Tissue plasminogen activator neurovascular toxicity is controlled by activated protein C.
Although thrombolytic effects of tissue plasminogen activator (tPA) are beneficial, its neurotoxicity is problematic. Here, we report that tPA potentiates apoptosis in ischemic human brain endothelium and in mouse cortical neurons treated with N-methyl-D-aspartate (NMDA) by shifting the apoptotic pathways from caspase-9 to caspase-8, which directly activates caspase-3 without amplification through the Bid-mediated mitochondrial pathway. In vivo, tPA-induced cerebral ischemic injury in mice was reduced by intracerebroventricular administration of caspase-8 inhibitor, but not by caspase-9 inhibitor, in contrast to controls in which caspase-9 inhibitor, but not caspase-8 inhibitor, was protective. Activated protein C (APC), a serine protease with anticoagulant, anti-inflammatory and antiapoptotic activities, which is neuroprotective during transient ischemia and promotes activation of antiapoptotic mechanisms in brain cells by acting directly on endothelium and neurons, blocked tPA vascular and neuronal toxicities in vitro and in vivo. APC inhibited tPA-induced caspase-8 activation of caspase-3 in endothelium and caspase-3-dependent nuclear translocation of apoptosis-inducing factor in NMDA-treated neurons and reduced tPA-mediated cerebral ischemic injury in mice. Data suggest that tPA shifts the apoptotic signal in stressed brain cells from the intrinsic to the extrinsic pathway which requires caspase-8. APC blocks tPA's neurovascular toxicity and may add substantially to the effectiveness of tPA therapy for stroke.
Liu
Dong
D
Frank P. Smith Laboratory for Neuroscience and Neurosurgical Research, Department of Neurosurgery and Division of Neurovascular Biology, University of Rochester Medical Center, 601 Elmwood Avenue, Box 645, Rochester, New York 14642, USA.
Cheng
Tong
T
Guo
Huang
H
Fernández
José A
JA
Griffin
John H
JH
Song
Xiaomei
X
Zlokovic
Berislav V
BV
D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001921:Brain / Q000187:drug effects* / Q000378:metabolism; D002545:Brain Ischemia / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D015151:Immunoblotting; D020287:In Situ Nick-End Labeling; D051379:Mice; D008810:Mice, Inbred C57BL; D016202:N-Methylaspartate / Q000378:metabolism; D009474:Neurons / Q000187:drug effects*; D011486:Protein C / Q000378:metabolism*; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000378:metabolism / Q000633:toxicity*
D061945:Caspase Inhibitors; D011486:Protein C; D016202:N-Methylaspartate; D010959:Tissue Plasminogen Activator; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C506433:CASP9 protein, human; C505409:Casp3 protein, mouse; C505526:Casp8 protein, mouse; C506434:Casp9 protein, mouse; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases