Activated microglia and cerebral amyloid deposits in Alzheimer's disease

Salvianolic acid B exerts protective effects against Aβ-induced neuroinflammation through the inhibition of NLRP3 inflammasome activation and switching of M1/M2 polarization

BACKGROUND

Salvianolic acid B (SalB) is a bioactive extract of Salvia miltiorrhiza with the ability to ameliorate amyloid beta (Aβ)-induced neuronal degeneration and neuroinflammation in Alzheimer's disease (AD). However, the underlying mechanisms of this action have not been elucidated. Herein, we aimed to investigate whether the neuroprotective effect of SalB is attributable to the modulation of microglial polarization and NLRP3 inflammasome-mediated neuroinflammation.

METHODS

Based on the TMT-labeled proteomics analysis, immunofluorescence, western blot and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were employed to investigate the effects of SalB on neuroinflammation in Aβ1-42-stimulated BV2 microglia cells.

RESULTS

At the proteomic level, a total of 6631 proteins were quantified, and of these, 104 were significantly influenced under Aβ1-42 treatment. The expression of 36 Aβ1-42-induced differentially expressed proteins were significantly recovered by SalB treatment (13 upregulated and 23 downregulated). NLRP3 was significantly recovered and was identified as one of the hub proteins. Consistent with the result of the proteomic analysis, western blot and qRT-PCR demonstrated that SalB reduced Aβ1-42-induced NLRP3 upregulation at both the protein and mRNA levels. In addition, SalB significantly blocked M1 microglia polarization, enhanced M2 microglial polarization, and inhibited the production of caspase-1 and interleukin-1β in BV2 microglia cells.

CONCLUSION

our study demonstrated, for the first time, that the anti-inflammatory effects of SalB were mediated by the regulation of NLRP3 activation and promotion of microglial M2 polarization, indicating the potential of SalB as a novel therapeutic candidate for AD.

Microglia and Cholesterol Handling: Implications for Alzheimer's Disease

Cholesterol is essential for brain function and structure, however altered cholesterol metabolism and transport are hallmarks of multiple neurodegenerative conditions, including Alzheimer's disease (AD). The well-established link between apolipoprotein E (APOE) genotype and increased AD risk highlights the importance of cholesterol and lipid transport in AD etiology. Whereas more is known about the regulation and dysregulation of cholesterol metabolism and transport in neurons and astrocytes, less is known about how microglia, the immune cells of the brain, handle cholesterol, and the subsequent implications for the ability of microglia to perform their essential functions. Evidence is emerging that a high-cholesterol environment, particularly in the context of defects in the ability to transport cholesterol (e.g., expression of the high-risk APOE4 isoform), can lead to chronic activation, increased inflammatory signaling, and reduced phagocytic capacity, which have been associated with AD pathology. In this narrative review we describe how cholesterol regulates microglia phenotype and function, and discuss what is known about the effects of statins on microglia, as well as highlighting areas of future research to advance knowledge that can lead to the development of novel therapies for the prevention and treatment of AD.

Possible Neuropathology of Sleep Disturbance Linking to Alzheimer's Disease: Astrocytic and Microglial Roles

Sleep disturbances not only deteriorate Alzheimer’s disease (AD) progress by affecting cognitive states but also accelerate the neuropathological changes of AD. Astrocytes and microglia are the principal players in the regulation of both sleep and AD. We proposed that possible astrocyte-mediated and microglia-mediated neuropathological changes of sleep disturbances linked to AD, such as astrocytic adenosinergic A1, A2, and A3 regulation; astrocytic dopamine and serotonin; astrocyte-mediated proinflammatory status (TNFα); sleep disturbance-attenuated microglial CX3CR1 and P2Y12; microglial Iba-1 and astrocytic glial fibrillary acidic protein (GFAP); and microglia-mediated proinflammatory status (IL-1b, IL-6, IL-10, and TNFα). Furthermore, astrocytic and microglial amyloid beta (Aβ) and tau in AD were reviewed, such as astrocytic Aβ interaction in AD; astrocyte-mediated proinflammation in AD; astrocytic interaction with Aβ in the central nervous system (CNS); astrocytic apolipoprotein E (ApoE)-induced Aβ clearance in AD, as well as microglial Aβ clearance and aggregation in AD; proinflammation-induced microglial Aβ aggregation in AD; microglial-accumulated tau in AD; and microglial ApoE and TREM2 in AD. We reviewed astrocytic and microglial roles in AD and sleep, such as astrocyte/microglial-mediated proinflammation in AD and sleep; astrocytic ApoE in sleep and AD; and accumulated Aβ-triggered synaptic abnormalities in sleep disturbance. This review will provide a possible astrocytic and microglial mechanism of sleep disturbance linked to AD.

Formulated Chinese medicine Shaoyao Gancao Tang reduces NLRP1 and NLRP3 in Alzheimer's disease cell and mouse models for neuroprotection and cognitive improvement

Amyloid β (Aβ) plays a major role in the neurodegeneration of Alzheimer’s disease (AD). The accumulation of misfolded Aβ causes oxidative stress and inflammatory damage leading to apoptotic cell death. Traditional Chinese herbal medicine (CHM) has been widely used in treating neurodegenerative diseases by reducing oxidative stress and neuroinflammation. We examined the neuroprotective effect of formulated CHM Shaoyao Gancao Tang (SG-Tang, made of Paeonia lactiflora and Glycyrrhiza uralensis at 1:1 ratio) in AD cell and mouse models. In Aβ-GFP SH-SY5Y cells, SG-Tang reduced Aβ aggregation and reactive oxygen species (ROS) production, as well as improved neurite outgrowth. When the Aβ-GFP-expressing cells were stimulated with conditioned medium from interferon (IFN)-γ-activated HMC3 microglia, SG-Tang suppressed expressions of inducible nitric oxide synthase (iNOS), NLR family pyrin domain containing 1 (NLRP1) and 3 (NLRP3), tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6, attenuated caspase-1 activity and ROS production, and promoted neurite outgrowth. In streptozocin-induced hyperglycemic APP/PS1/Tau triple transgenic (3×Tg-AD) mice, SG-Tang also reduced expressions of NLRP1, NLRP3, Aβ and Tau in hippocampus and cortex, as well as improved working and spatial memories in Y maze and Morris water maze. Collectively, our results demonstrate the potential of SG-Tang in treating AD by moderating neuroinflammation.

Cell-Type-Specific Gene Modules Related to the Regional Homogeneity of Spontaneous Brain Activity and Their Associations With Common Brain Disorders

Mapping gene expression profiles to neuroimaging phenotypes in the same anatomical space provides opportunities to discover molecular substrates for human brain functional properties. Here, we aimed to identify cell-type-specific gene modules associated with the regional homogeneity (ReHo) of spontaneous brain activity and their associations with brain disorders. Fourteen gene modules were consistently associated with ReHo in the three datasets, five of which showed cell-type-specific expression (one neuron-endothelial module, one neuron module, one astrocyte module and two microglial modules) in two independent cell series of the human cerebral cortex. The neuron-endothelial module was mainly enriched for transporter complexes, the neuron module for the synaptic membrane, the astrocyte module for amino acid metabolism, and microglial modules for leukocyte activation and ribose phosphate biosynthesis. In enrichment analyses of cell-type-specific modules for 10 common brain disorders, only the microglial module was significantly enriched for genes obtained from genome-wide association studies of multiple sclerosis (MS) and Alzheimer's disease (AD). The ReHo of spontaneous brain activity is associated with the gene expression profiles of neurons, astrocytes, microglia and endothelial cells. The microglia-related genes associated with MS and AD may provide possible molecular substrates for ReHo abnormality in both brain disorders.

Platycodin D Inhibits β-Amyloid-Induced Inflammation and Oxidative Stress in BV-2 Cells Via Suppressing TLR4/NF-κB Signaling Pathway and Activating Nrf2/HO-1 Signaling Pathway

Alzheimer's disease (AD) is a common neurodegenerative disease associated with deposition of β-amyloid peptide (Aβ). Platycodin D (PLD), a triterpenesaponin, may possess neuro-protective effect. In the current study, we aimed to explore the effects of PLD on Aβ-induced inflammation and oxidative stress in microglial BV-2 cells. Our study showed that PLD treatment improved cell viability in Aβ-induced BV-2 cells. PLD attenuated Aβ-induced inflammation with deceased production of TNF-α, IL-1β and IL-6 in Aβ-induced BV-2 cells. PLD also mitigated the oxidative stress in Aβ-induced BV-2 cells, as evidenced by deceased production of ROS and MDA, and increased SOD activity. Furthermore, the increased expression levels of TLR4 and p-p65 and decreased IκBα expression in the Aβ-stimulated BV-2 cells were attenuated by PLD treatment. Overexpression of TLR4 reversed the anti-inflammatory effect of PLD in Aβ-stimulated BV-2 cells. In addition, PLD treatment enhanced the Aβ-stimulated increase in the expression levels of Nrf2, HO-1, and NQO1 in BV-2 cells. Knockdown of Nrf2 abrogated the anti-oxidative effect of PLD in Aβ-stimulated BV-2 cells. In conclusion, these findings indicated that PLD protected BV-2 cells from Aβ-induced oxidative stress and inflammation via regulating the TLR4/NF-κB and Nrf2/HO-1 signaling pathways. Thus, PLD may be a potential candidate for the treatment of AD.

Chronic stress as a risk factor for Alzheimer's disease: Roles of microglia-mediated synaptic remodeling, inflammation, and oxidative stress

Microglia are the predominant immune cells of the central nervous system (CNS) that exert key physiological roles required for maintaining CNS homeostasis, notably in response to chronic stress, as well as mediating synaptic plasticity, learning and memory. The repeated exposure to stress confers a higher risk of developing neurodegenerative diseases including sporadic Alzheimer's disease (AD). While microglia have been causally linked to amyloid beta (Aβ) accumulation, tau pathology, neurodegeneration, and synaptic loss in AD, they were also attributed beneficial roles, notably in the phagocytic elimination of Aβ. In this review, we discuss the interactions between chronic stress and AD pathology, overview the roles played by microglia in AD, especially focusing on chronic stress as an environmental risk factor modulating their function, and present recently-described microglial phenotypes associated with neuroprotection in AD. These microglial phenotypes observed under both chronic stress and AD pathology may provide novel opportunities for the development of better-targeted therapeutic interventions.

Using animal models to determine the significance of complement activation in Alzheimer's disease

Complement inflammation is a major inflammatory mechanism whose function is to promote the removal of microorganisms and the processing of immune complexes. Numerous studies have provided evidence for an increase in this process in areas of pathology in the Alzheimer's disease (AD) brain. Because complement activation proteins have been demonstrated in vitro to exert both neuroprotective and neurotoxic effects, the significance of this process in the development and progression of AD is unclear. Studies in animal models of AD, in which brain complement activation can be experimentally altered, should be of value for clarifying this issue. However, surprisingly little is known about complement activation in the transgenic animal models that are popular for studying this disorder. An optimal animal model for studying the significance of complement activation on Alzheimer's – related neuropathology should have complete complement activation associated with senile plaques, neurofibrillary tangles (if present), and dystrophic neurites. Other desirable features include both classical and alternative pathway activation, increased neuronal synthesis of native complement proteins, and evidence for an increase in complement activation prior to the development of extensive pathology. In order to determine the suitability of different animal models for studying the role of complement activation in AD, the extent of complement activation and its association with neuropathology in these models must be understood.

Activation of microglia: a neuroinflammatory role for CAP37

Recent evidence suggests that inflammation and immune function in the central nervous system (CNS) may play a considerable role in the progression of many neurodegenerative diseases. It is known that microglia, the CNS equivalent of peripheral blood monocytes, may be instrumental in causing neurotoxicity. However, the mediator(s) that activates microglia to produce toxic substances that orchestrate cell death has yet to be elucidated. We have identified a novel inflammatory molecule, cationic antimicrobial protein of molecular weight 37 kDa (CAP37), to the brains of patients dying from Alzheimer's disease. CAP37 is known to be a potent activator and regulator of monocyte function in the systemic circulation. We hypothesize that CAP37, a mediator previously shown to recruit and activate monocytes in the systemic circulation, may also play a role in CNS inflammation by modulating microglial function. Here we demonstrate that CAP37 is a chemoattractant for microglia and that CAP37-treated microglia express class II major histocompatibility antigens and produce proinflammatory cytokines and chemokines. We conclude that CAP37 has the ability to activate microglial cells and suggest that it has the potential to serve as a neuroinflammatory molecule.

Evidence of functional modulation of the MEKK/JNK/cJun signaling cascade by the low density lipoprotein receptor-related protein (LRP)

Lipoprotein receptors, such as LRP, have been shown to assemble multiprotein complexes containing intracellular signaling molecules; however, in vivo, their signaling function is poorly understood. Using a novel LRP receptor fusion construct, a type I transmembrane protein chimera, termed sIgG-LRP (bearing the intracellular COOH-terminal tail of human LRP as recombinant fusion to a transmembrane region plus the extracellular IgG-F(c) domain), we here investigated LRP signal transduction specificity in intact cells. First and similar to activated alpha2-macroglobulin as agonist of endogenous LRP, expression of sIgG-LRP demonstrated significant apoptosis protection. Second and similar to alpha2-macroglobulin-induced endogenous LRP, sIgG-LRP is sufficient to negatively modulate mitogen-induced Elk-1 and cJun (but not NF-kappaB) transcriptional activity. Third, expression of sIgG-LRP also impaired cJun transactivation mediated by constitutive active mutants of Rac-1 and MEKK-1. Fourth and unexpectedly, sIgG-LRP expression was found to be associated with a marked enhancement of mitogen-induced cJun amino-terminal kinase (JNK) activation. Fifth, confocal microscopic examination and subcellular fractionation demonstrated that sIgG-LRP and JNK co-localize in transfected cells. Therefore, sIgG-LRP expression was found to significantly impair activation-induced translocation of JNK into the nucleus. Taken together, we here demonstrate that sIgG-LRP protein sequesters activated JNK into the plasma membrane compartment in intact cells, inhibiting nuclear activation of the JNK-dependent transcription factors Elk-1 and cJun.

Alzheimer's disease: its diagnosis and pathogenesis

A hypothesis has been presented that links many of the identified and putative risk factors for AD and suggests a mechanism for their action. Crawford (1996, 1998) proposes an association between AD and cerebral blood flow (CBF) by citing evidence that many of the factors that are linked with an increased risk of AD also decrease CBF (e.g., old age, depression, underactivity, head trauma). Similarly, it is suggested factors that increase CBF are associated with a decreased risk of AD (e.g., education, exercise, smoking, NSAIDs). Although the authors acknowledge that reduced CBF is not sufficient to cause AD, the reported positive and negative associations provide tantalizing evidence for a common mode of action for many of the equivocal risk factors reported to date. This hypothesis is also consistent with other data that links microvascular damage and impaired blood flow (de la Torre, 1997, 2000) and low education with increased cerebrovascular disease (Del Ser et al., 1999). Gaining a better understanding of the interaction between AD and vascular disease is of great importance. Not only will it provide insights into the pathogenesis of AD, but it may also provide us with a rare opportunity for the treatment and possible prevention of AD. A great many risk factors for vascular disease have been identified and intervention programs have successfully reduced the incidence of heart disease and stroke. The potential exists to provide the same level of success with AD.

Inflammatory pathogenesis in Alzheimer's disease: biological mechanisms and cognitive sequeli

Experimental evidence from molecular biology, biochemistry, epidemiology and behavioral research support the conclusion that brain inflammation contributes to the pathogenesis of Alzheimer's disease and other types of human dementias. Aspects of neuroimmunology relating to the pathogenesis of Alzheimer's disease are briefly reviewed. The effects of brain inflammation, mediated through cytokines and other secretory products of activated glial cells, on neurotransmission (specifically, nitric oxide, glutamate, and acetylcholine), amyloidogenesis, proteolysis, and oxidative stress are discussed within the context of the pathogenesis of learning and memory dysfunction in Alzheimer's disease. Alzheimer's disease is proposed to be an etiologically heterogeneous syndrome with the common elements of amyloid deposition and inflammatory neuronal damage.

NSAIDS inhibit the IL-1 beta-induced IL-6 release from human post-mortem astrocytes: the involvement of prostaglandin E2

Epidemiological studies have shown that steroidal as well as non-steroidal anti-inflammatory drugs lower the risk of developing Alzheimer's Disease (AD). A suppressive effect of these anti-inflammatory drugs on local inflammatory events in AD brains has been suggested, however the mechanisms responsible are still unknown. In this study we investigated at cellular level the influence of two anti-inflammatory drugs-dexamethasone and indomethacin--and an experimental specific cyclooxygenase-2 inhibitor, BF389, on the production of the pro-inflammatory cytokine IL-6 and the inflammatory mediator PGE2 by human astrocytes. Two human post-mortem astrocyte cultures (A157 and A295) and astroglioma cell lines (U251 and U373 MG) were found to secrete considerable amounts of IL-6 upon stimulation with IL-1beta. The glucocorticoid dexamethasone inhibited the IL-1beta-activated release of IL-6 from the postmortem astrocyte cultures A157 and A295 and from the astroglioma cell lines. The non-specific cyclooxygenase inhibitor indomethacin and BF389 only suppressed the IL-6 release by post-mortem astrocyte culture A157. This post-mortem astrocyte culture was found to produce large amounts of PGE2 upon stimulation with IL-1beta, whereas in the supernatants of the postmortem astrocyte culture A295 and the astroglioma cell lines, low PGE2 concentrations were detected. Addition of exogenous PGE2 prevented the inhibitory effect of indomethacin and BF389 on the IL-1beta-activated IL-6 release from A157 astrocytes and largely potentiated the IL-1-induced release of IL-6 from all astrocytes/astroglioma cells tested. Dexamethasone also inhibited the PGE2 release from the astrocytes and astroglioma cells, however the inhibitory effect of dexamethasone on the IL-1beta-activated IL-6 release could not be prevented by the addition of PGE2. The observed reduction of IL-6 and/or PGE2 from astrocytes may be involved in the mechanism underlying the beneficial effects of these drugs in AD.

Factors secreted by activated microglia and monocytes reduce amyloidogenesis in vascular smooth muscle cells

Smooth muscle cells cultured from amyloid-beta-affected arteries accumulate amyloid-beta peptide A beta. We now show that accumulation of "A beta" deposits in this model can be significantly reduced by culture in conditioned media from microglia and monocytes. Reduced A beta accumulation was associated with (i) lower secretion of A beta, (ii) increased secretion, but not cellular levels of amyloid-beta-precursor protein (A beta PP), and (iii) increased cell proliferation and metabolic activity. We suggest that improper regulation of A beta PP metabolism by monokines may facilitate vascular amyloidogenesis.

Factors produced by activated macrophages reduce accumulation of Alzheimer's beta-amyloid protein in vascular smooth muscle cells

Smooth muscle cells (SMCs) isolated from amyloid-angiopathy affected brain vessels accumulate intracellularly amyloid-beta peptide (A beta). Now we demonstrate that accumulation of A beta in SMCs can be reduced by factors secreted by macrophages - IL-1alpha, IL-6, TNF-alpha, TGF-beta1 or PGE2 - probably by stimulating the non-amyloidogenic processing of A beta precursor protein (PP). It is suggested that brain macrophages may regulate A betaPP/A beta metabolism under physiological conditions and prevent beta-amyloidosis. The disturbance of this regulatory function of brain macrophages may result in excessive production and accumulation of A beta.

The role of complement and activated microglia in the pathogenesis of Alzheimer's disease

A variety of inflammatory mediators including complement activation products, protease inhibitors, and cytokines are colocalized with beta-amyloid (A beta) deposits in the Alzeimer's disease (AD) brain. Activation products of the early complement components C1, C4, and C3 are always found in neuritic plaques and to a lesser extent in varying numbers of diffuse plaques. In contrast to these findings, no immunohistochemical evidence was obtained for the presence of the late complement components C7 and C9 and the complement membrane attack complex in the neuropathological lesions in AD brains. The mRNA encoding the late complement components C7 and C9 appears to be hardly or not detectable. These findings indicate that in AD the complement system does not act as an inflammatory mediator through membrane attack complex formation, but through the actions of the early complement products. In this review we focus on the role of complement in the pathological amyloid cascade in AD. In our opinion, the early complement activation products play a crucial role as mediators between the A beta deposits and the inflammatory responses leading to neurotoxicity.

Inflammatory mechanisms in neurodegeneration and Alzheimer's disease: the role of the complement system

This review discusses key findings indicating potential roles of the complement (C)-system in chronic inflammation in Alzheimer's disease (AD) brain. Although there is no means to cure or prevent the disease, recent studies suggest that antiinflammatory drugs may delay the onset of AD dementia. One target of these drugs may be the (C)-system, which is best known for its roles in inflammatory processes in peripheral tissues. However, recent data show C-system expression and regulation in brain cells, and C-system protein deposition in AD plaques. It is still nuclear whether C-system activation contributes to neuropathology in the AD brain, as shown in multiple sclerosis (MS). New clinical studies with antiinflammatory agents are now under general consideration by the Alzheimer's Disease Cooperative Study program. In this review I outline research directions which address possible C-system contributions to neurodegeneration. Finally, I discuss potential pharmacological interventions designed to control segments of classical inflammatory cascades in which the C-system is highly implicated. These aspects are critical to the understanding of C-mediated responses in normal and pathologic brain.

A lysosomal marker for activated microglial cells involved in Alzheimer classic senile plaques

One of the major histopathological lesions in brains of patients with dementia of the Alzheimer type (DAT) is the senile plaque. Although previous studies have shown that senile plaques are often accompanied by microglial cells, the role of these cells in DAT pathology is still unclear. In an immunohistochemical and immunoelectron microscopical analysis of DAT and control brain tissues we addressed this issue using two monoclonal antibodies (mAbs KP1 and 25F9) directed against lysosomal antigens in monocytes and macrophages. Whereas KP1 stained lysosomes in both resting and activated microglial cells, 25F9-staining was predominantly found in lysosomes of activated microglial cells in classic senile plaques. The number and size of 25F9-positive lysosomes in activated microglial cells was increased compared to 25F9-staining in unaffected areas in DAT and control sections. We conclude that mAb 25F9 is a unique and useful lysosomal marker, with a higher specificity than other known markers, for activated microglial cells associated with classic, but not with diffuse, senile plaques.

Increased serum alpha 1-antichymotrypsin in patients with probable Alzheimer's disease: an acute phase reactant without the peripheral acute phase response

Serum levels of alpha 1-antichymotrypsin (alpha 1-ACT) were measured in patients with early and late onset Alzheimer's disease (e-AD, 1-AD), patients with vascular dementia (VD) and healthy elderly. Patients with 1-AD were divided into two groups, one had normal alpha 1-ACT values and one had increased serum levels of alpha 1-ACT. Other acute phase proteins were also measured. The serum levels of alpha 2-macroglobulin (alpha 2-MG), alpha 1-antitrypsin (alpha 1-AT), ceruloplasmin (CER), transferrin (TRSF) and alpha 1-acid glycoprotein (alpha 1-ac.GL) were within the normal range. The C reactive protein (CRP) was occasionally detectable at low concentrations in e-AD, in both groups of 1-AD patients and in VD patients. Low serum concentrations of interleukin-6 (IL-6) were found in a higher proportion of 1-AD than in patients with e-AD or VD. These results indicated that increased levels of alpha 1-ACT along with occasional detection of IL-6 might be peripheral markers of the 'acute reaction' in the brain.

Increased monoamine oxidase B activity in plaque-associated astrocytes of Alzheimer brains revealed by quantitative enzyme radioautography

The aetiology and pathogenesis of Alzheimer's disease are currently poorly understood, but symptomatic disease is associated with amyloid plaques, neurofibrillary tangles, neuronal loss and numerous alterations of neurotransmitter systems in the CNS. Monoamine oxidase type B is known to be increased in Alzheimer diseased brains. The distribution and abundance of catalytic sites for monoamine oxidases A and B in post mortem human brains of 11 Alzheimer disease cases and five age-matched controls were investigated by quantitative enzyme radioautography. Using tritiated monoamine oxidase inhibitors (Ro41-1049 and lazabemide)--as high affinity substrates selective for monoamine oxidases A and B, respectively--it was found that monoamine oxidase B activity increased up to three-fold exclusively in temporal, parietal and frontal cortices of Alzheimer disease cases compared with controls. This increase was restricted to discrete patches (approximately 185 microns in diameter) which occupied approximately 12% of the cortical areas examined. In other brain regions (hippocampal formation >> caudate-putamen > cerebellum), patches of [3H]lazabemide-enriched binding were less abundant. [3H]Ro41-1049 binding (i.e. monoamine oxidase A) was unchanged in all tissues of diseased versus control brains. The monoamine oxidase B-enriched patches in all cortical regions correlated, in their distribution and frequency, with glial fibrillary acidic protein-immunoreactive clusters of astrocytes. Diffuse and mature beta-amyloid-immunoreactive senile plaques as well as patches of high density binding of [3H]PK-11195--a high-affinity ligand for peripheral-type (mitochondrial) benzodiazepine binding sites in microglia/macrophages--were found throughout Alzheimer diseased cortices. The up-regulation of monoamine oxidase B in plaque-associated astrocytes in Alzheimer's disease--in analogy to its proposed role in neurodegenerative disorders such as Parkinson's disease--might, indirectly, be a potential source of cytotoxic free radicals. Lazabemide, a selective reversible monoamine oxidase B inhibitor, is currently under clinical evaluation for the treatment of Parkinson's and Alzheimer's diseases. We conclude that enzyme radioautography with [3H]lazabemide is a reliable high resolution assay for plaque-associated astroglioses in Alzheimer's disease. Its clinical diagnostic utility for positron emission tomography or single photon emission computer tomography studies is being investigated.

Cytokine indices in Alzheimer's temporal cortex: no changes in mature IL-1 beta or IL-1RA but increases in the associated acute phase proteins IL-6, alpha 2-macroglobulin and C-reactive protein

Recent immunocytochemical data have demonstrated increases in interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6) and the IL-6-inducible acute phase protein, alpha 2-macroglobulin (alpha 2-M), in Alzheimer's disease (AD) brains. We investigated the levels of these proteins quantitatively using ELISA procedures and determined if increases in IL-1 beta were compensated for by a parallel increase in the endogenous interleukin-1 receptor antagonist (IL-1RA). Comparing control vs. Alzheimer's temporal cortex, we examined mature IL-1 beta, IL-1RA, IL-6, alpha 2-M and C-reactive protein (CRP). The specificities of the ELISA procedures were verified by serial dilutions of the samples; by chromatofocusing, and by Sephadex G-150 gel filtration. There were no differences in the levels of mature IL-1 beta or IL-1RA in AD and control brains. However, IL-6 levels were detectable in 14 of the 16 Alzheimer samples but only 2 of the 14 control samples. There were also significant increases seen in alpha 2-M and CRP levels in the Alzheimer's group compared to controls. These data support previous studies demonstrating a possible up-regulation of neuroimmune function in Alzheimer's cortex; however, we cannot determine, at this time, if this immune reaction is initiated by IL-1 beta.