Reduced neuronal cell death after experimental brain injury in mice lacking a functional alternative pathway of complement activation
Open Access
- 14 July 2006
- journal article
- research article
- Published by Springer Science and Business Media LLC in BMC Neuroscience
- Vol. 7 (1), 55
- https://doi.org/10.1186/1471-2202-7-55
Abstract
Background: Neuroprotective strategies for prevention of the neuropathological sequelae of traumatic brain injury (TBI) have largely failed in translation to clinical treatment. Thus, there is a substantial need for further understanding the molecular mechanisms and pathways which lead to secondary neuronal cell death in the injured brain. The intracerebral activation of the complement cascade was shown to mediate inflammation and tissue destruction after TBI. However, the exact pathways of complement activation involved in the induction of posttraumatic neurodegeneration have not yet been assessed. In the present study, we investigated the role of the alternative complement activation pathway in contributing to neuronal cell death, based on a standardized TBI model in mice with targeted deletion of the factor B gene (fB-/-), a "key" component required for activation of the alternative complement pathway.Results: After experimental TBI in wild-type (fB+/+) mice, there was a massive time-dependent systemic complement activation, as determined by enhanced C5a serum levels for up to 7 days. In contrast, the extent of systemic complement activation was significantly attenuated infB-/- mice (P< 0.05,fB-/-vs.fB+/+;t= 4 h, 24 h, and 7 days after TBI). TUNEL histochemistry experiments revealed that posttraumatic neuronal cell death was clearly reduced for up to 7 days in the injured brain hemispheres offB-/- mice, compared tofB+/+ littermates. Furthermore, a strong upregulation of the anti-apoptotic mediator Bcl-2 and downregulation of the pro-apoptotic Fas receptor was detected in brain homogenates of head-injuredfB-/- vs.fB+/+ mice by Western blot analysis.Conclusion: The alternative pathway of complement activation appears to play a more crucial role in the pathophysiology of TBI than previously appreciated. This notion is based on the findings of (a) the significant attenuation of overall complement activation in head-injuredfB-/- mice, as determined by a reduction of serum C5a concentrations to constitutive levels in normal mice, and (b) by a dramatic reduction of TUNEL-positive neurons in conjunction with an upregulation of Bcl-2 and downregulation of the Fas receptor in head-injuredfB-/- mice, compared tofB+/+ littermates. Pharmacological targeting of the alternative complement pathway during the "time-window of opportunity" after TBI may represent a promising new strategy to be pursued in future studies.Keywords
This publication has 69 references indexed in Scilit:
- Pharmacological complement inhibition at the C3 convertase level promotes neuronal survival, neuroprotective intracerebral gene expression, and neurological outcome after traumatic brain injuryExperimental Neurology, 2006
- Complement regulator loss on apoptotic neuronal cells causes increased complement activation and promotes both phagocytosis and cell lysisMolecular Immunology, 2006
- Erythropoietin is neuroprotective, improves functional recovery, and reduces neuronal apoptosis and inflammation in a rodent model of experimental closed head injuryThe FASEB Journal, 2005
- Progesterone Differentially Regulates Pro- and Anti-Apoptotic Gene Expression in Cerebral Cortex Following Traumatic Brain Injury in RatsJournal of Neurotrauma, 2005
- The alternative pathway of complement in disease: opportunities for therapeutic targetingMolecular Immunology, 2004
- Neuron-Specific mRNA Complexity Responses during Hippocampal Apoptosis after Traumatic Brain InjuryJournal of Neuroscience, 2004
- Complement Activation following Optic Nerve Crush in the Adult RatJournal of Neurotrauma, 2003
- Vaccinia Virus Complement Control Protein Enhances Functional Recovery after Traumatic Brain InjuryJournal of Neurotrauma, 2002
- Elevated levels of the complement components C3 and factor B in ventricular cerebrospinal fluid of patients with traumatic brain injuryJournal of Neuroimmunology, 1997
- Expression of complement in the brain: role in health and diseaseImmunology Today, 1996