Erythropoietin is a novel vascular protectant through activation of Akt1 and mitochondrial modulation of cysteine proteases.
BACKGROUND
Erythropoietin (EPO) is a critical regulator for the proliferation of immature erythroid precursors, but its role as a potential cytoprotectant in the cerebrovasculature system has not been defined.


RESULTS
We examined the ability of EPO to regulate a cascade of apoptotic death-related cellular pathways during anoxia-induced vascular injury in endothelial cells (ECs). EC injury was evaluated by trypan blue, DNA fragmentation, membrane phosphatidylserine (PS) exposure, protein kinase B activity, mitochondrial membrane potential, and cysteine protease induction. Exposure to anoxia alone rapidly increased genomic DNA fragmentation from 2+/-1% to 40+/-5% and membrane PS exposure from 3+/-2% to 56+/-5% over 24 hours. Administration of a cytoprotective concentration of EPO (10 ng/mL) prevented DNA destruction and PS exposure. Cytoprotection by EPO was completely abolished by cotreatment with anti-EPO neutralizing antibody, which suggests that EPO was necessary and sufficient for the prevention of apoptosis. Protection by EPO was intimately dependent on the activation of protein kinase B (Akt1) and the maintenance of mitochondrial membrane potential. Subsequently, EPO inhibited caspase 8-, caspase 1-, and caspase 3-like activities that were linked to mitochondrial cytochrome c release.


CONCLUSIONS
The present work serves to illustrate that EPO can offer novel cytoprotection during ischemic vascular injury through direct modulation of Akt1 phosphorylation, mitochondrial membrane potential, and cysteine protease activity.
Chong
Zhao Zhong
ZZ
Division of Cellular and Molecular Cerebral Ischemia, Department of Neurology, Wayne State University School of Medicine, Detroit, Mich 48201, USA.
Kang
Jing-Qiong
JQ
Maiese
Kenneth
K
D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D001921:Brain / Q000098:blood supply; D015687:Cell Hypoxia / Q000502:physiology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D019610:Cytoprotection / Q000187:drug effects / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004921:Erythropoietin / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D007425:Intracellular Membranes / Q000187:drug effects / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008833:Microcirculation / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008928:Mitochondria / Q000737:chemistry / Q000187:drug effects / Q000201:enzymology*; D010718:Phosphatidylserines / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000187:drug effects
D000906:Antibodies; D004791:Enzyme Inhibitors; D010718:Phosphatidylserines; D011518:Proto-Oncogene Proteins; D004921:Erythropoietin; C494920:Akt1 protein, rat; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; D003546:Cysteine Endopeptidases