Use of antibacterial toothpaste is associated with higher urinary triclosan concentrations in Asian immigrant women living in Vancouver, Canada

Maternal concentrations of environmental phenols during early pregnancy and behavioral problems in children aged 4 years from the Shanghai Birth Cohort

BACKGROUND

Prenatal exposure to environmental phenols such as bisphenol (BPs), paraben (PBs), benzophenone (BzPs), and triclosan (TCS) is ubiquitous and occurs in mixtures. Although some of them have been suspected to impact child behavioral development, evidence is still insufficient, and their mixed effects remain unclear.

OBJECTIVES

To explore the association of prenatal exposure to multiple phenols with child behavioral problems.

METHOD

In a sample of 600 mother-child pairs from the Shanghai Birth Cohort, we quantified 18 phenols (6 PBs, 7 BPs, 4 BzPs, and TCS) in urine samples collected during early pregnancy. Parent-reported Strengths and Difficulties Questionnaires were utilized to evaluate child behavioral difficulties across four subscales, namely conduct, hyperactivity/inattention, emotion, and peer relationship problems, at 4 years of age. Multivariable linear regression was conducted to estimate the relationships between single phenolic compounds and behavioral problems. Additionally, weighted quantile sum (WQS) regression was employed to examine the overall effects of the phenol mixture. Sex-stratified analyses were also performed.

RESULTS

Our population was extensively exposed to 10 phenols (direction rates >50 %), with low median concentrations (1.00 × 10-3-6.89 ng/mL). Among them, single chemical analyses revealed that 2,4-dihydroxy benzophenone (BP1), TCS, and methyl 4-hydroxybenzoate (MeP) were associated with increased behavior problems, including hyperactivity/inattention (BP1: β = 0.16; 95 % confidence interval [CI]: 0.04, 0.30), emotional problems (BP1: β = 0.11; 95 % CI: 0.02, 0.20; TCS: β = 0.08; 95 % CI: 0.02, 0.14), and peer problems (MeP: β = 0.10; 95 % CI: 0.02, 0.18); however, we did not identify any significant association with conduct problems. Further phenol mixture analyses in the WQS model yielded similar results. Stratification for child sex showed stronger positive associations in boys.

CONCLUSION

Our findings indicated that maternal phenol levels during early pregnancy, specifically BP1, TCS, and MeP, are associated with high behavioral problem scores in 4-year-old children.

In vitro metabolism of triclosan and chemoprevention against its cytotoxicity

Triclosan (TCS), a broad-spectrum antibacterial chemical, has been extensively used in personal daily care items, household commodities, and clinical medications; therefore, humans are at risk of being exposed to TCS in their daily lives. This chemical also accumulated in food chains, and potential risks were associated with its metabolism in vivo. The aim of this study was to investigate the difference in metabolic profile of TCS by hepatic P450 enzymes and extrahepatic P450s, and also identify chemical structures of its metabolites. The results showed that RLM mediated the hydroxylation and cleavage of the ether moiety of TCS, resulting in phenolic metabolites that are more polar than the parent compound, including 4-chlorocatechol, 2,4-dichlorophenol and monohydroxylated triclosan. The major metabolite of CYP1A1 and CYP1B1 mediated TCS metabolism is 4-chlorochol. We also performed molecular docking experiments to investigate possible binding modes of TCS in the active sites of human CYP1B1, CYP1A1, and CYP3A4. In addition to in vitro experiments, we further examined the cytotoxic effects of TCS on HepG2 cells expressing hepatic P450 and MCF-7/1B1 cells expressing CYP1B1. It exhibited significant cytotoxicity on HepG2, MCF-10A and MCF-7/1B1 cells, with IC50 values of 70 ± 10 μM, 20 ± 10 μM and 60 ± 20 μM, respectively. The co-incubation of TCS with glutathione (GSH) as a chemopreventive agent could reduce the cytotoxicity of TCS in vitro. The chemopreventive effects of GSH might be ascribed to the promotion of TCS efflux mediated by membrane transporter MRP1 and also its antioxidant property, which partially neutralized the oxidative stress of TCS on mammalian cells. This study contributed to our understanding of the relationship between the P450 metabolism and the toxicity of TCS. It also had implications for the use of specific chemopreventive agents against the toxicity of TCS.

Dental health status, dentist visiting, and dental insurance of Asian immigrants in Canada

OBJECTIVE

This study examined the dental care utilization and self-preserved dental health of Asian immigrants relative to non-immigrants in Canada. Factors associated with oral health-related disparities between Asian immigrants and other Canadians were further examined.

METHODS

We analyzed 37,935 Canadian residents aged 12 years and older in the Canadian Community Health Survey 2012-2014 microdata file. Factors (e.g., demographics, socioeconomic status, lifestyles, dental insurance coverage, and year of immigration) associated with disparities in dental health (e.g., self-perceived teeth health, dental symptoms during past one month, and teeth removed due to decay in past one year) and service utilization (e.g., visiting dentist within the last three years, visiting dentist more than once per year) between Asian immigrants and other Canadians were examined using multi-variable logistic regression models.

RESULTS

The frequency of dental care utilization was significantly lower in Asian immigrants than their non-immigrant counterparts. Asian immigrants had lower self-perceived dental health, were less likely to be aware of recent dental symptoms, and more likely to report tooth extractions due to tooth decay. Low education (OR = 0.42), male gender(OR = 1.51), low household income(OR = 1.60), non-diabetes(OR = 1.87), no dental insurance(OR = 0.24), short immigration length (OR = 1.75) may discourage Asian immigrants from dental care utilization. Additionally, a perceived lack of necessity to dentist-visiting was a crucial factor accounting for the disparities in dental care uptake between Asian immigrants and non-immigrants.

CONCLUSION

Asian immigrants showed lower dental care utilization and oral health than native-born Canadians.

Single-cell transcriptomic dissection of the cellular and molecular events underlying the triclosan-induced liver fibrosis in mice

BACKGROUND

Triclosan [5-chloro-2-(2,4-dichlorophenoxy) phenol, TCS], a common antimicrobial additive in many personal care and health care products, is frequently detected in human blood and urine. Therefore, it has been considered an emerging and potentially toxic pollutant in recent years. Long-term exposure to TCS has been suggested to exert endocrine disruption effects, and promote liver fibrogenesis and tumorigenesis. This study was aimed at clarifying the underlying cellular and molecular mechanisms of hepatotoxicity effect of TCS at the initiation stage.

METHODS

C57BL/6 mice were exposed to different dosages of TCS for 2 weeks and the organ toxicity was evaluated by various measurements including complete blood count, histological analysis and TCS quantification. Single cell RNA sequencing (scRNA-seq) was then carried out on TCS- or mock-treated mouse livers to delineate the TCS-induced hepatotoxicity. The acquired single-cell transcriptomic data were analyzed from different aspects including differential gene expression, transcription factor (TF) regulatory network, pseudotime trajectory, and cellular communication, to systematically dissect the molecular and cellular events after TCS exposure. To verify the TCS-induced liver fibrosis, the expression levels of key fibrogenic proteins were examined by Western blotting, immunofluorescence, Masson's trichrome and Sirius red staining. In addition, normal hepatocyte cell MIHA and hepatic stellate cell LX-2 were used as in vitro cell models to experimentally validate the effects of TCS by immunological, proteomic and metabolomic technologies.

RESULTS

We established a relatively short term TCS exposure murine model and found the TCS mainly accumulated in the liver. The scRNA-seq performed on the livers of the TCS-treated and control group profiled the gene expressions of > 76,000 cells belonging to 13 major cell types. Among these types, hepatocytes and hepatic stellate cells (HSCs) were significantly increased in TCS-treated group. We found that TCS promoted fibrosis-associated proliferation of hepatocytes, in which Gata2 and Mef2c are the key driving TFs. Our data also suggested that TCS induced the proliferation and activation of HSCs, which was experimentally verified in both liver tissue and cell model. In addition, other changes including the dysfunction and capillarization of endothelial cells, an increase of fibrotic characteristics in B plasma cells, and M2 phenotype-skewing of macrophage cells, were also deduced from the scRNA-seq analysis, and these changes are likely to contribute to the progression of liver fibrosis. Lastly, the key differential ligand-receptor pairs involved in cellular communications were identified and we confirmed the role of GAS6_AXL interaction-mediated cellular communication in promoting liver fibrosis.

CONCLUSIONS

TCS modulates the cellular activities and fates of several specific cell types (including hepatocytes, HSCs, endothelial cells, B cells, Kupffer cells and liver capsular macrophages) in the liver, and regulates the ligand-receptor interactions between these cells, thereby promoting the proliferation and activation of HSCs, leading to liver fibrosis. Overall, we provide the first comprehensive single-cell atlas of mouse livers in response to TCS and delineate the key cellular and molecular processes involved in TCS-induced hepatotoxicity and fibrosis.

Triclosan and triclocarban as potential risk factors of colitis and colon cancer: Roles of gut microbiota involved

In recent decades there has been a dramatic increase in the incidence and prevalence of inflammatory bowel disease (IBD), a chronic inflammatory disease of the intestinal tissues and a major risk factor of developing colon cancer. While accumulating evidence supports that the rapid increase of IBD is mainly caused by exposure to environmental risk factors, the identities of the risk factors, as well as the mechanisms connecting environmental exposure with IBD, remain largely unknown. Triclosan (TCS) and triclocarban (TCC) are high-volume chemicals that are used as antimicrobial ingredients in consumer and industrial products. They are ubiquitous contaminants in the environment and are frequently detected in human populations. Recent studies showed that exposure to TCS/TCC, at human exposure-relevant doses, increases the severity of colitis and exacerbates colon tumorigenesis in mice, suggesting that they could be risk factors of IBD and associated diseases. The gut toxicities of these compounds require the presence of gut microbiota, since they fail to induce colonic inflammation in mice lacking the microbiota. Regarding the functional roles of the microbiota involved, gut commensal microbes and specific microbial β-glucuronidase (GUS) enzymes mediate colonic metabolism of TCS, leading to metabolic reactivation of TCS in the colon and contributing to its subsequent gut toxicity. Overall, these results support that these commonly used compounds could be environmental risk factors of IBD and associated diseases through gut microbiota-dependent mechanisms.

Triclosan: A Small Molecule with Controversial Roles

Triclosan (TCS), a broad-spectrum antimicrobial agent, has been widely used in personal care products, medical products, plastic cutting boards, and food storage containers. Colgate Total® toothpaste, containing 10 mM TCS, is effective in controlling biofilm formation and maintaining gingival health. Given its broad usage, TCS is present ubiquitously in the environment. Given its strong lipophilicity and accumulation ability in organisms, it is potentially harmful to biohealth. Several reports suggest the toxicity of this compound, which is inserted in the class of endocrine disrupting chemicals (EDCs). In September 2016, TCS was banned by the U.S. Food and Drug Administration (FDA) and the European Union in soap products. Despite these problems, its application in personal care products within certain limits is still allowed. Today, it is still unclear whether TCS is truly toxic to mammals and the adverse effects of continuous, long-term, and low concentration exposure remain unknown. Indeed, some recent reports suggest the use of TCS as a repositioned drug for cancer treatment and cutaneous leishmaniasis. In this scenario it is necessary to investigate the advantages and disadvantages of TCS, to understand whether its use is advisable or not. This review intends to highlight the pros and cons that are associated with the use of TCS in humans.

Gut microbiota exaggerates triclosan-induced liver injury via gut-liver axis

Triclosan (TCS) is an antimicrobial ingredient that has been widely incorporated in consumer products. TCS can cause hepatic damage by disturbing lipid metabolism, which is often accompanied with gut microbiota dysbiosis. However, the effects of gut microbiota on the TCS-induced liver injury are still unknown. Therefore, we constructed a mouse model based on five-week-old male C57BL/6 mice to investigate the effects of dietary TCS exposure (40 ppm) on liver injury. We found that TCS treatment for 4 weeks dramatically disturbed gut microbiota homeostasis, resulting in overproduction of lipopolysaccharides (LPS) and deficiency of secondary bile acids such as deoxycholic acid (DCA) and lithocholic acid (LCA). In addition, TCS considerably increased intestinal permeability by reducing mucus excretion and expression of tight junction proteins (ZO-1, occludin and claudin 4), which facilitated translocation of LPS. The LPS accumulation in blood contributed to liver injury by triggering the inflammatory response via TLR4 pathway. In summary, this study provides novel insights into the underlying mechanisms of TCS-associated liver injury induced by gut microbiota via the gut-liver axis, and contributes to better interpretation of the health impact of the environmentally emerging contaminant TCS.

Profiles of parabens, benzophenone-type ultraviolet filters, triclosan, and triclocarban in paired urine and indoor dust samples from Chinese university students: Implications for human exposure

Parabens, benzophenone (BP)-type UV filters, triclosan (TCS), and triclocarban (TCC) are commonly used in personal care products. Human exposure to these compounds has received increasing concern because of their adverse health effects. However, the levels of these chemicals in paired urine and indoor samples have never been simultaneously measured. In this work, eight parabens, eight BP-type UV filters, TCS, and TCC were measured in paired urine and indoor dust samples collected from university students and their dormitories in South China. The target analytes were commonly measured in urine (71%-100%) and indoor dust (30%-98%), with median concentrations ranging from 0.16 ng/mL to 19.3 ng/mL in urine and from <0.01 ng/g to 3700 ng/g in indoor dust samples. Females had high levels of most of these target compounds, and gender-related differences were found in the levels of most target analytes. Positive correlations were found in the levels of methylparaben, ethyl paraben, benzophenone-3, and TCS between urine and indoor dust samples. This finding suggested that indoor dust is an important source for human exposure to these compounds. The estimated daily intake (EDI) of these analytes in paired samples was also evaluated. The median EDI_-urine values of target analytes varied in the range of 4.02-59,280 ng/kg bw/day. Females had higher median EDI_-urine values for most of target analytes than males. In addition, the median EDI_{-indoor dust} values of most target analytes in dust from female dormitories were higher than those in dust from male dormitories. Indoor dust ingestion only had minor contribution (<0.5%) to the total exposure. To the best of the authors' knowledge, this study is the first to simultaneously analyze the concentrations of parabens, BP-type UV filters, TCS, and TCC in the paired urine and indoor samples from university students in South China.

Racial/Ethnic Disparities in Pregnancy and Prenatal Exposure to Endocrine-Disrupting Chemicals Commonly Used in Personal Care Products

PURPOSE OF REVIEW

Endocrine-disrupting chemical (EDC) exposure during pregnancy is linked to adverse maternal and child health outcomes that are racially/ethnically disparate. Personal care products (PCP) are one source of EDCs where differences in racial/ethnic patterns of use exist. We assessed the literature for racial/ethnic disparities in pregnancy and prenatal PCP chemical exposures.

RECENT FINDINGS

Only 3 studies explicitly examined racial/ethnic disparities in pregnancy and prenatal exposure to PCP-associated EDCs. Fifty-three articles from 12 cohorts presented EDC concentrations stratified by race/ethnicity or among homogenous US minority populations. Studies reported on phthalates and phenols. Higher phthalate metabolites and paraben concentrations were observed for pregnant non-Hispanic Black and Hispanic women. Higher concentrations of benzophenone-3 were observed in non-Hispanic White women; results were inconsistent for triclosan. This review highlights need for future research examining pregnancy and prenatal PCP-associated EDCs disparities to understand and reduce racial/ethnic disparities in maternal and child health.

Exploring the multilevel effects of triclosan from development, reproduction to behavior using Drosophila melanogaster

Triclosan (TCS) is widely used as an antibacterial agent, but its residue in the environment poses a great threat. In this study, Drosophila melanogaster were treated with series concentrations of TCS and the effects on development, behavior, reproduction, and oxidative stress indicators were investigated. The results showed that high concentrations of TCS severely interfered with the metamorphosis, resulting in lower hatching rate and longer development time. The hatching rate was only 75.00% ± 4.08% in 0.80 mg/mL TCS group. TCS also showed dose-dependent damage to the fertility of flies, causing ovarian defects and decreased the number of offspring. Almost no offspring adults hatched when exposed to high concentrations of TCS (0.50 and 0.80 mg/mL), and the hatching rate was 0% in 0.80 mg/mL TCS group. Larvae crawling, adult climbing and anti-starvation ability were also affected to varying degrees and showed hormesis. TCS could damage larval intestinal cells in a dose-dependent manner, and injury was lightened with culture time prolonging to 30 h. It is noteworthy that TCS caused redox imbalance with an increase on catalase (CAT) activity and decrease on reactive oxygen species (ROS) level. Our results conclude that TCS elicits multiple impacts on Drosophila and its rational use should be strengthened.

Insights into the electrochemical degradation of triclosan from human urine: Kinetics, mechanism and toxicity

Electrochemical degradation of triclosan in human urine was firstly studied by using Ti/SnO₂-Sb/PbO₂ anode doped with rare-earth elements. The results indicated that the Ti/SnO₂-Sb/Gd-PbO₂ anode demonstrated the best performance with the degradation rate constants being 0.095 min^-1 in fresh urine and 0.045 min^-1 in hydrolyzed urine at a current density of 10 mA cm^-2. The electrochemical degradation was improved in the presence of phosphate and chloride, while the degradation was obviously inhibited by urea, bicarbonate and ammonia. Degradation mechanism mainly involved ether-bond cleavage, hydroxylation, cyclization, dehydrogenation and carboxylation. Quantitative structure-activity relationship model showed that ecological risks of cyclization products to fish, daphnid and green algae was higher than the parent compound, implying that the potential risks to aquatic organism should not be ignored before triclosan mineralized completely. Energy consumption for 90% triclosan degradation ranged from 4.5 to 47.8 Wh L^-1, and the consumption increased along with the hydrolysis of urine. The results indicate that electrochemical oxidation is a feasible and energy-saving technique to effectively remove triclosan from human urine.

Associations among urinary triclosan and bisphenol A concentrations and serum sex steroid hormone measures in the Canadian and U.S. Populations

Exposure to triclosan, an antimicrobial agent, and bisphenol A (BPA), the monomer of polycarbonate plastics, is widespread. Endocrine-disrupting impacts of these chemicals have been demonstrated in in vitro studies, rodent toxicology studies, and some human observational studies. Here we compared urinary concentrations of triclosan and BPA in the Canadian and U.S. populations using nationally-representative data from the 2012-2015 Canadian Health Measures Survey (CHMS) and the 2013-2016 National Health and Nutrition Examination Survey (NHANES). We then examined the cross-sectional associations of urinary triclosan or BPA with serum sex steroid hormones, including estradiol (E2), progesterone (P4), and testosterone (T), using multivariable regression. We observed differences in creatinine-standardized chemical concentrations between countries; urinary triclosan was higher in Canadian females aged 12-19 years, while BPA was higher in U.S. females aged 20-49 years. We also found significant associations among urinary chemicals and serum E2 and T, but not P4. Increasing triclosan was associated with higher levels of E2 in 6-11-year-old girls, but with lower levels of E2 and T in adolescent boys aged 12-19 years. Increasing BPA was associated with lower levels of E2 in 6-11-year-old boys and in adolescents aged 12-19 years of either sex. We observed a U-shaped association between urinary triclosan and E2 in male adults aged 50-79 years; no associations between BPA and hormones were detected in adults. These results, in accordance with the in vitro and animal literature, suggest that triclosan and BPA exposures may be cross-sectionally associated with altered reproductive hormone levels, especially in children and adolescents. Further research and prospective studies are necessary to elucidate country-specific differences in chemical exposures and the potential public health significance of these findings.

Prenatal exposure to multiple phenolic compounds, fetal reproductive hormones, and the second to fourth digit ratio of children aged 10 years in a prospective birth cohort

Select phenols are known to possess hormone-disrupting properties, but no previous study has addressed the potential effects of prenatal exposure to phenol mixtures on fetal reproductive hormones and children's second to fourth digit (2D: 4D) ratio, a marker for in utero testosterone (T) exposure. We aimed to explore interrelations of prenatal phenol exposures individually and in mixtures, cord serum reproductive hormones, and 2D: 4D ratio of children aged 10 years. Urinary 11 phenol concentrations were determined from 392 pregnant women participating in a longitudinal birth cohort. We estimated associations of prenatal phenol exposures individually and in mixtures with cord reproductive hormones and children's 2D:4D ratio using three statistical approaches, including generalized linear models (GLMs), elastic net regression (ENR) models and Bayesian kernel machine regression (BKMR) models. In female newborns, the three models showed that maternal triclosan (TCS) concentrations were significantly negatively associated with cord serum T levels [regression coefficient (β) = -0.076, 95% confidence interval (CI): 0.138, -0.013; p = 0.018]. Additionally, maternal urinary bisphenol A (BPA) levels were related to decreases in 2D:4D ratio of the left hand in girls by GLMs (β = -0.003, 95% CI: 0.007, -0.001; p = 0.024) and ENR models, but not BKMR models. We provided evidence that prenatal TCS exposure predicted lower cord serum T levels, and maternal BPA exposure was related to decreased 2D:4D ratio of the left hand in females.

Ultrafast physical bacterial inactivation and photocatalytic self-cleaning of ZnO nanoarrays for rapid and sustainable bactericidal applications

Various nanostructured surfaces have been developed recently to physically inactivate bacteria, for reducing the rapidly spreading threat of pathogenic bacteria. However, it generally takes several hours for these surfaces to inactivate most of the bacteria, which greatly limits their application in the fields favoring rapid bactericidal performance. Besides, the accumulated bacteria debris left on these surfaces is rarely discussed in the previous reports. Herein we report the nanotip-engineered ZnO nanoarrays (NAs) with ultrafast physical bactericidal rate and the ability to photocatalytically remove the bacteria debris. Neither chemical (Zn2+ or reactive oxygen species) nor photocatalytic effect leads to the ultrafast bactericidal rate, where 97.5% of E. coli and 94.9% of S. aureus are inactivated within only 1 min. The simulation analysis further supported our proposed mechanism attributing the ultrafast bactericidal activity to the great stress enabled by the uneven topography. Moreover, the re-exposure of the ZnO NAs nanotips can be achieved in only 10 min under a mild UV light source. This study not only presents an ultrafast physical bactericidal activity, but also demonstrates the potential of the recyclable and photocatalytic self-cleaning functions of theses surfaces for applications that desire rapid and sustainable bactericidal performance.

miR-142-5p/DAX1-dependent regulation of P450c17 contributes to triclosan-mediated testosterone suppression

Triclosan (TCS) is a potent antibacterial and antifungal compound that is extensively used in various daily products. TCS is also considered as an underlying endocrine disruptor and has anti-androgenic effects. In our previous work, we found that TCS suppressed testicular steroidogenesis via the miR-6321/JNK/Nur77 cascade, but roles of the abnormal expression of miR-142-5p and P450c17 in this molecular event were still unknown. Therefore, to verify the hypothesis that miR-142-5p and P450c17 might significantly function in other manner in testosterone decline after TCS exposure, Sprague-Dawley rats and the rat Leydig cell line were used in this study. Results showed that after TCS exposure, testicular histomorphology was abnormally changed and testosterone level was declined. Overexpressed miR-142-5p by TCS directly targeted the JAK1/STAT1 pathway. Bidirectional Co-IP assays and the use of STAT1 activator demonstrated that STAT1 could interact with and regulate Sp1. The activity, mRNA level, and protein expression of DNMT1 and DNMT3β were all decreased after TCS treatment. Sp1 silencing, ChIP, and qPCR assays showed that Sp1 regulated DNMT1 expressions by directly binding to the promoter region of DNMT1. Though the DNA methylation status of the DAX1 promoter was not affected, TCS induced the transcription and translation of DAX1 by DNMT1, in turn leading to the inhibition of steroidogenic P450c17. Taken together, TCS-induced miR-142-5p inhibits P450c17 by the JAK1/STAT1 pathway and downstream Sp1/DNMT1/DAX1 cascade, finally facilitating the decrease in testosterone levels.

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.

Electrochemical degradation of triclosan in aqueous solution. A study of the performance of an electro-Fenton reactor

The electro-Fenton degradation of Triclosan in aqueous solution was studied using a cylindrical reactor in which polarized carbon cloth electrodes and a cation exchange resin were employed. Using a factorial design of experiments approach, the effect of four variables (considering two levels for each one), was measured on four response parameters that reflect the electrooxidation efficiency of the electrochemical reactor. The results revealed that in all cases triclosan degradation was very efficient (above 95%) and that while there is a reasonable effect of all variables and their interactions, the one with the strongest influence on the process is the nature and magnitude of the ionic strength of the electrolytic solution. In this way, while the presence of a buffer species in this solution can keep the pH in a value that affects the generation of ^•OH radicals from the Fenton mixture, a high ionic strength solution can promote the elimination of Fe ionic species from the reactor by decreasing resin Fe retention due to competition effects of other ions for the binding sites of the substrate. HPLC experiments of the effluent solutions, also revealed that the degradation by-products of triclosan were dependent on the nature and ionic strength of the electrolytic solution in the electro-Fenton process under study. Finally, comparison of the different operation modes, also suggested that electro-adsorption of Fe cationic species in the negatively polarized cathode surface, is the main factor that controls Fe ion retention within the reactor.