Conjugated linoleic acids suppress inflammatory response and ICAM-1 expression through inhibition of NF-κB and MAPK signaling in human bronchial epithelial cells

Conjugated linoleic acids (CLAs) comprise a group of natural unsaturated fatty acids. CLA was reported to have anti-asthma, anti-adiposity, and anti-tumor effects. The present study aimed to evaluate the suppressive effects of cis-9, trans-11-CLA (c9, t11-CLA) on the expression of proinflammatory cytokines and intercellular adhesion molecule 1 (ICAM-1) in TNF-alpha-stimulated human bronchial epithelial (BEAS-2B) cells. After treating with various doses of c9, t11-CLA (12.5-100 mu g ml(-1)), BEAS-2B cells were induced into an inflamed state by adding TNF-alpha or TNF-alpha/IL-4. The presence of c9, t11-CLA significantly suppressed the secretion of cytokines IL-6, IL-8, CCL5, and MCP-1. We also found that c9, t11-CLA inhibited ICAM-1 expression, and decreased monocyte adhesion to inflamed bronchial epithelial cells. Interestingly, c9, t11-CLA attenuated the phosphorylation of mitogen-activated protein kinase (MAPK) and down-regulated the activation of nuclear factor-kappa B (NF-kappa B). These results suggested that the anti-inflammatory effects of c9, t11-CLA were mediated by inhibiting proinflammatory cytokines, chemokines, and ICAM-1 expression by blocking NF-kappa B transcription regulation and by attenuating MAPK signaling pathways.