Head injury and dementia

Neuropsychiatric complications of traumatic brain injury

Traumatic brain injury (TBI) may be defined as any extracranial mechanical force to the brain that results in any period of loss of consciousness, any loss of memory for events immediately before or after the event, or any alteration in mental status at the time of the event. The major causes are automobile accidents, falls, sporting injuries, and assaults. Many soldiers returning from combat in Afghanistan and Iraq have also experienced TBI. This article provides an overview of the neuropsychiatric complications of TBI, including impairment of consciousness, posttraumatic amnesia, cognitive disorders and dementia, posttraumatic epilepsy, aphasia, depression, mania, psychosis, anxiety disorders, personality changes, aggression, behavioral dyscontrol, fatigue/apathy, and increased risk of suicide. Discussion will focus primarily on issues affecting mental health clinicians. Because mental health providers are more involved in care of chronic issues related to TBI, these issues will be discussed in more detail, although acute neuropsychiatric complications of TBI will be briefly explained.

Endurance training and cardiorespiratory conditioning after traumatic brain injury

OBJECTIVE

To examine the importance of cardiorespiratory conditioning after traumatic brain injury (TBI) and provide recommendations for patients recovering from TBI.

METHOD

Review of literature assessing the effectiveness of endurance training programs.

MAIN OUTCOMES AND RESULTS

A sedentary lifestyle and lack of endurance are common characteristics of individuals with TBI who have a reduction in peak aerobic capacity of 25% to 30% compared with healthy sedentary persons. Increased physical activity and exercise training improves cardiorespiratory fitness in many populations with physical and cognitive impairments. Therefore, increasing the endurance and cardiorespiratory fitness of persons with TBI would seem to have important health implications. However, review of the TBI literature reveals that there have been few well-designed, well-controlled studies of physiologic and psychological adaptations of fitness training. Also lacking are long-term follow-up studies of persons with TBI.

CONCLUSIONS

Assessing endurance capacity and cardiorespiratory fitness early in the TBI rehabilitation process merits consideration as a standard of care by professional rehabilitation societies. Also, providing effective, safe, and accessible training modalities would seem to be an important consideration for persons with TBI, given the mobility impairments many possess. Long-term follow-up studies are needed to assess the effectiveness of cardiorespiratory training programs on overall morbidity and mortality.

Blast-related brain injury: imaging for clinical and research applications: report of the 2008 st. Louis workshop

Blast-related traumatic brain injury (bTBI) and post-traumatic stress disorder (PTSD) have been of particular relevance to the military and civilian health care sectors since the onset of the Global War on Terror, and TBI has been called the "signature injury" of this war. Currently there are many questions about the fundamental nature, diagnosis, and long-term consequences of bTBI and its relationship to PTSD. This workshop was organized to consider these questions and focus on how brain imaging techniques may be used to enhance current diagnosis, research, and treatment of bTBI. The general conclusion was that although the study of blast physics in non-biological systems is mature, few data are presently available on key topics such as blast exposure in combat scenarios, the pathological characteristics of human bTBI, and imaging signatures of bTBI. Addressing these gaps is critical to the success of bTBI research. Foremost among our recommendations is that human autopsy and pathoanatomical data from bTBI patients need to be obtained and disseminated to the military and civilian research communities, and advanced neuroimaging used in studies of acute, subacute, and chronic cases, to determine whether there is a distinct pathoanatomical signature that correlates with long-term functional impairment, including PTSD. These data are also critical for the development of animal models to illuminate fundamental mechanisms of bTBI and provide leads for new treatment approaches. Brain imaging will need to play an increasingly important role as gaps in the scientific knowledge of bTBI and PTSD are addressed through increased coordination, cooperation, and data sharing among the academic and military biomedical research communities.

Lipid oxidation and peroxidation in CNS health and disease: from molecular mechanisms to therapeutic opportunities

Reactive oxygen species (ROS) are produced at low levels in mammalian cells by various metabolic processes, such as oxidative phosphorylation by the mitochondrial respiratory chain, NAD(P)H oxidases, and arachidonic acid oxidative metabolism. To maintain physiological redox balance, cells have endogenous antioxidant defenses regulated at the transcriptional level by Nrf2/ARE. Oxidative stress results when ROS production exceeds the cell's ability to detoxify ROS. Overproduction of ROS damages cellular components, including lipids, leading to decline in physiological function and cell death. Reaction of ROS with lipids produces oxidized phospholipids, which give rise to 4-hydroxynonenal, 4-oxo-2-nonenal, and acrolein. The brain is susceptible to oxidative damage due to its high lipid content and oxygen consumption. Neurodegenerative diseases (AD, ALS, bipolar disorder, epilepsy, Friedreich's ataxia, HD, MS, NBIA, NPC, PD, peroxisomal disorders, schizophrenia, Wallerian degeneration, Zellweger syndrome) and CNS traumas (stroke, TBI, SCI) are problems of vast clinical importance. Free iron can react with H(2)O(2) via the Fenton reaction, a primary cause of lipid peroxidation, and may be of particular importance for these CNS injuries and disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Atherosclerosis, the major risk factor for ischemic stroke, involves accumulation of oxidized LDL in the arteries, leading to foam cell formation and plaque development. This review will discuss the role of lipid oxidation/peroxidation in various CNS injuries/disorders.

Olfaction in aging and Alzheimer's disease: event-related potentials to a cross-modal odor-recognition memory task discriminate ApoE epsilon4+ and ApoE epsilon 4- individuals

Alzheimer's disease (AD) is a devastating neurodegenerative condition that affects more than 5 million Americans. Currently, a definitive and unequivocal diagnosis of AD can only be confirmed histopathogically via postmortem autopsy, demonstrating the need for objective measures of cognitive functioning for those at risk for AD. The single most important genetic risk factor of AD is the apolipoprotein E (ApoE) epsilon4 allele. The present study investigated olfactory and cognitive processing deficits in ApoE epsilon4(+) individuals using a cross-modal recognition memory task and an objective electrophysiological measure, the event-related potential (ERP). Ten epsilon4(+) individuals (5 M, 5 F, mean [M]= 75.1 years) and 10 age- and gender-matched epsilon4(-) individuals (5 M, 5 F, M = 71 years) sequentially encoded a set of 16 olfactory stimuli and were subsequently shown names of odors previously presented (targets) or not (foils). EEG activity was recorded from 19 electrodes as participants distinguished targets from foils using a two-button mouse. P3 latencies were significantly longer in epsilon4(+) individuals, and intraclass correlations demonstrated differential activity between the two groups. These findings are consistent with a compensatory hypothesis, which posits that nondemented epsilon4(+) individuals will expend greater effort in cognitive processing or engage in alternative strategies and therefore require greater activation of neural tissue or recruitment of different neural populations. The findings also suggest that cross-modal ERP studies of recognition memory discriminate early neurocognitive changes in ApoE epsilon4(+) and ApoE epsilon4(-) individuals and may contribute to identifying the phenotype of persons who will develop Alzheimer's disease.

Neuropsychological consequences of boxing and recommendations to improve safety: a National Academy of Neuropsychology education paper

Boxing has held appeal for many athletes and audiences for centuries, and injuries have been part of boxing since its inception. Although permanent and irreversible neurologic dysfunction does not occur in the majority of participants, an association has been reported between the number of bouts fought and the development of neurologic, psychiatric, or histopathological signs and symptoms of encephalopathy in boxers. The purpose of this paper is to (i) provide clinical neuropsychologists, other health-care professionals, and the general public with information about the potential neuropsychological consequences of boxing, and (ii) provide recommendations to improve safety standards for those who participate in the sport.

The prevalence, correlates and impact of dementia in Cuba. A 10/66 group population-based survey

BACKGROUND

We aimed to estimate the prevalence, correlates and impact of dementia in Havana and Matanzas, Cuba.

METHODS

A 1-phase catchment area survey of all over 65-year-old residents of 7 catchment areas in Havana and 1 in Matanzas was conducted. Dementia diagnosis was established according to DSM-IV and our own, pre-validated 10/66 criteria. The impact of dementia was assessed through associations with needs for care, cutting back on work to care and caregiver psychological morbidity.

RESULTS

We interviewed 2,944 older people, a response proportion of 96.4%. The prevalence of DSM-IV dementia was 6.4% and that of 10/66 dementia 10.8%. Both dementia outcomes were associated with older age, less education, a family history of dementia, shorter leg length and smaller skull circumference. Dementia, rather than physical health problems or depression, was the main contributor to needs for care (population-attributable prevalence fraction = 64.6%) and caregiver cutting back on work (population-attributable prevalence fraction = 57.3%).

CONCLUSION

The prevalence of dementia in Cuba is similar to Europe. Among health conditions, dementia is the major contributor to dependency and caregiver economic and psychological strain. More attention needs to be given to it and other chronic diseases associated more with disability than premature mortality.

Time-dependent alterations of cholinergic markers after experimental traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of death and disability. Cognitive deficits are believed to be connected with impairments of the cholinergic system. The present study was conducted to evaluate the cholinergic system in a model of focal brain injury with special attention to the time course of posttraumatic events in critical brain regions. Three groups of male Sprague-Dawley rats (post-TBI survival time: 2 h, 24 h and 72 h) were subjected to sham-operation (control) or controlled cortical impact injury. Receptor densities were determined on frozen ipsilateral sagittal brain sections with [(3)H]epibatidine (nicotinic acetylcholine receptors) and [(3)H]QNB (muscarinic acetylcholine receptors). The density of the vesicular acetylcholine transporter (vAChT) was evaluated with (-)[(3)H]vesamicol. Compared to control, vAChT was lowered (up to 50%) at each time point after trauma, with reductions in olfactory tubercle, basal forebrain, motor cortex, putamen, thalamic and hypothalamic areas and the gigantocellular reticular nucleus. Time-dependent reductions of about 20% of nAChR-density in the thalamus, hypothalamus, olfactory tubercle, gigantocellular reticular nucleus and motor cortex were observed post-TBI at 24 and 72 h. The same brain regions showed reductions of mAChR at 24 and 72 h after trauma with additional decreases in the corpus callosum, basal forebrain and anterior olfactory nucleus. In conclusion, cholinergic markers showed significant time-dependent impairments after TBI. Considering the role of the cholinergic system for cognitive processes in the brain, it seems likely that these impairments contribute to clinically relevant cognitive deficits.

Active and passive immunotherapy for neurodegenerative disorders

Immunotherapeutic strategies to combat neurodegenerative disorders have galvanized the scientific community since the first dramatic successes in mouse models recreating aspects of Alzheimer disease (AD) were reported. However, initial human trials of active amyloid-beta (Abeta) vaccination were halted early because of a serious safety issue: meningoencephalitis in 6% of subjects. Nonetheless, some encouraging preliminary data were obtained, and rapid progress has been made toward developing alternative, possibly safer active and passive immunotherapeutic approaches for several neurodegenerative conditions. Many of these are currently in human trials for AD. Despite these advances, our understanding of the essential mechanisms underlying the effects seen in preclinical models and human subjects is still incomplete. Antibody-induced phagocytosis of pathological protein deposits, direct antibody-mediated disruption of aggregates, neutralization of toxic soluble proteins, a shift in equilibrium toward efflux of specific proteins from the brain, cell-mediated immune responses, and other mechanisms may all play roles depending on the specific immunotherapeutic scenario.

Amyloid-beta dynamics correlate with neurological status in the injured human brain

The amyloid-beta peptide (Abeta) plays a central pathophysiological role in Alzheimer's disease, but little is known about the concentration and dynamics of this secreted peptide in the extracellular space of the human brain. We used intracerebral microdialysis to obtain serial brain interstitial fluid (ISF) samples in 18 patients who were undergoing invasive intracranial monitoring after acute brain injury. We found a strong positive correlation between changes in brain ISF Abeta concentrations and neurological status, with Abeta concentrations increasing as neurological status improved and falling when neurological status declined. Brain ISF Abeta concentrations were also lower when other cerebral physiological and metabolic abnormalities reflected depressed neuronal function. Such dynamics fit well with the hypothesis that neuronal activity regulates extracellular Abeta concentration.

Introspective analysis of amyloid as the cause of Alzheimer’s disease: alternative model proposed

As the lifespan of the population of developed countries increases, we are faced with managing a disease that is taking almost epidemic proportions and has a high social and economical cost; Alzheimer’s disease (AD). As everyone knows, AD robs the person not only of their memories but also their personalities and leaves only the shell of a once vibrant and functional human being that now requires care 24-h a day. Similar to the race to prevent, treat or cure cancer and heart diseases, it is essential and of extreme urgency to spearhead efforts against AD. To date, there are no effective treatments against AD. Amyloid is largely favored as the cause of the disease. Immense resources and efforts have been dedicated to anti-amyloid therapies and we are at the cusp of finding out if these will work of not. However, the arguments supporting the amyloid hypothesis can be challenged and an alternate model is presented herein.

Association of APOE with age at onset of sporadic amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a neurodegenerative syndrome with familial and sporadic forms. We conducted a study including 60 sporadic and 19 familial ALS patients, 206 reference patients with other neurological disorders and 1265 neurologically healthy controls to assess the Alzheimer-associated apolipoprotein E (APOE) epsilon4 gene variant as a possible risk factor for ALS. While no major influence of APOE epsilon4 on disease risk was detected, a gene dose-dependent effect with lower age at onset of sporadic ALS in epsilon4 carriers was found (p=0.027). These data support APOE epsilon4 as a subordinate contributing factor in ALS.

Alterations of acetylcholinesterase activity after traumatic brain injury in rats

OBJECTIVE

The cholinergic system is highly vulnerable to traumatic brain injury (TBI). However, limited information is available to what extent the degrading enzyme acetylcholinesterase (AChE) is involved. The present study addresses this question.

METHOD

Thirty-six anaesthetized Sprague-Dawley rats were subjected to sham operation or to TBI using controlled cortical impact (CCI). The AChE activity was histochemically determined in frozen brain slices at 2, 24 and 72 hours after TBI.

RESULTS

High enzyme activity was observed in regions rich in cholinergic innervation such as the olfactory tubercle, basal forebrain, putamen and superior colliculi. Low activity was found in the cortex, cerebellum and particularly in the white matter. A decrease of AchE activity (20-35%) was found in the hippocampus and hypothalamus already at 2 hours after TBI. An increase of approximately 30% was found in the basal forebrain at 2 and 24 hours. No changes occurred at 72 hours.

CONCLUSION

The findings are consistent with impairment of the cholinergic neurotransmission after TBI and suggest the involvement of the AChE in short-term regulatory mechanisms.

Neuropsychological contributions to the early identification of Alzheimer's disease

A wealth of evidence demonstrates that a prodromal period of Alzheimer's disease (AD) exists for some years prior to the appearance of significant cognitive and functional declines required for the clinical diagnosis. This prodromal period of decline is characterized by a number of different neuropsychological and brain changes, and reliable identification of individuals prior to the development of significant clinical symptoms remains a top priority of research. In this review we provide an overview of those neuropsychological changes. In particular, we examine specific domains of cognition that appear to be negatively affected during the prodromal period of AD, and we review newer analytic strategies designed to examine cognitive asymmetries or discrepancies between higher-order cognitive functions versus fundamental skills. Finally, we provide a critical examination of the clinical concept of Mild Cognitive Impairment and offer suggestions for an increased focus on the impact of cerebrovascular disease (CVD) and CVD risk during the prodromal period of AD.

Antiinflammatory and neuroprotective actions of COX2 inhibitors in the injured brain

Overexpression of COX2 appears to be both a marker and an effector of neural damage after a variety of acquired brain injuries, and in natural or pathological aging of the brain. COX2 inhibitors may be neuroprotective in the brain by reducing prostanoid and free radical synthesis, or by directing arachidonic acid down alternate metabolic pathways. The arachidonic acid shunting hypothesis proposes that COX2 inhibitors' neuroprotective effects may be mediated by increased formation of potentially beneficial eicosanoids. Under conditions where COX2 activity is inhibited, arachidonic acid accumulates or is converted to eicosanoids via lipoxygenases and cytochrome P450 (CYP) epoxygenases. Several P450 eicosanoids have been demonstrated to have beneficial effects in the brain and/or periphery. We suspect that arachidonic acid shunting may be as important to functional recovery after brain injuries as altered prostanoid formation per se. Thus, COX2 inhibition and arachidonic acid shunting have therapeutic implications beyond the suppression of prostaglandin synthesis and free radical formation.

Neuropsychological contributions to the early identification of Alzheimer's disease

A wealth of evidence demonstrates that a prodromal period of Alzheimer's disease (AD) exists for some years prior to the appearance of significant cognitive and functional declines required for the clinical diagnosis. This prodromal period of decline is characterized by a number of different neuropsychological and brain changes, and reliable identification of individuals prior to the development of significant clinical symptoms remains a top priority of research. In this review we provide an overview of those neuropsychological changes. In particular, we examine specific domains of cognition that appear to be negatively affected during the prodromal period of AD, and we review newer analytic strategies designed to examine cognitive asymmetries or discrepancies between higher-order cognitive functions versus fundamental skills. Finally, we provide a critical examination of the clinical concept of Mild Cognitive Impairment and offer suggestions for an increased focus on the impact of cerebrovascular disease (CVD) and CVD risk during the prodromal period of AD.

Neurobehavioral sequelae of traumatic brain injury: evaluation and management

Traumatic brain injury (TBI) is a worldwide public health problem. Over the last several decades, improvements in acute care have resulted in higher survival rates. Unfortunately, the majority of survivors of moderate and severe TBI have chronic neurobehavioral sequelae, including cognitive deficits, changes in personality and increased rates of psychiatric illness. These neurobehavioral problems are understandable in the context of the typical profile of regional brain damage associated with trauma. This paper presents an overview of the neurobehavioral sequelae of TBI and outlines issues to consider in the evaluation and management of these challenges.

Altered lipid metabolism in brain injury and disorders

Deregulated lipid metabolism may be of particular importance for CNS injuries and disorders, as this organ has the highest lipid concentration next to adipose tissue. Atherosclerosis (a risk factor for ischemic stroke) results from accumulation of LDL-derived lipids in the arterial wall. Pro-inflammatory cytokines (TNF-alpha and IL-1), secretory phospholipase A2 IIA and lipoprotein-PLA2 are implicated in vascular inflammation. These inflammatory responses promote atherosclerotic plaques, formation and release of the blood clot that can induce ischemic stroke. TNF-alpha and IL-1 alter lipid metabolism and stimulate production of eicosanoids, ceramide, and reactive oxygen species that potentiate CNS injuries and certain neurological disorders. Cholesterol is an important regulator of lipid organization and the precursor for neurosteroid biosynthesis. Low levels of neurosteroids were related to poor outcome in many brain pathologies. Apolipoprotein E is the principal cholesterol carrier protein in the brain, and the gene encoding the variant Apolipoprotein E4 is a significant risk factor for Alzheimer's disease. Parkinson's disease is to some degree caused by lipid peroxidation due to phospholipases activation. Niemann-Pick diseases A and B are due to acidic sphingomyelinase deficiency, resulting in sphingomyelin accumulation, while Niemann-Pick disease C is due to mutations in either the NPC1 or NPC2 genes, resulting in defective cholesterol transport and cholesterol accumulation. Multiple sclerosis is an autoimmune inflammatory demyelinating condition of the CNS. Inhibiting phospholipase A2 attenuated the onset and progression of experimental autoimmune encephalomyelitis. The endocannabinoid system is hypoactive in Huntington's disease. Ethyl-eicosapetaenoate showed promise in clinical trials. Amyotrophic lateral sclerosis causes loss of motorneurons. Cyclooxygenase-2 inhibition reduced spinal neurodegeneration in amyotrophic lateral sclerosis transgenic mice. Eicosapentaenoic acid supplementation provided improvement in schizophrenia patients, while the combination of (eicosapentaenoic acid + docosahexaenoic acid) provided benefit in bipolar disorders. The ketogenic diet where >90% of calories are derived from fat is an effective treatment for epilepsy. Understanding cytokine-induced changes in lipid metabolism will promote novel concepts and steer towards bench-to-bedside transition for therapies.

Alzheimer's disease-related changes in diseases characterized by elevation of intracranial or intraocular pressure

In this review, we focus on the coexistence of Alzheimer's disease-related changes in brain diseases, such as normal pressure hydrocephalus and traumatic brain injury, and in glaucoma at the level of the retinal ganglion cells. This is a group of diseases that affect central nervous system tissue and are characterized by elevation of intracranial or intraocular pressure and/or local shear stress and strain. In considering possible mechanisms underlying Alzheimer-type changes in these diseases, we briefly summarize recent evidence indicating that caspase activation and abnormal processing of beta-amyloid precursor protein, which are important events in Alzheimer's disease, may play a role both in glaucoma and following traumatic brain injury. With regard to normal pressure hydrocephalus, evidence suggests that changes in cerebrospinal fluid circulatory dynamics ultimately may result in reduced clearance of neurotoxins, such as beta-amyloid peptides and tau protein, that play a role in the pathogenesis of Alzheimer's disease. Data presented in this review could be interpreted to suggest that Alzheimer-type changes in these diseases may result at least in part from exposure of central nervous system tissue to increased levels of mechanical stress. Evidence for such a relationship is of major importance because it may support an association between elevated mechanical load and the development of Alzheimer-type lesions. Further studies are warranted, however, especially to elucidate the role of elevated mechanical forces in Alzheimer's disease neuropathogenesis.

Role of Lipids in Brain Injury and Diseases

Lipid metabolism is of particular interest due to its high concentration in CNS. The importance of lipids in cell signaling and tissue physiology is demonstrated by many CNS disorders and injuries that involve deregulated metabolism. The long suffering lipid field is gaining reputation and respect as evidenced through the Center of Biomedical Research Excellence in Lipidomics and Pathobiology (COBRE), Lipid MAPS (Metabolites And Pathways Strategy) Consortium sponsored by NIH, European initiatives for decoding the lipids through genomic approaches, and Genomics of Lipid-associated Disorder (GOLD) project initiated by Austrian government. This review attempts to provide an overview of the lipid imbalances associated with neurological disorders (Alzheimer's, Parkinson's; Niemann-Pick; Multiple sclerosis, Huntington, amyotrophic lateral sclerosis, schizophrenia, bipolar disorders and epilepsy) and CNS injury (Stroke, traumatic brain injury; and spinal cord injury) and a few provocative thoughts. Lipidomic analyses along with RNA silencing will provide new insights into the role of lipid intermediates in cell signaling and hopefully open new avenues for prevention or treatment options.

Electromagnetic controlled cortical impact device for precise, graded experimental traumatic brain injury

Genetically modified mice represent useful tools for traumatic brain injury (TBI) research and attractive preclinical models for the development of novel therapeutics. Experimental methods that minimize the number of mice needed may increase the pace of discovery. With this in mind, we developed and characterized a prototype electromagnetic (EM) controlled cortical impact device along with refined surgical and behavioral testing techniques. By varying the depth of impact between 1.0 and 3.0 mm, we found that the EM device was capable of producing a broad range of injury severities. Histologically, 2.0-mm impact depth injuries produced by the EM device were similar to 1.0-mm impact depth injuries produced by a commercially available pneumatic device. Behaviorally, 2.0-, 2.5-, and 3.0-mm impacts impaired hidden platform and probe trial water maze performance, whereas 1.5-mm impacts did not. Rotorod and visible platform water maze deficits were also found following 2.5- and 3.0-mm impacts. No impairment of conditioned fear performance was detected. No differences were found between sexes of mice. Inter-operator reliability was very good. Behaviorally, we found that we could statistically distinguish between injury depths differing by 0.5 mm using 12 mice per group and between injury depths differing by 1.0 mm with 7-8 mice per group. Thus, the EM impactor and refined surgical and behavioral testing techniques may offer a reliable and convenient framework for preclinical TBI research involving mice.

Age-related inflammatory diseases: role of genetics and gender in the pathophysiology of Alzheimer's disease

Alzheimer's disease (AD) is a heterogeneous and progressive neurodegenerative disease which in Western societies mainly accounts for clinical dementia. A high proportion of women are affected by this disease, especially at a very advanced age, which might to a large extent be associated with the fact that women live longer. However, some studies suggest that incidence rates may be really increased in women. For this reason the influence of estrogens on the brain and the decrease of it during menopause are of special interest. After menopause, circulating levels of estrogens markedly decline, influencing several brain processes predicted to influence AD risk. The control of estrogens on oxidative stress, inflammation, and the cerebral vasculature might also be expected to increase AD risk. During the Women's Health Initiative Memory Study--a randomized, placebo-controlled trial of women 65-79 years of age--oral estrogen plus progestin was seen to double the rate of developing dementia, with risk appearing soon after the treatment was initiated. On the basis of current evidence, hormone therapy (HT) is thus not indicated for the prevention of AD. Inflammation clearly occurs in pathologically vulnerable regions of the AD brain and the search for genetic factors influencing the pathogenesis of AD has led to the identification of numerous gene polymorphisms that act as susceptibility modifiers. Accordingly, several reports have indicated that the risk of AD is substantially influenced by several genetic polymorphisms in the promoter region, or other untranslated regions, of genes encoding inflammatory mediators. Here we review several data suggesting that inflammatory genetic variation may contribute to higher AD susceptibility in women too. All together this information may represent the basis both for future recognition of individuals at risk as well as for a pharmacogenomic approach in achieving drug responsiveness.

Structure and functions of the human amyloid precursor protein: the whole is more than the sum of its parts

The amyloid precursor protein (APP) is a transmembrane protein that plays major roles in the regulation of several important cellular functions, especially in the nervous system, where it is involved in synaptogenesis and synaptic plasticity. The secreted extracellular domain of APP, sAPPalpha, acts as a growth factor for many types of cells and promotes neuritogenesis in post-mitotic neurons. Alternative proteolytic processing of APP releases potentially neurotoxic species, including the amyloid-beta (Abeta) peptide that is centrally implicated in the pathogenesis of Alzheimer's disease (AD). Reinforcing this biochemical link to neuronal dysfunction and neurodegeneration, APP is also genetically linked to AD. In this review, we discuss the biological functions of APP in the context of tissue morphogenesis and restructuring, where APP appears to play significant roles both as a contact receptor and as a diffusible factor. Structural investigation of APP, which is necessary for a deeper understanding of its roles at a molecular level, has also been advancing rapidly. We summarize recent progress in the determination of the structure of isolated APP fragments and of the conformations of full-length sAPPalpha, in both monomeric and dimeric states. The potential role of APP dimerization for the regulation of its biological functions is also discussed.

Traumatic brain injury and Alzheimer's disease: a review

In an effort to identify the factors that are involved in the pathogenesis of Alzheimer's disease (AD), epidemiological studies have featured prominently in contemporary research. Of those epidemiological factors, accumulating evidence implicates traumatic brain injury (TBI) as a possible predisposing factor in AD development. Exactly how TBI triggers the neurodegenerative cascade of events in AD remains controversial. There has been extensive research directed towards understanding the potential relationship between TBI and AD and the putative influence that apolipoprotein E (APOE) genotype has on this relationship. The aim of the current paper is to provide a critical summary of the experimental and human studies regarding the association between TBI, AD and APOE genotype. It will be shown that despite significant discrepancies in the literature, there still appears to be an increasing trend to support the hypothesis that TBI is a potential risk factor for AD. Furthermore, although it is known that APOE genotype plays an important role in AD, its link to a deleterious outcome following TBI remains inconclusive and ambiguous.

The neurosteroid allopregnanolone is reduced in prefrontal cortex in Alzheimer's disease

BACKGROUND

Few data are currently available investigating neurosteroids (NS) in Alzheimer's disease (AD). The NS allopregnanolone may be decreased in serum and plasma in patients with AD, but it is unclear if allopregnanolone is also reduced in brain. Because a number of NS exhibit neuroprotective effects and impact cognitive performance in rodent models, these molecules may be relevant to the pathophysiology of neurodegenerative disorders. We therefore investigated prefrontal cortex (PFC) NS levels in AD.

METHODS

Neurosteroid levels (allopregnanolone, pregnenolone, dehydroepiandrosterone [DHEA]) were determined in postmortem PFC in 14 male subjects with AD and 15 cognitively intact male control subjects by gas chromatography/mass spectrometry preceded by high-performance liquid chromatography purification.

RESULTS

Subjects with AD exhibit significant reductions in allopregnanolone compared with cognitively intact control subjects (median levels = 2.50 ng/g vs. 5.59 ng/g, respectively; p = .02). Allopregnanolone levels are inversely correlated with neuropathological disease stage (Braak), r = -.49, p = .007. Median DHEA levels are elevated in subjects with AD (p = .01).

CONCLUSIONS

Subjects with AD demonstrate significant reductions in PFC allopregnanolone levels, a finding that may be relevant to neuropathological disease stage severity. Neurosteroids may have utility as candidate biomarkers in AD.

Promoter polymorphisms which modulate APP expression may increase susceptibility to Alzheimer's disease

Increasing evidence indicates that variants in promoter of the beta-amyloid precursor protein (APP) gene could up-regulate the APP gene expression and aggravate the amyloid beta protein (A beta) accumulation, thus contributing to the development of Alzheimer's disease (AD). In Chinese Han populations we found three polymorphisms in APP promoter: -877T/C(rs466433), -955A/G(rs364048) and -9G/C. The -877T and -955A alleles were over-represented in 209 sporadic AD (SAD) patients when compared to those in 437 healthy individuals. Furthermore, -877T/C and -955A/G were in strong linkage disequilibrium and they constructed a relatively risky -877T/-955A and a relatively protective -877C/-955G. Luciferase reporter assay indicated -877T/-955A had four times higher transcriptional activity than -877C/-955G. A more marked increase in -877T/-955A transcriptional activity was seen when under A beta(25-35) treatment. As for the -9G/C polymorphism, significant differences between the two alleles were not observed either in genetic evaluation or in functional assay. The present study provides strong evidence that APP promoter polymorphisms that significantly increase APP expression levels are associated with development of SAD.

Association of DSC1, a gene modulated by adrenergic stimulation, with Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial disorder involving a number of genetic and environmental factors, with severe head injury consistently reported as a major non-genetic risk factor. The adrenergic activation that occurs during major trauma increases cAMP levels, therefore the cAMP signaling pathway might be involved in AD pathogenesis. Time course of candidate gene expression following adrenergic stimulation with isoproterenol was assayed in neuroblastoma cells by quantitative reverse transcription (RT)-PCR. Then, genetic association studies of polymorphisms in several of these candidate genes were performed. Association studies in two independent case-control samples showed a polymorphism in DSC1, encoding desmocollin 1--a member of the desmosomal cadherins--which modulated AD susceptibility in a gender-specific manner. These results are in accordance with the potential involvement of the adrenergic signaling pathway in AD pathogenesis.

Risk factors for Alzheimer's disease in Russia: a case-control study

No reliable data on risk factors of Alzheimer's disease (AD) are available in Russia. We aimed to evaluate the relative importance of various putative environmental and medical risk factors of AD in a Russian population. We conducted a hospital-based case-control study. Two hundred and sixty consecutive AD patients and an equal number of cognitive impairment-free control subjects matched for sex, age, level of education and place of birth selected from nursing homes and other long-term healthcare facilities in the Novosibirsk region for the period from 1998 to 2002 were examined. A conditional logistic regression analysis was employed to calculate odds ratios (OR) and corresponding 95% confidence intervals (CI) for various putative risk factors. Of the 260 patients with AD, 187 (72%) were females. Patients' age varied from 40 to 89 years (mean +/- SD: 69.2 +/- 7.7 years). The majority of the patients (77%) had secondary education and 12% had university education. Risk factors independently associated with AD were family history of parkinsonism among first-degree relatives (OR = 4.2; 95% CI 1.2-15.1), hypothyroidism (OR = 2.7; 95% CI 1.1-6.7), and history of head trauma with loss of consciousness (OR = 1.7; 95% CI 1.0-2.8). The most important risk factors for AD in the Russian community are family history of parkinsonism, hypothyroidism and a history of head trauma with loss of consciousness. These findings have implications for developing preventive strategies of AD.

Polyethylene glycol treatment after traumatic brain injury reduces beta-amyloid precursor protein accumulation in degenerating axons

Polyethylene glycol (PEG; 2,000 MW; 30% v/v) is a nontoxic molecule that can be injected intravenously and possesses well-documented neuroprotective properties in the spinal cord of the guinea pig. Recent studies have shown that intravenous PEG can also enter the rat brain parenchyma after injury and repair cellular membrane damage in the region of the corpus callosum. Disrupted anterograde axonal transport and resulting beta-amyloid precursor protein (APP) accumulation are byproducts of traumatic axonal injury (TAI) in the brain. APP accumulation indicates axonal degeneration as a result of axotomy, a detriment that can lead to cell death. In this study, we show that PEG treatment can eliminate APP accumulation in specific brain areas of rats receiving TAI. Six areas of the brain were analyzed: the medial cortex, hippocampus, lateral cortex, thalamus, medial lemniscus, and medial longitudinal fasciculus. Increased APP expression after injury was abolished in the thalamus and reduced in the medial longitudinal fasciculus by PEG treatment. In all remaining areas except for the lateral cortex, APP expression was not increased between injured and uninjured brains, indicating that damage was undetected in those brain areas in this study.

Alzheimer's disease

Alzheimer's disease is the most common cause of dementia. Research advances have enabled detailed understanding of the molecular pathogenesis of the hallmarks of the disease--ie, plaques, composed of amyloid beta (Abeta), and tangles, composed of hyperphosphorylated tau. However, as our knowledge increases so does our appreciation for the pathogenic complexity of the disorder. Familial Alzheimer's disease is a very rare autosomal dominant disease with early onset, caused by mutations in the amyloid precursor protein and presenilin genes, both linked to Abeta metabolism. By contrast with familial disease, sporadic Alzheimer's disease is very common with more than 15 million people affected worldwide. The cause of the sporadic form of the disease is unknown, probably because the disease is heterogeneous, caused by ageing in concert with a complex interaction of both genetic and environmental risk factors. This seminar reviews the key aspects of the disease, including epidemiology, genetics, pathogenesis, diagnosis, and treatment, as well as recent developments and controversies.

Evaluating Spousal Abuse as a Potential Risk Factor for Alzheimer’s Disease: Rationale, Needs and Challenges

BACKGROUND

Repetitive head trauma is an identified risk factor for Alzheimer's disease (AD). The violence in wife assault is repetitive and targets the head. This association provides a rationale for studying the relationship between spousal abuse and AD.

DESIGN

To preliminarily evaluate the possibility of an increased susceptibility for AD in women subjected to spousal abuse and to identify challenges associated with such a study, we performed a pilot case-control study involving women with AD and compared the incidence of spousal abuse against two control groups. Forty consecutive women with AD referred to a Memory Disorders Clinic were enrolled. Individuals were evaluated at three visits (0, 3, 9 months) and were followed for an additional 12 months to ensure that no other diagnosis emerged. Two control groups were likewise assessed.

RESULTS

17.5% (7/40) of the women (average age 71 years) with AD reported spousal abuse with head trauma. In control group 1, 5.0% (2/40) and in control group 2, 7.5% (3/40) of the women reported spousal abuse with head trauma.

CONCLUSIONS

The development of AD may be a potential long-term consequence of wife assault. Our study suggests spousal abuse as a possible risk factor for AD, and supports the need for larger studies. However, there are practical challenges associated with the successful execution of such a study.

Amyloid excess in Alzheimer's disease: What is cholesterol to be blamed for?

A link between alterations in cholesterol homeostasis and Alzheimer's disease (AD) is nowadays widely accepted. However, the molecular mechanism/s underlying such link remain unclear. Numerous experimental evidences support the view that changes in neuronal membrane cholesterol levels and/or subcellular distribution determine the aberrant accumulation of the amyloid peptide in the disease. Still, this view comes from rather contradictory data supporting the existence of either high or low brain cholesterol content. This is of particular concern considering that therapeutical strategies aimed to reduce cholesterol levels are already being tested in humans. Here, we review the molecular mechanisms proposed and discuss the perspectives they open.

Overexpression of Abeta is associated with acceleration of onset of motor impairment and superoxide dismutase 1 aggregation in an amyotrophic lateral sclerosis mouse model

Transgenic mice carrying mutant Cu/Zn superoxide dismutase (SOD1) recapitulate the motor impairment of human amyotrophic lateral sclerosis (ALS). The amyloid-beta (Abeta) peptide associated with Alzheimer's disease is neurotoxic. To investigate the potential role of Abeta in ALS development, we generated a double transgenic mouse line that overexpresses SOD1(G93A) and amyloid precursor protein (APP)-C100. The transgenic mouse C100.SOD1(G93A) overexpresses Abeta and shows earlier onset of motor impairment but has the same lifespan as the single transgenic SOD1(G93A) mouse. To determine the mechanism associated with this early-onset phenotype, we measured copper and zinc levels in brain and spinal cord and found both significantly elevated in the single and double transgenic mice compared with their littermate control mice. Increased glial fibrillary acidic protein and decreased APP levels in the spinal cord of C100.SOD1(G93A) mice compared with the SOD1(G93A) mice agree with the neuronal damage observed by immunohistochemical analysis. In the spinal cords of C100.SOD1(G93A) double transgenic mice, soluble Abeta was elevated in mice at end-stage disease compared with the pre-symptomatic stage. Buffer-insoluble SOD1 aggregates were significantly elevated in the pre-symptomatic mice of C100.SOD1(G93A) compared with the age-matched SOD1(G93A) mice, correlating with the earlier onset of motor impairment in the C100.SOD1(G93A) mice. This study supports abnormal SOD1 protein aggregation as the pathogenic mechanism in ALS, and implicates a potential role for Abeta in the development of ALS by exacerbating SOD1(G93A) aggregation.

Alzheimer-type neuropathology in a 28 year old patient with iatrogenic Creutzfeldt-Jakob disease after dural grafting

We report the case of a 28 year old man who had received a cadaverous dura mater graft after a traumatic open skull fracture with tearing of the dura at the age of 5 years. A clinical suspicion of Creutzfeldt-Jakob disease (CJD) was confirmed by a brain biopsy 5 months prior to death and by autopsy, thus warranting the diagnosis of iatrogenic CJD (iCJD) according to WHO criteria. Immunohistochemistry showed widespread cortical depositions of disease associated prion protein (PrP(sc)) in a synaptic pattern, and western blot analysis identified PrP(sc) of type 2A according to Parchi et al. Surprisingly, we found Alzheimer-type senile plaques and cerebral amyloid angiopathy in widespread areas of the brain. Plaque-type and vascular amyloid was immunohistochemically identified as deposits of beta-A4 peptide. CERAD criteria for diagnosis of definite Alzheimer's disease (AD) were met in the absence of neurofibrillar tangles or alpha-synuclein immunoreactive inclusions. There was no family history of AD, CJD, or any other neurological disease, and genetic analysis showed no disease specific mutations of the prion protein, presenilin 1 and 2, or amyloid precursor protein genes. This case represents (a) the iCJD case with the longest incubation time after dural grafting reported so far, (b) the youngest documented patient with concomitant CJD and Alzheimer-type neuropathology to date, (c) the first description of Alzheimer-type changes in iCJD, and (d) the second case of iCJD in Austria. Despite the young patient age, the Alzheimer-type changes may be an incidental finding, possibly related to the childhood trauma.

Pathophysiology of Alzheimer's Disease

Tremendous progress has been made in understanding the processes of the Alzheimer's disease (AD) cascade, laying the groundwork for improvements in diagnosis and treatment. Advancement has been made in understanding the genetic basis of AD, with identification of causative genes for early-onset familial AD, and the role of the polymorphism of the APOE gene in the late-onset form of the disease. Understanding cerebral degeneration and accumulation of beta-amyloid has generated hopes for discovery of disease-modifying treatments. Progress is needed in understanding the mechanisms that link beta-amyloid accumulation and neuronal death. The next 5 years will be crucial in this respect.

Amyloid precursor protein promotes post-developmental neurite arborization in the Drosophila brain

The mechanisms regulating the outgrowth of neurites during development, as well as after injury, are key to the understanding of the wiring and functioning of the brain under normal and pathological conditions. The amyloid precursor protein (APP) is involved in the pathogenesis of Alzheimer's disease (AD). However, its physiological role in the central nervous system is not known. Many physical interactions between APP and intracellular signalling molecules have been described, but their functional relevance remains unclear. We show here that human APP and Drosophila APP-Like (APPL) can induce postdevelopmental axonal arborization, which depends critically on a conserved motif in the C-terminus and requires interaction with the Abelson (Abl) tyrosine kinase. Brain injury induces APPL upregulation in Drosophila neurons, correlating with increased post-traumatic mortality in appl(d) mutant flies. Finally, we also found interactions between APP and the JNK stress kinase cascade. Our findings suggest a role for APP in axonal outgrowth after traumatic brain injury.