Polyspecific cation transporters mediate luminal release of acetylcholine from bronchial epithelium.
In airway epithelia, non-neuronal cholinergic regulations have been described; however, the route for acetylcholine (ACh) release has not been verified. To investigate whether organic cation transporters (OCTs) serve this function, we studied the expression of OCTs in airway epithelia and their capability to translocate ACh. Using immunohistochemistry in rats and humans, OCT1, OCT2, and OCT3 were localized to the luminal membrane of ciliated epithelial cells. In humans, OCT2 showed the strongest expression in the luminal membrane. We expressed the OCT isoforms in oocytes of Xenopus laevis and measured uptake and efflux of ACh. Tracer flux measurements showed that ACh is transported by OCT1 and OCT2 but not by OCT3. Two-electrode-voltage-clamp measurements revealed that OCT2 mediates electrogenic uptake and efflux of ACh. For ACh uptake by human OCT2, a K(M) value of approximately 0.15 mM was determined. At -50 mV, ACh efflux by human OCT2 was trans-inhibited by micromolar concentrations of the inhalational glucocorticoid budesonide, which is used in treatment of asthma (K(i) approximately 2.7 microM). The data show that OCT1 and OCT2 mediate luminal ACh release in human airways and suggest that ACh release is blocked after inhalation of budesonide.
Lips
Katrin Susanne
KS
Institute of Anatomy and Cell Biology, Justus-Liebig-University, Giessen, Germany.
Volk
Christopher
C
Schmitt
Bernhard Matthias
BM
Pfeil
Uwe
U
Arndt
Petra
P
Miska
Dagmar
D
Ermert
Leander
L
Kummer
Wolfgang
W
Koepsell
Hermann
H
D000109:Acetylcholine / Q000737:chemistry*; D000818:Animals; D001249:Asthma / Q000473:pathology; D001692:Biological Transport; D001980:Bronchi / Q000378:metabolism*; D019819:Budesonide / Q000494:pharmacology; D016466:CHO Cells; D050482:Catecholamine Plasma Membrane Transport Proteins; D027682:Cation Transport Proteins / Q000378:metabolism*; D002460:Cell Line; D003345:Corticosterone / Q000494:pharmacology; D006224:Cricetinae; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004848:Epithelium / Q000378:metabolism*; D005938:Glucocorticoids / Q000494:pharmacology; D006801:Humans; D007150:Immunohistochemistry; D020128:Inhibitory Concentration 50; D007700:Kinetics; D026901:Membrane Transport Proteins / Q000096:biosynthesis; D008856:Microscopy, Fluorescence; D009538:Nicotine / Q000494:pharmacology; D050811:Octamer Transcription Factor-1; D009865:Oocytes / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000096:biosynthesis; D000075102:Organic Cation Transporter 2; D018408:Patch-Clamp Techniques; D020033:Protein Isoforms; D021381:Protein Transport; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D014132:Trachea / Q000378:metabolism*; D014157:Transcription Factors / Q000096:biosynthesis; D014981:Xenopus; D029867:Xenopus Proteins; D014982:Xenopus laevis; D000099254:Organic Cation Transporter 3
D000109:Acetylcholine; D019819:Budesonide; D050482:Catecholamine Plasma Membrane Transport Proteins; D027682:Cation Transport Proteins; D003345:Corticosterone; D017931:DNA Primers; D004268:DNA-Binding Proteins; D005938:Glucocorticoids; D026901:Membrane Transport Proteins; D009538:Nicotine; D050811:Octamer Transcription Factor-1; D027701:Organic Cation Transport Proteins; D000075102:Organic Cation Transporter 2; D020033:Protein Isoforms; D014157:Transcription Factors; D029867:Xenopus Proteins; D000099254:Organic Cation Transporter 3; C494169:POU2F1 protein, Xenopus; C494165:POU2F1 protein, human; C494168:Pou2f1 protein, rat; C491013:SLC22A2 protein, human; C493212:Slc22a1 protein, rat; C100590:Slc22a2 protein, rat