CSE triggered a rapid loss of CBF in differentiated human bronchial epithelial cells, an effect which was reversed by forskolin and roflumilast N-oxide (A, B). Following an initial 20 min baseline period, differentiated bronchial epithelial cells (D-BECs) were exposed to CSE at 10% for up to 3 h. From the time point the reduction in CBF was optimal (at 80 min), forskolin (FSK) at 10 µM (A) or roflumilast N-oxide (RNO) at 2 nM or 1 µM (B), or vehicle was added. CBF was monitored for 3 h by DHSV and quantified by Fourier transformation as detailed in Methods. Results are shown as the means ± SEM of three experiments per donor based on cultures from two to four different donors per condition. *P < 0.05 versus control, #P < 0.05 versus CSE. CSE rapidly reduced cAMP content in differentiated human bronchial epithelial cells (C). D-BECs were exposed to vehicle (baseline), RNO at 2 nM, CSE at 10% followed by vehicle or RNO (2 nM) at the indicated times and cellular cAMP content was measured at different time points. Results are shown as the means ± SEM from cultures of two donors in duplicates. *P < 0.05 versus control.