Overview of the Pathophysiological Implications of Organotins on the Endocrine System

Long-term tributyltin exposure alters behavior, oocyte maturation, and histomorphology of the ovary due to oxidative stress in adult zebrafish

Tributyltin (TBT), an organotin endocrine-disrupting substance, is recognized as one of the important toxic environmental pollutants. The present study was carried out to investigate the toxic effects of TBT on behavior and the ovary of adult zebrafish with a focus on oxidative stress markers and oocyte maturation. Adult zebrafish were exposed to three different concentrations (125, 250, and 500 ng/L of water) of TBT for 28 days. TBT exposure produced a concentration-dependent negative effect on the body weight and behavior (anxiety-like symptoms) of adult zebrafish. Alterations in the activity of superoxide dismutase (SOD) and catalase (CAT), the total antioxidant capacity of ovarian tissue by the highest exposure level of TBT resulted in lipid peroxidation as indicated by increased malondialdehyde (MDA) level. The numbers of early-vitellogenic oocytes were significantly increased in zebrafish exposed to TBT as low as 125 ng/L. However, the numbers and size of fully-grown (mature) oocytes were significantly reduced in the highest exposure group only. Correlation between the MDA level and pre-vitellogenic oocytes in the 500 ng/L group indicated that lipid peroxidation prevented the maturation of pre-vitellogenic oocytes. TBT exposure produced significant histological changes in the ovary as evidenced by disturbed maturation of oocytes. In conclusion, TBT adversely affected the maturation of oocytes in zebrafish ovary through oxidative stress-mediated mechanisms.

Triphenyltin chloride exposure inhibits meiotic maturation of mouse oocytes by disrupting cytoskeleton assembly and cell cycle progression

Triphenyltin chloride (TPTCL) is widely used in various industrial and agricultural applications. This study aimed to elucidate the mechanisms underlying the toxicological effects of TPTCL on oocytes. The obtained findings revealed that TPTCL exposure reduced polar body extrusion (PBE) and induced meiotic arrest. Mechanistically, TPTCL disrupted meiotic spindle assembly and chromosome alignment. Further analysis indicated a significant decrease in p-MAPK expression, and disturbances in the localization of Pericentrin and p-Aurora A in TPTCL exposed oocytes, which suggesting impaired microtubule organizing center (MTOC)function. Moreover, TPTCL exposure enhance microtubule acetylation and microtubule instability. Therefore, the spindle assembly checkpoint (SAC) remained activated, and the activity of the anaphase-promoting complex (APC) was inhibited, thereby preventing oocytes from progressing into the entering anaphase I (AI) stage. TPTCL exposure also augmented the actin filaments in the cytoplasm. Notably, mitochondrial function appeared unaffected by TPTCL, as evidenced indicated by stable mitochondrial membrane potential and ATP content. Furthermore, TPTCL treatment altered H3K27me2, H3K27me3 and H3K9me3 levels, suggesting changes in epigenetic modifications in oocytes. Taken together, our results suggest that TPTCL disrupts cytoskeleton assembly, continuously activates SAC, inhibits APC activity, and blocks meiotic progression, ultimately impair oocyte maturation.

Molecular mechanisms of environmental pollutant-induced cartilage damage: from developmental disorders to osteoarthritis

The objective of the present study was to review the molecular mechanisms of the adverse effects of environmental pollutants on chondrocytes and extracellular matrix (ECM). Existing data demonstrate that both heavy metals, including cadmium (Cd), lead (Pb), and arsenic (As), as well as organic pollutants, including polychlorinated dioxins and furans (PCDD/Fs) and polychlorinated biphenyls (PCB), bisphenol A, phthalates, polycyclic aromatic hydrocarbons (PAH), pesticides, and certain other organic pollutants that target cartilage ontogeny and functioning. Overall, environmental pollutants reduce chondrocyte viability through the induction apoptosis, senescence, and inflammatory response, resulting in cell death and impaired ECM production. The effects of organic pollutants on chondrocyte development and viability were shown to be mediated by binding to the aryl hydrocarbon receptor (AhR) signaling and modulation of non-coding RNA expression. Adverse effects of pollutant exposures were observed in articular and growth plate chondrocytes. These mechanisms also damage chondrocyte precursors and subsequently hinder cartilage development. In addition, pollutant exposure was shown to impair chondrogenesis by inhibiting the expression of Sox9 and other regulators. Along with altered Runx2 signaling, these effects also contribute to impaired chondrocyte hypertrophy and chondrocyte-to-osteoblast trans-differentiation, resulting in altered endochondral ossification. Several organic pollutants including PCDD/Fs, PCBs and PAHs, were shown to induce transgenerational adverse effects on cartilage development and the resulting skeletal deformities. Despite of epidemiological evidence linking human environmental pollutant exposure to osteoarthritis or other cartilage pathologies, the data on the molecular mechanisms of adverse effects of environmental pollutant exposure on cartilage tissue were obtained from studies in laboratory rodents, fish, or cell cultures and should be carefully extrapolated to humans, although they clearly demonstrate that cartilage should be considered a putative target for environmental pollutant toxicity.

Environmental Health and Toxicology: Immunomodulation Promoted by Endocrine-Disrupting Chemical Tributyltin

Tributyltin (TBT) is an environmental contaminant present on all continents, including Antarctica, with a potent biocidal action. Its use began to be intensified during the 1960s. It was effectively banned in 2003 but remains in the environment to this day due to several factors that increase its half-life and its misuse despite the bans. In addition to the endocrine-disrupting effect of TBT, which may lead to imposex induction in some invertebrate species, there are several studies that demonstrate that TBT also has an immunotoxic effect. The immunotoxic effects that have been observed experimentally in vertebrates using in vitro and in vivo models involve different mechanisms; mainly, there are alterations in the expression and/or secretion of cytokines. In this review, we summarize and update the literature on the impacts of TBT on the immune system, and we discuss issues that still need to be explored to fill the knowledge gaps regarding the impact of this endocrine-disrupting chemical on immune system homeostasis.

Evaluating the histomorphological and biochemical changes induced by Tributyltin Chloride on pituitary-testicular axis of adult albino rats and the possible ameliorative role of hesperidin

This study was performed to explore in detail the toxic effects of Tributyltin Chloride (TBT) on the pituitary-testicular axis and the possible amelioration with Hesperidin. Seventy-two adult male albino rats were divided into four groups: Control group (I), TBT-treated group (II), TBT+Hesperidin group (III), and Recovery group (IV). Body and testicular weights were measured. Blood samples were taken to estimate serum levels of testosterone, FSH and LH hormones by enzyme-linked immunosorbent assay (ELISA). Malondialdehyde (MDA) level was measured in testes homogenates. Tissue samples from the pituitary glands and testes were processed for light, electron microscope examination, and immunohistochemical detection of anti-FSH, and Ki67 proteins. Results showed a statistically significant decrease in testicular weight, serum testosterone, FSH and LH levels and a significant increase in tissue MDA in the TBT group when compared to the control group. TBT treatment caused severe histopathological changes with decreased area percent of PAS-stained basophils, and anti FSH immuno-stained gonadotrophs in the pituitary gland. The testes of group II also showed marked tissue damage, cell loss with decreased epithelial height and decreased number of proliferating spermatogenic cells. Hesperidin supplementation with TBT proved significant amelioration of the previously mentioned parameters in both glands which could improve male fertility. In conclusion: The flavonoid Hesperidin has the potential to protect against the reproductive damage induced by TBT in susceptible individuals.

Triphenyltin (TPT) exposure causes SD rat liver injury via lipid metabolism disorder and ER stress revealed by transcriptome analysis

BACKGROUND

TPT is an environmental endocrine disruptor that can interfere with endocrine function. However, whether TPT can cause damage to liver structure and function and abnormal lipid metabolism and whether it can cause ER stress is still unclear.

OBJECTIVE

To explore the effect of TPT on liver structure, function and lipid metabolism and whether ER stress occurs.

METHODS

Male SD rats were divided into 4 groups: control group (Ctrl group, TPT-L group (0.5mg/kg/d), TPT-M group (1mg/kg/d), and TPT-H group (2mg/kg/d). After 10 days of continuous gavage, HE staining was used to observe the morphological structure of liver tissue, serum biochemical indicators were detected, gene expression and functional enrichment analysis were performed by RNA-seq, Western Blot was used to detect the protein expression level of liver tissue, and qRT-PCR was used to detect the gene expression.

RESULTS

After TPT exposure, the liver structure damaged; serum TBIL, AST and m-AST levels were significantly increased in the TPT-M group, and serum TG levels were significantly decreased in the TPT-H group. TCHO and TG in liver tissues were significantly increased; transcriptomic analysis detected 105 differential genes. Enrichment analysis showed that TPT exposure mainly affected fatty acid metabolism and drug metabolism in liver tissue, and also affected the redox process of liver tissue; the protein expression levels of PPARα, PPARγ, AMPK, RXRα, IRE1α and PERK were significantly increased after TPT exposure; the expression levels of lipid metabolism-related genes Acsl1, Elovl5, Hmgcr, Hmgcs1 and Srebf1 were significantly increased in the TPT-L group, while in the TPT-M and TPT-H groups had no significant change.

CONCLUSIONS

TPT exposure can cause liver injury, lipid metabolism disorder and ER stress.

The Minderoo-Monaco Commission on Plastics and Human Health

Background

Plastics have conveyed great benefits to humanity and made possible some of the most significant advances of modern civilization in fields as diverse as medicine, electronics, aerospace, construction, food packaging, and sports. It is now clear, however, that plastics are also responsible for significant harms to human health, the economy, and the earth's environment. These harms occur at every stage of the plastic life cycle, from extraction of the coal, oil, and gas that are its main feedstocks through to ultimate disposal into the environment. The extent of these harms not been systematically assessed, their magnitude not fully quantified, and their economic costs not comprehensively counted.

Goals

The goals of this Minderoo-Monaco Commission on Plastics and Human Health are to comprehensively examine plastics' impacts across their life cycle on: (1) human health and well-being; (2) the global environment, especially the ocean; (3) the economy; and (4) vulnerable populations-the poor, minorities, and the world's children. On the basis of this examination, the Commission offers science-based recommendations designed to support development of a Global Plastics Treaty, protect human health, and save lives.

Report Structure

This Commission report contains seven Sections. Following an Introduction, Section 2 presents a narrative review of the processes involved in plastic production, use, and disposal and notes the hazards to human health and the environment associated with each of these stages. Section 3 describes plastics' impacts on the ocean and notes the potential for plastic in the ocean to enter the marine food web and result in human exposure. Section 4 details plastics' impacts on human health. Section 5 presents a first-order estimate of plastics' health-related economic costs. Section 6 examines the intersection between plastic, social inequity, and environmental injustice. Section 7 presents the Commission's findings and recommendations.

Plastics

Plastics are complex, highly heterogeneous, synthetic chemical materials. Over 98% of plastics are produced from fossil carbon- coal, oil and gas. Plastics are comprised of a carbon-based polymer backbone and thousands of additional chemicals that are incorporated into polymers to convey specific properties such as color, flexibility, stability, water repellence, flame retardation, and ultraviolet resistance. Many of these added chemicals are highly toxic. They include carcinogens, neurotoxicants and endocrine disruptors such as phthalates, bisphenols, per- and poly-fluoroalkyl substances (PFAS), brominated flame retardants, and organophosphate flame retardants. They are integral components of plastic and are responsible for many of plastics' harms to human health and the environment.Global plastic production has increased almost exponentially since World War II, and in this time more than 8,300 megatons (Mt) of plastic have been manufactured. Annual production volume has grown from under 2 Mt in 1950 to 460 Mt in 2019, a 230-fold increase, and is on track to triple by 2060. More than half of all plastic ever made has been produced since 2002. Single-use plastics account for 35-40% of current plastic production and represent the most rapidly growing segment of plastic manufacture.Explosive recent growth in plastics production reflects a deliberate pivot by the integrated multinational fossil-carbon corporations that produce coal, oil and gas and that also manufacture plastics. These corporations are reducing their production of fossil fuels and increasing plastics manufacture. The two principal factors responsible for this pivot are decreasing global demand for carbon-based fuels due to increases in 'green' energy, and massive expansion of oil and gas production due to fracking.Plastic manufacture is energy-intensive and contributes significantly to climate change. At present, plastic production is responsible for an estimated 3.7% of global greenhouse gas emissions, more than the contribution of Brazil. This fraction is projected to increase to 4.5% by 2060 if current trends continue unchecked.

Plastic Life Cycle

The plastic life cycle has three phases: production, use, and disposal. In production, carbon feedstocks-coal, gas, and oil-are transformed through energy-intensive, catalytic processes into a vast array of products. Plastic use occurs in every aspect of modern life and results in widespread human exposure to the chemicals contained in plastic. Single-use plastics constitute the largest portion of current use, followed by synthetic fibers and construction.Plastic disposal is highly inefficient, with recovery and recycling rates below 10% globally. The result is that an estimated 22 Mt of plastic waste enters the environment each year, much of it single-use plastic and are added to the more than 6 gigatons of plastic waste that have accumulated since 1950. Strategies for disposal of plastic waste include controlled and uncontrolled landfilling, open burning, thermal conversion, and export. Vast quantities of plastic waste are exported each year from high-income to low-income countries, where it accumulates in landfills, pollutes air and water, degrades vital ecosystems, befouls beaches and estuaries, and harms human health-environmental injustice on a global scale. Plastic-laden e-waste is particularly problematic.

Environmental Findings

Plastics and plastic-associated chemicals are responsible for widespread pollution. They contaminate aquatic (marine and freshwater), terrestrial, and atmospheric environments globally. The ocean is the ultimate destination for much plastic, and plastics are found throughout the ocean, including coastal regions, the sea surface, the deep sea, and polar sea ice. Many plastics appear to resist breakdown in the ocean and could persist in the global environment for decades. Macro- and micro-plastic particles have been identified in hundreds of marine species in all major taxa, including species consumed by humans. Trophic transfer of microplastic particles and the chemicals within them has been demonstrated. Although microplastic particles themselves (>10 µm) appear not to undergo biomagnification, hydrophobic plastic-associated chemicals bioaccumulate in marine animals and biomagnify in marine food webs. The amounts and fates of smaller microplastic and nanoplastic particles (MNPs <10 µm) in aquatic environments are poorly understood, but the potential for harm is worrying given their mobility in biological systems. Adverse environmental impacts of plastic pollution occur at multiple levels from molecular and biochemical to population and ecosystem. MNP contamination of seafood results in direct, though not well quantified, human exposure to plastics and plastic-associated chemicals. Marine plastic pollution endangers the ocean ecosystems upon which all humanity depends for food, oxygen, livelihood, and well-being.

Human Health Findings

Coal miners, oil workers and gas field workers who extract fossil carbon feedstocks for plastic production suffer increased mortality from traumatic injury, coal workers' pneumoconiosis, silicosis, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer. Plastic production workers are at increased risk of leukemia, lymphoma, hepatic angiosarcoma, brain cancer, breast cancer, mesothelioma, neurotoxic injury, and decreased fertility. Workers producing plastic textiles die of bladder cancer, lung cancer, mesothelioma, and interstitial lung disease at increased rates. Plastic recycling workers have increased rates of cardiovascular disease, toxic metal poisoning, neuropathy, and lung cancer. Residents of "fenceline" communities adjacent to plastic production and waste disposal sites experience increased risks of premature birth, low birth weight, asthma, childhood leukemia, cardiovascular disease, chronic obstructive pulmonary disease, and lung cancer.During use and also in disposal, plastics release toxic chemicals including additives and residual monomers into the environment and into people. National biomonitoring surveys in the USA document population-wide exposures to these chemicals. Plastic additives disrupt endocrine function and increase risk for premature births, neurodevelopmental disorders, male reproductive birth defects, infertility, obesity, cardiovascular disease, renal disease, and cancers. Chemical-laden MNPs formed through the environmental degradation of plastic waste can enter living organisms, including humans. Emerging, albeit still incomplete evidence indicates that MNPs may cause toxicity due to their physical and toxicological effects as well as by acting as vectors that transport toxic chemicals and bacterial pathogens into tissues and cells.Infants in the womb and young children are two populations at particularly high risk of plastic-related health effects. Because of the exquisite sensitivity of early development to hazardous chemicals and children's unique patterns of exposure, plastic-associated exposures are linked to increased risks of prematurity, stillbirth, low birth weight, birth defects of the reproductive organs, neurodevelopmental impairment, impaired lung growth, and childhood cancer. Early-life exposures to plastic-associated chemicals also increase the risk of multiple non-communicable diseases later in life.

Economic Findings

Plastic's harms to human health result in significant economic costs. We estimate that in 2015 the health-related costs of plastic production exceeded $250 billion (2015 Int$) globally, and that in the USA alone the health costs of disease and disability caused by the plastic-associated chemicals PBDE, BPA and DEHP exceeded $920 billion (2015 Int$). Plastic production results in greenhouse gas (GHG) emissions equivalent to 1.96 gigatons of carbon dioxide (CO2e) annually. Using the US Environmental Protection Agency's (EPA) social cost of carbon metric, we estimate the annual costs of these GHG emissions to be $341 billion (2015 Int$).These costs, large as they are, almost certainly underestimate the full economic losses resulting from plastics' negative impacts on human health and the global environment. All of plastics' economic costs-and also its social costs-are externalized by the petrochemical and plastic manufacturing industry and are borne by citizens, taxpayers, and governments in countries around the world without compensation.

Social Justice Findings

The adverse effects of plastics and plastic pollution on human health, the economy and the environment are not evenly distributed. They disproportionately affect poor, disempowered, and marginalized populations such as workers, racial and ethnic minorities, "fenceline" communities, Indigenous groups, women, and children, all of whom had little to do with creating the current plastics crisis and lack the political influence or the resources to address it. Plastics' harmful impacts across its life cycle are most keenly felt in the Global South, in small island states, and in disenfranchised areas in the Global North. Social and environmental justice (SEJ) principles require reversal of these inequitable burdens to ensure that no group bears a disproportionate share of plastics' negative impacts and that those who benefit economically from plastic bear their fair share of its currently externalized costs.

Conclusions

It is now clear that current patterns of plastic production, use, and disposal are not sustainable and are responsible for significant harms to human health, the environment, and the economy as well as for deep societal injustices.The main driver of these worsening harms is an almost exponential and still accelerating increase in global plastic production. Plastics' harms are further magnified by low rates of recovery and recycling and by the long persistence of plastic waste in the environment.The thousands of chemicals in plastics-monomers, additives, processing agents, and non-intentionally added substances-include amongst their number known human carcinogens, endocrine disruptors, neurotoxicants, and persistent organic pollutants. These chemicals are responsible for many of plastics' known harms to human and planetary health. The chemicals leach out of plastics, enter the environment, cause pollution, and result in human exposure and disease. All efforts to reduce plastics' hazards must address the hazards of plastic-associated chemicals.

Recommendations

To protect human and planetary health, especially the health of vulnerable and at-risk populations, and put the world on track to end plastic pollution by 2040, this Commission supports urgent adoption by the world's nations of a strong and comprehensive Global Plastics Treaty in accord with the mandate set forth in the March 2022 resolution of the United Nations Environment Assembly (UNEA).International measures such as a Global Plastics Treaty are needed to curb plastic production and pollution, because the harms to human health and the environment caused by plastics, plastic-associated chemicals and plastic waste transcend national boundaries, are planetary in their scale, and have disproportionate impacts on the health and well-being of people in the world's poorest nations. Effective implementation of the Global Plastics Treaty will require that international action be coordinated and complemented by interventions at the national, regional, and local levels.This Commission urges that a cap on global plastic production with targets, timetables, and national contributions be a central provision of the Global Plastics Treaty. We recommend inclusion of the following additional provisions:The Treaty needs to extend beyond microplastics and marine litter to include all of the many thousands of chemicals incorporated into plastics.The Treaty needs to include a provision banning or severely restricting manufacture and use of unnecessary, avoidable, and problematic plastic items, especially single-use items such as manufactured plastic microbeads.The Treaty needs to include requirements on extended producer responsibility (EPR) that make fossil carbon producers, plastic producers, and the manufacturers of plastic products legally and financially responsible for the safety and end-of-life management of all the materials they produce and sell.The Treaty needs to mandate reductions in the chemical complexity of plastic products; health-protective standards for plastics and plastic additives; a requirement for use of sustainable non-toxic materials; full disclosure of all components; and traceability of components. International cooperation will be essential to implementing and enforcing these standards.The Treaty needs to include SEJ remedies at each stage of the plastic life cycle designed to fill gaps in community knowledge and advance both distributional and procedural equity.This Commission encourages inclusion in the Global Plastic Treaty of a provision calling for exploration of listing at least some plastic polymers as persistent organic pollutants (POPs) under the Stockholm Convention.This Commission encourages a strong interface between the Global Plastics Treaty and the Basel and London Conventions to enhance management of hazardous plastic waste and slow current massive exports of plastic waste into the world's least-developed countries.This Commission recommends the creation of a Permanent Science Policy Advisory Body to guide the Treaty's implementation. The main priorities of this Body would be to guide Member States and other stakeholders in evaluating which solutions are most effective in reducing plastic consumption, enhancing plastic waste recovery and recycling, and curbing the generation of plastic waste. This Body could also assess trade-offs among these solutions and evaluate safer alternatives to current plastics. It could monitor the transnational export of plastic waste. It could coordinate robust oceanic-, land-, and air-based MNP monitoring programs.This Commission recommends urgent investment by national governments in research into solutions to the global plastic crisis. This research will need to determine which solutions are most effective and cost-effective in the context of particular countries and assess the risks and benefits of proposed solutions. Oceanographic and environmental research is needed to better measure concentrations and impacts of plastics <10 µm and understand their distribution and fate in the global environment. Biomedical research is needed to elucidate the human health impacts of plastics, especially MNPs.

Summary

This Commission finds that plastics are both a boon to humanity and a stealth threat to human and planetary health. Plastics convey enormous benefits, but current linear patterns of plastic production, use, and disposal that pay little attention to sustainable design or safe materials and a near absence of recovery, reuse, and recycling are responsible for grave harms to health, widespread environmental damage, great economic costs, and deep societal injustices. These harms are rapidly worsening.While there remain gaps in knowledge about plastics' harms and uncertainties about their full magnitude, the evidence available today demonstrates unequivocally that these impacts are great and that they will increase in severity in the absence of urgent and effective intervention at global scale. Manufacture and use of essential plastics may continue. However, reckless increases in plastic production, and especially increases in the manufacture of an ever-increasing array of unnecessary single-use plastic products, need to be curbed.Global intervention against the plastic crisis is needed now because the costs of failure to act will be immense.

Obesogens in Foods

Obesogens, as environmental endocrine-disrupting chemicals, are supposed to have had an impact on the prevalence of rising obesity around the world over the last forty years. These chemicals are probably able to contribute not only to the development of obesity and metabolic disturbances in individuals, but also in their progeny, having the capability to epigenetically reprogram genetically inherited set-up points for body weight and body composition control during critical periods of development, such as fetal, early life, and puberty. In individuals, they may act on myriads of neuro-endocrine–immune metabolic regulatory pathways, leading to pathophysiological consequences in adipogenesis, lipogenesis, lipolysis, immunity, the influencing of central appetite and energy expenditure regulations, changes in gut microbiota–intestine functioning, and many other processes. Evidence-based medical data have recently brought much more convincing data about associations of particular chemicals and the probability of the raised risk of developing obesity. Foods are the main source of obesogens. Some obesogens occur naturally in food, but most are environmental chemicals, entering food as a foreign substance, whether in the form of contaminants or additives, and they are used in a large amount in highly processed food. This review article contributes to a better overview of obesogens, their occurrence in foods, and their impact on the human organism.

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.

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.

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.

The impact of endocrine-disrupting chemical exposure in the mammalian hypothalamic-pituitary axis

The hypothalamic-pituitary axis (HP axis) plays a critical and integrative role in the endocrine system control to maintain homeostasis. The HP axis is responsible for the hormonal events necessary to regulate the thyroid, adrenal glands, gonads, somatic growth, among other functions. Endocrine-disrupting chemicals (EDCs) are a worldwide public health concern. There is growing evidence that exposure to EDCs such as bisphenol A (BPA), some phthalates, polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs) and biphenyls (PBBs), dichlorodiphenyltrichloroethane (DDT), tributyltin (TBT), and atrazine (ATR), is associated with HP axis abnormalities. EDCs act on hormone receptors and their downstream signaling pathways and can interfere with hormone synthesis, metabolism, and actions. Because the HP axis function is particularly sensitive to endogenous hormonal changes, disruptions by EDCs can alter HP axis proper function, leading to important endocrine irregularities. Here, we review the evidence that EDCs could directly affect the mammalian HP axis function.

Disruptive effects of two organotin pesticides on the thyroid signaling pathway in Xenopus laevis during metamorphosis

Organotin compounds are the ubiquitous environmental pollutants due to their wide industrial and agricultural applications and unexpected releasing into the environment, which show characteristic of endocrine disruptors to interfere with the synthesis, receptor binding or action of endogenous-hormones. Organotin pesticides (OTPs) are used in agriculture and may impact endocrine functions on organisms. Thyroid hormones (THs) play fundamental roles in regulating the basal metabolism and energy balance, while thyroid function can be impaired by environmental contaminants. Therefore, it is crucial to clarify the effects and mechanisms of OTPs on hypothalamus-pituitary-thyroid (HPT) axis. In this study, Xenopus laevis tadpoles at stage 51 were exposed to fentin hydroxide and fenbutatin oxide (0.04, 0.20 and 1.00 μg·L^-1) for 21 days. It was found that both compounds caused inhibitory effects on metamorphic development of tadpoles (e.g., significant decrease in hindlimb length and retarding development). Triiodothyronine (T₃) significantly decreased in tadpoles exposed to 0.20 μg/L and 1.00 μg/L of the two OTPs for 14 days or 21 days. The expressions of TH responsive genes trβ, bteb and dio2 were down-regulated, while tshβ and slc5a5 were up-regulated. Surface plasmon resonance (SPR) binding assays showed that fentin hydroxide had a moderate affinity to recombinant human thyroid hormone receptor β but fenbutatin oxide did not have. Result of the SPR assay was highly consistent with the luciferase reporter gene assays that fentin hydroxide suppressed the relative luciferase activity in the presence of T₃ while fenbutatin oxide did not, demonstrating fentin hydroxide but not fenbutatin oxide displayed an antagonistic activity against T₃-TR complex mediated transcriptional activation. Overall, the findings elucidated the mechanisms induced by OTPs along HPT axis. These results highlighted the adverse influences of organotin pesticides on thyroid hormone- dependent development in vertebrates and the need for more comprehensive investigations of their potential ecological risks.

Tributyltin chloride (TBT) induces RXRA down-regulation and lipid accumulation in human liver cells

A subset of environmental chemicals acts as "obesogens" as they increase adipose mass and lipid content in livers of treated rodents. One of the most studied class of obesogens are the tin-containing chemicals that have as a central moiety tributyltin (TBT), which bind and activate two nuclear hormone receptors, Peroxisome Proliferator Activated Receptor Gamma (PPARG) and Retinoid X Receptor Alpha (RXRA), at nanomolar concentrations. Here, we have tested whether TBT chloride at such concentrations may affect the neutral lipid level in two cell line models of human liver. Indeed, using high content image analysis (HCA), TBT significantly increased neutral lipid content in a time- and concentration-dependent manner. Consistent with the observed increased lipid accumulation, RNA fluorescence in situ hybridization (RNA FISH) and RT-qPCR experiments revealed that TBT enhanced the steady-state mRNA levels of two key genes for de novo lipogenesis, the transcription factor SREBF1 and its downstream enzymatic target, FASN. Importantly, pre-treatment of cells with 2-deoxy-D-glucose reduced TBT-mediated lipid accumulation, thereby suggesting a role for active glycolysis during the process of lipid accumulation. As other RXRA binding ligands can promote RXRA protein turnover via the 26S proteasome, TBT was tested for such an effect in the two liver cell lines. We found that TBT, in a time- and dose-dependent manner, significantly reduced steady-state RXRA levels in a proteasome-dependent manner. While TBT promotes both RXRA protein turnover and lipid accumulation, we found no correlation between these two events at the single cell level, thereby suggesting an additional mechanism may be involved in TBT promotion of lipid accumulation, such as glycolysis.

Down-regulation of vimentin by triorganotin isothiocyanates-nuclear retinoid X receptor agonists: A proteomic approach

An attempt has been made to delineate the role of natural and synthetic retinoid receptor ligands on vimentin expression in the human triple-negative breast cancer cells. The effects of currently synthesized triorganotin derivatives of the general formula R₃SnX (R is butyl or phenyl, X is isothiocyanate), which are considered RXR ligands, were investigated in the human MDA-MB-231 breast cancer cell line. Studies were evaluated in the presence and absence of all-trans retinoic acid (ATRA), a natural RAR ligand. Vimentin represents the major protein associated with epithelial-mesenchymal transition (EMT), an essential process when the primary tumour transforms into a malignant one. mRNA and proteomic data obtained in this study, based on the PDQuest software protein evaluation and further quantification of proteins by iTRAQ analysis, suggest that vimentin was significantly reduced in the combination of RAR ligand and RXR ligand treatment. Both tested triorganotin compounds showed similarly reduced expression of vimentin, but tributyltin isothiocyanate (TBT-ITC) proved to be more effective than triphenyltin isothiocyanate (TPT-ITC). Furthermore, the effect of natural (9cRA) and synthetic RXR ligands, both chloride and isothiocyanate derivatives, on vimentin expression was compared.

Metabolism Disrupting Chemicals and Alteration of Neuroendocrine Circuits Controlling Food Intake and Energy Metabolism

The metabolism-disrupting chemicals (MDCs) are molecules (largely belonging to the category of endocrine disrupting chemicals, EDCs) that can cause important diseases as the metabolic syndrome, obesity, Type 2 Diabetes Mellitus or fatty liver. MDCs act on fat tissue and liver, may regulate gut functions (influencing absorption), but they may also alter the hypothalamic peptidergic circuits that control food intake and energy metabolism. These circuits are normally regulated by several factors, including estrogens, therefore those EDCs that are able to bind estrogen receptors may promote metabolic changes through their action on the same hypothalamic circuits. Here, we discuss data showing how the exposure to some MDCs can alter the expression of neuropeptides within the hypothalamic circuits involved in food intake and energy metabolism. In particular, in this review we have described the effects at hypothalamic level of three known EDCs: Genistein, an isoflavone (phytoestrogen) abundant in soy-based food (a possible new not-synthetic MDC), Bisphenol A (compound involved in the manufacturing of many consumer plastic products), and Tributyltin chloride (one of the most dangerous and toxic endocrine disruptor, used in antifouling paint for boats).