MyD88 is essential to sustain mTOR activation necessary to promote T helper 17 cell proliferation by linking IL-1 and IL-23 signaling

IL-1R–associated kinase (IRAK) 1 is an important component of the IL-1R and TLR signaling pathways, which influence Th cell differentiation. In this study, we show that IRAK1 promotes Th17 development by mediating IL-1β–induced upregulation of IL-23R and subsequent STAT3 phosphorylation, thus enabling sustained IL-17 production. Moreover, we show that IRAK1 signaling fosters Th1 differentiation by mediating T-bet induction and counteracts regulatory T cell generation. Cotransfer experiments revealed that Irak1-deficient CD4+ T cells have a cell-intrinsic defect in generating Th1 and Th17 cells under inflammatory conditions in spleen, mesenteric lymph nodes, and colon tissue. Furthermore, IRAK1 expression in T cells was shown to be essential for T cell accumulation in the inflamed intestine and mesenteric lymph nodes. Transcriptome analysis ex vivo revealed that IRAK1 promotes T cell activation and induction of gut-homing molecules in a cell-intrinsic manner. Accordingly, Irak1-deficient T cells failed to upregulate surface expression of α4β7 integrin after transfer into Rag1−/− mice, and their ability to induce colitis was greatly impaired. Lack of IRAK1 in recipient mice provided additional protection from colitis. Therefore, IRAK1 plays an important role in intestinal inflammation by mediating T cell activation, differentiation, and accumulation in the gut. Thus, IRAK1 is a promising novel target for therapy of inflammatory bowel diseases.

Section: Discussionsupporting

confidence: 79%

IRAK1 Drives Intestinal Inflammation by Promoting the Generation of Effector Th Cells with Optimal Gut-Homing Capacity

Heiseke¹,

Jeuk²,

Markota³

et al. 2015

“…The absence of an IL-17 response in IL-12p35/40-deficient mutants is most likely due to a dual role for IL-12p40 as a common component with IL-23, which drives Th-17 differentiation. Our results also suggest that NE activity may link IL-12 and MyD88 for the activation of mTOR to promote Th-17 via IL-1 and IL-23 signaling (77,78). Similar to the TLR-MyD88 deficiency, lack of either IL-12 or IL-12Rb1 had no detrimental effect on Ab responses with NE adjuvant.…”

Section: Discussionsupporting

confidence: 58%

Distinct Pathways of Humoral and Cellular Immunity Induced with the Mucosal Administration of a Nanoemulsion Adjuvant

Bielinska

Makidon

Janczak

et al. 2014

Nasal administration of an oil-in-water nanoemulsion (NE) adjuvant W805EC produces potent systemic and mucosal, Th-1– and Th-17–balanced cellular responses. However, its molecular mechanism of action has not been fully characterized and is of particular interest because NE does not contain specific ligands for innate immune receptors. In these studies, we demonstrate that W805EC NE adjuvant activates innate immunity, induces specific gene transcription, and modulates NF-κB activity via TLR2 and TLR4 by a mechanism that appears to be distinct from typical TLR agonists. Nasal immunization with NE-based vaccine showed that the TLR2, TLR4, and MyD88 pathways and IL-12 and IL-12Rβ1 expression are not required for an Ab response, but they are essential for the induction of balanced Th-1 polarization and Th-17 cellular immunity. NE adjuvant induces MHC class II, CD80, and CD86 costimulatory molecule expression and dendritic cell maturation. Further, upon immunization with NE, adjuvant mice deficient in the CD86 receptor had normal Ab responses but significantly reduced Th-1 cellular responses, whereas animals deficient in both CD80 and CD86 or lacking CD40 failed to produce either humoral or cellular immunity. Overall, our data show that intranasal administration of Ag with NE induces TLR2 and TLR4 activation along with a MyD88-independent Ab response and a MyD88-dependent Th-1 and Th-17 cell–mediated immune response. These findings suggest that the unique properties of NE adjuvant may offer novel opportunities for understanding previously unrecognized mechanisms of immune activation important for generating effective mucosal and systemic immune responses.

“…Hyperactivated mTOR is observed in many types of cancers and autoimmune disease (55,56). Although the PI3K/AKT pathway is considered a canonical upstream regulator of mTOR, the activation of mTOR also can occur through AKT-independent mechanisms (57)(58)(59).…”

Section: Ly6gmentioning

confidence: 99%

Targeting S1P1 Receptor Protects against Murine Immunological Hepatic Injury through Myeloid-Derived Suppressor Cells

Liu

Wang

et al. 2014

Although FTY720 may alter migration and homing of lymphocytes via sphingosine-1-phosphate (S1P) receptors, our recent studies indicated that FTY720 directly controls the differentiation of Th1 cells to regulatory T cells (Tregs) by targeting S1P1. However, the pharmacological function of FTY720 in immunological hepatic injury remains unknown. In this study, the role and regulatory signaling pathway of S1P receptor were investigated using a pharmacological approach in immune-mediated hepatic injury (IMH). In the context of IMH, FTY720 significantly ameliorated mortality and hepatic pathology. In FTY720-treated mice, recruited CD11b+Gr1+ myeloid-derived suppressor cells (MDSCs) mediate protection against IMH and are functional suppressive immune modulators that result in fewer IFN-γ–producing Th1 cells and more Foxp3+ Tregs. In agreement, FTY720-treated MDSCs promote the reciprocal differentiation between Th1 cells and Tregs in vitro and in vivo. Mechanistically, FTY720 treatment induced inducible NO synthase expression and NO production in MDSCs. Pharmacologic inhibition of inducible NO synthase completely eliminates MDSC suppressive function and eradicates their inducible effects on T cell differentiation. Finally, the mTOR inhibitor, rapamycin, photocopies the effects of FTY720 on MDSCs, implicating mTOR as a downstream effector of S1P1 signaling. This study identifies MDSCs as an essential component that provides protection against IMH following FTY720 or rapamycin treatment, validating the S1P1–mTOR signaling axis as a potential therapeutic target in hepatic injury.