Comparison of Inhibitory Potency of Various Antioxidants on the Activation of BV2 Microglial Cell Lines Induced by LPS

Antioxidant properties have been proposed as a mechanism for the putative anti-inflammatory effects of phenolic compounds. To reveal the relationship between antioxidant activity and anti-inflammatory effects of various antioxidants, we measured 1, 1-diphenyl-2-picryhydrazyl(DPPH)-reducing activity and examined the inhibitory effects on LPS-induced inflammation-related gene expression in the BV2 microglial cell line. Lipopolysaccharide(LPS)(0.2 ${\mu}g/ml$) was used with or without antioxidants to treat cells, and the regulation of iNOS and cytokine gene expression was monitored using an RNase protection assay(RPA). Although, all tested antioxidants had similar DPPH-reducing activity and inhibited nitrite production, but the curcuminoid antioxidants(ferulic acid, caffeic acid, and curcumin) inhibited LPS-induced gene expression(iNOS, $TNF-\alpha,\;IL-1{\beta}$, IL-6, and IL-1 Ra) in a concentration-dependent manner. Other tested antioxidants did not exhibit the same effects; N-acetylcysteine(NAC) only began to suppress $IL-1{\beta}$ gene expression just below the concentration at which cytotoxicity occurred. Moreover, the antioxidant potency of curcuminoids appeared to have no correlation with anti-inflammatory potency. Only curcumin could inhibit LPS-induced microglial activation at a micromolar level. These data suggest that curcumin may be a safe antioxidant possessing anti-inflammatory activity.