Immunodetection of the amyloid P component in Alzheimer's disease

Dementia in the older population is associated with neocortex content of serum amyloid P component

Despite many reported associations, the direct cause of neurodegeneration responsible for cognitive loss in Alzheimer’s disease and some other common dementias is not known. The normal human plasma protein, serum amyloid P component, a constituent of all human fibrillar amyloid deposits and present on most neurofibrillary tangles, is cytotoxic for cerebral neurones in vitro and in experimental animals in vivo. The neocortical content of serum amyloid P component was immunoassayed in 157 subjects aged 65 or more with known dementia status at death, in the large scale, population-representative, brain donor cohort of the Cognitive Function and Ageing Study, which avoids the biases inherent in studies of predefined clinico-pathological groups. The serum amyloid P component values were significantly higher in individuals with dementia, independent of serum albumin content measured as a control for plasma in the cortex samples. The odds ratio for dementia at death in the high serum amyloid P component tertile was 5.24 (95% confidence interval 1.79–15.29) and was independent of Braak tangle stages and Thal amyloid-β phases of neuropathological severity. The strong and specific association of higher brain content of serum amyloid P component with dementia, independent of neuropathology, is consistent with a pathogenetic role in dementia.

Extracellular protein components of amyloid plaques and their roles in Alzheimer's disease pathology

Alzheimer's disease (AD) is pathologically defined by the presence of fibrillar amyloid β (Aβ) peptide in extracellular senile plaques and tau filaments in intracellular neurofibrillary tangles. Extensive research has focused on understanding the assembly mechanisms and neurotoxic effects of Aβ during the last decades but still we only have a brief understanding of the disease associated biological processes. This review highlights the many other constituents that, beside Aβ, are accumulated in the plaques, with the focus on extracellular proteins. All living organisms rely on a delicate network of protein functionality. Deposition of significant amounts of certain proteins in insoluble inclusions will unquestionably lead to disturbances in the network, which may contribute to AD and copathology. This paper provide a comprehensive overview of extracellular proteins that have been shown to interact with Aβ and a discussion of their potential roles in AD pathology. Methods that can expand the knowledge about how the proteins are incorporated in plaques are described. Top-down methods to analyze post-mortem tissue and bottom-up approaches with the potential to provide molecular insights on the organization of plaque-like particles are compared. Finally, a network analysis of Aβ-interacting partners with enriched functional and structural key words is presented.

On the Role of Platelet-Generated Amyloid Beta Peptides in Certain Amyloidosis Health Complications

As do many other immunity-related blood cells, platelets release antimicrobial peptides that kill bacteria, fungi, and even certain viruses. Here we review the literature suggesting that there is a similarity between the antimicrobials released by other blood cells and the amyloid-related Aβ peptide released by platelets. Analyzing the literature, we also propose that platelet-generated Aβ amyloidosis may be more common than currently recognized. This systemic Aβ from a platelet source may participate in various forms of amyloidosis in pathologies ranging from brain cancer, glaucoma, skin Aβ accumulation, and preeclampsia to Alzheimer’s disease and late-stage Parkinson’s disease. We also discuss the advantages and disadvantages of specific animal models for studying platelet-related Aβ. This field is undergoing rapid change, as it evaluates competing ideas in the light of new experimental observations. We summarized both in order to clarify the role of platelet-generated Aβ peptides in amyloidosis-related health disorders, which may be helpful to researchers interested in this growing area of investigation.

Brain injury-induced dysfunction of the blood brain barrier as a risk for dementia

The blood-brain barrier (BBB) is a complex and dynamic physiological interface between brain parenchyma and cerebral vasculature. It is composed of closely interacting cells and signaling molecules that regulate movement of solutes, ions, nutrients, macromolecules, and immune cells into the brain and removal of products of normal and abnormal brain cell metabolism. Dysfunction of multiple components of the BBB occurs in aging, inflammatory diseases, traumatic brain injury (TBI, severe or mild repetitive), and in chronic degenerative dementing disorders for which aging, inflammation, and TBI are considered risk factors. BBB permeability changes after TBI result in leakage of serum proteins, influx of immune cells, perivascular inflammation, as well as impairment of efflux transporter systems and accumulation of aggregation-prone molecules involved in hallmark pathologies of neurodegenerative diseases with dementia. In addition, cerebral vascular dysfunction with persistent alterations in cerebral blood flow and neurovascular coupling contribute to brain ischemia, neuronal degeneration, and synaptic dysfunction. While the idea of TBI as a risk factor for dementia is supported by many shared pathological features, it remains a hypothesis that needs further testing in experimental models and in human studies. The current review focusses on pathological mechanisms shared between TBI and neurodegenerative disorders characterized by accumulation of pathological protein aggregates, such as Alzheimer's disease and chronic traumatic encephalopathy. We discuss critical knowledge gaps in the field that need to be explored to clarify the relationship between TBI and risk for dementia and emphasize the need for longitudinal in vivo studies using imaging and biomarkers of BBB dysfunction in people with single or multiple TBI.

Aβ Peptide Originated from Platelets Promises New Strategy in Anti-Alzheimer's Drug Development

The amyloid beta (Aβ) peptide and its deposits in the brain are known to be implicated in the neurodegeneration that occurs during Alzheimer's disease (AD). Recently, alternative theories views concerning both the source of this peptide and its functions have been developed. It has been shown that, as in all other known types of amyloidosis, the production of Aβ originates in blood cells or cells related to blood plasma, from which it can then spread from the blood to inside the brain, with the greatest concentration around brain blood vessels. In this review, we summarize research progress in this new area and outline some future perspectives. While it is still unclear whether the main source of Aβ deposits in AD is the blood, the possibility of blocking the chain of reactions that lead to constant Aβ release from the blood to the brain may be exploited in an attempt to reduce the amyloid burden in AD. Solving the problem of Aβ accumulation in this way may provide an alternative strategy for developing anti-AD drugs.

A wellness study of 108 individuals using personal, dense, dynamic data clouds

Personal data for 108 individuals were collected during a 9-month period, including whole genome sequences; clinical tests, metabolomes, proteomes, and microbiomes at three time points; and daily activity tracking. Using all of these data, we generated a correlation network that revealed communities of related analytes associated with physiology and disease. Connectivity within analyte communities enabled the identification of known and candidate biomarkers (e.g., gamma-glutamyltyrosine was densely interconnected with clinical analytes for cardiometabolic disease). We calculated polygenic scores from genome-wide association studies (GWAS) for 127 traits and diseases, and used these to discover molecular correlates of polygenic risk (e.g., genetic risk for inflammatory bowel disease was negatively correlated with plasma cystine). Finally, behavioral coaching informed by personal data helped participants to improve clinical biomarkers. Our results show that measurement of personal data clouds over time can improve our understanding of health and disease, including early transitions to disease states.

Proteomic differences in amyloid plaques in rapidly progressive and sporadic Alzheimer's disease

Rapidly progressive Alzheimer's disease (rpAD) is a particularly aggressive form of Alzheimer's disease, with a median survival time of 7-10 months after diagnosis. Why these patients have such a rapid progression of Alzheimer's disease is currently unknown. To further understand pathological differences between rpAD and typical sporadic Alzheimer's disease (sAD) we used localized proteomics to analyze the protein differences in amyloid plaques in rpAD and sAD. Label-free quantitative LC-MS/MS was performed on amyloid plaques microdissected from rpAD and sAD patients (n = 22 for each patient group) and protein expression differences were quantified. On average, 913 ± 30 (mean ± SEM) proteins were quantified in plaques from each patient and 279 of these proteins were consistently found in plaques from every patient. We found significant differences in protein composition between rpAD and sAD plaques. We found that rpAD plaques contained significantly higher levels of neuronal proteins (p = 0.0017) and significantly lower levels of astrocytic proteins (p = 1.08 × 10^-6). Unexpectedly, cumulative protein differences in rpAD plaques did not suggest accelerated typical sAD. Plaques from patients with rpAD were particularly abundant in synaptic proteins, especially those involved in synaptic vesicle release, highlighting the potential importance of synaptic dysfunction in the accelerated development of plaque pathology in rpAD. Combined, our data provide new direct evidence that amyloid plaques do not all have the same protein composition and that the proteomic differences in plaques could provide important insight into the factors that contribute to plaque development. The cumulative protein differences in rpAD plaques suggest rpAD may be a novel subtype of Alzheimer's disease.

Pharmacological removal of serum amyloid P component from intracerebral plaques and cerebrovascular Aβ amyloid deposits in vivo

Human amyloid deposits always contain the normal plasma protein serum amyloid P component (SAP), owing to its avid but reversible binding to all amyloid fibrils, including the amyloid β (Aβ) fibrils in the cerebral parenchyma plaques and cerebrovascular amyloid deposits of Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). SAP promotes amyloid fibril formation in vitro, contributes to persistence of amyloid in vivo and is also itself directly toxic to cerebral neurons. We therefore developed (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), a drug that removes SAP from the blood, and thereby also from the cerebrospinal fluid (CSF), in patients with AD. Here we report that, after introduction of transgenic human SAP expression in the TASTPM double transgenic mouse model of AD, all the amyloid deposits contained human SAP. Depletion of circulating human SAP by CPHPC administration in these mice removed all detectable human SAP from both the intracerebral and cerebrovascular amyloid. The demonstration that removal of SAP from the blood and CSF also removes it from these amyloid deposits crucially validates the strategy of the forthcoming ‘Depletion of serum amyloid P component in Alzheimer's disease (DESPIAD)’ clinical trial of CPHPC. The results also strongly support clinical testing of CPHPC in patients with CAA.

Longitudinal Protein Changes in Blood Plasma Associated with the Rate of Cognitive Decline in Alzheimer's Disease

Biomarkers of Alzheimer's disease (AD) progression are needed to support the development of urgently needed disease modifying drugs. We employed a SOMAscan assay for quantifying 1,001 proteins in blood samples from 90 AD subjects, 37 stable mild cognitive impaired (MCI) subjects, 39 MCI subjects converting to AD within a year and 69 controls at baseline and one year follow up. We used linear mixed effects models to identify proteins changing significantly over one year with the rate of cognitive decline, which was quantified as the reduction in Mini Mental State Examination (MMSE) scores. Additionally, we investigated proteins changing differently across disease groups and during the conversion from MCI to AD. We found that levels of proteins belonging to the complement cascade increase significantly in fast declining AD patients. Longitudinal changes in the complement cascade might be a surrogate biomarker for disease progression. We also found that members of the cytokine-cytokine receptor interaction pathway change during AD when compared to healthy aging subjects.

The potential of pathological protein fragmentation in blood-based biomarker development for dementia - with emphasis on Alzheimer's disease

The diagnosis of dementia is challenging and early stages are rarely detected limiting the possibilities for early intervention. Another challenge is the overlap in the clinical features across the different dementia types leading to difficulties in the differential diagnosis. Identifying biomarkers that can detect the pre-dementia stage and allow differential diagnosis could provide an opportunity for timely and optimal intervention strategies. Also, such biomarkers could help in selection and inclusion of the right patients in clinical trials of both Alzheimer’s disease and other dementia treatment candidates. The cerebrospinal fluid (CSF) has been the most investigated source of biomarkers and several candidate proteins have been identified. However, looking solely at protein levels is too simplistic to provide enough detailed information to differentiate between dementias, as there is a significant crossover between the proteins involved in the different types of dementia. Additionally, CSF sampling makes these biomarkers challenging for presymptomatic identification. We need to focus on disease-specific protein fragmentation to find a fragment pattern unique for each separate dementia type – a form of protein fragmentology. Targeting protein fragments generated by disease-specific combinations of proteins and proteases opposed to detecting the intact protein could reduce the overlap between diagnostic groups as the extent of processing as well as which proteins and proteases constitute the major hallmark of each dementia type differ. In addition, the fragments could be detectable in blood as they may be able to cross the blood–brain barrier due to their smaller size. In this review, the potential of the fragment-based biomarker discovery for dementia diagnosis and prognosis is discussed, especially highlighting how the knowledge from CSF protein biomarkers can be used to guide blood-based biomarker development.

Pentraxins and Alzheimer's disease: at the interface between biomarkers and pharmacological targets

Alzheimer's disease (AD) is a neurodegenerative disorder involving deposition of misfolded proteins in vulnerable brain regions leading to inexorable and progressive neuronal loss and deterioration of cognitive functions. The AD brain displays features typical of chronic inflammation as defined by the presence of activated microglia and by an excessive amount of neuroinflammatory components such as cytokines and acute-phase proteins. This review aims to shed light on the role of the immune processes involved in AD, focusing on a family of inflammatory modulators belonging to the acute-phase proteins and crucial components of the humoral arm of innate immunity: pentraxins. In particular we analyze function of the pentraxins in AD, their upregulation in the brain and their contribution to neurodegeneration. Additionally, we highlight the role of pentraxins as putative AD biomarkers and as pharmacological therapeutic targets.

Brain serum amyloid P levels are reduced in individuals that lack dementia while having Alzheimer's disease neuropathology

The neuropathological signs of Alzheimer's disease (AD) include beta amyloid plaques and neurofibrillary tangles. There is a significant population of individuals that have these key hallmarks but show no signs of cognitive impairment, termed non-demented with AD neuropathology (NDAN). The protective mechanism allowing these individuals to escape dementia is unknown. Serum amyloid P (SAP) is a serum protein associated with wound repair that is elevated in the brains of Alzheimer's patients and binds to amyloid plaques. Using immunoblotting and immunohistochemistry, we evaluated SAP levels in postmortem samples of hippocampus and frontal cortex in age-matched controls, AD, and NDAN individuals. AD individuals had significantly increased SAP levels compared to normal controls, while NDAN samples had no significant difference in SAP levels compared to normal controls. Our results suggest that low levels of SAP in plaques marks the brains of individuals that escape dementia despite the presence of beta amyloid plaques and tangles.

Evidence for three loci modifying age-at-onset of Alzheimer's disease in early-onset PSEN2 families

Families with early-onset Alzheimer's disease (AD) sharing a single PSEN2 mutation exhibit a wide range of age-at-onset, suggesting that modifier loci segregate within these families. While APOE is known to be an age-at-onset modifier, it does not explain all of this variation. We performed a genome scan within nine such families for loci influencing age-at-onset, while simultaneously controlling for variation in the primary PSEN2 mutation (N141I) and APOE. We found significant evidence of linkage between age-at-onset and chromosome 1q23.3 (P < 0.001) when analysis included all families, and to chromosomes 1q23.3 (P < 0.001), 17p13.2 (P = 0.0002), 7q33 (P = 0.017), and 11p14.2 (P = 0.017) in a single large pedigree. Simultaneous analysis of these four chromosomes maintained strong evidence of linkage to chromosomes 1q23.3 and 17p13.2 when all families were analyzed, and to chromosomes 1q23.3, 7q33, and 17p13.2 within the same single pedigree. Inclusion of major gene covariates proved essential to detect these linkage signals, as all linkage signals dissipated when PSEN2 and APOE were excluded from the model. The four chromosomal regions with evidence of linkage all coincide with previous linkage signals, associated SNPs, and/or candidate genes identified in independent AD study populations. This study establishes several candidate regions for further analysis and is consistent with an oligogenic model of AD risk and age-at-onset. More generally, this study also demonstrates the value of searching for modifier loci in existing datasets previously used to identify primary causal variants for complex disease traits.

Molecular dissection of Alzheimer's disease neuropathology by depletion of serum amyloid P component

New therapeutic approaches in Alzheimer's disease are urgently needed. The normal plasma protein, serum amyloid P component (SAP), is always present in cerebrospinal fluid (CSF) and in the pathognomonic lesions of Alzheimer's disease, cerebrovascular and intracerebral Abeta amyloid plaques and neurofibrillary tangles, as a result of its binding to amyloid fibrils and to paired helical filaments, respectively. SAP itself may also be directly neurocytotoxic. Here, in this unique study in Alzheimer's disease of the bis(d-proline) compound, (R)-1-[6-[(R)-2-carboxy-pyrrolidin-1-yl]-6-oxo-hexanoyl]pyrrolidine-2-carboxylic acid (CPHPC), we observed depletion of circulating SAP and also remarkable, almost complete, disappearance of SAP from the CSF. We demonstrate that SAP depletion in vivo is caused by CPHPC cross-linking pairs of SAP molecules in solution to form complexes that are immediately cleared from the plasma. We have also solved the structure of SAP complexed with phosphothreonine, its likely ligand on hyperphosphorylated tau protein. These results support further clinical study of SAP depletion in Alzheimer's disease and potentially other neurodegenerative diseases.

Application of proteomics for the identification of differentially expressed protein markers for Down syndrome in maternal plasma

BACKGROUND

Despite the large impact of ultrasonographic and biochemical markers on prenatal screening, the ability to accurately diagnose Down syndrome (DS) is still limited and better diagnostic testing is needed.

METHODS

Plasma from 8 women carrying a DS foetus and 12 with non-DS foetuses matched for gestational age, maternal age and ethnicity, in the second trimester of pregnancy, was analysed by two-dimensional gel electrophoresis (2-DE) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) in order to identify biomarkers for DS.

RESULTS

Gel comparison revealed nine proteins differentially expressed in maternal plasma in women with DS foetuses. Eight proteins, transthyretin (TTHY), ceruloplasmin (CERU), afamin (AFAM), alpha-1-microglobulin (AMBP), apolipoprotein E (APOE), serum amyloid P-component (SAMP), histidine-rich glycoprotein (HRG) and alpha-1-antitrypsin (A1AT) were up-regulated and one, clusterin (CLUS), down-regulated. All nine proteins are known to be involved in foetal growth and development. APOE, SAMP, AFAM and CLUS are associated with the DS phenotype. Western blot and densitometric analysis of APOE and SAMP confirmed the increase of both proteins by 19 and 48% respectively.

CONCLUSIONS

All differentially expressed proteins are candidate biomarkers for DS, providing opportunities for the development of non-invasive prenatal diagnosis. As these are preliminary findings, follow-up experiments are needed for their evaluation.

Complement component C1q inhibits beta-amyloid- and serum amyloid P-induced neurotoxicity via caspase- and calpain-independent mechanisms

Alzheimer's disease is a neurodegenerative disorder characterized by neuronal loss, beta-amyloid (Abeta) plaques, and neurofibrillary tangles. Complement protein C1q has been found associated with fibrillar Abeta deposits, however the exact contributions of C1q to Alzheimer's disease is still unknown. There is evidence that C1q, as an initiator of the inflammatory complement cascade, may accelerate disease progression. However, neuronal C1q synthesis is induced after injury/infection suggesting that it may be a beneficial response to injury. In this study, we report that C1q enhances the viability of neurons in culture and protects neurons against Abeta- and serum amyloid P (SAP)-induced neurotoxicity. Investigation of potential signaling pathways indicates that caspase and calpain are activated by Abeta, but C1q had no effect on either of these pathways. Interestingly, SAP did not induce caspase and calpain activation, suggesting that C1q neuroprotection is in distinct from caspase and calpain pathways. In contrast to Abeta- and SAP-induced neurotoxicity, neurotoxicity induced by etoposide or FCCP was unaffected by the addition of C1q, indicating pathway selectivity for C1q neuroprotection. These data support a neuroprotective role for C1q which should be further investigated to uncover mechanisms which may be therapeutically targeted to slow neurodegeneration via direct inhibition of neuronal loss.

Preferential association of serum amyloid P component with fibrillar deposits in familial British and Danish dementias: Similarities with Alzheimer's disease

Two hereditary forms of cerebrovascular amyloidosis, familial British and Danish dementias (FBD and FDD), share striking similarities with Alzheimer's disease (AD) despite structural differences among their amyloid subunits (ABri in FBD, ADan in FDD, and Abeta in AD). Neuropathological lesions in these disorders include neurofibrillary tangles, parenchymal amyloid and pre-amyloid deposits and overwhelming cerebral amyloid angiopathy co-localizing with reactive microglia and multiple amyloid associated proteins including activation products of the complement cascade. Immunohistochemical analysis of FBD and FDD brain lesions unveiled the presence of serum amyloid P-component (SAP) primarily associated with thioflavin positive amyloid deposits in spite of the significant pre-amyloid burden existing in both disorders. Using affinity chromatography and ELISA binding assays we demonstrated specific, calcium-dependent, saturable, high affinity binding interactions between SAP and ABri/ADan peptides, with dissociation constant values in the sub-nanomolar range and within the same order of magnitude as those resulting from the interaction of SAP with Alzheimer's Abeta1-40 and Abeta1-42. The preferential association of SAP with fibrillar amyloid lesions and not with non-fibrillar pre-amyloid deposits is puzzling, suggesting that SAP modulates the assembly and stability of the final fibril rather than participating in the early steps of protein misfolding and oligomerization.

Structure and function of amyloid in Alzheimer's disease

This review is focused on the structure and function of Alzheimer's amyloid deposits. Amyloid formation is a process in which normal well-folded cellular proteins undergo a self-assembly process that leads to the formation of large and ordered protein structures. Amyloid deposition, oligomerization, and higher order polymerization, and the structure adopted by these assemblies, as well as their functional relationship with cell biology are underscored. Numerous efforts have been directed to elucidate these issues and their relation with senile dementia. Significant advances made in the last decade in amyloid structure, dynamics and cell biology are summarized and discussed. The mechanism of amyloid neurotoxicity is discussed with emphasis on the Wnt signaling pathway. This review is focused on Alzheimer's amyloid fibrils in general and has been divided into two parts dealing with the structure and function of amyloid.

Progressive degeneration of nonphosphorylated neurofilament protein-enriched pyramidal neurons predicts cognitive impairment in Alzheimer's disease: stereologic analysis of prefrontal cortex area 9

We performed a stereologic analysis of a subset of pyramidal neurons known to be vulnerable in Alzheimer's disease (AD) and characterized by particularly high somatodendritic levels of nonphosphorylated neurofilament protein. In the neocortex, these large pyramidal neurons reside in the deep part of layer III (layer IIIc) and the superficial part of layer V (layer Va). We focused on prefrontal cortex area 9 in elderly control cases in comparison to cases with different degrees of cognitive dysfunction. The results confirmed that these neurons are preferentially vulnerable in AD, as their numbers decrease dramatically in cases with definite dementia, correlating strongly with the severity of the disease, to a nearly complete loss (>90%) in the endstages of AD. Furthermore, a triple-labeling experimental paradigm revealed that these particular neurons are far more likely to develop neurofibrillary tangles (NFT) and do so at a faster rate than other pyramidal cells. Nonphosphorylated neurofilament protein-rich neurons also shrink considerably during formation of NFT and the largest among them are preferentially affected. Laminar differences in the severity of these effects were observed, layer Va being more severely affected, possibly correlating with the involvement of specific cortical projections. These data reveal that different populations of neurons prone to NFT formation are lost at different rates in AD, and that nonphosphorylated neurofilament protein-enriched neurons emerge as a strikingly vulnerable subpopulation of neurons. Their preferential involvement suggests that neurons providing specific corticocortical connections between association areas are at high risk for degeneration in AD.

Senile plaque composition and posttranslational modification of amyloid-beta peptide and associated proteins

Amyloid deposits are primarily composed of the amyloid-beta protein, although other proteins (and metal ions) also have been colocalized to these lesions. The pattern of oxidative modifications in amyloid plaques is very different to that associated with neurofibrillary tangles and neuronal cell bodies, likely reflecting the different composition of these structures, accessibility of oxidants, the generation of oxidants in and around these structures and the intrinsic antioxidant defense systems to protect these structures. Future studies directed at understanding Abeta interactions with other amyloid components, the role of oxidative modifications in stabilizing amyloid deposits and the determination of protease cleavage sites on Abeta may provide mechanistic insights regarding both amyloid formation and removal.

Accumulation of heparan sulfate proteoglycans in cerebellar senile plaques

Alzheimer's disease (AD) brains are characterized by the presence of senile plaques (SPs), which primarily consist of amyloid beta protein (Abeta). Besides Abeta, several other proteins with the ability to modulate amyloid fibril formation accumulate in SPs, e.g. heparan sulfate proteoglycans (HSPGs). Cerebellar SPs are predominantly of the diffuse type, whereas fibrillar SPs are rarely observed. Furthermore, because of the spatial separation of non-fibrillar and fibrillar SPs in the cerebellum, this brain region provides a model for the study of the association of Abeta-associated factors with various stages of SP formation. In the present study, we performed an immunohistochemical analysis to investigate the expression of the HSPG species agrin, perlecan, glypican-1 and the syndecans 1-3 as well as glycosaminoglycan side-chains in cerebellar SPs. We demonstrated that agrin and glypican-1 were expressed in both non-fibrillar and fibrillar cerebellar SPs, whereas the syndecans were only associated with fibrillar cerebellar SPs. Perlecan expression was absent in all cerebellar SPs. Since fibrillar and non-fibrillar SPs may develop independently in the cerebellum, it is likely that agrin, glypican-1 as well as heparan sulfate glycosaminoglycans may contribute to the formation of both cerebellar plaque types, whereas syndecan only seems to play a role in the generation of cerebellar fibrillar plaques.

The systemic and local acute phase response following acute brain injury

It is not known whether acute brain injury results in a systemic acute phase response (APR) or whether an APR influences outcome after an insult to the CNS. The present study sought to establish whether brain injury elicits a systemic or local APR. The expression of acute phase protein (APP) mRNA in liver and brain tissues was measured by Taqman reverse transcriptase-polymerase chain reaction after an excitotoxic lesion in the striatum or challenge with a proinflammatory cytokine. N-methyl-d-aspartate (NMDA)-induced brain lesion did not elicit a systemic APR. In contrast, proinflammatory challenge with mouse recombinant interleukin-1beta (mrIL-1beta) resulted in a significant hepatic APP mRNA expression within 6 hours. Thus, an inflammatory challenge that results in a meningitis leads to a hepatic APR, whereas acute brain injury alone, with no evidence of a meningitis, does not produce an APR. This is surprising because NMDA leads to an increase in endogenous IL-1beta synthesis. This suggests that the brain has an endogenous antiinflammatory mechanism, which protects against the spread of inflammation after an acute injury. In the brain, both excitotoxic lesions and proinflammatory challenge resulted in a profound parenchymal upregulation of APP mRNA after 6 and 12 hours in the injected hemisphere. These results suggest that the local APR may play a role as an antiinflammatory mechanism. These findings indicate a potentially pivotal role for peripheral and local APP production on outcome after brain injury.

Effect of cytokines, dexamethasone and the A/T-signal peptide polymorphism on the expression of alpha(1)-antichymotrypsin in astrocytes: significance for Alzheimer's disease

Proinflammatory cytokines and acute phase proteins, such as alpha(1)-antichymotrypsin, are over expressed in microglia and astrocytes in brain regions with abundant mature amyloid plaques, suggesting a glial cell-led brain acute phase response in the Alzheimer neuropathology. In this paper, we show that alpha(1)-antichymotrypsin gene expression in human astrocytes is elevated by interleukin-1 and interleukin-6, and further enhanced by glucocorticoid, while the homologous contrapsin gene in rat astrocytes is unaffected by these cytokines. These distinct gene regulation mechanisms might help to explain the differential susceptibility of humans and rodents to amyloid formation of the Alzheimer's type. In addition, we demonstrate that the alpha(1)-antichymotrypsin A-allele that encodes a different signal peptide and is a suggested risk factor for Alzheimer's disease gives rise to a reduced level of immature alpha(1)-antichymotrypsin in transfected cells. The physiological result would be an enhanced ability of the A-encoded alpha(1)-antichymotrypsin protein to become secreted and promote extracellular amyloid formation. We discuss our findings in terms of a model in which cytokine-induced alpha(1)-antichymotrypsin synthesis in astrocytes constitutes a specific inflammatory pathway that accelerates the development of Alzheimer's disease and could at least partly underlie the regional specificity and species restriction of the neuropathology.

Human neurons generate C-reactive protein and amyloid P: upregulation in Alzheimer's disease

C-reactive protein (CRP) and amyloid P (AP) are pentraxins which are associated with many pathological lesions, including the amyloid deposits and neurofibrillary tangles (NFTs) of Alzheimer disease (AD). It has always been assumed that they are generated by liver and delivered to their sites of action by serum. Here we report by in situ hydridization, reverse transcriptase-polymerase chain reaction analysis, Western blotting and immunohistochemistry that the mRNAs and proteins of both CRP and AP are concentrated in pyramidal neurons and are upregulated in affected areas of AD brain. Controlling pentraxin production at the tissue level may be important in reducing inflammatory damage in AD.

Complement activation by the amyloid proteins A beta peptide and beta 2-microglobulin

Complement activation (CA) has been reported to play a role in the pathogenesis of Alzheimer's disease (AD). To investigate whether CA may contribute to amyloidogenesis in general, the CA potential of different amyloid fibril proteins was tested. CA induced by A beta preparations containing soluble protein, protofilaments and some fibrils or only fibrils in a solid phase system (ELISA) was modest with a slow kinetics compared to the positive delta IgG control. Soluble A beta induced no detectable CA in a liquid phase system (complement consumption assay) while fibrillar A beta caused CA at 200 mg/ml and higher concentrations. Soluble beta 2-microglobulin (beta 2M) purified from peritoneal dialysates was found to be as potent a complement activator as A beta in both solid and liquid phase systems while beta 2M purified from urine exhibited lower activity, a difference which may be explained by differences observed in SDS-resistant oligomers and isoforms. Soluble Amyloid A-protein caused no significant CA. A beta and beta 2M activated complement via the classical pathway. The modifying influence by amyloid-associated molecules on A beta-induced CA was also investigated, but neither serum amyloid P component nor heparan sulfate did significantly alter the A beta-induced CA. The results indicate that not only fibrillar A beta but also oligomers of, in particular, beta 2M from patients with dialysis-associated amyloidosis are capable of inducing CA at supra-physiological concentrations.

New insights into the role of serum amyloid P component, a novel lipopolysaccharide-binding protein

Serum amyloid P component (SAP) is a highly preserved plasma protein named for its ubiquitous presence in amyloid deposits. Although SAP is described to bind many ligands, no clear biological function has been ascribed to it as yet. This review summarizes the current knowledge about the protein SAP, its ligands and functional properties. Finally, the author focuses on the recent finding of the binding of SAP to lipopolysaccharide (LPS) and Gram-negative bacteria and the possible functional consequences of these interactions.

Assessment of cerebrospinal fluid levels of serum amyloid P component in patients with Alzheimer's disease

Serum amyloid P component (SAP) is a normal plasma constituent that is observed both in senile plaque and in neurofibrillary tangle in brains of patients with Alzheimer's disease (AD). In this study, we evaluated the SAP levels in cerebrospinal fluid (CSF) of 72 patients with AD, 11 frontotemporal dementia and nine normal control subjects. There was no significant difference in the SAP levels between the AD group and other groups. However, among AD patients, cognitive function was rated using the Mini-Mental State Examination and was correlated with the SAP level (R = 0.38, P < 0.05). Our results suggest that measurement of the SAP levels in CSF can be useful for assessing the degree of cognitive impairment in AD patients.

Up-regulated production and activation of the complement system in Alzheimer's disease brain

We used reverse transcriptase-polymerase chain reaction and Western blotting techniques to measure the levels of complement mRNAs and their protein products in Alzheimer's disease (AD) brain compared with non-AD brain. mRNAs for C1q, C1r, C1s, C2, C3, C4, C5, C6, C7, C8, and C9 were detected in the 11 regions of brain that were investigated. The mRNA levels were markedly up-regulated in affected areas of AD brain. In the entorhinal cortex, hippocampus, and midtemporal gyrus, which had dense accumulations of plaques and tangles, C1q mRNA was increased 11- to 80-fold over control levels, and C9 mRNA 10- to 27-fold. These levels were substantially higher than in the livers of the same cases. Western blot analysis of AD hippocampus established the presence of all of the native complement proteins as well as their activation products C4d, C3d, and the membrane attack complex. These data indicate that high levels of complement are being produced in affected areas of AD brain, that full activation of the classical complement pathway is continuously taking place, and that this activation may be contributing significantly to AD pathology.

The in vitro neuronal toxicity of pentraxins associated with Alzheimer's disease brain lesions

Serum amyloid P component (AP) and C-reactive protein (CRP) are normal serum components which belong to the pentraxin family of proteins. These proteins have been previously localized by immunohistochemical method to the brain lesions of Alzheimer's disease (AD). AP is a constant constituent of amyloid deposits including those found in AD. Both AP and CRP have been localized to AD neurofibrillary tangles. An indirect role for these proteins has been previously suggested in the etiology of AD. We studied the effects of serum AP and CRP on a human-derived neuronal cell line (hNT). In treated cell cultures, AP and CRP were detected immunohistochemically within hNT neurons, indicating cellular uptake of these proteins. Serum AP at the lowest serum physiological concentration (8 microgram/ml) showed a marked toxicity to hNT neurons. CRP also displayed toxicity to the hNT neurons but at a level compatible with inflammatory states (50 microgram/ml). These results suggest a more direct role for serum AP and CRP in the pathogenesis of AD.

The combined inactivation of tumor necrosis factor and interleukin-6 prevents induction of the major acute phase proteins by endotoxin

The constellation of changes known as the acute phase response (APR) is a cytokine-driven process initiated by tissue inflammation. The proinflammatory cytokines, TNF, IL-1 and IL-6, are considered to be the primary mediators of the APR. IL-6 and IL-1beta gene-deleted mice (Fattori et al., J. Exp. Med. 1994. 180: 1243-1250; Kopf et al., Nature 1994. 368: 339-342; Fantuzzi et al., J. Immunol. 1996. 157: 291-296, respectively), exhibit impaired APR to turpentine injection but only a slight reduction in plasma acute phase protein levels in response to lipopolysaccharide (LPS). This infers an important role for TNF in the LPS-induced APR, however, in the present study, normal APR to both turpentine and LPS were observed in TNF/LTalpha-deficient mice. A striking absence of elevated major acute phase proteins, SAP and SAA, was observed in mice deficient in TNF/LTalpha and IL-6, suggesting that TNF-alpha or LTalpha do indeed exert important nonredundant synergism in the IL-1/IL-6 primary response. The regulation of other parameters typically altered in an APR, body weight, blood glucose and haptoglobin, was normal in LPS-dosed TNF/LTalpha-deficient and wild-type mice. The observed transcriptional response for SAA and SAP in these TNF/LTalpha/IL-6-deficient mice, in lieu of elevated plasma levels, suggests that SAA and SAP expression is possibly posttranscriptionally regulated.

Isoforms of murine and human serum amyloid P component

Isoelectric focusing (IEF) and immunofixation of murine serum amyloid P component (SAP), purified and in serum, showed a distinct and strain-dependent isoform pattern with up to seven bands (pI 5.1-5.7). Neuraminidase treatment caused a shift of the isoforms to more basic pI values, but did not affect their number. When the acute-phase response was analysed in three mouse strains, CBA/J and C3H/HeN initially showed seven SAP isoforms in serum and C57BL/6 J three or four. The responses in all three strains peaked at day 2 and were normalized within 14 days. On days 2 and 4, CBA/J and C3H/HeN mice showed one more acidic isoform and an increase in the concentration of the most basic isoform. C57BL/6 J mice exhibited two to three new isoforms during the acute-phase response. This appears to be the first demonstration of the physiological existence of SAP isoforms. In contrast, demonstration of isoforms of human SAP required the presence of urea and higher SAP concentrations. TEF and immunofixation of SAP monomers showed five to eight isoforms, ranging from pI 4.7-5.7. IEF of SAP in human serum resulted in a less distinct pattern and more acidic isoforms. As with murine SAP, neuraminidase treatment caused a shift of the isoforms, but no reduction in isoform number. Two-dimensional gel electrophoresis confirmed the existence of multiple isoforms of human SAP monomers.

Serum apolipoprotein E level is not increased in Alzheimer's disease: the Rotterdam study

The APOE*4 allele of the apolipoprotein E gene (APOE) is an important risk factor for Alzheimer's disease. It has been suggested that levels of apolipoprotein E (apoE) in plasma are increased in Alzheimer's disease. In this population-based study, we found that serum apoE levels were lower in Alzheimer patients compared to non-demented controls (0.75 micromol/l (SD 0.35), vs. 0.83 micromol/l (SD 0.40), P < 0.05). This finding is in accordance with lower serum apoE levels as observed in carriers of the APOE*4 allele, who are over-represented in Alzheimer's disease. After adjustment for age, sex, total protein, albumin level, body mass index and the APOE genotype, the difference in serum apoE levels largely disappeared. Our population-based study suggests that the differences in serum apoE level between Alzheimer patients and controls are mainly the result of differences in the distribution of the APOE genotype.

Butyrylcholinesterase in the life cycle of amyloid plaques

Deposits of diffuse beta-amyloid (Abeta) may exist in the brain for many years before leading to neuritic degeneration and dementia. The factors that contribute to the putative transformation of the Abeta amyloid from a relatively inert to a pathogenic state remain unknown and may involve interactions with additional plaque constituents. Matching brain sections from 2 demented and 4 nondemented subjects were processed for the demonstration of Abeta immunoreactivity, butyrylcholinesterase (BChE) enzyme activity, and thioflavine S binding. Additional sections were processed for the concurrent demonstration of two or three of these markers. A comparative analysis of multiple cytoarchitectonic areas processed with each of these markers indicated that Abeta plaque deposits are likely to undergo three stages of maturation, ie, a "diffuse" thioflavine S-negative stage, a thioflavine S-positive (ie, compact) but nonneuritic stage, and a compact neuritic stage. A multiregional analysis showed that BChE-positive plaques were not found in cytoarchitectonic areas or cortical layers that contained only the thioflavine S-negative, diffuse type of Abeta plaques. The BChE-positive plaques were found only in areas containing thioflavine S-positive compact plaques, both neuritic and nonneuritic. Within such areas, almost all (>98%) BChE-containing plaques bound thioflavine S, and almost all (93%) thioflavine S plaques contained BChE. These results suggest that BChE becomes associated with amyloid plaques at approximately the same time that the Abeta deposit assumes a compact beta-pleated conformation. BChE may therefore participate in the transformation of Abeta from an initially benign form to an eventually malignant form associated with neuritic tissue degeneration and clinical dementia.

Serum protein leakage in Alzheimer's disease revisited

Leakage of serum proteins into the brain parenchyma has been repeatedly used as evidence of blood-brain barrier (BBB) damage in experimental and human studies. However, there is no consensus in the literature concerning this phenomenon in Alzheimer's disease (AD). We have examined this question by comparing frontal lobe sections in seven groups of patients: Multi-infarct dementia (n = 6), AD with (n = 10) and without (n = 10) infarcts, age-matched controls with (n = 10) and without (n = 10) infarcts, controls with neurodegenerative diseases other than AD, and young controls (n = 10). An additional series compared prospectively followed patients with a diagnosis of either multi-infarct dementia (n = 5) or AD (n = 4). Albumin was detected in white-matter astrocytes in all cases, without significant variation in intensity. In addition, diverse combinations of neurons, astrocytes, and (in AD patients) senile plaques were present in the cerebral cortex in an inconsistent manner. Semiquantitative analysis showed no statistically significant differences among groups. Anti-IgG labeled astrocytes in infarcts only. Complement C3c component was detected in rare amyloid plaques in a minority (15%) of AD cases. Selective labeling of AD-specific lesions in a patchy manner was observed for serum amyloid P. We conclude that there is no immunohistochemical evidence of alteration of the BBB in Alzheimer's disease with or without vascular factors or in old age. Serum amyloid P binds avidly to AD lesions, but our findings are consistent with leakage through the BBB during the agonal or immediate postmortem period. Finally, no specific pattern of abnormality in the BBB was detected in multi-infarct dementia.

The role of amyloid in the pathogenesis of Alzheimer's disease

Since the identification in 1984 of the amyloid beta protein (Abeta) as the major component of senile plaques and cerebrovascular amyloid in Alzheimer's disease (AD) brains, it is well accepted that the production of this protein is a crucial factor in the pathogenesis of AD. Abeta is produced by cleavage from the amyloid precursor protein (APP) and can form fibrils in vivo and in vitro. The formation of these fibrils is influenced by proteins that are found in association with Abeta-containing lesions in the AD brain. Several of these proteins arise by an inflammatory response of the brain to Abeta production. The distribution of different isoforms of Abeta, varying at the C-terminus of the peptide, varies among the Abeta-containing lesions in AD brains. Such variations may have consequences for the pathogenesis of AD because the various Abeta isoforms differ in their capacity to form fibrils, and they have different toxic effects on neurons and vascular cells, respectively. The experimental data indicate that the pathogenesis of senile plaques is different from the generation of cerebrovascular amyloidosis. Summarizing models for either type of AD pathology are presented.

Amyloid deposition is delayed in mice with targeted deletion of the serum amyloid P component gene

The tissue amyloid deposits that characterize systemic amyloidosis, Alzheimer's disease and the transmissible spongiform encephalopathies always contain serum amyloid P component (SAP) bound to the amyloid fibrils. We have previously proposed that this normal plasma protein may contribute to amyloidogenesis by stabilizing the deposits. Here we show that the induction of reactive amyloidosis is retarded in mice with targeted deletion of the SAP gene. This first demonstration of the participation of SAP in pathogenesis of amyloidosis in vivo confirms that inhibition of SAP binding to amyloid fibrils is an attractive therapeutic target in a range of serious human diseases.

beta-Amyloid-induced IL-1 beta release from an activated human monocyte cell line is calcium- and G-protein-dependent

The proinflammatory cytokine, interleukin-1 (IL-1) is elevated in the Alzheimer's disease (AD) brain. Studies from our laboratory have demonstrated that beta-amyloid (A beta) 1-42, fibrillar A beta 1-40 and A beta 25-35 induce the release of IL-1 beta from activated THP-1 cells, a human monocyte cell line. A beta also is chemotactic for primary rodent microglia and peritoneal macrophages. We hypothesize that A beta is a chemokine and induces these responses by interaction with chemotactic receptors. If this is true, then these A beta-induced responses should be calcium-dependent and require activation of pertussis toxin-sensitive G-proteins. To test this hypothesis, THP-1 cells were grown in culture with lipopolysaccharide (LPS) and incubated with A beta 1-42 (5 muM) in the presence and absence of a calcium chelator, an inhibitor of intracellular calcium mobilization, a calcium channel blocker, or pertussis toxin, a bacterial endotoxin which uncouples G proteins from receptors by catalyzing the ADP ribosylation of cysteine near the carboxy-terminus of the alpha subunit. The media was collected and IL-1 beta present in the media was measured using an ELISA. Treatment of LPS-activated THP-1 cells with A beta 1-42 significantly elevated IL-1 beta released into the media as previously shown. Addition or ethylene glycol-bis (beta-aminothyl ether) N,N,N'N'-tetraacetic acid (EGTA) (0.5 mM), a calcium chelator, to the media blocked A beta-induced IL-1 beta release, but had no effect on LPS-activated THP-1 cell release of IL-1 beta. The presence of 3,4,5-trimethoxybenzoic acid 8-(diethyl amino)-octyl ester (TMB-8), an inhibitor of intracellular calcium mobilization, as well as nickel chloride, a non-specific calcium channel blocker, in the media also inhibited A beta-induced IL-1 release from LPS-activated THP-1 cells. IL- 1 beta release from activated THP-1 monocytes incubated with TMB-8 and nickel chloride without A beta remained at baseline values. Pretreatment of THP-1 monocytes with pertussis toxin for 4 h, followed by LPS activation and incubation with A beta, antagonized the release of IL-1 beta from these cells, but did not alter IL-1 beta release from activated THP-1 monocytes. These data suggest that A beta-induced IL-1 beta release from these cells is calcium-dependent and requires the activation of specific G-proteins. These findings are consistent with known second messengers that are activated following stimulation of chemotactic receptors.

C-reactive protein-like immunoreactivity in the neurofibrillary tangles of Alzheimer's disease

C-reactive protein (CRP) is a plasma acute-phase protein, normally not found in the brain. Previous studies have demonstrated the presence of CRP in the senile plaques of Alzheimer's disease (AD). In this study, the presence of CRP-like immunoreactivity in AD neurofibrillary tangles (NFT) was demonstrated following pre-treatment of tissue sections with formic acid. CRP-like immunoreactivity was observed in both extracellular and intracellular NFT and was co-localized with the NFT marker PHF-1 and the amyloid P component (AP). The CRP-like immunoreactive NFT were less numerous and more limited in their distribution than PHF-1 or AP-immunoreactive NFT. The present results further support an involvement of inflammatory processes in the etiology of AD.

Inflammation and Alzheimer's disease pathogenesis

Appreciation of the role that inflammatory mediators play in Alzheimer's disease (AD) pathogenesis continues to be hampered by two related misconceptions. The first is that to be pathogenically significant a neurodegenerative mechanism must be primary. The second is that inflammation merely occurs to clear the detritis of already existent pathology. The present review addresses these issues by showing that 1) inflammatory molecules and mechanisms are uniquely present or significantly elevated in the AD brain, 2) inflammation may be a necessary component of AD pathogenesis, 3) inflammation may be sufficient to cause AD neurodegeneration, and 4) retrospective and direct clinical trials suggest a therapeutic benefit of conventional antiinflammatory medications in slowing the progress or even delaying the onset of AD.

Molecular aspects of inflammatory and immune responses in Alzheimer's disease

Recent advances indicate numerous molecular and cellular elements of the immune system are involved in the pathogenesis of Alzheimer's disease. Amyloid beta protein deposition induces many molecules associated with a predominantly local inflammatory response within the brain parenchyma. These responses also provoke the release of immune system mediators including cytokines, which all seem largely to be produced by reactive cells such as astrocytes and microglia. Classical acute phase proteins of the pentraxin and serine protease inhibitor (serpin) families as well as a host of complement proteins and some coagulation factor seem the most intrinsically involved. These secreted molecules display variable binding with the amyloidotic lesions. Although our understanding of the molecular specificity and significance of the interaction of these proteins within the lesions is not replete, the development of unique inhibitors of the inflammatory reactions could provide therapeutic strategies to impede the pathogenetic process. Currently, this appears a more viable option than to inhibit amyloid beta production or modify amyloid beta precursor protein processing, an approach which seems more complex.

beta-Amyloid induces increased release of interleukin-1 beta from lipopolysaccharide-activated human monocytes

Previous reports have demonstrated that IL-1 is elevated in the Alzheimer's disease brain. We propose that beta-amyloid (A beta) in senile plaques triggers microglial interleukin-1(IL-1) release. Since microglia and monocytes have similar lineage and functions, the human monocyte cell line, THP-1, was used to determine whether A beta peptides can stimulate release of IL-1 beta. THP-1 cells were grown in culture with LPS and incubated with various A beta peptides (0.5-10 microM). IL-1 released into the medium was measured using either an IL-1 beta ELISA or an IL-1 bioassay. Treatment of activated THP-1 cells with A beta 25-35, fibrillar A beta 1-40, or A beta 1-42 significantly elevated IL-1 beta release. A beta 25-35 with a scrambled sequence or non-fibrillar A beta 1-40 did not significantly change IL-1 beta release from activated THP-1 cells. The A beta 25-35- and fibrillar A beta 1-40 induced IL-1 beta release was dose-dependent. IL-1 released following treatment with A beta 25-35 and measured using an IL-1 bioassay gave similar results. The present report provides evidence that A beta is capable of elevating release of functional IL-1 beta, a potent pro-inflammatory cytokine, from macrophages/microglia and provides support that a chronic local inflammatory response is an ongoing phenomenon within and surrounding senile plaques.

Demonstration of a heparin-binding site in serum amyloid P component using affinity capillary electrophoresis as an adjunct technique

Linear heparin-binding sites in the DNA- and heparin-binding serum protein amyloid P component were investigated using affinity capillary electrophoresis and reversed-phase HPLC in conjunction with affinity chromatography. Peptide fragments were generated from amyloid P component by treatment with Glu-C and Asp-N endoproteinases. This peptide mixture was separated by HPLC before and after passage through a column of immobilized heparin. In addition, the proteolytic digest was separated by capillary electrophoresis in the presence of various amounts of heparin in solution. Migration shift patterns in the presence of heparin were in agreement with one of the components shown by HPLC to interact with immobilized heparin. The identity of this fragment was established by mass spectrometry after preparative HPLC and represents a novel heparin-binding sequence. The results illustrate the potential synergy in the combination of the two high-resolution separation techniques HPLC and CE. HPLC has the advantages of high recovery and preparative power while capillary electrophoresis is noted for highly efficient separations under physiological conditions. The possibility of using unmodified ligands in the study of biological activities of protein substructures while consuming very little material makes CE further attractive.

The inflammatory response system of brain: implications for therapy of Alzheimer and other neurodegenerative diseases

Cultured brain cells are capable of generating many molecules associated with inflammatory and immune functions. They constitute the endogenous immune response system of brain. They include complement proteins and their regulators, inflammatory cytokines, acute phase reactants and many proteases and protease inhibitors. Most of the proteins are made by microglia and astrocytes, but even neurons are producers. Many appear in association with Alzheimer disease lesions, indicating a state of chronic inflammation in Alzheimer disease brain. Such a state can apparently exist without stimulation by peripheral inflammatory mediators or the peripheral immune system. A strong inflammatory response may be autotoxic to neurons, exacerbating the fundamental pathology in Alzheimer disease and perhaps other neurological disorders. Autotoxic processes may contribute to cellular death in chronic inflammatory diseases affecting other parts of the body, suggesting the general therapeutic value of anti-inflammatory agents. With respect to Alzheimer disease, multiple epidemiological studies indicate that patients taking anti-inflammatory drugs or suffering from conditions in which such drugs are routinely used, have a decreased risk of developing Alzheimer disease. In one very preliminary clinical trial, the anti-inflammatory drug indomethacin arrested progress of the disease. New agents directed against the inflammatory processes revealed in studies of Alzheimer disease lesions may have broad therapeutic applications.

The distribution of fibronectin and P component in Descemet's membrane: an immunoelectron microscopic study

Descemet's membrane consists of two zones, the 'anterior banded zone' which contains wide-spaced collagen and the amorphous 'posterior non-banded zone'. It is attached anteriorly to the corneal stroma by a narrow transitional zone termed the 'interfacial matrix'. The distribution of fibronectin and P component within the different layers of Descemet's membrane was investigated using an ultrastructural immunogold technique. Seven normal human corneas from an eye bank and one specimen from an orbital exenteration were examined. Fibronectin was predominantly present in the posterior part of the posterior non-banded zone and in the anterior banded zone. The anterior part of the posterior non-banded zone contained less fibronectin. P component was present throughout the anterior banded and posterior non-banded zones. There was a sharp demarcation at the interfacial matrix since neither substance was observed in the corneal stroma. The differences shown in the distribution of fibronectin and P component within Descemet's membrane may have resulted from their binding to other substances or alternatively from differences in the quantities laid down during the evolution of this basement membrane.

Apolipoprotein E carboxyl-terminal fragments are complexed to amyloids A and L. Implications for amyloidogenesis and Alzheimer's disease

Apolipoprotein E (ApoE) immunoreactivity is consistently present in the senile plaques and neurofibrillary tangles of Alzheimer's disease (AD) brain. In vitro, apoE, and in particular its apoE4 isoform, can bind to and promote fibrillogenesis of the amyloid A beta peptide, the main constituent of senile plaques. These findings, together with the strong genetic association between late onset AD and the E4 allele of apoE, have strengthened the hypothesis that apoE may have a central role in the pathogenesis of AD by modulating A beta cerebral accumulation. However, apoE immunoreactivity is present in all cerebral and systemic amyloidoses tested, and tryptic apoE fragments have been identified in association with amyloid A (AA). In order to further elucidate the interaction between apoE and amyloids, we purified AA and amyloid L (AL) fibrils from patients with familial Mediterranean fever and primary amyloidosis, respectively, and studied the association of apoE with AA and AL proteins. In each case, apoE fragments, detected by Western blot, co-purified with the amyloid fibrils. Microsequencing analysis identified COOH-terminal fragments of apoE, similar to the 10-kDa fragment produced by thrombin digestion that contains the purported binding region to A beta. In vitro co-incubation of AA with purified human apoE resulted in the formation of an SDS-resistant AA.apoE complex and a higher degree of polymerization of the AA peptide. These findings and similar results obtained from AD senile plaques suggest that 1) the carboxyl-terminal fragment of apoE is complexed to amyloid fibrils and resists proteolysis in vivo and 2) apoE may promote amyloidogenesis through a conformation-dependent interaction regardless of the primary structure of the amyloid precursors.

Serum amyloid P component prevents proteolysis of the amyloid fibrils of Alzheimer disease and systemic amyloidosis

Extracellular deposition of amyloid fibrils is responsible for the pathology in the systemic amyloidoses and probably also in Alzheimer disease [Haass, C. & Selkoe, D. J. (1993) Cell 75, 1039-1042] and type II diabetes mellitus [Lorenzo, A., Razzaboni, B., Weir, G. C. & Yankner, B. A. (1994) Nature (London) 368, 756-760]. The fibrils themselves are relatively resistant to proteolysis in vitro but amyloid deposits do regress in vivo, usually with clinical benefit, if new amyloid fibril formation can be halted. Serum amyloid P component (SAP) binds to all types of amyloid fibrils and is a universal constituent of amyloid deposits, including the plaques, amorphous amyloid beta protein deposits and neurofibrillary tangles of Alzheimer disease [Coria, F., Castano, E., Prelli, F., Larrondo-Lillo, M., van Duinen, S., Shelanski, M. L. & Frangione, B. (1988) Lab. Invest. 58, 454-458; Duong, T., Pommier, E. C. & Scheibel, A. B. (1989) Acta Neuropathol. 78, 429-437]. Here we show that SAP prevents proteolysis of the amyloid fibrils of Alzheimer disease, of systemic amyloid A amyloidosis and of systemic monoclonal light chain amyloidosis and may thereby contribute to their persistence in vivo. SAP is not an enzyme inhibitor and is protective only when bound to the fibrils. Interference with binding of SAP to amyloid fibrils in vivo is thus an attractive therapeutic objective, achievement of which should promote regression of the deposits.

Apolipoprotein E alleles but neither apolipoprotein B nor apolipoprotein AI/CIII alleles are associated with late onset, familial Alzheimer's disease

The possibility of a genetic association between late onset, familial Alzheimer's disease and alleles at the apolipoprotein B and AI/CIII loci have been examined. In contrast to the genetic association with the apolipoprotein E locus, no evidence for genetic associations to these loci was found.