Anti-Inflammatory Effects of Gingerol on Lipopolysaccharide-Stimulated RAW 264.7 Cells by Inhibiting NF-κB Signaling Pathway

Gingerol was the main functional substance of Zingiberaceous plant which has been known as traditional medicine for thousands of years. The purpose of this experiment was to explore anti-inflammatory effects of gingerol and study the possible mechanism in lipopolysaccharide (LPS)-stimulated RAW246.7 cells. The cells were treated with 10 μg/mL LPS and 300, 200, 100, and 50 μg/mL gingerol for 24 h. The cytotoxicity of gingerol was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetra-zoliumbromide (MTT) method. Nitric oxide (NO) production was observed using Griess assays. Prostaglandin E₂ (PGE₂) and pro-inflammatory cytokines tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 have been analyzed by ELISA. Real-time PCR was used to detect the mRNA expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), IL-6, and IL-1β in LPS-induced RAW246.7 cells. Nuclear transcription factor kappa-B (NF-κB) signaling pathway-related proteins have been assessed by western blot assays. The determination of MTT showed that cell viability was not significantly affected by up to 300 μg/mL gingerol. Compared with LPS group, 50, 100, 200, and 300 μg/mL gingerol can inhibit the production of NO and the inhibitory rate was 10.4, 29.1, 58.9, and 62.4%, respectively. The results indicated gingerol existed anti-inflammatory effect. In addition, gingerol also observably inhibited LPS-induced TNF-α, IL-1β, IL-6, and PGE₂ (p < 0.01) expression and secretion in a dose-dependent manner. At the genetic level, after the intervention of gingerol, mRNA transcriptions of iNOS, COX-2, IL-6, and IL-1β were all decreased. The protein expressions of iNOS, NF-κB, p-p65, and p-IκB were significantly increased in LPS-induced cells, while these changes were reversed by the treatment with gingerol. This study suggested that gingerol exerts its anti-inflammatory activities in LPS-induced macrophages which can inhibit the production of inflammatory cytokines by targeting the NF-κB signaling pathway.