Increased expression of HIF-1alpha, nNOS, and VEGF in the cerebral cortex of anemic rats.
This study tested the hypothesis that specific hypoxic molecules, including hypoxia-inducible factor-1alpha (HIF-1alpha), neuronal nitric oxide synthase (nNOS), and vascular endothelial growth factor (VEGF), are upregulated within the cerebral cortex of acutely anemic rats. Isoflurane-anesthetized rats underwent acute hemodilution by exchanging 50% of their blood volume with pentastarch. Following hemodilution, mean arterial pressure and arterial Pa(O(2)) values did not differ between control and anemic rats while the hemoglobin concentration decreased to 57 +/- 2 g/l. In anemic rats, cerebral cortical HIF-1alpha protein levels were increased, relative to controls (1.7 +/- 0.5-fold, P < 0.05). This increase was associated with an increase in mRNA levels for VEGF, erythropoietin, CXCR4, iNOS, and nNOS (P < 0.05 for all), but not endothelial NOS. Cerebral cortical nNOS and VEGF protein levels were increased in anemic rats, relative to controls (2.0 +/- 0.2- and 1.5 +/- 0.4-fold, respectively, P < 0.05 for both). Immunohistochemistry demonstrated increased HIF-1alpha and VEGF staining in perivascular regions of the anemic cerebral cortex and an increase in the number of nNOS-positive cerebral cortical cells (3.2 +/- 1.0-fold, P < 0.001). The nNOS-positive cells costained with the neuronal marker, Neu-N, but not with the astrocytic marker glial fibrillary acidic protein (GFAP). These nNOS-positive neurons frequently sent axonal projections toward cerebral blood vessels. Conversely, VEGF immunostaining colocalized with both neuronal (NeuN) and astrocytic markers (GFAP). In conclusion, acute normotensive, normoxemic hemodilution increased the levels of HIF-1alpha protein and mRNA for HIF-1-responsive molecules. nNOS and VEGF protein levels were also increased within the cerebral cortex of anemic rats at clinically relevant hemoglobin concentrations.
McLaren
Anya T
AT
Department of Anesthesia, Cara Phelan Trauma Research Centre, University of Toronto, St. Michael's Hospital, 30 Bond St., Toronto, Ontario, M5B 1W8, Canada.
Marsden
Philip A
PA
Mazer
C David
CD
Baker
Andrew J
AJ
Stewart
Duncan J
DJ
Tsui
Albert K Y
AK
Li
Xiaomao
X
Yucel
Yeni
Y
Robb
Malcolm
M
Boyd
Shelley R
SR
Liu
Elaine
E
Yu
Julie
J
Hare
Gregory M T
GM
D000740:Anemia / Q000378:metabolism* / Q000503:physiopathology; D000818:Animals; D001794:Blood Pressure / Q000502:physiology; D015153:Blotting, Western; D002540:Cerebral Cortex / Q000187:drug effects / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005455:Fluorescent Antibody Technique; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000378:metabolism; D006438:Hemodilution; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis*; D007150:Immunohistochemistry; D008297:Male; D052248:Nitric Oxide Synthase Type I / Q000096:biosynthesis*; D010100:Oxygen / Q000097:blood; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000096:biosynthesis*
C497444:Hif1a protein, rat; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D012333:RNA, Messenger; D042461:Vascular Endothelial Growth Factor A; D052248:Nitric Oxide Synthase Type I; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases; D010100:Oxygen