MAP kinase mediates epidermal growth factor- and phorbol ester-induced prostacyclin formation in cardiomyocytes.
We studied the role of protein kinase C (PKC) and mitogen-activated protein kinase (MAPK) in epidermal growth factor (EGF)-induced prostacyclin (PGI2) production in cultured, spontaneously-beating neonatal ventricular rat cardiomyocytes. To this purpose, the effect of EGF on cardiomyocyte MAPK phosphorylation, MAPK activity and PGI2-production were investigated, and compared to those induced by the PKC activator 4 beta phorbol 12-myristate 13-acetate (PMA). Both EGF (0.1 microM) and PMA (0.1 microM) induced the rapid and reversible phosphorylation of 42 KDa-MAPK in ventricular cardiomyocytes, responses that were accompanied by transient increases in MAPK activity (190-230% of control values within 5 min), and two- to three-fold increases in PGI2 formation. The tyrosine kinase inhibitors lavendustin (1 microM) and genistein (10 microM) strongly inhibited EGF-induced MAPK activation and PGI2-formation, but had no effect on PMA-stimulated responses. Experiments with the PKC inhibitor CGP 41251 (1 microM) or with PKC-downregulated cells demonstrated that in contrast to the PMA-stimulated responses, EGF-induced MAPK activation and PGI2-production were PKC-independent processes. Investigating the role of MAPK in EGF- and in PMA-promoted PGI2-formation, we found that the MAPK-inhibitor 6-thioguanine (500 microM), as well as the MAPK-kinase-inhibitor PD98059 (50 microM) abolished both EGF- and PMA-stimulated PGI2-production in cardiomyocytes. Our results indicate that MAPK-activation is at the basis of both growth factor receptor and PKC-dependent eicosanoid-formation in ventricular cardiomyocytes, where EGF-induced prostaglandin-production takes place via a PKC-independent pathway.
Braconi Quintaje
S
S
Division of Endocrinology, University Hospital, Geneva, Switzerland.
Rebsamen
M
M
Church
D J
DJ
Vallotton
M B
MB
Lang
U
U
D000704:Analysis of Variance; D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000502:physiology*; D002478:Cells, Cultured; D004789:Enzyme Activation; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D011464:Epoprostenol / Q000096:biosynthesis*; D006352:Heart Ventricles / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017208:Rats, Wistar; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*
D004815:Epidermal Growth Factor; D011464:Epoprostenol; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D013755:Tetradecanoylphorbol Acetate