Molecular mechanisms of traumatic brain injury: the missing link in management
© Veenith et al; licensee BioMed Central Ltd. 2009
Received: 26 October 2008
Accepted: 02 February 2009
Published: 02 February 2009
Head injury is common, sometimes requires intensive care unit admission, and is associated with significant mortality and morbidity. A gap still remains in the understanding of the molecular mechanism of this condition. This review is aimed at providing a general overview of the molecular mechanisms involved in traumatic brain injury to a busy clinician. It will encompass the pathophysiology in traumatic brain injury including apoptosis, the role of molecules and genes, and a brief mention of possible pharmacological therapies.
Introduction and epidemiology
Our understanding of the molecular mechanisms of traumatic brain injury (TBI) has improved over the last decade, but a gap still exists between these advances and their translation into direct clinical care. About 0.5–1 million patients present to hospitals in the UK with TBI. It is the leading cause of disability in people under 40, and severely disables 150–200 people per million annually [1, 2]. In the US, TBI affects 1.4 million people, at an estimated annual cost of $56 billion . Diseases of the nervous system (International Classification of Diseases-revision 9) accounted for 8.4% of the total health and social services net public expenditure for 1992 and 1993 in England . The purpose of this review is to look at genetic and molecular influences after an acute head injury and the long term outcome.
Although our ability to assess and predict neurological outcome following TBI has improved, most of the prognostic tools are still poorly validated and therefore rarely used . Understanding the molecular mechanisms and integrating these into clinical practice will help us to predict outcomes more accurately, and will also pave the way for newer treatment modalities and further research.
Current understanding of the basic molecular mechanisms resulting in neurological damage following TBI has sparked several significant attempts to synthesise drugs (e.g. Selfotel) . So far these attempts have universally met with little success clinically, but they have provided some insights for future research . Such research has been hampered by a lack of translation of results from animal models into humans. Despite this it is likely that such work, both in animal models and observational studies in patients with acute TBI will continue to shed light in this important subject.
Pathophysiology of brain injury
Acute TBI is characterised by two injury phases, primary and secondary. The primary brain injury is the direct injury to the brain cells incurred at the time of the initial impact. This results in a series of, biochemical processes which then result in secondary brain injury. The primary aim for the acute management of TBI is to limit the secondary injury. The secondary brain injury is caused by a dynamic interplay between ischaemic, inflammatory and cytotoxic processes. Studies with microdialysis techniques have shown that one of the most significant factors causing secondary brain injury is the excessive release of excitotoxins such as glutamate and aspartate that occurs at the time of the primary brain injury. These excitotoxins act on the N-methyl-D-aspartate channel, altering cell wall permeability with an increase in intracellular calcium and sodium and activation of calcineurin and calmodulin. This ultimately, leads to destruction of the axon [7, 8]. Potassium is also released from the cells and absorbed by the astrocytes, in an attempt to restrict the ionic imbalance causing swelling of the cells and ultimately cell death.
There is a complex cascade of cellular inflammatory response following TBI which propagates secondary brain damage. This inflammatory process lasts from hours to days contributing continuously to secondary brain damage. The inflammatory response resulting from an acute TBI is not limited to the brain and multiple organ dysfunction syndromes are commonly seen. The major molecules in the brain involved in this cascade are growth factors, catecholamines, neurokinins, cytokines and chemokines .
Interleukins (IL) are proinflammatory cytokines, the levels of interleukins seen in intracerebral bleeds, and clinical signs of inflammation at admission, have correlated well with the magnitude of perilesional oedema and mortality [10, 11]. There is a rise in IL-6 and 10 in children following a TBI. The increased level of IL-10 was directly related to mortality in TBI . The rise in inflammatory cytokines (e.g. IL-6) following TBI is a double edged sword; both neurotoxicity and neuroprotection may be induced by it. Inflammatory cytokines facilitate neurotoxicity by encouraging excitotoxicity and the inflammatory response, but simultaneously they facilitate the neurotrophic mechanisms and induction of cell growth factors which are neuroprotective . It has also been shown by Vuylsteke et al that there is an increased gradient of inflammatory marker IL-8 in the brain after cardiopulmonary bypass, which is attenuated by hypothermia . This gradient continued into the postoperative period.
The primary insult also results in an immediate disturbance of the cerebral circulation, resulting in cerebral ischaemia and which contributes significantly to about 90% of deaths after closed head injuries. . Ischaemic brain damage is perpetuated by factors such as hypotension, hypoxia, raised intracranial pressure, oedema, focal tissue compression, damage to microvasculature, and in late phases, vasospasm in the remaining vessels [16, 17]. The time sequence after TBI can be arbitrarily divided into an early (phase 1, immediate, with hypoperfusion), intermediate (phase 2, on days 1–3, when hyperaemia can be seen) and a late vasospastic phase (phase 3, on days 4–15, with a marked reduction in blood flow) . These different phases are associated with marked regional variations in cerebral blood flow, with a reduction in blood flow to the surrounding of the ischaemic core, which does not respond to augmentation of cerebral perfusion pressure .
Programmed cell death (which is often referred to as apoptosis although strictly speaking this refers to the distinct morphological changes after programmed cell death) is a genetic mechanism by which cells are eliminated during development, and is the physiological mechanism by which cells are normally removed in the adult animal . This involves specific genes and proteins which were first described in neuronal development of the round worm . Following TBI there is increased expression of two main sets of genes which are genes encoding for the caspase family of cysteine proteases [including interleukin-1β converting enzyme (ICE) and cpp32] and a family of genes that are homologous to the oncogene Bcl-2 that either promote or suppress cell death. The Bcl-2 gene family controls both caspase dependent and independent apoptosis. [19, 21–23]. The endpoint of all these steps is fragmentation of cellular DNA with collapse of the nuclear structure, followed by the formation of membrane-wrapped apoptotic bodies, cleared by macrophages .
Apoptosis is now recognised as an important factor in secondary brain injury . Following TBI, two different types of cells are visible; type 1 and 2 cells. The type 1 cells show a classic necrotic pattern (this follows the primary brain injury) and type 2 cells shows a classic apoptotic pattern on microscopy [25, 19]. Cells undergoing apoptosis die without membrane rupture and therefore elicit less inflammatory reactions. This is in contrast to the cells undergoing necrosis . There is therefore a suggestion that neuronal apoptosis after TBI may be a protective response by the brain in order to remove injured tissue cells whilst having little effect on remaining brain tissue . Apoptotic cells have been identified within contusions in the acute post-traumatic period, and in regions remote from the site of injury days and weeks after trauma.
Pharmacological strategies to reduce apoptotic cell death have been investigated,  For example, rats treated with the caspase-3 inhibitor N-benzyloxycarbonyl-Asp-Glu-Val-Asp-fluoromethylketone (DEVD) demonstrate a 30% reduction in lesion volume measured 3 weeks after TBI when compared with vehicle-treated controls .
Long term pathophysiology
Recent advances in the management of severe acute TBI has resulted in improved outcomes for patients who might previously have had poor outcomes. In particular the management of such patients in specialist units has had a significant impact, although the definitive factors contributing to improved outcomes remain elusive. . In recent years there has been increasing interest in elucidating the long term problems experienced by patients following TBI. Further, there have been reports of people developing dementia-like symptoms following relatively minor head injuries (Brain injury with a GCS greater than 13 and without loss of consciousness, as well as an increased incidence of post traumatic stress disorders and depression . TBI causes a generalised atrophy of brain which is proportional to the severity of the injury. . The mechanisms for this are yet to be fully determined. In rats it has been shown that there are multiple antibodies to the amyloid precursor protein and amyloid precursor protein-like proteins for up to six months, which predisposes them to degeneration of the striatum and corpus callosum. This degeneration then leads to progressive brain atrophy and calcifications . In moderate to severe TBI there is a high incidence of hippocampal atrophy which predisposes patients to cognitive decline. When anoxic brain damage was compared to TBI there was no overwhelming evidence of localised nerve damage. This supports the theory that the final mechanism for neurological injury is the same irrespective of the type of initial insult .
Surviving the ischaemic insult: the role of genes
Surprisingly humans are made up of only 20,000 – 25,000 protein-coding genes, and these genes have profound implications on our survival . The genetic constituents not only modify the risk of development of disease and its severity, but also the ability of an organ to repair, heal and function after an injury. In head injured patients the outcomes are variable and cannot easily be predicted. This variability cannot be fully explained by clinical features or by the character of the injury . One of the mechanisms which could explain this is genetic polymorphism. This may also contribute to variability in outcome in the acute response, and functional recovery. A greater understanding of the genetics could aid in the prediction of outcomes and could be targeted for treatment strategies.
Studies in animals using cDNA microarray hybridization technique have shown differential regulation of 86 genes (seven classes) which take part in the physiological and pathological response to TBI. The key classes they encompass include transcription factors, signal transduction genes and inflammatory proteins . Such changes in gene expression are interlinked with both disease processes (for example IL-6 and haemoxygenase-1), and outcome in TBI.
Genes regulating the inflammatory process
Genetic polymorphisms which involve interleukin-6 (IL-6) and haemoxygenase -1 (HO-1) may influence the inflammatory effects seen after TBI . There are two genetic polymorphisms associated with increased IL-6 levels in blood -174G>C and -572G>C, the presence of which not only increased the risk of development of coronary and cerebral aneurysms but also increased the mortality when they ruptured . Haemoxygenase is a rate-limiting enzyme in haem catabolism and the inducible form of haemoxygenase is haemoxygenase-1 (HO-1). There is an increased expression of HO-1 in the injured rat brain model. The end product molecules influence tissue redox homeostasis under a wide range of pathophysiological conditions including TBI .
Genes regulating the vascular responses
Cerebral ischaemia results in an activation of the hypoxia-inducible factor-1 and 2 (HIF 1&2) genes. HIF-1 activates the transcription of numerous genes including vascular endothelial growth factor (VEGF), glucose transporter-1 (Glut1), Epo, transferrin (Tf), and the transferrin receptor (TfR) all of which have been shown to be neuroprotective in animal models after TBI . Vascular endothelial growth factor (VEGF) is the main regulator of angiogenesis, and in the normal adult brain and is predominantly expressed in the epithelial cells of the choroid plexus, astrocytes and neurons (such as granule cells of the cerebellum) . Following cerebral ischaemia there is upregulation of both VEGFR-2 and VEGF expression. . Somewhat confusingly HIF-1 upregulation and increased VEGF expression have been associated with the development of cerebral oedema and neuronal death following brain injury [Chen et al, 2008, Neurobiology of Disease] whilst also being implicated in peri infarct neuroprotection  Deficiencies of HIF genes in mice are associated with embryonic death due to cardiac, vascular, and neural malformations .
Genes regulating the neuronal response to TBI
Apolipoprotein epsilon (APOE) is a multifunctional protein involved predominantly in the transport of cholesterol, maintenance of microtubules, neurones, and neural transmission. This gene is important in the neuronal response of the brain to injury and in the subsequent repair processes. There are three different variants (ε2, ε3, and ε4) to this gene and the variant ε4 situated on chromosome 19 is associated with the development of Alzheimer's disease, and predisposes to worse outcome in TBI [44–46].
The presence APOE-ε4 is associated with a poor outcome in cognitive dysfunction and functionality following brain injury rehabilitation [47–49]. It is also associated with a rapid cognitive decline in Alzheimer's disease  and in autopsy studies has been demonstrated to incur a significantly increased risk of development of cerebral amyloid angiopathy . In larger retrospective studies of outcome following TBI, the presence of APOE-ε4 correlates with a significantly worse outcome in young patiens (aged 0–15 years). This correlation reduces with age, with, neutralisation at 55 years .
The P53 gene is important in the regulation of apoptosis; this gene exhibits a common polymorphism that results in either proline or arginine at amino acid 72. Arg/Arg genotype of the Arg72Pro polymorphism in p53 is associated with an increased likelihood of a poor outcome at discharge from the surgical intensive care unit following TBI. 
Genes regulating the catecholamines
There are three isoforms of the enzyme catechol-o-methyltransferase (COMT) encoded by 3 genetic polymorphisms (COMT Val/Val, COMT Val/Met, and COMT Met/Met). This enzyme is associated with inactivation of dopamine and norepinephrine and is thought to functionally modulate dopamine neurons, thus influencing frontal-executive functioning. In a study by Lipsky et al (2005) in patients with TBI, polymorphism (Val/Val), and presumably lower cortical DA levels, resulted in worse performance on the Wisconsin Card Sorting Test compared to patients with the low activity polymorphism (Met/Met) and presumably higher cortical DA levels .
A variety of pharmacological agents have been trialed, all of which have shown promising results in animal models, but when translated into the clinical setting have universally failed to influence outcome following TBI. These agents include Selfotel, Cerestat, CP 101–606, D-CPP-ene, Steroids, tirilazad, PEG-SOD, IGF-1/growth hormone, Nimodipine, Bradycor, Dexanabinol, SNX-III, and anticonvulsants (such as Valproate and Magnesium Sulphate). The neuroprotective actions of these agents result from a variety of mechanisms of action, including antagonism of glutamate (Selfotel and CP 101–606), and free radical scavenging (PEG-SOD) .
Dexanabinol is a synthetic chemical analogue of the active component of marijuana. It is a non-competitive inhibitor of the NMDA receptor, a free radical scavenger and antioxidant, and an inhibitor of the pro-inflammatory cytokine TNF alpha .
Steroids are used with good effect in the treatment of brain oedema associated with brain tumours, and have been shown in laboratory studies to reduce free radical production and have a protective effect on the brain. However, several clinical studies in TBI have shown no clear beneficial effect on outcome or intracranial pressure .
One of the key factors in the management of TBI is maintenance of cerebral perfusion pressure and cerebral blood flow, and systemic administration of catecholamines is often used to achieve this. Circulating endogenous catecholamines are increased in TBI due to stimulation of the sympatho-adrenal axis. Endogenous circulating catecholamines are a readily quantifiable marker that predicts the outcome in TBI [52, 54]. It has been shown in rodents that optimal synthesis of catecholamines in the brain is critical to a working memory. TBI results in activation of tyrosine hydroxylase (TH) in the brain. This is the rate limiting step in catecholamine synthesis and changes in activation of TH result in altered catecholamine signalling in the prefrontal cortex which impacts on memory .
Neurotrophins are normally found in cell bodies and the projections of neurons, and they facilitate neuronal survival and differentiation [56, 57]. They include nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), neurotrophin-4 (NT-4) and neurotrophin-5 (NT-5). Of the neurotrophic agents, BDNF shows the most promise in the future management of brain injury. Animals treated with BDNF following TBI, showed an improvement in cognitive function and regeneration of the neural network which resembled developmental neuroplasticity. This was directly related to improvement in synchronized movement and spatial orientation [58, 59]. Unfortunately there is no convincing evidence for the use of these drugs in humans .
This review emphasises that the molecular mechanisms underlying secondary brain damage following TBI are complex. Our understanding of these mechanisms has increased significantly in recent years, but is far from complete. Advances in the acute management of TBI, is likely to be dependant both on an improved understanding of these mechanisms, as well as the translation of such knowledge into the development of new molecules and techniques to improve the clinical outcome.
- Sultan HY, Boyle A, Pereira M, Antoun N, Maimaris C: Application of the Canadian CT head rules in managing minor head injuries in a UK emergency department: implications for the implementation of the NICE guidelines. Emerg Med J. 2004, 21 (4): 420-5. 10.1136/emj.2003.011353.PubMed CentralView ArticlePubMedGoogle Scholar
- Fleminger S, Ponsford J: Long term outcome after traumatic brain injury (Editorial). BMJ. 2005, 331: 1419-20. 10.1136/bmj.331.7530.1419.PubMed CentralView ArticlePubMedGoogle Scholar
- Langlois JA, Rutland-Brown W, Thomas KE: Traumatic brain injury in the United States: emergency department visits, hospitalizations, and deaths. 2004, Atlanta (GA): Centers for Disease Control and Prevention. National Center for Injury Prevention and ControlGoogle Scholar
- Burdens of disease a discussion document. 1996, London: Department of Health, NHS Executive
- Perel P, Edwards P, Wentz R, Roberts I: Systematic review of prognostic models in traumatic brain injury. BMC Med Inform Decis Mak. 2006, 14 (6): 38-10.1186/1472-6947-6-38.View ArticleGoogle Scholar
- Narayan RK, Michel ME, Ansell B, Baethmann A, Biegon A, Bracken MB, Bullock MR, Choi SC, Clifton GL, Contant CF, Coplin WM, Dietrich WD, Ghajar J, Grady SM, Grossman RG, Hall ED, Heetderks W, Hovda DA, Jallo J, Katz RL, Knoller N, Kochanek PM, Maas AI, Majde J, Marion DW, Marmarou A, Marshall LF, McIntosh TK, Miller E, Mohberg N, Muizelaar JP, Pitts LH, Quinn P, Riesenfeld G, Robertson CS, Strauss KI, Teasdale G, Temkin N, Tuma R, Wade C, Walker MD, Weinrich M, Whyte J, Wilberger J, Young AB, Yurkewicz L: Clinical trials in head injury. J Neurotrauma. 2002, 19 (5): 503-57. 10.1089/089771502753754037. Review.PubMed CentralView ArticlePubMedGoogle Scholar
- Smith DH, Meaney DF: Axonal Damage in Traumatic Brain Injury. The Neuroscientist. 2000, 6: 483-495.View ArticleGoogle Scholar
- Bullock RM, Zauner A, Woodward JJ, Myseros J, Sung SC, Ward JD, Marmarou A, Young HF: Factors affecting excitatory amino acid release following severe human head injury. J Neurosurg. 1998, 89 (4): 507-18.View ArticlePubMedGoogle Scholar
- Ghirnikar RS, Lee YL, Eng LF: Inflammation in traumatic brain injury: role of cytokines and chemokines. Neurochem Res. 1998, 23 (3): 329-40. 10.1023/A:1022453332560.View ArticlePubMedGoogle Scholar
- Horvitz HR: Genetic control of programmed cell death in the nematode Caenorhabditis elegans. Cancer Res. 1999, 59 (7 Suppl): 1701s-1706s.PubMedGoogle Scholar
- Leira R, Dávalos A, Silva Y, Gil-Peralta A, Tejada J, Garcia M, Castillo J, Stroke Project, Cerebrovascular Diseases Group of the Spanish Neurological Society: Early neurologic deterioration in intracerebral hemorrhage: predictors and associated factors. Neurology. 2004, 63 (3): 461-7.View ArticlePubMedGoogle Scholar
- Martin NA, Patwardhan RV, Alexander MJ, Africk CZ, Lee JH, Shalmon E, Hovda DA, Becker DP: Characterization of cerebral hemodynamic phases following severe head trauma: hypoperfusion, hyperemia, and vasospasm. J Neurosurg. 1997, 87 (1): 9-19.View ArticlePubMedGoogle Scholar
- Morganti-Kossmann MC, Satgunaseelan L, Bye N, Kossmann T: Modulation of immune response by head injury. Injury. 2007, 38 (12): 1392-400. 10.1016/j.injury.2007.10.005.View ArticlePubMedGoogle Scholar
- Hlatky R, Valadka AB, Robertson CS: Intracranial hypertension and cerebral ischemia after severe traumatic brain injury. Neurosurg Focus. 2003, 14 (4): e2-10.3171/foc.2003.14.4.2. Review.View ArticlePubMedGoogle Scholar
- Graham DI, Adams JH, Doyle D: Ischaemic brain damage in fatal non-missile head injuries. J Neurol Sci. 1978, 39 (2–3): 213-34. 10.1016/0022-510X(78)90124-7.View ArticlePubMedGoogle Scholar
- Nandate K, Vuylsteke A, Crosbie AE, Messahel S, Oduro-Dominah A, Menon DK: Cerebrovascular cytokine responses during coronary artery bypass surgery: specific production of interleukin-8 and its attenuation by hypothermic cardiopulmonary bypass. Anesth Analg. 1999, 89 (4): 823-8. 10.1097/00000539-199910000-00003.PubMedGoogle Scholar
- Bell MJ, Kochanek PM, Doughty LA, Carcillo JA, Adelson PD, Clark RS, Wisniewski SR, Whalen MJ, DeKosky ST: Interleukin-6 and interleukin-10 in cerebrospinal fluid after severe traumatic brain injury in children. J Neurotrauma. 1997, 14 (7): 451-7. 10.1089/neu.1997.14.451.View ArticlePubMedGoogle Scholar
- Steiner LA, Coles JP, Johnston AJ, Czosnyka M, Fryer TD, Smielewski P, Chatfield DA, Salvador R, Aigbirhio FI, Clark JC, Menon DK, Pickard JD: Responses of posttraumatic pericontusional cerebral blood flow and blood volume to an increase in cerebral perfusion pressure. J Cereb Blood Flow Metab. 2003, 23 (11): 1371-1377. 10.1097/01.WCB.0000090861.67713.10.View ArticlePubMedGoogle Scholar
- Clark RS, Kochanek PM, Chen M, Watkins SC, Marion DW, Chen J, Hamilton RL, Loeffert JE, Graham SH: Increases in Bcl-2 and cleavage of caspase-1 and caspase-3 in human brain after head injury. FASEB J. 1999, 13 (8): 813-21.PubMedGoogle Scholar
- Castillo J, Dávalos A, Alvarez-Sabín J, Pumar JM, Leira R, Silva Y, Montaner J, Kase CS: Molecular signatures of brain injury after intracerebral hemorrhage. Neurology. 2002, 58 (4): 624-9.View ArticlePubMedGoogle Scholar
- Yang E, Korsmeyer SJ: Molecular thanatopsis: a discourse on the bcl2 family and cell death. Blood. 1996, 88 (2): 386-401.PubMedGoogle Scholar
- Kroemer G: The proto-oncogene Bcl-2 and its role in regulating apoptosis. Nat Med. 1997, 3 (6): 614-20. 10.1038/nm0697-614.View ArticlePubMedGoogle Scholar
- Graham SH, Chen J, Clark RS: Bcl-2 family gene products in cerebral ischemia and traumatic brain injury. J Neurotrauma. 2000, 17 (10): 831-841. 10.1089/neu.2000.17.831.View ArticlePubMedGoogle Scholar
- Kerr JF, Wyllie AH, Currie AR: Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics. Br J Cancer. 1972, 26 (4): 239-57.PubMed CentralView ArticlePubMedGoogle Scholar
- Rink A, Fung KM, Trojanowski JQ, Lee VM, Neugebauer E, McIntosh TK: Evidence of apoptotic cell death after experimental traumatic brain injury in the rat. Am J Pathol. 1995, 147 (6): 1575-83.PubMed CentralPubMedGoogle Scholar
- Tolias CM, Bullock MR: Critical appraisal of neuroprotection trials in head injury: what have we learned?. NeuroRx. 2004, 1 (1): 71-9. 10.1602/neurorx.1.1.71.PubMed CentralView ArticlePubMedGoogle Scholar
- Raghupathi R: Cell death mechanisms following traumatic brain injury. Brain Pathol. 2004, 14: 215-222.View ArticlePubMedGoogle Scholar
- Raghupathi R, Graham DI, McIntosh TK: Apoptosis after traumatic brain injury. J Neurotrauma. 2000, 17 (10): 927-38. 10.1089/neu.2000.17.927.View ArticlePubMedGoogle Scholar
- Okie S: Traumatic brain injury in the war zone. N Engl J Med. 2005, 352 (20): 2043-7. 10.1056/NEJMp058102.View ArticlePubMedGoogle Scholar
- Hoge CW, McGurk D, Thomas JL, Cox AL, Engel CC, Castro CA: Mild traumatic brain injury in U.S. Soldiers Returning from Iraq. N Engl J Med. 2008, 358 (5): 453-63. 10.1056/NEJMoa072972.View ArticlePubMedGoogle Scholar
- Yount R, Raschke KA, Biru M, Tate DF, Miller MJ, Abildskov T, Gandhi P, Ryser D, Hopkins RO, Bigler ED: Traumatic brain injury and atrophy of the cingulate gyrus. J Neuropsychiatry Clin Neurosci. 2002, 14 (4): 416-23.View ArticlePubMedGoogle Scholar
- Pierce JE, Smith DH, Trojanowski JQ, McIntosh TK: Enduring cognitive, neurobehavioral and histopathological changes persist for up to one year following severe experimental brain injury in rats. Neuroscience. 1998, 87 (2): 359-69. 10.1016/S0306-4522(98)00142-0.View ArticlePubMedGoogle Scholar
- Hopkins RO, Tate DF, Bigler ED: Anoxic versus traumatic brain injury: amount of tissue loss, not etiology, alters cognitive and emotional function. Neuropsychology. 2005, 19 (2): 233-42.z. 10.1037/0894-4184.108.40.206.View ArticlePubMedGoogle Scholar
- Stein LD: Human genome: end of the beginning. Nature. 2004, 431 (7011): 915-6. 10.1038/431915a.View ArticlePubMedGoogle Scholar
- Jennett B, Teasdale G, Braakman R, Minderhoud J, Heiden J, Kurze T: Prognosis of patients with severe head injury. Neurosurgery. 1979, 4 (4): 283-289. 10.1097/00006123-197904000-00001.View ArticlePubMedGoogle Scholar
- Kobori N, Clifton GL, Dash P: Altered expression of novel genes in the cerebral cortex following experimental brain injury. Brain Res Mol Brain Res. 2002, 104 (2): 148-58. 10.1016/S0169-328X(02)00331-5.View ArticlePubMedGoogle Scholar
- Takeda A, Onodera H, Sugimoto A, Itoyama Y, Kogure K, Shibahara S: Increased expression of heme oxygenase mRNA in rat brain following transient forebrain ischemia. Brain Res. 1994, 666 (1): 120-4. 10.1016/0006-8993(94)90292-5.View ArticlePubMedGoogle Scholar
- Morgan L, Cooper J, Montgomery H, Kitchen N, Humphries SE: The interleukin-6 gene -174G>C and -572G>C promoter polymorphisms are related to cerebral aneurysms. J Neurol Neurosurg Psychiatry. 2006, 77 (8): 915-7. 10.1136/jnnp.2005.081976.PubMed CentralView ArticlePubMedGoogle Scholar
- Yoon D, Pastore YD, Divoky V, Liu E, Mlodnicka AE, Rainey K, Ponka P, Semenza GL, Schumacher A, Prchal JT: Hypoxia-inducible factor-1 deficiency results in dysregulated erythropoiesis signaling and iron homeostasis in mouse development. J Biol Chem. 2006, 281 (35): 25703-11. 10.1074/jbc.M602329200.View ArticlePubMedGoogle Scholar
- Monacci WT, Merrill MJ, Oldfield EH: Expression of vascular permeability factor/vascular endothelial growth factor in normal rat tissues. Am J Physiol. 1993, 264 (4 Pt1): C995-1002.PubMedGoogle Scholar
- Stowe AM, Plautz EJ, Eisner-Janowicz I, Frost SB, Barbay S, Zoubina E, Dancause N, Taylor MD, Nudo RJ: VEGF protein associates to neurons in remote regions following cortical infarct. Journal of Cerebral Blood Flow & Metabolism. 2007, 27: 76-85. 10.1038/sj.jcbfm.9600320.View ArticleGoogle Scholar
- Stowe AM, Plautz EJ, Nguyen P, BFrost S, Eisner-Janowicz I, Barbay S, Dancause N, Sensarma A, Taylor MD, Zoubina EV, Nudo RJ: Neuronal HIF-1 protein and VEGFR-2 immunoreactivity in functionally related motor areas following a focal M1 infarct. Journal of Cerebral Blood Flow & Metabolism. 2008, 28: 612-620. 10.1038/sj.jcbfm.9600560.View ArticleGoogle Scholar
- Iyer NV, Kotch LE, Agani F, Leung SW, Laughner E, Wenger RH, Gassmann M, Gearhart JD, Lawler AM, Yu AY, Semenza GL: Cellular and developmental control of O2 homeostasis by hypoxia-inducible factor 1 alpha. Genes Dev. 1998, 12 (2): 149-162. 10.1101/gad.12.2.149.PubMed CentralView ArticlePubMedGoogle Scholar
- Teasdale TW: The apolipoprotein-epsilon4 gene: always harmful?. J Neurol Neurosurg Psychiatry. 2008, 79 (4): 364-5. 10.1136/jnnp.2007.138081.View ArticlePubMedGoogle Scholar
- Teasdale GM, Murray GD, Nicoll JAR: The association between APOE ε4, age and outcome after head injury: a prospective cohort study. Brain. 2005, 128: 2556-2561. 10.1093/brain/awh595.View ArticlePubMedGoogle Scholar
- Fine EM, Delis DC, Wetter SR, Jacobson MW, Jak AJ, McDonald CR, Braga JC, Thal LJ, Salmon DP, Bondi MW: Cognitive discrepancies versus APOE genotype as predictors of cognitive decline in normal-functioning elderly individuals: a longitudinal study. Am J Geriatr Psychiatry. 2008, 16 (5): 366-74. 10.1097/JGP.0b013e3181629957.PubMed CentralView ArticlePubMedGoogle Scholar
- Liberman JN, Stewart WF, Wesnes K, Troncoso J: Apolipoprotein E epsilon 4 and short-term recovery from predominantly mild brain injury. Neurology. 2002, 58 (7): 1038-44.View ArticlePubMedGoogle Scholar
- Koponen S, Taiminen T, Kairisto V, Portin R, Isoniemi H, Hinkka S, Tenovuo O: APOE-epsilon4 predicts dementia but not other psychiatric disorders after traumatic brain injury. Neurology. 2004, 63 (4): 749-50.View ArticlePubMedGoogle Scholar
- Crawford FC, Vanderploeg RD, Freeman MJ, Singh S, Waisman M, Michaels L, Abdullah L, Warden D, Lipsky R, Salazar A, Mullan MJ: APOE genotype influences acquisition and recall following traumatic brain injury. Neurology. 2002, 58 (7): 1115-8.View ArticlePubMedGoogle Scholar
- Wilson M, Montgomery H: Impact of genetic factors on outcome from. Br J Anaesth. 2007, 99 (1): 43-48. 10.1093/bja/aem142.View ArticlePubMedGoogle Scholar
- Leclercq PD, Graham DI, Nicoll JA, Gentleman SM: Influence of ApoE genotype on cerebral amyloid angiopathy after closed head injury. Neuropathol Appl Neurobiol. 2002, 28 (2): 161-2. 10.1046/j.1365-2990.2002.39286_37.x.View ArticleGoogle Scholar
- Martínez-Lucas P, Moreno-Cuesta J, García-Olmo DC, Sánchez-Sánchez F, Escribano-Martínez J, del Pozo AC, Lizán-García M, García-Olmo D: Relationship between the Arg72Pro polymorphism of p53 and outcome for patients with traumatic brain injury. Intensive Care Med. 2005, 31 (9): 1168-73. 10.1007/s00134-005-2715-0.View ArticlePubMedGoogle Scholar
- Lipsky RH, Sparling MB, Ryan LM, Xu K, Salazar AM, Goldman D, Warden DL: Association of COMT Val158Met genotype with executive functioning following traumatic brain injury. J Neuropsychiatry Clin Neurosci. 2005, 17 (4): 465-71.View ArticlePubMedGoogle Scholar
- Hamill RW, Woolf PD, McDonald JV, Lee LA, Kelly M: Catecholamines predict outcome in traumatic brain injury. Ann Neurol. 1987, 21 (5): 438-443. 10.1002/ana.410210504.View ArticlePubMedGoogle Scholar
- Kobori N, Clifton GL, Dash PK: Enhanced catecholamine synthesis in the prefrontal cortex after traumatic brain injury: implications for prefrontal dysfunction. J Neurotrauma. 2006, 23 (7): 1094-102. 10.1089/neu.2006.23.1094.View ArticlePubMedGoogle Scholar
- Cheng B, Mattson MP: NT-3 and BDNF protect CNS neurons against metabolic/excitotoxic insults. Brain Res. 1994, 640 (1–2): 56-67. 10.1016/0006-8993(94)91857-0.View ArticlePubMedGoogle Scholar
- Mahmood A, Lu D, Wang L, Chopp M: Intracerebral transplantation of marrow stromal cells cultured with neurotrophic factors promotes functional recovery in adult rats subjected to traumatic brain injury. J Neurotrauma. 2002, 19 (12): 1609-17. 10.1089/089771502762300265.View ArticlePubMedGoogle Scholar
- Willson ML, McElnea C, Mariani J, Lohof AM, Sherrard RM: BDNF increases homotypic olivocerebellar reinnervation and associated fine motor and cognitive skill. Brain. 2008, 131 (Pt 4): 1099-112. 10.1093/brain/awn024.View ArticlePubMedGoogle Scholar
- Dixon KJ, Sherrard RM: Brain-derived neurotrophic factor induces post-lesion transcommissural growth of olivary axons that develop normal climbing fibers on mature Purkinje cells. Exp Neurol. 2006, 202 (1): 44-56. 10.1016/j.expneurol.2006.05.010.View ArticlePubMedGoogle Scholar
- Faden AI: Neuroprotection and traumatic brain injury: theoretical option or realistic proposition. Curr Opin Neurol. 2002, 15 (6): 707-12. 10.1097/00019052-200212000-00008.View ArticlePubMedGoogle Scholar
This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.