Subacute exposure to a mixture of tributyltin plus mercury impairs reproductive axis function, exacerbating premature ovarian insufficiency features and reducing fertility in female rats.

Tributyltin (TBT) and mercury (Hg) are endocrine-disrupting chemicals that individually cause reproductive complications. However, the reproductive consequences of exposure to a mixture of TBT plus Hg are not well known. We hypothesized that exposure to a mixture of TBT plus Hg would alter hypothalamic-pituitary-gonadal (HPG) axis function. Female rats were exposed to this mixture daily for 15 days, after which chemical accumulation in the tissues, morphology, hormone levels, inflammation, fibrosis, and protein expression in the reproductive organs were assessed. Increases in tin (Sn) and Hg levels were detected in the serum, HPG axis, and uterus of TBT-Hg rats. TBT-Hg rats exhibited irregular estrous cycles. TBT-Hg rats showed an increase in gonadotropin-releasing hormone (GnRH) protein expression and follicle-stimulating hormone (FSH) levels and a reduction in luteinizing hormone (LH) levels. Reduced ovarian reserve, antral follicles, corpora lutea (CL) number, and estrogen levels and increased atretic and cystic follicles were found, suggesting that TBT-Hg exposure exacerbated premature ovarian insufficiency (POI) features. Furthermore, TBT-Hg rats exhibited increased ovarian mast cell numbers, expression of the inflammatory markers IL-6 and collagen deposition. Apoptosis and reduced gland number were observed in the uteri of TBT-Hg rats. A reduction in the number of pups/litter for 90 days was found in TBT-Hg rats, suggesting impaired fertility. Strong negative correlations were found between serum and ovarian Sn levels and ovarian Hg levels and ovarian reserve and CL number. Collectively, these data suggest that TBT plus Hg exposure leads to abnormalities in the HPG axis, exacerbating POI features and reducing fertility in female rats.

Environmental obesogen tributyltin chloride leads to abnormal hypothalamic-pituitary-gonadal axis function by disruption in kisspeptin/leptin signaling in female rats.

Tributyltin chloride (TBT) is a xenobiotic used as a biocide in antifouling paints that has been demonstrated to induce endocrine-disrupting effects, such as obesity and reproductive abnormalities. An integrative metabolic control in the hypothalamus-pituitary-gonadal (HPG) axis was exerted by leptin. However, studies that have investigated the obesogenic TBT effects on the HPG axis are especially rare. We investigated whether metabolic disorders as a result of TBT are correlated with abnormal hypothalamus-pituitary-gonadal (HPG) axis function, as well as kisspeptin (Kiss) action. Female Wistar rats were administered vehicle and TBT (100ng/kg/day) for 15days via gavage. We analyzed their effects on the tin serum and ovary accumulation (as biomarker of TBT exposure), estrous cyclicity, surge LH levels, GnRH expression, Kiss action, fertility, testosterone levels, ovarian apoptosis, uterine inflammation, fibrosis, estrogen negative feedback, body weight gain, insulin, leptin, adiponectin levels, as well as the glucose tolerance (GTT) and insulin sensitivity tests (IST). TBT led to increased serum and ovary tin levels, irregular estrous cyclicity, and decreased surge LH levels, GnRH expression and Kiss responsiveness. A strong negative correlation between the serum and ovary tin levels with lower Kiss responsiveness and GnRH mRNA expression was observed in TBT rats. An increase in the testosterone levels, ovarian and uterine fibrosis, ovarian apoptosis, and uterine inflammation and a decrease in fertility and estrogen negative feedback were demonstrated in the TBT rats. We also identified an increase in the body weight gain and abnormal GTT and IST tests, which were associated with hyperinsulinemia, hyperleptinemia and hypoadiponectinemia, in the TBT rats. TBT disrupted proper functioning of the HPG axis as a result of abnormal Kiss action. The metabolic dysfunctions co-occur with the HPG axis abnormalities. Hyperleptinemia as a result of obesity induced by TBT may be associated with abnormal HPG function. A strong negative correlation between the hyperleptinemia and lower Kiss responsiveness was observed in the TBT rats. These findings provide evidence that TBT leads to toxic effects direct on the HPG axis and/or indirectly by abnormal metabolic regulation of the HPG axis.

Tributyltin chloride induces renal dysfunction by inflammation and oxidative stress in female rats.

Tributyltin chloride (TBT) is an organometallic pollutant that is used as a biocide in antifouling paints. TBT induces several toxic and endocrine-disrupting effects. However, studies evaluating the effects of TBT on renal function are rare. This study demonstrates that TBT exposure is responsible for improper renal function as well as the development of abnormal morphophysiology in mammalian kidneys. Female rats were treated with TBT, and their renal morphophysiology was assessed. Morphophysiological abnormalities such as decreased glomerular filtration rate and increased proteinuria levels were observed in TBT rats. In addition, increases in inflammation, collagen deposition and α-smooth muscle actin (α-SMA) protein expression were observed in TBT kidneys. A disrupted cellular redox balance and apoptosis in kidney tissue were also observed in TBT rats. TBT rats demonstrated reduced serum estrogen levels and estrogen receptor-α (ERα) protein expression in renal cortex. Together, these data provide in vivo evidence that TBT is toxic to normal renal function and that these effects may be associated with renal histopathology complications, such as inflammation and fibrosis.

Acute iron overload leads to hypothalamic-pituitary-gonadal axis abnormalities in female rats.

Iron plays a critical role in a mammal's physiological processes. However, iron tissue deposits have been shown to act as endocrine disrupters. Studies that evaluate the effect of acute iron overload on hypothalamic-pituitary-gonadal (HPG) axis health are particularly sparse. This study demonstrates that acute iron overload leads to HPG axis abnormalities, including iron accumulation and impairment in reproductive tract morphology. Female rats were treated with iron-dextran (Fe rats) to assess their HPG morphophysiology. The increasing serum iron levels due to iron-dextran treatment were positively correlated with higher iron accumulation in the HPG axis and uterus of Fe rats than in control rats. An increase in the production of superoxide anions was observed in the pituitary, uterus and ovary of Fe rats. Morphophysiological reproductive tract abnormalities, such as abnormal ovarian follicular development and the reduction of serum estrogen levels, were observed in Fe rats. In addition, a significant negative correlation was obtained between ovary superoxide anion and serum estrogen levels. Together, these data provide in vivo evidence that acute iron overload is toxic for the HPG axis, a finding that may be associated with the subsequent development of the risk of reproductive dysfunction.

Accumulation of organotins in seafood leads to reproductive tract abnormalities in female rats.

Organotins (OTs) are environmental contaminants used as biocides in antifouling paints that have been shown to be endocrine disrupters. However, studies evaluating the effects of OTs accumulated in seafood (LNI) on reproductive health are particularly sparse. This study demonstrates that LNI leads to impairment in the reproductive tract of female rats, as the estrous cycle development, as well as for ovary and uterus morphology. Rats were treated with LNI, and their reproductive morphophysiology was assessed. Morphophysiological abnormalities, such as irregular estrous cycles, abnormal ovarian follicular development and ovarian collagen deposition, were observed in LNI rats. An increase in luminal epithelia and ERα expression was observed in the LNI uteri. Together, these data provide in vivo evidence that LNI are toxic for reproductive morphophysiology, which may be associated with risks to reproductive function.

Tributyltin chloride leads to adiposity and impairs metabolic functions in the rat liver and pancreas.

Tributyltin chloride (TBT) is an environmental contaminant used in antifouling paints of boats. Endocrine disruptor effects of TBT are well established in animal models. However, the adverse effects on metabolism are less well understood. The toxicity of TBT in the white adipose tissue (WAT), liver and pancreas of female rats were assessed. Animals were divided into control and TBT (0.1 µg/kg/day) groups. TBT induced an increase in the body weight of the rats by the 15th day of oral exposure. The weight gain was associated with high parametrial (PR) and retroperitoneal (RP) WAT weights. TBT-treatment increased the adiposity, inflammation and expression of ERα and PPARγ proteins in both RP and PR WAT. In 3T3-L1 cells, estrogen treatment reduced lipid droplets accumulation, however increased the ERα protein expression. In contrast, TBT-treatment increased the lipid accumulation and reduced the ERα expression. WAT metabolic changes led to hepatic inflammation, lipid accumulation, increase of PPARγ and reduction of ERα protein expression. Accordingly, there were increases in the glucose tolerance and insulin sensitivity tests with increases in the number of pancreatic islets and insulin levels. These findings suggest that TBT leads to adiposity in WAT specifically, impairing the metabolic functions of the liver and pancreas.

Effect of dietary cadmium on fitness, growth, genotoxicity and accumulation in the Yellow-spotted River Turtle, Podocnemis unifilis.

The aim of this study was to expose the Yellow-spotted River Turtle, Podocnemis unifilis, to dietary cadmium (Cd) contamination. The P. unifilis were fed with a Cd contaminated diet (590 µgg(-1)) or a control diet for 30 and 60 days. After the Cd feeding period, the locomotor performance and specific growth rate were assessed. Blood samples were drawn for micronuclei analysis and tissues were collected to analyze the Cd concentration. Dietary Cd influenced the fitness of turtles at 30 days (righting time 752s), but not after 60 days (righting time 43.67s). Micronuclei in erythrocytes (12 ± 5‰) were significantly greater in contaminated turtle at 60 days. Cd accumulation is found in gut, intestine, kidney, fat, liver and blood of animals from contaminated diet group and the Cd concentration of almost all the tissues had increased following the 30-60-day feeding period. Cd does not impair animal the fitness after sixty days of dietary treatment, but it does can cause an accumulation on P. unifilis.