Oliver I. Schmidt

Inhibition of the alternative complement activation pathway in traumatic brain injury by a monoclonal anti-factor B antibody: a randomized placebo-controlled study in mice

BackgroundThe posttraumatic response to traumatic brain injury (TBI) is characterized, in part, by activation of the innate immune response, including the complement system. We have recently shown that mice devoid of a functional alternative pathway of complement activation (factor B-/- mice) are protected from complement-mediated neuroinflammation and neuropathology after TBI. In the present study, we extrapolated this knowledge from studies in genetically engineered mice to a pharmacological approach using a monoclonal anti-factor B antibody. This neutralizing antibody represents a specific and potent inhibitor of the alternative complement pathway in mice.MethodsA focal trauma was applied to the left hemisphere of C57BL/6 mice (n = 89) using a standardized electric weight-drop model. Animals were randomly assigned to two treatment groups: (1) Systemic injection of 1 mg monoclonal anti-factor B antibody (mAb 1379) in 400 μl phosphate-buffered saline (PBS) at 1 hour and 24 hours after trauma; (2) Systemic injection of vehicle only (400 μl PBS), as placebo control, at identical time-points after trauma. Sham-operated and untreated mice served as additional negative controls. Evaluation of neurological scores and analysis of brain tissue specimens and serum samples was performed at defined time-points for up to 1 week. Complement activation in serum was assessed by zymosan assay and by murine C5a ELISA. Brain samples were analyzed by immunohistochemistry, terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) histochemistry, and real-time RT-PCR.ResultsThe mAb 1379 leads to a significant inhibition of alternative pathway complement activity and to significantly attenuated C5a levels in serum, as compared to head-injured placebo-treated control mice. TBI induced histomorphological signs of neuroinflammation and neuronal apoptosis in the injured brain hemisphere of placebo-treated control mice for up to 7 days. In contrast, the systemic administration of an inhibitory anti-factor B antibody led to a substantial attenuation of cerebral tissue damage and neuronal cell death. In addition, the posttraumatic administration of the mAb 1379 induced a neuroprotective pattern of intracerebral gene expression.ConclusionInhibition of the alternative complement pathway by posttraumatic administration of a neutralizing anti-factor B antibody appears to represent a new promising avenue for pharmacological attenuation of the complement-mediated neuroinflammatory response after head injury.

Absence of the complement regulatory molecule CD59a leads to exacerbated neuropathology after traumatic brain injury in mice

BackgroundComplement 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.MethodsMice 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.ResultsClinically, 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.ConclusionThese 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.

The Role of Neuroinflammation in Traumatic Brain Injury

In industrialized countries, traumatic brain injury (TBI) still represents the leading cause of death and persisting neurologic impairment among young individuals < 45 years of age. Patients who survive the initial injury are susceptible to sustaining secondary cerebral insults which are initiated by the release of neurotoxic and inflammatory endogenous mediators by resident cells of the central nervous system (CNS). The presence of hypoxia and hypotension in the early resuscitative period further aggravates the inflammatory response due to ischemia/reperfusion-mediated injuries. These are induced by the intrathecal generation of free radicals and activation of the complement cascade. Posttraumatic neuroinflammation is further exacerbated by the subsequent intracranial recruitment of blood-derived immunocompetent cells, leading to secondary cerebral edema and increased intracranial pressure. The profound endogenous neuroinflammatory response after TBI, which is phylogenetically aimed at defending the CNS from invading pathogens and repairing lesioned tissue, is, in large part, responsible for the development of secondary brain damage and adverse outcome. However, aside from these deleterious effects, posttraumatic inflammation mediates neuroreparative mechanisms after TBI as well. This “dual effect” of neuroinflammation has been the focus of extensive experimental and clinical research in the past years and has led to an expanded basic knowledge on the cellular and molecular mechanisms which regulate the intracranial inflammatory response after trauma. The present article provides an up-to-date overview on the pathophysiological mechanisms of neuroinflammation after TBI. New potential therapeutic strategies for reducing the extent of secondary brain damage after neurotrauma are discussed.

Role of early minimal-invasive spine fixation in acute thoracic and lumbar spine trauma

Polytraumatized patients following a severe trauma suffer from substantial disturbances of the immune system. Secondary organ dysfunction syndromes due to early hyperinflammation and late immunparalysis contribute to adverse outcome. Consequently the principle of damage control surgery / orthopedics developed in the last two decades to limit secondary iatrogenic insult in these patients. New percutaneous internal fixators provide implants for a damage control approach of spinal trauma in polytraumatized patients. The goal of this study is to evaluate the feasibility of minimal-invasive instrumentation in the setting of minor and major trauma and to discuss the potential benefits and drawbacks of this procedure. Materials and Methods: The present study is a prospective analysis of 76 consecutive patients (mean age 53.3 years) with thoracolumbar spine fractures following major or minor trauma from August 2003 to January 2007 who were subjected to minimal-invasive dorsal instrumentation using CD Horizon® Sextant™ Rod Insertion System and Longitude™ Rod Insertion System (Medtronic® Sofamor Danek). Perioperative and postoperative outcome measures including e.g. local and systemic complications were assessed and discussed. Results: Forty-nine patients (64.5%) suffered from minor trauma (Injury Severity Score <16). Polytraumatized patients (n=27; 35.5%) had associated chest (n=20) and traumatic brain injuries (n=22). For mono- and bisegmental dorsal instrumentation the Sextant™ was used in 60 patients, whereas in 16 longer ranging instrumentations the (prototype) Longitude™ system was implanted. Operation time was substantially lower than in conventional approach at minimum 22.5 min for Sextant and 36.2 min for Longitude™, respectively. Geriatric patients with high perioperative risk according to ASA classification benefited from the less invasive approach and lack of approach-related complications including no substantial blood loss. Conclusion: Low rate of approach-related complications in association with short operation time and virtually no blood loss is beneficial in the setting of polytraumatized patients regarding damage control orthopedics, as well as in geriatric patients with high perioperative risk. The minimal-invasive instrumentation of the spine is associated with beneficial outcome in a selected patient population.

Percutaneous Internal Fixation of Thoracolumbar Spine Fractures

Background: Prospective clinical outcome measures in a large cohort of patients with thoracolumbar spinal injuries have not been reported to date. Objective: To evaluate the outcomes of traumatic pathologic or nonpathologic thoracolumbar spine injuries treated with a percutaneous posterior internal fixation using the CD Horizon® Sextant™ Rod Insertion System (Medtronic® Sofamor Danek). Patients and Method: We performed a prospective clinical study evaluating a novel method of internal fixation of traumatic thoracolumbar spinal injuries. Over a 2-year period from August 2003 to July 2005, a total of 156 patients with thoracolumbar spinal injuries were treated with percutaneous posterior internal fixation using the CD Horizon® Sextant™ Rod Insertion System (Medtronic® Sofamor Danek). Indications for surgery included (1) AO Type A and Type B spinal fractures, (2) the presence of polytrauma, or (3) a pathologic traumatic fracture in the setting of osteoporosis or metastatic disease with or without prior anter...

Die pharmakologische Inhibition der intrazerebralen Entzündungsreaktion durch systemische Administration des rekombinanten Komplement-Inhibitors Crry-Ig vermittelt eine Neuroprotektion im experimentellen Schädel-Hirn-Trauma in der Maus

Activation of complement plays a central role in the pathogenesis of neuroinflammation leading to secondary brain injury following a traumatic insult to the brain. In a previous study, we were able to show improved neurological recovery in brain-injured transgenic mice with central nervous system-targeted overexpression of the soluble inhibitor of complement C3 convertases, sCrry. Here, we present the first data on systemic administration of recombinant Crry-Ig in a model of closed-head injury (CHI). Thirty-seven C57BL/6 mice were randomized into 4 cohorts: group 1 — normal mice without CHI; group 2 — sham-operated mice without CHI; group 3 — CHI with posttraumatic i.p. injection of 0.4 ml PBS (vehicle); group 4 — CHI with posttraumatic i.p. injection of recombinant Crry-Ig (1mg in 0.4 ml PBS). Vehicle-injected mice with experimental CHI (group 3) showed massive histomorphological signs of neuroinflammation associated with neuronal apoptosis. Western-Blot analysis of homogenized mouse brains revealed significant mismatch of mitochondrial anti- and pro-apoptotic proteins (Bcl-2, Bax, Bcl-Xs) favouring programmed cell death up to one week post trauma. In contrast, administration of Crry-Ig (group 4) induced a decrease of pro- and an increase of anti-apoptotic protein levels, with as- sociated attenuation of histomorphological tissue damage and improved neurological recovery.

Einfluss von TNF auf die intrakranielle Regulation von IL-18 nach Schädel-Hirn-Trauma bei Patienten und im experimentellen Modell

Interleukin-18 (IL-18) and tumor necrosis factor (TNF) are potent mediators of intracerebral inflammation following brain injury. Regulation of IL-18 expression in the intracranial compartment through TNF has not yet been evaluated. We examined the posttraumatic release of IL-18 and TNF in cerebrospinal fluid of 28 patients following severe traumatic brain injury. Using a model of intracranial TNF injection in C57BL/6 mice, the effects of TNF on IL-18 expression were investigated. In addition, IL-18 concentrations were assessed in brains of wild-type C57BL/6 and TNF/ lymphotoxin-α – /– mice in a model of closed head injury for up to 7 days after trauma. Significant inverse correlations for IL-18 and TNF levels were found in patients following traumatic brain injury (r= -0.6 to -0.8, P< 0.05). In the experimental setting, increased IL-18 concentrations were detected in brain homogenates of mice injected PBS (vehicle) only, while the intracerebral injection of 200 ng mouse-recombinant TNF blocked IL-18 increase significantly. Both groups subjected to experimental brain injury showed significant increase of IL-18 concentrations, however no significant differences between wild-type and TNF/lymphotoxin-α – /– mice were found. Based on the proposed „dual“ role of TNF as pro- and anti-inflammatory mediator in neuroinflammation, we suggest that the TNF-mediated inhibition of IL-18 expression may represent a so far unknown anti-inflammatory mechanism after brain injury.