Interleukin-8 Expression by Human Neutrophils Activated by <i>Helicobacter pylori</i> Soluble Proteins

Abstract

BACKGROUND: Helicobacter pylori soluble proteins may serve as chemoattractants for neutrophils. Once extravasated and attracted to the gastric mucosa, neutrophils themselves may be a source of interleukin-8 (IL-8), further amplifying the inflammatory response. We evaluated IL-8 expression and the activation of human neutrophils by H. pylori products. METHODS: After neutrophils had been stimulated with H. pylori culture supernatant, IL-8 mRNA expression was assessed by quantitative reverse transcription polymerase chain reaction, using synthetic standard RNA at 0, 1, 2, 4, and 9 h. The amount of IL-8 protein was measured by enzyme-linked immunosorbent assay (ELISA). Lymphocyte function-associated antigen-1beta (LFA-1beta) (CD18) expression was determined with flow cytometry, and myeloperoxidase secretion was analyzed with ELISA. After acetohydroxamic acid (AHA) and/or N-tert-butoxycarbonyl-methionyl-leucyl-phenylalanine (BOC-MLP) was added to H. pylori culture supernatant, IL-8 ELISA was analyzed for 9 h. RESULTS: IL-8 mRNA expression by stimulated neutrophils was 16 to 67 times greater than by controls, peaking at 2 h after stimulation. The amount of IL-8 protein was markedly increased at 4 h after stimulation. H. pylori culture supernatant enhanced LFA-1beta expression and myeloperoxidase secretion by neutrophils. AHA and/or BOC-MLP decreased IL-8 production at 2-4 h after stimulation. CONCLUSIONS: H. pylori-induced neutrophil recruitment may be mediated via IL-8 expressed by neutrophils activated by H. pylori soluble proteins. This may explain the gastric mucosal inflammatory response to the non-invasive organism.