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PLoS Pathog. 2008 Aug 1;4(8):e1000112.
Commensal-induced regulatory T cells
mediate protection against pathogenstimulated NF-kappaB activation.
O'Mahony C, Scully P, O'Mahony D, Murphy S, O'Brien F, Lyons A, Sherlock G, MacSharry
J, Kiely B, Shanahan F, O'Mahony L.
Source
Alimentary Pharmabiotic Centre, University College Cork, Cork, Ireland.
Abstract
Host defence against infection requires a range of innate and adaptive immune responses that
may lead to tissue damage. Such immune-mediated pathologies can be controlled with
appropriate T regulatory (Treg) activity. The aim of the present study was to determine the
influence of gut microbiota composition on Treg cellular activity and NF-kappaB activation
associated with infection. Mice consumed the commensal microbe Bifidobacterium infantis
35624 followed by infection with Salmonella typhimurium or injection with LPS. In vivo NFkappaB activation was quantified using biophotonic imaging. CD4+CD25+Foxp3+ T cell
phenotypes and cytokine levels were assessed using flow cytometry while CD4+ T cells were
isolated using magnetic beads for adoptive transfer to naïve animals. In vivo imaging revealed
profound inhibition of infection and LPS induced NF-kappaB activity that preceded a
reduction in S. typhimurium numbers and murine sickness behaviour scores in B. infantis-fed
mice. In addition, pro-inflammatory cytokine secretion, T cell proliferation, and dendritic cell
co-stimulatory molecule expression were significantly reduced. In contrast,
CD4+CD25+Foxp3+ T cell numbers were significantly increased in the mucosa and spleen of
mice fed B. infantis. Adoptive transfer of CD4+CD25+ T cells transferred the NF-kappaB
inhibitory activity. Consumption of a single commensal micro-organism drives the generation
and function of Treg cells which control excessive NF-kappaB activation in vivo. These
cellular interactions provide the basis for a more complete understanding of the commensalhost-pathogen trilogue that contribute to host homeostatic mechanisms underpinning
protection against aberrant activation of the innate immune system in response to a
translocating pathogen or systemic LPS.
Supplemental Content
Benef Microbes. 2010 Sep;1(3):211-27. doi: 10.3920/BM2010.0009.
Homeostatic impact of indigenous
microbiota and secretory immunity.
Brandtzaeg P.
Source
Department and Institute of Pathology, Laboratory for Immunohistochemistry and
Immunopathology (LIIPAT), Centre for Immune Regulation (CIR), Oslo University Hospital,
Rikshospitalet, Norway.
Abstract
In the process of evolution, the mucosal immune system has generated two layers of antiinflammatory defence: (1) immune exclusion performed by secretory IgA (and secretory IgM)
antibodies to modulate or inhibit surface colonisation of microorganisms and dampen
penetration of potentially dangerous antigens; and (2) suppressive mechanisms to avoid local
and peripheral hypersensitivity to innocuous antigens, particularly food proteins and
components of commensal bacteria. When induced via the gut, the latter phenomenon is
called 'oral tolerance', which mainly depends on the development of regulatory T (Treg) cells
in mesenteric lymph nodes to which mucosal dendritic cells (DCs) carry exogenous antigens
and become conditioned for induction of Treg cells. Mucosally induced tolerance appears to
be a rather robust adaptive immune function in view of the fact that large amounts of food
proteins pass through the gut, while overt and persistent food allergy is not so common. DCs
are 'decision makers' in the immune system when they perform their antigen-presenting
function, thus linking innate and adaptive immunity by sensing the exogenous mucosal impact
(e.g. conserved microbial molecular patterns). A balanced indigenous microbiota is required
to drive the normal development of both mucosa-associated lymphoid tissue, the epithelial
barrier with its secretory IgA (and IgM) system, and mucosally induced tolerance mechanisms
including the generation of Treg cells. Notably, polymeric Ig receptor (pIgR/SC) knock-out
mice that lack secretory IgA and IgM antibodies show reduced epithelial barrier function and
increased uptake of antigens from food and commensal bacteria. They therefore have a hyperreactive immune system and show predisposition for systemic anaphylaxis after sensitisation;
but this development is counteracted by enhanced oral tolerance induction as a homeostatic
back-up mechanism.
Supplemental Content
http://wageningenacademic.metapress.com/content/x054308538p3k787/fulltext.pdf FREE
Gut. 2005 Nov;54(11):1546-52. Epub 2005 Jun 29.
Influence of intestinal bacteria on induction
of regulatory T cells: lessons from a transfer
model of colitis.
Strauch UG, Obermeier F, Grunwald N, Gürster S, Dunger N, Schultz M, Griese DP, Mähler
M, Schölmerich J, Rath HC.
Source
Department of Internal Medicine I, University of Regensburg, D-93053 Regensburg,
Germany. [email protected]
Abstract
BACKGROUND:
The resident flora plays a critical role in initiation and perpetuation of intestinal inflammation,
as demonstrated in experimental models of colitis where animals fail to develop disease under
germ free conditions. However, the importance of exposure to commensal bacteria before the
onset of colitis is unclear. Our aim was to investigate the influence of previous exposure of
donor animals to bacterial antigens on colitis development using a transfer model.
METHODS:
Clinical course and histology were evaluated after transfer of CD4(+)CD62L(+) lymphocytes
from germ free and conventionally housed donor mice into SCID recipients. Cotransfer of
CD4(+)CD62L(+) cells with CD4(+)CD62L(- )lymphocytes from both groups of mice was
initiated. Lymphocytes were analysed by FACS, polarisation potential of cells determined,
and cytokines measured within the supernatant by enzyme linked immunosorbent assay.
RESULTS:
Animals that received cells from germ free donors developed an earlier onset of colitis
compared with mice reconstituted with lymphocytes from conventionally housed animals.
Additionally, CD4(+)CD62L(- )cells from germ free mice were not able to abrogate colitis
induced by cotransfer with CD4(+)CD62L(+) lymphocytes whereas CD4(+)CD62L(- )T cells
from normal mice ameliorated disease. The higher percentage of CD4(+)GITR(+) expressing
lymphocytes and the production of interleukin 10 after priming by dendritic cells suggests the
presence of T(reg) cells within the CD4(+)CD62L(+) lymphocyte subset derived from
conventional housed mice and assumes a lack of T(reg) cells within germ free mice.
CONCLUSION:
The results indicate that bacterial antigens are crucial for the generation and/or expansion of
T(reg) cells in a healthy individual. Therefore, bacterial colonisation is of great importance in
maintaining the immunological balance.
Supplemental Content
J Biomed Sci. 2010 Jun 12;17:48.
Commensal microflora induce host defense
and decrease bacterial translocation in burn
mice through toll-like receptor 4.
Chen LW, Chang WJ, Chen PH, Hsu CM.
Source
Institute of Emergency and Critical Care Medicine, National Yang-Ming University, Taipei,
Taiwan. [email protected]
Abstract
BACKGROUND:
Major burn is associated with decreased gut barrier function and increased bacterial
translocation (BT). This study is to investigate whether commensal microflora induce host
defense and decrease BT in burn mice.
METHODS:
First, we treated Wild type (WT) mice with antibiotics in drinking water for 4 weeks to
deplete gut commensal microflora. At week 3, drinking water was supplemented with
lipopolysaccharide (LPS); a ligand for TLR4, to trigger TLRs in gut. The intestinal
permeability, glutathione level, NF-kappaB DNA-binding activity, TLR4 expression of
intestinal mucosa, BT to mesenteric lymph nodes (MLNs), and bacterial killing activity of
peritoneal cells were measured after thermal injury. Second, lung of animals were harvested
for MPO activity and TNFalpha mRNA expression assay. Third, WT animals were treated
with oral antibiotics with or without LPS supplement after burn. At 48 hr after burn, TLR4
expression of intestinal mucosa and bacterial killing activity of cells were examined. Finally,
bacterial killing activity and BT to MLNs after thermal injury in C3H/HeJ (TLR4 mutant)
mice were measured.
RESULTS:
Burn induced BT to MLNs in WT mice. Commensal depletion decreased TLR4 expression as
well as NF-kappaB activation of intestine, myeloperoxidase (MPO) activity as well as
TNFalpha expression of lung, and bacterial killing activity of peritoneal cells. Oral LPS
supplement markedly reduced 81% of burn-induced BT and increased TLR4 expression,
MPO activity of lung, as well as bacterial killing activity of peritoneal cells. LPS supplement
did not change BT or bacterial killing activity in C3H/HeJ mice.
CONCLUSIONS:
Collectively, commensal microflora induce TLR4 expression of intestine and bacterial killing
activity of inflammatory cells in burn. TLR4 ligand increases bacterial killing activity and
decreases burn-induced BT. Taken together with the abolition of LPS effect in TLR4 mutant
mice, we conclude that commensal microflora induce host defense and decrease bacterial
translocation in burn mice through toll-like receptor 4.
Supplemental Content
JPEN J Parenter Enteral Nutr. 2006 Sep-Oct;30(5):395-8; discussion 399.
Influences of long-term antibiotic
administration on Peyer's patch
lymphocytes and mucosal immunoglobulin
A levels in a mouse model.
Yaguchi Y, Fukatsu K, Moriya T, Maeshima Y, Ikezawa F, Omata J, Ueno C, Okamoto K,
Hara E, Ichikura T, Hiraide H, Mochizuki H, Touger-Decker RE.
Source
Department of Surgery I, National Defense Medical College, Tokorozawa, Japan.
Abstract
BACKGROUND:
Long-term antibiotic administration is sometimes necessary to control bacterial infections
during the perioperative period. However, antibiotic administration may alter gut bacterial
flora, possibly impairing gut mucosal immunity. We hypothesized that 1 week of
subcutaneous (SC) antibiotic injections would affect Peyer's patch (PP) lymphocyte numbers
and phenotypes, as well as mucosal immunoglobulin A (IgA) levels.
METHODS:
Sixty-one male Institute of Cancer Research mice were randomized to CMZ (cefmetazole 100
mg/kg, administered SC twice a day), IPM (imipenem/cilastatin 50 mg/kg x 2), and control
(saline 0.1 mL x 2) groups. After 7 days of treatment, the mice were killed and their small
intestines removed. Bacterial numbers in the small intestine were determined using sheep
blood agar plates under aerobic conditions (n = 21). PP lymphocytes were isolated to
determine cell numbers and phenotypes (CD4, CD8, alphabetaTCR, gammadeltaTCR, B220;
n = 40). IgA levels in the small intestinal and bronchoalveolar washings were also measured
with ELISA.
RESULTS:
Antibiotic administration decreased both bacterial number and the PP cell yield compared
with the control group. There were no significant differences in either phenotype percentages
or IgA levels at any mucosal sites among the 3 groups.
CONCLUSIONS:
Long-term antibiotic treatment reduces PP cell numbers while decreasing bacterial numbers in
the small intestine. It may be important to recognize changes in gut mucosal immunity during
long-term antibiotic administration.
Supplemental Content
Front Physiol. 2011 Jan 26;1:168.
Microbial induction of immunity,
inflammation, and cancer.
Greer JB, O'Keefe SJ.
Source
Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine, University
of Pittsburgh School of Medicine Pittsburgh, PA, USA.
Abstract
The human microbiota presents a highly active metabolic that influences the state of health of
our gastrointestinal tracts as well as our susceptibility to disease. Although much of our initial
microbiota is adopted from our mothers, its final composition and diversity is determined by
environmental factors. Westernization has significantly altered our microbial function.
Extensive experimental and clinical evidence indicates that the westernized diet, rich in
animal products and low in complex carbohydrates, plus the overuse of antibiotics and
underuse of breastfeeding, leads to a heightened inflammatory potential of the microbiota.
Chronic inflammation leads to the expression of certain diseases in genetically predisposed
individuals. Antibiotics and a "clean" environment, termed the "hygiene hypothesis," has been
linked to the rise in allergy and inflammatory bowel disease, due to impaired beneficial
bacterial exposure and education of the gut immune system, which comprises the largest
immune organ within the body. The elevated risk of colon cancer is associated with the
suppression of microbial fermentation and butyrate production, as butyrate provides fuel for
the mucosa and is anti-inflammatory and anti-proliferative. This article will summarize the
work to date highlighting the complicated and dynamic relationship between the gut
microbiota and immunity, inflammation and carcinogenesis.
Supplemental Content
Am J Physiol Gastrointest Liver Physiol. 2008 Mar;294(3):G669-78. Epub 2008 Jan 10.
Decreased epithelial barrier function
evoked by exposure to metabolic stress and
nonpathogenic E. coli is enhanced by TNFalpha.
Lewis K, Caldwell J, Phan V, Prescott D, Nazli A, Wang A, Soderhölm JD, Perdue MH,
Sherman PM, McKay DM.
Source
Gastrointestinal Research Group, Department of Physiology and Biophysics, University of
Calgary, Calgary, Alberta, Canada.
Abstract
A defect in mitochondrial activity contributes to many diseases. We have shown that
monolayers of the human colonic T84 epithelial cell line exposed to dinitrophenol (DNP,
uncouples oxidative phosphorylation) and nonpathogenic Escherichia coli (E. coli) (strain
HB101) display decreased barrier function. Here the impact of DNP on macrophage activity
and the effect of TNF-alpha, DNP, and E. coli on epithelial permeability were assessed. DNP
treatment of the human THP-1 macrophage cell line resulted in reduced ATP synthesis, and,
although hyporesponsive to LPS, the metabolically stressed macrophages produced IL-1beta,
IL-6, and TNF-alpha. Given the role of TNF-alpha in inflammatory bowel disease (IBD) and
the association between increased permeability and IBD, recombinant TNF-alpha (10 ng/ml)
was added to the DNP (0.1 mM) + E. coli (10(6) colony-forming units), and this resulted in a
significantly greater loss of T84 epithelial barrier function than that elicited by DNP + E. coli.
This increased epithelial permeability was not due to epithelial death, and the enhanced E.
coli translocation was reduced by pharmacological inhibitors of NF-kappabeta signaling
(pyrrolidine dithiocarbamate, NF-kappabeta essential modifier-binding peptide, BAY 117082, and the proteosome inhibitor, MG132). In contrast, the drop in transepithelial electrical
resistance was unaffected by the inhibitors of NF-kappabeta. Thus, as an integrative model
system, our findings support the induction of a positive feedback loop that can severely impair
epithelial barrier function and, as such, could contribute to existing inflammation or trigger
relapses in IBD. Thus metabolically stressed epithelia display increased permeability in the
presence of viable nonpathogenic E. coli that is exaggerated by TNF-alpha released by
activated immune cells, such as macrophages, that retain this ability even if they themselves
are experiencing a degree of metabolic stress.
Supplemental Content
Infect Immun. 2006 Jan;74(1):192-201.
Enterocyte cytoskeleton changes are crucial
for enhanced translocation of
nonpathogenic Escherichia coli across
metabolically stressed gut epithelia.
Nazli A, Wang A, Steen O, Prescott D, Lu J, Perdue MH, Söderholm JD, Sherman PM,
McKay DM.
Source
Intestinal Disease Research Programme, HSC-3N5C, McMaster University, 1200 Main Street
West, Hamilton, Ontario L8N 3Z5, Canada.
Abstract
Substantial data implicate the commensal flora as triggers for the initiation of enteric
inflammation or inflammatory disease relapse. We have shown that enteric epithelia under
metabolic stress respond to nonpathogenic bacteria by increases in epithelial paracellular
permeability and bacterial translocation. Here we assessed the structural basis of these
findings. Confluent filter-grown monolayers of the human colonic T84 epithelial cell line
were treated with 0.1 mM dinitrophenol (which uncouples oxidative phosphorylation) and
noninvasive, nonpathogenic Escherichia coli (strain HB101, 10(6) CFU) with or without
pretreatment with various pharmacological agents. At 24 h later, apoptosis, tight-junction
protein expression, transepithelial resistance (TER; a marker of paracellular permeability),
and bacterial internalization and translocation were assessed. Treatment with stabilizers of
microtubules (i.e., colchicine), microfilaments (i.e., jasplakinolide) and clathrin-coated pit
endocytosis (i.e., phenylarsine oxide) all failed to block DNP+E. coli HB101-induced
reductions in TER but effectively prevented bacterial internalization and translocation.
Neither the TER defect nor the enhanced bacterial translocations were a consequence of
increased apoptosis. These data show that epithelial paracellular and transcellular (i.e.,
bacterial internalization) permeation pathways are controlled by different mechanisms. Thus,
epithelia under metabolic stress increase their endocytotic activity that can result in a
microtubule-, microfilament-dependent internalization and transcytosis of bacteria. We
speculate that similar events in vivo would allow excess unprocessed antigen and bacteria into
the mucosa and could evoke an inflammatory response by, for example, the activation of
resident or recruited immune cells.
Supplemental Content
Am J Pathol. 2008 Nov;173(5):1243-52. Epub 2008 Oct 2.
Physiological, pathological, and therapeutic
implications of zonulin-mediated intestinal
barrier modulation: living life on the edge
of the wall.
Fasano A.
Source
University of Maryland School of Medicine, Mucosal Biology Research Center, Health
Science Facility II, Baltimore, MD 21201, USA. [email protected]
Abstract
The anatomical and functional arrangement of the gastrointestinal tract suggests that this
organ, beside its digestive and absorptive functions, regulates the trafficking of
macromolecules between the environment and the host through a barrier mechanism. Under
physiological circumstances, this trafficking is safeguarded by the competency of intercellular
tight junctions, structures whose physiological modulation is mediated by, among others, the
recently described protein zonulin. To prevent harm and minimize inflammation, the same
paracellular pathway, in concert with the gut-associated lymphoid tissue and the
neuroendocrine network, controls the equilibrium between tolerance and immunity to nonself
antigens. The zonulin pathway has been exploited to deliver drugs, macromolecules, or
vaccines that normally would not be absorbed through the gastrointestinal mucosal barrier.
However, if the tightly regulated trafficking of macromolecules is jeopardized secondary to
prolonged zonulin up-regulation, the excessive flow of nonself antigens in the intestinal
submucosa can cause both intestinal and extraintestinal autoimmune disorders in genetically
susceptible individuals. This new paradigm subverts traditional theories underlying the
development of autoimmunity, which are based on molecular mimicry and/or the bystander
effect, and suggests that the autoimmune process can be arrested if the interplay between
genes and environmental triggers is prevented by re-establishing intestinal barrier
competency. Understanding the role of zonulin-dependent intestinal barrier dysfunction in the
pathogenesis of autoimmune diseases is an area of translational research that encompasses
many fields.
Supplemental Content
Alcohol. 2008 Aug;42(5):349-61. Epub 2008 May 27.
Alcohol, intestinal bacterial growth,
intestinal permeability to endotoxin, and
medical consequences: summary of a
symposium.
Purohit V, Bode JC, Bode C, Brenner DA, Choudhry MA, Hamilton F, Kang YJ,
Keshavarzian A, Rao R, Sartor RB, Swanson C, Turner JR.
Source
Division of Metabolism and Health Effects, National Institute on Alcohol Abuse and
Alcoholism, National Institutes of Health, 5635 Fishers Lane, Room 2035, MSC 9304,
Bethesda, MD 20892-9304, USA. [email protected]
Abstract
This report is a summary of the symposium on Alcohol, Intestinal Bacterial Growth, Intestinal
Permeability to Endotoxin, and Medical Consequences, organized by National Institute on
Alcohol Abuse and Alcoholism, Office of Dietary Supplements, and National Institute of
Diabetes and Digestive and Kidney Diseases of National Institutes of Health in Rockville,
Maryland, October 11, 2006. Alcohol exposure can promote the growth of Gram-negative
bacteria in the intestine, which may result in accumulation of endotoxin. In addition, alcohol
metabolism by Gram-negative bacteria and intestinal epithelial cells can result in
accumulation of acetaldehyde, which in turn can increase intestinal permeability to endotoxin
by increasing tyrosine phosphorylation of tight junction and adherens junction proteins.
Alcohol-induced generation of nitric oxide may also contribute to increased permeability to
endotoxin by reacting with tubulin, which may cause damage to microtubule cytoskeleton and
subsequent disruption of intestinal barrier function. Increased intestinal permeability can lead
to increased transfer of endotoxin from the intestine to the liver and general circulation where
endotoxin may trigger inflammatory changes in the liver and other organs. Alcohol may also
increase intestinal permeability to peptidoglycan, which can initiate inflammatory response in
liver and other organs. In addition, acute alcohol exposure may potentiate the effect of burn
injury on intestinal bacterial growth and permeability. Decreasing the number of Gramnegative bacteria in the intestine can result in decreased production of endotoxin as well as
acetaldehyde which is expected to decrease intestinal permeability to endotoxin. In addition,
intestinal permeability may be preserved by administering epidermal growth factor, lglutamine, oats supplementation, or zinc, thereby preventing the transfer of endotoxin to the
general circulation. Thus reducing the number of intestinal Gram-negative bacteria and
preserving intestinal permeability to endotoxin may attenuate alcoholic liver and other organ
injuries.
Supplemental Content