Extra virgin olive oil inhibits Helicobacter pylori growth in vitro and the development of mice gastric mucosa lesions in vivo

Abstract

Helicobacter pylori infection is widespread worldwide, with more than a half of the world population infected. H. pylori antibiotic-resistant strains and non-compliance to therapy are the major causes of H. pylori eradication failure. The search for new therapies based on plant extracts is a scientific interest field. The present study was conducted to evaluate the effect in vitro of extra virgin olive oil (EVOO), hydroxytyrosol (HT), and oleuropein (Olp) against two H. pylori strains and the effect in vivo of the oral administration of EVOO on the gastric mucosa of BALB/c mice infected with this microorganism. The broth microdilution method assayed the antibacterial in vitro activity of EVOO, HT, and Olp against H. pylori strains. For in vivo studies, male BALB/c mice were infected orally with an H. pylori suspension every 72 h. Four groups were used: (1) Control, (2) H. pylori-infected (HP), (3) EVOO, and (4) HP + EVOO. Mice were sacrificed at 7, 15, and 30 days. The stomachs were removed and observed under a microscope. Scoring of the degree of erosion was determined. Samples were processed by histological techniques for light microscopy. Macroscopic analysis showed that the presence of small erosions increased, both in number and size, in the infected group. Animals infected and treated with EVOO exhibited the presence of fewer erosions, which decreased in number as the treatment progressed. The mucosa of the control and EVOO groups showed normal histological characteristics at the three times studied. The mucosa of animals infected with H. pylori showed disruptions of the lining epithelium, damage to gastric glands, and vasodilation. The mucosa of animals infected with H. pylori and treated with EVOO showed morphological characteristics similar to those of normal and EVOO mucosa. For the first time, the current study showed the effect in vitro and in vivo of EVOO and combined administration of HT and Olp against H. pylori using an animal model. Future studies are needed to establish the mechanism of EVOO's action at the gastric mucosa level to propose this product as a natural antimicrobial agent for the treatment of gastric H. pylori infections.

Keywords: EVOO; Helicobacter pylori; gastric mucosa; hydroxytyrosol; oleuropein; olive oil.

FIGURE 1

Flow diagram of the in vitro study of extra virgin olive oil (EVOO), sunflower oil (SFO), hydroxytyrosol (HT), oleuropein (Olp), and amoxicillin (AMX) against Helicobacter pylori strains NCTC 11638 and HP661 (Behzadi and Gajdács, 2021).

FIGURE 2

Flow diagram of the in vitro study of different concentrations of hydroxytyrosol (HT) together with oleuropein (Olp) against Helicobacter pylori strains NCTC 11638 and HP661 (Behzadi and Gajdács, 2021).

FIGURE 3

Flow diagram of the in vivo study of extra virgin olive oil (EVOO) against the infection of Helicobacter pylori strains NCTC 11638 in the gastric mucosa of mice (Behzadi and Gajdács, 2021).

FIGURE 4

Macroscopic evaluation of the gastric mucosa surface of mice after 7, 15, or 30 days of treatment from four experimental groups: (1) Control, (2) Extra virgin olive oil (EVOO), (3) Helicobacter pylori, and (4) EVOO + H. pylori. Gastric mucosa from the control and EVOO groups shows a healthy appearance, with a score of 1 and 2 (control) and 2 (EVOO) at different infection times. Helicobacter pylori group had an increasing scoring with the time, reaching the highest value at 30 days, while in the group infected and treated with EVOO, the gastric mucosa structure is similar to that of the control and EVOO groups.

FIGURE 5

Effects of extra virgin olive oil (EVOO) on gastric lesions induced by the infection of Helicobacter pylori in mice. Asterisks denote significant differences between groups (*p < 0.05, **p < 0.01, and ****p < 0.001). All values are expressed as mean ± S.E.M.

FIGURE 6

Hematoxylin–Eosin stain at 7 days after infection. The mucosa of the control and extra virgin olive oil (EVOO) groups shows normal histological characteristics. The mucosa of animals infected with Helicobacter pylori shows apparent injuries, mainly disruptions of the lining epithelium and damage in the isthmus and the neck of gastric glands. A decrease in the size of the gland epithelial cells can be observed. Blood, remnants of injured tissue, and some mucus filaments are observed in the lumen. The mucosa of animals infected with H. pylori and treated with EVOO shows morphological characteristics similar to those of normal and EVOO mucosa, even though slight damage is observed. Scale bar: 40 μm.

FIGURE 7

Hematoxylin–Eosin stain of Helicobacter pylori group and H. pylori and treatment group at 15 days. The mucosa of animals infected with H. pylori shows structural alterations, such as an increase of the gland gastric, vasodilation, and increased blood supply. The mucosa of animals infected with H. pylori and treated simultaneously with EVOO show morphological characteristics similar to those of normal and EVOO mucosa, even though slight vasodilation is observed. Scale bar: 40 μm.

FIGURE 8

Hematoxylin–Eosin stain of Helicobacter pylori group and H. pylori and treatment group at 30 days. Significantly damaged tissue is observed with many blood vessels in gastric mucosa from the H. pylori group. At 30 days, significantly damaged tissue is observed with the presence of a large number of blood vessels. The mucosa of animals infected with H. pylori and treated with EVOO shows morphological characteristics similar to those of normal and EVOO mucosa. HP + EVOO group shows a cytoprotected gastric mucosa. Scale bar: 40 μm.