Acute Exposure to Ozone Affects Circulating Estradiol Levels and Gonadotropin Gene Expression in Female Mice

Abstract

Ozone, a critical air pollutant, has been shown to lead to systemic inflammation that can alter bodily functions, including hormone secretion, fertility, and the hypothalamic-pituitary-gonadal (HPG) axis. This study aimed to quantify changes in hormone production and follicle development after acute exposure to ozone using an animal model to identify the potential mechanisms underlying the observed effects of air pollution exposures on fertility and hormone secretion. To accomplish this, regularly cycling 8-week-old female C57BL/6J mice were exposed to 2 ppm of ozone or filtered air (control) for 3 h on the day of proestrus. Blood, ovaries, brain tissues, and pituitary glands were collected at 4 h after exposure to evaluate hormone levels, ovarian follicle distribution, and gene expression. Ovaries were also harvested at 24 h post-exposure. We found that at 4 h after ozone exposure, mice had significantly higher (30%) circulating estradiol levels than mice exposed to filtered air. This effect was accompanied by a decrease in mRNA expression of gonadotropin genes (LH, FSH) and gonadotropin-releasing hormone in the pituitary gland. Analysis of ovarian tissue at 4 h and 24 h after exposure showed no significant changes in follicle composition or the expression of steroidogenesis genes. We conclude that acute ozone exposure affects sex hormone levels and disrupts the HPG axis. Future studies addressing chronic or long-term effects of air pollution exposure are needed to elucidate the mechanisms by which ambient ozone affects endocrine function.