Darbepoetin-mediated cardioprotection after myocardial infarction involves multiple mechanisms independent of erythropoietin receptor-common beta-chain heteroreceptor.
OBJECTIVE
Darbepoetin, a long-acting erythropoietin derivative, attenuates cardiomyocyte apoptosis and improves short-term (3 days) cardiac function, but the mechanisms responsible are unknown. We investigated potential mechanisms by which darbepoetin exerts cardioprotection following myocardial infarction in mice and the significance of the erythropoietin receptor (EPOR)-common beta-chain (c-beta-chain) heteroreceptor.


METHODS
Mice underwent 60 min coronary occlusion followed by treatment with vehicle or a single dose of darbepoetin. Effects on gene expression, apoptosis and neutrophil accumulation in infarcted left ventricle were assessed 24 h later. Cardiac function, effects on vascularization and fibrosis were assessed 28 days later. The significance of EPOR-c-beta-chain heteroreceptor was examined 28 days after infarction using mice deficient in c-beta-chain.


RESULTS
Twenty-four hours after darbepoetin, mRNAs encoding haeme oxygenase-1 (HO-1), iNOS and brain natriuretic peptide (BNP) were markedly elevated only in infarcted regions, and the frequency of apoptotic cells attenuated. Inflammation was also attenuated with reductions in neutrophil numbers. Darbepoetin also elevated mRNAs encoding angiogenic factors: placental growth factor, monocyte chemoattractant protein-1 and interleukin-1beta. Twenty-eight days after treatment, CD31+ vessels in the infarct zone doubled and fibrosis reduced. Cardiac haemodynamics were improved. Darbepoetin also improved cardiac haemodynamics in c-beta-chain-deficient mice, increased HO-1 and iNOS expression and vessel numbers and attenuated fibrosis.


CONCLUSIONS
Darbepoetin stimulates expression of haeme oxygenase, iNOS, BNP and angiogenic factors specifically in infarcted left ventricle that attenuates inflammation, apoptosis and fibrosis; elevate vessel numbers; and improve cardiac function. The EPOR-c-beta-chain heteroreceptor is not essential for these effects.
Kanellakis
Peter
P
Vascular Biology & Atherosclerosis, BakerIDI Heart and Diabetes Institute, Melbourne, Australia.
Pomilio
Giovanna
G
Agrotis
Alex
A
Gao
Xiaoming
X
Du
Xiao-Jun
XJ
Curtis
David
D
Bobik
Alexander
A
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology*; D000068256:Darbepoetin alfa; D004195:Disease Models, Animal; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000031:analogs & derivatives* / Q000494:pharmacology; D005355:Fibrosis; D005786:Gene Expression Regulation / Q000187:drug effects; D051547:Heme Oxygenase-1 / Q000235:genetics; D006439:Hemodynamics / Q000187:drug effects*; D008565:Membrane Proteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009203:Myocardial Infarction / Q000178:diet therapy* / Q000235:genetics / Q000378:metabolism / Q000473:pathology / Q000503:physiopathology; D009206:Myocardium / Q000378:metabolism / Q000473:pathology*; D020097:Natriuretic Peptide, Brain / Q000235:genetics; D018919:Neovascularization, Physiologic / Q000187:drug effects / Q000235:genetics; D020556:Neutrophil Infiltration / Q000187:drug effects; D052247:Nitric Oxide Synthase Type II / Q000235:genetics; D017467:Receptors, Erythropoietin / Q000172:deficiency / Q000187:drug effects* / Q000235:genetics; D013997:Time Factors; D016277:Ventricular Function, Left / Q000187:drug effects*
D002316:Cardiotonic Agents; D008565:Membrane Proteins; D017467:Receptors, Erythropoietin; D004921:Erythropoietin; D020097:Natriuretic Peptide, Brain; D000068256:Darbepoetin alfa; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse