Ovarian Metabolism of an Environmentally Relevant Phthalate Mixture

Abstract

Phthalates are synthetic chemicals with widespread human exposure due to their use as additives in consumer products. Phthalate diesters are hydrolyzed in the environment and in the body to monoesters that may be more toxic than the parent compounds. This study tested the hypothesis that adult mouse antral follicles, but not neonatal ovaries, are able to metabolize an environmentally relevant mixture of phthalates. Whole neonatal ovaries and isolated adult antral follicles from CD-1 mice were cultured in media treated with vehicle control or 0.1-10 mg/ml of a mixture composed of 35% diethyl phthalate (DEP), 21% di(2-ethylhexyl) phthalate (DEHP), 15% dibutyl phthalate (DBP), 15% diisononyl phthalate (DiNP), 8% diisobutyl phthalate (DiBP), and 5% benzylbutyl phthalate (BzBP). After 4 days of culture, media were subjected to highperformance liquid chromatography tandem mass spectrometry to measure the amounts of diester phthalates and monoester metabolites. Ovaries and follicles were collected to measure the gene and protein expression of the enzymes required for phthalate metabolism. Monoester metabolites for all phthalates except DiNP were detected in the media for both culture types at most doses. The long-chain phthalates (BzBP, DEHP, and DiNP) were metabolized less than the shortchain phthalates (DEP, DBP, and DiBP) compared with respective controls. Expression of metabolizing enzymes was observed for all treatment groups in both culture types. These data indicate that mouse ovaries are capable of metabolizing low doses of phthalates and suggest that metabolic capacity differs for follicles at different stages of development.

Phthalates and Bisphenol A: Presence in Blood Serum and Follicular Fluid of Italian Women Undergoing Assisted Reproduction Techniques

“…This variability might suggest that the follicular environment has some capability of metabolizing these EDCs (esterase activity), which may vary between subjects and among ethnic groups (enzymes polymorphisms), although this aspect should be deepened by further studies. Warner et al, (2019) showed that the mouse ovary can metabolize a mixture of phthalates with varying metabolizing capacity at different stages of folliculogenesis [ 2 ]. However, together with a different exposure profile deriving from a different geographical area, a different clearance rate could explain the different concentrations of phthalate esters among these studies.…”

“…Phthalates are mainly used as a plasticizer in polyvinylchloride (PVC) products and are produced through esterification with different substituents of phthalic anhydride. However, phthalates are a broad group of substances and they are classified as short-chain (low molecular weight: diethyl phthalate, di-butyl phthalate, and di-isobutyl phthalate) or long-chain (high molecular weight: benzyl-butyl phthalate, di(2-ethylhexyl) phthalate, and di-isononyl phthalate) phthalates [ 2 ]. The most common types of phthalates include di(2-ethylhexyl) phthalate (DEHP), dibutyl phthalate (DBP), dibenzyl phthalate (DBzP), diethyl phthalate (DEP) and dimethyl phthalate (DMP).…”

Phthalates in albumin from human serum: implications for assisted reproductive technology

“…This study examined media and protein directly from the manufacturer and not after incubation over varying lengths of time. An incubation period may influence the ratio of DEHP to MEHP because the conversion of DEHP to MEHP requires unspecific ligases that are present in RBCs (41) and are possibly present in gametes or embryos (56). Overall, this work established a foundation for further inquiry about potential contamination of proteins supplied to gamete or embryo cultures.…”

Prenatal Phthalates Exposure and Cord Thyroid Hormones: A Birth Cohort Study in Southern Taiwan

“…Urinary MBP, MEHP and MEP contributed over 95% of total phthalate exposure, whereas MBP and MEHP were dominantly compounds in serum and cord blood samples. Short-chain phthalates, like DEP and DMP, were rapidly metabolized to their metabolites in a few hours [ 62 ], which instantly excreted to urine and may not cause significant placenta transportation [ 63 , 64 ]. For long-chain phthalates with longer half-lives, like DBP and DEHP, continuous exposure to these phthalates through food and food packaging materials [ 18 , 65 ] are possible reasons that MBP and MEHP were both dominant compounds in serum and urine samples.…”