Trans-10, cis-12 Conjugated Linoleic Acid Modulates Tumor Necrosis Factor-${alpha}$ Production and Nuclear Factor-${kappa}B$ Activation in RAW 264.7 Macrophages Through Formation of Reactive Oxygen Species

Abstract

The aims of this study were to explore the effects of conjugated linoleic acid (CLA) on reactive oxygen species (ROS) production in lipopolysaccharide (LPS)-naive and LPS-stimulated RAW 264.7 macrophages and to examine whether these effects affect the regulation of tumor necrosis factor-alpha (TNF-α) production, and nuclear factor-kappa B (NF-κB) and peroxisome proliferator-activated receptor gamma (PPARγ) activation. Trans-10, cis-12 (t10c12)-CLA increased the production of ROS, as well as TNF-α in LPS-naive RAW 264.7 cells. The CLA-induced TNF-α production was suppressed by treatment of diphenyleneiodonium chloride (DPI), a NADPH oxidase inhibitor. In addition, CLA enhanced the activities of NF-κB and PPARγ in LPS-naive RAW 264.7 cells, and this effect was abolished with DPI treatment. LPS treatment increased ROS production, whereas CLA reduced LPS-induced ROS production. LPS increased both TNF-α production and NF-κB activity, whereas t10c12-CLA reduced TNF-α production and NF-κB activity in LPS-stimulated RAW 264.7 cells. DPI treatment suppressed LPS-induced ROS production and NF-κB activity. Moreover, DPI enhanced the inhibitory effects of t10c12-CLA on TNF-α production and NF-κB activation in LPS-stimulated RAW 264.7 cells. However, neither t10c12-CLA nor DPI affected PPARγ activity in LPSstimulated RAW 264.7 cells. Taken together, these data indicate that t10c12-CLA induces TNF-α production by increasing ROS production in LPS-naive RAW 264.7 cells, which is mediated by the enhancement of NF-κB activity via PPARγ activation. By contrast, t10c12-CLA suppresses TNF-α production by inhibiting ROS production and NF- κB activation via a PPARγ-independent pathway in LPS-stimulated RAW 264.7 cells. These results suggest that t10c12- CLA can modulate TNF-α production and NF-κB activation through formation of ROS in RAW 264.7 macrophages.