A Mixture of Ammonium Perchlorate and Sodium Chlorate Enhances Alterations of the Pitutary-Thyroid Axis Caused by the Individual Chemicals in Adult Male F344 Rats

Nigella sativa oil restores hormonal levels, and endocrine signals among thyroid, ovarian, and uterine tissues of female Wistar rats following sodium fluoride toxicity

The current study aimed to explore the possible prophylactic and therapeutic effect of Nigella sativa L. oil (NSO) against disruption of endocrine signals and injuries in the thyroid gland, ovary, and uterine tissues induced by sodium fluoride (NaF). Twenty-eight mature female Wistar rats were randomly allocated into four experimental groups (n = 7/group) as follows: control group; NaF group, orally received NaF (20 mg/kg b.wt.) daily; NSO/NaF, orally received NSO (300 mg/kg b.wt.) two weeks before being given NaF and continued throughout the experiment; and NSO+NaF group orally received NSO concurrently with NaF. Our results indicated that NSO restored hormonal balance and suppressed oxidative damage and inflammation. Moreover, the levels of triiodothyronine, thyroxine, thyroid peroxidase, estrogen (E2), progesterone, follicle-stimulating hormone, and luteinizing hormone were elevated, while prostaglandins F2-α and cortisol levels were decreased in NSO treated groups compared to NaF-intoxicated rats. As well, NSO significantly boosted levels of antioxidant molecules, and lowered lipid peroxidation of examined tissues, unlike NaF-treated group. NSO also up-regulated antioxidant enzymes, anti-apoptotic protein, zona pellucida sperm-binding protein, bone morphogenetic protein, and thyroid stimulating hormone, conversely down-regulated inflammatory cytokines, apoptotic proteins, estrogen receptor-α, estrogen receptor-β, and thyroid stimulating hormone receptors compared to NaF-intoxicated group. Additionally, NSO ameliorated tissue damage of the thyroid gland, ovary, and uterus induced by NaF. -Overall, the prophylactic group (NSO/NaF) performed better antioxidant and anti-inflammatory activities than the treated group almost in all examined tissues, which is reflected by the improvement in the structure of the thyroid, ovarian, and uterine tissues.

Exogenous Melatonin Protects against Oxidative Damage to Membrane Lipids Caused by Some Sodium/Iodide Symporter Inhibitors in the Thyroid

The thyroid gland is the primary site of sodium/iodide symporter (NIS), an intrinsic plasma membrane protein responsible for the active uptake of iodine, which is indispensable for thyroid hormone synthesis. Since exposure of the thyroid to NIS inhibitors can potentially have harmful effects on the entire organism, it is important to investigate the potential protective effects of known antioxidants, such as melatonin and indole-3-propionic acid (IPA), against pro-oxidative action of classic NIS inhibitors. The study aimed to check if and to what extent melatonin and IPA interact with some confirmed NIS inhibitors regarding their effects on oxidative damage to membrane lipids in the thyroid. For comparison with the thyroid gland, in which NIS is typically present, the liver tissue-not possessing NIS-was applied in the present study. Thyroid and liver homogenates were incubated in the presence of tested NIS inhibitors (i.e., NaClO3, NH4SCN, KSeCN, KNO3, NaF, KClO4, and BPA) in different ranges of concentrations with/without melatonin (5 mM) or IPA (5 mM). The malondialdehyde+4-hydroxyalkenals (MDA + 4-HDA) concentration (LPO index) was measured spectrophotometrically. NaClO3 increased LPO in the thyroid and in the liver, but these pro-oxidative effects were not prevented by either melatonin or IPA. Instead, pro-oxidative effects of NH4SCN observed in both tissues were prevented by both indole substances. KSeCN and NaF increased LPO only in the thyroid, and these pro-oxidative effects were prevented by melatonin and IPA. KNO3, KClO4, and BPA did not increase LPO, which can be due to their low concentrations resulting from restricted solubility. In conclusion, as melatonin prevented oxidative damage to membrane lipids in the thyroid caused by some sodium/iodide symporter inhibitors, this indoleamine shoud be considered as a potential protective agent when produced appropriately in living organisms but also as an exogenous substance recommended to individuals overexposed to NIS inhibitors.

Protective effects of curcumin against thyroid hormone imbalance after gas explosion-induced traumatic brain injury via activation of the hypothalamic-pituitary-thyroid axis in male rats

Gas explosion (GE)-induced traumatic brain injury (TBI) can affect thyroid hormone (TH) homeostasis in miners. This study evaluated the effects of hepatic transthyretin and hypothalamic-pituitary-thyroid (HPT) axis on thyroids and explored the protective effect and mechanism of curcumin on GE-induced TBI. Thirty rats were randomly divided into three groups (10 per group): first group (control group)-rats received GE treatment once; second group (GE group)-rats received GE treatment (200 m from the source of the explosion once); third group (GE + Cur group)-rats received curcumin (Cur) by lavage at a dose of 100 mg/kg/day once every other day for 7 days after receiving GE. After GE, the pathological changes were analyzed by hemotoxylin and eosin staining, and the levels of serum reactive oxygen species (ROS), urine iodine (UI), THs, nuclear factor-kappa B (NF-κB), superoxide dismutase (SOD), glutathione peroxidase (Gpx), and malondialdehyde (MDA) were analyzed using ELISA. Expression of proteins in the HPT axis of rats was examined by immunohistochemistry and Western blotting. We found that GE could induce pathologic changes in rat thyroid and liver. Serum levels of THs, NF-κB and serum redox state became unbalanced in rats after GE. GE could inhibit the biosynthesis and biotransformation of THs by affecting key HPT axis proteins. Additionally, GE reduced the level of hepatic transthyretin. Serum THs levels and thyroid sections were almost recovered to normal after curcumin treatment. The aforementioned key HPT axis proteins in the curcumin group showed opposite expression trends. In summary, GE affected THs balance while curcumin can protect against these injury effects by affecting TH biosynthesis, biotransformation, and transport, and inducing oxidative stress and inflammatory responses.

Detection of chlorite, chlorate and perchlorate in ozonated saline

Medical ozone is used to treat various diseases, including numerous pathologies associated with chronic pain. Chronic pain may be treated by systemic administration of ozone, with ozonated autohemotherapy (OAH) being the commonly used method. In the clinic, intravenous infusion of ozonized saline has been used to treat various diseases. Compared with OAH, ozonized saline infusion is less technically demanding and causes minimal damage to veins. However, it has been indicated that ozone may oxidize saline and generate toxic substances, and therefore, the safety of ozone treatment has been questioned. In the present study, the potential chemical compounds produced from ozone and saline, including chlorite, chlorate and perchlorate, were examined at various time-points with ion chromatography-mass spectrometry (IC-MS). A control group (pure oxygen group) and an ozone group were included in the present study. Two subgroups were included within each group: A saline bottle (made from polypropylene) subgroup and an ozone-resistant blood transfusion bag [made from medical polyvinyl chloride, di(2-ethyl) hexyl phthalate plasticized] subgroup. For the ozone group, 100 ml saline and 100 ml medical ozone at various concentrations (20, 40 or 60 µg/ml in pure oxygen) were injected into the saline bottle or blood bag, and for the control group, 100 ml of pure oxygen was injected into the saline bottle or blood bag. The presence and the content of chlorite, chlorate and perchlorate were determined at different time-points (3, 6 and 15 days after mixing) by IC-MS. Chlorate was detected in the ozone groups at three time-points and its content increased as the ozone concentration and the reaction time increased. Under the same conditions (the same ozone concentration and the same incubation time), the chlorate content (0.90±0.14-7.69±0.48 µg/l) in the blood bag subgroup was significantly lower than that in the saline bottle subgroup (45.23±6.14-207.6±15.63 µg/l). However, chlorite and perchlorate were not detected at any time-point in the two groups. In addition, in the control group (pure oxygen group), chlorite, chlorate and perchlorate were not detected at any time-point. These results indicate that ozone reacts with saline to produce chlorate. Ozone may also react with the polypropylene saline bottle to increase the chlorate content in the bottled solution. Due to a lack of toxicology studies of chlorate in blood, it remains elusive whether ozonated saline and chlorate at the range of 0.90±0.14-7.69±0.48 µg/l has any toxic effects. The potential toxicity of chlorate should be considered when ozonated saline is used for clinical infusions.

Possible protective effect of curcumin on the thyroid gland changes induced by sodium fluoride in albino rats: light and electron microscopic study

OBJECTIVES

Thyroid gland regulates the body's metabolic rate and plays an exquisitely important role in the human health. Fluoride exposure can affect thyroid function. Curcumin is a potent antioxidant that works through several mechanisms. The aim of the present study was to demonstrate the hormonal, histological, and ultrastructural changes occurred in the thyroid gland induced by exposure to sodium fluoride (NaF) and study the possible protective effect of curcumin on the NaF-induced effects.

METHODS

Thirty male albino rats were randomly divided into 3 equal groups (10 rats each): the control group, NaF group, and NaF+Curcumin (NaF+Cur) group. Thyroid-stimulating hormone (TSH), triiodothyronine (T3) and thyroxine (T4) levels were assayed and thyroid tissues processed for light and transmission electron microscopic study.

RESULTS

In NaF group, serum T3 and T4 levels were significantly decreased whereas TSH level was significantly increased compared to the control group. Thyroid tissues showed flattening of the epithelial lining with several follicular cell degenerations, hyperplasia, decreased colloid, disrupted basement membrane, cytoplasmic vacuolations, degenerated mitochondria, widening of rough endoplasmic reticulum cisternae, and vascular congestion compared to the control group. In the NaF+Cur group, serum TSH levels were significantly decreased in comparison with NaF group and no significant difference in comparison with the control group. Thyroid sections appeared apparently normal compared to the control group and NaF group.

CONCLUSIONS

Sodium fluoride affected both the function and structure of the thyroid gland while curcumin was protective against these toxic effects.

Acute renal toxicity of sodium chlorate: Redox imbalance, enhanced DNA damage, metabolic alterations and inhibition of brush border membrane enzymes in rats

Sodium chlorate (NaClO₃ ) is widely used in paper and pulp industries and as a non-selective herbicide. Humans can be exposed to NaClO₃ through contaminated drinking water due to its improper and unchecked usage in industries and as herbicide. NaClO₃ is also present as a major stable by-product in drinking water that has been disinfected with chlorine dioxide. In this study, we have investigated the effect of a single acute oral dose of NaClO₃ on rat kidney. Adult male Wistar rats were divided into one control and four NaClO₃ treated groups that were orally given different doses of NaClO₃ and euthanized 24 hr after the treatment. Oral administration of NaClO₃ resulted in increased hydrogen peroxide levels, lipid, and protein oxidation while thiol and glutathione content and activities of brush border membrane enzymes were decreased in kidney in a NaClO₃ dose-dependent manner. Significant alterations in the activities of enzymes involved in carbohydrate metabolism and antioxidant defense were also observed. Administration of NaClO₃ induced DNA fragmentation and increased DNA-protein cross-linking. Histological studies showed marked damage in kidney from NaClO₃ treated animals. These results strongly suggest that NaClO₃ induces nephrotoxicity via redox imbalance that results in DNA and membrane damage, metabolic alterations and brush border membrane enzyme dysfunction.

Sodium chlorate, a major water disinfection byproduct, alters brush border membrane enzymes, carbohydrate metabolism and impairs antioxidant system of Wistar rat intestine

Sodium chlorate (NaClO₃ ) is a widely used nonselective herbicide. It is also generated as a by-product during disinfection of drinking water by chlorine dioxide. The purpose of this study was to evaluate the effect of NaClO₃ on rat intestine. Adult male rats were randomly divided into five groups: control and remaining four groups were administered orally different doses of NaClO₃ and sacrificed 24 h after the treatment. The administration of NaClO₃ produced acute oxidative stress in the intestine, which manifested in the form of markedly enhanced malondialdehyde levels and carbonyl content and lowered total sulfhydryl groups and glutathione levels. The activities of several brush border membrane (BBM) enzymes were greatly reduced as compared to control. There were alterations in the activities of various enzymes of carbohydrate metabolism and those involved in maintaining the antioxidant defense system. Histological studies support the biochemical results showing NaClO₃ dose-dependent increase in tissue damage. Thus, the present study shows that oral administration of NaClO₃ decreases the activities of BBM enzymes, induces oxidative stress, alters metabolic pathways, and impairs the antioxidant system of rat intestine. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1607-1616, 2017.

Toxicity Profiles in Rats Treated with Tumorigenic and Nontumorigenic Triazole Conazole Fungicides: Propiconazole, Triadimefon, and Myclobutanil

Conazoles are a class of azole based fungicides used in agriculture and as pharmaceutical products. They have a common mode of antifungal action through inhibition of ergosterol biosynthesis. Some members of this class have been shown to be hepatotoxic and will induce mouse hepatocellular tumors and/or rat thyroid follicular cell tumors. The particular mode of toxic and tumorigenic action for these compounds is not known, however it has been proposed that triadimefon-induced rat thyroid tumors arise through the specific mechanism of increased TSH. The present study was designed to identify commonalities of effects across the different conazoles and to determine unique features of the tissue responses that suggest a toxicity pathway and a mode of action for the observed thyroid response for triadimefon. Male Wistar/Han rats were treated with triadimefon (100, 500, 1800 ppm), propiconazole (100, 500, 2500 ppm), or myclobutanil (100, 500, 2000 ppm) in feed for 4, 30, or 90 days. The rats were evaluated for clinical signs, body and liver weight, histopathology of thyroid and liver, hepatic metabolizing enzyme activity, and serum T3, T4, TSH, and cholesterol levels. There was a dose-dependent increase in liver weight but not body weight for all treatments. The indication of cytochrome induction, pentoxyresorufin O-dealkylation (PROD) activity, had a dose-related increase at all time points for all conazoles. Uridine diphopho-glucuronosyl transferase (UDPGT), the T4 metabolizing enzyme measured as glucuronidation of 1-naphthol, was induced to the same extent after 30 and 90 days for all three conazoles. Livers from all high dose treated rats had centrilobular hepatocyte hypertrophy after 4 days, while only triadimefon and propiconazole treated rats had hepatocyte hypertrophy after 30 days, and only triadimefon treated rats had hepatocyte hypertrophy after 90 days. Thyroid follicular cell hypertrophy, increased follicular cell proliferation, and colloid depletion were present only after 30 days in rats treated with the high dose of triadimefon. A dose-dependent decrease in T4 was present after 4 days with all 3 compounds but only the high doses of propiconazole and triadimefon produced decreased T4 after 30 days. T3 was decreased after high-dose triadimefon after 4 days and in a dose-dependent manner for all compounds after 30 days. Thyroid hormone levels did not differ from control values after 90 days and TSH was not increased in any exposure group. A unique pattern of toxic responses was not identified for each conazole and the hypothesized mode of action for triadimefon-induced thyroid gland tumors was not supported by the data.

An investigation of the formation of chlorate and perchlorate during electrolysis using Pt/Ti electrodes: the effects of pH and reactive oxygen species and the results of kinetic studies

The characteristics of chlorate (ClO(3)(-)) and perchlorate (ClO(4)(-)) formation were studied during the electrolysis of water containing chloride ions (Cl(-)). The experiments were performed using an undivided Pt/Ti plate electrode under different pH conditions (pH 3.6, 5.5, 7.2, 8.0 and 9.0). ClO(3)(-) and ClO(4)(-) were formed during electrolysis in proportion to the Cl(-) concentration. The generation rates of ClO(3)(-) and ClO(4)(-) under acidic conditions (pH 3.6 and 5.5) were lower than in basic pH conditions (pH 7.2, 8.0 and 9.0). However, the pH of the solution did not influence the conversion of ClO(3)(-) to ClO(4)(-). The effects of intermediately formed oxidants on the production of ClO(3)(-) and ClO(4)(-) were observed using sodium thiosulfate (Na(2)S(2)O(3)) as the active chlorine scavenger and tertiary butyl alcohol (t-BuOH) as the hydroxyl radical (OH) scavenger. The results revealed that electrolysis reactions that involved active chlorine contributed dominantly to ClO(3)(-) production. The direct oxidation reaction rate of Cl(-) to ClO(3)(-) was 13%. The OH species that were intermediately formed during electrolysis were also found to significantly affect ClO(3)(-) and ClO(4)(-) production. The key formation pathways of ClO(3)(-) and ClO(4)(-) were studied using kinetic model development.

Thyroid-disrupting chemicals: interpreting upstream biomarkers of adverse outcomes

BACKGROUND

There is increasing evidence in humans and in experimental animals for a relationship between exposure to specific environmental chemicals and perturbations in levels of critically important thyroid hormones (THs). Identification and proper interpretation of these relationships are required for accurate assessment of risk to public health.

OBJECTIVES

We review the role of TH in nervous system development and specific outcomes in adults, the impact of xenobiotics on thyroid signaling, the relationship between adverse outcomes of thyroid disruption and upstream causal biomarkers, and the societal implications of perturbations in thyroid signaling by xenobiotic chemicals.

DATA SOURCES

We drew on an extensive body of epidemiologic, toxicologic, and mechanistic studies.

DATA SYNTHESIS

THs are critical for normal nervous system development, and decreased maternal TH levels are associated with adverse neuropsychological development in children. In adult humans, increased thyroid-stimulating hormone is associated with increased blood pressure and poorer blood lipid profiles, both risk factors for cardiovascular disease and death. These effects of thyroid suppression are observed even within the "normal" range for the population. Environmental chemicals may affect thyroid homeostasis by a number of mechanisms, and multiple chemicals have been identified that interfere with thyroid function by each of the identified mechanisms.

CONCLUSIONS

Individuals are potentially vulnerable to adverse effects as a consequence of exposure to thyroid-disrupting chemicals. Any degree of thyroid disruption that affects TH levels on a population basis should be considered a biomarker of adverse outcomes, which may have important societal outcomes.

Identification of interspecies concordance of mechanisms of arsenic-induced bladder cancer

Exposure to arsenic causes cancer by inducing a variety of responses that affect the expression of genes associated with numerous biological pathways leading to altered cell growth and proliferation, signaling, apoptosis and oxidative stress response. Affymetrix GeneChip arrays were used to detect gene expression changes following dimethylarsinic acid (DMA) exposure to human bladder cells (UROtsa) or rat bladder cells (MYP3) and rat bladder epithelium in vivo at comparable doses. Using different experimental models coupled with transcriptional profiling allowed investigation of the correlation of mechanisms of DMA-induced toxicity between in vitro and in vivo treatment and across species. Our observations suggest that DMA-induced gene expression in UROtsa cells is distinct from that observed in the MYP3 cells. Principal component analysis shows a more distinct separation by treatment and dose in MYP3 cells as compared to UROtsa cells. However, at the level of pathways and biological networks, DMA affects both common and unique processes in the bladder transitional cells of human and rats. Twelve pathways were found common between human in vitro, rat in vitro and rat in vivo systems. These included signaling pathways involved in adhesion, cellular growth and differentiation. Fifty-five genes found to be commonly expressed between rat in vivo and rat in vitro systems were involved in diverse functions such as cell cycle regulation, lipid metabolism and protein degradation. Many of the genes, processes and pathways have previously been associated with arsenic-induced toxicity. Our finding reiterates and also identifies new biological processes that might provide more information regarding the mechanisms of DMA-induced toxicity. The results of our analysis further suggest that gene expression profiles can address pertinent issues of relevance to risk assessment, namely interspecies extrapolation of mechanistic information as well as comparison of in vitro to in vivo response.

Low-Dose Effects of Ammonium Perchlorate on the Hypothalamic-Pituitary-Thyroid Axis of Adult Male Rats Pretreated with PCB126

The objective of this research was to characterize the disturbances in the hypothalamic-pituitary-thyroid (HPT) axis resulting from exposure to a binary mixture, 3,3',4,4',5-pentachlorobiphenyl (PCB126) and perchlorate (ClO(4)(-)), known to cause hypothyroidism by different modes of action. Two studies were conducted to determine the HPT axis effects of ClO(4)(-) on adult male Sprague-Dawley rats pretreated with PCB126. In dosing study I, rats were administered a single oral dose of PCB126 (0, 7.5, or 75 microg/kg) on day 0 and 9 days later ClO(4)(-) (0, 0.01, 0.1, or 1 mg/kg day) was added to the drinking water until euthanasia on day 22. Significant dose-dependent trends were found for all thyroid function indices measured following ClO(4)(-) in drinking water for 14 days. Seventy-five micrograms PCB126/kg resulted in a significant increase in hepatic T(4)-glucuronide formation, causing a decline in serum thyroxine and fT(4), and resulting in increased serum thyroid-stimulating hormone (TSH). Serum TSH was also increased in animals that received 7.5 microg PCB126/kg; no other HPT axis alterations were found in these animals. When pretreated with PCB126, the ClO(4)(-) dose trends disappeared, suggesting a less than additive effect on the HPT axis. In dosing study II, animals were given lower doses of PCB126 (0, 0.075, 0.75, or 7.5 microg/kg) on day 0, and followed with ClO(4)(-) (0 or 0.01 mg/kg day) in drinking water beginning on day 1 and continuing for several days to explore transient HPT axis effects. No statistical effects were seen for PCB126 or ClO(4)(-) alone, and no perturbations were found when administered sequentially in dosing study II. In conclusion, these studies demonstrate that HPT axis disturbances following exposure to ClO(4)(-) are less than additive when pretreated with relatively high doses of PCB126. At relatively low doses, at or near the no-observed-effect-level for PCB126 and ClO(4)(-), no interactions between the chemicals occur.