Oscillations in ciliary beat frequency and intracellular calcium concentration in rabbit tracheal epithelial cells induced by ATP

Aerosolized Particulate Matter and Blunting of Ciliary Dynamic Responses: Implications for Veterans and Active Duty Military in Southwest Asia

INTRODUCTION

Respiratory diseases such as chronic rhinosinusitis and asthma are observed at increased rates in active duty and veteran military members, and they are especially prevalent in individuals who have been deployed in Southwest Asia during Operation Iraqi Freedom and Operation Enduring Freedom. Particulate matter, specifically the fine-grain desert sand found in the Middle East, may be a key source of this pathology because of deleterious effects on mucociliary clearance.

MATERIALS AND METHODS

With IRB approval, human sinonasal tissue was grown at an air-liquid interface and cultures were exposed to different types and sizes of particulate matter, including sand from Afghanistan and Kuwait. Ciliary dynamic responses to mechanical stimulation and ATP application were assessed following particulate exposure.

RESULTS

Particle size of the commercial sand was substantially larger than that of the sand of Afghan or Kuwaiti origin. Following exposure to particulate matter, normal dynamic ciliary responses to mechanical stimulation and ATP application were significantly decreased (P < .01), with corresponding decreases in ATP-induced calcium flux (P < .05). These changes were partially reversible with apical washing after a 16-h period of exposure. After 36 h of exposure to Middle Eastern sand, ciliary responses to purinergic stimulation were completely abolished.

CONCLUSIONS

There is a neutralization of the dynamic ciliary response following chronic particulate matter exposure, similar to ciliary pathologies observed in patients with chronic rhinosinusitis. Aerosolized particulate matter endured by military personnel in the Southwest Asia may cause dysfunctional mucociliary clearance; these data help to explain the increased prevalence of respiratory pathology in individuals who are or have been deployed in this region.

Silybin regulates P450s activity by attenuating endoplasmic reticulum stress in mouse nonalcoholic fatty liver disease

Cytochrome P450s are important phase I metabolic enzymes located on endoplasmic reticulum (ER) involved in the metabolism of endogenous and exogenous substances. Our previous study showed that a hepatoprotective agent silybin restored CYP3A expression in mouse nonalcoholic fatty liver disease (NAFLD). In this study we investigated how silybin regulated P450s activity during NAFLD. C57BL/6 mice were fed a high-fat-diet (HFD) for 8 weeks to induce NAFLD, and were administered silybin (50, 100 mg ·kg^-1 ·d^-1, i.g.) in the last 4 weeks. We showed that HFD intake induced hepatic steatosis and ER stress, leading to significant inhibition on the activity of five primary P450s including CYP1A2, CYP2B6, CYP2C19, CYP2D6, and CYP3A in liver microsomes. These changes were dose-dependently reversed by silybin administration. The beneficial effects of silybin were also observed in TG-stimulated HepG2 cells in vitro. To clarify the underlying mechanism, we examined the components involved in the P450 catalytic system, membrane phospholipids and ER membrane fluidity, and found that cytochrome b5 (cyt b5) was significantly downregulated during ER stress, and ER membrane fluidity was also reduced evidenced by DPH polarization and lower polyunsaturated phospholipids levels. The increased ratios of NADP⁺/NADPH and PC/PE implied Ca²⁺ release and disruption of cellular Ca²⁺ homeostasis resulted from mitochondria dysfunction and cytochrome c (cyt c) release. The interaction between cyt c and cyt b5 under ER stress was an important reason for P450s activity inhibition. The effect of silybin throughout the whole course suggested that it regulated P450s activity through its anti-ER stress effect in NAFLD. Our results suggest that ER stress may be crucial for the inhibition of P450s activity in mouse NAFLD and silybin regulates P450s activity by attenuating ER stress.

Differential Regulation of ATP- and UTP-Evoked Prostaglandin E2 and IL-6 Production from Human Airway Epithelial Cells

The airway epithelial cells (AECs) lining the conducting passageways of the lung secrete a variety of immunomodulatory factors. Among these, PGE2 limits lung inflammation and promotes bronchodilation. By contrast, IL-6 drives intense airway inflammation, remodeling, and fibrosis. The signaling that differentiates the production of these opposing mediators is not understood. In this study, we find that the production of PGE2 and IL-6 following stimulation of human AECs by the damage-associated molecular pattern extracellular ATP shares a common requirement for Ca2+ release-activated Ca2+ (CRAC) channels. ATP-mediated synthesis of PGE2 required activation of metabotropic P2Y2 receptors and CRAC channel-mediated cytosolic phospholipase A2 signaling. By contrast, ATP-evoked synthesis of IL-6 occurred via activation of ionotropic P2X receptors and CRAC channel-mediated calcineurin/NFAT signaling. In contrast to ATP, which elicited the production of both PGE2 and IL-6, the uridine nucleotide, UTP, stimulated PGE2 but not IL-6 production. These results reveal that human AECs employ unique receptor-specific signaling mechanisms with CRAC channels as a signaling nexus to regulate release of opposing immunomodulatory mediators. Collectively, our results identify P2Y2 receptors, CRAC channels, and P2X receptors as potential intervention targets for airway diseases.

Blocking ATP-releasing channels prevents high extracellular ATP levels and airway hyperreactivity in an asthmatic mouse model

Allergic asthma is a chronic airway inflammatory response to different triggers like inhaled allergens. Excessive ATP in fluids from patients with asthma is considered an inflammatory signal and an important autocrine/paracrine modulator of airway physiology. Here, we investigated the deleterious effect of increased extracellular ATP (eATP) concentration on the mucociliary clearance (MCC) effectiveness and determined the role of ATP releasing channels during airway inflammation in an ovalbumin (OVA)-sensitized mouse model. Our allergic mouse model exhibited high levels of eATP measured in the tracheal fluid with a luciferin-luciferase assay and reduced MCC velocity determined by microspheres tracking in the trachea ex vivo. Addition of ATP had a dual effect on MCC, where lower ATP concentration (µM) increased microspheres velocity, whereas higher concentration (mM) transiently stopped microspheres movement. Also, an augmented ethidium bromide uptake by the allergic tracheal airway epithelium suggests an increase in ATP release channel functionality during inflammatory conditions. The use of carbenoxolone, a nonspecific inhibitor of connexin and pannexin1 channels reduced the eATP concentration in the allergic mouse tracheal fluid and dye uptake by the airway epithelium, providing evidence that these ATP release channels are facilitating the net flux of ATP to the lumen during airway inflammation. However, only the specific inhibition of pannexin1 with ¹⁰Panx peptide significantly reduced eATP in bronchoalveolar lavage and decreased airway hyperresponsiveness in OVA-allergic mouse model. These data provide evidence that blocking eATP may be a pharmacological alternative to be explored in rescue therapy during episodes of airflow restriction in patients with asthma.

First contact: the role of respiratory cilia in host-pathogen interactions in the airways

Respiratory cilia are the driving force of the mucociliary escalator, working in conjunction with secreted airway mucus to clear inhaled debris and pathogens from the conducting airways. Respiratory cilia are also one of the first contact points between host and inhaled pathogens. Impaired ciliary function is a common pathological feature in patients with chronic airway diseases, increasing susceptibility to respiratory infections. Common respiratory pathogens, including viruses, bacteria, and fungi, have been shown to target cilia and/or ciliated airway epithelial cells, resulting in a disruption of mucociliary clearance that may facilitate host infection. Despite being an integral component of airway innate immunity, the role of respiratory cilia and their clinical significance during airway infections are still poorly understood. This review examines the expression, structure, and function of respiratory cilia during pathogenic infection of the airways. This review also discusses specific known points of interaction of bacteria, fungi, and viruses with respiratory cilia function. The emerging biological functions of motile cilia relating to intracellular signaling and their potential immunoregulatory roles during infection will also be discussed.

Lack of Kcnn4 improves mucociliary clearance in muco-obstructive lung disease

Airway mucociliary clearance (MCC) is the main mechanism of lung defense keeping airways free of infection and mucus obstruction. Airway surface liquid volume, ciliary beating, and mucus are central for proper MCC and critically regulated by sodium absorption and anion secretion. Impaired MCC is a key feature of muco-obstructive diseases. The calcium-activated potassium channel KCa.3.1, encoded by Kcnn4, participates in ion secretion, and studies showed that its activation increases Na⁺ absorption in airway epithelia, suggesting that KCa3.1-induced hyperpolarization was sufficient to drive Na⁺ absorption. However, its role in airway epithelium is not fully understood. We aimed to elucidate the role of KCa3.1 in MCC using a genetically engineered mouse. KCa3.1 inhibition reduced Na⁺ absorption in mouse and human airway epithelium. Furthermore, the genetic deletion of Kcnn4 enhanced cilia beating frequency and MCC ex vivo and in vivo. Kcnn4 silencing in the Scnn1b-transgenic mouse (Scnn1b^tg/+), a model of muco-obstructive lung disease triggered by increased epithelial Na⁺ absorption, improved MCC, reduced Na⁺ absorption, and did not change the amount of mucus but did reduce mucus adhesion, neutrophil infiltration, and emphysema. Our data support that KCa3.1 inhibition attenuated muco-obstructive disease in the Scnn1b^tg/+ mice. K⁺ channel modulation may be a therapeutic strategy to treat muco-obstructive lung diseases.

Silencing the calcium-activated potassium channel KCa.3.1 improves mucociliary clearance in muco-obstructive lung disease by decreasing sodium absorption in the airways.

Calmodulin and protein kinases A/G mediate ciliary beat response in the human nasal epithelium

BACKGROUND

Mucociliary clearance of the airway epithelium is an essential function for mucosal defense. We recently proposed a hypothetical mechanism of ciliary beat regulation, in which the pannexin-1 (Panx1)-P2X7 unit serves as an oscillator generating a periodic increase in intracellular Ca²⁺ ([Ca²⁺ ]_i ). In the present study, we examined the localization of Panx1 and P2X7 at the ultrastructural level, and investigated the regulatory pathway subsequent to [Ca²⁺ ]_i increase.

METHODS

The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic sinonasal surgery. The mucosa was examined by transmission immunoelectron microscopy for Panx1 and P2X7. Alternatively, the mucosa was cut into thin strips, and ciliary beat frequency (CBF) was measured under a phase-contrast light microscope with a high-speed digital video camera.

RESULTS

In immunoelectron microscopy, immunoreactivities for Panx1 and P2X7 were localized along the plasma membrane of the entire length of the cilia. CBF was significantly increased by stimulation with 100 µM acetylcholine (Ach). The Ach-induced CBF increase was significantly inhibited by calmidazolium (calmodulin antagonist), SQ22536 (adenylate cyclase inhibitor), ODQ (guanylate cyclase inhibitor), KT5720 (protein kinase A inhibitor), and KT5823 (protein kinase G inhibitor). Fluorodinitrobenzene (creatine kinase inhibitor) completely inhibited the ciliary beat in a time- and dose-dependent manner.

CONCLUSION

These results indicate that Panx1 and P2X7 coexist at the cilia of the human nasal epithelial cells and that the ciliary beat is regulated by calmodulin, adenylate/guanylate cyclases and protein kinases A/G, and crucially depends on creatine kinase.

Decreased ciliary beat responsiveness to acetylcholine in the nasal polyp epithelium

OBJECTIVE

We investigated the difference in ciliary beat responsiveness to acetylcholine in ex vivo and the difference in the expressions of associated molecules (M1/M3 muscarinic receptors, pannexin-1 and P2X7 purinergic receptor) between the nasal polyp and turbinate mucosa.

STUDY DESIGN

Laboratorial study.

PARTICIPANTS

Nasal polyp and inferior turbinate were collected from patients with hypertrophic rhinitis and/or nasal polyp during endoscopic sinonasal surgery.

MAIN OUTCOME MEASURES

The mucosa was cut into thin strips, and ciliary movement was observed under a phase-contrast light microscope equipped with a high-speed digital video camera. The samples were also examined by scanning electron microscopy, fluorescence immunohistochemistry, and quantitative reverse transcription-polymerase chain reaction.

RESULTS

Cilia were well preserved in both tissues at the ultrastructural level. The baseline ciliary beat frequency (CBF) was not different between the two tissues. The CBF of the turbinate was significantly increased by stimulation with acetylcholine (P < 0.001), but that of the polyp was not. The ratio of the acetylcholine-stimulated CBF to the baseline CBF was significantly lower in the polyp than in the turbinate (P < 0.001). Immunohistochemical study revealed that immunoreactivities for M3, pannexin-1 and P2X7 were weaker in the polyp than in the turbinate. The mRNA expressions of M1, M3 and P2X7 were significantly lower and that of pannexin-1 tended to be lower in the polyp than in the turbinate.

CONCLUSIONS

These results indicate that ciliary beat responsiveness to acetylcholine is decreased in the nasal polyp. This may be explained by the decreased expressions of M3, P2X7 and probably pannexin-1 in this tissue.

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.

Thyme extract increases mucociliary-beating frequency in primary cell lines from chronic obstructive pulmonary disease patients

Chronic obstructive pulmonary disease (COPD) is a respiratory disorder characterized by a progressive and irreversible airflow limitation. COPD is associated to a chronic inflammatory response with infiltration of inflammatory cells in the surface epithelium of large airways and abnormalities in structure and functions of cilia. Thyme (Thymus vulgaris L.) is a traditional medicinal plant of the Mediterranean area used to treat respiratory disorders. We previously evidenced that thyme extract reduce IL-1beta and IL-8, by downregulating the activated NF-κB levels, suggesting its potential therapeutically use in COPD. Cilia beating frequency (CBF) is dramatically impaired in COPD and different pharmacological agents can modulate cilia function. Herein we evaluated the effect of a commercial thyme extract in modulating CBF by measuring its activity in stimulating cAMP, Ca²⁺ levels and CBF in a MucilAir 3D human COPD airway epithelia reconstituted in vitro system using salmeterol, YM976, isoproterenol and GSK1016790 A as positive controls. Results showed that thyme extract increased cAMP levels starting from 12 h post-treatment, decreased extracellular Ca²⁺ levels and increased the CBF in airway epithelia from COPD donors. Overall, this work demonstrated that thyme extract is effective in stimulating CBF by inducing an increase of cAMP and Ca²⁺ levels, thus supporting its therapeutical use in the treatment of COPD.

Acetylcholine-induced Ciliary Beat of the Human Nasal Mucosa Is Regulated by the Pannexin-1 Channel and Purinergic P2X Receptor

Background Airway mucociliary transport is an important function for the clearance of inhaled foreign particulates in the respiratory tract. The present study aimed at investigating the regulatory mechanism of acetylcholine (Ach)-induced ciliary beat of the human nasal mucosa in ex vivo. Methods The inferior turbinate mucosa was collected from patients with chronic hypertrophic rhinitis during endoscopic surgery. The mucosa was cut into thin strips, and ciliary movement was observed under a phase-contrast light microscope with a high-speed digital video camera. The sample was alternatively subjected to scanning electron microscopic observation. Results Cilia on the turbinate epithelium were well preserved at the ultrastructural level. The baseline ciliary beat frequency (CBF) was 6.45 ± 0.32 Hz. CBF was significantly increased by stimulation with 100 µM Ach and 100 µM adenosine triphosphate. The Ach-induced CBF increase was completely inhibited by removing extracellular Ca²⁺. Significant inhibition of the Ach-induced CBF was also observed by the addition of 1 µM atropine, 40 µM 2-aminoethoxydiphenyl borate (inositol trisphosphate [IP₃] receptor antagonist), 10 µM carbenoxolone (pannexin-1 blocker), 1 mM probenecid (pannexin-1 blocker), 100 µM pyridoxalphosphate-6-azophenyl-20,40-disulfonic acid (P2X antagonist), and 300 µM flufenamic acid (connexin blocker). Meanwhile, 30 nM bafilomycin A1 (vesicular transport inhibitor) did not inhibit the Ach-induced CBF increase.

CONCLUSIONS

These results indicate that the regulatory mechanism of the Ach-induced ciliary beat is dependent on extracellular Ca²⁺ and involves the muscarinic Ach receptor, IP₃ receptor, pannexin-1 channel, purinergic P2X receptor, and connexin channel. We proposed a tentative intracellular signaling pathway of the Ach-induced ciliary beat, in which the pannexin-1-P2X unit may play a central role in ciliary beat regulation.

ATP Release Channels

Adenosine triphosphate (ATP) has been well established as an important extracellular ligand of autocrine signaling, intercellular communication, and neurotransmission with numerous physiological and pathophysiological roles. In addition to the classical exocytosis, non-vesicular mechanisms of cellular ATP release have been demonstrated in many cell types. Although large and negatively charged ATP molecules cannot diffuse across the lipid bilayer of the plasma membrane, conductive ATP release from the cytosol into the extracellular space is possible through ATP-permeable channels. Such channels must possess two minimum qualifications for ATP permeation: anion permeability and a large ion-conducting pore. Currently, five groups of channels are acknowledged as ATP-release channels: connexin hemichannels, pannexin 1, calcium homeostasis modulator 1 (CALHM1), volume-regulated anion channels (VRACs, also known as volume-sensitive outwardly rectifying (VSOR) anion channels), and maxi-anion channels (MACs). Recently, major breakthroughs have been made in the field by molecular identification of CALHM1 as the action potential-dependent ATP-release channel in taste bud cells, LRRC8s as components of VRACs, and SLCO2A1 as a core subunit of MACs. Here, the function and physiological roles of these five groups of ATP-release channels are summarized, along with a discussion on the future implications of understanding these channels.

Visualization and Detection of Ciliary Beating Pattern and Frequency in the Upper Airway using Phase Resolved Doppler Optical Coherence Tomography

Ciliary motion plays a critical role in the overall respiratory health of the upper airway. These cilia beat at a native frequency and in a synchronized pattern to continuously transport foreign particulate trapped in a layer of mucous out of the upper airway. Disruption of ciliary motion can lead to severe respiratory diseases and compromised respiratory function. Currently, the study of cilia requires expensive high speed cameras and high powered microscopes which is unsuitable for in vivo imaging and diagnosis. Doppler based optical coherence tomography has the potential to visualize the microscopic motion of cilia during their beating cycle. We demonstrate the development of a high-speed Doppler optical coherence tomography system that not only can rapidly determine the cilia beat frequency, but also simultaneously visualize the temporal cilia beating pattern which plays critical roles in cilia function.

CALHM1-Mediated ATP Release and Ciliary Beat Frequency Modulation in Nasal Epithelial Cells

Mechanical stimulation of airway epithelial cells causes apical release of ATP, which increases ciliary beat frequency (CBF) and speeds up mucociliary clearance. The mechanisms responsible for this ATP release are poorly understood. CALHM1, a transmembrane protein with shared structural features to connexins and pannexins, has been implicated in ATP release from taste buds, but it has not been evaluated for a functional role in the airway. In the present study, Calhm1 knockout, Panx1 knockout, and wild-type mouse nasal septal epithelial cells were grown at an air-liquid interface (ALI) and subjected to light mechanical stimulation from an air puff. Apical ATP release was attenuated in Calhm1 knockout cultures following mechanical stimulation at a pressure of 55 mmHg for 50 milliseconds (p < 0.05). Addition of carbenoxolone, a PANX1 channel blocker, completely abolished ATP release in Calhm1 knockout cultures but not in wild type or Panx1 knockout cultures. An increase in CBF was observed in wild-type ALIs following mechanical stimulation, and this increase was significantly lower (p < 0.01) in Calhm1 knockout cultures. These results demonstrate that CALHM1 plays a newly defined role, complementary to PANX1, in ATP release and downstream CBF modulation following a mechanical stimulus in airway epithelial cells.

An autocrine ATP release mechanism regulates basal ciliary activity in airway epithelium

KEY POINTS

Extracellular ATP, in association with [Ca²⁺ ]_i regulation, is required to maintain basal ciliary beat frequency. Increasing extracellular ATP levels increases ciliary beating in airway epithelial cells, maintaining a sustained response by inducing the release of additional ATP. Extracellular ATP levels in the millimolar range, previously associated with pathophysiological conditions of the airway epithelium, produce a transient arrest of ciliary activity. The regulation of ciliary beat frequency is dependent on ATP release by hemichannels (connexin/pannexin) and P2X receptor activation, the blockage of which may even stop ciliary movement. The force exerted by cilia, measured by atomic force microscopy, is reduced following extracellular ATP hydrolysis. This result complements the current understanding of the ciliary beating regulatory mechanism, with special relevance to inflammatory diseases of the airway epithelium that affect mucociliary clearance.

ABSTRACT

Extracellular nucleotides, including ATP, are locally released by the airway epithelium and stimulate ciliary activity in a [Ca²⁺ ]_i -dependent manner after mechanical stimulation of ciliated cells. However, it is unclear whether the ATP released is involved in regulating basal ciliary activity and mediating changes in ciliary activity in response to chemical stimulation. In the present study, we evaluated ciliary beat frequency (CBF) and ciliary beating forces in primary cultures from mouse tracheal epithelium, using videomicroscopy and atomic force microscopy (AFM), respectively. Extracellular ATP levels and [Ca²⁺ ]_i were measured by luminometric and fluorimetric assays, respectively. Uptake of ethidium bromide was measured to evaluate hemichannel functionality. We show that hydrolysis of constitutive extracellular ATP levels with apyrase (50 U ml^-1 ) reduced basal CBF by 45% and ciliary force by 67%. The apyrase effect on CBF was potentiated by carbenoxolone, a hemichannel inhibitor, and oxidized ATP, an antagonist used to block P2X7 receptors, which reduced basal CBF by 85%. Additionally, increasing extracellular ATP levels (0.1-100 μm) increased CBF, maintaining a sustained response that was suppressed in the presence of carbenoxolone. We also show that high levels of ATP (1 mm), associated with inflammatory conditions, lowered basal CBF by reducing [Ca²⁺ ]_i and hemichannel functionality. In summary, we provide evidence indicating that airway epithelium ATP release is the molecular autocrine mechanism regulating basal ciliary activity and is also the mediator of the ciliary response to chemical stimulation.

Sinonasal Mucociliary Clearance in Health and Disease

Although much has been elucidated in the past 170 years concerning the precise mechanism of ciliary function in the healthy or diseased human respiratory system, significant questions remain. The first description of ciliary action is credited to Sharpey in 1835. However, the importance of mucosal function was not apparent until Hilding's investigations of the postsurgical canine sinus demonstrated scar formation and disruption of mucociliary clearance. Subsequently, several techniques for mucosal coverage of exposed bone, most notably by Sewall and Boyden, were reported. The underlying physiology explaining the importance of the mucosa and the concept of mucosal preservation became apparent with the description of the sinonasal mucociliary flow patterns by Messerklinger; and thus the restoration of natural sinus physiology, ie, mucociliary clearance, became the goal of both medical and surgical treatment of sinonasal inflammatory disease. Clearance of benign and pathological substances in the mucus is governed by the propulsive force of the beating cilia and the physical characteristics of the overlying mucus. The respiratory cilia continually beat in a coordinated fashion, and in times of stress (eg, exercise, infection, or fever) ciliary beat frequency increases to accelerate mucus clearance. Thus, upper airway ciliary motility is under dynamic modulation. Multiple investigations incontrovertibly demonstrate a marked decrease in sinonasal mucociliary clearance in patients with chronic rhinosinusitis. Possible explanations for this finding are 1) a reduced basal ciliary beat frequency, 2) an alteration of the viscoelastic properties of airway secretions, and/or 3) a blunted dynamic response of sinonasal cilia to environmental stimuli. Studies of the first two explanations yield conflicting results, and to date, the third possibility remains uninvestigated. A review of the current understanding of the cellular regulation of respiratory ciliary activity and its contribution to chronic rhinosinusitis is presented.

Airway Epithelial Cell Cilia and Obstructive Lung Disease

Airway epithelium is the first line of defense against exposure of the airway and lung to various inflammatory stimuli. Ciliary beating of airway epithelial cells constitutes an important part of the mucociliary transport apparatus. To be effective in transporting secretions out of the lung, the mucociliary transport apparatus must exhibit a cohesive beating of all ciliated epithelial cells that line the upper and lower respiratory tract. Cilia function can be modulated by exposures to endogenous and exogenous factors and by the viscosity of the mucus lining the epithelium. Cilia function is impaired in lung diseases such as COPD and asthma, and pharmacologic agents can modulate cilia function and mucus viscosity. Cilia beating is reduced in COPD, however, more research is needed to determine the structural-functional regulation of ciliary beating via all signaling pathways and how this might relate to the initiation or progression of obstructive lung diseases. Additionally, genotypes and how these can influence phenotypes and epithelial cell cilia function and structure should be taken into consideration in future investigations.

Acetylcholine-induced ex vivo ATP release from the human nasal mucosa

OBJECTIVE

The present study aimed at investigating ATP release in response to acetylcholine (Ach) and pharmacologically elucidating the intracellular signal transduction pathway of this reaction in an ex vivo experiment.

METHODS

The inferior turbinate mucosa was collected from 21 patients with chronic hypertrophic rhinitis who underwent endoscopic turbinectomy. The mucosa was shaped into a filmy round piece, and incubated with chemical(s) in Hank's balanced salt solution for 10min. After incubation, the ATP concentration was measured by a luciferin-luciferase assay.

RESULTS

The baseline release of ATP without stimulus was 57.2±10.3fM. The ATP release was significantly increased by stimulation with 100μM Ach. The Ach-induced ATP release was completely inhibited by removing extracellular Ca²⁺. Significant inhibition of the Ach-induced ATP release was also observed by the addition of 1μM atropine, 40μM 2-APB, 10μM CBX, and 100μM PPADS, whereas 30nM bafilomycin A1 did not affect the ATP release.

CONCLUSION

These results indicate that the Ach-induced ATP release from the human nasal mucosa is dependent on the pannexin-1 channel and purinergic P2X7 receptor, suggesting that these two molecules constitute a local autocrine/paracrine signaling system in the human nasal epithelium.

Mitochondrial Transplantation Attenuates Airway Hyperresponsiveness by Inhibition of Cholinergic Hyperactivity

Increased cholinergic activity has been highlighted in the pathogenesis of airway hyperresponsiveness, and alternations of mitochondrial structure and function appear to be involved in many lung diseases including airway hyperresponsiveness. It is crucial to clarify the cause-effect association between mitochondrial dysfunction and cholinergic hyperactivity in the pathogenesis of airway hyperresponsiveness. Male SD rats and cultured airway epithelial cells were exposed to cigarette smoke plus lipopolysaccharide administration; mitochondria isolated from airway epithelium were delivered into epithelial cells in vitro and in vivo. Both the cigarette smoke plus lipopolysaccharide-induced cholinergic hyperactivity in vitro and the airway hyperresponsiveness to acetylcholine in vivo were reversed by the transplantation of exogenous mitochondria. The rescue effects of exogenous mitochondria were imitated by the elimination of excessive reactive oxygen species or blockage of muscarinic M₃ receptor, but inhibited by M receptor enhancer. Mitochondrial transplantation effectively attenuates cigarette smoke plus lipopolysaccharide-stimulated airway hyperresponsiveness through the inhibition of ROS-enhanced epithelial cholinergic hyperactivity.

DRC3 connects the N-DRC to dynein g to regulate flagellar waveform

The nexin-dynein regulatory complex (N-DRC), which is a major hub for the control of flagellar motility, contains at least 11 different subunits. A major challenge is to determine the location and function of each of these subunits within the N-DRC. We characterized a Chlamydomonas mutant defective in the N-DRC subunit DRC3. Of the known N-DRC subunits, the drc3 mutant is missing only DRC3. Like other N-DRC mutants, the drc3 mutant has a defect in flagellar motility. However, in contrast to other mutations affecting the N-DRC, drc3 does not suppress flagellar paralysis caused by loss of radial spokes. Cryo-electron tomography revealed that the drc3 mutant lacks a portion of the N-DRC linker domain, including the L1 protrusion, part of the distal lobe, and the connection between these two structures, thus localizing DRC3 to this part of the N-DRC. This and additional considerations enable us to assign DRC3 to the L1 protrusion. Because the L1 protrusion is the only non-dynein structure in contact with the dynein g motor domain in wild-type axonemes and this is the only N-DRC-dynein connection missing in the drc3 mutant, we conclude that DRC3 interacts with dynein g to regulate flagellar waveform.

Effects of histamine on ciliary beat frequency of ciliated cells from guinea pigs nasal mucosa

We aimed to investigate the effect of histamine on ciliary beat frequency (CBF) through combining high-speed digital microscopy and patch-clamp technology. Ciliated cells were obtained from septum and turbinate of 90-120-day-old healthy male guinea pigs. Tight seal was formed by applying negative pressure on the glass electrode after the drawing and pushing progress. Then, we enrolled high-speed digital microscopy to measure CBF before and after treatment with histamine of different concentrations ranging from 10(-6) to 10(-1) mol/L in Hank's solution and D-Hank's solution as well as after administrating adenosine triphosphate. One-way ANOVA, Student's t test or Kruskal-Wallis test was used for statistical comparisons. Glass electrode fix up ciliated cell is available at tip diameter of 2-5 μm and negative pressure of 10-20 cmH2O column. The baseline CBF in Hank's solution was higher than in D-Hank's solution. Treatment with 10(-6)-l0(-3) mol/L histamine of concentrations can stimulate a rise of CBF. Nevertheless, CBF in all groups decreased to baseline CBF within 20 min. Generally, 10(-2) mol/L histamine can stimulate a rise of CBF; meanwhile, the high concentration of histamine killed 50% ciliated cell. Histamine at 10(-1) mol/L killed all ciliated cells. Ciliary beating activity decreased in Ca(2+)-free solution. Moreover, adenosine triphosphate could increase CBF effectively after the stimulation effect of histamine. We construct an effective technology integrating patch-clamp technique with CBF measurements on ciliated cells. Extracellular histamine stimulation could increase CBF effectively.

Polyhexanide-containing solution reduces ciliary beat frequency of human nasal epithelial cells in vitro

In ENT, polyhexanide-containing solutions are used to treat nasal infections caused by multiresistant bacteria like methicillin-resistant Staphylococcus aureus. Many forms of commercial nasal solutions containing polyhexanide exist, such as gels or solutions for topical use. Data regarding the influence of polyhexanide on ciliary beat frequency (CBF) are lacking to date. We tested the CBF of nasal ciliated epithelial cells under the influence of a commercially available polyhexanide-containing solution (Lavasept(®) Concentrate) in a therapeutic concentration (0.04, 0.02%). In addition, we tested the concentrations of 0.1 and 0.01%. Cells were visualized with a phase contrast microscope, and the CBF was measured with the SAVA system's region of interest method. Ringer's solution and macrogol served as negative controls. A therapeutic concentration of Lavasept significantly reduced CBF in a time- and concentration-dependent manner. After 1 min, the CBF was reduced from 8.90 ± 1.64 to 5.00 ± 3.72 Hz with a concentration of 0.04% (p value = 0.001). After 10 min, all cilia stopped beating. After 5 min, a 0.02% solution of Lavasept concentrate decreased CBF significantly from 8.64 ± 1.71 to 3.30 ± 3.27 Hz (p value < 0.001). In conclusion, CBF of human nasal epithelia is significantly reduced with the use of the polyhexanide-containing solution Lavasept in some therapeutic concentrations. Due to our findings in this study, Lavasept should be used on ciliated mucosa only with caution and in a concentration of 0.02%.

Possible contribution of pannexin-1 to ATP release in human upper airway epithelia

Pannexins are a family of transmembrane nonselective channel proteins that participate in the release of ATP into extracellular space. Previous studies have suggested that pannexin-1 (Panx1) may constitute a local autocrine/paracrine system via transmitter ATP in association with the purinergic P2X7 receptor. In this study, we investigate the expressions of Panx1 and P2X7 in human nasal mucosa, together with hypotonic stress-induced ATP release from this tissue. Twenty men and one woman ranging in age from 10 to 82 years with an average age of 44.2 ± 4.4 years participated in the study. Inferior turbinates were collected from patients with chronic hypertrophic rhinitis during endoscopic endonasal surgery. The expressions of Panx1 and P2X7 were examined by fluorescence immunohistochemistry and quantitative reverse transcription-polymerase chain reaction (qRT-PCR). We also examined hypotonic stress-induced ATP release from the turbinate mucosa and the effects of channel blockers in an ex vivo experiment. Substantial expressions of both proteins were observed in human nasal mucosa. The immunoreactivity for Panx1 was stronger than that for P2X7. The presence of the transcripts of Panx1 and P2X7 was also shown by qRT-PCR. Ten and 100 μmol/L carbenoxolone (a Panx1 channel blocker) significantly inhibited the ATP release from the nasal mucosa, but flufenamic acid (a connexin channel blocker) and gadolinium (a stretch-activated channel blocker) did not. These results indicate the coexistence of Panx1 and P2X7 in, and Panx1-dependent ATP release from, the human nasal mucosa, suggesting the possible participation of these molecules in the physiological functions of the upper airway.

Functional short- and long-term effects of nasal CPAP with and without humidification on the ciliary function of the nasal respiratory epithelium

PURPOSE

Continuous positive airway pressure (CPAP) is the gold standard in the treatment of obstructive sleep apnea (OSA), but its impact on ciliary function is unclear to date. Furthermore, CPAP is associated with numerous side effects related to the nose and upper airway. Humidified CPAP is used to relieve these symptoms, but again, little is known regarding its effect on ciliary function of the nasal respiratory epithelium.

METHODS

In this prospective, randomized, crossover trial, 31 patients with OSA (AHI >15/h) were randomized to two treatment arms: nasal continuous positive airway pressure (nCPAP) with humidification or nCPAP without humidification for one night in each modality to assess short-term effects of ciliary beat frequency (CBF) and mucus transport time (MTT) and consecutively for 8 weeks in each modality to assess long-term effects in a crossover fashion.

RESULTS

The baseline CBF was 4.8 ± 0.6 Hz, and baseline MTT was 540 ± 221 s. After one night of CPAP with and without humidification, ciliary function increased moderately yet with statistical significance (p <0.05). The short-term groups with and without humidification did not differ statistically significant. Regarding long-term effects of CPAP, a statistically significant increase in ciliary function above the baseline level and above the short-term level was shown without humidification (7.2 ± 0.4 Hz; 402 ± 176 s; p <0.01). The increase above baseline level was even more pronounced with humidification (9.3 ± 0.7 Hz; 313 ± 95 s; p <0.01). There was a statistically significant difference between both groups at long-term assessment with regard to CBF (p <0.01).

CONCLUSIONS

Independent of airway humidification, nCPAP has moderate effects on short-term ciliary function of the nasal respiratory epithelium. However, a significant increase in ciliary function-both in terms of an increased CBF and a decreased MTT-was detected after long-term use. The effect was more pronounced when humidification was used during nCPAP.

Epithelial cell culture from human adenoids: a functional study model for ciliated and secretory cells

Background. Mucociliary transport (MCT) is a defense mechanism of the airway. To study the underlying mechanisms of MCT, we have both developed an experimental model of cultures, from human adenoid tissue of ciliated and secretory cells, and characterized the response to local chemical signals that control ciliary activity and the secretion of respiratory mucins in vitro. Materials and Methods. In ciliated cell cultures, ciliary beat frequency (CBF) and intracellular Ca²⁺ levels were measured in response to ATP, UTP, and adenosine. In secretory cultures, mucin synthesis and secretion were identified by using immunodetection. Mucin content was taken from conditioned medium and analyzed in the presence or absence of UTP. Results. Enriched ciliated cell monolayers and secretory cells were obtained. Ciliated cells showed a basal CBF of 10.7 Hz that increased significantly after exposure to ATP, UTP, or adenosine. Mature secretory cells showed active secretion of granules containing different glycoproteins, including MUC5AC. Conclusion. Culture of ciliated and secretory cells grown from adenoid epithelium is a reproducible and feasible experimental model, in which it is possible to observe ciliary and secretory activities, with a potential use as a model to understand mucociliary transport control mechanisms.

Human airway ciliary dynamics

Airway cilia depend on precise changes in shape to transport the mucus gel overlying mucosal surfaces. The ciliary motion can be recorded in several planes using video microscopy. However, cilia are densely packed, and automated computerized systems are not available to convert these ciliary shape changes into forms that are useful for testing theoretical models of ciliary function. We developed a system for converting planar ciliary motions recorded by video microscopy into an empirical quantitative model, which is easy to use in validating mathematical models, or in examining ciliary function, e.g., in primary ciliary dyskinesia (PCD). The system we developed allows the manipulation of a model cilium superimposed over a video of beating cilia. Data were analyzed to determine shear angles and velocity vectors of points along the cilium. Extracted waveforms were used to construct a composite waveform, which could be used as a standard. Variability was measured as the mean difference in position of points on individual waveforms and the standard. The shapes analyzed were the end-recovery, end-effective, and fastest moving effective and recovery with mean (± SE) differences of 0.31(0.04), 0.25(0.06), 0.50(0.12), 0.50(0.10), μm, respectively. In contrast, the same measures for three different PCD waveforms had values far outside this range.

T2R38 taste receptor polymorphisms underlie susceptibility to upper respiratory infection

Innate and adaptive defense mechanisms protect the respiratory system from attack by microbes. Here, we present evidence that the bitter taste receptor T2R38 regulates the mucosal innate defense of the human upper airway. Utilizing immunofluorescent and live cell imaging techniques in polarized primary human sinonasal cells, we demonstrate that T2R38 is expressed in human upper respiratory epithelium and is activated in response to acyl-homoserine lactone quorum-sensing molecules secreted by Pseudomonas aeruginosa and other gram-negative bacteria. Receptor activation regulates calcium-dependent NO production, resulting in stimulation of mucociliary clearance and direct antibacterial effects. Moreover, common polymorphisms of the TAS2R38 gene were linked to significant differences in the ability of upper respiratory cells to clear and kill bacteria. Lastly, TAS2R38 genotype correlated with human sinonasal gram-negative bacterial infection. These data suggest that T2R38 is an upper airway sentinel in innate defense and that genetic variation contributes to individual differences in susceptibility to respiratory infection.

Methods to measure and analyze ciliary beat activity: Ca2+ influx-mediated cilia mechanosensitivity

Airway ciliary beat activity (CBA) plays a pivotal role in protecting the body by removing mucus and pathogens from the respiratory tract. Since CBA is complicated and cannot be characterized by merely frequency, we recorded CBA using laser confocal line scanning and defined six parameters for describing CBA. The values of these parameters were all above 0 when measured in beating ciliated cells from mouse tracheae. We subsequently used 10 μM adenosine-5'-triphosphate (ATP) to stimulate ciliated cells and simultaneously recorded intracellular Ca(2+) levels and CBA. We found that intracellular Ca(2+) levels first increased, followed by an increase in CBA. Among the six parameters, frequency, amplitude, and integrated area significantly increased, whereas rise time, decay time, and full duration at half maximum markedly decreased. The results suggest that these six parameters are appropriate for assessing CBA and that increased intracellular Ca(2+) levels might enhance CBA. We next used our established methods to observe changes in mechanically stimulated cilia tips. We found that mechanical stimulation-induced changes in both intracellular Ca(2+) levels and CBA were not only similar to those induced by ATP, but were also blocked by treatment with a Ca(2+) chelator, BAPTA-AM, (10 μM) for 10 min. Moreover, while the same blockage was observed under Ca(2+)-free conditions, addition of 2 mM Ca(2+) into the chamber restored increases in both intracellular Ca(2+) levels and CBA. Taken together, we have provided a novel method for real-time measurement and complete analysis of CBA as well as demonstrated that mechanical stimulation of cilia tips resulted in Ca(2+) influx that led to increased intracellular Ca(2+) levels, which in turn triggered CBA enhancement.

A pilot study to examine the effect of chronic treatment with immunosuppressive drugs on mucociliary clearance in a vagotomized murine model

BACKGROUND

Previously, we have demonstrated that mucociliary clearance (MCC) is diminished within the first months after surgery in lung transplant patients and the explanation for the reduction in MCC is unknown. We hypothesized that chronic treatment with a commonly prescribed regimen of immunosuppressive drugs significantly impairs MCC. We tested this hypothesis in a murine model of lung transplantation.

METHODS

Fifteen C57BL/6 mice underwent vagotomy on the right side to simulate denervation associated with lung transplantation in humans. For 6 days, seven mice (controls) were intraperitoneally injected with three 100 µL doses of phosphate buffered saline and eight mice (immunosuppressed) were injected with three 100 µL injections of tacrolimus (1 mg/kg), mycophenolate mofetil (30 mg/kg), and prednisone (2 mg/kg) once daily. Then, mice inhaled the radioisotope (99m)technetium and underwent gamma camera imaging of their lungs for 6.5 hrs. Counts in the right lung at 1-1.5 hrs and at 6-6.5 hrs were first background-corrected and then decay-corrected to time 0 counts. Decay-corrected counts were then divided by time 0 counts. Retention at each time point was subtracted from 1.00 and multiplied by 100% to obtain percent removed by mucociliary clearance.

RESULTS

Although there was a slowing of MCC at 1-1.5 hrs for the immunosuppressed mice, there was no statistical difference in MCC measured at 1-1.5 hrs for the two groups of mice. At 6-6.5 hrs, MCC was significantly slower in the immunosuppressed mice, compared to controls, with 7.78±5.9% cleared versus 23.01±11.7% cleared, respectively (p = 0.006).

CONCLUSIONS

These preliminary results suggest that chronic treatment with immunosuppressive medications significantly slows MCC in vagotomized C57BL/6 mice. These findings could shed light on why MCC is reduced in lung transplant patients whose lungs are denervated during surgery and who are chronically treated with immunosuppressive drugs post surgery.

Purinergic signaling in the airways

Evidence for a significant role and impact of purinergic signaling in normal and diseased airways is now beyond dispute. The present review intends to provide the current state of knowledge of the involvement of purinergic pathways in the upper and lower airways and lungs, thereby differentiating the involvement of different tissues, such as the epithelial lining, immune cells, airway smooth muscle, vasculature, peripheral and central innervation, and neuroendocrine system. In addition to the vast number of well illustrated functions for purinergic signaling in the healthy respiratory tract, increasing data pointing to enhanced levels of ATP and/or adenosine in airway secretions of patients with airway damage and respiratory diseases corroborates the emerging view that purines act as clinically important mediators resulting in either proinflammatory or protective responses. Purinergic signaling has been implicated in lung injury and in the pathogenesis of a wide range of respiratory disorders and diseases, including asthma, chronic obstructive pulmonary disease, inflammation, cystic fibrosis, lung cancer, and pulmonary hypertension. These ostensibly enigmatic actions are based on widely different mechanisms, which are influenced by the cellular microenvironment, but especially the subtypes of purine receptors involved and the activity of distinct members of the ectonucleotidase family, the latter being potential protein targets for therapeutic implementation.

Molecular modulation of airway epithelial ciliary response to sneezing

Our purpose was to evaluate the effect of the mechanical force of a sneeze on sinonasal cilia function and determine the molecular mechanism responsible for eliciting the ciliary response to a sneeze. A novel model was developed to deliver a stimulation simulating a sneeze (55 mmHg for 50 ms) at 26°C to the apical surface of mouse and human nasal epithelial cells. Ciliary beating was visualized, and changes in ciliary beat frequency (CBF) were determined. To interrogate the molecular cascades driving sneeze-induced changes of CBF, pharmacologic manipulation of intra- and extracellular calcium, purinergic, PKA, and nitric oxide (NO) signaling were performed. CBF rapidly increases by ≥150% in response to a sneeze, which is dependent on the release of adenosine triphosphate (ATP), calcium influx, and PKA activation. Furthermore, apical release of ATP is independent of calcium influx, but calcium influx and subsequent increase in CBF are dependent on the ATP release. Lastly, we observed a blunted ciliary response in surgical specimens derived from patients with chronic rhinosinusitis compared to control patients. Apical ATP release with subsequent calcium mobilization and PKA activation are involved in sinonasal ciliary response to sneezing, which is blunted in patients with upper-airway disease.

A comparative study of mouse nasal septal and turbinal epithelium for in vitro cell cultures

BACKGROUND

The small number of epithelial cells that can be isolated from mouse respiratory tract has limited its application to study of the airway. Our purpose in this work was to compare the potential of mouse nasal septal and turbinal epithelium for serving as a cell source for in vitro cell cultures.

METHODS

The distribution of ciliated epithelial cells in the mouse nasal cavity, and the surface area of the respiratory epithelium in the mouse nasal septum and turbinate were determined by β-tubulin IV immunohistochemistry. Ciliated epithelial cell density of native mouse nasal septum and turbinate, and the morphology of cultured mouse nasal septal and turbinal epithelial cells were examined by scanning electron microscopy (SEM) and β-tubulin IV and zona occludens (ZO)-1 dual-label fluorescent cytochemistry, respectively. Cilia reactivity to exogenous stimuli (adenosine triphosphate or benzalkonium chloride) in cultured nasal septal and turbinal epithelial cells was studied using high-speed digital microscopy.

RESULTS

The ciliated epithelial cell density of native nasal epithelium, the morphology and cell yield of in vitro cultured epithelial cells, and cilia reactivity to exogenous stimuli of mouse turbinate are comparable to that of the nasal septum. However, the respiratory epithelium surface area of mouse turbinate is significantly larger than that of the nasal septum.

CONCLUSION

Mouse turbinate may also serve as an ideal source of in vitro epithelial cell cultures. Both nasal septum and turbinate should be harvested to optimize animal use in the establishment of primary murine respiratory epithelial cultures.

Centrin depletion causes cyst formation and other ciliopathy-related phenotypes in zebrafish

Most bona fide centrosome proteins including centrins, small calcium-binding proteins, participate in spindle function during mitosis and play a role in cilia assembly in non-cycling cells. Although the basic cellular functions of centrins have been studied in lower eukaryotes and vertebrate cells in culture, phenotypes associated with centrin depletion in vertebrates in vivo has not been directly addressed. To test this, we depleted centrin2 in zebrafish and found that it leads to ciliopathy phenotypes including enlarged pronephric tubules and pronephric cysts. Consistent with the ciliopathy phenotypes, cilia defects were observed in differentiated epithelial cells of ciliated organs such as the olfactory bulb and pronephric duct. The organ phenotypes were also accompanied by cell cycle deregulation namely mitotic delay resulting from mitotic defects. Overall, this work demonstrates that centrin2 depletion causes cilia-related disorders in zebrafish. Moreover, given the presence of both cilia and mitotic defects in the affected organs, it suggests that cilia disorders may arise from a combination of these defects.

Ciliary beat co-ordination by calcium

Motile cilia in the airway epithelium are the engine for mucociliary clearance, the mechanism responsible for cleaning the airways from inhaled particles. Human airway epithelial cilia appear to have a slow constitutive rate of beating, driven by inherent and spontaneous dynein ATPase activity. Additionally, cilia can increase their beating frequency by activation of several different control mechanisms. One of these controllers is calcium. Its intracellular concentration is regulated by purinergic and acetylcholine receptors. Besides the rate regulatory effect of calcium on ciliary beat, calcium is also involved in synchronizing the beat among cilia of one single cell as well as between cilia on different cells. This article gives an overview of the complex effects of calcium on the beating of motile cilia in the airways.

An Automated Measurement of Ciliary Beating Frequency using a Combined Optical Flow and Peak Detection

Objectives

The mucociliary transport system is a major defense mechanism of the respiratory tract. The performance of mucous transportation in the nasal cavity can be represented by a ciliary beating frequency (CBF). This study proposes a novel method to measure CBF by using optical flow.

Methods

To obtain objective estimates of CBF from video images, an automated computer-based image processing technique is developed. This study proposes a new method based on optical flow for image processing and peak detection for signal processing. We compare the measuring accuracy of the method in various combinations of image processing (optical flow versus difference image) and signal processing (fast Fourier transform [FFT] vs. peak detection [PD]). The digital high-speed video method with a manual count of CBF in slow motion video play, is the gold-standard in CBF measurement. We obtained a total of fifty recorded ciliated sinonasal epithelium images to measure CBF from the Department of Otolaryngology. The ciliated sinonasal epithelium images were recorded at 50-100 frames per second using a charge coupled device camera with an inverted microscope at a magnification of ×1,000.

Results

The mean square errors and variance for each method were 1.24, 0.84 Hz; 11.8, 2.63 Hz; 3.22, 1.46 Hz; and 3.82, 1.53 Hz for optical flow (OF) + PD, OF + FFT, difference image [DI] + PD, and DI + FFT, respectively. Of the four methods, PD using optical flow showed the best performance for measuring the CBF of nasal mucosa.

Conclusions

The proposed method was able to measure CBF more objectively and efficiently than what is currently possible.

Exploring lung physiology in health and disease with lung slices

The development of therapeutic approaches to treat lung disease requires an understanding of both the normal and disease physiology of the lung. Although traditional experimental approaches only address either organ or cellular physiology, the use of lung slice preparations provides a unique approach to investigate integrated physiology that links the cellular and organ responses. Living lung slices are robust and can be prepared from a variety of species, including humans, and they retain many aspects of the cellular and structural organization of the lung. Functional portions of intrapulmonary airways, arterioles and veins are present within the alveoli parenchyma. The dynamics of macroscopic changes of contraction and relaxation associated with the airways and vessels are readily observed with conventional low-magnification microscopy. The microscopic changes associated with cellular events, that determine the macroscopic responses, can be observed with confocal or two-photon microscopy. To investigate disease processes, lung slices can either be prepared from animal models of disease or animals exposed to disease invoking conditions. Alternatively, the lung slices themselves can be experimentally manipulated. Because of the ability to observe changes in cell physiology and how these responses manifest themselves at the level of the organ, lung slices have become a standard tool for the investigation of lung disease.

Hysteresis modeling for calcium-mediated ciliary beat frequency in airway epithelial cells

A hysteresis model is proposed to describe calcium-mediated Ciliary beat frequency (CBF) in airway epithelial cells. In this dynamic model, the kinetics of coupling between calcium and CBF is posited as a two-step configuration. First, Ca²+ directly binds to or indirectly acts on the axonemal proteins to modulate the activity of axonemal proteins. This step can be modeled by a Hill function in biochemistry. In the second step, the activity of axonemal proteins interacts with the sliding velocity of axonemal microtubules, the equivalent to regulating the CBF. The well-known Bouc-Wen model for hysteresis in mechanical engineering, which can only generate the stable clockwise hysteresis loops, is modified to describe the counter clockwise hysteresis loops commonly observed in the biological experiments. Based upon this new hysteresis model, the dynamic behavior of calcium-regulated CBF in epithelial airway cells is investigated through simulation studies. The numerical results demonstrate that the CBF dynamics in airway epithelial cells predicted by the hysteresis model is more consistent with the experimental observations than that predicted by previous static model in the literature.

Mechanisms of mammalian ciliary motility: Insights from primary ciliary dyskinesia genetics

Motile cilia and flagella are organelles that, historically, have been poorly understood and inadequately investigated. However, cilia play critical roles in fluid clearance in the respiratory system and the brain, and flagella are required for sperm motility. Genetic studies involving human patients and mouse models of primary ciliary dyskinesia over the last decade have uncovered a number of important ciliary proteins and have begun to elucidate the mechanisms underlying ciliary motility. When combined with genetic, biochemical, and cell biological studies in Chlamydomonas reinhardtii, these mammalian genetic analyses begin to reveal the mechanisms by which ciliary motility is regulated.

P2Y1 and P2Y13 purinergic receptors mediate Ca2+ signaling and proliferative responses in pulmonary artery vasa vasorum endothelial cells

Extracellular ATP and ADP have been shown to exhibit potent angiogenic effects on pulmonary artery adventitial vasa vasorum endothelial cells (VVEC). However, the molecular signaling mechanisms of extracellular nucleotide-mediated angiogenesis remain not fully elucidated. Since elevation of intracellular Ca(2+) concentration ([Ca(2+)](i)) is required for cell proliferation and occurs in response to extracellular nucleotides, this study was undertaken to delineate the purinergic receptor subtypes involved in Ca(2+) signaling and extracellular nucleotide-mediated mitogenic responses in VVEC. Our data indicate that stimulation of VVEC with extracellular ATP resulted in the elevation of [Ca(2+)](i) via Ca(2+) influx through plasma membrane channels as well as Ca(2+) mobilization from intracellular stores. Moreover, extracellular ATP induced simultaneous Ca(2+) responses in both cytosolic and nuclear compartments. An increase in [Ca(2+)](i) was observed in response to a wide range of purinergic receptor agonists, including ATP, ADP, ATPγS, ADPβS, UTP, UDP, 2-methylthio-ATP (MeSATP), 2-methylthio-ADP (MeSADP), and BzATP, but not adenosine, AMP, diadenosine tetraphosphate, αβMeATP, and βγMeATP. Using RT-PCR, we identified mRNA for the P2Y1, P2Y2, P2Y4, P2Y13, P2Y14, P2X2, P2X5, P2X7, A1, A2b, and A3 purinergic receptors in VVEC. Preincubation of VVEC with the P2Y1 selective antagonist MRS2179 and the P2Y13 selective antagonist MRS2211, as well as with pertussis toxin, attenuated at varying degrees agonist-induced intracellular Ca(2+) responses and activation of ERK1/2, Akt, and S6 ribosomal protein, indicating that P2Y1 and P2Y13 receptors play a major role in VVEC growth responses. Considering the broad physiological implications of purinergic signaling in the regulation of angiogenesis and vascular homeostasis, our findings suggest that P2Y1 and P2Y13 receptors may represent novel and specific targets for treatment of pathological vascular remodeling involving vasa vasorum expansion.

The effect of intracellular calcium oscillations on fluid secretion in airway epithelium

Airway epithelium has been shown to elicit fluid secretion after a rise in intracellular calcium. This rise in intracellular calcium has been shown to display complex oscillations in many species after the binding of particular agonists to extracellular receptors. Fluid secreted by the airway epithelium is used to maintain the depth of the periciliary liquid (PCL) above the apical membrane of the epithelial cells lining the bronchial airways. Previous mathematical models have been published which separately consider the electrophysiology involved in regulating periciliary liquid depth, and the transmission of intracellular calcium waves in airway epithelial tissue. In this paper we present a mathematical model that combines these previous models and allows the effect of oscillations in intracellular calcium on fluid secretion by airway epithelial cells to be investigated. We show that an oscillatory calcium response produces different fluid secretion properties to that elicited by a tonic rise in intracellular calcium. These differences are shown to be due to saturation of the Ca(2+) activated ion channels.

Multiple Ca2+ signaling pathways regulate intracellular Ca2+ activity in human cardiac fibroblasts

Ca(2+) signaling pathways are well studied in cardiac myocytes, but not in cardiac fibroblasts. The aim of the present study is to characterize Ca(2+) signaling pathways in cultured human cardiac fibroblasts using confocal scanning microscope and RT-PCR techniques. It was found that spontaneous intracellular Ca(2+) (Ca(i) (2+)) oscillations were present in about 29% of human cardiac fibroblasts, and the number of cells with Ca(i) (2+) oscillations was increased to 57.3% by application of 3% fetal bovine serum. Ca(i) (2+) oscillations were dependent on Ca(2+) entry. Ca(i) (2+) oscillations were abolished by the store-operated Ca(2+) (SOC) entry channel blocker La(3+), the phospholipase C inhibitor U-73122, and the inositol trisphosphate receptors (IP3Rs) inhibitor 2-aminoethoxydiphenyl borate, but not by ryanodine. The IP3R agonist thimerosal enhanced Ca(i) (2+) oscillations. Inhibition of plasma membrane Ca(2+) pump (PMCA) and Na(+)-Ca(2+) exchanger (NCX) also suppressed Ca(i) (2+) oscillations. In addition, the frequency of Ca(i) (2+) oscillations was reduced by nifedipine, and increased by Bay K8644 in cells with spontaneous Ca(2+) oscillations. RT-PCR revealed that mRNAs for IP3R1-3, SERCA1-3, Ca(V)1.2, NCX3, PMCA1,3,4, TRPC1,3,4,6, STIM1, and Orai1-3, were readily detectable, but not RyRs. Our results demonstrate for the first time that spontaneous Ca(i) (2+) oscillations are present in cultured human cardiac fibroblasts and are regulated by multiple Ca(2+) pathways, which are not identical to those of the well-studied contractile cardiomyocytes. This study provides a base for future investigations into how Ca(2+) signals regulate biological activity in human cardiac fibroblasts and cardiac remodeling under pathological conditions.

Time-dependent changes in nasal ciliary beat frequency

As the ex vivo lifetime of nasal ciliary cells is limited, these cells have to be transferred to a culture medium for analysis with vital cytology immediately. Although the ciliary beat frequency (CBF) is likely to change over time, sufficient data regarding changes in the ex vivo CBF has not been published to date. In the present study, nasal epithelial cells were harvested from the mucosa of the inferior turbinate of 19 healthy volunteers with a cytology brush. Beating cilia were visualized with phase-contrast microscopy. Over a 12-h timeframe, 2 s epochs of video were captured every 5 min from the identical group of cells using a high-speed digital camera with a sampling rate of 100 fps. Temperature was maintained at about 22 degrees C and controlled by an infrared pyrometer. The CBF rapidly increased by 47 +/- 53% during the first 3 h of measurement. A relative plateau followed this increase from 3 to 9 h. After 9 h, CBF reduced linearly. After 12 h, the mean frequency reduced to 20 +/- 69% of baseline. However, there was considerable variance between the samples. The initial increase in CBF has not been reported previously. This interval seems to be unsuitable for meaningful measurements. Measurements of CBF are most reliable during the plateau phase between 3 and 9 h. After 9 h, there is clearly a significant decrease in CBF, together with a considerable interindividual variance.

Zinc Increases Ciliary Beat Frequency in a Calcium-Dependent Manner

Background

Dynamic regulation of respiratory ciliary beat frequency (CBF) is regulated by fluxes in intracellular calcium (Ca2+). P2X receptors (P2XR) are extracellular ATP-gated, Ca2+-permeable, nonselective cation channels. Zinc increases intracellular Ca2+ in a sodium (Na+)-free environment through activation of P2XR channels. We hypothesize that topical zinc increases CBF in a Ca2+-dependent fashion as a result of this mechanism.

Methods

The apical surface of mouse sinonasal air–liquid interface cultures were bathed in zinc in a Na+-free solution with or without Ca2+. High-speed digital video imaging captured and analyzed CBF at a sampling rate of 100 frames/s.

Results

CBF significantly increased fourfold over baseline from 5.99 ± 3.16 Hz to 22.4 ± 4.33 Hz in the presence of zinc chloride (50 micromoles) and calcium chloride (3 mM). This effect is abolished in the presence of extracellular Na+ and was pH dependent.

Conclusions

Zinc stimulates CBF in the presence of Ca2+ likely through activation of P2X receptors. Thus, zinc represents a promising agent for stimulation of mucociliary clearance.

Cigarette smoke condensate inhibits transepithelial chloride transport and ciliary beat frequency

OBJECTIVES/HYPOTHESIS

Although the pathophysiology leading to rhinosinusitis is complex, evidence indicates that decreased mucociliary clearance (MCC) is a major contributing feature. Normal respiratory epithelial MCC is an important host defense mechanism that is dependent on proper ciliary beating and the biological properties of the airway surface liquid (ASL). The role that tobacco smoke exposure plays as an inhibitor of MCC has yet to be elucidated. The present study investigates the consequences of cigarette smoke exposure on ciliary function and transepithelial chloride (Cl(-)) secretion, a major determinant of ASL.

STUDY DESIGN

In vitro investigation.

METHODS

Well-characterized primary murine nasal septal epithelial (MNSE) and human sinonasal epithelial (HSNE) cultures were exposed to cigarette smoke condensate (CSC) and compared to control cultures. Effects on ciliary beat frequency (CBF) and Cl(-) secretion were investigated using pharmacologic manipulation.

RESULTS

Change in forskolin-stimulated current (DeltaI(SC)), representing transepithelial Cl(-) secretion, was significantly decreased in CSC exposed MNSE (14.97 +/- 1.2 microA/cm(2) vs. control, 19.1 +/- 1.56 microA/cm(2) [P = .04]) and HSNE (2.68 +/- 0.79 muA/cm(2) vs. control, 10.8 +/- 1.73 microA/cm(2)) cultures (P = .001). Forskolin-stimulated CBF was also significantly reduced when acutely exposed to CSC (5.64 +/- 0.06 Hz vs. control 7.15 +/- 0.18 Hz).

CONCLUSIONS

The present study provides direct evidence that tobacco smoke diminishes two major components of MCC. This links tobacco smoke as a potential contributing and/or exacerbating factor in exposed individuals with chronic rhinosinusitis.

The effect of myrtol standardized on human nasal ciliary beat frequency and mucociliary transport time

BACKGROUND

This study was designed to observe the effects of myrtol standardized (Gelomyrtol forte), a secretomucolytic phytomedicine, on both ciliary beat frequency (CBF) in vitro and mucociliary transport time (MTT) in vivo.

METHODS

Changes in cultured human nasal CBF in response to immediate treatment with 75, 150, or 300 ng/mL of myrtol standardized and prolonged treatment (12 or 24 hours) with 300 ng/mL of myrtol standardized were quantified by using high-speed digital microscopy. In addition, MTT before and after oral application of myrtol standardized (three times a day, 900 mg/day, 10 days) was determined using the saccharine test, and the effects of this treatment regime on nasal patency was measured by acoustic rhinometry and active anterior rhinomanometry in 22 patients with nonallergic chronic rhinitis. Another 10 patients without medication, who had the same examinations twice with a 10-day interval, were involved as controls.

RESULTS

Neither immediate nor prolonged treatment with myrtol standardized produced a distinguishable change in CBF. Meanwhile, only in patients with treatment, MTT, as well as a unilateral minimum cross-sectional area, the volume of 0-5 cm inside the nasal cavity, the unilateral nasal resistance at 75 Pa and total symptom visual analog score were significantly improved after treatment.

CONCLUSION

Based on these results we propose that a 10-day treatment with an herbal medicine, myrtol standardized, improves nasal mucociliary clearance as well as nasal patency in patients with chronic rhinitis. However, it has no impact on ex vivo CBF.

Mathematical modelling of calcium wave propagation in mammalian airway epithelium: evidence for regenerative ATP release

Airway epithelium has been shown to exhibit intracellular calcium waves after mechanical stimulation. Two classes of mechanism have been proposed to explain calcium wave propagation: diffusion through gap junctions of the intracellular messenger inositol 1,4,5-trisphosphate (IP3), and diffusion of paracrine extracellular messengers such as ATP. We have used single cell recordings of airway epithelium to parameterize a model of an airway epithelial cell. This was then incorporated into a spatial model of a cell culture where both mechanisms for calcium wave propagation are possible. It is shown that a decreasing return on the radius of Ca2+ wave propagation is achieved as the amount of ATP released from the stimulated cell increases. It is therefore shown that for a Ca2+ wave to propagate large distances, a significant fraction of the intracellular ATP pool would be required to be released. Further to this, the radial distribution of maximal calcium response from the stimulated cell does not produce the same flat profile of maximal calcium response seen in experiential studies. This suggests that an additional mechanism is important in Ca2+ wave propagation, such as regenerative release of ATP from cells downstream of the stimulated cell.