In vivo chronic and in vitro acute effects of di(2-ethylhexyl) phthalate on pseudopregnant rabbit corpora lutea: possible involvement of peroxisome proliferator-activated receptor gamma

Involvement of the peroxisome proliferator-activated receptor gamma (Pparγ) and matrix metalloproteinases-2 and -9 (Mmp-2 and -9) in the mechanism of action of di(2-ethylhexyl)phthalate (DEHP) in cultured mouse brain astrocytes and neurons

Di(2-ethylhexyl)phthalate (DEHP) is one of the most widely used phthalates in industry. It has been shown that, after entering the body, DEHP has the ability to cross the blood-placenta and blood-brain barriers. One of the proposed mechanisms of action of DEHP is the activation of peroxisome proliferator-activated receptors (PPARs). Many different functions of PPARγ in cells have been demonstrated, one of which is the modulation of the activation of matrix metalloproteinases (MMPs). The aim of this study was to investigate the role of Pparγ, Mmp-2, and Mmp-9 in the mechanism of action of DEHP. The experiments were performed on in vitro primary murine neurons and astrocytes. The results showed that DEHP has a pro-apototic effect on neurons, causing an increase in caspase-3 activity and in the number of apoptotic bodies. However, in astrocytes, the increase in caspase-3 activity was not related to the apoptosis process, as no increase in the formation of apoptotic bodies was observed. Moreover, DEHP increased the proliferation of astrocytes, which was confirmed by the increase in the amount and expression of the Ki-67 protein. In astrocytes, DEHP decreased the expression of the Pparγ and Mmp-9 proteins but increased the expression of the Mmp-2 protein. In DEHP neurons, it increased the expression of the Pparγ protein but decreased the expression of the Mmp-2 and Mmp-9 proteins.

Role of COX-2/PGE2 signaling pathway in the apoptosis of rat ovarian granulosa cells induced by MEHP

OBJECTIVE

MEHP, as the metabolite of DEHP, is a widely used environmental endocrine disruptor. Ovarian granulosa cells participate in maintaining the function of ovary and COX2/PGE2 pathway may regulate the function of granulosa cells. We aimed to explore how COX-2/PGE2 pathway affects cell apoptosis in ovarian granulosa cells caused by MEHP.

METHODS

Primary rat ovarian granulosa cells were treated with MEHP (0, 200, 250, 300 and 350 μM) for 48 h. Adenovirus was used for over-expression of COX-2 gene. The cell viability was tested with CCK8 kits. The apoptosis level was tested by flow cytometry. The levels of PGE2 were tested with ELISA kits. The expression levels of COX-2/PGE2 pathway related genes, ovulation-related genes and apoptosis-related genes, were measured with RT-qPCR and Western blot.

RESULTS

MEHP decreased the cell viability. After MEHP exposure, the cell apoptosis level increased. The level of PGE2 markedly decreased. The expression levels of COX-2/PGE2 pathway related genes, ovulation-related genes and anti-apoptotic genes decreased; the expression levels of pro-apoptotic genes increased. The apoptosis level was alleviated after over-expression of COX-2, and the level of PGE2 slightly increased. The expression levels of PTGER2 and PTGER4, and the levels of ovulation-related genes increased; the levels of pro-apoptotic genes decreased.

CONCLUSION

MEHP can cause cell apoptosis by down-regulating the levels of ovulation-related genes via COX-2/PGE2 pathway in rat ovarian granulosa cells.

PPARβ/δ Ligands Regulate Oxidative Status and Inflammatory Response in Inflamed Corpus Luteum-An In Vitro Study

Inflammation in the female reproductive system causes serious health problems including infertility. The aim of this study was to determine the in vitro effects of peroxisome proliferator-activated receptor-beta/delta (PPARβ/δ) ligands on the transcriptomic profile of the lipopolysaccharide (LPS)-stimulated pig corpus luteum (CL) in the mid-luteal phase of the estrous cycle using RNA-seq technology. The CL slices were incubated in the presence of LPS or in combination with LPS and the PPARβ/δ agonist-GW0724 (1 μmol/L or 10 μmol/L) or the antagonist-GSK3787 (25 μmol/L). We identified 117 differentially expressed genes after treatment with LPS; 102 and 97 differentially expressed genes after treatment, respectively, with the PPARβ/δ agonist at a concentration of 1 μmol/L or 10 μmol/L, as well as 88 after the treatment with the PPARβ/δ antagonist. In addition, biochemical analyses of oxidative status were performed (total antioxidant capacity and activity of peroxidase, catalase, superoxide dismutase, and glutathione S-transferase). This study revealed that PPARβ/δ agonists regulate genes involved in the inflammatory response in a dose-dependent manner. The results indicate that the lower dose of GW0724 showed an anti-inflammatory character, while the higher dose seems to be pro-inflammatory. We propose that GW0724 should be considered for further research to alleviate chronic inflammation (at the lower dose) or to support the natural immune response against pathogens (at the higher dose) in the inflamed corpus luteum.

Integrated Genomic and Bioinformatics Approaches to Identify Molecular Links between Endocrine Disruptors and Adverse Outcomes

Exposure to Endocrine Disrupting Chemicals (EDC) has been linked with several adverse outcomes. In this review, we examine EDCs that are pervasive in the environment and are of concern in the context of human, animal, and environmental health. We explore the consequences of EDC exposure on aquatic life, terrestrial animals, and humans. We focus on the exploitation of genomics technologies and in particular whole transcriptome sequencing. Genome-wide analyses using RNAseq provides snap shots of cellular, tissue and whole organism transcriptomes under normal physiological and EDC perturbed conditions. A global view of gene expression provides highly valuable information as it uncovers gene families or more specifically, pathways that are affected by EDC exposures, but also reveals those that are unaffected. Hypotheses about genes with unknown functions can also be formed by comparison of their expression levels with genes of known function. Risk assessment strategies leveraging genomic technologies and the development of toxicology databases are explored. Finally, we review how the Adverse Outcome Pathway (AOP) has exploited this high throughput data to provide a framework for toxicology studies.

Ovarian Toxicity and Epigenetic Mechanisms of Phthalates and Their Metabolites

Ovary plays an important role in the female reproductive system. The maintenance and regulation of ovarian function are affected by various physical and chemical factors. With the development of industrialization, environmental pollutants have caused great harm to public health. Phthalates, as a class of endocrine-disrupting chemicals (EDCs), are synthesized and used in large quantities as plasticizers due to their chemical properties. They are easily released into environment because of their noncovalent interactions with substances, causing human exposure and possibly impairing ovary. In recent years, more and more attention has been paid to the role of epigenetics in the occurrence and development of diseases. And it is urgent to study the role of methylation, gene imprinting, miRNA, and other epigenetic mechanisms in reproductive toxicology.

Evaluation of Triclosan Effects on Cultured Swine Luteal Cells

Simple Summary

A great concern has been raised against many chemicals, both natural and man-made, that can mimic or interfere with the hormones. Among these, using swine ovarian cells, we were aimed to explore the potential effect of triclosan, an antimicrobial agent widely used in cosmetics and home products. Our results demonstrate that triclosan disrupts cellular function, in particular interfering with hormone production and proliferation, thus suggesting a critical evaluation of its effects.

Abstract

Triclosan is a chlorinated phenolic, used in many personal and home care products for its powerful antimicrobial effect. Several studies have shown triclosan toxicity and the American Food and Drug Administration (FDA) in 2016 has limited its use. It has been recently included in endocrine-disrupting chemicals (EDCs), a list of chemicals known for their ability to interfere with hormonal signaling with particular critical effects on reproduction both in animals and humans. In order to deepen the knowledge in this specific field, the present study was undertaken to explore the effect of different concentrations of triclosan (1, 10, and 50 µM) on cultured luteal cells, isolated from swine ovaries, evaluating effects on growth Bromodeoxyuridine (BrDU) incorporation and Adenosine TriPhosphate (ATP) production, steroidogenesis (progesterone secretion) and redox status (superoxide and nitric oxide production, enzymatic and non-enzymatic scavenging activity). A biphasic effect was exerted by triclosan on P4 production. In fact, the highest concentration inhibited, while the others stimulated P4 production (p < 0.05). Triclosan significantly inhibited cell proliferation, metabolic activity, and enzymatic scavenger activity (p < 0.05). On the contrary, nitric oxide production was significantly increased by triclosan (p < 0.01), while superoxide anion generation and non-enzymatic scavenging activity were unaffected.

Current Knowledge on the Multifactorial Regulation of Corpora Lutea Lifespan: The Rabbit Model

Simple Summary

Corpora lutea (CL) are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. A variety of regulatory factors come into play in modulating the functional lifespan of CL, with luteotropic and luteolytic effects. Many aspects of luteal phase physiology have been clarified, yet many others have not yet been determined, including the molecular and/or cellular mechanisms that maintain the CL from the beginning of luteolysis during early CL development. This paper summarizes our current knowledge of the endocrine and cellular mechanisms involved in multifactorial CL lifespan regulation, using the pseudopregnant rabbit model.

Abstract

Our research group studied the biological regulatory mechanisms of the corpora lutea (CL), paying particular attention to the pseudopregnant rabbit model, which has the advantage that the relative luteal age following ovulation is induced by the gonadotrophin-releasing hormone (GnRH). CL are temporary endocrine structures that secrete progesterone, which is essential for maintaining a healthy pregnancy. It is now clear that, besides the classical regulatory mechanism exerted by prostaglandin E2 (luteotropic) and prostaglandin F2α (luteolytic), a considerable number of other effectors assist in the regulation of CL. The aim of this paper is to summarize our current knowledge of the multifactorial mechanisms regulating CL lifespan in rabbits. Given the essential role of CL in reproductive success, a deeper understanding of the regulatory mechanisms will provide us with valuable insights on various reproductive issues that hinder fertility in this and other mammalian species, allowing to overcome the challenges for new and more efficient breeding strategies.

Effects of bisphenol A, diethylhexyl phthalate and pentabrominated diphenyl ether 99 on steroid synthesis in cultured bovine luteal cells

Bisphenol A (BPA), diethylhexyl phthalate (DEHP) and pentabrominated diphenyl ether 99 (PBDE 99) are environmental toxicants belonging to the endocrine disrupting compounds (EDCs). They exert adverse effects on the various physiological systems, especially the reproductive system of humans and animals. The aim of this study was to investigate the effects of BPA, DEHP and PBDE 99 on progesterone (P4) synthesis in cultured bovine luteal cells. The bovine luteal cells isolated from the mid-luteal corpora lutea were exposed to different concentrations of BPA (1, 3, 10 and 30 µM), DEHP (1, 3, 10 and 30 µM) and PBDE 99 (0.1, 0.3, 1 and 3 µM) in a serum-free culture media for 48 and 96 hr. At 48 hr, the P4 level in the luteal cells decreased after treatment with all concentrations of BPA; 3, 10 and 30 µM of DEHP; and 3 µM of PBDE 99 compared to the control (p < .05). Treatment of cells with 3-30 µM of BPA, 1-30 µM of DEHP and 1-3 µM of PBDE 99 for 96 hr resulted in reduction in P4 synthesis (p < .05). However, lower concentrations of PBDE 99 (0.1 and 0.3 µM) increased P4 levels at 48 and 96 hr. Synthesis of P4 was lower at 96 hr compared to the 48 hr in the groups treated with BPA (30 µM), DEHP (1-30 µM), PBDE 99 (0.3-3 µM) and control group. Our results showed that BPA, DEHP and PBDE 99 are able to alter luteal steroidogenesis in bovine cells and can disrupt hormonal balance in the ovary. However, it is necessary to evaluate the exact mechanism underlying these effects in future studies.

Proteomics Analysis Reveals an Important Role for the PPAR Signaling Pathway in DBDCT-Induced Hepatotoxicity Mechanisms

A patented organotin di-n-butyl-di-(4-chlorobenzohydroxamato)tin (DBDCT) with high a antitumor activity was designed, however, its antitumor and toxic mechanisms have not yet been clearly illustrated. Hepatic proteins of DBDCT-treated rats were identified and analyzed using LC-MS/MS with label-free quantitative technology. In total, 149 differentially expressed proteins were successfully identified. Five protein and mRNA expressions were involved in the peroxisome proliferator-activated receptor (PPAR) signaling pathway, including a scavenger receptor (CD36), adipocyte fatty acid binding protein 4 (FABP4), enoyl-CoA hydratase (EHHADH), acetyl-CoA acyltransferase 1 (ACAA1), and phosphoenolpyruvate carboxykinase (PEPCK) in DBDCT-treated Rat Liver (BRL) cells. PPAR-α and PPAR-λ were also significantly decreased at both protein and mRNA levels. Furthermore, compared with the DBDCT treatment group, a special blocking agent of PPAR-λ T0070907 was used to evaluate the relationship between PPAR-λ and its downstream genes. Our studies indicated that DBDCT may serve as a modulator of PPAR-λ, further up-regulating CD36, FABP4 and EHHADH on the PPAR signal pathway.

Possible role of PPARγ in the negative regulation of ovulatory cascade and luteal development in rats

Peroxisome proliferator-activated receptor γ (PPARγ), a member of a nuclear receptor family, has been shown to be implicated in various reproductive processes. Here, we evaluated possible roles of PPARγ in ovulation and luteal development in a gonadotropins-primed immature rat model. Immunoreactive PPARγ was expressed in granulosa cells of eCG-stimulated mature follicles, and its expression level decreased following ovulatory hCG stimulus. Intra-bursal treatment with rosiglitazone (a PPARγ agonist) simultaneously with subcutaneously administered hCG blocked the induction of cyclooxygenase-2 and steroidogenic acute regulatory protein (StAR) in preovulatory follicles. Consistently, tissue levels of their respective products, prostaglandin (PG) E₂ and progesterone (P4), were reduced, leading to significantly decreased ovulation rate. GW9662, a PPARγ antagonist, was almost ineffective to alter those values. Local treatment with rosiglitazone 24 hr after hCG administration caused reductions in the size, StAR expression and P4 secretion of corpus luteum 48 hr later. Obtained data are possible functional evidence with rats for granulosa cell PPARγ as a negative regulator of PG and P4 synthesis during follicle rupture and transformation to luteal tissue. LH/hCG-induced decreases in PPARγ expression and its activity would be an early component in the proper induction of following ovulatory cascade and luteal development.

The impact of flutamide on prostaglandin F2α synthase and prostaglandin F2α receptor expression, and prostaglandin F2α concentration in the porcine corpus luteum of pregnancy

Recently, we have indicated that flutamide-induced androgen deficiency diminished progesterone production in the porcine corpus luteum (CL) during late pregnancy and before parturition, as a sign of functional luteolysis. In pigs, the main luteolytic factor is prostaglandin F_2α (PGF_2α), which acts via specific receptors (PTGFRs), and its biosynthesis is catalyzed by prostaglandin F_2α synthase (PGFS). The present study investigated the impact of flutamide on luteal PGFS and PTGFR expression, as well as intraluteal PGF_2α content during pregnancy in pigs. Flutamide (50 mg/kg BW per day, for 7 d) or corn oil (control groups) were administered subcutaneously into pregnant gilts (n = 3 per group) between 83 and 89 (GD90) or 101-107 (GD108) days of gestation (GD). On GD90 and GD108 ovaries were collected and CLs were obtained. Real-time PCR and Western blot analyses were conducted to quantify PGFS and PTGFR mRNA and protein expression, respectively. In addition, immunohistochemical localization of both proteins was performed and the concentration of PGF_2α was analyzed by enzyme immunoassay method. Flutamide caused upregulation of PGFS mRNA and protein in GD90F (P = 0.008; P = 0.008, respectively) and GD108F (P = 0.041; P = 0.009, respectively) groups. The level of PTGFR mRNA increased only in the GD90F (P = 0.007) group, whereas PTGFR protein expression was greater in both gestational periods (P = 0.035; P = 0.038, respectively). On GD90 PGFS was immunolocalized in the cytoplasm of large luteal cells only, whereas on GD108, sparse small luteal cells also displayed positive staining. PTGFR showed membranous localization within large luteal cells on both days of pregnancy. In luteal tissue, PGF_2α concentration was greater after flutamide exposure on both days (P = 0.041; P = 0.038, respectively), when compared with control groups. Overall, the enhanced luteal PGF_2α content due to increased PGFS expression after flutamide administration might contribute to premature CL regression. Moreover, higher PTGFR protein levels indicate enhanced sensitivity of luteal cells to PGF_2α under androgen deficiency.

A systematic review on the adverse health effects of di-2-ethylhexyl phthalate

Di (ethylhexyl) phthalate (DEHP) is a global environmental pollutant. This study aims to systematically review the literature on health effects of exposure to DEHP including effects on reproductive health, carcinogenesis, pregnancy outcome, and respiratory system. The literature search was done through Scopus, ISI Web of Science, Google Scholar, PubMed, Medline, and the reference lists of previous review articles to identify relevant articles published to June 2016 in each subject area. The inclusion criteria were as follows: original research, cross-sectional studies, case-control studies, cohort studies, interventional studies, and review articles. Both human and animal studies were included. The search was limited to English language papers. Conference papers, editorials, and letters were not included. The systematic review was conducted and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Overall, 152 of the 407 papers met the inclusion criteria. We provided an up-to-date comprehensive and critical assessment of both human and animal studies undertaken to explore the effects of DEHP. It revealed that in experimental studies, exposure to DEHP mainly targeted the reproductive, neurodevelopment, and respiratory systems. Human studies reported that exposure to this contaminant had carcinogenic effects and influenced neurodevelopment in early life. This systematic review underscored the adverse health effects of DEHP for pregnant women and the pediatric age group. It summarizes different response of humans and experimental animals to DEHP exposure, and some suggested underlying mechanisms.

Exposure to di(2-ethylhexyl) phthalate inhibits luteal function via dysregulation of CD31 and prostaglandin F2alpha in pregnant mice

BACKGROUND

Di(2-ethylhexyl) phthalate (DEHP) exposure reduces embryo implantations, increases embryonic loss, and decreases fetal body weights. However, whether it is associated with the alteration of luteal function remains unknown. Thus, our aim in this study was to explore the effect and mechanism of DEHP on luteal function in pregnant mice in vivo.

METHODS

Mice were administered DEHP by gavage at 125, 250, 500 mg/kg/day from gestational days (GD) 1 to 9 or 13. Levels of serum progesterone and estradiol were measured by radioimmunoassay. The numbers and sizes of corpora lutea were calculated by ovarian histomorphology. Steroidogenic enzymes were assessed by qRT-PCR. CD31 protein was detected by immunocytochemistry, and prostaglandin F2alpha (PGF2alpha) levels were evaluated by enzyme immunoassay.

RESULTS

Treatment with DEHP significantly inhibited progesterone secretion in pregnant mice in a dose-dependent manner but did not inhibit estradiol production on GD 9 and 13. Treatment also showed concomitant decreases in transcript levels for key steroidogenic enzymes (CYP11A, 3β-HSD, and StAR) on GD 13. Furthermore, DEHP administration significantly reduced the numbers and sizes of corpora lutea on GD 13. No significant changes in the ratio of ovary weight vs. body weight were observed between the control group and treated animals on GD 9 and 13. In addition, treatment with DEHP significantly inhibited CD31 expression of corpora lutea, whereas plasma PGF2alpha levels in DEHP treatment groups were significantly higher compared with the control groups on GD 9 and 13.

CONCLUSIONS

The results show DEHP significantly inhibits luteal function of pregnant mice in vivo, with a mechanism that seems to involve the down-regulation of progesterone and steroidogenic enzymes message RNA, the decrease in CD31 expression, and the increase in PGF2alpha secretion.