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Aquaporin-1-mediated cerebral edema following traumatic brain injury: effects of acidosis and corticosteroid administration.
- Source :
-
Journal of neurosurgery [J Neurosurg] 2010 May; Vol. 112 (5), pp. 1095-104. - Publication Year :
- 2010
-
Abstract
- Object: Dysregulation of water homeostasis induces cerebral edema. Edema is a major cause of morbidity and mortality following traumatic brain injury (TBI). Aquaporin-1 (AQP-1), a water channel found in the brain, can function as a transporter for CO2 across the cellular membrane. Additionally, AQP-1's promoter contains a glucocorticoid response element. Thus, AQP-1 may be involved with edema-related brain injury and might be modulated by external conditions such as the pH and the presence of steroids. In this study, the authors investigated the hypotheses that: 1) AQP-1 participates in brain water homeostasis following TBI; 2) secondary injury (for example, acidosis) alters the expression of AQP-1 and exacerbates cerebral edema; and 3) corticosteroids augment brain AQP-1 expression and differentially affect cerebral edema under nonacidotic and acidotic conditions.<br />Methods: Anesthetized Sprague-Dawley rats were subjected to moderate to severe TBI (2.5-3.5 atm) or surgery without injury, and they were randomized to receive a 3-mg/kg bolus of intravenous dexamethasone within 10 minutes after injury or surgery, a 3-mg/kg bolus of dexamethasone followed by 1-mg/kg maintenance doses every 8 hours for 24 hours, or saline boluses at similar time intervals. A second group of animals was subjected to respiratory acidosis with target arterial blood pH 6.8-7.2 for 1 hour following the surgery or injury. To evaluate selective blockage of AQP-1, some animals received a single intraperitoneal dose of HgCl2 (0.3-30.0 mmol/L) within 30 minutes of injury or surgery. At 4 or 24 hours postinjury, animals were killed and their brains were harvested for mRNA, protein, or water content analyses.<br />Results: The authors demonstrated elevated cerebral edema levels at 4 and 24 hours following TBI. Dexamethasone administration within 1 hour of TBI attenuated the cerebral edema under nonacidotic conditions but worsened it under acidotic conditions. Selective blockage of AQP-1 channels with HgCl2 attenuated the edematous effects of corticosteroids and acidosis. Reverse transcriptase polymerase chain reaction and immunohistochemical analyses demonstrated a paucity of AQP-1 in the cerebral cortices of the uninjured animals. In contrast, AQP-1 mRNA and protein levels were higher in the cerebral cortices of animals that sustained a TBI.<br />Conclusions: These findings implicate an important, modifiable role for AQP-1 in water homeostasis within the CNS following TBI.
- Subjects :
- Animals
Blotting, Western
DNA Primers genetics
Dexamethasone administration & dosage
Immunoblotting
Immunohistochemistry
Infusions, Intravenous
Random Allocation
Rats
Rats, Sprague-Dawley
Reverse Transcriptase Polymerase Chain Reaction
Acidosis diagnosis
Acidosis etiology
Anti-Inflammatory Agents therapeutic use
Aquaporin 1 genetics
Brain Edema drug therapy
Brain Edema etiology
Brain Edema genetics
Brain Injuries complications
Dexamethasone therapeutic use
Subjects
Details
- Language :
- English
- ISSN :
- 1933-0693
- Volume :
- 112
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- Journal of neurosurgery
- Publication Type :
- Academic Journal
- Accession number :
- 19731985
- Full Text :
- https://doi.org/10.3171/2009.8.JNS081704