Abstract
Objectives
To investigate whether cornus officinalis (CO) polyphenol extract attenuate the inflammatory response induced by lipopolysaccharide (LPS) in RAW 264.7 macrophages.
Methods
CO polyphenol extract was prepared using methanolic extraction, followed by solvent evaporation and freeze-drying. RAW 264.7 macrophages were treated with 0, 50, 100, 200 and 400 μg/ml of CO polyphenol extract. After 2 h, cells were then treated with 100 ng/ml of LPS for 6 h. Cells were then collected for whole cell protein expression analysis of signaling and inflammatory molecules via western blot. Results were analyzed using ANOVA followed by Tukey-Kramer post-hoc test.
Results
LPS treatment significantly increased Akt phosphorylation compared to control (1.00 ± 0.00 vs 0.16 ± 0.02 fold, P < 0.0001). However, pre-treatment with 100, 200 and 400 µg/ml of CO polyphenol extract significantly reduced Akt phosphorylation (0.57 ± 0.08 fold, P = 0.0030; 0.49 ± 0.08 fold, P = 0.0003 and 0.44 ± 0.09 fold, P < 0.0001, respectively) in LPS stimulated macrophages compared to LPS alone. Control cells did not express inducible nitric oxide synthase (iNOS); however, LPS induced iNOS expression, which was significantly decreased by treatment with 400 µg/ml CO polyphenol extract (1.00 ± 0.00 vs 0.36 ± 0.1 fold, P = 0.0098). Similarly, inflammatory cytokines such as interleukin (IL)-1β and 6 were not expressed in control macrophages; however, their expression was induced by LPS. CO polyphenol extract dose-dependently decreased LPS-induced expression of IL-1β (P < 0.0001) and IL-6 (P < 0.0001).
Conclusions
CO polyphenol extract attenuated the inflammatory response induced by LPS in RAW 264.7 macrophages. This effect is likely due to Akt downstream signaling inhibition.
Funding Sources
Lewis Foundation Grant Program.