Modulation of the lung inflammatory response to ozone by the estrous cycle

Abstract

BackgroundStudies have shown that women are at increased risk of adverse health outcomes from air pollution (e.g. ozone) than men. Emerging data indicate that hormones could play a role in the regulation of lung innate immunity and inflammation in response to environmental challenges, but the molecular mechanisms involved in these responses remain unknown. The goal of this project was to investigate whether fluctuations in circulating hormone levels during the estrous cycle could modulate the inflammatory response to ambient ozone.MethodsAdult female C57BL/6 mice, in different stages of the estrous cycle, were exposed to ozone (2ppm) or filtered air (FA) for 3 hours (n=6/group). The estrous cycle stage was determined by vaginal smear, and cyclicity was confirmed for at least 3 cycles. Four hours after exposure, lungs were harvested and RNA was extracted using Trizol. The mRNA expression of inflammatory cytokines and chemokines was analyzed by Real Time PCR (mouse genes: Ccl2, Ccl3, Cxcl2, Ccl20, Il1b, Il6, Tnf, and RANTES) using TaqMan probes, and normalized to 18S. Serum levels of LH, estradiol, and progesterone were also measured by ELISA to confirm the estrous cycle stage.ResultsExposure to ozone significantly increased expression of Cxcl2, Ccl20, and Il6 genes in female mice exposed in all estrous cycle stages, with higher expression levels in proestrus vs. other stages (p<0.05). In contrast, the expression of both Ccl2 and Ccl3 was only increased in mice exposed to ozone at the proestrus stage (p<0.05), but not in animals exposed in diestrus/estrus. Ozone exposure did not affect the expression of Il1a, Tnf or RANTES, when compared to females exposed to FA. Serum hormone levels confirmed proper estrus cycle stage in all animals.ConclusionsOur results confirmed differences in lung inflammatory gene expression in response to ozone in female mice exposed at different stages of the estrous cycle. Our observations suggest that the negative effects of air pollution in women's lung health may be affected by their hormonal status. Future studies investigating adverse health effects of ozone in women should consider their menstrual cycle phase, and/or circulating hormone levels.Support or Funding InformationSupported by NIH HL‐133520