Comparison of the immunomodulatory and epigenetic regulatory effects of natural estrogen 17-β estradiol and its synthetic analog 17α-ethinyl estradiol in NZB/WF1 mice

Abstract Concern is increasing regarding the effects of environmental exposures to different Estrogenic Endocrine Disrupting Chemicals (EEDCs) on immune system function. 17α-ethinyl estradiol (EE), a synthetic analog of natural estrogen 17-β estradiol (E2), is a primary component in oral contraceptive pills (OCP) and has been found in sewage effluents. In this study, to compare the immune and epigenetic regulatory effects of environmental E2 and EE exposure in NZB/WF1 mice, we implanted gonadal intact female NZB/WF1 mice with E2 or EE. While the effect of EE was more profound, both E2 and EE exposures caused splenomegaly, altered splenic and thymic T cell composition and activation, increased splenic neutrophil percentage, and promoted inflammatory molecules iNOS/NO and the chemokine MCP-1 in ex vivo-activated splenocytes. Impressively, we found that E2 and EE had differential effects on the induction of different inflammatory cytokines in ex vivo activated splenocytes (e.g. IFNβ and IL-1β were increased in LPS-activated splenocytes from EE-treated NZB/WF1 mice, but were decreased in LPS-activated splenocytes from E2-treated mice when compared to placebo controls). Also, in vivo EE exposure promoted, and E2 reduced, TLR9 agonist-induced IFNα production in splenocytes. We further demonstrated that E2 and EE regulated the expression of numerous immune-related genes and miRNAs in a similar manner, while EE had a stronger effect than E2 on the regulation of miRNAs expression. Moreover, we found that EE, but not E2 treatment, significantly reduced the global DNA methylation level in NZB/WF1 splenocytes. Together, our data revealed similar and also differential regulatory effects of E2 and EE on the different aspects of immune function.