Shinji Toki

Pulmonary group 2 innate lymphoid cells (ILC2s) are key drivers of Type 2 inflammation in diseases like asthma, yet the molecular mechanisms regulating their function are incompletely understood. Using the genetically diverse Collaborative Cross (CC) mouse panel, we mapped a quantitative trait locus (QTL) that governs ILC2 prevalence in the lung after aeroallergen exposure. This QTL induces a large population of ILC2s in the lung that are resistant to activation and have diminished Type 2 effector function. We identified free-fatty acid receptor 3 ( Ffar3 ) as a gene responsible for this effect and demonstrated that FFAR3 signaling reprograms ILC2s to an anti-inflammatory state by promoting their survival, reducing Type 2 cytokine production, and enhancing IL-10 expression. This anti-inflammatory state is dependent on IL-2 signaling, is characterized by decreased ST2 expression, and is distinct from previously described IL-10-producing ILC2 phenotypes. FFAR3-dependent reprogramming is mediated by epidermal growth factor receptor (EGFR) upregulation, and FFAR3’s anti-inflammatory effect is partially conserved in human ILC2s.

Type 2 inflammatory diseases, including asthma, sinusitis, and allergic bronchopulmonary aspergillosis, are common in cystic fibrosis (CF). CD4 ⁺ Th2 cells promote these diseases through secretion of IL-4, IL-5, and IL-13. Whether the CF transmembrane conductance regulator (CFTR), the mutated protein in CF, has a direct effect on Th2 development is unknown. Using murine models of CFTR deficiency and human CD4 ⁺ T cells, we show that CD4 ⁺ T cells expressed Cftr transcript and CFTR protein following activation. Loss of T cell CFTR expression increased Th2 cytokine production compared with control cells. Mice with CFTR-deficient T cells developed increased allergic airway disease to Alternaria alternata extract compared with control mice. Culture of CFTR-deficient Th2 cells demonstrated increased IL-4Rα expression and increased sensitivity to IL-4 with greater induction of GATA3 and IL-13 compared with control Th2 cell cultures. The CFTR potentiator ivacaftor reduced allergic inflammation and type 2 cytokine secretion in bronchoalveolar lavage of humanized CFTR mice following Alternaria alternata extract challenge and decreased Th2 development in human T cell culture. These data support a direct role of CFTR in regulating T cell sensitivity to IL-4 and demonstrate a potential CFTR-specific therapeutic strategy for Th2 cell–mediated allergic disease.

Background: Anti‐inflammatory effects of incretin signaling through the glucagon‐like peptide‐1 receptor (GLP‐1R) and the glucose‐dependent insulinotropic polypeptide receptor (GIPR) in mice have been reported. Therefore, we hypothesized that signaling through the endogenous GLP‐1R and the GIPR individually decreases allergic airway inflammation and that the combination of GLP‐1R and GIPR signaling together additively inhibits allergen‐induced lung and airway inflammation.Methods: WT (C57BL/6J), GLP‐1R knockout (KO), GIPR KO, and GLP‐1R/GIPR double KO (DKO) mice were challenged intranasally with Alternaria alternata extract (Alt‐Ext) or vehicle to evaluate the impact of signaling through these receptors on the innate allergen‐induced inflammatory response that is primarily driven by group 2 innate lymphoid cells (ILC2).Results: Alt‐Ext‐induced IL‐33 release in the bronchoalveolar lavage fluid (BALF) was not different between the mouse strains, but thymic stromal lymphopoietin (TSLP) was significantly increased in GLP‐1R/GIPR DKO mice challenged with Alt‐Ext compared to the other strains. Furthermore, Alt‐Ext‐induced protein expression of IL‐5, IL‐13, CCL11, and CCL24 in the lung homogenates, the number of eosinophils, lymphocytes, and neutrophils in the BALF, and the number of lung GATA3+ ILC2 were significantly increased in GLP‐1R/GIPR DKO mice compared to the other 3 strains. Furthermore, ICAM‐1 expression on lung epithelial cells was increased in GLP‐1R/GIPR DKO mice challenged with Alt‐Ext compared to the other 3 strains.Conclusions: Deficiency of both GLP‐1R and GIPR signaling together increased TSLP release, ILC2 activation, and early type 2 innate immune responses to aeroallergen exposure. Combined GLP‐1R and GIPR signaling should be explored for the treatment of asthma.

All cells of the immune system reside in adipose tissue (AT), and increasing type 2 immune cells may be a therapeutic strategy to improve metabolic health. In our previous study using i.p. IL-5 injections to increase eosinophils, we observed that a standard vehicle control of 0.1% BSA also elicited profound AT eosinophilia. In this study, we aimed to determine whether BSA-induced AT eosinophilia results in metabolic benefits in murine models of diet-induced obesity. I.p. 0.1% BSA injections increased AT eosinophils after 4 wk. Despite elevating eosinophils to >50% of immune cells in the AT, body weight and glucose tolerance were not different between groups. Interestingly, BSA elicited epithelial IL-33 production, as well as gene expression for type 2 cytokines and IgE production that were dependent on IL-33. Moreover, multiple models of OVA sensitization also drove AT eosinophilia. Following transplantation of a donor fat pad with BSA-induced eosinophilia, OVA-sensitized recipient mice had higher numbers of bronchoalveolar lavage eosinophils that were recipient derived. Interestingly, lungs of recipient mice contained eosinophils, macrophages, and CD8 T cells from the donor AT. These trafficked similarly from BSA- and non-BSA–treated AT, suggesting even otherwise healthy AT serves as a reservoir of immune cells capable of migrating to the lungs. In conclusion, our studies suggest that i.p. injections of BSA and OVA induce an allergic response in the AT that elicits eosinophil recruitment, which may be an important consideration for those using OVA in animal models of allergic disease.

In this study, pretreatment with liraglutide, a commonly used diabetes medication and glucagon-like peptide-1 (GLP-1) receptor agonist, attenuated sepsis-induced acute lung injury in a two-hit mouse model (sepsis + hyperoxia). Septic mice who received the drug were less sick, lived longer, and displayed reduced lung inflammation, edema, and injury. These therapeutic effects were not dependent on weight loss. GLP-1 receptor activation may hold promise as a new treatment strategy for sepsis-induced acute respiratory distress syndrome.

Background: Obesity is a risk factor for the development of asthma. However, pharmacologic therapeutic strategies that specifically target obese asthmatics have not been identified. We hypothesize that glucagon‐like peptide‐1 receptor agonist (GLP‐1RA) treatment inhibits aeroallergen‐induced early innate airway inflammation in a mouse model of asthma in the setting of obesity.Methods: SWR (lean) and TALLYHO (obese) mice were challenged intranasally with Alternaria alternata extract (Alt‐Ext) or PBS for 4 consecutive days concurrent with GLP‐1RA or vehicle treatment.Results: TALLYHO mice had greater Alt‐Ext‐induced airway neutrophilia and lung protein expression of IL‐5, IL‐13, CCL11, CXCL1, and CXCL5, in addition to ICAM‐1 expression on lung epithelial cells compared with SWR mice, and all endpoints were reduced by GLP‐1RA treatment. Alt‐Ext significantly increased BALF IL‐33 in both TALLYHO and SWR mice compared to PBS challenge, but there was no difference in the BALF IL‐33 levels between these two strains. However, TALLYHO, but not SWR, mice had significantly higher airway TSLP in BALF following Alt‐Ext challenge compared to PBS, and BALF TSLP was significantly greater in TALLYHO mice compared to SWR mice following airway Alt‐Ext challenge. GLP‐1RA treatment significantly decreased the Alt‐Ext‐induced TSLP and IL‐33 release in TALLYHO mice. While TSLP or ST2 inhibition with a neutralizing antibody decreased airway eosinophils, they did not reduce airway neutrophils in TALLYHO mice.Conclusions: These results suggest that GLP‐1RA treatment may be a novel pharmacologic therapeutic strategy for obese persons with asthma by inhibiting aeroallergen‐induced neutrophilia, a feature not seen with either TSLP or ST2 inhibition.

Tregs restrain both the innate and adaptive immune systems to maintain homeostasis. Allergic airway inflammation, characterized by a Th2 response that results from a breakdown of tolerance to innocuous environmental antigens, is negatively regulated by Tregs. We previously reported that prostaglandin I₂ (PGI₂) promoted immune tolerance in models of allergic inflammation; however, the effect of PGI₂ on Treg function was not investigated. Tregs from mice deficient in the PGI₂ receptor IP (IP KO) had impaired suppressive capabilities during allergic airway inflammatory responses compared with mice in which PGI₂ signaling was intact. IP KO Tregs had significantly enhanced expression of immunoglobulin-like transcript 3 (ILT3) compared with WT Tregs, which may contribute to the impairment of the IP KO Treg’s ability to suppress Th2 responses. Using fate-mapping mice, we reported that PGI₂ signaling prevents Treg reprogramming toward a pathogenic phenotype. PGI₂ analogs promoted the differentiation of naive T cells to Tregs in both mice and humans via repression of β-catenin signaling. Finally, a missense variant in IP in humans was strongly associated with chronic obstructive asthma. Together, these data support that PGI₂ signaling licenses Treg suppressive function and that PGI₂ is a therapeutic target for enhancing Treg function.

Background: The epithelial cell‐derived danger signal mediators thymic stromal lymphopoietin (TSLP) and IL‐33 are consistently associated with adaptive Th2 immune responses in asthma. In addition, TSLP and IL‐33 synergistically promoted group 2 innate lymphoid cell (ILC2) activation to induce innate allergic inflammation. However, the mechanism of this synergistic ILC2 activation is unknown.Methods: BALB/c WT and TSLP receptor‐deficient (TSLPR^−/−) mice were challenged intranasally with Alternaria extract (Alt‐Ext) or PBS for 4 consecutive days to evaluate innate airway allergic inflammation. WT mice pre‐administered with rTSLP or vehicle, TSLPR^−/− mice, and IL‐33 receptor‐deficient (ST2^−/−) mice were challenged intranasally with Alt‐Ext or vehicle once or twice to evaluate IL‐33 release and TSLP expression in the lung. TSLPR and ST2 expression on lung ILC2 were measured by flow cytometry after treatment of rTSLP, rIL‐33, rTSLP + rIL‐33, or vehicle.Results: Thymic stromal lymphopoietin receptor deficient mice had significantly decreased the number of lung ILC2 expressing IL‐5 and IL‐13 following Alt‐Ext‐challenge compared to WT mice. Further, eosinophilia, protein level of lung IL‐4, IL‐5, and IL‐13, and airway mucus score were also significantly decreased in TSLPR^−/− mice compared to WT mice. Endogenous and exogenous TSLP increased Alt‐Ext‐induced IL‐33 release into BALF, and ST2 deficiency decreased Alt‐Ext‐induced TSLP expression in the lung. Further, rTSLP and rIL‐33 treatment reciprocally increased each other's receptor expression on lung ILC2 in vivo and in vitro.Conclusion: Thymic stromal lymphopoietin and IL‐33 signaling reciprocally enhanced each other's protein release and expression in the lung following Alt‐Ext‐challenge and each other's receptor expression on lung ILC2 to enhance ILC2 activation.

Calprotectin is a heterodimer of the proteins S100A8 and S100A9, and it is an abundant innate immune protein associated with inflammation. In humans, calprotectin transcription and protein abundance are associated with asthma and disease severity. However, mechanistic studies in experimental asthma models have been inconclusive, identifying both protective and pathogenic effects of calprotectin. To clarify the role of calprotectin in asthma, calprotectin-deficient S100A9−/− and wild-type (WT) C57BL/6 mice were compared in a murine model of allergic airway inflammation. Mice were intranasally challenged with extracts of the clinically relevant allergen, Alternaria alternata (Alt Ext), or PBS every third day over 9 days. On Day 10, BAL fluid and lung tissue homogenates were harvested and allergic airway inflammation was assessed. Alt Ext challenge induced release of S100A8/S100A9 to the alveolar space and increased protein expression in the alveolar epithelium of WT mice. Compared with WT mice, S100A9−/− mice displayed significantly enhanced allergic airway inflammation, including production of IL-13, CCL11, CCL24, serum IgE, eosinophil recruitment, and airway resistance and elastance. In response to Alt Ext, S100A9−/− mice accumulated significantly more IL-13+IL-5+CD4+ T-helper type 2 cells. S100A9−/− mice also accumulated a significantly lower proportion of CD4+ T regulatory (Treg) cells in the lung that had significantly lower expression of CD25. Calprotectin enhanced WT Treg cell suppressive activity in vitro. Therefore, this study identifies a role for the innate immune protein, S100A9, in protection from CD4+ T-helper type 2 cell hyperinflammation in response to Alt Ext. This protection is mediated, at least in part, by CD4+ Treg cell function.