LACTOBACILLUS - MEDIATED MODULATION OF IL-8 PRODUCTION IN HELICOBACTER PYLORI - STIMULATED GASTRIC EPITHELIAL CELLS

Abstract

Helicobacter pylori causes gastritis, peptic ulcers, and is considered an important risk factor of gastric cancer. Infection with H. pylori induces the release of interleukin (IL)-8 from gastric epithelial cells leading to tissue inflammation and damage. Lactobacillus plantarum strain XB7 (LP-XB7), Lactobacillus salivarius strains B37 (LS-B37), and B60 (LS-B60) have been shown to suppress H. pylori-induced IL-8 production from AGS gastric epithelial cells. LP-XB7 was also shown to decrease IL-8 transcription via the suppression of NF-κB and c-Jun activation. This study aimed to investigate the mechanisms of IL-8 suppression in H. pylori-stimulated AGS cells by these lactobacilli. The effects of Lactobacillus conditioned media (LCM) on IL-8 transcription were tested by quantitative real-time PCR. Changes in the signaling pathway associated with IL-8 production were determined by western blot analysis. Expression of genes cagA and cagE was determined by quantitative real-time PCR. Immunomodulatory factors responsible for suppressing IL-8 production in H. pylori-induced AGS cells were characterized by testing thermal stability, size estimation, and enzyme sensitivity. LCM of LS-B37 and LS-B60 attenuated IL-8 mRNA expression (p < 0.01 and p < 0.001, respectively) like that of LP-XB7. However, LS-B37 and LS-B60 interfered with IL-8 mRNA transcription via the suppression of NF-kB activation (p < 0.01), while LP-XB7 did via NF-κB and c-Jun. Expression of H. pylori virulence genes cagA and cagE was not affected by LCM of these strains. IL-8 inhibitory substances of LP-XB7, LS-B37, and LS-B60 are heat-stable and more than 100 kDa in size. Additionally, IL-8 inhibitory substance of LS-B37 was sensitive to amylase, whereas those of LP-XB7 and LS-B60 were sensitive to amylase, lipase, proteinase K, and trypsin. It was thus suggested that the polysaccharide in LCM of LS-B37 is responsible for the inhibition of NF-κB activation in AGS cells stimulated with H. pylori and IL-8 inhibitory effect of LP-XB7 and LS-B60 is probably due to different complex components of polysaccharides, lipids and, proteins. These results showed that human gastric-derived Lactobacillus strains produce multiple immunomodulatory factors capable of suppressing H. pylori-induced IL-8 production from gastric epithelial cells and supported the potential of these strains as probiotics for adjunctive therapy of H. pylori infection.