Effects of radix curcumae-derived diterpenoid C onHelicobacter pylori-induced inflammation and nuclear factor kappa B signal pathways

Abstract

To study effect of diterpenoid C extracted from radix curcumae on Helicobacter pylori (H. pylori)-infected inflammation, intestinal metaplasia, and nuclear factor kappa B (NF-κB) signaling pathway in vitro. We used I-type H. pylori to infect human gastric epithelial gastric epithelium cell line (GES-1) cell lines, and then H. pylori-infected GES-1 cells were treated with radix curcumae (RC)-derived diterpenoid C of different concentrations (5, 10, 20 μg/mL) and amoxicillin. The expression of p65, IκB kinase (IKK) α and IKKγ proteins was detected with Western blotting, and the expression of interleukin (IL)-8, IL-6 and IL-4 was determined with enzyme-linked immunosorbent assay method. Data were analyzed using SPSS software ver18.0. For comparisons between groups of more than two unpaired values, one-way analysis of variance (ANOVA) was used. If an ANOVA F value was significant, post hoc comparisons were performed between groups. If results were not normally distributed, the Mann-Whitney U test was used to compare two groups of unpaired values, whereas for comparisons between groups of more than two unpaired values, the Kruskal-Wallis H test was used. Statistical significance was established at P < 0.05. The MTT assay results revealed the inhibited rate of GES-1, and indicated that the IC5 of RC-derived diterpenoid C and amoxicillin all were 5 μg/mL for gastric GES-1 cells. The expression of IL-8 was significantly increased, especially at 12 h time point; and the expression of IL-4 was decreased in H. pylori-infected GES-1 cells. After H. pylori-infected GES-1 cells were treated with RC-derived diterpenoid C of different concentrations and amoxicillin, the expression of IL-8 was decreased at 12, 24, 48, 72 h points (P < 0.01), especially in high-concentration diterpenoid C (20 μg/mL) group; and the expression of IL-4 was increased, especially in moderate and high-concentration diterpenoid C (10 and 20 μg/mL) groups. RC-derived diterpenoid C had the inhibitory effects on H. pylori-induced p65 translocation from cytoplasm into cell nucleus, H. pylori-stimulant IkBα degradation, the phosphorylation of p65 and IkBα, and the expression of IKKα and IKKβ proteins. RC-derived diterpenoid C can block NF-κB signal pathway, effectively reducing the secretion of H. pylori-induced proinflammatory cytokine and increasing the secretion of anti-inflammatory cytokine.