Younglim Kho

Effects of bisphenol s exposure on endocrine functions and reproduction of zebrafish.

While bisphenol S (BPS) has been frequently detected both in environment and biota, limited information is available on their effects of endocrine system. In the present study, adult zebrafish pairs were exposed to 0.5, 5, and 50 μg/L of BPS for 21 d, and the effects on reproduction, sex steroid hormones, and transcription of the genes belonging to the hypothalamic-pituitary-gonad (HPG) axis were investigated. The adverse effects on performances of F1 generation were further examined with or without subsequent exposure to BPS. Egg production and the gonadosomatic index in female fish were significantly decreased at ≥0.5 μg/L BPS. Plasma concentrations of 17β-estradiol were significantly increased in both male and female fish. In male fish, however, significant decreases of testosterone concentration were observed along with up-regulation of cyp19a and down-regulation of cyp17 and 17βhsd transcripts. Parental exposure to BPS resulted in delayed and lesser rates of hatching even when they were hatched in clean water. Continuous BPS exposure in the F1 embryos resulted in worse hatchability and increased malformation rates compared to those without BPS exposure. Our observations showed that exposure to low level BPS could affect the feedback regulatory circuits of HPG axis and impair the development of offspring.

Trans-Placental Transfer of Thirteen Perfluorinated Compounds and Relations with Fetal Thyroid Hormones

While the results of animal studies have shown that perfluorinated compounds (PFCs) can modulate concentrations of thyroid hormones in blood, limited information is available on relationships between concentrations of PFCs in human blood serum and fetal thyroid hormones. The relationship between concentrations of PFCs in blood and fetal thyroid hormone concentrations or birth weight, and ratios of major PFCs between maternal and fetal serum were determined. Concentrations of PFCs were measured in blood serum of pregnant women (n = 44), fetal cord blood serum (n = 43) and breast milk (n = 35). Total concentrations of thyroxin (T4), triiodothyronin (T3) and thyroid stimulating hormone (TSH) in blood serum were also quantified. The ratios of major PFCs in maternal versus fetal serum were 1:1.93, 1.02, 0.72, and 0.48 for perfluorotridecanoic acid (PFTrDA), perfluorooctanoic acid (PFOA), perfluorohexane sulfonate (PFHxS), and perfluorooctane sulfonate (PFOS), respectively. Fetal PFOS, PFOA, PFTrDA and maternal PFTrDA were correlated with fetal total T4 concentrations, but after adjusting for major covariates, most of the relationships were no longer statistically significant. However, the significant negative correlations between maternal PFOS and fetal T3, and maternal PFTrDA and fetal T4 and T3 remained. Since thyroid hormones are crucial in the early development of the fetus, its clinical implication should be evaluated. Given the observed trans-placental transfer of PFCs, efforts should be also made to elucidate the exposure sources among pregnant women.

Serum concentrations of major perfluorinated compounds among the general population in Korea: dietary sources and potential impact on thyroid hormones.

Perfluorinated compounds (PFCs) have been frequently detected in both the environment and biota, and have become a growing concern. However, information is limited on the potential sources and human health implications of such exposure. We evaluated the exposure levels of 13 major PFCs among a population (n=633, >12 years of age) in a mid-sized city of Korea, and investigated for their potential dietary sources and the impact on thyroid hormone concentrations. For this purpose, we collected blood samples from a general population in Siheung, Korea and measured for 13 PFCs, total thyroxine (T4), and thyroid stimulating hormone (TSH). In addition, a questionnaire survey on diet was conducted. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), perfluorohexane sulfonic acid (PFHxS), and perfluorononanoic acid (PFNA) were detected in relatively greater concentrations than the other 9 PFCs in the blood serum. Males tend to have greater concentrations than females for most PFCs, and the concentrations were elevated as age increased up to 50s. Body mass index (BMI) was also shown to influence the serum concentrations of several PFCs. After adjustment for age, sex, and BMI, the consumption of vegetable, potato, fish/shellfish, and popcorn was identified to be significantly related with concentrations of major PFCs in blood. Among the studied PFCs, the concentrations of perfluorotridecanoic acid (PFTrDA) were negatively correlated with total T4, and positively with TSH levels, especially among females. The result of this study will provide information useful for developing public health and safety management measures for PFCs.

Effects of non-steroidal anti-inflammatory drugs on hormones and genes of the hypothalamic-pituitary-gonad axis, and reproduction of zebrafish

This study was conducted in two experiments, to identify non-steroidal anti-inflammatory drugs (NSAIDs) with high endocrine disruption potentials, and to understand consequences of exposure to such NSAIDs in fish. In the first experiment, the effects of five NSAIDs on hormones and gene transcriptions of the hypothalamic-pituitary-gonad (HPG) axis were evaluated after 14 d exposure of adult zebrafish. Ibuprofen and mefenamic acids were identified to increase the concentrations of 17β-estradiol and testosterone in females significantly, while decreased those of testosterone among male fish. Significant up-regulation of fshβ, lhβ, fshr and lhr were observed in females, whereas down-regulation was observed in males exposed to each NSAID. In the second experiment, ibuprofen was chosen as a model chemical. Adult zebrafish pairs were exposed to ibuprofen for 21 d, and the effects on reproduction and development of offspring were examined. The egg production was significantly decreased at ≥1 μg/L ibuprofen, and parental exposure resulted in delayed hatching even when they were transferred to clean water for hatching. The results demonstrated that ibuprofen could modulate hormone production and related gene transcription of the HPG axis in a sex-dependent way, which could cause adverse effects on reproduction and the development of offspring.

Major pharmaceutical residues in wastewater treatment plants and receiving waters in Bangkok, Thailand, and associated ecological risks.

Pharmaceuticals have been frequently detected in aquatic environment worldwide and suspected for potential ecological consequences. However, occurrences, sources and potential risks of pharmaceutical residues have rarely been investigated in Bangkok, Thailand, one of most densely populated cities in the world. We collected water samples from five wastewater treatment plants (WWTPs), six canals, and in mainstream Chao Phraya River of Bangkok, in three sampling events representing different seasonal flow conditions, i.e., June and September 2011 and January 2012. Fourteen major pharmaceuticals including acetaminophen, acetylsalicylic acid, atenolol, caffeine, ciprofloxacin, diclofenac, ibuprofen, mefenamic acid, naproxen, roxithromycin, sulfamethazine, sulfamethoxazole, sulfathiazole and trimethoprim were analyzed. Levels of pharmaceutical residues in WWTP influents on average were the highest for acetylsalicylic acid (4700 ng L(-1)), followed by caffeine (2250 ng L(-1)) and ibuprofen (702 ng L(-1)). In effluents, the concentration of caffeine was the highest (307 ng L(-1)), followed by acetylsalicylic acid (261 ng L(-1)) and mefenamic acid (251 ng L(-1)). In surface water, acetylsalicylic acid showed the highest levels (on average 1360 ng L(-1) in canals and 313 ng L(-1) in the river). Removal efficiencies of WWTPs for roxithromycin, sulfamethoxazole and sulfamethazine were determined negligible. For several compounds, the concentrations in ambient water were higher than those detected in the effluents, implying contribution of the WWTPs to be negligible. Hazard quotients estimated for acetylsalicylic acid, ciprofloxacin, diclofenac and mefenamic acid in most of the canals and that of ciprofloxacin in the river, were greater than or close to 1, suggesting potential ecological risks. Ecological implications of the pharmaceutical residues in Bangkok waterway warrant further investigation.

Risk assessment of chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin in aquatic environment: are the current environmental concentrations safe?

To understand potential risks of major pharmaceutical residues in waters, we evaluated ecotoxicities of five major veterinary pharmaceuticals, i.e., chlortetracycline, oxytetracycline, sulfamethazine, sulfathiazole, and erythromycin, which have been frequently detected in freshwater environment worldwide. We conducted acute and chronic toxicity tests using two freshwater invertebrates (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). In general, D. magna exhibited greater sensitivity than M. macrocopa, and chronic reproduction was the most sensitive endpoints for both organisms. The population growth rate was adversely influenced by exposure to chlortetracycline, sulfamethazine, or sulfathiazole in water fleas, but reduction in population size was not expected. In O. latipes, the tested pharmaceuticals affected several reproduction related endpoints including time to hatch and growth. Based on the toxicity values from the present study and literature, algae appeared to be the most sensitive organism, followed by Daphnia and fish. Hazard quotients derived from measured environmental concentrations (MECs) and predicted no effect concentrations (PNECs) for erythromycin and oxytetracycline exceeded unity, suggesting that potential ecological effects at highly contaminated sites cannot be ruled out. Long-term consequences of veterinary pharmaceutical contamination in the environment deserve further investigation.

Effects of benzophenone-3 exposure on endocrine disruption and reproduction of Japanese medaka (Oryzias latipes)--a two generation exposure study.

Benzophenone-3 (BP-3) has been widely used in sunscreens and cosmetics to protect human skin from the harmful effects of UV irradiation. While BP-3 has been frequently detected in surface waters, sediments and biota, only limited information is available on its in vivo toxicity, particularly in fish. In the present study the endocrine disrupting capacity of BP-3 and its underlying mechanisms were investigated using Japanese medaka (Oryzias latipes). Adult Japanese medaka pairs (F0) were exposed to 0, 4.7, 8.4, 26, or 90 μg/L (or 0, 15, 50, 150, or 500 μg/L of BP-3 based on nominal concentration) for 14 d and its effects on sex steroid hormones, and transcription of various associated genes were determined. Following additional 14 d of exposure, the F1 eggs reproduced were counted and were further exposed to 0, 5.4, 12, or 30 μg/L of BP-3 (or 0, 15, 50, or 150 μg/L based on nominal concentrations) until 30 d after hatching. Chemical analysis of the exposed media confirmed transformation of BP-3 to benzophenone-1 (BP-1), a more potent estrogen agonist. After 14 d of the adult fish exposure, plasma concentrations of testosterone (T) significantly increased in male fish. The 17β-estradiol (E2) to T (E2/T) ratio showed significant decreases in both male and female fish. Overall down-regulation of gonadal steroidogenic genes such as star, cyp11a, cyp17, hsd3b, hsd17b3, and cyp19a was also observed. After 28 d of exposure, the daily average egg reproduction per female was significantly reduced at 26 μg/L of BP-3. However, hatchability of F1 eggs was not affected by continuous exposure. After continued exposure until 30 dph, juvenile fish showed concentration-dependent decrease of condition factor, but mortality was not affected. Our observation clearly indicates that endocrine balance and reproduction performance in fish could be affected by μg/L level exposure to BP-3. Consequences of longer term exposure over multi-generations warrant further investigation.

Perfluorooctane sulfonic acid exposure increases cadmium toxicity in early life stage of zebrafish, Danio rerio

Exposure to perfluorooctane sulfonic acid (PFOS) is known to induce thyroid-related adverse effects in aquatic organisms. Because an antioxidant defense mechanism is one of the key functions of the thyroid gland, we examined whether preexposure to PFOS could disrupt thyroid function and enhance cadmium (Cd)-induced oxidative stress in fish. Zebrafish embryos were exposed to control or 0.5 mg/L PFOS for 7 d after fertilization and subsequently exposed to 0.038 mg/L of Cd(2+) or a mixture of the PFOS and Cd for an additional 3 d until 10 d postfertilization (dpf). Survival rates, body length, messenger RNA (mRNA) expressions related to thyroid function and oxidative stress, the levels of thyroid hormones, and malondialdehyde and antioxidant enzyme activities were measured. Significant down-regulation of mRNAs related to thyroid function (thyroid hormone receptor-alpha [THRα], thyroid hormone receptor-beta [THRβ], hematopoietically expressed homeobox [hhex], and paired box gene 8 [pax8]) and decrease of throxine (T4) levels were observed in the PFOS preexposure group, suggesting that PFOS preexposure would influence the performance of thyroid gland in the later stages of life. Certain genes relative to oxidative stress, such as superoxide dismutase 1 (sod1) and heat shock protein 70 (hsp70), in the PFOS preexposure group were significantly up-regulated when the larvae were subsequently exposed to Cd or to the mixture of PFOS and Cd. Glutathione S-transferase activity and malondialdehyde levels of the PFOS-preexposed group were increased significantly by Cd exposure. Significant decrease of the survival rates and body length of fish were observed at 10 dpf among the larvae that were previously exposed to PFOS. These results suggest that preexposure to PFOS could affect antioxidant defense mechanisms and potentially increase the toxicity of Cd on mRNA expression and enzyme activity level responses, as well as on survival or growth of individuals.

Effect of chronic exposure to acetaminophen and lincomycin on Japanese medaka (Oryzias latipes) and freshwater cladocerans Daphnia magna and Moina macrocopa, and potential mechanisms of endocrine disruption.

Chronic toxicity of acetaminophen and lincomycin were evaluated using freshwater organisms including two crustaceans (Daphnia magna and Moina macrocopa) and a fish (Oryzias latipes). H295R, a human adrenal cell was also used to understand the effects on steroidogenesis. In 21 d D. magna exposure, survival NOEC was found at 5.72 mg L(-1) and no reproduction related effects were noted at this level of exposure to acetaminophen, while 21 d survival or growth effects were not observed even at the highest exposure levels (153 mg L(-1)) for lincomycin. In the chronic fish toxicity test, significant reduction in juvenile survival was observed at 30 d post-hatch (dph) at 95 mg L(-1) of acetaminophen, and 0.42 mg L(-1) of lincomycin. After the exposure to both pharmaceuticals, vitellogenin levels tended to increase in male fish at 90 dph. In the eggs which were prenatally exposed to 9.5 mg L(-1) of acetaminophen, reduced hatchability was observed. The results of H295R cell assay showed that both pharmaceuticals could alter steroidogenic pathway and increase estrogenicity. Endocrine disruption potentials and their ecological implication may deserve further studies. Our observations suggest however that ecological risks of both pharmaceuticals are negligible at the concentrations currently found in the environment.

Major perfluoroalkyl acid (PFAA) concentrations and influence of food consumption among the general population of Daegu, Korea.

Perfluoroalkyl acids (PFAAs) have been used in various industrial and consumer products for decades, and have consequently been detected in human blood worldwide. In the present study, general adult population in Daegu, Korea (n=140, >20 years of old) was recruited, collected for serum, and analyzed for 13 major PFAAs. The influence of dietary and water consumption on serum PFAA levels was also evaluated. Perfluorooctane sulfonic acid (PFOS), perfluorooctanoic acid (PFOA), and perfluorohexane sulfonic acid (PFHxS) were frequently detected with relatively higher concentrations in blood serum. Most PFAA concentrations except for PFOA were detected in higher concentrations among males, and were positively correlated with age and body mass index (BMI). PFOA concentrations were relatively higher among the female of childbearing age, e.g., 20-49years old, raising concerns on potential impacts on fetus through transplacental transfer or lactation. In addition, the concentrations of PFOA in Daegu population were higher than other areas of Korea, suggesting a presence of distinctive sources in the area. Among food items, potato consumption was identified to be significant contributor to serum PFOA. For PFUnDA and PFTrDA levels, intake of fish/shellfish was positively associated. The results of this study will be useful in developing public health management options for PFAAs.