting a major role of RXR in the induction of imposex.

Tributyltin and triphenyltin induce 11β-hydroxysteroid dehydrogenase 2 expression and activity through activation of retinoid X receptor α

Exposure to the environmental pollutants organotins is of toxicological concern for the marine ecosystem and sensitive human populations, including pregnant women and their unborn children. Using a placenta cell model, we investigated whether organotins at nanomolar concentrations affect the expression and activity of 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2). 11β-HSD2 represents a placental barrier controlling access of maternal glucocorticoids to the fetus. The organotins tributyltin (TBT) and triphenyltin (TPT) induced 11β-HSD2 expression and activity in JEG-3 placenta cells, an effect confirmed at the mRNA level in primary human trophoblast cells. Inhibition/knock-down of retinoid X receptor alpha (RXRα) in JEG-3 cells reduced the effect of organotins on 11β-HSD2 activity, mRNA and protein levels, revealing involvement of RXRα. Experiments using RNA and protein synthesis inhibitors indicated that the effect of organotins on 11β-HSD2 expression was direct and caused by increased transcription. Induction of placental 11β-HSD2 activity by TBT, TPT and other endocrine disrupting chemicals acting as RXRα agonists may affect placental barrier function by altering the expression of glucocorticoid-dependent genes and resulting in decreased availability of active glucocorticoids for the fetus, disturbing development and increasing the risk for metabolic and cardiovascular complications in later life.