A vitamin D receptor agonist converts CD4+ T cells to Foxp3+ regulatory T cells in patients with ulcerative colitis

Vitamin D treatment distinctly modulates cytokine production by peripheral blood mononuclear cells among patients with chronic cardiac and indeterminate clinical forms of Chagas disease

INTRODUCTION

Chagas disease is caused by the protozoan Trypanosoma cruzi and is clinically divided into acute and chronic phases. Chronic Chagas cardiomyopathy is the most studied manifestation of the disease. Vitamin D deficiency has been suggested as a risk factor for cardiovascular disease. No studies demonstrate the action of this hormone in the cells of patients with chronic Chagas heart disease.

OBJECTIVE

To evaluate the in vitro immunomodulatory effect of vitamin D on peripheral blood mononuclear cells of patients with the different chronic clinical forms of Chagas disease. Evaluating vitamin D's in vitro effect on blood cells by producing cytokines.

METHODS

Thirteen patients of the undetermined form (IND), 13 of the mild cardiac form (CARD1) and 14 of the severe cardiac form (CARD2) of Chagas disease, and 12 with idiopathic heart disease (CARDid) were included. The cells obtained from peripheral blood were treated in vitro with vitamin D (1 × 10-7 M) for 24 h and cytokines were dosed in the culture supernatant.

RESULTS

Although it was not possible to demonstrate statistically significant differences between the groups studied, our data showed that the cells treated with vitamin D modify (p < .05) the production of interferon-γ (IFN-γ) (decrease in IND), tumor necrosis factor-α (TNF-α) (decreased in CARD1 and CARDid), interleukin (IL)-6 (increased in all groups), and IL-10 (decreased in CARD1, CARD2, and CARDid) when compared to untreated cells.

CONCLUSION

In vitro treatment with vitamin D distinctly modulated the production of cytokines by mononuclear cells of peripheral blood among patients with chronic and indeterminate cardiac clinical forms of Chagas disease.

Biomaterial-enhanced treg cell immunotherapy: A promising approach for transplant medicine and autoimmune disease treatment

Regulatory T cells (Tregs) are crucial for preserving tolerance in the body, rendering Treg immunotherapy a promising treatment option for both organ transplants and autoimmune diseases. Presently, organ transplant recipients must undergo lifelong immunosuppression to prevent allograft rejection, while autoimmune disorders lack definitive cures. In the last years, there has been notable advancement in comprehending the biology of both antigen-specific and polyclonal Tregs. Clinical trials involving Tregs have demonstrated their safety and effectiveness. To maximize the efficacy of Treg immunotherapy, it is essential for these cells to migrate to specific target tissues, maintain stability within local organs, bolster their suppressive capabilities, and ensure their intended function's longevity. In pursuit of these goals, the utilization of biomaterials emerges as an attractive supportive strategy for Treg immunotherapy in addressing these challenges. As a result, the prospect of employing biomaterial-enhanced Treg immunotherapy holds tremendous promise as a treatment option for organ transplant recipients and individuals grappling with autoimmune diseases in the near future. This paper introduces strategies based on biomaterial-assisted Treg immunotherapy to enhance transplant medicine and autoimmune treatments.

Immunology of bile acids regulated receptors

Bile acids are steroids formed at the interface of host metabolism and intestinal microbiota. While primary bile acids are generated in the liver from cholesterol metabolism, secondary bile acids represent the products of microbial enzymes. Close to 100 different enzymatic modifications of bile acids structures occur in the human intestine and clinically guided metagenomic and metabolomic analyses have led to the identification of an extraordinary number of novel metabolites. These chemical mediators make an essential contribution to the composition and function of the postbiota, participating to the bidirectional communications of the intestinal microbiota with the host and contributing to the architecture of intestinal-liver and -brain and -endocrine axes. Bile acids exert their function by binding to a group of cell membrane and nuclear receptors collectively known as bile acid-regulated receptors (BARRs), expressed in monocytes, tissue-resident macrophages, CD4+ T effector cells, including Th17, T regulatory cells, dendritic cells and type 3 of intestinal lymphoid cells and NKT cells, highlighting their role in immune regulation. In this review we report on how bile acids and their metabolitesmodulate the immune system in inflammations and cancers and could be exploiting for developing novel therapeutic approaches in these disorders.

Bile acid-activated receptors in innate and adaptive immunity: targeted drugs and biological agents

Bile acid-activated receptors (BARs) such as a G-protein bile acid receptor 1 and the farnesol X receptor are activated by bile acids (BAs) and have been implicated in the regulation of microbiota-host immunity in the intestine. The mechanistic roles of these receptors in immune signaling suggest that they may also influence the development of metabolic disorders. In this perspective, we provide a summary of recent literature describing the main regulatory pathways and mechanisms of BARs and how they affect both innate and adaptive immune system, cell proliferation, and signaling in the context of inflammatory diseases. We also discuss new approaches for therapy and summarize clinical projects on BAs for the treatment of diseases. In parallel, some drugs that are classically used for other therapeutic purposes and BAR activity have recently been proposed as regulators of immune cells phenotype. Another strategy consists of using specific strains of gut bacteria to regulate BA production in the intestine.

Group A Streptococcus induces CD1a-autoreactive T cells and promotes psoriatic inflammation

Group A Streptococcus (GAS) infection is associated with multiple clinical sequelae, including different subtypes of psoriasis. Such post-streptococcal disorders have been long known but are largely unexplained. CD1a is expressed at constitutively high levels by Langerhans cells and presents lipid antigens to T cells, but the potential relevance to GAS infection has not been studied. Here, we investigated whether GAS-responsive CD1a-restricted T cells contribute to the pathogenesis of psoriasis. Healthy individuals had high frequencies of circulating and cutaneous GAS-responsive CD4+ and CD8+ T cells with rapid effector functions, including the production of interleukin-22 (IL-22). Human skin and blood single-cell CITE-seq analyses of IL-22-producing T cells showed a type 17 signature with proliferative potential, whereas IFN-γ-producing T cells displayed cytotoxic T lymphocyte characteristics. Furthermore, individuals with psoriasis had significantly higher frequencies of circulating GAS-reactive T cells, enriched for markers of activation, cytolytic potential, and tissue association. In addition to responding to GAS, subsets of expanded GAS-reactive T cell clones/lines were found to be autoreactive, which included the recognition of the self-lipid antigen lysophosphatidylcholine. CD8+ T cell clones/lines produced cytolytic mediators and lysed infected CD1a-expressing cells. Furthermore, we established cutaneous models of GAS infection in a humanized CD1a transgenic mouse model and identified enhanced and prolonged local and systemic inflammation, with resolution through a psoriasis-like phenotype. Together, these findings link GAS infection to the CD1a pathway and show that GAS infection promotes the proliferation and activation of CD1a-autoreactive T cells, with relevance to post-streptococcal disease, including the pathogenesis and treatment of psoriasis.

Tissue Nutrient Environments and Their Effect on Regulatory T Cell Biology

Regulatory T cells (Tregs) are essential for mitigating inflammation. Tregs are found in nearly every tissue and play either beneficial or harmful roles in the host. The availability of various nutrients can either enhance or impair Treg function. Mitochondrial oxidative metabolism plays a major role in supporting Treg differentiation and fitness. While Tregs rely heavily on oxidation of fatty acids to support mitochondrial activity, they have found ways to adapt to different tissue types, such as tumors, to survive in competitive environments. In addition, metabolic by-products from commensal organisms in the gut also have a profound impact on Treg differentiation. In this review, we will focus on the core metabolic pathways engaged in Tregs, especially in the context of tissue nutrient environments, and how they can affect Treg function, stability and differentiation.

Knockdown of NCOA2 Inhibits the Growth and Progression of Gastric Cancer by Affecting the Wnt Signaling Pathway-Related Protein Expression

Objective:

The aim of the study is to determine the role of nuclear receptor coactivator 2 in cell proliferation and invasion ability of gastric cancer cells and to explore its possible mechanisms.

Methods:

Immunohistochemical staining was used to determine NCOA2 gene expression in gastric cancer. Western blotting was used to detect Wnt signal pathways–related protein expression. Colony formation assays, Cell Counting Kit-8 assays, and transwell assays were used to determine cell proliferation, metastasis, and invasion ability of gastric cancer cells. A flow cytometric apoptosis tests determine gastric cancer cell apoptosis ability after inhibition of the expression of nuclear receptor coactivator 2. Subcutaneous mouse models were used to determine the gastric cancer growth and peritoneal metastasis differences after inhibition the expression of nuclear receptor coactivator 2.

Results:

The expression of nuclear receptor coactivator 2 in gastric cancer cells is high (P < .01), including lymph node metastasis, TNM staging, and gender differences in nuclear receptor coactivator 2 expression were statistically significant (P < .01). Short interfering nuclear receptor coactivator 2 could inhibit the proliferation and invasion ability of gastric cancer cells. Short interfering nuclear receptor coactivator 2 promotes the apoptosis of gastric cancer cells. Animal experiments showed that short interfering nuclear receptor coactivator 2 could inhibit the growth and invasion of gastric cancer-transplantable tumors. Knockdown of the expression of nuclear receptor coactivator 2 inhibited the Wnt/β-catenin signaling pathway in the gastric cancer cells.

Conclusions:

Knockdown of the expression of nuclear receptor coactivator 2 can inhibit the proliferation and invasion of human gastric cancer in vitro and in vivo. The underlying mechanism of NOCA2 affects the Wnt signaling pathway.

Vitamin D and Immune Regulation: Antibacterial, Antiviral, Anti-Inflammatory

Regulation of immune function continues to be one of the most well-recognized extraskeletal actions of vitamin D. This stemmed initially from the discovery that antigen presenting cells such as macrophages could actively metabolize precursor 25-hydroxyvitamin D (25D) to active 1,25-dihydroxyvitamin D (1,25D). Parallel observation that activated cells from the immune system expressed the intracellular vitamin D receptor (VDR) for 1,25D suggested a potential role for vitamin D as a localized endogenous modulator of immune function. Subsequent studies have expanded our understanding of how vitamin D exerts effects on both the innate and adaptive arms of the immune system. At an innate level, intracrine synthesis of 1,25D by macrophages and dendritic cells stimulates expression of antimicrobial proteins such as cathelicidin, as well as lowering intracellular iron concentrations via suppression of hepcidin. By potently enhancing autophagy, 1,25D may also play an important role in combatting intracellular pathogens such as M. tuberculosis and viral infections. Local synthesis of 1,25D by macrophages and dendritic cells also appears to play a pivotal role in mediating T-cell responses to vitamin D, leading to suppression of inflammatory T helper (Th)1 and Th17 cells, and concomitant induction of immunotolerogenic T-regulatory responses. The aim of this review is to provide an update on our current understanding of these prominent immune actions of vitamin D, as well as highlighting new, less well-recognized immune effects of vitamin D. The review also aims to place this mechanistic basis for the link between vitamin D and immunity with studies in vivo that have explored a role for vitamin D supplementation as a strategy for improved immune health. This has gained prominence in recent months with the global coronavirus disease 2019 health crisis and highlights important new objectives for future studies of vitamin D and immune function. © 2020 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Metabolic Optimisation of Regulatory T Cells in Transplantation

Regulatory T (Treg) cells expressing the FOXP3 transcription factor are presently under investigation by many teams globally as a cellular therapy to induce tolerance in transplantation. This is primarily due to their immunosuppressive and homeostatic functions. Depending on the type of allograft, Treg cells will need to infiltrate and function in metabolically diverse microenvironments. This means that any resident and circulating Treg cells need to differentially adapt to counter acute or chronic allograft rejection. However, the links between Treg cell metabolism and function are still not entirely delineated. Current data suggest that Treg cells and their effector counterparts have different metabolite dependencies and metabolic programs. These properties could be exploited to optimize intragraft Treg cell function. In this review, we discuss the current paradigms regarding Treg cell metabolism and outline critical intracellular axes that link metabolism and function. Finally, we discuss how this knowledge could be clinically translated for the benefit of transplant patients.

Medical Treatment Can Unintentionally Alter the Regulatory T-Cell Compartment in Patients with Widespread Pathophysiologic Conditions

Regulatory T cells (Tregs) are non-redundant mediators of immune tolerance that are critical to prevent autoimmune disease and promote an anti-inflammatory tissue environment. Many individuals experience chronic diseases and physiologic changes associated with aging requiring long-term medication. Unfortunately, adverse effects accompany every pharmacologic intervention and may affect overall outcomes. We focus on medications typically prescribed during the treatment of prevalent chronic diseases and disorders, including cardiovascular disease, autoimmune disease, and menopausal symptoms, that affect >200 million individuals in the United States. Increasing studies continue to report that treatment of patients with estrogen, metformin, statins, vitamin D, and tumor necrosis factor blockers are unintentionally modulating the Treg compartment. Effects of these medications likely comprise direct and/or indirect interaction with Tregs via other immune and parenchymal populations. Differing and sometimes opposing effects on the Treg compartment have been observed using the same medication. The length of treatment, dosing regimen and stage of disease, patient age, ethnicity, and sex may account for such findings and determine the specific signaling pathways affected by the medication. Enhancing the Treg compartment can skew the patient's immune system toward an anti-inflammatory phenotype and therefore could provide unanticipated benefit. Currently, multiple medicines prescribed to large numbers of patients influence the Treg compartment; however, how such effects affect their disease outcome and long-term health remains unclear.

Immunohistochemical expression of vitamin D receptor and forkhead box P3 in classic Hodgkin lymphoma: correlation with clinical and pathologic findings

Background

Expression of forkhead box P3 (FOXP3), a key regulator of T-cell function, in the tumor immune microenvironment is related to survival in classic Hodgkin lymphoma (CHL). Vitamin D receptor (VDR), a transcription factor agonists have been shown to induce FOXP3 expression in T-cells and enhance recruitment of these cells to the inflammatory sites. VDR expression is CHL has been described. However, there is no data on expression of VDR in context of quantity of FOXP3 positive cells in CHL.

Methods

We examined and correlated immunohistochemical expression of VDR and FOXP3 along with clinical and pathology findings in 29 cases of CHL.

Results

VDR was expressed in Hodgkin Reed-Sternberg (HRS) cells and background lymphocytes and FOXP3 was expressed in background lymphocytes. 82% of CHL cases, regardless of the subtype, expressed VDR and in majority of the cases, VDR expression was directly proportional to the quantity of FOXP3 expressing lymphocytes in the tumor microenvironment. In cases with higher clinical stage (III/IV), only 28.5% of cases diffusely expressed VDR and FOXP3 compared to 71.4% showing focal positivity. Whereas in cases with lower clinical stages (I/II), the expression pattern of VDR and FOXP3 was almost similar (41.6% diffuse versus 33.3% focal). Interestingly, focal VDR and FOXP3 expression pattern was significantly higher among males. Mixed cellularity cases showed predilection for focal VDR and FOXP3 expression (80% cases); whereas nodular sclerosis subtype had focal and diffuse VDR and FOXP3 expression patterns in similar proportion. Cases with diffuse VDR and FOXP3 expression were less likely to have bone marrow involvement. Epstein Barr virus- encoded small RNA (EBER) positive cases were predominantly focally positive (80%) for VDR and FOXP3.

Conclusions

In summary, quantity of FOXP3 positive T-cells in CHL microenvironment seems to correlate with VDR expression. Clinical stage show a trend of inverse correlation with expression of VDR and quantity of FOXP3 positive T-cells. These findings suggest that VDR could be a possible prognostic and therapeutic target in CHL.

Vitamin D and intestinal homeostasis: Barrier, microbiota, and immune modulation

Vitamin D plays a pivotal role in intestinal homeostasis. Vitamin D can impact the function of virtually every cell in the gut by binding to its intracellular receptor (VDR) and subsequently transcribing relevant genes. In the lumen, the mucus layer and the underlying epithelium serve to keep resident microbiota at bay. Vitamin D ensures an appropriate level of antimicrobial peptides in the mucus and maintains epithelial integrity by reinforcing intercellular junctions. Should bacteria penetrate the epithelial layer and enter the interstitium, immune sentinel cells (e.g. macrophages, dendritic cells, and innate lymphoid cells) elicit inflammation and trigger the adaptive immune response by activating Th1/Th17 cells. Vitamin D/VDR signaling in these cells ensures clearance of the bacteria. Subsequently, vitamin D also quiets the adaptive immune system by suppressing the Th1/Th17 cells and favoring Treg cells. The importance of vitamin D/VDR signaling in intestinal homeostasis is evidenced by the development of a chronic inflammatory state (e.g. IBD) when this signaling system is disrupted.

Expansion of the CD4+ effector T-cell repertoire characterizes peanut-allergic patients with heightened clinical sensitivity

BACKGROUND

Individuals with peanut allergy range in clinical sensitivity: some can consume grams of peanut before experiencing any symptoms, whereas others suffer systemic reactions to 10 mg or less. Current diagnostic testing only partially predicts this clinical heterogeneity.

OBJECTIVE

We sought to identify characteristics of the peanut-specific CD4+ T-cell response in peanut-allergic patients that correlate with high clinical sensitivity.

METHODS

We studied the T-cell receptor β-chain (TCRβ) usage and phenotypes of peanut-activated, CD154+ CD4+ memory T cells using fluorescence-activated cell sorting, TCRβ sequencing, and RNA-Seq, in reactive and hyporeactive patients who were stratified by clinical sensitivity.

RESULTS

TCRβ analysis of the CD154+ and CD154- fractions revealed more than 6000 complementarity determining region 3 sequences and motifs that were significantly enriched in the activated cells and 17% of the sequences were shared between peanut-allergic individuals, suggesting strong convergent selection of peanut-specific clones. These clones were more numerous among the reactive patients, and this expansion was identified within effector, but not regulatory T-cell populations. The transcriptional profile of CD154+ T cells in the reactive group skewed toward a polarized TH2 effector phenotype, and expression of TH2 cytokines strongly correlated with peanut-specific IgE levels. There were, however, also non-TH2-related differences in phenotype. Furthermore, the ratio of peanut-specific clones in the effector versus regulatory T-cell compartment, which distinguished the clinical groups, was independent of specific IgE concentration.

CONCLUSIONS

Expansion of the peanut-specific effector T-cell repertoire is correlated with clinical sensitivity, and this observation may be useful to inform our assessment of disease phenotype and to monitor disease longitudinally.

Systematic review with meta-analysis: association of vitamin D status with clinical outcomes in adult patients with inflammatory bowel disease

BACKGROUND

Vitamin D deficiency is highly prevalent among patients with IBD, however, data on its association with clinical outcomes are conflicting.

AIM

To perform a systematic review and meta-analysis to explore the association of low vitamin D status with clinical outcomes in patients with IBD.

METHODS

We searched PubMed, Embase, Scopus and Web of Science from inception to February 2018 for observational studies evaluating the association of low 25(OH)D status on IBD disease activity, mucosal inflammation, clinical relapse and quality of life. Odds ratios (ORs) were pooled and analysed using a random effects model.

RESULTS

Twenty-seven studies were eligible for inclusion comprising 8316 IBD patients (3115 ulcerative colitis, 5201 Crohn's disease). Among IBD patients, low 25(OH)D status was associated with increased odds of disease activity (OR 1.53, 95% CI 1.32-1.77, I²  = 0%), mucosal inflammation (OR 1.25, 95% CI 1.06-1.47, I²  = 0%), low quality of life (QOL) scores (OR 1.30, 95% CI 1.06-1.60, I²  = 0%) and future clinical relapse (OR 1.23, 95% CI 1.03-1.47, I²  = 0%). In subgroup analysis, low vitamin D status was associated with Crohn's disease activity (OR 1.66, 95% CI 1.36-2.03, I²  = 0%), mucosal inflammation (OR 1.39, 95% CI 1.03-1.85, I²  = 0%), clinical relapse (OR 1.35, 95% CI 1.14-1.59, I²  = 0%), and low QOL scores (OR 1.25, 95% CI 1.04-1.50, I²  = 0%) and ulcerative colitis disease activity (OR 1.47, 95% CI 1.03-2.09, I²  = 0%) and clinical relapse (OR 1.20, 95% 1.01-1.43, I²  = 0%).

CONCLUSIONS

Low 25(OH)D status is a biomarker for disease activity and predictor of poor clinical outcomes in IBD patients.

Survivin Impairs the Apoptotic Machinery in CD4+ T Cells of Patients with Ulcerative Colitis

BACKGROUND

The increase in CD4+ T cell infiltration and overproduction of CD4+ T cell-associated cytokines have been observed in the inflamed colon mucosa of patients with ulcerative colitis (UC); the underlying mechanisms are not fully understood. Survivin plays a critical role in the interference with apoptotic machinery. This study aims to elucidate the role of survivin in the interference with the apoptotic machinery in CD4+ T cells of UC patients.

METHODS

Peripheral blood samples were collected from UC patients (UC group) and healthy subjects (healthy group). The apoptotic status in CD4+ T cells was analyzed by flow cytometry.

RESULTS

We observed that the expression of survivin was significantly higher in CD4+ T cells of UC patients than in healthy subjects. UC CD4+ T cells were resistant to apoptosis induction. A complex of survivin and c-Myc, the transcription factor of FasL, was detected in CD4+ T cells in UC patients, which prevented the binding of c-Myc to the FasL promoter and interfered with the expression of FasL. Increased expression of survivin prevented the activation-induced CD4+ T cells from apoptosis.

CONCLUSIONS

The data indicate that UC CD4+ T cells express high levels of survivin, which impairs the apoptotic machinery in CD4+ T cells and prevents the activation-induced CD4+ T cell apoptosis. Therefore, target therapy against survivin has translational potential in the treatment of UC patients.

The role of vitamin D testing and replacement in fibromyalgia: a systematic literature review

BACKGROUND

Fibromyalgia is a debilitating condition, characterized by extensive muscular pain and fatigue. Vitamin D is essential for overall health, with ubiquitous involvement in various inflammatory and pain pathways. Little is known about its role in fibromyalgia. We performed a systematic literature review to determine if vitamin D contributes to the pathology and disability of patients with fibromyalgia, and to assess the role of vitamin D supplementation in disease management.

METHODS

We searched Medline, EMBASE and the Cochrane Library for clinical studies and randomized controlled trials published in English during January 2000 to June 2017, using the terms vitamin D or hypovitaminosis D combined with fibromyalgia or FMS. References were reviewed manually and articles were only included if they were specific in their diagnosis of fibromyalgia and used appropriate control groups.

RESULTS

Four hundred and sixty-six studies were retrieved, of which fourteen fulfilled the inclusion criteria. Six studies, of which two had the best quality evidence, found that patients with fibromyalgia have low levels of vitamin D compared to healthy controls. Conflicting results were obtained on the effect of vitamin D on pain or symptom control, with no clear consensus as to the role of supplementation in the management of fibromyalgia.

CONCLUSIONS

Our results highlight an association between vitamin D deficiency and fibromyalgia. However, its role in the pathophysiology of fibromyalgia and the clinical relevance of identifying and treating this requires further elucidation with appropriately controlled studies.

Regulation of Microbiota by Vitamin D Receptor: A Nuclear Weapon in Metabolic Diseases

Metabolic syndrome is a multi-faceted disease. The microbiota, as a newly discovered organ, contributes to the pathogenesis and progression of metabolic syndrome. Recent studies have demonstrated that nuclear receptors play critical roles in metabolic diseases. In the current review, we discuss the general role of the microbiome in health and metabolic syndrome. We summarize the functions of the nuclear receptor vitamin D receptor (VDR) in metabolism. The focus of this review is the novel roles of vitamin D/VDR signaling in regulating inflammation and the microbiome, especially in obesity. Furthermore, we extend our discussion of potential gut-liver axis mediated by VDR signaling and microbiota in obesity. Finally, we discuss the potential clinical application of probiotics and fecal microbiota transplantation in prevention and treatment of metabolic syndrome. Insights into nuclear receptors in metabolism and metabolic diseases will allow us to develop new strategies for fighting metabolic diseases.

Emerging role of lncRNAs in the normal and diseased intestinal barrier

OBJECTIVE

A significant effort has been made to understand the intestinal barrier, but the effective means to prevent, reduce, and restore intestinal mucosal damage remains unclear. Recently, a few of studies have explained the mechanism of the intestinal barrier in long noncoding RNAs (lncRNAs). This review aims to summarize recent views on the function of lncRNAs in the intestinal barrier and discuss the emerging role of lncRNAs in intestinal barrier diseases caused by inflammatory diseases.

METHODS

Observations led us to believe that lncRNAs participate in inflammatory responses, cell proliferation, and control microbial susceptibility. In view of these, lncRNAs have been proved to involve in the intestinal barrier.

RESULTS

lncRNAs directly or indirectly affect TJ mRNA translation and intestinal epithelial cells (IECs) paracellular permeability, as well as IECs proliferation and susceptibility to apoptosis, to modulate the function of the intestinal barrier. miRNAs play a pivotal role in this process.

CONCLUSIONS

lncRNAs have been shown to be fundamentally involved in intestinal mucosal regeneration, protection, and epithelial barrier function. It may emerge as new and potential factors to be evaluated in the intestinal barrier diseases caused by acute pancreatitis, inflammatory bowel diseases, and imbalance of intestinal flora.

Vitamin D in inflammatory bowel disease: more than just a supplement

PURPOSE OF REVIEW

The aim of this review is to explore the protective role of vitamin D on the gastrointestinal tract, summarize the epidemiology of vitamin D deficiency in inflammatory bowel disease (IBD), and highlight recent studies examining the impact of low vitamin D and vitamin D supplementation on IBD clinical outcomes.

RECENT FINDINGS

Vitamin D protects the gut barrier by regulating tight junction proteins and inhibiting intestinal apoptosis. Vitamin D enhances innate immunity by inducing antimicrobial peptides and regulates adaptive immunity by promoting anti-inflammatory T cells and cytokines. Vitamin D may also alter the gut microbiota. The prevalence of vitamin D deficiency in IBD is 30-40%. Predictors of vitamin D deficiency in IBD include non-white ethnicity, IBD-related surgery, BMI more than 30, female sex, and pregnancy. Low vitamin D is associated with increased disease activity, inflammation, and clinical relapse. The effect of vitamin D supplementation on IBD clinical outcomes is inconclusive.

SUMMARY

Vitamin D plays a protective role on gut health. Vitamin D deficiency in IBD is prevalent and associated with poor outcomes. The benefits of vitamin D supplementation in IBD is unclear. Measuring novel vitamin D metabolites and vitamin D absorption in IBD patients may help guide future studies.

Emerging Functions of Regulatory T Cells in Tissue Homeostasis

CD4⁺Foxp3⁺ regulatory T-cells (Tregs) are a unique subset of helper T-cells, which regulate immune response and establish peripheral tolerance. Tregs not only maintain the tone and tenor of an immune response by dominant tolerance but, in recent years, have also been identified as key players in resolving tissue inflammation and as mediators of tissue healing. Apart from being diverse in their origin (thymic and peripheral) and location (lymphoid and tissue resident), Tregs are also phenotypically heterogeneous as per the orientation of ongoing immune response. In this review, we discuss the recent advances in the field of Treg biology in general, and non-lymphoid and tissue-resident Tregs in particular. We elaborate upon well-known visceral adipose tissue, colon, skin, and tumor-infiltrating Tregs and newly identified tissue Treg populations as in lungs, skeletal muscle, placenta, and other tissues. Our attempt is to differentiate Tregs based on distinctive properties of their location, origin, ligand specificity, chemotaxis, and specific suppressive mechanisms. Despite ever expanding roles in maintaining systemic homeostasis, Tregs are employed by large varieties of tumors to dampen antitumor immunity. Thus, a comprehensive understanding of Treg biology in the context of inflammation can be instrumental in effectively managing tissue transplantation, autoimmunity, and antitumor immune responses.