Induction of protein synthesis in cardiac fibroblasts by cardiotrophin-1: integration of multiple signaling pathways.
OBJECTIVE
Cardiotrophin-1 (CT-1) is a member of the IL-6 family of cytokines and is expressed in various cardiovascular disease states. CT-1 induces cardiomyocyte hypertrophy, and protects myocytes from ischemia reperfusion injury. We sought to elucidate CT-1 signaling in cardiac fibroblasts with respect to initiation of protein synthesis.


METHODS
Cardiac fibroblasts were isolated from the ventricles of 200-g Sprague-Dawley rats and stimulated with CT-1 at specified concentrations with or without inhibitors of cell signaling pathways. Activation of intracellular signaling pathways was determined by Western analysis and immunocytochemistry. Protein synthesis was measured by incorporation of [3H]leucine.


RESULTS
CT-1 treatment resulted in activation of the Jak/STAT, MAPK, and Akt pathways in addition to protein synthesis regulatory proteins with resultant increase in overall protein synthesis. Analysis with phospho-specific antibodies revealed that AG490 (Jak inhibitor), PD98059 (MEK1/2 inhibitor), SB203580 (p38 MAPK inhibitor), LY294002 (PI3-K inhibitor) and rapamycin (mTOR inhibitor) act at different levels in the signaling cascade to inhibit CT-1 induced protein synthesis.


CONCLUSIONS
Cardiotrophin-1 activates the Jak/STAT, PI3K/Akt, p38 and p42/44 MAPK pathways in cardiac fibroblasts. Use of pharmacologic inhibitors reveals that each of these pathways play a role in CT-1 induced protein synthesis.
Freed
Darren H
DH
Institute of Cardiovascular Sciences, St Boniface General Hospital Research Centre, Faculty of Medicine, University of Manitoba, 351 Tache Ave, Winnipeg, Manitoba, Canada R2H 2A6.
Borowiec
Anna M
AM
Angelovska
Tatjana
T
Dixon
Ian M C
IM
D000818:Animals; D015153:Blotting, Western / Q000379:methods; D002478:Cells, Cultured; D002867:Chromones / Q000494:pharmacology; D016207:Cytokines / Q000494:pharmacology*; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D053613:Janus Kinase 1; D020935:MAP Kinase Signaling System; D008297:Male; D009025:Morpholines / Q000494:pharmacology; D009206:Myocardium / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011233:Precipitin Tests; D014176:Protein Biosynthesis; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction; D020123:Sirolimus / Q000494:pharmacology; D020032:Tyrphostins / Q000494:pharmacology
D002867:Chromones; D016207:Cytokines; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D053613:Janus Kinase 1; D009025:Morpholines; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011505:Protein-Tyrosine Kinases; D011725:Pyridines; D020123:Sirolimus; D020032:Tyrphostins; C095512:alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C092073:cardiotrophin 1; C507906:Jak1 protein, rat; C093642:SB 203580; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one