Apaf-1, Bcl-xL, cytochrome c, and caspase-9 form the critical elements for cerebral vascular protection by erythropoietin.
Erythropoietin (EPO) plays a prominent role in the regulation of the hematopoietic system, but the potential function of this trophic factor as a cytoprotectant in the cerebral vascular system is not known. The authors examined the ability of EPO to modulate a series of death-related cellular pathways during free radical-induced injury in cerebral microvascular endothelial cells (ECs). Endothelial cell injury was evaluated by trypan blue, DNA fragmentation, membrane phosphatidylserine exposure, apoptotic protease-activating factor-1 (Apaf-1), and Bcl-XL expression, mitochondrial membrane potential, cytochrome c release, and cysteine protease activity. They show that constitutive EPO is present in ECs but is insufficient to prevent cellular injury. Signaling through the EPO receptor, however, remains biologically responsive to exogenous EPO administration to offer significant protection against nitric oxide-induced injury. Exogenous EPO maintains both genomic DNA integrity and cellular membrane asymmetry through parallel pathways that prevent the induction of Apaf-1 and preserve mitochondrial membrane potential in conjunction with enhanced Bcl-XL expression. Consistent with the modulation of Apaf-1 and the release of cytochrome c, EPO also inhibits the activation of caspase-9 and caspase-3-like activities. Identification of novel cytoprotective pathways used by EPO may serve as therapeutic targets for cerebral vascular disease.
Chong
Zhao Zhong
ZZ
Division of Cellular and Molecular Cerebral Ischemia, Wayne State University School of Medicine, 4201 St. Antoine, Detroit, MI 42801, USA.
Kang
Jing-Qiong
JQ
Maiese
Kenneth
K
D000818:Animals; D053477:Apoptotic Protease-Activating Factor 1; D001692:Biological Transport / Q000187:drug effects; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000502:physiology*; D002462:Cell Membrane / Q000187:drug effects; D002478:Cells, Cultured; D002560:Cerebrovascular Circulation / Q000502:physiology*; D003574:Cytochrome c Group / Q000037:antagonists & inhibitors / Q000502:physiology*; D019610:Cytoprotection / Q000502:physiology; D053938:DNA Fragmentation / Q000187:drug effects; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D004921:Erythropoietin / Q000494:pharmacology / Q000502:physiology*; D066298:In Vitro Techniques; D009569:Nitric Oxide / Q000494:pharmacology; D010718:Phosphatidylserines / Q000037:antagonists & inhibitors / Q000378:metabolism; D011506:Proteins / Q000037:antagonists & inhibitors / Q000502:physiology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D017467:Receptors, Erythropoietin / Q000378:metabolism; D051020:bcl-X Protein
C506594:Apaf1 protein, rat; D053477:Apoptotic Protease-Activating Factor 1; C494813:Bcl2l1 protein, rat; D061945:Caspase Inhibitors; D003574:Cytochrome c Group; D010718:Phosphatidylserines; D011506:Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D017467:Receptors, Erythropoietin; D051020:bcl-X Protein; D004921:Erythropoietin; D009569:Nitric Oxide; C506435:Casp9 protein, rat; D053453:Caspase 9; D020169:Caspases