Epithelial adhesion mediated by pilin SpaC is required for Lactobacillus rhamnosus GG-induced probiotic effects 公开
Ardita, Courtney St Clair (2014)
Published
Abstract
Lactobacilli preparations are marketed for their health benefits and have shown promising efficacy as treatments for intestinal disease. Studies exploring the effect of lactobacilli in the alimentary canals of two common laboratory models, Drosophila and mice, have demonstrated that exposure to lactobacilli positively impacts development, homeostasis, and immune functioning in these systems. However, despite their clinical potential and the existence of laboratory models to investigate them, the nature of the relationship between commensal lactobacilli and host health is poorly characterized. The studies described in this dissertation elucidate some molecular mechanisms behind how probiotic lactobacilli induce salutary effects in the gastrointestinal tracts of flies and mice. Here, we found that Lactobacillus plantarum naturally colonizes laboratory-raised strains of Drosophila and that this bacterium induces cellular reactive oxygen species (ROS) generation in the Drosophila midgut. This cellular ROS generation also activates cell proliferation in the fly midgut. Lactobacilli-induced ROS generation was also shown to occur in cultured mammalian cells, and in the murine intestine. Indeed, Lactobacillus rhamnosus GG (LGG) induces particularly robust ROS generation in mammalian systems. We also established that ROS-generation is dependent on cellular expression of NADPH oxidase (Nox). Lactobacilli-induced ROS generation is significantly diminished in enterocyte specific dNox null Drosophila and in gut epithelial-specific Nox1 null mice. Furthermore, we demonstrated that the LGG pilin adhesion protein, SpaC, is required for LGG-induced ROS generation. An isogenic Lactobacillus rhamnosus GG strain that lacks SpaC (LGGΩspaC) does not adhere to intestinal mucus or murine intestines as well as the wild type strain. SpaC was shown to contribute to the capacity of LGG to induce cellular ROS generation, potentiate ERK MAPK signaling in enterocytes, stimulate cellular proliferation, and protect against radiation-induced injury. Collectively, these data show that commensal lactobacilli found in the alimentary canal lead to beneficial effects in their hosts by inducing cellular ROS generation through a Nox-dependent mechanism. In addition, LGG requires intimate contact with intestinal epithelial cells in order to elicit this ROS induction and its probiotic effects are dependent on bacterial expression of the SpaC pilin protein.
Table of Contents
Chapter 1 Introduction 1
References 30
Chapter 2 Symbiotic lactobacilli stimulate gut epithelial proliferation via Nox-mediated generation of reactive oxygen species 45
Abstract 46
Introduction 46
Materials and Methods 50
Results 55
Discussion 62
References 95
Chapter 3 Epithelial adhesion mediated by pilin SpaC is required for Lactobacillus rhamnosus GG-induced probiotic effects 102
Abstract 103
Introduction 103
Materials and Methods 106
Results 113
Discussion 118
References 133
Chapter 4 Discussion 140
References 144
Appendix 1 Probing the Spatial Organization of Measles Virus Fusion Complexes 145
Abstract 146
Introduction 147
Materials and Methods 151
Results 159
Discussion 169
References 189
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