Adenosine activation of A_2Breceptor(s) is essential for stimulated epithelial ciliary motility and clearance

Abstract

sine activation of A2B receptor(s) is essential for stimulated epithelial ciliary motility and clearance. Am J Physiol Lung Cell Mol Physiol 301: L171-L180, 2011. First published May 27, 2011 doi:10.1152/ajplung.00203.2010.-Mucociliary clearance, vital to lung clearance, is dependent on cilia beat frequency (CBF), coordination of cilia, and the maintenance of periciliary fluid. Adenosine, the metabolic breakdown product of ATP, is an important modulator of ciliary motility. However, the contributions of specific adenosine receptors to key airway ciliary motility processes are unclear. We hypothesized that adenosine modulates ciliary motility via activation of its cell surface receptors (A1, A2A, A2B, or A3). To test this hypothesis, mouse tracheal rings (MTRs) excised from wild-type and adenosine receptor knockout mice (A1, A2A, A2B, or A3, respectively), and bovine ciliated bronchial epithelial cells (BBECs) were stimulated with known cilia activators, isoproterenol (ISO; 10 M) and/or procaterol (10 M), in the presence or absence of 5=-(Nethylcarboxamido) adenosine (NECA), a nonselective adenosine receptor agonist [100 nM (A1, A2A, A3); 10 M (A2B)], and CBF was measured. Cells and MTRs were also stimulated with NECA (100 nM or 10 M) in the presence and absence of adenosine deaminase inhibitor, erythro-9-(2-hydroxy-3-nonyl) adenine hydrochloride (10 M). Both ISO and procaterol stimulated CBF in untreated cells and/or MTRs from both wild-type and adenosine knockout mice by ϳ3 Hz. Likewise, CBF significantly increased ϳ2-3 Hz in BBECs and wild-type MTRs stimulated with NECA. MTRs from A1, A2A, and A3 knockout mice stimulated with NECA also demonstrated an increase in CBF. However, NECA failed to stimulate CBF in MTRs from A2B knockout mice. To confirm the mechanism by which adenosine modulates CBF, protein kinase activity assays were conducted. The data revealed that NECA-stimulated CBF is mediated by the activation of cAMP-dependent PKA. Collectively, these data indicate that purinergic stimulation of CBF requires A2B adenosine receptor activation, likely via a PKA-dependent pathway. mucociliary clearance; knockout mouse model; bovine bronchial epithelial cells MUCOCILIARY TRANSPORT is an important host defense mechanism in the lung by which the coordinated beating of cilia continuously clears the lung of aspirated microorganisms and inhaled debris. This transport is dependent on the ciliary motion of airway epithelium, physicochemical properties of periciliary fluid, and mucus secretion (45, 50). Regulation of airway ciliary motility is critical because mucociliary transport is considered the first line of defense between the lung and the environment. Stressful conditions such as exercise or inflammation cause cilia in the airway to beat faster, increase clearance, and move an increased number of inhaled particles (2). As a consequence, mucociliary transport is a regulable host defense that can be activated under numerous conditions. It has been well described that ATP, a signaling molecule released by the airw...

Roflumilast N‐oxide, a PDE4 inhibitor, improves cilia motility and ciliated human bronchial epithelial cells compromised by cigarette smoke in vitro

“…Because endogenously produced adenosine may regulate the homeostasis of bronchial epithelial cells (Rollins et al ., 2008) and adenosine (by stimulating A 2B receptors) was reported to augment CBF in airway epithelial cells (Lazarowski and Boucher, 2009; Allen‐Gipson et al ., 2011), the effects of theophylline at 10 µM, a concentration at which the xanthine is a non‐specific antagonist to adenosine receptors including A 2B but does not interfere with PDE activities, were studied. Strikingly, there was a rapid and persistent fall in CBF following theophylline (Figure 1C).…”

“…Cellular effects emanating from PDE4 inhibition require prior cAMP synthesis. A candidate cAMP increasing molecule released by bronchial epithelial cells into the periciliary lining fluid is adenosine that enhances CBF (Lazarowski and Boucher, 2009; Allen‐Gipson et al ., 2011). Conversely, antagonism at adenosine receptors (10 µM theophylline) reduced baseline CBF and compromised the increase in CBF by roflumilast N‐oxide (2 nM).…”

“…Secondly, in human nasal epithelial cells, CBF is enhanced by 5′‐(N‐ethylcarboxamide)adenosine (NECA) but not a selective A 2A adenosine receptor agonist (Morse et al ., 2001). Thirdly, CBF in tracheal rings from mice deficient in A 2B receptors failed to respond to NECA while mice deficient in either A 1 , A 2A or A 3 receptors displayed the expected increase in CBF following the non‐selective adenosine receptor agonist (Allen‐Gipson et al . , 2011).…”

A1 adenosine receptor signaling reducesStreptococcus pneumoniaeadherence to pulmonary epithelial cells by targeting expression of platelet‐activating factor receptor

“…Extracellular adenosine can then act as a signaling molecule by binding to and activating one of four G-protein coupled adenosine receptors, A1, A2A, A2B, and A3 (Hasko et al, 2008). The enzymes and receptors of the extracellular adenosine pathway are expressed by lung epithelial cells (Burnstock, Brouns, Adriaensen, & Timmermans, 2012) and were shown to control acute lung injury (Hoegl et al, 2015), ciliary motility (Allen-Gipson et al, 2011), wound healing (Allen-Gipson, Wong, Spurzem, Sisson, & Wyatt, 2006), activation of ion channels (Factor et al, 2007), surfactant secretion (Gobran & Rooney, 1990), fibronectin release (Roman, Rivera, Roser-Page, Sitaraman, & Ritzenthaler, 2006), mucin expression (McNamara et al, 2004), and production of cytokines (Zhong, Wu, Belardinelli, & Zeng, 2006). Extracellular adenosine is thought to control host resistance to lung infections by influencing recruitment and function of innate immune cells (Aeffner, Woods, & Davis, 2014Barletta, Cagnina, Burdick, Linden, & Mehrad, 2012;Barletta, Ley, & Mehrad, 2012; Bou Ghanem, Clark, Roggensack, et al, 2015;Theatre et al, 2012).…”

Adenosine Receptors in Health and Disease

“…Furthermore, the dependence of epithelial ciliary motility and pulmonary clearance on A 2B AR activation has recently been reported (Allen-Gipson et al, 2011).…”