title: Epithelium integrity is crucial for the relaxant activity of brain natriuretic peptide in human isolated bronchi.
abstract: BACKGROUND AND PURPOSE Brain natriuretic peptide (BNP) plays an important role in several biological functions, including bronchial relaxation. Here, we have investigated the role of BNP and its cognate receptors in human bronchial tone. EXPERIMENTAL APPROACH Effects of BNP on responses to carbachol and histamine were evaluated in non-sensitized, passively sensitized, epithelium-intact or denuded isolated bronchi and in the presence of methoctramine, N(ω) -nitro-L-arginine methyl ester (L-NAME) and aminoguanidine. Natriuretic peptide receptors (NPRs) were investigated by immunohistochemistry, RT-PCR and real-time PCR. Release of NO and acetylcholine from bronchial tissues and cultured BEAS-2B bronchial epithelial cells was also investigated. KEY RESULTS BNP reduced contractions mediated by carbachol and histamine, with decreased E(max) (carbachol: 22.7 ± 4.7%; histamine: 59.3 ± 1.8%) and increased EC(50) (carbachol: control 3.33 ± 0.88 µM, BNP 100 ± 52.9 µM; histamine: control 16.7 ± 1.7 µM, BNP 90 ± 30.6 µM); BNP was ineffective in epithelium-denuded bronchi. Among NPRs, only atrial NPR (NPR1) transcripts were detected in bronchial tissue. Bronchial NPR1 immunoreactivity was detected in epithelium and inflammatory cells but faint or absent in airway smooth muscle cells. NPR1 transcripts in bronchi increased after incubation with BNP, but not after sensitization. Methoctramine and quinine abolished BNP-induced relaxant activity. The latter was associated with increased bronchial mRNA for NO synthase and NO release, inhibited by L-NAME and aminoguanidine. In vitro, BNP increased acetylcholine release from bronchial epithelial cells, whereas NO release was unchanged. CONCLUSIONS AND IMPLICATIONS Epithelial cells mediate the BNP-induced relaxant activity in human isolated bronchi.
authors.affiliation: Unit of Pharmacology, Department of Experimental Medicine, Second University of Naples, Naples, Italy.
authors.forename: Maria G
authors.initials: MG
authors.lastname: Matera
authors.forename: Luigino
authors.initials: L
authors.lastname: Calzetta
authors.forename: Daniela
authors.initials: D
authors.lastname: Passeri
authors.forename: Francesco
authors.initials: F
authors.lastname: Facciolo
authors.forename: Erino A
authors.initials: EA
authors.lastname: Rendina
authors.forename: Clive
authors.initials: C
authors.lastname: Page
authors.forename: Mario
authors.initials: M
authors.lastname: Cazzola
authors.forename: Augusto
authors.initials: A
authors.lastname: Orlandi
mesh_terms: D000109:Acetylcholine / Q000096:biosynthesis; D001980:Bronchi / Q000166:cytology / Q000502:physiology*; D002217:Carbachol / Q000494:pharmacology; D018929:Cell Culture Techniques; D018679:Cholinergic Agonists / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004847:Epithelial Cells / Q000187:drug effects; D004848:Epithelium / Q000187:drug effects* / Q000293:injuries / Q000502:physiology; D005260:Female; D006632:Histamine / Q000494:pharmacology; D017442:Histamine Agonists / Q000494:pharmacology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009129:Muscle Tonus / Q000187:drug effects; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology; D020097:Natriuretic Peptide, Brain / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D043585:Receptor, Muscarinic M2 / Q000037:antagonists & inhibitors / Q000187:drug effects; D017461:Receptors, Atrial Natriuretic Factor / Q000187:drug effects / Q000378:metabolism; D012130:Respiratory Hypersensitivity / Q000139:chemically induced / Q000503:physiopathology
chemical_list: D018679:Cholinergic Agonists; D004791:Enzyme Inhibitors; D017442:Histamine Agonists; D043585:Receptor, Muscarinic M2; D020097:Natriuretic Peptide, Brain; D009569:Nitric Oxide; D006632:Histamine; D002217:Carbachol; D052247:Nitric Oxide Synthase Type II; C496318:Nos2 protein, rat; D017461:Receptors, Atrial Natriuretic Factor; D000109:Acetylcholine; D019331:NG-Nitroarginine Methyl Ester