Helicobacter pylori is a gram negative bacterium that infects the human stomach of approximately half of the world's population. It produces oxidative stress, and mitochondria are one of the possible targets and the major intracellular source of free radicals. The present study was aimed at determining mitochondrial alterations in H. pylori-infected gastric epithelial cells and its relationship with oxidative stress, one of the recognized causes of apoptotic processes. Cells were treated with a strain of H. pylori for 24 h. Cellular oxidative burst, antioxidant defense analysis, mitochondrial alterations and apoptosis-related processes were measured. Our data provide evidence on how superoxide acts on mitochondria to initiate apoptotic pathways, with these changes occurring in the presence of mitochondrial depolarization and other morphological and functional changes. Treatment of infected cells with Vitamin E prevented increases in intracellular ROS and mitochondrial damage consistent with H. pylori inducing a mitochondrial ROS mediated programmed cell death pathway.

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Infection with H. pylori plays a role in the pathogenesis of gastritis, peptic ulcer, gastric carcinoma, and gastric lymphoma, but mechanisms leading to the various clinical manifestations remain obscure and are the primary focus of research in this field. Proliferation and apoptosis are essential in the maintenance of gastric tissue homeostasis, and changes seen in their balance may condition gastric mucosal changes during infection. Thus, excessive apoptosis or proliferation inhibition will result in cell mass loss, which is observed in gastric ulcers. On the other hand, accelerated epithelial cell turnover is characteristic of carcinogenic mucosas. There is also scientific evidence that demonstrates an association between H. pylori infection and exacerbated synthesis of free radicals, the latter being well known as a primary cause of cell death. A thorough review of the literature and the results of our experimental research lead to conclude that H. pylori-induced oxidative stress activates the intrinsic pathway of apoptosis. Structural and functional changes caused by this process on mitochondrial organelles lie at the origin of gastric mucosal toxicity, and lead to the development of the various manifestations associated with this infection. Based on these data we suggest that therapy with antioxidants should prove beneficial for the clinical management of patients with H. pylori infection.

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