ITK independent development of Th17 responses during hypersensitivity pneumonitis driven lung inflammation.

T helper 17 (Th17) cells develop in response to T cell receptor signals (TCR) in the presence of specific environments, and produce the inflammatory cytokine IL17A. These cells have been implicated in a number of inflammatory diseases and represent a potential target for ameliorating such diseases. The kinase ITK, a critical regulator of TCR signals, has been shown to be required for the development of Th17 cells. However, we show here that lung inflammation induced by Saccharopolyspora rectivirgula (SR) induced Hypersensitivity pneumonitis (SR-HP) results in a neutrophil independent, and ITK independent Th17 responses, although ITK signals are required for γδ T cell production of IL17A. Transcriptomic analysis of resultant ITK independent Th17 cells suggest that the SR-HP-induced extrinsic inflammatory signals may override intrinsic T cell signals downstream of ITK to rescue Th17 responses in the absence of ITK. These findings suggest that the ability to pharmaceutically target ITK to suppress Th17 responses may be dependent on the type of inflammation.

cGAS restricts colon cancer development by protecting intestinal barrier integrity.

The DNA-sensing enzyme cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS) regulates inflammation and immune defense against pathogens and malignant cells. Although cGAS has been shown to exert antitumor effects in several mouse models harboring transplanted tumor cell lines, its role in tumors arising from endogenous tissues remains unknown. Here, we show that deletion of cGAS in mice exacerbated chemical-induced colitis and colitis-associated colon cancer (CAC). Interestingly, mice lacking cGAS were more susceptible to CAC than those lacking stimulator of interferon genes (STING) or type I interferon receptor under the same conditions. cGAS but not STING is highly expressed in intestinal stem cells. cGAS deficiency led to intestinal stem cell loss and compromised intestinal barrier integrity upon dextran sodium sulfate-induced acute injury. Loss of cGAS exacerbated inflammation, led to activation of STAT3, and accelerated proliferation of intestinal epithelial cells during CAC development. Mice lacking cGAS also accumulated myeloid-derived suppressive cells within the tumor, displayed enhanced Th17 differentiation, but reduced interleukin (IL)-10 production. These results indicate that cGAS plays an important role in controlling CAC development by defending the integrity of the intestinal mucosa.

Thiomyristoyl ameliorates colitis by blocking the differentiation of Th17 cells and inhibiting SIRT2-induced metabolic reprogramming.

BACKGROUND: The pathogenesis of inflammatory bowel diseases (IBD), including Crohn's disease (CD) and ulcerative colitis (UC) has not been fully elucidated. However, a strong correlation between IBD and high T helper 17 (Th17) levels has been found. Sirtuin 2 (SIRT2) has recently been found to play an important role in metabolic reprogramming, but its potential anti-inflammatory properties remain unclear. METHODS: The expression levels of SIRT2 and glucose metabolism-related proteins in peripheral blood mononuclear cells (PBMCs) of IBD patients and healthy volunteers were detected. Human PBMCs were differentiated into Th17 cells in vitro and were treated with TM simultaneously. The ratio of Th17 cells and apoptotic cells and the production of Interleukin (IL)-17A and the expression levels of transcription factors of classical signaling pathway related to Th17 differentiation were determined. The acetylation of LDHA and glucose metabolism was assessed. Subsequently, C57BL/6J colitis mice induced by 2.5% dextran sulfatesodiumsalt (DSS) were treated with or without TM, Disease activity index, T cell subsets in the mice spleen, relevant inflammatory cytokines in serum, specific mRNA, and proteins in mice colon were evaluated respectively. RESULTS: SIRT2 and glucose metabolism-related proteins in PBMCs of patients were overexpressed. Compared with the positive control group, human PBMCs treated with TM had lower levels of IL-17A, percentage of Th17 cells, levels of phospho-signal transducer and activator of transcription (p-STAT) 3 and phospho-nuclear transcription factor-κB (p-NF-κB), but higher levels of acetylated LDHA. Compared with colitis mice, TM-treated colitis mice had longer colons, reduced weight-losses, and lower disease activity index and histopathologic scores. Interestingly, although the expression levels of interferon (IFN)-γ, IL-17A, and retinoic acid receptor-related orphan receptor (ROR)-γt were inhibited in the colons of TM-treated colitis mice, the expression of forkhead box protein P3 (FOXP3) didn't change. Consistently, relative to the high percentage of splenic Th17 cells in colitis mice, the percentage of splenic Th17 cells in TM-treated colitis mice was as normal as PBS-treated mice, while the percentage of Treg cells was not affected. Additionally, the TM group had reduced levels of IL-23 and hypoxiainduciblefactor-1α (HIF-1α), and an increased level of IL-10 in the colon, compared with the colitis group. CONCLUSION: Our results indicate that TM reduces UC progression by reducing metabolic reprogramming and T cell differentiation. Specifically, TM prevented Th17 differentiation by reducing the expression of related transcription factors and promoting acetylation of LDHA (weakening glycolysis). SIRT2 may be a potential target for IBD treatment.

Protein Arginine Methyltransferase 5 in T Lymphocyte Biology.

Protein arginine methyltransferase 5 (PRMT5) is the major methyltransferase (MT) catalyzing symmetric dimethylation (SDM). PRMT5 regulates developmental, homeostatic and disease processes in vertebrates and invertebrates, and a carcinogenic role has been observed in mammals. Recently, tools generated for PRMT5 loss of function have allowed researchers to demonstrate essential roles for PRMT5 in mouse and human lymphocyte biology. PRMT5 modulates CD4+ and CD8+ T cell development in the thymus, peripheral homeostasis, and differentiation into CD4+ helper T lymphocyte (Th)17 cell phenotypes. Here, we provide a timely review of the milestones leading to our current understanding of PRMT5 in T cell biology, discuss current tools to modify PRMT5 expression/activity, and highlight mechanistic pathways.

Pyruvate kinase M2 is requisite for Th1 and Th17 differentiation.

Th1 and Th17 are important in the pathogenesis of autoimmune diseases and they depend on glycolysis as a source of energy. T cell antigen receptor signaling phosphorylates a serine/threonine kinase, calcium/calmodulin-dependent protein kinase IV (CaMK4), and promotes glycolysis. Based on these findings we hypothesized that CaMK4 promotes glycolysis. Camk4-deficient CD4+ T cells and cells treated with a CaMK4 inhibitor had less glycolysis compared with their counterparts. Pull-down of CaMK4 and mass spectrometry identified pyruvate kinase muscle isozyme (PKM), the final rate-limiting enzyme in glycolysis, as a binding partner. Coimmunoprecipitation and Western blotting showed that CaMK4 interacts directly with PKM2. Camk4-deficient CD4+ T cells displayed decreased pyruvate kinase activity. Silencing or pharmacological inhibition of PKM2 reduced glycolysis and in vitro differentiation to Th1 and Th17 cells, while PKM2 overexpression restored Th17 cell differentiation. Treatment with a PKM2 inhibitor ameliorated experimental autoimmune encephalomyelitis and CD4+ T cells treated with PKM2 inhibitor or Pkm2-shRNA caused limited disease activity in an adoptive cell transfer model of experimental autoimmune encephalomyelitis. Our data demonstrate that CaMK4 binds to PKM2 and promotes its activity, which is requisite for Th1 and Th17 differentiation in vitro and in vivo. PKM2 represents a therapeutic target for T cell-dependent autoimmune diseases.

Regulation of Recombinase Rag-1 Expression by Female Sex Steroids in Treg and Th17 Lymphocytes: Role of Oncostatin M.

The effect of estradiol (E2), progesterone (P4), and oncostatin M (OSM) on the differentiation of CD4+ T cells to T regulatory (Treg) lymphocytes and T helpers 17 (Th17) was investigated. The possibility of revision of the T cell receptor in these subpopulations by evaluating the expression of RAG-1 recombinase was also studied. E2 at concentrations characteristic of pregnancy trimester I, but no P4 or OSM, increased the Treg level. Combination of sex steroids with OSM increased the percent of CD4+FOXP3+ cells and enhanced RAG-1 expression in these cells, thus promoting the development of immune tolerance during pregnancy. In the study of Th17, such effect of the hormones and OSM was not detected.

GdX/UBL4A-knockout mice resist collagen-induced arthritis by balancing the population of Th1/Th17 and regulatory T cells.

Rheumatoid arthritis (RA) is an autoimmune disease associated with synovial hyperplasia and bone and cartilage destruction. T cells, notably T helper (Th)-1 and Th17 cells, play a critical role in the pathologic process of RA. However, it remains unclear how Th1 and Th17 cells are regulated during RA. In this study, we report that the small ubiquitin-like protein X-linked gene in the G6PD cluster at Xq28 (GdX) regulates the balance of Th17 and regulatory T (Treg) cells during collagen-induced arthritis (CIA). We discovered that the splenocytes of GdX-knockout (KO) mice were insensitive to T-cell stimulants. Correspondingly, GdX-KO mice showed alleviative Th1-mediated delayed-type hypersensitivity and were resistant to CIA compared with wild-type mice. GdX-KO mice showed fewer swollen paws, lower serum proinflammatory cytokine and anti-collagen IgG levels, and decreased synovial hyperplasia. Mechanistically, we observed that deletion of GdX decreased the transcription of proinflammatory cytokines and impaired the Th1 and Th17 differentiation but increased the Treg cell proliferation. Consistently, deletion of GdX decreased the transcription level of T-cell-specific T-box transcription factor and RAR-related orphan receptor-γ transcription factor but increased that of forkhead box P3 after being challenged with type-II collagen. These findings suggested that GdX functions as an important regulator of Th1 or Th17 and Treg cell balance during the inflammatory responses. Therefore, GdX may be a potential target for the therapy of RA.-Fu, Y., Liu, S., Wang, Y., Ren, F., Fan, X., Liang, J., Liu, C., Li, J., Ju, Y., Chang, Z. GdX/UBL4A-knockout mice resist collagen-induced arthritis by balancing the population of Th1/Th17 and regulatory T cells.

Inhibition of spleen tyrosine kinase attenuates psoriasis-like inflammation in mice through blockade of dendritic cell-Th17 inflammation axis.

Psoriasis is a debilitating autoimmune disease of the skin characterized by acanthosis and hyperkeratosis resulting from excessive growth of keratinocytes in the epidermis and inflammatory infiltrates in the dermis. Innate immune cells such as dendritic cells (DCs), perform a critical role in the pathophysiology of psoriasis by presenting inflammatory/costimulatory signals for differentiation of Th17 cells. Recent studies point to the involvement of spleen tyrosine kinase (SYK) in inflammatory signaling cascade of DCs. However, it is yet to be determined whether SYK inhibition in DCs would lead to diminishment of psoriatic inflammation. Therefore, our study evaluated the effects of SYK inhibitor, R406 on imiquimod (IMQ)-induced psoriasis-like inflammation, expression of costimulatory/inflammatory molecules in DCs and their relationship with Th17/Treg cells. Our data show that R406 causes attenuation of IMQ-induced dermal inflammation as shown by reduction in ear/back skin thickness, acanthosis and myeloperoxidase activity. This was concurrent with reduction in inflammatory cytokines and co-stimulatory molecules in CD11c + DCs such as IL-6, IL-23, MHCII, and CD40. This favoured the suppression of Th17 cells and upregulation of Treg cells in R406-treated mice with psoriasis-like inflammation. Direct activation of TLR7 by IMQ in splenocytic cultures led to increased SYK expression in CD11c + DCs and release of IL-23/IL-6. IMQ-induced IL-6/IL-23 levels were significantly diminished by SYK inhibitor, R406 in splenocytic cultures. In essence, our study shows that SYK inhibition supresses psoriasis-like inflammation by modifying DC function in mice. Further, it implies that SYK inhibition could be a prospective therapeutic approach for the treatment of psoriasis-like inflammation.

Improvement of the resistance against early Mycobacterium tuberculosis-infection in the absence of PI3Kγ enzyme is associated with increase of CD4+IL-17+ cells and neutrophils.

Given the impossibility to study the lung immune response during Mycobacterium tuberculosis-latent infection, and consequently, the mechanisms that control the bacterial load, it is reasonable to determine the activation of local immunity in the early phase of the infection. The phosphatidylinositol-3-kinase gamma enzyme (PI3Kγ) is involved in the leukocyte recruitment, phagocytosis and cellular differentiation, and therefore, it is considered a promising target for the development of immunotherapies for chronic inflammatory diseases. Mice genetically deficient in PI3Kγ (PI3Kγ-/-) or WT (Wild Type) were evaluated 15 days post-infection. The enzyme deficiency improved the resistance against infection, increased the frequency of CD4+IL-17+ cells, the production of IL-17 as well as the gene and protein expression of molecules associated with Th17 cell differentiation and neutrophil recruitment. Our findings show, for the first time, the participation of the PI3Kγ in vivo in the M. tuberculosis-infection, and suggest an association of Th17 cells with protection in the early phase of tuberculosis.

Pyruvate dehydrogenase phosphatase catalytic subunit 2 limits Th17 differentiation.

Th17 cells favor glycolytic metabolism, and pyruvate dehydrogenase (PDH) is the key bifurcation enzyme, which in its active dephosphorylated form advances the oxidative phosphorylation from glycolytic pathway. The transcriptional factor, inducible cAMP early repressor/cAMP response element modulator (ICER/CREM), has been shown to be induced in Th17 cells and to be overexpressed in CD4+ T cells from the patients with systemic lupus erythematosus (SLE). We found that glycolysis and lactate production in in vitro Th17-polarized T cells was reduced and that the expression of pyruvate dehydrogenase phosphatase catalytic subunit 2 (PDP2), an enzyme that converts the inactive PDH to its active form, and PDH enzyme activity were increased in Th17 cells from ICER/CREM-deficient animals. ICER was found to bind to the Pdp2 promoter and suppress its expression. Furthermore, forced expression of PDP2 in CD4+ cells reduced the in vitro Th17 differentiation, whereas shRNA-based suppression of PDP2 expression increased in vitro Th17 differentiation and augmented experimental autoimmune encephalomyelitis. At the translational level, PDP2 expression was decreased in memory Th17 cells from patients with SLE and forced expression of PDP2 in CD4+ T cells from lupus-prone MRL/lpr mice and patients with SLE suppressed Th17 differentiation. These data demonstrate the direct control of energy production during Th17 differentiation in health and disease by the transcription factor ICER/CREM at the PDH metabolism bifurcation level.

SGK1 Governs the Reciprocal Development of Th17 and Regulatory T Cells.

A balance between Th17 and regulatory T (Treg) cells is critical for immune homeostasis and tolerance. Our previous work has shown Serum- and glucocorticoid-induced kinase 1 (SGK1) is critical for the development and function of Th17 cells. Here, we show that SGK1 restrains the function of Treg cells and reciprocally regulates development of Th17/Treg balance. SGK1 deficiency leads to protection against autoimmunity and enhances self-tolerance by promoting Treg cell development and disarming Th17 cells. Treg cell-specific deletion of SGK1 results in enhanced Treg cell-suppressive function through preventing Foxo1 out of the nucleus, thereby promoting Foxp3 expression by binding to Foxp3 CNS1 region. Furthermore, our data suggest that SGK1 also plays a critical role in IL-23R-mediated inhibition of Treg and development of Th17 cells. Therefore, we demonstrate that SGK1 functions as a pivotal node in regulating the reciprocal development of pro-inflammatory Th17 and Foxp3+ Treg cells during autoimmune tissue inflammation.

An Overview of l-Amino Acid Oxidase Functions from Bacteria to Mammals: Focus on the Immunoregulatory Phenylalanine Oxidase IL4I1.

l-amino acid oxidases are flavin adenine dinucleotide-dependent enzymes present in all major kingdom of life, from bacteria to mammals. They participate in defense mechanisms by limiting the growth of most bacteria and parasites. A few mammalian LAAOs have been described, of which the enzyme "interleukin-4 induced gene 1" (IL4I1) is the best characterized. IL4I1 mainly oxidizes l-phenylalanine. It is a secreted enzyme physiologically produced by antigen presenting cells of the myeloid and B cell lineages and T helper type (Th) 17 cells. Important roles of IL4I1 in the fine control of the adaptive immune response in mice and humans have emerged during the last few years. Indeed, IL4I1 inhibits T cell proliferation and cytokine production and facilitates naïve CD4⁺ T-cell differentiation into regulatory T cells in vitro by limiting the capacity of T lymphocytes to respond to clonal receptor stimulation. It may also play a role in controlling the germinal center reaction for antibody production and limiting Th1 and Th17 responses. IL4I1 is expressed in tumor-associated macrophages of most human cancers and in some tumor cell types. Such expression, associated with its capacity to facilitate tumor growth by inhibiting the anti-tumor T-cell response, makes IL4I1 a new potential druggable target in the field of immunomodulation in cancer.

KLK5 induces shedding of DPP4 from circulatory Th17 cells in type 2 diabetes.

OBJECTIVE: Increasing plasma levels and activity of dipeptidyl peptidase-4 (DPP4 or CD26) are associated with rapid progression of metabolic syndrome to overt type 2 diabetes mellitus (T2DM). While DPP4 inhibitors are increasingly used as anti-hyperglycemic agents, the reason for the increase in plasma DPP4 activity in T2DM patients remains elusive. METHODS: We looked into the source of plasma DPP4 activity in a cohort of 135 treatment naive nonobese (BMI < 30) T2DM patients. A wide array of ex vivo, in vitro, and in silico methods were employed to study enzyme activity, gene expression, subcellular localization, protease identification, surface expression, and protein-protein interactions. RESULTS: We show that circulating immune cells, particularly CD4+ T cells, served as an important source for the increase in plasma DPP4 activity in T2DM. Moreover, we found kallikrein-related peptidase 5 (KLK5) as the enzyme responsible for cleaving DPP4 from the cell surface by directly interacting with the extracellular loop. Expression and secretion of KLK5 is induced in CD4+ T cells of T2DM patients. In addition, KLK5 shed DPP4 from circulating CD4+ T helper (Th)17 cells and shed it into the plasma of T2DM patients. Similar cleavage and shedding activities were not seen in controls. CONCLUSIONS: Our study provides mechanistic insights into the molecular interaction between KLK5 and DPP4 as well as CD4+ T cell derived KLK5 mediated enzymatic cleavage of DPP4 from cell surface. Thus, our study uncovers a hitherto unknown cellular source and mechanism behind enhanced plasma DPP4 activity in T2DM.

Differential modulation of IL-12 family cytokines in autoimmune islet graft failure in mice.

AIMS/HYPOTHESIS: The relative contribution of T helper (Th)1 and Th17 cells in graft rejection is inconclusive, on the basis of evidence provided by different T cell-related cytokine-deficient animal models and graft types. METHODS: We used novel antigen-presenting-cell-specific Il-12p35 (also known as Il12a)-knockout (KO), IL-23p19-knockdown (KD) and IL-27p28-KD strategies to investigate T cell differentiation in islet graft rejection. RESULTS: In vitro dendritic cell-T cell coculture experiments revealed that dendritic cells from Il-12p35-KO and IL-23p19-KD mice showed reduced ability to stimulate IFN-γ and IL-17 production in T cells, respectively. To further explore the T cell responses in islet graft rejection, we transplanted islets into streptozotocin-induced diabetic NOD/severe combined immunodeficiency (SCID) recipient mice with IL-12-, IL-23-, or IL-27-deficient backgrounds and then challenged them with NOD.BDC2.5 T cells. The survival of islet grafts was significantly prolonged in Il-12p35-KO and IL-23p19-KD recipients compared with the control recipients. T cell infiltrations and Th1 cell populations were also decreased in the grafts, correlating with prolonged graft survival. CONCLUSIONS/INTERPRETATION: Our results suggest that IL-12 and IL-23 promote and/or maintain Th1 cell-mediated islet graft rejection. Thus, blockade of IL-12 and IL-23 might act as therapeutic strategies for reducing rejection responses.

Distinct Roles of Brd2 and Brd4 in Potentiating the Transcriptional Program for Th17 Cell Differentiation.

The BET proteins are major transcriptional regulators and have emerged as new drug targets, but their functional distinction has remained elusive. In this study, we report that the BET family members Brd2 and Brd4 exert distinct genomic functions at genes whose transcription they co-regulate during mouse T helper 17 (Th17) cell differentiation. Brd2 is associated with the chromatin insulator CTCF and the cohesin complex to support cis-regulatory enhancer assembly for gene transcriptional activation. In this context, Brd2 binds the transcription factor Stat3 in an acetylation-sensitive manner and facilitates Stat3 recruitment to active enhancers occupied with transcription factors Irf4 and Batf. In parallel, Brd4 temporally controls RNA polymerase II (Pol II) processivity during transcription elongation through cyclin T1 and Cdk9 recruitment and Pol II Ser2 phosphorylation. Collectively, our study uncovers both separate and interdependent Brd2 and Brd4 functions in potentiating the genetic program required for Th17 cell development and adaptive immunity.

Targeting the RhoA-ROCK pathway to reverse T-cell dysfunction in SLE.

OBJECTIVES: Deregulated production of interleukin (IL)-17 and IL-21 contributes to the pathogenesis of autoimmune disorders such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Production of IL-17 and IL-21 can be regulated by ROCK2, one of the two Rho kinases. Increased ROCK activation was previously observed in an SLE cohort. Here, we evaluated ROCK activity in a new SLE cohort, and an RA cohort, and assessed the ability of distinct inhibitors of the ROCK pathway to suppress production of IL-17 and IL-21 by SLE T cells or human Th17 cells. METHODS: ROCK activity in peripheral blood mononuclear cells (PBMCs) from 29 patients with SLE, 31 patients with RA and 28 healthy controls was determined by ELISA. SLE T cells or in vitro-differentiated Th17 cells were treated with Y27632 (a pan-ROCK inhibitor), KD025 (a selective ROCK2 inhibitor) or simvastatin (which inhibits RhoA, a major ROCK activator). ROCK activity and IL-17 and IL-21 production were assessed. The transcriptional profile altered by ROCK inhibitors was evaluated by NanoString technology. RESULTS: ROCK activity levels were significantly higher in patients with SLE and RA than healthy controls. Th17 cells exhibited high ROCK activity that was inhibited by Y27632, KD025 or simvastatin; each also decreased IL-17 and IL-21 production by purified SLE T cells or Th17 cells. Immune profiling revealed both overlapping and distinct effects of the different ROCK inhibitors. CONCLUSIONS: ROCK activity is elevated in PBMCs from patients with SLE and RA. Production of IL-17 and IL-21 by SLE T cells or Th17 cells can furthermore be inhibited by targeting the RhoA-ROCK pathway via both non-selective and selective approaches.

Lysyl Oxidase 3 Is a Dual-Specificity Enzyme Involved in STAT3 Deacetylation and Deacetylimination Modulation.

In mammalian cells, histone deacetylase (HDAC) and Sirtuin (SIRT) are two families responsible for removing acetyl groups from acetylated proteins. Here, we describe protein deacetylation coupled with deacetylimination as a function of lysyl oxidase (LOX) family members. LOX-like 3 (Loxl3) associates with Stat3 in the nucleus to deacetylate and deacetyliminate Stat3 on multiple acetyl-lysine sites. Surprisingly, Loxl3 N-terminal scavenger receptor cysteine-rich (SRCR) repeats, rather than the C-terminal oxidase catalytic domain, represent the major deacetylase/deacetyliminase activity. Loxl3-mediated deacetylation/deacetylimination disrupts Stat3 dimerization, abolishes Stat3 transcription activity, and restricts cell proliferation. In Loxl3-/- mice, Stat3 is constitutively acetylated and naive CD4+ T cells are potentiated in Th17/Treg cell differentiation. When overexpressed, the SRCR repeats from other LOX family members can catalyze protein deacetylation/deacetylimination. Thus, our findings delineate a hitherto-unknown mechanism of protein deacetylation and deacetylimination catalyzed by lysyl oxidases.

Arctigenin functions as a selective agonist of estrogen receptor ß to restrict mTORC1 activation and consequent Th17 differentiation.

Arctigenin was previously proven to inhibit Th17 cell differentiation and thereby attenuate colitis in mice by down-regulating the activation of mechanistic target of rapamycin complex 1 (mTORC1). The present study was performed to address its underlying mechanism in view of estrogen receptor (ER). The specific antagonist PHTPP or siRNA of ERß largely diminished the inhibitory effect of arctigenin on the mTORC1 activation in T cell lines and primary CD4+ T cells under Th17-polarization condition, suggesting that arctigenin functioned in an ERß-dependent manner. Moreover, arctigenin was recognized to be an agonist of ERß, which could bind to ERß with a moderate affinity, promote dissociation of ERß/HSP90 complex and nuclear translocation and phosphorylation of ERß, and increase the transcription activity. Following activation of ERß, arctigenin inhibited the activity of mTORC1 by disruption of ERß-raptor-mTOR complex assembly. Deficiency of ERß markedly abolished arctigenin-mediated inhibition of Th17 cell differentiation. In colitis mice, the activation of ERß, inhibition of mTORC1 activation and Th17 response by arctigenin were abolished by PHTPP treatment. In conclusion, ERß might be the target protein of arctigenin responsible for inhibition of mTORC1 activation and resultant prevention of Th17 cell differentiation and colitis development.

Human Th17 Cells Lack HIV-Inhibitory RNases and Are Highly Permissive to Productive HIV Infection.

UNLABELLED: Human immunodeficiency virus (HIV) infects and depletes CD4(+) T cells, but subsets of CD4(+) T cells vary in their susceptibility and permissiveness to infection. For example, HIV preferentially depletes interleukin-17 (IL-17)-producing T helper 17 (Th17) cells and T follicular helper (Tfh) cells. The preferential loss of Th17 cells during the acute phase of infection impairs the integrity of the gut mucosal barrier, which drives chronic immune activation-a key determinant of disease progression. The preferential loss of Th17 cells has been attributed to high CD4, CCR5, and CXCR4 expression. Here, we show that Th17 cells also exhibit heightened permissiveness to productive HIV infection. Primary human CD4(+) T cells were sorted, activated under Th17- or Th0-polarizing conditions and infected, and then analyzed by flow cytometry. Th17-polarizing cytokines increased HIV infection, and HIV infection was disproportionately higher among Th17 cells than among IL-17(-) or gamma interferon-positive (IFN-γ(+)) cells, even upon infection with a replication-defective HIV vector with a pseudotype envelope. Further, Th17-polarized cells produced more viral capsid protein. Our data also reveal that Th17-polarized cells have diminished expression of RNase A superfamily proteins, and we report for the first time that RNase 6 inhibits HIV. Thus, our findings link Th17 polarization to increased HIV replication. IMPORTANCE: Our study compares the intracellular replicative capacities of several different HIV isolates among different T cell subsets, providing a link between the differentiation of Th17 cells and HIV replication. Th17 cells are of key importance in mucosal integrity and in the immune response to certain pathogens. Based on our findings and the work of others, we propose a model in which HIV replication is favored by the intracellular environment of two CD4(+) T cell subsets that share several requirements for their differentiation: Th17 and Tfh cells. Characterizing cells that support high levels of viral replication (rather than becoming latently infected or undergoing cell death) informs the search for new therapeutics aimed at manipulating intracellular signaling pathways and/or transcriptional factors that affect HIV replication.

The p38 mitogen-activated protein kinase cascade modulates T helper type 17 differentiation and functionality in multiple sclerosis.

The p38 mitogen-activated protein kinase cascade is required for the induction of a T helper type 17 (Th17) -mediated autoimmune response, which underlies the development and progression of several autoimmune diseases, such as experimental autoimmune encephalomyelitis, the animal model of multiple sclerosis (MS). However, the contribution of p38 phosphorylation to human Th cell differentiation has not been clarified. Here we demonstrate that the p38 signalling pathway is implicated in the generation of Th17 lymphocytes from human CD4(+)  CD27(+)  CD45RA(+) naive T cells, both in healthy donors and in patients affected by the relapsing-remitting form of MS. Our data also indicate that p38 activation is essential for interleukin-17 release from central memory lymphocytes and committed Th17 cell clones. Furthermore, CD4(+) T cells isolated from individuals with relapsing-remitting MS display an altered responsiveness of the p38 cascade, resulting in increased p38 phosphorylation upon stimulation. These findings suggest that the p38 signalling pathway, by modulating the Th17 differentiation and response, is involved in the pathogenesis of MS, and open new perspectives for the use of p38 inhibitors in the treatment of Th17-mediated autoimmune diseases.