NF-κB-mediated inhibition of neuroinflammation by formononetin: role of ERβ.

NF-κB activation has been shown to regulate the release of mediators in neuroinflammation [1]. Studies have shown that estrogen receptor beta (ERβ) agonists showed antineuroinflammatory and neuroprotective activities [2]. Formononetin(FMN) is a chemical substance present in food supplements like red clover and soya bean. As a phytoestrogen [3] it has been demonstrated to exhibit diverse pharmacological benefits. Previously we showed that FMN suppressed the release of pro-inflammatory cytokines by lipopolysaccharide (LPS)-activated BV2 microglia [4]. In this study we have evaluated the role of NF-κB in the anti-neuroinflammatory effects of FMN. We also examined whether ERβ contributed to the anti-inflammatory activity of FMN. BV2 cells were stimulated with LPS in the presence or absence of FMN (2.5, 5 and 10 µM). Western blot analysis was used to evaluate the effects of FMN on LPS-activated expression of IkBα and p.p65 in BV2 cells. Electrophoretic mobility shift assay (EMSA) was used to examine the effect of FMN on NF-κB/DNA binding. ERβ siRNA (m): sc-35326 (Santa Cruz) was transfected into BV2 microglia, followed by analyses of TNFα, NO, and PGE2 production in control and ERβ-silenced cells. Resultsshowed that FMN (10µM) significantly (p<0.01) inhibited the phosphorylation of IκBα and nuclear translocation of the p65 subunit. The compound suppressed NF-κB/DNA binding activity in LPS- stimulated BV2 microglia. Further results showed that the presence of ERβ siRNA significantly reversed the effect of FMN (10µM) on nitrite production (figure a), TNFαproduction (figure b) and PGE2 (figure c). These results suggest that FMNmight suppress microglial activation through mechanisms involving the NF-κB signalling pathway. We propose that ERβ activation might be contributing to the anti-neuroinflammatory effect of FMN.

1. Nakajima, K., et al., Differential suppression of endotoxin-inducible inflammatory cytokines by nuclear factor kappa B (NFκB) inhibitor in rat microglia. Neuroscience letters, 2006. 401(3): p. 199-202.

2. Catley, M.C., et al., Estrogen receptor β: expression profile and possible anti-inflammatory role in disease. Journal of Pharmacology and Experimental Therapeutics, 2008. 326(1): p. 83-88.

3. Park, J., et al., Formononetin, a phyto-oestrogen, and its metabolites up-regulate interleukin-4 production in activated T cells via increased AP-1 DNA binding activity. Immunology, 2005. 116(1): p. 71-81.

4. Abdel, E. Olumayokun,O, Formononetin a phytoestrogen in red clover inhibits neuroinflammation in LPS activated microglia. https://bps.conference-services net/resources/344/3811/pdf/PHARM14_0110.pdf.