Nicotinic Cholinergic Receptor Expression in the Human Nasal Mucosa

Abstract

Twenty-four nasal mucosa specimens were obtained from the inferior or middle turbinates of 6 normal subjects and 18 patients with chronic sinusitis, inflammatory polyp formation, or sinus allergies. Reverse transcription—polymerase chain reaction analysis was used to identify the non-neuronal nicotinic cholinergic receptor (nAChR) subunits that were expressed in the nasal mucosa. Collectively, transcripts for α (α1, α2, α3, α4, α6, α7) and β (β2, β3, β4) nAChR subunit genes were detected in the respiratory mucosa. The α3, α7, and β2 subunits were expressed in 92%, 88%, and 75% of the subjects, respectively. There was a high degree of interindividual variation in nAChR subunit gene expression among subjects. A significant univariate association was found between tissue type and β4 expression and between gender and β3 expression. These data suggest that cells in the nasal mucosa express the necessary messenger RNAs (mRNAs) for numerous nAChR combinations. Moreover, our identification of nAChR subunit mRNAs in the nasal mucosa extends the findings of other functional studies of nAChRs in nasal epithelial cells and implies that nicotine from tobacco products such as cigarette smoke and nicotine nasal spray may have direct cellular effects on nasal mucosa cells through activation of homogeneous or heterogeneous nAChRs. A significant number of patients receiving nicotine nasal spray have reported nasal irritation, and there are reports of transient irritation of the throat and trachea with the use of smoke-free nicotine cigarettes. These adverse respiratory effects may be due to activation of nAChRs in epithelial cells of the nose and trachea.