Beta(2)-adrenergic receptor agonists increase intracellular free Ca(2+) concentration cycling in ventricular cardiomyocytes through p38 and p42/44 MAPK-mediated cytosolic phospholipase A(2) activation.
We have recently reported that arachidonic acid mediates beta(2)-adrenergic receptor (AR) stimulation of [Ca(2+)](i) cycling and cell contraction in embryonic chick ventricular cardiomyocytes (Pavoine, C., Magne, S., Sauvadet, A., and Pecker, F. (1999) J. Biol. Chem. 274, 628-637). In the present work, we demonstrate that beta(2)-AR agonists trigger arachidonic acid release via translocation and activation of cytosolic phospholipase A(2) (cPLA(2)) and increase caffeine-releasable Ca(2+) pools from Fura-2-loaded cells. We also show that beta(2)-AR agonists trigger a rapid and dose-dependent phosphorylation of both p38 and p42/44 MAPKs. Translocation and activation of cPLA(2), as well as Ca(2+) accumulation in sarcoplasmic reticulum stores sensitive to caffeine and amplification of [Ca(2+)](i) cycling in response to beta(2)-AR agonists, were blocked by inhibitors of the p38 or p42/44 MAPK pathway (SB203580 and PD98059, respectively), suggesting a role of both MAPK subtypes in beta(2)-AR stimulation. In contrast, beta(1)-AR stimulation of [Ca(2+)](i) cycling was rather limited by the MAPKs, clearly proving the divergence between beta(2)-AR and beta(1)-AR signaling systems. This study presents the first evidence for the coupling of beta(2)-AR to cardiac cPLA(2) and points out the key role of the MAPK pathway in the intracellular signaling elicited by positive inotropic beta(2)-AR agonists in heart.
Magne
S
S
INSERM Unité 99, Hôpital Henri Mondor, 94010 Créteil, France.
Couchie
D
D
Pecker
F
F
Pavoine
C
C
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002451:Cell Compartmentation / Q000187:drug effects; D002478:Cells, Cultured; D002642:Chick Embryo; D003600:Cytosol / Q000201:enzymology; D004336:Drug Antagonism; D004789:Enzyme Activation; D004983:Ethanolamines / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000196:embryology / Q000378:metabolism*; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010741:Phospholipases A / Q000378:metabolism; D021381:Protein Transport; D018343:Receptors, Adrenergic, beta-2 / Q000187:drug effects*; D015398:Signal Transduction; D048051:p38 Mitogen-Activated Protein Kinases
D000317:Adrenergic alpha-Antagonists; D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D018343:Receptors, Adrenergic, beta-2; D002110:Caffeine; C002904:zinterol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D010741:Phospholipases A; D002118:Calcium