Absence of the complement regulatory molecule CD59a leads to exacerbated neuropathology after traumatic brain injury in mice.
BACKGROUND
Complement represents a crucial mediator of neuroinflammation and neurodegeneration after traumatic brain injury. The role of the terminal complement activation pathway, leading to generation of the membrane attack complex (MAC), has not been thoroughly investigated. CD59 is the major regulator of MAC formation and represents an essential protector from homologous cell injury after complement activation in the injured brain.


METHODS
Mice deleted in the Cd59a gene (CD59a-/-) and wild-type littermates (n = 60) were subjected to focal closed head injury. Sham-operated (n = 60) and normal untreated mice (n = 14) served as negative controls. The posttraumatic neurological impairment was assessed for up to one week after trauma, using a standardized Neurological Severity Score (NSS). The extent of neuronal cell death was determined by serum levels of neuron-specific enolase (NSE) and by staining of brain tissue sections in TUNEL technique. The expression profiles of pro-apoptotic (Fas, FasL, Bax) and anti-apoptotic (Bcl-2) mediators were determined at the gene and protein level by real-time RT-PCR and Western blot, respectively.


RESULTS
Clinically, the brain-injured CD59a-/- mice showed a significantly impaired neurological outcome within 7 days, as determined by a higher NSS, compared to wild-type controls. The NSE serum levels, an indirect marker of neuronal cell death, were significantly elevated in CD59a-/- mice at 4 h and 24 h after trauma, compared to wild-type littermates. At the tissue level, increased neuronal cell death and brain tissue destruction was detected by TUNEL histochemistry in CD59a-/- mice within 24 hours to 7 days after head trauma. The analysis of brain homogenates for potential mediators and regulators of cell death other than the complement MAC (Fas, FasL, Bax, Bcl-2) revealed no difference in gene expression and protein levels between CD59a-/- and wild-type mice.


CONCLUSIONS
These data emphasize an important role of CD59 in mediating protection from secondary neuronal cell death and further underscore the key role of the terminal complement pathway in the pathophysiology of traumatic brain injury. The exact mechanisms of complement MAC-induced secondary neuronal cell death after head injury require further investigation.
Stahel
Philip F
PF
Department of Orthopedic Surgery, Denver Health Medical Center, University of Colorado School of Medicine, Denver, CO 80204, USA. philip.stahel@dhha.org
Flierl
Michael A
MA
Morgan
B Paul
BP
Persigehl
Ivonne
I
Stoll
Christiane
C
Conrad
Claudia
C
Touban
Basel M
BM
Smith
Wade R
WR
Beauchamp
Kathryn
K
Schmidt
Oliver I
OI
Ertel
Wolfgang
W
Leinhase
Iris
I
D000818:Animals; D017209:Apoptosis; D001921:Brain / Q000378:metabolism* / Q000473:pathology*; D001930:Brain Injuries / Q000378:metabolism* / Q000473:pathology*; D018957:CD59 Antigens / Q000235:genetics / Q000378:metabolism*; D015938:Complement Membrane Attack Complex / Q000378:metabolism; D003711:Demyelinating Diseases / Q000473:pathology; D004195:Disease Models, Animal; D053222:Fas Ligand Protein / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000378:metabolism / Q000473:pathology; D010751:Phosphopyruvate Hydratase / Q000378:metabolism; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D019014:fas Receptor / Q000378:metabolism
D018957:CD59 Antigens; D015938:Complement Membrane Attack Complex; D053222:Fas Ligand Protein; C491899:Fas protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D051028:bcl-2-Associated X Protein; D019014:fas Receptor; D010751:Phosphopyruvate Hydratase