Analysis of Antioxidant and Anti-inflammatory Activity of Silicon in Murine Macrophages

The purpose of this study is to investigate the antioxidant and anti-inflammatory properties of silicon (Si) in the RAW 264.7 murine macrophage cell line. Lipopolysaccharide (LPS) was used to induce inflammatory conditions, and cells were treated with 0, 1, 5, 10, 25, 50, and 100 mu M Si in the form of sodium metasilicate. Tert-butylhydroquinone (TBHQ), a well-known antioxidative substance, was used as a positive control to assess the degree of antioxidative and anti-inflammatory properties of Si. Sodium metasilicate at 100 mu M suppressed LPS-induced nitric oxide generation from macrophages 36 h after treatment. In addition, 50 mu M sodium metasilicate decreased interleukin-6 production, and the degree of suppression was comparable to that of 10 mu M TBHQ treatment. LPS-induced messenger RNA (mRNA) expression of tumor necrosis factor-alpha and inducible nitric oxide synthase was significantly decreased by 1, 5, 10, and 50 mu M sodium metasilicate. Cyclooxygenase-2 mRNA expression was also suppressed by 1, 5, 25, and 50 mu M sodium metasilicate. Based on these data, Si has the ability to suppress the production of inflammatory cytokines and mediators, possibly through the suppression of radical scavenger activity and down-regulation of gene expression of inflammatory mediators.