A New Role for Helicobacter pylori Urease: Contributions to Angiogenesis

Abstract

Helicobacter pylori is a pathogen involved in gastric diseases such as ulcers and carcinomas. H. pylori’s urease is an important virulence factor produced in large amounts by this bacterium. In previous studies, we have shown that this protein is able to activate several cell types like neutrophils, monocytes, platelets, endothelial cells, and gastric epithelial cells. Angiogenesis is a physiological process implicated in growth, invasion and metastization of tumors. Here, we have analyzed the angiogenic potential of H. pylori urease (HPU) in gastric epithelial cells. No cytotoxicity was observed in AGS, Kato-III, and MKN28 gastric cell lines treated with 300 nM HPU, as evaluated by the 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. As we previously reported in neutrophils, treatment with 300 nM HPU also had an anti-apoptotic effect in gastric epithelial cells leading to a 2.2-fold increase in the levels of Bcl-XL after 6 h, and a decrease of 80% in the content of BAD, after 48 h, two mitochondrial proteins involved in regulation of apoptosis. Within 10 min of exposure, HPU is rapidly internalized by gastric epithelial cells. Treatment of the gastric cells with methyl-β-cyclodextrin abolished HPU internalization suggesting a cholesterol-dependent process. HPU induces the expression of pro-angiogenic factors and the decrease of expression of anti-angiogenic factors by AGS cells. The angiogenic activity of HPU was analyzed using in vitro and in vivo models. HPU induced formation of tube-like structures by human umbilical vascular endothelial cells in a 9 h experiment. In the chicken embryo chorioallantoic membrane model, HPU induced intense neo-vascularization after 3 days. In conclusion, our results indicate that besides allowing bacterial colonization of the gastric mucosa, H. pylori’s urease triggers processes that initiate pro-angiogenic responses in different cellular models. Thus, this bacterial urease, a major virulence factor, may also play a role in gastric carcinoma development.

Helicobacter pylori urease induces pro‐inflammatory effects and differentiation of human endothelial cells: Cellular and molecular mechanism

“…The upregulation of this receptor is a strong indicative that HPU prompts endothelial cells to a more responsive phenotype that, associated with increased migration and invasion, may result in the differentiation of new blood vessels. The data give further support to previous observations on the pro‐angiogenic properties of HPU …”

“…We have previously reported that non‐catalytic HPU has pro‐inflammatory activity in mice and activates host cells, inducing blood platelet aggregation, chemotaxis, and ROS production by human neutrophils . More recently, it was demonstrated that HPU was internalized by epithelial gastric cells, triggering the expression of pro‐angiogenic mediators, and induced angiogenesis in vivo in the chicken chorioallantoic membrane model . We are now showing that HPU directly activates human microvasculature endothelial cells, modulating the molecular mechanisms that lead to their differentiation toward a pro‐inflammatory profile.…”

“…[11][12][13] More recently, it was demonstrated that HPU was internalized by epithelial gastric cells, triggering the expression of pro-angiogenic mediators, and induced angiogenesis in vivo in the chicken chorioallantoic membrane model. 14 We are now showing that HPU directly activates human microvasculature endothelial cells, modulating the molecular mechanisms that lead to their differentiation toward a pro-inflammatory profile. The severe local inflammation that occurs during H pylori infection is associated with peptic ulcers and gastric cancers, and its outcome is mostly determined by the expression of specific virulence factors.…”

“…HPU activity was shown to be required for triggering gastric epithelial barrier dysfunction during bacterial infection . More recently, our group demonstrated that HPU can be internalized by gastric epithelial cells inducing the expression of pro‐angiogenic mediators …”

“…5 More recently, our group demonstrated that HPU can be internalized by gastric epithelial cells inducing the expression of pro-angiogenic mediators. 14 The interaction ofH pylori with endothelial cells was shown to upregulate the expression of adhesion molecules and the secretion of neutrophil-recruiting chemokines. 15,16 Thus, a persistent endothelial cell activation induced by bacterial products could be involved in the continuous recruitment of neutrophils to H pylori-infected gastric mucosa and may therefore contribute to tissue damage and ulcer generation.…”