Intestinal microbiota and the innate immune system – a crosstalk in Crohn’s disease pathogenesis

Crohn’s disease (CD) is a chronic, relapsing inflammatory disorder that can occur anywhere along the gastrointestinal tract. The precise etiology of CD is still unclear but it is widely accepted that a complex series of interactions between susceptibility genes, the immune system and environmental factors are implicated in the onset and perpetuation of the disease. Increasing evidence from experimental and clinical studies implies the intestinal microbiota in disease pathogenesis, thereby supporting the hypothesis that chronic intestinal inflammation arises from an abnormal immune response against the microorganisms of the intestinal flora in genetically susceptible individuals. Given that CD patients display changes in their gut microbiota composition, collectively termed “dysbiosis,” the question raises whether the altered microbiota composition is a cause of disease or rather a consequence of the inflammatory state of the intestinal environment. This review will focus on the crosstalk between the gut microbiota and the innate immune system during intestinal inflammation, thereby unraveling the role of the microbiota in CD pathogenesis

Depletion of Murine Intestinal Microbiota: Effects on Gut Mucosa and Epithelial Gene Expression

Background Inappropriate cross talk between mammals and their gut microbiota may trigger intestinal inflammation and drive extra-intestinal immune-mediated diseases. Epithelial cells constitute the interface between gut microbiota and host tissue, and may regulate host responses to commensal enteric bacteria. Gnotobiotic animals represent a powerful approach to study bacterial-host interaction but are not readily accessible to the wide scientific community. We aimed at refining a protocol that in a robust manner would deplete the cultivable intestinal microbiota of conventionally raised mice and that would prove to have significant biologic validity. Methodology/Principal Findings Previously published protocols for depleting mice of their intestinal microbiota by administering broad-spectrum antibiotics in drinking water were difficult to reproduce. We show that twice daily delivery of antibiotics by gavage depleted mice of their cultivable fecal microbiota and reduced the fecal bacterial DNA load by 400 fold while ensuring the animals' health. Mice subjected to the protocol for 17 days displayed enlarged ceca, reduced Peyer's patches and small spleens. Antibiotic treatment significantly reduced the expression of antimicrobial factors to a level similar to that of germ-free mice and altered the expression of 517 genes in total in the colonic epithelium. Genes involved in cell cycle were significantly altered concomitant with reduced epithelial proliferative activity in situ assessed by Ki-67 expression, suggesting that commensal microbiota drives cellular proliferation in colonic epithelium. Conclusion We present a robust protocol for depleting conventionally raised mice of their cultivatable intestinal microbiota with antibiotics by gavage and show that the biological effect of this depletion phenocopies physiological characteristics of germ-free mice

Host-Bacterial Symbiosis in Health and Disease

All animals live in symbiosis. Shaped by eons of co-evolution, host bacterial associations have developed into prosperous relationships creating mechanisms for mutual benefits to both microbe and host. No better example exists in biology than the astounding numbers of bacteria harbored by the lower gastrointestinal tract of mammals. The mammalian gut represents a complex ecosystem consisting of an extraordinary number of resident commensal bacteria existing in homeostasis with the host’s immune system. Most impressive about this relationship may be the concept that the host not only tolerates, but has evolved to require colonization by beneficial microorganisms, known as commensals, for various aspects of immune development and function. The microbiota provides critical signals that promote maturation of immune cells and tissues, leading to protection from infections by pathogens. Gut bacteria also appear to contribute to non-infectious immune disorders such as inflammatory bowel disease and autoimmunity. How the microbiota influences host immune responses is an active area of research with important implications for human health. This review synthesizes emerging findings and concepts that describe the mutualism between the microbiota and mammals, specifically emphasizing the role of gut bacteria in shaping an immune response that mediates the balance between health and disease. Unlocking how beneficial bacteria affect the development of the immune system may lead to novel and natural therapies based on harnessing the immunomodulatory properties of the microbiota

Comparing Quality of Surgical Care Between the US Department of Veterans Affairs and Non-Veterans Affairs Settings: A Systematic Review.

In response to concerns about healthcare access and long wait times within the Veterans Health Administration (VA), Congress passed the Choice Act of 2014 and the Maintaining Internal Systems and Strengthening Integrated Outside Networks (MISSION) Act of 2018 to create a program for patients to receive care in non-VA sites of care, paid by VA. Questions remain about the quality of surgical care between these sites in specific and between VA and non-VA care in general. This review synthesizes recent evidence comparing surgical care between VA and non-VA delivered care across the domains of quality and safety, access, patient experience, and comparative cost/efficiency (2015 to 2021). Eighteen studies met the inclusion criteria. Of 13 studies reporting quality and safety outcomes, 11 reported that quality and safety of VA surgical care were as good as or better than non-VA sites of care. Six studies of access did not have a preponderance of evidence favoring care in either setting. One study of patient experience reported VA care as about equal to non-VA care. All 4 studies of cost/efficiency outcomes favored non-VA care. Based on limited data, these findings suggest that expanding eligibility for veterans to get care in the community may not provide benefits in terms of increasing access to surgical procedures, will not result in better quality, and may result in worse quality of care, but may reduce inpatient length of stay and perhaps cost less

Intestinal Microbial Metabolites Are Linked to Severity of Myocardial Infarction in Rats

<div><p>Intestinal microbiota determine severity of myocardial infarction in rats. We determined whether low molecular weight metabolites derived from intestinal microbiota and transported to the systemic circulation are linked to severity of myocardial infarction. Plasma from rats treated for seven days with the non-absorbed antibiotic vancomycin or a mixture of streptomycin, neomycin, polymyxin B and bacitracin was analyzed using mass spectrometry-based metabolite profiling platforms. Antibiotic-induced changes in the abundance of individual groups of intestinal microbiota dramatically altered the host’s metabolism. Hierarchical clustering of dissimilarities separated the levels of 284 identified metabolites from treated vs. untreated rats; 193 were altered by the antibiotic treatments with a tendency towards decreased metabolite levels. Catabolism of the aromatic amino acids phenylalanine, tryptophan and tyrosine was the most affected pathway comprising 33 affected metabolites. Both antibiotic treatments decreased the severity of an induced myocardial infarction <i>in vivo</i> by 27% and 29%, respectively. We then determined whether microbial metabolites of the amino acids phenylalanine, tryptophan and tyrosine were linked to decreased severity of myocardial infarction. Vancomycin-treated rats were administered amino acid metabolites prior to ischemia/reperfusion studies. Oral or intravenous pretreatment of rats with these amino acid metabolites abolished the decrease in infarct size conferred by vancomycin. Inhibition of JAK-2 (AG-490, 10 μM), Src kinase (PP1, 20 μM), Akt/PI₃ kinase (Wortmannin, 100 nM), p44/42 MAPK (PD98059, 10 μM), p38 MAPK (SB203580, 10 μM), or K_ATP channels (glibenclamide, 3 μM) abolished cardioprotection by vancomycin, indicating microbial metabolites are interacting with cell surface receptors to transduce their signals through Src kinase, cell survival pathways and K_ATP channels. These inhibitors have no effect on myocardial infarct size in untreated rats. This study links gut microbiota metabolites to severity of myocardial infarction and may provide future opportunities for novel diagnostic tests and interventions for the prevention of cardiovascular disease.</p></div

Gut microbiota determines severity of myocardial infarction.

<p>A. Antibiotics added to the drinking water reduced infarct size (IS) <i>in vivo</i>. B. Antibiotics added directly to the coronary circulation of isolated hearts did not reduce IS <i>in vitro</i>. C. Antibiotics added to the drinking water and then excluded from the coronary circulation of isolated hearts reduced IS. Data are means ± SD; <i>n</i> = 6/group. AAR, area at risk. LV, left ventricle. Reduction in infarct size was similar for <i>in vitro</i> and <i>in vivo</i> studies (A, C). *<i>P</i> < 0.01 <i>vs</i>. control. Representative images of rat heart slices for measurement of infarct size are shown in the Supporting Information (<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0160840#pone.0160840.s001" target="_blank">S1 Fig</a>).</p

Microbial populations in the feces of antibiotic treated rats.

<p>(A) Vancomycin (60mg/kg/day) and (B) a mixture of streptomycin (120 mg/kg/day), neomycin (60 mg/kg/day), polymyxin B (60 mg/kg/day), and bacitracin (120 mg/kg/day) administered orally reduced total microbial numbers and altered abundance of microbial taxa. Microbial abundance was determined using PCR. The X-axis labels show taxa of microbes grouped by bacteria (black), fungi (green), and archaea (red). Data are mean ±SD, n = 6/group. * p ≤ 0.05; day 0 vs. day 7. ND = not detected. The results from the vancomycin treatment in Fig 2A are reproduced with permission from reference 5.</p