NEUROPEPTIDE-Y INHIBITS CILIARY BEAT FREQUENCY IN HUMAN CILIATED CELLS VIA NPKC, INDEPENDENTLY OF PKA

The intracellular mechanisms whereby the inhibitory neurotransmitter n europeptide Y (NPY) decreases ciliary beat frequency (CBF) were invest igated in cultured human tracheal and bronchial ciliated cells. CBF wa s measured by nonstationary analysis laser light scattering. NPY at 1 and 10 mu M decreased CBF from a baseline of 6.7 +/- 0.5 (n = 12) to 6 .1 +/- 0.5 (P < 0.05) and 5.8 +/- 0.4 (P < 0.01) Hz, respectively. Pri or application of PYX-1, an NPY antagonist, prevented the decreases of CBF induced by both doses of NPY. Two broad protein kinase C (PKC) ki nase inhibitors, staurosporine and calphostin C, also abolished the NP Y-induced decrease in CBF. The NPY-induced decrease in CBF was abolish ed by GF 109203X, a novel PKC (nPKC) isoform inhibitor whereas this de crease in CBF was not attenuated by Go-6976, a specific inhibitor of c onventional PKC isoforms. Because pretreatment with NPY did not block the stimulation of CBF by forskolin and pretreatment with forskolin di d not abolish the NPY-induced inhibition of CBF, this NPY receptor-med iated signal transduction mechanism appears to be independent of the a denylate cyclase-protein kinase A (PKA) pathway. inhibition of Ca2+-AT Pase by thapsigargin also prevented the suppression of CBF induced by subsequent application of NPY. These novel data indicate that, in cult ured human epithelia, NPY decreases CBF below its basal level via the activation of an nPKC isoform and Ca2+-ATPase, independent of the acti vity of PKA. This is consistent with the proposition that NPY is an au tonomic efferent inhibitory neurotransmitter regulating mucociliary tr ansport.