Transcriptome reveals the crucial role of exogenous hydrogen sulfide in alleviation of thiocyanate (SCN-) toxicity in rice seedlings

Application of exogenous hydrogen sulfide (H₂S) is a novel strategy for alleviation of the adverse effects caused by abiotic stresses. However, little is known about H₂S-mediated global molecular response of rice seedlings to thiocyanate (SCN^-) exposure. Herein, a hydroponic experiment was carried out to investigate the crucial role of exogenous H₂S in alleviation of SCN^- toxicity generated at different effective concentrations (EC₂₀: 24.0 mg SCN/L, EC₅₀: 96.0 mg SCN/L, and EC₇₅: 300.0 mg SCN/L) in rice seedlings through transcriptome analysis. The results showed that the total numbers of differentially expressed genes (DEGs, upregulated genes/downregulated genes) in rice roots were 755/313, 1114/3303, and 2184/7427, while they were 427/292, 2134/526, and 2378/890 in rice shoots at EC₂₀, EC₅₀, and EC₇₅ of SCN^-, respectively. When exogenous H₂S was supplied to rice seedlings exposed to SCN^-, the total number of DEGs (upregulated genes/downregulated genes) in rice roots was 1158/316, 1943/2959, and 1737/5392, while it was 2067/937, 2689/683, and 3492/1062 in rice shoots at EC₂₀, EC₅₀, and EC₇₅ of SCN^-, respectively. Upregulated DEGs in shoots were positively correlated with SCN^- concentration in the presence of exogenous H₂S, suggesting its crucial role in regulating the phytotoxicity of SCN^-. Gene function and pathway enrichment analyses showed that exogenous H₂S triggered "secondary metabolite synthesis," "metabolic pathways," and "signal transduction mechanisms" in rice seedlings corresponding to different effective concentrations of SCN^- exposure.

A newly developed consortium with a highly efficient thiocyanate degradation capacity: A comprehensive investigation of the degradation and detoxification potential

Thiocyanate-containing wastewater harms ecosystems and can cause serious damage to animals and plants, so it is urgent to treat it effectively. In this study, a new efficient thiocyanate-degrading consortium was developed and its degradation characteristics were studied. It was found that up to 154.64 mM thiocyanate could be completely degraded by this consortium over 6 days of incubation, with a maximum degradation rate of 1.53 mM h^-1. High-throughput sequencing analysis showed that Thiobacillus (77.78%) was the predominant thiocyanate-degrading bacterial genus. Plant toxicology tests showed that the germination index of mung bean and rice seeds cultured with media obtained after thiocyanate degradation by the consortium increased by 94% and 84.83%, respectively, compared with the control group without thiocyanate degradation. Cytotoxicity tests showed that thiocyanate without degradation significantly decreased the Neuro-2a cell activity and mitochondrial membrane potential; induced reactive oxygen species generation and apoptosis; increased the cellular Ca²⁺ concentration; and damaged the cell nucleus and DNA. Furthermore, the thiocyanate degradation products produced the consortium were almost totally non-toxic, revealing the same characteristics as those of the control using distilled water. This study shows that the consortium has a high degradation efficiency and detoxification characteristics, as well as great application potential in bioremediation of industrial thiocyanate-containing wastewater.

Fuzzy synthetic evaluation of the impact of plant growth regulators on the root phenotype traits of rice seedlings under thiocyanate stress

Application of plant growth regulators (PGRs) is a novel strategy for allay of the adverse effects caused by biotic/abiotic stresses. However, no studies have vividly executed mathematic evaluation for the assessment of various PGRs on root phenotype traits (RPTs) against pollutants. In the present study, a microcosm hydroponic experiment was conducted to examine responses of RPTs under SCN^- (0, 24, 96, and 300 mg SCN/L) stress in the presence of PGRs such as jasmonic acid (JA), indole-3-acetic acid (IAA), and sodium hydrosulfide (NaHS) in rice plants. Fuzzy synthetic evaluation was applied to determine the outcome of the effects of various PGRs on the RPTs under SCN^- exposure. Root scanning results indicated that exogenous IAA and NaHS has the greater potential for improving the RPTs of rice seedlings under SCN^- stress, while JA failed to uplift the RPTs in response to SCN^- stress. Fuzzy synthetic evaluation indicated that in control plants (without SCN^-), the effect of three PGRs applied on the RPTs is as follows: NaHS > IAA > JA. At 24 mg SCN/L, NaHS and IAA had consistent actuate in regulating RPTs of rice seedlings, while all PGRs amended have an affirmative impact on RPTs at 96 and 300 mg SCN/L. The present research highlights the utilization of contemporary mathematic method to screen the superior species of PGRs through the RPTs test of plants under pollutant belt.

Familial Aggregation of Endemic Congenital Hypothyroidism Syndrome in Congo (DR): Historical Data

Familial aggregation of endemic congenital hypothyroidism (CH) in an iodine-deficient population from northern Congo (Democratic Republic (DR)) was analysed on data collected four decades ago (1979-1980). During a systematic survey of 62 families, 46 endemic CH subjects (44 myxedematous and 2 neurological) were identified based on clinical evidence within a village cohort of 468 subjects. A distribution analysis showed that two families presented significant excess of cases versus a random background distribution. Both families were characterised by two healthy parents having all of their five offspring affected by some form of endemic CH. Goitre prevalence in endemic CH was lower than that in the general population, while goitre prevalence in the unaffected part of the cohort (parents and siblings) was similar to that of the general population. Some unidentified genetic/epigenetic factor(s) could contribute to the evolution of some iodine-deficient hypothyroid neonates through irreversible and progressive loss of thyroid functional capacity during early childhood (<5 years old). Besides severe iodine deficiency, environmental exposure to thiocyanate overload and selenium deficiency, factors not randomly distributed within families and population, intervened in the full expression of endemic CH. Further exploration in the field will remain open, as iodine deficiency in Congo (DR) was eliminated in the 1990s.

Environmental exposure to perchlorate, nitrate, and thiocyanate in relation to obesity: A population-based study

BACKGROUND

Perchlorate, nitrate, and thiocyanate are well-known thyroid disrupters and may contribute to changes in body weight. However, the associations between environmental exposure to these chemicals and obesity-related outcomes remain unclear.

OBJECTIVES

We aim to examine the urinary levels of perchlorate, nitrate, and thiocyanate and their associations with obesity and abdominal obesity in the U.S.

METHODS

Here, we investigated the data of 16,265 adults aged 20-85 years from the National Health and Nutritional Examination Survey (NHANES) in 2001-2014. Urinary levels of perchlorate, nitrate, and thiocyanate were measured by ion chromatography combined with electrospray tandem mass spectrometry. Obesity and abdominal obesity were defined by the body mass index and waist circumference, respectively. Logistic regression models were used to estimate the associations.

RESULTS

Overall, 5794 (35.6%) cases of obesity and 9090 cases (55.9%) of abdominal obesity were observed among the participants. In multivariable-adjusted logistic regression models, urinary nitrate was inversely associated with obesity (p = 0.0022 for trend), while urinary thiocyanate was positively related to obesity (p < 0.001 for trend). Compared with the lowest quartile, the odds ratios with 95% confidence intervals (CIs) across increasing quartiles were 0.95 (95% CI, 0.83-1.08), 0.88 (0.75-1.03), and 0.74 (0.60-0.90) for urinary nitrate and 1.31 (1.16-1.48), 1.53 (1.36-1.73), and 1.73 (1.47-2.03) for urinary thiocyanate. Urinary perchlorate was not correlated with obesity. Similar associations were also found between exposure to these chemicals and abdominal obesity.

CONCLUSIONS

A higher exposure to urinary nitrate was associated with a lower risk of obesity, while a positive association was observed for urinary thiocyanate. These findings emphasize the need to longitudinally evaluate environmental exposure to perchlorate, nitrate, and thiocyanate with respect to their effect on obesity in humans.

Transcriptome analysis of Oryza sativa in responses to different concentrations of thiocyanate

Effective concentrations of potassium thiocyanate (KSCN) to rice seedlings were experimentally determined using relative growth rate as a sensitive endpoint. Agilent 44-K rice microarray was used to profile the molecular responses of rice seedlings exposed to thiocyanate ion (SCN^-) at three different effective concentrations (EC₁₀, EC₂₀, and EC₅₀). A total of 18,498 known genes were collected from SCN-treated rice microarray analysis. Out of all, 1603, 1882, and 5085 differentially expressed genes (DEGs) were observed at EC₁₀, EC₂₀, and EC₅₀ concentrations, respectively. More upregulated/downregulated DEGs were detected in shoots than in roots after SCN^- exposure. Gene functions and pathway enrichment analysis of DEGs indicated that different effective concentrations of SCN^- resulted in multiple enriched GO categories and KEGG pathways and outcomes were quite tissue-specific. Different regulations and adaptations of gene expression in molecular function (MF), biological process (BP), and cellular components (CC) were observed in rice tissues at different effective concentrations of SCN^-, suggesting their different responsive and adaptive strategies. Information collected here presents a detailed description of SCN-induced alternations of gene expression in rice seedlings and provide valuable information for further searching specific genes participating in transportation, phytotoxic responses, and detoxification of SCN^- in rice seedlings.

Assessing effects of germline exposure to environmental toxicants by high-throughput screening in C. elegans

Chemicals that are highly prevalent in our environment, such as phthalates and pesticides, have been linked to problems associated with reproductive health. However, rapid assessment of their impact on reproductive health and understanding how they cause such deleterious effects, remain challenging due to their fast-growing numbers and the limitations of various current toxicity assessment model systems. Here, we performed a high-throughput screen in C. elegans to identify chemicals inducing aneuploidy as a result of impaired germline function. We screened 46 chemicals that are widely present in our environment, but for which effects in the germline remain poorly understood. These included pesticides, phthalates, and chemicals used in hydraulic fracturing and crude oil processing. Of the 46 chemicals tested, 41% exhibited levels of aneuploidy higher than those detected for bisphenol A (BPA), an endocrine disruptor shown to affect meiosis, at concentrations correlating well with mammalian reproductive endpoints. We further examined three candidates eliciting aneuploidy: dibutyl phthalate (DBP), a likely endocrine disruptor and frequently used plasticizer, and the pesticides 2-(thiocyanomethylthio) benzothiazole (TCMTB) and permethrin. Exposure to these chemicals resulted in increased embryonic lethality, elevated DNA double-strand break (DSB) formation, activation of p53/CEP-1-dependent germ cell apoptosis, chromosomal abnormalities in oocytes at diakinesis, impaired chromosome segregation during early embryogenesis, and germline-specific alterations in gene expression. This study indicates that this high-throughput screening system is highly reliable for the identification of environmental chemicals inducing aneuploidy, and provides new insights into the impact of exposure to three widely used chemicals on meiosis and germline function.

The ever-increasing number of new chemicals introduced into our environment poses a significant problem for risk assessment. In addition, assessing the direct impact of toxicants on human meiosis remains challenging. We successfully utilized a high-throughput platform in the nematode C. elegans, a genetically tractable model organism which shares a high degree of gene conservation with humans, to identify chemicals that affect the germline leading to aneuploidy. We assessed chemicals that are highly prevalent in the environment in worms carrying a fluorescent reporter construct allowing for the identification of X chromosome nondisjunction combined with a mutation increasing cuticle permeability for analysis of low doses of exposure. Follow up analysis of three chemicals: DBP, permethrin and TCMTB, further validated the use of this strategy. Exposure to these chemicals resulted in elevated levels of DNA double-strand breaks, activation of a DNA damage checkpoint, chromosome morphology defects in late meiotic prophase I as well as impaired early embryogenesis and germline-specific changes in gene expression. Our results support the use of this high-throughput screening system to identify environmental chemicals inducing aneuploidy, and provide new insights into the effects of exposure to DBP, permethrin, and TCMTB on meiosis and germline function.

Individual and combined inhibition of phenol and thiocyanate on microbial activity of partial nitritation

This study evaluated the individual and interactive effect of phenol and thiocyanate (SCN^-) on partial nitritation (PN) activity using batch test and response surface methodology. The IC₅₀ of phenol and SCN^- on PN sludge were 5.6 and 351 mg L^-1, respectively. The PN sludge was insensitive to phenol and SCN^- at levels lower than 1.77 and 43.3 mg L^-1, respectively. A regression model equation was developed and validated to predict the relative specific respiration rate (RSRR) of PN sludge exposed to different phenol and SCN^- concentrations. In the range of independent variables, the most severe inhibition was observed with a valley value (17%) for RSRR, when the phenol and SCN^- concentrations were 4.08 and 198 mg L^-1, respectively. An isobole plot was used to judge the combined toxicity of phenol and SCN^-, and the joint inhibitory effect was variable depending on the composition and concentration of the toxic components. Furthermore, the toxic compounds showed independent effects, which is the most common type of combined toxicity.

Thyroid Antagonists (Perchlorate, Thiocyanate, and Nitrate) and Childhood Growth in a Longitudinal Study of U.S. Girls

BACKGROUND

Perchlorate, thiocyanate, and nitrate are sodium/iodide symporter (NIS) inhibitors that block iodide uptake into the thyroid, thus affecting thyroid function. Thyroid dysfunction can adversely affect somatic growth and development in children. To our knowledge, no studies have examined effects of NIS inhibitors on body size measures.

OBJECTIVE

We investigated associations between NIS inhibitors and childhood growth in 940 girls from the Puberty Study of the Breast Cancer and Environment Research Program.

METHODS

Urine samples collected from girls 6-8 years of age at enrollment (2004-2007) from New York City, greater Cincinnati, Ohio, and the Bay Area in California were analyzed for NIS inhibitors and creatinine (C). The longitudinal association between NIS inhibitors and anthropometric measures [height, waist circumference, and body mass index (BMI)] during at least three visits was examined using mixed effects linear models, adjusted for race and site.

RESULTS

Compared with girls in the low-exposure group (3.6, 626, and 500 mg/gC, median perchlorate, thiocyanate, and nitrate, respectively) girls with the highest NIS inhibitor exposure (9.6, 2,343, and 955 mg/gC, median perchlorate, thiocyanate, and nitrate, respectively) had slower growth in waist circumference and BMI but not height. Significant differences in the predicted mean waist circumference and BMI between the low- and high-exposure groups were observed beginning at 11 years of age.

CONCLUSIONS

Higher NIS inhibitor exposure biomarkers were associated with reductions in waist circumference and BMI. These findings underscore the need to assess exposure to NIS inhibitors with respect to their influence on childhood growth.

CITATION

Mervish NA, Pajak A, Teitelbaum SL, Pinney SM, Windham GC, Kushi LH, Biro FM, Valentin-Blasini L, Blount BC, Wolff MS, for the Breast Cancer and Environment Research Project (BCERP). 2016. Thyroid antagonists (perchlorate, thiocyanate, and nitrate) and childhood growth in a longitudinal study of U.S. girls. Environ Health Perspect 124:542-549; http://dx.doi.org/10.1289/ehp.1409309.

CO-occurring exposure to perchlorate, nitrate and thiocyanate alters thyroid function in healthy pregnant women

BACKGROUND

Adequate maternal thyroid function during pregnancy is necessary for normal fetal brain development, making pregnancy a critical window of vulnerability to thyroid disrupting insults. Sodium/iodide symporter (NIS) inhibitors, namely perchlorate, nitrate, and thiocyanate, have been shown individually to competitively inhibit uptake of iodine by the thyroid. Several epidemiologic studies examined the association between these individual exposures and thyroid function. Few studies have examined the effect of this chemical mixture on thyroid function during pregnancy

OBJECTIVES

We examined the cross sectional association between urinary perchlorate, thiocyanate and nitrate concentrations and thyroid function among healthy pregnant women living in New York City using weighted quantile sum (WQS) regression.

METHODS

We measured thyroid stimulating hormone (TSH) and free thyroxine (FreeT4) in blood samples; perchlorate, thiocyanate, nitrate and iodide in urine samples collected from 284 pregnant women at 12 (±2.8) weeks gestation. We examined associations between urinary analyte concentrations and TSH or FreeT4 using linear regression or WQS adjusting for gestational age, urinary iodide and creatinine.

RESULTS

Individual analyte concentrations in urine were significantly correlated (Spearman's r 0.4-0.5, p<0.001). Linear regression analyses did not suggest associations between individual concentrations and thyroid function. The WQS revealed a significant positive association between the weighted sum of urinary concentrations of the three analytes and increased TSH. Perchlorate had the largest weight in the index, indicating the largest contribution to the WQS.

CONCLUSIONS

Co-exposure to perchlorate, nitrate and thiocyanate may alter maternal thyroid function, specifically TSH, during pregnancy.

Urinary thiocyanate concentrations are associated with adult cancer and lung problems: US NHANES, 2009-2012

Links between environmental chemicals and human health have emerged but the effects from perchlorate, nitrate and thiocyanate were unclear. Therefore, it was aimed to study the relationships of urinary perchlorate, nitrate and thiocyanate concentrations and adult health conditions in a national and population-based study. Data was retrieved from US National Health and Nutrition Examination Surveys, 2009-2012, including demographics, blood pressure readings, self-reported health conditions and urinary perchlorate, nitrate and thiocyanate concentrations. Analyses included chi-square test, t test survey-weighted logistic regression models and population attributable risk estimation. There were no clear associations between urinary perchlorate concentrations and adult health conditions, although people with hearing loss and diabetes could be at the borderline risk. Urinary thiocyanate concentrations were significantly associated with emphysema (odds ratio (OR) 2.70 95% confidence intervals (CI) 1.91-3.82, P < 0.001), cancer (OR 1.21 95%CI 1.06-1.39, P = 0.008), chronic bronchitis (OR 1.23 95%CI 1.10-1.52, P = 0.003), wheezing (OR 1.24 95%CI 1.05-1.46, P = 0.011), coughing (OR 1.19 95%CI 1.03-1.37, P = 0.018) and sleep complaints (OR 1.14 95%CI 1.02-1.26, P = 0.019). The population attributable risks accounted for 3.3% (1.8-5.3%), 1.9% (0.6-3.5%), 1.2% (0.5-2.6%), 2.2% (0.5-4.1%), 1.8% (0.3-6.2%) and 1.3% (0.2-2.4%) for emphysema, cancer, chronic bronchitis, wheezing, coughing and sleep complaints, respectively. In addition, there was an inverse association observed between urinary nitrate level and heart failure. This is for the first time observing significant risk effects of urinary thiocyanate concentrations on adult cancer and lung problems, although the causality cannot be established. Elimination of such environmental chemical in humans should be included in future health policy and intervention programs.

The association between perchlorate and thiocyanate exposure and thyroid function in first-trimester pregnant Thai women

CONTEXT

Thyroid hormone is critical for fetal neurodevelopment. Perchlorate and thiocyanate decrease thyroidal iodine uptake by competitively inhibiting the sodium/iodide symporter. It is clear that perchlorate and thiocyanate anions can influence thyroid function. However, as pollutants in the environment, their impact is conflicting.

OBJECTIVE

The objective was to determine the effects of environmental perchlorate and/or thiocyanate exposure on thyroid function in first-trimester pregnant women.

DESIGN AND PATIENTS

A cross-sectional study was conducted in 200 pregnant Thai women with a gestational age of 14 weeks or less.

MEASURES

Urinary iodide, perchlorate, thiocyanate, and serum thyroid function tests were measured.

RESULTS

The women were aged 28.6 ± 6.1 years and the mean gestational age was 9.6 ± 2.7 weeks. Median urinary iodide, perchlorate, and thiocyanate concentrations were 153.5 μg/L, 1.9 μg/L, and 510.5 μg/L, respectively. Using Spearman's rank correlation analyses, there were positive correlations between serum TSH and urine perchlorate to creatinine (r = 0.20, P = .005) and TSH and thiocyanate to creatinine ratios (r = 0.22, P = .001). There were negative correlations between free T4 and the perchlorate to creatinine ratio (r = -0.18, P = .01) and free T4 and the thiocyanate to creatinine ratio (r = -0.19, P = .008). In multivariate analyses adjusting for log thiocyanate to creatinine ratio, log iodide to creatinine ratio, and gestational age, log perchlorate to creatinine ratio was positively associated with log TSH (P = .002) and inversely associated with log free T4 (P = .002). Log thiocyanate to creatinine ratio was a significant positive predictor of log TSH (P = .02) in women with a urine iodide level of less than 100 μg/L.

CONCLUSIONS

Low-level environmental exposure to perchlorate and thiocyanate is common in Thailand. Low-level exposure to perchlorate is positively associated with TSH and negatively associated with free T4 in first-trimester pregnant women using multivariate analyses. In multivariate analyses, thiocyanate exposure is also positively associated with TSH in a subgroup of pregnant women with low iodine excretion.

Iodine deficiency, pollutant chemicals, and the thyroid: new information on an old problem

Many women of reproductive age in the United States are marginally iodine deficient, perhaps because the salt in processed foods is not iodized. Iodine deficiency, per se, can interfere with normal brain development in their offspring; in addition, it increases vulnerability to the effects of certain environmental pollutants, such as nitrate, thiocyanate, and perchlorate. Although pregnant and lactating women should take a supplement containing adequate iodide, only about 15% do so. Such supplements, however, may not contain enough iodide and may not be labeled accurately. The American Thyroid Association recommends that pregnant and lactating women take a supplement with adequate iodide. The American Academy of Pediatrics recommends that pregnant and lactating women also avoid exposure to excess nitrate, which would usually occur from contaminated well water, and thiocyanate, which is in cigarette smoke. Perchlorate is currently a candidate for regulation as a water pollutant. The Environmental Protection Agency should proceed with appropriate regulation, and the Food and Drug Administration should address the mislabeling of the iodine content of prenatal/lactation supplements.

Effect of maternal nicotine/thiocyanate exposure during gestational period upon pituitary, thyroid and parathyroid function/morphology of 1-month-old rat offspring

INTRODUCTION

Impact of in utero exposure to nicotine, on the structure of the thyroid-pituitary axis and the parathyroid glands have been examined in 1-month-old rats and compared with that of thiocyanate.

MATERIALS AND METHODS

Three pregnant female groups were used; control, nicotine and thiocyanate. Treatment started from gestation day (4-20) and the specimens were harvested from the male offspring of all groups at the age of 1 month and processed for light, electronmicroscopic and immunohistochemical examination. Total triiodothyronine (tT3), total thyroxine (tT4) and total thyrotropin (TSH) were quantitatively determined in serum.

RESULTS

Both nicotine and thiocyanate activated the thyroid follicular cells, with an increase in height (about 30 %) and a negative feedback on the pituitary thyrotrophs which revealed a reduction in the number of cytoplasmic secretory granules, particularly the thiocyanate group. However, in thiocyanate group there was signs of impaired secretory activity of the thyroid gland. The arbitrary area of parathyroid chief cells, increased (about 45 %) particularly in nicotine group, with signs of reduced activity and a positive feedback on the parafollicular cells which revealed hypertrophy, proliferation (25 %) and increased intensity of positive immunohistochemical reaction for calcitonin.

CONCLUSION

Nicotine impaired chief parathyroid cells activity and consequently activated parafollicular cells. Thiocyanate reduced pituitary thyrotrophs activity, whereas both nicotine and thiocyanate increased thyroid follicular cells activity. This impact of in utero exposure persisted for 1-month postnatal.

Microalgae-mediated simultaneous treatment of toxic thiocyanate and production of biodiesel

In this work, a method for simultaneously degrading the toxic pollutant, thiocyanate, and producing microalgal lipids using mixed microbial communities was developed. Aerobic activated sludge was used as the seed culture and thiocyanate was used as the sole nitrogen source. Two cultivation methods were sequentially employed: a lithoautotrophic mode and a photoautotrophic mode. Thiocyanate hydrolysis and a nitrification was found to occur under the first (lithoautotrophic) condition, while the oxidized forms of nitrogen were assimilated by the photoautotrophic consortium and lipids were produced under the second condition. The final culture exhibited good settling efficiency (∼ 70% settling over 10 min), which can benefit downstream processing. The highest CO2 fixation rate and lipid productivity were observed with 2.5% and 5% CO2, respectively. The proposed integrated algal-bacterial system appears to be a feasible and even beneficial option for thiocyanate treatment and production of microbial lipids.

Effects of exogenous thiocyanate on mineral nutrients, antioxidative responses and free amino acids in rice seedlings

The effects of exogenous thiocyanate (SCN(-)) on amino acids composition, content of mineral nutrients and antioxidative systems in plants were investigated. Young rice seedlings (Oryza sativa L. cv. XZX 45) were grown in nutrient solutions amended with potassium thiocyanate (KSCN). Activities of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in plant materials were analyzed in vivo. Mineral nutrients and free amino acids in rice seedlings were also measured to determine metabolic responses to SCN(-) exposure. A significant reduction in transpiration and relative growth was recorded with all treatments (p < 0.05), while changes of total chlorophyll content in leaves was negligible (p > 0.05). SCN-induced toxicity appeared to be more sensitive to activities of POD in shoots and APX activities in roots than the others. The content of nutrient elements in rice seedlings exposed to exogenous SCN(-) was variable, while the effects were more evident at the highest SCN-treatment (p < 0.05). Although the change of total free amino acids in shoots of SCN-exposed seedlings was negligible (p > 0.05), responses of different amino acids to SCN(-) application were quite different. Among fifteen free amino acids detected, serine (Ser), proline (Pro), and methionine (Met) increased, while asparagine (Asp) decreased with an increase of the doses of SCN(-) supplied. Phyto-transport of SCN(-) was apparent and the removal rates were positively correlated to the doses, suggesting that phyto-assimilation of SCN(-) is an enzymatic process through a potentially un-identified degradation pathway.

Phytotoxicity of thiocyanate to rice seedlings

The acute toxicity of potassium thiocyanate (KSCN) and ammonium thiocyanate (NH(4)SCN) to rice seedlings was tested. Hydroponically-grown plants showed different responses to the two species of thiocyanate. NH(4)SCN caused more severe stress to rice seedlings than KSCN. A significant reduction in transpiration and relative growth was observed with all NH(4)SCN treatments (p < 0.01), while the effect of KSCN on rice seedlings was more evident at greater than 100 mg SCN/L (p < 0.01). Both chemicals had a negligible effect on total chlorophyll content in shoots of rice seedlings (p > 0.05). Although phyto-transport of thiocyanate was apparent, rice seedlings showed significantly higher removal potential for NH(4)SCN than KSCN.

Non-invasive biological fluid matrices analysed to assess exposure to environmental tobacco smoke

Human biomonitoring (analysis of biological fluids) is increasingly being used for assessing exposure to environmental pollutants. Smoking tobacco is a significant source of indoor air pollution and is harmful to human health. The aim of this research was to find both the best non-invasive matrices (from among saliva, urine, semen and sweat) for evaluating environmental exposure to tobacco smoke and the relationships between thiocyanates (biomarkers of environmental tobacco smoke exposure) and other inorganic ions in these matrices collected from active and passive smokers and also non-smokers.

Iodine status and thyroid function of Boston-area vegetarians and vegans

CONTEXT

Adequate dietary iodine is required for normal thyroid function. The iodine status and thyroid function of U.S. vegetarians and vegans have not been previously studied. Environmental perchlorate and thiocyanate (inhibitors of thyroid iodine uptake) exposures may adversely affect thyroid function.

OBJECTIVE

The objective of the study was to assess the iodine status and thyroid function of U.S. vegetarians (consume plant based products, eggs, milk; abstain from meat, poultry, fish, shellfish) and vegans (avoid all animal products) and whether these may be affected by environmental perchlorate and thiocyanate exposures.

DESIGN AND SETTING

This was a cross-sectional assessment of urinary iodine, perchlorate, and thiocyanate concentrations and serum thyroid function in Boston-area vegetarians and vegans.

SUBJECTS

One hundred forty-one subjects (78 vegetarians, 63 vegans) were recruited; one vegan was excluded.

RESULTS

Median urinary iodine concentration of vegans (78.5 μg/liter; range 6.8-964.7 μg/liter) was lower than vegetarians (147.0 μg/liter; range 9.3-778.6 μg/liter) (P < 0.01). Adjusted for cigarette smoking (confirmed by urinary cotinine levels) and thiocyanate-rich food consumption, median urinary thiocyanate concentration of vegans (630 μg/liter; range 108-3085 μg/liter) was higher than vegetarians (341 μg/liter; range 31-1963 μg/liter) (P < 0.01). There were no between-group differences in urinary perchlorate concentrations (P = 0.75), TSH (P = 0.46), and free T(4) (P = 0.77). Urinary iodine, perchlorate, and thiocyanate levels were not associated with TSH (P = 0.59) or free T(4) (P = 0.14), even when adjusted for multiple variables.

CONCLUSIONS

U.S. vegetarians are iodine sufficient. U.S. vegans may be at risk for low iodine intake, and vegan women of child-bearing age should supplement with 150 μg iodine daily. Environmental perchlorate and thiocyanate exposures are not associated with thyroid dysfunction in these groups.

Sulforaphane induces cytotoxicity and lysosome- and mitochondria-dependent cell death in colon cancer cells with deleted p53

Mechanisms and pathways responsible for cytotoxicity of sulforaphane (SF) in colon cancer cells with deleted p53 were investigated during 48 h of exposure. SF showed dose-dependent cytotoxicity and proapoptotic activity in the present model. In addition, in HCT-116 p53KO cells SF induced DNA damage with the subsequent cellular response and signaling not including p53 and caspase-2 pathways. Conversely, in SF-treated cells JNK was activated which led to an early lysosomal membrane permeabilization, release of cathepsin B and D and activation of Bid by specific cleavage. Concomitantly, the expression of Bax increased in the presence of JNK-mediated Bcl-2 inhibition which was followed by mitochondrial release of cytochrome c and activation of apoptosis. These results suggest that SF may be useful as a chemopreventive agent in colon cancer with inactivated or lost p53.

Thiocyanate, calcium and sulfate as causes of toxicity to Ceriodaphnia dubia in a hard rock mining effluent

A series of Toxicity Identification Evaluations (TIEs) to identify the cause(s) of observed toxicity to Ceriodaphnia dubia have been conducted on a hard rock mining effluent. Characteristic of hard rock mining discharges, the effluent has elevated (∼3000 mg l(-1)) total dissolved solids (TDS) composed primarily of Ca(2+) and SO(4)(2-). The effluent typically exhibits 6-12 toxic units (TUs) when tested with C. dubia. Phase I and II toxicity identification evaluations (TIEs) indicated Ca(2+) and SO(4)(2-) contributed only ∼4 TUs of toxicity, but this was likely an underestimate due to problems with simulating the supersaturated CaSO(4) concentrations in the effluent. Treatment of the effluent with BaCO(3) to precipitate Ca(2+) and SO(4)(2-) revealed that these ions contribute ∼6 TUs of the observed toxicity, but the remaining source(s) of toxicity (up to 6 TUs) remained unidentified. Subsequent investigations identified thiocyanate (SCN(-)) in the effluent at 100-150 μM. Toxicity tests reveal that C. dubia are sensitive to SCN(-) with an estimated IC25 of 8.3 μΜ for reproduction in moderately hard water suggesting between 12 and 18 TUs of toxicity in the effluent. Additional experiments demonstrated that SCN(-) toxicity is reduced in the high TDS matrix of the mining effluent. Testing of a mock effluent simulating the major ion and SCN(-) concentrations resulted in 10.4 TUs, suggesting that Ca(2+), SO(4)(2-) and SCN(-) are the three toxicants present in this effluent. This research suggests SCN(-) may be a more common cause of toxicity in mining effluents than is generally recognized.

Sulforaphane modulates the expression of Cyp6a2 and Cyp6g1 in larvae of the ST and HB crosses of the Drosophila wing spot test and is genotoxic in the ST cross

Constitutive overexpression of Cyp6g1 and Cyp6a2 genes in DDT-resistant line Oregon-flare of the Drosophila melanogaster wing spot test (SMART) has been reported. Cyp6g1 and Cyp6a2 expression levels were compared against the β-actin gene in the standard (ST) and high bioactivation (HB) crosses of the Somatic Mutation and Recombination test (SMART) treated with sulforaphane or phenobarbital as the control inductor. The CYP450s' enzymatic activity was determined by overall NADH consumption. The expression levels of both genes and the CYP450s activity was higher in the HB cross. The Cyp6g1 levels were higher than those of Cyp6a2 in both crosses, but lower than the expression of β-actin. Sulforaphane decreased Cyp6g1 in the HB cross and increased it in the ST cross; Cyp6a2 expression was inhibited in the ST cross. Sulforaphane resulted mutagenic in the ST cross, which could be related to the inhibition of Cyp6a2. Phenobarbital did not modify the Cyp6g1 levels but increased the Cyp6a2 and CYP450s basal activity. Although the transcript levels were always higher in the HB cross than in the ST, the expression of Cyp6a2 and Cyp6g1 was not constitutive and was independent one from the other. Sulforaphane modulated both genes in a differential way in each cross and, in contrast to its putative protective effect, it resulted to be mutagenic.

Goitrogenic anions, thyroid-stimulating hormone, and thyroid hormone in infants

BACKGROUND

Environmental exposure of infants to perchlorate, thiocyanate, nitrate, might interfere with thyroid function. U.S. women with higher background perchlorate exposure have higher thyroid-stimulating hormone (TSH) and lower thyroxine (T4). There are no studies with individual measures of thyroid function and these goitrogens available in infants.

OBJECTIVE

We examined the association of urinary perchlorate, nitrate, iodide, and thiocyanate with urinary T4 and TSH in infants and whether that association differed by sex or iodide status.

METHODS

We used data and samples from the Study of Estrogen Activity and Development, which assessed hormone levels of full-term infants over the first 12 months of life. The study included 92 full-term infants between birth and 1 year of age seen up to four times. Perchlorate, thiocyanate, nitrate, and iodide were measured in 206 urine samples; TSH and T4 and were measured in urines and in 50 blood samples.

RESULTS

In separate mixed models, adjusting for creatinine, age, sex, and body mass index, infants with higher urinary perchlorate, nitrate or thiocyanate had higher urinary TSH. With all three modeled, children with higher nitrate and thiocyanate had higher TSH, but higher perchlorate was associated with TSH only in children with low iodide. Unexpectedly, exposure to the three chemicals was generally associated with higher T4.

CONCLUSIONS

The association of perchlorate exposure with increased urinary TSH in infants with low urinary iodide is consistent with previous findings. Higher thiocyanate and nitrate exposure were also associated with higher TSH in infants.

Sulforaphane induces DNA single strand breaks in cultured human cells

Sulforaphane (SFR), an isothiocyanate from cruciferous vegetables, possesses growth-inhibiting and apoptosis-inducing activities in cancer cell lines. Recently, SFR has been shown to promote the mitochondrial formation of reactive oxygen species (ROS) in human cancer cell lines. The present study was undertaken to see whether SFR-derived ROS might cause DNA damage in cultured human cells, namely T limphoblastoid Jurkat and human umbilical vein endothelial cells (HUVEC). 1-3 h treatments with 10-30 microM SFR elicited intracellular ROS formation (as assayed with dihydrorhodamine, DHR, oxidation) as well as DNA breakage (as assessed with fast halo assay, FHA). These effects lacked cell-type specificity, since could be observed in both Jurkat and HUVEC. Differential-pH FHA analysis of damaged DNA showed that SFR causes frank DNA single strand breaks (SSBs); no DNA double strand breaks (DSBs) were found within the considered treatment times (up to 3 h). SFR-derived ROS were formed at the mitochondrial respiratory chain (MRC) level: indeed rotenone or myxothiazol (MRC Complex I and III inhibitors, respectively) abrogated ROS formation. Furthermore ROS were not formed in Jurkat cells pharmacologically depleted of respiring mitochondria (MRC-/Jurkat). Formation of ROS was causally linked to the induction of SSBs: indeed all the experimental conditions capable of preventing ROS formation also prevented the damage of nuclear DNA from SFR-intoxicated cells. As to the toxicological relevance of SSBs, we found that their prevention slightly but significantly attenuated SFR cytotoxicity, suggesting that high-dose SFR toxicity is the result of a complex series of events among which GSH depletion seems to play a pivotal role. In conclusion, the present study identifies a novel mechanism contributing to SFR toxicity which - since DNA damage is a prominent mechanism underlying the cytotoxic activity of established antineoplastic agents - might help to exploit the therapeutic value of SFR in anticancer drug protocols.

Perchlorate and thiocyanate exposure and thyroid function in first-trimester pregnant women

CONTEXT

Thyroid hormone, requiring adequate maternal iodine intake, is critical for fetal neurodevelopment. Perchlorate decreases thyroidal iodine uptake by competitively inhibiting the sodium/iodide symporter. It is unclear whether environmental perchlorate exposure adversely affects thyroid function in pregnant women. Thiocyanate, derived from foods and cigarette smoke, is a less potent competitive sodium/iodide symporter inhibitor than perchlorate.

OBJECTIVE

Our objective was to determine whether environmental perchlorate and/or thiocyanate exposure is associated with alterations in thyroid function in pregnancy.

DESIGN AND SETTING

We conducted a cross-sectional study at health centers in Cardiff, Wales, and Turin, Italy.

PATIENTS

During 2002-2006, 22,000 women at less than 16 wk gestation were enrolled in the Controlled Antenatal Thyroid Screening Study. Subsets of 261 hypothyroid/hypothyroxinemic and 526 euthyroid women from Turin and 374 hypothyroid/hypothyroxinemic and 480 euthyroid women from Cardiff were selected based on availability of stored urine samples and thyroid function data.

MAIN OUTCOME MEASURES

Urinary iodine, thiocyanate, and perchlorate and serum TSH, free T(4) (FT(4)), and thyroperoxidase antibody were measured.

RESULTS

Urinary iodine was low: median 98 microg/liter in Cardiff and 52 microg/liter in Turin. Urine perchlorate was detectable in all women. The median (range) urinary perchlorate concentration was 5 microg/liter (0.04-168 microg/liter) in Turin and 2 microg/liter (0.02-368 microg/liter) in Cardiff. There were no associations between urine perchlorate concentrations and serum TSH or FT(4) in the individual euthyroid or hypothyroid/hypothyroxinemic cohorts. In multivariable linear analyses, log perchlorate was not a predictor of serum FT(4) or TSH.

CONCLUSIONS

Low-level perchlorate exposure is ubiquitous but did not affect thyroid function in this cohort of iodine-deficient pregnant women.

Novel thiocyanato complexes with potent cytotoxic and antimicrobial properties

The aim of the present study was to assess the cytotoxic and antimicrobial properties of seven new thiocyanato complexes: Ni(C9H11N2O)(SCN), Cu(C9H11N2O)(SCN), Pd(C9H11N2O)(SCN), Pt(C9H11N2O) (SCN), K[Ti(C9H11N2O)(SCN)3], Au(C9H11N2O)(SCN), and K[V(O)(C9H11N2O)(SCN)] (T1-T7, respectively). All the complexes showed toxicity against brine shrimp nauplii (Artemia salina L.). The titanium-based complex, T5, exhibited potent toxicity, with a lethal concentration 50% (the concentration of test compound that kills 50% of A. salina) value of 1.59 μg mL−1. These new complexes also exhibited promising antibacterial and antifungal properties. A macrodilution technique was used to estimate the minimum inhibitory concentrations of the seven bioactive complexes. Minimum inhibitory concentrations were found to be 8–64 μg mL−1 against the tested bacterial species.

Estimated dietary intake of thiocyanate from Brassicaceae family in Korean diet

Glucosinolate, sulfur-containing organic anions bonded to glucose, is found in plants including the family of Brassicaceae. Glucosinolate is hydrolyzed by myrosinase and produces various by-products that possess biological activities. Among the decomposed products, thiocyanate is known for its adverse effects on thyroid metabolism due to competition with iodine. This is of concern in that Korean dietary habits consist of consumption of large amounts of Brassicaceae vegetables such as cabbage and radishes, which may be correlated with high incidence of thyroid dysfunction. Thus, quantification of thiocyanate in Brassicaceae vegetables was performed by hydrolysis and spectrophotometrical detection. Average daily intake of Brassicaceae vegetables was obtained from the Third Korea National Health and Nutrition Examination Survey (KNHANES III), 2005-Nutrition Survey and from The Vegetable Production Statistics, 2007. Average daily intake of thiocyanate through Brassicaceae vegetables in Korea was estimated to be 16.3 micromol SCN(-)/d/person. When this was compared to published animal studies, average thiocyanate intake per person was lower than doses required to produce adverse effects. However, further studies may be warranted to ensure safety with sufficient margins of safety.

Comparative effects of prolonged administration of cyanide, thiocyanate and chokecherry (Prunus virginiana) to goats

The aim of the present study was to determine and compare the clinical, hematological, biochemical and histopathological changes induced by cyanide, thiocyanate and chokecherry (Prunus virginiana) in goats. Sixteen Boer-Spanish cross-bred female goats were divided into four treatment groups: (1) control, (2) potassium cyanide (KCN) at 3.8 mg kg(-1) day(-1), (3) potassium thiocyanate (KSCN) at 4.5 mg kg(-1) day(-1) and (4) ground frozen chokecherry leaves and flowers at a target dose of 2.5 mg HCN kg(-1) day(-1), all for 4 weeks. Clinical signs were observed in two goats treated with chokecherry. Only sporadic changes were found in the hematological and blood chemical panel. Goats treated with chokecherry and thiocyanate had an increased number of vacuoles in the colloid of thyroid glands. Spongiosis and spheroids were found in the mesencephalon from goats treated with KCN and chokecherry. These findings suggest the thyroid lesions can be attributed to thiocyanate, whereas the effects on the nervous system were most likely caused by cyanide.

Impact of smoking and thiocyanate on perchlorate and thyroid hormone associations in the 2001-2002 national health and nutrition examination survey

BACKGROUND

Findings from a recent large study suggest that perchlorate at commonly occurring exposure concentrations may decrease thyroid hormone levels in some women. Decreases in thyroid hormone seen with perchlorate exposure could be even greater in people with concomitant exposure to agents such as thiocyanate that may affect the thyroid by mechanisms similar to those of perchlorate.

OBJECTIVES AND METHODS

We used data from the National Health and Nutrition Examination Survey to assess the impact of smoking and thiocyanate on the relationship between urinary per-chlorate and serum thyroxine (T(4)) and thyroid-stimulating hormone (TSH).

RESULTS

In women with urinary iodine levels < 100 microg/L, the association between the logarithm of perchlorate and decreased T(4) was greater in smokers [regression coefficient (beta) = -1.66, p = 0.0005] than in nonsmokers (beta = -0.54, p = 0.04). In subjects with high, medium, and low cotinine levels, these regression coefficients were -1.47 (p = 0.0002), -0.57 (p = 0.03), and -0.16 (p = 0.59). For high, medium, and low thiocyanate tertiles they were -1.67 (p = 0.0009), -0.68 (p = 0.09), and -0.49 (p = 0.11). Clear interactions between perchlorate and smoking were not seen with TSH or with T(4) in women with urinary iodine levels > or = 100 microg/L or in men.

CONCLUSIONS

These results suggest that thiocyanate in tobacco smoke and perchlorate interact in affecting thyroid function, and this effect can take place at commonly occurring perchlorate exposures. Agents other than tobacco smoke might cause similar interactions, and further research on these agents could help identify people who are particularly susceptible to perchlorate.

Role of increased expression of the proteasome in the protective effects of sulforaphane against hydrogen peroxide-mediated cytotoxicity in murine neuroblastoma cells

The 26S proteasome is responsible for degradation of abnormal proteins and may play a role in cell survival upon oxidative stress. The indirect antioxidant sulforaphane (SFN) protects animal tissues from chemical toxicants by increasing the expression of several families of Nrf2-regulated genes. The role of induction of the 26S proteasome in cytoprotection by SFN was investigated in murine neuroblastoma Neuro2A cells. SFN enhanced the expression of the catalytic subunits of the proteasome, as well as proteasomal peptidase activities in these cells. Such treatment with SFN protected cells from hydrogen peroxide-mediated cytotoxicity in a manner dependent on proteasomal function. Inhibition of proteasome activities using pharmacological interventions significantly attenuated the protective effects of SFN against hydrogen peroxide cytotoxicity, as well as protein oxidation. Moreover, overexpression of the catalytic subunit PSMB5 enhanced proteasome function and led to elevated resistance against hydrogen peroxide toxicity and extent of protein oxidation compared to blank-plasmid-transfected cells. Pretreatment of PSMB5-overexpressing cells with SFN did not further enhance this resistance. Collectively, these results suggest that the cytoprotective effects of SFN against oxidative stress are in part due to up-regulation of the proteasome system. Therefore, inducers of proteasome expression may ameliorate the accumulation of damaged proteins associated with neurodegeneration and other diseases in whose etiologies protein oxidation plays a role.

Evaluation of effects of prenatal exposure to the cyanide and thiocyanate in wistar rats☆

A study was performed at term and at weaning to verify the toxic effects of the prenatal exposure to potassium cyanide (KCN) and potassium thiocyanate (KSCN) in pregnant Wistar rats. Females received daily in drinking water the doses: 1, 3 and 30mg KCN/kg or 0.8, 2.4 and 24mg KSCN/kg from GD 6 to GD 20 and were euthanized on GD 20 (trial A) or one day after weaning (trial B). Skeletal and visceral analyses of the fetuses (trial A) were performed and samples of blood and different organs, from both dams (trials A and B) and weaned pups (trial B), were collected in order to perform the biochemical evaluation and histopathology. Results showed high thiocyanate levels in dams of the different experimental groups from both trials. The intensity of the histological lesions observed in dams of trial B was similar to that of trial A, except those lesions found in the pancreas. The histopathological study of this organ revealed loss of cells in the Islets of Langerhans from dams of trial A which received the highest dose of cyanide (CN). There was an increase in the number of biliary ducts in animals treated with the highest doses of both thiocyanate and cyanide. The histopathological study of the spleen and the lungs of experimental and control groups did not reveal any significant alteration. In relation to fetuses (trial A), the visceral and skeletal evaluations did not reveal any significant malformation; on the other hand, pups from trial B showed some histological alterations similar to those observed in their dams. It is concluded that the cyanide and/or thiocyanate promoted toxic effects in the fetuses some of which could also be observed at weaning.

Pretreatment of human epidermal keratinocytes with D,L-sulforaphane protects against sulfur mustard cytotoxicity

Sulfur mustard (SM) is a powerful cytotoxic agent as well as a potent vesicant, mutagen, and carcinogen. This compound reacts with glutathione (GSH) and forms GSH-SM conjugates that appear to be excreted through the mercapturic acid pathway in mammals. The question of whether glutathione-S-transferases (GST) are involved in enzymatic formation of these conjugates remains unresolved. In previous studies, ethacrynic acid (EAA), a putative inhibitor of this transferase, and oltipraz, a known inducer,were ineffective in modulating this enzyme in cultured normal human epidermal keratinocytes (NHEK) so this hypothesis could not be tested. Higher levels of intracellular GSH appeared to be solely responsible for resistance of EAA-pretreated cells to SM. A better inducer of GST was needed to test whether this enzyme could be used to modify cytotoxicity following SM exposure. D,L-sulforaphane (DLS), a compound from broccoli extract known to be a potent inducer of this enzyme, was tested for GST induction in cultured NHEK. The enzyme levels increased optimally (40%) in these cells within 4 hours using 0.5 microg DLS/mL over a 48 hour incubation period. When the drug was removed by washing, and pretreated cells were challenged with 0-200 microM SM, there was a 10%-15% increase in survival at 24 hours compared with non-pretreated SM controls. This protective effect due to increased levels of GST was abolished at 300 microM sulfur mustard, where there was no difference in survival between pretreated and non-pretreated controls. Glutathione levels were also assessed and showed no increase at 4 hours in cultured NHEK with DLS pretreatment and appear not to be responsible for this protection against SM.

Dialysis for Thiocyanate Intoxication: A Case Report and Review of the Literature

Limited data are available on the use of dialysis to treat cyanide or thiocyanate intoxication. This report describes the case of a 65-year-old woman with renal insufficiency who had development of thiocyanate toxicity secondary to a nitroprusside infusion. A rapid decline in her blood thiocyanate level was observed in response to initiation of continuous venovenous hemodiafiltration.

Perchlorate versus other environmental sodium/iodide symporter inhibitors: potential thyroid-related health effects

OBJECTIVE

Perchlorate is a known competitive inhibitor of the sodium/iodide symporter (NIS). Possible thyroid-related effects of environmental perchlorate have created great health concerns, especially in the US, resulting in a debated reference dose (RfD) of 0.0007 mg/kg per day in drinking water recommended by the National Academy of Sciences (NAS). However, the impact of other environmental NIS inhibitors and the role of iodine seem to have received little attention in the whole debate.

METHODS

We performed a PubMed search for articles published up to February 2006, using the key terms perchlorate, nitrate, thiocyanate, iodine, NIS, RfD, thyroid (alone or in combinations), with particular attention for human studies. In parallel, we critically analysed the January 2005 NAS' report, entitled 'Health implications of perchlorate ingestion'.

RESULTS

The relative potencies of prevalent environmental NIS inhibitors (nitrate, thiocyanate and perchlorate) to inhibit iodine uptake have been estimated repeatedly with robust results. Our calculations show that nitrate and thiocyanate, acquired through drinking water or food, account for a much larger proportion of iodine uptake inhibition than perchlorate. Furthermore, the iodine uptake inhibitory effects of nitrate and thiocyanate - as defined by their legally accepted maximal contaminant levels in drinking water - exceed the potential effect of the proposed RfD for perchlorate by far.

CONCLUSIONS

Iodine uptake inhibition and any potential downstream effect by perchlorate are highly dependent on the presence of other environmental NIS inhibitors and iodine intake itself. These potential confounders should therefore be considered in future studies and calculations for risk assessment.

An anthraquinone with potent quinone reductase-inducing activity and other constituents of the fruits of Morinda citrifolia (noni)

Morinda citrifolia, commonly known as noni, has a long history of utilization throughout much of tropical Polynesia and is considered to be the second most important medicinal plant in the Hawaiian Islands. Recently, the use of noni as a dietary supplement in the United States has greatly increased. Bioassay-guided fractionation of a dichloromethane-soluble partition of a MeOH extract of noni fruits has led to the isolation of an extremely potent quinone reductase inducer, 2-methoxy-1,3,6-trihydroxyanthraquinone (1). This new anthraquinone (1) was nearly 40 times more potent than a positive control, l-sulforaphane. Furthermore, compound 1 demonstrated no discernible cytotoxicity at the highest dose tested. In addition to compound 1, 11 known compounds were also isolated and identified in the present investigation. This is the first report of the isolation of anthraquinones from noni fruits.

Comparative aquatic toxicity evaluation of 2-(thiocyanomethylthio)benzothiazole and selected degradation products using Ceriodaphnia dubia

2-(Thiocyanomethylthio)benzothiazole (TCMTB) is a biocide used in the leather, pulp and paper, and water-treatment industries. TCMTB may enter aquatic ecosystems during its manufacture and use. TCMTB is environmentally unstable; therefore, it is important to evaluate the toxicity of the more persistent degradation products. This study compared the toxicity of TCMTB with its degradation products 2-mercaptobenzothiazole (2-MBT), 2-(methylthio)benzothiazole (MTBT), benzothiazole (BT), and 2-hydroxybenzothiazole (HOBT). Toxicity was determined using Ceriodaphnia dubia 48-hour acute and 7-day chronic test protocols. TCMTB was the most toxic compound evaluated in both the acute and chronic tests with EC50s of 15.3 and 9.64 microg/L, respectively. 2-MBT, the first degradation product, was the second most toxic compound with acute and chronic EC50s of 4.19 and 1.25 mg/L, respectively. The toxicity of MTBT and HOBT were similar with acute EC50s of 12.7 and 15.1 mg/L and chronic EC50s of 6.36 and 8.31 mg/L, respectively. The least toxic compound was BT with acute and chronic EC50s of 24.6 and 54.9 mg/L, respectively. TCMTB was orders of magnitude more toxic than its degradation products. Toxicity data on these benzothiazole degradation products is important because of concerns regarding their release, degradation, persistence, and non-target organism effects in aquatic ecosystems.

The effect of perchlorate, thiocyanate, and nitrate on thyroid function in workers exposed to perchlorate long-term

Perchlorate (ClO(4)(-)) and thiocyanate (SCN(-)) are potent and nitrate (NO(3)(-)) a weak competitive inhibitor of the thyroid sodium-iodide symporter. To determine the effects of long-term, high ClO(4)(-) exposure on thyroid function, we conducted a study of 29 workers employed for at least 1.7 yr (50% over 5.9 yr) in an ammonium ClO(4)(-) production plant in Utah. Serum ClO(4)(-), SCN(-), and NO(3)(-); serum T(4), free T(4) index, total T(3), thyroglobulin (Tg), and TSH; 14-h thyroid radioactive iodine uptake (RAIU); and urine iodine (I) and ClO(4)(-) were assessed after 3 d off (Pre) and during the last of three 12-h night shifts in the plant (During) and in 12 volunteers (C) not working in the plant. Serum and urine ClO(4)(-) were not detected in C; urine ClO(4)(-) was not detected in 12 of 29 and was 272 microg/liter in 17 Pre workers; serum ClO(4)(-) was not detected in 27 of 29 Pre; and serum and urine ClO(4)(-) were markedly elevated during ClO(4)(-) exposure to 868 microg/liter and 43 mg/g creatinine, respectively. Serum SCN(-) and NO(3)(-) concentrations were similar in all groups. Thyroid RAIUs were markedly decreased in During compared with Pre (13.5 vs. 21.5%; P < 0.01, paired t) and were associated with an increase in urine I excretion (230 vs. 148 microg I/g Cr; P = 0.02, paired t) but were similar to those in the C group (14.4%). Serum TSH and Tg concentrations were normal and similar in the three groups. Serum T(4) (8.3 vs. 7.7 microg/dl), free T(4) index (2.4 vs. 2.2), and total T(3) (147 vs. 134 ng/dl) were slightly but significantly increased in the During vs. Pre workers (P < 0.01, paired t). Thyroid volumes and patterns by ultrasound were similar in the 29 workers and 12 community volunteers. In conclusion, high ClO(4)(-) absorption during three nights work exposure decreased the 14-h thyroid RAIU by 38% in ClO(4)(-) production workers compared with the RAIU after 3 d off. However, serum TSH and Tg concentrations and thyroid volume by ultrasound were not affected by ClO(4)(-), suggesting that long-term, intermittent, high exposure to ClO(4)(-) does not induce hypothyroidism or goiter in adults.

Do folic acid and thiocyanate have a preventive effect on exogenously induced disturbances of embryonic cranial development?

The preventive influence of folic acid and thiocyanate on procarbazine-induced disturbances of embryonic cranial development was investigated on experimental animals. Low dosages of folic acid or thiocyanate demonstrated no prophylactic effect. When thiocyanate was administered alone, an increased cleft rate was unexpectedly found for the secondary palate. The combined application of folic acid and thiocyanate showed a cleft-prophylactic effect in the secondary palate in addition to growth protection in the primary palate. It can be assumed that thiocyanate has a positive effect on chondral and osseous growth of the palate during the post-sensitive phase of embryogenesis, while in the sensitive phase, it can function as a carrier for teratogenous and toxic substances.

Thiocyanate induces cell necrosis and fibrosis in selenium- and iodine-deficient rat thyroids: a potential experimental model for myxedematous endemic cretinism in central Africa

Thyroid destruction leading to endemic myxoedematous cretinism is highly prevalent in central Africa, where iodine (I) and selenium (SE) deficiencies as well as thiocyanate (SCN) overload are combined. All three factors have been studied experimentally in the etiology of the disease, but they have never been studied in combination. In a model using rats, we have previously shown that combining I and SE deficiencies increases the sensitivity of the thyroid to necrosis after iodide overload, an event unlikely to occur in the African situation. To develop a model that would more closely fit with the epidemiological findings, we have determined whether an SCN overload would also result in thyroid necrosis as does the I overload. The combination of the three factors increased by 3.5 times the amount of necrotic cells, from 5.5 +/- 0.3% in the I-SE+ thyroids to 18.9 +/- 1.6% in the I-SE-SCN-overloaded ones. Methimazole administration prevented the SCN-induced necrosis. SE- thyroids evolved to fibrosis, whereas SE+ thyroids did not. TGFbeta was prominent in macrophages present in SE- glands. Thyroid destruction in central Africa might therefore originate from the interaction of three factors: I and SE deficiencies by increasing H(2)O(2) accumulation, SE deficiency by decreasing cell defense and promoting fibrosis, and SCN overload by triggering follicular cell necrosis.

Bioluminescence inhibition assays for toxicity screening of wood extractives and biocides in paper mill process waters

The risk associated with wood extractives, biocides, and other additives in pulp and paper mill effluents was evaluated by performing a characterization of process waters and effluents in terms of toxicity and chemical analysis. The individual toxicity of 10 resin acids, two unsaturated fatty acids, and three biocides was estimated by measuring the bioluminescence inhibition with a ToxAlert 100 system. Median effective concentration values (EC50) of 4.3 to 17.9, 1.2 to 1.5, and 0.022 to 0.50 mg/L were obtained, respectively. Mixtures of these three families of compounds showed antagonistic effects. Chemical analysis of process waters was performed by liquid chromatography- and gas chromatography-mass spectrometry. Biocides such as 2-(thiocyanomethylthio)-benzotiazole (TCMTB) (EC50 = 0.022 mg/L) and 2,2-dibromo-3-nitrilpropionamide (DBNPA) (EC50 = 0.50 mg/L) were the most toxic compounds tested and were detected at concentrations of 16 and 59 microg/L, respectively, in a closed-circuit recycling paper mill. Process waters from kraft pulp mills, printing paper mills, and packing board paper mills showed the highest concentration of resin acids (up to 400 microg/L) and accounted for inhibition percentages up to 100%. Detergent degradation products such as nonylphenol (NP) and octylphenol (OP) and the plasticizer bisphenol A (BPA) were also detected in the waters at levels of 0.6 to 10.6, 0.3 to 1.4, and 0.7 to 187 microg/L, respectively. However, once these waters were biologically treated, the concentration of detected organic compounds diminished and the toxicity decreased in most cases to values of inhibition lower than 20%.

Mutagenicity of sulfoscanate: a comparative study

The mutagenic activity of sulfoscanate (SSC) (4-isothiocyanate-4'-nitrodiphenyl sulphide) has been compared with that of the following reported drugs: (a) nitroscanate (NSC) (4-isothiocyanate-4'-nitrodiphenyl ether) which is a veterinary anthelmintic drug and (b) amoscanate (ASC) (4-isothiocyanate-4'-nitrodiphenyl amine) which is effective against schistosomes. SSC has been found to be a very potent mutagen towards TA98 and TA100 inducing 26.0 and 475.5revertants/nmole, respectively. NSC was found to induce mutations at a rate of 11.1 and 21.5revertants/nmole in TA98 and TA100, respectively. ASC was found to be non-mutagenic as such, but the urine of animals given the drug displayed mutagenicity. When SSC was tested in TA98/1,8-DNP(6), deficient in O-acetyltransferase, the activity decreased to 10.0revertants/nmole. However, in case of NSC the mutagenic activity was reduced to 0.24revertants/nmole, indicating the importance of O-acetyltransferase in generating N-acetoxyarylamine. In TA98NR, deficient in nitroreductase, the mutagenicity of SSC and NSC was totally absent. The positional isomers of SSC, 4-isothiocyanate-3'-nitro- and 4-isothiocyanate-2'-nitrodiphenyl sulphide, were found to be non-mutagenic in both TA98 and TA100. Our comparison of the mutagenic activity of SSC, NSC and ASC indicates that the pattern of activity is SSC>NSC>ASC.

Effect of various alkyl and unsaturated substituents on the mutagenicity of some nitrophenyl thioethers

A variety of nitro-substituted phenyl alkyl/aryl thioethers and nitroso-substituted phenyl alkyl/aryl thioethers have been synthesized and tested for their mutagenicity towards Salmonella typhimurium strain TA100, TA98, TA98NR and TA98/1,8-DNP(6) in the absence of S9 mix. The relative order of mutagenicity in TA98 and TA100 among p-nitrophenyl thioethers having alkyl or aryl substituents is allyl>phenyl>benzyl>butyl>propyl>ethyl>methyl. Compounds having an alkyl chain C(6) to C(12) were found to be non-mutagenic. Among the various positional isomers (ortho, meta and para) of nitro-substituted diphenyl thioethers only the compounds having the -NO(2) function at the para position is mutagenic, whereas compounds having a -NO(2) function at ortho and meta are non-mutagenic. However, the reduced intermediate, ortho-nitroso derivative was found to be mutagenic in all the four strains but the meta-nitroso derivative was found to be non-mutagenic. All mutagens were found to be non-mutagenic when tested in nitroreductase deficient strain TA98NR, whereas their nitroso intermediates are found to be mutagenic. A substantial fall in the mutagenic activity is observed when some mutagens are tested in O-acetyltransferase deficient strain TA98/1,8-DNP(6).

Eosinophil peroxidase oxidation of thiocyanate. Characterization of major reaction products and a potential sulfhydryl-targeted cytotoxicity system

Although the pseudohalide thiocyanate (SCN(-)) is the preferred substrate for eosinophil peroxidase (EPO) in fluids of physiologic halide composition, the product(s) of this reaction have not been directly identified, and mechanisms underlying their cytotoxic potential are poorly characterized. We used nuclear magnetic resonance spectroscopy (NMR), electrospray ionization mass spectrometry, and quantitative chemical analysis to identify the principal reaction products of both the EPO/SCN(-)/H(2)O(2) system and activated eosinophils as roughly equimolar amounts of OSCN(-) (hypothiocyanite) and OCN(-) (cyanate). Red blood cells exposed to increasing concentrations of OSCN(-)/OCN(-) are first depleted of glutathione, after which glutathione S-transferase and glyceraldehyde-3-phosphate dehydrogenase then ATPases undergo sulfhydryl (SH) reductant-reversible inactivation before lysing. OSCN(-)/OCN(-) inactivates red blood cell membrane ATPases 10-1000 times more potently than do HOCl, HOBr, and H(2)O(2). Exposure of glutathione S-transferase to [(14)C]OSCN(-)/OCN(-) causes SH reductant-reversible disulfide bonding and covalent isotope labeling. We propose that EPO/SCN(-)/H(2)O(2) reaction products comprise a potential SH-targeted cytotoxic system that functions in striking contrast to HOCl, the highly but relatively indiscriminantly reactive product of the neutrophil myeloperoxidase system.

Mechanism of DNA damage by thiocyanate radicals

PURPOSE

It was previously shown that gamma-irradiation of aqueous solutions of plasmid DNA in the presence of millimolar concentrations of thiocyanate ions leads to the formation in very high yields of sites recognized by the base excision repair endonuclease formamido-pyrimidine-DNA N-glycosylase (FPG). The authors wished to characterize the mechanism responsible for the production of these FPG-sensitive sites.

MATERIALS AND METHODS

An aqueous solution of plasmid DNA containing thiocyanate ions was irradiated with 137Cs gamma-rays. After irradiation, aliquots were treated with FPG. Break yields were determined using neutral agarose gel electrophoresis.

RESULTS

The yield of FPG-sensitive sites decreased with decreasing enzyme activity, increasing thiocyanate concentration, increasing dose-rate, increasing ionic strength, increasing nitrite or iodide concentration, and decreasing oxygen concentration.

CONCLUSION

The observations suggest that the monomeric thiocyanate radical SCN* is an intermediate in the reaction, and that the yields of FPG-sensitive sites are determined by competition between the disproportionation of the dimeric radical anion (SCN)*2- and the fate of a one-electron oxidized guanine species in DNA. The latter can react with oxygen to produce an FPG-sensitive site or can be reduced without producing an FPG-sensitive site. The results help to clarify the mechanisms responsible for DNA damage by the direct effect of ionizing radiation.

Effect of thiocyanate induced hypothyroidism on 5'deiodinase activity and T3 receptors in developing rat brain

Experiments were performed in weaning rats to understand the influence of thiocyanate, an hydrolytic product of glucosinolates present in foods, on the generation of T3 in situ by type II 5'deiodinase and the binding of 125I T3 to specific nuclear receptors in developing brain. Feeding of thiocyanate through gestation and lactation resulted in an increase in type II 5'deiodinase activity in cerebrum, cerebellum and brainstem of the 21 day old pups compared to controls. Hypothyroidism induced by thiocyanate further resulted in augmentation of the maximum binding capacity of receptors in the cerebrum of the weaning pups. Affinity constants for binding of 125I T3 were however, unaltered. Increase in type II 5'deiodinase activity and the number of binding sites point to an adaptive increase in response to thiocyanate induced hypothyroidism to maintain the cellular T3 levels within a narrow limit.

Magnesium modulates contractile responses of rat aorta to thiocyanate: A possible relationship to smoking-induced atherosclerosis

Thiocyanate anions (SCN-) as the end products of tobacco smoke and found in the blood of cigarette smokers have been implicated in atherogenesis and heart diseases. Magnesium deficiency has also been implicated in the etiology of atherogenesis. The contractile responses of rat aorta to SCN- and the modulation of extracellular magnesium ions ([Mg2+]o) on the effect of SCN- were, therefore, studied in isolated rat aortic rings. SCN- exposure at a range of concentrations (from 10(-5) to 5 x 10(-2) M) induces contractile responses of isolated rat aortic rings with and without endothelium in a concentration-dependent manner. Significant differences in responsiveness to SCN- were found in rat aortic ring segments with and without endothelial cells. Preincubation of these vessels with low [Mg2+]o markedly shifted the contractile concentration-effect curves to the left, and the contractile effects of SCN- in rat aortic rings were potentiated. In contrast to lowering [Mg2+]o, increasing [Mg2+]o to 2.4 mM was found to dramatically attenuate the contractile responses to SCN-. In the absence of extracellular Ca2+ ([Ca2+]o), SCN--induced contractions were, however, almost abolished after exposure to Mg2+-free medium. In order to investigate the mechanisms of [Mg2+]o modulation of SCN--induced contractile response of rat aorta, changes in intracellular Ca2+ ([Ca2+]i) were measured in cultured primary smooth muscle cells isolated from rat aorta. The resting level of [Ca2+]i in the rat aortic smooth muscle cells was 80.6 +/- 6.6 nM. Exposure of these cells to SCN- (5 x 10(-5) to 5 x 10(-3) M) produced rises in [Ca2+]i in a concentration-dependent manner. Preincubation of these cells with low [Mg2+]o (0 or 0.3 mM, the lowest physiological range) for 24 h significantly potentiated increments in [Ca2+]i induced by SCN-. These rises in [Ca2+]i induced by SCN- were completely inhibited by pretreating the cells with 2.4 mM [Mg2+]o for 24 h. These results support a hypothesis whereby cigarette smoking or exposure to smoking can induce cardiovascular diseases, at least partly, probably by causing spasm and thickening of arterial blood vessels as a consequence of large rises in [Ca2+]i in vascular smooth muscle cells. The chronic presence of or exposure to both thiocyanate and low Mg2+ in the blood of smokers can result in rapid flux of Ca2+ into vascular smooth muscle cells, thus accelerating or initiating atherosclerotic processes in smokers.

Re-evaluation of the culture condition of polymorphonuclear cells for the study of apoptosis induction

The culture conditions of human peripheral blood polymorphonuclear leukocytes (PMN) in the study of apoptosis induction were re-evaluated. The changes in the relative viable cell number of PMNs after tumor necrosis factor (TNF) treatment were colorimetrically investigated using a cell counting kit. The relative potency of PMNs to produce the superoxide anion (O2-) was measured as the reduction of color intensity by addition of superoxide dismutase (SOD). When the PMNs were cultured in conventional RPMI1640 medium supplemented with 10% fetal bovine serum (FBS), the stimulation effect of TNF on O2- generation by PMNs was observed only for the first 6 hours. When FBS was replaced with human serum, the effect of TNF was maintained for longer incubation periods. Prolonged incubation of PMNs spontaneously produced large DNA fragments, and the extent of DNA fragmentation was relatively smaller in human serum-containing medium. TNF, LPS, hyperthermia or potassium thiocyanate slightly accelerated the production of large DNA fragments, as well as the induction of trace amounts of internucleosomal DNA cleavage in PMNs, which became detectable only after concentration by fractional isopropanol precipitation. The present study suggests the importance of the use of human serum rather than conventional FBS for the study of apoptosis induction in PMNs.

Histopathological and ultrastructural examination of the rat conjunctiva after exposure to tobacco smoke

Exposure to tobacco smoke can cause irritation of the conjunctiva. We conducted this study to identify the effect of tobacco on rat conjunctiva. Animals were divided into experimental and control groups and we exposed the experimental group to tobacco smoke. Control group rats inhaled only room air. Spectrophotometric analysis of the smoke-air mixture revealed that many toxic substances were present in this compound. We found very high levels of plasma thiocyanate after exposure to smoke in experimental group animals but no increase in the control group. So, this data indicates that these animals inhaled smoke effectively in our method. After 3 months conjunctivas were examined by light and electron microscopy. In the experimental group, conjunctivas were thinned, atrophied and microvillous projections and desmosomal connections were absent in comparison with the control conjunctivas. This pathologic change is very similar to conjunctival response to chronic irritants of any type.