title: Regulation of norepinephrine-induced proliferation in cardiac fibroblasts by interleukin-6 and p42/p44 mitogen activated protein kinase.
abstract: Norepinephrine (NE) is involved in many cardiovascular diseases such as congestive heart failure. We have recently reported that NE had a comitogenic effect in isolated cardiac fibroblasts, and that it activated p42/p44 mitogen activated protein kinase (MAPK). This study was designed to characterize a possible mechanism involved in the proliferative effect of NE. Isolated rat cardiac fibroblasts were exposed to NE (10 microM) for up to 8 h, and interleukin-6 (IL-6) expression was measured by Ribonuclease Protection Assay and Western blotting. The activity of p42/p44MAPK was analyzed by Western blotting. Cell number was assessed by use of a Coulter Counter. IL-6/GAPDH mRNA was increased by NE in a time-dependent manner reaching 23 fold stimulation after 1 h compared to untreated samples. Immunoreactivity to IL-6 was not found in controls. After 16 h of exposure to NE, IL-6 protein was detected. It further increased up to 48 h. The effect of NE on IL-6 mRNA was abolished by the beta-adrenoceptor blockers propranolol, metoprolol (beta1) and ICI 118.551 (beta2), but not by the alpha-adrenoceptor blockers prazosin (alpha1) and yohimbine (alpha2). The MAPK-inhibitor PD98059 suppressed the NE-induced MAPK activation in a concentration-dependent fashion after 5 min, attenuated the NE-induced IL-6 expression after 2 h, and suppressed the proliferative effect of NE from 53 to 18% after 48 h. Recombinant IL-6 caused an increase in proliferation by 31% after 48 h. Simultaneous application of the IL-6 antibody reduced the NE-induced proliferation to 34%, and completely prevented the IL-6 induced effect. These results suggest that NE induces proliferation of rat cardiac fibroblasts in part by increasing the expression of IL-6 through regulation of MAPK.
authors.affiliation: Carl-Ludwig-Institute of Physiology, University of Leipzig, Germany.
authors.forename: Monika
authors.initials: M
authors.lastname: Leicht
authors.forename: Wilfried
authors.initials: W
authors.lastname: Briest
authors.forename: Heinz-Gerd
authors.initials: HG
authors.lastname: Zimmer
mesh_terms: D000319:Adrenergic beta-Antagonists / Q000494:pharmacology; D000818:Animals; D015153:Blotting, Western; D002455:Cell Division; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D015850:Interleukin-6 / Q000378:metabolism*; D008790:Metoprolol / Q000494:pharmacology; 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*; D009638:Norepinephrine / Q000494:pharmacology*; D011412:Propanolamines / Q000494:pharmacology; D011433:Propranolol / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012260:Ribonucleases / Q000378:metabolism; D015398:Signal Transduction; D013997:Time Factors
chemical_list: D000319:Adrenergic beta-Antagonists; D004791:Enzyme Inhibitors; D005419:Flavonoids; D015850:Interleukin-6; D011412:Propanolamines; D012333:RNA, Messenger; C026777:ICI 118551; D011433:Propranolol; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D012260:Ribonucleases; D008790:Metoprolol; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D009638:Norepinephrine