Effect of traumatic brain injury on cognitive function in mice lacking p55 and p75 tumor necrosis factor receptors.
BACKGROUND
Tumor necrosis factor (TNF)-alpha has been suggested to play both a deleterious and beneficial role in neurobehavioral dysfunction and recovery following traumatic brain injury (TBI). The goal of this study was to evaluate the specific role of tumor necrosis factor (TNF) receptors p55 and p75 in mediating cognitive outcome following controlled cortical impact (CCI) brain injury by comparing post-traumatic cognitive function in mice with genetically engineered deletion of the gene for either p55 (-/-) or p75 (-/-) receptors.


METHODS
Male C57B1/6 mice (WT, n=29), and mice genetically engineered to delete p55 TNF (p55 (-/-), n=8) or p75 TNF (p75 (-/-), n=23) receptors were used. They were anesthetized with intraperitoneal (i.p.) administration of sodium pentobarbital (65 mg/kg) and subjected to CCI brain injury of moderate severity. Sham-injured control mice were anesthetized and surgically prepared similarly but they received no impact. Assessment of mRNA expression of inflammatory, proapoptotic and antiapoptotic genes was done by real time-polymerase chain reaction (RT-PCR). Cognitive outcome was evaluated at 4 weeks postinjury using the Morris water maze (MWM).


RESULTS
mRNA expression of inflammatory, proapoptotic and antiapoptotic genes prior to TBI did not reveal any baseline difference between p55 and p75 (-/-) mice. WT mice showed greater baseline expression of inflammatory genes. The learning ability of p55 (-/-) brain-injured mice was significantly better than that observed in p75 (-/-) brain-injured mice (p < 0.05). Cognitive learning in WT control mice fell between the p55 (-/-) and p75 (-/-) mice.


CONCLUSIONS
These data suggest that TNF-alpha may both exacerbate cognitive dysfunction via p55 receptor and attenuate it via p75 receptor.
Longhi
L
L
Neurosurgical Intensive Care Unit, Department of Anesthesia and Critical Care Medicine, Fondazione IRCCS Ospedale Maggiore Policlinico, University of Milano, Mangiagalli e Regina Elena, Milano, Italy.
Ortolano
F
F
Zanier
E R
ER
Perego
C
C
Stocchetti
N
N
De Simoni
M G
MG
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D001930:Brain Injuries / Q000150:complications; D003072:Cognition Disorders / Q000209:etiology* / Q000235:genetics*; D016207:Cytokines / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D008297:Male; D018782:Maze Learning / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D010775:Photic Stimulation / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism; D011930:Reaction Time / Q000235:genetics; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000172:deficiency*; D047889:Receptors, Tumor Necrosis Factor, Type II / Q000172:deficiency*; D013028:Space Perception / Q000502:physiology; D013997:Time Factors; D053319:Tumor Necrosis Factor Decoy Receptors / Q000172:deficiency*
D016207:Cytokines; D012333:RNA, Messenger; D047888:Receptors, Tumor Necrosis Factor, Type I; D047889:Receptors, Tumor Necrosis Factor, Type II; D053319:Tumor Necrosis Factor Decoy Receptors; C069521:recombinant human tumor necrosis factor-binding protein-1