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

17 Alpha-estradiol (17 α-E2) is a natural, non-feminizing stereoisomer of 17 beta-estradiol (17 β-E2). Whereas much is known about the physiological effects of 17 β-E2, much less is known about 17 α-E2. For example, 17 β-E2 exerts anti-inflammatory effects in neurons and adipocytes through binding and activation of estrogen receptor alpha (ERα); however, if 17 α-E2 has similar effects on inflammation is currently unknown.

To begin to address this, we analyzed the ability of 17 α-E2 and 17 β-E2 to suppress lipopolysaccharide (LPS)-induced inflammation in vitro using embryonic fibroblast cells (MEF) from wild type and total body ERα (ERKO) male and female mice. Additionally, we further probed if there were sex differences with respect to the effects of E2s using primary pre-adipocyte cells from C57BL/6J male and female mice. Also, we probed mechanistically the effects of E2s in fully differentiated 3T3-L1 cells.

Both E2s decreased LPS-induced markers of inflammation Tnf-α and Il-6, and increased the anti-inflammatory markers Il-4 and IL-6 receptor (Il-6ra) in MEF cells. To begin to understand the mechanisms by which both E2's mediate their anti-inflammatory effects, we probed the role of ERα using two methods. First, we used MEF cells from ERKO mice and found reductions in ERα diminished the ability of 17 α-E2 to suppress Tnf-α in female but not in male cells, demonstrating a sexual dimorphism in regard to the role of ERα to mediate 17 α-E2's effects. Second, we selectively reduced the expression of ERα in 3T3-L1 cells using siRNA and found reductions in ERα diminished the ability of both E2s to suppress Tnf-α and Il-6 expression. Lastly, to determine the mechanisms by which E2s reduce inflammation, we explored the role of NFκB-p65 and found both E2s decreased NFκB-p65 expression.

In conclusion, we demonstrate for the first time that 17 α-E2, as well as 17 β-E2, suppresses inflammation through their effects on ERα and NFκB-p65.