Adenosine A2B receptors are highly expressed on murine type II alveolar epithelial cells.
The adenosine A(2B) receptor (A(2B)R) has a wide tissue distribution that includes fibroblasts and endothelial and epithelial cells. The recent generation of an A(2B)R(-/-) mouse constructed with a beta-galactosidase (beta-gal) reporter gene under control of the endogenous promoter has provided a valuable tool to quantify A(2B)R promoter activity (29). To determine the sites of expression of the A(2B) receptor in the mouse lung, histological and flow cytometric analysis of beta-gal reporter gene expression in various lung cell populations was performed. The major site of A(2B)R promoter activity was found to be the type II alveolar epithelial cells (AECs), identified by coexpression of prosurfactant protein C, with relatively less expression in alveolar macrophages, bronchial epithelial cells, and cells of the vasculature. Highly purified type II AECs were prepared by fluorescence-activated sorting of enhanced green fluorescent protein (eGFP)-positive cells from transgenic mice expressing eGFP under control of the surfactant protein C promoter (21). The type II cells expressed 89-fold higher A(2B)R mRNA than pulmonary leukocytes, and the A(2B)R was shown to be functional, as treatment of purified type II AECs with the nonspecific adenosine receptor agonist 5'-N-ethylcarboxamidoadenosine (NECA) induced an increase in intracellular cAMP greater that the beta-adrenergic agonist isoproterenol that was inhibited completely following treatment by ATL-802, a novel, highly potent (K(i) = 8.6 nM), and selective (>900 fold over other adenosine receptor subtypes) antagonist of the mouse A(2B)R.
Cagnina
Rebecca E
RE
Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA.
Ramos
Susan I
SI
Marshall
Melissa A
MA
Wang
Guoquan
G
Frazier
C Renea
CR
Linden
Joel
J
D058917:Adenosine A2 Receptor Antagonists; D000818:Animals; D001980:Bronchi / Q000166:cytology; D000242:Cyclic AMP / Q000378:metabolism; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D005786:Gene Expression Regulation; D017930:Genes, Reporter; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011650:Pulmonary Alveoli / Q000166:cytology*; D037721:Pulmonary Surfactant-Associated Protein C / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D043704:Receptor, Adenosine A2B / Q000235:genetics / Q000378:metabolism*; D011994:Recombinant Proteins / Q000378:metabolism; D001616:beta-Galactosidase / Q000378:metabolism
D058917:Adenosine A2 Receptor Antagonists; D037721:Pulmonary Surfactant-Associated Protein C; D012333:RNA, Messenger; D043704:Receptor, Adenosine A2B; D011994:Recombinant Proteins; D000242:Cyclic AMP; D001616:beta-Galactosidase