Uncoupling of endothelial nitric oxide synthase after experimental subarachnoid hemorrhage.
We studied whether endothelial nitric oxide synthase (eNOS) is upregulated and uncoupled in large cerebral arteries after subarachnoid hemorrhage (SAH) and also whether this causes cerebral vasospasm in a mouse model of anterior circulation SAH. Control animals underwent injection of saline instead of blood (n=16 SAH and n=16 controls). There was significant vasospasm of the middle cerebral artery 2 days after SAH (lumen radius/wall thickness ratio 4.3 ± 1.3 for SAH, 23.2 ± 2.1 for saline, P<0.001). Subarachnoid hemorrhage was associated with terminal deoxynucleotidyl transferase dUTP nick-end labeling, cleaved caspase-3, and Fluoro-Jade-positive neurons in the cortex and with CA1 and dentate regions in the hippocampus. There were multiple fibrinogen-positive microthromboemboli in the cortex and hippocampus after SAH. Transgenic mice expressing lacZ under control of the eNOS promoter had increased X-gal staining in large arteries after SAH, and this was confirmed by the increased eNOS protein on western blotting. Evidence that eNOS was uncoupled was found in that nitric oxide availability was decreased, and superoxide and peroxynitrite concentrations were increased in the brains of mice with SAH. This study suggests that artery constriction by SAH upregulates eNOS but that it is uncoupled and produces peroxynitrite that may generate microemboli that travel distally and contribute to brain injury.
Division of Neurosurgery, St Michael's Hospital, Keenan Research Centre in Li Ka Shing Knowledge Institute of St Michael's Hospital and Department of Surgery, University of Toronto, Toronto, Ontario, Canada.
Mohammed
M
Sabri
Jinglu
J
Ai
Britta
B
Knight
Asma
A
Tariq
Hyojin
H
Jeon
Xueyuan
X
Shang
Philip Anthony
PA
Marsden
Robert
R
Loch Macdonald
D000818:Animals; D001160:Arterioles / Q000201:enzymology / Q000473:pathology; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002536:Cerebral Arteries / Q000201:enzymology / Q000473:pathology; D005340:Fibrinogen / Q000378:metabolism; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D020767:Intracranial Thrombosis / Q000201:enzymology / Q000473:pathology; D007763:Lac Operon / Q000235:genetics; D051379:Mice; D008822:Mice, Transgenic; D009569:Nitric Oxide / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II / Q000235:genetics / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000235:genetics / Q000378:metabolism*; D030421:Peroxynitrous Acid / Q000378:metabolism; D013345:Subarachnoid Hemorrhage / Q000201:enzymology* / Q000235:genetics; D013481:Superoxides / Q000378:metabolism; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism; D020301:Vasospasm, Intracranial / Q000201:enzymology
D013481:Superoxides; D030421:Peroxynitrous Acid; D009569:Nitric Oxide; C002744:3-nitrotyrosine; D014443:Tyrosine; D005340:Fibrinogen; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D053148:Caspase 3