Prostaglandin E₂ activates the ciliary beat frequency of cultured human nasal mucosa via the second messenger cyclic adenosine monophosphate

Abstract

Prostaglandins influence the ciliary beat frequency (CBF) of ciliated nasal epithelial cells and a stimulatory effect has been described for prostaglandin E₂ (PGE₂). Until now, it is not known whether PGE₂ has direct ciliostimulatory properties or acts through a second messenger. In this study we investigated whether cyclic adenosine monophosphate (cAMP) is implicated in the signal transduction pathway of PGE₂-induced activation of CBF. Ciliated cells of the nasal mucosa were cultured for up to 5 days whereafter the culture medium was removed and the cells were incubated with different concentrations of test solutions. The ciliated cells were recorded under a phase-contrast microscope and viewed in slow motion to count the frequency. PGE₂ led to a dose-dependent increase in CBF. This became significant at concentrations of 10^–10 and 10^–5 M (P < 0.01) but not at 10–¹³ M (P > 0.05). Addition of cAMP (10^–10 to 10^–5 M) caused a significant (P < 0.01) increase in CBF, whereas depletion of endogenous cAMP after pre-incubation with the adenylate cyclase activator forskolin (10^–5 M) prevented the PGE₂-induced increase in CBF (P > 0.05). The ciliostimulatory effect of PGE₂ depends on an intact functioning of adenylate cyclase. These results point out that cAMP is directly implicated in the signal transduction pathway of PGE₂-induced stimulation of CBF in cultured human ciliated cells of the nasal mucosa.