A Decade of Th9 Cells: Role of Th9 Cells in Inflammatory Bowel Disease

Inflammatory Bowel Disease: A Comprehensive Analysis of Molecular Bases, Predictive Biomarkers, Diagnostic Methods, and Therapeutic Options

In inflammatory bowel diseases (IBDs), such as Crohn's disease (CD) and ulcerative colitis (UC), the immune system relentlessly attacks intestinal cells, causing recurrent tissue damage over the lifetime of patients. The etiology of IBD is complex and multifactorial, involving environmental, microbiota, genetic, and immunological factors that alter the molecular basis of the organism. Among these, the microbiota and immune cells play pivotal roles; the microbiota generates antigens recognized by immune cells and antibodies, while autoantibodies target and attack the intestinal membrane, exacerbating inflammation and tissue damage. Given the altered molecular framework, the analysis of multiple molecular biomarkers in patients proves exceedingly valuable for diagnosing and prognosing IBD, including markers like C reactive protein and fecal calprotectin. Upon detection and classification of patients, specific treatments are administered, ranging from conventional drugs to new biological therapies, such as antibodies to neutralize inflammatory molecules like tumor necrosis factor (TNF) and integrin. This review delves into the molecular basis and targets, biomarkers, treatment options, monitoring techniques, and, ultimately, current challenges in IBD management.

The emerging role of T helper 9 (Th9) cells in immunopathophysiology: A comprehensive review of their effects and responsiveness in various disease states

Th9 cells, a subset of T-helper cells producing interleukin-9 (IL-9), play a vital role in the adaptive immune response and have diverse effects in different diseases. Regulated by transcription factors like PU.1 and IRF4, and cytokines such as IL-4 and TGF-β, Th9 cells drive tissue inflammation. This review focuses on their emerging role in immunopathophysiology. Th9 cells exhibit immune-mediated cancer cell destruction, showing promise in glioma and cervical cancer treatment. However, their role in breast and lung cancer is intricate, requiring a deeper understanding of pro- and anti-tumor aspects. Th9 cells, along with IL-9, foster T cell and immune cell proliferation, contributing to autoimmune disorders. They are implicated in psoriasis, atopic dermatitis, and infections. In allergic reactions and asthma, Th9 cells fuel pro-inflammatory responses. Targeting Foxo1 may regulate innate and adaptive immune responses, alleviating disease symptoms. This comprehensive review outlines Th9 cells' evolving immunopathophysiological role, emphasizing the necessity for further research to grasp their effects and potential therapeutic applications across diseases.

Cerebral malaria pathogenesis: Dissecting the role of CD4+ and CD8+ T-cells as major effectors in disease pathology

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum (P. falciparum) infection, with complex pathogenesis involving multiple factors, including the host's immunological response. T lymphocytes, specifically CD4+ T helper cells and CD8+ cytotoxic T cells, are crucial in controlling parasite growth and activating cells for parasite clearance via cytokine secretion. Contrary to this, reports also suggest the pathogenic nature of T lymphocytes as they are often involved in disease progression and severity. CD8+ cytotoxic T cells migrate to the host's brain vasculature, disrupting the blood-brain barrier and causing neurological manifestations. CD4+ T helper cells on the other hand play a variety of functions as they differentiate into different subtypes which may function as pro-inflammatory or anti-inflammatory. The excessive pro-inflammatory response in CM can lead to multi-organ failure, necessitating a check mechanism to maintain immune homeostasis. This is achieved by regulatory T cells and their characteristic cytokines, which counterbalance the pro-inflammatory immune response. Maintaining a critical balance between pro and anti-inflammatory responses is crucial for determining disease outcomes in CM. A slight change in this balance may contribute to a disease severity owing to an extreme inflammatory response or unrestricted parasite growth, a potential target for designing immunotherapeutic treatment approaches. The review briefly discusses the pathogenesis of CM and various mechanisms responsible for the disruption of the blood-brain barrier. It also highlights the role of different T cell subsets during infection and emphasizes the importance of balance between pro and anti-inflammatory T cells that ultimately decides the outcome of the disease.

Regulatory role of T helper 9/interleukin-9: Transplantation view

T helper 9 (Th9) cells, a subset of CD4+ T helper cells, have emerged as a valuable target for immune cell therapy due to their potential to induce immunomodulation and tolerance. The Th9 cells mainly produce interleukin (IL)-9 and are known for their defensive effects against helminth infections, allergic and autoimmune responses, and tumor suppression. This paper explores the mechanisms involved in the generation and differentiation of Th9 cells, including the cytokines responsible for their polarization and stabilization, the transcription factors necessary for their differentiation, as well as the role of Th9 cells in inflammatory and autoimmune diseases, allergic reactions, and cancer immunotherapies. Recent research has shown that the differentiation of Th9 cells is coregulated by the transcription factors transforming growth factor β (TGF-β), IL-4, and PU.1, which are also known to secrete IL-10 and IL-21. Multiple cell types, such as T and B cells, mast cells, and airway epithelial cells, are influenced by IL-9 due to its pleiotropic effects.

Sustained long-term disease correction in a murine model of MPSII following stem cell gene therapy

Mucopolysaccharidosis type II (MPSII) is a pediatric lysosomal storage disease caused by deficiencies in the IDS (iduronate-2-sulfatase) gene resulting in accumulation of glycosaminoglycans, multisystem disease, and profound neurodegeneration in severe forms. Although enzyme replacement therapy is available for somatic forms of disease, the inability of native IDS to pass the blood-brain barrier renders it ineffective for the brain. We previously demonstrated the short-term efficacy of a brain-targeted hematopoietic stem cell gene therapy approach to treat MPSII mice using lentiviral IDS fused to the blood-brain-barrier-crossing peptide ApoEII (IDS.ApoEII) in comparison with a lentivirus expressing native IDS and an unmanipulated bone marrow transplant. Here we evaluated the longevity of disease correction for 12-16 months following treatment. We observed sustained IDS enzyme activity in organs of long-term IDS.ApoEII-treated MPSII mice, similar to those analyzed 6 months post-treatment, with continued clearance of storage material in the brain and peripheral organs, maintained correction of astrogliosis, microgliosis, and correction of altered cytokines and chemokines. IDS.ApoEII also significantly reduced retinal atrophy, characteristic of MPSII. Overall, IDS.ApoEII resulted in systemic prevention of the MPSII phenotype, with no observed toxicity following treatment. This provides evidence of the sustained efficacy and safety of this treatment ahead of a recently opened clinical trial.

A Narrative Review of Cytokine Networks: Pathophysiological and Therapeutic Implications for Inflammatory Bowel Disease Pathogenesis

Inflammatory bowel disease (IBD) is a lifelong inflammatory immune mediated disorder, encompassing Crohn's disease (CD) and ulcerative colitis (UC); however, the cause and specific pathogenesis of IBD is yet incompletely understood. Multiple cytokines produced by different immune cell types results in complex functional networks that constitute a highly regulated messaging network of signaling pathways. Applying biological mechanisms underlying IBD at the single omic level, technologies and genetic engineering enable the quantification of the pattern of released cytokines and new insights into the cytokine landscape of IBD. We focus on the existing literature dealing with the biology of pro- or anti-inflammatory cytokines and interactions that facilitate cell-based modulation of the immune system for IBD inflammation. We summarize the main roles of substantial cytokines in IBD related to homeostatic tissue functions and the remodeling of cytokine networks in IBD, which may be specifically valuable for successful cytokine-targeted therapies via marketed products. Cytokines and their receptors are validated targets for multiple therapeutic areas, we review the current strategies for therapeutic intervention and developing cytokine-targeted therapies. New biologics have shown efficacy in the last few decades for the management of IBD; unfortunately, many patients are nonresponsive or develop therapy resistance over time, creating a need for novel therapeutics. Thus, the treatment options for IBD beyond the immune-modifying anti-TNF agents or combination therapies are expanding rapidly. Further studies are needed to fully understand the immune response, networks of cytokines, and the direct pathogenetic relevance regarding individually tailored, safe and efficient targeted-biotherapeutics.

Understanding the molecular mechanisms of anti-trafficking therapies and their clinical relevance in inflammatory bowel disease

In patients with inflammatory bowel disease (IBD), a combination of dysbiosis, increased intestinal permeability, and insufficient regulatory responses facilitate the development of chronic inflammation, which is driven by a complex interplay between the mucosal immune system and the environment and sustained by immune priming and ongoing cellular recruitment to the gut. The localization of immune cells is mediated by their expression of chemokine receptors and integrins, which bind to chemokines and adhesion molecules, respectively. In this article, we review the mechanisms of action of anti-trafficking therapies for IBD and consider clinical observations in the context of the different mechanisms of action. Furthermore, we discuss the evolution of molecular resistance to anti-cytokines, in which the composition of immune cells in the gut changes in response to treatment, and the potential implications of this for treatment sequencing. Lastly, we discuss the relevance of mechanism of action to combination therapy for IBD.

DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-mediated allergic inflammation by promoting nuclear export of Pur-α

Dual-specificity phosphatase 8 (DUSP8) is a MAPK phosphatase that dephosphorylates and inactivates the kinase JNK. DUSP8 is highly expressed in T cells; however, the in vivo role of DUSP8 in T cells remains unclear. Using T cell-specific Dusp8 conditional KO (T-Dusp8 cKO) mice, mass spectrometry analysis, ChIP-Seq, and immune analysis, we found that DUSP8 interacted with Pur-α, stimulated interleukin-9 (IL-9) gene expression, and promoted Th9 differentiation. Mechanistically, DUSP8 dephosphorylated the transcriptional repressor Pur-α upon TGF-β signaling, leading to the nuclear export of Pur-α and subsequent IL-9 transcriptional activation. Furthermore, Il-9 mRNA levels were induced in Pur-α-deficient T cells. In addition, T-Dusp8-cKO mice displayed reduction of IL-9 and Th9-mediated immune responses in the allergic asthma model. Reduction of Il-9 mRNA levels in T cells and allergic responses of T-Dusp8-cKO mice was reversed by Pur-α knockout. Remarkably, DUSP8 protein levels and the DUSP8-Pur-α interaction were indeed increased in the cytoplasm of T cells from people with asthma and patients with atopic dermatitis. Collectively, DUSP8 induces TGF-β-stimulated IL-9 transcription and Th9-induced allergic responses by inhibiting the nuclear translocation of the transcriptional repressor Pur-α. DUSP8 may be a T-cell biomarker and therapeutic target for asthma and atopic dermatitis.

Mechanism of Acupuncture and Moxibustion on Promoting Mucosal Healing in Ulcerative Colitis

The latest guideline about ulcerative colitis (UC) clinical practice stresses that mucosal healing, rather than anti-inflammation, is the main target in UC clinical management. Current mucosal dysfunction mainly closely relates to the endoscopic intestinal wall (mechanical barrier) injury with the imbalance between intestinal epithelial cells (IECs) regeneration and death, as well as tight junction (TJ) dysfunction. It is suggested that biological barrier (gut microbiota), chemical barrier (mucus protein layer, MUC) and immune barrier (immune cells) all take part in the imbalance, leading to mechanical barrier injury. Lots of experimental studies reported that acupuncture and moxibustion on UC recovery by adjusting the gut microbiota, MUC and immune cells on multiple targets and pathways, which contributes to the balance of IEC regeneration and death, as well as TJ structure recovery in animals. Moreover, the validity and superiority of acupuncture and moxibustion were also demonstrated in clinic. This study aims to review the achievements of acupuncture and moxibustion on mucosal healing and analyse the underlying mechanisms.

T cells in health and disease

T cells are crucial for immune functions to maintain health and prevent disease. T cell development occurs in a stepwise process in the thymus and mainly generates CD4⁺ and CD8⁺ T cell subsets. Upon antigen stimulation, naïve T cells differentiate into CD4⁺ helper and CD8⁺ cytotoxic effector and memory cells, mediating direct killing, diverse immune regulatory function, and long-term protection. In response to acute and chronic infections and tumors, T cells adopt distinct differentiation trajectories and develop into a range of heterogeneous populations with various phenotype, differentiation potential, and functionality under precise and elaborate regulations of transcriptional and epigenetic programs. Abnormal T-cell immunity can initiate and promote the pathogenesis of autoimmune diseases. In this review, we summarize the current understanding of T cell development, CD4⁺ and CD8⁺ T cell classification, and differentiation in physiological settings. We further elaborate the heterogeneity, differentiation, functionality, and regulation network of CD4⁺ and CD8⁺ T cells in infectious disease, chronic infection and tumor, and autoimmune disease, highlighting the exhausted CD8⁺ T cell differentiation trajectory, CD4⁺ T cell helper function, T cell contributions to immunotherapy and autoimmune pathogenesis. We also discuss the development and function of γδ T cells in tissue surveillance, infection, and tumor immunity. Finally, we summarized current T-cell-based immunotherapies in both cancer and autoimmune diseases, with an emphasis on their clinical applications. A better understanding of T cell immunity provides insight into developing novel prophylactic and therapeutic strategies in human diseases.

Molecular Markers of Blood Cell Populations Can Help Estimate Aging of the Immune System

Aging of the immune system involves functional changes in individual cell populations, in hematopoietic tissues and at the systemic level. They are mediated by factors produced by circulating cells, niche cells, and at the systemic level. Age-related alterations in the microenvironment of the bone marrow and thymus cause a decrease in the production of naive immune cells and functional immunodeficiencies. Another result of aging and reduced tissue immune surveillance is the accumulation of senescent cells. Some viral infections deplete adaptive immune cells, increasing the risk of autoimmune and immunodeficiency conditions, leading to a general degradation in the specificity and effectiveness of the immune system in old age. During the COVID-19 pandemic, the state-of-the-art application of mass spectrometry, multichannel flow cytometry, and single-cell genetic analysis have provided vast data on the mechanisms of aging of the immune system. These data require systematic analysis and functional verification. In addition, the prediction of age-related complications is a priority task of modern medicine in the context of the increase in the aged population and the risk of premature death during epidemics. In this review, based on the latest data, we discuss the mechanisms of immune aging and highlight some cellular markers as indicators of age-related immune disbalance that increase the risk of senile diseases and infectious complications.

The Differentially Expressed Genes Responsible for the Development of T Helper 9 Cells From T Helper 2 Cells in Various Disease States: Immuno-Interactomics Study

BACKGROUND

T helper (Th) 9 cells are a novel subset of Th cells that develop independently from Th2 cells and are characterized by the secretion of interleukin (IL)-9. Studies have suggested the involvement of Th9 cells in variable diseases such as allergic and pulmonary diseases (eg, asthma, chronic obstructive airway disease, chronic rhinosinusitis, nasal polyps, and pulmonary hypoplasia), metabolic diseases (eg, acute leukemia, myelocytic leukemia, breast cancer, lung cancer, melanoma, pancreatic cancer), neuropsychiatric disorders (eg, Alzheimer disease), autoimmune diseases (eg, Graves disease, Crohn disease, colitis, psoriasis, systemic lupus erythematosus, systemic scleroderma, rheumatoid arthritis, multiple sclerosis, inflammatory bowel disease, atopic dermatitis, eczema), and infectious diseases (eg, tuberculosis, hepatitis). However, there is a dearth of information on its involvement in other metabolic, neuropsychiatric, and infectious diseases.

OBJECTIVE

This study aims to identify significant differentially altered genes in the conversion of Th2 to Th9 cells, and their regulating microRNAs (miRs) from publicly available Gene Expression Omnibus data sets of the mouse model using in silico analysis to unravel various pathogenic pathways involved in disease processes.

METHODS

Using differentially expressed genes (DEGs) identified from 2 publicly available data sets (GSE99166 and GSE123501) we performed functional enrichment and network analyses to identify pathways, protein-protein interactions, miR-messenger RNA associations, and disease-gene associations related to significant differentially altered genes implicated in the conversion of Th2 to Th9 cells.

RESULTS

We extracted 260 common downregulated, 236 common upregulated, and 634 common DEGs from the expression profiles of data sets GSE99166 and GSE123501. Codifferentially expressed ILs, cytokines, receptors, and transcription factors (TFs) were enriched in 7 crucial Kyoto Encyclopedia of Genes and Genomes pathways and Gene Ontology. We constructed the protein-protein interaction network and predicted the top regulatory miRs involved in the Th2 to Th9 differentiation pathways. We also identified various metabolic, allergic and pulmonary, neuropsychiatric, autoimmune, and infectious diseases as well as carcinomas where the differentiation of Th2 to Th9 may play a crucial role.

CONCLUSIONS

This study identified hitherto unexplored possible associations between Th9 and disease states. Some important ILs, including CCL1 (chemokine [C-C motif] ligand 1), CCL20 (chemokine [C-C motif] ligand 20), IL-13, IL-4, IL-12A, and IL-9; receptors, including IL-12RB1, IL-4RA (interleukin 9 receptor alpha), CD53 (cluster of differentiation 53), CD6 (cluster of differentiation 6), CD5 (cluster of differentiation 5), CD83 (cluster of differentiation 83), CD197 (cluster of differentiation 197), IL-1RL1 (interleukin 1 receptor-like 1), CD101 (cluster of differentiation 101), CD96 (cluster of differentiation 96), CD72 (cluster of differentiation 72), CD7 (cluster of differentiation 7), CD152 (cytotoxic T lymphocyte-associated protein 4), CD38 (cluster of differentiation 38), CX3CR1 (chemokine [C-X3-C motif] receptor 1), CTLA2A (cytotoxic T lymphocyte-associated protein 2 alpha), CTLA28, and CD196 (cluster of differentiation 196); and TFs, including FOXP3 (forkhead box P3), IRF8 (interferon regulatory factor 8), FOXP2 (forkhead box P2), RORA (RAR-related orphan receptor alpha), AHR (aryl-hydrocarbon receptor), MAF (avian musculoaponeurotic fibrosarcoma oncogene homolog), SMAD6 (SMAD family member 6), JUN (Jun proto-oncogene), JAK2 (Janus kinase 2), EP300 (E1A binding protein p300), ATF6 (activating transcription factor 6), BTAF1 (B-TFIID TATA-box binding protein associated factor 1), BAFT (basic leucine zipper transcription factor), NOTCH1 (neurogenic locus notch homolog protein 1), GATA3 (GATA binding protein 3), SATB1 (special AT-rich sequence binding protein 1), BMP7 (bone morphogenetic protein 7), and PPARG (peroxisome proliferator-activated receptor gamma, were able to identify significant differentially altered genes in the conversion of Th2 to Th9 cells. We identified some common miRs that could target the DEGs. The scarcity of studies on the role of Th9 in metabolic diseases highlights the lacunae in this field. Our study provides the rationale for exploring the role of Th9 in various metabolic disorders such as diabetes mellitus, diabetic nephropathy, hypertensive disease, ischemic stroke, steatohepatitis, liver fibrosis, obesity, adenocarcinoma, glioblastoma and glioma, malignant neoplasm of stomach, melanoma, neuroblastoma, osteosarcoma, pancreatic carcinoma, prostate carcinoma, and stomach carcinoma.

The immune response as a therapeutic target in non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is a complex and heterogeneous disorder considered a liver-damaging manifestation of metabolic syndrome. Its prevalence has increased in the last decades due to modern-day lifestyle factors associated with overweight and obesity, making it a relevant public health problem worldwide. The clinical progression of NAFLD is associated with advanced forms of liver injury such as fibrosis, cirrhosis, and hepatocellular carcinoma (HCC). As such, diverse pharmacological strategies have been implemented over the last few years, principally focused on metabolic pathways involved in NAFLD progression. However, a variable response rate has been observed in NAFLD patients, which is explained by the interindividual heterogeneity of susceptibility to liver damage. In this scenario, it is necessary to search for different therapeutic approaches. It is worth noting that chronic low-grade inflammation constitutes a central mechanism in the pathogenesis and progression of NAFLD, associated with abnormal composition of the intestinal microbiota, increased lymphocyte activation in the intestine and immune effector mechanisms in liver. This review aims to discuss the current knowledge about the role of the immune response in NAFLD development. We have focused mainly on the impact of altered gut-liver-microbiota axis communication on immune cell activation in the intestinal mucosa and the role of subsequent lymphocyte homing to the liver in NAFLD development. We further discuss novel clinical trials that addressed the control of the liver and intestinal immune response to complement current NAFLD therapies.

The role of the adaptive immune system and T cell dysfunction in neurodegenerative diseases

The adaptive immune system and associated inflammation are vital in surveillance and host protection against internal and external threats, but can secondarily damage host tissues. The central nervous system is immune-privileged and largely protected from the circulating inflammatory pathways. However, T cell involvement and the disruption of the blood-brain barriers have been linked to several neurodegenerative diseases including Parkinson's disease, Alzheimer's disease, and multiple sclerosis. Under normal physiological conditions, regulatory T cells (Treg cells) dampen the inflammatory response of effector T cells. In the pathological states of many neurodegenerative disorders, the ability of Treg cells to mitigate inflammation is reduced, and a pro-inflammatory environment persists. This perspective review provides current knowledge on the roles of T cell subsets (e.g., effector T cells, Treg cells) in neurodegenerative and ocular diseases, including uveitis, diabetic retinopathy, age-related macular degeneration, and glaucoma. Many neurodegenerative and ocular diseases have been linked to immune dysregulation, but the cellular events and molecular mechanisms involved in such processes remain largely unknown. Moreover, the role of T cells in ocular pathologies remains poorly defined and limited literature is available in this area of research. Adoptive transfer of Treg cells appears to be a vital immunological approach to control ocular pathologies. Similarities in T cell dysfunction seen among non-ocular neurodegenerative diseases suggest that this area of research has a great potential to develop better therapeutic agents for ocular diseases and warrants further studies. Overall, this perspective review article provides significant information on the roles of T cells in numerous ocular and non-ocular neurodegenerative diseases.

Fingolimod ameliorates acetic acid-induced ulcerative colitis: An insight into its modulatory impact on pro/anti-inflammatory cytokines and AKT/mTOR signalling

BACKGROUND

Because of the approved immunomodulatory activities of fingolimod, the current study aimed at studying the curative potential of fingolimod against experimentally induced ulcerative colitis (UC) via modulating pro/anti-inflammatory cytokines release and AKT/mTOR signalling.

METHODS

UC was induced in rats by intracolonic instillation of acetic acid. Fingo (0.5 mg/kg/day, p.o.) was given for 8 consecutive days that started 48 h after UC induction.

RESULTS

Fingolimod increased body weight growth rate and colon body/weight and colon weight/length indices compared to the UC group. Fingolimod significantly decreased clinical evaluation score and macroscopic score compared to the UC group. The curative potential of fingolimod was further confirmed by histopathological examination revealing marked attenuation of mucosal injury and inflammatory cells infiltration. Fingolimod significantly decreased colon malondialdehyde content and increased colon glutathione contents compared to the UC group. Fingolimod also significantly decreased the expressions of pro-inflammatory cytokines interleukin-9 and T-helper 17 along with increasing the expression of anti-inflammatory interleukin-10 and transforming growth factor-β compared to the UC group. In addition, fingolimod decreased the expressions of AKT and mTOR compared to the UC group.

CONCLUSION

Fingolimod attenuated acetic acid-induced UC through its immunomodulatory effect by shifting the balance to favour anti-inflammatory cytokine production rather than pro-inflammatory cytokines and modulating the AKT/mTOR signalling.

Mesenchymal stromal cells-derived small extracellular vesicles modulate DC function to suppress Th2 responses via IL-10 in patients with allergic rhinitis

Mesenchymal stromal cells (MSCs) are well known for their immunoregulatory roles on allergic inflammation particularly by acting on T cells, B cells, and dendritic cells (DCs). MSC‐derived small extracellular vesicles (MSC‐sEV) are increasingly considered as one of the main factors for the effects of MSCs on immune responses. However, the effects of MSC‐sEV on DCs in allergic diseases remain unclear.

Interleukin-9 attenuates inflammatory response and hepatocyte apoptosis in alcoholic liver injury

Alcoholic liver injury is a liver cell dysfunction disease caused by long-term or excessive alcohol consumption. Inhibiting the production of inflammatory factors is an important way to alleviate liver injury. Interleukin-9 (IL-9) is one of the members of IL-2Rγc family. It has multiple biological functions. Previous studies have shown that IL-9 is a cytokine that is closely related to inflammatory disease, allergic diseases, autoimmune diseases, and parasitic infections. However, no systematic studies have been performed to address the role of IL-9 in ALI. This project aims to investigate the effects of IL-9 on macrophage-related inflammatory response and hepatocyte apoptosis in alcohol-induced liver injury by injecting adeno-associated virus (AAV9) into tail vein. In the ALI model group, western blot and ELISA assays demonstrated that the expression of IL-9 was reduced. Overexpression of IL-9 relieved the injury and reduced the serum levels of IL-6, TNF-α in EtOH-induced ALI mouse model. Moreover, by using western blot, it was indicated that IL-9 can inhibit the expression of pro-apoptotic protein, such as cleaved caspase 3 and Bax. In vitro, mouse recombinant protein IL-9 inhibited the expression of IL-6, TNF-α in EtOH-induced RAW264.7 cells. Moreover, flow cytometry and western blot results displayed that macrophage-derived IL-9 inhibited hepatocyte apoptosis. After silencing STAT3 in AML-12 cells, the anti-apoptotic effect of macrophage-derived IL-9 was further enhanced. These results indicate that IL-9 reduces the production of pro-inflammatory factors in ALI. Furthermore, macrophage-derived IL-9 can reduce hepatocyte apoptosis by inhibiting the activation of the STAT3 pathway.

Calcitriol and Retinoic acid antagonize each other to suppress the production of IL-9 by Th9 cells

Distinct T helper cells, including Th9 cells help maintain homeostasis in the immune system. Vitamins play pivotal role in the immune system through many mechanisms, including regulating the differentiation of T helper cells. Calcitriol (1,25-dihydroxyvitamin D3) and retinoic acid possess hormone-like properties and are the bioactive metabolites of vitamin D and A, respectively, that signal through heterodimers containing the common retinoid X receptor. In contrast to individual treatment with the vitamins that significantly attenuates IL-9 production from Th9 cells, Th9 cells treated with both vitamins demonstrated IL-9 production similar to untreated Th9 cells. This is associated with reciprocal expression of PU.1 and Foxp3. While the recruitment of PU.1 was significantly impaired to the Il9 gene in the presence of calcitriol or retinoic acid in Th9 cells, addition of both vitamins together increased the recruitment of PU.1 to the Il9 gene. Calcitriol and retinoic acid together impaired the recruitment of HDAC1 to the Il9 gene without impacting Gcn5 recruitment. Importantly, retinoic acid negated the effect of calcitriol and impaired the binding of VDR on the Il9 gene by dampened VDR-RXR formation. Collectively, our data show that calcitriol and retinoic acid antagonize each other to regulate the differentiation of Th9 cells.

Preclinical Development of FA5, a Novel AMP-Activated Protein Kinase (AMPK) Activator as an Innovative Drug for the Management of Bowel Inflammation

Acadesine (ACA), a pharmacological activator of AMP-activated protein kinase (AMPK), showed a promising beneficial effect in a mouse model of colitis, indicating this drug as an alternative tool to manage IBDs. However, ACA displays some pharmacodynamic limitations precluding its therapeutical applications. Our study was aimed at evaluating the in vitro and in vivo effects of FA-5 (a novel direct AMPK activator synthesized in our laboratories) in an experimental model of colitis in rats. A set of experiments evaluated the ability of FA5 to activate AMPK and to compare the efficacy of FA5 with ACA in an experimental model of colitis. The effects of FA-5, ACA, or dexamethasone were tested in rats with 2,4-dinitrobenzenesulfonic acid (DNBS)-induced colitis to assess systemic and tissue inflammatory parameters. In in vitro experiments, FA5 induced phosphorylation, and thus the activation, of AMPK, contextually to the activation of SIRT-1. In vivo, FA5 counteracted the increase in spleen weight, improved the colon length, ameliorated macroscopic damage score, and reduced TNF and MDA tissue levels in DNBS-treated rats. Of note, FA-5 displayed an increased anti-inflammatory efficacy as compared with ACA. The novel AMPK activator FA-5 displays an improved anti-inflammatory efficacy representing a promising pharmacological tool against bowel inflammation.

From inflammation to colitis-associated colorectal cancer in inflammatory bowel disease: Pathogenesis and impact of current therapies

The risk of colorectal cancer (CRC) is higher in patients with inflammatory bowel disease (IBD). Population-based data from patients with ulcerative colitis (UC) estimate that the risk of CRC is approximately 2- to 3-fold that of the general population; patients with Crohn's disease appear to have a similar increased risk. However, the true extent of colitis-associated cancer (CAC) in undertreated IBD is unclear. Data suggest that the size (i.e., severity and extent) and persistence of the inflammatory process is largely responsible for the development of CRC in IBD. As patients with IBD and CRC have a worse prognosis than those without a history of IBD, the impact of current therapies for IBD on CAC is of importance. Chronic inflammation of the gut has been shown to increase the risk of developing CAC in both UC and CD. Therefore, control of inflammation is pivotal to the prevention of CAC. This review presents an overview of the current knowledge of CAC in IBD patients, focusing on the role of inflammation in the pathogenesis of CAC and the potential for IBD drugs to interfere with the process of carcinogenesis by reducing the inflammatory process or by modulating pathways directly involved in carcinogenesis.

OX40L/OX40 Signal Promotes IL-9 Production by Mucosal MAIT Cells During Helicobacter pylori Infection

Mucosal associated invariant T (MAIT) cells play a critical role in Helicobacter pylori (H. pylori)-induced gastritis by promoting mucosal inflammation and aggravating mucosal injuries (1, 2). However, the underlying mechanism and key molecules involved are still uncertain. Here we identified OX40, a co-stimulatory molecule mainly expressed on T cells, as a critical regulator to promote proliferation and IL-9 production by MAIT cells and facilitate mucosal inflammation in H. pylori-positive gastritis patients. Serum examination revealed an increased level of IL-9 in gastritis patients. Meanwhile, OX40 expression was increased in mucosal MAIT cells, and its ligand OX40L was also up-regulated in mucosal dendritic cells (DCs) of gastritis patients, compared with healthy controls. Further results demonstrated that activation of the OX40/OX40L pathway promoted IL-9 production by MAIT cells, and MAIT cells displayed a highly-activated phenotype after the cross-linking of OX40 and OX40L. Moreover, the level of IL-9 produced by MAIT cells was positively correlated with inflammatory indexes in the gastric mucosa, suggesting the potential role of IL-9-producing MAIT cells in mucosal inflammation. Taken together, we elucidated that OX40/OX40L axis promoted mucosal MAIT cell proliferation and IL-9 production in H. pylori-induced gastritis, which may provide potential targeting strategies for gastritis treatment.

The Many Faces of CD4+ T Cells: Immunological and Structural Characteristics

As a major arm of the cellular immune response, CD4⁺ T cells are important in the control and clearance of infections. Primarily described as helpers, CD4⁺ T cells play an integral role in the development and activation of B cells and CD8⁺ T cells. CD4⁺ T cells are incredibly heterogeneous, and can be divided into six main lineages based on distinct profiles, namely T helper 1, 2, 17 and 22 (Th1, Th2, Th17, Th22), regulatory T cells (Treg) and T follicular helper cells (Tfh). Recent advances in structural biology have allowed for a detailed characterisation of the molecular mechanisms that drive CD4⁺ T cell recognition. In this review, we discuss the defining features of the main human CD4⁺ T cell lineages and their role in immunity, as well as their structural characteristics underlying their detection of pathogens.

Bach2 overexpression represses Th9 cell differentiation by suppressing IRF4 expression in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by abnormal activation of T cells and caused by an imbalance in the production and clearance of apoptotic cells. We previously showed that the transcription regulator Bach2 regulated abnormal B‐cell activation in SLE. Here, we investigated whether Bach2 was also involved in Th9 cell differentiation in SLE. We found that the proportion of Th9 cells was enhanced in the peripheral blood mononuclear cells (PBMC) of SLE patients. The PBMC and CD4⁺ T cells of SLE patients exhibited a decrease of Bach2 expression and an increase of IL‐9 expression. Furthermore, Bach2 overexpression significantly repressed the levels of PU.1, IRF4, IL‐9, and Th9 cells in the CD4⁺ T cells of SLE patients and healthy volunteers. In addition, Bach2 overexpression inhibited the levels of IL‐9 and Th9 cells, whereas IRF4 upregulation enhanced the levels of IRF4 and IL‐9 and Th9 cells in the CD4⁺ T cells of SLE patients and healthy volunteers. The effect of IRF4 up‐regulation was abolished by Bach2 overexpression. In summary, our work suggests that Bach2 overexpression represses Th9 cell differentiation by suppressing IRF4 expression in SLE, and thus, Bach2 may be a novel potential target for SLE treatment.

The Regulation of Intestinal Inflammation and Cancer Development by Type 2 Immune Responses

The gut is among the most complex organs of the human body. It has to exert several functions including food and water absorption while setting up an efficient barrier to the outside world. Dysfunction of the gut can be life-threatening. Diseases of the gastrointestinal tract such as inflammatory bowel disease, infections, or colorectal cancer, therefore, pose substantial challenges to clinical care. The intestinal epithelium plays an important role in intestinal disease development. It not only establishes an important barrier against the gut lumen but also constantly signals information about the gut lumen and its composition to immune cells in the bowel wall. Such signaling across the epithelial barrier also occurs in the other direction. Intestinal epithelial cells respond to cytokines and other mediators of immune cells in the lamina propria and shape the microbial community within the gut by producing various antimicrobial peptides. Thus, the epithelium can be considered as an interpreter between the microbiota and the mucosal immune system, safeguarding and moderating communication to the benefit of the host. Type 2 immune responses play important roles in immune-epithelial communication. They contribute to gut tissue homeostasis and protect the host against infections with helminths. However, they are also involved in pathogenic pathways in inflammatory bowel disease and colorectal cancer. The current review provides an overview of current concepts regarding type 2 immune responses in intestinal physiology and pathophysiology.

IL-33/ST2/IL-9/IL-9R signaling disrupts ocular surface barrier in allergic inflammation

This study was to explore a novel IL-33/ST2/IL-9/IL-9R signaling pathway that disrupts ocular surface barrier and amplifies allergic inflammation. Two murine models of experimental allergic conjunctivitis (EAC) and IL-9 topical challenge in wild type Balb/c and ST2^-/- mice, and two culture models of primarily human corneal epithelial cells (HCECs) and mouse CD4⁺ T cells were performed. Clinical manifestations, Oregon-Green Dextran (OGD) staining, the apical junction complexes (AJCs), IL-33/ST2 and IL-9/IL-9R signaling molecules were evaluated in ocular surface and its draining cervical lymph nodes (CLNs) by RT-qPCR, immunostaining and ELISA. The typical allergic signs, enhanced OGD staining intensity, disrupted morphology of AJCs, including ZO-1, claudin 1, occludin, and E-cadherin, and the stimulated signaling of IL-33/ST2 and IL-9/IL-9R were observed in ocular mucosa and draining CLNs in EAC-Balb/c mice, but significantly reduced or eliminated in EAC-ST2^-/- mice. Topical challenge of IL-9 resulted in the obvious OGD staining and disrupted ocular surface AJCs in Balb/c mice and in HCECs in vitro. IL-9 production was found to be stimulated by IL-33 in CD4⁺ cells from Balb/c mice in vitro. Our findings uncovered a novel phenomenon and mechanism by which ocular surface barrier integrity is disrupted in allergic conjunctivitis by IL-33/ST2/IL-9/IL-9R signaling pathway, which may amplify the allergic inflammation.

Weissella paramesenteroides WpK4 plays an immunobiotic role in gut-brain axis, reducing gut permeability, anxiety-like and depressive-like behaviors in murine models of colitis and chronic stress

The relationship between inflammatory bowel disease (IBD) and mood disorders is complex and involves overlapping metabolic pathways, which may determine comorbidity. Several studies have been shown that this comorbidity could worsen IBD clinical course. The treatment of ulcerative colitis is complex, and involves traditional therapy to promote the function of epithelial barrier, reducing exacerbated inflammatory responses. Recently, it has been shown that some probiotic strains could modulate gut-brain axis, reducing depressive and anxiety scores in humans, including IBD patients. Accordingly, this study aimed to evaluate the role of Weissella paramesenteroides WpK4 in murine models of ulcerative colitis and chronic stress. It was observed that bacterium ingestion improved health of colitis mice, reducing intestinal permeability, besides improving colon histopathological appearance. In stressed mice, bacterial consumption was associated with a reduced anxiety-like and depressive-like behaviors. In both assays, the beneficial role of W. paramesenteroides WpK4 was related to its immunomodulatory feature. It is possible to state that W. paramesenteroides WpK4 exerted their beneficial roles in gut-brain axis through their immunomodulatory effects with consequences in several metabolic pathways related to intestinal permeability and hippocampal physiology.

Polyamines polarized Th2/Th9 cell-fate decision by regulating GATA3 expression

Polyamines produced by both prokaryotes and eukaryotes are bioactive substances with pleiotropic effects. Accumulating evidence has demonstrated that polyamines contribute to anti-inflammatory responses by suppressing the expression of proinflammatory cytokines in mononuclear cells and macrophages. However, the effects of polyamines on CD4⁺ T cell responses remain to be elucidated. Here, we investigated the effect of polyamines on cell fate decisions of naïve CD4⁺ T cells in vitro. We found that endogenously generated polyamines are essential for the development of T helper 2 (Th2) cells. Treatment with DL-2-difluoromethylornithine (DFMO), an inhibitor of polyamine biosynthesis, diminished GATA3 expression in CD4⁺ T cells under Th2-skewed conditions. Supplementation of exogenous polyamines rescued GATA3 downregulation caused by DFMO treatment in CD4⁺ T cells. Transcriptome analysis revealed that deprivation of endogenous polyamines resulted in upregulated Th9-related genes, such as Il9, Irf4, and Batf3, even under the Th2-skewing conditions. Depletion of intracellular polyamines reduced GATA3 expression but increased IL-9-producing CD4⁺ T cells under both Th2 and Th9-skewing conditions. Furthermore, oral administration of DFMO increased IL-9-producing CD4⁺ T cells in small intestine in mice. Thus, our data indicate that polyamines play a critical role in the regulation of the Th2/Th9 balance.

IL-9 exerts biological function on antigen-experienced murine T cells and exacerbates colitis induced by adoptive transfer

IL-9 is involved in various T cell-dependent inflammatory models including colitis, encepahlitis, and asthma. However, the regulation and specificity of IL-9 responsiveness by T cells during immune responses remains poorly understood. Here, we addressed this question using two different models: experimental colitis induced by transfer of naive CD4⁺ CD45RB^high T cells into immunodeficient mice, and OVA-specific T cell activation. In the colitis model, constitutive IL-9 expression exacerbated inflammation upon transfer of CD4⁺ CD45RB^high T cells from WT but not from Il9r^-/- mice, indicating that IL-9 acts directly on T cells. Suprisingly, such naïve CD4⁺ CD45RB^high T cells failed to express the Il9r or respond to IL-9 in vitro, in contrast with CD4⁺ CD45RB^low T cells. By using OVA-specific T cells, we observed that T cells acquired the capacity to respond to IL-9 along with CD44 upregulation, after long-lasting (5 to 12 days) in vivo antigenic stimulation. Il9r expression was associated with Th2 and Th17 phenotypes. Interestingly, in contrast to the IL-2 response, antigen restimulation downregulated IL-9 responsiveness. Taken together, our results demonstrate that IL-9 does not act on naïve T cells but that IL-9 responsiveness is acquired by CD4⁺ T cells after in vivo activation and acquisition of memory markers such as CD44.

Interleukin-9 Deletion Relieves Vascular Dysfunction and Decreases Blood Pressure via the STAT3 Pathway in Angiotensin II-Treated Mice

Background

Multiple interleukin (IL) family members were reported to be closely related to hypertension. We aimed to investigate whether IL-9 affects angiotensin II- (Ang II-) induced hypertension in mice.

Methods

Mice were treated with Ang II, and IL-9 expression was determined. In addition, effects of IL-9 knockout (KO) on blood pressure were observed in Ang II-infused mice. To determine whether the effects of IL-9 on blood pressure was mediated by the signal transducer and activator of the transcription 3 (STAT3) pathway, Ang II-treated mice were given S31-201. Furthermore, circulating IL-9 levels in patients with hypertension were measured.

Results

Ang II treatment increased serum and aortic IL-9 expression in a dose-dependent manner; IL-9 levels were the highest in the second week and continued to remain high into the fourth week after the treatment. IL-9 KO downregulated proinflammatory cytokine expression, whereas it upregulated anti-inflammatory cytokine levels, relieved vascular dysfunction, and decreased blood pressure in Ang II-infused mice. IL-9 also reduced smooth muscle 22α (SM22α (SM22

Conclusions

IL-9 KO alleviates inflammatory response, prevents phenotypic transformation of smooth muscle, reduces vascular dysfunction, and lowers blood pressure via the STAT3 pathway in Ang II-infused mice. IL-9 might be a novel target for the treatment and prevention of clinical hypertension.

IL-9 Blockade Suppresses Silica-induced Lung Inflammation and Fibrosis in Mice

Recapitulative animal models of idiopathic pulmonary fibrosis (IPF) and related diseases are lacking, which inhibits our ability to fully clarify the pathogenesis of these diseases. Although lung fibrosis in mouse models is often induced by bleomycin, silica-induced lung fibrosis is more sustainable and more progressive. Therefore, in this study, we sought to elucidate the mediator(s) responsible for the pathogenesis of lung fibrosis, through the use of a mouse model of silica-induced lung fibrosis. With a single nasal administration of 16 mg of silica, lung inflammation (assessed by elevated cellular components in the BAL fluids [BALFs]) and lung fibrosis (assessed by lung histology and lung hydroxyproline levels) were induced and sustained for as long as 24 weeks. Of the mediators measured in the BALFs, IL-9 was characteristically elevated gradually, and peaked at 24 weeks after silica administration. Treatment of silica-challenged mice with anti-IL-9-neutralizing antibody inhibited lung fibrosis, as assessed by lung hydroxyproline level, and suppressed the levels of major mediators, including IL-1β, IL-6, IL-12, CCL2, CXCL1, and TNF-α in BALFs. Moreover, human lung specimens from patients with IPF have shown high expression of IL-9 in alveolar macrophages, CD4-positive cells, and receptors for IL-9 in airway epithelial cells. Collectively, these data suggest that IL-9 plays an important role in the pathogenesis of lung fibrosis in diseases such as IPF.

Th9 cells in allergic diseases: A role for the microbiota?

Since their discovery about 10 years ago, Th9 cells have been increasingly linked to allergic pathologies. Within this review, we summarize the current knowledge on associations between Th9 cells and allergic diseases and acknowledge Th9 cells as important targets in future treatment of allergic diseases. However, until today, it is not fully understood how these Th9 cell responses are modulated. We describe current literature suggesting that these Th9 cell responses might be stimulated by microbial species such as Staphylococcus aureus and Candida albicans, while on the other hand, microbial and dietary compounds such as retinoic acid (RA), butyrate and vitamin D show suppressive capacity on allergy‐related Th9 responses. By reviewing this recent research, we provide new insights into the modulating capacity of the microbiota on Th9 cell responses. Consequently, microbial and dietary factors may be used as innovative tools to target Th9 cells in the treatment of allergic diseases. However, further research is needed to elucidate the mechanisms behind these interactions in order to translate this knowledge into clinical allergy settings.

TH9, TH17, and TH22 Cell Subsets and Their Main Cytokine Products in the Pathogenesis of Colorectal Cancer

In recent years, several newly identified T helper (T_H) cell subsets, such as T_H9, T_H17, and T_H22 cells, and their respective cytokine products, IL-9, IL-17, and IL-22, have been reported to play critical roles in the development of chronic inflammation in the colorectum. Since chronic inflammation is a potent driving force for the development of human colorectal cancer (CRC), the contributions of T_H9/IL-9, T_H17/IL-17, and T_H22/IL-22 in the pathogenesis of CRC have recently become an increasingly popular area of scientific investigation. Extensive laboratory and clinical evidence suggests a positive relationship between these new T_H subsets and the growth and formation of CRC, whereas, administration of IL-9, IL-17, and IL-22 signaling inhibitors can significantly alter the formation of colorectal chronic inflammation or CRC lesions in animal models, suggesting that blocking these cytokine signals might represent promising immunotherapeutic strategies. This review summarizes recent findings and currently available data for understanding the vital role and therapeutic significance of T_H9/IL-9, T_H17/IL-17, and T_H22/IL-22 in the development of colorectal tumorigenesis.

Beneficial and Deleterious Effects of Female Sex Hormones, Oral Contraceptives, and Phytoestrogens by Immunomodulation on the Liver

The liver is considered the laboratory of the human body because of its many metabolic processes. It accomplishes diverse activities as a mixed gland and is in continuous cross-talk with the endocrine system. Not only do hormones from the gastrointestinal tract that participate in digestion regulate the liver functions, but the sex hormones also exert a strong influence on this sexually dimorphic organ, via their receptors expressed in liver, in both health and disease. Besides, the liver modifies the actions of sex hormones through their metabolism and transport proteins. Given the anatomical position and physiological importance of liver, this organ is evidenced as an immune vigilante that mediates the systemic immune response, and, in turn, the immune system regulates the hepatic functions. Such feedback is performed by cytokines. Pro-inflammatory and anti-inflammatory cytokines are strongly involved in hepatic homeostasis and in pathological states; indeed, female sex hormones, oral contraceptives, and phytoestrogens have immunomodulatory effects in the liver and the whole organism. To analyze the complex and interesting beneficial or deleterious effects of these drugs by their immunomodulatory actions in the liver can provide the basis for either their pharmacological use in therapeutic treatments or to avoid their intake in some diseases.

Transcription factor networks in aged naïve CD4 T cells bias lineage differentiation

With reduced thymic activity, the population of naïve T cells in humans is maintained by homeostatic proliferation throughout adult life. In young adults, naïve CD4 T cells have enormous proliferative potential and plasticity to differentiate into different lineages. Here, we explored whether naïve CD4 T-cell aging is associated with a partial loss of this unbiased multipotency. We find that naïve CD4 T cells from older individuals have developed a propensity to develop into TH9 cells. Two major mechanisms contribute to this predisposition. First, responsiveness to transforming growth factor β (TGFβ) stimulation is enhanced with age due to an upregulation of the TGFβR3 receptor that results in increased expression of the transcription factor PU.1. Secondly, aged naïve CD4 T cells display altered transcription factor profiles in response to T-cell receptor stimulation, including enhanced expression of BATF and IRF4 and reduced expression of ID3 and BCL6. These transcription factors are involved in TH9 differentiation as well as IL9 transcription suggesting that the aging-associated changes in the transcription factor profile favor TH9 commitment.

TL1A modulates the severity of colitis by promoting Th9 differentiation and IL-9 secretion

AIMS

TL1A was reported to contribute to the susceptibility to ulcerative colitis (UC). However, the molecular mechanisms of TL1A in UC development are poorly understood. We aimed to investigate the role of TL1A in colitis, and reveal the regulatory mechanism of TL1A in chronic colitis development.

MAIN METHODS

Wild-type mice and transgenic mice with overexpressing TL1A in lymphocytes were used to construct chronic DSS colitis models. To investigate the molecular mechanism in vitro, CD4⁺ T cells were sorted from spleens and mesenteric lymph node cells to induce Th9 cells. Biopsy specimens from ulcerative colitis patients were collected for in vivo validation.

KEY FINDINGS

The elevated TL1A expression in chronic DSS colitis models exacerbated intestinal inflammation. The differentiation of Th9 cells, IL-9 secretion and production of TGF-β, IL-4 and PU.1 was significantly enhanced in transgenic mice with TL1A overexpression. In vitro results showed that TL1A enhanced the Th9 cells, IL-9 and PU.1 production, while TL1A antibodies inhibited their production. In human translational studies, patients with ulcerative colitis with elevated TL1A expression also exhibited more serious inflammation with higher levels of Th9 cells, IL-9 and PU.1 expression.

SIGNIFICANCE

We presented a possible mechanism of TL1A in UC development that TL1A may promote the differentiation of Th9 cells and enhanced IL-9 secretion by up-regulating the expression of TGF-β, IL-4 and PU.1, which provided a novel perspective to study the UC pathogenesis, and indicated that targeting of TL1A signal pathway may by a likely strategy for the treatment of chronic colitis.

The Multifactorial Etiopathogeneses Interplay of Inflammatory Bowel Disease: An Overview

The gastrointestinal system where inflammatory bowel disease occurs is central to the immune system where the innate and the adaptive/acquired immune systems are balanced in interactions with gut microbes under homeostasis conditions. This article overviews the high-throughput research screening on multifactorial interplay between genetic risk factors, the intestinal microbiota, urbanization, modernization, Westernization, the environmental influences and immune responses in the etiopathogenesis of inflammatory bowel disease in humans. Inflammatory bowel disease is an expensive multifactorial debilitating disease that affects thousands new people annually worldwide with no known etiology or cure. The conservative therapeutics focus on the established pathology where the immune dysfunction and gut injury have already happened but do not preclude or delay the progression. Inflammatory bowel disease is evolving globally and has become a global emergence disease. It is largely known to be a disease in industrial-urbanized societies attributed to modernization and Westernized lifestyle associated with environmental factors to genetically susceptible individuals with determined failure to process certain commensal antigens. In the developing nations, increasing incidence and prevalence of inflammatory bowel disease (IBD) has been associated with rapid urbanization, modernization and Westernization of the population. In summary, there are identified multiple associations to host exposures potentiating the landscape risk hazards of inflammatory bowel disease trigger, that include: Western life-style and diet, host genetics, altered innate and/or acquired/adaptive host immune responses, early-life microbiota exposure, change in microbiome symbiotic relationship (dysbiosis/dysbacteriosis), pollution, changing hygiene status, socioeconomic status and several other environmental factors have long-standing effects/influence tolerance. The ongoing multipronged robotic studies on gut microbiota composition disparate patterns between the rural vs. urban locations may help elucidate and better understand the contribution of microbiome disciplines/ecology and evolutionary biology in potentially protecting against the development of inflammatory bowel disease.

Inflammation and Lymphatic Function

The lymphatic vasculature plays a crucial role in regulating the inflammatory response by influencing drainage of extravasated fluid, inflammatory mediators, and leukocytes. Lymphatic vessels undergo pronounced enlargement in inflamed tissue and display increased leakiness, indicating reduced functionality. Interfering with lymphatic expansion by blocking the vascular endothelial growth factor C (VEGF-C)/vascular endothelial growth factor receptor 3 (VEGFR-3) signaling axis exacerbates inflammation in a variety of disease models, including inflammatory bowel disease (IBD), rheumatoid arthritis and skin inflammation. In contrast, stimulation of the lymphatic vasculature, e.g., by transgenic or viral overexpression as well as local injections of VEGF-C, has been shown to reduce inflammation severity in models of rheumatoid arthritis, skin inflammation, and IBD. Strikingly, the induced expansion of the lymphatic vasculature improves lymphatic function as assessed by the drainage of dyes, fluorescent tracers or inflammatory cells and labeled antigens. The drainage performance of lymphatic vessels is influenced by vascular permeability and pumping activity, which are influenced by VEGF-C/VEGFR-3 signaling as well as several inflammatory mediators, including TNF-α, IL-1β, and nitric oxide. Considering the beneficial effects of lymphatic activation in inflammation, administration of pro-lymphangiogenic factors like VEGF-C, preferably in a targeted, inflammation site-specific fashion, represents a promising therapeutic approach in the setting of inflammatory pathologies.

Regulation of Adaptive Immune Cells by Sirtuins

It is now well-established that the pathways that control lymphocyte metabolism and function are intimately linked, and changes in lymphocyte metabolism can influence and direct cellular function. Interestingly, a number of recent advances indicate that lymphocyte identity and metabolism is partially controlled via epigenetic regulation. Epigenetic mechanisms, such as changes in DNA methylation or histone acetylation, have been found to alter immune function and play a role in numerous chronic disease states. There are several enzymes that can mediate epigenetic changes; of particular interest are sirtuins, protein deacetylases that mediate adaptive responses to a variety of stresses (including calorie restriction and metabolic stress) and are now understood to play a significant role in immunity. This review will focus on recent advances in the understanding of how sirtuins affect the adaptive immune system. These pathways are of significant interest as therapeutic targets for the treatment of autoimmunity, cancer, and transplant tolerance.