Anti-Helicobacter pylori Properties of the Ant-Venom Peptide Bicarinalin

Abstract

The venom peptide bicarinalin, previously isolated from the ant Tetramorium bicarinatum, is an antimicrobial agent with a broad spectrum of activity. In this study, we investigate the potential of bicarinalin as a novel agent against Helicobacter pylori, which causes several gastric diseases. First, the effects of synthetic bicarinalin have been tested against Helicobacter pylori: one ATCC strain, and forty-four isolated from stomach ulcer biopsies of Peruvian patients. Then the cytoxicity of bicarinalin on human gastric cells and murine peritoneal macrophages was measured using XTT and MTT assays, respectively. Finally, the preventive effect of bicarinalin was evaluated by scanning electron microscopy using an adherence assay of H. pylori on human gastric cells treated with bicarinalin. This peptide has a potent antibacterial activity at the same magnitude as four antibiotics currently used in therapies against H. pylori. Bicarinalin also inhibited adherence of H. pylori to gastric cells with an IC₅₀ of 0.12 μg·mL^-1 and had low toxicity for human cells. Scanning electron microscopy confirmed that bicarinalin can significantly decrease the density of H. pylori on gastric cells. We conclude that Bicarinalin is a promising compound for the development of a novel and effective anti-H. pylori agent for both curative and preventive use.

Keywords: Helicobacter pylori; SEM; antimicrobial peptide; bacterial adhesion; bicarinalin; gastric cells.

Figure 1

Antimicrobial resistance rates of Peruvian clinical H. pylori strains to conventional antibiotics according the EUCAST antimicrobial breakpoints for H. pylori: clarithromycin: S ≤ 0.7 μmol·L⁻¹, R > 1.4 μmol·L⁻¹; metronidazole: S ≤ 46.8 μmol·L⁻¹, R > 46.8 μmol·L⁻¹; levofloxacin: S ≤ 1.34 μmol·L⁻¹, R > 1.34 μmol·L⁻¹; amoxicillin: S ≤ 0.28 μmol·L⁻¹, R > 0.28 μmol·L⁻¹.

Figure 2

Scanning-electron microscopy analysis of H. pilori. (a) Without antimicrobial peptide; (b) with bicarinalin (60 μg·mL⁻¹). (SEM mag = 20,000).

Figure 3

Anti-adhesive effect of helicobacter pylori on gastric cells.

Figure 4

SEM images of cultured cellular carpet of human stomach: (a) no H. pylori; (b) H. pylori present; (c) H. pylori present with 0.015 μg·mL⁻¹ of bicarinalin or (d) with 0.25 μg·mL⁻¹ of bicarinalin (SEM mag = 1000; Arrows show single or aggregated bacteria).