Male rat exposure to low dose of di(2-ethylhexyl) phthalate during pre-pubertal, pubertal and post-pubertal periods: Impact on sperm count, gonad histology and testosterone secretion

Di-(2-ethylhexyl) phthalate exposure induces premature testicular senescence by disrupting mitochondrial respiratory chain through STAT5B-mitoSTAT3 in Leydig cell

Di-(2-ethylhexyl) phthalate (DEHP), a prevalent plasticizer, is known to have endocrine-disrupting effects on males and cause reproductive toxicity. There were causal effects of DEHP on testosterone levels in the real world by Mendelian randomization analysis. Exposure to DEHP during the preadult stage might lead to premature testicular senescence, but the mechanisms responsible for this have yet to be determined. In this study, we administered DEHP (300 mg/kg/day) to male C57BL/6 mice from postnatal days 21 to 49. The mice were kept for 6 months without DEHP. RNA sequencing was conducted on testicular tissue at PNM6. The results indicated that DEHP hindered testicular development, lowered serum testosterone levels in male mice, and induced premature testicular senescence. TM3 Leydig cells were exposed to 300 μM of mono(2-ethylhexyl) phthalate (MEHP), the bioactive metabolite of DEHP, for 72 h. The results also found that DEHP/MEHP induced senescence in vivo and in vitro. The mitochondrial respiratory chain was disrupted in Leydig cells. The expression and stability of STAT5B were elevated by MEHP treatment in TM3 cells. Furthermore, p-ERK1/2 was significantly decreased by STAT5B, and mitochondria-STAT3 (p-STAT3 ser727) was significantly decreased due to the decrease of p-ERK1/2. Additionally, the senescence level of TM3 cells was decreased and treated with 5 mM NAC for 1 h after MEHP treatment. In conclusion, these findings provided a novel mechanistic understanding of Leydig cells by disrupting the mitochondrial respiratory chain through STAT5B-mitoSTAT3.

The effects of inhaled pollutants on reproduction in marginalized communities: a contemporary review

Important differences in health that are closely linked with social disadvantage exist within and between countries. According to the World Health Organization, life expectancy and good health continue to increase in many parts of the world, but fail to improve in other parts of the world, indicating that differences in life expectancy and health arise due to the circumstances in which people grow, live, work, and age, and the systems put in place to deal with illness. Marginalized communities experience higher rates of certain diseases and more deaths compared to the general population, indicating a profound disparity in health status. Although several factors place marginalized communities at high risk for poor health outcomes, one important factor is exposure to air pollutants. Marginalized communities and minorities are exposed to higher levels of air pollutants than the majority population. Interestingly, a link exists between air pollutant exposure and adverse reproductive outcomes, suggesting that marginalized communities may have increased reproductive disorders due to increased exposure to air pollutants compared to the general population. This review summarizes different studies showing that marginalized communities have higher exposure to air pollutants, the types of air pollutants present in our environment, and the associations between air pollution and adverse reproductive outcomes, focusing on marginalized communities.

X-box binding protein 1 caused an imbalance in pyroptosis and mitophagy in immature rats with di-(2-ethylhexyl) phthalate-induced testis toxicity

As a widely used plasticizer, di-(2-ethylhexyl) phthalate (DEHP) is known to induce significant testicular injury. However, the potential mechanism and effects of pubertal exposure to DEHP on testis development remain unclear. In vivo, postnatal day (PND) 21 male rats were gavaged with 0, 250, and 500 mg/kg DEHP for ten days. Damage to the seminiferous epithelium and disturbed spermatogenesis were observed after DEHP exposure. Meanwhile, oxidative stress-induced injury and pyroptosis were activated. Both endoplasmic reticulum (ER) stress and mitophagy were involved in this process. Monoethylhexyl phthalate (MEHP) was used as the biometabolite of DEHP in vitro. The GC-1 and GC-2 cell lines were exposed to 0, 100 μM, 200 μM, and 400 μM MEHP for 24 h. Reactive oxygen species (ROS) generation, oxidative stress damage, ER stress, mitophagy, and pyroptosis were significantly increased after MEHP exposure. The ultrastructure of the ER and mitochondria was destroyed. X-box binding protein 1 (XBP1) was observed to be activated and translocated into the nucleus. ROS generation was inhibited by acetylcysteine. The levels of antioxidative stress, ER stress, mitophagy, and pyroptosis were decreased as well. After the administration of the ER stress inhibitor 4-phenyl-butyric acid, both mitophagy and pyroptosis were inhibited. Toyocamycin-induced XBP1 down-regulation decreased the levels of mitophagy and pyroptosis. The equilibrium between pyroptosis and mitophagy was disturbed by XBP1 accumulation. In summary, our findings confirmed that DEHP induced a ROS-mediated imbalance in pyroptosis and mitophagy in immature rat testes via XBP1. Moreover, XBP1 might be the key target in DEHP-related testis dysfunction.

Long-term exposure to the mixture of phthalates induced male reproductive toxicity in rats and the alleviative effects of quercetin

Phthalates (PEs), such as di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP) and butyl benzyl phthalate (BBP) could cause reproductive and developmental toxicities, while human beings are increasingly exposed to them at low-doses. Phytochemical quercetin (Que) is a flavonoid that has estrogenic effect, anti-inflammatory and anti-oxidant effects. This study was conducted to assess the alleviative effect of Que. on male reproductive toxicity induced by the mixture of three commonly used PEs (MPEs) at low-dose in rats, and explore the underlying mechanism. Male rats were treated with MPEs (16 mg/kg/day) and/or Que. (50 mg/kg/d) for 91 days. The results showed that MPEs exposure caused male reproductive injuries, such as decreased serum sex hormones levels, abnormal testicular pathological structure, increased abnormal sperm rate and changed expressions of PIWIL1 and PIWIL2. Furthermore, MPEs also changed the expression of steroidogenic proteins in steroid hormone metabolism, including StAR, CYP11A1, CYP17A1, 17β-HSD, CYP19A1. However, the alterations of these parameters were reversed by Que. MPEs caused male reproductive injuries in rats; Que. inhibited MPEs' male reproductive toxicity, which might relate to the improvement of testosterone biosynthesis.

Integrated Studies on Male Reproductive Toxicity of Bis(2-ethylhexyl)-tetrabromophthalate: in Silico, in Vitro, ex Vivo, and in Vivo

Bis(2-ethylhexyl)tetrabromophthalate (TBPH) has been widely detected in the environment and organisms; thus, its toxic effects on male reproduction were systematically studied. First, we found that TBPH can stably bind to the androgen receptor (AR) based on in silico molecular docking results and observed an antagonistic activity, but not agonistic activity, on the AR signaling pathway using a constructed AR-GRIP1 yeast assay. Subsequently, we validated the adverse effects on male germ cells by observing inhibited androgen production and proliferation in Leydig cells upon in vitro exposure and affected general motility and motive tracks of zebrafish sperm upon ex vivo exposure. Finally, the in vivo reproductive toxicity was demonstrated in male zebrafish by reduced mating behavior in F0 generation when paired with unexposed females and abnormal development of their offspring. In addition, reduced sperm motility and impaired germ cells in male zebrafish were also observed, which may be related to the disturbed homeostasis of sex hormones. Notably, the specifically suppressed AR in the brain provides further evidence for the antagonistic effects as above-mentioned. These results confirmed that TBPH affected male reproduction through a classical nuclear receptor-mediated pathway, which would be helpful for assessing the ecological and health risks of TBPH.

Development of Eco-Friendly Biocomposite Films Based on Opuntia ficus-indica Cladodes Powder Blended with Gum Arabic and Xanthan Envisaging Food Packaging Applications

Currently, food packaging is facing a critical transition period and a major challenge: it must preserve the food products' quality and, at the same time, it must meet the current requirements of the circular economy and the fundamental principles of packaging materials eco-design. Our research presents the development of eco-friendly packaging films based on Opuntia ficus-indica cladodes (OFIC) as renewable resources. OFIC powder (OFICP)-agar, OFICP-agar-gum arabic (GA), and OFICP-agar-xanthan (XG) blend films were eco-friendlily prepared by a solution casting method. The films' properties were investigated by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (X-RD), and differential scanning calorimeter (DSC). Water solubility and moisture content were also determined. Morphology, thickness, molecular interactions, miscibility, crystallinity, and thermal properties, were affected by adjusting the gums (GA and XG) content and glycerol in the blend films. Moisture content increased with increasing glycerol and XG content, and when 1.5 g of GA was added. Water solubility decreased when glycerol was added at 50% and increased with increasing GA and XG content. FTIR and XRD confirmed strong intermolecular interactions between the different blend film compounds, which were reflected in the shifting, appearance, and disappearance of FTIR bands and XRD peaks, indicating excellent miscibility. DSC results revealed a glass transition temperature (Tg) below room temperature for all prepared blend films, indicating that they are flexible and soft at room temperature. The results corroborated that the addition of glycerol at 30% and the GA to the OFICP increased the stability of the film, making it ideal for different food packaging applications.

Combined cytotoxicity of phthalate esters on HepG2 cells: A comprehensive analysis of transcriptomics and metabolomics

Phthalate esters (PAEs), widely used as plasticizers, may pose a potential environmental and human hazard. The aim of this study was to compare the cytotoxicity of di(2-ethylhexyl) phthalates (DEHP) and dibutyl phthalate (DBP)) after their exposure to HepG2 cells alone or in combination. HepG2 cells treated with individual/combined DEHP and DBP at a dose of 10-2 M for 24 h were selected for metabolome and transcriptome analysis. The results demonstrated that exposure to the mixtures of DEHP and DBP caused enhanced or reduced toxic effects regarding 8 pathways with 1065 downregulated genes and 643 upregulated genes, in comparison with those of single chemicals. The combined toxicity of mixture revealed both synergistic and antagonistic interactions between DEHP and DBP. Besides, combined exposure to DEHP and DBP promoted TCA cycle, pyrimidine, and purine metabolism, while an antagonistic effect on fatty acid derangement should require further investigation. To summarize, our results suggest that DEHP exposed alone or combined with DBP caused a variety of metabolic disorders, and the type of combination effects varied among metabolic pathways.

Effect of prenatal perfluoroheptanoic acid exposure on spermatogenesis in offspring mice

BACKGROUND

Perfluoroheptanoic acid (PFHpA), a persistent organic pollutant widespread in the environment, is suspected as an environmental endocrine disruptor for its disturbance effect on hormone homeostasis and reproductive development. Whereas the effect of intrauterine PFHpA exposure during gestation on spermatogenesis of male offspring mice is still unknown.

OBJECTIVE

This study aimed to explore the effect of prenatal PFHpA exposure on the reproductive development of male offspring mice and the role of N⁶-methyladenosine (m⁶A) during the process.

METHODS

Fifty-six C57BL/6 pregnant mice were randomly divided into 4 groups. During the gestation period, the pregnant mice were exposed to 0, 0.0015, 0.015, and 0.15 mg/kg bw/d PFHpA from gestational day 1 (GD1) to GD16 by oral gavage. The male offspring mice were sacrificed by spinal dislocation at 7 weeks old. The body weight, testicular weight, and brain weight were weighed, and the intra-testicular testosterone was detected. The sperm qualities were analyzed with computer-aided sperm analysis (CASA). The testicular tissues were taken to analyze the pathological changes and examine the global m⁶A RNA methylation levels. Quantitative real-time PCR (qRT-PCR) was adopted to figure out the mRNA expression levels of m⁶A-related enzymes in testicular tissues of different PFHpA treated groups. Methylated RNA immunoprecipitation sequencing (MeRIP-seq) was applied to further explore the m⁶A RNA methylation at a whole-genome scale.

RESULTS

Compared with the control group, no significant differences were observed in body weight, testicular weight, testicular coefficient, and the visceral-brain ratio of testicular tissue in the PFHpA treated groups. And no significant change was observed in intra-testicular testosterone among the four groups. CASA results showed a decrease of sperm count, sperm concentration, and total cell count, as well as an increase of sperm progressive cells' head area after prenatal PFHpA exposure (P < 0.05). Hematoxylin and eosin staining of pathological sections showed seminiferous tubules morphological change, disorder arrangement of seminiferous epithelium, and reduction of spermatogenic cells in the PFHpA treated groups. PFHpA significantly decreased global levels of m⁶A RNA methylation in testicular tissue (P < 0.05). Besides, qRT-PCR results showed significant alteration of the mRNA expression levels of seven m⁶A-related enzymes (Mettl3, Mettl5, Mettl14, Pcif1, Wtap, Hnrnpa2b1, and Hnrnpc) in the PFHpA treated groups (P < 0.05). MeRIP-seq results showed a correlation between prenatal PFHpA exposure and activation and binding of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP). Cnga3 and Mpzl3 showed differential expression in the enrichment subcategories or pathways.

CONCLUSIONS

Exposure to PFHpA during the gestation period would adversely affect the development of seminiferous tubules and testicular m⁶A RNA methylation in offspring mice, which subsequently interferes with spermatogenesis and leads to reproductive toxicity.

Phthalate exposure with sperm quality among healthy Chinese male adults: The role of sperm cellular function

Adverse male reproduction caused by phthalate ester (PAE) exposure has been well documented in vivo. However, existing evidence from population studies remains inadequate to demonstrate the impact of PAE exposure on spermatogenesis and underlying mechanisms. Our present study aimed to explore the potential link between PAE exposure and sperm quality and the possible mediation by sperm mitochondrial and telomere in healthy male adults recruited from the Hubei Province Human Sperm Bank, China. Nine PAEs were determined in one pooled urine sample prepared from multiple collections during the spermatogenesis period from the same participant. Sperm telomere length (TL) and mitochondrial DNA copy number (mtDNAcn) were determined in sperm samples. The sperm concentration and count per quartile increment in mixture concentrations were -4.10 million/mL (-7.12, -1.08) and -13.52% (-21.62%, -4.59%), respectively. We found one quartile increase in PAE mixture concentrations to be marginally associated with sperm mtDNAcn (β = 0.09, 95% CI: -0.01, 0.19). Mediation analysis showed that sperm mtDNAcn significantly explained 24.6% and 32.5% of the relationships of mono-2-ethylhexyl phthalate (MEHP) with sperm concentration and sperm count (β = -0.44 million/mL, 95% CI: -0.82, -0.08; β = -1.35, 95% CI: -2.54, -0.26, respectively). Our study provided a novel insight into the mixed effect of PAEs on adverse semen quality and the potential mediation role of sperm mtDNAcn.

Reproductive toxicity of maternal exposure to di(2-ethylhexyl)phthalate and butyl paraben (alone or in association) on both male and female Wistar offspring

Parabens and phthalates are commonly found as contaminants in human fluids and are able to provoke reproductive toxicity, being considered endocrine disruptors. To evaluate the effects of phthalate and paraben, alone or in combination, on reproductive development of the offspring, female pregnant Wistar rats were allocated in six experimental groups: Three control groups (gavage [CG], subcutaneous [CS], and gavage + subcutaneous) received corn oil as vehicle, and the remaining groups were exposed to di(2-ethylhexyl)phthalate (DEHP) (500 mg/kg, gavage), butyl paraben (BP) (100 mg/kg, subcutaneously), or MIX (DEHP + BP), from Gestational Day 12 until Postnatal Day (PND) 21. The following parameters were assessed on the offspring: anogenital distance and weight at PND 1, nipple counting at PND 13, puberty onset, estrous cycle, weights of reproductive and detoxifying organs, histological evaluation of reproductive organs, and sperm evaluations (counts, morphology, and motility). Female pups from MIX group presented reduced body weight at PND 1, lower AGD, and decreased endometrium thickness. Male animals showed decreased body weight at PND 1 and lower number of Sertoli cells on DEHP and MIX groups, MIX group revealed increase of abnormal seminiferous tubules, DEHP animals presented delayed preputial separation and higher percentage of immotile sperms, and BP males presented diminished number of Leydig cells. In conclusion, the male offspring was more susceptible to DEHP toxicity; even when mixed to paraben, the main negative effects observed seem to be due to antiandrogenic phthalate action. On the other hand, DEHP seems to be necessary to improve the effects of BP on reducing estrogen-dependent and increasing androgen-dependent events.

Applying the adverse outcome pathway concept for assessing non-monotonic dose responses: biphasic effect of bis(2-ethylhexyl) phthalate (DEHP) on testosterone levels

Male reproduction is one of the primary health endpoints identified in rodent studies for some phthalates, such as DEHP (Bis(2-ethylhexyl) phthalate), DBP (Dibutyl phthalate), and BBP (Benzyl butyl phthalate). The reduction in testosterone level was used as an intermediate key event for grouping some phthalates and to establish a reference point for risk assessment. Phthalates, and specifically DEHP, are one of the chemicals for which the greatest number of non-monotonic dose responses (NMDRs) are observed. These NMDRs cover different endpoints and situations, often including testosterone levels. The presence of NMDR has been the subject of some debate within the area of chemical risk assessment, which is traditionally anchored around driving health-based guidance values for apical endpoints that typically follow a clear monotonic dose-response. The consequence of NMDR for chemical risk assessment has recently received considerable attention amongst regulatory agencies, which confirmed its relevance particularly for receptor-mediated effects. The present review explores the relationship between DEHP exposure and testosterone levels, investigating the biological plausibility of the observed NMDRs. The Adverse Outcome Pathway (AOP) concept is applied to integrate NMDRs into Key Event Relationships (KERs) for exploring a mechanistic understanding of initial key events and possibly associated reproductive and non-reproductive adverse outcomes.

Urinary concentrations of polycyclic aromatic hydrocarbon and phthalate metabolite mixtures in relation to semen quality among men attending an infertility clinic

Previous studies have reported that exposure to phthalates and polycyclic aromatic hydrocarbons (PAHs) is individually associated with altered semen quality, but no human studies have evaluated their joint effects of exposure mixtures, a more real-world scenario. We aimed to explore urinary metabolite mixtures of phthalates and PAHs in associations with semen quality. Repeated spot-urine samples gathered from 695 men attending a fertility clinic were analyzed for urinary metabolites of eight phthalates and ten monohydroxylated-PAHs (OH-PAHs). Principal component analysis (PCA)-multivariable linear regression (MLR) model, quantile g-computation (qg-comp), and Bayesian kernel machine regression (BKMR) were applied to estimate the associations of urinary mixtures of phthalate and OH-PAH metabolites with semen quality. The overall effects of urinary mixtures of phthalate and PAH metabolites on semen quality were not statistically significant. However, hydroxynaphthalene (OHNa) factor identified from PCA was monotonically associated with decreased total sperm count and sperm concentration, whereas di(2-ethylhexyl) phthalate (DEHP) factor was non-monotonically related to increased progressive sperm motility and total sperm motility. Qg-comp and BKMR models confirmed these findings and identified 2-OHNa and 2-OHFlu as the primary negative contributors, whereas MEOHP and MEHP as the primary positive contributors. Our findings suggest that exposure to mixtures of naphthalene and DEHP is associated with altered semen quality. The finding is warranted to confirm in further well-designed epidemiological studies.

Associations of environmental phthalate exposure with male steroid hormone synthesis and metabolism: An integrated epidemiology and toxicology study

Humans are simultaneously and constantly exposed to various lipophilic chain phthalate acid esters. The association of urinary phthalate metabolites with altered male steroid hormone synthesis and metabolism was examined using epidemiology and toxicology studies. We measured 8 phthalate metabolites [monomethyl phthalate (MMP), monoethyl phthalate (MEP), mono-n-butyl phthalate (MBP), mono-benzyl phthalate (MBzP), mono-n-octylphthalate (MOP), mono-(2-ethylhexyl) phthalate (MEHP), mono-(2-ethyl-5-hydroxyhexyl) phthalate (MEHHP) and mono (2-ethyl-5-oxohexyl) phthalate (MEOHP)] and two sex hormones [testosterone (T) and estradiol (E₂)] in single serum and repeated spot urine samples among 451 reproductive-age males. Moreover, in vitro experiments with Leydig cell MLTC-1 steroidogenesis and liver cell HepG2 efflux in response to mixed and individual phthalates were designed to simulate real-world scenarios of human exposure. As a joint mixture, the phthalate metabolite was inversely associated with serum T and E₂ concentrations but positively associated with urinary T and E₂ concentrations. Combined with in vitro experiments, DEHP metabolites were identified as the predominant contributor to the decline in hormone synthesis, and ATP-binding cassette (ABC) gene activation might be involved in hormone excretion. Exposure to environmentally relevant phthalates was associated with both altered steroid synthesis and excretion, which provides additional insights into the endocrine-disrupting potential of phthalates.

Lactic acid bacteria alleviate di-(2-ethylhexyl) phthalate-induced liver and testis toxicity via their bio-binding capacity, antioxidant capacity and regulation of the gut microbiota

Di-(2-ethylhexyl) phthalate (DEHP) is a plasticiser that, if absorbed into the human body, can cause various adverse effects including reproductive toxicity, liver toxicity and gut microbiota dysbiosis. So far, some studies have proved that the toxicity of DEHP can be reduced by using antioxidants. However, these candidates all show potential side effects and cannot prevent the accumulation of DEHP in the body, making them unable to be used as a daily dietary supplement to relieve the toxic effects of DEHP. Lactic acid bacteria (LAB) have antioxidant capacity and the ability to adsorb harmful substances. Herein, we investigated the protective effects of five strains of LAB, selected based on our in vitro assessments on antioxidant capacities or bio-binding capacities, against the adverse effects of DEHP exposure in rats. Our results showed that LAB strains with outstanding DEHP/MEHP binding capacities, Lactococcus lactis subsp. lactis CCFM1018 and Lactobacillus plantarum CCFM1019, possess the ability to facilitate the elimination of DEHP and its metabolite mono-(2-ethylhexyl) phthalate (MEHP) with the faeces, decrease DEHP and MEHP level in serum further. Meanwhile, DEHP-induced liver and testicular injuries were effectively alleviated by CCFM1018 and CCFM1019. In addition, CCFM1018 effectively alleviated the DEHP-induced oxidative stress with its strong antioxidant ability. Furthermore, both CCFM1018 and CCFM1019 modulated the gut microbiota, which in turn increased the concentrations of faecal propionate and butyrate and regulated the pathways related to host metabolism. Correlation analysis indicate that DEHP/MEHP bio-binding capacity of LAB plays a crucial role in protecting the body from DEHP exposure, and its antioxidant capacity and the ability to alleviate the gut microbiota dysbiosis are also involved in the alleviation of damage. Thus, LAB with powerful bio-binding capacity of DEHP and MEHP can be considered as a potential therapeutic dietary strategy against DEHP exposure.

Trans-disciplinary diagnosis for an in-depth reform of regulatory expertise in the field of environmental toxicology and security

Repeated health and environmental scandals, the loss of biodiversity and the recent burst of chronic diseases constantly remind us the inability of public authorities and risk assessment agencies to protect health and the environment. After reviewing the main shortcomings of our evaluation system of chemicals and new technologies, supported by some concrete examples, we develop a number of proposals to reform both the risk assessment agencies and the evaluation processes. We especially propose the establishment of an independent structure, a High Authority of Expertise, supervising, either at European level or at national level, all the evaluation agencies, and ensuring the transparency, the methodology and the deontology of the expertise. In addition to modifying the evaluation protocols, both in their nature and in their content, especially in order to adapt them to current pollutants such as endocrine disruptors, we propose a reform of the expertise processes based on transparency, contradiction, and greater democracy, including close collaboration between the institutional and scientific parties on the one hand and the whole civil society on the other. All the proposals we make are inspired by the desire to prevent, through appropriate mechanisms, the human, health, ecological, but also economic consequences of contemporary technological choices.

Relationship between endocrine disruptors and obesity with a focus on bisphenol A: a narrative review

Introduction: Scientific data suggest that early exposure to endocrine-disrupting chemicals (EDCs) affect -repro, -neuro, -metabolic systems, to which are added other notions such as mixtures, window and duration of exposure, trans-generational effects, and epigenetic mechanisms. Methods: In the present narrative review, we studied the relationship between exposure to EDCs with the appearance and development of obesity. Results: Exposure to EDCs like Bisphenol A during the early stages of development has been shown to lead to weight gain and obesity. EDCs can interfere with endocrine signaling, affect adipocytes differentiation and endocrine function and disrupt metabolic processes, especially if exposure occurs at very low doses, in the mixture, during early development stages for several generations. Conclusion: Exposure to EDCs is positively associated with obesity development. Moreover, the use of integrative approaches which mimicking environmental conditions are necessary and recommended to evaluate EDCs' effects in future studies.

Folpet induces mitochondrial dysfunction and ROS-mediated apoptosis in mouse Sertoli cells

Folpet is a phthalimide type of fungicide and has been used to control several crop diseases. Although it has adverse effects on the gastrointestinal tract, its mechanism and toxic effects on testis have not been demonstrated. In the present study, we elucidated the cytotoxic effect of folpet on the mouse Sertoli cell line, TM4. Our results revealed that folpet suppressed viability and proliferative capacity of TM4 cells and further inhibited 3D spheroid formation. Moreover, folpet impeded appropriate cell cycle progression and induced apoptotic cell death in TM4 cells. It disrupted the electrochemical gradient of mitochondria and calcium homeostasis in TM4 cells. Furthermore, endoplasmic reticulum stress-related proteins were activated in folpet-treated TM4 cells, and relative reactive oxygen species (ROS) production was also increased. N-acetylcysteine (NAC) treatment reinstated the folpet-induced ROS generation in TM4 cells. Additionally, NAC restored the proliferative capacity and reduced the apoptotic cells in folpet-treated TM4 cells. Collectively, we demonstrated that folpet causes ROS-mediated apoptotic cell death with mitochondrial dysfunction and calcium dysregulation in TM4 cells.

Di-(2-ethylhexyl) phthalate induces testicular endoplasmic reticulum stress and germ cell apoptosis in adolescent mice

Di-(2-ethylhexyl) phthalate (DEHP) is a male reproductive toxicant. This research is aimed at investigating the effect of pubertal DEHP exposure on testicular endoplasmic reticulum (ER) stress and germ cell apoptosis. Five-week-old male mice were orally administered with DEHP (0, 0.5, 50, or 500 mg/kg/day) for 35 days. Testis weight and sperm count were reduced in mice exposed to 500 mg/kg/day DEHP. The number of seminiferous tubules in stages VII-VIII, mature seminiferous tubules, was reduced and the number of seminiferous tubules in stages IX-XII, immature seminiferous tubules, was elevated in mice treated with 500 mg/kg/day DEHP. Numerous apoptotic germ cells were observed in mouse seminiferous tubules exposed to 50 and 500 mg/kg/day DEHP. Moreover, cleaved caspase-3 was elevated in mouse testes exposed to 500 mg/kg/day DEHP. In addition, Bcl-2 was reduced and Bax/Bcl-2 was elevated in mouse testes exposed to 500 mg/kg/day DEHP. Additional experiment showed that GRP78, an ER molecular chaperone, was downregulated in mouse testes exposed to 500 mg/kg/day DEHP. Testicular p-IRE-1α, p-JNK, and CHOP, three markers of ER stress, were upregulated in mice exposed to 500 mg/kg/day DEHP. These results suggest that pubertal exposure to high doses of DEHP induces germ cell apoptosis partially through initiating ER stress in testes.

Multiple transcriptomic profiling: p53 signaling pathway is involved in DEHP-induced prepubertal testicular injury via promoting cell apoptosis and inhibiting cell proliferation of Leydig cells

Di(2-ethylhexyl) phthalate (DEHP) is a widely-used plasticizer and has long been recognized as an endocrine-disrupting chemical with male reproductive toxicities. DEHP exposure at the prepubertal stage may lead to extensive testicular injury. However, the underlying mechanisms remain to be elucidated. In the present study, we gavaged male C57BL/6 mice with different concentrations of DEHP (0, 250, and 500 mg/kg-bw·d) from postnatal day 22-35, and exposed TM3 Leydig cells with 0, 100, 200, 300, and 400 μM of MEHP (bioactive metabolite of DEHP) for 12-48 h. RNA sequencing was performed both in testicular tissue and TM3 cells. The results showed that DEHP disrupts testicular development and reduces serum testosterone levels in male prepubertal mice. Bioinformatic analysis and experimental verification have revealed that DEHP/MEHP induces cell cycle arrest in TM3 cells and increases apoptosis both in vivo and in vitro. Furthermore, the p53 signaling pathway was found to be activated upon DEHP/MEHP treatment. The inhibition of p53 by pifithrin-α significantly reduced MEHP-induced injuries in TM3 cells. Cumulatively, these findings revealed the involvement of the p53 signaling pathway in DEHP-induced prepubertal testicular injury by promoting cell apoptosis and inhibiting cell proliferation of Leydig cells.

Combining in vivo pathohistological and redox status analysis with in silico toxicogenomic study to explore the phthalates and bisphenol A mixture-induced testicular toxicity

The aim of this study was to: (i) determine and compare the capacity of bis (2 -ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), bisphenol A (BPA), and their mixture to produce testicular toxicity after the subacute exposure; (ii) explore the mechanisms behind the observed changes using in silico toxicogenomic approach. Male rats were randomly split into groups (n = 6): (1) Control (corn oil); (2) DEHP (50 mg/kg b.w./day); (3) DBP (50 mg/kg b.w./day); (4) BPA (25 mg/kg b.w./day); and (5) MIX (50 mg/kg b.w./day DEHP + 50 mg/kg b.w/day DBP + 25 mg/kg b.w./day BPA). Animals were sacrificed after 28 days of oral exposure, testes were extracted and prepared for histological assessments under the light microscope (haematoxylin and eosin staining) and redox status analysis. The Comparative Toxicogenomics Database (CTD; http://CTD.mdibl.org), Cytoscape software (https://cytoscape.org) and ToppGene Suite (https://toppgene.cchmc.org) were used for data-mining. Present pathohistological study has demonstrated more pronounced testicular toxicity of the MIX group (desquamated germinal epithelium cells, enlarged cells with hyperchromatic nuclei, multinucleated cell forms and intracytoplasmic vacuoles) in comparison with the single substances, while effects on redox status parameters were either more prominent, or present only in the MIX group. In silico investigation revealed 20 genes linked to male reproductive disorders, affected by all three investigated substances. Effects on metabolism, AhR pathway, apoptosis and oxidative stress could be singled out as the most probable mechanisms involved in the subacute DEHP, DBP and BPA mixture testicular toxicity, while the effect on oxidative stress parameters was confirmed by in vivo experiment.

Lycopene Ameliorates Di(2-ethylhexyl) Phthalate-Induced Pyroptosis in Spleen via Suppression of Classic Caspase-1/NLRP3 Pathway

Lycopene (Lyc) as a natural antioxidant has attracted widespread attention. Di(2-ethylhexyl) phthalate (DEHP) can cause serious spleen injury in animals via the environment and food chain. For investigation of whether Lyc could alleviate DEHP-exerted pyroptosis in spleen through inhibiting the Caspase-1/NLRP3 pathway activation, 140 male mice were randomly divided into 7 groups: control group, vehicle control group, Lyc group (5 mg/kg BW/day), DEHP-exposed group (500 or 1000 mg/kg BW/day, respectively), and DEHP + Lyc groups by daily administration for 28 days. Pathological results showed that the supplementation of Lyc alleviated DEHP-induced inflammatory infiltration. Moreover, the addition of Lyc inhibited DEHP-induced Caspase-1, NLRP3, ASC, NF-κB, IL-1β, and IL-18 overexpression and GSDMD down-expression. These results indicate that Lyc could inhibit DEHP-induced Caspase-1-dependent pyroptosis and the inflammatory response. Taken together, the study provided new evidence that Lyc may be a strategy to mitigate spleen injury induced by DEHP.

Exposure to benzo(a)pyrene from juvenile period to peripubertal impairs male reproductive parameters in adult rats

Benzo(a)pyrene (BaP) is a persistent organic pollutant and endocrine disruptor that can compromise the steroidogenesis process by interacting with the StAR protein, causing adverse effects on male reproduction. However, consequences of prepubertal BaP exposure and its impacts on adult life are yet unknown. This study investigated the effects of BaP exposure from the juvenile period to peripubertal on reproductive parameters in adult male rats. Males were exposed to 0; 0.1; 1 or 10 μg/kg/day of BaP from post-natal (PND) 23 to PND 53 (by gavage). The lowest dose of BaP was able to compromise the male copulatory behavior, as evidenced by the delay in the first mount, intromission and ejaculation. Furthermore, BaP-treated groups showed lower sperm quality (disrupted motility and morphology) and quantity, reduced relative weights of the thyroid and seminal gland. Serum testosterone levels and the Leydig cells nuclei volume were decreased by BaP exposure whereas the StAR expression was increased. Histopathological changes in the testis also were detected in the males exposed to BaP. These results showed that prepubertal BaP-exposure adversely influenced the male reproductive system in the adult life, indicating that a comprehensive risk assessment of BaP-exposure on prepubertal period is necessary.

Effects of pubertal exposure to low doses of di-(2-ethylexyl)phthalate on reproductive behaviors in male mice

Reproductive behaviors are tightly regulated by sex steroid hormones. Interference with these hormones or their neural signaling pathways leads to behavioral alterations. We have previously shown that oral exposure of adult male mice to di(2-ethylhexyl) phthalate (DEHP), an organic environmental endocrine disruptor, altered sexual behavior. In this study, we examined the effects of pubertal exposure to DEHP and analyzed whether pubertal and adult exposures to DEHP trigger long-term effects. For pubertal exposure, male mice were exposed orally to the vehicle or DEHP at 5 or 50 μg/kg/d from postnatal day (PND) 30 to PND60. Exposure was arrested and animals were analyzed on PND120. They exhibited normal olfactory preference but showed modified emission of ultrasonic vocalizations. DEHP exposure also affected partner preference and mating components. These modifications were associated with normal circulating testosterone levels and weight of androgen-sensitive tissues. In contrast, androgen receptor (AR) protein amount was reduced in the hypothalamic preoptic area in particular for the DEHP-50 group. Pubertal exposure also increased the anxiety-state level without changing circadian activity. When adult male mice were exposed to DEHP at the same doses from PND60 to PND105 and analyzed two months later, no effects of treatment on reproductive and anxiety-related behaviors or hypothalamic AR protein amount were seen. Our data show that pubertal exposure of male mice to DEHP induces long-term behavioral changes in contrast to the adult exposure. This highlights the sensitivity of the nervous system to low doses of DEHP during the critical period of puberty.

Increased m6A modification of RNA methylation related to the inhibition of demethylase FTO contributes to MEHP-induced Leydig cell injury☆

N⁶-methyladenosine (m6A) modification, the most prevalent form of RNA methylation, modulates gene expression post-transcriptionally. Di-(2-ethylhexyl) phthalate (DEHP) is a common environmental endocrine disrupting chemical that induces testicular injury due to the inhibition of the demethylase fat mass and obesity-associated protein (FTO) and increases the m6A modification. How FTO-mediated m6A modification in testicular Leydig cell injury induced by DEHP remains unclear. Here, the TM3 Leydig cell line was treated with mono-(2-ethylhexyl) phthalate (MEHP), the main metabolite of DEHP in the body, as well as FB23-2, an inhibitor of FTO. Decreased levels of testosterone in the culture supernatant, significantly increased apoptosis, and a remarkable upregulation of global m6A modification were found in both TM3 cells treated with MEHP and FB23-2. Transcriptome sequencing showed that both treatments significantly induced apoptosis-associated gene expression. Methylated RNA immunoprecipitation sequencing showed that the Leydig cell injury induced by upregulated m6A modification could be associated with multiple physiological disorders, including histone acetylation, reactive oxygen species biosynthesis, MAPK signaling pathway, hormone secretion regulation, autophagy regulation, and male gonadal development. Overall, the inhibition of FTO-mediated up-regulation of m6A could be involved in MEHP-induced Leydig cell apoptosis.

Toluene induces hormetic response of soil alkaline phosphatase and the potential enzyme kinetic mechanism

Hormesis of soil enzyme that involved in heavy metal has been attracting much more attention for risk assessment of heavy metal toxicity, but insufficient studies were conducted to define the hormetic responses induced by toluene or other organic pollutions. The objectives of this study were to investigate the hormetic responses of soil enzyme induced by toluene and explore the potential enzyme kinetic mechanism. Soil alkaline phosphatase (ALP) activity was regarded as the endpoint to explore the hormetic responses under different doses of toluene (0.0, 0.1, 0.5, 1.0, 2.0, 3.0, 5.0, 10.0, 50.0 and 100.0 μL g^-1). Subsequently, we conducted the experiments of enzymatic reaction kinetics and pure enzyme to further verify the potential mechanisms of soil ALP's hormesis. Results showed that ALP activities at 0.1-1.0 μL g^-1 toluene were significantly increased in contrast to the control (0 μL g^-1 toluene) (P < 0.05) at the exposure time of 30, 36, 48 and 54 h, with the maximum stimulation magnitudes of 24-43%. ALP activities were almost not affected by toluene (2-100 μL L^-1) in the whole experimental period (6-54 h). Meanwhile, the values of catalytic efficiency (the radio V_max/K_m, V_max: maximum reaction velocity and K_m: Michaelis constant) and V_max significantly increased compared with the control, but the value of K_m decreased from 2.5 to 1.6. Overall, low dose toluene can induce hormesis of soil ALP. The potential reason is that low-dose toluene could enhance the combination of soil ALP and substrates. We believe that this study will provide a new viewpoint for ecological risk assessment of toluene contaminated soils.

Ameliorative effect of selenium nanoparticles on the structure and function of testis and in vitro embryo development in Aflatoxin B1-exposed male mice

The purpose of the research was to investigate the therapeutic ability of selenium nanoparticles (Se-NPs) on the aflatoxin B1 (AFB1) toxicity induced in the male reproductive system. For this experiment, the mature male mice were put into four groups. Control (0.5 ml PBS, 60 days; IP, n = 7), Se-NPs (0.5 µg kg^-1  day^-1 for 60 days; IP), AFB1 (4.5 mg kg^-1  day^-1 for 60 days; IP) and AFB1 + Se-NPs (4.5 mg kg^-1  day^-1  + 0.5 µg kg^-1  day^-1 for 60 days; IP). After treatment, the histological structure of testis, serum testosterone level and sperm parameters, including concentration, motility, viability, morphology and DNA fragmentation, were examined. The results demonstrated that the AFB1 destroyed the testicular tissue structure and decreased the sperm concentration, motility, viability and normal morphology significantly. AFB1 also could significantly increase sperm DNA fragmentation and reduce in vitro fertilisation and embryo development compared to the control group (p < .001). Our data show that Se-NPs could inhibit AFB1-induced damage to the testis and improve sperm parameters as well as in vitro fertilisation and embryo production in AFB1 exposed male mice. This study revealed that the administration of Se-NPs could attenuate the testicular injury of AFB1 and improve the male reproductive system function in AFB1 exposed mice.

Citrate ester substitutes for di-2-ethylhexyl phthalate: In vivo reproductive and in vitro cytotoxicity assessments

Di-2-ethylhexyl phthalate (DEHP) is frequently used as a plasticizer for wrapping films, in toys, and in medical devices. Previous studies demonstrated that DEHP in mouse reduced testicular and epididymis weights, suppressed levels of serum testosterone, luteinizing hormone, and follicle-stimulating hormone, and decreased synthesis of testosterone by Leydig cells. Due to these anti-androgenic effects of DEHP on the reproductive system, the aim of this study was to examine whether substitutes such as acetyl triethyl citrate (ATEC) and acetyl tributyl citrate (ATBC) also damaged the reproductive system. In particular, this study investigated the anti-androgenic effects and cytotoxicity of DEHP substitutes using castrated male Sprague--Dawley rats employing the in vivo Hershberger assay and in vitro mouse Leydig (TM3) cells and mouse fibroblast (NIH-3T3) cell lines. In the Hershberger assay, rats were administered testosterone propionate and ATEC or ATBC at 20, 100, or 500 mg/kg b.w./day or DEHP (500 mg/kg b.w./day). Controls received testosterone antagonist flutamide (positive control), testosterone only (negative control), or corn oil only (vehicle control). ATEC/ATBC treatment produced no significant differences compared with testosterone in 5-androgen-dependent tissues weights including ventral prostate, seminal vesicles, levator ani-bulbocavernosus muscle, Cowper's glands, and glans penis. In the 500 mg/kg ATBC group, there was a significant reduction in liver weight. The MTT assay revealed that cell viability of both TM3 and NIH-3T3 cells treated with ATEC was not markedly altered. However, ATBC significantly reduced TM3 and NIH-3T3 cell viability in a concentration-dependent manner. Further, ATBC reduced cell viability to greater extent in TM3 versus NIH-3T3 cells. Based upon the observed effects of citrate ester substitutes on reproductive tissue responses and cytotoxicity, ATEC compared to ATBC may be a better alternative to DEHP for potential commercial uses.

ABBREVIATIONS

ATEC: acetyl triethyl citrate; ATBC: acetyl tributyl citrate; CG: Cowper's glands; DEHP: di-2-ethylhexyl phthalate; DMEM: Dulbecco's modified Eagle's medium; DMSO: dimethyl sulfoxide; GP: glans penis; LABC: levator ani-bulbocavernosus muscle; MTT: methyl tetrazolium; NC: negative control; NT: untreated control; PC: positive control; SV: seminal vesicle; TP: testosterone propionate; VC: vehicle control; VP: ventral prostate.

Aryl Hydrocarbon Receptor as a Target for Lycopene Preventing DEHP-Induced Spermatogenic Disorders

Di(2-ethylhexyl)phthalate (DEHP) is widely used as a plasticizer to improve product flexibility and workability. Lycopene (LYC) is a natural compound and has promising preventive potentials, especially antireproductive toxicity, but the specific underlying mechanism is yet to be fully defined. Our study investigated the effect of LYC on DEHP-induced spermatogenesis disorders. Male ICR mice were treated with DEHP (500 or 1000 mg/kg BW/day) and/or LYC (5 mg/kg BW/day) for 28 days. Our results indicated that LYC could relieve the DEHP-induced injury of seminiferous tubules and spermatogenic cells, swelling of endoplasmic reticulum (ER), and an increase of mitochondria. LYC prevented increased levels of nuclear damage to DNA and the deformity rate and decreased values of sperm motility, number, and density. Moreover, LYC treatment decreased DEHP-induced nuclear accumulation of aryl hydrocarbon receptor (AHR) and AHR nuclear translocator (ARNT), and the expressions of their downstream target genes such as cytochrome P450-dependent monooxygenases (CYP) 1A1, 1A2, and 1B1 were markedly reduced to normal in the LYC treatment group. Our study showed that LYC can prevent DEHP-induced spermatogenic disorders via an AHR/ARNT signaling system. This study provided new evidence of AHR as a target for LYC, which can prevent DEHP-induced toxicity.

Mediation of the relationship between phthalate exposure and semen quality by oxidative stress among 1034 reproductive-aged Chinese men

BACKGROUND

Emerging evidence from animals indicates that oxidative stress plays a crucial role in the effects of phthalate exposure on male reproductive dysfunctions, which has never been thoroughly explored in humans.

OBJECTIVE

To explore the potential mediating role of oxidative stress in the association of phthalate exposure with semen quality among 1034 Chinese men.

METHOD

Repeated urine samples gathered from the male partners of sub-fertile couples were analyzed for 3 oxidative stress markers [8-hydroxy-2-deoxyguanosine (8-OHdG), 8-iso-prostaglandin F_2α (8-isoPGF_2α) and 4-hydroxy-2-nonenal-mercapturic acid (HNE-MA)], using a liquid chromatography-tandem mass spectrometry. Multivariate regression models were constructed to evaluate the associations of urinary oxidative stress markers with urinary phthalate metabolites and semen quality. We also explored the potential mediation effects by oxidative stress markers.

RESULTS

Significantly positive dose-dependent relationships were observed between each individual phthalate metabolite and all analyzed oxidative stress markers (all p for trend<0.05), except for monoethyl phthalate (MEP) in relation to HNE-MA. Additionally, significantly or suggestively inverse dose-dependent relationships were exhibited between urinary 8-isoPGF_2α and sperm concentration (p for trend = 0.05), and between urinary 8-OHdG and percent of normal sperm morphology (p for trend = 0.01). Mediation analysis showed that urinary 8-isoPGF_2α suggestively mediated 12% of the inverse association between monobutyl phthalate (MBP) and sperm concentration, and that urinary 8-OHdG suggestively mediated 32% of the inverse association of MEP with percent of normal sperm morphology (both p < 0.10).

CONCLUSIONS

Although further investigations are required, our results suggest that oxidative stress may play a mediating role in the effects of phthalate exposure on impaired semen quality.

Biphasic effects of perfluorooctanoic acid on steroidogenesis in mouse Leydig tumour cells

Perfluorooctanoic acid (PFOA) is a persistent organic pollutant, which may possess endocrine disrupting properties. Herein, we investigated the possible mechanism(s) of toxicity and steroidogenesis in mouse Leydig cells. MLTC-1 (mouse Leydig tumour cells) cells were exposed to 0, 50, 100 or 200 μM PFOA for 48 h to ascertain their effects on the nuclear (membrane) receptor responses, steroidogenesis pathway and related regulated gene expression and steroid hormone secretion profiles. Our results reveal that nuclear receptors PXR, SR-B1 and LHR are sensitive to PFOA exposure. PFOA can accumulate in mitochondria and alter cholesterol precursor (fatty acid) mitochondrial transport process-related gene expression and thus inhibit steroid hormone precursor (cholesterol) production. In particular, PFOA exhibits biphasic effects on testosterone and progesterone production at differing levels of exposure. These findings indicate the potential endocrine-related effects of PFOA on steroid hormone secretion in Leydig cells and point to a novel disruption model.