Norepinephrine transport by the extraneuronal monoamine transporter in human bronchial arterial smooth muscle cells

• Published in: American journal of physiology. Lung cellular and molecular physiology Vol. 285; no. 4; pp. 829 - L837
• Main Authors: Horvath, Gabor, Sutto, Zoltan, Torbati, Aliza, Conner, Gregory E, Salathe, Matthias, Wanner, Adam
• Format: Journal Article
• Language: English
• Published: United States 01.10.2003
• Subjects: Arteries - cytology; Arteries - metabolism; Binding Sites; Biological Transport - drug effects; Bronchi - blood supply; Cell Membrane - metabolism; Cells, Cultured; Corticosterone - metabolism; Corticosterone - pharmacology; Glucocorticoids - pharmacology; Humans; Membrane Glycoproteins - antagonists & inhibitors; Membrane Glycoproteins - genetics; Membrane Glycoproteins - metabolism; Membrane Transport Proteins; Muscle, Smooth, Vascular - cytology; Muscle, Smooth, Vascular - metabolism; Myocytes, Smooth Muscle - metabolism; Neuropeptides; Norepinephrine - antagonists & inhibitors; Norepinephrine - metabolism; Norepinephrine Plasma Membrane Transport Proteins; Organic Cation Transport Proteins - genetics; Organic Cation Transporter 1 - genetics; Organic Cation Transporter 2; RNA, Messenger - metabolism; Symporters - genetics; Vesicular Biogenic Amine Transport Proteins; Vesicular Monoamine Transport Proteins
• ISSN: 1040-0605; 1522-1504
• DOI: 10.1152/ajplung.00054.2003

1 Division of Pulmonary and Critical Care Medicine and 2 Department of Cell Biology and Anatomy, University of Miami School of Medicine, Miami, Florida 33133; and 3 Department of Respiratory Medicine, Semmelweis University, Budapest, Hungary Submitted 27 February 2003 ; accepted in final form 5 June 2003 Inhaled glucocorticosteroids (GSs) cause acute, 1 -adrenoreceptor (AR)-mediated bronchial vasoconstriction. After release from sympathetic nerves, norepinephrine (NE) must be taken up into cells for deactivation by intracellular enzymes. Because postsynaptic cellular NE uptake is steroid sensitive, GSs could increase NE concentrations at 1 -AR, causing vasoconstriction. We therefore evaluated mRNA expression of different NE transporters in human bronchial arterial smooth muscle and pharmacologically characterized NE uptake into these cells. RT-PCR demonstrated mRNA expression of the extraneuronal monoamine transporter (EMT) and organic cation transporter 1 (OCT-1). Fluorometric uptake assay showed time (within minutes)- and concentration-dependent NE uptake by freshly isolated bronchial arterial smooth muscle cells (SMC) with an estimated K m of 240 µM. Corticosterone and O -methylisoprenaline (1 µM each), but not desipramine, inhibited NE uptake, a profile indicative of NE uptake by EMT, but not OCT-1. Budesonide and methylprednisolone inhibited uptake with IC 50 values of 0.9 and 5.6 µM, respectively. Corticosterone's action was reversible and not sensitive to RU-486 (GS receptor antagonist), actinomycin D (transcription inhibitor), or cycloheximide (protein synthesis inhibitor). Corticosterone made membrane impermeant by coupling to BSA also blocked NE uptake. Immunocytochemistry indicated a specific membrane binding site for corticosterone on bronchial arterial SMC. These data demonstrate that although human bronchial arterial SMC express OCT-1 and EMT, EMT is the predominant plasma membrane transporter for NE uptake. This process can be inhibited by GSs, likely via a specific membrane binding site. This nongenomic GS action (increasing NE concentrations at 1 -AR) could explain acute bronchial vasoconstriction caused by inhaled GSs. vasoconstriction; glucocorticosteroids; budesonide; nongenomic; plasma membrane binding site Address for reprint requests and other correspondence: A. Wanner, Div. of Pulmonary and Critical Care Medicine, University of Miami School of Medicine, PO Box 016960 (R-47), Miami, FL 33101 (E-mail: awanner{at}miami.edu ).