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

Maternal exposure to tributyltin alters the breast milk, hormonal profile, and thyroid morphology of dams and induces sex-specific changes in neonate rat offspring

Tributyltin (TBT) is the chemical substance commonly used worldwide to prevent biofouling of vessels. Due to its ability to bioaccumulate and biomagnify, even after being banned, significant concentrations of TBT can be detected in sediment, affecting marine and human life. Although studies have shown that direct exposure to TBT alters physiological parameters in mammals, the relationship between exposure to TBT during pregnancy and lactation, considered critical windows for metabolic programming, has not been fully elucidated. Our hypothesis is that offspring whose mothers were exposed to TBT during critical stages of development may exhibit dysfunctions in endocrine-metabolic parameters. We used pregnant Wistar rats that were divided into groups and received the following treatments from gestational day 7 until the end of lactation by intragastric gavage: vehicle (ethanol 0.01%; Control), low TBT dose (100 ng/kg of body weight (bw)/day; TBT100ng) and high TBT dose (1000 ng/kg bw/day; TBT1000ng). Dams and offspring at birth and weaning (21 days old) were studied. Maternal exposure to TBT promoted dose-dependent changes in dams. The findings for adiposity, milk composition and lipid profile were more pronounced in TBT100 ng dam; however, thyroid morphology was altered in TBT1000 ng dam. Female offspring were differentially affected by the dose of exposure. At birth, females in the TBT100ng group had low body weight, lower naso-anal length (NAL), and higher plasma T4, and at weaning, females in the TBT100ng group had lower insulin and leptin levels. Females in the TBT1000ng group had lower NAL at birth and lower leptinemia and weight of white adipose tissue at weaning. Male offspring from TBT groups showed high T3 at birth, without biometric alterations at birth or weaning. Despite these findings, both sexes exhibited dose-dependent morphological changes in the thyroid gland. Thus, maternal exposure to TBT constitutes an important route of contamination for both dams and offspring.

Subacute cadmium exposure changes different metabolic functions, leading to type 1 and 2 diabetes mellitus features in female rats

Cadmium (Cd) is a heavy metal that acts as endocrine disrupting chemical (EDC). Few studies have investigated the effects of Cd exposure on metabolic dysfunctions, such as type 1 and 2 diabetes mellitus (T1DM and T2DM). Thus, we assessed whether subacute Cd exposure at occupational levels causes abnormalities in white adipose tissue (WAT), liver, pancreas, and skeletal muscle. We administered cadmium chloride (CdCl2) (100 ppm in drinking water for 30 days) to female rats and evaluated Cd levels in serum and metabolic organs, morphophysiology, inflammation, oxidative stress, fibrosis, and gene expression. High Cd levels were found in serum, WAT, liver, pancreas, and skeletal muscle. Cd-exposed rats showed low adiposity, dyslipidemia, insulin resistance, systemic inflammation, and oxidative stress compared to controls. Cd exposure reduced adipocyte size, hyperleptinemia, increased cholesterol levels, inflammation, apoptosis and fibrosis in WAT. Cd-exposed rats had increased liver cholesterol levels, insulin receptor beta (IRβ) and peroxisome proliferator-activated receptor-gamma coactivator-1alpha (PGC1α) expression, karyomegaly, inflammation, and fibrosis. Cd exposure reduced insulin levels and pancreatic islet size and increased inflammation and fibrosis. Cd exposure reduced skeletal muscle fiber diameter and increased IR expression and inflammation. Finally, strong positive correlations were observed between serum, tissue Cd levels, abnormal morphology, tissue inflammation and fibrosis. Thus, these data suggest that subacute Cd exposure impairs WAT, liver, pancreas and skeletal muscle function, leading to T1DM and T2DM features and other complications in female rats.

Environmental Endocrinology: Parabens Hazardous Effects on Hypothalamic-Pituitary-Thyroid Axis

Parabens are classified as endocrine-disrupting chemicals (EDCs) capable of interfering with the normal functioning of the thyroid, affecting the proper regulation of the biosynthesis of thyroid hormones (THs), which is controlled by the hypothalamic-pituitary-thyroid axis (HPT). Given the crucial role of these hormones in health and the growing evidence of diseases related to thyroid dysfunction, this review looks at the effects of paraben exposure on the thyroid. In this study, we considered research carried out in vitro and in vivo and epidemiological studies published between 1951 and 2023, which demonstrated an association between exposure to parabens and dysfunctions of the HPT axis. In humans, exposure to parabens increases thyroid-stimulating hormone (TSH) levels, while exposure decreases TSH levels in rodents. The effects on THs levels are also poorly described, as well as peripheral metabolism. Regardless, recent studies have shown different actions between different subtypes of parabens on the HPT axis, which allows us to speculate that the mechanism of action of these parabens is different. Furthermore, studies of exposure to parabens are more evident in women than in men. Therefore, future studies are needed to clarify the effects of exposure to parabens and their mechanisms of action on this axis.

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.

Tributyltin chloride (TBTCL) induces cell injury via dysregulation of endoplasmic reticulum stress and autophagy in Leydig cells

Tributyltin chloride (TBTCL), a commonly used antiseptic substance, is commonly found in the environment. Human exposure to TBTCL through the consumption of contaminated seafood, fish, or drinking water has aroused concern. It is well-characterized that TBTCL has multiple detrimental effects on the male reproductive system. However, the potential cellular mechanisms are not fully elucidated. Here, we characterized molecular mechanisms of TBTCL-induced cell injury in Leydig cells, a critical supporter for spermatogenesis. We showed that TBTCL induces apoptosis and cell cycle arrest in TM3 mouse Leydig cells. RNA sequencing analyses revealed that endoplasmic reticulum (ER) stress and autophagy were potentially involved in TBTCL-induced cytotoxicity. We further showed that TBTCL causes ER stress and inhibited autophagy flux. Notably, the inhibition of ER stress attenuates not only TBTCL-induces autophagy flux inhibition but also apoptosis and cell cycle arrest. Meanwhile, the activation of autophagy alleviates, and inhibition of autophagy exaggerates TBTCL-induced apoptosis and cell cycle arrest flux. These results suggest that TBTCL-induced ER stress and autophagy flux inhibition contributed to apoptosis and cell cycle arrest in Leydig cells, providing novel understanding into the mechanisms of TBTCL-induced testis toxicity.

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

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

Organotin Antifouling Compounds and Sex-Steroid Nuclear Receptor Perturbation: Some Structural Insights

Organotin compounds (OTCs) are a commercially important group of organometallic compounds of tin used globally as polyvinyl chloride stabilizers and marine antifouling biocides. Worldwide use of OTCs has resulted in their ubiquitous presence in ecosystems across all the continents. OTCs have metabolic and endocrine disrupting effects in marine and terrestrial organisms. Thus, harmful OTCs (tributyltin) have been banned by the International Convention on the Control of Harmful Antifouling Systems since 2008. However, continued manufacturing by non-member countries poses a substantial risk for animal and human health. In this study, structural binding of common commercial OTCs, tributyltin (TBT), dibutyltin (DBT), monobutyltin (MBT), triphenyltin (TPT), diphenyltin (DPT), monophenyltin (MPT), and azocyclotin (ACT) against sex-steroid nuclear receptors, androgen receptor (AR), and estrogen receptors (ERα, ERβ) was performed using molecular docking and MD simulation. TBT, DBT, DPT, and MPT bound deep within the binding sites of AR, ERα, and Erβ, showing good dock score, binding energy and dissociation constants that were comparable to bound native ligands, testosterone and estradiol. The stability of docking complex was shown by MD simulation of organotin/receptor complex with RMSD, RMSF, Rg, and SASA plots showing stable interaction, low deviation, and compactness of the complex. A high commonality (50-100%) of interacting residues of ERα and ERβ for the docked ligands and bound native ligand (estradiol) indicated that the organotin compounds bound in the same binding site of the receptor as the native ligand. The results suggested that organotins may interfere with the natural steroid/receptor binding and perturb steroid signaling.

High-refined carbohydrate diet alters different metabolic functions in female rats

A diet containing refined carbohydrate (HCD) caused obesity and white adipose tissue (WAT) abnormalities, but it is unclear if HCD is linked with other metabolic dysfunctions in female models. Thus, we assessed whether HCD results in WAT, pancreas, liver, skeletal muscle (SM) and thyroid (TH) abnormalities in female rats. Female rats were fed with HCD for 15 days and metabolic morphophysiology, inflammation, oxidative stress (OS), and fibrosis markers were assessed. HCD rats presented large adipocytes, hyperleptinemia, and WAT OS. HCD caused irregular glucose metabolism, low insulin levels, and large pancreatic isle. Granulomas, reduced glycogen, and OS were observed in HCD livers. HCD caused hypertrophy and increased in glycogen in SM. HCD caused irregular TH morphophysiology, reduced colloid area and high T3 levels. In all selected tissues, inflammation and fibrosis were observed in HCD rats. Collectively, these data suggest that the HCD impairs metabolic function linked with irregularities in WAT, pancreas, liver, SM and TH in female rats.