Heme oxygenase-1 inhibition of MAP kinases, calcineurin/NFAT signaling, and hypertrophy in cardiac myocytes.
OBJECTIVE
Heme oxygenases (HO) are the rate-limiting enzymes in heme degradation, catalyzing the breakdown of heme to equimolar quantities of biliverdin (BV), carbon monoxide (CO), and ferrous iron. The inducible HO isoform, HO-1, confers protection against ischemia/reperfusion (I/R)-injury in the heart. We hypothesized that HO-1 and its catalytic by-products constitute an antihypertrophic signaling module in cardiac myocytes.


RESULTS
The G protein-coupled receptor (GPCR) agonist endothelin-1 (ET-1) (30 nmol/l) stimulated a robust hypertrophic response in cardiac myocytes isolated from 1- to 3-day-old Sprague-Dawley rats, with increases in cell surface area (planimetry), sarcomere assembly (confocal laser scanning microscopy), and prepro-atrial natriuretic peptide (ANP) mRNA expression. Adenoviral overexpression of HO-1, but not beta-galactosidase, significantly inhibited ET-1 induced cardiac myocyte hypertrophy. The antihypertrophic effects of HO-1 were mimicked by BV (10 micromol/l) and the CO-releasing molecule [Ru(CO)3Cl2]2 (10 micromol/l), strongly suggesting a critical involvement of BV and CO in the antihypertrophic effects of HO-1. Both BV and CO suppressed extracellular signal-regulated kinases (ERK1/ERK2) and p38 mitogen-activated protein kinase (MAPK) activation by ET-1 stimulation. Moreover, BV and CO inhibited the prohypertrophic calcineurin/NFAT pathway. This inhibition occurred upstream from calcineurin because BV and CO inhibited NFAT activation in response to ET-1 stimulation but not in response to adenoviral expression of a constitutively active calcineurin mutant. Upstream-inhibition of the calcineurin/NFAT pathway by CO occurred independent from cGMP and cGMP-dependent protein kinase type I (PKG I).


CONCLUSIONS
Heme oxygenase-1 and its catalytic by-products, BV and CO, constitute a novel antihypertrophic signaling pathway in cardiac myocytes. Biliverdin and CO inhibition of MAPKs and calcineurin/NFAT signaling provides a mechanistic framework how heme degradation products may promote their antihypertrophic effects.
Tongers
Jörn
J
Department of Cardiology and Angiology, Hannover Medical School, 30625 Hannover, Germany.
Fiedler
Beate
B
König
Danny
D
Kempf
Tibor
T
Klein
Gunnar
G
Heineke
Jörg
J
Kraft
Theresia
T
Gambaryan
Stepan
S
Lohmann
Suzanne M
SM
Drexler
Helmut
H
Wollert
Kai C
KC
D000818:Animals; D001664:Biliverdine / Q000494:pharmacology; D019703:Calcineurin / Q000378:metabolism*; D002248:Carbon Monoxide / Q000494:pharmacology; D048429:Cell Size / Q000187:drug effects; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism*; D019332:Endothelin-1 / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006419:Heme Oxygenase (Decyclizing) / Q000494:pharmacology*; D051547:Heme Oxygenase-1; D020935:MAP Kinase Signaling System / Q000187:drug effects*; D032383:Myocytes, Cardiac / Q000187:drug effects / Q000378:metabolism*; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects*; D014157:Transcription Factors / Q000378:metabolism*
D004268:DNA-Binding Proteins; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D014157:Transcription Factors; D002248:Carbon Monoxide; D006419:Heme Oxygenase (Decyclizing); D051547:Heme Oxygenase-1; D019703:Calcineurin; D001664:Biliverdine