TY - JOUR
T1 - Norepinephrine transport by the extraneuronal monoamine transporter in human bronchial arterial smooth muscle cells
AU - Horvath, Gabor
AU - Sutto, Zoltan
AU - Torbati, Aliza
AU - Conner, Gregory E.
AU - Salathe, Matthias
AU - Wanner, Adam
PY - 2003/10/1
Y1 - 2003/10/1
N2 - Inhaled glucocorticosteroids (GSs) cause acute, α 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 α1-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 Km 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 non-genomic GS action (increasing NE concentrations at α1-AR) could explain acute bronchial vasoconstriction caused by inhaled GSs.
AB - Inhaled glucocorticosteroids (GSs) cause acute, α 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 α1-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 Km 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 non-genomic GS action (increasing NE concentrations at α1-AR) could explain acute bronchial vasoconstriction caused by inhaled GSs.
KW - Budesonide
KW - Glucocorticosteroids
KW - Non-genomic
KW - Plasma membrane binding site
KW - Vasoconstriction
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U2 - 10.1152/ajplung.00054.2003
DO - 10.1152/ajplung.00054.2003
M3 - Article
C2 - 12807698
AN - SCOPUS:0141679439
VL - 285
SP - L829-L837
JO - American Journal of Physiology - Cell Physiology
JF - American Journal of Physiology - Cell Physiology
SN - 0363-6143
IS - 4 29-4
ER -