Mechanistic roles of bitter taste receptors in the pathogenesis and treatment of chronic rhinosinusitis - PROJECT SUMMARY / ABSTRACT Chronic rhinosinusitis (CRS) is a common and debilitating upper airway disease characterized by persistent sinonasal inflammation and infection. Affecting >10% of the U.S. population and accounting for ~20% of all adult antibiotic prescriptions, CRS imposes a substantial health and economic burden. Despite aggressive medical and surgical interventions, many patients fail to achieve lasting relief, highlighting the need for novel, mechanism- based therapies. Recent discoveries have identified bitter taste receptors (TAS2Rs), a family of G-protein- coupled receptors, as important modulators of airway host defense and inflammation. In the nasal epithelium, TAS2Rs are expressed in two critical cell types—ciliated cells and tuft cells. It has been proposed that ciliated cells utilize TAS2Rs, such as TAS2R38 and TAS2R14, to detect microbial metabolites and trigger nitric oxide (NO)-mediated antimicrobial responses. Tuft cells are a major regulator for interleukin-25 (IL-25), acetylcholine (ACh), and defensins, and express TAS2R receptors like TAS2R10 that may regulate type 2 inflammation relevant to CRS with nasal polyps (CRSwNP). Progress in the field has been hampered by key limitations: (1) reliance on in vitro systems, (2) lack of functional orthology between human and mouse TAS2Rs, and (3) functional redundancy within the large Tas2r gene family in mice. To overcome these barriers, we have developed novel Tas2r-deficient mice. We will build on this unique platform by generating humanized mouse models expressing selected human TAS2Rs in specific cell types for CRS-related studies. Aim 1 will determine how cilia-localized TAS2Rs, particularly TAS2R38 and TAS2R14, regulate NO production that controls ciliary function and antimicrobial defense. Using air-liquid interface (ALI) cultures and ex vivo explants from wild-type, Tas2r mutants, and humanized mice, we will test responses to specific TAS2R agonists (e.g., PTC and quinine) in mucociliary transport and bacterial killing assays. These mice will also be tested in vivo using an eosinophilic CRS-like inflammation challenge (ovalbumin and fungal protease), live Pseudomonas aeruginosa infection, and stimulation with the bacterial quorum-sensing molecule (and TAS2R agonist) 3-oxo-C12HSL. We will assess inflammatory responses, epithelial damage, and cytokine profiles in nasal tissues and lavage fluid. Aim 2 will investigate how tuft cell-localized TAS2Rs, particularly TAS2R10, influence IL-25 and ACh secretion to contribute to airway inflammation. We will assess how tuft cells affect calcium signaling, cytokine secretion, and defensin production using ALI cultures and nasal explants. Further analysis of tuft cells will parallel the in vivo challenges described above in Aim 1 to determine how tuft cell TAS2Rs contribute to immune activation and epithelial remodeling. Both aims will also incorporate single-cell RNA-seq and immunophenotyping to reveal the cellular and molecular changes associated with TAS2R-dependent responses. This project will dissect the cell-type- specific roles of TAS2Rs in airway defense and inflammation, provide conclusive mechanistic insight into their functions, and establish the basis for developing TAS2R-targeted therapies for CRS and related airway diseases.
