ABSTRACT
BACKGROUND Bitter compounds increase ciliary beating and nitric oxide (NO) production in nasal epithelial cells through T2Rs in motile cilia. We examined expression of cilia T2Rs and both host and bacterial responses to T2R14 agonist diphenhydramine.
METHOD Using cultured human nasal epithelial cells grown at air liquid interface, we measured expression of T2Rs via qPCR. We measured effects of diphenhydramine on ciliary beat frequency via high-speed imaging and nitric oxide production via fluorescent dye DAF-FM. We measured effects of diphenhydramine on growth of lab and clinical strains of Pseudomonas aeruginosa. We measured biofilm formation of P. aeruginosa using crystal violet staining and surface attachment of P. aeruginosa to cystic fibrosis bronchial epithelial (CBFE41o-) cells using CFU counting.
RESULTS T2R expression increased with mucocilliary differentiation and did not vary between CF and non-CF ALIs. Treatment with P. aeruginosa flagellin decreased expression of diphenhydramine-responsive T2R14 and 40, among other isoforms. Diphenhydramine increased both NO and CBF. Increases in CBF were disrupted after flagellin treatment. Diphenhydramine impaired growth, biofilm production, and surface attachment of P. aeruginosa.
CONCLUSIONS T2R expression is similar between normal and CF cells but decreases with flagellin treatment. Utilizing T2R agonists as therapeutics within the context of CF, P. aeruginosa infections may require co-treatment with anti-inflammatories to prevent the reduction of T2R expression with TLR activation. T2R agonist diphenhydramine increases NO production and CBF while also decreasing bacterial growth and biofilm production, and thus diphenhydramine or derivate compounds may have potential clinical usefulness in CF infections as a topical therapy.
HIGHLIGHTS
T2R14 agonist diphenhydramine increases nitric oxide production and cilia beating
Flagellin decreases T2R14 expression in primary airway epithelial cells
T2R14 agonist Diphenhydramine inhibits Pseudomonas growth and biofilm formation
Competing Interest Statement
The authors have declared no competing interest.
ABBREVIATIONS
- ALI
- air liquid interface
- CBF
- ciliary beat frequency
- CF
- cystic fibrosis
- CFBE
- cystic fibrosis bronchial epithelial cell
- CRS
- chronic rhinosinusitis
- DPD
- diphenhydramine
- eNOS
- endothelial nitric oxide synthase
- GPCR
- G protein-coupled receptor
- MCC
- muciliary clearance
- NO
- nitric oxide
- NOS
- nitric oxide synthase
- T2R
- taste family 2 bitter GPCR
- TAS2R
- encoding T2R receptor
- TLR
- toll like receptor