TRPA1/M8 agonists upregulate ciliary beating through the pannexin-1 channel in the human nasal mucosa

Abstract

Background Nasal breathing is important for maintaining physiological respiration. However, airflow in the nasal cavity has an inherent cooling effect and may suppress ciliary beating, an essential frontline defense in the airway. Nasal airflow is thought to be perceived by thermoreceptors for cool temperatures. We herein investigated the effect of the activation of thermosensitive transient receptor potentials (TRPs) for cool/cold temperatures on ciliary beating to search for a compensatory mechanism. Methods Inferior turbinates were collected from patients with chronic hypertrophic rhinitis. Ex vivo ciliary beat frequency (CBF) and ATP release were measured using a high-speed digital video camera and by luciferin-luciferase assay, respectively. Intracellular Ca2+ ([Ca2+]i) imaging of isolated ciliated cells was performed using Fluo-8. The nasal mucosae were also subjected to fluorescence immunohistochemistry and real-time RT-PCR for TRPA1/TRPM8. Results CBF was significantly increased by adding either cinnamaldehyde (TRPA1 agonist) or l-menthol (TRPM8 agonist). This increase was inhibited by pannexin-1 blockers, carbenoxolone and probenecid. Cinnamaldehyde and l-menthol also increased the ATP release from the nasal mucosa and [Ca2+]i of isolated ciliated cells. Immunohistochemistry detected TRPA1 and TRPM8 on the epithelial surface including the cilia and in the submucosal nasal glands. Existence of these receptors were confirmed at the transcriptional level by real-time RT-PCR. Conclusions These results indicate the stimulatory effect of the activation of TRPA1/TRPM8 on ciliary beating in the nasal mucosa, which would be advantageous to maintain airway mucosal defense against the fall of temperature under normal nasal breathing. This stimulatory effect is likely to be mediated by pannexin-1.

Nasal ciliary beating controlled by carbonic anhydrase IV and Na+/HCO3- co-transport under an extremely low CO2 condition (air)

“…In the presence of brinzolamide, S0859 did not decrease the CBF ratio. Thus, the prior treatment with brinzolamide abolished the decrease in CBF induced by S0857, suggesting that CAII, in addition to CAIV and NBC, may function as the bicarbonate transport metabolon in c-hNECs [19].…”

“…Nasal epithelium is a special tissue directly exposing the fresh air. The c-hNECs have some tools to keep the ciliary beating, such as thermosensitive transient receptor potentials (TRP) A1 and M8 activated by cool temperature [19]. Beating cilia including nasal cilia are activated by many substances including intracellular ions, such as Ca 2+ , H + and Cl − [4, 6-11, 12-14, 21-23, 26, 31].…”

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

“…The beating cilia in the airways express many ion channels, including Ca 2+ -permeable channels, such as Ca V 1.2, transient receptor potential (TRP) V4, TRPA1 and TRPM8 [6][7][8]. However, it is still controversial how these channels enhance the ciliary beating.…”

“…However, it is still controversial how these channels enhance the ciliary beating. The beating cilia in the airways are activated by many substances, such as cAMP, Ca 2+ , ATP, β 2agonists, Cl − and H + (intracellular pH (pH i )) [4,[6][7][8][9][10][11][12]. Among them, Ca 2+ is an important ion that activates the beating cilia [3,4,[6][7][8].…”

“…The beating cilia in the airways are activated by many substances, such as cAMP, Ca 2+ , ATP, β 2agonists, Cl − and H + (intracellular pH (pH i )) [4,[6][7][8][9][10][11][12]. Among them, Ca 2+ is an important ion that activates the beating cilia [3,4,[6][7][8]. ABX stimulates Ca V 1.2 and a small transient Ca 2+ release from the acidic stores in the c-LAECs [6,13].…”