Effects of the antimicrobial contaminant triclocarban, and co-exposure with the androgen 17β-trenbolone, on reproductive function and ovarian transcriptome of the fathead minnow (Pimephales promelas)

Multi-omic responses of fish exposed to complex chemical mixtures in the Shenandoah River watershed

To evaluate relationships between different anthropogenic impacts, contaminant occurrence, and fish health, we conducted in situ fish exposures across the Shenandoah River watershed at five sites with different land use. Exposure water was analyzed for over 500 chemical constituents, and organismal, metabolomic, and transcriptomic endpoints were measured in fathead minnows. Adverse reproductive outcomes were observed in fish exposed in the upper watershed at both wastewater treatment plant (WWTP) effluent- and agriculture-impacted sites, including decreased gonadosomatic index and altered secondary sex characteristics. This was accompanied with increased mortality at the site most impacted by agricultural activities. Molecular biomarkers of estrogen exposure were unchanged and consistent with low or non-detectable concentrations of common estrogens, indicating that alternative mechanisms were involved in organismal adverse outcomes. Hepatic metabolomic and transcriptomic profiles were altered in a site-specific manner, consistent with variation in land use and contaminant profiles. Integrated biomarker response data were useful for evaluating mechanistic linkages between contaminants and adverse outcomes, suggesting that reproductive endocrine disruption, altered lipid processes, and immunosuppression may have been involved in these organismal impacts. This study demonstrated linkages between human-impact, contaminant occurrence, and exposure effects in the Shenandoah River watershed and showed increased risk of adverse outcomes in fathead minnows exposed to complex mixtures at sites impacted by municipal wastewater discharges and agricultural practices.

Photocatalytic degradation of triclocarban in aqueous solution using a modified zeolite/TiO2 composite: kinetic, mechanism study and toxicity assessment

The current work aimed to investigate the degradation of the triclocarban (TCC) in aqueous solution using a modified zeolite/TiO₂ composite (MZTC) synthesized by applying the electrochemical anodization (ECA). The synthesis process was conducted at different voltages (10, 40, and 60) V in 1 h and using electrophoresis deposition (EPD) in doping zeolite. The MZTC was covered with the array ordered, smooth and optimum elongated nanotubes with 5.1 μm of the length, 120.3 nm of the inner diameter 14.5 nm of the wall thickness with pure titanium and crystalline titania as determined by FESEM/EDS, and XRD. The kinetic study by following Langmuir-Hinshelwood(L-H) model and pseudo first order, the significant constant rate was obtained at pH 11 which was 0.079 ppm/min, 0.75 cm² of MZTC catalyst loading size achieved 0.076 ppm/min and 5 ppm of TCC initial concentration reached 0.162 ppm/min. The high-performance liquid chromatography (HPLC) analysis for mechanism study of TCC photocatalytic degradation revealed eleven intermediate products after the whole process of photocatalysis. In regard of toxicology assessment by the bacteria which is Photobacterium phosphoreum, the obtained concentration of TCC at minute 60 was less satisfied with remained 0.36 ppm of TCC was detected indicates that the concentration was above allowable level. Where the allowable level of TCC in stream is 0.1 ppm.

Endocrine Disrupting Chemicals in Polycystic Ovary Syndrome: The Relevant Role of the Theca and Granulosa Cells in the Pathogenesis of the Ovarian Dysfunction

Polycystic ovary syndrome (PCOS) is the most common heterogeneous endocrine disorder among women of reproductive age. The pathogenesis of PCOS remains elusive; however, there is evidence suggesting the potential contribution of genetic interactions or predispositions combined with environmental factors. Among these, endocrine disrupting chemicals (EDCs) have been proposed to potentially contribute to the etiology of PCOS. Granulosa and theca cells are known to cooperate to maintain ovarian function, and any disturbance can lead to endocrine disorders, such as PCOS. This article provides a review of the recent knowledge on PCOS pathophysiology, the role of granulosa and theca cells in PCOS pathogenesis, and the evidence linking exposure to EDCs with reproductive disorders such as PCOS.

Developmental Phenotypic and Transcriptomic Effects of Exposure to Nanomolar Levels of 4-Nonylphenol, Triclosan, and Triclocarban in Zebrafish (Danio rerio)

Triclosan, triclocarban and 4-nonylphenol are all chemicals of emerging concern found in a wide variety of consumer products that have exhibited a wide range of endocrine-disrupting effects and are present in increasing amounts in groundwater worldwide. Results of the present study indicate that exposure to these chemicals at critical developmental periods, whether long-term or short-term in duration, leads to significant mortality, morphologic, behavioral and transcriptomic effects in zebrafish (Danio rerio). These effects range from total mortality with either long- or short-term exposure at 100 and 1000 nM of triclosan, to abnormalities in uninflated swim bladder seen with long-term exposure to triclocarban and short-term exposure to 4-nonylphenol, and cardiac edema seen with short-term 4-nonylphenol exposure. Additionally, a significant number of genes involved in neurological and cardiovascular development were differentially expressed after the exposures, as well as lipid metabolism genes and metabolic pathways after exposure to each chemical. Such changes in behavior, gene expression, and pathway abnormalities caused by these three known endocrine disruptors have the potential to impact not only the local ecosystem, but human health as well.

Understanding the interaction between triclocarban and denitrifiers

The widespread use of triclocarban (TCC) has led to its substantial release into aquatic environment. As an important microbial community in wastewater treatment, denitrifying cultures likely remove TCC and also may be affected by TCC which has not been revealed. This work therefore aims to add knowledge to these questions. Experimental results showed that 71.2 %-79.4 % of TCC was removed by denitrifying sludge in stable operation when TCC concentration was 1∼20 mg/L. Mass balance analyses revealed that TCC was dominantly removed by adsorption rather than biodegradation, and non-homogeneous multilayer adsorption was responsible for this removal, with hydroxyl groups, amides and polysaccharides acting as the possible adsorption sites. Although the physicochemical properties of denitrifying cultures were unaffected after short-term exposure, long-term exposure to TCC deteriorated the settleability, dewaterability, flocculability and hydrophobicity of denitrifying biomass. It was observed that 20 mg/L TCC decreased denitrification efficiency by 70 % in long-term operation. Mechanism studies revealed that long-term exposure to TCC resulted in the increase of extracellular polymeric substances especially proteins, and the decrease of denitrifiers' activities. High-throughput sequencing revealed that TCC decreased the diversity of microbial community and the abundances of denitrifier genera such as Hyphomicrobium, Paracoccus, Saprospiraceae and unclassified-f-Rhodocyclaceae.

Fathead minnow exposed to environmentally relevant concentrations of metformin for one life cycle show no adverse effects

Metformin is a glucose-lowering drug taken for diabetes. It is excreted by humans in urine and detected in municipal wastewater effluents and rivers. Fathead minnows ( Pimephales promelas) were exposed over a life cycle to measured concentrations of metformin: 3.0, 31, and 322 μg/L. No significant changes were observed in survival, maturation, growth, condition factor, or liver size. Relative ovary size of females exposed to 322 μg/L metformin was significantly larger than controls. There was no induction of vitellogenin in plasma of minnows, and gonad maturation was not statistically different from controls. The start of breeding was delayed by 9–10 d in the mid- and high metformin treatments (statistically significant only in the mid-concentration), but numbers and quality of eggs were not statistically different from controls. There were no effects of metformin on survival or growth of offspring. Exposure to metformin at environmentally relevant concentrations (i.e., 3.0 and 31 μg/L metformin) caused no adverse effects in fathead minnows exposed for a life cycle, with the exception of a delay in time to first breeding (that did not impact overall egg production). The results of the study are important to help understand whether metformin concentrations in rivers and lakes can harm fishes.

In vitro effects of Triclocarban on adipogenesis in murine preadipocyte and human hepatocyte

Triclocarban (TCC), a widely used antibacterial agent, has aroused considerable public concern due to its potential toxicity. In the current study, we applied targeted metabolite profiling (LC/GC-MS) and untargeted ¹H NMR-based metabolomics in combination with biological assays to unveil TCC exposure-induced cellular metabolic responses in murine preadipocyte and human normal hepatocytes. We found that TCC promoted adipocyte differentiation in 3T3L1 preadipocytes, manifested by marked triglyceride (TG) and fatty acids accumulation, which were consistent with significant up-regulation of mRNA levels in the key adipogenic markers Fasn, Srebp1 and Ap2. In human hepatocytes (L02), TCC exposure dose-dependently interfered with the cellular redox state with down-regulated levels of antioxidant reduced-GSH and XBP1 and further induced the accumulation of TG, ceramides and saturated fatty acid (16:0). We also found that TCC exposure triggered unfold protein response (UPR) and endoplasmic reticulum (ER) stress in both cells through activation of ATF4 and ATF6, resulting in toxic lipid accumulation. These findings about lipid metabolism and metabolic responses to TCC exposure in both preadipocytes and hepatocytes provide novel perspectives for revealing the mechanisms of TCC toxicity.

Bioaugmentation of triclocarban and its dechlorinated congeners contaminated soil with functional degraders and the bacterial community response

Partial removal of haloaromatic antimicrobial triclocarban (TCC) during wastewater treatment caused the final introduction of residual TCC into soils. Bioaugmentation has been proposed for the biodegradation of TCC and its dechlorinated congeners 4,4'-dichlorocarbanilide (DCC) and carbanilide (NCC) in soil. The isolated TCC-degrading strain Ochrobactrum sp. TCC-2 and chloroanilines-degrading strain Diaphorobacter sp. LD72 were used to study the removal efficiency of TCC, DCC and NCC mixture and their chloroanilines intermediates, respectively. The potential degradation competition between TCC and its dechlorinated congeners, and the response of bacterial community during the bioremediation were also investigated. The biodegradation of DCC and TCC was significantly enhanced for soil with inoculums compared with sterilized and natural soils. Chloroanilines products could also be effectively removed. For the degradation of combined substrates in the aqueous medium, NCC had negative effect on the degradation of TCC and DCC, while TCC and DCC negatively influenced each other. The bioaugmentation with two degraders obviously changed the phylogenetic composition and function of indigenous soil microbiome. Importantly, the inoculated degraders could be maintained, suggesting their adaptability and potential application in bioaugmentation for such recalcitrant contaminants. This study offers new insights into the enhanced bioremediation of TCC and its dechlorinated congeners contaminated soils by the bioaugmentation of functional degraders and the structure and function response of the indigenous soil microbiome to the bioremediation process.

Fate of Triclocarban (TCC) in aquatic and terrestrial systems and human exposure

Triclocarban (TCC) is considered as contaminant of emerging concern (CEC), and ranked in the top 10 CEC occurrence. TCC is a high production volume synthetic chemical used extensively in various personal care products. This chemical will be released into the environment via incomplete wastewater treatment and untreated wastewater discharge. TCC and its transformation products (4,4'-dichlorocarbilide (DCC),1-(3-chlorophenyl)-3-phenylurea (MCC) and carbanilide (NCC),2'OH-TCC, 3'OH-TCC) were detected in the environmental matrices. Sediment organic carbon will influence TCC concentrations in suspended and bed sediments. TCC is an antimicrobial agent and also emerging endocrine disruptor that can cause immune dysfunction and affect human reproductive outcomes. Furthermore, TCC alters the expression of proteins related to binding and metabolism, skeletal muscle development and function, nervous system development and immune response. TCC has potential health risks in wildlife and humans. Several animal studies illustrate that it can cause various adverse effects, which can be monitored by antioxidant biomarkers (CAT, GST and LPO). Accumulation of TCC in organisms depends on the lipophilicity and bioavailability of TCC in sediment and water. TCC was continuously detected in aquatic system. TCC is a lipophilic compound, which can efficiently bind with lipid content. Women are more vulnerable to TCC due to substantially higher frequency and extended exposure to TCC. This review provides basic information of occurrence of TCC and the exposure levels in aquatic organisms. Several literature have shown the higher usage and human exposure levels of TCC, which provides useful information for the chemical management approaches.

The risk of endometriosis after exposure to endocrine-disrupting chemicals: a meta-analysis of 30 epidemiology studies

Endocrine-disrupting chemicals (EDCs) are suspected to be associated with endometriosis (EMs). This study aimed to synthesize published data and evaluate the relationship between four classic EDCs exposure and the risk of EMs. A systematic literature search for original peer reviewed papers was performed in the databases PubMed, EMBASE, and Web of Science based on inclusion criteria up to January 2018. Subsequently, a total of 20 papers conducting 30 studies fulfilled the eligibility criteria and were included in this meta-analysis (four studies for bisphenol A (BPA), 12 studies for polychlorinated biphenyls (PCBs), eight studies for organochlorine pesticides (OCPs), and six studies for phthalate esters (PAEs)). The overall odds ratio (OR) across all exposures and EMs was 1.41 (95% confidence interval (CI): 1.23-1.60). When assessing four specific chemicals, respectively, consistent increases in the risk of EMs were found in PCBs group (OR = 1.58; 95% CI: 1.18-2.12), OCPs group (OR = 1.40; 95% CI: 1.02-1.92) and PAEs group (OR = 1.27; 95% CI: 1.00-1.60), while BPA showed no significant association with EMs. Besides, in the di-(2-ethylhexyl)-phthalate (DEHP) group - the most commonly used PAEs, significant risk was also found (OR = 1.42; 95% CI: 1.19-1.70). The current meta-analysis strengthens the evidence that specific EDCs or their metabolites may promote the occurrence of EMs.

Developmental toxicity of triclocarban in zebrafish (Danio rerio) embryos

Triclocarban (TCC), which is used as an antimicrobial agent in personal care products, has been widely detected in aquatic ecosystems. However, the consequence of TCC exposure on embryo development is still elusive. Here, by using zebrafish embryos, we aimed to understand the developmental defects caused by TCC exposure. After exposure to 0.3, 30, and 300 μg/L TCC from 4-hour postfertilization (hpf) to 120 hpf, we observed that TCC exposure significantly increased the mortality and malformation, delayed hatching, and reduced body length. Exposure to TCC also affected the heart rate and expressions of cardiac development-related genes in zebrafish embryos. In addition, TCC exposure altered the expressions of the genes involved in hormonal pathways, indicating its endocrine disrupting effects. In sum, our data highlight the impact of TCC on embryo development and its interference with the hormone system of zebrafish.

Effects of triclocarban on oxidative stress and innate immune response in zebrafish embryos

Triclocarban (TCC) is used in many household and personal hygiene products. TCC has been widely detected in wastewater around the world. The present study reveals that TCC can activate oxidative stress, induce total antioxidant capacity expression and lipid peroxidation, and increase the activities of superoxide dismutase and other antioxidant enzymes to resist oxidative damage. A significant induction of concentrations of proinflammatory mediator and nitric oxide (NO), accompanied by an upregulated expression of inducible NO synthase gene, was detected in zebrafish embryos exposed to TCC. The transcription of immune-response-related genes, including tnf-α, il-1β, il-4, il-8, and cxcl-clc, was significantly upregulated on exposure to TCC. Furthermore, we found that the exposure of zebrafish embryos to TCC decreased immune cell recruiting in the head. Expressions of nf-κb, trif, myd88, irak4, and traf6 were altered on exposure to TCC. These results demonstrated that exposure to TCC at environmental concentrations significantly affects the expression of immune-response-related genes in zebrafish embryos following oxidative stress and the release of proinflammatory mediators through Toll-like receptor signaling pathway. Thus, we assumed that the ecological risk of TCC on aquatic organisms could not be ignored.

A critical review of the environmental occurrence and potential effects in aquatic vertebrates of the potent androgen receptor agonist 17β-trenbolone

Trenbolone acetate is widely used in some parts of the world for its desirable anabolic effects on livestock. Several metabolites of the acetate, including 17β-trenbolone, have been detected at low nanograms per liter concentrations in surface waters associated with animal feedlots. The 17β-trenbolone isomer can affect androgen receptor signaling pathways in various vertebrate species at comparatively low concentrations/doses. The present article provides a comprehensive review and synthesis of the existing literature concerning exposure to and biological effects of 17β-trenbolone, with an emphasis on potential risks to aquatic animals. In vitro studies indicate that, although 17β-trenbolone can activate several nuclear hormone receptors, its highest affinity is for the androgen receptor in all vertebrate taxa examined, including fish. Exposure of fish to nanograms per liter water concentrations of 17β-trenbolone can cause changes in endocrine function in the short term, and adverse apical effects in longer exposures during development and reproduction. Impacts on endocrine function typically are indicative of inappropriate androgen receptor signaling, such as changes in sex steroid metabolism, impacts on gonadal stage, and masculinization of females. Exposure of fish to 17β-trenbolone during sexual differentiation in early development can greatly skew sex ratios, whereas adult exposures can adversely impact fertility and fecundity. To fully assess ecosystem-level risks, additional research is warranted to address uncertainties as to the degree/breadth of environmental exposures and potential population-level effects of 17β-trenbolone in sensitive species. Environ Toxicol Chem 2018;37:2064-2078. Published 2018 Wiley Periodicals Inc. on behalf of SETAC. This article is a US government work and, as such, is in the public domain in the United States of America.

Bioconcentration model for non-ionic, polar, and ionizable organic compounds in amphipod

The present study presents a bioconcentration model for non-ionic, polar, and ionizable organic compounds in amphipod based on first-order kinetics. Uptake rate constant k₁ is modeled as logk1=10.81logKOW + 0.15 (root mean square error [RMSE] = 0.52). Biotransformation rate constant k_M is estimated using an existing polyparameter linear free energy relationship model. Respiratory elimination k₂ is calculated as modeled k₁ over theoretical biota-water partition coefficient K_biow considering the contributions of lipid, protein, carbohydrate, and water. With negligible contributions of growth and egestion over a typical amphipod bioconcentration experiment, the bioconcentration factor (BCF) is modeled as k₁ /(k_M + k₂ ) (RMSE = 0.68). The proposed model performs well for non-ionic organic compounds (log K_OW range = 3.3-7.62) within 1 log-unit error margin. Approximately 12% of the BCFs are underpredicted for polar and ionizable compounds. However, >50% of the estimated k₂ values are found to exceed the total depuration rate constants. Analyses suggest that these excessive k₂ values and underpredicted BCFs reflect underestimation in K_biow , which may be improved by incorporating exoskeleton as a relevant partitioning component and refining the membrane-water partitioning model. The immediate needs to build up high-quality experimental k_M values, explore the sorptive role of exoskeleton, and investigate the prevalence of k₂ overestimation in other bioconcentration models are also identified. The resulting BCF model can support, within its limitations, the ecotoxicological and risk assessment of emerging polar and ionizable organic contaminants in aquatic environments and advance the science of invertebrate bioaccumulation. Environ Toxicol Chem 2018;37:1378-1386. © 2018 SETAC.

Multiple bioanalytical method to reveal developmental biological responses in zebrafish embryos exposed to triclocarban

Triclocarban (TCC) is a well-known antibacterial agent that is frequently detected in environmental, wildlife and human samples. The potential toxicological effects and action mechanism of TCC on vertebrate development has remained unclear. In the present study, we analyzed phenotypic alterations, thyroid hormone levels, thyroid hormone responsive genes, and proteomic profiles of zebrafish embryos after exposure to a series of concentrations of TCC from 6 h post-fertilization (hpf) to 120 hpf. The most nonlethal concentration (MNLC), lethal concentration 10% (LC₁₀) and lethal concentration 50% (LC₅₀) of TCC for exposures of 96 h were 133.3 μg/L, 147.5 μg/L and 215.8 μg/L, respectively. Our results showed that exposure to TCC decreased heart rate, delayed yolk absorption and swim bladder development at MNLC and LC₁₀. Exposure to MNLC of TCC inhibited thyroid hormone and altered expression of thyroid hormone responsive genes. Furthermore, exposure to 1/20 MNLC of TCC altered expression of proteins related to binding and metabolism, skeletal muscle development and function, as well as proteins involved in nervous system development and immune response, indicating TCC has potential health risks in wildlife and humans at low concentration level.

Environmentally Relevant Concentrations of Carbamazepine Caused Endocrine-Disrupting Effects on Nontarget Organisms, Chinese Rare Minnows (Gobiocypris rarus)

In the present study, Chinese rare minnows (Gobiocypris rarus) were exposed to 1, 10, and 100 μg/L of carbamazepine (CBZ) under flow-through conditions for 28 d. A hepatic-specific custom microarray identified 111 and 71 differentially expressed genes in the livers of females and males, respectively, exposed to 100 μg/L of CBZ (ratio ≥ 2, p ≤ 0.05). The levels of five differentially expressed genes associated with the hypothalamic-pituitary-gonadal (HPG) axis were quantified by qPCR, and the results indicated the feasibility of screening endocrine-disrupting chemicals using a custom microarray. The mRNA levels of genes related to the HPG axis differed significantly in different organs of Chinese rare minnows (p < 0.05). Significant differences were observed in the 11-ketotestosterone and plasma vitellogenin levels in all treatments and in the 17β-estradiol (E2) levels in the 100 μg/L CBZ treatment. In contrast, the gonadosomatic index was significantly higher in females and slightly higher in males without significant differences. A pathological analysis determined that 10 and 100 μg/L of CBZ could lead to ova-testis in males and significantly promoted ovum maturation in females. Therefore, our results demonstrate that environmentally relevant concentrations of CBZ have homologous estrogenic activity and induce reproductive toxicity in Chinese rare minnows.

Potential Developmental and Reproductive Impacts of Triclocarban: A Scoping Review

Triclocarban (TCC) is an antimicrobial agent used in personal care products. Although frequently studied with another antimicrobial, triclosan, it is not as well researched, and there are very few reviews of the biological activity of TCC. TCC has been shown to be a possible endocrine disruptor, acting by enhancing the activity of endogenous hormones. TCC has been banned in the US for certain applications; however, many human populations, in and outside the US, exhibit exposure to TCC. Because of the concern of the health effects of TCC, we conducted a scoping review in order to map the current body of literature on the endocrine, reproductive, and developmental effects of TCC. The aim of this scoping review was to identify possible endpoints for future systematic review and to make recommendations for future research. A search of the literature until August 2017 yielded 32 relevant studies in humans, rodents, fish, invertebrates, and in vitro. Based on the robustness of the literature in all three evidence streams (human, animal, and in vitro), we identified three endpoints for possible systematic review: estrogenic activity, androgenic activity, and offspring growth. In this review, we describe the body of evidence and make recommendations for future research.