Raloxifene, a selective estrogen receptor modulator, inhibits lipopolysaccharide-induced nitric oxide production by inhibiting the phosphatidylinositol 3-kinase/Akt/nuclear factor-kappa B pathway in RAW264.7 macrophage cells

We here demonstrate an anti-inflammatory action of raloxifene, a selective estrogen receptor modulator, in lipopolysaccharide (LPS)-induced murine macrophage RAW264.7 cells. Treatment with raloxifene at micromolar concentrations suppressed the production of nitric oxide (NO) by down-regulating expression of the inducible nitric oxide synthase (iNOS) gene in LPS-activated cells. The decreased expression of iNOS and subsequent reduction of NO were due to inhibition of nuclear translocation of transcription factor NF-kappaB. These effects were significantly inhibited by exposure to the phosphatidylinositol 3-kinase (PI 3-kinase) inhibitor, LY294002, or by expression of a dominant negative mutant of PI 3-kinase. In addition, pretreatment with raloxifene reduced LPS-induced Akt phosphorylation as well as NF-kappa B DNA binding activity and NF-kappa B-dependent reporter gene activity. Thus our findings indicate that raloxifene exerts its anti-inflammatory action in LPS-stimulated macrophages by blocking the PI 3-kinase-Akt-NF-kappa B signaling cascade, and eventually reduces expression of pro-inflammatory genes such as iNOS.