ABSTRACT
Beneficial microbes that target molecules and pathways, such as oxidative stress, which can negatively affect both host and microbiota, may hold promise as an inflammatory bowel disease therapy. Prior work showed that a five-strain fermented milk product (FMP) improved colitis in T-bet(-/-) Rag2(-/-) mice. By varying the number of strains used in the FMP, we found that Lactococcus lactis I-1631 was sufficient to ameliorate colitis. Using comparative genomic analyses, we identified genes unique to L. lactis I-1631 involved in oxygen respiration. Respiration of oxygen results in reactive oxygen species (ROS) generation. Also, ROS are produced at high levels during intestinal inflammation and cause tissue damage. L. lactis I-1631 possesses genes encoding enzymes that detoxify ROS, such as superoxide dismutase (SodA). Thus, we hypothesized that lactococcal SodA played a role in attenuating colitis. Inactivation of the sodA gene abolished L. lactis I-1631's beneficial effect in the T-bet(-/-) Rag2(-/-) model. Similar effects were obtained in two additional colonic inflammation models, Il10(-/-) mice and dextran sulfate sodium-treated mice. Efforts to understand how a lipophobic superoxide anion (O2 (-)) can be detoxified by cytoplasmic lactoccocal SodA led to the finding that host antimicrobial-mediated lysis is a prerequisite for SodA release and SodA's extracytoplasmic O2 (-) scavenging. L. lactis I-1631 may represent a promising vehicle to deliver antioxidant, colitis-attenuating SodA to the inflamed intestinal mucosa, and host antimicrobials may play a critical role in mediating SodA's bioaccessibility.
Subject(s)
Colitis/metabolism , Lactococcus lactis/metabolism , Muramidase/metabolism , Superoxide Dismutase/metabolism , Animals , Colitis/enzymology , Colitis/microbiology , Intestinal Mucosa/enzymology , Intestinal Mucosa/metabolism , Intestinal Mucosa/microbiology , Mice , Reactive Oxygen Species/metabolismABSTRACT
Dysregulated immune responses to gut microbes are central to inflammatory bowel disease (IBD), and gut microbial activity can fuel chronic inflammation. Examining how IBD-directed therapies influence gut microbiomes may identify microbial community features integral to mitigating disease and maintaining health. However, IBD patients often receive multiple treatments during disease flares, confounding such analyses. Preclinical models of IBD with well-defined disease courses and opportunities for controlled treatment exposures provide a valuable solution. Here, we surveyed the gut microbiome of the T-bet(-/-) Rag2(-/-) mouse model of colitis during active disease and treatment-induced remission. Microbial features modified among these conditions included altered potential for carbohydrate and energy metabolism and bacterial pathogenesis, specifically cell motility and signal transduction pathways. We also observed an increased capacity for xenobiotics metabolism, including benzoate degradation, a pathway linking host adrenergic stress with enhanced bacterial virulence, and found decreased levels of fecal dopamine in active colitis. When transferred to gnotobiotic mice, gut microbiomes from mice with active disease versus treatment-induced remission elicited varying degrees of colitis. Thus, our study provides insight into specific microbial clades and pathways associated with health, active disease and treatment interventions in a mouse model of colitis.
Subject(s)
Colitis/microbiology , Gastrointestinal Tract/microbiology , Inflammatory Bowel Diseases/microbiology , Microbiota/genetics , Animals , Anti-Bacterial Agents/pharmacology , Benzoic Acid/metabolism , Carbohydrate Metabolism , Cell Movement , Colitis/drug therapy , Colitis/genetics , Colitis/pathology , DNA-Binding Proteins/deficiency , DNA-Binding Proteins/genetics , Dopamine/metabolism , Energy Metabolism , Humans , Inflammation/drug therapy , Inflammation/genetics , Inflammation/microbiology , Inflammation/pathology , Inflammatory Bowel Diseases/drug therapy , Inflammatory Bowel Diseases/genetics , Inflammatory Bowel Diseases/pathology , Mice , Mice, Knockout , Microbiota/drug effects , Phylogeny , RNA, Ribosomal, 16S/classification , RNA, Ribosomal, 16S/genetics , Remission Induction , Signal Transduction , T-Box Domain Proteins/deficiency , T-Box Domain Proteins/geneticsABSTRACT
Intestinal health requires the coexistence of eukaryotic self with the gut microbiota and dysregulated host-microbial interactions can result in intestinal inflammation. Here, we show that colitis improved in T-bet(-/-)Rag2(-/-) mice that consumed a fermented milk product containing Bifidobacterium animalis subsp. lactis DN-173 010 strain. A decrease in cecal pH and alterations in short chain fatty acid profiles occurred with consumption, and there were concomitant increases in the abundance of select lactate-consuming and butyrate-producing bacteria. These metabolic shifts created a nonpermissive environment for the Enterobacteriaceae recently identified as colitogenic in a T-bet(-/-)Rag2(-/-) ulcerative colitis mouse model. In addition, 16S rRNA-based analysis of the T-bet(-/-)Rag2(-/-) fecal microbiota suggest that the structure of the endogenous gut microbiota played a key role in shaping the host response to the bacterial strains studied herein. We have identified features of the gut microbiota, at the membership and functional level, associated with response to this B. lactis-containing fermented milk product, and therefore this model provides a framework for evaluating and optimizing probiotic-based functional foods.
