Ciliary Motility Decreased by a CO2/HCO3--Free Solution in Ciliated Human Nasal Epithelial Cells Having a pH Elevated by Carbonic Anhydrase IV.

An application of CO2/HCO3--free solution (Zero-CO2) did not increase intracellular pH (pHi) 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 pHi of c-hNECs expressing carbonic anhydrase IV (CAIV) is high (7.64), while the pHi of ciliated human bronchial epithelial cells (c-hBECs) expressing no CAIV is low (7.10). An extremely high pHi of c-hNECs caused pHi, CBF and CBA to decrease upon Zero-CO2 application, while a low pHi of c-hBECs caused them to increase. An extremely high pHi 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 pHi, 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 pHi in c-hNECs. This novel mechanism causes pHi 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 pHi, CBF and CBA in c-hNECs periodically exposed to air (0.04% CO2) with respiration.

The Increase in the Frequency and Amplitude of the Beating of Isolated Mouse Tracheal Cilia Reactivated by ATP and cAMP with Elevation in pH.

Single cilia, 100 nm in diameter and 10 µm in length, were isolated from mouse tracheae with Triton X-100 (0.02%) treatment, and the effects of pH on ciliary beating were examined by measuring the ciliary beat frequency (CBF) and the ciliary bend distance (CBD-an index of amplitude) using a high-speed video microscope (250 fps). ATP (2.5 mM) plus 8Br-cAMP (10 µM) reactivated the CBF and CBD in the isolated cilia, similar to the cilia of in vivo tracheae. In the reactivated isolated cilia, an elevation in pH from 7.0 to 8.0 increased the CBF from 3 to 15 Hz and the CBD from 0.6 to 1.5 µm. The pH elevation also increased the velocity of the effective stroke; however, it did not increase the recovery stroke, and, moreover, it decreased the intervals between beats. This indicates that H+ (pHi) directly acts on the axonemal machinery to regulate CBF and CBD. In isolated cilia priorly treated with 1 µM PKI-amide (a PKA inhibitor), 8Br-cAMP did not increase the CBF or CBD in the ATP-stimulated isolated cilia. pH modulates the PKA signal, which enhances the axonemal beating generated by the ATP-activated inner and outer dyneins.

Ambroxol-Enhanced Frequency and Amplitude of Beating Cilia Controlled by a Voltage-Gated Ca2+ Channel, Cav1.2, via pHi Increase and [Cl-]i Decrease in the Lung Airway Epithelial Cells of Mice.

Ambroxol (ABX), a frequently prescribed secretolytic agent which enhances the ciliary beat frequency (CBF) and ciliary bend angle (CBA, an index of amplitude) by 30%, activates a voltage-dependent Ca2+ channel (CaV1.2) and a small transient Ca2+ release in the ciliated lung airway epithelial cells (c-LAECs) of mice. The activation of CaV1.2 alone enhanced the CBF and CBA by 20%, mediated by a pHi increasei and a [Cl-]i decrease in the c-LAECs. The increase in pHi, which was induced by the activation of the Na+-HCO3- cotransporter (NBC), enhanced the CBF (by 30%) and CBA (by 15-20%), and a decrease in [Cl-]i, which was induced by the Cl- release via anoctamine 1 (ANO1), enhanced the CBA (by 10-15%). While a Ca2+-free solution or nifedipine (an inhibitor of CaV1.2) inhibited 70% of the CBF and CBA enhancement using ABX, CaV1.2 enhanced most of the CBF and CBA increases using ABX. The activation of the CaV1.2 existing in the cilia stimulates the NBC to increase pHi and ANO1 to decrease the [Cl-]i in the c-LAECs. In conclusion, the pHi increase and the [Cl-]i decrease enhanced the CBF and CBA in the ABX-stimulated c-LAECs.

Mumefural prevents insulin resistance and amyloid-beta accumulation in the brain by improving lowered interstitial fluid pH in type 2 diabetes mellitus.

The present study tried to clarify if mumefural would prevent hyperglycemia, one of the typical symptoms of type 2 diabetes mellitus (T2DM), since mumefural is an extract from Japanese apricots preventing hyperglycemia. To clarify if mumefural would prevent T2DM pathogenesis, we used Otsuka Long-Evans Tokushima fatty (OLETF) rats, T2DM model. Mumefural diminished hyperglycemia, HOMA-IR and plasma triglyceride concentration in OLETF rats under fasting conditions. In addition, mumefural elevated protein expression of sodium-coupled monocarboxylate transporter 1 (SMCT1) in the distal colon participating in absorption of weak organic acids, which behave as bases but not acids after absorption into the body. Mumefural also increased the interstitial fluid pH around the brain hippocampus lowered in OLETF rats compared with non-T2DM LETO rats used as control for OLETF rats. Amyloid-beta accumulation in the brain decreased in accordance with the pH elevation. On the one hand, mumefural didn't affect plasma concentrations of glucagon, GLP-1, GIP or PYY under fasting conditions. Taken together, these observations indicate that: 1) mumefural would be a useful functional food improving hyperglycemia, insulin resistance and the lowered interstitial fluid pH in T2DM; 2) the interstitial fluid pH would be one of key factors influencing the accumulation of amyloid-beta.

Ambroxol-enhanced ciliary beating via voltage-gated Ca2+ channels in mouse airway ciliated cells.

Ambroxol (ABX) facilitates the mucociliary clearance (MC) by enhancing ciliary beating in airways. In this study, we focused on airway ciliary beating enhanced by ABX. However, little is known about the ABX-stimulated Ca2+ signalling activating airway ciliary beating. Airway ciliated cells isolated from mice lungs were observed by a high-speed video microscope, and the activities of beating cilia were assessed by CBF (ciliary beat frequency) and CBD (ciliary bend distance, an index of amplitude). ABX (10 µM) enhanced the CBF and CBD by 30%, and the enhancement was inhibited by nifedipine (20 µM, a L-type voltage-gated Ca2+ channel (CaV) inhibitor), or a Ca2+-free solution (approximately 50%). Pre-treatment with BAPTA-AM (10 µM, a chelator of intracellular Ca2+) abolished ABX-stimulated increases in CBF, CBD and [Ca2+]i. Thus, ABX increases [Ca2+]i (intracellular Ca2+ concentration) by stimulating Ca2+ release from the internal stores and nifedipine-sensitive Ca2+ entry. A previous study demonstrated the expression of CaV1.2 in airway cilia. ABX enhanced CBF, CBD and [Ca2+]i even in a high extracellular K+ concentration (155.5 mM), suggesting that it activates CaV1.2 except by depolarization. These enhancements were inhibited by nifedipine. In conclusion, ABX, which increases [Ca2+]i by stimulating Ca2+ release from internal stores and Ca2+ entry through CaV1.2s, enhanced CBF and CBD in airway ciliated cells. ABX is a novel agonist that modulates CaV1.2 of airway beating cilia to enhance CBF and CBD.

Transforming Growth Factor-ß1 and Bone Morphogenetic Protein-2 Inhibit Differentiation into Mature Ependymal Multiciliated Cells.

Ependymal cilia play pivotal roles in cerebrospinal fluid flow. In the primary culture system, undifferentiated glial cells differentiate well into ependymal multiciliated cells (MCCs) in the absence of fetal bovine serum (FBS). However, the substances included in FBS which inhibit this differentiation process have not been clarified yet. Here, we constructed the polarized primary culture system of ependymal cells using a permeable filter in which they retained ciliary movement. We found that transforming growth factor-ß1 (TGF-ß1) as well as Bone morphogenetic protein (BMP)-2 inhibited the differentiation with ciliary movement. The inhibition on the differentiation by FBS was recovered by the TGF-ß1 and BMP-2 inhibitors in combination.

Enhancement of airway ciliary beating mediated via voltage-gated Ca2+ channels/α7-nicotinic receptors in mice.

Acetylcholine (ACh), which activates muscarinic ACh receptors (mAChRs) and nicotinic ACh receptors (nAChRs), enhances airway ciliary beating by increasing the intracellular Ca2+ concentration ([Ca2+]i). The mechanisms enhancing airway ciliary beating by nAChRs have remained largely unknown, although those by mAChRs are well understood. In this study, we focused on the effects of α7-nAChRs and voltage-gated Ca2+ channels (CaVs) on the airway ciliary beating. The activities of ciliary beating were assessed by frequency (CBF, ciliary beat frequency) and amplitude (CBD, ciliary bend distance) measured by high-speed video microscopy. ACh enhanced CBF and CBD by 25% mediated by an [Ca2+]i increase stimulated by mAChRs and α7-nAChRs (a subunit of nAChR) in airway ciliary cells of mice. Experiments using PNU282987 (an agonist of α7-nAChR) and MLA (an inhibitor of α7-nAChR) revealed that CBF and CBD enhanced by α7-nAChR are approximately 50% of those enhanced by ACh. CBF, CBD, and [Ca2+]i enhanced by α7-nAChRs were inhibited by nifedipine, suggesting activation of CaVs by α7-nAChRs. Experiments using a high K+ solution with/without nifedipine (155.5 mM K+) showed that the activation of CaVs enhances CBF and CBD via an [Ca2+]i increase. Immunofluorescence and immunoblotting studies demonstrated that Cav1.2 and α7-nAChR are expressed in airway cilia. Moreover, IL-13 stimulated MLA-sensitive increases in CBF and CBD in airway ciliary cells, suggesting an autocrine regulation of ciliary beating by CaV1.2/α7-nAChR/ACh. In conclusion, a novel Ca2+ signalling pathway in airway cilia, CaV1.2/α7-nAChR, enhances CBF and CBD and activates mucociliary clearance maintaining healthy airways.

Ezrin knockdown reduces procaterol-stimulated ciliary beating without morphological changes in mouse airway cilia.

Mucociliary clearance, which is conducted by beating cilia cooperating with the surface mucous layer, is a major host defense mechanism of the airway epithelium. Ezrin, a crosslinker between membrane proteins and the actin cytoskeleton, is located in microvilli and around the basal bodies in airway ciliary cells. It is also likely that ezrin plays an important role in apical localization of ß2 adrenergic receptor (ß2AR) in airway ciliary cells. Here, we studied the physiological roles of ezrin by using trachea and airway epithelial cells prepared from ezrin-knockdown (Vil2kd/kd) mice. The trachea and airway ciliary cells of Vil2kd/kd mice presented a normal morphology and basal body orientation, suggesting that ezrin is not directly involved in development and planar cell polarity of cilia. Procaterol stimulates ciliary beating (frequency and amplitude) via ß2AR in the airway ciliary cells. In the Vil2kd/kd mice, airway ciliary beating stimulated with procaterol was partly inhibited due to the impairment of cell surface expression of ß2AR. These results suggest that ezrin regulates the beating of airway ciliary cells by promoting the apical surface localization of ß2AR. This article has an associated First Person interview with the first author of the paper.

Possibility of Venous Serum Cl- Concentration ([Cl-]s) as a Marker for Human Metabolic Status: Correlation of [Cl-]s to Age, Fasting Blood Sugar (FBS), and Glycated Hemoglobin (HbA1c).

The HCO3- concentration in venous serum ([HCO3-]s) is a factor commonly used for detecting the body pH and metabolic conditions. To exactly detect [HCO3-]s, the venous CO2 pressure should be kept as it is in the vein. The [HCO3-]s measurement is technically complicated to apply for huge numbers of almost heathy persons taking only basic medical examinations. The summation of [HCO3-]s and the venous serum Cl- concentration ([Cl-]s) is approximately constant; therefore, we studied if [Cl-]s could be a marker detecting metabolic conditions instead of [HCO3-]s. Venous blood was obtained from persons taking basic medical examinations (the number of persons = 107,630). Older persons showed higher values of [Cl-]s, fasting blood sugar (FBS), and glycated hemoglobin (HbA1c) than younger ones. [Cl-]s showed positive correlation to age and negative correlation to FBS and HBA1c. The negative correlation of [Cl-]s to FBS/HbA1c was obvious in persons with high FBS/HbA1c, leading us to an idea that persons with high FBS/HbA1c show high [HCO3-]s, which might be caused by low activity of carbonic anhydrase in the lung observed in persons with diabetes mellitus under acidotic conditions. Taken together, an easily measured serum electrolyte, [Cl-]s, could be a useful marker estimating metabolic conditions.

Nitric oxide synthesis stimulated by arachidonic acid accumulation via PPARα in acetylcholine-stimulated gastric mucous cells.

NEW FINDINGS: What is the central question of this study? Arachidonic acid (AA) stimulates NO production in antral mucous cells without any increase in [Ca2+ ]i . Given that the intracellular AA concentration is too low to measure, the relationship between AA accumulation and NO production remains uncertain. Is AA accumulation a key step for NO production? What is the main finding and its importance? We demonstrated that AA accumulation is a key step for NO production. The amount of AA released could be measured using fluorescence-HPLC. The intracellular AA concentration was maintained at < 1 µM. Nitric oxide is produced by AA accumulation in antral mucous cells, not as a direct effect of [Ca2+ ]i . ABSTRACT: In the present study, we demonstrate that NO production is stimulated by an accumulation of arachidonic acid (AA) mediated via peroxisome proliferation-activated receptor α (PPARα) and that the NO produced enhances Ca2+ -regulated exocytosis in ACh-stimulated antral mucous cells. The amount of AA released from the antral mucosa, measured by fluorescence high-performance liquid chromatography (F-HPLC), was increased by addition of ionomycin (10 µM) or ACh, suggesting that AA accumulation is stimulated by an increase in [Ca2+ ]i . The AA production was inhibited by an inhibitor of cytosolic phospholipase A2 (cPLA2-inhα). GW6471 (a PPARα inhibitor) and cPLA2-inhα inhibited NO synthesis stimulated by ACh. Moreover, indomethacin, an inhibitor of cyclooxygenase, stimulated AA accumulation and NO production. However, acetylsalicylic acid did not stimulate AA production and NO synthesis. An analogue of AA (AACOCF3) alone stimulated NO synthesis, which was inhibited by GW6471. In antral mucous cells, indomethacin enhanced Ca2+ -regulated exocytosis by increasing NO via PPARα, and the enhancement was abolished by GW6471 and cPLA2-inhα. Thus, AA produced via PLA2 activation is the key step for NO synthesis in ACh-stimulated antral mucous cells and plays important roles in maintaining antral mucous secretion, especially in Ca2+ -regulated exocytosis.

Moesin is involved in microglial activation accompanying morphological changes and reorganization of the actin cytoskeleton.

Moesin is a member of the ezrin, radixin and moesin (ERM) proteins that are involved in the formation and/or maintenance of cortical actin organization through their cross-linking activity between actin filaments and proteins located on the plasma membranes as well as through regulation of small GTPase activities. Microglia, immune cells in the central nervous system, show dynamic reorganization of the actin cytoskeleton in their process elongation and retraction as well as phagocytosis and migration. In microglia, moesin is the predominant ERM protein. Here, we show that microglial activation after systemic lipopolysaccharide application is partly inhibited in moesin knockout (Msn-KO) mice. We prepared primary microglia from wild-type and Msn-KO mice, and studied them to compare their phenotypes accompanying morphological changes and reorganization of the actin cytoskeleton induced by UDP-stimulated phagocytosis and ADP-stimulated migration. The Msn-KO microglia showed higher phagocytotic activity in the absence of UDP, which was not further increased by the treatment with UDP. They also exhibited decreased ADP-stimulated migration activities compared with the wild-type microglia. However, the Msn-KO microglia retained their ability to secrete tumor necrosis factor α and nitric oxide in response to lipopolysaccharide.

Intracellular Cl- Regulation of Ciliary Beating in Ciliated Human Nasal Epithelial Cells: Frequency and Distance of Ciliary Beating Observed by High-Speed Video Microscopy.

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.

Airway Ciliary Beating Affected by the Pcp4 Dose-Dependent [Ca2+]i Increase in Down Syndrome Mice, Ts1Rhr.

In Ts1Rhr, a Down syndrome model mouse, the airway ciliary beatings are impaired; that is, decreases in ciliary beat frequency (CBF) and ciliary bend angle (CBA, an index of ciliary beat amplitude)). A resumption to two copies of the Pcp4 gene on the Ts1Rhr trisomic segment (Ts1Rhr:Pcp4+/+/-) rescues the decreases in CBF and CBA that occur in Ts1Rhr. In airway cilia, upon stimulation with procaterol (a ß2-agonist), the CBF increase is slower over the time course than the CBA increase because of cAMP degradation by Ca2+/calmodulin-dependent phosphodiesterase 1 (PDE1) existing in the metabolon regulating CBF. In Ts1Rhr, procaterol-stimulated CBF increase was much slower over the time course than in the wild-type mouse (Wt) or Ts1Rhr:Pcp4+/+/-. However, in the presence of 8MmIBMX (8-methoxymethyl isobutylmethyl xanthine, an inhibitor of PDE1) or calmidazolium (an inhibitor of calmodulin), in both Wt and Ts1Rhr, procaterol stimulates CBF and CBA increases over a similar time course. Measurements of cAMP revealed that the cAMP contents were lower in Ts1Rhr than in Wt or in Ts1Rhr:Pcp4+/+/-, suggesting the activation of PDE1A that is present in Ts1Rhr airway cilia. Measurements of the intracellular Ca2+ concentration ([Ca2+]i) in airway ciliary cells revealed that temperature (increasing from 25 to 37 °C) or 4αPDD (a selective transient receptor potential vanilloid 4 (TRPV4) agonist) stimulates a larger [Ca2+]i increase in Ts1Rhr than in Wt or Ts1Rhr:Pcp4+/+/-. In airway ciliary cells of Ts1Rhr, Pcp4-dose dependent activation of TRPV4 appears to induce an increase in the basal [Ca2+]i. In early embryonic day mice, a basal [Ca2+]i increased by PCP4 expressed may affect axonemal regulatory complexes regulated by the Ca2+-signal in Ts1Rhr, leading to a decrease in the basal CBF and CBA of airway cilia.

Enhancement of ciliary beat amplitude by carbocisteine in ciliated human nasal epithelial cells.

OBJECTIVE: Carbocisteine (CCis), a mucoactive agent, is used to improve the symptoms of sinonasal diseases. However, the effect of CCis on nasal ciliary beating remains uncertain. We examined the effects of CCis on ciliary beat distance (CBD, an index of amplitude), and ciliary beat frequency (CBF) in ciliated human nasal epithelial cells (cHNECs) in primary culture. METHODS: The cHNECs were prepared from the nasal tissue resected from patients required surgery for chronic sinusitis (CS) or allergic rhinitis (AR). CBD and CBF were measured using videomicroscopy equipped with a high-speed camera. RESULTS: CCis increased CBD by 30%, but not CBF, and decreased intracellular Cl- concentration ([Cl- ]i ) in cHNECs. The CCis' actions were mimicked by the Cl- -free NO3- solution. In contrast, prior treatment of NPPB (20 µM) or CFTR(inh)-172 (1 µM), which increased [Cl- ]i by 20%, decreased CBF by 10% and CBD by 25% and inhibited the CCis' actions. However, prior treatment of T16Ainh-A01 (10 µM) did not inhibit the CCis' actions, although it decreased [Cl- ]i by 10% and CBD by 15%. Thus, CCis stimulates Cl- channels including cystic fibrosis transmembrane conductance regulator (CFTR). Moreover, CCis enhanced the transport of microbeads driven by the beating cilia in cHNECs. The CCis actions were similar in cHNECs from both types of pateints. CONCLUSION: CCis increased CBD by 30% in cHNECs via an [Cl- ]i decrease stimulated by activation of Cl- channels, including CFTR. CCis may stimulate nasal mucociliary clearance by increasing CBD in patients contracting CS or AR. LEVEL OF EVIDENCE: NA. Laryngoscope, 130:E289-E297, 2020.

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 NO3- 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 CO2/HCO3--free solution did not change intracellular pH (pHi), and addition of an inhibitor of carbonic anhydrase (acetazolamide) sustained pHi increase induced by the NH4+ pulse, which transiently increased pHi in the absence of acetazolamide. These results indicate that the cHNEC produces a large amount of CO2, which maintains a constant pHi even under the CO2/HCO3--free condition.

Carbocisteine stimulated an increase in ciliary bend angle via a decrease in [Cl-]i in mouse airway cilia.

Carbocisteine (CCis), a mucoactive agent, is widely used to improve respiratory diseases. This study demonstrated that CCis increases ciliary bend angle (CBA) by 30% and ciliary beat frequency (CBF) by 10% in mouse airway ciliary cells. These increases were induced by an elevation in intracellular pH (pHi; the pHi pathway) and a decrease in the intracellular Cl- concentration ([Cl-]i; the Cl- pathway) stimulated by CCis. The Cl- pathway, which is independent of CO2/HCO3-, increased CBA by 20%. This pathway activated Cl- release via activation of Cl- channels, leading to a decrease in [Cl-]i, and was inhibited by Cl- channel blockers (5-nitro-2-(3-phenylpropylamino) benzoic acid and CFTR(inh)-172). Under the CO2/HCO3--free condition, the CBA increase stimulated by CCis was mimicked by the Cl--free NO3- solution. The pHi pathway, which depends on CO2/HCO3-, increased CBF and CBA by 10%. This pathway activated HCO3- entry via Na+/HCO3- cotransport (NBC), leading to a pHi elevation, and was inhibited by 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid. The effects of CCis were not affected by a protein kinase A inhibitor (1 µM PKI-A) or Ca2+-free solution. Thus, CCis decreased [Cl-]i via activation of Cl- channels including CFTR, increasing CBA by 20%, and elevated pHi via NBC activation, increasing CBF and CBA by 10%.

Spontaneous oscillation of the ciliary beat frequency regulated by release of Ca2+ from intracellular stores in mouse nasal epithelia.

Ciliary beating frequency (CBF) was investigated in ciliated nasal epithelial cells (cMNECs) isolated from mice using video microscopy equipped with a high-speed camera. In cMNECs, a spontaneous CBF oscillation was observed. The CBF oscillation was abolished by BAPTA-AM but not by Ca2+-free solution. The addition of thapsigargin, which depletes Ca2+ from internal stores, also abolished CBF oscillation. Moreover, the intracellular Ca2+ concentration [Ca2+]i, spontaneously oscillated even with the Ca2+-free solution. Moreover, 2APB (an inhibitor of the IP3 receptor) abolished CBF oscillation in cMNECs. Overall, these findings suggest that the CBF oscillation in cMNECs is triggered by the release of Ca2+ from the IP3-sensitive internal stores. Moreover, IBMX, an inhibitor of phosphodiesterase, did not affect CBF oscillation in cMNECs, although it slightly increased CBF. These results suggest that CBF oscillations were induced by [Ca2+]i oscillation controlled via the release of Ca2+ from IP3-sensitive stores, rather than via cAMP accumulation. CBF oscillation possibly plays a crucial role in maintaining an efficient mucociliary clearance in the nasal epithelia.

Daidzein-Stimulated Increase in the Ciliary Beating Amplitude via an [Cl-]i Decrease in Ciliated Human Nasal Epithelial Cells.

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.

Seihai-to (TJ-90)-Induced Activation of Airway Ciliary Beatings of Mice: Ca2+ Modulation of cAMP-Stimulated Ciliary Beatings via PDE1.

Sei-hai-to (TJ-90, Qing Fei Tang), a Chinese traditional medicine, increases ciliary beat frequency (CBF) and ciliary bend angle (CBA) mediated via cAMP (3',5'-cyclic adenosine monophosphate) accumulation modulated by Ca2+-activated phosphodiesterase 1 (PDE1A). A high concentration of TJ-90 (≥40 µg/mL) induced two types of CBF increases, a transient increase (an initial increase, followed by a decrease) and a sustained increase without any decline, while it only sustained the CBA increase. Upon inhibiting increases in intracellular Ca2+ concentration ([Ca2+]i) by 10 µM BAPTA-AM (Ca2+-chelator, 1,2-Bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid tetrakis(acetoxymethyl ester) or Ca2+/calmodulin-dependent PDE1 by 8MmIBMX (a selective PDE1 inhibitor), TJ-90 (400 µg/mL) induced only the sustained CBF increase without any transient CBF increase. The two types of the CBF increase (the transient increase and the sustained increase) induced by TJ-90 (≥40 µg/mL) were mimicked by the stimulation with both procaterol (100 pM) and ionomycin (500 nM). Thus, TJ-90 stimulates small increases in the intracellular cAMP concentration ([cAMP]i) and [Ca2+]i in airway ciliary cells of mice. These small increases in [cAMP]i and [Ca2+]i cause inducing a transient CBF increase or a sustained CBF increase in an airway ciliary cells, depending on the dominant signal, Ca2+-signal, or cAMP-signal.

Measurement of [Cl-]i unaffected by the cell volume change using MQAE-based two-photon microscopy in airway ciliary cells of mice.

MQAE is a 'non-ratiometric' chloride ion (Cl-)-quenched fluorescent indicator that is used to determine intracellular Cl- concentration ([Cl-]i). MQAE-based two-photon microscopy is reported to be a useful method to measure [Cl-]i, but it is still controversial because a change in cell volume may alter the MQAE concentration, leading to a change in the fluorescence intensity without any change in [Cl-]i. In an attempt to elucidate the effect or lack of effect of cell volume on MQAE concentration, we studied the effects of changes in cell volume, achieved by applying different levels of osmotic stress, on the intensity of MQAE fluorescence in airway ciliary cells. To study solely the effect of changes in cell volume on MQAE fluorescence intensity, i.e., excluding the effect of any change in [Cl-]i, we first conducted the experiments in a Cl--free nitrate (NO3-) solution to substitute NO3- (non-quenching anion for MQAE fluorescence) for Cl- in the intracellular fluid. Hypo- (- 30 mM NaNO3) or hyper-osmotic stress (+ 30 mM NaNO3) effected changes in cell volume, but the stress did not result in any significant change in MQAE fluorescence intensity. The experiments were also carried out in Cl--containing solution. Hypo-osmotic stress (- 30 mM NaCl) increased both MQAE fluorescence intensity and cell volume, while hyper-osmotic stress (+ 30 mM NaCl) decreased both of these properties. These results suggest that the osmotic stress-induced change in MQAE fluorescence intensity was caused by the change in [Cl-]i and not by the MQAE concentration. Moreover, the intracellular distribution of MQAEs was heterogeneous and not affected by the changes in osmotic stress-induced cell volume, suggesting that MQAEs are bound to un-identified subcellular structures. These bound MQAEs appear to have enabled the measurement of [Cl-]i in airway ciliary cells, even under conditions of cell volume change.