Mediation of the JNC/ILC2 pathway in DBP-exacerbated allergic asthma: A molecular toxicological study on neuroimmune positive feedback mechanism

BACKGROUND

Dibutyl phthalate (DBP), a commonly used plasticizer, has been found to be strongly linked to a consistently high prevalence of allergic diseases, particularly allergic asthma. Previous animal experiments have demonstrated that exposure to DBP can worsen asthma by triggering the production of calcitonin gene-related peptide (CGRP), a neuropeptide in the lung tissue. However, the precise neuroimmune mechanism and pathophysiology of DBP-exacerbated allergic asthma with the assistance of CGRP remain unclear.

OBJECTIVE

The present study was to investigate the potential pathophysiological mechanism in DBP-exacerbated asthma from the perspective of neural-immune interactions.

METHODS AND RESULTS

C57BL/6 mice were orally exposed to different concentrations (0.4, 4, 40 mg/kg) of DBP for 28 days. They were then sensitized with OVA and nebulized with OVA for 7 consecutive excitations. To investigate whether DBP exacerbates allergic asthma in OVA induced mice, we analyzed airway hyperresponsiveness and lung histopathology. To investigate the activation of JNC and TRPV1 neurons and the release of CGRP by JNC cells, we measured the levels of TRPV1 channels, calcium inward flow, and downstream neuropeptide CGRP. Results showed that TRPV1 expression, inward calcium flux, and CGRP levels were significantly elevated in the lung tissues of the 40DBP + OVA group, suggesting the release of CGRP by JNC cells. To counteract the detrimental effects of DBP mediated by CGRP, we employed olcegepant (also known as BIBN-4096), a CGRP receptor specific antagonist. Results revealed that 40DBP + OVA + olcegepant led to notable decreases in TRPV1, calcium inward flow, and CGRP expression in lung tissues compare with 40DBP + OVA, further supporting the efficacy of olcegepant. Additionally, we also conducted ILC2 flow sorting and observed that neuropeptide CGRP-activated ILC2 cells have a crucial role as key effector cells in DBP-induced neuroimmune positive feedback regulation. Finally, we examined the protein expression of CGRP, GATA3 and P-GATA3, and found that significant upregulations of CGRP and P-GATA3 in the 40DBP + OVA group, suggest that GATA3 acted as a key regulator of CGRP-activated ILC2.

CONCLUSION

The aforementioned studies indicate that exposure to DBP can exacerbate allergic asthma, leading to airway inflammation. This exacerbation occurs through the activation of TRPV1 in JNC, resulting in the release of CGRP. The excessive release of CGRP further promotes the release of Th2 cytokines by inducing the activation of ILC2 through GATA phosphorylation. Consequently, this process contributes to the development of airway inflammation and allergic asthma. The increased production of Th2 cytokines also triggers the production of IgE, which interacts with FcεRI on JNC neurons, thereby mediating neuro-immune positive feedback regulation.

Impacts of dibutyl phthalate on bacterial community composition and carbon and nitrogen metabolic pathways in a municipal wastewater treatment system

Dibutyl phthalate (DBP) is a typical toxic and hazardous pollutant in pharmaceutical wastewater, affecting the metabolism of microbial flora, leading to decreased treatment efficiency, and deteriorated effluent quality in municipal wastewater treatment plants (WWTPs). This study conducted a long-term experiment with 6 operational stages in a pilot-scale A²O-MBR system, analyzing the effect of DBP on the bacterial community and their carbon and nitrogen metabolic pathways. 16S rRNA gene amplicon sequencing analysis and principal components analysis (PCA) showed that DBP at 8 mg/L significantly influenced the structure of bacterial community (P < 0.05), resulting in reduced bacterial community diversity. Metagenomic analysis was used to explore the embedded carbon and nitrogen metabolic pathways. At the presence of DBP, the metabolism of saccharides, lipids, and aromatic compounds were blocked owing to the vanishment of key enzyme (such as acetylaminohexosyltransferase (EC 2.4.1.92) and UDP-sugar pyro phosphorylase (EC 2.7.7.64)) encoding genes, resulting in weakened carbon metabolism, and thus reduced COD removal performance. The resultant deficiency of the genes such as those encoding hydroxyproline dehydrogenase (EC 1.5.5.3) gave rise to interrupted metabolic pathways of amino acid (arginine, proline, tyrosine, and tryptophan), resulting in declined function of nitrogen metabolism and thus reduced TN removal efficiency. The uncovery of the mechanisms by which DBP affects wastewater treatment system efficiency and microbial metabolism is of theoretical importance for the efficient operation of municipal and pharmaceutical wastewater treatment systems.

Hydrolysis of dibutyl phthalate and di(2-ethylhexyl) phthalate in human liver, small intestine, kidney, and lung: An in vitro analysis using organ subcellular fractions and recombinant carboxylesterases

Phthalates are widely used plasticizers that are primarily and rapidly metabolized to monoester phthalates in mammals. In the present study, the hydrolysis of dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) in the human liver, small intestine, kidney, and lung was examined by the catalytic, kinetic, and inhibition analyses using organ microsomal and cytosolic fractions and recombinant carboxylesterases (CESs). The V_max (y-intercept) values based on the Eadie-Hofstee plots of DBP hydrolysis were liver > small intestine > kidney > lung in microsomes, and liver > small intestine > lung > kidney in cytosol, respectively. The CL_int values (x-intercept) were small intestine > liver > kidney > lung in both microsomes and cytosol. The V_max and CL_int or CL_max values of DEHP hydrolysis were small intestine > liver > kidney > lung in both microsomes and cytosol. Bis(4-nitrophenyl) phosphate (BNPP) effectively inhibited the activities of DBP and DEHP hydrolysis in the microsomes and cytosol of liver, small intestine, kidney, and lung. Although physostigmine also potently inhibited DBP and DEHP hydrolysis activities in both the microsomes and cytosol of the small intestine and kidney, the inhibitory effects in the liver and lung were weak. In recombinant CESs, the V_max values of DBP hydrolysis were CES1 (CES1b, CES1c) > CES2, whereas the CL_max values were CES2 > CES1 (CES1b, CES1c). On the other hand, the V_max and CL_max values of DEHP hydrolysis were CES2 > CES1 (CES1b, CES1c). These results suggest an extensive organ-dependence of DBP and DEHP hydrolysis due to CES expression, and that CESs are responsible for the metabolic activation of phthalates.

Impacts of dibutyl phthalate on biological municipal wastewater treatment in a pilot-scale A2/O-MBR system

Dibutyl phthalate (DBP) is a typical contaminant in pharmaceutical wastewater with strong bio-depressive properties which potentially affects the operation of municipal wastewater treatment systems. Based on a year-round monitoring of the quality of influent and effluent of a full-scale pharmaceutical wastewater treatment plant in Northeast China, the DBP was found to be the representative pollutant and its concentration in the effluent ranged 4.28 ± 0.93 mg/L. In this study, the negative effects of DBP on a pilot-scale A²/O-MBR system was investigated. When the influent DBP concentration reached 8.0 mg/L, the removals of chemical oxygen demand (COD) and total nitrogen (TN) were significantly inhabited (P < 0.01), with the effluent concentration of 54.7 ± 2.6 mg/L and 22.8 ± 3.7 mg/L, respectively. The analysis of pollutant removal characteristics of each process unit showed that DBP had the most significant effects on the removals of COD and TN in the anoxic tank. The α- and β-diversity in the system decreased significantly when the influent DBP concentration reached 8.0 mg/L. The impacts of DBP on known nitrifying bacteria, such as Nitrospira, and phosphorus accumulating organisms (PAOs), such as Cadidatus Accumulibacter, were not remarkable. Whereas, DBP negatively affected the proliferation of key denitrifying bacteria, represented by Simplicispira, Dechloromonas and Acinetobacter. This study systematically revealed the impacts of DBP on the pollutants removal performance and the bacterial community structure of the biological municipal wastewater treatment process, which would provide insights for understanding the potential impacts of residues in treated pharmaceutical wastewater on biological municipal wastewater treatment.

Ecotoxicological evaluation of zebrafish liver (Danio rerio) induced by dibutyl phthalate

Dibutyl phthalate (DBP), one of the most commonly applied plasticizers, has been frequently detected in the aquatic environment, posing potential risks to aquatic organisms. Currently, reports about the toxicity of zebrafish liver with DBP exposure are rare, and the toxic mechanism is still not clear. In this study, zebrafish (Danio rerio) were used to explore the ecotoxicological effects of DBP from the physiological, biochemical, genetic, and molecular levels. The results showed oxidative stress, lipid peroxidation, and DNA damage occurred in zebrafish liver according to changes in antioxidant enzymes, MDA and 8-OHdG content. AchE activity was always active, and negatively correlated with the DBP concentration. The expression of Cu/Zn-sod and gpx genes were similar to that of antioxidant enzymes from 7 to 21 days, while in the end, the inconsistent result appeared due to the time lag effect in protein modification, gene transcription and translation. Besides, the mRNA abundance of Caspase-3 and p53 were upregulated, showing a "dose-response" relationship. The integrated biomarker reaction indicated that the effects of exposure time on zebrafish liver was 14th day> 28th day> 7th day> 21th day. These results are of great significance to evaluate the toxicological effects and explore the toxic mechanism of DBP on aquatic organisms.

Systematic comparison of the male reproductive tract in fetal and adult Wistar rats exposed to DBP and DINP in utero during the masculinisation programming window

This study investigates possible effects of in utero exposure of rats to a low dose (125 mg/kg bw/day) and a high dose (750 mg/kg bw/day) of Diisononyl phthalate (DINP) during the masculinisation programming window (MPW) which is embryonic days 15.5-18.5 (e15.5 - e18.5). Dibutyl phthalate (DBP) was used at a high dose level (750 mg/kg bw/day) as an established positive control substance for anti-androgenic effects on the developing male reproductive tract. We focussed on the MPW and measured a multitude of biological endpoints at various life stages and applied state of the art histopathology staining techniques to refine the characterization of potential changes to the testis, beyond what is currently available with DINP. If DINP can mediate testicular dysgenesis (TDS) disorders, this exposure window would be sufficient to induce androgen impacts and alter male reproductive tract development as shown earlier in this validated experimental model with DBP. Overall, the results of this systematic comparison provide convincing evidence on the differences between the effects occurring with DBP and DINP. In contrast to what was seen with DBP, DINP did not cause cryptorchidism or hypospadias, had no effect on anogenital distance/anogenital index (AGD/AGi) and Leydig cell aggregates on e17.5 and e21.5 did not increase. With DINP no reduction of intratesticular testosterone, no effects on sperm motility and sperm count and no effect on adult testosterone or luteinizing hormone (LH) levels were seen. Our results demonstrate that DINP does not cause the adverse reproductive effects known to occur with DBP, a well-established endocrine disruptor.

Degradation of dibutyl phthalate (DBP) by a bacterial consortium and characterization of two novel esterases capable of hydrolyzing PAEs sequentially

Phthalate esters (PAEs), a class of toxic anthropogenic compounds, have been predominantly used as additives or plasticizers, and great concern and interests have been raised regarding its environmental behavior and degradation mechanism. In the present study, a bacterial consortium consisting of Microbacterium sp. PAE-1 and Pandoraea sp. PAE-2 was isolated by the enrichment method, which could degrade dibutyl phthalate (DBP) completely by biochemical cooperation. DBP was converted to phthalic acid (PA) via monobutyl phthalate (MBP) by two sequential hydrolysis steps in strain PAE-1, and then PA was further degraded by strain PAE-2. Strain PAE-1 could hydrolyze many dialkyl Phthalate esters (PAEs) including dimethyl, diethyl, dibutyl, dipentyl, benzyl butyl, dihexyl, di-(2-ethyhexyl) and their corresponding monoalkyl PAEs. Two esterase genes named dpeH and mpeH, located in the same transcription unit, were cloned from strain PAE-1 by the shotgun method and heterologously expressed in Escherichia. coli (DE3). The Km and kcat values of DpeH for DBP were 9.60 ± 0.97 μM and (2.72 ± 0.06) × 10⁶ s^-1, while those of MpeH for MBP were 18.61 ± 2.00 μM and (5.83 ± 1.00) × 10⁵ s^-1, respectively. DpeH could only hydrolyze dialkyl PAEs to the corresponding monoalkyl PAEs, which were then hydrolyzed to PA by MpeH. DpeH shares the highest similarity (53%) with an alpha/beta hydrolase from Microbacterium sp. MED-G48 and MpeH shows only 25% identity with a secreted lipase from Trichophyton benhamiae CBS 112371, indicating that DpeH and MpeH are two novel hydrolases against PAEs.

Analysis of phthalic acid esters in agricultural soils

The aim of the study was monitoring of phthalic acid esters in agricultural soils of the Czech Republic over the period of 6 years, namely dibutyl phthalate (DBP) and di-2-ethylhexyl phthalate (DEHP). Monitoring took place in twelve regions of the Czech Republic. Soil samples were taken evenly from the top and bottom soil horizons using a zig-zag pattern. Soil samples were taken from arable land, permanent grassland, and hop field. Lyophilisation of the samples was done by ultrasound-assisted extraction using a mixture acetone-hexane (1:1). Phthalic acid esters were analysed using high-performance liquid chromatography with UV detection. Subsequently, the results were statistically compared by analysing the principal components (PCA) to determine the effect of individual factors on the content of phthalic acid esters in agricultural soil. Factors such as precipitation, distance from a pollution source, amount of pesticides, and amount of artificial and organic fertilizers were taken into account. If we compare the concentrations established in this study with the limits set out in the Methodological Instruction of the Ministry of the Environment of the Czech Republic based on RSLs (Regional Screening Levels) issued by the USEPA (United States Environmental Protection Agency), none of these values were exceeded.

Metabolism and distribution of dibutyl phthalate in wheat grown on different soil types

Herein, we investigated the distribution of dibutyl phthalate (DBP) in the tissues of wheat grown on DBP-contaminated soils and determined the activity of detoxifying enzymes [cytochrome P450 (P450) and glutathione S-transferase (GST)] in these tissues at different growth stages of wheat. The content of DBP in wheat grown on all soil types increased with increasing DBP stress concentration, and the DBP content of each tissue decreased as wheat growth progressed. Under the same conditions, the DBP content of roots exceeded that of leaves and stems, and the DBP content of all tissues decreased in the order of brown soil > fluvo-aquic soil > cinnamon soil. The decrease of DBP content with growth and the content of mono-n-butyl dicarboxylate (MBP, main metabolite of DBP) followed the order of cinnamon soil > fluvo-aquic soil > brown soil; the latter parameter initially increased and then decreased as growth progressed. The changes in P450 content and GST activities in wheat tissues were highly consistent with the corresponding changes in DBP and MBP content, except for the DBP stress level of 40 mg kg^-1 at the seedling stage. Based on the obtained results, it was speculated that P450 and GST were strongly involved in the metabolism of DBP in wheat: oxygen atoms were inserted into the aldehyde C-H bond of the species generated after hydrolysis of ester groups under the action of P450 to achieve hydrocarbon hydroxylation under mild conditions and generate MBP.

Effects of bok choy on the dissipation of dibutyl phthalate (DBP) in mollisol and its possible mechanisms of biochemistry and microorganisms

Phytoremediation is an ecologically sustainable method for remediating contaminated soils, however, research on phytoremediation and its mechanisms are still rarely reported. The highest dibutyl phthalate (DBP) dissipation rate was 91% in 0-3mm bok choy rhizosphere via a 45-day rhizo-box experiment, and bok choy could regulate soil nutrients by increasing soil ammonia nitrogen (AN) and available phosphorus (AP). The biochemistry mechanism of interaction between dissolved organic matter (DOM) and DBP was also elucidated by various spectroscopy techniques. It was found that the alkyl ester in DBP produced the fastest response during the binding process, and the aromatic, hydroxyl and phenolic groups of the DOM humic-like substances preceded amide in DOM protein-like substance. It was found that DBP pollution reduced the Chao1 richness and Shannon index of bacteria in black soil via a pot experiment and high-throughput sequencing, which disturbed the metabolic activities and functional diversity of microorganisms in Mollisol. The microbial abundance increased in bok choy amendments, which has a specific microbial community structure and a high abundance of Actinobacteria and Acidobacteria. We concluded that some enriched genera were responsible for DBP dissipation, Alsobacter, Lacibacter, Myceligenerans, Schrenkiella parvula and Undibacterium. The findings of this study revealed that the possible biochemistry and microbial mechanisms of phytoremediation promoting the DBP dissipation in rhizosphere Mollisol and provided more useful information for phytoremediation of organic pollutants.

One overlooked source of phthalate exposure - oral intake from vegetables produced in plastic greenhouses in China

With increasing consumption of Vegetables planted in Plastic Greenhouses (VPGs) in China, phthalate exposure from VPGs represents an overlooked source of total daily exposure, since VPGs are not included in current phthalate exposure scenarios. For this reason, current exposure scenario modeling may underestimate the daily phthalate exposure in relation to adverse health impacts. Thus, in this paper we estimated the oral intake exposure to phthalates from VPGs by studying four provinces ranging from the north to the south in eastern China, based on published data. Exposures to di(2-ethylhexyl)-phthalate (DEHP) and dibutyl phthalate (DBP) were assessed for various population groups differentiated by age, sex, income, and region. Younger children experienced the highest exposure from VPG intake (mean 1.55 (0.19 and 6.20) (2.5th and 97.5th percentiles) μg/kg/body weight (bw)/day), followed by older children, teenagers, and adults (0.53 (0.06 and 1.80)). Exposures in urban populations were significantly higher than those in rural areas, and when examined by income, urban populations with low-income had the lowest exposures and the upper-middle income group was associated with the highest levels. Exposures in northeastern and southern provinces were higher than the levels in middle provinces due to regional disparities in dietary habits. Proportions of the mean oral intake exposures to DEHP and DBP from VPGs to the total daily exposure by modeling different exposure pathways and media were over 10% for all age groups. The DEHP and DBP exposure from VPG intake in China were found to be much higher than the levels in western countries. For example, exposures of older children to DBP and DEHP were respectively 17 and 4 times higher than European levels. The authors recommend policy interventions to protect populations from future risk of phthalate exposure.

The joint toxicity effect of five antibiotics and dibutyl phthalate to luminescent bacteria (Vibrio fischeri)

Antibiotics and phthalate esters are two kinds of emerging pollutants and are ubiquitous in the aquatic ecosystem. To date, few studies analyzed the combined toxicity of the mixtures of antibiotics and phthalate esters, and their joint toxicity effect mode remains unknown. Here, we investigated the single and joint toxicity of dibutyl phthalate (DBP) and five antibiotics, namely, oxytetracycline hydrochloride (OTC), chlortetracycline hydrochloride (CTC), sulfamethazine (SMZ), sulfamerazine (SMR), and sulfadiazine (SD), to luminescent bacteria of Vibrio fischeri. The median effect concentration (EC₅₀) values of the test chemicals were ranked as CTC (6.67 mg/L) > OTC (25.12 mg/L) > SD (67.61 mg/L) > SMR (141.51 mg/L) > DBP (148.38 mg/L) > SMZ (245.07 mg/L). The joint toxicities of the binary mixtures of antibiotics and DBP were evaluated by the concentration addition (CA) and independent action (IA) models. The joint toxicity effects of CTC-DBP, OTC-DBP, SMZ-DBP, SMR-DBP, and SD-DBP all appeared to be synergism. Our study revealed that sulfonamides combined with DBP could be as toxic as or even more toxic than tetracycline. Thus, the joint toxicity effect should be considered when assessing the ecological risks of binary or multicomponent pollutants.

Removal efficiency and enzymatic mechanism of dibutyl phthalate (DBP) by constructed wetlands

Four vertical-flow constructed wetland systems were set up in the field in order to study the removal efficiency and possible enzymatic mechanism of the constructed wetlands in treating sewage containing different concentrations of dibutyl phthalate (DBP). Under DBP spiked concentrations of 0.5, 1.0, and 2.0 mg/L, good DBP removal rates of 62.08, 82.17, and 84.17% were achieved, respectively. Meanwhile, certain removal effects of general water quality parameters were observed in all four constructed wetlands: with high average removal rates of nitrate nitrogen (NO₃^--N) and chemical oxygen demand (COD) of 91.10~93.89 and 82.83~89.17%, respectively, with moderate removal efficiencies of total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₄⁺-N) of 44.59~49.67, 30.58~37.18, and 28.52~37.45%, respectively. Compared to the control, an increase of enzyme activities of urease, phosphatase, dehydrogenase, and nitrate reductase was observed in the treatments with DBP addition. In the presence of 0.5 mg/L of DBP concentration, the urease, phosphatase, and dehydrogenase activities reached the highest levels, with an increase of 350.02, 36.57, and 417.88% compared with the control, respectively. It appeared that the low concentration of DBP might better stimulate the release of enzymes.

Effect of dibutyl phthalate on expression of connexin 43 and testosterone production of leydig cells in adult rats

To investigate the adverse effect of dibutyl phthalate (DBP) on Leydig cells and its mechanism related to gap junction, Leydig cells isolated from adult rats were treated with 0.1% dimethylsulfoxide (DMSO), 50mg/L DBP, 50mg/L DBP+10μM prostaglandin E2 (PGE2) and 40μM flutamide respectively. Radioimmunoassay, semi-quantitative RT-PCR, immunofluorescence and Western blot were applied to determine the expression of testosterone and Connexin 43 (Cx43) in Leydig cells. The expression of testosterone and Cx43 were both decreased in DBP group (P<0.05). While Cx43 was up-regulated after administered to PGE2, there was no significant change in testosterone. However, testosterone was down-regulated with a significant decrease of Cx43 in flutamide group. The results indicated that the inhibitory effect of DBP on testosterone production was not through the down-regulation of Cx43. On the contrary, the change of testosterone can influence the expression of Cx43 in Leydig cells.

Reaction pathway and oxidation mechanisms of dibutyl phthalate by persulfate activated with zero-valent iron

This study investigated reaction pathway and oxidation mechanisms of dibutyl phthalate (DBP) by persulfate (PS) activated with zero-valent iron (ZVI). The DBP degradation was studied at three pH values (acidic, neutral and basic) in the presence of different organic scavengers. Using a chemical probe method, both sulfate radical (SO4(-)) and hydroxyl radical (·OH) were found to be primary oxidants at pH3.0 and pH7.0, respectively while ·OH was the major specie to oxidize DBP at pH11.0. A similar result was found in an experiment of Electron Spin Resonance spin-trapping where in addition to OH, superoxide radical (O2(-)) was detected at pH11.0. The transformation of degradation products including dimethyl phthalate (DMP), diethyl phthalate (DEP), phthalic anhydride, and acetophenone exhibited diverse variation during the reaction processes. The phthalic anhydride concentration appeared to be maximum at all pHs. Another eleven intermediate products were also found at pH3.0 by GC-MS and HPLC analysis, and their degradation mechanisms and pathways were proposed. It was suggested that dealkylation, hydroxylation, decarboxylation and hydrogen extraction were the dominant degradation mechanisms of DBP at pH3.0.

Oxidative stress mediates dibutyl phthalateinduced anxiety-like behavior in Kunming mice

Among all phthalate esters, dibutyl phthalate (DBP) is only second to di-(2-ethylhexyl) phthalate (DEHP) in terms of adverse health outcomes, and its potential cerebral neurotoxicity has raised concern in recent years. DBP exposure has been reported to be responsible for neurobehavioral effects and related neurological diseases. In this study, we found that neurobehavioral changes induced by DBP may be mediated by oxidative damage in the mouse brain, and that the co-administration of Mangiferin (MAG, 50mg/kg/day) may protect the brain against oxidative damage caused by DBP exposure. The results of ethological analysis (elevated plus maze test and open-field test), histopathological examination of the brain, and assessments of oxidative stress (OS) in the mouse brain showed that there is a link between oxidative stress and anxiety-like behavior produced by DBP at higher doses (25 or 125mg/kg/day). Biomarkers of oxidative stress encompass reactive oxygen species (ROS), glutathione (GSH), malondialdehyde (MDA) and DPC coefficients (DPC). MAG (50mg/kg/day),administered as an antioxidant,can attenuatetheanxiety-like behavior of the tested mice.

Estrogenic effects in the influents and effluents of the drinking water treatment plants

Estrogen-like endocrine disrupting compounds (EEDC) such as bisphenol A, nonylphenol, and phthalic acid esters are toxic compounds that may occur in both raw- and drinking water. The aim of this study was to combine chemical- and bioassay to evaluate the risk of EEDCs in the drinking water treatment plants (DWTPs). Fifty-six samples were collected from seven DWTPs located in northern-, central-, and southern Taiwan from 2011 to 2012 and subjected to chemical analyses and two bioassay methods for total estrogenic activity (E-Screen and T47D-KBluc assay). Among of the considered EEDCs, only dibutyl phthalate (DBP) and di (2-ethylhexyl) phthalate (DEHP) were detected in both drinking and raw water samples. DBP levels in drinking water ranged from <MDL to 0.840 μg/L and from <MDL to 0.760 μg/L in raw water. DEHP had higher detection rate (82.1 %) than other compounds and was present in both drinking water and raw water from all the DWTPs. The highest daily drinking water intake calculated for male and female were 0.0823 and 0.115 μg/kg per day. The two selected bioassays were conducted for the first batch of 56 samples and a detection rate of 23 % for estradiol equivalent (EEQ) lower than the LOQ to 1.3 and 15 % for EEQ lower than LOQ to 0.757 for the second 53 samples. Our results showed a good correlation between E-screen and chemical assay which indicates that a combination of both can be used in detecting EEDCs in environmental samples.

The mechanism underlying dibutyl phthalate induced shortened anogenital distance and hypospadias in rats

PURPOSE

The purpose of this study was to investigate the mechanism of dibutyl phthalate (DBP) induced hypospadias and shortened anogenital distance (AGD).

METHODS

AGD, hypospadias, and cryptorchidism incidence was observed in male offspring of DBP treated pregnant Wistar rats. Testicular development and testosterone levels of normal and DBP-treated rat embryos were compared.

RESULTS

Male offspring of 300mg and 900mg DBP-treated pregnant Wistar rats exhibited shortened average AGD compared with the control group. A 22.7% hypospadias incidence was observed in the 300mg group, but no offspring with cryptorchidism were identified. In the 900mg group, hypospadias and cryptorchidism incidence reached 43.5% and 17.4%, respectively. Between E15.5 and E17.5, the 300mg group exhibited delayed testicular development and testosterone secretion. However, testicular development and testosterone secretion subsequently recovered. The 300mg treated and control groups had similar measures after E19.5. Contrastingly, testicular development and testosterone secretion were significantly diminished throughout development in the 900mg group. Exogenous testosterone partially counteracted DBP-induced changes in the reproductive organs of male offspring of DBP-treated rats.

CONCLUSIONS

High-dose DBP exposure may induce testicular dysgenesis in rat embryos. Additionally, low-dose DBP may delay testicular development and testosterone secretion during urethral development. This disruption may result in hypospadias.

Effects of combined exposure to 17α-ethynylestradiol and dibutyl phthalate on the growth and reproduction of adult male zebrafish (Danio rerio)

To evaluate the combined effects of 17α-ethynylestradiol (EE2) and dibutyl phthalate (DBP) on the growth and reproduction of male zebrafish, three-month-old fish were exposed to 0.005 or 0.020µg/L EE2, 100 or 500µg/L DBP or their binary mixtures under semi-static conditions. Investigated parameters include the length, weight, condition factor, vitellogenin (VTG) induction, acyl-CoA oxidase (AOX) protein level, histopathological alteration of testis, liver and gill, and reproductive capacity. After 21d exposure, no statistical difference was found among the weights, lengths and condition factors of different treatment groups. In all binary mixture groups, decreased VTG levels were detected compared to EE2-only groups; and the AOX levels were significantly lower than DBP-only treatments while both chemicals can individually induce AOX synthesis. Therefore, EE2 and DBP may act additively on VTG and antagonistically on AOX induction in males. After 45d exposure, delayed gametogenesis was observed for the DBP-only groups, indicated by fewer spermatozoa and more spermatocytes, which was further aggravated with the addition of EE2. The developmental delay of testis partially recovered after a 30d depuration in clean water. Combined exposure also caused liver and gill lesions, which were not alleviated during the 30d depuration, suggesting a nonreversible harmful effect the same as single exposure. Mixed EE2 and DBP were observed to impair the reproductive capability (the fecundity and fertilization rate) of males, while single exposure did not. Co-exposed to 0.020µg/L EE2 and 100µg/L DBP promoted the early hatching of offspring (F1 generation) at 48h post-fertilization (hpf), but the survival rates of the F1 generation were similar in all treatments. Our findings indicate that the effects of mixed EE2 and DBP at environmentally relevant levels can be either antagonistic or additive relying on the specific toxicological endpoints and the respective doses of each chemical.

Single-solute and bi-solute sorption of phenanthrene and dibutyl phthalate by plant- and manure-derived biochars

The spatial arrangement of biochar and the exact underlying interaction mechanisms of biochar and hydrophobic organic compounds both remain largely unknown. The sorption of dibutyl phthalate (DBP) and phenanthrene (PHE) to plant- and manure-derived biochars in both single- and bi-solute systems was investigated. The significant positive relation between surface polarity and ash content suggests that minerals benefit the external distribution of polar groups on particle surfaces. PHE and DBP sorption by the biochars was regulated by their surface polarity. The PHE generally displayed a pronounced enhancement of DBP sorption, likely resulting from the formation of biochar-PHE-DBP complexes, suggesting that DBP and PHE had different sorption sites on the biochars. The enhancement of Cd(2+) (a soft Lewis acid) on DBP sorption implied that π-π interactions should not dominate DBP sorption by biochars. The influence of Cd(2+) on PHE sorption by biochars would depend on the balance between suppressive sorption by Cd(2+)PHE bonding and enhanced sorption by Cd(2+)-complexed functionalities, and the amounts of Cd(2+) adsorbed by biochars determined the relative role of increased sorption by Cd(2+) in the overall PHE sorption.