Gestational exposure to an epidemiologically defined mixture of phthalates leads to gonadal dysfunction in mouse offspring of both sexes

Abstract

The increasing concern for the reproductive toxicity of abundantly used phthalates requires reliable tools for exposure risk assessment to mixtures of chemicals, based on real life human exposure and disorder-associated epidemiological evidence. We herein used a mixture of four phthalate monoesters (33% mono-butyl phthalate, 16% mono-benzyl phthalate, 21% mono-ethyl hexyl phthalate, and 30% mono-isononyl phthalate), detected in 1 st trimester urine of 194 pregnant women and identified as bad actors for a shorter anogenital distance (AGD) in their baby boys. Mice were treated with 0, 0.26, 2.6 and 13 mg/kg/d of the mixture, corresponding to 0x, 10x, 100x, 500x levels detected in the pregnant women. Adverse outcomes detected in the reproductive system of the offspring in pre-puberty and adulthood included reduced AGD index and gonadal weight, changes in gonadal histology and altered expression of key regulators of gonadal growth and steroidogenesis. Most aberrations were apparent in both sexes, though more pronounced in males, and exhibited a non-monotonic pattern. The phthalate mixture directly affected expression of steroidogenesis as demonstrated in a relevant in vitro model. The detected adversities at exposures close to the levels detected in pregnant women, raise concern on the existing safety limits for early-life human exposures and emphasizes the need for re-evaluation of the exposure risk.

Effects and Mechanisms of Phthalates’ Action on Reproductive Processes and Reproductive Health: A Literature Review

“…There are specific intersexual differences in the activities of those enzymes as well [ 189 , 190 ]. According to Reposukou et al [ 191 ] the exposure to mixture of phthalates (DBP, BBzP, DEHP, DiNP) at 13 mg/kg/day decreased levels of Cyp17a1 in female C57/BL6 mice, contrarily to female C57/BL6 mice with increased levels of Cyp17a1 at same dose. The timing of the exposure to phthalates can be the source of discrepancies.…”

“…Postnatal exposure to DEHP in female and male CD-1 mice at 0.5 and 5 mg/kg/day decreased the expression of Fshr and Lhr [ 217 ]. According to Repouskou et al [ 191 ], postnatal exposure to a mixture of phthalates (DBP, BBzP, DEHP, DiNP) in male C57/BL6 mice at 0.26 mg/kg/day decreased the expression of Lhr. Contrarily, at 13 mg/kg/day, the mixture of phthalates (DBP, BBzP, DEHP, DiNP) increased the expression of Lhr in male C57/BL6 mice [ 191 ].…”

“…According to Repouskou et al [ 191 ], postnatal exposure to a mixture of phthalates (DBP, BBzP, DEHP, DiNP) in male C57/BL6 mice at 0.26 mg/kg/day decreased the expression of Lhr. Contrarily, at 13 mg/kg/day, the mixture of phthalates (DBP, BBzP, DEHP, DiNP) increased the expression of Lhr in male C57/BL6 mice [ 191 ]. Taken together, the higher exposure to phthalates was associated with an increased expression of Gnrhr, Fshr and Lhr in rats and mice.…”

A suggested bisphenol A metabolite (MBP) interfered with reproductive organ development in the chicken embryo while a human-relevant mixture of phthalate monoesters had no such effects

“…monobutyl phthalate, monoisononyl phthalate, monoethylhexyl phthalate, and monobenzyl phthalate, with mixing proportions based on geometric means of estimated serum concentrations in the SELMA mothers (Bornehag et al 2019). Gestational exposure to Mixture S in mice led to reduced AGD and gonadal weight, histological changes in the gonads, and altered mRNA expression of regulators of steroidogenesis in the offspring (Repouskou et al 2019). Elevated levels of testosterone, estradiol, and luteinizing hormone have been found in male offspring (Repouskou et al 2019).…”

“…Gestational exposure to Mixture S in mice led to reduced AGD and gonadal weight, histological changes in the gonads, and altered mRNA expression of regulators of steroidogenesis in the offspring (Repouskou et al 2019). Elevated levels of testosterone, estradiol, and luteinizing hormone have been found in male offspring (Repouskou et al 2019). The indication that Mixture S may disrupt reproductive organ development in humans and the effects found in mice warranted us to further explore the potential influence on reproductive organ development in an avian model.…”