Estrogen Signaling Modulates Mitochondrial ROS Production and Mitochondrial Function in Mouse Bone Marrow Macrophages

Estrogen (E2), the female sex hormone has anti-inflammatory and anti-oxidant properties which have been proposed to play a role its cardioprotective effects. Women have an increase incidence of cardiovascular disease (CVD) in the postmenopausal period when E2 levels are at their lowest. E2 receptors are found on the cell surface, cytoplasm, nucleus, and mitochondria where they can modulate both nuclear and mitochondrial genes. Previous work has shown that E2 receptor levels decrease with age in rodents and humans. We were specifically interested in the role of E2 signaling in macrophages, an inflammatory cell dysregulated in CVD. We hypothesize that E2 preserves mitochondrial function by decreasing reactive oxygen species (ROS) and preserving mitochondrial membrane potential. In order to better study the effects of E2 signaling on mitochondrial function and anti-inflammatory capacity we isolated bone marrow macrophages (BMMs) from 8-13 month old wild type (wt), E2 receptor α knockout (ERα KO) and E2 receptor β knock out (ERβ KO) mice and measured mitochondrial function with the Seahorse Extracellular Flux Analyzer, mitochondrial membrane potential with TMRM and ROS production with DCF-DA. There was no difference in mitochondrial membrane potential in BMMs isolated from wt and ERβ KO mice. To induce inflammation, we treated the BMMS with LPS for 4 hours. There was a significant increase in LPS induced ROS in BMMS isolated from wt and ERβ KO which was further exacerbated in BMMs isolated from ERα KO mice. The maximal and reserve OCR and ECAR was significantly less in BMMs isolated from both ERα KO and ERβ KO compared to wt. These data suggest E2 partially regulates mitochondrial function in macrophages through both ERα and ERβ while ROS production is less dependent on ERα in BMMs. Taken together, these data provide evidence of E2 signaling modulating mitochondrial function and regulating ROS production through specific E2 receptors in BMMs. These results may help us to understand the anti-inflammatory role of E2 in pre-menopausal women and the increased incidence of CVD in post-menopausal women.