Alzheimer's disease: pathology to potential treatments?

Analysis of HGF, MACC1, C-met and apoptosis-related genes in cervical carcinoma mice

To understand the underlying pharmacological basis and the molecular mechanism of Taxol in therapy of cervical carcinoma (CC) disease, we need to explore the effect of Taxol on CC-related genes and pro-apoptosis and anti-apoptosis genes expression. Immunohistochemistry, western blot and reverse transcription-polymerase chain reaction were applied to examine postive expression levels of Bcl-2, Bax and Caspase-3, HGF, MACC1, Caspase-3 and C-met proteins and MACC1 mRNA expression in tumour of CC mice. Results showed that treatment of Taxol could increase the inhibition rate of tumour growth, positive expression levels of Caspase-3, Bax and decrease positive expression levels of Bcl-2 and Bcl-2/Bax, expression levels of HGF, MACC1 and C-met proteins and MACC1 mRNA in tumour tissue of CC mice. It can be concluded that inhibitory activity of Taxol against tumour growth in CC mice is closely associated with its modulating positive expression of Bcl-2, Bax, Caspase-3, expression of HGF, MACC1, Caspase-3 and C-met proteins and MACC1 mRNA in tumour of CC mice. In conclusion, HGF, MACC1 and C-met genes involve into malignant cervical tumors occurrence, development and prognosis, and might become potential molecular target therapy site of cervical cancer. Taxol intervention may serve as a multi-targeted CC therapeutic capable of inducing selective cancer cell death.

The comorbidity of HIV-associated neurocognitive disorders and Alzheimer's disease: a foreseeable medical challenge in post-HAART era

Although the introduction of highly active antiretroviral therapy (HAART) has led to a strong reduction of HIV-associated dementia (HAD) incidence, the prevalence of minor HIV-1-associated neurocognitive disorder (HAND) is rising among AIDS patients. HAART medication has shifted neuropathology from a subacute encephalitic condition to a subtle neurodegenerative process involving synaptic and dendritic degeneration, particularly of hippocampal neurons that are spared prior to HAART medication. Considerable neuroinflammation coupled with mononuclear phagocyte activation is present in HAART-medicated brains, particularly in the hippocampus. Accumulating evidence suggests that the resultant elevated secretion of pro-inflammatory cytokines such as interferon-gamma, tumor necrosis factor-alpha, and interleukin-1beta can increase amyloid-beta peptide (Abeta) generation and reduce Abeta clearance. Recent advancements in Alzheimer's disease (AD) research identified Abeta biogenesis and clearance venues that are potentially influenced by HIV viral infection, providing new insights into beta-amyloidosis segregation in HIV patients. Our study suggests enhanced beta-amyloidosis in ART-treated HAD and HIV-associated encephalitis brains and suppression of Abeta clearance by viral infection of human primary macrophages. A growing awareness of potential convergent mechanisms leading to neurodegeneration shared by HIV and Abeta points to a significant chance of comorbidity of AD and HAND in senile HIV patients, which calls for a need of basic studies.

Interleukin-1-induced neurotoxicity is mediated by glia and requires caspase activation and free radical release

Interleukin (IL)-1 expression is induced rapidly in response to diverse CNS insults and is a key mediator of experimentally induced neuronal injury. However, the mechanisms of IL-1-induced neurotoxicity are unknown. The aim of the present study was to examine the toxic effects of IL-1 on rat cortical cell cultures. Treatment with IL-1beta did not affect the viability of pure cortical neurones. However, IL-1 treatment of cocultures of neurones with glia or purified astrocytes induced caspase activation resulting in neuronal death. Neuronal cell death induced by IL-1 was prevented by pre-treatment with the IL-1 receptor antagonist, the broad spectrum caspase inhibitor Boc-Asp-(OMe)-CH(2)F or the antioxidant alpha-tocopherol. The NMDA receptor antagonist dizolcipine (MK-801) attenuated cell death induced by low doses of IL-1beta but the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline (NBQX) had no effect. Inhibition of inducible nitric oxide synthase with N(omega)-nitro-l-arginine methyl ester had no effect on neuronal cell death induced by IL-1beta. Thus, IL-1 activates the IL-1 type 1 receptor in astrocytes to induce caspase-dependent neuronal death, which is dependent on the release of free radicals and may contribute to neuronal cell death in CNS diseases.

Association of interleukin-I beta and receptor antagonist gene polymorphisms with late onset Alzheimer's disease in Taiwan Chinese

Interleukin (IL)-1 is markedly overexpressed in the brains of patients with Alzheimer's disease (AD). We aimed to evaluate the relationship between three polymorphisms of the IL1 gene (IL-1beta promoter -511T/C, IL-1beta exon 5 E1/E2 and IL-1-RA) and late onset AD in Taiwan Chinese. Forty-six late onset AD patients and 103 unrelated, age-matched, healthy controls living in the same area were included. PCR was used to resolve the two IL-1beta polymorphisms and the IL-1Ra intron 2 polymorphism. The -511T/T type of the IL-1beta promoter (unlike IL-1beta exon 5 and IL-1-RA) was more frequently found in AD than in healthy patients (-511C/C type versus T/T type, OR = 0.944, CI = 0.393, 2.269, P = 0.898; -511C/T type versus T/T type, OR = 0.375, CI = 0.156, 0.902, P = 0.028). The -511T/T genotype (unlike the other two polymorphisms) is a marker demonstrating that late onset AD in Chinese patients in Taiwan is genetically determined.

Interleukin-1beta activates forebrain glial cells and increases nitric oxide production and cortical glutamate and GABA release in vivo: implications for Alzheimer's disease

Interleukin-1beta (10 U) was injected into the nucleus basalis of adult male Wistar rats. The inflammation-induced changes in glial cell morphology and expression of inducible nitric oxide synthase in the injected area, the release of acetylcholine, GABA and glutamate from the ipsilateral cortex, the production of nitrite levels in the injected area and ipsilateral cortex, and changes in motor activity were investigated. Saline-injected rats were used as control. Interleukin-1beta induced an activation of both microglia and astrocytes which was already evident 24 h after injection. Seven days after injection, many reactive microglial cells and astrocytes were seen in the injected area and in other brain regions of the same hemisphere. Microglia reaction, but not astrocyte activation, disappeared 30 days post-injection. Seven days after interleukin-1beta injection, many cells immunopositive for inducible nitric oxide synthase were found surrounding the injection site. Inducible nitric oxide synthase-positive cells were identified, by double staining immunohistochemistry, in the reactive microglial cells and, by electron microscope examination, in the perineuronal subpopulation of resident activated microglia. Microdialysis investigations revealed a transient increase in reactive nitrogen intermediates (at seven days post-injection), a delayed (at 30 days post-injection) increase in GABA and glutamate release, and no changes in acetylcholine release in the ipsilateral cortex in interleukin-1beta, but not saline, injected rats. Inhibition of inducible nitric oxide synthase expression by N(G)-nitro-L-arginine methyl ester administration prevented the increase in nitrogen intermediates and GABA release, but not in glutamate release. Our findings suggest that an inflammatory reaction of the basal forebrain facilitates GABA release through the production of nitric oxide.

Acute-phase responses in transgenic mice with CNS overexpression of IL-1 receptor antagonist

The interleukin-1 (IL-1) receptor antagonist (IL-1ra) is an endogenous antagonist that blocks the effects of the proinflammatory cytokines IL-1alpha and IL-1beta by occupying the type I IL-1 receptor. Here we describe transgenic mice with astrocyte-directed overexpression of the human secreted IL-1ra (hsIL-1ra) under the control of the murine glial fibrillary acidic protein (GFAP) promoter. Two GFAP-hsIL-1ra strains have been generated and characterized further: GILRA2 and GILRA4. These strains show a brain-specific expression of the hsIL-1ra at the mRNA and protein levels. The hsIL-1ra protein was approximated to approximately 50 ng/brain in cytosolic fractions of whole brain homogenates, with no differences between male and female mice or between the two strains. Furthermore, the protein is secreted, inasmuch as the concentration of hsIL-1ra in the cerebrospinal fluid was 13 (GILRA2) to 28 (GILRA4) times higher in the transgenic mice than in the control animals. To characterize the transgenic phenotype, GILRA mice and nontransgenic controls were injected with recombinant human IL-1beta (central injection) or lipopolysaccharide (LPS, peripheral injection). The febrile response elicited by IL-1beta (50 ng/mouse icv) was abolished in hsIL-1ra-overexpressing animals, suggesting that the central IL-1 receptors were occupied by antagonist. The peripheral LPS injection (25 micrograms/kg ip) triggered a fever in overexpressing and control animals. Moreover, no differences were found in LPS-induced (100 and 1,000 micrograms/kg ip; 1 and 6 h after injection) IL-1beta and IL-6 serum levels between GILRA and wild-type mice. On the basis of these results, we suggest that binding of central IL-1 to central IL-1 receptors is not important in LPS-induced fever or LPS-induced IL-1beta and IL-6 plasma levels.

Is there a genetic basis for the deposition of beta-amyloid after fatal head injury?

1. Alzheimer's disease is a heterogeneous disorder that may be caused by genetic or environmental factors or by a combination of both. Abnormalities in chromosomes 1, 14, and 21 have all been implicated in the pathogenesis of the early-onset form of the disease, while the epsilon 4 allele of the apolipoprotein E gene (on chromosome 19) is now recognized as a risk factor for early- and late-onset sporadic and familial Alzheimer's disease. 2. The best-established environmental trigger for the disease is a head injury, based on epidemiological and neuropathological evidence. Approximately 30% of patients who die after a single episode of severe head injury show intracerebral deposition of beta-amyloid protein (A beta), a protein that is thought to be central to the pathogenesis of Alzheimer's disease. 3. Recent studies have revealed an over-representation of the apoE epsilon 4 allele in those head-injured patients displaying A beta pathology, thus providing the first evidence for a link between a genetic susceptibility (apoE epsilon 4) and an environmental trigger (head injury) in the development of Alzheimer-type pathology.

Annual review prize lecture cytokines - killers in the brain?

Given at the Meeting of the Physiological Society held at the University of Southampton on 10 September 1998

Increased interleukin-6 expression by microglia from brain of aged mice

Over expression of inflammatory cytokines in the brain may establish a state that is permissive to the onset of neurodegenerative disease. Because the occurrence of certain neurodegenerative diseases increases with age, in the present study we examined the expression of the inflammatory cytokine, interleukin-6 (IL-6), in the brain of aged mice. In an initial experiment, IL-6 was measured in crude protein extracts from brains of juvenile (1-month-old), adult (3-month-old), and aged (24-month-old) male BALB/c mice. The concentration of IL-6 in crude protein extracts from the cerebellum, cerebral cortex, and hippocampus increased with age. The increase in IL-6 was discrete, as levels in the hypothalamus were not age-dependent. To begin evaluating spontaneous IL-6 production in aging, glial cells were cultured from brains of neonate, adult, and aged mice. An age-associated increase in IL-6 mRNA and supernatant IL-6 concentration was evident, indicating glia from aged mice spontaneously express high levels of IL-6 relative to glia from adult and neonate mice. Flow cytometric analysis revealed that cultures established from aged brain compared to either adult or neonate brain comprised more microglia (i.e., MAC-1-positive cells). Furthermore, the proportion of microglia that was positive for IL-6 increased with age, whereas the proportion of astrocytes that were positive for IL-6 was not age-dependent. The present results suggest that IL-6 increases in the mouse brain with age, and that microglia cultured from aged mice spontaneously produce more IL-6 than those from neonate or adult mice. Therefore, microglia may contribute to the increased level of IL-6 present in aged brain.

Inflammation and Alzheimer's disease: relationships between pathogenic mechanisms and clinical expression

During the past 15 years a variety of inflammatory proteins has been identified in the brains of patients with Alzheimer's disease (AD) postmortem. There is now considerable evidence that in AD the deposition of amyloid-beta (A beta) protein precedes a cascade of events that ultimately leads to a local "brain inflammatory response." Here we reviewed the evidence (i) that inflammatory mechanisms can be a part of the relevant etiological factors for AD in patients with head trauma, ischemia, and Down's syndrome; (ii) that in cerebral A beta disorders the clinical symptoms are determined to a great extent by the site of inflammation; and (iii) that a brain inflammatory response can explain some poorly understood characteristics of the clinical picture, among others the susceptibility of AD patients to delirium. The present data indicate that inflammatory processes in the brain contribute to the etiology, the pathogenesis, and the clinical expression of AD.

The role of tumour necrosis factor, interleukin 6, interferon-gamma and inducible nitric oxide synthase in the development and pathology of the nervous system

Proinflammatory cytokines, tumour necrosis factor (TNF)-alpha, interferon (IFN)-gamma and interleukin (IL)-6, have multiple effects in the central nervous system (CNS) not strictly cytotoxic being involved in controlling neuronal and glial activation, proliferation, differentiation and survival, thus influencing neuronal and glial plasticity, degeneration as well as development and regeneration of the nervous system. Moreover, they can contribute to CNS disorders, including multiple sclerosis. Alzheimer's disease and human immunodeficiency virus-associated dementia complex. Recent results with deficient mice in the expression of those cytokines indicate that they are in general more sensible to insults resulting in neural damage. Some of the actions induced by TNF-alpha, and IFN-gamma, including both beneficial and detrimental, are mediated by inducible nitric oxide synthase (iNOS)-derived nitric oxide (NO) production. NO produced by iNOS may be beneficial by promoting the differentiation and survival of neurons. IL-6 does not induce iNOS, explaining why this cytokine is less often involved in this dual role protection pathology. Some of the proinflammatory as well as the neurotrophic effects of those cytokines also involve upregulation of cell adhesion molecules (CAM). Those apparently conflicting results may be reconciled considering that proinflammatory cytokines are involved in promoting the disease, mostly by inducing expression of CAM leading to alteration of the blood-brain barrier integrity, whereas they have a protective role once disease is established due to its immunosuppressive or neurotrophic role. Understanding the dichotomy pathogenesis/neuroprotection of those cytokines may provide a rationale for better therapeutic strategies.

Cytokines in dementia of the Alzheimer's type (DAT): relevance to research and treatment

There is indirect evidence suggesting that some cytokines may be involved in the pathophysiology of dementia of the Alzheimer type (DAT). Measurement of proinflammatory cytokines in the biologic fluids and brain tissues of DAT patients have provided some support for such a role. However, these studies are limited in scope and have included a relatively small number of patients. Future studies are needed to elucidate the role of cytokines in the pathogenesis and treatment of DAT.

Intracerebral inflammation after human brain contusion

OBJECTIVE

This study was undertaken to analyze the inflammatory components in contused human brain tissue to compare the findings with previous experimental data regarding the pathogenesis of brain contusions.

METHODS

Contused brain tissue biopsies were obtained from 12 consecutive patients undergoing surgery for brain contusions 3 hours to 5 days after trauma. Inflammatory and immunological components were analyzed by immunohistochemistry.

RESULTS

In patients undergoing surgery less than 24 hours after trauma, the inflammatory response was limited to vascular margination of polymorphonuclear cells. In patients undergoing surgery 3 to 5 days after trauma, however, a massive inflammatory response consisting of monocytes/macrophages, reactive microglia, polymorphonuclear cells, and CD4- and CD8-positive T lymphocytes was detected. Human lymphocyte antigen-DQ was expressed on reactive microglia and infiltrating leukocytes in the late patient group. In addition, CD1a, which is a marker for antigen-presenting dendritic cells, was detected in a subgroup of microglial cells.

CONCLUSION

The results corroborated hypotheses derived from experimental data. In the early phase after contusional trauma, inflammation is mainly intravascular and dominated by polymorphonuclear cells. The inflammation was parenchymal in patients undergoing surgery 3 to 5 days after trauma. The brain swelling seemed to be biphasic, the delayed phase correlating with a parenchymal inflammation. The inflammatory cells may produce several potentially harmful effects, such as acute cellular degeneration; they may also lead to degenerative long-term effects.

Glial-neuronal interactions in Alzheimer's disease: the potential role of a 'cytokine cycle' in disease progression

The role of glial inflammatory processes in Alzheimer's disease has been highlighted by recent epidemiological work establishing head trauma as an important risk factor, and the use of anti-inflammatory agents as an important ameliorating factor, in this disease. This review advances the hypothesis that chronic activation of glial inflammatory processes, arising from genetic or environmental insults to neurons and accompanied by chronic elaboration of neuroactive glia-derived cytokines and other proteins, sets in motion a cytokine cycle of cellular and molecular events with neurodegenerative consequences. In this cycle, interleukin-1 is a key initiating and coordinating agent. Interleukin-1 promotes neuronal synthesis and processing of the beta-amyloid precursor protein, thus favoring continuing deposition of beta-amyloid, and activates astrocytes and promotes astrocytic synthesis and release of a number of inflammatory and neuroactive molecules. One of these, S100beta, is a neurite growth-promoting cytokine that stresses neurons through its trophic actions and fosters neuronal cell dysfunction and death by raising intraneuronal free calcium concentrations. Neuronal injury arising from these cytokine-induced neuronal insults can activate microglia with further overexpression of interleukin-1, thus producing feedback amplification and self-propagation of this cytokine cycle. Additional feedback amplification is provided through other elements of the cycle. Chronic propagation of this cytokine cycle represents a possible mechanism for progression of neurodegenerative changes culminating in Alzheimer's disease.

The protective effects of alpha-melanocyte stimulating hormone on canine brain stem ischemia

OBJECTIVE

To evaluate the influence of alpha-melanocyte stimulating hormone (alpha-MSH), an anti-inflammatory antagonist of the production and action of proinflammatory cytokines, 26 dogs were divided into four groups and exposed to isolated, reversible brain stem ischemia in the presence or absence of alpha-MSH treatment.

METHODS

Brain stem auditory evoked potentials (BAEPs) and regional cerebral blood flow were measured during ischemia and for 5 hours after reperfusion. Group I was composed of five dogs that underwent surgical preparation only. Group II was composed of seven dogs that were exposed to 20 minutes of ischemia without treatment. Group III was comprised of seven dogs exposed to 20 minutes of ischemia with alpha-MSH treatment before and during ischemia. Group IV was composed of seven dogs exposed to 20 minutes of brain stem ischemia with alpha-MSH treatment only during reperfusion.

RESULTS

During the ischemic period, BAEPs were abolished in all animals within 10 minutes. With reperfusion, the BAEPs increased to approximately 36% of baseline in Group II dogs that received no treatment. However, this increase was approximately 63% in animals that received alpha-MSH both before and during ischemia (Group III). In Group IV dogs that received alpha-MSH only during reperfusion, BAEPs were increased approximately 10 to 14% more than in Group II during the late reperfusion period.

CONCLUSION

The improved recovery of BAEPs in dogs treated with alpha-MSH suggests that this peptide may have neuroprotective effects in brain stem ischemia and reperfusion injury. This effect may be caused by an antagonistic action of alpha-MSH on cytokine-induced ischemic brain damage.

Neurodegeneration, sleep, and cerebral energy metabolism: a testable hypothesis

Varying degrees of metabolic arrest are used by many living species to survive in a harsh environment. For example, in hibernating mammals, neuronal activity and cerebral metabolism are profoundly depressed in most regions of the brain and limited energy resources are deployed to maintain vital cell functions. Gathering evidence suggests that energy resources are also limited in both Alzheimer's and Parkinson's diseases, and that this promotes metabolic stress and the degenerative process. Key steps in this process are energy requiring, and this further compromises cell energy reserves. It may be possible to slow the progress of these diseases by inducing slow-wave sleep (SWS) at night with gammahydroxybutyrate. Patients with these diseases sleep poorly and generate little SWS. SWS and hibernation are thought to be on a continuum of energy conservation. Thus, the induction of SWS may retard the degenerative process by depressing cell metabolism and by directing energy utilization to vital cell functions. In this way, GHB-induced SWS may duplicate the effects of hibernation and extend biologic time.

In vivo and in vitro evidence supporting a role for the inflammatory cytokine interleukin-1 as a driving force in Alzheimer pathogenesis

Interleukin-1 (IL-1), an inflammatory cytokine overexpressed in the neuritic plaques of Alzheimer's disease, activates astrocytes and enhances production and processing of beta-amyloid precursor protein (beta-APP). Activated astrocytes, overexpressing S100 beta, are a prominent feature of these neuritic plaques, and the neurite growth-promoting properties of S100 beta have been implicated in the formation of dystrophic neurites overexpressing beta-APP in neuritic plaques. These facts collectively suggest that elevated levels of the inflammatory cytokine IL-1 drive S100 beta and beta-APP overexpression and dystrophic neurite formation in Alzheimer's disease. To more directly assess this driver potential for IL-1, we analyzed IL-1 induction of S100 beta expression in vivo and in vitro, and of beta-APP expression in vivo. Synthetic IL-1 beta was injected into the right cerebral hemispheres of 13 rats. Nine additional rats were injected with phosphate-buffered saline, and seven rats served as uninjected controls. The number of astrocytes expressing detectable levels of S100 beta in tissue sections from IL-1-injected brains was 1.5 fold that of either control group (p < 0.01), while tissue S100 beta levels were approximately threefold that of controls (p < 0.05). The tissue levels of two beta-APP isoforms (approximately 130 and 135 kDa) were also significantly elevated in IL-1-injected brains (p < 0.05). C6 glioma cells, treated in vitro for 24 h with either IL-1 beta or IL-1 alpha, showed significant increases in both S100 beta and S100 beta mRNA levels. These results provide evidence that IL-1 upregulates both S100 beta and beta-APP expression, in vivo and vitro, and support the idea that overexpression of IL-1 in Alzheimer's disease drives astrocytic overexpression of S100 beta, favoring the growth of dystrophic neurites necessary for evolution of diffuse amyloid deposits into neuritic beta-amyloid plaques.

Altered beta-APP metabolism after head injury and its relationship to the aetiology of Alzheimer's disease

There is increasing evidence of a link between head injury and the subsequent onset of Alzheimer's disease. Deposits of amyloid beta-protein (A beta) are found not only in cases of dementia pugilistica but in some 30% of patients dying after a single episode of severe head injury. Detailed clinicopathological studies have shown that A beta deposition is most likely, but not exclusively, to occur, the older the patient at the time of injury, and if the injury is the result of a fall. Distribution studies have shown that the A beta is widely deposited in the neocortex and there is no apparent association with any of the multiple primary or secondary pathologies of traumatic brain injury. There is an increased expression of beta-APP particularly in the pre-alpha cells of the entorhinal cortex and in areas of axonal damage. Recent molecular genetic studies have shown that there is a strong association between deposits of A beta and the apolipoprotein E genotype of the individual.

Cytokines and their receptors in the central nervous system: physiology, pharmacology, and pathology

Numerous cytokines and their receptors have been identified in the brain, where they act as mediators of host defence responses and have direct effects on neuronal and glial function. Experimental tools for studying cytokine actions, their source and control of synthesis in the brain, actions and mechanisms of action will be reviewed here. In particular, the cytokines interleukin-1, interleukin-6, and tumour necrosis factor-alpha have been implicated in the central control of responses to systemic disease and injury and activation of fever, neuroendocrine, immune, and behavioural responses. The recent discovery of specific inhibitors of cytokine synthesis, release, or action may offer significant therapeutic benefit.

Alzheimer's disease: fundamental and therapeutic aspects

Alzheimer's disease is the most common type of progressive and debilitating dementia affecting aged people. In some early--as well as late--onset familial cases, a genetic linkage with chromosomes 14, 21 (early-onset) or 19 (late-onset) has been indicated. Furthermore, a direct or indirect role has been attributed to normal or structurally altered amyloid beta-protein (concentrated in senile plaques) and/or excessively phosphorylated tau protein (located in neurofibrillary tangles). Degeneration of cholinergic neurons and concomitant impairment of cortical and hippocampal neurotransmission lead to cognitive and memory deficits. Several compounds are being tested in attempts to prevent and/or cure Alzheimer's disease, including tacrine, which has very modest efficacy in a sub-group of patients, and new acetylcholinesterase inhibitors. Pilot experiments have also been launched using nerve growth factor (NGF) to prevent or stabilize the processes of cholinergic pathway degeneration. Alternatively, antioxidants, free radical scavengers and/or non steroidal anti-inflammatory agents may be screened as potential therapies for neurodegenerative diseases induced by multiple endogenous and/or exogenous factors. The recent use of transgenic mice, in parallel with other genetic, biochemical and neurobiological systems, in vivo and/or in vitro (cell cultures), should accelerate the discovery and development of specific drugs for the treatment of Alzheimer's disease.

Distribution of beta-amyloid protein in the brain following severe head injury

Deposits of beta-amyloid protein (beta AP) can be found in the brains of 30% of fatally head-injured patients; they have been found in children and after survival times of only 4 h. The principal aims of this study were to map the distribution of beta AP in 14 patients aged 65 years or less in whom it was known that the protein had been deposited, and to correlate its distribution with the pathologies of traumatic brain injury. The results show that beta AP is widely distributed, and that there is no correlation between its presence and cerebral contusions, intracranial haematoma, axonal injury, ischaemic brain damage, brain swelling or the pathology of raised intracranial pressure. These findings suggest that the deposition of beta AP is a consequence of the acute phase response of nerve cells to stress in susceptible individuals. Further studies will be required to establish the possible relationship between the deposition of beta AP following head injury and the molecular neuropathology of Alzheimer's disease.

Inflammatory mechanisms in Alzheimer's disease

Alzheimer's disease is aetiologically heterogeneous, but the pathogenesis is often considered to be initiated by the deposition of amyloid fibrils, followed by neuritic tau pathology and neuronal death. A variety of inflammatory proteins has been identified in the brains of patients with Alzheimer's disease post mortem. In this article, Piet Eikelenboom and colleagues review evidence to suggest that the inflammatory processes are intimately involved in several crucial events in the pathological cascade. This suggests possibilities for the treatment of Alzheimer's disease with anti-inflammatory drugs.

Expression of intracellular calcium-binding proteins in cultured skin fibroblasts from Alzheimer and normal aged donors

Disturbed calcium homeostasis may play a role in the etiology in Alzheimer's and other neurodegenerative diseases. A protective role against cellular degeneration has been postulated for Ca(2+)-binding proteins in certain neuron populations. Recent data suggest that intracellular free calcium regulation is also altered in several non-neuronal cells, including skin fibroblasts, from patients with Alzheimer's disease. In this study we analyzed the expression of several EF-hand Ca(2+)-binding proteins in cultured skin fibroblasts from Alzheimer patients and age-matched normal donors. We detected a strong expression of some members of the S100 Ca(2+)-binding protein family and of calcineurin A. However, no significant differences were found between both types of donors by Northern blot and Western blot analysis. In addition, similar signals were detected on 45Ca(2+)-blots of fibroblasts extracts of Alzheimer patients and control donors. The present findings indicate that the altered level of some intracellular calcium-binding proteins in certain brain areas of Alzheimer patients is not found in skin fibroblasts of these patients.

Microglial interleukin-1 alpha expression in human head injury: correlations with neuronal and neuritic beta-amyloid precursor protein expression

Activated microglia containing IL-1 alpha-immunoreactive (IL-1 alpha +) product were increased 3-fold in number in the acute phase following head injury, a risk factor for later development of Alzheimer's disease, and this increase was correlated with a 7-fold increase in the number of neurons with elevated beta-amyloid precursor protein (beta-APP) levels (R = 0.78; P < 0.05). Furthermore, clusters of beta-APP+ dystrophic neurites present in these patients were invariably associated with activated IL-1 alpha + microglia. These findings suggest that early overexpression of IL-1 alpha and beta-APP is a priming event for later neuropathological changes evident at end stages of Alzheimer's disease.

Neuropathobiology of senile dementia and mechanism of action of nootropic drugs

Recent advances in neuroscience and molecular neurochemistry have substantially increased the knowledge of the neuropathobiology of senile dementia and Alzheimer's disease. On the basis of various hypotheses concerning degenerative processes in aging brains, new therapeutic strategies have been developed, including nootropic drugs with different mechanisms of action and heterogenous chemical structures. Mutual relationships exist between neuroscientific research and nootropic drug development. To date, such areas of research and drug development have involved deficits of brain neurotransmission (cholinergic, monoaminergic, peptidergic), free radical-induced damage, disturbances of calcium homeostasis and excitatory amino acid function, and deposition of amyloid protein.

Beta amyloid protein deposition in the brain after severe head injury: implications for the pathogenesis of Alzheimer's disease

In a recent preliminary study it was reported that a severe head injury resulted in the deposition of beta amyloid protein (beta AP) in the cortical ribbon of 30% of patients who survived for less than two weeks. Multiple cortical areas have now been examined from 152 patients (age range 8 weeks-81 years) after a severe head injury with a survival time of between four hours and 2.5 years. This series was compared with a group of 44 neurologically normal controls (age range 51 to 80 years). Immunostaining with an antibody to beta AP confirmed the original findings that 30% of cases of head injury have beta AP deposits in one or more cortical areas. Increasing age seemed to accentuate the extent of beta AP deposition and potential correlations with other pathological changes associated with head injury were also investigated. In addition, beta amyloid precursor protein (beta APP) immunoreactivity was increased in the perikarya of neurons in the vicinity of beta AP deposits. The data from this study support proposals that increased expression of beta APP is part of an acute phase response to neuronal injury in the human brain, that extensive overexpression of beta APP can lead to deposition of beta AP and the initiation of an Alzheimer disease-type process within days, and that head injury may be an important aetiological factor in Alzheimer's disease.

Chronic administration of flumazenil increases life span and protects rats from age-related loss of cognitive functions: a benzodiazepine/GABAergic hypothesis of brain aging

Under barrier condition and with ad lib access to food and water, 20 Fischer-344 rats were chronically treated for 10 months with the benzodiazepine (BDZ) antagonist, flumazenil (FL; 4 mg/kg/day in drinking water acidified to pH = 3.0), beginning at the age of 13 months, while the group of 20 control age-matched rats received plain acidified water. The life span of the first 8 deceased rats treated with FL was significantly longer than that of the first 8 deceased rats in the age-matched control group. In tests for spontaneous ambulation and exploratory behavior in the Holeboard apparatus, conducted during the 3rd and the 8th month of treatment, the FL group, relative to controls, had significantly higher scores for the ambulation and exploratory behavior. In tests for unrewarded spontaneous alternation in the T maze, conducted at days 7, 39, 42, and 47 through 54 after drug withdrawal, i.e., at the age of 24-25 months, the FL-exposed group, compared to age-matched controls, showed a significantly higher percent of alternating choices, a behavior that was statistically comparable to that of the "young" 6-month-old controls. In the Radial Maze tests conducted 2 months after drug withdrawal, the FL group made significantly less "working memory" errors and "reference memory" errors, relative to the age-matched 25-month-old control group, a performance that was comparable to that of the young 7-month-old control group. In conclusion, chronic FL significantly protected rats from age-related loss of cognitive functions. It is postulated that the age-related alterations in brain function may be attributable to the negative metabolic/trophic influences of the "endogenous" benzodiazepine (BDZ) ligands and/or those ingested with food. A BDZ/GABAergic hypothesis of brain aging has been formulated which assumes that age-related and abnormally strong BDZ/GABAergic influences promote neurodegeneration by suppressing trophic functions of the aminergic and peptidergic neurons through opening of chloride channels in soma membrane and axon terminals, causing excessive hyperpolarizing and depolarizing inhibition, respectively. The review of human clinical and animal data indicates that FL has nootropic actions by enhancing vigilance cognitive and habituation processes.

Extracellular proteolysis in the adult murine brain

Plasminogen activators are important mediators of extracellular metabolism. In the nervous system, plasminogen activators are thought to be involved in the remodeling events required for cell migration during development and regeneration. We have now explored the expression of the plasminogen activator/plasmin system in the adult murine central nervous system. Tissue-type plasminogen activator is synthesized by neurons of most brain regions, while prominent tissue-type plasminogen activator-catalyzed proteolysis is restricted to discrete areas, in particular within the hippocampus and hypothalamus. Our observations indicate that tissue-type plasminogen activator-catalyzed proteolysis in neural tissues is not limited to ontogeny, but may also contribute to adult central nervous system physiology, for instance by influencing neuronal plasticity and synaptic reorganization. The identification of an extracellular proteolytic system active in the adult central nervous system may also help gain insights into the pathogeny of neurodegenerative disorders associated with extracellular protein deposition.

Macrophages and inflammation in the central nervous system

Acute inflammation plays an important role in host tissue defense against injury and infection, and also subsequent tissue repair. In the central nervous system parenchyma, following many types of insults, the acute inflammatory response to rapid neuronal degeneration or challenge with inflammatory substances differs dramatically from that of other tissues. The rapid recruitment of neutrophils is virtually absent and monocytes are only recruited after a delay of several days. It appears that the microenvironment of the central nervous system has evolved mechanisms to protect it from the potentially damaging consequences of some aspects of the acute inflammatory response.

Alzheimer's disease and chromosome 14. Different gene, same process?

Over the past three years, progress in the molecular genetics of familial Alzheimer's disease has been fast and fundamental. The seminal finding that some cases are due to a mutation in the β-amyloid precursor protein (APP) gene has been followed by the discovery of a major additional locus for the disease on chromosome 14. The combined data suggest that the genetic sites accounting for most early-onset familial Alzheimer's disease cases have now been located. In addition, research is revealing the mechanisms by which the genes exert their pathogenicity. This promises to provide the explanatory link between the genes and the clinicopathological syndrome. The ultimate goal, an understanding in similar terms of the much commoner senile, sporadic form of Alzheimer's disease, is now a realistic target.

Involvement of cytokines in acute neurodegeneration in the CNS

Cytokines, (particularly interleukins and growth factors) are synthesised in the brain, and induced by brain damage. Interleukin-I appears to directly mediate ischaemic and excitotoxic brain damage, whereas growth factors (e.g., bFGF, NGF), and the phospholipid binding protein lipocortin-1 exhibit neuroprotective actions. Central administration of recombinant interleukin-1 receptor antagonist markedly attenuates damage induced by focal cerebral ischaemia, or pharmacological activation of NMDA receptors in the rat brain. The mechanisms of action of these cytokines on neurodegeneration are unknown, but indirect evidence has implicated corticotropin releasing factor, arachidonic acid, and nitric oxide. In vitro effects of interleukin-1, growth factors, and lipocortin-1 have been reported on intracellular calcium homeostasis, which is critically important in neurodegeneration. Pharmacological modulation of the expression and/or actions of cytokines in the brain may be of considerable therapeutic benefit in the treatment of acute neurodegeneration.