Aplicación de técnicas moleculares avanzadas para la evaluación de mecanismos de acción de bacterias probióticas frente al estrés oxidativo

Zusammenfassung

Certain foods, such as those subjected to severe technological processes, provide the diet with lipid (malondialdehyde, MDA) and protein (aminoadipic acid, AAA) oxidation products. These compounds display potential harmful effects, such as the alteration of the cellular redox state, which leads to the appearance of oxidative stress. In intestinal cells such stress is related to pathologies of the gastrointestinal tract (GIT). To counteract the negative effects of the intake of oxidized products, antioxidant strategies have been proposed in food, among which are the supplementation with phenolic compounds and probiotic bacteria. The beneficial effect of probiotic bacteria responds to little-known molecular mechanisms. The progress in this field requires the application of advanced techniques of molecular biology, such as real-time PCR, flow cytometry or bacterial proteome analysis. In this Doctoral Thesis, two potentially probiotic bacteria, Lactobacillus reuteri and Enterococcus faecium, have been exposed to MDA, AAA and hydrogen peroxide at different concentrations in addition to combining the exposure to the latter with a phenolic compound (chlorogenic acid). Prooxidant compounds have been shown to produce reactive oxygen species (ROS), promote oxidation of bacterial lipids and proteins and induce the activation of bacterial antioxidant responses. On the other hand, the phenolic compound stimulates protein carbonylation and cell signalling, and hence, enhancing the antioxidant responses. The advanced techniques used in this Doctoral Thesis have allowed gaining precise information on the mechanisms of gene expression and protein synthesis that are activated in probiotic bacteria against the damage caused by dietary oxidation products.