PROJECT SUMMARY Dysfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel impedes mucus clearance and leads to the airway disease, cystic fibrosis (CF). New CFTR modulators improve mucociliary transport (MCT) and pathophysiologic manifestations of the disease in genetic mutation-specific patients, but do not completely restore airway function. We recently discovered ginsenosides derived from Korean Red Ginseng serve as potentiators of the Ca2+-activated Cl− channel (CaCC) [TMEM16A] and can restore MCT in vitro and in vivo through this alternative Cl- pathway. Yet, poor clinical trial results with activators of TMEM16A and a recently described role for the channel in mucus hypersecretion in infected airways has led to some to suggest that inhibiting TMEM16A is a better strategy. However, we hypothesize that potentiating TMEM16A, rather than channel activation through purinergic, intracellular Ca2+- driven pathways, will rescue MCT in infected CF airways. Specific Aim 1 will isolate the ginsenoside that most effectively potentiates TMEM16A and measure its effects on MCT parameters and mucus pathology. We anticipate finding the optimal ginsenoside through Ussing chamber and patch clamp experiments, while also measuring the impact on markers of MCT and mucus viscosity. Specific Aim 2 will assess whether a TMEM16A potentiator improves epithelial Cl- secretion, histopathology, and MCT parameters in infected CF rat airways. We will determine single dose pharmacokinetics for the selected ginsenoside and administer to Pseudomonas-infected CF rats to evaluate nasal potential difference, MCT, lung micro-CTs, histopathology, mucus properties (viscosity, solids, mass, density), and inflammatory cytokines. We will answer questions about the therapeutic utility of targeting the TMEM16A pathway and identify a new TMEM16A potentiator as an effective treatment for CF airway disease.