Ciliary beating amplitude controlled by intracellular Cl− and a high rate of CO2 production in ciliated human nasal epithelial cells

The ciliary transport is controlled by two parameters of the ciliary beating, frequency (CBF) and amplitude. In this study, we developed a novel method to measure both CBF and ciliary bend distance (CBD, an index of ciliary beating amplitude) in ciliated human nasal epithelial cells (cHNECs) in primary culture, which are prepared from patients contracting allergic rhinitis and chronic sinusitis. An application of Cl − -free NO 3 − solution or bumetanide (an inhibitor of Na + /K + /2Cl − cotransport), which decreases intracellular Cl − concentration ([Cl − ] i ), increased CBD, not CBF, at 37 °C; however, it increased both CBD and CBF at 25 °C. Conversely, addition of Cl − channel blockers (5-nitro-2-(3-phenylpropylamino) benzoic acid (NPPB) and 4-[[4-Oxo-2-thioxo-3-[3-trifluoromethyl]phenyl]-5-thiazolidinylidene]methyl] benzoic acid (CFTR(inh)-172)), which increase [Cl − ] i , decreased both CBD and CBF, suggesting that CFTR plays a crucial role for maintaining [Cl − ] i in these cells. We speculate that Cl − modulates activities of the molecular motors regulating both CBD and CBF in cHNECs. Moreover, application of the CO 2 /HCO 3 − -free solution did not change intracellular pH (pH i ), and addition of an inhibitor of carbonic anhydrase (acetazolamide) sustained pH i increase induced by the NH 4 + pulse, which transiently increased pH i in the absence of acetazolamide. These results indicate that the cHNEC produces a large amount of CO 2 , which maintains a constant pH i even under the CO 2 /HCO 3 − -free condition.