Expression of the endocannabinoid system in the human airway epithelial cells: Impact of sex and chronic respiratory disease status
Recreational and medicinal cannabis consumption in the past 12 months has been reported in 1/5th of Canadians, with greater use in males relative to females. Cannabis smoking is the dominant route of delivery in consumers, with the airway epithelium functioning as the site of first contact for inhaled phytocannabinoids. The endocannabinoid system is responsible for mediating the physiological effects of inhaled phytocannabinoids. Acute cannabis smoke inhalation can result in bronchodilation, which may have applications in chronic respiratory disease management. In contrast, chronic cannabis smoke inhalation is associated with reduced lung function and bronchitis, which challenges potential applications in the lung. The contribution of the endocannabinoid system in the airway epithelium to either beneficial or harmful physiological responses remains to be clearly defined in males and females and those with underlying chronic respiratory disease. To begin to address this knowledge gap, a curated dataset of 1090 unique human bronchial brushing gene expression profiles was created from Gene Expression Omnibus deposited microarray datasets. The dataset included 616 healthy subjects, 136 subjects with asthma, and 338 subjects with COPD. A 27-gene endocannabinoid signature was analyzed across all samples with sex and disease specific-analyses performed. Immunohistochemistry and immunoblots were performed to confirm in situ and in vitro protein expression of select genes in human airway epithelial cells. We confirm three receptors for cannabinoids, CB1, CB2, and TRPV1, are expressed at the protein level in human airway epithelial cells in situ and in vitro, justifying examining the downstream endocannabinoid pathway more extensively at the gene expression level. Sex status was associated with differential expression of 6/27 genes. In contrast, disease status was associated with differential expression of 18/27 genes in asthmatics and 22/27 genes in COPD subjects. We confirm at the protein level that TRPV1, the most differentially expressed candidate in our analyses, was up-regulated in airway epithelial cells from asthmatics relative to healthy subjects. Our data demonstrate that endocannabinoid system is expressed in human airway epithelial cells with expression impacted by disease status and minimally by sex. The data suggest that cannabis consumers may have differential physiological responses in the respiratory mucosa, which could impact both acute and chronic effects of cannabis smoke inhalation.