Vitamin D receptor negatively regulates bacterial-stimulated NF-kappaB activity in intestine

Vitamin D deficiency promotes epithelial barrier dysfunction and intestinal inflammation

BACKGROUND

Vitamin D, an important modulator of the immune system, has been shown to protect mucosal barrier homeostasis. This study investigates the effects of vitamin D deficiency on infection-induced changes in intestinal epithelial barrier function in vitro and on Citrobacter rodentium-induced colitis in mice.

METHODS

Polarized epithelial Caco2-bbe cells were grown in medium with or without vitamin D and challenged with enterohemorrhagic Escherichia coli O157:H7. Barrier function and tight junction protein expression were assessed. Weaned C57BL/6 mice were fed either a vitamin D-sufficient or vitamin D-deficient diet and then infected with C. rodentium. Disease severity was assessed by histological analysis, intestinal permeability assay, measurement of inflammatory cytokine levels, and microbiome analysis.

RESULTS

1,25(OH)2D3 altered E. coli O157:H7-induced reductions in transepithelial electrical resistance (P < .01), decreased permeability (P < .05), and preserved barrier integrity. Vitamin D-deficient mice challenged with C. rodentium demonstrated increased colonic hyperplasia and epithelial barrier dysfunction (P < .0001 and P < .05, respectively). Vitamin D deficiency resulted in an altered composition of the fecal microbiome both in the absence and presence of C. rodentium infection.

CONCLUSIONS

This study demonstrates that vitamin D is an important mediator of intestinal epithelial defenses against infectious agents. Vitamin D deficiency predisposes to more-severe intestinal injury in an infectious model of colitis.

Nutrigenetics, nutrigenomics and inflammatory bowel diseases

Inflammatory bowel disease includes ulcerative colitis and Crohn's disease, which are both inflammatory disorders of the gastrointestinal tract. Both types of inflammatory bowel disease have a complex etiology, resulting from a genetically determined susceptibility interacting with environmental factors, including the diet and gut microbiota. Genome Wide Association Studies have implicated more than 160 single-nucleotide polymorphisms in disease susceptibility. Consideration of the different pathways suggested to be involved implies that specific dietary interventions are likely to be appropriate, dependent upon the nature of the genes involved. Epigenetics and the gut microbiota are also responsive to dietary interventions. Nutrigenetics may lead to personalized nutrition for disease prevention and treatment, while nutrigenomics may help to understand the nature of the disease and individual response to nutrients.

Helicobacter pylori induces increased expression of the vitamin d receptor in immune responses

BACKGROUND

Vitamin D receptor (VDR) is a member of the nuclear receptor family of transcription factors that play a critical role in innate immunity. This study examined the role of VDR in gastric innate immune defence against the gastric pathogen Helicobacter pylori.

MATERIALS AND METHODS

Seventeen H. pylori-infected patients and sixteen controls participated in the study. The GES-1 cells were transfected with siRNA or incubated with or without 1α,25(OH)2 D3 (100 nmol/L) then infected with H. pylori. VDR, cathelicidin antimicrobial protein (CAMP), and cytokine mRNA expression levels in normal and H. pylori-infected gastric mucosa and GES-1 cells was determined by qRT-PCR and correlated with the histopathologic degree of gastritis. Bactericidal activity was measured by using a colony-forming unit assay.

RESULTS

Vitamin D receptor mRNA expression levels were significantly upregulated in H. pylori-infected patients and positively correlated with chronic inflammation scores. There was a significant positive correlation between VDR and CAMP mRNA expression in H. pylori-positive gastric mucosa. VDR siRNA reduced H. pylori-induced CAMP production and conversely increased IL-6 and IL8/CXCL8 expression levels. The vitamin D agonist 1α,25(OH)2 D3 increased CAMP expression and reduced cytokine activation in GES-1 cells infected with H. pylori. 1α,25(OH)2 D3 could enhance the intracellular killing of the replicating bacteria, but the presence of siVDR and siCAMP led to a decline in its bactericidal ability.

CONCLUSIONS

The expression of VDR and CAMP in the gastric epithelium is up-regulated in the case of H. pylori infection; thus, VDR plays an important role in gastric mucosa homeostasis and host protection from H. pylori infection.

Relationship between vitamin D and inflammatory markers in older individuals

In older persons, vitamin D insufficiency and a subclinical chronic inflammatory status frequently coexist. Vitamin D has immune-modulatory and in vitro anti-inflammatory properties. However, there is inconclusive evidence about the anti-inflammatory role of vitamin D in older subjects. Thus, we investigated the hypothesis of an inverse relationship between 25-hydroxyvitamin D (25(OH)D) and inflammatory markers in a population-based study of older individuals. After excluding participants with high-sensitivity C-reactive protein (hsCRP) ≥ 10 mg/dl and those who were on chronic anti-inflammatory treatment, we evaluated 867 older adults ≥65 years from the InCHIANTI Study. Participants had complete data on serum concentrations of 25(OH)D, hsCRP, tumor necrosis factor (TNF)-α, soluble TNF-α receptors 1 and 2, interleukin (IL)-1β, IL-1 receptor antagonist, IL-10, IL-18, IL-6, and soluble IL-6 receptors (sIL6r and sgp130). Two general linear models were fit (model 1-adjusted for age, sex, and parathyroid hormone (PTH); model 2-including covariates of model 1 plus dietary and smoking habits, physical activity, ADL disability, season, osteoporosis, depressive status, and comorbidities). The mean age was 75.1 ± 17.1 years ± SD. In model 1, log(25OH-D) was significantly and inversely associated with log(IL-6) (β ± SE = -0.11 ± 0.03, p = <0.0001) and log (hsCRP) (β ± SE = -0.04 ± 0.02, p = 0.04) and positively associated with log(sIL6r) (β ± SE = 0.11 ± 0.04, p = 0.003) but not with other inflammatory markers. In model 2, log (25OH-D) remained negatively associated with log (IL-6) (β ± SE = -0.10 ± 0.03, p = 0.0001) and positively associated with log(sIL6r) (β ± SE = 0.11 ± 0.03, p = 0.004) but not with log(hsCRP) (β ± SE = -0.01 ± 0.03, p = 0.07). 25(OH)D is independently and inversely associated with IL-6 and positively with sIL6r, suggesting a potential anti-inflammatory role for vitamin D in older individuals.

Report of the CCFA pediatric bone, growth and muscle health workshop, New York City, November 11-12, 2011, with updates

Growth retardation, delayed puberty, decreased bone mass, altered bone architecture, hypovitaminosis D and skeletal muscle mass deficits are common in children with inflammatory bowel diseases. The Crohn's and Colitis Foundation of America sponsored a multidisciplinary workshop on the subject of Bone and Skeletal Growth in Pediatric IBD, held in New York City in November 2011. The topic of the workshop was a key recommendation of the Foundation's Pediatric Challenges meeting in 2005. The Litwin Foundation provided a generous grant to support this crucial research and workshop through the CCFA. The workshop featured 15 presentations by researchers from the United States, Canada, Switzerland, Germany, and the United Kingdom and a number of posters elucidating diverse aspects of the problem of growth retardation and compromised bone health in pediatric Crohn's disease and ulcerative colitis. The workshop comprised original, basic, and clinical research and relevant reviews of underlying genetics, molecular biology, endocrinology, immunology, and bone physiology research. Investigators funded by CCFA and the Litwin Family Foundation are marked by an asterisk after their name in the text. Workshop presentations fell under 3 broad categories: "Mechanisms of Suppression and Growth of Bone Cell Function by Inflammation," "Impact of IBD on Growth and Bone Health," and "Approaches to Address Growth Failure and Low Bone Mass in Children with IBD," summarized herein. We have cited the publications that resulted from this granting mechanism in the appropriate section and references for pertinent updates on each topic.

The role of gut microbiota in nutritional status

PURPOSE OF REVIEW

The objective of this review is to outline the contribution of the gut microbiota to nutritional status and to highlight the mechanisms by which this can occur.

RECENT FINDINGS

Historically, research linking intestinal bacteria with nutritional status focused on the degradation of indigestible food components by bacterial enzymes and metabolites. Of late, emerging evidence suggests an independent role of the gut microbiota in the regulation of glucose and energy homeostasis via complex interactions between microbially derived metabolites and specific target tissue cells. In addition, novel findings highlight specific microbial species involved in the production of a number of micronutrient components, which could potentially improve nutritional status in certain population groups, if available to the host at sufficiently abundant levels.

SUMMARY

New insights into the role of the gut microbiota and its holistic effects on the host are now emerging. High-throughput technologies allow for a greater insight into the role of the intestinal microbiota and the mechanisms by which it can contribute to overall nutritional status. Further, exploration of this evolving field of research will advance our understanding of how this complex ecosystem could advance the area of personalized nutrition in the future.

Probiotic Lactobacillus rhamnosus GG mono-association suppresses human rotavirus-induced autophagy in the gnotobiotic piglet intestine

BACKGROUND

Human rotavirus (HRV) is the most important cause of severe diarrhea in infants and young children. Probiotic Lactobacillus rhamnosus GG (LGG) reduces rotavirus infection and diarrhea. However, the molecular mechanisms of LGG-mediated protection from rotavirus infection are poorly understood. Autophagy plays an essential role in responses to microbial pathogens. However, the role of autophagy in HRV infection and LGG treatment is unknown. We hypothesize that rotavirus gastroenteritis activates autophagy and that LGG suppresses virus-induced autophagy and prevents intestinal damage in infected piglets.

METHODS

We used LGG feeding to combat viral gastroenteritis in the gnotobiotic pig model of virulent HRV infection.

RESULTS

We found that LGG feeding did not increase autophagy, whereas virus infection induced autophagy in the piglet intestine. Virus infection increased the protein levels of the autophagy markers ATG16L1 and Beclin-1 and the autophagy regulator mTOR. LGG treatment during viral gastroenteritis reduced autophagy marker expression to normal levels, induced apoptosis and partially prevented virus-induced tissue damage.

CONCLUSION

Our study provides new insights into virus-induced autophagy and LGG suppression of uncontrolled autophagy and intestinal injury. A better understanding of the antiviral activity of LGG will lead to novel therapeutic strategies for infant infectious diseases.

Functional profiling of the gut microbiome in disease-associated inflammation

The microbial residents of the human gut are a major factor in the development and lifelong maintenance of health. The gut microbiota differs to a large degree from person to person and has an important influence on health and disease due to its interaction with the human immune system. Its overall composition and microbial ecology have been implicated in many autoimmune diseases, and it represents a particularly important area for translational research as a new target for diagnostics and therapeutics in complex inflammatory conditions. Determining the biomolecular mechanisms by which altered microbial communities contribute to human disease will be an important outcome of current functional studies of the human microbiome. In this review, we discuss functional profiling of the human microbiome using metagenomic and metatranscriptomic approaches, focusing on the implications for inflammatory conditions such as inflammatory bowel disease and rheumatoid arthritis. Common themes in gut microbial ecology have emerged among these diverse diseases, but they have not yet been linked to targetable mechanisms such as microbial gene and genome composition, pathway and transcript activity, and metabolism. Combining these microbial activities with host gene, transcript and metabolic information will be necessary to understand how and why these complex interacting systems are altered in disease-associated inflammation.

Vitamin D in allergic disease: shedding light on a complex problem

Vitamin D is unique among nutritional factors because the intake of this special vitamin represents the sum of vitamin D obtained from diet, nutritional supplements, and endogenous production after exposure to sunlight. The current recommended nutritional intake requirements reflect needs based on its established role in calcium absorption and bone health. However, recent studies have revealed that vitamin D has important functions in the immune system and might influence the course of immune-mediated disorders, including atopic dermatitis and asthma. This review discusses the scientific rationale for a role for vitamin D in immune function, gives an update on allergic disease associations with lower vitamin D serum levels, and discusses recent observations relating to vitamin D in immune function.

Vitamin D deficiency associated with increased incidence of gastrointestinal and ear infections in school-age children

BACKGROUND

Vitamin D deficiency (VDD) is highly prevalent among children worldwide. The effects of VDD include alterations of the immune response and increased risk of infection but little evidence exists in school-age children. We investigated the association of vitamin D status with morbidity in a prospective study of school-age children from Bogotá, Colombia.

METHODS

We measured plasma 25-hydroxyvitamin D (25(OH)D) concentrations in a random sample of 475 children (mean ± standard deviation age: 8.9 ± 1.6 years) and followed them for an academic year. Caregivers were asked to record daily information on the incidence of morbidity episodes using pictorial diaries. Baseline vitamin D status was classified according to 25(OH)D concentrations as deficient (<50 nmol/L), insufficient (≥50 and <75 nmol/L) or sufficient (≥75 nmol/L). We used Poisson regression to estimate incidence rate ratios and 95% confidence intervals for days with diarrhea, vomiting, diarrhea with vomiting, cough with fever and earache or discharge with fever, comparing vitamin D-deficient with vitamin D-sufficient children. Estimates were adjusted for child's age, sex and household socioeconomic status.

RESULTS

The prevalence of VDD was 10%; an additional 47% of children were vitamin D-insufficient. VDD was associated with increased rates of diarrhea with vomiting (adjusted incidence rate ratio: 2.05; 95% confidence interval: 1.19, 3.53) and earache/discharge with fever (adjusted incidence rate ratio: 2.36; 95% confidence interval: 1.26, 4.44). VDD was not significantly related to cough with fever.

CONCLUSIONS

These results suggest that VDD is related to increased incidence of gastrointestinal and ear infections in school-age children. The effect of correcting VDD on reducing risk of these infections needs to be tested in supplementation trials.

How important is vitamin D in preventing infections?

Interaction with the immune system is one of the most recently established nonclassic effects of vitamin D (VitD). For many years, this was considered to be limited to granulomatous diseases in which synthesis of active 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) or calcitriol is known to be increased. However, recent reports have supported a role for 1,25(OH)2D3 in promoting normal function of the innate and adaptive immune systems. Crucially, these effects seem to be mediated not only by the endocrine function of circulating calcitriol but also via paracrine (i.e., refers to effects to adjacent or nearby cells) and/or intracrine activity (i.e., refers to a hormone acting inside a cell) of 1,25(OH)2D3 from its precursor 25(OH)D3, the main circulating metabolite of VitD. The ability of this vitamin to influence human immune responsiveness seems to be highly dependent on the 25(OH)D3 status of individuals and may lead to aberrant response to infection or even to autoimmunity in those who are lacking VitD. The potential health significance of this has been underlined by increasing awareness of impaired status in populations across the globe. This review will examine the current understanding of how VitD status may modulate the responsiveness of the human immune system. Furthermore, we discuss how it may play a role in host resistance to common pathogens and how effective is its supplementation for treatment or prevention of infectious diseases in humans.

Critical role of non-muscle myosin light chain kinase in thrombin-induced endothelial cell inflammation and lung PMN infiltration

The pathogenesis of acute lung injury (ALI) involves bidirectional cooperation and close interaction between inflammatory and coagulation pathways. A key molecule linking coagulation and inflammation is the procoagulant thrombin, a serine protease whose concentration is elevated in plasma and lavage fluids of patients with ALI and acute respiratory distress syndrome (ARDS). However, little is known about the mechanism by which thrombin contributes to lung inflammatory response. In this study, we developed a new mouse model that permits investigation of lung inflammation associated with intravascular coagulation. Using this mouse model and in vitro approaches, we addressed the role of non-muscle myosin light chain kinase (nmMLCK) in thrombin-induced endothelial cell (EC) inflammation and lung neutrophil (PMN) infiltration. Our in vitro experiments revealed a key role of nmMLCK in ICAM-1 expression by its ability to control nuclear translocation and transcriptional capacity of RelA/p65 in EC. When subjected to intraperitoneal thrombin challenge, wild type mice showed a marked increase in lung PMN infiltration via expression of ICAM-1. However, these responses were markedly attenuated in mice deficient in nmMLCK. These results provide mechanistic insight into lung inflammatory response associated with intravascular coagulation and identify nmMLCK as a critical target for modulation of lung inflammation.

Salmonella infection upregulates the leaky protein claudin-2 in intestinal epithelial cells

Background

Tight junctions seal the space between adjacent epithelial cells. Mounting evidence suggests that tight junction proteins play a key role in the pathogenesis of human disease. Claudin is a member of the tight junction protein family, which has 24 members in humans. To regulate cellular function, claudins interact structurally and functionally with membrane and scaffolding proteins via their cytoplasmic domain. In particular, claudin-2 is known to be a leaky protein that contributes to inflammatory bowel disease and colon cancer. However, the involvement of claudin-2 in bacterial infection in the intestine remains unknown.

Methods/Principal Findings

We hypothesized that Salmonella elevates the leaky protein claudin-2 for its own benefit to facilitate bacterial invasion in the colon. Using a Salmonella-colitis mouse model and cultured colonic epithelial cells, we found that pathogenic Salmonella colonization significantly increases the levels of claudin-2 protein and mRNA in the intestine, but not that of claudin-3 or claudin-7 in the colon, in a time-dependent manner. Immunostaining studies showed that the claudin-2 expression along the crypt-villous axis postinfection. In vitro, Salmonella stimulated claudin-2 expression in the human intestinal epithelial cell lines SKCO15 and HT29C19A. Further analysis by siRNA knockdown revealed that claudin-2 is associated with the Salmonella-induced elevation of cell permeability. Epithelial cells with claudin-2 knockdown had significantly less internalized Salmonella than control cells with normal claudin-2 expression. Inhibitor assays demonstrated that this regulation is mediated through activation of the EGFR pathway and the downstream protein JNK.

Conclusion/Significance

We have shown that Salmonella targets the tight junction protein claudin-2 to facilitate bacterial invasion. We speculate that this disruption of barrier function contributes to a new mechanism by which bacteria interact with their host cells and suggests the possibility of blocking claudin-2 as a potential therapeutic strategy to prevent bacterial invasion.

Vitamin D, Vitamin D Receptor, and Tissue Barriers

Tissue barriers are critical in the pathogenesis of human diseases, such as atopic dermatitis, inflammatory bowel diseases and various cancers. Preserving or restoring barrier functions of the epithelia cells is a therapeutic strategy to prevent and treat the illness. Mounting evidence indicates that vitamin D and the vitamin D receptor (VDR) play key roles in the pathogenesis of human diseases. In particular, we note an interesting link between vitamin D/VDR signaling and tissue barriers. In the current review, we summarize the recent progress on vitamin D and cell junction complexes. We focus on the functions of VDR and VDR-associated intracellular junction proteins, such as β-catenin and claudins. We also discuss the potential therapeutic functions of vitamin D in treating defective tissue barriers that involve skin, intestine, lung, kidney and other organs. However, the mechanisms for the vitamin D/VDR signaling in tissue barriers remain largely unknown. Further studies on vitamin D/VDR’s multiple functions in physiological models will suggest new therapeutic targets for prevention and treatment diseases with defective barrier functions.

Impairment of bilirubin clearance and intestinal interleukin-6 expression in bile duct-ligated vitamin D receptor null mice

The vitamin D receptor (VDR) mediates the physiological and pharmacological actions of 1α,25-dihydroxyvitamin D₃ in bone and calcium metabolism, cellular growth and differentiation, and immunity. VDR also responds to secondary bile acids and belongs to the NR1I subfamily of the nuclear receptor superfamily, which regulates expression of xenobiotic metabolism genes. When compared to knockout mouse investigations of the other NR1I nuclear receptors, pregnane X receptor and constitutive androstane receptor, an understanding of the role of VDR in xenobiotic metabolism remains limited. We examined the effect of VDR deletion in a mouse model of cholestasis. We performed bile duct ligation (BDL) on VDR-null mice and compared blood biochemistry, mRNA expression of genes involved in bile acid and bilirubin metabolism, cytokine production, and expression of inflammatory regulators with those of wild-type mice. VDR-null mice had elevated plasma conjugated bilirubin levels three days after BDL compared with wild-type mice. Urine bilirubin levels and renal mRNA and/or protein expression of multidrug resistance-associated proteins 2 and 4 were decreased in VDR-null mice, suggesting impaired excretion of conjugated bilirubin into urine. While VDR-null kidney showed mRNA expression of interleukin-6 (IL-6) after BDL and VDR-null macrophages had higher IL-6 protein levels after lipopolysaccharide stimulation, the induction of intestinal Il6 mRNA expression and plasma IL-6 protein levels after BDL was impaired in VDR-null mice. Immunoblotting analysis showed that expression of an immune regulator, IκBα, was elevated in the jejunum of VDR-null mice, a possible mechanism for the attenuated induction of Il6 expression in the intestine after BDL. Increased expression of IκBα may be a consequence of compensatory mechanisms for VDR deletion. These results reveal a role of VDR in bilirubin clearance during cholestasis. VDR is also suggested to contribute to tissue-selective immune regulation.

Probiotics, prebiotics, energy balance, and obesity: mechanistic insights and therapeutic implications

Obesity-related disorders derive from a combination of genetic susceptibility and environmental factors. Recent evidence supports the role of gut microbiota in the pathogenesis of obesity, type 2 diabetes mellitus, and insulin resistance by increasing energy harvest from diet and by inducing chronic, low-grade inflammation. Several studies describe characteristic differences between composition and activity of gut microbiota of lean individuals and those with obesity. Despite this evidence, some pathophysiological mechanisms remain to be clarified. This article discusses mechanisms connecting gut microbiota to obesity and fat storage and the potential therapeutic role of probiotics and prebiotics.

Consistent activation of the β-catenin pathway by Salmonella type-three secretion effector protein AvrA in chronically infected intestine

Salmonella infection is a common public health problem that can become chronic and increase the risk of cancer. Live, mutated Salmonella is used to target cancer cells. However, few studies have addressed chronic Salmonella infection in vivo. AvrA is a Salmonella type-three secretion effector that is multifunctional, inhibiting intestinal inflammation and enhancing proliferation. β-catenin is a key player in intestinal renewal, inflammation, and tumorigenesis. We hypothesize that in Salmonella-infected intestine, AvrA chronically activates the β-catenin pathway and increases cell proliferation, thus deregulating the intestinal responses to bacterial infection. We followed mice with Salmonella infection for 27 wk and investigated the physiological effects and role of AvrA on β-catenin in chronically infected intestine. We found that AvrA persistently regulated β-catenin posttranslational modifications, including phosphorylation and acetylation. Moreover, the upstream regulator Akt, transcription factors, T cell factors, nuclear β-catenin, and β-catenin target genes were enhanced in mice infected with Salmonella-expressing AvrA. AvrA has a chronic functional role in promoting intestinal renewal. In summary, we have uncovered an essential role of Salmonella AvrA in chronically activating β-catenin and impacting intestinal renewal in small intestine and colon. Our study emphasizes the importance of AvrA in chronic bacterial infection.

Vitamin D attenuates high fat diet-induced hepatic steatosis in rats by modulating lipid metabolism

BACKGROUND

Vitamin D has been reported to be reversely associated with type 2 diabetes and metabolic syndrome and is involved in modulation of lipid metabolism. The purpose of the present study was to determine whether 1,25-dihydroxyvitamin D(3) (1,25(OH)(2) D(3) ) has a protective effect on high fat diet (HFD)-induced hepatic steatosis in rats and to elucidate its underlying molecular mechanisms.

MATERIALS AND METHODS

Male Sprague-Dawley (SD) rats were fed with normal fat diet, HFD or HFD with intraperitoneal injection of 1, 2.5 and 5 μg/kg 1,25(OH)(2) D(3) , respectively, each 2 days for 8 weeks. Serum lipid profile and liver triglyceride were determined. Hepatic histology was examined by haematoxylin/eosin (H&E) and Oil Red O stainings. Hepatic gene expression involved in lipogenesis and lipid oxidation was analysed by quantitative reverse transcription-polymerase chain reaction (RT-PCR).

RESULTS

The administration of 1,25(OH)(2) D(3) prevented HFD-induced body weight gain and reduced liver weight. 1,25(OH)(2) D(3) attenuated hepatic steatosis in a dose-dependent manner along with improved serum lipid profile. Furthermore, 1,25(OH)(2) D(3) downregulated mRNA expression of sterol regulatory element binding protein-1c (SREBP-1c) and its target genes acetyl-CoA carboxylase (ACC) and fatty acid synthase (FAS) involved in lipogenesis. Peroxisome proliferator-activated receptor α (PPARα) and its target gene carnitine palmitoyltransferase-1 (CPT-1) involved in hepatic fatty acid (FA) oxidation were upregulated by 1,25(OH)(2) D(3) .

CONCLUSIONS

These results suggest that the preventing effect of 1,25(OH)(2) D(3) against HFD-induced hepatic steatosis is related to the inhibition of lipogenesis and the promotion of FA oxidation in rat liver.

Microbiome and immunological interactions

The healthy human gut supports a complex and diverse microbiota, dominated by bacterial phylotypes belonging to Bacteroidetes and Firmicutes. In the inflamed gut, overall diversity decreases, coincident with a greater representation of Proteobacteria. There is growing evidence supporting an important role for human gut bacteria in mucosal immunity; interactions at the level of both intestinal and colonic epithelial cells, dendritic cells, and T and B immune cells have been documented. These interactions influence gut barrier and defense mechanisms that include antimicrobial peptide and secretory IgA synthesis. The functional effects of commensal bacteria on T helper cell differentiation have led to the emerging concept that microbiota composition determines T effector- and T regulatory-cell balance, immune responsiveness, and homeostasis. The importance of this biology in relation to immune homeostasis, inflammatory bowel disease, and the rising incidence of autoimmune diseases will be discussed. The detailed description of the human gut microbiota, integrated with evidence-based mechanisms of immune modulation, provides an exciting platform for the identification of next-generation probiotics and related pharmaceutical products.

Effects of Vitamin D Supplementation during the Induction and Progression of Osteoarthritis in a Rat Model

Epidemiological studies correlate low levels of vitamin D with the osteoarthritis (OA) progression. Cytokines and metalloproteases play a major role in OA promoting the inflammation and degradation of the cartilage and can be induced through the Toll-like receptor (TLR) pathway. The aim of this study was to evaluate the protective effect of vitamin D supplementation on the development of osteoarthritis (OA) through examining the genetic regulation of TLRs, cytokines, and metalloproteases in chondrocytes as well as the wideness of cartilage in rats with OA. Our results demonstrate that the signaling through TLR-4 is a proinflammatory mechanism in osteoarthritis that drives the upregulation of MMP-3, IL-1β, and TNF-α gene expression, leading to cartilage degradation and inflammation. Vitamin D supplementation had a protective effect during the onset but not during the chronic stage of OA in the rat model.

PTH/PTHrP and vitamin D control antimicrobial peptide expression and susceptibility to bacterial skin infection

The production of antimicrobial peptides is essential for protection against a wide variety of microbial pathogens and plays an important role in the pathogenesis of several diseases. The mechanisms responsible for expression of antimicrobial peptides are incompletely understood, but a role for vitamin D as a transcriptional inducer of the antimicrobial peptide cathelicidin has been proposed. We show that 1,25-dihydroxyvitamin D(3) (1,25-D3) acts together with parathyroid hormone (PTH), or the shared amino-terminal domain of PTH-related peptide (PTHrP), to synergistically increase cathelicidin and immune defense. Administration of PTH to mouse skin decreased susceptibility to skin infection by group A Streptococcus. Mice on dietary vitamin D(3) restriction that responded with an elevation in PTH have an increased risk of infection if they lack 1,25-D3. These results identify PTH/PTHrP as a variable that serves to compensate for inadequate vitamin D during activation of antimicrobial peptide production.

Gut microbiota, immune development and function

The microbiota of Westerners is significantly reduced in comparison to rural individuals living a similar lifestyle to our Paleolithic forefathers but also to that of other free-living primates such as the chimpanzee. The great majority of ingredients in the industrially produced foods consumed in the West are absorbed in the upper part of small intestine and thus of limited benefit to the microbiota. Lack of proper nutrition for microbiota is a major factor under-pinning dysfunctional microbiota, dysbiosis, chronically elevated inflammation, and the production and leakage of endotoxins through the various tissue barriers. Furthermore, the over-comsumption of insulinogenic foods and proteotoxins, such as advanced glycation and lipoxidation molecules, gluten and zein, and a reduced intake of fruit and vegetables, are key factors behind the commonly observed elevated inflammation and the endemic of obesity and chronic diseases, factors which are also likely to be detrimental to microbiota. As a consequence of this lifestyle and the associated eating habits, most barriers, including the gut, the airways, the skin, the oral cavity, the vagina, the placenta, the blood-brain barrier, etc., are increasingly permeable. Attempts to recondition these barriers through the use of so called 'probiotics', normally applied to the gut, are rarely successful, and sometimes fail, as they are usually applied as adjunctive treatments, e.g. in parallel with heavy pharmaceutical treatment, not rarely consisting in antibiotics and chemotherapy. It is increasingly observed that the majority of pharmaceutical drugs, even those believed to have minimal adverse effects, such as proton pump inhibitors and anti-hypertensives, in fact adversely affect immune development and functions and are most likely also deleterious to microbiota. Equally, it appears that probiotic treatment is not compatible with pharmacological treatments. Eco-biological treatments, with plant-derived substances, or phytochemicals, e.g. curcumin and resveratrol, and pre-, pro- and syn-biotics offers similar effects as use of biologicals, although milder but also free from adverse effects. Such treatments should be tried as alternative therapies; mainly, to begin with, for disease prevention but also in early cases of chronic diseases. Pharmaceutical treatment has, thus far, failed to inhibit the tsunami of endemic diseases spreading around the world, and no new tools are in sight. Dramatic alterations, in direction of a paleolithic-like lifestyle and food habits, seem to be the only alternatives with the potential to control the present escalating crisis. The present review focuses on human studies, especially those of clinical relevance.

Axin1 prevents Salmonella invasiveness and inflammatory response in intestinal epithelial cells

Background

Axin1 and its homolog Axin2 are scaffold proteins essential for regulating Wnt signaling. Axin-dependent regulation of Wnt is important for various developmental processes and human diseases. However, the involvement of Axin1 and Axin2 in host defense and inflammation remains to be determined.

Methods/Principal Findings

Here, we report that Axin1, but not Axin2, plays an essential role in host-pathogen interaction mediated by the Wnt pathway. Pathogenic Salmonella colonization greatly reduces the level of Axin1 in intestinal epithelial cells. This reduction is regulated at the posttranslational level in early onset of the bacterial infection. Further analysis reveals that the DIX domain and Ser614 of Axin1 are necessary for the Salmonella-mediated modulation through ubiquitination and SUMOylation.

Conclusion/Significance

Axin1 apparently has a preventive effect on bacterial invasiveness and inflammatory response during the early stages of infection. The results suggest a distinct biological function of Axin1 and Axin2 in infectious disease and intestinal inflammation while they are functionally equivalent in developmental settings.

Wnt2 inhibits enteric bacterial-induced inflammation in intestinal epithelial cells

BACKGROUND

Wnt signaling plays an essential role in gastrointestinal epithelial proliferation. Most investigations have focused on developmental and immune responses. Bacterial infection can be chronic and increases the risk of inflammatory bowel disease and colitis-associated cancer. However, we lack studies on how bacteria regulate Wnt proteins and how Wnts modulate the host responses to enteric bacteria. This study investigated the effects of Salmonella and Escherichia coli on Wnt2, one of the Wnt family members, in intestinal epithelia cells.

METHODS

Using cultured epithelial cells, a Salmonella-colitis mouse model, and a gnotobiotic mouse model, we found that Wnt2 mRNA and protein expression levels were elevated after bacterial infection. Enteric bacteria regulate Wnt2 location in the intestine. Furthermore, we found that elevation of Wnt2 was a strategy for host defense by inhibiting cell apoptosis and inflammatory responses to infection.

RESULTS

Using Wnt2 siRNA analysis, we show enhanced inflammatory cytokine IL-8 in epithelial cells. Cells overexpressed Wnt2 had less bacterial-induced IL-8 secretion. AvrA is a bacterial protein that inhibits inflammation by stabilizing β-catenin, the downstream target of Wnt. We found that the stabilization of Wnt2 was regulated through ubiquitination. Moreover, the bacterial protein AvrA from Salmonella and E. coli stabilized Wnt2 protein expression in vivo. In an ex-germ-free system, E. coli F18 expressing AvrA increased Wnt2 expression and changed Wnt2 distribution in intestine.

CONCLUSIONS

Wnt2 contributes to host protection in response to enteric bacteria. Our findings thus reveal a previously undefined role of Wnt for host-pathogen interaction and inflammation.

The Vitamin D Receptor, Inflammatory Bowel Diseases, and Colon Cancer

The nuclear receptor is an emerging therapeutic target in various human diseases. Vitamin D receptor (VDR), a nuclear receptor, mediates the biological functions of vitamin D. Classically, vitamin D is recognized as an essential contributor to mineral and bone homeostasis. Increasing evidence demonstrates that vitamin D is involved in inflammatory responses. Persistent intestinal inflammation is associated with colon cancer. This review focuses on vitamin D and VDR in inflammatory bowel diseases and colon cancer. We place emphasis on the regulatory roles of vitamin D/VDR on in inflammation, enteric bacteria, and tumorigenesis. We summarize the signaling pathways regulated by VDR in intestinal homeostasis. Finally, we discuss the potential application of the insights gleaned from these findings to personalized therapies in chronic inflammation and colon cancer.

Wingless homolog Wnt11 suppresses bacterial invasion and inflammation in intestinal epithelial cells

Wnt11 plays an essential role in gastrointestinal epithelial proliferation, and previous investigations have focused on development and immune responses. However, the roles of how enteric bacteria regulate Wnt11 and how Wnt11 modulates the host response to pathogenic bacteria remain unexplored. This study investigated the effects of Salmonella infection on Wnt activation in intestinal epithelial cells. We found that Wnt11 mRNA and protein expression were elevated after Salmonella colonization. Wnt11 protein secretion in epithelial cells was also elevated after bacterial infection. Furthermore, we demonstrated that pathogenic Salmonella regulated Wnt11 expression and localization in vivo. We found a decrease in Salmonella invasion in cells with Wnt11 overexpression compared with cells with normal Wnt11 level. IL-8 mRNA in Wnt11-transfected cells was low; however, it was enhanced in cells with a low level of Wnt11 expression. Functionally, Wnt11 overexpression inhibited Salmonella-induced apoptosis. AvrA is a known bacterial effector protein that stabilizes β-catenin, the downstream regulator of Wnt signaling, and inhibits bacterially induced intestinal inflammation. We observed that Wnt11 expression, secretion, and transcriptional activity were regulated by Salmonella AvrA. Overall, Wnt11 is involved in the protection of the host intestinal cells by blocking the invasion of pathogenic bacteria, suppressing inflammation, and inhibiting apoptosis. Wnt11 is a novel and important contributor to intestinal homeostasis and host defense.

Seasonal variation of serum 25-hydroxyvitamin D levels in adult patients with inflammatory bowel disease

Patients with inflammatory bowel disease (IBD) are at risk of osteoporosis. Vitamin D (vitD) deficiency is known as a risk factor of osteoporosis. We observed low vitD blood levels in adult IBD patients both at the end of summer and winter. Furthermore, effects of oral vitD supplementation in (generally low) daily dosages were poor.

INTRODUCTION

Patients with IBD are at risk of osteoporosis. This study evaluates seasonal vitD status, determinants of vitD deficiency and effects of vitD supplementation in adult IBD patients.

METHODS

Patients were screened for vitD deficiency at the end of summer and winter using serum 25OHD(3) (cut-off point, <50 nmol/L) combined with routine laboratory tests. A standardized questionnaire was used for demographic/lifestyle data i.e. IBD activity, health behaviour and vitD intake through diet and ultraviolet light.

RESULTS

Late-summer, 39% of the included 316 patients were vitD deficient. Late-winter, 57% of the follow-up patients (n=281) were deficient. Independent protective determinants of vitD deficiency were oral vitD supplementation (summer/winter: odds ratio [OR], 0.52 [95% confidence interval [CI], 0.29-0.94]/OR, 0.44 [95% CI, 0.26-0.75]), recent sun holiday (summer: OR, 0.42 [95% CI, 0.24-0.74]) and regular solarium visits (summer/winter: OR, 0.28 [95% CI, 0.13-0.63]/OR, 0.17 [0.06-0.50]). IBD activity (p=0.031), red blood cell distribution width (RDW; p=0.04) and erythrocyte sedimentation rate (p=0.03) were associated with low vitD levels using univariate analyses of the extreme 25OHD quartiles. In a subgroup with vitD supplementation, still 30% (late-summer) and 44% (late-winter) were vitD deficient.

CONCLUSION

VitD deficiency is common in IBD patients, but prevalence might be comparable with the general population. Ultraviolet light is essential for adequate vitD levels. Effects of oral vitD supplementation in (generally low) daily dosages are poor. Determinants for low vitD levels were IBD activity and elevated inflammatory markers, suggesting that increased risk of osteoporosis in IBD might be more related to the inflammation than to vitD deficiency.

Antimicrobial implications of vitamin D

Evidence exists that vitamin D has a potential antimicrobial activity and its deficiency has deleterious effects on general well-being and longevity. Vitamin D may reduce the risk of infection through multiple mechanisms. Vitamin D boosts innate immunity by modulating production of anti-microbial peptides (AMPs) and cytokine response. Vitamin D and its analogues via these mechanisms are playing an increasing role in the management of atopic dermatitis, psoriasis, vitiligo, acne and rosacea. Vitamin D may reduce susceptibility to infection in patients with atopic dermatitis and the ability to regulate local immune and inflammatory responses offers exciting potential for understanding and treating chronic inflammatory dermatitides. Moreover, B and T cell activation as well as boosting the activity of monocytes and macrophages also contribute to a potent systemic anti-microbial effect. The direct invasion by pathogenic organisms may be minimized at sites such as the respiratory tract by enhancing clearance of invading organisms. A vitamin D replete state appears to benefit most infections, with the possible noteworthy exception of Leishmaniasis. Antibiotics remain an expensive option and misuse of these agents results in significant antibiotic resistance and contributes to escalating health care costs. Vitamin D constitutes an inexpensive prophylactic option and possibly therapeutic product either by itself or as a synergistic agent to traditional antimicrobial agents. This review outlines the specific antimicrobial properties of vitamin D in combating a wide range of organisms. We discuss the possible mechanisms by which vitamin D may have a therapeutic role in managing a variety of infections.

Vitamin d and susceptibility of chronic lung diseases: role of epigenetics

Vitamin D deficiency is linked to accelerated decline in lung function, increased inflammation, and reduced immunity in chronic lung diseases. Epidemiological studies have suggested that vitamin D insufficiency is associated with low lung function in susceptible subjects who are exposed to higher levels of environmental agents (airborne particulates). Recent studies have highlighted the role of vitamin D and vitamin D receptor (VDR) in regulation of several genes that are involved in inflammation, immunity, cellular proliferation, differentiation, and apoptosis. Vitamin D has also been implicated in reversal of steroid resistance and airway remodeling, which are the hallmarks of chronic obstructive pulmonary disease (COPD) and severe asthma. VDR protein level is decreased in lungs of patients with COPD. VDR deficient mice develop an abnormal lung phenotype with characteristics of COPD, such as airspace enlargement and decline in lung function associated with increased lung inflammatory cellular influx, and immune-lymphoid aggregates formation. Dietary vitamin D may regulate epigenetic events, in particular on genes which are responsible for COPD susceptibility. Active metabolite of vitamin D, 1,25-dihydroxyvitamin D₃ plays an essential role in cellular metabolism and differentiation via its nuclear receptor (VDR) that cooperates with several other chromatin modification enzymes (histone acetyltransferases and histone deacetylases), thereby mediating complex epigenetic events in vitamin D signaling and metabolism. This review provides an update on the current knowledge and understanding on vitamin D, and susceptibility of chronic lung diseases in relation to the possible role of epigenetics in its molecular action. Understanding the molecular epigenetic mechanism of vitamin D/VDR would provide rationale for dietary vitamin D-mediated intervention in prevention and management of chronic lung diseases linked with vitamin D deficiency.

Probiotics, nuclear receptor signaling, and anti-inflammatory pathways

There is increased investigation of the human microbiome as it relates to health and disease. Dysbiosis is implicated in various clinical conditions including inflammatory bowel disease (IBD). Probiotics have been explored as a potential treatment for IBD and other diseases. The mechanism of action for probiotics has yet to be fully elucidated. This paper discusses novel mechanisms of action for probiotics involving anti-inflammatory signaling pathways. We highlight recent progress in probiotics and nuclear receptor signaling, such as peroxisome-proliferator-activated receptor gamma (PPARγ) and vitamin D receptor (VDR). We also discuss future areas of investigation.

Vitamin D, vitamin D receptor, and macroautophagy in inflammation and infection

Vitamin D is involved in mineral and bone homeostasis, immune responses, anti-inflammation, anti-infection, and cancer prevention. Vitamin D receptor (VDR) is a nuclear receptor that mediates most biological functions of 1,25(OH)(2)D(3) or vitamin D(3), the active form of vitamin D. Recently, vitamin D(3)-induced autophagy has been reported. Autophagy is a lysosome-mediated catabolic pathway classified into three different types: macroautophagy, microautophagy, and chaperone-mediated autophagy. Autophagy contributes to anti-aging, antimicrobial defense, and tumor suppression. The functions of autophagy overlap remarkably with those of vitamin D/VDR signaling. This review focuses on vitamin D(3), VDR, and macroautophagy in inflammation and infection. We place emphasis on the regulatory roles of vitamin D(3) on autophagy at different steps, including induction, nucleation, elongation to maturation, and degradation. We summarize the known molecular mechanisms of vitamin D/VDR signaling on autophagy homeostasis. The potential application of the insights gleaned from these research findings to anti-inflammation and anti-infection is also discussed.

Gut microbiota, probiotics, and vitamin D: interrelated exposures influencing allergy, asthma, and obesity?

Current evidence supports a role for gut colonization in promoting and maintaining a balanced immune response in early life. An altered or less diverse gut microbiota composition has been associated with atopic diseases, obesity, or both. Moreover, certain gut microbial strains have been shown to inhibit or attenuate immune responses associated with chronic inflammation in experimental models. However, there has been no fully adequate longitudinal study of the relation between the neonatal gut microbiota and the development of allergic diseases (eg, atopic asthma) and obesity. The emergence of promising experimental studies has led to several clinical trials of probiotics (live bacteria given orally that allow for intestinal colonization) in human subjects. Probiotic trials thus far have failed to show a consistent preventive or therapeutic effect on asthma or obesity. Previous trials of probiotics have been limited by small sample size, short duration of follow-up, or lack of state-of-the art analyses of the gut microbiota. Finally, there is emerging evidence that the vitamin D pathway might be important in gut homeostasis and in signaling between the microbiota and the host. Given the complexity of the gut micriobiota, additional research is needed before we can confidently establish whether its manipulation in early life can prevent or treat asthma, obesity, or both.

Deletion of vitamin D receptor leads to premature emphysema/COPD by increased matrix metalloproteinases and lymphoid aggregates formation

Deficiency of vitamin D is associated with accelerated decline in lung function. Vitamin D is a ligand for nuclear hormone vitamin D receptor (VDR), and upon binding it modulates various cellular functions. The level of VDR is reduced in lungs of patients with chronic obstructive pulmonary disease (COPD) which led us to hypothesize that deficiency of VDR leads to significant alterations in lung phenotype that are characteristics of COPD/emphysema associated with increased inflammatory response. We found that VDR knock-out (VDR(-/-)) mice had increased influx of inflammatory cells, phospho-acetylation of nuclear factor-kappaB (NF-κB) associated with increased proinflammatory mediators, and up-regulation of matrix metalloproteinases (MMPs) MMP-2, MMP-9, and MMP-12 in the lung. This was associated with emphysema and decline in lung function associated with lymphoid aggregates formation compared to WT mice. These findings suggest that deficiency of VDR in mouse lung can lead to an early onset of emphysema/COPD because of chronic inflammation, immune dysregulation, and lung destruction.

Prevalence of 25-hydroxyvitamin D deficiency in subgroups of elderly persons with anemia: association with anemia of inflammation

Anemia and vitamin D deficiency are conditions that both result in significant morbidity and increase with age. The potential relationship between them remains poorly understood, particularly in the elderly. We used the Third National Health and Nutrition Examination Survey to examine the association of vitamin D deficiency with anemia subtypes in persons aged ≥ 60 years. Vitamin D deficiency was defined as serum levels < 20 ng/mL, and anemia was defined according to World Health Organization criteria. Vitamin D deficiency was associated with anemia prevalence independent of age, sex, or race/ethnicity (odds ratio, 1.47; 95% confidence interval, 1.06-2.05; P = .02) and varied significantly by anemia subtype (P overall = .003). The prevalence of vitamin D deficiency was 33.3% in the nonanemic population, 56% in anemia of inflammation (AI; P = .008), and 33.0% in unexplained anemia (P = .55). Non-Hispanic blacks had a 7-fold increased risk of AI compared with whites, and this was partially attenuated after adjusting for vitamin D deficiency. These data show that vitamin D deficiency is associated with specific subtypes of anemia in the elderly, especially in those with AI. Vitamin D may suppress inflammatory pathways, and studies to determine whether vitamin D supplementation ameliorates AI are warranted.

Global analysis of the eukaryotic pathways and networks regulated by Salmonella typhimurium in mouse intestinal infection in vivo

BACKGROUND

Acute enteritis caused by Salmonella is a public health concern. Salmonella infection is also known to increase the risk of inflammatory bowel diseases and cancer. Therefore, it is important to understand how Salmonella works in targeting eukaryotic pathways in intestinal infection. However, the global physiological function of Salmonella typhimurium in intestinal mucosa in vivo is unclear. In this study, a whole genome approach combined with bioinformatics assays was used to investigate the in vivo genetic responses of the mouse colon to Salmonella. We focused on the intestinal responses in the early stage (8 hours) and late stage (4 days) after Salmonella infection.

RESULTS

Of the 28,000 genes represented on the array, our analysis of mRNA expression in mouse colon mucosa showed that a total of 856 genes were expressed differentially at 8 hours post-infection. At 4 days post-infection, a total of 7558 genes were expressed differentially. 23 differentially expressed genes from the microarray data was further examined by real-time PCR. Ingenuity Pathways Analysis identified that the most significant pathway associated with the differentially expressed genes in 8 hours post-infection is oxidative phosphorylation, which targets the mitochondria. At the late stage of infection, a series of pathways associated with immune and inflammatory response, proliferation, and apoptosis were identified, whereas the oxidative phosphorylation was shut off. Histology analysis confirmed the biological role of Salmonella, which induced a physiological state of inflammation and proliferation in the colon mucosa through the regulation of multiple signaling pathways. Most of the metabolism-related pathways were targeted by down-regulated genes, and a general repression process of metabolic pathways was observed. Network analysis supported IFN-γ and TNF-α function as mediators of the immune/inflammatory response for host defense against pathogen.

CONCLUSION

Our study provides novel genome-wide transcriptional profiling data on the mouse colon mucosa's response to the Salmonella typhimurium infection. Building the pathways and networks of interactions between these genes help us to understand the complex interplay in the mice colon during Salmonella infection, and further provide new insights into the molecular cascade, which is mobilized to combat Salmonella-associated colon infection in vivo.

Vitamin D and mucosal immune function

PURPOSE OF REVIEW

Significant advances have been made in the characterization of Vitamin D and the Vitamin D receptor (VDR) in immune function. The studies of signaling pathways involved in the response to infection and inflammation have led to a more detailed understanding of the cellular response to Vitamin D through VDR. This review summarizes recent progress in understanding how Vitamin D contributes to mucosal immune function, particularly in relation to the molecular mechanisms by which Vitamin D and VDR influence mucosal immunity, bacterial infection, and inflammation.

RECENT FINDINGS

Recently, it was shown that Vitamin D modulates the T cell antigen receptor, further demonstrating that Vitamin D has a nonclassical role in immunoregulation. The anti-inflammation and anti-infection functions for Vitamin D are newly identified and highly significant activities. Vitamin D/VDR have multiple critical functions in regulating the response to intestinal homeostasis, tight junctions, pathogen invasion, commensal bacterial colonization, antimicrobe peptide secretion, and mucosal defense. Interestingly, microorganisms modulate the VDR signaling pathway.

SUMMARY

Vitamin D is known as a key player in calcium homeostasis and electrolyte and blood pressure regulation. Recently, important progress has been made in understanding how the noncanonical activities of Vitamin D influence the pathogenesis and prevention of human disease. Vitamin D and VDR are directly involved in T cell antigen receptor signaling. The involvement of Vitamin D/VDR in anti-inflammation and anti-infection represents a newly identified and highly significant activity for VDR. Studies have indicated that the dysregulation of VDR may lead to exaggerated inflammatory responses, raising the possibility that defects in Vitamin D and VDR signaling transduction may be linked to bacterial infection and chronic inflammation. Further characterization of Vitamin D/VDR will help elucidate the pathogenesis of various human diseases and in the design of new approaches for prevention and treatment.