Helicobacter pylori in a Korean isolate activates mitogen-activated protein kinases, AP-1, and NF-κB and induces chemokine expression in gastric epithelial AGS cells

Oxidant-sensitive transcription factors, nuclear factor-κB (NF-κB), and activator protein-1 (AP-1) have been considered as the regulators of inducible genes such as chemokines. Since oxygen radicals are considered as an important regulator in the pathogenesis of Helicobacter pylori (H. pylori)-induced gastric ulceration and carcinogenesis, chemokines such as interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) may be regulated by NF-κB and/or AP-1. Ras, the upstream activator for mitogen-activated protein kinase (MAPK) and MAPK cascade regulate AP-1 activation. The present study aims to investigate whether H. pylori in a Korean isolate (HP99) induces the expression of chemokines (IL-8, MCP-1), which is regulated by Ras, MAPK, AP-1, and NF-κB in gastric epithelial AGS cells, and whether these transcriptional regulations of chemokines are inhibited by transfection with mutant genes for Ras (ras N-17), c-Jun (TAM-67), and IκBα (MAD-3) or treatment with MAPK inhibitors (U0126 for extracellular signal-regulated kinase or SB203580 for p38 kinase). In addition, virulence factors of HP99 were characterized by PCR analysis for the isolated DNA. As a result, HP99 is identified as cagA +, vacA s1b, m2, iceA1 H. pylori strain. HP99 induced a time-dependent expression of mRNA and protein for IL-8 and MCP-1 via mediation of MAPK, AP-1, and NF-κB. Transfection with mutant genes for Ras, c-Jun, and IκBα and treatment with MAPK inhibitors suppressed H. pylori-induced activation of transcription factors (NF-κB, AP-1) and expression of chemokines (IL-8, MCP-1) in AGS cells. In conclusion, Ras and MAPK cascade may act as the upstream signaling for the activation of AP-1 and NF-κB, which induce chemokine expression in H. pylori-infected AGS cells. Specific targeting of the activation of NF-κB and AP-1 may be effective for the prevention or treatment of gastric inflammation associated with H. pylori infection.