Caffeine citrate increases ciliary beat frequency in human respiratory epithelial cells

Area of Science:

• Respiratory Physiology
• Pharmacology

Background:

• Caffeine citrate is a standard treatment for apnea of prematurity.
• Its direct effects on the respiratory epithelium, particularly ciliary function, are not well understood.
• Caffeine's known molecular actions may influence ciliary beat frequency (CBF).

Purpose of the Study:

• To investigate whether caffeine citrate directly enhances CBF in human respiratory epithelial cells (hRECs).
• To explore the underlying cellular mechanisms of caffeine's effect on CBF.
• To assess caffeine's potential to improve airway defense mechanisms.

Main Methods:

• Quantified CBF using high-speed video microscopy in hRECs from healthy donors and cystic fibrosis (CF) patients.
• Utilized air-liquid interface cultures for hRECs.
• Performed mechanistic studies involving pharmacological blockade of specific ion channels.

Main Results:

• Caffeine citrate significantly increased CBF in both healthy and CF-derived hRECs.
• The stimulatory effect was robust and reproducible.
• Ryanodine receptor (RYR)-mediated calcium release was identified as the key pathway, as its blockade abolished the caffeine effect.

Conclusions:

• Caffeine citrate directly stimulates CBF in primary hRECs via RYR-dependent calcium signaling.
• This action enhances mucociliary clearance, potentially offering peripheral airway benefits.
• Caffeine citrate shows promise as a dual-action therapy for respiratory diseases with impaired clearance, such as CF and bronchopulmonary dysplasia.