Tributyltin Research Articles

Evaluation of female masculinization in Pomacea canaliculata (Caenogastropoda, Ampullariidae) induced by tributyltin, heavy metals, and uranium in culture water.

All female Pomacea canaliculata develop a small, male-like copulatory apparatus a few days after birth, which growths slowly until sexual maturity, and even further in older age. Previous studies have found trace elements like mercury (Hg), arsenic (As) and uranium (U) in tap water used for snail culture, and that these elements were accumulated in snail tissues. Here, we test whether the presence of these metals at maximum allowed concentrations (Environmental Protection Agency - EPA) in aquarium water could affect the development of the copulatory apparatus in mature females. Females of different ages were used as controls, grown in reconstituted metal-free water with or without the addition of Hg, As and U, as well as tributyltin (TBT), a compound used as masculinizing agent. Six and seven months old females cultured in tap water showed a longer penis and penile sheath, and a greater overall development of the copulatory apparatus, measured by an index (DI), as compared with same-age females cultured in reconstituted water. Moreover, when females were exposed to Hg, As or U at the maximum contaminant levels for human consumption allowed by EPA regulations, there was no further development of the copulatory apparatus, while there was a clearly positive effect in TBT-exposed females. This study confirms the masculinizing effect of organotin compounds on female copulatory apparatus and discusses the usefulness of the development of these organs as a bioindicator of environmental pollution.

IChip increases the success of cultivation of TBT-resistant and TBT-degrading bacteria from estuarine sediment

Standard methods of microbial cultivation only enable the isolation of a fraction of the total environmental bacteria. Numerous techniques have been developed to increase the success of isolation and cultivation in the laboratory, some of which derive from diffusion chambers. In a diffusion chamber, environmental bacteria in agar medium are put back in the environment to grow as close to their natural conditions as possible, only separated from the environment by semi-permeable membranes. In this study, the iChip, a device that possesses hundreds of mini diffusion chambers, was used to isolate tributyltin (TBT) resistant and degrading bacteria. IChip was shown to be efficient at increasing the number of cultivable bacteria compared to standard methods. TBT-resistant strains belonging to Oceanisphaera sp., Pseudomonas sp., Bacillus sp. and Shewanella sp. were identified from Liverpool Dock sediment. Among the isolates in the present study, only members of Pseudomonas sp. were able to use TBT as a sole carbon source. It is the first time that members of the genus Oceanisphaera have been shown to be TBT-resistant. Although iChip has been used in the search for molecules of biomedical interest here we demonstrate its promising application in bioremediation.

Effects of tributyltin (TBT) on the intermediate metabolism of the crab Callinectes sapidus

This study investigated if the exposure to tributyltin (TBT), a chemical used worldwide in boat antifouling paints, could result in metabolic disturbances in the blue crab Callinectes sapidus. After the exposure to TBT 100 or 1000 ng.L−1 for 48 and 96 h, hemolymph and tissues were collected to determine the concentration of metabolites and lipid peroxidation. The levels of glucose, lactate, cholesterol, and triglycerides in the hemolymph were not affected by TBT exposure. Hemolymph protein and heart glycogen increased in the crabs exposed to TBT 1000 for 96 h. Anterior gills protein and lipoperoxidation decreased after 96 h in all groups. These results suggest that C. sapidus can maintain energy homeostasis when challenged by the TBT exposure for 48 h and that metabolic alterations initiate after 96 h.

Contribution to the determination of tributyltin in water by stir bar sorptive extraction‒thermal desorption‒gas chromatography‒tandem mass spectrometry

An environmentally friendly method was developed to determine tributyltin (TBT) in water at the levels required by the European Union Water Framework Directive (EU WFD) using stir bar sorptive extraction (SBSE) in combination with thermal desorption‒gas chromatography‒triple quadrupole tandem mass spectrometry. The main focus of the method development was on addressing some aspects of reducing blank values (minimizing the use of chemicals, glassware cleaning, pretreatment of sorptive stir bars) and optimizing the SBSE procedure variables (sample volume, polarity of sample solution, extraction time). The performance of the method was studied in terms of linearity, matrix effect, method limits and accuracy (precision and trueness) using MilliQ, tap and surface water. TBT quantification limit for the studied matrices ranged from 0.049 to 0.055 ng L‒1 and repeatability (RSD%, n = 10) and recovery at the environmental quality standard (EQS) concentration of 0.2 ng L‒1 were in the range of 6‒18% and 88‒107%, respectively, indicating good performance of the method. The matrix effect of river water (‒78%) and artificial seawater (‒83%) compared to MilliQ water showed the necessity to use a matrix-matched calibration when analysing TBT in surface water samples. The developed sample preparation was further evaluated for greenness using the recently introduced AGREEprep assessment, which revealed a much greener performance of the proposed method over the compared CEN/TS 16692 method. The method meets the requirements of the EU WFD and is suitable for monitoring, evaluation and classification of the chemical status of surface waters.

Organotins in a food web from the Three Gorges Reservoir, China: Trophic enrichment and potential health risk

Triphenyltin (TPhT) and tributyltin (TBT) remain widely present in various aquatic environments despite restrictions on their use in many countries for many years. The biomagnification of these compounds in the aquatic food web remains controversial. This study reports the bioaccumulation of TPhT and TBT in aquatic animals in the Three Gorges Reservoir (TGR), a deep-water river channel-type reservoir and the largest reservoir in China. We measured TPhT, TBT and their metabolites in 2 invertebrates, 27 fish and the aquatic environment. The logarithmic bioaccumulation factors of TPhT and TBT were 4.37 and 3.77, respectively, indicating that TPhT and TBT were enriched in organisms of the TGR. Both TPhT and TBT concentrations were significantly and positively correlated with trophic level, with trophic magnification factors of 3.71 and 3.63, respectively, indicating that TPhT and TBT exhibited similar trophic enrichment in the freshwater food web of the TGR. The results of health risk assessment showed that although all hazard index (HI) values were <1, more attention should be paid to the health risk to children associated with consumption of aquatic products (HI = 0.67). This study provides powerful evidence of trophic enrichment of TPhT and TBT in a freshwater food web in a deep-water river channel-type reservoir and provides valuable data regarding organotins in aquatic animals in the TGR.

Toxicological Effects of Tributyltin in Zebrafish (Danio rerio) Embryos

Tributyltin (TBT) is known as an endocrine-disrupting chemical abundant in the aquatic environment. In the present study, zebrafish fish embryos were used to observe the chronic toxicity of TBT. Fish embryo toxicity analysis was carried out for different TBT concentrations (100, 50, 25, 12.5, 6.2, and 3.1 ng/L) and fertilized eggs were used to test each concentration effect. Fertilized eggs in 24-well plates (20 eggs in each well) were incubated at 26°C for four days and embryo coagulation, heartbeat of the embryo and mortality lethal endpoints (LC50 values) were recorded after 8, 24, 48, and 96 h. The results revealed that 100% coagulations of the embryos occurred at TBT doses of 50 and 100 ng/L. The coagulation significantly increased in a dose-dependent manner and TBT might induce coagulation of zebrafish embryos. Heartbeat changes were significantly decreased (p&lt;0.05) in a dose-dependent manner at different TBT doses. LC50 values of TBT for zebrafish embryos were 19.9, 11.7, 7.3, and 5.2 ng/L at 8, 24, 48, and 96 h, respectively. The percentage of mortality was higher in embryos for the trace level of TBT, indicating that embryos are more sensitive to TBT toxicity. Hence, TBT is highly toxic and leads to a lethal effect on the zebrafish embryo, resulting in species extinction and declining biodiversity in the aquatic environment.

Environmentally relevant dose of the endocrine disruptor tributyltin disturbs redox balance in female thyroid gland

Tributyltin (TBT) is an endocrine disruptor used as a biocide in nautical paints. Even though many TBT effects in marine species are known, data in mammals are scarce, especially regarding the thyroid gland. The present study aimed to evaluate the effect of a subchronic exposure to TBT on thyroid oxidative stress of female Wistar rats. Rats received vehicle (control group), 200 or 1000 ng TBT/kg body weight/day for 40 days. After euthanasia, one part of the thyroids were collected in order to assess iodide uptake; activity and/or mRNA expression of thyroperoxidase (TPO) and dual oxidases (DUOXs); activity and/or mRNA expression of catalase, glutathione peroxidase, superoxide dismutase and NADPH oxidase 4 (CAT, GPx, SOD and NOX4); 4-hydroxynonenal (4-HNE) expression and total thiol groups levels; and mRNA expression of estrogen receptors alpha and beta (ERα and ERβ). The remaining part of the thyroid was processed for morphological analysis of estrogen receptor alpha (ERα) and for collagen deposition. Iodide uptake was not changed with treatments. TPO activity and expression were increased in the TBT1000 group (259.81% and 95.17%). The activity, but not mRNA, of CAT (17.36% TBT200; 27.10% TBT1000) and GPx (29.24% TBT200; 28.97% TBT1000) were decreased by TBT. SOD and NADPH oxidase activity, as well as thiol group and 4-HNE levels remained unchanged. Interstitial collagen deposition increased in the TBT200 group (39.54%). The mRNA expression of ERα increased in TBT-treated rats (44.87% TBT200; 36.43% TBT1000), while protein expression was increased but not reaching significance (TBT1000, p = 0.056) by TBT. Therefore, our results show that TBT increases TPO expression and reduces antioxidant enzyme activities in the thyroid gland leading to oxidative stress. Some of these effects could be mediated by the ERα pathway.

Synthesis of an Organotin Specific Molecularly Imprinted Polymer for Organotin Passive Sampling in Seawater

Environmental contaminations can sometimes be difficult to measure, particularly in complex matrices such as seawater. This is the case of organotin compounds (OSn) such as the monobutyltin (MBT), dibutyltin (DBT), and tributyltin (TBT), whose range of polarity is wide. These compounds, mostly coming from antifouling paints used on ship shell, can be found in water and sediments where they are stable and can persist for years. Passive sampling is gaining in interest to offer solutions to monitor these kinds of compounds even in low concentrations. However, due to the diversity of pollutants present in the environment nowadays, it is important to propose solutions that allow a specific sampling. This work aims to highlight the usability of molecularly imprinted polymers (MIPs) in passive sampling for the monitoring of OSn. MIPs were synthetized using three synthesis ways (bulk, suspension, and mini-emulsion processes) and kinetics were realized in order to estimate the retention of OSn by the solid MIP phase. Results highlighted a good retention of OSn with mean retention kinetic constants near 10−5, 10−6 and 10−7 L·ng·s−1 for DBT, TBT and MBT respectively. The synthesis mode showed no impact on retention kinetics, therefore, bulk synthesis is recommended because of its simplicity. If the elimination of OSn from MIPs is to be optimized, the retention of OSn on MIPs has been demonstrated, and is very promising for their use in specific passive samplers.

Tributyltin in Wastewater: Influence on the Performance of Suspended Growth Biological Processes

The aim of this study was to evaluate the potential effect of tributyltin (TBT) on the performance of suspended-growth biological processes. The influence of TBT was evaluated for (i) the endogenous and exogenous respirations of heterotrophic micro-organisms in laboratory-scale batch reactors, taken from a municipal wastewater treatment plant and (ii) chemical oxygen demand (COD) removal, sludge production and oxygen consumption of a pilot-sale membrane bioreactor (MBR) system inoculated with heterotrophic micro-organisms taken from a MBR system. The batch experiments showed that the presence of TBT was likely to modify the activity of bacterial populations in endogenous conditions. The increase in endogenous oxygen needs suggested an increase in the maintenance requirements, essentially to manage the chemical stress induced by the presence of TBT. If the addition of TBT did not perturb COD removal in an MBR system, it limited sludge production and increased oxygen requirements; it is assumed that these modifications were linked with the necessity for the biomass to adapt in this stressful environment, as reflected by an increase in the maintenance requirements. These results emphasised that the respiratory activity of the bacterial cultures was modified by the presence of TBT, in the sense that an excess of oxygen was required to adapt to this chemical stress.

In Vitro Assays to Identify Metabolism-Disrupting Chemicals with Diabetogenic Activity in a Human Pancreatic β-Cell Model.

There is a need to develop identification tests for Metabolism Disrupting Chemicals (MDCs) with diabetogenic activity. Here we used the human EndoC-βH1 β-cell line, the rat β-cell line INS-1E and dispersed mouse islet cells to assess the effects of endocrine disruptors on cell viability and glucose-stimulated insulin secretion (GSIS). We tested six chemicals at concentrations within human exposure (from 0.1 pM to 1 µM). Bisphenol-A (BPA) and tributyltin (TBT) were used as controls while four other chemicals, namely perfluorooctanoic acid (PFOA), triphenylphosphate (TPP), triclosan (TCS) and dichlorodiphenyldichloroethylene (DDE), were used as “unknowns”. Regarding cell viability, BPA and TBT increased cell death as previously observed. Their mode of action involved the activation of estrogen receptors and PPARγ, respectively. ROS production was a consistent key event in BPA-and TBT-treated cells. None of the other MDCs tested modified viability or ROS production. Concerning GSIS, TBT increased insulin secretion while BPA produced no effects. PFOA decreased GSIS, suggesting that this chemical could be a “new” diabetogenic agent. Our results indicate that the EndoC-βH1 cell line is a suitable human β-cell model for testing diabetogenic MDCs. Optimization of the test methods proposed here could be incorporated into a set of protocols for the identification of MDCs.

Energetic metabolic reprogramming in Jurkat DFF40-deficient cancer cells.

DNA fragmentation factor 40 (DFF40), or the caspase-activated DNase (CAD), is an endonuclease specific for double-stranded DNA. Alterations in its function and expression have been linked to apoptosis resistance, a mechanism likely used by cancer cells. However, how the DFF40-related apoptosis resistance pathway occurs remains unclear. Here, we sought to determine if DFF40 expression could be linked to cell metabolism through the regulation of mitochondrial integrity and function. We demonstrated that DFF40-deficient cells are more resistant to staurosporine and tributyltin (TBT)-induced apoptosis, and express higher levels of Mcl-1 at basal state. Treatment with TBT induces higher Bcl-2 and caspase-9 mRNA transcripts in DFF40 KO Jurkat cells, as well as enhanced Bcl-2 phosphorylation. A loss of DFF40 expression induces a higher mitochondrial mass, mtDNA copy number, mitochondrial membrane potential, and glycolysis rates in resting T cells. DFF40-deficient cells exhibit the Warburg effect phenotype, where they rely significantly more on glycolysis than oxidative phosphorylation and have a higher proliferative state, demonstrated by a higher Ki-67 transcription factor expression and AKT phosphorylation. Finally, we demonstrated with cell fractioning that DFF40 can translocate to the mitochondria following apoptosis induction. Our study reveals that DFF40 may act as a regulator of mitochondria during cell death and its loss could compromise mitochondrial integrity and cause an energetic reprogramming in pathologies such as cancer.

Tributyltin inhibits development of pubertal Leydig cells in rats

Tributyltin (TBT) is extensively applied as an antifouling mediator, and it is well-known as an endocrine disrupting chemical. However, it remains elusive whether TBT can affect the development of pubertal Leydig cells (LCs), as a part of its endocrine mechanism of action. In this study, male Sprague Dawley rats (35-day-old) orally received TBT (0, 1, or 5 mg/kg) for 24 days. Immature LCs (ILCs) were separated from 35-day-old rats, and the cells were exposed to TBT at various concentrations (0, 0.05, 0.5, 1, or 5 μM) for 24 h. In vivo TBT treatment decreased the number of LCs and inhibited androgen production (2.92 ± 0.44, 1.16 ± 0.29, and 0.67 ± 0.10 ng/ml after treatment with TBT at 0, 1, and 5 mg/kg, respectively). In vitro TBT treatment reduced androgen production, cell viability, and cell cycle progression, while increased the levels of reactive oxygen species (ROS) along with subsequent apoptosis, particularly at the concentration of 5 μM. According to in vitro and in vivo findings, TBT downregulated the expression levels of genes that could control steroidogenesis (Hsd17b3, Scarb1, Hsd3b1, and Star), and decreased protein levels due to potential reduction of NR5A1 (Nr5a1). In summary, TBT inhibited cholesterol transport and activities of certain steroidogenic enzymes, thereby leading to the reduction of androgen production.

Biofouling and Mitigation Methods: A Review

Biofouling accumulates living organisms on surfaces in contact with the water and causes significant economic, structural, and microbial problems on ship hulls, piers, oil rigs, power plants, pipework, water treatment facilities as well as medical devices. In order to mitigate problems associated with biofouling, many toxic and non-toxic antifouling methods have been developed. Unfortunately, most of the methods used to control biofouling are either harmful to the environment or, in some cases, considered effective. Thus, antifouling research's main objective is to develop green, sustainable, viable, widely applicable, and environmentally friendly antifouling technology. In this review, chemical, physical, and biological mitigation methods to prevent biofilm formation employed in the past and present have been discussed along with the current literature. Chemical antifouling methods generally contain antifouling (AF) paints with biocides including copper, silver, thiocyanate, Copper powder, Irgarol 1051, Zinc pyrithione, and Tributyltin (TBT). The physical antifouling control methods employ physical force or surface modifications such as low drag, low adhesion, wettability (super hydrophobicity or super hydrophilicity), as well as microtextured structures that minimize microorganism adhesion and/or accumulation on contact surfaces, hindering the formation of biofouling. The use of nature-inspired antibiological and biomimetic surfaces like shark skin, whale skin, dolphin skin, and lotus leaves are promising for the effective control of biofouling and present opportunities for developing non-polluting technologies.

Toll-like receptors in the mechanism of tributyltin-induced production of pro-inflammatory cytokines, IL-1β and IL-6

Tributyltin (TBT) is an environmental contaminant due to its use in a variety of applications as a biocide, including in marine anti-fouling paints. It has been detected in a number of human tissues including blood. Previous studies have shown that exposure to TBT increases the cellular production (secretion plus intracellular levels) of the pro-inflammatory cytokines IL-1β and IL-6 by peripheral blood mononuclear cells (PMBCs) and this increase requires MAPK activation. Toll-like receptors (TLR) activate immune cells to produce pro-inflammatory cytokines in response to pathogen associated molecular patterns (PAMPs) and damage associated molecular patterns (DAMPs) leading to activation of MAPKs as well as other intracellular components that regulate cytokine production. The current study shows that selective inhibition of TLRs 4,1/2, and 8 diminishes the ability of TBT to stimulate IL-1β and IL-6 production. However, selective inhibition of TLR3 enhanced the TBT-induced production of IL-1β. This indicates that TBT may be either directly or indirectly interacting with certain TLR receptors as part of its mechanism of stimulating pro-inflammatory cytokine production. These results provide an important advance in understanding TBT stimulation of IL-1β and IL-6, which has the potential to cause chronic inflammation and its attendant pathologies.

Effect of ultra-low concentrations of TBT on the microalgae Tetraselmis sp. and Chattonella subsalsa

ABSTRACT Bioencrustation is a natural process resulting from the colonisation and growth of organisms on solid substrates. For more than 40 years, Tributyltin (TBT) has been used as a biocide in antifouling paint. Since microalgae are constantly exposed to TBT, the growth of two microalgae species of the Guanabara Bay (Tetraselmis sp. and Chattonella subsalsa) was analysed in the present study. For this, the microalgae were grown using f/2 medium; potassium dichromate was used to guarantee the validity of the used method. To assess the effects on both genera of microalgae, different concentrations of TBT (ranging from 0.1 to 50 ng.L−1 diluted in f/2 medium) were used. All tests were carried out under a germination chamber, and the cell density was measured after 96 h. The results indicated that concentrations below 4.2 ng.L−1 were sufficient to inhibit 50% of the microalgae growth, demonstrating TBT can still be toxic even in ultra-low concentrations.

Butyltin Contamination in Fishing Port Sediments after the Ban of Tributyltin Antifouling Paint: A Case of Qianzhen Fishing Port in Taiwan

This study investigated the concentrations of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in the sediments of the Qianzhen Fishing Port (Taiwan) in 2020. Further, the pollution status, composition, and potential ecotoxicity of BTs were evaluated. This case study provides a reference for the benefits of the ban of TBT-based antifouling paint to date. Results showed that the total butyltin (ΣBTs, sum of TBT, DBT, and MBT) concentrations measured in the sediments of the Qianzhen Fishing Port ranged between 14.2–807 ngSn·g−1 dw, with an average of 356 ± 305 ngSn·g−1 dw. TBT was the most dominant species, with an average concentration of 303 ± 287 ngSn·g−1 dw. This average TBT concentration is about 4.3 times lower than in 2003, showing the progress of gradual degradation of TBT in the sediments. Still, the degradation is rather slow, with a half-life of about 8.09 years. An analysis of the effects of TBT on organisms in the sediments of the Qianzhen Fishing Port was carried out according to the TBT toxicity guidelines of the US Environmental Protection Agency and the assessment class criterion for imposex (ACCI) of the Oslo and Paris Commission (OSPAR). The results showed that TBT levels in 80% of the sediments may pose negative effects on sensitive gastropods, and half of the sediments may even have an impact on gastropod reproduction. These show that marine life is still affected and threatened by TBT compounds, despite the decline of TBT concentrations since the ban of TBT-containing antifouling paints on ships in 2008. Therefore, it is necessary to continue paying attention to the changes of TBT concentrations and their potential ecological risks in the marine environment, and to formulate TBT management plans and strategies to mitigate their impacts in marine ecosystems.

A reassessment of TBT action levels for determining the fate of dredged sediments in the United Kingdom

As part of reviewing the United Kingdom (UK) action levels (ALs) of contaminants for managing the disposal of dredged marine sediment material, tributyl tin (TBT) has been reassessed. TBT is a banned biocide capable of causing severe harm to the marine environment. Its presence is routinely screened for prior to marine disposal of dredged sediment material. Dredged sediment TBT concentrations have been studied using UK monitoring data obtained between 2000 and 2018. The changes in these TBT concentrations have guided the reassessment of ALs. Recent toxicity studies have also guided the reassessment of TBT ALs. This study, which itself forms part of a larger review by the Department for Environment, Food and Rural Affairs, has concluded that current UK TBT ALs may no longer be fit for purpose. A more environmentally protective approach for controlling release of TBT into the marine environment is recommended.

Pollution levels in Sri Lanka’s west-south coastal waters: Making progress toward a cleaner environment

Sri Lanka’s Western-Southern coastal area, home to more than 40% of the country’s population and the commercial capital city of Colombo, receives the most attention. Fisheries, tourism, hotel and restaurant, commercials, and administrations are among the government and non-government enterprises established in the area, demonstrating localization that impacts people’s lifestyles. This study aimed to identify point sources of coastal water pollution in the west-south coastal belt using the standard physico-chemical and microbiological methods, for 65 sampling sites from Negombo to Mirissa. The study area was divided into 11 land segments based on the environment type. 6 land segments and 5 land segments were used to cover the Western province and Southern province respectively. Each parameter was compared by province. Temperature and pH fluctuated less over the coastal belt between Negombo and Mirissa. The average temperature was 28.89 ±1.5 °C, and the pH ranged from 7.41 ± 1.5 to 9.64 ± 1.6. Electrical Conductivity (EC) and Dissolved Oxygen (DO) displayed dynamic changes, with average values of 40.88 ± 16.90 mS/cm and 7.66 ± 2.78 mg/L, respectively. The chemical limiting factor of the study areas was nitrogen. Nitrate was 0.01 mg/dm3 for almost all sampling locations and the highest Nitrite was 2.94 ± 0.8 μg/dm3. The highest Ammonia was 62.18 ±6.1μg/dm3, and Total Phosphorus (TP) was ranged from 92.41 ± 6.4 to 421 ±7.2μg/dm3. The Chemical Oxygen Demand (COD) was recorded between 112.5 ± 8.7 and 7318 ± 8.9 mg/dm3 and the maximum oil and grease concentration of 192.34 ± 7.6 mg/dm3. Unsurprisingly, fecal coliform was found in practically all of the coastal waterways, indicating fecal contamination, and the discovery of Salmonella sp. pathogenic bacteria from the Dehiwala canal and Rathmalana sampling locations drew additional attention. The highest level of Tributyltin (TBT) pollution was found in the Dikkovita fishery harbor (241 ± 4 ng/L), with TBT levels ranging from 51 ± 2 to 158 ± 2 ng/L in the remaining locations. The findings revealed that the study area has begun to decline due to anthropogenic activities and that there is less care for environmental friendliness as development stories progress.

Subacute and low-dose tributyltin exposure disturbs the mammalian hypothalamus-pituitary-thyroid axis in a sex-dependent manner

Tributyltin (TBT) is an endocrine disruptor chemical (EDC) capable of altering the proper function of the hypothalamus-pituitary thyroid (HPT) axis. This study aimed to evaluate the subacute effects of TBT on the HPT axis of male and female rats. A dose of 100 ng/kg/day TBT was used in both sexes over a 15-day period, and the morphophysiology and gene expression of the HPT axis were assessed. TBT exposure increased the body weight in both sexes, while food efficiency increased - only in male rats. It was also possible to note alterations in the thyroid, with the presence of a stratified epithelium, cystic degeneration, and increased interstitial collagen deposition. A reduction in T3 and T4 levels was only observed in TBT male rats. A reduction in TSH levels was observed in TBT female rats. Evaluating mRNA expression, we observed a decrease in hepatic D1 and TRH mRNA levels in TBT female rats. An increase in D2 mRNA expression in the hypothalamus was observed in TBT male rats. Additionally, no significant changes in TRH or hepatic D1 mRNA expression in TBT male rats or in hypothalamic D1 and D2 mRNA expression in TBT female rats were observed. Thus, we can conclude that TBT has different toxicological effects on male and female rats by altering thyroid gland morphophysiology, leading to abnormal HPT axis function, and even at subacute and low doses, it may be involved in complex endocrine and metabolic disorders.

Transgenerational Transcriptomic and DNA Methylome Profiling of Mouse Fetal Testicular Germline and Somatic Cells after Exposure of Pregnant Mothers to Tributyltin, a Potent Obesogen.

Obesogens such as tributyltin (TBT) are xenobiotic compounds that promote obesity, in part by distorting the normal balance of lipid metabolism. The obesogenic effects of TBT can be observed in directly exposed (F1 and F2 generations) and also subsequent generations (F3 and beyond) that were never exposed. To address the effects of TBT exposure on germ cells, we exposed pregnant transgenic OG2 mouse dams (F0), which specifically express EGFP in germline cells, to an environmentally relevant dose of TBT or DMSO throughout gestation through drinking water. When fed with a high-fat diet, F3 male offspring of TBT-exposed F0 dams (TBT-F3) accumulated much more body fat than did DMSO-F3 males. TBT-F3 males also lost more body fluid and lean compositions than did DMSO-F3 males. Expression of genes involved in transcriptional regulation or mesenchymal differentiation was up-regulated in somatic cells of TBT-F1 (but not TBT-F3) E18.5 fetal testes, and promoter-associated CpG islands were hyper-methylated in TBT-F1 somatic cells. Global mRNA expression of protein-coding genes in F1 or F3 fetal testicular cells was unaffected by F0 exposure to TBT; however, expression of a subset of endogenous retroviruses was significantly affected in F1 and F3. We infer that TBT may directly target testicular somatic cells in F1 testes to irreversibly affect epigenetic suppression of endogenous retroviruses in both germline and somatic cells.