Ultrasensitive, Label-Free Voltammetric Detection of Dibutyl Phthalate Based on Poly-l-lysine/poly(3,4-ethylenedioxythiophene)-porous Graphene Nanocomposite and Molecularly Imprinted Polymers

Development of an efficient technique for accurate and sensitive dibutyl phthalate (DBP) determination is crucial for food safety and environment protection. An ultrasensitive molecularly imprinted polymers (MIP) voltammetric sensor was herein engineered for the specific determination of DBP using poly-l-lysine/poly(3,4-ethylenedioxythiophene)/porous graphene nanocomposite (PLL/PEDOT-PG) and poly(o-phenylenediamine)-imprinted film as a label-free and sensing platform. Fabrication of PEDOT-PG nanocomposites was achieved through a simple liquid-liquid interfacial polymerization. Subsequently, poly-l-lysine (PLL) functionalization was employed to enhance the dispersibility and stability of the prepared PEDOT-PG, as well as promote its adhesion on the sensor surface. In the presence of DBP, the imprinted poly(o-phenylenediamine) film was formed on the surface of PLL/PEDOT-PG. Investigation of the physical properties and electrochemical behavior of the MIP/PLL/PEDOT-PG indicates that the incorporation of PG into PEDOT, with PLL uniformly wrapping its surface, significantly enhanced conductivity, carrier mobility, stability, and provided a larger surface area for specific recognition sites. Under optimal experimental conditions, the electrochemical response exhibited a linear relationship with a logarithm of DBP concentration within the range of 1 fM to 5 µM, with the detection limit as low as 0.88 fM. The method demonstrated exceptional stability and repeatability and has been successfully applied to quantify DBP in plastic packaging materials.

Extended exposure to tetrabromobisphenol A-bis(2,3-dibromopropyl ether) leads to subfertility in male mice at the late reproductive age

Tetrabromobisphenol A-bis(2,3-dibromopropyl ether) (TBBPA-BDBPE), a commonly used brominated flame retardant as a decabromodiphenyl ether substitute, has been detected in various environmental compartments, but its health hazards remain largely unknown. Our recent study showed that low-dose exposure of male mice to TBBPA-BDBPE from postnatal day (PND) 0 to 56 caused remarkable damage to the microtubule skeleton in Sertoli cells and the blood-testis barrier (BTB) but exerted little effect on conventional reproductive endpoints in adulthood. To investigate whether TBBPA-BDBPE may cause severe reproductive impairments at late reproductive age, here, we extended exposure of historically administrated male mice to 8-month age and allowed them to mate with non-treated females for the evaluation of fertility, followed by a general examination for the reproductive system. As expected, we found that 8-month exposure to 50 μg/kg/d as well as 1000 μg/kg/d TBBPA-BDBPE caused severe damage to the reproductive system, including reduced sperm counts, increased sperm abnormality, histological alterations of testes. Moreover, microtubule damage and BTB-related impairment were still observed following 8-month exposure. Noticeably, high-dose TBBPA-BDBPE-treated mice had fewer offspring with a female-biased sex ratio. All results show that long-term exposure to TBBPA-BDBPE caused severe reproductive impairment, including poor fertility at late reproductive age. It is therefore concluded that slight testicular injuries in early life can contribute to reproductive impairment at late reproductive age, highlighting that alterations in certain non-conventional endpoints should be noticed as well as conventional endpoints in future reproductive toxicity studies.

Exposure to Dibutyl Phthalate and Reproductive-Related Outcomes in Animal Models: Evidence From Rodents Study

Background: Dibutyl phthalate (DBP) was an endocrine disruptor, which may lead to cancer and affects reproductive function when accumulated in the body. But the precise role of DBP in the reproductive system remained controversial.

Objective: We employed the meta-analysis to explore the relationship between DBP and reproductive-related outcomes.

Methods: We searched relevant literature in PubMed, EMBASE, and Web of Science databases. The standardized mean differences (SMDs) and their 95% CIs were measured by random-effects models. Funnel plots and Egger’s regression test were applied to assess publication bias.

Results: Finally, 19 literatures were included in this research. The outcomes revealed that DBP was negatively correlated with reproductive organs weight (testis weight: SMD: −0.59; 95% Cl: −1.23, −0.23; seminal vesicles weight: SMD: −0.74; 95% Cl: −1.21, −0.27; prostate weight: SMD: −0.46; 95% Cl: −0.76, −0.16) and sperm parameters (sperm morphology: SMD: 1.29; 95% Cl: 0.63, 1.94; sperm count: SMD: −1.81; 95% Cl: −2.39, −1.23; sperm motility: SMD: −1.92; 95% Cl: −2.62, −1.23).

Conclusion: Our research demonstrated that DBP may be negatively associated with reproductive-related indicators, especially at Gestation exposure period and middle dose (100–500 mg/kg/day).

Rutin prevents cardiac oxidative stress and inflammation induced by bisphenol A and dibutyl phthalate exposure via NRF-2/NF-κB pathway

AIM

Environmental pollutants such as plastic-component substances (phthalates and bisphenol A) that coexist in natural ecosystems have been linked to an increase in the occurrence of human health hazards, particularly cardiovascular health. This study was designed to investigate single and combined cardio-toxic effects of dibutyl phthalate and bisphenol-A and the possible interventional role of rutin.

MATERIALS AND METHODS

Forty-two rats were randomized into 7 groups of 6 animals each and were treated as follows for 28 days: Control (0.1% DMSO), Bisphenol-A (BPA, 25 mg/kg, p.o), Dibutyl phthalate (DBP, 25 mg/kg, p.o), BPA + Rutin (25 mg/kg, Rt 50 mg/kg), DBP + Rt (25 mg/kg, Rt 50 mg/kg), BPA + DBP, BPA + DBP + Rt. Cardiac lipid peroxidation, antioxidants and inflammatory markers activities were measured.

KEY FINDINGS

The result showed that BPA reduced the superoxide dismutase (SOD) activity, DBP and DBP+ BPA reduced the catalase (CAT) activity, DBP reduced glutathione (GSH) and nuclear factor erythroid 2-related factor 2 (Nrf2) while malondialdehyde (MDA) increased in DBP + BPA group. Also, DBP increased tissue C-reactive protein (CRP); DBP, DBP + BPA increased tissue nuclear factor kappa B (NF-κB); DBP + BPA increased plasma CRP; BPA increased plasma NF-κB. However, rutin efficiently reduced MDA level, CRP and NF-κB; increasing SOD, GSH and Nrf2 levels in DBP and BPA exposed rats.

SIGNIFICANCE

These results revealed that bisphenol and dibutyl phthalate exposure caused oxidative stress and inflammation in the heart through Nrf2/NF-κB signaling pathway while oral administration of rutin prevents these effects via upregulation of Nrf2 and suppression of NF-κB signaling pathway.

Taxifolin attenuates the developmental testicular toxicity induced by di-n-butyl phthalate in fetal male rats

Di-n-butyl phthalate (DBP) is widely used in consumer products as a plasticizer. Here, we report a natural product taxifolin that can attenuate developmental and reproductive toxicity of DBP. Pregnant rats were daily gavaged with 500 mg/kg DBP alone or together with taxifolin (10 and 20 mg/kg) from gestational day (GD) 12-21. At GD21, sera and testes of male fetus were collected. DBP significantly lowered serum testosterone level at 500 mg/kg and taxifolin can completely reverse its action. DBP caused abnormal aggregation of fetal Leydig cells and taxifolin can reverse it. DBP down-regulated the expression of the genes of cholesterol side-chain cleavage enzyme (Cyp11a1), 17β-hydroxysteroid dehydrogenase 3 (Hsd17b3), and insulin-like 3 (Insl3) and taxifolin can reverse its action. DBP increased malondialdehyde levels and decreased superoxide dismutase and glutathione peroxidase expression and taxifolin can reverse it. DBP increased incidence of multinucleated gonocytes and taxifolin can prevent it. Moreover, DBP lowered sirtuin 1 (SIRT1)/peroxisome proliferator-activated receptor γ coactivator 1-α (PGC-1α) and phosphorylated AMP-activated protein kinase (pAMPK) signalling and taxifolin antagonized DBP. In conclusion, in utero exposure to DBP caused developmental/reproductive toxicity of male offspring via increasing reactive oxygen species and taxifolin is an effective food component that completely reverses DBP-mediated action.

Exposure of DBP in gestation induces inflammation of testicular Sertoli cells in progeny by activating NLRP3 inflammasomes

Di-n-butyl phthalate (DBP), as one of the environmental chemicals, can cause male reproductive decline including testicular hypoplasia and impairments of spermatogenesis. Testicular inflammation is positively related to decline in male reproductive function. However, whether exposure to DBP in utero can cause testicular inflammation in progeny has not been studied. In this study, we established an animal model and observed that DBP exposure during gestation induced testicular inflammation in progeny with the increased expression of pro-inflammatory cytokines and chemokines including tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), monocyte chemotactic protein-1 (MCP-1) and CXC chemokine ligand-10 (CXCL-10), representing the activation of the nuclear factor kappa B (NF-κB). However, NF-κB was activated within 1 h in Sertoli cells (SCs) when exposed to MBP (a metabolite of DBP) in vitro. Meanwhile, we detected increased expression of inflammatory NLR family pyrin domain containing 3 (NLRP3), resulting from Pellino2-mediated NLRP3 inflammasome priming. Further, we confirmed that the activation of the NLRP3/caspase-1/IL-1β canonical inflammasome pathway induced secretion of inflammatory factors of SCs and immune response, and INF39 (an inhibitor of NLRP3) could inhibit the inflammation in vitro. Collectively, these findings indicated that NLRP3 inflammasomes played key roles in DBP-induced inflammation in testicular SCs.

Major factors dominating the fate of dibutyl phthalate in agricultural soils

Dibutyl phthalate (DBP) is a ubiquitous soil contaminant. We have investigated the sorption, degradation and residue of DBP in 20 types of agricultural soils and aimed to identify the major soil properties that dominate the fate of DBP. Sorption isotherms of DBP in all soils were fitted well with the Freundlich model. The sorption coefficient (K_f) varied between 3.99 and 36.1 mg^1-1/nL^1/n/kg. Path analysis indicated that 59.9% of variation in K_f could be explained by the combination of pH, organic carbon (OC) and clay content. Degradation of DBP in the 20 soils was well described by the first-order kinetic model, with half-lives (t_1/2) ranging from 0.430 to 4.99 d. The residual DBP concentration after 60 d of incubation (R₆₀) ranged from 0.756 to 2.15 mg/kg and the residual rates ranged from 3.97% to 9.63%. The K_f value was significantly positively correlated with t_1/2 and R₆₀. Moreover, soil pH, microbial biomass carbon (C_mic) and OC were identified as dominating factors that explained 84.4% of variation in t_1/2. The R₆₀ data indicated 72.2% of its variability attributable to the combination of OC and C_mic. The orders of the relative importance of dominating factors on the K_f, t_1/2 and R₆₀ were OC > pH > clay, C_mic > pH > OC and OC > C_mic, respectively. This work contributes to better understand the fate of DBP in soils and make scientific decisions about accelerating its dissipation in different soils.

The role of ANXA5 in DBP-induced oxidative stress through ERK/Nrf2 pathway

Di-N-butylphthalate (DBP) have given rise to more and more attention due to its unique endocrine toxicity to male reproductive system. Our previous studies have demonstrated antioxidative Nrf2 (nuclear factor erythroid related factor 2) pathway play a vital role in DBP induced oxidative stress injury. ANXA5 (annexin A5), which is highly expressed in testicular Leydig and Sertoli cells, was found upregulated after DBP stimulation. Mouse Leydig and Sertoli cells were exposed to different concentration of DBP for 24 h to examine the ROS (Reactive oxygen species), MDA (Malondialdehyde), SOD (superoxide dismutase) level and ANXA5, Nrf2, NQO1 (NAD(P)H-quinone oxidoreductase 1), HO-1 (heme oxygenase 1) and ERK/P-ERK protein expression by DHE (Dihydroethidium) staining, ELISA (enzyme-linked immunosorbent assay) and Western blot respectively. Firstly, the oxidative stress injury induced by DBP was re-validated. Then, we confirmed the change of Nrf2 pathway and ANXA5 level after DBP exposure to testicular cells. Additionally, overexpressed ANXA5 could activate Nrf2/HO-1/NQO1 antioxidant pathway and significantly attenuate DBP-induced oxidative stress. Ultimately, we demonstrated ANXA5 could increase ERK phosphorylated level and the activated role of ANXA5 on ERK/Nrf2 pathway could be reversed by ERK inhibitor. Overall, this study illuminated that ANXA5 could defend testicle Leydig and Sertoli cells against DBP-induced oxidative stress injury through ERK/Nrf2 pathway.

Effects of phthalates on bovine primary testicular culture and spermatozoa

Among environmental endocrine-active chemicals, phthalates, commonly known as plasticizers, disrupt the development of the male reproductive tract. In this study, the effects of phthalates (DIBP, BBP, DINP, DBP, DEP, DEHP and DMP) were evaluated on cultures of bovine primary male reproductive cells (n = 3) and spermatozoa (n = 4). Epididymal (caput and corpus epididymis), testicular (parenchymal and mediastinal/tubular) and vas deferens cells (VDC) were prepared from samples collected from slaughterhouse. Second part of caput epididymis which have fewer amount of principal cells, were found to be less affected compared to the first part except DEHP; while corpus epididymis was found to be more affected with IC50 values below 0.976 ng/mL (except for DEP at 4.97 ng/mL). In testicular parenchymal cells, IC50 ranged from 0.15 to 4.11 ng/mL and for mediastinum from 0.01 to 7.31 ng/mL; where cytotoxic effects were more evident in mediastinal section. Least cytotoxic and even proliferational effects (DEHP, DMP and DEP) were observed in VDC, the muscular tube carrying sperm from epididymis to the ejaculatory duct. Least spermiotoxic phthalate was DBP (3.928 ng/mL); while DINP (0.550 ng/mL) induced highest cytotoxic effect on bovine spermatozoa. Differences in the cellular structure and/or the androgen receptor distribution effect the toxicity of phthalates. Our preliminary findings on bovine spermatozoa indicate possible morphological and motility alterations; which challenges further investigation of the transition of phthalates on semen straws used in cryopreservation. Increase of exposure to environmental contaminants raise the issue of the requirement of a new perspective on reproductive health, species and tissue specific differences should further be emphasized.

Use of the Adverse Outcome Pathway (AOP) framework to evaluate species concordance and human relevance of Dibutyl phthalate (DBP)-induced male reproductive toxicity

Dibutyl phthalate (DBP) is a phthalate ester used as a plasticizer, and solvent. Studies using rats consistently report that DBP exposure disrupts normal development of the male reproductive system in part via inhibition of androgen synthesis. However, studies using xenograft models report that in human fetal testis DBP exposure is unlikely to impair testosterone synthesis. These results question the validity of the rat model for assessment of male reproductive effects caused by DBP. The Adverse Outcome Pathway (AOP) framework was used to evaluate the available evidence for DBP-induced toxicity to the male reproductive system. Three relevant biological elements were identified: 1) fetal rats are more sensitive than other rodents and human fetal xenografts to DBP-induced anti-androgenic effects, 2) DBP-induced androgen-independent adverse outcomes are conserved amongst different mammalian models and human fetal testis xenografts, and 3) DBP-induced anti-androgenic effects are conserved in different mammalian species when exposure occurs during postnatal life stages.

The effect of preconceptional exposure of F0 male mice to di(2-ethylhexyl)phthalate on the induction of reproductive toxicity in F2 generation

The aim of the study was the estimation of the effects of 8 weeks exposure mature and pubescent male mice to DEHP on the prenatal development of the offspring F2 generation. The F1 offspring, of males exposed for whole cycle of spermatogenesis to DEHP (2000 mg/kg bw or 8000 mg/kg bw) and unexposed females, at 8-9 weeks of age were caged males with females from the same group, but from different litter. Eight weeks preconceptional exposure of mature F0 males to 2000 mg/kg bw DEHP induced the significantly higher number of dead fetuses in the F2 offspring; however, the effect on the sperm count and quality of F1 males was not seen. Contrary, after such exposure of pubescent males not significantly decrease in the number of live implants was noted. Results showed that the subchronical, preconceptional exposure of F0 males to DEHP did not influence strongly on the F2 generation of the offspring. Our study did not confirm higher sensitivity germ cells of pubescent males to harmful effects induced by DEHP. The developmental effect was present as the enhanced number of dead implants of F2 generation after exposure of mature F0 males and slight reduction in the number of live fetuses following the exposure of immature males. It may confirm ability to male mediated developmental toxicity.

Evaluating the potential genotoxicity of phthalates esters (PAEs) in perfumes using in vitro assays

We previously reported high levels of phthalate esters (PAEs) added as solvents or fixatives in 47 brands of perfumes. Diethyl phthalate was the most abundant compound (0.232-23,649 ppm), and 83.3% of the perfumes had levels >1 ppm, the threshold limit cited by a Greenpeace investigation. All samples had dimethyl phthalate levels higher than its threshold limit of 0.1 ppm, and 88, 38, and 7% of the perfumes had benzyl butyl phthalate, di(2-ethylhexyl) phthalate, and dibutyl phthalate levels, respectively, above their threshold limits. The role of PAEs as endocrine disruptors has been well documented, but their effect on genotoxic behavior has received little attention. We used in vitro single-cell gel electrophoresis (comet) and micronucleus (MN) assays with human lymphoblastoid TK6 cells to evaluate the genotoxic potency of 42 of the same perfumes and to determine its association with PAEs. All perfumes induced more DNA damage than a negative control (NEG), ≥ 90% of the samples caused more damage than cells treated with the vehicles possibly used in perfume's preparations such as methanol (ME) and ethanol (ET), and 11.6% of the perfumes caused more DNA damage than a positive control (hydrogen peroxide). Chromosome breakage expressed as MN frequency was higher in cells treated with 71.4, 64.3, 57.1, and 4.8% of the perfumes than in NEG, cells treated with ME or ET, and another positive control (x-rays), respectively. The genotoxic responses in the comet and MN assays were not correlated. The comet assay indicated that the damage in TK6 cells treated with five PAEs at concentrations of 0.05 and 0.2 ppm either individually or as a mixture did not differ significantly from the damage in cells treated with the perfumes. Unlike the comet assay, the sensitivity of the MN assay to PAEs was weak at both low and high concentrations, and MN frequencies were generally low. This study demonstrates for the first time the possible contribution of PAEs in perfumes to DNA damage and suggests that their use as solvents or fixatives should be regulated. Other ingredients with mutagenic/genotoxic properties, however, may also have contributed to the DNA damage. Future studies should focus on applying a series of assays that use different cellular models with various endpoints to identify the spectrum of genotoxic mechanisms involved.