Hypoxic damage to the periventricular white matter in neonatal brain: role of vascular endothelial growth factor, nitric oxide and excitotoxicity.
The present study examined factors that may be involved in the development of hypoxic periventricular white matter damage in the neonatal brain. Wistar rats (1-day old) were subjected to hypoxia and the periventricular white matter (corpus callosum) was examined for the mRNA and protein expression of hypoxia-inducible factor-1alpha (HIF-1alpha), endothelial, neuronal and inducible nitric oxide synthase (eNOS, nNOS and iNOS), vascular endothelial growth factor (VEGF) and N-methyl-D-aspartate receptor subunit 1 (NMDAR1) between 3 h and 14 days after hypoxic exposure by real-time RT-PCR, western blotting and immunohistochemistry. Up-regulated mRNA and protein expression of HIF-1alpha, VEGF, NMDAR1, eNOS, nNOS and iNOS in corpus callosum was observed in response to hypoxia. NMDAR1 and iNOS expression was found in the activated microglial cells, whereas VEGF was localized to astrocytes. An enzyme immunoassay showed that the VEGF concentration in corpus callosum was significantly higher up to 7 days after hypoxic exposure. NO levels, measured by colorimetric assay, were also significantly higher in hypoxic rats up to 14 days after hypoxic exposure as compared with the controls. A large number of axons undergoing degeneration were observed between 3 h and 7 days after the hypoxic exposure at electron-microscopic level. Our findings point towards the involvement of excitotoxicity, VEGF and NO in periventricular white matter damage in response to hypoxia.
Kaur
Charanjit
C
Department of Anatomy, Yong Loo Lin School of Medicine, National University of Singapore, Singapore. antkaurc@nus.edu.sg
Sivakumar
Viswanathan
V
Ang
Lin Stella
LS
Sundaresan
Alamelu
A
D000818:Animals; D000831:Animals, Newborn / Q000502:physiology*; D015153:Blotting, Western; D001921:Brain / Q000473:pathology*; D003124:Colorimetry; D003337:Corpus Callosum / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism; D020925:Hypoxia-Ischemia, Brain / Q000473:pathology*; D007124:Immunoenzyme Techniques; D007150:Immunohistochemistry; D020547:Lateral Ventricles / Q000378:metabolism; D008854:Microscopy, Electron; D004676:Myelin Basic Protein / Q000378:metabolism; D009186:Myelin Sheath / Q000473:pathology; D009569:Nitric Oxide / Q000378:metabolism / Q000502:physiology*; D052247:Nitric Oxide Synthase Type II / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D016194:Receptors, N-Methyl-D-Aspartate / Q000096:biosynthesis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D042461:Vascular Endothelial Growth Factor A / Q000502:physiology*
D005904:Glial Fibrillary Acidic Protein; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D004676:Myelin Basic Protein; D009569:Nitric Oxide; D052247:Nitric Oxide Synthase Type II; D052250:Nitric Oxide Synthase Type III; D012333:RNA, Messenger; D016194:Receptors, N-Methyl-D-Aspartate; D042461:Vascular Endothelial Growth Factor A