Release of ATP Through Hemichannels Affects Basal Ciliary Activity in the Human Airways

Abstract

The frequency of ciliary beat (CBF) is the main factor that determines the effectiveness of mucociliary clearance in the airways. ATP is a known agonist of the CBF, since addition of ATP (10 μM) to the extracellular medium, increases the CBF in different ciliated epithelial cells. There is evidence that epithelial cells constitutively secrete ATP in the airways; however the contribution of extracellular ATP to the control of basal CBF has not been studied. We propose that the airway epithelium release ATP through hemichannels followed by an activation of purinergic receptors, contributes to the control of basal CBF. Methods: CBF was recorded using microphotodensitometry technique using primary cultures of human adenoid explants. We also used Western Blot analysis to determinate the expression of P2Y2 purinergic receptor, Pannexin 1 and Connexin 43 hemichannels and used different channel blockers to determinate the contribution of each channel to the control of CBF. Results: The spontaneous basal CBF in the cultures was 9.3 ± 0.1 Hz (n=91) and the extracellular ATP concentration was 1.04 ± 0.36 nM in 1.5 mL (n=3). Apyrase (50 U/mL), an extracellular ATP ectonucleotidase, decrease the basal CBF in 19.4% ± 7.0 (n=7). Suramine, a purinergic receptor antagonist, reduce the basal CBF in a 12% and the hemichannels blockers 18β-Glycyrrhetinic acid (50 μM), Carbenoxolone (50 μM) and La3+ (100 μM), reduce the basal CBF in a 33.5% ± 4.9, 7.9% ± 1.3 and 21.74% ± 4.3 respectively (n=3). These results provide evidence that affecting the channels or hemichannels associated to the release of ATP or the paracrine/autocrine effects of ATP on the epithelium affects the CBF and suggest that extracellular ATP concentration might contribute to the control of basal CBF in the airways. FONDECYT 1080679.