title: Dextromethorphan mediated bitter taste receptor activation in the pulmonary circuit causes vasoconstriction.
abstract: Activation of bitter taste receptors (T2Rs) in human airway smooth muscle cells leads to muscle relaxation and bronchodilation. This finding led to our hypothesis that T2Rs are expressed in human pulmonary artery smooth muscle cells and might be involved in regulating the vascular tone. RT-PCR was performed to reveal the expression of T2Rs in human pulmonary artery smooth muscle cells. Of the 25 T2Rs, 21 were expressed in these cells. Functional characterization was done by calcium imaging after stimulating the cells with different bitter agonists. Increased calcium responses were observed with most of the agonists, the largest increase seen for dextromethorphan. Previously in site-directed mutational studies, we have characterized the response of T2R1 to dextromethorphan, therefore, T2R1 was selected for further analysis in this study. Knockdown with T2R1 specific shRNA decreased mRNA levels, protein levels and dextromethorphan-induced calcium responses in pulmonary artery smooth muscle cells by up to 50%. To analyze if T2Rs are involved in regulating the pulmonary vascular tone, ex vivo studies using pulmonary arterial and airway rings were pursued. Myographic studies using porcine pulmonary arterial and airway rings showed that stimulation with dextromethorphan led to contraction of the pulmonary arterial and relaxation of the airway rings. This study shows that dextromethorphan, acting through T2R1, causes vasoconstrictor responses in the pulmonary circuit and relaxation in the airways.
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Jasbir D
authors.initials: JD
authors.lastname: Upadhyaya
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Nisha
authors.initials: N
authors.lastname: Singh
authors.affiliation: Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Anurag S
authors.initials: AS
authors.lastname: Sikarwar
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Raja
authors.initials: R
authors.lastname: Chakraborty
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Sai P
authors.initials: SP
authors.lastname: Pydi
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada.
authors.forename: Rajinder P
authors.initials: RP
authors.lastname: Bhullar
authors.affiliation: Departments of Pediatrics, Physiology, University of Manitoba, Winnipeg, MB, Canada; Manitoba Institute of Child Health, Winnipeg, MB, Canada.
authors.forename: Shyamala
authors.initials: S
authors.lastname: Dakshinamurti
authors.affiliation: Department of Oral Biology, University of Manitoba, Winnipeg, MB, Canada; Manitoba Institute of Child Health, Winnipeg, MB, Canada.
authors.forename: Prashen
authors.initials: P
authors.lastname: Chelikani
mesh_terms: D000818:Animals; D003915:Dextromethorphan / Q000494:pharmacology*; D005455:Fluorescent Antibody Technique; D005786:Gene Expression Regulation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008168:Lung / Q000098:blood supply*; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism; D009213:Myography; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011651:Pulmonary Artery / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013481:Superoxides / Q000378:metabolism; D034421:Sus scrofa; D013649:Taste / Q000187:drug effects*; D014661:Vasoconstriction / Q000187:drug effects*; D000098706:Taste Receptors, Type 2
chemical_list: D018994:Myosin Light Chains; D012333:RNA, Messenger; D043562:Receptors, G-Protein-Coupled; D000098706:Taste Receptors, Type 2; D013481:Superoxides; D003915:Dextromethorphan; D015544:Inositol 1,4,5-Trisphosphate