Harald Braun

Interleukin-1α controls allergic sensitization to inhaled house dust mite via the epithelial release of GM-CSF and IL-33

IL-1α promotes a cascade of cytokine production from epithelial cells culminating in Th2 immunity to house dust mite allergens.

Interleukin-21-Producing CD4+ T Cells Promote Type 2 Immunity to House Dust Mites

Asthma is a T helper 2 (Th2)-cell-mediated disease; however, recent findings implicate Th17 and innate lymphoid cells also in regulating airway inflammation. Herein, we have demonstrated profound interleukin-21 (IL-21) production after house dust mite (HDM)-driven asthma by using T cell receptor (TCR) transgenic mice reactive to Dermatophagoides pteronyssinus 1 and an IL-21GFP reporter mouse. IL-21-producing cells in the mediastinal lymph node (mLN) bore characteristics of T follicular helper (Tfh) cells, whereas IL-21(+) cells in the lung did not express CXCR5 (a chemokine receptor expressed by Tfh cells) and were distinct from effector Th2 or Th17 cells. Il21r(-/-) mice developed reduced type 2 responses and the IL-21 receptor (IL-21R) enhanced Th2 cell function in a cell-intrinsic manner. Finally, administration of recombinant IL-21 and IL-25 synergistically promoted airway eosinophilia primarily via effects on CD4(+) lymphocytes. This highlights an important Th2-cell-amplifying function of IL-21-producing CD4(+) T cells in allergic airway inflammation.

IL-33 targeting attenuates intestinal mucositis and enhances effective tumor chemotherapy in mice

Intestinal damage and severe diarrhea are serious side effects of cancer chemotherapy and constrain the usage of most such therapies. Here we show that interleukin-33 (IL-33) mediates the severe intestinal mucositis in mice treated with irinotecan (CPT-11), a commonly used cancer chemotherapeutic agent. Systemic CPT-11 administration led to severe mucosal damage, diarrhea, and body weight loss concomitant with the induction of IL-33 in the small intestine (SI). This mucositis was markedly reduced in mice deficient in the IL-33R (ST2−/−). Moreover, recombinant IL-33 exacerbated the CPT-11-induced mucositis, whereas IL-33 blockade with anti-IL-33 antibody or soluble ST2 markedly attenuated the disease. CPT-11 treatment increased neutrophil accumulation in the SI and adhesion to mesenteric veins. Supernatants from SI explants treated with CPT-11 enhanced transmigration of neutrophils in vitro in an IL-33-, CXCL1/2-, and CXCR2-dependent manner. Importantly, IL-33 blockade reduced mucositis and enabled prolonged CPT-11 treatment of ectopic CT26 colon carcinoma, leading to a beneficial outcome of the chemotherapy. These results suggest that inhibition of the IL-33/ST2 pathway may represent a novel approach to limit mucositis and thus improve the effectiveness of chemotherapy.

The PDGF-BB-SOX7 axis-modulated IL-33 in pericytes and stromal cells promotes metastasis through tumour-associated macrophages

Signalling molecules and pathways that mediate crosstalk between various tumour cellular compartments in cancer metastasis remain largely unknown. We report a mechanism of the interaction between perivascular cells and tumour-associated macrophages (TAMs) in promoting metastasis through the IL-33–ST2-dependent pathway in xenograft mouse models of cancer. IL-33 is the highest upregulated gene through activation of SOX7 transcription factor in PDGF-BB-stimulated pericytes. Gain- and loss-of-function experiments validate that IL-33 promotes metastasis through recruitment of TAMs. Pharmacological inhibition of the IL-33–ST2 signalling by a soluble ST2 significantly inhibits TAMs and metastasis. Genetic deletion of host IL-33 in mice also blocks PDGF-BB-induced TAM recruitment and metastasis. These findings shed light on the role of tumour stroma in promoting metastasis and have therapeutic implications for cancer therapy.

Structure and antagonism of the receptor complex mediated by human TSLP in allergy and asthma.

The pro-inflammatory cytokine thymic stromal lymphopoietin (TSLP) is pivotal to the pathophysiology of widespread allergic diseases mediated by type 2 helper T cell (Th2) responses, including asthma and atopic dermatitis. The emergence of human TSLP as a clinical target against asthma calls for maximally harnessing its therapeutic potential via structural and mechanistic considerations. Here we employ an integrative experimental approach focusing on productive and antagonized TSLP complexes and free cytokine. We reveal how cognate receptor TSLPR allosterically activates TSLP to potentiate the recruitment of the shared interleukin 7 receptor α-chain (IL-7Rα) by leveraging the flexibility, conformational heterogeneity and electrostatics of the cytokine. We further show that the monoclonal antibody Tezepelumab partly exploits these principles to neutralize TSLP activity. Finally, we introduce a fusion protein comprising a tandem of the TSLPR and IL-7Rα extracellular domains, which harnesses the mechanistic intricacies of the TSLP-driven receptor complex to manifest high antagonistic potency.

The IL-33/ST2 axis is crucial in type 2 airway responses induced by Staphylococcus aureus–derived serine protease–like protein D

Background: Chronic airway inflammatory diseases, such as chronic rhinosinusitis with nasal polyps and asthma, show increased nasal Staphylococcus aureus colonization. Staphylococcus aureus–derived serine protease–like protein (Spl) D and other closely related proteases secreted by S aureus have recently been identified as inducers of allergic asthma in human subjects and mice, but their mechanism of action is largely unknown. Objective: We investigated the role of recombinant SplD in driving TH2‐biased responses and IgE formation in a murine model of allergic asthma. Methods: Allergic asthma was induced in C57BL/6 J wild‐type mice, Toll‐like receptor (TLR) 4 knockout (Tlr4−/−) mice, and recombination‐activating gene (Rag2) knockout (Rag2−/−) mice by means of repeated intratracheal applications of SplD. Inflammatory parameters in the airways were assessed by means of flow cytometry, ELISA, Luminex, and immunohistochemistry. Serum SplD‐specific IgE levels were analyzed by using ELISA. Results: We observed that repeated intratracheal exposure to SplD led to IL‐33 and eotaxin production, eosinophilia, bronchial hyperreactivity, and goblet cell hyperplasia in the airways. Blocking IL‐33 activity with a soluble ST2 receptor significantly decreased the numbers of eosinophils, IL‐13+ type 2 innate lymphoid cells and IL‐13+CD4+ T cells and IL‐5 and IL‐13 production by lymph node cells but had no effect on IgE production. SplD‐induced airway inflammation and IgE production were largely dependent on the presence of the functional adaptive immune system and independent of TLR4 signaling. Conclusion: The S aureus–derived protein SplD is a potent allergen of S aureus and induces a TH2‐biased inflammatory response in the airways in an IL‐33–dependent but TRL4‐independent manner. The soluble ST2 receptor could be an efficient strategy to interfere with SplD‐induced TH2 inflammation but does not prevent the allergic sensitization. Graphical abstract Figure. No caption available.

Dichotomous function of IL-33 in health and disease : from biology to clinical implications

Graphical abstract Figure. No caption available. ABSTRACT Interleukin (IL)‐33 is a cytokine that is released from epithelial and endothelial cells at barrier surfaces upon tissue stress or damage to operate as an alarmin. IL‐33 has been primarily implicated in the induction of T helper (Th) 2 type immune responses. Therefore, IL‐33 has attracted a lot of interest as a potential therapeutic target in asthma and other allergic diseases. Over the years, it has become clear that IL‐33 has a much broader activity and also contributes to Th1 immunity, expanding the possibilities for therapeutic modulation of IL‐33 activity to multiple inflammatory diseases. However, more recently IL‐33 has also been shown to mediate immunosuppression and tissue repair by activating regulatory T cells (Treg) and promoting M2 macrophage polarization. These pleiotropic activities of IL‐33 illustrate the need for a tight molecular regulation of IL‐33 activity, and have to be taken into account when IL‐33 or its receptor is targeted for therapeutic modulation. Here we review the multiple molecular mechanisms that regulate IL‐33 activity and describe how IL‐33 can shape innate and adaptive immune responses by promoting Th1, Th2 and Treg function. Finally, we will discuss the possibilities for therapeutic modulation of IL‐33 signaling as well as possible safety issues.

Structure-activity relationship in monosaccharide-based Toll-like receptor 4 (TLR4) antagonists

The structure-activity relationship was investigated in a series of synthetic TLR4 antagonists formed by a glucosamine core linked to two phosphate esters and two linear carbon chains. Molecular modeling showed that the compounds with 10, 12, and 14 carbons chains are associated with higher stabilization of the MD-2/TLR4 antagonist conformation than in the case of the C16 variant. Binding experiments with human MD-2 showed that the C12 and C14 variants have higher affinity than C10, while the C16 variant did not interact with the protein. The molecules, with the exception of the C16 variant, inhibited the LPS-stimulated TLR4 signal in human and murine cells, and the antagonist potency mirrored the MD-2 affinity calculated from in vitro binding experiments. Fourier-transform infrared, nuclear magnetic resonance, and small angle X-ray scattering measurements suggested that the aggregation state in aqueous solution depends on fatty acid chain lengths and that this property can influence TLR4 activity in this series of compounds.

Molecular mechanisms of IL-33–mediated stromal interactions in cancer metastasis

Molecular mechanisms underlying the cancer stroma in metastasis need further exploration. Here, we discovered that cancer-associated fibroblasts (CAFs) produced high levels of IL-33 that acted on tumor-associated macrophages (TAMs), causing them to undergo the M1 to M2 transition. Genomic profiling of metastasis-related genes in the IL-33-stimulated TAMs showed a >200-fold increase of MMP9. Signaling analysis demonstrated the IL-33-ST2-NF-κB-MMP9-laminin pathway that governed tumor stroma-mediated metastasis. In mouse and human fibroblast-rich pancreatic cancers, genetic deletion of IL-33, ST2, or MMP9 markedly blocked metastasis. Pharmacological inhibition of NF-κB and MMP9 also blocked cancer metastasis. Deletion of IL-33, ST2, or MMP9 restored laminin, a key basement membrane component associated with tumor microvessels. Together, our data provide mechanistic insights on the IL-33-NF-κB-MMP9-laminin axis that mediates the CAF-TAM-committed cancer metastasis. Thus, targeting the CAF-TAM-vessel axis provides an outstanding therapeutic opportunity for cancer treatment.

Staphylococcus aureus Induces a Mucosal Type 2 Immune Response via Epithelial Cell–derived Cytokines

Rationale: Chronic rhinosinusitis with nasal polyps is characterized by a T‐helper cell type 2‐skewed upper airway inflammation. Mucosal Staphylococcus aureus colonization is found in the majority of patients with nasal polyps. S. aureus is known to induce type 2 cytokine release via enterotoxins. Objectives: To investigate the impact of non‐enterotoxin‐producing S. aureus on type 2 cytokine release. Methods: TSLP (thymic stromal lymphopoietin), IL‐33, and type 2 cytokines were assessed in a human mucosal tissue model upon S. aureus infection. Measurements and Main Results: S. aureus exposure increased the expression of IL‐33, TSLP, IL‐5, and IL‐13 in nasal polyp tissue, accompanied by elevated expression levels of TSLP and IL‐33 receptors, predominantly on CD3+ T cells. S. aureus infection led to the release of TSLP, but not IL‐33, IL‐5, or IL‐13, from healthy inferior turbinate tissue. In contrast, S. epidermidis did not induce any epithelial cell‐derived cytokines in nasal polyp or healthy tissue. S. aureus infection also increased the release of IL‐33 and TSLP in BEAS‐2B epithelial cells, accompanied by activation of NF‐&kgr;B (nuclear factor &kgr;B) pathways. Incubation with CU‐CPT22, a specific Toll‐like receptor 2 antagonist, significantly reduced the S. aureus‐induced release of TSLP and IL‐33, and the activity of the NF‐&kgr;B signal in BEAS‐2B cells. Conclusions: This study demonstrates for the first time that S. aureus can directly induce epithelial cell‐derived cytokine release via binding to Toll‐like receptor 2, and may thereby propagate type 2 cytokine expression in nasal polyp tissue.