Cystic fibrosis remodels the regulation of purinergic signaling by NTPDase1 (CD39) and NTPDase3

Abstract

Airway defenses are regulated by a complex purinergic signaling network located on the epithelial surfaces, where ATP stimulates the clearance of mucin and pathogens. The present study shows that the obstructive disease cystic fibrosis (CF) affects the activity, expression, and tissue distribution of two ectonucleotidases found critical for the regulation of ATP on airway surfaces: NTPDase1 and NTPDase3. Functional polarities and mRNA expression levels were determined on primary cultures of human bronchial epithelial (HBE) cells from healthy donors and CF patients. The in vitro model of the disease was completed by exposing CF HBE cultures for 4 days to supernatant of the mucopurulent material (SMM) collected from the airways of CF patients. We report that NTPDase1 and NTPDase3 are coexpressed on HBE cultures, where they regulate physiological and excess nucleotide concentrations, respectively. In aseptic conditions, CF epithelia exhibit >50% lower NTPDase1 activity, protein, and mRNA levels than normal epithelia, whereas these parameters are threefold higher for NTPDase3. Exposure to SMM induced opposite polarity shifts of the two NTPDases on both normal and CF epithelia, apical NTPDase1 being mobilized to basolateral surfaces and bilateral NTPDase3 to the apical surface. Their immunolocalization in human tissue revealed that NTPDase1 is expressed in epithelial, inflammatory, and endothelial cells, whereas NTPDase3 is restricted to epithelial cells. Furthermore, the SMM-exposed CF HBE cultures reproduced the impact of the disease on their in vivo distribution. This study provides evidence that an extensive remodeling of the enzymatic network regulating clearance occurs in the airways of CF patients.