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

Plaque complement activation and cognitive loss in Alzheimer's disease

<p>Abstract</p> <p>Background</p> <p>Complement activation is increased in Alzheimer's disease (AD), but its significance is unclear. The objective of this study was to determine the relationship between complement activation and cognition during the development of AD.</p> <p>Methods</p> <p>iC3b, C9, Bielschowsky, and Gallyas staining was performed on aged normal (n = 17), mild cognitively impaired (n = 12), and AD (n = 17–18) inferior temporal gyrus specimens. Plaques were counted in 10× fields with high numbers of Bielschowsky-stained plaques. One-way ANOVA was used to determine between-group differences for plaque counts and measures of cognitive function, and linear regression was used to evaluate global cognition as a function of Bielschowsky-stained plaques. Terms for iC3b- and C9-stained plaques were then added sequentially as additional predictors in a "mediation analysis" model.</p> <p>Results</p> <p>Complement was detected on plaques in all groups, and on neurofibrillary tangles only in AD specimens. iC3b, C9, and Bielschowsky-stained plaque counts increased 2.5- to 3-fold in AD vs. other groups (all <it>p </it>≤ 0.01). C9 staining was present on some diffuse plaques, as well as on neuritic plaques. Bielschowsky-stained and complement-stained plaque counts were highly correlated, and were negatively correlated with cognitive measures. When the Bielschowsky plaque count was used as a predictor, its correlations with cognitive measures were statistically significant, but when iC3b and C9 plaque counts were added as additional predictors, these correlations were no longer significant. This loss of significance was attributed to multicollinearity, i.e., high correlations between Bielschowsky-stained and complement-stained plaque counts.</p> <p>Conclusion</p> <p>Both early-stage (iC3b) and late-stage (C9) complement activation occurs on neocortical plaques in subjects across the cognitive spectrum; contrary to previous reports, C9 is present on some diffuse plaques. Because of high correlations between complement-stained and Bielschowsky-stained plaque counts, quantitative assessment of the extent to which complement activation may mediate the relationship between plaques and cognitive function could not be performed. Additional studies with animal models of AD (if late-stage complement activation can be demonstrated), or possibly a trial in AD patients with an inhibitor of late-stage complement activation, may be necessary to determine the significance of this process in AD.</p

Influence of Normal Aging on Brain Autophagy: A Complex Scenario

Misfolded proteins are pathological findings in some chronic neurodegenerative disorders including Alzheimer’s, Parkinson’s, and Huntington’s diseases. Aging is a major risk factor for these disorders, suggesting that the mechanisms responsible for clearing misfolded proteins from the brain, the ubiquitin-proteasome system and the autophagy-lysosomal pathway, may decline with age. Although autophagic mechanisms have been found to decrease with age in many experimental models, whether they do so in the brain is unclear. This review examines the literature with regard to age-associated changes in macroautophagy and chaperone-mediated autophagy (CMA) in the central nervous system (CNS). Beclin 1, LC3-II, and the LC3-II/LC3-I ratio have frequently been used to examine changes in macroautophagic activity, while lamp2a and HSPA8 (also known as hsc70) have been used to measure CMA activity. Three gene expression analyses found evidence for an age-related downregulation of macroautophagy in human brain, but no published studies were found of age-related changes in CMA in human brain, although cerebrospinal fluid concentrations of HSPA8 were reported to decrease with age. Most studies of age-related changes in brain autophagy in experimental animals have found age-related declines in macroautophagy, and macroautophagy is necessary for normal lifespan in Caenorhabditis elegans, Drosophila, and mice. However, the few studies of age-related changes in brain CMA in experimental animals have produced conflicting results. Investigations of the influence of aging on macroautophagy in experimental animals in systems other than the CNS have generally found an age-related decrease in Beclin 1, but conflicting results for LC3-II and the LC3-II/LC3-I ratio, while CMA decreases with age in most models. CONCLUSION: while indirect evidence suggests that brain autophagy may decrease with normal aging, this issue has not been investigated sufficiently, particularly in human brain. Measuring autophagic activity in the brain can be challenging because of differences in basal autophagic activity between experimental models, and the inability to include lysosomal inhibitors when measuring the LC3-II/LC3-I ratio in postmortem specimens. If autophagy does decrease in the brain with aging, then pharmacological interventions and/or lifestyle alterations to slow this decline could reduce the risk of developing age-related neurodegenerative disorders

Complement activation in the Parkinson's disease substantia nigra: an immunocytochemical study

BACKGROUND: Inflammatory processes are increased in the Parkinson's disease (PD) brain. The long-term use of nonsteroidal anti-inflammatory drugs has been associated, in retrospective studies, with decreased risk for PD, suggesting that inflammation may contribute to development of this disorder. The objective of this study was to determine the extent of complement activation, a major inflammatory mechanism, in PD. METHODS: Substantia nigra specimens from young normal subjects (n = 11–13), aged normal subjects (n = 24–28), and subjects with PD (n = 19–20), Alzheimer's disease (AD; n = 12–13), and dementia with Lewy bodies (DLB; n = 9) were stained for iC3b and C9, representing early- and late-stage complement activation, respectively. Numbers of iC3b(+), C9(+), and total melanized neurons in each section were counted in a blinded fashion. Nonparametric analyses were used to evaluate differences between groups and to evaluate correlations between complement staining, numbers of melanized neurons, and the duration of PD. RESULTS: Lewy bodies in both PD and DLB specimens stained for iC3b and C9. Staining was also prominent on melanized neurons. The percentage of iC3b(+ )neurons was significantly increased in PD vs. aged normal and AD specimens, and in young normal vs. aged normal specimens. C9 immunoreactivity was significantly increased in PD vs. AD specimens, but unlike iC3b, the increased C9 staining in PD and young normal specimens did not achieve statistical significance vs. aged normal specimens. iC3b and C9 staining in PD specimens was not correlated with the numbers of remaining melanized neurons, nor with the duration of PD. CONCLUSION: Complement activation occurs on Lewy bodies and melanized neurons in the PD substantia nigra. Early complement activation (iC3b) is increased on melanized neurons in PD vs. aged normal specimens, and late-stage complement activation (C9) also tends to increase. This latter finding suggests that complement activation may contribute to loss of dopaminergic neurons in some individuals with PD. Complement activation on melanized neurons appears to decrease with normal aging, suggesting a possible neuroprotective role for this process in the normal substantia nigra

Antibody Concentrations to A Beta 1-42 Monomer and Soluble Oligomers in Untreated and Antibody-Antigen-Dissociated Intravenous Immunoglobulin Preparations

Cognitive improvement in Alzheimer\u27s disease (AD) patients treated with intravenous immunoglobulin (IvIg) has been attributed to its antibodies to amyloid beta (A beta) We compared the concentrations of specific antibodies to soluble A beta 1-42 conformations, namely A beta 1-42 monomer and A beta 1-42 soluble oligomers, between three IvIg preparations. Gamunex, Gammagard. and Flebogamma. To determine specific antibody Concentrations to these A beta 1-42 conformations. nonspecific binding of the IvIg preparations to the An reverse sequence, A beta 42-1. was subtracted These antibodies were measured in untreated IvIg preparations and also after they were treated to dissociate antibody-antigen complexes. because this procedure has been reported to increase the detectable levels of serum anti-A beta antibodies. Antibody levels to A beta 1-42 monomer were significantly higher in untreated Gamunex than in the other two IvIg preparations, and antibody-antigen dissociation increased the measured anti-A beta monomer concentrations in Gamunex and Gammagard Dissociated Gamunex and Gammagard had higher anti-A beta monomer levels than Flebogamma. Generally similar results were found for antibodies to soluble A beta 1-42 oligomers. with the exception that after antibody-antigen dissociation, only Gammagard had significantly higher antibody levels than Flebogamma. These differences in antibody concentrations to A beta 1-42 conformations (particularly to A beta 1-42 soluble oligomers, thought to be the most neurotoxic conformation of soluble A beta) and the increased availability of these antibodies after antibody-antigen complex dissociation have important implications for IvIg treatment of AD patients

Cellular immune response to intrastriatally implanted allogeneic bone marrow stromal cells in a rat model of Parkinson's disease

<p>Abstract</p> <p>Background</p> <p>Marrow stromal cells (MSC), the non-hematopoietic precursor cells in bone marrow, are being investigated for therapeutic potential in CNS disorders. Although <it>in vitro </it>studies have suggested that MSC may be immunologically inert, their immunogenicity following transplantation into allogeneic recipients is unclear. The primary objective of this study was to investigate the cellular immune response to MSC injected into the striatum of allogeneic recipients (6-hydroxydopamine [6-OHDA]-hemilesioned rats, an animal model of Parkinson's disease [PD]), and the secondary objective was to determine the ability of these cells to prevent nigrostriatal dopamine depletion and associated motor deficits in these animals.</p> <p>Methods</p> <p>5-Bromo-2-deoxyuridine (BrdU) – labeled MSC from two allogeneic sources (Wistar and ACI rats) were implanted into the striatum of adult Wistar rats at the same time as 6-OHDA was administered into the substantia nigra. Behavioral tests were administered one to two weeks before and 16–20 days after 6-OHDA lesioning and MSC transplantation. Immunocytochemical staining for T helper and T cytotoxic lymphocytes, microglia/macrophages, and major histocompatibility class I and II antigens was performed on post-transplantation days 22–24. MSC were detected with an anti-BrdU antibody.</p> <p>Results</p> <p>Tissue injury due to the transplantation procedure produced a localized cellular immune response. Unexpectedly, both sources of allogeneic MSC generated robust cellular immune responses in the host striatum; the extent of this response was similar in the two allograft systems. Despite these immune responses, BrdU⁺cells (presumptive MSC) remained in the striatum of all animals that received MSC. The numbers of remaining MSC tended to be increased (<it>p </it>= 0.055) in rats receiving Wistar MSC versus those receiving ACI MSC. MSC administration did not prevent behavioral deficits or dopamine depletion in the 6-OHDA-lesioned animals.</p> <p>Conclusion</p> <p>MSC, when implanted into the striatum of allogeneic animals, provoke a marked immune response which is not sufficient to clear these cells by 22–24 days post-transplantation. In the experimental paradigm in this study, MSC did not prevent nigrostriatal dopamine depletion and its associated behavioral deficits. Additional studies are indicated to clarify the effects of this immune response on MSC survival and function before initiating trials with these cells in patients with PD or other neurodegenerative disorders.</p

ELISA Measurement of Specific Non-antigen-bound Antibodies to Ab1-42 Monomer and Soluble Oligomers in Sera from Alzheimer\u27s Disease, Mild Cognitively Impaired, and Noncognitively Impaired Subjects

The article presents a study for enzyme-linked immunosorbent assay (ELISA) measurement of specific non-antigen-bound antibodies to Aβ1-42 monomer and soluble oligomers in Alzheimer\u27s disease (AD), mild cognitively impaired (MCI), and noncognitively impaired (NCI) sera. In the study, serum samples were obtained from the Rush Alzheimer\u27s Disease Center, Chicago, Illinois

Effects of External Beam Radiation on \u3ci\u3eIn Vitro\u3c/i\u3e Formation of Abeta1-42 Fibrils and Preformed Fibrils

Plaques containing fibrillar amyloid-beta (Abeta) are a characteristic finding in Alzheimer\u27s disease. Although plaque counts correlate poorly with the extent of cognitive deficits in this disorder, fibrillar Abeta can promote neuronal damage through a variety of mechanisms. External beam radiotherapy has been reported to be an effective treatment for tracheobronchial amyloidosis, in which amyloid is deposited as submucosal plaques and tumor-like masses in the trachea and/or bronchi. Radiotherapy\u27s effectiveness in this disorder is thought to be due to its toxicity to plasma cells, but direct effects of radiotherapy on amyloid may also be involved. On this basis, whole-brain radiotherapy has been suggested as a treatment for Alzheimer\u27s disease. The objective of this study was to determine the effects of external beam radiation on preformed Abeta1-42 fibrils and on the formation of these fibrils. Using the Thioflavin-T assay, no effects of radiation were found on either of these parameters. Our results in this in vitro study suggest that whole-brain irradiation is unlikely to directly reduce plaque counts in the Alzheimer\u27s disease brain. This treatment might still lower plaque counts indirectly, but any potential benefits would need to be weighed against its possible neurotoxic effects, which could induce further cognitive deficits

A STAT3 Gene Expression Signature in Gliomas is Associated with a Poor Prognosis

Gliomas frequently display constitutive activation of the transcription factor STAT3, a protein that is known to be able to mediate neoplastic transformation. STAT3 regulates genes that play a central role in cellular survival, proliferation, self-renewal, and invasion, and a cohort of STAT3 target genes have been found that are commonly coexpressed in human cancers. Thus, these genes likely subserve the transforming ability of constitutively activated STAT3. To determine whether the coordinated expression of STAT3 target genes is present in a subset of human gliomas, and whether this changes the biology of these tumors in patients, gene expression analysis was performed in four distinct human glioma data sets for which patient survival information was available. Coordinate expression of STAT3 targets was significantly associated with poor patient outcome in each data set. Specifically, patients with tumors displaying high expression of STAT3 targets had a shorter median survival time compared to patients whose tumors had low expression of STAT3 targets. These data suggest that constitutively activated STAT3 in gliomas can alter the biology of these tumors, and that development of targeted STAT3 inhibitors would likely be of particular benefit in treatment of this disease

A MIQE-Compliant Real-Time PCR Assay for Aspergillus Detection

PMCID: PMC3393739This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited