Prepubertal Di-n-Butyl Phthalate Exposure Alters Sertoli and Leydig Cell Function and Lowers Bone Density in Adult Male Mice

Maternal exposure to Di-n-butyl phthalate (DBP) inhibit orexin receptor 1 (OX1R) expression to prevent Sertoli cells proliferation through the AKT signaling pathway

BACKGROUND

Studies have demonstrated that Sertoli cells are the direct target of Dibutyl phthalate (DBP). However, the role of neurotransmitter receptors is not elucidated.

METHODS

Based on our previous studies, maternal Sprague-Dawley (SD) rats in Gestation Day (GD) 14-18 and TM4 cells exposure to 750 mg/kg/day and 100 μM DBP were regarded as treated groups. Firstly, qRT-PCR array was used to determine the different expression of neurotransmitter receptors. We examined the OX1R expression on Rats in Control and DBP groups by immunohistochemistry. Real-time PCR and Western Blot were used to detect the protein and mRNA expression levels of OX1R in vivo and in vitro. The potential downstream signaling pathways were explored by analyzing the GSE99690 cohort. In addition, we extracted Primary Sertoli Cells (PSCs) from the testis of control group. The apoptosis-related proteins, AKT signaling pathway-related proteins and mRNA expressions were detected by Western Blot and Real-time PCR in PSCs. The validity of PSCs was measured by CCK-8 assay and flow cytometric analysis was used to demonstrate the apoptotic rates of PSCs after DBP exposure.

RESULTS

The Orexin receptor 1 (OX1R) was screened out by qRT-PCR array. Our results showed that DBP could significantly suppress the OX1R expression of Sertoli cells in vivo and in vitro. Functional analysis showed the AKT signaling pathway was mediated by OX1R. The highly expressed apoptosis level and impaired cell activity were observed in PSCs, which can be reversed by Orexin A. Meanwhile, the p-AKT signaling pathway were hindered after DBP exposure while rescued in DBP + Orexin-A group.

CONCLUSIONS

DBP can induce Sertoli cell apoptosis through its toxicological effect by suppressing OX1R and p-AKT expression, which provide a novel insight on the role of neurotransmitter receptors.

Effects of Endocrine-Disrupting Chemicals on Bone Health

This comprehensive review critically examines the detrimental impacts of endocrine-disrupting chemicals (EDCs) on bone health, with a specific focus on substances such as bisphenol A (BPA), per- and polyfluoroalkyl substances (PFASs), phthalates, and dioxins. These EDCs, by interfering with the endocrine system's normal functioning, pose a significant risk to bone metabolism, potentially leading to a heightened susceptibility to bone-related disorders and diseases. Notably, BPA has been shown to inhibit the differentiation of osteoblasts and promote the apoptosis of osteoblasts, which results in altered bone turnover status. PFASs, known for their environmental persistence and ability to bioaccumulate in the human body, have been linked to an increased osteoporosis risk. Similarly, phthalates, which are widely used in the production of plastics, have been associated with adverse bone health outcomes, showing an inverse relationship between phthalate exposure and bone mineral density. Dioxins present a more complex picture, with research findings suggesting both potential benefits and adverse effects on bone structure and density, depending on factors such as the timing and level of exposure. This review underscores the urgent need for further research to better understand the specific pathways through which EDCs affect bone health and to develop targeted strategies for mitigating their potentially harmful impacts.

Cytoprotective potency of naringin against di-n-butylphthalate (DBP)-induced oxidative testicular damage in male rats

The present study aimed to investigate the protective potential of naringin (NG) against di-n-butyl phthalate (DBP)- induced testicular damage and impairment of spermatogenesis in rats. Forty-two male Wistar albino rats were divided into six equal groups, and treated orally, 3 times weekly for 8 successive weeks. Control vehicle group was administrated olive oil, naringin-treated group was administered NG (80 mg/kg), DBP 250- and DBP 500- intoxicated groups received DBP (250 mg/kg) and (500 mg/kg), respectively, NG + DBP 250 and NG + DBP 500 groups received NG, an hour prior to DBP 250 and 500 administration. The results revealed that DBP induced dose-dependent male reproductive dysfunctions, included a significant decrease in the serum testosterone level concomitantly with significant decreases in the sperm count, viability, and total motility. Meanwhile, DBP significantly increased the testicular malondialdehyde level with significant reductions of glutathione content and catalase activity. Histopathologically, DBP provoked absence of spermatozoa, degenerative changes in the cell layers of seminiferous tubules and a significant decrease in the thickness of the seminiferous tubules epithelium. Conversely, the concomitant treatment with NG, one hour before DBP 250 or 500- intoxication mitigated the dose-dependent reproductive dysfunctions induced by DBP, evidenced by significant increases of serum testosterone level, sperm motility, count and viability along with marked improvement of the oxidant/antioxidant status and testicular histoarchitecture. In conclusion, the findings recorded herein proved that NG could mitigate DBP-induced testicular damage and impairment of spermatogenesis, suggesting the perspective of using NG as a natural protective and therapeutic agent for alleviating the reproductive dysfunctions and improving reproductive performance, mainly via its potent antioxidant activity.

Melatonin alleviates di-butyl phthalate (DBP)-induced ferroptosis of mouse leydig cells via inhibiting Sp2/VDAC2 signals

As one of the endocrine-disrupting chemicals (EDCs), dibutyl phthalate (DBP) has been extensively used in industry. DBP has been shown to cause damage to Leydig cells, yet its underlying mechanism remains elusive. In this study, we show that DBP induces ferroptosis of mouse Leydig cells via upregulating the expression of Sp2, a transcription factor. Also, Sp2 is identified to promote the transcription of Vdac2 gene by binding to its promoter and subsequently involved in DBP-induced ferroptosis of Leydig cells. In addition, DBP is proved to induce ferroptosis via inducing oxidative stress, while inhibition of oxidative stress by melatonin alleviates DBP-induced ferroptosis and upregulation of Sp2 and VDAC2. Taken together, our findings demonstrate that melatonin can alleviate DBP-induced ferroptosis of mouse Leydig cells via inhibiting oxidative stress-triggered Sp2/VDAC2 signals.

Role of mitochondrial disruption and oxidative stress in plasticizer phthalate-induced cytotoxicity to human bone osteoblasts

Phthalates are frequently utilized in a wide range of products such as plasticizers with reported negative effects on bones. The current study evaluated the effect of butyl cyclohexyl phthalate on the human osteoblasts via different assays. MTT and lactate dehydrogenase assays were used to examine the in-vitro cytotoxic effect of butyl cyclohexyl phthalate on human bone osteoblasts in concentrations 0.1, 1, 10, and 100 μM for 12 to 72 h postexposures. Incubation of osteoblasts with butyl cyclohexyl phthalate significantly reduced cell viability based on its concentrations and durations of exposure. In parallel, osteoblast secretion of procollagen type 1, osteocalcin, as well as alkaline phosphatase was significantly decreased by butyl cyclohexyl phthalate in concentrations (1 or 2 μM). Butyl cyclohexyl phthalate decreased ATP synthesis and mitochondrial complexes I and III activities, with increased lactate production, all of which were detrimental to cellular bioenergetics. The cellular redox defense systems were significantly depleted by increased lipid peroxidation, elevated reactive oxygen species, decreased catalase and superoxide dismutase enzymes activities, and decreased intracellular reduced glutathione (GSH). Redox stress was also induced. Interestingly, preincubating osteoblasts with reduced GSH before exposing them to butyl cyclohexyl phthalate significantly lowered the cytotoxicity of the butyl cyclohexyl phthalate, suggesting that antioxidants may play a helpful protective effect.

Joint effects of phenol, chlorophenol pesticide, phthalate, and polycyclic aromatic hydrocarbon on bone mineral density: comparison of four statistical models

Exposure to phenols, phthalates, pesticides, and polycyclic aromatic hydrocarbons (PAHs) can harm the skeleton. However, data about the joint effects of these chemicals' mixture on bone health are limited. The final analysis involved 6766 participants aged over 20 years recruited from the National Health and Nutrition Examination Survey. Generalized linear regression, weighted quantile sum (WQS) regression, Bayesian kernel machine regression (BKMR), and quantile g-computation (qgcomp) were performed to investigate the association of the urinary levels of chemicals (three phenols, two chlorophenol pesticides, nine phthalates, and six polycyclic aromatic hydrocarbon [PAH] metabolites) with bone mineral density (BMD) measurements and osteoporosis (OP) risk. Generalized linear regression identified that benzophenone-3, 2,4-dichlorophenol, mono-n-butyl phthalate, 1-napthol, 3-fluorene, 2-fluorene, and 1-phenanthrene were significantly associated with lower BMD and increased OP risk. The WQS index was negatively associated with total femur, femoral neck, and lumbar spine vertebra 1 (L1) BMD among all the participants, with corresponding β (95% confidence interval) values of -0.028 g/cm2 (-0.040, -0.017), -0.015 g/cm2 (-0.025, -0.004), and -0.018 g/cm2 (-0.033, -0.003). In the BKMR analysis, the overall effect of the mixture was significantly associated with femoral neck BMD among males and OP risk among females. The qgcomp model found a significant association between co-exposure and L1 BMD among all the participants and among males. Our study presents compelling epidemiological evidence that co-exposure to phenols, chlorophenol pesticides, phthalates, and PAHs is associated with reduced BMD and elevated OP risk. It provides epidemiologic evidence for the detrimental effects of these chemicals on bone health.

Developmental exposures to common environmental contaminants, DEHP and lead, alter adult brain and blood hydroxymethylation in mice

Introduction: The developing epigenome changes rapidly, potentially making it more sensitive to toxicant exposures. DNA modifications, including methylation and hydroxymethylation, are important parts of the epigenome that may be affected by environmental exposures. However, most studies do not differentiate between these two DNA modifications, possibly masking significant effects. Methods: To investigate the relationship between DNA hydroxymethylation and developmental exposure to common contaminants, a collaborative, NIEHS-sponsored consortium, TaRGET II, initiated longitudinal mouse studies of developmental exposure to human-relevant levels of the phthalate plasticizer di(2-ethylhexyl) phthalate (DEHP), and the metal lead (Pb). Exposures to 25 mg DEHP/kg of food (approximately 5 mg DEHP/kg body weight) or 32 ppm Pb-acetate in drinking water were administered to nulliparous adult female mice. Exposure began 2 weeks before breeding and continued throughout pregnancy and lactation, until offspring were 21 days old. At 5 months, perinatally exposed offspring blood and cortex tissue were collected, for a total of 25 male mice and 17 female mice (n = 5-7 per tissue and exposure). DNA was extracted and hydroxymethylation was measured using hydroxymethylated DNA immunoprecipitation sequencing (hMeDIP-seq). Differential peak and pathway analysis was conducted comparing across exposure groups, tissue types, and animal sex, using an FDR cutoff of 0.15. Results: DEHP-exposed females had two genomic regions with lower hydroxymethylation in blood and no differences in cortex hydroxymethylation. For DEHP-exposed males, ten regions in blood (six higher and four lower) and 246 regions (242 higher and four lower) and four pathways in cortex were identified. Pb-exposed females had no statistically significant differences in blood or cortex hydroxymethylation compared to controls. Pb-exposed males, however, had 385 regions (all higher) and six pathways altered in cortex, but no differential hydroxymethylation was identified in blood. Discussion: Overall, perinatal exposure to human-relevant levels of two common toxicants showed differences in adult DNA hydroxymethylation that was specific to sex, exposure type, and tissue, but male cortex was most susceptible to hydroxymethylation differences by exposure. Future assessments should focus on understanding if these findings indicate potential biomarkers of exposure or are related to functional long-term health effects.

Phthalates and bone mineral density: a systematic review

BACKGROUND

Exposure to endocrine disruptors, such as phthalates, may impact bone mineral density (BMD) through a variety of mechanisms. Studies of phthalate exposure and BMD in humans are scarce.

OBJECTIVES

To synthesize published data on the association between phthalate metabolites and BMD in humans and to provide methodological suggestions for future research.

METHODS

A single investigator searched PubMed for relevant studies, including observational studies of phthalate exposure and BMD in children and postmenopausal women. Twelve studies were screened with 5 meeting the eligibility criteria and included for review. A quality assessment form was used as a quality measure and key information was extracted from the included studies.

RESULTS

In one prospective study among postmenopausal women, higher levels of monocarboxyoctyl phthalate (MCOP) and monocarboxynonyl phthalate (MCNP) were significantly associated with lower BMD among nonusers of hormone therapy (HT). In cross-sectional studies of postmenopausal women, monoethyl phthalate (MEP), mono-n-butyl phthalate (MnBP), mono (3-carboxypropyl) phthalate (MCPP), and mono-benzyl phthalate (MBzP) were negatively associated with BMD, and MCNP was positively associated with BMD, but these results were not replicated across studies. In studies of fetal exposure to phthalates and childhood BMD, significant positive associations between MCPP and BMD in children at age 12 years were found in 1 study, while associations were null in the other study.

CONCLUSIONS

Studies among postmenopausal women provide suggestive evidence of an association between urinary phthalate metabolite concentration and decreased BMD. Results from studies of childhood BMD are inconclusive given the limited data and their limitations. More research is needed to address limitations and further investigate the association between phthalate exposure and human BMD.

Dibutyl phthalate causes MC3T3-E1 cell damage by increasing ROS to promote the PINK1/Parkin-mediated mitophagy

Dibutyl phthalate (DBP) is a plasticizer widely used in daily production, which causes serious environmental pollution, and damage to brain, liver, kidney, and lung by producing excessive reactive oxygen species (ROS) after entering the body. DBP can also cause skeletal dysplasia, but it is unclear whether ROS is involved. In addition, overproduction of ROS can activate mitophagy, which is an important mechanism for regulating mitochondrial quality and cell homeostasis. In order to investigate whether DBP can damage MC3T3-E1 cells (osteoblast cell line) and whether ROS and mitophagy are involved, DBP toxicity experiment, Parkin gene silencing experiment, and N-acetylcysteine (NAC) intervention experiment were performed on MC3T3-E1 cells in turn. First, we found that DBP caused MC3T3-E1 cell viability decline and osteogenic dysfunction, accompanied by the overproduction of ROS and the activation of mitophagy. Then, we found that silencing Parkin expression alleviated DBP-induced apoptosis and osteogenic dysfunction of MC3T3-E1 cells. In addition, NAC treatment inhibited the PINK1/Parkin-mediated mitophagy and alleviated the apoptosis and osteogenic dysfunction of MC3T3-E1 cells caused by DBP. Our research results showed that DBP could cause MC3T3-E1 cell damage by increasing ROS to promote the PINK1/Parkin-mediated mitophagy.

Associations of pregnancy phthalate concentrations and their mixture with early adolescent bone mineral content and density: The Health Outcomes and Measures of the Environment (HOME) study

BACKGROUND

The developing fetus may be particularly susceptibility to environmental osteotoxicants, but studies of pregnancy phthalate exposures and childhood bone health are scarce.

OBJECTIVES

To examine relations of pregnancy phthalate exposure biomarkers with early adolescent bone mineral density (BMD) and bone mineral content (BMC) in a prospective birth cohort.

METHODS

We used data from 223 pregnant mothers and their children enrolled in a Cincinnati, OH area cohort from 2003 to 2006. We quantified monoethyl phthalate (MEP), monoisobutyl phthalate, monobutyl phthalate, monobenzyl phthalate, mono-(3-carboxypropyl) phthalate (MCPP), and four metabolites of di-2-ethylhexyl phthalate in maternal urine collected at 16 and 26 weeks gestation, and calculated the average of creatinine-standardized concentrations. Using dual x-ray absorptiometry measures at age 12 years, we calculated BMD and BMC Z-scores for six skeletal sites. In overall and sex-stratified models, we estimated covariate-adjusted associations per 2-fold increase in phthalate biomarker concentrations using linear regression, and estimated joint effects of the phthalate biomarkers mixture using Bayesian kernel machine regression (BKMR) and quantile g-computation.

RESULTS

In single phthalate models, several biomarkers were positively associated with BMC and BMD. For example, each doubling of MEP and MCPP, 1/3rd distal radius BMD Z-score increased by 0.09 (95% CI: 0.01, 0.17) and 0.16 (95% CI: 0.01, 0.31), respectively. For phthalate mixtures, associations were generally U-shaped among males and positive-linear among females, using both statistical methods. Mixture associations were strongest with forearm sites: in BKMR models, increasing all biomarkers from the 50th to 90th percentile was associated with a 0.64 (95% CI: 0.01, 1.28) greater 1/3rd distal radius BMD Z-score in males, and a 0.49 (95% CI: -0.13, 1.10) greater ultradistal radius BMD Z-score in females.

DISCUSSION

In this study, phthalate exposures during gestation were associated with increased BMD Z-scores in early adolescence, though further research is needed to determine implications for long-term skeletal health.

Urinary Phthalate Biomarkers and Bone Mineral Density in Postmenopausal Women

CONTEXT

Phthalates are endocrine-disrupting chemicals that could disrupt normal physiologic function, triggering detrimental impacts on bone.

OBJECTIVE

We evaluated associations between urinary phthalate biomarkers and BMD in postmenopausal women participating in the prospective Women's Health Initiative (WHI).

METHODS

We included WHI participants enrolled in the BMD substudy and selected for a nested case-control study of phthalates and breast cancer (N = 1255). We measured 13 phthalate biomarkers and creatinine in 2 to 3 urine samples per participant collected over 3 years, when all participants were cancer free. Total hip and femoral neck BMD were measured at baseline and year 3, concurrent with urine collection, via dual-energy x-ray absorptiometry. We fit multivariable generalized estimating equation models and linear mixed-effects models to estimate cross-sectional and longitudinal associations, respectively, with stratification on postmenopausal hormone therapy (HT) use.

RESULTS

In cross-sectional analyses, mono-3-carboxypropyl phthalate and the sum of di-isobutyl phthalate metabolites were inversely associated with total hip BMD among HT nonusers, but not among HT users. Longitudinal analyses showed greater declines in total hip BMD among HT nonusers and with highest concentrations of mono-3-carboxyoctyl phthalate (-1.80%; 95% CI, -2.81% to -0.78%) or monocarboxynonyl phthalate (-1.84%; 95% CI, -2.80% to -0.89%); similar associations were observed with femoral neck BMD. Among HT users, phthalate biomarkers were not associated with total hip or femoral neck BMD change.

CONCLUSION

Certain phthalate biomarkers are associated with greater percentage decreases in total hip and femoral neck BMD. These findings suggest that phthalate exposure may have clinically important effects on BMD, and potentially fracture risk.

Low dose of fire retardant, 2,2',4,4'-tetrabromodiphenyl ether (BDE47), stimulates the proliferation and differentiation of progenitor Leydig cells of male rats during prepuberty

2,2',4,4'-Tetrabromodiphenyl ether (BDE47), a flame retardant, is extensively distributed in the food chain. However, whether BDE47 affects Leydig cell development during prepuberty remains unclear. BDE47 was daily gavaged to 21-day-old Sprague-Dawley male rats with 0 (corn oil), 0.1, 0.2, and 0.4 mg/kg for 14 days. BDE47 did not affect the body weight or testis weight of rats. It significantly increased serum testosterone level at 0.4 mg/kg, but decreased luteinizing hormone (LH) level without affecting estradiol level. BDE47 induced Leydig cell hyperplasia (the number of CYP11A1-positive Leydig cells increased), and up-regulated the expression of Scarb1, Star, Hsd11b1, Pcna, and Ccnd1 in the testis. BDE47 significantly reduced p53 and p21 levels but increased CCND1 level. It also markedly increased the phosphorylation of AKT1, AKT2, ERK1/2, and CREB. BDE47 significantly up-regulated the expression of Scarb1, Star, and Hsd11b1 and stimulated androgen production by immature Leydig cells from rats under basal, LH, and 8Br-cAMP stimulated conditions at 100 nM in vitro. In conclusion, BDE47 increased Leydig cell number and up-regulated the expression of Scarb1 and Star, thereby leading to increased testosterone synthesis.

Overexpression of miR-506-3p Aggravates DBP-Induced Testicular Oxidative Stress in Rats by Downregulating ANXA5 via Nrf2/HO-1 Signaling Pathway

Background

Di-N-butylphthalate (DBP) is a kind of unique endocrine toxicity linked to hormonal disruptions that affects the male reproductive system and has given rise to more and more attention. However, the mechanism of DBP-induced testicular injury remains unclear. Here, the objective of this study was to investigate the potential molecular mechanism of miR-506-3p in DBP-induced rat testicular oxidative stress injury via ANXA5 (Annexin A5)/Nrf2/HO-1 signaling pathway.

Methods

In vivo, a total of 40 adolescent male rats were treated from 2 weeks with 800 mg/kg/day of DBP in 1 mL/kg corn oil administered daily by oral gavage. Among them, some rats were also injected subcutaneously with 2 nmol agomir-506-3p and/or 10 nmol recombinant rat ANXA5. The pathomorphological changes of testicular tissue were assessed by histological examination, and the antioxidant factors were evaluated. Subsequently, ANXA5, Nrf2, and its dependent antioxidant enzymes, such as HO-1, NQO1, and GST, were detected by Western blotting or immunohistochemical staining. In vitro, TM3 cells (Leydig cells) were used to detect the cell activity by CCK-8 and the transfection in the DBP-treated group.

Results

Differentially expressed miRNAs between the DBP-treated and normal rats were analyzed, and qRT-PCR showed miR-506-3p was highly expressed in testicular tissues of the DBP-treated rats. DBP-treated rats presented severe inflammatory infiltration, increased abnormal germ cells, and missed cell layers frequently existed in seminiferous tubules, resulted in oxidative stress and decreased testicular function. Meanwhile, upregulation of miR-506-3p aggravated the above changes. In addition, miR-506-3p directly bound to ANXA5, and overexpression of miR-506-3p could reduce the ANXA5 expression and also decrease the protein levels of Nrf2/HO-1 signaling pathway. Additionally, we found that recombinant rat ANXA5 reversed the DBP-treated testicular oxidative stress promoting injury of miR-506-3p in rats. In vivo results were reproduced in in vitro experiments.

Conclusions

This study provided evidence that miR-506-3p could aggravate the DBP-treated testicular oxidative stress injury in vivo and in vitro by inhibiting ANXA5 expression and downregulating Nrf2/HO-1 signaling pathway, which might provide novel understanding in DBP-induced testicular injury therapy.

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.

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.

A strategy to validate a selection of human effect biomarkers using adverse outcome pathways: Proof of concept for phthalates and reproductive effects

Human biomonitoring measures the concentrations of environmental chemicals or their metabolites in body fluids or tissues. Complementing exposure biomarkers with mechanistically based effect biomarkers may further elucidate causal pathways between chemical exposure and adverse health outcomes. We combined information on effect biomarkers previously implemented in human observational studies with mechanisms of action reported in experimental studies and with information from published Adverse Outcome Pathways (AOPs), focusing on adverse reproductive effects of phthalate exposure. Phthalates constitute a group of chemicals that are ubiquitous in consumer products and have been related to a wide range of adverse health effects. As a result of a comprehensive literature search, we present an overview of effect biomarkers for reproductive toxicity that are substantiated by mechanistic information. The activation of several receptors, such as PPARα, PPARγ, and GR, may initiate events leading to impaired male and female fertility as well as other adverse effects of phthalate exposure. Therefore, these receptors appear as promising targets for the development of novel effect biomarkers. The proposed strategy connects the fields of epidemiology and toxicology and may strengthen the weight of evidence in observational studies that link chemical exposures to health outcomes.

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.

MiR-301b-3p/3584-5p enhances low-dose mono-n-butyl phthalate (MBP)-induced proliferation by targeting Rasd1 in Sertoli cells

To investigate the possible molecular mechanism of low concentration plasticizer mono-n-butyl phthalate (MBP) -induced juvenile Sertoli cells (SCs) proliferation, we evaluated global alterations of miRNA and mRNA expression in rat SCs treated with 0.1mM MBP. Microarray analysis revealed that miR-3584-5p and miR-301b-3p were up-regulated and their common target gene Dexamethasone-induced Ras-related protein 1 (Rasd1) was down-regulated. Further work suggested that SCs proliferation induced by low concentration MBP in vitro might be mediated by Rasd1 regulating ERK1/2 signaling pathway. The present study is first to investigate the effect of low-dose MBP on SCs proliferation and may enhance our understanding on the modes of action of low concentration MBP on male reproductive system. We hope the results will contribute to explain the causes of precocious puberty and testicular tumors induced by exogenous chemicals.