The effects of 17 alpha-estradiol to inhibit inflammation in vitro

Background: 17 Alphaestradiol (17 alpha E2) is a natural, non-feminizing stereoisomer of 17 beta-estradiol (17 beta-E2). Whereas much is known about the physiological effects of 17 beta-E2, much less is known about 17 alpha-E2. For example, 17 beta E2 exerts anti-inflammatory effects in neurons and adipocytes through binding and activation of estrogen receptor alpha (ERa); however, if 17 alpha-E2 has similar effects on inflammation is currently unknown. Methods: To begin to address this, we analyzed the ability of 17 alpha-E2 and 17 beta-E2 to suppress lipopolysaccharide (LPS)-induced inflammation in vitro using embryonic fibroblast cells (MEF) from wild type and total body ERa (ERKO) male and female mice. Additionally, we further probed if there were sex differences with respect to the effects of E2s using primary preadipocyte cells from C57BL/6J male and female mice. Also, we probed mechanistically the effects of E2s in fully differentiated 3T3-L1 cells. Results: Both E2s decreased LPSinduced markers of inflammation Tnf-alpha and Il6, and increased the antinflammatory markers Il4 and IL6 receptor (Il6ra) in MEF cells. To begin to understand the mechanisms by which both E2's mediate their antiinflammatory effects, we probed the role of ERa using two methods. First, we used MEF cells from ERKO mice and found reductions in ERa diminished the ability of 17 aE2 to suppress Tnf-alpha in female but not in male cells, demonstrating a sexual dimorphism in regard to the role of ERa to mediate 17 aE2's effects. Second, we selectively reduced the expression of ERa in 3T3-L1 cells using siRNA and found reductions in ERa diminished the ability of both E2s to suppress Tnfa and Il6 expression. Lastly, to determine the mechanisms by which E2s reduce inflammation, we explored the role of NF kappa Bp65 and found both E2s decreased NF kappa Bp65 expression. Conclusions: In conclusion, we demonstrate for the first time that 17 alpha-E2, as well as 17 beta-E2, suppresses inflammation through their effects on ERa and NF kappa Bp-65.