Influence of thyroxine and n-propylthiouracil on nephro-toxicity of inorganic arsenic in rat

Significance of Inflammation and Apoptosis in Hepatocellular Death in Rat, Co-treated with Arsenic and Fluoride

Health effects elicited by combined environmental exposures to xenobiotics, in many instances, still remain unresolved. One of these examples is the combined toxicity of arsenic and fluoride. The present study was undertaken to delineate the role of inflammation and apoptosis in hepatocellular death caused by co-exposure to arsenic and fluoride in rat. Sodium arsenate (4 mg/kg body weight) and sodium fluoride (4 mg/kg body weight) were administered to female Wistar rats, individually and in combination, for 90 days. Results on tumor necrotic factor-α (TNF-α), interleukin-12 (IL-12), and comet assay showed increased values in comparison to those obtained in arsenic- or fluoride-treated rats. Results on NO, TBARS, and caspase-9 showed higher values than fluoride-treated rats but lower levels than arsenic-treated rats. It is hypothesized that increased generation of nitric oxide induces the release of cytokines that activates caspase-9. Caspase-9 promotes the synthesis of caspase-3 that executes apoptosis. Histopathological observations on apoptotic bodies and Kupffer cells support these observations.

Thyrotoxicity of arsenate and arsenite on juvenile mice at organism, subcellular, and gene levels under low exposure

Arsenic contamination in drinking water is a worldwide issue, posing threat to human health. Arsenic is an endocrine system disruptor, however, limited information is available regarding its long-term effects on thyroid endocrine system at low exposure. In this study, we assessed the thyroid toxicity of arsenate (AsV) and arsenite (AsIII) at 10-100 μg L^-1 in juvenile mice after 8-week of exposure via drinking water. After 1-2 week, AsV and AsIII had little influence on thyroxine (T4) level (56.3-64.7 μg L^-1) in mouse blood compared to control mice at 57.3-60.7 μg L^-1. However, after 4-8 weeks, 10 μg L^-1 AsIII or AsV increased T4 levels to 83.8-88.8 μg L^-1 compared to control treatment at 77.2-80.0 μg L^-1, while 100 μg L^-1 AsV or AsIII decreased T4 levels except for 100 μg L^-1 AsIII for 8 weeks. Based on transmission electron microscopy, exposure to 100 μg L^-1 AsIII or AsV for 8 weeks caused thyroid gland damage. In addition, exposure to AsV or AsIII at 10 or 100 μg L^-1 impacted gene transcription of hypothalamic-pituitary-thyroid axis including thyroid stimulating hormone and iodothyronine deiodinases. Our data demonstrated that exposing to low levels of AsIII or AsV disrupted T4 homeostasis, influenced the related gene transcription and damaged the thyroid glands in juvenile mice.

Arsenic impacted the development, thyroid hormone and gene transcription of thyroid hormone receptors in bighead carp larvae (Hypophthalmichthys nobilis)

Arsenic (As) contamination in aquatic environment adversely impacts aquatic organisms. The present study assessed the toxicity of different As species and concentrations on bighead carp (Hypophthalmichthys nobilis) at early life stage, a major fish in Yangtze River, China. We measured the changes in embryo and larvae survival rate, larvae aberration, concentrations of thyroid hormone thyroxine, and transcription levels of thyroid hormone receptors (TRs) in fish larvae after exposing to arsenite (AsIII) or arsenate (AsV) at 0, 10, 30, 50, 100, or 150 μg L(-1) for 78 h. As concentrations ≤ 150 μg L(-1) had limited effect on embryo survival rate (6-8% inhibition), but larvae survival rate decreased to 53-57% and larvae aberration rate increased to 20-24% after As exposure. Moreover, thyroxine levels elevated by 23% and 50% at 100 μg L(-1) AsIII and 150 μg L(-1) AsV. Besides, AsIII and AsV decreased the transcriptional levels of TRα by 72 and 53%, and TRβ by 91 and 81% at 150 μg L(-1) As. Our data showed that AsIII and AsV had limited effect on carp embryo survival, but they were both toxic to carp larvae, with AsIII showing more effect than AsV. As concentrations <150μg L(-1) adversely influenced the development of bighead carp larvae and disturbed their thyroid hormone homeostasis.

The protective effect of propylthiouracil against hepatotoxicity induced by chromium in adult mice

Environmental and occupational exposure to chromium compounds, especially hexavalent chromium (Cr(VI)), is widely recognized as potentially hepatotoxic in humans and animals. Its toxicity is associated with overproduction of free radicals, which induces oxidative damage. This study focused on the possible protective effect of propylthiouracil (PTU) against potassium dichromate (K2Cr2O7). Female mice were divided into four groups (groups I–IV) with seven animals in each group. Group I served as a control, which received tap water; group II received K2Cr2O7 alone (75 mg kg−1 body weight (b.w.)) via drinking water; group III received both K2Cr2O7 via drinking water and PTU by intramuscular injection at a dose 2.5 mg/100 g−1 b.w. twice a week, and group IV received PTU alone twice a week for 30 days. Exposure of mice to Cr promoted oxidative stress with an increase in malondialdehyde, protein carbonyl, and advanced oxidation protein product levels. Nonenzymatic antioxidants such as glutathione, nonprotein thiol, vitamin C levels and enzymatic antioxidant activities such as glutathione peroxidase and superoxide dismutase were decreased, while catalase activity was increased. Biomarkers of liver injury such as aspartate and alanine transaminases, lactate dehydrogenase activities, bilirubin, albumin, and glucose levels were increased, while triglyceride and cholesterol levels decreased. Coadministration of PTU restored the above-mentioned parameters to near-normal values. The histological findings confirmed the biochemical results.

Hypothyroidism protects di(n-butyl) phthalate-induced reproductive organs damage in Sprague-Dawley male rats

This study examined the deleterious effects of di(n-butyl) phthalate (DBP) on the male reproductive organs in hypothyroid rats. Hypothyroidism was induced in prepubertal male rats (28 days of age) by an intraperitonial (i.p.) injection of 10 mg/kg/day propylthiouracil (PTU) for 30 days. DBP (100 and 500 mg/kg/day) was administered by oral gavages to the intact or hypothyroid rats for 30 days. The body weight of the PTU-treated rats was significantly lower than the control group. The total triiodothyronine (T3) and thyroxine (T4) serum level was lower, and the thyroid-stimulating hormone (TSH) level was higher in the hypothyroid rats than in the control rats. The DBP treatment rats showed significantly lower testes, epididymides, seminal vesicles, and ventral prostate weights than the untreated rats. The hypothyroid rats had significantly higher thyroid weights and lower adrenal glands weights than the control rats. The histomorphological examination showed diffused Leydig cells hyperplasias and germ cells loss in the DBP (500 mg/kg)-treated rats, whereas these effects were mild in the DBP-treated hypothyroid rats. The serum levels of monobutyl phthalate (MBP) were significantly lower in PTU-induced hypothyroid rats than in the DBP-treated rats. This data suggests that the hypothyroid status might offer some protection from male reproductive organ toxicity caused by a disturbance in the metabolic activation of the parent compound, DBP.

Effect of n-propylthiouracil or thyroxine on arsenic trioxide toxicity in the liver of rat

Involvement of thyroid gland in the hepatotoxic manifestations of arsenic trioxide (As(III)) has been studied in rat. The effects of n-propylthiouracil (PTU) (a thyrotoxic compound) and L-thyroxine (a thyroid hormone) have been studied with reference to T(3) and T(4) values in the serum, arsenic concentration in the liver, Ca(2+) accumulation in the liver, aspartate transaminase, alanine transaminase and bilirubin values as the indicators of liver function, histopathological observations and finally the ultrastructural studies. It is concluded that hypothyroid condition protects against As(III) toxicity. Scavenging of reactive oxygen species (ROS) that significantly contribute in As(III) toxicity, by high intracellular concentration of reduced glutathione, as a consequence of PTU treatment is proposed as the plausible protective mechanism.