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Mitogen-activated protein kinases and nuclear factor-kappaB regulate Helicobacter pylori-mediated interleukin-8
Asima Bhattacharyya1, Shresh Pathak, Simanti Datta
1Department of Chemistry, Bose Institute, 93/1 Acharya Prafulla Chandra Road, Kolkata 700009, India.
Abstract:
Gastric infection, as well as inflammation, caused by Helicobacter pylori, activates the production of cytokines and chemokines by mononuclear cells; interleukin-8 (IL-8) is one of the major inflammatory chemokines. Since H. pylori does not invade mucosal tissue, we observed the effect of the water extract of H. pylori (HPE), containing shed factors, on the production of IL-8 by human peripheral blood monocytes and the human monocyte cell line THP-1. HPE-treatment induced activation of the mitogen-activated protein kinases (MAPKs) ERK (extracellular signal-regulated kinase), p38 and JNK (c-Jun N-terminal kinase), an effect which was not dependent on the presence of the cag pathogenicity island. p38 MAPK activation was sustained. The specific inhibitors, U0126 (for ERK1/2 signalling) and SB203580 (for p38 MAPK signalling), both abrogated IL-8 secretion from HPE-treated THP-1. Dominant-negative mutants of the upstream kinases MEK1 (MAPK/ERK kinase 1), MKK (MAPK kinase) 6 and MKK7 also inhibited IL-8 secretion, pointing to a role of all three MAPKs in HPE-mediated IL-8 release. The inhibitory effects of polymyxin B and anti-CD14 antibody suggested that the effect of HPE on MAPKs was mediated by H. pylori lipopolysaccharide (LPS). By analysis of IL-8-promoter-driven luciferase gene expression, we observed that the effects of HPE-induced nuclear factor-kappaB (NF-kappaB) activation and MAPK signalling were mediated at the level of the IL-8 promoter. While ERK1/2 activation could be linked to enhanced DNA binding of activator protein-1 (AP-1), p38 MAPK signalling did not affect AP-1 DNA binding. Taken together, these results provide the first evidence that LPS from H. pylori stimulates IL-8 release from cells of the monocytic lineage through activation of NF-kappaB and signalling along MAPK cascades. The stimulation of MAPK signalling in macrophages by LPS of H. pylori amplifies the inflammatory response associated with gastric H. pylori infection and needs to be taken into consideration when developing therapeutics based on these signalling pathways.
Insights
Helicobacter pylori lipopolysaccharide (LPS) triggers interleukin-8 (IL-8) release from monocytes by activating nuclear factor-kappaB (NF-kappaB) and mitogen-activated protein kinase (MAPK) pathways. This inflammatory response is crucial for understanding gastric infection therapies.
Area of Science:
- Immunology
- Microbiology
- Cell Biology
Background:
- Gastric infection by Helicobacter pylori (H. pylori) causes inflammation via cytokine and chemokine production by mononuclear cells.
- Interleukin-8 (IL-8) is a key chemokine in H. pylori-induced inflammation.
- H. pylori does not invade mucosal tissue, suggesting shed factors mediate inflammation.
Purpose of the Study:
- To investigate the effect of H. pylori water extract (HPE) on IL-8 production by human monocytes.
- To elucidate the signaling pathways involved in HPE-induced IL-8 release.
Main Methods:
- Treatment of human peripheral blood monocytes and THP-1 cells with HPE.
- Analysis of mitogen-activated protein kinase (MAPK) activation (ERK, p38, JNK).
- Use of specific MAPK inhibitors (U0126, SB203580) and dominant-negative mutants.
- Investigation of the role of lipopolysaccharide (LPS) using polymyxin B and anti-CD14 antibody.
- Luciferase gene expression assays to study IL-8 promoter activity, nuclear factor-kappaB (NF-kappaB), and activator protein-1 (AP-1) activation.
Main Results:
- HPE treatment activated ERK, p38, and JNK MAPKs, independent of the cag pathogenicity island.
- Sustained p38 MAPK activation was observed.
- Inhibitors of ERK and p38 MAPK, as well as upstream kinases, abrogated IL-8 secretion.
- H. pylori LPS was identified as the mediator of HPE's effect on MAPKs.
- HPE-induced NF-kappaB activation and MAPK signaling occurred at the IL-8 promoter level.
- ERK1/2 activation correlated with enhanced AP-1 DNA binding, while p38 MAPK did not.
Conclusions:
- H. pylori LPS stimulates IL-8 release from monocytic cells via NF-kappaB and MAPK signaling cascades.
- MAPK activation by H. pylori LPS amplifies the inflammatory response in gastric infections.
- Understanding these pathways is critical for developing targeted therapeutics.