Fig. 5

Effect of roflumilast on ciliary beat frequency (CBF). a CBF measurement after roflumilast exposure for 4 h (baseline in white bars on the left of the graph after 1 h; five lungs; n = 14–40). Roflumilast-treated cultures did not show an increase in CBF compared to untreated cultures (baseline). Smoke (4 h after roflumilast) significantly decreases CBF 3 h after exposure, an effect reversed by roflumilast. Exposure to air (air control) increases CBF upon administration of roflumilast (gray bars). Bars on a blue background indicate measurements of CBF after rehydration of the apical surface with 50 μl PBS. CBF of cells exposed to smoke vs air equalizes, indicating a role of ASL volume depletion in the CBF changes (* p < 0.05). b CBF measurements after short-term exposure of roflumilast for 15 min followed by addition of 10 μM forskolin in a submerged, two chamber perfusion system (three lungs; n = 10-14). In air control cultures, forskolin increases CBF, but the addition of roflumilast does not further enhance CBF. In smoke-exposed cells, CBF increases upon forskolin addition, and again with roflumilast. CBF baselines are low in smoke-exposed cells, possibly correlating to the lower baseline cAMP levels in smoke exposed cells as assessed by FRET (taken at the same time points). * p < 0.05