Increased transcription factor expression and permeability of the blood brain barrier associated with cardiopulmonary bypass in lambs.
BACKGROUND
The pathophysiology of neurocognitive dysfunction and developmental delay after cardiopulmonary bypass (CPB) in infants is not known. It is known that head trauma, stroke, and seizures cause dysfunction of the blood brain barrier (BBB) that is associated with increased inducible transcription factor gene expression in the cells of the barrier. The purpose of this study was to determine the effects of CPB and hypothermic circulatory arrest on expression of the transcription factor FOS and the function of the BBB in an infant animal model.


METHODS
Infant lambs (n = 36; 10-12 days) were exposed to 0, 15, 30, 60, or 120 minutes of normothermic (38 degrees C) CPB or 2 hours of hypothermic circulatory arrest at 16 degrees C. After terminating bypass 15 animals had their brains perfusion-fixed and removed for immunohistochemical analysis of expression of the transcription factor FOS. The other animals were perfused with fluorescent albumin to visualize the brain microvasculature. Brain sections were analyzed with a laser scanning confocal microscope.


RESULTS
Control animals (n = 6, sham operated and cannulated) exhibited normal vasculature with negligible leakage and no FOS protein expression in neurons or endothelial cells anywhere in the brain. Significant FOS expression in barrier-associated structures including the blood vessels, choroid plexus, and ependyma but not neurons occurred at all times on bypass. CPB caused leakage of fluorescent albumin from blood vessels in all animals. Two hours of normothermic CPB (n = 4) caused significant (p < 0.01) leakage in the cerebellum, cortex, hippocampus, and corpus callosum. Animals exposed to circulatory arrest experienced severe leakage throughout the brain (p < 0.001) and FOS expression in all cells.


CONCLUSIONS
These experiments indicate that the BBB is dysfunctional after all time points on normothermic CPB, BBB dysfunction is worsened by hypothermic circulatory arrest, and BBB dysfunction is associated with intense molecular activity within the barrier-forming cells. Dysfunction of the BBB may contribute to neurologic complications after heart surgery.
Cavaglia
Marco
M
Department of Anesthesia Research, The Cleveland Clinic Foundation, Cleveland, Ohio, USA.
Seshadri
Shivaprakash G
SG
Marchand
James E
JE
Ochocki
Carrie L
CL
Mee
Roger B B
RB
Bokesch
Paula M
PM
D000818:Animals; D000831:Animals, Newborn; D001812:Blood-Brain Barrier; D001921:Brain / Q000648:ultrastructure; D001925:Brain Damage, Chronic / Q000209:etiology* / Q000503:physiopathology; D001929:Brain Edema / Q000209:etiology / Q000503:physiopathology; D019559:Capillary Leak Syndrome / Q000209:etiology / Q000503:physiopathology; D002315:Cardiopulmonary Bypass / Q000009:adverse effects*; D003072:Cognition Disorders / Q000209:etiology* / Q000503:physiopathology; D005119:Extravasation of Diagnostic and Therapeutic Materials; D016650:Fluorescein-5-isothiocyanate / Q000031:analogs & derivatives* / Q000493:pharmacokinetics; D005456:Fluorescent Dyes / Q000493:pharmacokinetics; D005786:Gene Expression Regulation; D016762:Genes, fos; D007036:Hypothermia, Induced / Q000009:adverse effects*; D018613:Microscopy, Confocal; D011183:Postoperative Complications / Q000209:etiology* / Q000503:physiopathology; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D012710:Serum Albumin, Bovine / Q000493:pharmacokinetics; D012756:Sheep; D016037:Single-Blind Method
D005456:Fluorescent Dyes; D016760:Proto-Oncogene Proteins c-fos; C039217:fluorescein isothiocyanate bovine serum albumin; D012710:Serum Albumin, Bovine; D016650:Fluorescein-5-isothiocyanate