A proinflammatory peptide from Helicobacter pylori activates monocytes to induce lymphocyte dysfunction and apoptosis

Area of Science:

• Immunology
• Gastroenterology
• Microbiology

Background:

• Helicobacter pylori infection causes chronic gastritis, a risk factor for gastric adenocarcinoma.
• Mechanisms linking H. pylori-induced inflammation to gastric carcinogenesis are not fully understood.

Purpose of the Study:

• To investigate the role of a specific H. pylori peptide, Hp(2-20), in modulating immune responses within the gastric mucosa.
• To identify the receptors and downstream effects of Hp(2-20) on immune cells, particularly monocytes and lymphocytes.

Main Methods:

• Identification of Hp(2-20) as a monocyte chemoattractant and activator of monocyte NADPH-oxidase.
• Characterization of monocyte receptors FPRL1 and FPRL2 for Hp(2-20).
• Assessment of Hp(2-20)-induced effects on natural killer (NK) cells and T cells, including cytotoxicity, CD3zeta expression, and apoptosis.

Main Results:

• Hp(2-20) activates monocytes, leading to the production of oxygen radicals.
• Hp(2-20)-activated monocytes inhibit the antitumor functions of NK cells and T cells.
• Hp(2-20)-induced oxygen radicals mediate reduced cytotoxicity, CD3zeta downregulation, and apoptosis in lymphocytes.
• Histamine rescues lymphocytes from Hp(2-20) effects by suppressing oxygen radical formation.

Conclusions:

• H. pylori's Hp(2-20) peptide contributes to immune dysregulation by attracting and activating monocytes, thereby impairing antineoplastic lymphocytes.
• These findings reveal novel mechanisms in H. pylori-associated carcinogenesis, potentially regulated by histamine in the gastric mucosa.