The lipopolysaccharide-induced pro-inflammatory response in RAW264.7 cells is attenuated by an unsaturated fatty acid–bovine serum albumin complex and enhanced by a saturated fatty acid–bovine serum albumin complex

Abstract

A 1:1 ratio of fatty acid (FA)-albumin complex was chosen to mimic physiological conditions, and the effects of FA-bovine serum albumin (BSA) complexes were tested in lipopolysaccharide (LPS)-stimulated RAW264.7 macrophage cells. Nitric oxide (NO) and various proteins/factors in RAW264.7 cells were quantified as follows: NO by the Griess assay; prostaglandin (PG) E(2), interleukin (IL)-6 and tumor necrosis factor (TNF)-α by ELISA; inducible nitric oxide synthase (iNOS) and cyclooxygenase (COX)-2 by Western blotting; and NF-κB and CD14/TLR4 by Western blotting or flow cytometry. BSA- or FA-BSA-treated RAW264.7 cells without LPS stimulation did not show any significant changes in NO or the tested proteins/factors and thus did not have any pro-inflammatory responses. Pre-treatment with unsaturated FA-BSA complexes significantly decreased the production of LPS-induced NO, PGE(2), IL-6 and TNF-α, the expression of iNOS, COX-2 and CD14, IκB degradation and NF-κB translocation. On the contrary, pre-treatment with saturated FA-BSA complexes enhanced these LPS-induced pro-inflammatory factors and the subsequent responses. We concluded that unsaturated FA-BSA complexes, but not saturated FA-BSA complexes, exert an inhibitory effect on the LPS-induced pro-inflammatory response and that this effect may be partially mediated through suppression of the NF-κB signaling pathway. We suggest that an increase of unsaturated FA-BSA complexes may enhance the host's defense against bacterial infection.