Activated protein C blocks p53-mediated apoptosis in ischemic human brain endothelium and is neuroprotective.
Activated protein C (APC) is a systemic anti-coagulant and anti-inflammatory factor. It reduces organ damage in animal models of sepsis, ischemic injury and stroke and substantially reduces mortality in patients with severe sepsis. It was not known whether APC acts as a direct cell survival factor or whether its neuroprotective effect is secondary to its anti-coagulant and anti-inflammatory effects. We report that APC directly prevents apoptosis in hypoxic human brain endothelium through transcriptionally dependent inhibition of tumor suppressor protein p53, normalization of the pro-apoptotic Bax/Bcl-2 ratio and reduction of caspase-3 signaling. These mechanisms are distinct from those involving upregulation of the genes encoding the anti-apoptotic Bcl-2 homolog A1 and inhibitor of apoptosis protein-1 (IAP-1) by APC in umbilical vein endothelial cells. Cytoprotection of brain endothelium by APC in vitro required endothelial protein C receptor (EPCR) and protease-activated receptor-1 (PAR-1), as did its in vivo neuroprotective activity in a stroke model of mice with a severe deficiency of EPCR. This is consistent with work showing the direct effects of APC on cultured cells via EPCR and PAR-1 (ref. 9). Moreover, the in vivo neuroprotective effects of low-dose mouse APC seemed to be independent of its anti-coagulant activity. Thus, APC protects the brain from ischemic injury by acting directly on brain cells.
Cheng
Tong
T
Frank P. Smith Neurosurgical Research Laboratory, Department of Neurosurgery and Center for Aging and Developmental Biology, Division of Neurovascular Biology, University of Rochester Medical Center, Rochester, New York, USA.
Liu
Dong
D
Griffin
John H
JH
Fernández
José A
JA
Castellino
Francis
F
Rosen
Elliot D
ED
Fukudome
Kenji
K
Zlokovic
Berislav V
BV
D000818:Animals; D000906:Antibodies / Q000378:metabolism; D017209:Apoptosis; D001779:Blood Coagulation Factors / Q000378:metabolism*; D001921:Brain / Q000098:blood supply* / Q000378:metabolism; D002545:Brain Ischemia / Q000503:physiopathology*; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D020287:In Situ Nick-End Labeling; D051379:Mice; D018696:Neuroprotective Agents / Q000378:metabolism*; D009842:Oligopeptides; D011486:Protein C / Q000378:metabolism*; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000235:genetics / Q000378:metabolism; D044463:Receptor, PAR-1; D011956:Receptors, Cell Surface / Q000378:metabolism*; D018179:Receptors, Thrombin / Q000235:genetics / Q000378:metabolism; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*; D051028:bcl-2-Associated X Protein
D000906:Antibodies; C494826:BAX protein, human; C494827:Bax protein, mouse; D001779:Blood Coagulation Factors; D018696:Neuroprotective Agents; D009842:Oligopeptides; C073248:Peptamen; D011486:Protein C; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D044463:Receptor, PAR-1; D011956:Receptors, Cell Surface; D018179:Receptors, Thrombin; D016159:Tumor Suppressor Protein p53; C091963:activated protein C receptor; D051028:bcl-2-Associated X Protein; C505407:CASP3 protein, human; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020169:Caspases