Inhibition of IL-21/IL-21R Signaling by Fucoxanthin: Structure-Based and Experimental Analysis.

Polyunsaturated fatty acids, including docosahexaenoic acid (DHA, 22:6n-3), modulate immune responses and exert beneficial immunosuppressive effects, but the molecular mechanisms inhibiting T-cell activation are not yet elucidated. Lipid rafts have been shown to play an important role in the compartmentalization and modulation of cell signaling. We investigated the role of DHA in modulating the lipid composition in lipid rafts and membrane subdomain distribution of interleukin-2 (IL-2) receptor signaling molecules. We found that DHA altered lipid components of rafts and modified the IL-2-induced Janus kinase-signal transducer and activator of transcription (STAT) signaling pathway by partially displacing IL-2 receptors from lipid rafts. We fractionated plasma membrane subcellular compartments and discovered that certain amounts of STAT5a and STAT5b existed in detergent-resistant plasma membrane fractions of T-cells. After DHA treatment, STAT5a and STAT5b were not detected in lipid raft fractions and were located in detergent-soluble fractions. These data demonstrate for the first time that DHA alters the lipid composition of membrane microdomains and suppresses IL-2 receptor signaling in T-cells. Thus, our data provide evidence for a functional modification in lipid rafts by DHA treatment and explain PUFA-mediated immunosuppressive effects.

Interplay between PI3K/mTOR Signaling and IRE1a-XBP1 Promotes Survival of Pre-B NRASG12D all Cells Providing a Therapeutic Vulnerability for the “Undruggable” Driver RAS

Interleukin-4 (IL-4) receptor (IL-4R) signaling plays a pivotal role in type 2 immune responses. Type 2 immunity ensures several host-protective processes such as defense against helminth parasites and wound repair, however, type 2 immune responses also drive the pathogenesis of allergic diseases. Neutrophil granulocytes (neutrophils) have not traditionally been considered a part of type 2 immunity. While neutrophils might be beneficial in initiating a type 2 immune response, their involvement and activation is rather unwanted at later stages. This is evidenced by examples of type 2 immune responses where increased neutrophil responses are able to enhance immunity, however, at the cost of increased tissue damage. Recent studies have linked the type 2 cytokines IL-4 and IL-13 and their signaling via type I and type II IL-4Rs on neutrophils to inhibition of several neutrophil effector functions. This mechanism directly curtails neutrophil chemotaxis toward potent intermediary chemoattractants, inhibits the formation of neutrophil extracellular traps, and antagonizes the effects of granulocyte colony-stimulating factor on neutrophils. These effects are observed in both mouse and human neutrophils. Thus, we propose for type 2 immune responses that neutrophils are, as in other immune responses, the first non-resident cells to arrive at a site of inflammation or infection, thereby guiding and attracting other innate and adaptive immune cells; however, as soon as the type 2 cytokines IL-4 and IL-13 predominate, neutrophil recruitment, chemotaxis, and effector functions are rapidly shut off by IL-4/IL-13-mediated IL-4R signaling in neutrophils to prevent them from damaging healthy tissues. Insight into this neutrophil checkpoint pathway will help understand regulation of neutrophilic type 2 inflammation and guide the design of targeted therapeutic approaches for modulating neutrophils during inflammation and neutropenia.

Pharmacologic Co-Blockade of IFNγR and IL6R Pathways to Prevent and Treat GvHD

Curcumin blocks interleukin (IL)-2 signaling in T-lymphocytes by inhibiting IL-2 synthesis, CD25 expression, and IL-2 receptor signaling

Intestinal Interleukin-17 Receptor Signaling Mediates Reciprocal Control of the Gut Microbiota and Autoimmune Inflammation

The many roles of IL-7 in B cell development; Mediator of survival, proliferation and differentiation

Mucosal homeostasis requires coordinated immune regulation and epithelial repair. Inflammatory bowel disease (IBD) arises from disrupted coordination between the immune system and intestinal epithelium, where resolution and repair must occur in parallel. Interleukin-6 (IL-6) plays a dual role: it promotes epithelial regeneration but destabilizes regulatory T cells (Tregs). We aimed to determine the contribution of Treg IL-6 receptor (IL-6R) signaling to intestinal inflammation and epithelial integrity. We developed a conditional knockout mouse model in which IL-6R was deleted from Tregs (Treg IL-6R knockout). These mice were subjected to dextran sodium sulfate (DSS)-induced colitis and a T cell transfer model of colitis. Soluble IL-6R production by Tregs was assessed in vitro, and transcriptional changes in epithelial cells were analyzed by RNA-seq. Human colonic organoids from patients with IBD were treated with IL-6 or hyper-IL-6 (IL-6/sIL-6R fusion protein) to test downstream signaling effects. Tregs lacking IL-6R improved colitis to a similar extent as control Tregs in the adoptive transfer model, indicating intact suppressive function. However, Treg IL-6R knockout mice were more susceptible to DSS colitis than controls, suggesting a physiologic role for Treg IL-6R signaling in epithelial protection. In vitro, Tregs shed soluble IL-6R, enabling IL-6 trans-signaling to epithelial cells. Intestinal epithelial cells from Treg IL-6R knockout mice compared with WTcre controls revealed widespread transcriptional downregulation of genes related to survival and repair pathways at baseline, and impaired transcriptional responses following DSS treatment. In human organoids, IL-6 trans-signaling elicited stronger STAT3 activation than IL-6 alone. These findings reveal a previously unrecognized role for Treg-derived IL-6R in promoting epithelial resilience and maintaining mucosal homeostasis.NEW & NOTEWORTHY This study reveals a novel role for Treg-derived IL-6R in supporting epithelial repair. Despite preserved immune-suppressive capacity, deletion of IL-6R from Tregs impairs epithelial transcription and worsens injury in colitis. We demonstrate that human intestinal organoids preferentially respond to trans- over classic IL-6 signaling. These findings introduce a Treg-specific role in immune-epithelial cross talk relevant to mucosal healing and inflammatory bowel disease.

Cutaneous T cell lymphomas (CTCLs) often show abnormal interleukin-2 (IL-2) receptor signaling. In this study, we investigated the role of Gab2, a recently identified adaptor molecule involved in IL-2 receptor signaling in CTCLs. We show that Gab2 was transiently phosphorylated by tyrosine in human mycosis fungoides (MF) tumor T cells upon IL-2 stimulation and that SHP2 as well as Stat5a associated inducibly with Gab2. IL-15, but not IL-4, also induced tyrosine phosphorylation of Gab2, suggesting that the IL-2 receptor β-chain is important for IL-2-induced Gab2 phosphorylation. Preincubation of cells with the Src family kinase inhibitor, PP1, surprisingly increased the IL-2- and IL-15-induced tyrosine phosphorylation of Gab2, indicating that an Src family kinase member negatively regulates IL-2 receptor signaling in MF T cells. Thus, although Gab2 seems to function normally in MF T cells compared to normal T cells, Gab2 itself might be abnormally regulated by an Src family kinase.

Interleukin 6 (IL-6) is a circulating cytokine implicated in inflammatory processes. However, the broad effects of IL-6 receptor (IL-6R) signalling on other circulating cytokines is not known. Using summary-level data from genome-wide association studies, we leveraged genetic variants that proxy IL-6R signalling in two-sample Mendelian randomization analyses to investigate effects on levels of 40 circulating cytokines. Increased genetically proxied IL-6R signalling was associated with reduced levels of 10 circulating interleukins, chemokines and growth factors. The significant results include IL-10 (Mendelian randomization estimate -0.306, standard error [SE] 0.093), IL-4 (estimate -0.393, SE 0.1007), eotaxin (estimate -0.510, SE 0.1213) and Fibroblast growth factor (estimate -0.334, SE 0.1005). The findings from this study support the feedback effects of IL-6R signalling on reducing levels of some circulating cytokines and identify compensatory mechanisms that maybe modulating its inflammatory effects. These results provide insight into the mechanisms by which IL-6R signalling may be contributing to inflammatory and autoimmune diseases.

Intestinal epithelial cells (IECs) provide a critical first line of defense against microbes through barrier function, production of antimicrobial peptides (AMPs), secretion of cytokines, and recruitment of inflammatory cells. Whether single or multiple upstream cues regulate this diverse set of responses from IECs is not clear. Here we discover an unexpected role for Interleukin-1 Receptor (IL-1R) signaling in IECs in regulating intestinal homeostasis and inflammation. Specifically, absence of IL-1R in epithelial cells abrogates a homeostatic anti-microbial program including production of AMPs. Although IL-1R signaling alone is not sufficient to drive the AMP gene induction in IECs, the IL-22-driven anti-microbial program requires synergistic IL-1R signaling. Mechanistically, IL-1R signaling results in enhancement and temporal stabilization of STAT3 phosphorylation downstream of IL-22R. Thus, we reveal an unexpected cooperation between IL-1R and IL-22R in directly regulating an intestinal anti-microbial program. In contrast, absence of IL-1R in IECs protects mice from chemically-induced acute intestinal inflammation suggesting that IEC specific IL-1R signaling contributes to inflammation and pathology. We find that IL-1R signaling directly induces expression of chemokines as well as genes involved in the production of reactive oxygen species in IECs, a process that likely evolved to protect against enteric pathogens. Our findings establish a critical role for IEC specific IL-1R signaling in both steady state anti-microbial gene induction as well as intestinal inflammation. Further studies are likely to reveal potential targets for developing therapies against Crohn’s Disease and Ulcerative Colitis.

The present study was undertaken to test the hypothesis that tumor necrosis factor (TNF) and/or interleukin-1 (IL-1) activity mediates lipopolysaccharide (LPS)-induced bone resorption in vivo. To test this hypothesis, Escherichia coli LPS or Porphyromonas gingivalis LPS was injected into the subcutaneous tissues overlying mouse calvariae. Histological sections, prepared from the center of the lesion, were stained for tartrate-resistant acid phosphatase, and histomorphometric analysis was performed to quantify the osteoclast number and the area of bone resorption. In time course experiments using normal mice, a peak of bone resorption occurred 5 days after endotoxin stimulation. In dose-response experiments, IL-1 receptor type 1 deletion (IL-1R(-/-)), TNF double-receptor p55/p75 deletion (TNF p55(-/-)/p75(-/-)), combined TNF p55 and IL-1 receptor type 1 deletion (TNF p55(-/-)/IL-1R(-/-)), and IL-1beta-converting enzyme-deficient (ICE(-/-)) mice and the respective wild-type mice were injected with 500, 100, or 20 micrograms of P. gingivalis LPS and sacrificed 5 days after LPS injection. At the highest dose (500 micrograms), significant decreases in osteoclast number occurred in mutant mice compared to wild-type mice: (i) a 64% reduction for the TNF p55(-/-)/IL-1R(-/-) mice, (ii) a 57% reduction for the IL-1R(-/-) mice, (iii) a 41% reduction for the TNF p55(-/-)/p75(-/-) mice, and (iv) a 38% reduction for the ICE(-/-) mice. At the two lower doses, bone resorption was apparent but no significant differences between mutant and wild-type animals were observed. The present data indicate that at higher doses, LPS-induced bone resorption is substantially mediated by IL-1 and TNF receptor signaling. Furthermore, IL-1 receptor signaling appears to be slightly more important than TNF receptor signaling. At lower LPS doses, other pathways leading to osteoclast activity that are independent of TNF and IL-1 are involved.

Defining the Role of Anti- and Pro-inflammatory Outcomes of Interleukin-6 in Mental Health

Understanding how the immune system decides between tolerance and activation by antigens requires addressing cytokine regulation as a highly dynamic process. We quantified the dynamics of interleukin-2 (IL-2) signaling in a population of T cells during an immune response by combining in silico modeling and single-cell measurements in vitro. We demonstrate that IL-2 receptor expression levels vary widely among T cells creating a large variability in the ability of the individual cells to consume, produce and participate in IL-2 signaling within the population. Our model reveals that at the population level, these heterogeneous cells are engaged in a tug-of-war for IL-2 between regulatory (T(reg)) and effector (T(eff)) T cells, whereby access to IL-2 can either increase the survival of T(eff) cells or the suppressive capacity of T(reg) cells. This tug-of-war is the mechanism enforcing, at the systems level, a core function of T(reg) cells, namely the specific suppression of survival signals for weakly activated T(eff) cells but not for strongly activated cells. Our integrated model yields quantitative, experimentally validated predictions for the manipulation of T(reg) suppression.

With over 8500 deaths each year in the USA, malignant melanoma is the deadliest of all skin cancers. Constitutive activation of the nuclear factor kappa B (NF-κB) is common in melanoma, promoting tumor growth, survival and metastasis. In light of its role in tumorigenesis, targeting of the NF-κB pathway has been considered a possible therapeutic option for the treatment of melanoma. However, NF- αB activation is critical for the development, survival, migration and function of immune cells. We hypothesized that systemic inhibition of the activation of NF-κB might have a deleterious effect on the tumor immune response. Melanoma bearing C57BL/6 mice received 50 mg/kg of BMS-345541, a selective inhibitor of the inhibitor of αB kinase (IKKα), twice daily. Tumors, spleens and bone marrow were harvested at different time points and analyzed by flow cytometry for leukocyte composition and cytokine production. Intracellular cytokine staining revealed an early induction of Interleukin-4 (IL-4) within the myeloid and B cell components of the tumor, as a result of BMS-345541 treatment. The production of IL-4 by these cells suggests an early switch to a tumor promoting T helper 2 (Th2) and M2 driven immune response, which may counteract the anti-tumor effect of IKKα inhibition by generating a pro-tumorigenic microenvironment. These results, in part, explain the modest delay in tumor growth demonstrated. IL-4 receptor (IL-4R) expression on human melanoma cells has been previously documented; however the effects of IL-4 on these cells have generated contradictory reports. IL-4R signaling has been shown to either inhibit growth of tumor cells in vitro or to promote survival of tumor cells. In C57Bl/6 mice bearing a murine melanoma, BMS345541 (75 mg/kg bid) was given in combination with 100 µg of IL-4R blocking antibody on day 4 and day 12 of treatment. This combination significantly inhibited tumor growth compared to BMS345541 treatment alone. These data suggest an important role for IL-4 in promoting melanoma growth in vivo. Dual targeting of IL-4R and NF-κB signaling pathways neutralizes the tumor promoting immune component. Currently, IL-4R antagonists are in clinical trials for the treatment of asthma, which makes the translational prospects of this study extraordinarily viable. We are grateful for support from the NCI (CA116021-07, 5T32CA119925-03) and the Department of Veterans Affairs for these studies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 4403. doi:1538-7445.AM2012-4403