When to use probiotics in luminal gastrointestinal disorders?

Highlights on two decades with microbiota and inflammatory bowel disease from etiology to therapy

Inflammatory Bowel diseases (IBDs) constitute a complex panel of disorders characterized with chronic inflammation affecting the alimentary canal along with extra intestinal manifestations. Its exact etiology is still unknown; however, it seems to be the result of uncharacterized environmental insults in the intestine and their immunological consequences along with dysbiosis, in genetically predisposed individuals. It was the main target of our team since 2002 to explore the etiology of IBD and the related role of bacteria. For almost two decades, our laboratory, among others, has been involved in the reciprocal interaction between the host gastrointestinal lining and the homing microbiota. In the first decade, the attention of scientists focused on the possible role of enteropathogenic E. coli and its relationship to the mechanistic pathways involved in IBD induced in both rats and mice by chemicals like Iodoacetamide, Dextran Sodium Sulfate, Trinitrobenzene, thus linking microbial alteration to IBD pathology. A thorough characterization of the various models was the focus of research in addition to exploring how to establish an active homeostatic composition of the commensal microbiota, including its wide diversity by restoration of gut microbiota by probiotics and moving from dysbiosis to eubiosis. In the last six years and in order to effectively translate such findings into clinical practice, it was critical to explore their relationship to colorectal cancer CRC both in solid tumors and chemically induced CRC. It was also critical to explore the degree of intestinal dysbiosis and linking to IBD, CRC and diabetes. Remarkably, the active mechanistic pathways were proposed as well as the role of microbiota or bacterial metabolites involved. This review covers two decades of investigations in our laboratory and sheds light on the different aspects of the relationship between microbiota and IBD with an emphasis on dysbiosis, probiotics and the multiple mechanistic pathways involved.

Pathways of Gastric Carcinogenesis, Helicobacter pylori Virulence and Interactions with Antioxidant Systems, Vitamin C and Phytochemicals

Helicobacter pylori is a class one carcinogen which causes chronic atrophic gastritis, gastric intestinal metaplasia, dysplasia and adenocarcinoma. The mechanisms by which H. pylori interacts with other risk and protective factors, particularly vitamin C in gastric carcinogenesis are complex. Gastric carcinogenesis includes metabolic, environmental, epigenetic, genomic, infective, inflammatory and oncogenic pathways. The molecular classification of gastric cancer subtypes has revolutionized the understanding of gastric carcinogenesis. This includes the tumour microenvironment, germline mutations, and the role of Helicobacter pylori bacteria, Epstein Barr virus and epigenetics in somatic mutations. There is evidence that ascorbic acid, phytochemicals and endogenous antioxidant systems can modify the risk of gastric cancer. Gastric juice ascorbate levels depend on dietary intake of ascorbic acid but can also be decreased by H. pylori infection, H. pylori CagA secretion, tobacco smoking, achlorhydria and chronic atrophic gastritis. Ascorbic acid may be protective against gastric cancer by its antioxidant effect in gastric cytoprotection, regenerating active vitamin E and glutathione, inhibiting endogenous N-nitrosation, reducing toxic effects of ingested nitrosodimethylamines and heterocyclic amines, and preventing H. pylori infection. The effectiveness of such cytoprotection is related to H. pylori strain virulence, particularly CagA expression. The role of vitamin C in epigenetic reprogramming in gastric cancer is still evolving. Other factors in conjunction with vitamin C also play a role in gastric carcinogenesis. Eradication of H. pylori may lead to recovery of vitamin C secretion by gastric epithelium and enable regression of premalignant gastric lesions, thereby interrupting the Correa cascade of gastric carcinogenesis.