Small inhaled particles, which are entrapped by the mucous layer that is maintained by mucous secretion via mucin exocytosis and fluid secretion, are removed from the nasal cavity by beating cilia. The functional activities of beating cilia are assessed by their frequency and the amplitude. Nasal ciliary beating is controlled by intracellular ions (Ca²⁺, H⁺ and Cl⁻), and is enhanced by a decreased concentration of intracellular Cl⁻ ([Cl⁻]_i) in ciliated human nasal epithelial cells (cHNECs) in primary culture, which increases the ciliary beat amplitude. A novel method to measure both ciliary beat frequency (CBF) and ciliary beat distance (CBD, an index of ciliary beat amplitude) in cHNECs has been developed using high-speed video microscopy, which revealed that a decrease in [Cl⁻]_i increased CBD, but not CBF, and an increase in [Cl⁻]_i decreased both CBD and CBF. Thus, [Cl⁻]_i inhibits ciliary beating in cHNECs, suggesting that axonemal structures controlling CBD and CBF may have Cl⁻ sensors and be regulated by [Cl⁻]_i. These observations indicate that the activation of Cl⁻ secretion stimulates ciliary beating (increased CBD) mediated via a decrease in [Cl⁻]_i in cHNECs. Thus, [Cl⁻]_i is critical for controlling ciliary beating in cHNECs. This review introduces the concept of Cl⁻ regulation of ciliary beating in cHNECs.

The effects of the isoflavone daidzein on the ciliary beat distance (CBD, which is a parameter assessing the amplitude of ciliary beating) and the ciliary beat frequency (CBF) were examined in ciliated human nasal epithelial cells (cHNECs) in primary culture. Daidzein decreased [Cl⁻]_i and enhanced CBD in cHNECs. The CBD increase that was stimulated by daidzein was mimicked by Cl⁻-free NO₃⁻ solution and bumetanide (an inhibitor of Na⁺/K⁺/2Cl⁻ cotransport), both of which decreased [Cl⁻]_i. Moreover, the CBD increase was inhibited by 5-Nitro-2-(3-phenylpropylamino)benzoic acid (NPPB, a Cl⁻ channel blocker), which increased [Cl⁻]_i. CBF was also decreased by NPPB. The rate of [Cl⁻]_i decrease evoked by Cl⁻-free NO₃⁻ solution was enhanced by daidzein. These results suggest that daidzein activates Cl⁻ channels in cHNECs. Moreover, daidzein enhanced the microbead transport driven by beating cilia in the cell sheet of cHNECs, suggesting that an increase in CBD enhances ciliary transport. An [Cl⁻]_i decrease enhanced CBD, but not CBF, in cHNECs at 37 °C, although it enhanced both at 25 °C. Intracellular Cl⁻ affects both CBD and CBF in a temperature-dependent manner. In conclusion, daidzein, which activates Cl⁻ channels to decrease [Cl⁻]_i, stimulated CBD increase in cHNECs at 37 °C. CBD is a crucial factor that can increase ciliary transport in the airways under physiological conditions.

An application of CO₂/HCO₃⁻-free solution (Zero-CO₂) did not increase intracellular pH (pH_i) in ciliated human nasal epithelial cells (c-hNECs), leading to no increase in frequency (CBF) or amplitude (CBA) of the ciliary beating. This study demonstrated that the pH_i of c-hNECs expressing carbonic anhydrase IV (CAIV) is high (7.64), while the pH_i of ciliated human bronchial epithelial cells (c-hBECs) expressing no CAIV is low (7.10). An extremely high pH_i of c-hNECs caused pH_i, CBF and CBA to decrease upon Zero-CO₂ application, while a low pH_i of c-hBECs caused them to increase. An extremely high pH_i was generated by a high rate of HCO₃⁻ influx via interactions between CAIV and Na⁺/HCO₃⁻ cotransport (NBC) in c-hNECs. An NBC inhibitor (S0859) decreased pH_i, CBF and CBA and increased CBF and CBA in c-hNECs upon Zero-CO₂ application. In conclusion, the interactions of CAIV and NBC maximize HCO₃⁻ influx to increase pH_i in c-hNECs. This novel mechanism causes pH_i to decrease, leading to no increase in CBF and CBA in c-hNECs upon Zero-CO₂ application, and appears to play a crucial role in maintaining pH_i, CBF and CBA in c-hNECs periodically exposed to air (0.04% CO₂) with respiration.

若年性血管線維腫は，思春期の男性に好発するまれな良性の血管腫瘍である。組織学的には良性腫瘍であるが骨を破壊しながら浸潤性に周囲に進展するため，臨床的には悪性腫瘍に準じて取り扱われる。近年は，内視鏡手術の普及，機器の発展，熟練者の増加などから，内視鏡下での治療報告は増加傾向である。本疾患の根治的な治療は外科的完全摘出であることに加え，腫瘍が顔面深部に存在し，易出血性であることから確実な止血操作が可能であるよう十分な視野を確保できる術式が求められる。また，術中の出血を抑える点で術前の選択的血管塞栓術が勧められている。しかし，本腫瘍はまれであるため治療に習熟している施設は少なく術式選択に統一した見解は今のところない。今回われわれは15歳の男児で翼状突起基部にまで進展する若年性血管線維腫例を経験した。術前に血管塞栓術を施行しDenker法に内視鏡を併用して腫瘍を一塊切除した。術後3年半経過しているが再発なく経過している。本疾患の治療は術中の十分な視野確保が重要であると考えられる。そのためには術前血管塞栓術を行い，出血量の減少を図ることと，また術式については内視鏡に拘らず，柔軟な術式選択を行うことが肝要であると考えられた。