Exposure to various antigens derived from house dust mites (HDM) is considered to be a risk factor for development of certain allergic diseases such as atopic asthma, atopic dermatitis, rhinitis and conjunctivitis. Chitin is an insoluble polysaccharide (β-(1-4)-poly-N-acetyl-D-glucosamine) and a major component in the outer shell of HDMs. Mice exposed to chitin develop asthma-like airway eosinophilia. On the other hand, several lines of evidence show that the effects of chitin on immune responses are highly dependent on the size of chitin particles. In the present study, we show that chitin induced production of IL-33 and TSLP by alveolar and bronchial epithelial cells, respectively, in mice. IL-25, IL-33 and TSLP were reported to be important for group 2 innate lymphoid cell (ILC2)-, but not Th2 cell-, dependent airway eosinophilia in a certain model using chitin beads. Here, we show that-in our murine models-epithelial cell-derived IL-33 and TSLP, but not IL-25, were crucial for activation of resident lung Th2 cells as well as group 2 innate lymphoid cells (ILC2s) to produce IL-5, resulting in development of chitin-induced airway eosinophilia. Our findings provide further insight into the underlying mechanisms of development of HDM-mediated allergic disorders.

Although human term placenta-derived primary cytotrophoblasts (pCTBs) represent a good human syncytiotrophoblast (STB) model, in vitro culture of pCTBs is not always easily accomplished. Y-27632, a specific inhibitor of Rho-associated coiled-coil containing kinases (ROCK), reportedly prevented apoptosis and improved cell-to-substrate adhesion and culture stability of dissociated cultured human embryonic stem cells and human corneal endothelial cells. The Rho kinase pathway regulates various kinds of cell behavior, some of which are involved in pCTB adhesion and differentiation. In this study, we examined Y-27632's potential for enhancing pCTB adhesion, viability and differentiation. pCTBs were isolated from term, uncomplicated placentas by trypsin-DNase I-Dispase II treatment and purified by HLA class I-positive cell depletion. Purified pCTBs were cultured on uncoated plates in the presence of epidermal growth factor (10 ng/ml) and various concentrations of Y-27632. pCTB adhesion to the plates was evaluated by phase-contrast imaging, viability was measured by WST-8 assay, and differentiation was evaluated by immunofluorescence staining, expression of fusogenic genes and hCG-β production. Ras-related C3 botulinum toxin substrate 1 (Rac1; one of the effector proteins of the Rho family) and protein kinase A (PKA) involvement was evaluated by using their specific inhibitors, NSC-23766 and H-89. We found that Y-27632 treatment significantly enhanced pCTB adhesion to plates, viability, cell-to-cell fusion and hCG-β production, but showed no effects on pCTB proliferation or apoptosis. Furthermore, NSC-23766 and H-89 each blocked the effects of Y-27632, suggesting that Y-27632 significantly enhanced pCTB differentiation via Rac1 and PKA activation. Our findings suggest that Rac1 and PKA may be interactively involved in CTB differentiation, and addition of Y-27632 to cultures may be an effective method for creating a stable culture model for studying CTB and STB biology in vitro.

Chitin, which is a major component of house dust mites (HDM), fungi, crustaceans, etc., can activate immune cells, suggesting that it contributes to development of allergic disorders such as asthma. Although the pathophysiological sensitization route of asthmatic patients to allergens is considered via the respiratory tract, the roles of intranasally-administered chitin in development of asthma remain unclear. After ovalbumin (OVA) challenge, development of airway inflammation was profoundly exacerbated in mice sensitized with OVA in the presence of chitin. The exacerbation was dependent on IL-33, but not IL-25, thymic stromal lymphopoietin or IL-17A. Chitin enhanced IL-33-dependent IL-1β production by dendritic cells (DCs). Furthermore, chitin- and IL-33-stimulated DC-derived IL-1β promoted OVA-specific Th2 cell activation, resulting in aggravation of OVA-induced airway inflammation. These findings indicate the adjuvant activity of chitin via a new mechanism and provide important clues for development of therapeutics for allergic disorders caused by HDM, fungi and crustaceans.

Cytokines employ downstream Janus kinases (JAKs) to promote chronic inflammatory diseases. JAK1-dependent type 2 cytokines drive allergic inflammation, and patients with JAK1 gain-of-function (GoF) variants develop atopic dermatitis (AD) and asthma. To explore tissue-specific functions, we inserted a human JAK1 GoF variant (JAK1GoF) into mice and observed the development of spontaneous AD-like skin disease but unexpected resistance to lung inflammation when JAK1GoF expression was restricted to the stroma. We identified a previously unrecognized role for JAK1 in vagal sensory neurons in suppressing airway inflammation. Additionally, expression of Calcb/CGRPβ was dependent on JAK1 in the vagus nerve, and CGRPβ suppressed group 2 innate lymphoid cell function and allergic airway inflammation. Our findings reveal evolutionarily conserved but distinct functions of JAK1 in sensory neurons across tissues. This biology raises the possibility that therapeutic JAK inhibitors may be further optimized for tissue-specific efficacy to enhance precision medicine in the future.

Group 2 innate lymphoid cells (ILC2s) play critical roles in induction and exacerbation of allergic airway inflammation. Thus clarification of the mechanisms that underlie regulation of ILC2 activation has received significant attention. Although innate lymphoid cells are divided into 3 major subsets that mirror helper effector T-cell subsets, counterpart subsets of regulatory T cells have not been well characterized.