Contribution of Conjugated Linoleic Acid to the Suppression of Inflammatory Responses through the Regulation of the NF-κB Pathway

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Abstract
Data from a number of researchers have shown that conjugated linoleic acid (CLA) has some beneficial health activities in animal models. Because inflammatory responses are associated with pathophysiology of many diseases, the aim of this study is to explore the effect and mechanism of CLA in the regulation of lipopolysaccharide (LPS)-induced inflammatory responses in RAW 264.7 macrophages. The addition of increasing levels of CLA proportionally augmented the incorporation of CLA in cultures. CLA diminished LPS-induced mRNA and protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2) as well as subsequent production of nitric oxide and prostaglandin E2, respectively. We further examined the effect of CLA on LPS-induced NF-κB activation by Western blot and the electrophoretic mobility shift assay. The addition of CLA at 200 μM significantly diminished LPS-induced protein expression of the cytoplasmic phosphorylated inhibitor κBα and nuclear p65 as well as NF-κB nuclear protein−DNA binding affinity. In conclusion, our data suggest that CLA may inhibit LPS-induced inflammatory events in RAW 264.7 macrophages and this inhibitory activity of CLA, at least in part, occurs through CLA modulating the NF-κB activation and therefore negatively regulating expression of inflammatory mediators. Keywords: Conjugated linoleic acid; inducible nitric oxide synthase; cyclooxygenase 2; nuclear transcription factor-κB