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Abstract Background Inflammation is a prominent feature in Alzheimer's disease (AD). It has been proposed that aging has an effect on the function of inflammation in the brain, thereby contributing to the development of age-related diseases like AD. However, the age-dependent relationship between inflammation and clinical phenotype of AD has never been investigated. Methods In this study we have analysed features of the neuroinflammatory response in clinically and pathologically confirmed AD and control cases in relation to age (range 52-97 years). The mid-temporal cortex of 19 controls and 19 AD cases was assessed for the occurrence of microglia and astrocytes by immunohistochemistry using antibodies directed against CD68 (KP1), HLA class II (CR3/43) and glial fibrillary acidic protein (GFAP). Results By measuring the area density of immunoreactivity we found significantly more microglia and astrocytes in AD cases younger than 80 years compared to older AD patients. In addition, the presence of KP1, CR3/43 and GFAP decreases significantly with increasing age in AD. Conclusion Our data suggest that the association between neuroinflammation and AD is stronger in relatively young patients than in the oldest patients. This age-dependent relationship between inflammation and clinical phenotype of AD has implications for the interpretation of biomarkers and treatment of the disease.

Abstract Neuronal expression of cyclooxygenase-2 (COX-2) and cell cycle proteins is suggested to contribute to neurodegeneration during Alzheimer's disease (AD). The stimulus that induces COX-2 and cell cycle protein expression in AD is still elusive. Activated glia cells are shown to secrete substances that can induce expression of COX-2 and cell cycle proteins in vitro. Using post mortem brain tissue we have investigated whether activation of microglia and astrocytes in AD brain can be correlated with the expression of COX-2 and phosphorylated retinoblastoma protein (ppRb). The highest levels of neuronal COX-2 and ppRb immunoreactivity are observed in the first stages of AD pathology (Braak 0–II, Braak A). No significant difference in COX-2 or ppRb neuronal immunoreactivity is observed between Braak stage 0 and later Braak stages for neurofibrillary changes or amyloid plaques. The mean number of COX-2 or ppRb immunoreactive neurons is significantly decreased in Braak stage C compared to Braak stage A for amyloid deposits. Immunoreactivity for glial markers KP1, CR3/43 and GFAP appears in the later Braak stages and is significantly increased in Braak stage V-VI compared to Braak stage 0 for neurofibrillary changes. In addition, a significant negative correlation is observed between the presence of KP1, CR3/43 and GFAP immunoreactivity and the presence of neuronal immunoreactivity for COX-2 and ppRb. These data show that maximal COX-2 and ppRb immunoreactivity in neurons occurs during early Braak stages prior to the maximal activation of astrocytes and microglia. In contrast to in vitro studies, post mortem data do not support a causal relation between the activation of microglia and astrocytes and the expression of neuronal COX-2 and ppRb in the pathological cascade of AD.

Introduction We performed a comprehensive quantitative proteomics study on human hippocampus tissue involving all Braak stages to assess changes in protein abundance over the various stages of Alzheimer's disease (AD). Methods Hippocampal subareas CA1 and subiculum of 40 cases were isolated using laser capture microdissection and analyzed using mass spectrometry. Immunoblotting and immunohistochemistry were used for validation. Results Over the Braak stages, an altered expression was found for 372 proteins including changes in levels of extracellular matrix components, and in calcium-dependent signaling proteins. Early changes were observed in levels of proteins related to cytoskeletal dynamics and synaptic components including an increase in RIMS1 and GRIK4. Several synaptic proteins, such as BSN, LIN7A, DLG2, -3, and -4, exhibit an early-up, late-down expression pattern. Discussion This study provides new insight into AD-dependent changes in protein levels in the hippocampus during AD pathology, identifying potential novel therapeutic targets and biomarkers. [ABSTRACT FROM AUTHOR]

A major neuropathological hallmark of Alzheimer's disease (AD) is the deposition of aggregated β amyloid (Aβ) peptide in the senile plaques. Aβ is a peptide of 38-43 amino acids and its accumulation and aggregation plays a key role early in the disease. A large fraction of β amyloid is N-terminally truncated rendering a glutamine that can subsequently be cyclized into pyroglutamate (pE). This makes the peptide more resistant to proteases, more prone to aggregation and increases its neurotoxicity. The enzyme glutaminyl cyclase (QC) catalyzes this conversion of glutamine to pE. In brains of AD patients, the expression of QC is increased in the earliest stages of pathology, which may be an important event in the pathogenesis. In this study we aimed to investigate the regulatory mechanism underlying the upregulation of QC expression in AD. Using differentiated SK-N-SH as a neuronal cell model, we found that neither the presence of Aβ peptides nor the unfolded protein response, two early events in AD, leads to increased QC levels. In contrast, we demonstrated increased QC mRNA levels and enzyme activity in response to another pathogenic factor in AD, perturbed intracellular Ca2+ homeostasis. The QC promoter contains a putative binding site for the Ca2+ dependent transcription factors c-fos and c-jun. C-fos and c-jun are induced by the same Ca2+-related stimuli as QC and their upregulation precedes QC expression. We show that in the human brain QC is predominantly expressed by neurons. Interestingly, the Ca2+- dependent regulation of both c-fos and QC is not observed in non-neuronal cells. Our results indicate that perturbed Ca2+ homeostasis results in upregulation of QC selectively in neuronal cells via Ca2+- dependent transcription factors. This suggests that disruption of Ca2+ homeostasis may contribute to the formation of the neurotoxic pE Aβ peptides in Alzheimer's disease. [ABSTRACT FROM AUTHOR]

Background: Alzheimer's disease (AD) and Parkinson's disease (PD) are characterized by the accumulation and aggregation of misfolded proteins. Disturbed homeostasis in the endoplasmic reticulum leads to accumulation of misfolded proteins, which triggers a stress response called the unfolded protein response (UPR) that protects the cell against the toxic buildup of misfolded proteins. Objective: In this paper, we will briefly review the early involvement of the UPR in the pathology of AD and PD. Methods: Expression of UPR activation markers was analyzed in human brain tissue using immunohistochemistry and Western blot analysis. Results: Neuropathological studies demonstrate that UPR activation markers are increased in neurons in AD and PD. In AD, UPR activation markers are observed in neurons with diffuse staining of phosphorylated tau protein. In PD, increased immunoreactivity for UPR activation markers is detected in neuromelanin containing dopaminergic neurons of the substantia nigra, which colocalize with diffuse α-synuclein staining. Conclusion: UPR activation is closely associated with the first stages of accumulation and aggregation of the toxic proteins involved in AD and PD. Studies of postmortem brain tissue indicate that UPR activation is an early event in neurodegeneration. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Alzheimer's disease (AD) pathology is accompanied by abnormalities of the microvasculature. Despite the potential importance of morphometric changes in the cortical capillary network on neuronal dysfunction and cognitive impairment, few autopsy studies have addressed this issue. In the present study, we investigated morphological microvascular changes and capillary length density (CLD) in ten well-characterized AD patients compared to ten age-matched controls using virtual isotropic hemispheres. The CLD in the temporal cortex was increased by 33% in AD patients compared to controls (p=0.04), whereas CLD in the occipital cortex was unchanged. An increase of CLD was correlated to a decrease of cortical diameter in the temporal cortex (Pearson's r -0.62, p=0.003), suggesting that the increase in temporal CLD results from, or contributes to cortical atrophy. In the occipital cortex, more string vessels, probably remnants of degenerated capillaries, were observed in AD patients than in controls (p=0.004). An exploratory analysis suggests co-localization of Aβ and string vessels. Our data indicate that morphometric changes in the cortical capillary network occur in AD in a region-specific manner and may be related to cortical atrophy in the affected regions. [ABSTRACT FROM AUTHOR]

Introduction: We performed a comprehensive quantitative proteomics study on human hippocampus tissue involving all Braak stages to assess changes in protein abundance over the various stages of Alzheimer's disease (AD)., Methods: Hippocampal subareas CA1 and subiculum of 40 cases were isolated using laser capture microdissection and analyzed using mass spectrometry. Immunoblotting and immunohistochemistry were used for validation., Results: Over the Braak stages, an altered expression was found for 372 proteins including changes in levels of extracellular matrix components, and in calcium-dependent signaling proteins. Early changes were observed in levels of proteins related to cytoskeletal dynamics and synaptic components including an increase in RIMS1 and GRIK4. Several synaptic proteins, such as BSN, LIN7A, DLG2, -3, and -4, exhibit an early-up, late-down expression pattern., Discussion: This study provides new insight into AD-dependent changes in protein levels in the hippocampus during AD pathology, identifying potential novel therapeutic targets and biomarkers., (Copyright © 2016 The Alzheimer's Association. Published by Elsevier Inc. All rights reserved.)

Cultured neurons exposed to synthetic beta-amyloid (Abeta) fragments reenter the cell cycle and initiate a pathway of DNA replication that involves the repair enzyme DNA polymerase-beta (DNA pol-beta) before undergoing apoptotic death. In this study, by performing coimmunoprecipitation experiments on cross-linked nucleoprotein fragments from Abeta-treated neurons, we demonstrate that DNA pol-beta coimmunoprecipitates with cell division cycle 45 (Cdc45) and with DNA primase in short nucleoprotein fragments. This indicates that DNA pol-beta is loaded into neuronal DNA replication forks after Abeta treatment. In response to Abeta the canonical DNA-synthesizing enzyme DNA pol-delta also was loaded into neuronal replication forks, but at later times than DNA pol-beta. Methoxyamine, an inhibitor of the apurinic/apyrimidinic endonuclease that allows for the recruitment of DNA pol-beta during the process of base excision repair (BER), failed to affect coimmunoprecipitation between DNA pol-beta and Cdc45, indicating that DNA pol-beta loading to the replication forks is independent of DNA breaks. However, methoxyamine reduced DNA replication and ensuing apoptosis in neurons exposed to Abeta, suggesting that an efficient BER process allows DNA replication to proceed up to the threshold for death. These data demonstrate that DNA pol-beta is an essential component of the DNA replication machinery in Abeta-treated neurons and additionally support the hypothesis of a close association of cell cycle events with neuronal death in Alzheimer's disease (AD). Accordingly, by investigating the neuronal expression of DNA pol-beta, along with phosphorylated retinoblastoma protein and neurofibrillary changes in AD brain, we show an early involvement of DNA pol-beta in the pathogenesis of AD.

An important role for CX3CL1 in neuroinflammation and neurodegeneration has been suggested in recent publications. In this study, we compared the expression of CX3CL1 and its receptor CX3CR1 in human brain tissue derived from control patients without neurological complications and in multiple sclerosis (MS) patients. Results from this study demonstrate that CX3CL1 is constitutively expressed in human central nervous system (CNS) astrocytes in vivo and under basal conditions in human adult astrocyte cultures. CX3CR1 is expressed on astrocytes and microglial cells both in vivo and in vitro. Chemotaxis assay shows a functional response upon CX3CR1 signaling in microglial cells. Although CX3CL1 expression is upregulated in cultured astrocytes in response to proinflammatory cytokines, no evidence for expression differences of CX3CL1 between control patients and MS patients was found. Our data suggest that CX3CL1 has more general physiological functions, which occur also in the absence of proinflammatory conditions.