Tributyltin exposure disrupted the locomotor activity rhythms in adult zebrafish (Danio rerio) and the mechanism involved

The fish circadian rhythm system might be an emerging target of tributyltin (TBT), however, the mechanism by which TBT interferes with the circadian rhythm is poorly understood. Therefore, in the present study, zebrafish were used to assess the effects of TBT at environmental concentrations (1 and 10 ng/L) on locomotor activity rhythm. Furthermore, we focused on the visual system to explore the potential mechanism involved. After 90 d of exposure, TBT disturbed the locomotor activity rhythms in zebrafish, which manifested as: (1) low activities and lethargy during the arousing period; (2) inability to fall asleep quickly and peacefully during the period of latency to sleep; and (3) no regular "waves" of locomotor activities during the active period. After TBT exposure, the histological structure of the eyes significantly changed, the boundary between layers became blurred, and the melanin concentrations significantly decreased. Using KEGG and GSEA pathway analyses, the differentially expressed genes in the eyes screened by transcriptomics were significantly enriched in the tyrosine metabolism pathway and retinol metabolism pathway. Furthermore, a decrease in melanin and disruption of retinoic acid were found after TBT exposure, which would affect the reception of phototransduction, and then interfere with the circadian rhythm in fish. The disruption of the circadian rhythm of fish by aquatic pollutants would decrease their ecological adaptability, which should be considered in future research.

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.

Effects of the antifouling agent tributyltin on the sinking behavior, photosynthetic rate and biochemical composition of the marine planktonic diatom Thalassiosira pseudonana

This study investigated the changes in the sinking rates and physiochemical characteristics of the planktonic marine diatom, Thalassiosira pseudonana, caused by 72 h exposure to antifouling agent tributyltin (TBT) at 1.0 µg L^-1 (72-h 10% effective concentration for growth rate, EC10), and 1.7 µg L^-1 (EC50). After 72 h of exposure, the sinking rates of T. pseudonana cells were changed from 0.13-0.08 m day^-1 in the control, 0.08-0.05 m day^-1 in the EC10 treatment, and 0.04-0.006 m day^-1 in the EC50 treatment. The results revealed that the sinking rate of T. pseudonana decreased significantly compared with the control at 48 h in the EC10 treatment group and at 24, 48, and 72 h in the EC50 treatment group. The photosynthetic performance index on an absorption basis and the maximum quantum yields of photosystem II also decreased significantly (P < 0.05) in the TBT treatments compared with the control. There was a significant (P < 0.05) positive correlation between sinking rates and cellular protein contents (ng cell^-1). Changes in the biochemical and physiochemical composition of the cells suggest that interference with photosynthetic processes by TBT may have reduced their specific gravity and thereby caused a decrease in the sinking rates of T. pseudonana. The results of this investigation suggest the importance of considering the effects of pollutants on the sinking behaviors of diatoms when evaluating the adverse effects of pollutants on marine primary production.

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.

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.

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.

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.

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.

Solid-state 1H NMR-based metabolomics assessment of tributylin effects in zebrafish bone

Tributyltin (TBT), an endocrine disruptor is used globally in agribusiness and industries as biocides, heat stabilizers, and in chemical catalysis. It is known for its deleterious effects on bone by negatively impacting the functions of osteoblasts, osteoclasts and mesenchymal stem cells. However, the impact of TBT on the metabolomics profile in bone is not yet studied. Here, we demonstrate alterations in chemical metabolomics profiles measured by solid state ¹H nuclear magnetic resonance (¹H NMR) spectroscopy in zebrafish bone following tributyltin (TBT) treatment. TBT of 0, 100, 200, 300, 400 and 500 μg/L were exposed to zebrafish. From this, zebrafish bone has subjected for further metabolomics profiling. Samples were measured via one-dimensional (1D) solvent -suppressed and T₂- filtered methods with in vivo zebrafish metabolites. A dose dependent alteration in the metabolomics profile was observed and results indicated a disturbed aminoacid metabolism, TCA cycle, and glycolysis. We found a significant alteration in the levels of glutamate, glutamine, glutathione, trimethylamine N-oxide (TMAO), and other metabolites. This investigation hints us the deleterious effects of TBT on zebrafish bone enabling a comprehensive understanding of metabolomics profile and is expected to play a crucial role in understanding the deleterious effects of various endocrine disruptor on bone.

Evaluation of the effects produced by subacute tributyltin administration on vascular reactivity of male wistar rats

Tributyltin chloride (TBT) is an organotin compound widely used in several high biocides for agroindustrial applications, such as fungicides, and marine antifouling paints leading to endocrine disrupting actions, such as imposex development in mollusks. In female rats, TBT has been shown to promote ovarian dysfunction, reduction of estrogen protective effect in the vascular morphophysiology, at least in part by oxidative stress consequences. Estrogen causes coronary endothelium-dependent and independent vasodilation. However, the TBT effects on cardiovascular system of male rats are not fully understood. The aim of this study was to evaluate the effects of subacute TBT exposure in aorta vascular reactivity from male wistar rats. Rats were randomly divided into three groups: control (C), TBT 500 ng/kg/day and TBT 1000 ng/kg/day. TBT was administered daily for 30 days by oral gavage. We found that TBT exposure enhanced testosterone serum levels and it was also observed obesogenic properties. TBT exposure evoked an increase in endothelium-dependent and independent phenylephrine-induced contraction, associated to an inhibition in eNOS activity. On the other hand, it was observed an enhancement of iNOS and NF-kB protein expression. We also observed an increase in oxidative stress parameters, such as superoxide dismutase (SOD) and catalase expression, and also an increase in malondialdehyde production. Finally, TBT exposure produced aortic intima-media thickness. Taken together, these data suggest a potential cardiovascular toxicological effect after subacute TBT exposure in male rats.

Tributyltin inhibits autophagy by decreasing lysosomal acidity in SH-SY5Y cells

Tributyltin (TBT) is an environmental pollutant that remains in marine sediments and is toxic to mammals. For example, TBT elicits neurotoxic and immunosuppressive effects on rats. However, it is not entirely understood how TBT causes toxicity. Autophagy plays a pivotal role in protein quality control and eliminates aggregated proteins and damaged organelles. We previously reported that TBT dephosphorylates mammalian target of rapamycin (mTOR), which may be involved in enhancement of autophagosome synthesis, in primary cultures of cortical neurons. Autophagosomes can accumulate due to enhancement of autophagosome synthesis or inhibition of autophagic degradation, and we did not clarify whether TBT alters autophagic flux. Here, we investigated the mechanism by which TBT causes accumulation of autophagosomes in SH-SY5Y cells. TBT inhibited autophagy without affecting autophagosome-lysosome fusion before it caused cell death. TBT dramatically decreased the acidity of lysosomes without affecting lysosomal membrane integrity. TBT decreased the mature protein level of cathepsin B, and this may be related to the decrease in lysosomal acidity. These results suggest that TBT inhibits autophagic degradation by decreasing lysosomal acidity. Autophagy impairment may be involved in the mechanism underlying neuronal death and/or T-cell-dependent thymus atrophy induced by TBT.

Effects of chronic exposure to environmental levels of tributyltin on the lined seahorse (Hippocampus erectus) liver: Analysis of bioaccumulation, antioxidant defense, and immune gene expression

Tributyltin (TBT), an organotin compound frequently detected in the coastal environments, poses a threat to aquatic organisms. The lined seahorse (Hippocampus erectus) is a vulnerable species found in nearshore water habitats. The mechanisms by which this fish responds to TBT exposure are not yet fully understood. Histological, biochemical, and transcriptional analyses were conducted, and the results showed that 60 days of exposure to 50 and 500 ng/L TBT caused significant tin accumulation and liver damage to seahorses. Antioxidant defenses and immune responses to TBT exposure in the livers of seahorses were further investigated. The enzymatic activity of superoxide dismutase and malondialdehyde content increased, while catalase activity decreased. Transcriptomic analysis revealed that a series of genes involved in the antioxidant defense system were highly induced to protect the hepatic cells from oxidative damage. TBT exposure also resulted in the induction of genes associated with immune and inflammatory processes, representing a stress response to combat the adverse environmental conditions in the exposed seahorses. Furthermore, seahorses showed an increased health risk, according to the elevation of the expression of genes with tumor-promoting effects, when exposed to TBT. These findings contribute to our understanding of the adverse effects of TBT exposure on seahorses, and their potential defense mechanisms.

Transgenerational metabolomic fingerprints in mice ancestrally exposed to the obesogen TBT

BACKGROUND

Endocrine disrupting chemicals (EDCs) contribute to the etiology of metabolic disorders such as obesity, insulin resistance and hepatic dysfunction. Concern is growing about the consequences of perinatal EDC exposure on disease predisposition later in life. Metabolomics are promising approaches for studying long-term consequences of early life EDC exposure. These approaches allow for the identification and characterization of biomarkers of direct or ancestral exposures that could be diagnostic for individual susceptibility to disease and help to understand mechanisms through which EDCs act.

OBJECTIVES

We sought to identify metabolomic fingerprints in mice ancestrally exposed to the model obesogen tributyltin (TBT), to assess whether metabolomics could discriminate potential trans-generational susceptibility to obesity and recognize metabolic pathways modulated by ancestral TBT exposure.

METHODS

We used non-targeted ¹H NMR metabolomic analyses of plasma and liver samples collected from male and female mice ancestrally exposed to TBT in two independent transgenerational experiments in which F3 and F4 males became obese when challenged with increased dietary fat.

RESULTS

Metabolomics confirmed transgenerational obesogenic effects of environmentally relevant doses of TBT in F3 and F4 males, in two independent studies. Although females never became obese, their specific metabolomic fingerprint evidenced distinct transgenerational effects of TBT in female mice consistent with impaired capacity for liver biotransformation.

DISCUSSION

This study is the first application of metabolomics to unveil the transgenerational effects of EDC exposure. Very early, significant changes in the plasma metabolome were observed in animals ancestrally exposed to TBT. These changes preceded the onset of obesogenic effects elicited by increased dietary fat in the TBT groups, and which ultimately resulted in significant changes in the liver metabolome. Development of metabolomic fingerprints could facilitate the identification of individuals carrying the signature of ancestral obesogen exposure that might increase their susceptibility to other risk factor such as increased dietary fat.

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.

Tributyltin protects against ovariectomy-induced trabecular bone loss in C57BL/6J mice with an attenuated effect in high fat fed mice

Risk factors for poor bone quality include estrogen loss at menopause, a high fat diet and exposures to drugs/chemicals that activate peroxisome proliferator activated receptor gamma (PPARγ). We previously reported that the PPARγ and retinoid X receptor dual ligand, tributyltin (TBT), repressed periosteal bone formation but enhanced trabecular bone formation in vivo. Here, we examined the interaction of diet, ovariectomy (OVX) and TBT exposure on bone structure. C57BL/6J mice underwent either sham surgery or OVX at 10 weeks of age. At 12 weeks of age, they were placed on a low (10% kcal) or high (45% kcal) fat, sucrose-matched diet and treated with vehicle or TBT (1 or 5 mg/kg) for 14 weeks. OVX increased body weight gain in mice on either diet. TBT enhanced body weight gain in intact mice fed a high fat diet, but decreased weight gain in OVX mice. Elemental tin concentrations increased dose-dependently in bone. TBT had marginal effects on cortical and trabecular bone in intact mice fed either diet. OVX caused a reduction in cortical and trabecular bone, regardless of diet. In high fat fed OVX mice, TBT further reduced cortical thickness, bone area and total area. Interestingly, TBT protected against OVX-induced trabecular bone loss in low fat fed mice. The protective effect of TBT was nullified by the high fat. These results show that TBT protects against trabecular bone loss, even in the presence of a strongly resorptive environment, at an even lower level of exposure than we showed repressed homeostatic resorption.

Effects of tributyltin on retinoid X receptor gene expression and global DNA methylation during intracapsular development of the gastropod Tritia mutabilis (Linnaeus, 1758)

The tributyltin (TBT)-mediated induction of imposex in marine snails is considered a common mechanism of endocrine disruption through the retinoid X receptor (RXR)-dependent pathway. However, there is evidence that regulation of RXR also relates to metabolic processes, differentiation, apoptosis, and embryonic development, playing a key role in molluscan neuronal differentiation and organogenesis. In this regard, very little is known about the gastropod Tritia mutabilis especially in relation to the effects of TBT exposure during intracapsular embryonic development. In this study, we have investigated the RXR expression fold changes of T. mutabilis encapsulated embryos exposed to different concentrations (10^-10 to 10^-12 M) of TBT up to 10 days of treatment. We demonstrate that RXR is sequentially expressed during development and that exposure to the lowest and highest TBT doses induces time-dependent changes in RXR gene transcription. We also show that TBT treatment is associated with global DNA demethylation and reduced DNA-methyltransferase I (DNMT1) expression and activity levels. Overall, our data indicate that RXR has important functions during the early stages of T. mutabilis embryo development and is involved in mediating the potential epigenetic alterations induced by TBT exposure.

Effects of microplastics (MPs) and tributyltin (TBT) alone and in combination on bile acids and gut microbiota crosstalk in mice

Microplastics (MPs) and tributyltin (TBT) are both potential environmental pollutants that enter organisms through the food chain and affect bodily functions. However, the effects and mechanisms of MPs and TBT exposure (especially the co-exposure of both pollutants) on mammals remain unclear. In this study, Ф5μm MPs (5MP) was administered alone or in combination with TBT to investigate the health risk of oral exposure in mice. All three treatments induced inflammation in the liver, altered gut microbiota composition and disturbed fecal bile acids profiles. In addition to decreasing triglyceride (TG) and increasing aspartate aminotransferase (AST) and macrophage-expressed gene 1 (Mpeg1), 5MP induced hepatic cholestasis by stimulating the expression of the cholesterol hydroxylase enzymes CYP8B1 and CYP27A1, and inhibiting multidrug resistance-associated protein 2 and 3 (MRP2, MRP3), and bile-salt export pump (BSEP) to prevent bile acids for entering the blood and bile. Correspondingly, 5MP treatment decreased 7-ketolithocholic acid (7-ketoLCA) and taurocholic acid (TCA), which were positively correlated with decreased Bacteroides and Marvinbryantia and negatively correlated with increased Bifidobacterium. In addition, TBT increased interferon γ (IFNγ) and Mpeg1 levels to induce inflammation, accompanied by decreased 7-ketoLCA, tauro-alpha-muricholic acid (T-alpha-MCA) and alpha-muricholic acid (alpha-MCA) levels, which were negatively related to Coriobacteriaceae_UCG-002 and Bifidobacterium. Co-exposure to 5MP and TBT also decreased TG and induced bile acids accumulation in the liver due to inhibited BSEP, which might be attributed to the co-regulation of decreased T-alpha-MCA and Harryflintia. In conclusion, the administration of 5MP and TBT alone and in combination could cause gut microbiome dysbiosis and subsequently alter bile acids profiles, while the combined exposure of 5MP and TBT weakened the toxic effects of 5MP and TBT alone.

Retinoids promote penis development in sequentially hermaphroditic snails

Sexual systems are surprisingly diverse, considering the ubiquity of sexual reproduction. Sequential hermaphroditism, the ability of an individual to change sex, has emerged multiple times independently across the animal kingdom. In molluscs, repeated shifts between ancestrally separate sexes and hermaphroditism are generally found at the level of family and above, suggesting recruitment of deeply conserved mechanisms. Despite this, molecular mechanisms of sexual development are poorly known. In molluscs with separate sexes, endocrine disrupting toxins bind the retinoid X receptor (RXR), activating ectopic male development in females, suggesting the retinoid pathway as a candidate controlling sexual transitions in sequential hermaphrodites. We therefore tested the role of retinoic acid signaling in sequentially hermaphroditic Crepidula snails, which develop first into males, then change sex, maturing into females. We show that retinoid agonists induce precocious penis growth in juveniles and superimposition of male development in females. Combining RXR antagonists with retinoid agonists significantly reduces penis length in induced juveniles, while similar treatments using retinoic acid receptor (RAR) antagonists increase penis length. Transcripts of both receptors are expressed in the induced penis. Our findings therefore show that retinoid signaling can initiate molluscan male genital development, and regulate penis length. Further, we show that retinoids induce ectopic male development in multiple Crepidula species. Species-specific influence of conspecific induction of sexual transitions correlates with responsiveness to retinoids. We propose that retinoid signaling plays a conserved role in molluscan male development, and that shifts in the timing of retinoid signaling may have been important for the origins of sequential hermaphroditism within molluscs.

Metal load and oxidative stress driven by organotin compounds on rainbow trout

Tributyltin-based (TBT) antifouling paints, widely used for the treatment of flooded surfaces, have been banned in 2008 for their high environmental persistence and bioaccumulation in aquatic organisms. Although it is still present in aquatic ecosystems, oxidative stress driven by TBT has been still poorly investigated in fish. The aim of the study was to examine the time-course stress responses in liver of rainbow trout that received a single intraperitoneal injection of tributyltin chloride (TBTC) or tributyltin ethoxide (TBTE), both at a dose of 0.05 and 0.5 mg/kg. Levels of metallothioneins, total glutathione, malondialdehyde, superoxide dismutase, catalase, glutathione peroxidase and glutathione S-transferase were evaluated at 3 and 6 days post-injection. Tin load was measured in the muscle of the same fish. Differences were observed in the time-course accumulation of tin with a clear dose-response relationship. Although individual oxidative stress biomarkers varied, the biomarker profile indicated different stress mechanisms caused by both TBTC and TBTE. The weak induction of metal-trapping metallothioneins and the changes of oxidative stress biomarkers suggested a stress-pressure in both TBT-treated trout, advising for an ecotoxicological risk for freshwater ecosystems.

Tributyltin perturbs femoral cortical architecture and polar moment of inertia in rat

Background

Tributyltin, a well-known endocrine disruptor, is widely used in agriculture and industry. Previous studies have shown that tributyltin could cause deleterious effects on bone health by impairing the adipo-osteogenic balance in bone marrow.

Methods

To investigate further the effects of tributyltin on bone, weaned male SD rats were treated with tributyltin (0.5, 5 or 50 μg·kg^− 1) or corn oil by gavage once every 3 days for 60 days in this study. Then, we analyzed the effects of tributyltin on geometry, the polar moment of inertia, mineral content, relative abundances of mRNA from representative genes related to adipogenesis and osteogenesis, serum calcium ion and inorganic phosphate levels.

Results

Micro-computed tomography analysis revealed that treatment with 50 μg·kg^− 1 tributyltin caused an obvious decrease in femoral cortical cross sectional area, marrow area, periosteal circumference and derived polar moment of inertia in rats. However, other test results showed that exposure to tributyltin resulted in no significant changes in the expression of genes detected, femoral cancellous architecture, ash content, as well as serum calcium ion and inorganic phosphate levels.

Conclusions

Exposure to a low dose of tributyltin from the prepubertal to adult stage produced adverse effects on skeletal architecture and strength.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-021-04298-2.

Legacy and emerging antifouling biocide residues in a tropical estuarine system (Espirito Santo state, SE, Brazil)

The contamination by antifouling biocide residues (booster biocides - diuron, Irgarol, chlorothalonil, dichlofluanid and DCOIT; butyltin compounds-BTs (TBT, DBT and MBT); and antifouling paint particles-APPs) was appraised in sediments of Vitoria Estuarine System (VES). Even at its historical lower (ΣBTs ≤113 ng Sn g^-1 dry wt), the current environmental levels of BTs in areas with a predominance of boatyards still pose a risk to the local biota and human population. DCOIT, among booster biocides, was the most frequently detected, especially in boatyards (≤40 ng g^-1 dry wt) and Vitoria Port (64 ng g^-1 dry wt), while APPs were also detected mainly in sediments of boatyards (≤5,969 μg g^-1 dry wt). Since levels of diuron and DCOIT in APPs were as high as 1,670,000 and 899,000 ng g^-1 dry wt, respectively, they are acting as secondary sources of these antifouling biocides. Therefore, VES is threatened by antifouling biocide residues due to the multiple diffuse sources of contamination, showing the need for more efforts on public policies (including temporal trend monitoring studies).

Neurotoxicity and physiological stress in brain of zebrafish chronically exposed to tributyltin

Tributyltin (TBT), an organotin compound, is hazardous in aquatic ecosystems. However, the mechanisms underlying TBT-induced central nervous system (CNS) toxicity remain to be determined especially in freshwater aquatic vertebrates. The aim of present study was to investigate the effects of chronic exposure to TBT on brain functions in a freshwater teleost the adult wild-type zebrafish (Danio rerio). Fish were exposed to sublethal concentrations of TBT (10, 100 or 300 ng/L) for 6 weeks. The influence of long-term TBT exposure was assessed in the brain of zebrafish with antioxidant related indices including malondialdehyde (MDA) levels and total antioxidant capacity, neurological parameters such as activities of acetylcholinesterase, and monoamine oxidase as well as levels of nitric oxide, dopamine, 5-hydroxytryptamine. In addition indices related to sensitivity of toxic insult such as cytochrome P450 1 regulation and heat shock protein 70 were determined. The regulation of related genes involved in endoplasmic reticulum stress (ERS), apoptosis and Nrf2 pathway were measured. Adverse physiological and biochemical responses were significantly enhanced in a concentration-dependent manner reflecting neurotoxicity attributed to TBT exposure. Our findings provide further insight into TBT-induced toxicity in wild-type zebrafish. and enhance our understanding of the molecular mechanisms underlying TBT-initiated CNS effects.

Effects of the tributyltin on the blood parameters, immune responses and thyroid hormone system in zebrafish

Tributyltin (TBT) is a widely used organotin compound around the world and was frequently detected in surface waters, which would pose risk to aquatic organisms. However, the mechanisms of TBT-induced toxicity is not full clear. The present study investigated the effects of the tributyltin (TBT) on the blood parameters, immune responses and thyroid hormone system in zebrafish. Fish were exposed to sublethal concentrations of TBT (10 ng/L, 100 ng/L and 300 ng/L) for 6 weeks. The effects of long-term exposure to TBT on blood parameters (NH3, ammonia; GLU, glucose; TP, total proteins; CK, creatine kinase; ALT, alanine aminotransferase; AST, aspartate aminotransferase), immune responses (Lys, lysozyme; IgM, immunoglobulin M) and some indexes related thyroid hormone system (T3, 3,5,3'-triiodothyronine; T4, thyroxine) were measured in zebrafish, as well as the expression of genes related to immune responses and thyroid hormone system. Based on the results, the physiological-biochemical responses was significantly enhanced with an increase in TBT concentration, reflected by the abnormal blood indices, dysregulation of endocrine system and immunotoxicity in zebrafish under TBT stress. The present study greatly extends our understanding of adverse effects of TBT on aquatic organisms.

Quantification of tributyltin in seawater using triple isotope dilution gas chromatography-inductively coupled plasma mass spectrometry achieving high accuracy and complying with European Water Framework Directive limits

A triple isotope dilution GC-ICPMS method for the determination of tributyltin (TBT) was developed and validated to meet the European Water Framework Directive (WFD) requirements. The validation procedure involved the evaluation of trueness, precision (repeatability, intermediate precision), limit of detection (LOD) and limit of quantification (LOQ), stability, measurement uncertainty and traceability studies. The method is one of the most sensitive methods published to date with good accuracy, 103% average recovery in the range with %RSDs of 2.8-6.7%. A LOD value of 0.015 ng L^-1 for the TBT cation was achieved with a sample volume of 12 mL seawater. TBT was derivatized using 20 µL sodium tetraethylborate solution (0.05% NaBEt₄) to make volatile for GC-ICPMS. Measurement uncertainty was in the range of 4.8-13% which was achieved through dissolution of tributyltinchloride (TBTCl) in 1-propanol, a low-volatility solvent combined with the use of a triple isotope dilution (ID) calibration technique. Isotope dilution calibration was performed by adding ¹¹⁷Sn isotopically enriched TBT to the seawater samples. The stability test results showed that TBT concentration was stable for three months in seawater samples after passing through a 0.2 µm filter and stored in amber glass bottles at 4°C. The response surface methodology (RSM) approach was successfully implemented to provide optimal conditions for large volume injection (LVI) to obtain the maximum analytical signal. The key variables selected in the experimental design were evaporation time, evaporation temperature, carrier flow, and injection speed. This method was applied to seawater samples collected from the Bay of Izmit, Kocaeli, Turkey, where TBT pollution has not been measured yet.

Tributyltin Induces the Tissue-Specific Stresses in Zebrafish, a Study in Various Tissues of Muscle, Gill and Intestine

Because the mechanism of tissue-specific toxicity of tributyltin (TBT) in aquatic organisms has not been explained clearly, the aim of this study is to investigate the effect of chronic exposure to TBT on muscle-related energy metabolism, gill-related ATPase enzymatic system and intestine-related digestive enzymes activities in zebrafish. Male zebrafish were exposed to sub-lethal concentrations of TBT (10, 100 and 300 ng/L) for 6 weeks. Multiple biomarkers were measured (such as glucose, lactate, hexokinase, pyruvate kinase, lactate dehydrogenase, ATP content, ATPases, trypsin, lipase and amylase), which reflected more serious physiological stress with increasing TBT concentrations during the experimental period. Through principal component analysis (PCA) and integrated biomarker response (IBR) analysis, the toxic effect of TBT in zebrafish was in a concentration-dependent manner. Shortly, the results of this study can provide new evidence for a comprehensive understanding of the toxic effects of TBT.