Commensal bacteria and epithelial cross talk in the developing intestine

From raw milk cheese to the gut: investigating the colonization strategies of Bifidobacterium mongoliense

The microbial ecology of raw milk cheeses is determined by bacteria originating from milk and milk-producing animals. Recently, it has been shown that members of the Bifidobacterium mongoliense species may become transmitted along the Parmigiano Reggiano cheese production chain and ultimately may colonize the consumer intestine. However, there is a lack of knowledge regarding the molecular mechanisms that mediate the interaction between B. mongoliense and the human gut. Based on 128 raw milk cheeses collected from different Italian regions, we isolated and characterized 10 B. mongoliense strains. Comparative genomics allowed us to unveil the presence of enzymes required for the degradation of sialylated host-glycans in B. mongoliense, corroborating the appreciable growth on de Man-Rogosa-Sharpe (MRS) medium supplemented with 3'-sialyllactose (3'-SL) or 6'-sialyllactose (6'-SL). The B. mongoliense BMONG18 was chosen, due to its superior ability to utilize 3'-SL and mucin as representative strain, to investigate its behavior when co-inoculated with other bifidobacterial species. Conversely, members of other bifidobacterial species did not appear to benefit from the presence of BMONG18, highlighting a competitive scenario for nutrient acquisition. Transcriptomic data of BMONG18 reveal no significant differences in gene expression when cultivated in a gut simulating medium (GSM), regardless of whether cheese was included or not. Furthermore, BMONG18 was shown to exhibit high adhesion capabilities to HT29-MTX human cells, in line with its colonization ability of a human host.IMPORTANCEFermented foods are nourishments produced through controlled microbial growth that play an essential role in worldwide human nutrition. Research interest in fermented foods has increased since the 80s, driven by growing awareness of their potential health benefits beyond mere nutritional content. Bifidobacterium mongoliense, previously identified throughout the production process of Parmigiano Reggiano cheese, was found to be capable of establishing itself in the intestines of its consumers. Our study underscores molecular mechanisms through which this bifidobacterial species, derived from food, interacts with the host and other gut microbiota members.

Advances in regulation of homeostasis through chromatin modifications by airway commensals

Commensal bacteria are residents of the human airway where they interact with both colonizing pathogens and host respiratory epithelial cells of this mucosal surface. It is here that commensals exert their influence through host signaling cascades, host transcriptional responses and host immunity, all of which are rooted in chromatin remodeling and histone modifications. Recent studies show that airway commensals impact host chromatin, but compared the what is known for gut commensals, the field remains in its infancy. The mechanisms by which airway commensals regulate respiratory health and homeostasis through chromatin modifications is of increasing interest, specifically since their displacement precedes the increased potential for respiratory disease. Herein we will discuss recent advances and intriguing avenues of future work aimed at deciphering how airway commensals protect and influence respiratory health.

Potential benefits of a blend of essential oils on metabolism, digestibility, organ development and gene expression of dairy calves

The objective of this study was to evaluate blood cells and metabolites, insulin-like growth factor-1 (IGF-1), digestibility, internal organs weight and histology, gene expression, and spleen cell proliferation of pre-weaned bull calves supplemented with a blend of essential oils in milk replacer (MR). Sixteen newborn Holstein × Gyr crossbred dairy bull calves, with body weight at birth of 33.3 ± 3.7 kg, were housed in individual sand bedded pens, blocked by genetic composition, and randomly assigned to 1 of 2 treatments in a randomized complete block design: Control (CON, n = 8) and blend of essential oils supplementation (BEO, n = 8, 1 g/day/calf, Apex Calf, Adisseo, China). The commercial blend was composed by plant extracts derived from anise, cinnamon, garlic, rosemary, and thyme. Animals were fed 5 L of MR/day reconstituted at 15% (dry matter basis), divided into two equal meals. Water and starter were provided ad libitum. ß-hydroxybutyrate, urea, and glucose were evaluated weekly, IGF-1 was evaluated biweekly, and total blood cell count was performed every four weeks until the end of the trial at eight weeks of age. Feed samples were collected three times a week and polled for weekly analysis. Apparent total nutrient digestibility was determined from d 56 to 60 of age. On d 60 ± 1, animals were euthanized for organ weight, histology, spleen cell proliferation, and intestinal gene expression analysis. Data were analyzed independently using linear mixed models using the REML method in the nlme package in R for continuous outcomes. A non-parametric test was used for ordered categorical outcomes using the Artools package in R. There were no differences between groups for blood evaluations, digestibility, gene expression, and a spleen cell proliferation assay. However, BEO calves presented a heavier pancreas, heavier intestines, bigger ileum villi, and higher cecum butyrate levels (P < 0.05), demonstrating that the EO supplementation helped intestinal development and symbiotic bacteria. It was also observed in CON animals' heavier respiratory tract and a higher eosinophil count (P < 0.05). Therefore, the organs where eosinophils are more active had a better response for BEO animals. No differences were found in the intestinal gene expression in the immune context. These results demonstrate that supplementing essential oils in MR could contribute to gut development and immune function. However, more research is needed to understand its impact on body development and define the best dosage and route of administration.

Direct Action of Non-Digestible Oligosaccharides against a Leaky Gut

The epithelial monolayer is the primary determinant of mucosal barrier function, and tight junction (TJ) complexes seal the paracellular space between the adjacent epithelial cells and represent the main "gate-keepers" of the paracellular route. Impaired TJ functionality results in increased permeation of the "pro-inflammatory" luminal contents to the circulation that induces local and systemic inflammatory and immune responses, ultimately triggering and/or perpetuating (chronic) systemic inflammatory disorders. Increased gut leakiness is associated with intestinal and systemic disease states such as inflammatory bowel disease and neurodegenerative diseases such as Parkinson's disease. Modulation of TJ dynamics is an appealing strategy aiming at inflammatory conditions associated with compromised intestinal epithelial function. Recently there has been a growing interest in nutraceuticals, particularly in non-digestible oligosaccharides (NDOs). NDOs confer innumerable health benefits via microbiome-shaping and gut microbiota-related immune responses, including enhancement of epithelial barrier integrity. Emerging evidence supports that NDOs also exert health-beneficial effects on microbiota independently via direct interactions with intestinal epithelial and immune cells. Among these valuable features, NDOs promote barrier function by directly regulating TJs via AMPK-, PKC-, MAPK-, and TLR-associated pathways. This review provides a comprehensive overview of the epithelial barrier-protective effects of different NDOs with a special focus on their microbiota-independent modulation of TJs.

A Narrative Review on the Unexplored Potential of Colostrum as a Preventative Treatment and Therapy for Diarrhea in Neonatal Dairy Calves

Diarrhea is the leading cause of morbidity and mortality in pre-weaned dairy calves and, as such, represents a significant animal health and welfare concern. Furthermore, digestive disease early in life is associated with several long-term consequences such as reduced growth rate and decreased milk yield during the first lactation, thus generating severe economic losses. The majority of diarrheic cases in young calves are treated with antimicrobials; however, it is necessary to develop alternative treatments, as excessive antimicrobial usage can lead to antimicrobial resistance and can negatively impact the gut microflora of a calf. Bovine colostrum is abundant in immune and bioactive factors that improve immune function and development. This rich and natural combination of immunoglobulins, natural antimicrobial factors, growth factors, anti-inflammatories and nutrients may be an attractive alternative to antimicrobials in the treatment of diarrhea in young dairy calves. There is evidence that supports the use of colostrum as an early treatment for diarrhea in young calves. Future research should investigate its therapeutic and economic effectiveness.

The Gut-Brain Axis: How Microbiota and Host Inflammasome Influence Brain Physiology and Pathology

The human microbiota has a fundamental role in host physiology and pathology. Gut microbial alteration, also known as dysbiosis, is a condition associated not only with gastrointestinal disorders but also with diseases affecting other distal organs. Recently it became evident that the intestinal bacteria can affect the central nervous system (CNS) physiology and inflammation. The nervous system and the gastrointestinal tract are communicating through a bidirectional network of signaling pathways called the gut-brain axis, which consists of multiple connections, including the vagus nerve, the immune system, and bacterial metabolites and products. During dysbiosis, these pathways are dysregulated and associated with altered permeability of the blood-brain barrier (BBB) and neuroinflammation. However, numerous mechanisms behind the impact of the gut microbiota in neuro-development and -pathogenesis remain poorly understood. There are several immune pathways involved in CNS homeostasis and inflammation. Among those, the inflammasome pathway has been linked to neuroinflammatory conditions such as multiple sclerosis, Alzheimer's and Parkinson's diseases, but also anxiety and depressive-like disorders. The inflammasome complex assembles upon cell activation due to exposure to microbes, danger signals, or stress and lead to the production of pro-inflammatory cytokines (interleukin-1β and interleukin-18) and to pyroptosis. Evidences suggest that there is a reciprocal influence of microbiota and inflammasome activation in the brain. However, how this influence is precisely working is yet to be discovered. Herein, we discuss the status of the knowledge and the open questions in the field focusing on the function of intestinal microbial metabolites or products on CNS cells during healthy and inflammatory conditions, such as multiple sclerosis, Alzheimer's and Parkinson's diseases, and also neuropsychiatric disorders. In particular, we focus on the innate inflammasome pathway as immune mechanism that can be involved in several of these conditions, upon exposure to certain microbes.

Lactobacillus species inhibitory effect on colorectal cancer progression through modulating the Wnt/β-catenin signaling pathway

Probiotic bacteria are known to exert a wide range of anticancer activities on their animal hosts. In the present study, the anticancer effect of a cocktail of several potential probiotic Lactobacillus species (potential probiotic L.C) was investigated in vitro and in vivo. MTT and Flow cytometry tests results showed that administration of live potential probiotic L.C significantly decreased the HT-29 and CT-26 cells proliferation and induced late apoptotis in a time-dependent manner. In addition, quantitative real-time polymerase chain reaction (qPCR) results showed that exposure of potential probiotic L.C to both HT-29 and CT-26 cells during the incubation times resulted in the upregulation (apc and CSNK1ε for HT-29, CSNK1ε and gsk3β for CT-26) and downregulation (CTNNB1, CCND1, pygo2, axin2 and id2) of the Wnt/β- catenin pathway-related genes in a time-dependent manner. The significance of in vitro anticancer effect of potential probiotic L.C was further confirmed in an experimental tumor model. Data from the murine model of colorectal cancer (CRC) induced by Azoxymethane (AOM) and Dextran Sulfate Sodium (DSS) showed significantly alleviated inflammation and tumor development in AOM/DSS/L.C-injected mice compared to the AOM/DSS-injected mice. Tumor growth inhibition was accompanied by potential probiotic L.C-driven upregulation and downregulation of the Wnt/β-catenin pathway-related genes, similar to the in vitro results. These results showed that potential probiotic L.C inhibited the tumor growth, and that its anticancer activity was at least partially mediated through suppressing the Wnt/β-catenin pathway. Overall, the present study suggested that this probiotic could be used clinically as a supplement for CRC prevention and treatment.

The mitochondrial negative regulator MCJ modulates the interplay between microbiota and the host during ulcerative colitis

Recent evidences indicate that mitochondrial genes and function are decreased in active ulcerative colitis (UC) patients, in particular, the activity of Complex I of the electron transport chain is heavily compromised. MCJ is a mitochondrial inner membrane protein identified as a natural inhibitor of respiratory chain Complex I. The induction of experimental colitis in MCJ-deficient mice leads to the upregulation of Timp3 expression resulting in the inhibition of TACE activity that likely inhibits Tnf and Tnfr1 shedding from the cell membrane in the colon. MCJ-deficient mice also show higher expression of Myd88 and Tlr9, proinflammatory genes and disease severity. Interestingly, the absence of MCJ resulted in distinct microbiota metabolism and composition, including a member of the gut community in UC patients, Ruminococcus gnavus. These changes provoked an effect on IgA levels. Gene expression analyses in UC patients showed decreased levels of MCJ and higher expression of TIMP3, suggesting a relevant role of mitochondrial genes and function among active UC. The MCJ deficiency disturbs the regulatory relationship between the host mitochondria and microbiota affecting disease severity. Our results indicate that mitochondria function may be an important factor in the pathogenesis. All together support the importance of MCJ regulation during UC.

Early life nutrition influences susceptibility to chronic inflammatory colitis in later life

The first thousand days of life are a critical time of development in humans during which the risk profile for diseases in later life can be modified. Nevertheless, long-term consequences of early environment on susceptibility to intestinal diseases have not yet been assessed. Using a mouse model of postnatal growth restriction (PNGR), we showed that early life nutrition influences intestinal maturation and gut health in later life. PNGR induced an alteration of the intestinal barrier in pups at weaning, resulting in increased intestinal permeability, and affected gut bacterial colonization. Specifically, pups with PNGR harbored a decreased bacterial diversity, higher Enterococcus spp., Staphylococcus spp., and Escherichia-Shigella spp., and lower Odoribacter spp. and several members of the Lachnospiraceae family. The lack of an efficient intestinal barrier in early life and the dysbiosis induced by PNGR were associated with a higher susceptibility to chronic colitis in adulthood.

A Critical Review of the Bacterial Baptism Hypothesis and the Impact of Cesarean Delivery on the Infant Microbiome

Numerous studies suggest that infants delivered by cesarean section are at a greater risk of non-communicable diseases than their vaginal counterparts. In particular, epidemiological studies have linked Cesarean delivery with increased rates of asthma, allergies, autoimmune disorders, and obesity. Mode of delivery has also been associated with differences in the infant microbiome. It has been suggested that these differences are attributable to the "bacterial baptism" of vaginal birth, which is bypassed in cesarean deliveries, and that the abnormal establishment of the early-life microbiome is the mediator of later-life adverse outcomes observed in cesarean delivered infants. This has led to the increasingly popular practice of "vaginal seeding": the iatrogenic transfer of vaginal microbiota to the neonate to promote establishment of a "normal" infant microbiome. In this review, we summarize and critically appraise the current evidence for a causal association between Cesarean delivery and neonatal dysbiosis. We suggest that, while Cesarean delivery is certainly associated with alterations in the infant microbiome, the lack of exposure to vaginal microbiota is unlikely to be a major contributing factor. Instead, it is likely that indication for Cesarean delivery, intrapartum antibiotic administration, absence of labor, differences in breastfeeding behaviors, maternal obesity, and gestational age are major drivers of the Cesarean delivery microbial phenotype. We, therefore, call into question the rationale for "vaginal seeding" and support calls for the halting of this practice until robust evidence of need, efficacy, and safety is available.

TLR9 Regulates the NF-κB-NLRP3-IL-1β Pathway Negatively in Salmonella-Induced NKG2D-Mediated Intestinal Inflammation

TLRs are key sensors for conserved bacterial molecules and play a critical role in host defense against invading pathogens. Although the roles of TLRs in defense against pathogen infection and in maintaining gut immune homeostasis have been studied, the precise functions of different TLRs in response to pathogen infection in the gut remain elusive. The present study investigated the role of TLR signaling in defense against the Gram-negative bacterial pathogen Salmonella typhimurium The results indicated that TLR9-deficient mice were more susceptible to S. typhimurium infection compared with wild-type and TLR2- or TLR4-deficient mice, as indicated by more severe intestinal damage and the highest bacterial load. TLR9 deficiency in intestinal epithelial cells (IECs) augmented the activation of NF-κB and NLRP3 inflammasomes significantly, resulting in increased secretion of IL-1β. IL-1β increased the expression of NKG2D on intestinal intraepithelial lymphocytes and NKG2D ligands on IECs, resulting in higher susceptibility of IECs to cytotoxicity of intestinal intraepithelial lymphocytes and damage to the epithelial barrier. We proposed that TLR9 regulates the NF-κB-NLRP3-IL-1β pathway negatively in Salmonella-induced NKG2D-mediated intestinal inflammation and plays a critical role in defense against S. typhimurium infection and in the protection of intestinal integrity.

Colonization and Succession within the Human Gut Microbiome by Archaea, Bacteria, and Microeukaryotes during the First Year of Life

Perturbations to the colonization process of the human gastrointestinal tract have been suggested to result in adverse health effects later in life. Although much research has been performed on bacterial colonization and succession, much less is known about the other two domains of life, archaea, and eukaryotes. Here we describe colonization and succession by bacteria, archaea and microeukaryotes during the first year of life (samples collected around days 1, 3, 5, 28, 150, and 365) within the gastrointestinal tract of infants delivered either vaginally or by cesarean section and using a combination of quantitative real-time PCR as well as 16S and 18S rRNA gene amplicon sequencing. Sequences from organisms belonging to all three domains of life were detectable in all of the collected meconium samples. The microeukaryotic community composition fluctuated strongly over time and early diversification was delayed in infants receiving formula milk. Cesarean section-delivered (CSD) infants experienced a delay in colonization and succession, which was observed for all three domains of life. Shifts in prokaryotic succession in CSD infants compared to vaginally delivered (VD) infants were apparent as early as days 3 and 5, which were characterized by increased relative abundances of the genera Streptococcus and Staphylococcus, and a decrease in relative abundance for the genera Bifidobacterium and Bacteroides. Generally, a depletion in Bacteroidetes was detected as early as day 5 postpartum in CSD infants, causing a significantly increased Firmicutes/Bacteroidetes ratio between days 5 and 150 when compared to VD infants. Although the delivery mode appeared to have the strongest influence on differences between the infants, other factors such as a younger gestational age or maternal antibiotics intake likely contributed to the observed patterns as well. Our findings complement previous observations of a delay in colonization and succession of CSD infants, which affects not only bacteria but also archaea and microeukaryotes. This further highlights the need for resolving bacterial, archaeal, and microeukaryotic dynamics in future longitudinal studies of microbial colonization and succession within the neonatal gastrointestinal tract.

Regulation of intestinal permeability: The role of proteases

The gastrointestinal barrier is - with approximately 400 m² - the human body’s largest surface separating the external environment from the internal milieu. This barrier serves a dual function: permitting the absorption of nutrients, water and electrolytes on the one hand, while limiting host contact with noxious luminal antigens on the other hand. To maintain this selective barrier, junction protein complexes seal the intercellular space between adjacent epithelial cells and regulate the paracellular transport. Increased intestinal permeability is associated with and suggested as a player in the pathophysiology of various gastrointestinal and extra-intestinal diseases such as inflammatory bowel disease, celiac disease and type 1 diabetes. The gastrointestinal tract is exposed to high levels of endogenous and exogenous proteases, both in the lumen and in the mucosa. There is increasing evidence to suggest that a dysregulation of the protease/antiprotease balance in the gut contributes to epithelial damage and increased permeability. Excessive proteolysis leads to direct cleavage of intercellular junction proteins, or to opening of the junction proteins via activation of protease activated receptors. In addition, proteases regulate the activity and availability of cytokines and growth factors, which are also known modulators of intestinal permeability. This review aims at outlining the mechanisms by which proteases alter the intestinal permeability. More knowledge on the role of proteases in mucosal homeostasis and gastrointestinal barrier function will definitely contribute to the identification of new therapeutic targets for permeability-related diseases.

Anaerobic Probiotics: The Key Microbes for Human Health

Human gastrointestinal microbiota (HGIM) incorporate a large number of microbes from different species. Anaerobic bacteria are the dominant organisms in this microbial consortium and play a crucial role in human health. In addition to their functional role as the main source of many essential metabolites for human health, they are considered as biotherapeutic agents in the regulation of different human metabolites. They are also important in the prevention and in the treatment of different physical and mental diseases. Bifidobacteria are the dominant anaerobic bacteria in HGIM and are widely used in the development of probiotic products for infants, children and adults. To develop bifidobacteria-based bioproducts, therefore, it is necessary to develop a large-scale biomass production platform based on a good understanding of the ideal medium and bioprocessing parameters for their growth and viability. In addition, high cell viability should be maintained during downstream processing and storage of probiotic cell powder or the final formulated product. In this work we review the latest information about the biology, therapeutic activities, cultivation and industrial production of bifidobacteria.

Lactobacillus rhamnosus GG supplementation during critical windows of gestation influences immune phenotype in Swiss albino mice offspring

Probiotic supplementation during critical windows of gestation might have a significant influence on the infant’s immune phenotype. Swiss albino mice (F0 generation) aged 31 days were supplemented orally with probiotic Lactobacillus rhamnosus GG (LGG); and the supplementation was continued throughout mating, gestation and lactation. The pups (F1 generation) born to them were separated post weaning and received either the same probiotic supplementation as their mothers or were denied supplementation postnatally. Neutrophil phagocytic ability, splenocyte proliferation, immunoglobulins and cytokines were determined in both F0 and F1 pups. In addition, antibody response against hepatitis-B surface antigen (HBsAg) was determined in F1 pups. Probiotic supplementation had no effect on the neutrophil phagocytic ability and splenocyte proliferation index. The serum immunoglobulin G (IgG) and secretory IgA (s-IgA) among the probiotic supplemented group of F0 generation were significantly (P<0.05) higher compared to the controls. Similarly, the mean concentration of interleukin (IL)-10, IL-17 and interferon gamma (IFN-γ) among F0 probiotic group were significantly higher (P<0.05) compared to the control. Prenatal and postnatal probiotic supplementation in F1 pups led to similar results as F0 dams. Prenatal probiotic supplementation in F1 pups led to significantly (P<0.05) higher serum IgG (55.15±1.35 ng/ml) and intestinal s-IgA (77.9 ± 2.86 ng/mg protein) concentration when compared to the control. Similarly, IFN-γ concentration increased (P<0.05) with prenatal probiotic supplementation compared to the control. However, IL-10 and IL-17 concentrations of prenatal probiotic supplemented F1 pups were comparable to the control. As for the antibody response to HBsAg, prenatal probiotic supplementation led to enhanced HBsAg antibody response (471.4±3.97 U/ml) compared to the control. LGG affected the immune regulation and immune responses favourably in mothers and offspring. In addition, some of the beneficial effects of prenatal LGG supplementation extended into postnatal life of the offspring, thus suggesting possible immunoprogramming effect of LGG.

Intestinal microbiota and faecal transplantation as treatment modality for insulin resistance and type 2 diabetes mellitus

The prevalence of obesity and diabetes mellitus type 2 is increasing rapidly around the globe. Recent insights have generated an entirely new perspective that the intestinal microbiota may play a significant role in the development of these metabolic disorders. Alterations in the intestinal microbiota composition promote systemic inflammation that is a hallmark of obesity and subsequent insulin resistance. Thus, it is important to understand the reciprocal relationship between intestinal microbiota composition and metabolic health in order to eventually prevent disease progression. In this respect, faecal transplantation studies have implicated that butyrate-producing intestinal bacteria are crucial in this process and be considered as key players in regulating diverse signalling cascades associated with human glucose and lipid metabolism.

Bacterial control of host gene expression through RNA polymerase II

The normal flora furnishes the host with ecological barriers that prevent pathogen attack while maintaining tissue homeostasis. Urinary tract infections (UTIs) constitute a highly relevant model of microbial adaptation in which some patients infected with Escherichia coli develop acute pyelonephritis, while other patients with bacteriuria exhibit an asymptomatic carrier state similar to bacterial commensalism. It remains unclear if the lack of destructive inflammation merely reflects low virulence or if carrier strains actively inhibit disease-associated responses in the host. Here, we identify a new mechanism of bacterial adaptation through broad suppression of RNA polymerase II–dependent (Pol II–dependent) host gene expression. Over 60% of all genes were suppressed 24 hours after human inoculation with the prototype asymptomatic bacteriuria (ABU) strain E. coli 83972, and inhibition was verified by infection of human cells. Specific repressors and activators of Pol II–dependent transcription were modified, Pol II phosphorylation was inhibited, and pathogen-specific signaling was suppressed in cell lines and inoculated patients. An increased frequency of strains inhibiting Pol II was epidemiologically verified in ABU and fecal strains compared with acute pyelonephritis, and a Pol II antagonist suppressed the disease-associated host response. These results suggest that by manipulating host gene expression, ABU strains promote tissue integrity while inhibiting pathology. Such bacterial modulation of host gene expression may be essential to sustain asymptomatic bacterial carriage by ensuring that potentially destructive immune activation will not occur.

Evaluation of adhesion properties and antibacterial activities of the infant gut commensal Bifidobacterium bifidum PRL2010

Bifidobacteria are extensively exploited by the food industry as health-promoting microorganisms. However, very little is known about the molecular mechanisms responsible for these beneficial activities, or the molecular players that sustain their ability to colonize and persist within the human gut. Here, we have investigated the enteric adaptation features of the gut commensal Bifidobacterium bifidum PRL2010, originally isolated from infant feces. This strain was able to survive under gastrointestinal challenges, while it was shown to adhere to human epithelial intestinal cell monolayers (Caco 2 and HT-29), thereby inhibiting adhesion of pathogenic bacteria such as Escherichia coli and Cronobacter sakazakii.

Probiotic therapy as a novel approach for allergic disease

The prevalence of allergic disease has increased dramatically in Western countries over the past few decades. The hygiene hypothesis, whereby reduced exposure to microbial stimuli in early life programs the immune system toward a Th2-type allergic response, is suggested to be a major mechanism to explain this phenomenon in developed populations. Such microbial exposures are recognized to be critical regulators of intestinal microbiota development. Furthermore, intestinal microbiota has an important role in signaling to the developing mucosal immune system. Intestinal dysbiosis has been shown to precede the onset of clinical allergy, possibly through altered immune regulation. Existing treatments for allergic diseases such as eczema, asthma, and food allergy are limited and so the focus has been to identify alternative treatment or preventive strategies. Over the past 10 years, a number of clinical studies have investigated the potential of probiotic bacteria to ameliorate the pathological features of allergic disease. This novel approach has stemmed from numerous data reporting the pleiotropic effects of probiotics that include immunomodulation, restoration of intestinal dysbiosis as well as maintaining epithelial barrier integrity. In this mini-review, the emerging role of probiotics in the prevention and/or treatment of allergic disease are discussed with a focus on the evidence from animal and human studies.

A Basal chordate model for studies of gut microbial immune interactions

Complex symbiotic interactions at the surface of host epithelia govern most encounters between host and microbe. The epithelium of the gut is a physiologically ancient structure that is comprised of a single layer of cells and is thought to possess fully developed immunological capabilities. Ciona intestinalis (sea squirt), which is a descendant of the last common ancestor of all vertebrates, is a potentially valuable model for studying barrier defenses and gut microbial immune interactions. A variety of innate immunological phenomena have been well characterized in Ciona, of which many are active in the gut tissues. Interactions with gut microbiota likely involve surface epithelium, secreted immune molecules including variable region-containing chitin-binding proteins, and hemocytes from a densely populated laminar tissue space. The microbial composition of representative gut luminal contents has been characterized by molecular screening and a potentially relevant, reproducible, dysbiosis can be induced via starvation. The dialog between host and microbe in the gut can be investigated in Ciona against the background of a competent innate immune system and in the absence of the integral elements and processes that are characteristic of vertebrate adaptive immunity.

TGF-β2 induces maturation of immature human intestinal epithelial cells and inhibits inflammatory cytokine responses induced via the NF-κB pathway

OBJECTIVES

Breast milk transforming growth factor (TGF)-β2 is associated with healthy immune maturation and reduced risk of immune-mediated disease in infants. We sought to investigate whether conditioning with TGF-β2 may result in a more mature immune responder phenotype in immature human intestinal epithelial cells (IECs).

METHODS

Primary human fetal IECs (hFIECs) and the human fetal small intestinal epithelial cell line (H4 cells) were conditioned with breast milk levels of TGF-β2, and an inflammatory response was subsequently induced. Inflammatory cytokine secretion and mRNA expression were measured by enzyme-linked immunosorbent assay and quantitative real-time polymerase chain reaction, respectively. Alterations in activation of inflammatory signaling pathways were detected from IECs by immunoblotting and immunofluorescence. The effects of TGF-β2 conditioning on gene expression patterns in hFIECs were assessed by cDNA microarray analysis and quantitative PCR.

RESULTS

Conditioning with TGF-β2 significantly attenuated subsequent interleukin (IL)-1β-, TNF-α-, and poly I:C-induced IL-8 and IL-6 responses in immature human IECs. Conditioning with TGF-β2 inhibited IL-1β-induced IκB-α degradation and NF-κB p65 nuclear translocation, which may partially result from TGF-β2-induced changes in the expression of genes in the NF-κB signaling pathway detected by cDNA microarray and qPCR.

CONCLUSIONS

Conditioning with TGF-β2 attenuates the subsequent inflammatory cytokine response in immature human IECs by inhibiting signaling in the NF-κB pathway. The immunomodulatory potential of breast milk may in part be mediated by TGF-β2, which may provide a novel means of supporting intestinal immune maturation in neonates.

Probiotics modulate host-microbe interaction in the placenta and fetal gut: a randomized, double-blind, placebo-controlled trial

BACKGROUND

Early host-microbe interaction provides important maturational stimuli for the developing immune system. The role of prenatal microbial contact remains elusive.

OBJECTIVES

Our aim was to investigate whether microbes in placenta or amniotic fluid affect fetal innate immune gene expression during late pregnancy and whether innate immune gene expression profiles in the placenta and the fetal gut may be modulated by dietary supplementation with specific probiotics.

METHODS

Altogether 43 pregnant women were randomized to receive (1) Bifidobacterium lactis, (2) B. lactis in combination with Lactobacillus rhamnosus GG (LGG) or (3) placebo for 14 days before elective cesarian section at full term in a double-blind clinical trial. Bacteria in amniotic fluid and placenta were detected by quantitative (q)PCR. The expression of Toll-like receptor (TLR)-related genes in the placenta and meconium samples was assessed by qPCR. Gene expression patterns in meconium were interpreted to reflect immune physiology in the fetal gut.

RESULTS

The study was completed by 29 mother-infant pairs. Bacterial DNA was detected in all placenta samples. Microbial DNA in amniotic fluid and placenta was associated with changes in TLR-related gene expression in the fetal intestine. Maternal probiotic supplementation significantly modulated the expression of TLR-related genes both in the placenta and in the fetal gut.

CONCLUSIONS

Microbial contact in utero is associated with changes in fetal intestinal innate immune gene expression profile. Fetal and placental immune physiology may be modulated by maternal dietary intervention using specific probiotics.

Secreted factors from Bifidobacterium animalis subsp. lactis inhibit NF-κB-mediated interleukin-8 gene expression in Caco-2 cells

The objective of the present study was to evaluate the anti-inflammatory effects of Bifidobacterium animalis subsp. lactis strain BB12 in stimulated Caco-2 cells and to characterize the factors responsible for these anti-inflammatory effects. Characterization and purification studies indicate that BB12's anti-inflammatory factors might include a 50-kDa proteinaceous compound that is stable under a variety of heat and pH conditions.

Investigating the biological and clinical significance of human dysbioses

Culture-independent microbiological technologies that interrogate complex microbial populations without prior axenic culture, coupled with high-throughput DNA sequencing, have revolutionized the scale, speed and economics of microbial ecological studies. Their application to the medical realm has led to a highly productive merger of clinical, experimental and environmental microbiology. The functional roles played by members of the human microbiota are being actively explored through experimental manipulation of animal model systems and studies of human populations. In concert, these studies have appreciably expanded our understanding of the composition and dynamics of human-associated microbial communities (microbiota). Of note, several human diseases have been linked to alterations in the composition of resident microbial communities, so-called dysbiosis. However, how changes in microbial communities contribute to disease etiology remains poorly defined. Correlation of microbial composition represents integration of only two datasets (phenotype and microbial composition). This article explores strategies for merging the human microbiome data with multiple additional datasets (e.g. host single nucleotide polymorphisms and host gene expression) and for integrating patient-based data with results from experimental animal models to gain deeper understanding of how host-microbe interactions impact disease.

Need for a comprehensive medical approach to the neuro-immuno-gastroenterology of irritable bowel syndrome

Irritable bowel syndrome (IBS) is defined by the Rome III criteria as symptoms of recurrent abdominal pain or discomfort with the onset of a marked change in bowel habits with no evidence of an inflammatory, anatomic, metabolic, or neoplastic process. As such, many clinicians regard IBS as a central nervous system problem of altered pain perception. Here, we review the recent literature and discuss the evidence that supports an organic based model, which views IBS as a complex, heterogeneous, inter-dependent, and multi-variable inflammatory process along the neuronal-gut axis. We delineate the organic pathophysiology of IBS, demonstrate the role of inflammation in IBS, review the possible differences between adult and pediatric IBS, discuss the merits of a comprehensive treatment model as taught by the Institute of Functional Medicine, and describe the potential for future research for this syndrome.

Cesarean versus vaginal delivery: long-term infant outcomes and the hygiene hypothesis

Concurrent with the trend of increasing cesarean delivery numbers, there has been an epidemic of both autoimmune diseases and allergic diseases. Several theories have emerged suggesting that environmental influences are contributing to this phenomenon, most notably, the hygiene hypothesis. This article provides background about the human microbiota and its relationship to the developing immune system as well as the relationship of mode of delivery on the colonization of the infant intestine, development of the immune system, and subsequent childhood allergies, asthma, and autoimmune diseases.

Opportunistic respiratory pathogens in the oral cavity of the elderly

The oral cavity of the hospitalized or bedridden elderly is often a reservoir for opportunistic pathogens associated with respiratory diseases. Commensal flora and the host interact in a balanced fashion and oral infections are considered to appear following an imbalance in the oral resident microbiota, leading to the emergence of potentially pathogenic bacteria. The definition of the process involved in colonization by opportunistic respiratory pathogens needs to elucidate the factors responsible for the transition of the microbiota from commensal to pathogenic flora. The regulatory factors influencing the oral ecosystem can be divided into three major categories: the host defense system, commensal bacteria, and external pathogens. In this article, we review the profile of these categories including the intricate cellular interaction between immune factors and commensal bacteria and the disturbance in homeostasis in the oral cavity of hospitalized or bedridden elderly, which facilitates oral colonization by opportunistic respiratory pathogens.

Time-resolved quantitative proteome analysis of in vivo intestinal development

Postnatal intestinal development is a very dynamic process characterized by substantial morphological changes that coincide with functional adaption to the nutritional change from a diet rich in fat (milk) to a diet rich in carbohydrates on from weaning. Time-resolved studies of intestinal development have so far been limited to investigation at the transcription level or to single or few proteins at a time. In the present study, we elucidate proteomic changes of primary intestinal epithelial cells from jejunum during early suckling (1-7 days of age), middle suckling (7-14 days), and weaning period (14-35 days) in mice, using a label-free proteomics approach. We show differential expression of 520 proteins during intestinal development and a pronounced change of the proteome during the middle suckling period and weaning. Proteins involved in several metabolic processes were found differentially expressed along the development. The temporal expression profiles of enzymes of the glycolysis were found to correlate with the increase in carbohydrate uptake at weaning, whereas the abundance changes of proteins involved in fatty acid metabolism as well as lactose metabolism indicated a nondiet driven preparation for the nutritional change at weaning. Further, we report the developmental abundance changes of proteins playing a vital role in the neonatal acquisition of passive immunity. In addition, different isoforms of several proteins were quantified, which may contribute to a better understanding of the roles of the specific isoforms in the small intestine. In summary, we provide a first, time-resolved proteome profile of intestinal epithelial cells along postnatal intestinal development.

Interrelations between the microbiotas in the litter and in the intestines of commercial broiler chickens

The intestinal microbiota of broiler chickens and the microbiota in the litter have been well studied, but the interactions between these two microbiotas remain to be determined. Therefore, we examined their reciprocal effects by analyzing the intestinal microbiotas of broilers reared on fresh pine shavings versus reused litter, as well as the litter microbiota over a 6-week cycle. Composite ileal mucosal and cecal luminal samples from birds (n = 10) reared with both litter conditions (fresh versus reused) were collected at 7, 14, 21, and 42 days of age. Litter samples were also collected at days 7, 14, 21, and 42. The microbiotas were profiled and compared within sample types based on litter condition using PCR and denaturing gradient gel electrophoresis (PCR-DGGE). The microbiotas were further analyzed using 16S rRNA gene clone libraries constructed from microbiota DNA extracted from both chick intestinal and litter samples collected at day 7. Results showed significant reciprocal effects between the microbiotas present in the litter and those in the intestines of broilers. Fresh litter had more environmental bacteria, while reused litter contained more bacteria of intestinal origin. Lactobacillus spp. dominated the ileal mucosal microbiota of fresh-litter chicks, while a group of bacteria yet to be classified within Clostridiales dominated in the ileal mucosal microbiota in the reused-litter chicks. The Litter condition (fresh versus reused) seemed to have a more profound impact on the ileal microbiota than on the cecal microbiota. The data suggest that the influence of fresh litter on ileal microbiota decreased as broilers grew, compared with temporal changes observed under reused-litter rearing conditions.

Comparison between killed and living probiotic usage versus placebo for the prevention of necrotizing enterocolitis and sepsis in neonates

The aim of the study is to compare the role of killed (KP) Lactobacillus acidophilus with living (LP) in reducing incidence of sepsis (NS) and necrotizing enterocolitis (NEC) in neonates. Randomized double blind placebo study, included 150 neonates admitted to NICU at day 1, sixty received oral (LP) and 60 received (KP) and 30 received placebo. One gram of stools was collected on admission, at day 7, at end of the study, as well as on suspected NEC or NS and was sent for culture.

RESULTS

LP and KP were preventive factors for NEC with absolute risk reduction (AAR) 16, 15%, respectively and 18% for NS compared to placebo. Incidence of NEC and NS did not differ significantly between neonates supplemented with LP and those with KP. Preterm neonates supplemented with KP showed significantly lower incidence of NEC compared to placebo, while incidence of NS showed no significant difference between both groups. There is significant reduction in NS and NEC among neonates with positive Lactobacillus colonization of gut compared to those none colonized at day 7 (27.9 vs. 85.9%, 0 vs. 7.8%) and at day 14 (48.7 vs. 91.7% for NS and 0 vs. 20.8% for NEC). Overall comparison between the three groups showed statistical significant reduction in the incidence of NEC. Present conclusions are that early gut colonization with beneficial bacteria lowers the incidence of NEC and NS. KP retained similar benefits to live bacteria.

Improving the use of human milk during and after the NICU stay

The feeding of human milk (milk from the infant's own mother; excluding donor milk) during the newborn intensive care unit (NICU) stay reduces the risk of costly and handicapping morbidities in premature infants. The mechanisms by which human milk provides this protection are varied and synergistic, and appear to change over the course of the NICU stay. The fact that these mechanisms include specific human milk components that are not present in the milk of other mammals means that human milk from the infant's mother cannot be replaced by commercial infant or donor human milk, and the feeding of human milk should be a NICU priority. Recent evidence suggests that the impact of human milk on improving infant health outcomes and reducing the risk of prematurity-specific morbidities is linked to specific critical exposure periods in the post-birth period during which the exclusive use of human milk and the avoidance of commercial formula may be most important. Similarly, there are other periods when high doses, but not necessarily exclusive use of human milk, may be important. This article reviews the concept of "dose and exposure period" for human milk feeding in the NICU to precisely measure and benchmark the amount and timing of human milk use in the NICU. The critical exposure periods when exclusive or high doses of human milk appear to have the greatest impact on specific morbidities are reviewed. Finally, the current best practices for the use of human milk during and after the NICU stay for premature infants are summarized.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

A novel mouse model of inflammatory bowel disease links mammalian target of rapamycin-dependent hyperproliferation of colonic epithelium to inflammation-associated tumorigenesis

Inflammatory bowel disease (IBD) is a high-risk condition for human colorectal cancer. However, our mechanistic understanding of the link between inflammation and tumorigenesis in the colon is limited. Here we established a novel mouse model of colitis-associated cancer by genetically inactivating signal transducer and activator of transcription 3 (Stat3) in macrophages, with partial deletion in other myeloid and lymphoid cells. Inflammation developed in the colon of mutant mice spontaneously, and tumor lesions, including invasive carcinoma, arose in the inflamed region of the intestine with a frequency similar to that observed in human IBD patients. The development of both inflammation and tumors in the mutant mice required the presence of microflora. Indeed, inflammation was associated with disruption of colonic homeostasis, fulminant epithelial/tumor cell proliferation, and activation of the mammalian target of rapamycin (mTOR)-Stat3 pathway in epithelial and tumor cells. The activation of this pathway was essential for both the excess proliferation of epithelial/tumor cells and the disruption of colonic homeostasis in the mutant mice. Notably, a similar abnormal up-regulation of mTOR-Stat3 signaling was consistently observed in the colonic epithelial cells of human IBD patients with active disease. These studies demonstrate a novel mouse model of IBD-colorectal cancer progression in which disrupted immune regulation, mTOR-Stat3 signaling, and epithelial hyperproliferation are integrated and simultaneously linked to the development of malignancy.

The effect of age and non-steroidal anti-inflammatory drugs on human intestinal microbiota composition

Ageing has been suggested to cause changes in the intestinal microbial community. In the present study, the microbiota of a previously well-defined group of elderly subjects aged between 70 and 85 years, both non-steroidal anti-inflammatory drugs (NSAID) users (n 9) and non-users (n 9), were further compared with young adults (n 14) with a mean age of 28 years, by two DNA-based techniques: percentage guanine+cytosine (%G+C) profiling and 16S rDNA sequencing. Remarkable changes in microbiota were described with both methods: compared with young adults a significant reduction in overall numbers of microbes in both elderly groups was measured. Moreover, the total number of microbes in elderly NSAID users was higher than in elderly without NSAID. In 16S rDNA sequencing, shifts in all major microbial phyla, such as lower numbers of Firmicutes and an increase in numbers of Bacteroidetes in the elderly were monitored. On the genus level an interesting link between reductions in the proportion of known butyrate producers belonging to Clostridium cluster XIVa, such as Roseburia and Ruminococcus, could be demonstrated in the elderly. Moreover, in the Actinobacteria group, lower numbers of Collinsella spp. were evident in the elderly subjects with NSAID compared both with young adults and the elderly without NSAID, suggesting that the use of NSAID along with age may also influence the composition of intestinal microbiota. Furthermore, relatively high numbers of Lactobacillus appeared only in the elderly subjects without NSAID. In general, the lowered numbers of microbial members in the major phyla, Firmicutes, together with changes in the epithelial layer functions can have a significant effect on the colon health of the elderly.

Academy of Breastfeeding Medicine founder's lecture 2008: breastfeeding--an extrauterine link between mother and child

In addition to a near-optimal combination of nutrients for the growing infant, breastmilk contains a wide array of bioactive molecules that are known to protect the infant against infectious disease and modulate the composition of the indigenous intestinal microbiota. A growing number of factors that modulate the infant's immunophysiology have also been identified in breastmilk. We suggest that this early immunomodulation via breastmilk is vital for infant health and may explain the epidemiological data indicating that breastmilk reduces the risk of immunoinflammatory conditions in infancy and also later in life. The body of scientific data regarding the role of transforming growth factor-beta in breastmilk in enhancing healthy immune maturation and reducing the risk of disease is reviewed in this article.

Alimentary Epigenetics: A Developmental Psychobiological Systems View of the Perception of Hunger, Thirst and Satiety

Hunger, thirst and satiety have an enormous influence on cognition, behavior and development, yet we often take for granted that they are simply inborn or innate. Converging data and theory from both comparative and human domains, however, supports the conclusion that the phenomena hunger, thirst and satiety are not innate but rather emerge probabilistically as a function of experience during individual development. The metatheoretical perspective provided by developmental psychobiological systems theory provides a useful framework for organizing and synthesizing findings related to the development of the perception of hunger, thirst and satiety, or alimentary interoception. It is argued that neither developmental psychology nor the psychology of eating and drinking have adequately dealt with the ontogeny of alimentary interoception and that a more serious consideration of the species-typical developmental system of food and fluid intake and the many modifications that have been made therein is likely necessary for a full understanding of both alimentary and emotional development.

Live and ultraviolet-inactivated Lactobacillus rhamnosus GG decrease flagellin-induced interleukin-8 production in Caco-2 cells

Probiotics are widely used in the treatment and prevention of gastrointestinal problems. However, in some immune-compromised populations, the administration of live microorganisms may not be appropriate. A potential alternative to live microorganisms is to inactivate them as long as the beneficial function is retained. We hypothesized that UV-inactivated Lactobacillus rhamnosus GG (LGG) could downregulate interleukin-8 (IL-8) production in intestinal epithelial cells stimulated by the pathogenic ligand, flagellin, using similar mechanisms as live LGG. Caco-2 cells were pretreated with live or UV-inactivated LGG at 10(11) colony-forming units/L and stimulated by flagellin at a dose of 500 mug/L. IL-8 production was measured by ELISA, inhibitor of kappaB (IkappaB) and ubiquitinated-IkappaB (Ub-IkappaB) expression by immunoblotting and nuclear factor (NF) kappaB localization by immunofluorescence staining. Flagellin induced a 17-fold increase in IL-8 production compared with control (P < 0.05), whereas pretreatment with either live LGG or UV-inactivated LGG resulted in 66 and 59% decreases, respectively, compared with the flagellin group (P < 0.05). Flagellin-induced NFkappaB nuclear translocation was prevented by both live and UV-inactivated LGG. Flagellin decreased IkappaB, which was reversed by either live or UV-inactivated LGG (P < 0.05). UV-inactivated LGG decreased Ub-IkappaB expression (P < 0.05), although live LGG had no effect. This study supports the concept that UV-inactivated and live LGG are equally effective in decreasing IL-8 production in the intestinal epithelium. Although the mechanism involves different pathways, both alter cytoplasmic IkappaB, thereby inhibiting NFkappaB nuclear translocation.