Reproductive disorders linked to the interaction between sex steroid and thyroid hormonal activities, oxidative stress responses, and the rate of metabolism of tris (1,3-dichloro-2-propyl) phosphate (TDCPP) in zebrafish.

The objective of this study was to assess the thyroid hormone disruption and reproductive dysfunction effects of the bioaccumulation and rate of mechanism in zebrafish exposed to tris(1,3-dichloro-2-propyl) phosphate (TDCPP), with stress responsiveness. The fish were exposed to test concentrations of TDCPP (0, 0.06, 0.3, 1.5 µg/mL) for 21 days, in accordance with no observed adverse effect level (i.e., < EC10) for zebrafish embryos. The bioaccumulation of TDCPP was found to be significantly higher in female zebrafish, while the metabolic rate was significantly higher in male zebrafish at all concentrations studied. The thyroid hormone (triiodothyronine [T3] and thyroxine [T4]) levels and sex steroid (i.e., estrogen, androgen, and progesterone) levels were significantly increased only in female zebrafish exposed to TDCPP, and no significant difference was observed in male zebrafish, although their cortisol levels increased. The response to TDCPP can, therefore, be considered sex-specific. The results of this study demonstrate for the first time, that the different response in the bioaccumulation and metabolic rate of TDCPP in males and females. The results also indicate that TDCPP alters thyroid hormone levels, furthermore, as steroidogenesis is related to reproductive function with differing response in males and females. TDCPP can be assumed to exert reproductive toxicity via disruption of thyroid and steroid synthesis through a slow metabolic rate in the whole body after exposure. Consequently, our proposed methodological approach to assess the interactions of thyroid and steroid biosynthesis and metabolic rate of TDCPP with reproductive toxicity will serve a testing strategy to examine the adverse outcomes of emerging environmental chemicals.

Chronic effects of nano and microplastics on reproduction and development of marine copepod Tigriopus japonicus.

This study aimed to examine the impact of chronic (30 days) exposure to polystyrene microplastics (PS-MPs) of different sizes (50 nm and 2 µm) and at different concentrations (0.5 µg/L and 100 mg/L) to marine copepod Tigriopus japonicus. Polystyrene microplastics affected survival rates in size- and concentration-dependent manners. The LC50s values of 50 nm and 2 µm PS-MPs were 0.10 mg/L and 3.92 mg/L, respectively. The developmental time was delayed by 50 nm PS-MPs, and Usp expression was downregulated. Reproduction was negatively affected by 2 µm PS-MPs even at environmentally relevant concentrations; however, the expression of Vtg was not altered. The production rates of reactive oxygen species and nitric oxide also increased after exposure to PS-MPs; but this effect was independent of particle size. The expression levels of Cat and Tnf, genes related to oxidative stress and inflammation, respectively, were upregulated by exposure to PS-MPs, independently of particle size. Meanwhile, the level of oxidative stress in T. japonicus was not significantly affected by PS-MPs at environmentally relevant concentrations. This study suggests that nano-sized PS-MPs are not always more toxic than micro-sized PS-MPs, and that oxidative stress is a key factor in determining the toxic effect on T. japonicus at high concentrations.

Sex-specific effects of bisphenol S with tissue-specific responsiveness in adult zebrafish: The antiandrogenic and antiestrogenic effects.

This study investigates the adverse effects and the associated underlying mechanism of bisphenol S (BPS) exposure on reproductive endocrine activity in adult zebrafish. Fish were exposed for 21 days to different BPS concentrations (0, 8, 40, and 200 µg/mL) determined via the lowest observed adverse effect level (LOAEL, i.e., < EC15 = 250 µg/mL) for zebrafish embryos. Exposure to 200 µg/mL BPS in female zebrafish in the absence of vitellogenic oocytes or the presence of degenerated oocytes in the ovary significantly decreased the biosynthesis of hepatic vitellogenin (VTG) mRNA, while hepatic VTG mRNA in male fish abundance was significantly elevated (P < 0.05). The levels of gonadal steroids were significantly increased in female zebrafish, while in male zebrafish, the levels of endogenous androgens were reduced (P < 0.05). However, the activities of 17ß-estradiol and aromatase in male zebrafish were significantly elevated in all BPS exposure groups in male zebrafish (P < 0.05). Interestingly, thyroid hormone levels and residual whole-body BPS levels increased in female and male zebrafish with increasing exposure concentrations. A novel finding is that the response to BPS depends on zebrafish sex and tissue-specific responsiveness to the accumulation of BPS, suggesting that BPS may cause long-term environmental problems in adult zebrafish through tissue-specific suppression and hormonal imbalance.

A Screening of the MMV Pandemic Response Box Reveals Epetraborole as a New Potent Inhibitor against Mycobacterium abscessus.

Mycobacterium abscessus is the one of the most feared bacterial respiratory pathogens in the world. Unfortunately, there are many problems with the current M. abscessus therapies available. These problems include misdiagnoses, high drug resistance, poor long-term treatment outcomes, and high costs. Until now, there have only been a few new compounds or drug formulations which are active against M. abscessus, and these are present in preclinical and clinical development only. With that in mind, new and more powerful anti-M. abscessus medicines need to be discovered and developed. In this study, we conducted an in vitro-dual screen against M. abscessus rough (R) and smooth (S) variants using a Pandemic Response Box and identified epetraborole as a new effective candidate for M. abscessus therapy. For further validation, epetraborole showed significant activity against the growth of the M. abscessus wild-type strain, three subspecies, drug-resistant strains and clinical isolates in vitro, while also inhibiting the growth of M. abscessus that reside in macrophages without cytotoxicity. Furthermore, the in vivo efficacy of epetraborole in the zebrafish infection model was greater than that of tigecycline. Thus, we concluded that epetraborole is a potential anti-M. abscessus candidate in the M. abscessus drug search.

Chronic toxicity of endocrine disrupting chemicals used in plastic products in Korean resident species: Implications for aquatic ecological risk assessment.

In this study, chronic toxicity of three endocrine disrupting chemicals (EDCs) used to make plastic products (i.e., bisphenol A (BPA), bis(2-ethylhexyl)phthalate (DEHP) and nonylphenol (NP)) in a Korean resident fish (Cyprinus carpio), crustacean (Moina macrocopa) and green alga (Pseudokirchneriella subcapitata) species was tested. It was found that M. macrocopa was particularly sensitive to those EDCs, especially DEHP and NP. We exposed M. macrocopa to DEHP (0.0012-0.1 mg/L) and NP (0.00037-0.03 mg/L), and as a result, both chemicals significantly delayed the first day of reproduction. The no observed effect concentrations (NOECs) of DEHP and NP for this endpoint were determined to be 0.0012 and 0.00037 mg/L, respectively, which are far lower than NOECs for any other freshwater species. Existing water quality criteria of various governmental agencies do not consider the toxicity of those EDCs on M. macrocopa, and thus, use of the existing criteria for the risk assessment of the Korean freshwater environment may underestimate the ecological risk. This study recommends using the water quality criteria derived in this study (0.95 µg/L for DEHP and 0.16 µg/L for NP) based on the chronic toxicity data on Korean resident species including M. macrocopa for the aquatic ecological risk assessment in Korea rather than adopting the existing water quality criteria.

Etamycin as a Novel Mycobacterium abscessus Inhibitor.

The increase in drug-resistant Mycobacterium abscessus, which has become resistant to existing standard-of-care agents, is a major concern, and new antibacterial agents are strongly needed. In this study, we introduced etamycin that showed an excellent activity against M. abscessus. We found that etamycin significantly inhibited the growth of M. abscessus wild-type strain, three subspecies, and clinical isolates in vitro and inhibited the growth of M. abscessus that resides in macrophages without cytotoxicity. Furthermore, the in vivo efficacy of etamycin in the zebrafish (Danio rerio) infection model was greater than that of clarithromycin, which is recommended as the core agent for treating M. abscessus infections. Thus, we concluded that etamycin is a potential anti-M. abscessus candidate for further development as a clinical drug candidate.

Rifamycin O, An Alternative Anti-Mycobacterium abscessus Agent.

Mycobacterium abscessus is the most difficult-to-treat nontuberculous mycobacteria because of its resistance to many antibiotics. In this study, we screened the Korea Chemical Bank library for a bioluminescent reporter assay to identify molecules capable of acting against M. abscessus. On application of the assay, rifamycin O showed excellent in vitro activity with a narrow range of the minimum inhibitory concentration required to inhibit the growth of 90% of the bacterium (MIC90 = 4.0-6.2 µM); its in vivo efficacy in the zebrafish (Danio rerio) infection model was comparable to that of rifabutin at 25 µM. Furthermore, rifamycin O did not show significant toxicity in cells and the zebrafish model. These results are the first in vivo indication that rifamycin O may be a drug candidate for treating M. abscessus infections.

Proteomic analysis of whole-body responses in medaka (Oryzias latipes) exposed to benzalkonium chloride.

Benzalkonium chloride (BAC) is a cationic surfactant commonly used as a disinfectant, and is discharged into the aquatic environment by various water sources such as wastewater. BAC may also interact with potentially toxic substances such as persistent organic chemicals. Although studies of BAC contamination toxicity and bioaccumulation have been widely reported, the biochemical responses to BAC toxicity remain incompletely understood, and the detailed molecular mechanisms are largely unknown. In this study, two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization tandem time-of-flight mass spectrometry-based proteomic approaches were applied to investigate the protein profiles in Oryzias latipes (medaka) chronically exposed to BAC. Fish were exposed to three different concentrations of BAC, 0.05, 0.1, and 0.2 mg/L, for 21 days. A total of 20 proteins involved in the cytoskeleton, the oxidative stress response, the nervous and endocrine systems, signaling pathways, and cellular proteolysis were significantly upregulated by BAC exposure. The proteomic information obtained in the present study will be useful in identification of potential biomarkers for BAC toxicity, and begins to elucidate its molecular mechanisms, providing new insights into the ecotoxicity of BAC.

Thiostrepton: A Novel Therapeutic Drug Candidate for Mycobacterium abscessus Infection.

Mycobacterium abscessus is a rapid-growing, multidrug-resistant, non-tuberculous mycobacterial species responsible for a variety of human infections, such as cutaneous and pulmonary infections. M. abscessus infections are very difficult to eradicate due to the natural and acquired multidrug resistance profiles of M. abscessus. Thus, there is an urgent need for the development of effective drugs or regimens against M. abscessus infections. Here, we report the activity of a US Food and Drug Administration approved drug, thiostrepton, against M. abscessus. We found that thiostrepton significantly inhibited the growth of M. abscessus wild-type strains, subspecies, clinical isolates, and drug-resistant mutants in vitro and in macrophages. In addition, treatment of macrophages with thiostrepton significantly decreased proinflammatory cytokine production in a dose-dependent manner, suggesting an inhibitory effect of thiostrepton on inflammation induced during M. abscessus infection. We further showed that thiostrepton exhibits antimicrobial effects in vivo using a zebrafish model of M. abscessus infection.

Introducing a new standardized nanomaterial environmental toxicity screening testing procedure, ISO/TS 20787: aquatic toxicity assessment of manufactured nanomaterials in saltwater Lakes using Artemia sp. nauplii.

This paper introduces a new standardized testing procedure for nanomaterial environmental toxicity (International Organization for Standardization/Technical Specification (ISO/TS) 20787): 'aquatic toxicity assessment of manufactured nanomaterials in saltwater lakes using Artemia sp. Nauplii' intended to generate more reliable and repeatable aquatic toxicity data testing manufactured nanomaterials, using Artemia sp., to evaluate their possible ecotoxicity in saltwater lake ecosystems. The principles behind testing with Artemia sp. are reviewed and the paper gives an overview of research published between 2009 and 2018 in which manufactured nanomaterials were tested using Artemia sp.

Differentially transcriptional regulation on cell cycle pathway by silver nanoparticles from ionic silver in larval zebrafish (Danio rerio).

Silver nanoparticles (AgNPs) have a strong antibacterial activity and the relevant modes of actions have regarded as direct or indirect causes of toxicity observed in the environment. In this study, the transcriptomic profiles in larval zebrafish (Danio rerio) exposed to AgNPs (about 50 nm in size) and AgNO3 as a comparative ionic silver were investigated and analyzed using differential expressed gene (DEG), Gene ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) pathway analyses. Results indicated that underlying molecular mechanisms are different each other. Interestingly, the global gene expression profiling showed that cell cycle pathway is affected by both AgNPs and dissolved Ag+, however its regulation pattern was opposite each other. To the best of our knowledge, the up-regulation of cell cycle pathway by AgNPs and down-regulation by Ag+ is the first reporting and suggests the distinguished toxicological perspective from a well-known hypothesis that Ag+ mainly regulates the cell cycle. This study provides novel insights onto the genotoxicological mechanisms of AgNPs.

Estrogenic potency of bisphenol S, polyethersulfone and their metabolites generated by the rat liver S9 fractions on a MVLN cell using a luciferase reporter gene assay.

BACKGROUND: Bisphenol A (BPA) is an applied chemical that is used in many industrial fields and is a potential endocrine disruption chemical (EDC) that is found in the environment. Bisphenol S (BPS) and polyethersulfone (PES) have been suggested as putative BPA alternatives. In this study, the estrogenic potency induced by the binding of 17-beta-estradiol (E2), BPA, BPS, PES and their metabolites formed by the rat liver S9 fraction to the human estrogen receptor (ER) was estimated. METHODS: We used an in vitro bioassay based on the luciferase reporter assay in MVLN cells to evaluate the estrogenic activity of 17-beta-estradiol (E2), BPA, BPS, PES (E2: 0.001 to 0.3 nM; BPA, BPS and PES: 0.0001 to 5 microM) and their metabolites (E2: 0.05 microM; BPA, BPS and PES: 0.1 mM) according to incubation times (0, 20 and 40 min). After chemical treatment to MVLN cells for 72 hrs, and the cell viability and luciferase intensity induced were estimated, from which the estrogenic activity of the chemicals tested was evaluated. RESULTS: BPA and BPS induced estrogenic activity whereas PES did not show any estrogenic activity in the concentrations tested. In an in vitro assay of metabolites, BPA metabolites displayed comparable estrogenic activity with BPA and metabolites of both BPS and PES showed increasing estrogenic activity. CONCLUSIONS: The results suggest that the metabolites of BPS and PES have estrogenic potential and the need for the assessment of both chemicals and their metabolites in other EDC evaluation studies. The estrogenic potency of PES and its metabolites is the first report in our best knowledge.

Uptake, tissue distribution, and depuration of total silver in common carp (Cyprinus carpio) after aqueous exposure to silver nanoparticles.

The increased use and disposal of silver nanoparticles (AgNPs) has led to their release from wastewater treatment plants into surface waters and concern over potential for negative effects in aquatic organisms. Investigations of the toxicity of AgNPs in fish have considered various species, exposure routes, and test end points; however, the toxicokinetics of total silver has not been studied in fish exposed to aqueous AgNPs. In this study, we investigated the toxicokinetics of total silver in common carp (Cayprinus carpio) exposed to AgNPs [0.62 ± 0.12 (mean ± standard deviation) mg L(-1)] for 7 days followed by a 2 week depuration period. During exposure and depuration, fish were sampled, tissues were excised (gills, brain, skeletal muscle, gastrointestinal tract, liver, and blood) and digested in acid, and total silver concentrations were analyzed by inductively coupled plasma-optical emission spectrometry. Total silver in tissues increased during the 7 day exposure, and mean concentrations were 5.61 mg/kg of liver, 3.32 mg/kg of gills, 2.93 mg/kg of gastrointestinal tract, 0.48 mg/kg of skeletal muscle, 0.14 mg/kg of brain, and 0.02 mg/kg of blood. Transmission electron microscopy energy-dispersive spectroscopy confirmed the presence of silver in the tissues. After depuration for 14 days, total silver returned to control levels in all tissues except liver (4.22 mg/kg), gastrointestinal tract (1.26 mg/kg), and gills (0.77 mg/kg).

Integration of multi-level biomarker responses to cadmium and benzo[k]fluoranthene in the pale chub (Zacco platypus).

The Cd exposure for 14 days significantly increased both the molecular (DNA single-strand breaks) and biochemical (metallothionein concentrations) biomarkers in the freshwater pale chub, Zacco platypus, whereas changes in the histological and physiological biomarker responses were negligible. The BkF exposure for 14 days led to significant increases in the mRNA expression of catalase and superoxide dismutase, 7-ethoxyresorufin-O-deethylase enzymatic activity and DNA single-strand breakage at the molecular and biochemical levels. In addition, exposure to 50µg/L of BkF induced histological alteration in the liver, with significant changes to the liver somatic index and condition factor at the physiological level. The integration of multi-level biomarker responses at the molecular, biochemical and physiological levels was highly correlated with the concentrations of Cd and BkF.

Toxicity of citrate-coated silver nanoparticles differs according to method of suspension preparation.

To evaluate substance toxicity, it is critical to maintain specific concentrations of test substances throughout the exposure period. During the last decade, the need to improve methods for nanoparticle (NP) suspension preparations has gained attention because many published results on NPs toxicity have been inconsistent. Here, we compared the toxicity of citrate-coated silver nanoparticles (AgNPs) suspended by two different methods (fractionated vs. colloidal) in freshwater organisms (daphnia and medaka). Analytical methods (ICP-OES, DLS and UV absorbance) were employed to characterize behavior of AgNPs in suspension. Results showed that fractionated (stirred and settled) solution was less toxic to daphnia (13.8 µg/L) than colloidal solution (6.1 µg/L), suggesting that method of preparation was a critical factor that affected toxicity. However, differences in toxicity caused by suspension methods were not observed in medaka. Results indicate that the method used to prepare suspensions of NPs can affect toxicity, and that differences can exist among test organisms.

Tissue-specific antioxidant responses in pale chub (Zacco platypus) exposed to copper and benzo[a]pyrene.

In this study, antioxidant responses including lipid peroxidation (LPO), superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), were evaluated in the liver, gill and muscle tissues of pale chub (Zacco platypus) exposed to copper (Cu) and benzo[a]pyrene (BaP). Cu exposure induced significant antioxidant responses in Z. platypus, particularly in the liver, whereas BaP exposure had a negligible effect. Following Cu exposure, both SOD and CAT activity increased in a concentration-dependent manner, showing significant correlations with malondialdehyde (MDA) levels as a measure of LPO (r = 0.646 and 0.663, respectively). SOD, CAT and GST mRNA levels were also enhanced following Cu exposure, except at 20 µg L(-1), although significant correlations with antioxidant enzyme activities were not found. The results of this study suggest that combined information on SOD and CAT activities together with LPO levels in the liver could be a useful indicator for assessing oxidative stress in freshwater fish.

Effects of physiochemical properties of test media on nanoparticle toxicity to Daphnia magna Straus.

The physicochemical property of standard test media significantly influenced the aggregation and dissolution of Ag, CuO and ZnO nanoparticles (NPs) and the toxicity of the NPs to Daphnia magna. For all the NPs, the highest amount of metal ions was released from the ISO medium, whereas acute toxicity to D. magna was highest in the moderately hard water medium (EC50 = 4.94, 980, and 1,950 µg L(-1) for Ag, CuO, and ZnO, respectively). By comparing EC50 values based on the total and dissolved concentrations of NPs with those of metal salt solutions, we found that both particulate and dissolved fractions were likely responsible for the toxicity of Ag NPs, whereas the dissolved fraction mostly contributed to the toxicity of CuO and ZnO NPs.

Ultra-high performance concrete alleviates ecotoxicological effects in aquatic organisms.

With the advancement of cementitious material technologies, ultra-high performance concretes incorporating nano- and(or) micro-sized particle materials have been developed; however, their environmental risks are still poorly understood. This study investigates the ecotoxicological effects of ultra-high performance concrete (UC) leachate by comparing with that of the conventional concrete (CC) leachate. For this purpose, a dynamic leaching test and a battery test with algae, water flea, and zebrafish were performed using standardized protocols. The conductivity, concentration of inorganic elements (Al, K, Na, and Fe), and total organic concentration were lower in the UC leachate than in the CC leachate. The EC50 values of the CC and UC leachates were 44.9 % and >100 % in algae, and 8.0 % and 63.1 % in water flea, respectively. All zebrafish exposed to the CC and UC leachates survived. A comprehensive evaluation of the ecotoxicity of the CC and UC leachate based on the toxicity classification system (TCS) showed that their toxicity classification was "highly acute toxicity" and "acute toxicity", respectively. Based on the hazard quotient and principal component analysis, Al and(or) K could be significant factors determining the ecotoxicity of concrete leachate. Furthermore, the ecotoxicity of UC could not be attributed to the use of silica-based materials or multi-wall carbon nanotubes. This study is the first of its kind on the ecotoxicity of UC leachate in aquatic environments, and the results of this study can be used to develop environment-friendly UC.

Co-exposure to microplastic and plastic additives causes development impairment in zebrafish embryos.

Since the run off of microplastic and plastic additives into the aquatic environment through the disposal of plastic products, we investigated the adverse effects of co-exposure to microplastics and plastic additives on zebrafish embryonic development. To elucidate the combined effects between microplastic mixtures composed of microplastics and plastic additives in zebrafish embryonic development, polystyrene (PS), bisphenol S (BPS), and mono-(2-ethylhexyl) phthalate (MEHP) were chosen as a target contaminant. Based on non-toxic concentration of each contaminant in zebrafish embryos, microplastic mixtures which is consisted of binary and ternary mixed forms were prepared. A strong phenotypic toxicity to zebrafish embryos was observed in the mixtures composed with non-toxic concentration of each contaminant. In particular, the mixture combination with ≤ EC10 values for BPS and MEHP showed a with a strong synergistic effect. Based on phenotypic toxicity to zebrafish embryos, change of transcription levels for target genes related to cell damage and thyroid hormone synthesis were analyzed in the ternary mixtures with low concentrations that were observed non-toxicity. Compared with the control group, cell damage genes linked to the oxidative stress response and thyroid hormone transcription factors were remarkably down-regulated in the ternary mixture-exposed groups, whereas the transcriptional levels of cyp1a1 and p53 were significantly up-regulated in the ternary mixture-exposed groups (P < 0.05). These results demonstrate that even at low concentrations, exposure to microplastic mixtures can cause embryonic damage and developmental malformations in zebrafish, depending on the mixed concentration-combination. Consequently, our findings will provide data to examine the action mode of zebrafish developmental toxicity caused by microplastic mixtures exposure composed with microplastics and plastic additives.

Comparison of gut toxicity and microbiome effects in zebrafish exposed to polypropylene microplastics: Interesting effects of UV-weathering on microbiome.

Weathered microplastics (MPs) exhibit different physicochemical properties compared to pristine MPs, thus, their effects on the environment and living organisms may also differ. In the present study, we investigated the gut-toxic effects of virgin polypropylene MPs (PP) and UV-weathered PP MPs (UV-PP) on zebrafish. The zebrafish were exposed to the two types of PP MPs at a concentration of 50 mg/L each for 14 days. After exposure, MPs accumulated primarily within the gastrointestinal tract, with UV-PP exhibiting a higher accumulation than PP. The ingestion of PP and UV-PP induced gut damage in zebrafish and increased the gene expression and levels of enzymes related to oxidative stress and inflammation, with no significant differences between the two MPs. Analysis of the microbial community confirmed alterations in the abundance and diversity of zebrafish gut microorganisms in the PP and UV-PP groups, with more pronounced changes in the PP-exposed group. Moreover, the Kyoto Encyclopedia of Genes and Genomes pathway analysis confirmed the association between changes in the gut microorganisms at the phylum and genus levels with cellular responses, such as oxidative stress, inflammation, and tissue damage. This study provides valuable insights regarding the environmental impact of MPs on organisms.