Abstract

TCDD (2,3,7,8-tetrachlorodibenzo-p-dioxin, commonly known as dioxin) is a ubiquitous environmental contaminant and known endocrine disruptor. Using a mouse model, we previously found that adult female mice exposed in utero to TCDD (F1 generation) as well as multiple subsequent generations (F2-F4) exhibited reduced fertility and an increased incidence of spontaneous preterm birth. Additional studies revealed that male F1 mice with a similar in utero/developmental TCDD exposure also exhibited diminished fertility and conferred an increased risk of preterm birth to their unexposed mating partners. Herein, we extend these previous observations, reporting that reduced fertility in male F1 mice is linked to testicular inflammation which coincides with apoptosis of developing spermatocytes, sub-fertility and an increased risk of preterm birth in their unexposed mating partners. Significantly, in the absence of additional toxicant exposure, testicular inflammation and reduced fertility persisted in F2 and F3 males and their control mating partners also frequently exhibited spontaneous preterm birth. Although a steady, global decline in male fertility has been noted over the last few decades, the reasons for these changes have not been firmly established. Likewise, the PTB rate in the U.S. and other countries has paralleled industrial development, suggesting a possible relationship between environmental toxicant exposure and adverse pregnancy outcomes. Most current clinical strategies to prevent preterm birth are focused solely on the mother and have yielded limited benefits. In contrast, our studies strongly suggest that the preconception testicular health of the father is a critical determinant of pregnancy outcomes in mice. Future clinical studies should examine the potential contribution of the male to gestation length in women and whether efforts to reduce the incidence of preterm birth should be initiated in both parents prior to pregnancy.

Highlights

  • Exposure to environmental toxicants and pharmaceutical chemicals is common across the human lifespan; understanding the potentially negative impact of exposure to bioactive chemicals is paramount to protecting our reproductive health [1]

  • The principal mechanism of action of TCDD is related to the binding of this toxicant to the aryl hydrocarbon receptor (AhR) [8], an orphan nuclear receptor which is expressed in the reproductive tract of both humans and rodents [10,11,12]

  • TCDD Exposure is Associated with Reduced Fertility and Preterm Birth

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Summary

Introduction

Exposure to environmental toxicants and pharmaceutical chemicals is common across the human lifespan; understanding the potentially negative impact of exposure to bioactive chemicals is paramount to protecting our reproductive health [1]. Recent animal models have shown that developmental exposure of a single generation to endocrine disrupting environmental toxicants can negatively impact reproductive capacity trangenerationally, likely due to epigenetic inheritance (reviewed by [2]). The tragic history of exposure to the pharmacologic agent diethylstilbestrol (DES) provides clear evidence that developmental exposure to an endocrine disrupting chemical can have multi-generational effects on human health (reviewed by [3]). Given this background, the rapidly emerging concept that the environmental exposure history of paternal and maternal ancestors may negatively affect an individual’s current reproductive health demands a shift in our medical assessments and treatments of infertility. Whereas AhR-binding toxicants frequently act as disruptors of reproductive function, male and female AhR knockout mice exhibit altered reproductive tract development and reduced adult fertility [16,17], implicating endogenous ligands for this receptor as necessary for normal reproduction

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