Alternative Activation of Human Macrophages Is Rescued by Estrogen Treatment in Vitro and Impaired by Menopausal Status.

Context and Objective: During their reproductive years, women are generally protected from cardiovascular disease events by their estrogen-replete status. Our starting hypothesis was that lower estrogen levels after menopause are associated with macrophage activation profiles skewed towards pro-inflammatory phenotypes. Research Design and Setting: This was an in vitro and ex vivo study in human blood-derived macrophages. Subjects: We obtained blood from 12 healthy male donors for the in vitro study, and from 5 pre-menopausal and 8 post-menopausal women for the ex vivo study. Outcome: measurements: We determined macrophage immunophenotypes in resting state and after activation with M1- (LPS/IFNγ) or M2-associated (IL-4/IL-13) stimuli, as well as expression of estrogen receptors (ER) and other transcription factors. Results: Unpolarized macrophages expressed both ERα and ERβ, and ERα but not ERβ levels were decreased by M1 stimuli. LPS/IFNγ also induced downregulation of CD163 and CD206, markers of alternative activation, and increased cell-bound TNF-α and IL-10. These effects were prevented by E2 treatment through impaired nuclear factor (NF)-κB liberation. In agreement with a role for E2 in attenuating the inflammatory response, M1/M2 subpopulations were similar in monocytes and unstimulated macrophages from pre- and post-menopausal donors. In contrast, M2 activation appeared to be blunted in macrophages from post-menopausal women, leading to increased M1/M2 response ratio. Conclusions: Estrogen treatment prevented LPS/IFNγ action on human M2 macrophage markers and cytokine production, whereas menopausal estrogen loss was associated with impaired response to alternative activation, suggesting that these mechanisms affect cardiovascular risk profile in relation to menopausal status.