Aralia elata   (Miquel) Seemann Suppresses Inflammatory Responses in Macrophage Cell by Regulation of NF-kappa B Signalling

Purpose: To investigate the antioxidant and anti-inflammatory effects of Aralia elata extract (AEE) in lipopolysaccharide (LPS)-stimulated Raw264.7 cells.
Methods: Antioxidant activity was measured using 1, 1-diphenyl-2-picryl-hydrazyl (DPPH) radical scavenging assay. Cell viability was evaluated using 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay. RAW264.7 cells were stimulated with LPS to study protein expression and production of inflammatory mediators, determined by Western blot analysis.
Results: AEE significantly inhibited DPPH-generated free radicals showing maximum inhibition at 40 μg/mL (p < 0.001). AEE alone did not exhibit any signs of cytotoxicity to RAW264.7 cells up to 200 μg/mL concentration. The LPS-induced increase in the production of nitric oxide was concentrationdependently suppressed with half-maximal concentration (IC₅₀) of 91.5 ug/ mL of AEE (p < 0.05 at 10 μg/mL, p < 0.01 at 20 μg/mL and p < 0.001 at 40 μg/mL, respectively). AEE also inhibited dosedependently the LPS-induced increase in inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) expressions with IC₅₀ of 72.5 ug/ mL. Furthermore, the production of pro-inflammatory cytokines, viz, tumor necrosis factor-α by LPS-stimulation in RAW264.7 cells was inhibited dosedependently with IC₅₀ of 34.9 ug/ mL by AEE pretreatment. Mechanistic studies revealed that AEE acts by regulation of nuclear factor kappa-B signaling pathway in LPS-stimulated RAW264.7 cells.
Conclusion: This study shows, for the first time, that AEE possesses antioxidant and anti-inflammatory effects and can be developed as a potential therapeutic agent for ameliorating macrophage-mediated inflammation.

Keywords
Aralia elata; Anti-inflammatory activity; Macrophage cells; Inducible nitric oxide synthase; nuclear factor kappa-B signaling