The role of the IRE1 pathway in excessive iodide- and/or fluoride-induced apoptosis in Nthy-ori 3-1 cells in vitro

Excessive iodide and fluoride coexist in the groundwater in many regions, causing a potential risk to the human thyroid. To investigate the mechanism of iodide- and fluoride-induced thyroid cytotoxicity, human thyroid follicular epithelial cells (Nthy-ori 3-1) were treated with different concentrations of potassium iodide (KI), with or without sodium fluoride (NaF). Cell morphology, viability, lactate dehydrogenase (LDH) leakage, apoptosis, and expression of inositol-requiring enzyme 1 (IRE1) pathway-related molecules were assessed. Results showed 50 mM of KI, 1 mM of NaF, and 50 mM of KI +1 mM of NaF changed cellular morphology, decreased viability, and increased LDH leakage and apoptosis. Elevated expression of binding protein (BiP), IRE1, and C/EBP homologous protein (CHOP) mRNA and protein, as well as spliced X-box-binding protein-1 (sXBP-1) mRNA, were observed in the 1 mM NaF and 50 mM KI +1 mM NaF groups. Collectively, excessive iodide and/or fluoride is cytotoxic to the human thyroid. Although these data do not manifest iodide could induce the IRE1 pathway, the cytotoxicity followed by exposure to fluoride alone or in combination with iodide may be related to IRE1 pathway-induced apoptosis. Furthermore, exposure to the combination of excessive iodide and fluoride may cause interactive effects on thyroid cytotoxicity.     

Studies on the carcinogenicity of potassium iodide in F344 rats.

A chronic toxicity and carcinogenicity study, in which male and female F344/DuCrj rats were given potassium iodide (KI) in the drinking water at concentrations of 0, 10, 100 or 1000 ppm for 104 weeks, and a two-stage carcinogenicity study of application at 0 or 1000 ppm for 83 weeks following a single injection of N-bis(2-hydroxypropyl)nitrosamine (DHPN), were conducted. In the former, squamous cell carcinomas were induced in the salivary glands of the 1000 ppm group, but no tumors were observed in the thyroid. In the two-stage carcinogenicity study, thyroidal weights and the incidence of thyroid tumors derived from the follicular epithelium were significantly increased in the DHPN+KI as compared with the DHPN alone group. The results of our studies suggest that excess KI has a thyroid tumor-promoting effect, but KI per se does not induce thyroid tumors in rats. In the salivary gland, KI was suggested to have carcinogenic potential via an epigenetic mechanism, only active at a high dose.     

The influence of chronic fluorosis on mitochondrial dynamics morphology and distribution in cortical neurons of the rat brain

The present study was designed to evaluate the effects of chronic fluorosis on the dynamics (including fusion and fission proteins), fragmentation, and distribution of mitochondria in the cortical neurons of the rat brain in an attempt to elucidate molecular mechanisms underlying the brain damage associated with excess accumulation of fluoride. Sixty Sprague–Dawley rats were divided randomly into three groups of 20 each, that is, the untreated control group (drinking water naturally containing <0.5 mg fluoride/l, NaF), the low-fluoride group (whose drinking water was supplemented with 10 mg fluoride/l) and the high-fluoride group (50 mg fluoride/l). After 6 months of exposure, the expression of mitofusin-1 (Mfn1), fission-1 (Fis1), and dynamin-related protein-1 (Drp1) at both the protein and mRNA levels were detected by Western blotting, immunohistochemistry, and real-time PCR, respectively. Moreover, mitochondrial morphology and distribution in neurons were observed by transmission electron or fluorescence microscopy. In the cortices of the brains of rats with chronic fluorosis, the level of Mfn1 protein was clearly reduced, whereas the levels of Fis1 and Drp1 were elevated. The alternations of expression of the mRNAs encoding all three of these proteins were almost the same as the corresponding changes at the protein levels. The mitochondria were fragmented and the redistributed away from the axons of the cortical neurons. These findings indicate that chronic fluorosis induces abnormal mitochondrial dynamics, which might in turn result in a high level of oxidative stress.     

硒、钼、硼对氟中毒大鼠氟斑牙发生的影响

目的 研究硒、钼、硼对氟中毒大鼠的氟斑牙发生的影响.方法 Wristar大鼠随机分为8组(雌雄各半):硒1组、硒2组、钼1组、钼2组、硼1组、硼2组、氟组、对照组.各组均喂以舍F-45mg/L的蒸馏水及舍不同浓度微量元素的饲料,观察大鼠的一般情况,氟斑牙的发生.结果 硒组体质量增加与对照组接近,优于钼组和硼组(P＜0....     

COMPARISON OF THE EFFECTS OF IODINE AND IODIDE ON THYROID FUNCTION IN HUMANS

Concerns have been raised over the use of iodine for disinfecting drinking water on extended space flights. Most fears revolve around effects of iodide on thyroid function. Iodine (I2) is the form used in drinking-water disinfection. Risk assessments have treated the various forms of iodine as if they were toxicologically equivalent. Recent experiments conducted in rats found that administration of iodine as I- (iodide) versus I2 had opposite effects on plasma thyroid hormone levels. I2-treated animals displayed elevated thyroxine (T4) and thyroxine/triiodothyronine (T4/T3) ratios, whereas those treated with I- displayed no change or reduced plasma concentrations of T4 at concentrations in drinking water of 30 or 100 mg/L. The study herein was designed to assess whether similar effects would be seen in humans as were observed in rats. A 14-d repeated-dose study utilizing total doses of iodine in the two forms at either 0.3 or 1 mg/kg body weight was conducted with 33 male volunteers. Thyroid hormones evaluated included T4, T3, and thyroid-stimulating hormone (TSH). TSH was significantly increased by the high dose of both I and I-2, as compared to the control. Decreases in T were observed with dose schedules with I-4 and I2, but none were statistically significant compared to each other, or compared to the control. This human experiment failed to confirm the differential effect of I2 on maintenance of serum T4 concentrations relative to the effect of I- that was observed in prior experiments in rats. However, based on the elevations in TSH, there should be some concern over the potential impacts of chronic consumption of iodine in drinking water.     

A comparative study of the influence of dimethyl sulfoxide on iodine metabolism in male Long-Evans rats and male CF1 mice

Young adult, male, Long-Evans rats 60–70 days of age, and young adult, male CF₁ mice, 90–100 days of age were injected with 85% dimethyl sulfoxide (DMSO). Several indices of thyroid function were examined in both mice and rats: iodide transport (T/S ratio), the response of the thyroid gland to injection of an acute substantial iodide load such as organification of the trapped iodide, and thyroidal ¹³¹I uptake as a function of time both in vivo and in vitro. There was no significant difference between saline-injected and DMSO-injected groups in thyroid: serum radioiodide concentration ratios (T/S) in either rats or mice. The injection of 200 μg carrier iodide elicited the acute Wolff-Chaikoff block in thyroid hormone synthesis in rats and mice and was not influenced by prior injection of 85% DMSO. Chromatographic analyses of thyroid Pronase hydrolysates in saline-injected and DMSO-injected groups of rats and mice revealed a pattern of distribution in thyroid labeling which was similar: a marked reduction in the percentage of labeled iodotyrosines and iodothyronines, an increased percentage of ¹³¹I-labeled iodide, and elevated monoiodotyrosine: diiodotyrosine ratios. DMSO did not influence thyroidal ¹³¹I uptake either in mice or rats. These findings indicate that 85% DMSO did not exert any significant influence on thyroid function either in the rat or mouse.     

Comparison of toxicity induced by iodine and iodide in male and female rats

In risk assessments the various forms of iodine have been treated as if they were toxicologically equivalent. While iodide (I-) and iodate (IO3-) have been studied, no studies concerned with the subchronic toxicity of iodine (I2) have been conducted in experimental animals. This study examined toxicities associated with iodine. Rats were treated with 0, 1, 3, 10, and 100 mg/l of either iodine or iodide (as Nal) in the drinking water for 100 d. Treatment had no effect on body, brain, or heart weights in either sex, or on testes weights in male rats. Although differences in kidney and liver weights were noted, they did not appear to be treatment related. Thyroid weight in male rats was significantly increased with an increasing concentration of iodide in the water, but not iodine. In contrast, thyroid weight decreased at the highest dose of iodide in female rats. Hematocrit, hemoglobin, and blood urea nitrogen (BUN) values were relatively constant and did not vary with treatment. There were no significant differences in AST, ALT, cholesterol, and triglyceride values. After 10 d on treatment a dose-related trend in increased plasma T4 concentrations was observed in both sexes treated with iodine. Statistically significant increases in the T4/T3 ratio in both sexes was also noted with iodine treatment. This increase was maintained for 100 d of treatment. Iodide did not produce this effect at 10 d. Although there was a significant increase in T4/T3 ratios in female rats after 100 d of treatment with iodide, the magnitude of the changes was smaller than that observed with iodine treatments. The results of this study indicate that iodine and iodide affect thyroid hormone status in substantially different ways.     

碘化钠诱导原代培养的猪甲状腺细胞凋亡的研究

目的:观察过量碘化钠对原代培养的猪甲状腺细胞凋亡的诱导作用。方法:取健康的猪甲状腺细胞培养24小时后,加入不同浓度的碘化钠,观察细胞的形态改变;琼脂糖凝胶电泳和流式细胞仪分析DNA的降解。结果:加入碘化钠后8小时左右,可见细胞凋亡,48小时左右达到高峰;琼脂糖凝胶电泳出现典型的梯状带;流式细胞仪可见亚二倍体高峰,细胞凋亡率随碘化钠浓度的升高而升高(P<0.05)。结论:过量碘化钠可诱导原代培养的猪甲状腺细胞发生凋亡,并呈剂量依赖关系。     

Effects of chronic ingestion of sodium fluoride on myocardium in a second generation of rats

Possible effects of long term exposure (6 months) to sodium fluoride (NaF) through drinking water on the morphology and biochemistry of myocardial tissue in second generation adult male rats were investigated. Wistar strain female and male rats were reared until the second generation of rats obtained, during which they were given 1, 10, 50 and 100 mg/L NaF in drinking water. Of the second generation, 28 male rats were divided into four groups and had the same treatment. All the second generation rats were sacrificed and autopsied at the end of the 6 months. In the samples of myocardial tissues, the levels of serum fluoride and the activities of principal antioxidant enzymes were determined, and a histopathological examination was conducted. Significant histopathological changes were found in the myocardial tissue of rats treated with 50 and 100 mg/L NaF. These were myocardial cell necrosis, extensive cytoplasmic vacuole formation, nucleus dissolution in myosits, swollen and clumped myocardial fibers, fibrillolysis, interstitial oedema, small hemorrhagic areas and hyperaemic vessels. Additionally, the increased activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), catalase (CAT) and thiobarbituric acid-reactive substance (TBARS) levels were observed in the myocardial tissues of rats treated with 10 and 50 mg/L NaF. On the other hand, the activities of SOD, GSH-Px, and CAT decreased, but the TBARS levels increased in the myocardial tissues of rats treated with 100 mg/L. The present results revealed that prolonged ingestion of fluoride through drinking water, particularly with high doses, induced significant histopathological and biochemical changes leading to myocardial tissue damage.     

siRNA抑制IRE1α蛋白表达对巨噬细胞凋亡的影响

目的研究游离胆固醇诱导内质网应激状态下,抑制IRE1α蛋白表达后对巨噬细胞凋亡的影响。方法取自C57BL6/J小鼠腹腔的野生型巨噬细胞和用IRE1α特异性siRNA干扰的巨噬细胞分别在普通培养基及普通培养基加胆固醇乙酰转移酶抑制剂和乙酰低密度脂蛋白(促进游离胆固醇聚集条件下)中进行培养,分组孵育8h后Annexin-V和碘化丙锭双染色后流式细胞仪检测细胞凋亡。结果在FC-loaded状态下经8h孵育,野生型巨噬细胞组大量巨噬细胞凋亡,达到(21.83±2.47)%;siRNA干扰组巨噬细胞的凋亡明显减少。结论结果表明游离胆固醇聚集到内质网后引起内质网应激,而激活内质网跨膜蛋白IRE1α是诱导巨噬细胞凋亡的关键。     

Developmental Toxicity Evaluation of Sodium Fluoride Administered to Rats and Rabbits in Drinking Water

Sodium fluoride (NaF; Cas No. 7681-49-4) is used in fluoridatingmunicipal water supplies, resulting in chronic exposure of millionsof people worldwide. Because of a lack of pertinent developmentaltoxicity studies in the literature, sodium fluoride was administeredad libitum in deionized/filtered drinking water (to mimic humanexposure) to Sprague-Dawley-derived rats (26/group) on GestationDays (GD) 6 through 15 at levels of 0, 50, 150, or 300 ppm andNew Zealand White rabbits (26/group) on GD 6 through 19 at levelsof 0, 100, 200, or 400 ppm. Higher concentrations via drinkingwater were not practicable due to the poor palatability of sodiumfluoride. Drinking water (vehicle) contained less than 0.6 ppmsodium fluoride (limit of detection) and sodium fluoride contentof the feed was 12.4 ppm fluoride (rats) and 15.6 ppm fluoride(rabbits). Maternal food, water, body weights, and clinicalsigns were recorded at regular intervals throughout these studies.Animals were killed on GD 20 (rats) or 30 (rabbits) and examinedfor implant status, fetal weight, sex, and morphological development.In the high-dose group of both studies there was an initialdecreased maternal body weight gain which recovered over timeand a decreased water consumption—attributed to decreasedpal atability. No clear clinical signs of toxicity were observed.Maternal exposure to sodium fluoride during organogenesis didnot significantly affect the frequency of postimplantation loss,mean fetal body weight/litter, or external, visceral or skeletalmalformations in either the rat or the rabbit. The NOAEL formaternal toxicity was 150 ppm sodium fluoride in drinking water({small tilde}18 mg/kg/day) for rats, and 200 ppm ({small tilde}18mg/kg/day) for rabbits. The NOAEL for developmental toxicitywas 300 ppm sodium fluoride ({small tilde}27 mg/kg/day) forrats and 400 ppm ({small tilde}29 mg/kg/day) for rabbits administeredduring organogenesis in drinking water. The total exposure tofluoride (mg F/kg body weight/day from food and drinking watercombined) in the mid- and high-dose groups for both specieswas >100-fold higher than the range at 0.014–0.08 mgF/kg/day estimated for a 70-kg person from food and fluoridated(1 ppm) drinking water.     

Two-generation reproduction study of ammonium perchlorate in drinking water in rats evaluates thyroid toxicity

Perchlorate is an inorganic ion that has recently been detected in drinking water supplies throughout the country, but little is known about its effects on reproductive function. This two-generation reproductive study examines the effects of ammonium perchlorate on the male and female reproductive systems in rats, and on the growth and development of offspring. Adult Sprague-Dawley rats (30/sex/group) were given continuous access to ammonium perchlorate in their drinking water at doses of 0, 0.3, 3.0, and 30.0 mg/kg-day. F1 generation rats were given the same ammonium perchlorate doses as their respective P1 generation sires and dams beginning at weaning and continuing through the day of sacrifice. Standard reproductive parameters were evaluated; blood was collected for determination of serum thyroid-stimulating hormone (TSH), triiodothyronine (T3), and thyroxine (T4) levels. Histopathological examination was conducted on major tissues, including the thyroid. No significant changes in developmental parameters were observed. In the F1 generation adult rats, relative thyroid weights were significantly increased in all dose groups for female rats and in the 3.0 and 30.0 mg/kg-day dose groups for male rats. Histopathologic changes in the thyroid consisted of hypertrophy and hyperplasia that increased in incidence and severity in a dose-related manner. Dose-related, statistically significant changes in TSH and T4 or T3 occurred at doses higher than those that resulted in changes in thyroid weight and thyroid histopathology, 30 mg/kg-day. Thus, perchlorate is not a reproductive toxicant in rats when administered in the drinking water at doses up to 30 mg/kg-day, but it can affect the thyroid at doses > or =3 mg/kg-day. Based on these findings, 0.3 mg/kg-day is identified to be the no-observable-adverse-effect level (NOAEL) for this study.     

Perchlorate inhibition of iodide uptake in normal and iodine-deficient rats

Perchlorate-induced inhibition of thyroidal iodide uptake was measured in normal and iodine-deficient female Sprague-Dawley rats. Rats that were made iodine-deficient by long-term restriction of iodine in the diet absorbed a gavage dose of 131I to the thyroid in proportionally greater amounts than rats fed a normal diet. Furthermore, the iodine-deficient rats maintained their high rates of absorption even when challenged by levels of perchlorate in their drinking water sufficient to produce pronounced inhibition of 131I uptake in rats fed a normal diet. Every dose of perchlorate used in this study (1.1, 5.6, and 28 mg/L) produced significant inhibition of iodide uptake in normally fed rats, but only the highest level of perchlorate (28 mg/L) significantly inhibited thyroidal uptake of 131I in the iodine-deficient rats. Taken together, these results demonstrate that iodide-deficient animals exhibit increased resistance to the inhibition of iodine absorption resulting from perchlorate exposure.     

Fluoride effects on ectopic bone formation in young and old rats

This study evaluated the effect of fluoride on bone fluoride levels and on ectopic bone formation in young and old rats. Eighty male Wistar rats were assigned to four groups (n = 20/g), which differed according to the fluoride concentration in their drinking water (0, 5, 15 and 50 mg/l). When half of the rats were 90 days old, demineralized bone matrix (DBM) was implanted. The other rats received DBM implants when they were 365 days old. The animals were killed 28 days after. Fluoride in the femur surface, whole femur and plasma was analyzed with an electrode. The implants were analyzed histomorphometrically. Data were tested for statistically significant differences by ANOVA, Tukey's test, t-test and linear regression (p < 0.05). Increases in plasma, femur surface and whole femur fluoride concentrations were observed as water fluoride levels increased. There was also a trend for increase in plasma and femur fluoride concentrations as age increased. Significant positive correlations were found between plasma and femur surface, plasma and femur and femur surface and femur fluoride concentrations. The morphometric analyses indicated an increase in bone formation for younger rats that received 5 mg/l of fluoride in the drinking water. However, this was not statistically significant. The younger rats that received 50 mg/l of fluoride showed impairment in bone formation. Bone formation was not significantly affected among the older rats. The results suggest that lower doses of fluoride in the drinking water, which slightly increase plasma fluoride levels, may have an anabolic effect on bone formation in younger rats.     

Indomethacin induces small intestinal damage and inhibits amitrole-associated thyroid carcinogenesis in rats initiated with N-bis(2-hydroxypropyl)nitrosamine

Effects of intestinal damage on thyroid carcinogenesis due to amitrole (AT) were examined in F344 male rats initiated with N-bis(2-hydroxypropyl)nitrosamine (DHPN). In experiment 1, rats were provided with diet containing 0.03% AT for 20 weeks after a single subcutaneous injection of DHPN (2800 mg/kg body weight), and concomitantly received 0.01% indomethacin (IM) in the diet to cause small intestinal damage or 1% dextran sodium sulfate (DSS) in the drinking water for induction of colitis following a schedule of intermittent 1-week administration and 1-week withdrawal for a total of 10 times. Groups without AT- and/or IM or DSS treatment were also included. Histopathological examination revealed significant reduction in the incidence and multiplicity of follicular cell adenomas and adenocarcinomas in the group concomitantly treated with IM, but no change in the DSS group, as compared with the AT alone group. In experiment 2, rats were similarly fed diet containing AT for 3 weeks with concomitant IM or DSS treatment after a DHPN initiation, and serum thyroid stimulating hormone levels were found to be significantly elevated only in the IM case. The increase in thyroid follicular cell proliferation due to AT was also clearly suppressed in the group concomitantly treated with IM. From these findings, IM-induced intestinal damage may inhibit thyroid carcinogeneisis in rats, although contributions of other factors, such as a direct inhibitory effect of IM to thyroid follicular cell proliferation cannot be ruled out.     

丁基苯酞对创伤性脑损伤模型大鼠神经功能的改善作用

目的探讨丁基苯酞(NBP)对创伤性脑损伤(TBI)模型大鼠神经功能的改善作用,以及对IRE1/XBP1信号通路的影响。方法将60只大鼠分为假手术组、模型组,以及NBP高、中、低剂量组(40,20,10mg/kg),各12只。采用改良Feeney自由落体撞击法复制大鼠TBI模型。建模后,各组大鼠腹腔注射相应药物,每天1次,持续7 d。评估大鼠神经功能缺损情况;测定大鼠脑组织含水量;采用TUNEL法评估大鼠脑细胞凋亡情况,并计算凋亡指数;采用酶联免疫吸附(ELISA)法测定大鼠脑组织匀浆中丙二醛(MDA)、超氧化物歧化酶(SOD)水平;采用聚合酶链式反应(PCR)法测定蛋白激酶C受体1(RACK1)、磷酸化IRE1(p-IRE1)、X-box结合蛋白1(XBP1)、葡萄糖调节蛋白78(GRP78)水平。结果与模型组比较,NBP高、中、低剂量组大鼠神经功能缺损评分,细胞凋亡指数,MDA,p-IRE1,XBP1,GRP78水平均显著降低;SOD和RACK1水平均显著升高,脑组织含水量显著增加(P <0.05)。结论 NBP对TBI模型大鼠神经功能有一定改善作用,其机制与抑制IRE1/XBP1信号通路有关。     

Marginal iodide deficiency and thyroid function: dose-response analysis for quantitative pharmacokinetic modeling

Severe iodine deficiency (ID) results in adverse health outcomes and remains a benchmark for understanding the effects of developmental hypothyroidism. The implications of marginal ID, however, remain less well known. The current study examined the relationship between graded levels of ID in rats and serum thyroid hormones, thyroid iodine content, and urinary iodide excretion. The goals of this study were to provide parametric and dose-response information for development of a quantitative model of the thyroid axis. Female Long Evans rats were fed casein-based diets containing varying iodine (I) concentrations for 8 weeks. Diets were created by adding 975, 200, 125, 25, or 0 μg/kg I to the base diet (∼25 μg I/kg chow) to produce 5 nominal I levels, ranging from excess (basal + added I, Treatment 1: 1000 μg I/kg chow) to deficient (Treatment 5: 25 μg I/kg chow). Food intake and body weight were monitored throughout and on 2 consecutive days each week over the 8-week exposure period, animals were placed in metabolism cages to capture urine. Food, water intake, and body weight gain did not differ among treatment groups. Serum T4 was dose-dependently reduced relative to Treatment 1 with significant declines (19 and 48%) at the two lowest I groups, and no significant changes in serum T3 or TSH were detected. Increases in thyroid weight and decreases in thyroidal and urinary iodide content were observed as a function of decreasing I in the diet. Data were compared with predictions from a recently published biologically based dose-response (BBDR) model for ID. Relative to model predictions, female Long Evans rats under the conditions of this study appeared more resilient to low I intake. These results challenge existing models and provide essential information for development of quantitative BBDR models for ID during pregnancy and lactation.     

Safety of iodine based water sterilization for travelers

The recent report by Khan et al. of an unexpectedly high concentration of free iodine in water filters, which may have led to the high proportion of abnormal thyroid function tests in Peace Corps workers, is of concern for travel advisors when asked to recommend suitable means of water sterilization. Many travelers use iodine based filters and/or chemicals for purification of water when traveling in areas with contaminated water supplies and may therefore be at risk of excess iodine intake. Aside from iodine impregnated resin filtration systems, tetraglycine hydroperiodide tablets, tincture of iodine 2% and more commonly, chlorine-based proprietary products are widely used to sterilize water for drinking, and usually purchased by travelers without advice on how they should be used. A single tetraglycine hydroperiodide tablet in a liter of water releases 8 mg of iodine in comparison to the 10 mg/liter released from the iodinated resin pumps described by Khan et al. Although the instructions for using iodine tincture are imprecise, the normal recommendation is 5 drops per liter of water, increasing this to 12 drops where Giardia cysts may be present. The lower of the two doses would yield about 2 mg/liter of free iodine per liter depending on the pipette used, although, because of the potassium iodide present in the formulation, a total of 4 mg iodine would be available for absorption.     

Effects of chlorine dioxide on thyroid function in the African green monkey and the rat

In a previous study from this laboratory, chlorine dioxide (ClO2) treated drinking water depressed thyroxine (T4) levels in the African green monkey. The present study again demonstrated a decrease in T4 levels in the same species after 4 wk of oral exposure. However, after 8 wk of treatment T4 levels rebounded to above pretreatment levels, coinciding with an increase in thyroid radioiodide uptake. This T4 rebound phenomenon and increased iodide uptake may be due to a compensatory endocrinological mechanism. In rats, T4 levels dropped during the 8-wk ClO2 treatment period in a dose-dependent manner, and no rebound effect was observed. Iodide uptake values in the rat were not affected. It appears that ClO2 may have an effect on thyroid function in both species.