TGFbeta1, a "Jack of all trades": the link with pro-inflammatory IL-17-producing T cells

Histone demethylase JARID1C/KDM5C regulates Th17 cells by increasing IL-6 expression in diabetic plasmacytoid dendritic cells

Plasmacytoid dendritic cells (pDCs) are first responders to tissue injury, where they prime naive T cells. The role of pDCs in physiologic wound repair has been examined, but little is known about pDCs in diabetic wound tissue and their interactions with naive CD4+ T cells. Diabetic wounds are characterized by increased levels of inflammatory IL-17A cytokine, partly due to increased Th17 CD4+ cells. This increased IL-17A cytokine, in excess, impairs tissue repair. Here, using human tissue and murine wound healing models, we found that diabetic wound pDCs produced excess IL-6 and TGF-β and that these cytokines skewed naive CD4+ T cells toward a Th17 inflammatory phenotype following cutaneous injury. Further, we identified that increased IL-6 cytokine production by diabetic wound pDCs is regulated by a histone demethylase, Jumonji AT-rich interactive domain 1C histone demethylase (JARID1C). Decreased JARID1C increased IL-6 transcription in diabetic pDCs, and this process was regulated upstream by an IFN-I/TYK2/JAK1,3 signaling pathway. When inhibited in nondiabetic wound pDCs, JARID1C skewed naive CD4+ T cells toward a Th17 phenotype and increased IL-17A production. Together, this suggests that diabetic wound pDCs are epigenetically altered to increase IL-6 expression that then affects T cell phenotype. These findings identify a therapeutically manipulable pathway in diabetic wounds.

MHC-II presentation by oral Langerhans cells impacts intraepithelial Tc17 abundance and Candida albicans oral infection via CD4 T cells

In a murine model (LCΔMHC-II) designed to abolish MHC-II expression in Langerhans cells (LCs), ∼18% of oral LCs retain MHC-II, yet oral mucosal CD4 T cells numbers are unaffected. In LCΔMHC-II mice, we now show that oral intraepithelial conventional CD8αβ T cell numbers expand 30-fold. Antibody-mediated ablation of CD4 T cells in wild-type mice also resulted in CD8αβ T cell expansion in the oral mucosa. Therefore, we hypothesize that MHC class II molecules uniquely expressed on Langerhans cells mediate the suppression of intraepithelial resident-memory CD8 T cell numbers via a CD4 T cell-dependent mechanism. The expanded oral CD8 T cells co-expressed CD69 and CD103 and the majority produced IL-17A [CD8 T cytotoxic (Tc)17 cells] with a minority expressing IFN-γ (Tc1 cells). These oral CD8 T cells showed broad T cell receptor Vβ gene usage indicating responsiveness to diverse oral antigens. Generally supporting Tc17 cells, transforming growth factor-β1 (TGF-β1) increased 4-fold in the oral mucosa. Surprisingly, blocking TGF-β1 signaling with the TGF-R1 kinase inhibitor, LY364947, did not reduce Tc17 or Tc1 numbers. Nonetheless, LY364947 increased γδ T cell numbers and decreased CD49a expression on Tc1 cells. Although IL-17A-expressing γδ T cells were reduced by 30%, LCΔMHC-II mice displayed greater resistance to Candida albicans in early stages of oral infection. These findings suggest that modulating MHC-II expression in oral LC may be an effective strategy against fungal infections at mucosal surfaces counteracted by IL-17A-dependent mechanisms.

Beyond Encapsulation: Exploring Macrophage-Fibroblast Cross Talk in Implant-Induced Fibrosis

The foreign body response (FBR) and organ fibrosis are complex biological processes involving the interaction between macrophages and fibroblasts. Understanding the molecular mechanisms underlying macrophage-fibroblast cross talk is crucial for developing strategies to mitigate implant encapsulation, a major cause of implant failure. This article reviews the current knowledge on the role of macrophages and fibroblasts in the FBR and organ fibrosis, highlighting the similarities between these processes. The FBR is characterized by the formation of a fibrotic tissue capsule around the implant, leading to functional impairment. Various factors, including material properties such as surface chemistry, stiffness, and topography, influence the degree of encapsulation. Cross talk between macrophages and fibroblasts plays a critical role in both the FBR and organ fibrosis. However, the precise molecular mechanisms remain poorly understood. Macrophages secrete a wide range of cytokines that modulate fibroblast behavior such as abundant collagen deposition and myofibroblast differentiation. However, the heterogeneity of macrophages and fibroblasts and their dynamic behavior in different tissue environments add complexity to this cross talk. Experimental evidence from in vitro studies demonstrates the impact of material properties on macrophage cytokine secretion and fibroblast physiology. However, the correlation between in vitro response and in vivo encapsulation outcomes is not robust. Adverse outcome pathways (AOPs) offer a potential framework to understand and predict process complexity. AOPs describe causal relationships between measurable events leading to adverse outcomes, providing mechanistic insights for in vitro testing and predictive modeling. However, the development of an AOP for the FBR does require a comprehensive understanding of the molecular initiating events and key event relationships to identify which events are essential. In this article, we describe the current knowledge on macrophage-fibroblast cross talk in the FBR and discuss how targeted research can help build an AOP for implant-related fibrosis.

Unraveling IL-17 and IL-22 role in occult hepatitis C versus chronic hepatitis C virus infection

BACKGROUND

Cytokines play a crucial role in regulating the function of the immune system by controlling the production, differentiation, and activity of immune cells. Occult hepatitis C virus (OHCV) infection can lead to liver damage, including cirrhosis and hepatocellular carcinoma. This study investigates the immunopathogenic impact of the cytokines IL-17 and IL-22 in OHCV infection compared to chronic hepatitis C (CHC) infection.

METHODS

We studied three groups of patients: 35 with OHCV, 100 untreated patients with CHC, and 30 healthy control subjects. All subjects underwent physical examination and biochemical testing. We used the sandwich enzyme-linked immunosorbent assay method to measure serum IL-17 and IL-22 levels in all groups.

RESULTS

Compared to the occult and control groups, the CHC group had significantly higher serum IL-17 levels (p < 0.001). The occult group also had higher serum IL-17 levels compared to the control group (p < 0.0001). There were no significant differences in IL-22 levels across the research groups. In the OHCV group, individuals with moderate inflammation (A2-A3) had significantly higher serum IL-17 levels than those with minimal inflammation (A0-A1), while in the CHC group, this difference was not statistically significant (p = 0.601). Neither the occult nor the CHC groups showed a correlation between serum IL-22 and inflammatory activity. There was no significant correlation between the levels of IL-17 or IL-22 and the stage of fibrosis/cirrhosis in either group. ROC curves were calculated for serum IL-17 and IL-22 levels and occult HCV infection, with cut-off values set at ≤ 32.1 pg/ml and < 14.3 pg/ml for IL-17 and IL-22, respectively. The AUROC (95%CI) was significantly higher for IL-17 than IL-22 (0.829 (0.732-0.902) vs. 0.504 (0.393-0.614), p < 0.001), suggesting that IL-17 has a stronger correlation with infection risk than IL-22.

CONCLUSION

This study suggests that IL-17 may be involved in the immunopathogenesis of OHCV infection, especially in patients with moderate inflammation.

Transcutaneous vagus nerve stimulation ameliorates cardiac abnormalities in chronically stressed rats

Chronically stressed patients often have low vagal tone and increased levels of proinflammatory cytokines, which increase their risk for developing cardiac dysfunction. Transcutaneous vagus nerve stimulation (taVNS) is a way to activate the parasympathetic system, which has the ability to reduce inflammation and antagonize excessive sympathetic responses. However, the effectiveness of taVNS in treating cardiac dysfunction caused by chronic unpredictable stress (CUS) has not been studied. To investigate this, we first validated a rat model of CUS, in which the rats were exposed to random stressors daily for 8 weeks. Post CUS, the rats were treated with taVNS (1.0 ms, 6 V, 6 Hz, for 40 min × 2 weeks, alternatively) and their cardiac function and cholinergic flow were evaluated. Furthermore, serum cardiac troponin I (cTnI), cardiac caspase-3, inducible nitric oxide synthase (iNOS), and transforming growth factor (TGF)-β1 expression in rats were also assessed. The chronically stressed rats showed depressed behavior with increased levels of serum corticosterone and proinflammatory cytokines. Electrocardiogram (ECG) and heart rate variability (HRV) studies revealed elevated heart rate, diminished vagal tone, and altered sinus rhythm in CUS rats. Furthermore, the CUS rats demonstrated cardiac hypertrophy and fibrosis with increased caspase-3, iNOS, and TGF-β expression in their myocardium and increased levels of serum cTnI. Interestingly, alternate taVNS therapy for 2 weeks, post CUS, helped alleviate these cardiac abnormalities. These suggest that taVNS could be a useful adjunctive and non-pharmacological approach for managing CUS induced cardiac dysfunction.

The dichotomic role of single cytokines: Fine-tuning immune responses

Cytokines are known for their pleiotropic effects. They can be classified by their function as pro-inflammatory, such as tumor necrosis factor (TNF), interleukin (IL) 1 and IL-12, or anti-inflammatory, like IL-10, IL-35 and transforming growth factor β (TGF-β). Though this type of classification is an important simplification for the understanding of the general cytokine's role, it can be misleading. Here, we discuss recent studies that show a dichotomic role of the so-called pro and anti-inflammatory cytokines, highlighting that their function can be dependent on the microenvironment and their concentrations. Furthermore, we discuss how the back-and-forth interplay between cytokines and immunometabolism can influence the dichotomic role of inflammatory responses as an important target to complement cytokine-based therapies.

Invasion and Secondary Site Colonization as a Function of In Vitro Primary Tumor Matrix Stiffness: Breast to Bone Metastasis

Increased breast tissue stiffness is correlated with breast cancer risk and invasive cancer progression. However, its role in promoting bone metastasis, a major cause of mortality, is not yet understood. It is previously identified that the composition and stiffness of alginate-based hydrogels mimicking normal (1-2 kPa) and cancerous (6-10 kPa) breast tissue govern phenotype of breast cancer cells (including MDA-MB-231) in vitro. Here, to understand the causal effect of primary tumor stiffness on metastatic potential, a new breast-to-bone in vitro model is described. Together with alginate-gelatin hydrogels to mimic breast tissue, 3D printed biohybrid poly-caprolactone (PCL)-composite scaffolds, decellularized following bone-ECM deposition through Saos-2 engraftment, are used to mimic the bone tissue. It is reported that higher hydrogel stiffness results in the increased migration and invasion capacity of MDA-MB 231 cells. Interestingly, increased expression of osteolytic factors PTHrP and IL-6 is observed when MDA-MB-231 cells pre-conditioned in stiffer hydrogels (10 kPa, 3% w/v gelatin) colonize the bone/PCL scaffolds. The new breast-to-bone in vitro models herein described are designed with relevant tissue microenvironmental factors and could emerge as future non-animal technological platforms for monitoring metastatic processes and therapeutic efficacy.

Allergic airway inflammation induces upregulation of the expression of IL-23R by macrophages and not in CD3 + T cells and CD11c+F4/80- dendritic cells of the lung

Interleukin 23 and the interleukin 23 receptor (IL-23-IL23R) are described as the major enhancing factors for Interleukin 17 (IL-17) in allergic airway inflammation. IL-17 is considered to induce neutrophilic inflammation in the lung, which is often observed in severe, steroid-resistant asthma-phenotypes. For that reason, understanding of IL-23 and IL-17 axis is very important for future therapy strategies, targeting neutrophil pathway of bronchial asthma.

This study aimed to investigate the distribution and expression of IL-23R under physiological and inflammatory conditions. Therefore, a house dust mite (HDM) model of allergic airway inflammation was performed by treating mice with HDM intranasally. Immunofluorescence staining with panel of antibodies was performed in lung tissues to examine the macrophage, dendritic cell, and T cell subpopulations. The allergic airway inflammation was quantified by histopathological analysis, ELISA measurements, and airway function.

HDM-treated mice exhibited a significant allergic airway inflammation including higher amounts of NE⁺ cells in lung parenchyma. We found only a small amount of IL-23R positives, out of total CD3⁺T cells, and no upregulation in HDM-treated animals. In contrast, the populations of F4/80⁺ macrophages and CD11c⁺F4/80⁻ dendritic cells (DCs) with IL-23R expression were found to be higher. But HDM treatment leads to a significant increase of IL-23R⁺ macrophages, only. IL-23R was expressed by every examined macrophage subpopulation, whereas only Mϕ1 and hybrids between Mϕ1 and Mϕ2 phenotype and not Mϕ2 were found to upregulate IL-23R. Co-localization of IL-23R and IL-17 was only observed in F4/80⁺ macrophages, suggesting F4/80⁺ macrophages express IL-23R along with IL-17 in lung tissue.

The study revealed that macrophages involving the IL-23 and IL-17 pathway may provide a potential interesting therapeutic target in neutrophilic bronchial asthma.

Effects of lipopolysaccharide exposure on the inflammatory response, butyrate flux, and metabolic function of the ruminal epithelium using an ex vivo model

Acidotic conditions in the rumen have been associated with compromised barrier function of the ruminal epithelium and translocation of microbe-associated molecular patterns (MAMP) such as lipopolysaccharide (LPS). Interaction of MAMP with the ruminal epithelium may also induce a local proinflammatory response. The aim of this study was to evaluate the potential proinflammatory response of the ruminal epithelium following LPS exposure in Ussing chambers, to investigate whether LPS exposure affects the flux and metabolism of butyrate. Ruminal epithelial tissue from 9 Holstein bull calves were mounted into Ussing chambers and exposed to 0, 10,000, 50,000, or 200,000 endotoxin units (EU)/mL LPS for a duration of 5 h. Radiolabeled ¹⁴C-butyrate (15 mM) was added to the mucosal buffer to assess the mucosal-to-serosal flux of ¹⁴C-butyrate. Additional Ussing chambers, without radioisotope, were exposed to either 0 or 200,000 EU/mL LPS and were used to measure the release of β-hydroxybutyrate (BHB) and IL1B into the buffer, and to collect epithelial tissue for analysis of gene expression. Genes associated with inflammation (TNF, IL1B, CXCL8, PTGS2, TGFB1, TLR2, TLR4), nutrient transport (MCT1, MCT4, SLC5A8, GLUT1), and metabolic function (ACAT1, BDH1, MCU, IGFBP3, IGFBP5) were selected and analyzed using quantitative real-time PCR. Butyrate flux was not significantly affected by LPS exposure; however, we detected a tendency for the mucosal-to-serosal butyrate flux to increase linearly with LPS dose. Bidirectional releases of BHB and IL1B were not affected by LPS exposure. Expression of PTGS2, TGFB1, TLR4, and MCU were downregulated following exposure to LPS ex vivo. We detected no effects on the expression of genes associated with nutrient transport. The results of the present study are interpreted to indicate that, although the inflammatory response of the ruminal epithelium was slightly suppressed, exposure to LPS may have altered metabolic function.

Bidirectional Cross-Talk between Biliary Epithelium and Th17 Cells Promotes Local Th17 Expansion and Bile Duct Proliferation in Biliary Liver Diseases

There is no effective treatment for autoimmune biliary diseases. Therefore, understanding their immunopathology is crucial. The biliary epithelial cells (BEC), expressing TLR-4, are constantly exposed to gut microbes and bacterial wall LPS, and in settings of inflammation, the immune infiltrate is dense within the peribiliary region of human liver. By dual immunohistochemistry, we affirm human intrahepatic T cell infiltrate includes CCR6+CD4+ and AhR+CD4+ T cells with potential for plasticity to Th17 phenotype. Mechanistically, we demonstrate that Th1 and Th17 inflammatory cytokines and LPS enhance human primary BEC release of the CCR6 ligand CCL20 and BEC secretion of Th17-polarizing cytokines IL-6 and IL-1β. Cell culture assays with human BEC secretome showed that secretome polarizes CD4 T cells toward a Th17 phenotype and supports the survival of Th17 cells. BEC secretome did not promote Th1 cell generation. Additionally, we give evidence for a mutually beneficial feedback of the type 17 cell infiltrate on BEC, showing that treatment with type 17 cytokines increases BEC proliferation, as monitored by Ki67 and activation of JAK2-STAT3 signaling. This study identifies human BEC as active players in determining the nature of the intrahepatic immune microenvironment. In settings of inflammation and/or infection, biliary epithelium establishes a prominent peribiliary type 17 infiltrate via recruitment and retention and enhances polarization of intrahepatic CD4 cells toward Th17 cells via type 17 cytokines, and, reciprocally, Th17 cells promote BEC proliferation for biliary regeneration. Altogether, we provide new insight into cross-talk between Th17 lymphocytes and human primary biliary epithelium in biliary regenerative pathologies.

The Multitasking Fasciola gigantica Cathepsin B Interferes With Various Functions of Goat Peripheral Blood Mononuclear Cells in vitro

Cathepsin B, a lysosomal cysteine protease, is thought to be involved in the pathogenesis of Fasciola gigantica infection, but its exact role remains unclear. In the present study, a recombinant F. gigantica cathepsin B (rFgCatB) protein was expressed in the methylotrophic yeast Pichia pastoris. Western blot analysis confirmed the reactivity of the purified rFgCatB protein to serum from F. gigantica-infected goats. The effects of serial concentrations (10, 20, 40, 80, and 160 μg/ml) of rFgCatB on various functions of goat peripheral blood mononuclear cells (PBMCs) were examined. We demonstrated that rFgCatB protein can specifically bind to the surface of PBMCs. In addition, rFgCatB increased the expression of cytokines (IL-2, IL-4, IL-10, IL-17, TGF-β, and IFN-γ), and increased nitric oxide production and cell apoptosis, but reduced cell viability. These data show that rFgCatB can influence cellular and immunological functions of goat PBMCs. Further characterization of the posttranslational modification and assessment of rFgCatB in immunogenicity studies is warranted.

Deciphering targets of Th17 cells fate: From metabolism to nuclear receptors

Evidence indicates that reprogramming of metabolism is critically important for the differentiation of CD4 + T lymphocytes, and the manipulation of metabolic pathways in these cells may shape their fate and function. Distinct subgroups from T lymphocytes, such as Th17, adopt specific metabolic programmes to support their needs. Some important metabolic reactions, such as glycolysis, oxidative phosphorylation, are considered important for the differentiation of these lymphocytes. Since their discovery nearly a decade ago, Th17 lymphocytes have received significant attention because of their role in the pathology of several immune-mediated inflammatory diseases such as multiple sclerosis. In this review, it will be discussed as the involvement of T cell metabolism and as metabolic reprogramming in activated T cells dictates fate decisions to Th17. The involvement of nuclear receptors such as RORyt e PPARs in the induction of Th17 cells was also discussed. Understanding the metabolic pathways involved in the differentiation of the distinct subgroups of T lymphocytes helps in the design of promising therapeutic proposals.

HSP90 inhibitor geldanamycin reverts IL-13- and IL-17-induced airway goblet cell metaplasia

Goblet cell metaplasia, a disabling hallmark of chronic lung disease, lacks curative treatments at present. To identify novel therapeutic targets for goblet cell metaplasia, we studied the transcriptional response profile of IL-13-exposed primary human airway epithelia in vitro and asthmatic airway epithelia in vivo. A perturbation-response profile connectivity approach identified geldanamycin, an inhibitor of heat shock protein 90 (HSP90) as a candidate therapeutic target. Our experiments confirmed that geldanamycin and other HSP90 inhibitors prevented IL-13-induced goblet cell metaplasia in vitro and in vivo. Geldanamycin also reverted established goblet cell metaplasia. Geldanamycin did not induce goblet cell death, nor did it solely block mucin synthesis or IL-13 receptor-proximal signaling. Geldanamycin affected the transcriptome of airway cells when exposed to IL-13, but not when exposed to vehicle. We hypothesized that the mechanism of action probably involves TGF-β, ERBB, or EHF, which would predict that geldanamycin would also revert IL-17-induced goblet cell metaplasia, a prediction confirmed by our experiments. Our findings suggest that persistent airway goblet cell metaplasia requires HSP90 activity and that HSP90 inhibitors will revert goblet cell metaplasia, despite active upstream inflammatory signaling. Moreover, HSP90 inhibitors may be a therapeutic option for airway diseases with goblet cell metaplasia of unknown mechanism.

Modulation of Inflammation-Related Genes in the Cornea of a Mouse Model of Dry Eye upon Treatment with Cyclosporine Eye Drops

Purpose/Aim: Inflammation is recognized as playing an etiological role in dry eye disease. This study aimed to assess the efficacy of various topical cyclosporine A (CsA) formulations on cornea inflammatory markers in a mouse model of dry eye.

MATERIAL AND METHODS

Six- to 7-week-old mice treated with scopolamine were housed in a controlled environment room to induce dry eye. Following dry eye confirmation by corneal fluorescein staining (CFS), the mice were treated three times a day with: 0.05%CsA (Restasis, Allergan), 0.1%CsA (Ikervis, Santen), 1%CsA oil solution, and 0.5% loteprednol etabonate (LE, Lotemax, Baush+Lomb), or left untreated. Aqueous tear production and CFS scores were assessed during the treatment period, and corneas were collected to measure the expression profile of a selection of inflammatory genes.

RESULTS

After 7 days of treatment, the CFS scores were reduced by 21%, 31%, and 44% with 0.05%CsA, 0.1%CsA, and 1%CsA eye drops, respectively. By contrast, 0.5% LE did not decrease corneal fluorescein staining at day 10. A statistically significant dose-dependent CFS reduction was observed only between the 0.05% and 1%CsA formulations. The gene expression profiles indicated that 12, 18, 17 genes were downregulated by 0.05%CsA, 0.1%CsA, 1%CsA, respectively. Among them, the genes significantly downregulated were: IL1A, IL1R1, and TLR4 with 0.05%CsA; H2-Eb1, IL1A, IL1B, IL1RN, IL6, TGFB2, TGFB3, TLR2, TLR3, and TLR4 with 0.1%CsA; IL1B, IL6, TGFB3, and TLR4 with 1%CsA. TGFB1 and TGFBR1 were the only genes upregulated in all groups, but only TGFB1 upregulation reached significance. IL6RA was significantly upregulated by 0.05%CsA.

CONCLUSIONS

This study indicates that the three CsA formulations effectively modulated TLR4, TGFβ1, IL1, and IL6 pathways to reduce corneal epithelium lesions in a mouse model of severe dry eye. The study also suggests that the different anti-inflammatory eye drops modulated inflammatory genes in a slightly different manner.

From stability to dynamics: understanding molecular mechanisms of regulatory T cells through Foxp3 transcriptional dynamics

Studies on regulatory T cells (T_reg) have focused on thymic T_reg as a stable lineage of immunosuppressive T cells, the differentiation of which is controlled by the transcription factor forkhead box protein 3 (Foxp3). This lineage perspective, however, may constrain hypotheses regarding the role of Foxp3 and T_regin vivo, particularly in clinical settings and immunotherapy development. In this review, we synthesize a new perspective on the role of Foxp3 as a dynamically expressed gene, and thereby revisit the molecular mechanisms for the transcriptional regulation of Foxp3. In particular, we introduce a recent advancement in the study of Foxp3‐mediated T cell regulation through the development of the Timer of cell kinetics and activity (Tocky) system, and show that the investigation of Foxp3 transcriptional dynamics can reveal temporal changes in the differentiation and function of T_regin vivo. We highlight the role of Foxp3 as a gene downstream of T cell receptor (TCR) signalling and show that temporally persistent TCR signals initiate Foxp3 transcription in self‐reactive thymocytes. In addition, we feature the autoregulatory transcriptional circuit for the Foxp3 gene as a mechanism for consolidating T_reg differentiation and activating their suppressive functions. Furthermore, we explore the potential mechanisms behind the dynamic regulation of epigenetic modifications and chromatin architecture for Foxp3 transcription. Lastly, we discuss the clinical relevance of temporal changes in the differentiation and activation of T_reg.

Invasive candidiasis: future directions in non-culture based diagnosis

INTRODUCTION

Delayed initial antifungal therapy is associated with high mortality rates caused by invasive candida infections, since accurate detection of the opportunistic pathogenic yeast and its identification display a diagnostic challenge. diagnosis of candida infections relies on time-consuming methods such as blood cultures, serologic and histopathologic examination. to allow for fast detection and characterization of invasive candidiasis, there is a need to improve diagnostic tools. trends in diagnostics switch to non-culture-based methods, which allow specified diagnosis within significantly shorter periods of time in order to provide early and appropriate antifungal treatment. Areas covered: within this review comprise novel pathogen- and host-related testing methods, e.g. multiplex-PCR analyses, T2 magnetic resonance, fungus-specific DNA microarrays, microRNA characterization or analyses of IL-17 as biomarker for early detection of invasive candidiasis. Expert commentary: Early recognition and diagnosis of fungal infections is a key issue for improved patient management. As shown in this review, a broad range of novel molecular based tests for the detection and identification of Candida species is available. However, several assays are in-house assays and lack standardization, clinical validation as well as data on sensitivity and specificity. This underscores the need for the development of faster and more accurate diagnostic tests.

Development of Inflammatory Bowel Disease Is Linked to a Longitudinal Restructuring of the Gut Metagenome in Mice

The gut microbiome is linked to inflammatory bowel disease (IBD) severity and altered in late-stage disease. However, it is unclear how gut microbial communities change over the course of IBD development, especially in regard to function. To investigate microbiome-mediated disease mechanisms and discover early biomarkers of IBD, we conducted a longitudinal metagenomic investigation in an established mouse model of IBD, where damped transforming growth factor β (TGF-β) signaling in T cells leads to peripheral immune activation, weight loss, and severe colitis. IBD development is associated with abnormal gut microbiome temporal dynamics, including damped acquisition of functional diversity and significant differences in abundance trajectories for KEGG modules such as glycosaminoglycan degradation, cellular chemotaxis, and type III and IV secretion systems. Most differences between sick and control mice emerge when mice begin to lose weight and heightened T cell activation is detected in peripheral blood. However, levels of lipooligosaccharide transporter abundance diverge prior to immune activation, indicating that it could be a predisease indicator or microbiome-mediated disease mechanism. Taxonomic structure of the gut microbiome also significantly changes in association with IBD development, and the abundances of particular taxa, including several species of Bacteroides, correlate with immune activation. These discoveries were enabled by our use of generalized linear mixed-effects models to test for differences in longitudinal profiles between healthy and diseased mice while accounting for the distributions of taxon and gene counts in metagenomic data. These findings demonstrate that longitudinal metagenomics is useful for discovering the potential mechanisms through which the gut microbiome becomes altered in IBD. IMPORTANCE IBD patients harbor distinct microbial communities with functional capabilities different from those seen with healthy people. But is this cause or effect? Answering this question requires data on changes in gut microbial communities leading to disease onset. By performing weekly metagenomic sequencing and mixed-effects modeling on an established mouse model of IBD, we identified several functional pathways encoded by the gut microbiome that covary with host immune status. These pathways are novel early biomarkers that may either enable microbes to live inside an inflamed gut or contribute to immune activation in IBD mice. Future work will validate the potential roles of these microbial pathways in host-microbe interactions and human disease. This study was novel in its longitudinal design and focus on microbial pathways, which provided new mechanistic insights into the role of gut microbes in IBD development.

Complex Roles of Microglial Cells in Ischemic Stroke Pathobiology: New Insights and Future Directions

Ischemic stroke constitutes the major cause of death and disability in the industrialized world. The interest in microglia arose from the evidence outlining the role of neuroinflammation in ischemic stroke pathobiology. Microglia constitute the powerhouse of innate immunity in the brain. Microglial cells are highly ramified, and use these ramifications as sentinels to detect changes in brain homeostasis. Once a danger signal is recognized, cells become activated and mount specialized responses that range from eliminating cell debris to secreting inflammatory signals and trophic factors. Originally, it was suggested that microglia play essentially a detrimental role in ischemic stroke. However, recent reports are providing evidence that the role of these cells is more complex than what was originally thought. Although these cells play detrimental role in the acute phase, they are required for tissue regeneration in the post-acute phases. This complex role of microglia in ischemic stroke pathobiology constitutes a major challenge for the development of efficient immunomodulatory therapies. This review aims at providing an overview regarding the role of resident microglia and peripherally recruited macrophages in ischemic pathobiology. Furthermore, the review will highlight future directions towards the development of novel fine-tuning immunomodulatory therapeutic interventions.

SH479, a Betulinic Acid Derivative, Ameliorates Experimental Autoimmune Encephalomyelitis by Regulating the T Helper 17/Regulatory T Cell Balance

CD4⁺ T helper cells, especially T helper 17 (T_H17) cells, combined with immune regulatory network dysfunction, play key roles in autoimmune diseases including multiple sclerosis (MS). Betulinic acid (BA), a natural pentacyclic triterpenoid, has been reported to be involved in anti-inflammation, in particular having an inhibitory effect on proinflammatory cytokine interleukin 17 (IL-17) and interferon-γ (IFN-γ) production. In this study, we screened BA derivatives and found a BA derivative, SH479, that had a greater inhibitory effect on T_H17 differentiation. Our further analysis showed that SH479 had a greater inhibitory effect on T_H17 and T_H1, and a more stimulatory effect on regulatory T (Treg) cells. To evaluate the effects of SH479 on autoimmune diseases in vivo, we employed the extensively used MS mouse model experimental autoimmune encephalomyelitis (EAE). Our results showed that SH479 ameliorated clinical and histologic signs of EAE in both prevention and therapeutic protocols by regulating the T_H17/Treg balance. SH479 dose-dependently reduced splenic lymphocyte proinflammatory factors and increased anti-inflammatory factors. Moreover, SH479 specifically inhibited splenic lymphocyte viability from EAE mice but not normal splenic lymphocyte viability. At the molecular level, SH479 inhibited T_H17 differentiation by regulating signal transducer and activator of transcription-3 (STAT3) phosphorylation, DNA binding activity, and recruitment to the Il-17a promoter in CD4⁺ T cells. Furthermore, SH479 promoted the STAT5 signaling pathway and inhibited the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signaling pathway. Together, our data demonstrated that SH479 ameliorated EAE by regulating the T_H17/Treg balance through inhibiting the STAT3 and NF-κB pathways while activating the STAT5 pathway, suggesting that SH479 is a potential novel drug candidate for autoimmune diseases including MS.

Expression of Treg/Th17 cells as well as related cytokines in patients with inflammatory bowel disease

OBJECTIVE

To investigate the expressions of peripheral regulatory T cells (Treg) and T helper cells (Th17) as well as related cytokines in peripheral blood of patients with inflammatory bowel disease (IBD).

METHODS

One hundred four cases of IBD patients admitted in our hospital were selected for this study. One hundred cases of people receiving healthy physical examination were included in the control group in the corresponding period. The levels of CD4⁺CD25⁺Treg and Th17 subsets were analyzed in peripheral blood of two groups using flow cytometry. The expressions of IL-10, TGF-β1, IL-17 and IL-23 mRNA and protein were detected using real-time fluorescence quantitative PCR and ELISA.

RESULTS

Compared with the control group, the proportion of Treg in peripheral blood was decreased significantly in observation group (P<0.05), the proportion of Th17 cells was increased significantly (P<0.05), and Treg/Th17 was decreased significantly (P<0.05). Compared with the control group, the expressions of IL-10 and TGF-β1 mRNA and protein in peripheral blood of patients were significantly down-regulated in observation group, while the expressions of Th17 cytokines IL-17 and IL-23 mRNA and protein were significantly increased (P<0.05).

CONCLUSION

The proportion of Th17 and increased cytokine level suggested the inflammatory level was higher in IBD patients. The down regulations of Treg and cytokine suggested that the immunosuppression function was down-regulated in IBD patients, and the disproportionality might be one of the mechanisms of IBD.

The many faces of interleukin-17 in inflammatory skin diseases

Interleukin (IL)-17 is an emerging target for inflammatory skin disorders. Given the remarkable success of its therapeutic inhibition in psoriasis, the pathogenic role of this cytokine is being explored in other immune-mediated diseases. Interestingly, IL-17 is linked to particular skin conditions where its activation coincides with disease flares. The leading hypothesis for its contribution to proinflammatory signalling cascades is driving inflammasome activation. However, IL-17 stimulation also releases a range of noninflammasome-related cytokines from human skin. Furthermore, a role in cytotoxic responses and an important interplay with the microbiome is hypothesized. While treatment failure would be surprising in neutrophilic dermatoses, the picture might be more complex in lymphocyte-mediated conditions. Nonetheless, increasing insights into the pathogenesis suggest that beneficial responses are also probable in the latter conditions. Study of this pathway in the skin reveals some intriguing aspects of the IL-17-related immunological network.

Astragalus polysaccharide attenuates rat experimental colitis by inducing regulatory T cells in intestinal Peyer’s patches

AIM: To explore probable mechanism underlying the therapeutic effect of Astragalus polysaccharide (APS) against experimental colitis.

METHODS: Thirty-two Sprague-Dawley rats were randomly divided into four groups. Colitis was induced with 2, 4, 6-trinitrobenzene sulfonic acid (TNBS). The rats with colitis were treated with 400 mg/kg of APS for 7 d. The therapeutic effect was evaluated by colonic weight, weight index of the colon, colonic length, and macroscopic and histological scores. The levels of regulatory T (Treg) cells in Peyer’s patches were measured by flow cytometry, and cytokines in colonic tissue homogenates were analyzed using enzyme-linked immunosorbent assay. The expression of related orphan receptor-γt (ROR-γt), IL-23 and STAT-5a was measured by Western blot.

RESULTS: After 7-d treatment with APS, the weight index of the colon, colonic weight, macroscopical and histological scores were decreased, while the colonic length was increased compared with the model group. The expression of interleukin (IL)-2, IL-6, IL-17, IL-23 and ROR-γt in the colonic tissues was down-regulated, but Treg cells in Peyer’s patches, TGF-β and STAT5a in the colonic tissues were up-regulated.

CONCLUSION: APS effectively ameliorates TNBS-induced experimental colitis in rats, probably through restoring the number of Treg cells, and inhibiting IL-17 levels in Peyer’s patches.

Molecular Mechanisms of the Action of Vitamin A in Th17/Treg Axis in Multiple Sclerosis

Multiple sclerosis (MS) is an autoinflammatory disease of the central nervous system (CNS). The immunopathogenesis of this disease involves an impaired balance of T helper (Th) 17 cells and regulatory T (Tregs) cells. MS is an autoinflammatory disease characterized by the degeneration of the CNS. For many years, MS has been considered to be an autoreactive Th1 and Th17 cell-dominated disease. The activity and number of Th17 cells are increased in MS; however, the function and number of Treg cells are reduced. Therefore, in MS, the balance between Th17 cells and Treg cells is impaired. Th17 cells produce pro-inflammatory cytokines, which play a role in experimental autoimmune encephalomyelitis (EAE) and MS. However, Treg cell-mediated production of cytokines maintains immune homeostasis and can ameliorate the progression of MS. These observations, therefore, confirm the pathogenic and protective role of Th17 and Treg cells, respectively, and highlight the importance of maintaining the balance of both of these cell types. Evidence suggests that vitamin A and its active metabolites (all-trans-retinoic acid and 9-cis-retinoic acid) modulate the imbalance of Th17 and Treg cells through multiple molecular pathways and can be considered as a promising target in the prevention and treatment of MS.

Interplay among cytokines and T cell subsets in the progression and control of immune-mediated diseases

Cytokines serve as key mediators of inflammation and tissue damage in a variety of immune-mediated disorders. The induction, progression, and resolution of inflammation in such disorders are characterized by a dynamic balance between both the pro-inflammatory and anti-inflammatory cytokines as well as the pathogenic and protective T cell subsets. Over the past two decades, the roles of the interleukin-17 (IL-17) /IL-23 axis and the T helper 17 (Th17)/ T regulatory (Treg) cell balance in the pathogenesis of autoimmunity and other inflammatory diseases have extensively been analyzed, and their significance validated. However, these studies, coupled with others devoted to well-established Th1/Th2 cytokines, have unraveled some challenging issues including the dual action of cytokines and the plasticity of T cell subsets. Nevertheless, major positive advances have also been made regarding cytokines and T cell subsets as therapeutic targets/agents. In this special issue, "Cytokines in Immune Pathology and Therapy," leading experts have shared their research work and perspectives on the roles of cytokines in the development and control of immune-mediated diseases. An outline of 14 articles in the first volume is presented here. The second volume will follow soon.

The Effect of Vitamin A Supplementation on FoxP3 and TGF-β Gene Expression in Avonex-Treated Multiple Sclerosis Patients

Multiple sclerosis (MS) is an autoinflammatory condition of the central nervous system with impaired T helper (Th)17 and regulatory T cell (Treg) balance that is involved in disease immunopathogenesis. The vitamin A active metabolite, retinoic acid, can re-establish this imbalance through the modulation of gene expression of specific nuclear receptors including Forkhead box P3 (FoxP3). At present, few data exist on the impact of vitamin A supplementation on T cell balance. This study reports the results of a clinical trial, over a 6-month period, of 36 relapsing-remitting MS (RRMS) patients that received vitamin A (25,000 IU retinyl palmitate) or placebo (one capsule of placebo per day). Peripheral blood mononuclear cells were isolated from patients, and the expression of FoxP3 and transforming growth factor (TGF)-β gene expression was measured using real-time PCR at the beginning and end of the study. The results of this study showed that vitamin A upregulated TGF-β and FoxP3 gene expression. Therefore, vitamin A supplementation can be considered as a new approach in MS prevention and treatment.

Normocaloric low cholesterol diet modulates Th17/Treg balance in patients with chronic hepatitis C virus infection

Hepatitis C virus (HCV) infection is associated with hepatic and extrahepatic manifestations, including immunological disorders. Chronic Hepatitis C (CHC) is often characterized by cholesterol and lipid metabolism alterations, leading to hepatic steatosis. Cholesterol metabolism, in fact, is crucial for the viral life cycle. Recent works described that a higher dietary cholesterol intake is associated with the progression of HCV-related liver disease. CHC patients have increased levels of T helper 17 (Th17)-cells, a lymphocytic population involved in the pathogenesis of liver inflammation and autoimmune hepatitis. The balance between Th17 and regulatory T (Treg) cells is crucial for chronic inflammation and autoimmunity. Th17-cell differentiation is deeply influenced by the activation LXRs, nuclear receptors modulating cholesterol homeostasis. Moreover, HCV may affect these nuclear receptors, and cholesterol metabolism, through both direct and indirect mechanisms. On these bases, we hypothesized that modulation of cholesterol levels through Normocaloric Low Cholesterol Diet (NLCD) may represent an innovative strategy to reduce the progression of HCV infection, through the modulation of peripheral Th17/Treg balance. To this end, we performed a pilot study to investigate whether a Normocaloric Low Cholesterol Diet may be able to modulate Th17/Treg balance in patients affected by chronic HCV infection. After 30 days of NLCD CHC patients showed a significant reduction in Th17 cells frequency, which correlated with strong reduction of IL-17 and IL-22 serum levels. At the same time, we appreciated an increase in the percentage of Treg cells, thus improving Treg/Th17 balance. Moreover, we observed an increased expression of LXRs and their target genes: SREBP-1c and ABCA-1. In conclusion, NLCD finely regulates Th17/Treg balance, improving immune system response in CHC patients. This study could pave the way for new treatments of CHC patients, suggesting that change in lifestyle could support the management of these patients, promoting well-being and possibly hindering disease progression.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02038387.

The nuclear IκB family protein IκBNS influences the susceptibility to experimental autoimmune encephalomyelitis in a murine model

The nuclear IκB family protein IκB_NS is expressed in T cells and plays an important role in Interferon (IFN)-γ and Interleukin (IL)-2 production. IκB-ζ, the most similar homolog of IκB_NS, plays an important role in the generation of T helper (Th)17 cells in cooperation with RORγt, a master regulator of Th17 cells. Thus, IκB-ζ deficient mice are resistant to Th17-dependent experimental autoimmune encephalomyelitis (EAE). However, IκB-ζ deficient mice develop the autoimmune-like Sjögren syndrome with aging. Here we found that IκB_NS-deficient (Nfkbid^−/−) mice show resistance against developing Th17-dependent EAE. We found that Nfkbid^−/− T cells have decreased expression of IL-17-related genes and RORγt in response to Transforming Growth Factor (TGF)-β1 and IL-6 stimulation. Thus, IκB_NS plays a pivotal role in the generation of Th17 cells and in the control of Th17-dependent EAE.

Human Th1 dichotomy: origin, phenotype and biologic activities

The great variety of pathogens present in the environment has obliged the immune system to evolve different mechanisms for tailored and maximally protective responses. Initially, two major types of CD4+ T helper (Th) effector cells were identified, and named as type 1 (Th1) and type (Th2) cells because of the different cytokines they produce. More recently, a third type of CD4+ Th effectors has been identified and named as Th17 cells. Th17 cells, however, have been found to exhibit high plasticity because they rapidly shift into the Th1 phenotype in the inflammatory sites. Therefore, in these sites usually there is a dichotomic mixture of classic and non classic (Th17-derived) Th1 cells. In humans, non classic Th1 cells express CD161, as well as the retinoic acid orphan receptor C, IL-17 receptor E, IL-1RI, CCR6, and IL-4-induced gene 1 and Tob-1, which are all virtually absent from classic Th1 cells. The possibility to distinguish these two cell subsets may allow the opportunity to better establish their respective pathogenic role in different chronic inflammatory disorders. In this review, we discuss the different origin, the distinctive phenotypic features and the major biologic activities of classic and non classic Th1 cells. This article is protected by copyright. All rights reserved.

Interplay of T Helper 17 Cells with CD4(+)CD25(high) FOXP3(+) Tregs in Regulation of Allergic Asthma in Pediatric Patients

Background. There is evidence that Tregs are important to prevent allergic diseases like asthma but limited literature exists on role of T_H17 cells in allergic diseases. Methods. Fifty children with asthma and respiratory allergy (study group) and twenty healthy children (control group) were recruited in this study. Total IgE levels and pulmonary function tests were assessed. The expression of Tregs and cytokines was determined by flow cytometry. Results. The average level of total IgE in study group (316.8 ± 189.8 IU/mL) was significantly higher than controls (50 ± 17.5 IU/mL, P < 0.0001). The frequency of T_H17 cells and culture supernatant level of IL-17 in study group (12.09 ± 8.67 pg/mL) was significantly higher than control group (2.01 ± 1.27 pg/mL, P < 0.001). Alternatively, the frequency of FOXP3 level was significantly lower in study group [(49.00 ± 13.47)%] than in control group [(95.91 ± 2.63)%] and CD4⁺CD25⁺FOXP3⁺ to CD4⁺CD25⁺ ratio was also significantly decreased in study group [(6.33 ± 2.18)%] compared to control group [(38.61 ± 11.04)%]. The total serum IgE level is negatively correlated with FOXP3 level (r = −0.5273, P < 0.0001). The FOXP3 expression is negatively correlated with the IL-17 levels (r = −0.5631, P < 0.0001) and IL-4 levels (r = −0.2836, P = 0.0460). Conclusions. Imbalance in T_H17/Tregs, elevated IL-17, and IL-4 response and downregulation of FOXP3 were associated with allergic asthma.

Microglial activation milieu controls regulatory T cell responses

Although mechanisms leading to brain-specific inflammation and T cell activation have been widely investigated, regulatory mechanisms of local innate immune cells in the brain are only poorly understood. In this study, to our knowledge we show for the first time that MHC class II(+)CD40(dim)CD86(dim)IL-10(+) microglia are potent inducers of Ag-specific CD4(+)Foxp3(+) regulatory T cells (Tregs) in vitro. Microglia differentially regulated MHC class II expression, costimulatory molecules, and IL-10 depending on the amount of IFN-γ challenge and Ag dose, promoting either effector T cell or Treg induction. Microglia-induced Tregs were functionally active in vitro by inhibiting Ag-specific proliferation of effector T cells, and in vivo by attenuating experimental autoimmune encephalomyelitis disease course after adoptive transfer. These results indicate that MHC class II(+)CD40(dim)CD86(dim)IL-10(+) microglia have regulatory properties potentially influencing local immune responses in the CNS.

Genome-wide analysis of the heat stress response in Zebu (Sahiwal) cattle

Environmental-induced hyperthermia compromises animal production with drastic economic consequences to global animal agriculture and jeopardizes animal welfare. Heat stress is a major stressor that occurs as a result of an imbalance between heat production within the body and its dissipation and it affects animals at cellular, molecular and ecological levels. The molecular mechanism underlying the physiology of heat stress in the cattle remains undefined. The present study sought to evaluate mRNA expression profiles in the cattle blood in response to heat stress. In this study we report the genes that were differentially expressed in response to heat stress using global scale genome expression technology (Microarray). Four Sahiwal heifers were exposed to 42°C with 90% humidity for 4h followed by normothermia. Gene expression changes include activation of heat shock transcription factor 1 (HSF1), increased expression of heat shock proteins (HSP) and decreased expression and synthesis of other proteins, immune system activation via extracellular secretion of HSP. A cDNA microarray analysis found 140 transcripts to be up-regulated and 77 down-regulated in the cattle blood after heat treatment (P<0.05). But still a comprehensive explanation for the direction of fold change and the specific genes involved in response to acute heat stress still remains to be explored. These findings may provide insights into the underlying mechanism of physiology of heat stress in cattle. Understanding the biology and mechanisms of heat stress is critical to developing approaches to ameliorate current production issues for improving animal performance and agriculture economics.

Metabolic control of the Treg/Th17 axis

The interplay of the immune system with other aspects of physiology is continually being revealed and in some cases studied in considerable mechanistic detail. A prime example is the influence of metabolic cues on immune responses. It is well appreciated that upon activation, T cells take on a metabolic profile profoundly distinct from that of their quiescent and anergic counterparts; however, a number of recent breakthroughs have greatly expanded our knowledge of how aspects of cellular metabolism can shape a T-cell response. Particularly important are findings that certain environmental cues can tilt the delicate balance between inflammation and immune tolerance by skewing T-cell fate decisions toward either the T-helper 17 (Th17) or T-regulatory (Treg) cell lineage. Recognizing the unappreciated immune-modifying potential of metabolic factors and particularly those involved in the generation of these functionally opposing T-cell subsets will likely add new and potent therapies to our repertoire for treating immune mediated pathologies. In this review, we summarize and discuss recent findings linking certain metabolic pathways, enzymes, and by-products to shifts in the balance between Th17 and Treg cell populations. These advances highlight numerous opportunities for immune modulation.

The Th17 family: flexibility follows function

Discovery of the T-helper 17 (Th17) subset heralded a major shift in T-cell biology and immune regulation. In addition to defining a new arm of the adaptive immune response, studies of the Th17 pathway have led to a greater appreciation of the developmental flexibility, or plasticity, that is a feature of T-cell developmental programs. Since the initial finding that differentiation of Th17 cells is promoted by transforming growth factor-β (TGFβ), it became clear that Th17 cell development overlapped that of induced regulatory T (iTreg) cells. Subsequent findings established that Th17 cells are also unusually flexible in their late developmental programming, demonstrating substantial overlap with conventional Th1 cells through mechanisms that are just beginning to be understood but would appear to have important implications for immunoregulation at homeostasis and in immune-mediated diseases. Herein we examine the developmental and functional features of Th17 cells in relation to iTreg cells, Th1 cells, and Th22 cells, as a basis for understanding the contributions of this pathway to host defense, immune homeostasis, and immune-mediated disease.

Cytokine mediated tissue fibrosis

Acute inflammation is a recognised part of normal wound healing. However, when inflammation fails to resolve and a chronic inflammatory response is established this process can become dysregulated resulting in pathological wound repair, accumulation of permanent fibrotic scar tissue at the site of injury and the failure to return the tissue to normal function. Fibrosis can affect any organ including the lung, skin, heart, kidney and liver and it is estimated that 45% of deaths in the western world can now be attributed to diseases where fibrosis plays a major aetiological role. In this review we examine the evidence that cytokines play a vital role in the acute and chronic inflammatory responses that drive fibrosis in injured tissues. This article is part of a Special Issue entitled: Fibrosis: Translation of basic research to human disease.

Myeloid TGF-β signaling contributes to colitis-associated tumorigenesis in mice

Myeloid cells have a critical role in maintaining intestinal homeostasis and regulating the development of inflammatory bowel disease and colitis-associated cancer (CAC). However, the signaling pathways that control the function of colonic myeloid cells in these pathological processes are still poorly defined. In this study, we demonstrate that transforming growth factor-β (TGF-β) signaling in colonic myeloid cells is significantly involved in the development of CAC. Myeloid TGF-β receptor II (Tgfbr2)-deficient mice showed reduced susceptibility to chemically induced colitis-associated tumorigenesis, as evidenced by decreases in number and size of tumors. Myeloid Tgfbr2 deficiency markedly decreased the production of interleukin-6 and tumor necrosis factor-α, two proinflammatory cytokines that are essential for colonic tumorigenesis; in addition, a marked increase in the proportions of Foxp3+CD4+ regulatory T cells was observed in the colonic lamina propria in the initial stage of CAC. Loss of myeloid Tgfbr2 was associated with a decrease in the presence of F4/80 positive macrophages and a downregulation of phosphorylated STAT3, proliferative cell nuclear antigen and cyclin D1 expression in colonic adenoma tissues. TGF-β enhanced macrophage recruitment, at least in part, through modulating the expression of the chemokine (C-C motif) receptor 2 (CCR2) ligands in tumor environment and the CCR2 signaling in macrophages. Collectively, these results suggest that myeloid TGF-β signaling modulates intestinal inflammation and significantly promotes tumorigenesis in the development of colitis-associated colon cancer.

TGFβ1, an epidermal controller of skin dendritic cell homeostasis

Transforming growth factor-β1 (TGFβ1) is generally regarded as an anti-inflammatory cytokine. However, previous studies suggest that TGFβ1 can promote immune responses under certain conditions. In this issue, Mohammed et al. report that epidermal keratinocyte-derived TGFβ1 alone can alter homeostasis of multiple cutaneous dendritic cell (DC) subsets, which may enhance skin inflammation. These findings may provide a better understanding of the pathogenesis of inflammatory skin disorders such as psoriasis, although how keratinocyte-derived TGFβ1 regulates cutaneous DCs under physiological and inflammatory conditions should be further addressed.

Increased peripheral RORα and RORγt mRNA expression is associated with acute-on-chronic hepatitis B liver failure

T helper cells17 (Th17) have accurate but inconclusive roles in the pathogenesis of acute-on-chronic hepatitis B liver failure (ACHBLF). Retinoic acid-related orphan receptor γ t(RORγt) and RORα are two lineage-specific nuclear receptors directly mediating Th17 differentiation. This study was aimed to evaluate the gene expression of RORα and RORγt and their potential role in ACHBLF. Forty patients with liver failure, 30 with chronic hepatitis B (CHB) and 20 healthy controls were studied. The mRNA levels of RORα and RORγt in peripheral mononuclear cells were determined by quantitative real-time polymerase chain reaction. The frequency of peripheral Th17 cells was determined using flow cytometry. The serum levels of interleukin-6(IL-6), transforming growth factor -β (TGF-β), interleukin-17(IL-17), interleukin-23(IL-23) and interferon-γ (IFN-γ) were measured by enzyme-linked immunosorbent assay. The frequency of peripheral Th17 cells in patients with liver failure was significantly increased compared to patients with CHB and controls. The peripheral mRNA levels of RORα and RORγt in hepatitis B-associated acute-on-chronic liver failure were significantly higher than in patients with CHB and controls as were the serum levels of IL-6 and TGF-β. The serum level of IFN-γ in patients with acute-on-chronic liver failure from HBV was significantly higher than patients with CHB but lower than controls. In patients with acute-on-chronic liver failure associated with HBV, RORγt, IL-6 and IL-23 were positively correlated with the frequency of Th17 cells, while RORα, TGF-β and IFN-γ had no correlation with the latter. The mRNA level of RORγt was positively correlated with model of end-stage liver disease (MELD) score, but there was no correlation of RORα and MELD score. RORγt plays an important role in the pathogenesis of acute-on-chronic HBV-associated liver failure and might be considered to be a candidate factor consistent with the severity of disease.

Nuclear orphan receptor NR2F6 directly antagonizes NFAT and RORγt binding to the Il17a promoter

Interleukin-17A (IL-17A) is the signature cytokine produced by Th17 CD4(+) T cells and has been tightly linked to autoimmune pathogenesis. In particular, the transcription factors NFAT and RORγt are known to activate Il17a transcription, although the detailed mechanism of action remains incompletely understood. Here, we show that the nuclear orphan receptor NR2F6 can attenuate the capacity of NFAT to bind to critical regions of the Il17a gene promoter. In addition, because NR2F6 binds to defined hormone response elements (HREs) within the Il17a locus, it interferes with the ability of RORγt to access the DNA. Consistently, NFAT and RORγt binding within the Il17a locus were enhanced in Nr2f6-deficient CD4(+) Th17 cells but decreased in Nr2f6-overexpressing transgenic CD4(+) Th17 cells. Taken together, our findings uncover an example of antagonistic regulation of Il17a transcription through the direct reciprocal actions of NR2F6 versus NFAT and RORγt.

Sphingosine kinase and sphingosine-1-phosphate receptors: novel therapeutic targets of rheumatoid arthritis?

Rheumatoid arthritis (RA) is a chronic, destructive, autoimmune joint disease characterized by elevated levels of proinflammatory cytokine production. Sphingosine kinase (SphK) phosphorylates sphingosine into sphingosine-1-phosphate. Synovial fluid of RA patients exhibits significantly higher levels of S1P than their non-inflammatory osteoarthritis counterparts. SphK blockade suppresses cytokines and MMP-9 release in RA peripheral blood mononuclear cells. In addition, downregulation of SphK1 either through a specific siRNA approach or transgenic human TNF-α SphK1-deficient mice (hTNF-α/SphK1(-/-)) exhibit significantly less synovial inflammation and joint pathology. By contrast, SphK2 modulation leads to disease exacerbation. These results clearly demonstrate that such anti- and proinflammatory potential of SphK1/2 modulation may alter the outcome in RA synovitis and raises the possibility that drugs that specifically target SphK1 activity may play a beneficial role in the treatment of RA and other autoimmune rheumatic diseases.

Defining the human T helper 17 cell phenotype

T helper (Th) 17 cells represent a third effector arm of CD4 T cells and complement the function of the Th1 and Th2 cell lineages. Here, we provide an overview of the transcription factors, cytokines, chemokines, and cytokine and chemokine receptors that characterize the Th17 cell phenotype. Data relevant for human Th17 cells are emphasized, with a focus on the function of two markers that have recently been associated with human Th17 cells, CD161 and interleukin-4-induced gene 1 (IL4I1). Also considered is the basis of Th17 cell plasticity towards the Th1 lineage, and we suggest that this plasticity together with the limited expansion of Th17 cells in response to T cell receptor (TCR) triggering accounts for the rarity of human Th17 cells in inflamed tissues.

T helper 17 cells and regulatory T-cell imbalance in paediatric patients with asthma

Asthma is a chronic inflammatory disorder of the lung, which is thought to be determined by the balance between the T helper (Th)2 and Th1 responses. This study evaluated whether the balance between Th17 cells and regulatory T cells (T(reg)) was impaired in asthma patients. The proportion of peripheral blood Th17 cells of the total CD4(+) cell population in asthma patients was significantly higher than in controls (mean ± SD 0.72 ± 0.5% versus 0.31 ± 0.4%, respectively). The proportion of peripheral T(reg) cells in asthma patients was significantly lower than in controls (mean ± SD 12.1 ± 4.6% versus 27.2 ± 7.5%, respectively). Analysis of mRNA generally confirmed the flow cytometry data, suggesting that the changes in cytokine levels were mediated at the transcription level. In paediatric asthma patients, the CD4(+) T-cell phenotype was skewed toward the Th17 phenotype, suggesting that a Th17/T(reg) functional imbalance plays a role in asthma.

Nuclear factor-κB in immunity and inflammation: the Treg and Th17 connection

Although nuclear factor-kB (NF-kB) is generally considered to be a pro-inflammatory transcription factor, recent studies indicate that it also plays a critical role in the development of an anti-inflammatory T cell subset called regulatory T (Treg) cells. Two NF-kB proteins, c-Rel and p65, drive the development of Treg cells by promoting the formation of a Foxp3-specific enhanceosome. Consequently, c-Rel-deficient mice have marked reductions in Treg cells, and c-Rel-deficient T cells are compromised in Treg cell differentiation. However, with the exception of Foxp3, most NF-kB target genes in immune cells are pro-inflammatory. These include several Th17-related cytokine genes and the retinoid-related orphan receptor-g (Rorg or Rorc) that specifies Th17 differentiation and lineage-specific function. T cells deficient in c-Rel or p65 are significantly compromised in Th17 differentiation, and c-Rel -deficient mice are defective in Th17 responses. Thus, NF-kB is required for the development of both anti-inflammatory Treg and pro-inflammatory Th17 cells.

Th17 cell accumulation is decreased during chronic experimental colitis by (n-3) PUFA in Fat-1 mice

During colon inflammation, Th17 cells and immunosuppressive regulatory T cells (Treg) are thought to play promotive and preventative roles, respectively. Dietary (n-3) PUFA favorably modulate intestinal inflammation in part by downregulating T-cell activation and functionality. We used the Fat-1 mouse, a genetic model that synthesizes long-chain (n-3) PUFA de novo, to test the hypothesis that (n-3) PUFA protect against colonic inflammation by modulating the polarization of Treg and Th17 cells during colitis. Male and female wild-type (WT) and Fat-1 mice were administered dextran sodium sulfate (DSS) in the drinking water (2.5%) to induce acute (5 d DSS) or chronic (3 cycles DSS) colitis and the percentage of Treg and Th17 cells residing locally [colonic lamina propria (cLP)] and systemically (spleen) was determined by flow cytometry. The percentage of Treg in either tissue site was unaffected by genotype (P > 0.05); however, during chronic colitis, the percentage of Th17 cells residing in both the spleen and cLP was lower in Fat-1 mice compared to WT mice (P < 0.05). Colonic mucosal mRNA expression of critical Th17 cell cytokines and chemokine receptors (IL-17F, IL-21, and CCR6) were lower, whereas expression of the Th17 cell suppressive cytokine, IL-27, was greater in Fat-1 mice compared to WT mice during chronic colitis (P < 0.05). Moreover, colon histological scores were improved in Fat-1 mice (P < 0.05). Collectively, these results demonstrate for the first time, to our knowledge, that (n-3) PUFA can modulate the colonic mucosal microenvironment to suppress Th17 cell accumulation and inflammatory damage following the induction of chronic colitis.