Inhibition of PDE7 activity blunts calcium‐mediated permeability in pulmonary arterial endothelial cells

Abstract

Intracellular concentrations of cAMP and Ca2+ regulate the permeability of pulmonary endothelium. For example, in pulmonary arterial endothelial cells (PAECs), activation of store‐operated Ca2+ channels leads to increased endothelial permeability. Pretreatment with rolipram, a selective PDE4 inhibitor, prevents increases in permeability. Recently, we demonstrated that PAECs also express the rolipram‐insensitive, cAMP‐specific PDE7. PDE7A and B proteins were detected in soluble and particulate fractions, respectively, using Western‐blot analysis. The subcellular distributions of PDE7A and 7B were determined using immunocytochemistry. We found that PDE7B is primarily at the plasma membrane, whereas PDE7A has a cytosolic distribution. PDE7 comprises ~50% of cAMP‐hydrolytic activity in soluble fractions and ~70% in particulate fractions. To elucidate the functional roles of PDE7 in PAECs, PDE7A levels were lowered by stable expression of shRNA. PDE7A shRNA cells had lower PDE7A expression levels, and lower, rolipram‐insensitive cAMP‐PDE activity in soluble fractions. No changes in PDE7B expression were observed. Ca2+‐induced increases in endothelial permeability were significantly reduced in PDE7A shRNA cells. These results suggest that PDE7A activity plays a key role in regulation of Ca2+‐mediated permeability of the pulmonary endothelium. HL66299 and HL074278.