Regulation of Ciliary Beat Frequency by the Nitric Oxide–Cyclic Guanosine Monophosphate Signaling Pathway in Rat Airway Epithelial Cells

Nitric oxide (NO) upregulates ciliary beat frequency (CBF). The present study evaluates mechanisms of the NO-cyclic guanosine monophosphate (cGMP) pathway regulation of CBF. Rat tracheal explants were loaded with 4,5-diaminofluorescein diacetate for the demonstration of NO production by ciliated epithelial cells after L-arginine (L-Arg) stimulation. CBF was measured using phase contrast microscopy and videotape analysis. The roles of NO, soluble guanylate cyclase (sGC), cGMP-dependent protein kinase (PK) G, and phosphodiesterase (PDE) V in regulation of CBF were evaluated. NO synthase (NOS) was activated with L-Arg or inhibited with N(G)-monomethyl-L-Arg. sGC was stimulated with NO donors 1-hydroxy-2-oxo-3- (N-ethyl-2-aminoethyl)-3-ethyl-1-triazene and S-nitroso-L-glutathione or mimicked by 8-bromo-guanosine 3', 5'-cyclic monophosphate (8-Br-cGMP) and inhibited with 1H-1,2, 4oxadiazole4,3-aquinoxalin-1-one. The effects of the PKG inhibition with KT5823 and PDE V inhibition with Zaprinast were also examined. The studies demonstrate that ciliated epithelial cells produce NO, which is correlated with CBF stimulation. L-Arg dose- and time-dependently increases CBF, and NO donors, 8-Br-cGMP, and Zaprinast also enhance CBF. Inhibitors of NOS, sGC, and PKG can block the stimulant effect of L-Arg on CBF. Thus, NO is a regulator of CBF acting via sGC and PKG. The NO-cGMP signaling pathway regulates CBF in an autocrine manner in cultured rat ciliated airway epithelium.