Abstract
Electrophysiological homeostasis is indispensable to vocal fold hydration. We investigate tight junction (TJ)-associated components, occludin and ZO-1, and permeability with or without the challenge of a permeability-augmenting agent, histamine. Freshly excised ovine larynges are obtained from a local abattoir. TJ markers are explored via reverse transcriptase polymerase chain reaction (RT-PCR). Paracellular permeabilities are measured in an Ussing system. The gene expression of both TJ markers is detected in native ovine vocal fold epithelium. Luminal histamine treatment significantly decreases transepithelial resistance (TER) (N = 72, p<0.01) and increases penetration of protein tracer (N = 35, p<0.001), respectively, in a time-, and dose-dependent fashion. The present study demonstrates that histamine compromises TJ-related paracellular barrier across vocal fold epithelium. The detection of TJ markers indicates the existence of typical TJ components in non-keratinized, stratified vocal fold epithelium. The responsiveness of paracellular permeabilities to histamine would highlight the functional significance of this TJ-equivalent system to the electrophysiological homeostasis, which, in turn, regulates the vocal fold superficial hydration.
Highlights
Vocal quality, the effort required for producing vocal sound, and laryngeal defense against inhaled particulates are directly correlated with the hydration of the vocal fold [1,2,3], but the knowledge of the regulation of vocal fold hydration remains incomplete
The present study demonstrates the expression of tight junction (TJ)-associated proteins, occludin and ZO-1 in ovine vocal fold epithelium
Histamine significantly decreases transepithelial resistance (TER) accompanied by increased penetration of horseradish peroxidase (HRP), in a time- and dose-dependent fashion
Summary
The effort required for producing vocal sound, and laryngeal defense against inhaled particulates are directly correlated with the hydration of the vocal fold [1,2,3], but the knowledge of the regulation of vocal fold hydration remains incomplete. The focus of the present study is to examine whether TJ-related barrier function is involved in the maintenance of bioelectrical asymmetry in vocal fold. ZO-1 belongs to the membrane-associated guanylate kinase homologs (MAGuKs) that bear multiple protein-binding domains It has a unique proline-rich domain toward the carboxylterminal [18]. We investigate the effects histamine on the TJ-related barrier and the expression of TJ markers in the vocal fold epithelium. To investigate TJ-related barrier function, transepithelial electrical resistance (TER) and permeability serve as reliable tools to study its ion and size selectivity in vocal fold epithelium. Consistent with the TJ-related barrier function, interference with TJ integrity by external stimuli, such as histamine, would result in certain pathophysiological conditions in native vocal fold epithelium. Our understanding in these areas would certainly grow with the clarification of regulatory mechanisms of TJ-related barrier function in the paracellular pathways
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