SMAD2 is essential for TGF beta-mediated Th17 cell generation

STAT3 and SOX-5 induce BRG1-mediated chromatin remodeling of RORCE2 in Th17 cells

Retinoid-related orphan receptor gamma t (RORγt) is the lineage-specific transcription factor for T helper 17 (Th17) cells. Our previous study demonstrated that STAT3 likely participates in the activation of RORCE2 (a novel enhancer of the RORγt gene) in Th17 cells. However, the detailed mechanism is still unclear. Here, we demonstrate that both STAT3 and SOX-5 mediate the enhancer activity of RORCE2 in vitro. Deletion of the STAT3 binding site (STAT3-BS) in RORCE2 impaired RORγt expression and Th17 differentiation, resulting in reduced severity of experimental autoimmune encephalomyelitis (EAE). Mechanistically, STAT3 and SOX-5 bind the RORCE2 region and recruit the chromatin remodeling factor BRG1 to remodel the nucleosomes positioned at this region. Collectively, our data suggest that STAT3 and SOX-5 mediate the differentiation of Th17 cells through the induction of BRG1-mediated chromatin remodeling of RORCE2 in Th17 cells.

Intricacies of TGF-β signaling in Treg and Th17 cell biology

Balanced immunity is pivotal for health and homeostasis. CD4+ helper T (Th) cells are central to the balance between immune tolerance and immune rejection. Th cells adopt distinct functions to maintain tolerance and clear pathogens. Dysregulation of Th cell function often leads to maladies, including autoimmunity, inflammatory disease, cancer, and infection. Regulatory T (Treg) and Th17 cells are critical Th cell types involved in immune tolerance, homeostasis, pathogenicity, and pathogen clearance. It is therefore critical to understand how Treg and Th17 cells are regulated in health and disease. Cytokines are instrumental in directing Treg and Th17 cell function. The evolutionarily conserved TGF-β (transforming growth factor-β) cytokine superfamily is of particular interest because it is central to the biology of both Treg cells that are predominantly immunosuppressive and Th17 cells that can be proinflammatory, pathogenic, and immune regulatory. How TGF-β superfamily members and their intricate signaling pathways regulate Treg and Th17 cell function is a question that has been intensely investigated for two decades. Here, we introduce the fundamental biology of TGF-β superfamily signaling, Treg cells, and Th17 cells and discuss in detail how the TGF-β superfamily contributes to Treg and Th17 cell biology through complex yet ordered and cooperative signaling networks.

Downregulation of lncRNA XIST may promote Th17 differentiation through KDM6A-TSAd pathway in neuromyelitis optica spectrum disorders

BACKGROUNDS

Neuromyelitis optica spectrum disorder (NMOSD) is an autoimmune disease with significant female preponderance. X inactive specific transcript (XIST) is a long non-coding RNA (lncRNA) and a key regulator of X-chromosome inactivation which is related to the sex-bias of autoimmunity. And Th17 cell proportion was significantly elevated in NMOSD according to our previous study.

OBJECTIVES

This study aimed to explore the expression levels of lncRNA XIST-KDM6A-TSAd pathway in lymphocytes of female NMOSD patients, and investigate its possible relationship with pathogenesis of NMOSD.

METHODS AND RESULTS

The study enrolled 30 acute-phase untreated female NMOSD patients and 30 age-matched female healthy controls, their lymphocytes were collected for experiments. Microarray as well as validation experiments showed lncRNA XIST was significantly downregulated in the NMOSD group. And the levels of lysine demethylase 6A (KDM6A) decreased in NMOSD and showed significant positive correlation with XIST. The levels of T cell-specific adapter (TSAd) mRNA and protein levels were significantly lower in NMOSD. And Chromatin immunoprecipitation assay demonstrated that NMOSD had more H3K27me3 modification than control at TSAd promoter region.

CONCLUSIONS

The present study introduced a potential pathway that following lncRNA XIST downregulation, which process may promote Th17 differentiation in NMOSD. These findings shed new light on the immune regulation mechanism about lncRNA XIST and related epigenetic features, which may contribute to develop female-specific treatment plans.

Differentiation of IL-26+ TH17 intermediates into IL-17A producers via epithelial crosstalk in psoriasis

Interleukin (IL)-26 is a TH17 cytokine with known antimicrobial and pro-inflammatory functions. However, the precise role of IL-26 in the context of pathogenic TH17 responses is unknown. Here we identify a population of blood TH17 intermediates that produce high levels of IL-26 and differentiate into IL-17A-producing TH17 cells upon TGF-β1 exposure. By combining single cell RNA sequencing, TCR sequencing and spatial transcriptomics we show that this process occurs in psoriatic skin. In fact, IL-26+ TH17 intermediates infiltrating psoriatic skin induce TGF-β1 expression in basal keratinocytes and thereby promote their own differentiation into IL-17A-producing cells. Thus, our study identifies IL-26-producing cells as an early differentiation stage of TH17 cells that infiltrates psoriatic skin and controls its own maturation into IL17A-producing TH17 cells, via epithelial crosstalk involving paracrine production of TGF-β1.

Akkermansia muciniphila, which is enriched in the gut microbiota by metformin, improves cognitive function in aged mice by reducing the proinflammatory cytokine interleukin-6

BACKGROUND

Metformin, a type 2 diabetes treatment, improves the cognitive function of aged mice; however, whether the protective effects of metformin on cognitive function in aged mice are associated with the gut microbiome is poorly understood. Although some studies suggest that the gut microbe composition influences cognitive function and that manipulating the gut microbiota might protect against age-related cognitive dysfunction, there is no direct evidence to validate that the gut microbiota mediates the effect of metformin on cognitive improvement.

RESULTS

In this study, we show that the gut microbiota is altered by metformin, which is necessary for protection against ageing-associated cognitive function declines in aged mice. Mice treated with antibiotics did not exhibit metformin-mediated cognitive function protection. Moreover, treatment with Akkermansia muciniphila, which is enriched by metformin, improved cognitive function in aged mice. Mechanistically, A. muciniphila decreased pro-inflammatory-associated pathways, particularly that of the pro-inflammatory cytokine interleukin (IL)-6, in both the peripheral blood and hippocampal profiles, which was correlated with cognitive function improvement. An IL-6 antibody protected cognitive function, and an IL-6 recombinant protein abolished the protective effect of A. muciniphila on cognitive function in aged mice.

CONCLUSION

This study reveals that A. muciniphila, which is mediated in the gut microbiota by metformin, modulates inflammation-related pathways in the host and improves cognitive function in aged mice by reducing the pro-inflammatory cytokine IL-6. Video Abstract.

Shifting gears: Id3 enables recruitment of E proteins to new targets during T cell development and differentiation

Shifting levels of E proteins and Id factors are pivotal in T cell commitment and differentiation, both in the thymus and in the periphery. Id2 and Id3 are two different factors that prevent E proteins from binding to their target gene cis-regulatory sequences and inducing gene expression. Although they use the same mechanism to suppress E protein activity, Id2 and Id3 play very different roles in T cell development and CD4 T cell differentiation. Id2 imposes an irreversible choice in early T cell precursors between innate and adaptive lineages, which can be thought of as a railway switch that directs T cells down one path or another. By contrast, Id3 acts in a transient fashion downstream of extracellular signals such as T cell receptor (TCR) signaling. TCR-dependent Id3 upregulation results in the dislodging of E proteins from their target sites while chromatin remodeling occurs. After the cessation of Id3 expression, E proteins can reassemble in the context of a new genomic landscape and molecular context that allows induction of different E protein target genes. To describe this mode of action, we have developed the “Clutch” model of differentiation. In this model, Id3 upregulation in response to TCR signaling acts as a clutch that stops E protein activity (“clutch in”) long enough to allow shifting of the genomic landscape into a different “gear”, resulting in accessibility to different E protein target genes once Id3 decreases (“clutch out”) and E proteins can form new complexes on the DNA. While TCR signal strength and cytokine signaling play a role in both peripheral and thymic lineage decisions, the remodeling of chromatin and E protein target genes appears to be more heavily influenced by the cytokine milieu in the periphery, whereas the outcome of Id3 activity during T cell development in the thymus appears to depend more on the TCR signal strength. Thus, while the Clutch model applies to both CD4 T cell differentiation and T cell developmental transitions within the thymus, changes in chromatin accessibility are modulated by biased inputs in these different environments. New emerging technologies should enable a better understanding of the molecular events that happen during these transitions, and how they fit into the gene regulatory networks that drive T cell development and differentiation.

Regenerating myofiber directs Tregs and Th17 responses in inflamed muscle through the intrinsic TGF-β signaling-mediated IL-6 production

Transforming growth factor-β (TGF-β) is considered to be an important immune regulatory cytokine. However, it remains unknown whether and how the muscle fiber specific-TGF-β signaling is directly involved in intramuscular inflammatory regulation by affecting T cells. Here, we addressed these in a mouse tibialis anterior muscle Cardiotoxin injection-induced injury repair model in muscle creatine kinase (MCK)-Cre control or transgenic mice with TGF-β receptor II (TGF-βr2) being specifically deleted in muscle cells (SM TGF-βr2^-/-). In control mice, TGF-β2 and TGF-βr2 were found significantly upregulated in muscle after the acute injury. In mutant mice, deficiency of TGF-β signaling in muscle cells caused more serious muscle inflammation, with the increased infiltration of macrophages and CD4⁺ T cells at the degeneration stage (D4) and the early stage of regeneration (D7) after myoinjury. Notably, the loss of TGF-β signaling in myofibers dramatically affected CD4⁺ T cell function and delayed T cells withdrawal at the later stage of muscle regeneration (D10 and D15), marked by the elevated Th17, but the impaired Tregs response. Furthermore, in vivo and in vitro, the intrinsic TGF-β signaling affected immune behaviors of muscle cells and directed CD4⁺ T cells differentiation by impairing IL-6 production and release. It suggests that local muscle inflammation can be inhibited potentially by directly activating the TGF-β signaling pathway in muscle cells to suppress Th17, but induce Tregs responses. Thus, according to the results of this study, we found a new idea for the control of local acute inflammation in skeletal muscle.NEW & NOTEWORTHY Myofiber mediates muscle inflammatory response through activating the intrinsic TGF-β signaling. The specific TGF-β signaling activation contributes to myofiber IL-6 production and directs muscle-specific Th17 and Treg cell responses.

Study on the Mechanism of Bu-Shen-He-Mai Granules in Improving Renal Damage of Ageing Spontaneously Hypertensive Rats by Regulating Th17 Cell/Tregs Balance

Methods

Blood pressure and urine biochemical indices were recorded. Renal blood flow was evaluated by renal ultrasonography. Transmission electron microscopy (TEM) and HE staining were used to assess kidney and spleen morphology. Renal fibrosis was assessed using Masson staining. Serum levels of IL-6, IL-10, and IL-17A were measured using ELISAs. The density of RORγ and Foxp3 in the spleen was observed by immunofluorescence staining. The levels of Th17 cells and Tregs in blood were detected via flow cytometry. Transcriptome sequencing was performed to screen the targets of BSHM granules in hypertensive kidneys.

Results

BSHM granules decreased SBP by 21.2 mm·Hg and DBP by 8.8 mm·Hg in ageing SHRs (P < 0.05), decreased the levels of urine mALB, β2-Mg, and NAG (P < 0.01), and improved renal blood flow and arteriosclerosis. BSHM granules increased IL-10 expression (P < 0.05) while decreasing IL-6 (P < 0.01) and IL-17A (P < 0.05) levels. BSHM granules improved Foxp3 density and the number of Tregs (P < 0.01) and reduced RORγt density and the number of Th17 cells (P < 0.01). Transcriptome sequencing identified 747 differentially expressed (DE) mRNAs in kidneys after BSHM treatment. GO analysis suggested that BSHM granules act through immunoregulation.

Conclusions

BSHM granules attenuated hypertensive renal damage in ageing SHRs, by significantly increasing Tregs and decreasing Th17 cells.

Mannan-Binding Lectin Regulates the Th17/Treg Axis Through JAK/STAT and TGF-β/SMAD Signaling Against Candida albicans Infection

Background

Mannan-binding lectin (MBL) is a key molecule in innate immunity and activates the lectin complement pathway, which plays an important role in resisting Candida albicans (C. albicans) infection. However, the underlying mechanism of this resistance to infection remains unclear.

Methods

In this study, we investigated how MBL regulates the differentiation of CD4⁺ T cells into T helper type 17 (Th17) and T regulatory (Treg) cells against C. albicans in mice, as well as the underlying mechanisms. We generated MBL double-knockout (KO) mice and infected them with C. albicans by intraperitoneal injection.

Results

Compared with that in wild-type (WT) mice, the percentage of Th17 cells increased in MBL-null mice, whereas Treg cells decreased, indicating that MBL might regulate the Th17/Treg balance. In addition, in MBL-null mice, the expression levels of interleukin (IL)-17A, IL-21, and the master transcription factor of Th17 cells, RORγt, significantly increased. Conversely, IL-10, IL-2, and the Treg-specific transcription factor, Foxp3, decreased. Moreover, we found that the levels of TGF-β and IL-6 upregulated in MBL-null mice. Mechanistically, we found that MBL regulated the TGF-β/SMAD pathway through the inhibition of p-SMAD2 and promotion of p-SMAD3, and mediated the JAK/STAT pathway through the inhibition of p-JAK2 and p-STAT3 and promotion of p-JAK3 and p-STAT5. MBL double-KO mice showed a more severe inflammatory response and significantly lower survival rates with C. albicans infection.

Conclusion

These results suggest that MBL regulates the Th17/Treg cell balance to inhibit inflammatory responses, possibly via IL-6- and TGF-β-mediated JAK/STAT and TGF-β/SMAD signaling, and play an important role in anti-C. albicans infection.

Targeting epigenetically maladapted vascular niche alleviates liver fibrosis in nonalcoholic steatohepatitis

[Figure: see text].

SKI Expression Suppresses Pathogenic Th17 Cell Response and Mitigates Experimental Autoimmune Encephalomyelitis

Pathogenic Th17 cells are critically involved in many autoimmune diseases, while non-pathogenic Th17 cells are more immune regulatory. Understanding the mechanisms of the induction and maintenance of pathogenic Th17 cells will benefit the development of therapeutic treatments of related diseases. We have shown that the transforming growth factor-β (TGFβ) induced SKI degradation and dissociation from Smad4 complex is a prerequisite for TGFβ-induced Th17 cell differentiation. However, it is unclear whether and how SKI regulates pathogenic Th17 differentiation, which does not require TGFβ cytokine. Here we showed that SKI expression was downregulated during pathogenic Th17 cell differentiation and the ectopic expression of SKI abrogated the differentiation of pathogenic Th17 cells. Functionally, using a knock-in mouse model, we found ectopic SKI expression specifically in T cells prevented myelin oligodendrocyte glycoprotein peptide (MOG_33-55) induced experimental autoimmune encephalomyelitis (EAE), an animal model of human multiple sclerosis. We further revealed that induced SKI expression in already differentiated pathogenic Th17 cells reduced the maintenance of Th17 program and ameliorated EAE in an adoptive T cell transfer model. Therefore, our study provides valuable insights of targeting SKI to modulate pathogenic Th17 cell function and treat Th17-related diseases.

Neonatal T Helper 17 Responses Are Skewed Towards an Immunoregulatory Interleukin-22 Phenotype

Newborns are frequently affected by mucocutaneous candidiasis. Th17 cells essentially limit mucosal invasion by commensal Candida spp. Here, we sought to understand the molecular basis for the developmental lack of Th17 cell responses in circulating blood neonatal T cells. Naive cord blood CD4 T cells stimulated in Th17-differentiating conditions inherently produced high levels of the interleukin-22 immunoregulatory cytokine, particularly in the presence of neonatal antigen-presenting cells. A genome-wide transcriptome analysis comparing neonatal and adult naïve CD4 T cells ex vivo revealed major developmental differences in gene networks regulating Small Drosophila Mothers Against Decapentaplegic (SMAD) and Signal Transducer and Activator of Transcription 3 (STAT3) signaling. These changes were functionally validated by experiments showing that the requirement for TGF-β in human Th17 cell differentiation is age-dependent. Moreover, STAT3 activity was profoundly diminished while overexpression of the STAT3 gene restored Th17 cell differentiation capacity in neonatal T cells. These data reveal that Th17 cell responses are developmentally regulated at the gene expression level in human neonates. These developmental changes may protect newborns against pathological Th17 cell responses, at the same time increasing their susceptibility to mucocutaneous candidiasis.

BFAR coordinates TGFβ signaling to modulate Th9-mediated cancer immunotherapy

TGFβ is essential for the generation of anti-tumor Th9 cells; on the other hand, it causes resistance against anti-tumor immunity. Despite recent progress, the underlying mechanism reconciling the double-edged effect of TGFβ signaling in Th9-mediated cancer immunotherapy remains elusive. Here, we find that TGFβ-induced down-regulation of bifunctional apoptosis regulator (BFAR) represents the key mechanism preventing the sustained activation of TGFβ signaling and thus impairing Th9 inducibility. Mechanistically, BFAR mediates K63-linked ubiquitination of TGFβR1 at K268, which is critical to activate TGFβ signaling. Thus, BFAR deficiency or K268R knock-in mutation suppresses TGFβR1 ubiquitination and Th9 differentiation, thereby inhibiting Th9-mediated cancer immunotherapy. More interestingly, BFAR-overexpressed Th9 cells exhibit promising therapeutic efficacy to curtail tumor growth and metastasis and promote the sensitivity of anti–PD-1–mediated checkpoint immunotherapy. Thus, our findings establish BFAR as a key TGFβ-regulated gene to fine-tune TGFβ signaling that causes Th9 induction insensitivity, and they highlight the translational potential of BFAR in promoting Th9-mediated cancer immunotherapy.

Schisandrin B-mediated TH17 cell differentiation attenuates bowel inflammation

Schisandrin B (Sch B) is the major active constituent of the traditional Chinese medicine Schisandra chinensis and has anti-inflammatory activity, but the target of Sch B remains unclear. T helper 17 (TH17) cells have been involved in the pathogenesis of many autoimmune and inflammatory diseases. Here, we showed that Sch B could decrease IL-17A production of CD4+ T cells by targeting STAT3 in vitro. Importantly, Sch B has therapeutic effects on DSS-induced acute and chronic colitis, CD4+CD45RBhigh T cell-induced colitis. Furthermore, we identified TH17 cells as the direct target of Sch B for mediating its anti-inflammatory activity. Sch B could serve as a lead for developing new therapeutics against TH17 cells or IL-17A cytokine-driven diseases.

Increased Interleukin-10 Expression by the Inhibition of Ca2+-Activated K+ Channel KCa3.1 in CD4+CD25+ Regulatory T Cells in the Recovery Phase in an Inflammatory Bowel Disease Mouse Model

Inflammatory bowel diseases (IBD) are chronic inflammatory diseases of the gastrointestinal tract arising from abnormal responses of the innate and adaptative immune systems. Interleukin (IL)-10-producing CD4⁺CD25⁺ regulatory T (T_reg) cells play a protective role in the recovery phase of IBD. In the present study, the effects of the administration of the selective Ca²⁺-activated K⁺ channel K_Ca3.1 inhibitor TRAM-34 on disease activities were examined in chemically induced IBD model mice. IBD disease severity, as assessed by diarrhea, visible fecal blood, inflammation, and crypt damage in the colon, was significantly lower in mice administered 1 mg/kg TRAM-34 than in vehicle-administered mice. Quantitative real-time polymerase chain reaction examinations showed that IL-10 expression levels in the recovery phase were markedly increased by the inhibition of K_Ca3.1 in mesenteric lymph node (mLN) T_reg cells of IBD model mice compared with vehicle-administered mice. Among several positive and negative transcriptional regulators (TRs) for IL-10, three positive TRs-E4BP4, KLF4, and Blimp1-were upregulated by the inhibition of K_Ca3.1 in the mLN T_reg cells of IBD model mice. In mouse peripheral CD4⁺CD25⁺ T_reg cells induced by lectin stimulation, IL-10 expression and secretion were enhanced by the treatment with TRAM-34, together with the upregulation of E4BP4, KLF4, and Blimp1. Collectively, the present results demonstrated that the pharmacological inhibition of K_Ca3.1 decreased IBD symptoms in the IBD model by increasing IL-10 production in peripheral T_reg cells and that IL-10^high T_reg cells produced by the treatment with K_Ca3.1 inhibitor may contribute to efficient T_reg therapy for chronic inflammatory disorders, including IBD. SIGNIFICANCE STATEMENT: Pharmacological inhibition of Ca²⁺-activated K⁺ channel K_Ca3.1 increased IL-10 expression in peripheral T_reg cells, together with the upregulation of the transcriptional regulators of IL-10: Krüppel-like factor 4, E4 promoter-binding protein 4, and/or B lymphocyte-induced maturation protein 1. The manipulation of IL-10^high-producing T_reg cells by the pharmacological inhibition of K_Ca3.1 may be beneficial in the treatment of chronic inflammatory diseases such as inflammatory bowel disease.

TSAd Plays a Major Role in Myo9b-Mediated Suppression of Malignant Pleural Effusion by Regulating TH1/TH17 Cell Response

Emerging evidence indicates that Myo9b is a cancer metastasis-related protein and functions in a variety of immune-related diseases. However, it is not clear whether and how Myo9b functions in malignant pleural effusion (MPE). In this study, our data showed that Myo9b expression levels correlated with lung cancer pleural metastasis, and nucleated cells in MPE from either patients or mice expressed a lower level of Myo9b than those in the corresponding blood. Myo9b deficiency in cancer cells suppressed MPE development via inhibition of migration. Myo9b deficiency in mice suppressed MPE development by decreasing T_H1 cells and increasing T_H17 cells. CD4⁺ naive T cells isolated from Myo9b^-/- mouse spleens exhibited less T_H1 cell differentiation and more T_H17 cell differentiation in vitro. mRNA sequencing of nucleated cells showed that T cell-specific adaptor protein (TSAd) was downregulated in Myo9b^-/- mouse MPE, and enrichment of the H3K27me3 mark in the TSAd promoter region was found in the Myo9b^-/- group. Naive T cells purified from wild type mouse spleens transfected with TSAd-specific small interfering RNAs (siRNAs) also showed less T_H1 cell differentiation and more T_H17 cell differentiation than those from the siRNA control group. Furthermore, downregulation of TSAd in mice using cholesterol-conjugated TSAd-specific siRNA suppressed MPE development, decreased T_H1 cells, and increased T_H17 cells in MPE in vivo. Taken together, Myo9b deficiency suppresses MPE development not only by suppressing pleural cancer metastasis but also by regulating T_H1/T_H17 cell response via a TSAd-dependent pathway. This work suggests Myo9b and TSAd as novel candidates for future basic and clinical investigations of cancer.

E3 Ubiquitin Ligase Von Hippel-Lindau Protein Promotes Th17 Differentiation

Von Hippel-Lindau (VHL) is an E3 ubiquitin ligase that targets proteins, including HIF-1α, for proteasomal degradation. VHL and HIF regulate the balance between glycolysis and oxidative phosphorylation, which is critical in highly dynamic T cells. HIF-1α positively regulates Th17 differentiation, a complex process in which quiescent naive CD4 T cells undergo transcriptional changes to effector cells, which are commonly dysregulated in autoimmune diseases. The role of VHL in Th17 cells is not known. In this study, we hypothesized VHL negatively regulates Th17 differentiation and deletion of VHL in CD4 T cells would elevate HIF-1α and increase Th17 differentiation. Unexpectedly, we found that VHL promotes Th17 differentiation. Mice deficient in VHL in their T cells were resistant to an autoimmune disease, experimental autoimmune encephalomyelitis, often mediated by Th17 cells. In vitro Th17 differentiation was impaired in VHL-deficient T cells. In the absence of VHL, Th17 cells had decreased activation of STAT3 and SMAD2, suggesting that VHL indirectly or directly regulates these critical signaling molecules. Gene expression analysis revealed that in Th17 cells, VHL regulates many cellular pathways, including genes encoding proteins involved indirectly or directly in the glycolysis pathway. Compared with wild-type, VHL-deficient Th17 cells had elevated glycolysis and glycolytic capacity. Our finding has implications on the design of therapeutics targeting the distinct metabolic needs of T cells to combat chronic inflammatory diseases.

Febrile Temperature Critically Controls the Differentiation and Pathogenicity of T Helper 17 Cells

Fever, an evolutionarily conserved physiological response to infection, is also commonly associated with many autoimmune diseases, but its role in T cell differentiation and autoimmunity remains largely unclear. T helper 17 (Th17) cells are critical in host defense and autoinflammatory diseases, with distinct phenotypes and pathogenicity. Here, we show that febrile temperature selectively regulated Th17 cell differentiation in vitro in enhancing interleukin-17 (IL-17), IL-17F, and IL-22 expression. Th17 cells generated under febrile temperature (38.5°C-39.5°C), compared with those under 37°C, showed enhanced pathogenic gene expression with increased pro-inflammatory activities in vivo. Mechanistically, febrile temperature promoted SUMOylation of SMAD4 transcription factor to facilitate its nuclear localization; SMAD4 deficiency selectively abrogated the effects of febrile temperature on Th17 cell differentiation both in vitro and ameliorated an autoimmune disease model. Our results thus demonstrate a critical role of fever in shaping adaptive immune responses with implications in autoimmune diseases.

Epigenetic initiation of the TH17 differentiation program is promoted by Cxxc finger protein 1

IL-6/STAT3 signaling is known to initiate the T_H17 differentiation program, but the upstream regulatory mechanisms remain minimally explored. Here, we show that Cxxc finger protein 1 (Cxxc1) promoted the generation of T_H17 cells as an epigenetic regulator and prevented their differentiation into T_reg cells. Mice with a T cell-specific deletion of Cxxc1 were protected from experimental autoimmune encephalomyelitis and were more susceptible to Citrobacter rodentium infection. Cxxc1 deficiency decreased IL-6Rα expression and impeded IL-6/STAT3 signaling, whereas the overexpression of IL-6Rα could partially reverse the defects in Cxxc1-deficient T_H17 cells in vitro and in vivo. Genome-wide occupancy analysis revealed that Cxxc1 bound to Il6rα gene loci by maintaining the appropriate H3K4me3 modification of its promoter. Therefore, these data highlight that Cxxc1 as a key regulator governs the balance between T_H17 and T_reg cells by controlling the expression of IL-6Rα, which affects IL-6/STAT3 signaling and has an impact on T_H17-related autoimmune diseases.

Frontline Science: Induction of experimental autoimmune encephalomyelitis mobilizes Th17-promoting myeloid derived suppressor cells to the lung

Myeloid-derived suppressor cells (MDSCs) are a diverse group of cells that are recognized for their remarkable suppressive effects on pro-inflammatory T cells. The pleiotropic nature of these cells, however, has been demonstrated by their differential effects on immune responses in different settings. Our and others' work has demonstrated suppressive effects of these cells. We previously demonstrated that these cells were mobilized to the lungs during experimental autoimmune encephalomyelitis (EAE), which is a murine model of multiple sclerosis, and potently inhibited CD8⁺ T cell responses against influenza infection. Interestingly, they appeared to have a lesser effect on CD4⁺ T cells, and in fact, others have demonstrated that spleen-derived MDSCs could actually promote Th17 differentiation. We sought to determine the role of lung-derived MDSCs on EAE pathogenesis, as excursion through the lungs by pathologic CNS-Ag targeted T cells was shown to be critical for EAE induction. Our results indicate a robust accumulation of granulocytic MDSCs in the lungs of mice during EAE, which could promote Th17 polarization, and which coincided with the trafficking of autoimmune-targeted T cells through the lungs. These studies underscore the pleiotropic effect of MDSCs on T cells and their potential pro-inflammatory phenotypes in neuro-inflammatory disease. Understanding both the intrinsic multifunctional nature of these cells and the ability to influence organ-specific targets such as the CNS from remote organs such as lungs will help to elucidate both mechanisms of disease and possible new therapeutic approaches.

Phosphatase PP2A is essential for TH17 differentiation

Phosphatase PP2A expression levels are positively correlated to the clinical severity of systemic lupus erythematosus (SLE) and IL17A cytokine overproduction, indicating a potential role of PP2A in controlling T_H17 differentiation and inflammation. By generating a mouse strain with ablation of the catalytic subunit α of PP2A in peripheral mature T cells (PP2A cKO), we demonstrate that the PP2A complex is essential for T_H17 differentiation. These PP2A cKO mice had reduced T_H17 cell numbers and less severe disease in an experimental autoimmune encephalomyelitis (EAE) model. PP2A deficiency also ablated C-terminal phosphorylation of SMAD2 but increased C-terminal phosphorylation of SMAD3. By regulating the activity of RORγt via binding, the changes in the phosphorylation status of these R-SMADs reduced Il17a gene transcription. Finally, PP2A inhibitors showed similar effects on T_H17 cells as were observed in PP2A cKO mice, i.e., decreased T_H17 differentiation and relative protection of mice from EAE. Taken together, these data demonstrate that phosphatase PP2A is essential for T_H17 differentiation and that inhibition of PP2A could be a possible therapeutic approach to controlling T_H17-driven autoimmune diseases.

The role of transforming growth factor β in T helper 17 differentiation

T helper 17 (Th17) cells play critical roles in inflammatory and autoimmune diseases. The lineage-specific transcription factor RORγt is the key regulator for Th17 cell fate commitment. A substantial number of studies have established the importance of transforming growth factor β (TGF-β) -dependent pathways in inducing RORγt expression and Th17 differentiation. TGF-β superfamily members TGF-β1 , TGF-β3 or activin A, in concert with interleukin-6 or interleukin-21, differentiate naive T cells into Th17 cells. Alternatively, Th17 differentiation can occur through TGF-β-independent pathways. However, the mechanism of how TGF-β-dependent and TGF-β-independent pathways control Th17 differentiation remains controversial. This review focuses on the perplexing role of TGF-β in Th17 differentiation, depicts the requirement of TGF-β for Th17 development, and underscores the multiple mechanisms underlying TGF-β-promoted Th17 generation, pathogenicity and plasticity. With new insights and comprehension from recent findings, this review specifically tackles the involvement of the canonical TGF-β signalling components, SMAD2, SMAD3 and SMAD4, summarizes diverse SMAD-independent mechanisms, and highlights the importance of TGF-β signalling in balancing the reciprocal conversion of Th17 and regulatory T cells. Finally, this review includes discussions and perspectives and raises important mechanistic questions about the role of TGF-β in Th17 generation and function.

TRIMming TGF-β signals in Th17 cells

The precise downstream mediators of TGF-β signaling in Th17 and T reg cells remain unclear. In this issue of JEM, Tanaka et al. report that Trim33 transduces TGF-β signals in Th17 cells to generate an optimal proinflammatory cytokine profile.

The precise downstream mediators of TGF-β signaling in Th17 and T reg cells remain unclear. In this issue of JEM, Tanaka et al. report that Trim33 transduces TGF-β signals in Th17 cells to generate an optimal proinflammatory cytokine profile.

Trim33 mediates the proinflammatory function of Th17 cells

Transforming growth factor-β (TGF-β) regulates reciprocal regulatory T cell (T reg) and T helper 17 (Th17) differentiation, the underlying mechanism of which is still not understood. Here, we report that tripartite motif-containing 33 (Trim33), a modulator of TGF-β signaling that associates with Smad2, regulates the proinflammatory function of Th17 cells. Trim33 deficiency in T cells ameliorated an autoimmune disease in vivo. Trim33 was required for induction in vitro of Th17, but not T reg cells. Moreover, Smad4 and Trim33 play contrasting roles in the regulation of IL-10 expression; loss of Trim33 enhanced IL-10 production. Furthermore, Trim33 was recruited to the Il17a and Il10 gene loci, dependent on Smad2, and mediated their chromatin remodeling during Th17 differentiation. Trim33 thus promotes the proinflammatory function of Th17 cells by inducing IL-17 and suppressing IL-10 expression.

Effector T Helper Cell Subsets in Inflammatory Bowel Diseases

The gastrointestinal tract is a site of high immune challenge, as it must maintain a delicate balance between tolerating luminal contents and generating an immune response toward pathogens. CD4⁺ T cells are key in mediating the host protective and homeostatic responses. Yet, CD4⁺ T cells are also known to be the main drivers of inflammatory bowel disease (IBD) when this balance is perturbed. Many subsets of CD4⁺ T cells have been identified as players in perpetuating chronic intestinal inflammation. Over the last few decades, understanding of how each subset of Th cells plays a role has dramatically increased. Simultaneously, this has allowed development of therapeutic innovation targeting specific molecules rather than broad immunosuppressive agents. Here, we review the emerging evidence of how each subset functions in promoting and sustaining the chronic inflammation that characterizes IBD.

Leucine-rich alpha 2 glycoprotein promotes Th17 differentiation and collagen-induced arthritis in mice through enhancement of TGF-β-Smad2 signaling in naïve helper T cells

Background

Leucine-rich alpha 2 glycoprotein (LRG) has been identified as a serum protein elevated in patients with active rheumatoid arthritis (RA). Although the function of LRG is ill-defined, LRG binds with transforming growth factor (TGF)-β and enhances Smad2 phosphorylation. Considering that the imbalance between T helper 17 (Th17) cells and regulatory T cells (Treg) plays important roles in the pathogenesis of RA, LRG may affect arthritic pathology by enhancing the TGF-β-Smad2 pathway that is pivotal for both Treg and Th17 differentiation. The purpose of this study was to explore the contribution of LRG to the pathogenesis of arthritis, with a focus on the role of LRG in T cell differentiation.

Methods

The differentiation of CD4 T cells and the development of collagen-induced arthritis (CIA) were examined in wild-type mice and LRG knockout (KO) mice. To examine the influence of LRG on T cell differentiation, naïve CD4 T cells were isolated from LRG KO mice and cultured under Treg- or Th17-polarization condition in the absence or presence of recombinant LRG.

Results

In the CIA model, LRG deficiency led to ameliorated arthritis and reduced Th17 differentiation with no influence on Treg differentiation. By addition of recombinant LRG, the expression of IL-6 receptor (IL-6R) was enhanced through TGF-β-Smad2 signaling. In LRG KO mice, the IL-6R expression and IL-6-STAT3 signaling was attenuated in naïve CD4 T cells, compared to wild-type mice.

Conclusions

Our findings suggest that LRG upregulates IL-6R expression in naïve CD4 T cells by the enhancement of TGF-β-smad2 pathway and promote Th17 differentiation and arthritis development.

Regulatory T-Cell Augmentation or Interleukin-17 Inhibition Prevents Calcineurin Inhibitor-Induced Hypertension in Mice

The immunosuppressive calcineurin inhibitors cyclosporine A and tacrolimus alter T-cell subsets and can cause hypertension, vascular dysfunction, and renal toxicity. We and others have reported that cyclosporine A and tacrolimus decrease anti-inflammatory regulatory T cells and increase proinflammatory interleukin-17-producing T cells; therefore, we hypothesized that inhibition of these effects using noncellular therapies would prevent the hypertension, endothelial dysfunction, and renal glomerular injury induced by calcineurin inhibitor therapy. Daily treatment of mice with cyclosporine A or tacrolimus for 1 week significantly decreased CD4⁺/FoxP3⁺ regulatory T cells in the spleen and lymph nodes, as well as induced hypertension, vascular injury and dysfunction, and glomerular mesangial expansion in mice. Daily cotreatment with all-trans retinoic acid reported to increase regulatory T cells and decrease interleukin-17-producing T cells, prevented all of the detrimental effects of cyclosporine A and tacrolimus. All-trans retinoic acid also increased regulatory T cells and prevented the hypertension, endothelial dysfunction, and glomerular injury in genetically modified mice that phenocopy calcineurin inhibitor-treated mice (FKBP12-Tie2 knockout). Treatment with an interleukin-17-neutralizing antibody also increased regulatory T-cell levels and prevented the hypertension, endothelial dysfunction, and glomerular injury in cyclosporine A-treated and tacrolimus-treated mice and FKBP12-Tie2 knockout mice, whereas an isotype control had no effect. Augmenting regulatory T cells and inhibiting interleukin-17 signaling using noncellular therapies prevents the cardiovascular and renal toxicity of calcineurin inhibitors in mice.

MINK1: The missing link between ROS and its inhibition of Th17 cells

In this issue of JEM, Fu et al. identified the kinase Mink1 as a novel negative regulator of Th17 cell generation. Mink1, activated by reactive oxygen species (ROS), prevents TGF-β activation of Smad2, therefore limiting Th17 cell differentiation.

In this issue of JEM, Fu et al. (https://doi.org/10.1084/jem.20161120) identified the kinase Mink1 as a novel negative regulator of Th17 cell generation. Mink1, activated by reactive oxygen species (ROS), prevents TGF-β activation of Smad2, therefore limiting Th17 cell differentiation.

Suppression of Th17 cell differentiation by misshapen/NIK-related kinase MINK1

T helper type 17 cells (Th17 cells) are major contributors to many autoimmune diseases. In this study, we demonstrate that the germinal center kinase family member MINK1 (misshapen/NIK-related kinase 1) negatively regulates Th17 cell differentiation. The suppressive effect of MINK1 on induction of Th17 cells is mediated by the inhibition of SMAD2 activation through direct phosphorylation of SMAD2 at the T324 residue. The importance of MINK1 to Th17 cell differentiation was strengthened in the animal model of experimental autoimmune encephalomyelitis (EAE). Moreover, we show that the reactive oxygen species (ROS) scavenger N-acetyl cysteine boosts Th17 cell differentiation in a MINK1-dependent manner and exacerbates the severity of EAE. Thus, we have not only established MINK1 as a critical regulator of Th17 cell differentiation, but also clarified that accumulation of ROS may limit the generation of Th17 cells. The contribution of MINK1 to ROS-regulated Th17 cell differentiation may suggest an important mechanism for the development of autoimmune diseases influenced by antioxidant dietary supplements.

RGC-32 Promotes Th17 Cell Differentiation and Enhances Experimental Autoimmune Encephalomyelitis

Th17 cells play a critical role in autoimmune diseases, including multiple sclerosis and its animal model, experimental autoimmune encephalomyelitis. Response gene to complement (RGC)-32 is a cell cycle regulator and a downstream target of TGF-β that mediates its profibrotic activity. In this study, we report that RGC-32 is preferentially upregulated during Th17 cell differentiation. RGC-32^-/- mice have normal Th1, Th2, and regulatory T cell differentiation but show defective Th17 differentiation in vitro. The impaired Th17 differentiation is associated with defects in IFN regulatory factor 4, B cell-activating transcription factor, retinoic acid-related orphan receptor γt, and SMAD2 activation. In vivo, RGC-32^-/- mice display an attenuated experimental autoimmune encephalomyelitis phenotype accompanied by decreased CNS inflammation and reduced frequency of IL-17- and GM-CSF-producing CD4⁺ T cells. Collectively, our results identify RGC-32 as a novel regulator of Th17 cell differentiation in vitro and in vivo and suggest that RGC-32 is a potential therapeutic target in multiple sclerosis and other Th17-mediated autoimmune diseases.

Regulation of Innate and Adaptive Immunity by TGFβ

Immune regulation by cytokines is crucial in maintaining immune homeostasis, promoting responses to infection, resolving inflammation, and promoting immunological memory. Additionally, cytokine responses drive pathology in immune-mediated disease. A crucial cytokine in the regulation of all aspects of an immune response is transforming growth factor beta (TGFβ). Although best known as a crucial regulator of T cell responses, TGFβ plays a vital role in regulating responses mediated by virtually every innate and adaptive immune cell, including dendritic cells, B cells, NK cells, innate lymphoid cells, and granulocytes. Here, we review our current knowledge of how TGFβ regulates the immune system, highlighting the multifunctional nature of TGFβ and how its function can change depending on location and context of action.

Fatty acid amide hydrolase (FAAH) blockade ameliorates experimental colitis by altering microRNA expression and suppressing inflammation

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), which is thought to result from immune-mediated inflammatory disorders, leads to high morbidity and health care cost. Fatty acid amide hydrolase (FAAH) is an enzyme crucially involved in the modulation of intestinal physiology through anandamide (AEA) and other endocannabinoids. Here we examined the effects of an FAAH inhibitor (FAAH-II), on dextran sodium sulphate (DSS)-induced experimental colitis in mice. Treatments with FAAH-II improved overall clinical scores by reversing weight loss and colitis-associated pathogenesis. The frequencies of activated CD4⁺ T cells in spleens, mesenteric lymph nodes (MLNs), Peyer's patches (PPs), and colon lamina propiria (LP) were reduced by FAAH inhibition. Similarly, the frequencies of macrophages, neutrophils, natural killer (NK), and NKT cells in the PPs and LP of mice with colitis declined after FAAH blockade, as did concentrations of systemic and colon inflammatory cytokines. Microarray analysis showed that 26 miRNAs from MLNs and 217 from PPs had a 1.5-fold greater difference in expression after FAAH inhibition. Among them, 8 miRNAs were determined by reverse-transcription polymerase chain reaction (RT-PCR) analysis to have anti-inflammatory properties. Pathway analysis demonstrated that differentially regulated miRNAs target mRNA associated with inflammation. Thus, FAAH-II ameliorates experimental colitis by reducing not only the number of activated T cells but also the frequency of macrophages, neutrophils, and NK/NKT cell, as well as inflammatory miRNAs and cytokine at effector sites in the colon. These studies demonstrate for the first time that FAAH-II inhibitor may suppress colitis through regulation of pro-inflammatory miRNAs expression.

Functions of Smad Transcription Factors in TGF-β1-Induced Selectin Ligand Expression on Murine CD4 Th Cells

Selectins are carbohydrate-binding adhesion molecules that control leukocyte traffic. Induction of selectin ligands on T cells is controlled primarily by cytokines, including TGF-β1, and requires p38α MAPK, but transcriptional mechanisms that underlie cytokine-driven selectin ligand expression are poorly understood. In this study, we show, using mice with conditional deletions of the TGF-β1-responsive transcription factors Smad2, Smad3, or Smad4, that induction of selectin ligands on CD4 cells in response to TGF-β1 requires Smad4 plus either Smad2 or Smad3. Analysis of CD4 cells from mice with only one functional Smad4 allele revealed a sharp gene dosage effect, suggesting the existence of a threshold of TGF-β1 signal strength required for selectin ligand induction. Both Smad4 plus either Smad2 or Smad3 were selectively required for induction of Fut7 and Gcnt1, glycosyltransferases critical for selectin ligand biosynthesis, but they were not required for St3gal4 or St3gal6 induction. Smad4 plus either Smad2 or Smad3 were also required for induction of Runx transcription factors by TGF-β1. Enforced expression of Runx2, but not Runx1 or Runx3, in Smad2/Smad3 doubly deficient CD4 cells restored selectin ligand expression to wild-type levels. In contrast, enforced expression of Runx1, Runx2, or Runx3 failed to restore differentiation of TGF-β1-dependent Th cell lineages, including Th17, Th9, and induced regulatory T cells. These results show that Smads are directly required for Th cell differentiation independent of Runx induction but only indirectly required via Runx2 for TGF-β1-induced selectin ligand induction on murine CD4 T cells.

Kaempferol Suppresses Transforming Growth Factor-β1-Induced Epithelial-to-Mesenchymal Transition and Migration of A549 Lung Cancer Cells by Inhibiting Akt1-Mediated Phosphorylation of Smad3 at Threonine-179

Kaempferol, a natural dietary flavonoid, is well known to possess chemopreventive and therapeutic anticancer efficacy; however, its antimetastatic effects have not been mechanistically studied so far in any cancer model. This study was aimed to investigate the inhibitory effect and accompanying mechanisms of kaempferol on epithelial-to-mesenchymal transition (EMT) and cell migration induced by transforming growth factor-β1 (TGF-β1). In human A549 non–small lung cancer cells, kaempferol strongly blocked the enhancement of cell migration by TGF-β1–induced EMT through recovering the loss of E-cadherin and suppressing the induction of mesenchymal markers as well as the upregulation of TGF-β1–mediated matrix metalloproteinase-2 activity. Interestingly, kaempferol reversed TGF-β1–mediated Snail induction and E-cadherin repression by weakening Smad3 binding to the Snail promoter without affecting its C-terminus phosphorylation, complex formation with Smad4, and nuclear translocation under TGF-β1 stimulation. Mechanism study revealed that the phosphorylation of Smad3 linker region induced by TGF-β1 was required for the induction of EMT and cell migration, and selective downregulation of the phosphorylation of Smad3 at Thr179 residue (not Ser204, Ser208, and Ser213) in the linker region was responsible for the inhibition by kaempferol of TGF-β1–induced EMT and cell migration. Furthermore, Akt1 was required for TGF-β1–mediated induction of EMT and cell migration and directly phosphorylated Smad3 at Thr179, and kaempferol completely abolished TGF-β1–induced Akt1 phosphorylation. In summary, kaempferol blocks TGF-β1–induced EMT and migration of lung cancer cells by inhibiting Akt1-mediated phosphorylation of Smad3 at Thr179 residue, providing the first evidence of a molecular mechanism for the anticancer effect of kaempferol.

Cholera Toxin Promotes Th17 Cell Differentiation by Modulating Expression of Polarizing Cytokines and the Antigen-Presenting Potential of Dendritic Cells

Cholera toxin (CT), an exotoxin produced by Vibrio cholera, acts as a mucosal adjuvant. In a previous study, we showed that CT skews differentiation of CD4 T cells to IL-17-producing Th17 cells. Here, we found that intranasal administration of CT induced migration of migratory dendritic cell (DC) populations, CD103⁺ DCs and CD11b^hi DCs, to the lung draining mediastinal lymph nodes (medLN). Among those DC subsets, CD11b^hi DCs that were relatively immature had a major role in Th17 cell differentiation after administration of CT. CT-treated BMDCs showed reduced expression of MHC class II and CD86, similar to CD11b^hi DCs in medLN, and these BMDCs promoted Th17 cell differentiation more potently than other BMDCs expressing higher levels of MHC class II and CD86. By analyzing the expression of activation markers such as CD25 and CD69, proliferation and IL-2 production, we determined that CT-treated BMDCs showed diminished antigen-presenting potential to CD4⁺ T cells compared with normal BMDCs. We also found that CT-stimulated BMDCs promote activin A expression as well as IL-6 and IL-1β, and activin A had a synergic role with TGF-β1 in CT-mediated Th17 cell differentiation. Taken together, our results suggest that CT-stimulated DCs promote Th17 cell differentiation by not only modulating antigen-presenting potential but also inducing Th polarizing cytokines.

Phosphorylation status determines the opposing functions of Smad2/Smad3 as STAT3 cofactors in TH17 differentiation

Transforming growth factor-β (TGF-β) and interleukin-6 (IL-6) are the pivotal cytokines to induce IL-17-producing CD4⁺ T helper cells (T_H17); yet their signalling network remains largely unknown. Here we show that the highly homologous TGF-β receptor-regulated Smads (R-Smads): Smad2 and Smad3 oppositely modify STAT3-induced transcription of IL-17A and retinoic acid receptor-related orphan nuclear receptor, RORγt encoded by Rorc, by acting as a co-activator and co-repressor of STAT3, respectively. Smad2 linker phosphorylated by extracellular signal-regulated kinase (ERK) at the serine 255 residue interacts with STAT3 and p300 to transactivate, whereas carboxy-terminal unphosphorylated Smad3 interacts with STAT3 and protein inhibitor of activated STAT3 (PIAS3) to repress the Rorc and Il17a genes. Our work uncovers carboxy-terminal phosphorylation-independent noncanonical R-Smad–STAT3 signalling network in T_H17 differentiation.

TGF-ß and IL-6 are the essential cytokines for mediating the differentiation of IL-17-producing CD4+ T helper cells (T_H17). Here, Yoon et al. provide more insights into this process and describe the opposing roles of TGFß-signalling intermediates Smad2 and Smad3 as STAT3 cofactors in Th17 differentiation.

MEK inhibition prevents tumour-shed transforming growth factor-β-induced T-regulatory cell augmentation in tumour milieu

Tumour progression is associated with immune-suppressive conditions that facilitate the escape of tumour cells from the regimen of immune cells, subsequently paralysing the host defence mechanisms. Induction of CD4(+)  CD25(+)  FoxP3(+) T regulatory (Treg) cells has been implicated in the tumour immune escape mechanism, although the novel anti-cancer treatment strategies targeting Treg cells remain unknown. The focus of this study is to define the interaction between tumour and immune system, i.e. how immune tolerance starts and gradually leads to the induction of adaptive Treg cells in the tumour microenvironment. Our study identified hyperactivated mitogen-activated protein kinase kinase (MEK)/extracellular signal-regulated kinase (ERK) -signalling as a potential target for reversing Treg cell augmentation in breast cancer patients. In more mechanistic detail, pharmacological inhibitors of MEK/ERK signalling inhibited transforming growth factor-β (TGF-β) production in tumour cells that essentially blocked TGF-β-SMAD3/SMAD4-mediated induction of CD25/interleukin-2 receptor α on CD4(+) T-cell surface. As a result high-affinity binding of interleukin-2 on those cells was prohibited, causing lack of Janus kinase 1 (JAK1)/JAK3-mediated signal transducer and activator of transcription 3 (STAT3)/STAT5 activation required for FoxP3 expression. Finally, for a more radical approach towards a safe MEK inhibitor, we validate the potential of multi-kinase inhibitor curcumin, especially the nano-curcumin made out of pure curcumin with greater bioavailability; in repealing tumour-shed TGF-β-induced Treg cell augmentation.

MicroRNA-144 dysregulates the transforming growth factor-β signaling cascade and contributes to the development of bronchiolitis obliterans syndrome after human lung transplantation

BACKGROUND

Bronchiolitis obliterans syndrome (BOS), chronic lung allograft rejection, remains an impediment for the function of the transplanted organ. In this study, we defined the role of the microRNA (miRNA) miR-144 in fibroproliferation leading to BOS.

METHODS

Biopsy specimens were obtained from 20 lung transplant recipients with BOS((+)) and 19 without BOS((-)). Expression of miR-144 and its target, transforming growth factor-β (TGF-β)-induced factor homeobox 1(TGIF1), were analyzed by real-time polymerase chain reaction and Western blot. Overexpression of miR-144 and luciferase reporter genes were performed to elucidate miRNA-target interactions. The function of miR-144 was evaluated by transfecting fibroblasts and determining the response to TGF-β by analyzing Sma- and Mad-related family (Smads), fibroblast growth factor, TGF-β, and vascular endothelial growth factor. Smooth muscle actin-α-positive stress fibers and F-actin filaments in lung fibroblasts were analyzed by immunofluorescence.

RESULTS

Analysis of miR-144 in the biopsy specimens demonstrated 4.1 ± 0.8-fold increases in BOS(+) compared with BOS(-) patients, with a significant reduction in TGIF1 (3.6 ± 1.2-fold), a corepressor of Smads. In vitro transfection confirmed that over-expression of miR-144 results in a reduction in TGIF1 and an increase in SMAD2, SMAD4, fibroblast growth factor-6, TGF-β, and vascular endothelial growth factor. Increasing miR-144 by transfecting, increased smooth muscle actin-α and fibronectin, and knockdown of miR-144 diminished fibrogenesis in MRC-5 fibroblasts.

CONCLUSIONS

miR-144 is a critical regulator of the TGF-β signaling cascade and is over-expressed in lungs with BOS. Therefore, miR-144 is a potential target toward preventing fibrosis leading to BOS after lung transplant.

IL10, TGF beta1, and IFN gamma modulate intracellular signaling pathways and cytokine production to control Toxoplasma gondii infection in BeWo trophoblast cells

Considering that interleukin 10 (IL10), transforming growth factor beta1 (TGFB1), and interferon gamma (IFNG) are involved in the susceptibility of BeWo trophoblast cells to Toxoplasma gondii infection, the aim of the present study was to investigate the effector mechanisms triggered by these cytokines in the control of T. gondii in BeWo cells. For this purpose, infected/uninfected BeWo cells were treated with IL10, TGFB1 (50 ng/ml), and IFNG (20 or 100 ng/ml) in order to verify the phosphorylation of signal transducers and activators of transcription 1 (STAT1), STAT3, and Smad2, parasite intracellular proliferation, as well as the Th1/Th2/IL17A cytokine production. The treatment of BeWo cells with IL10 and TGFB1 favored T. gondii proliferation, and these findings were associated with STAT3 and Smad2 phosphorylation, respectively (P < 0.05). Also, these cytokine treatments were able to down-modulate TNF alpha (TNFA) and IL6 production (P < 0.05). Low concentration of IFNG was unable to control T. gondii infection but was able to trigger STAT1 phosphorylation and up-regulate IL6 and IL17A production; whereas a high concentration of IFNG was unable to activate STAT1 but down-modulated IL6 and TNFA and increased T. gondii proliferation (P < 0.05). IL10, TGFB1, and IFNG regulate a differential T. gondii proliferation in BeWo cells because they distinctly trigger intracellular signaling pathways and cytokine production, especially IL6 and TNFA. Our data open new windows to understand the mechanisms triggered by IL10, TGFB1, and IFNG at the maternal-fetal interface in the presence of T. gondii, contributing to recognizing the importance of these effector mechanisms involved in the vertical transmission of this parasite.

MicroRNA-21 promotes Th17 differentiation and mediates experimental autoimmune encephalomyelitis

Accumulation of IL-17-producing Th17 cells is associated with the development of multiple autoimmune diseases; however, the contribution of microRNA (miRNA) pathways to the intrinsic control of Th17 development remains unclear. Here, we demonstrated that miR-21 expression is elevated in Th17 cells and that mice lacking miR-21 have a defect in Th17 differentiation and are resistant to experimental autoimmune encephalomyelitis (EAE). Furthermore, we determined that miR-21 promotes Th17 differentiation by targeting and depleting SMAD-7, a negative regulator of TGF-β signaling. Moreover, the decreases in Th17 differentiation in miR-21-deficient T cells were associated with defects in SMAD-2/3 activation and IL-2 suppression. Finally, we found that treatment of WT mice with an anti-miR-21 oligonucleotide reduced the clinical severity of EAE, which was associated with a decrease in Th17 cells. Thus, we have characterized a T cell-intrinsic miRNA pathway that enhances TGF-β signaling, limits the autocrine inhibitory effects of IL-2, and thereby promotes Th17 differentiation and autoimmunity.

TGF-β/Smad signaling pathway regulates Th17/Treg balance during Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a severe parasitic disease caused by the infection of Echinococcus multilocularis (Em). Very little is known on the relationship between TGF-β/Smad signaling pathway and Treg/Th17 balance in the infected liver at different periods after Em infection. Using qRT-PCR, immunohistochemistry, flow cytometry and CBA assay, we measured the expression levels of TGF-β, Smad2/3/7, ROR-γt, Foxp3, IL-17, IL-10 and percentages of Th17 cells and Treg cells in mouse AE model, from day 2 to day 270 after infection. In the early stage of infection (day 2 to day 30), Smad7 was up-regulated and the TGF-β pathway was inactivated. In the middle stage of infection (day 30 to day 90), TGF-β and Smad2/3 were up-regulated. And levels of Treg cells, Foxp3, Th17 cells, RORγt, IL-17, IL-10 and IL-6 were significantly increased. In the late stage of infection (day 90 to day 270), Treg cells, Foxp3, TGF-β and IL-10 maintained at high levels whereas Th17 cells and IL-17 decreased significantly. TGF-β/Smad signaling pathway was activated during the chronic infection. Our data suggest that there were Treg/Th17 imbalance in the middle and especially in the late stage of Em infection and that Treg/Th17 imbalance may be regulated by TGF-β/Smad signaling pathway. Treg and Th17 subsets may be involved in regulating immune tolerance and tissue inflammation, and facilitating the long-term survival of Em in the host.

The transcription factor IRF8 activates integrin-mediated TGF-β signaling and promotes neuroinflammation

Recent epidemiological studies have identified interferon regulatory factor 8 (IRF8) as a susceptibility factor for multiple sclerosis (MS). However, how IRF8 influences the neuroinflammatory disease has remained unknown. By studying the role of IRF8 in experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, we found that Irf8(-/-) mice are resistant to EAE. Furthermore, expression of IRF8 in antigen-presenting cells (APCs, such as macrophages, dendritic cells, and microglia), but not in T cells, facilitated disease onset and progression through multiple pathways. IRF8 enhanced αvβ8 integrin expression in APCs and activated TGF-β signaling leading to T helper 17 (Th17) cell differentiation. IRF8 induced a cytokine milieu that favored growth and maintenance of Th1 and Th17 cells, by stimulating interleukin-12 (IL-12) and IL-23 production, but inhibiting IL-27 during EAE. Finally, IRF8 activated microglia and exacerbated neuroinflammation. Together, this work provides mechanistic bases by which IRF8 contributes to the pathogenesis of MS.

TGF-β activation and function in immunity

The cytokine TGF-β plays an integral role in regulating immune responses. TGF-β has pleiotropic effects on adaptive immunity, especially in the regulation of effector and regulatory CD4(+) T cell responses. Many immune and nonimmune cells can produce TGF-β, but it is always produced as an inactive complex that must be activated to exert functional effects. Thus, activation of latent TGF-β provides a crucial layer of regulation that controls TGF-β function. In this review, we highlight some of the important functional roles for TGF-β in immunity, focusing on its context-specific roles in either dampening or promoting T cell responses. We also describe how activation of TGF-β controls its function in the immune system, with a focus on the key roles for members of the integrin family in this process.

Inhibition of TGF-β1 signaling promotes central memory T cell differentiation

This study affirmed that isolated CD8(+) T cells express mRNA and produce TGF-β following cognate peptide recognition. Blockage of endogenous TGF-β with either a TGF-β-blocking Ab or a small molecule inhibitor of TGF-βRI enhances the generation of CD62L(high)/CD44(high) central memory CD8(+) T cells accompanied with a robust recall response. Interestingly, the augmentation within the central memory T cell pool occurs in lieu of cellular proliferation or activation, but with the expected increase in the ratio of the Eomesoderm/T-bet transcriptional factors. Yet, the signal transduction pathway(s) seems to be noncanonical, independent of SMAD or mammalian target of rapamycin signaling. Enhancement of central memory generation by TGF-β blockade is also confirmed in human PBMCs. The findings underscore the role(s) that autocrine TGF-β plays in T cell homeostasis and, in particular, the balance of effector/memory and central/memory T cells. These results may provide a rationale to targeting TGF-β signaling to enhance Ag-specific CD8(+) T cell memory against a lethal infection or cancer.

SMAD regulatory networks construct a balanced immune system

A balanced immune response requires combating infectious assaults while striving to maintain quiescence towards the self. One of the central players in this process is the pleiotropic cytokine transforming growth factor-β (TGF-β), whose deficiency results in spontaneous systemic autoimmunity in mice. The dominant function of TGF-β is to regulate the peripheral immune homeostasis, particularly in the microbe-rich and antigen-rich environment of the gut. To maintain intestinal integrity, the epithelial cells, myeloid cells and lymphocytes that inhabit the gut secrete TGF-β, which acts in both paracrine and autocrine fashions to activate its signal transducers, the SMAD transcription factors. The SMAD pathway regulates the production of IgA by B cells, maintains the protective mucosal barrier and promotes the balanced differentiation of CD4(+) T cells into inflammatory T helper type 17 cells and suppressive FOXP3(+) T regulatory cells. While encounters with pathogenic microbes activate SMAD proteins to evoke a protective inflammatory immune response, SMAD activation and synergism with immunoregulatory factors such as the vitamin A metabolite retinoic acid enforce immunosuppression toward commensal microbes and innocuous food antigens. Such complementary context-dependent functions of TGF-β are achieved by the co-operation of SMAD proteins with distinct dominant transcription activators and accessory chromatin modifiers. This review highlights recent advances in unravelling the molecular basis for the multi-faceted functions of TGF-β in the gut that are dictacted by fluid orchestrations of SMADs and their myriad partners.