Effects of triclosan (TCS) on hormonal balance and genes of hypothalamus-pituitary- gonad axis of juvenile male Yellow River carp (Cyprinus carpio)

Assessment of triclosan induced histopathological and biochemical alterations, and molecular docking simulation analysis of acetylcholinesterase enzyme in the gills of fish, Cyprinus carpio

Triclosan (TCS), an antimicrobial additive in various personal and health care products, has been widely detected in aquatic environment around the world. The present study investigated the impacts of TCS in the gills of the fish, Cyprinus carpio employing histopathological, biochemical, molecular docking and simulation analysis. The 96 h LC50 value of TCS in C. carpio was found to be 0.968 mg/L. Fish were exposed to 1/1000th (1 µg/L), 1/100th (10 µg/L), and 1/10th (100 µg/L) of 96 h LC50 value for a period of 28 days. The histopathological alterations observed in the gills were hypertrophy, hyperplasia, edematous swellings, and fusion of secondary lamellae in TCS exposed groups. The severity of these alterations increased with both the concentration as well as the duration of exposure. The present study revealed that the activity of antioxidant enzymes such as superoxide dismutase, catalase, glutathione-S-transferase, glutathione reductase, glutathione peroxidase, and reduced glutathione content decreased significantly (p < 0.05) in both concentration and duration dependent manner. However, a significant (p < 0.05) increase in the activity of the metabolic enzymes such as acid phosphatase and alkaline phosphatase was observed in all three exposure concentrations of TCS from 7 to 28 days. The activity of acetylcholinesterase declined significantly (p < 0.05) from 7 to 28 days whereas the content of acetylcholine increased significantly at the end of 28 day. The experimental results were further confirmed by molecular docking and simulation analysis that showed strong binding of TCS with acetylcholinesterase enzyme. The study revealed that long-term exposure to sublethal concentrations of TCS can lead to severe physiological and histopathological alterations in the fish.

Triclosan, an antimicrobial drug, induced reproductive impairment in the freshwater fish, Anabas testudineus (Bloch, 1792)

Triclosan (TCS), an antimicrobial drug, is known to occupy different compartments in aquatic ecosystems. The present study focused to evaluate the reproductive toxicity of triclosan, at environmentally relevant (0.009 and 9 μg L-1) and sublethal (176.7 μg L-1) concentrations for 90 days in the pre-spawning phase of the fish, Anabas testudineus. The reproductive biomarkers, namely, gonadal steroidogenic enzymes, expression of aromatic genes, levels of serum gonadotropins, sex hormones, and histology of gonads were analyzed. The weight of the animal, brain weights along with gonadosomatic index decreased while mucus deposition increased significantly at all concentrations of triclosan as the primary defensive mechanism to prevent the entry of toxicants. Triclosan disrupted gonadal steroidogenesis as evidenced by a reduction in the activities of gonadal steroidogenic enzymes. The expressions of cyp19a1a and cyp19a1b genes were up-regulated in the brain of both sexes and testis, while down-regulated in the ovary indicating estrogenic effects of the compound. The endocrine-disrupting effects of triclosan were confirmed. The current results suggest that chronic exposure to triclosan altered reproductive endpoints thereby impairing normal reproductive functions in fish.

Reproductive endocrine disruption effect and mechanism in male zebrafish after life cycle exposure to environmental relevant triclosan

Triclosan (TCS) is a wide-spectrum antibacterial agent that is found in various water environments. It has been reported to have estrogenic effects. However, the impact of TCS exposure on the reproductive system of zebrafish (Danio rerio) throughout their life cycle is not well understood. In this study, zebrafish fertilized eggs were exposed to 0, 10, and 50 μg/L TCS for 120 days. The study investigated the effects of TCS exposure on brain and testis coefficients, the expression of genes related to the hypothalamus-pituitary-gonadal (HPG) axis, hormone levels, vitellogenin (VTG) content, histopathological sections, and performed RNA sequencing of male zebrafish. The results revealed that life cycle TCS exposure had significant effects on zebrafish reproductive parameters. It increased the testis coefficient, while decreasing the brain coefficient. TCS exposure also led to a decrease in mature spermatozoa and altered the expression of genes related to the HPG axis. Furthermore, TCS disrupted the balance of sex hormone levels and increased VTG content of male zebrafish. Transcriptome sequencing analysis indicated that TCS affected reproductive endocrine related pathways, including PPAR signaling pathway, cell cycle, GnRH signaling pathway, steroid biosynthesis, cytokine-cytokine receptor interaction, and steroid hormone biosynthesis. Protein-protein interaction (PPI) network analysis confirmed the enrichment of hub genes in these pathways, including bub1bb, ccnb1, cdc20, cdk1, mcm2, mcm5, mcm6, plk1, and ttk in the brain, as well as fabp1b.1, fabp2, fabp6, ccr7, cxcl11.8, hsd11b2, and hsd3b1 in the testis. This study sheds light on the reproductive endocrine-disrupting mechanisms of life cycle exposure to TCS.

Personal care products: an emerging threat to the marine bivalve Ruditapes philippinarum

In the last few decades, there has been a growing interest in understanding the behavior of personal care products (PCPs) in the aquatic environment. In this regard, the aim of this study is to estimate the accumulation and effects of four PCPs within the clam Ruditapes philippinarum. The PCPs selected were triclosan, OTNE, benzophenone-3, and octocrylene. A progressive uptake was observed and maximum concentrations in tissues were reached at the end of the exposure phase, up to levels of 0.68 µg g-1, 24 µg g-1, 0.81 µg g-1, and 1.52 µg g-1 for OTNE, BP-3, OC, and TCS, respectively. After the PCP post-exposure period, the removal percentages were higher than 65%. The estimated logarithm bioconcentration factor ranged from 3.34 to 2.93, in concordance with the lipophobicity of each substance. No lethal effects were found although significant changes were observed for ethoxyresorufin O-demethylase activity, glutathione S-transferase activity, lipid peroxidation, and DNA damage.

Variations in life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to triclosan

Triclosan (TCS) poses an ecological health risk due to its lipophilic nature, long half-life, and bioconcentration. To evaluate the toxicity of TCS on aquatic organisms, the life history parameters, population dynamics, and transcriptome regulation of Brachionus plicatilis exposed to TCS were investigated. In this study, the fecundity of rotifers was promoted by 25 μg/L of TCS and inhibited by higher concentrations (100 μg/L, 200 μg/L). The reproductive period of rotifers was shortened by 46.24 % but the post-reproductive period was prolonged by 176.47 % in 200 μg/L TCS. Both population growth and life table parameters indicated that a high concentration of TCS (200 μg/L) had negative impacts on population growth. Transcriptomic analysis showed that the effects of TCS on the life history parameters and population dynamics of rotifers were determined by regulating the expression of functional genes in cilium organization and cilium assembly and involved in pathways of focal adhesion.

Mechanism-based understanding of the potential cellular targets of triclosan in zebrafish larvae

Triclosan (TCS) has become widely distributed due to its widespread use. In this study, we investigated the mechanisms of TCS's potential effects on cellular targets in zebrafish (Danio rerio) larvae using transcriptome sequencing. The expressions of 772, 368, and 1039 genes were significantly altered in zebrafish after embryos were exposed to 2, 10, and 50 μg/L TCS for consecutive 50 d, respectively, and 33 differentially expressed genes (DEGs) were found. DEGs were significantly enriched in the biological processes, including inflammatory response and purine ribonucleoside bisphosphate biosynthetic process by Go analysis, and in processes such as egg coat formation, binding of sperm to zona pellucida, positive regulation of acrosome reaction, and immune response by Gene set enrichment analysis (GSEA). Both KEGG pathway analysis and GSEA showed that NOD-like receptor signaling pathway and Steroid biosynthesis were significantly affected. Results showed that TCS potentially affected reproduction, immune, and metabolism of zebrafish larvae.

Adverse effects of triclosan exposure on health and potential molecular mechanisms

With the COVID-19 pandemic, the use of disinfectants has grown significantly around the world. Triclosan (TCS), namely 5-chloro-2-(2,4-dichlorophenoxy) phenol or 2,4,4'-trichloro-2'-hydroxydiphenyl ether, is a broad-spectrum, lipophilic, antibacterial agent that is extensively used in multifarious consumer products. Due to the widespread use and bioaccumulation, TCS is frequently detected in the environment and human biological samples. Accumulating evidence suggests that TCS is considered as a novel endocrine disruptor and may have potential unfavorable effects on human health, but studies on the toxic effect mediated by TCS exposure as well as its underlying mechanisms of action are relatively sparse. Therefore, in this review, we attempted to summarize the potential detrimental effects of TCS exposure on human reproductive health, liver function, intestinal homeostasis, kidney function, thyroid endocrine, and other tissue health, and further explore its mechanisms of action, thereby contributing to the better understanding of TCS characteristics and safety. Moreover, our work suggested the need to further investigate the biological effects of TCS exposure at the metabolic level in vivo.

Analysis of the effect of triclosan on gonadal differentiation of zebrafish based on metabolome

Although the previous research confirmed that triclosan (TCS) affects the female proportion at the early stage of zebrafish (Danio rerio) and has an estrogen effect, the mechanism by which TCS affects the sex differentiation of zebrafish is not entirely clear. In this study, zebrafish embryos were exposed to different concentrations of TCS (0, 2, 10, and 50 μg/L) for 50 consecutive days. The expression of sex differentiation related genes and metabolites were then determined in larvae using reverse transcription quantitative polymerase chain reaction (RT-qPCR) and Liquid Chromatography-Mass Spectrometer (LC-MS), respectively. TCS upregulated the expression of the sox9a, dmrt1a and amh genes, down-regulating the expression of wnt4a, cyp19a1b, cyp19a1a, and vtg2 gene. The overlapped classification of Significant Differential Metabolites (SDMs) between the control group and three TCS treated groups related to gonadal differentiation was Steroids and steroid derivatives, including 24 down-regulated SDMs. The enriched pathways related to gonadal differentiation were Steroid hormone biosynthesis, Retinol metabolism, Metabolism of xenobiotics by cytochrome P450, and Cortisol synthesis and secretion. Moreover, SDMs were significantly enriched in Steroid hormone biosynthesis in the 2 μg/L TCS group, which included Dihydrotestosterone, Cortisol, 11beta-hydroxyandrost-4-ene-3, 17-dione, 21-Hydroxypregnenolone, Androsterone, Androsterone glucuronide, Estriol, Estradiol, 19-Hydroxytestosterone, Cholesterol, Testosterone, and Cortisone acetate. Results showed that TCS affects the female proportion mainly through Steroid hormone biosynthesis, in which aromatase plays a key role in zebrafish. Retinol metabolism, metabolism of xenobiotics by cytochrome P450, and cortisol synthesis and secretion may also participate in TCS-mediated sex differentiation. These findings reveal the molecular mechanisms of TCS-induced sex differentiation, and provide theoretical guidance for the maintenance of water ecological balance.

Endocrine Disruption of Propylparaben in the Male Mosquitofish (Gambusia affinis): Tissue Injuries and Abnormal Gene Expressions of Hypothalamic-Pituitary-Gonadal-Liver Axis

Propylparaben (PrP) is a widely used preservative that is constantly detected in aquatic environments and poses a potential threat to aquatic ecosystems. In the present work, adult male mosquitofish were acutely (4d) and chronically (32d) exposed to environmentally and humanly realistic concentrations of PrP (0, 0.15, 6.00 and 240 μg/L), aimed to investigate the toxic effects, endocrine disruption and possible mechanisms of PrP. Histological analysis showed time- and dose-dependent manners in the morphological injuries of brain, liver and testes. Histopathological alterations in the liver were found in 4d and severe damage was identified in 32d, including hepatic sinus dilatation, cytoplasmic vacuolation, cytolysis and nuclear aggregation. Tissue impairments in the brain and testes were detected in 32d; cell cavitation, cytomorphosis and blurred cell boundaries appeared in the brain, while the testes lesions contained spermatogenic cell lesion, decreased mature seminal vesicle, sperm cells gathering, seminiferous tubules disorder and dilated intercellular space. Furthermore, delayed spermatogenesis had occurred. The transcriptional changes of 19 genes along the hypothalamus-pituitary-gonadal-liver (HPGL) axis were investigated across the three organs. The disrupted expression of genes such as Ers, Ars, Vtgs, cyp19a, star, hsd3b, hsd17b3 and shh indicated the possible abnormal steroidogenesis, estrogenic or antiandrogen effects of PrP. Overall, the present results provided evidences for the toxigenicity and endocrine disruptive effects on the male mosquitofish of chronic PrP exposure, which highlights the need for more investigations of its potential health risks.

Environmental relevant concentrations of triclosan affected developmental toxicity, oxidative stress, and apoptosis in zebrafish embryos

Triclosan (TCS), as a broad-spectrum antibacterial agent, is widely used in various pharmaceutical and personal care products. However, the details of ecological environmental health risks of TCS are not clear. In this study, zebrafish embryos/larval were exposed to environmentally relevant concentrations of TCS to evaluate the developmental toxicity. Four-hour post-fertilization (hpf) zebrafish embryos were exposed to 0, 2, 10, 50, and 250 μg/L TCS until 96 h. The heart beats at 72 hpf were significantly increased in 2 μg/L TCS group, while significantly decreased in 250 μg/L TCS treated group compared with control. The results of acridine orange staining, terminal deoxynucleotide transferase-mediated UTPnick end labeling assay, and detection of mitochondrial membrane potential showed that 50 and 250 μg/L TCS resulted in apoptosis. Meanwhile, reactive oxygen species (ROS) and DNA damage were induced, but SOD activity was significantly decreased in 250 μg/L TCS treated group. In addition, SOD(Mn) and GPx gene mRNA expressions were significantly down-regulated in 50 and 250 μg/L TCS treated groups, while Casp3, Casp9, Puma, Casp8, Apaf1, and Bid genes in 250 μg/L TCS and Mdm2 gene in 50 μg/L treated groups were significantly up-regulated. P53 protein was significantly up-regulated in 250 μg/L TCS treated group. The overall results showed that TCS can cause oxidative stress and result in apoptosis via the involvement of ROS-p53-caspase-dependent apoptotic pathway in zebrafish embryos. The present findings suggest the potential mechanisms of TCS-induced developmental toxicity appears to be the generation of ROS and the consequent triggering of apoptosis genes.

Histopathology and transcriptome reveals the tissue-specific hepatotoxicity and gills injury in mosquitofish (Gambusia affinis) induced by sublethal concentration of triclosan

Triclosan (TCS), a ubiquitous antimicrobial agent, has been frequently detected in wild fish, leading to concerns regarding TCS safety in the aquatic environment. The present work aims to investigate the TCS-mediated effects on various tissues (the liver, gills, brain, and testes) of wild-sourced adult mosquitofish based on histological analysis and transcriptome. Severe morphological injuries were only found in the liver and gills. The histopathological alterations in the liver were characterized by cytoplasmic vacuolation and degeneration, eosinophilic cytoplasmic inclusions, and nuclear polymorphism. The gill lesions contained epithelial lifting, intraepithelial edema, fusion and shortening of the secondary lamellae. Consistently, the numbers of differently expressed genes (DEGs) identified by transcriptome were in the order of liver (1627) > gills (182) > brain (9) > testes (4). Trend-aligned histopathological and transcriptomic changes in the 4 tissues, suggesting the tissue-specific response manner of mosquitofish to TCS, and the liver and gills were the target organs. TCS interrupted many biological pathways associated with lipogenesis and lipid metabolism, transmembrane transporters, protein synthesis, and carbohydrate metabolism in the liver, and it induced nonspecific immune response in the gills. TCS-triggered hepatotoxicity and gills damnification may lead to inflammation, apoptosis, diseases, and even death in mosquitofish. TCS showed moderate acute toxicity and bioaccumulative property on mosquitofish, suggesting that prolonged or massive use of TCS may pose an ecological risk.

Integrated Proteomics and Metabolomics Assessment Indicated Metabolic Alterations in Hypothalamus of Mice Exposed to Triclosan

Triclosan (TCS) is a ubiquitous antimicrobial used in many daily consumer products. It has been reported to induce endocrine disrupting effects at low doses in mammals, disturbing sex hormone function and thyroid function. The hypothalamus plays a crucial role in the maintenance of neuroendocrine function and energy homeostasis. We speculated that the adverse effects of TCS might be related to the disturbance of metabolic processes in hypothalamus. The present study aimed at investigating the effects of TCS exposure on the protein and metabolite profiles in hypothalamus of mice. Male C57BL/6 mice were orally exposed to TCS at the dosage of 10 mg/kg/d for 13 weeks. The hypothalamus was isolated and processed for mass spectrometry (MS)-based proteomics and metabolomics analyses. The results showed that a 10.6% decrease (P = 0.066) in body weight gain was observed in the TCS exposure group compared with vehicle control group. Differential analysis defined 52 proteins and 57 metabolites that delineated TCS exposed mice from vehicle controls. Among the differential features, multiple proteins and metabolites were found to play vital roles in neuronal signaling and function. Bioinformatics analysis revealed that these differentially expressed proteins and metabolites were involved in four major biological processes, including glucose metabolism, purine metabolism, neurotransmitter release, and neural plasticity, suggesting the disturbance of homeostasis in energy metabolism, mitochondria function, neurotransmitter system, and neuronal function. Our results may provide insights into the neurotoxicity of TCS and extend our understanding of the biological effects induced by TCS exposure.

Nonsteroidal anti-inflammatory drugs act as endocrine disruptors in Astyanax lacustris (Teleostei: Characidae) reproduction: An ex vivo approach

Pharmaceutical products can act as endocrine-disrupting compounds (EDCs), affecting the physiological processes of animals, such as development or reproduction. This study aimed to investigate the influence of different concentrations of nonsteroidal anti-inflammatory drugs (NSAIDs) diclofenac (DCF) and ibuprofen (IBU) alone and mixed (MIX) on gonadotropin gene expression and gonadal steroid release using Astyanax lacustris pituitary and testes explant systems, respectively. The explant organs were maintained for 12 h in Leibovitz (L-15) medium supplemented with 0, 0.1, 1, 10, 100, and 1000 ng L-1 of DCF, IBU, and MIX (ratio 1:1 of the same concentrations of DCF and IBU alone) and gonadotropin releasing-hormone (cGnRH2) stimulation in pituitary explants and human chorionic gonadotropin (hCG) stimulation in testes explants. The pituitary glands and the media from the testicular explants were collected for gene expression analysis including the β subunit of the follicle-stimulating hormone (fshβ) and luteinizing hormone (lhβ) and secreted gonadal steroid concentration analysis, respectively. Both DCF and IBU (alone and mixed) decreased pituitary gene expression of fshβ and lhβ and this inhibitory effect was evident even at low concentrations. In the testes, DCF and IBU did not change the levels of estradiol, and both pharmaceuticals increased the release of 11-ketotestosterone at low doses, while only IBU decreased the levels of testosterone in all concentrations. IBU's inhibitory effect in the testes was not triggered by the mixture of the two drugs. These results suggest that NSAIDs, may interfere in fish reproduction by acting as EDCs, thereby negatively affecting A. lacustris spermatogenesis and maturation.

Developmental abnormalities and epigenetic alterations in medaka (Oryzias latipes) embryos induced by triclosan exposure

Triclosan (TCS), an antibacterial and antifungal agent present in some consumer products, has been detected in the environment at varying concentrations. TCS exposure has been found to cause developmental abnormalities and endocrine disruption in various species of fish. It is not clearly understood whether TCS exposure causes epigenetic alterations in developing embryos and their germ cells. In the present study, we examined the effects of TCS exposure (0, 50, 100 and, 200 μg/L) on embryonic development and primordial germ cells (PGCs), which are precursors of sperm and eggs, in medaka (Oyzias latipes). Developmental TCS exposure from 8 h post-fertilization through 15 days post-fertilization (dpf) resulted in several developmental abnormalities, including enlarged yolk sac, decreased head trunk angle (HTA), and severe edema in the pericardial region. The male ratio increased in the 100 μg/L TCS exposure group, which was negatively correlated with the expression of cyp19ala (a gene encoding aromatase) and arα (androgen receptor alpha). Developmental 50 μg/L TCS exposure resulted in global hypomethylation in the whole body but not in the isolated PGCs. Expression of the gene encoding DNA methyltransferases (dnmt1 and dnmt3aa) was decreased by 50 μg/L TCS exposure both in the whole body and PGCs. TCS altered the expression of genes encoding enzymes involved in DNA methylation and demethylation in PGCs, suggesting epigenetic effects on germ cells. The present results demonstrate that the embryos exposed to the tested concentrations of TCS develop deformities during the early life stages and that the TCS within this range possesses endocrine disrupting properties potential enough to alter sex ratios of developing embryos.

Triclocarban, Triclosan, Bromochlorophene, Chlorophene, and Climbazole Effects on Nuclear Receptors: An in Silico and in Vitro Study

BACKGROUND

Endocrine-disrupting chemicals can interfere with hormonal homeostasis and have adverse effects for both humans and the environment. Their identification is increasingly difficult due to lack of adequate toxicological tests. This difficulty is particularly problematic for cosmetic ingredients, because in vivo testing is now banned completely in the European Union.

OBJECTIVES

The aim was to identify candidate preservatives as endocrine disruptors by in silico methods and to confirm endocrine receptors' activities through nuclear receptors in vitro.

METHODS

We screened preservatives listed in Annex V in the European Union Regulation on cosmetic products to predict their binding to nuclear receptors using the Endocrine Disruptome and VirtualToxLab™ version 5.8 in silico tools. Five candidate preservatives were further evaluated for androgen receptor (AR), estrogen receptor (ER α ), glucocorticoid receptor (GR), and thyroid receptor (TR) agonist and antagonist activities in cell-based luciferase reporter assays in vitro in AR-EcoScreen, hER α -HeLa- 9903 , MDA-kb2, and GH3.TRE-Luc cell lines. Additionally, assays to test for false positives were used (nonspecific luciferase gene induction and luciferase inhibition).

RESULTS

Triclocarban had agonist activity on AR and ER α at 1 μ M and antagonist activity on GR at 5 μ M and TR at 1 μ M . Triclosan showed antagonist effects on AR, ER α , GR at 10 μ M and TR at 5 μ M , and bromochlorophene at 1 μ M (AR and TR) and at 10 μ M (ER α and GR). AR antagonist activity of chlorophene was observed [inhibitory concentration at 50% (IC50) IC 50 = 2.4 μ M ], as for its substantial ER α agonist at > 5 μ M and TR antagonist activity at 10 μ M . Climbazole showed AR antagonist (IC 50 = 13.6 μ M ), ER α agonist at > 10 μ M , and TR antagonist activity at 10 μ M .

DISCUSSION

These data support the concerns of regulatory authorities about the endocrine-disrupting potential of preservatives. These data also define the need to further determine their effects on the endocrine system and the need to reassess the risks they pose to human health and the environment. https://doi.org/10.1289/EHP6596.

Metabolomics and phenotype assessment reveal cellular toxicity of triclosan in Caenorhabditis elegans

Triclosan (TCS) is an antibiotic that is added to household and personal care products. Recently, it has become more popular, turning into one of the major contaminants of the environment. This raises a dawning awareness regarding health and environmental issues. In this study, the toxicity of TCS to Caenorhabditis elegans was evaluated using a metabolomics approach. Additionally, the lifespan, locomotion, and reproduction of C. elegans were monitored for a better interpretation of toxic effects. In C. elegans exposed to TCS at the concentration of 1 mg/L, the average lifespan decreased in approximately 3 days. Reproduction and locomotion were also decreased with TCS exposure. The number of progenies, head thrashes, and body bends decreased to 45.15 ± 11.63, 39.60 ± 5.90, and 9.20 ± 1.56 with the exposure to TCS, respectively. Oxidative stress was induced by TCS exposure, which was confirmed by using DAF-16:GFP strain and H₂DCF-DA-based ROS assay. Metabolomics analysis revealed that carbohydrates and amino acids related to energy production were considerably affected by TCS exposure. Additionally, levels of tyrosine, serine, and polyamines, responsible for neurotransmitter and stress response, were significantly altered. Collectively, our findings suggest that TCS induces toxic effects by various mechanisms and exerts a strong influence in various phenotypes of the tested model.

Triclosan induces PC12 cells injury is accompanied by inhibition of AKT/mTOR and activation of p38 pathway

Triclosan (TCS) has been widely used as a disinfectant and antiseptic in multiple consumer and healthcare products due to its clinical effectiveness against various bacteria, fungi and protozoa. Recently, several studies have reported the adverse effects of TCS on various nerve cells, arousing concerns about its potential neurotoxicity. The present study aimed to investigate the neurotoxicity of TCS in rat pheochromocytoma PC12 cells. After differentiation, the stabilized PC12 cells were treated with 1, 10, 50 μM TCS for 12 h. At the end of the treatment, the generation of reactive oxygen species (ROS), protein expression of apoptotic-related genes, AMPK-AKT/mTOR, as well as p38 in PC12 cells were determined. The concentrations were chosen based on the results of cell viability and lactic dehydrogenase (LDH) assays in response to TCS treatment (ranging from 0.001 to 100 μM) for varied time periods. The results showed that TCS is cytotoxic to PC12 cells, causing decreased cell viability accompanied by increased LDH release. TCS treatment at 10 and 50 μM for 12 h increased the mRNA and protein expression of the pro-apoptotic gene Bax, while Bcl-2 levels remained unchanged. Moreover, an increase in the generation of reactive oxygen species (ROS) was found in TCS-treated PC12 cells at the concentrations of 1 and 10 μM. Pretreatment with 100 μM N-acetyl cysteine (NAC- ROS scavenger) for 1 h normalized the ROS generations in TCS-treated PC12 cells. Additionally, the suppression of the phosphorylation of Akt and mTOR was observed in TCS-treated PC12 cells at 10 and 50 μM for 12 h, concomitant with the activation of p38 MAPK pathway at 50 μM TCS. However, there were no effects of TCS on the phosphorylation of AMPK in these cells. Taken together, these results suggest that TCS may cause adverse effects and oxidative stress in PC12 cells accompanied by inhibition of Akt/mTOR and activation of p38.

Larval exposure to environmentally relevant concentrations of triclosan impairs metamorphosis and reproductive fitness in zebrafish

Developmental exposure to endocrine disruptors can cause organizational changes resulting in latent and transgenerational disease. We exposed zebrafish to environmentally relevant concentrations of triclosan during the critical period of metamorphosis and somatic sex differentiation to determine effects on metamorphosis and reproduction. We use biological and morphological biomarkers to predict potential modes of action. Larval exposure to environmentally relevant concentrations of triclosan was sufficient to cause adverse effects in adults and their offspring. TCS exposure delays metamorphosis and impairs fecundity and fertility. Offspring from TCS-exposed fish show decreased survival and delayed maturation, but their reproductive capacity is not altered. Delays in metamorphosis in conjunction with morphological indicators suggest that toxicity may result from lowered thyroid hormones in parental fish. This work illustrates the importance of evaluating the latent effects of early exposure to environmental contaminants, and that further studies to evaluate the effects of triclosan on the thyroid axis are warranted.

Exposure to triclosan changes the expression of microRNA in male juvenile zebrafish (Danio rerio)

Triclosan (TCS) is a broad-spectrum antibacterial agent which is widely used in various personal care products and cosmetics. It has been found that TCS affects endocrine, immune, nervous, reproductive, and developmental system. Although microRNAs (miRNAs) act a pivotal part in lots of metabolic activities, whether and how they are related to the process of TCS-induced toxicity is unknown. In the present study, TCS induced changes in miRNAs and target gene expression in male zebrafish (Danio rerio) brain, and the potential mechanism was studied. Male juvenile zebrafish were exposed to 0 and 68 μg/L TCS for 42 d. miRNA was isolated from the brain pool of the zebrafish and the expression profiles of 255 known zebrafish miRNAs were analysed by using Affymetrix miRNA 4.0 microarrays. Quantitative real-time polymerase chain reaction (qRT-PCR) was used to assay the expression of 5 differentially expressed miRNAs in the microarray data and some related-genes in brains. The GO term analysis revealed that miRNAs significantly affected by TCS exposure were mainly involved in translation, transcription, DNA-templated, protein transport, and motor neuron axon guidance biological process. Pathway analysis showed that target genes of 5 differentially expressed miRNAs prominently participate in basal transcription factors, purine metabolism, and ribosome biogenesis in eukaryotes. In addition, key genes in purine metabolism pathway and oxidative stress related-genes were significantly changed. These findings offer novel insight into the mechanisms of epigenetic regulation in TCS-induced toxicity in male zebrafish, and distinguish novel miRNA biomarkers for exposure to TCS.

DNA methylation and gene expression alterations in zebrafish early-life stages exposed to the antibacterial agent triclosan

There is increasing evidence that toxicant exposure can alter DNA methylation profile, one of the main epigenetic mechanisms, particularly during embryogenesis when DNA methylation patterns are being established. In order to investigate the effects of the antibacterial agent Triclosan on DNA methylation and its correlation with gene expression, zebrafish embryos were exposed during 7 days post-fertilization (starting at maximum 8-cells stage) to 50 and 100 μg/l, two conditions for which increased sensitivity and acclimation have been respectively reported. Although global DNA methylation was not significantly affected, a total of 171 differentially methylated fragments were identified by Reduced Representation Bisulfite Sequencing. The majority of these fragments were found between the two exposed groups, reflecting dose-dependant specific responses. Gene ontology analysis revealed that pathways involved in TGF-β signaling were enriched in larvae exposed to 50 μg/l, while de novo pyrimidine biosynthesis functions were overrepresented in fish exposed to 100 μg/l. In addition, gene expression analysis revealed a positive correlation between mRNA levels and DNA methylation patterns in introns, together with significant alterations of the transcription of genes involved in nervous system development, transcriptional factors and histone methyltransferases. Overall this work provides evidence that Triclosan alters DNA methylation in zebrafish exposed during embryogenesis as well as related genes expression and proposes concentration specific modes of action. Further studies will investigate the possible long-term consequences of these alterations, i.e. latent defects associated with developmental exposure and transgenerational effects, and the possible implications in terms of fitness and adaptation to environmental pollutants.

The effects and possible mechanisms of triclosan on steroidogenesis in primary rat granulosa cells

BACKGROUND

Triclosan (TCS) has been detected in human tissues. It can disrupt steroidogenesis in vivo. The study on the effects of TCS on ovarian granulosa cells was lacking.

METHODS

Primary rat granulosa cells (rGCs) were treated with TCS. Concentrations of estradiol (E₂), progesterone (P₄) in the cell culture supernatants were measured. Microarray was used to measure gene expression profiles. Pathway analysis was performed to identify signaling networks that linked differentially expressed genes (DEGs). Genes related with steroidogenesis were analyzed.

RESULTS

TCS increased E₂ and P₄ production. A total of 2006 DEGs were identified. Pathway analysis revealed that ovarian steroidogenesis pathway was upregulated. Both PCR and Western-blot demonstrated that the expressions of key genes involved in this pathway were significantly increased.

CONCLUSIONS

TCS co-administered with follicle-stimulating hormone (FSH) could increase E₂ and P₄ production in rGCs and up-regulate ovarian steroidogenesis pathway. StAR and aromatase protein were increased by TCS, while P450scc protein wasn't changed significantly.

Applying analytical decision methods for determination of the best treatment alternative to remove emerging micropollutants from drinking water and wastewater: triclosan example

Increasing human activities have not only substantially altered the natural material cycle but also created new synthetic chemicals flows. Some of these chemicals, which are described as micropollutants (MPs), may result in adverse effects on human health, aquatic organisms, and ecosystems. MPs can be transported to the environment and water resources in a variety ways including domestic and industrial wastewater. Unfortunately, most MPs are only partially removed in existing conventional treatment plants. Therefore, conventional treatment plants should be modernized by advanced treatment technologies to protect the environment and human health. However, there are various mysteries about best treatment techniques, evaluation criteria, and decision-making methods. In this study, it was aimed to determine the best treatment alternatives for triclosan (TCS) which is one of the priority MPs. A total of 18 evaluation criteria were identified and prioritized by employing analytical hierarchy process (AHP) and entropy methods. Treatment alternatives were identified and their performance was assessed through a comprehensive literature investigation. In decision-making processes of determining these alternatives, "technique for order preference by similarity to ideal solution (TOPSIS)," "preference ranking organization method for enrichment evaluation (PROMETHEE)," and "Višekriterijumsko kompromisno rangiranje (VIKOR)" analytical decision-making methods were employed, and priority rankings were determined according to each decision method. The final priority ranking was found as adsorption > membrane filtration > hybrid processes > advanced oxidation processes > constructed wetlands > conventional treatment processes > biological treatment > other treatment processes. Although the obtained results are specific to TCS, the employed analytical decision methods can be also used to decide the best treatment alternatives for other MPs.

Unexpected metabolic disorders induced by endocrine disruptors in Xenopus tropicalis provide new lead for understanding amphibian decline

Despite numerous studies suggesting that amphibians are highly sensitive to endocrine disruptors (EDs), both their role in the decline of populations and the underlying mechanisms remain unclear. This study showed that frogs exposed throughout their life cycle to ED concentrations low enough to be considered safe for drinking water, developed a prediabetes phenotype and, more commonly, a metabolic syndrome. Female Xenopus tropicalis exposed from tadpole stage to benzo(a)pyrene or triclosan at concentrations of 50 ng⋅L-1 displayed glucose intolerance syndrome, liver steatosis, liver mitochondrial dysfunction, liver transcriptomic signature, and pancreatic insulin hypersecretion, all typical of a prediabetes state. This metabolic syndrome led to progeny whose metamorphosis was delayed and occurred while the individuals were both smaller and lighter, all factors that have been linked to reduced adult recruitment and likelihood of reproduction. We found that F1 animals did indeed have reduced reproductive success, demonstrating a lower fitness in ED-exposed Xenopus Moreover, after 1 year of depuration, Xenopus that had been exposed to benzo(a)pyrene still displayed hepatic disorders and a marked insulin secretory defect resulting in glucose intolerance. Our results demonstrate that amphibians are highly sensitive to EDs at concentrations well below the thresholds reported to induce stress in other vertebrates. This study introduces EDs as a possible key contributing factor to amphibian population decline through metabolism disruption. Overall, our results show that EDs cause metabolic disorders, which is in agreement with epidemiological studies suggesting that environmental EDs might be one of the principal causes of metabolic disease in humans.

Triclosan Lacks Anti-Estrogenic Effects in Zebrafish Cells but Modulates Estrogen Response in Zebrafish Embryos

Triclosan (TCS), an antimicrobial agent widely found in the aquatic environment, is suspected to act as an endocrine disrupting compound, however mechanistic information is lacking in regards to aquatic species. This study assessed the ability of TCS to interfere with estrogen receptor (ER) transcriptional activity, in zebrafish-specific in vitro and in vivo reporter gene assays. We report that TCS exhibits a lack of either agonistic or antagonistic effects on a panel of ER-expressing zebrafish (ZELH-zfERα and -zfERβ) and human (MELN) cell lines. At the organism level, TCS at concentrations of up to 0.3 µM had no effect on ER-regulated brain aromatase gene expression in transgenic cyp19a1b-GFP zebrafish embryos. At a concentration of 1 µM, TCS interfered with the E2 response in an ambivalent manner by potentializing a low E2 response (0.625 nM), but decreasing a high E2 response (10 nM). Altogether, our study suggests that while modulation of ER-regulated genes by TCS may occur in zebrafish, it does so irrespective of a direct binding and activation of zfERs.