Title

Adenosine A1 receptors mediate mobilization of calcium in human bronchial smooth muscle cells

UMMS Affiliation

Department of Pulmonary Medicine

Date

5-20-2006

Document Type

Article

Subjects

Adenosine-5'-(N-ethylcarboxamide); Biological Transport, Active; Bronchi; *Calcium Signaling; Cells, Cultured; Cyclic AMP; GTP-Binding Proteins; Humans; Myocytes, Smooth Muscle; Phosphotransferases (Alcohol Group Acceptor); Receptor, Adenosine A1; Signal Transduction

Disciplines

Life Sciences | Medicine and Health Sciences

Abstract

Adenosine stimulates contraction of airway smooth muscle, but the mechanism is widely considered indirect, depending on release of contractile agonists from mast cells and nerves. The goal was to determine whether adenosine, by itself, directly regulates calcium signaling in human bronchial smooth muscle cells (HBSMC). Primary cultures of HBSMC from normal subjects were loaded with fura 2-AM, and cytosolic calcium concentrations ([Ca(2+)](i)) were determined ratiometrically by imaging single cells. The nonselective adenosine receptor agonist, 5'-N-ethylcarboxamidoadenosine (NECA), and the adenosine A(1) receptor agonist, N(6)-cyclopentyladenosine (CPA), both stimulated rapid, transient increases in [Ca(2+)](i). In contrast, there were no calcium responses to 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamido-adenosine (100 nM) or N(6)-(3-iodobenzyl)-adenosine-5'-N-methyluronamide (100 nM), selective agonists at adenosine A(2A) receptors and adenosine A(3) receptors, respectively. Calcium responses to NECA and CPA were inhibited by 8-cyclopentyl-1,3-dipropylxanthine, an adenosine A(1) receptor antagonist, and by pertussis toxin (PTX). In other experiments, NECA stimulated calcium transients in the absence of extracellular calcium, but not when cells were preincubated in cyclopiazonic acid or thapsigargin to empty intracellular calcium stores. Calcium responses were attenuated by xestospongin C and 2-aminoethoxydiphenylborane, inhibitors of inositol trisphosphate (IP(3)) receptors, and by U73122, an inhibitor of phospholipase C. It was concluded that stimulation of adenosine A(1) receptors on HBSMC rapidly mobilizes intracellular calcium stores by a mechanism dependent on PTX-sensitive G proteins, and IP(3) signaling. These findings suggest that, in addition to its well-established indirect effects on HBSMC, adenosine also has direct effects on contractile signaling pathways.

Rights and Permissions

Citation: Am J Respir Cell Mol Biol. 2006 Oct;35(4):496-502. Epub 2006 May 18. Link to article on publisher's site

DOI of Published Version

10.1165/rcmb.2005-0290OC

Related Resources

Link to article in PubMed

Journal Title

American journal of respiratory cell and molecular biology

PubMed ID

16709961