Identification and Function of Cyclic Nucleotide Phosphodiesterase Isoenzymes in Airway Epithelial Cells

Abstract

Epithelial cells actively participate in inflammatory airway disease by liberating mediators such as arachidonate metabolites and cytokines. Inhibition of phosphodiesterases (PDEs) may be a useful anti-inflammatory approach. The PDE isoenzyme pattern and the effects of PDE inhibition on mediator generation were analyzed in primary cultures of human and porcine airway epithelial cells (AEC) and in the bronchial epithelial cell line BEAS-2B. PDE4 and PDE5 were detected in lysates of all cell types studied. In primary cultures of human AEC, the PDE4 variants PDE4A5, PDE4C1, PDE4D2, and PDE4D3 were identified by polymerase chain reaction analysis. Evidence of the recently described PDE7 was obtained by rolipram- insensitive cyclic adenosine monophosphate (cAMP) degradation, and its presence was verified by the demonstration of PDE7 messenger RNA. Primary cultures of human airway epithelium also expressed PDE1. Enhanced epithelial cAMP levels, induced by forskolin and PDE4 inhibition, increased formation of prostaglandin E2 (PGE2), but not of interleukin (IL)-8 or 15-hydroxyeicosatetraenoic acid (15-HETE) in airway epithelial cells. Increased cyclic guanosine monophosphate levels in these cells provoked by sodium nitroprusside and the PDE5 inhibitor zaprinast reduced the PGE2 synthesis, whereas 15-HETE and IL-8 formation were unchanged. The data suggest that PDE isoenzymes are important in airway inflammation and that PDE inhibitors exert anti-inflammatory effects by acting on AEC.

Phosphodiesterase 4D Forms a cAMP Diffusion Barrier at the Apical Membrane of the Airway Epithelium

“…1B). These results are consistent with previous reports of PDE expression in well-differentiated human bronchial epithelium (WD-HBE) (20,21) and with in situ hybridization studies in mice (32). In a similar fashion, more than half of the total PDE activity in WD-HBE was due to PDE4, and ϳ50% of PDE4 activity in these cells was immunoprecipitated with PDE4D-selective antibodies.…”

“…Although data exist concerning a role for phosphodiesterases in the compartmentation of cAMP in nonpolarized cells (17)(18)(19), little is known about the distribution and actions of cAMP in microdomains such as the apical regions of polarized epithelia. Several PDEs are ex-pressed in both human airway and intestinal epithelia based on molecular (20,21) and pharmacologic approaches (22,23). At least one PDE, PDE3, can augment CFTR responses ex vivo (24), in some animal models (25), but not in humans (26).…”

Induction of Regulator of G-Protein Signaling 2 Expression by Long-Acting β2-Adrenoceptor Agonists and Glucocorticoids in Human Airway Epithelial Cells

“…3C). Equally, inhibition of phosphodiesterase 4 (PDE4), which is highly expressed in BEAS-2B and primary HBE cells (Fuhrmann et al, 1999;Dent et al, 1998), enhances GRE-dependent transcription . Therefore, Fig.…”

Streptococcus pneumoniae-Induced Caspase 6-Dependent Apoptosis in Lung Epithelium

“…Bronchial epithelial cell line BEAS-2B was a kindly gift from Curtis Harris, National Institutes of Health, Bethesda, Md. (16,43). Alveolar epithelial cell line A549 was purchased from the American Type Culture Collection, Rockville, Md.…”