CSF ApoE predicts clinical progression in nondemented APOEε4 carriers.

Possible associations between cerebrospinal fluid (CSF) and plasma apolipoprotein E (ApoE) concentration and early clinical and pathophysiological manifestation of Alzheimer's disease were studied in a large and well-defined population of nondemented patients. CSF and plasma ApoE concentrations were related to CSF Aß42, Tau and pTau levels and clinical characteristics in patients with subjective cognitive decline (n = 207) or mild cognitive impairment (n = 213) aged 64.2 ± 9.0 years, with a 2.5 ± 1.5 years follow-up. A 1 standard deviation increase in log-transformed CSF ApoE concentrations increased the risk of clinical progression in APOEε4 carriers 1.5 times (hazard ratio [95% confidence interval] 1.5 [1.1-2.0]), while this was not the case in APOEε4 noncarriers (hazard ratio [95% confidence interval] 1.0 [0.8-1.2]). Plasma ApoE did not predict clinical progression. Using linear regression models, strong associations between CSF ApoE levels and CSF Tau (ß 0.51 [0.38-0.65]) and pTau (ß 0.53 [0.40-0.60]) values were observed in APOEε4 carriers. We hypothesize CSF ApoE4 increases risk of clinical progression through its association with CSF Tau in APOEε4 carriers. Development of Alzheimer's disease in APOEε4 noncarriers may be unrelated to ApoE concentration.

Aminobisphosphonates inhibit dendritic cell-mediated antigen-specific activation of CD1d-restricted iNKT cells.

CD1d-restricted invariant natural killer T (iNKT) cells constitute an important immunoregulatory T cell subset that can be activated by the synthetic glycolipid α-galactosylceramide (α-GalCer) and initiate antitumor immune responses. As cancer patients are frequently treated with aminobisphosphonates (NBP), it is relevant to determine possible effects of NBP on CD1d-restricted glycolipid Ag-presentation to iNKT cells. We report a striking reduction of α-GalCer-induced iNKT cell activation by monocyte derived dendritic cells (moDC) upon their exposure to NBP during maturation. We found that production of apolipoprotein E (apoE), which is a known facilitator of trans-membrane transport of exogenously derived glycolipids, was significantly diminished in moDC exposed to NBP. As the inhibitory effect of NBP on iNKT cell activation was alleviated by exogenous apoE, our data indicate that reduced apoE production by antigen presenting cells (APC) through NBP limits glycolipid-induced iNKT cell activation. This should be taken into account in the design of iNKT cell-based anti-cancer therapies.

Amyloid-ß oligomer detection by ELISA in cerebrospinal fluid and brain tissue.

Amyloid-ß (Aß) deposits are important pathological hallmarks of Alzheimer's disease (AD). Aß aggregates into fibrils; however, the intermediate oligomers are believed to be the most neurotoxic species and, therefore, are of great interest as potential biomarkers. Here, we have developed an enzyme-linked immunosorbent assay (ELISA) specific for Aß oligomers by using the same capture and (labeled) detection antibody. The ELISA predominantly recognizes relatively small oligomers (10-25 kDa) and not monomers. In brain tissue of APP/PS1 transgenic mice, we found that Aß oligomer levels increase with age. However, for measurements in human samples, pretreatment to remove human anti-mouse antibodies (HAMAs) was required. In HAMA-depleted human hippocampal extracts, the Aß oligomer concentration was significantly increased in AD compared with nondemented controls. Aß oligomer levels could also be quantified in pretreated cerebrospinal fluid (CSF) samples; however, no difference was detected between AD and control groups. Our data suggest that levels of small oligomers might not be suitable as biomarkers for AD. In addition, we demonstrate the importance of avoiding HAMA interference in assays to quantify Aß oligomers in human body fluids.

Whether, when and how chronic inflammation increases the risk of developing late-onset Alzheimer's disease.

Neuropathological studies have revealed the presence of a broad variety of inflammation-related proteins (complement factors, acute-phase proteins, pro-inflammatory cytokines) in Alzheimer's disease (AD) brains. These constituents of innate immunity are involved in several crucial pathogenic events of the underlying pathological cascade in AD, and recent studies have shown that innate immunity is involved in the etiology of late-onset AD. Genome-wide association studies have demonstrated gene loci that are linked to the complement system. Neuropathological and experimental studies indicate that fibrillar amyloid-ß (Aß) can activate the innate immunity-related CD14 and Toll-like receptor signaling pathways of glial cells for pro-inflammatory cytokine production. The production capacity of this pathway is under genetic control and offspring with a parental history of late-onset AD have a higher production capacity for pro-inflammatory cytokines. The activation of microglia by fibrillar Aß deposits in the early preclinical stages of AD can make the brain susceptible later on for a second immune challenge leading to enhanced production of pro-inflammatory cytokines. An example of a second immune challenge could be systemic inflammation in patients with preclinical AD. Prospective epidemiological studies show that elevated serum levels of acute phase reactants can be considered as a risk factor for AD. Clinical studies suggest that peripheral inflammation increases the risk of dementia, especially in patients with preexistent cognitive impairment, and accelerates further deterioration in demented patients. The view that peripheral inflammation can increase the risk of dementia in older people provides scope for prevention.

Direct downregulation of CNTNAP2 by STOX1A is associated with Alzheimer's disease.

STOX1A is a transcription factor which is functionally and structurally similar to the forkhead box protein family. STOX1A has been shown to be associated with pre-eclampsia, a pregnancy associated disease, and to have potential implications in late onset Alzheimer's disease. However, the exact function of STOX1A and its target genes are still largely unknown. Therefore, in this study we performed chromatin immunoprecipitation coupled to shotgun cloning to discover novel STOX1A target genes. Our results show that CNTNAP2, a member of the neurexin family, is directly downregulated by STOX1A. Additionally, we show that CNTNAP2 expression is downregulated in the hippocampus of Alzheimer's disease patients where STOX1A expression has been shown to be upregulated. In conclusion, these results further indicate the potential involvement of STOX1A and its target genes in the etiology of Alzheimer's disease.

Innate immunity and the etiology of late-onset Alzheimer's disease.

BACKGROUND: Neuropathological studies supported by experimental animal studies show that the constituents of the innate immunity are intimately involved in the early steps of the pathological cascade of Alzheimer's disease (AD). OBJECTIVES: To show the evidence that constituents of the innate immunity contribute to the etiology of late-onset AD. METHODS: Evaluation of the relationship between the constituents of the innate immunity and genetic risk factors for late-onset AD. RESULTS: Complement activation and activated microglia are early neuropathogical events in AD brains. Genome-wide association studies have demonstrated gene loci that are linked to the complement system. The production capacity for inflammatory cytokines is under genetic control and the offspring with a parental history of late-onset AD have a higher production capacity for inflammatory cytokines. CONCLUSION: Epidemiological and genetic data suggest that the innate immunity is involved in the etiology of late-onset AD.

Neuroinflammation - an early event in both the history and pathogenesis of Alzheimer's disease.

BACKGROUND: About hundred years ago, Oskar Fischer proposed that the senile plaques are the consequence of the deposition of a foreign substance that could induce an inflammatory response leading to an abnormal neuritic response of the surrounding neurons. OBJECTIVES: To show that the interest in inflammation in Alzheimer's disease (AD) is not only an early event in the history of AD but that inflammation is also an early event in the pathogenesis of AD. METHODS: Evaluation of the neuropathological, epidemiological and genetic evidence for a role of inflammation early in the pathogenesis of AD. RESULTS: Neuropathological studies show presence of activated microglia and inflammation-related mediators in the cerebral neocortex of autopsied patients with a low Braak stage for AD pathology. Prospective population-based cohort studies indicate that higher serum levels of acute phase proteins predict dementia. On a genetic level, it was found that the production capacity of proinflammatory cytokines after stimulation with lipopolysaccharide (a process that is under strong genetic control) is higher in offspring with a parental history of late-onset AD. CONCLUSION: Neuropathological studies show that a neuroinflammatory response in the cerebral neocortex parallels the early stages of AD pathology and precedes the late stage, tau-related pathology. Epidemiological and genetic studies indicate that systemic markers of the innate immunity are risk factors for late-onset AD.

Small heat shock proteins associated with cerebral amyloid angiopathy of hereditary cerebral hemorrhage with amyloidosis (Dutch type) induce interleukin-6 secretion.

In hereditary cerebral hemorrhage with amyloidosis of the Dutch type (HCHWA-D), severe cerebral amyloid angiopathy (CAA) is associated with an inflammatory reaction. Small heat shock proteins (sHsps) are molecular chaperones and association of HspB8 with CAA in HCHWA-D has been observed. The aims of this study were to investigate (1) if other sHsps are associated with the pathological lesions in HCHWA-D brains, (2) if the amyloid-beta protein (A beta) increases production of sHsps in cultured cerebral cells and (3) if sHsps are involved in the cerebral inflammatory processes in both Alzheimer's disease (AD) and HCHWA-D. We conclude that Hsp20, HspB8 and HspB2 are present in CAA in HCHWA-D, and that A beta did not affect cellular sHsps expression in cultured human brain pericytes and astrocytes. In addition, we demonstrated that Hsp20, HspB2 and HspB8 induced interleukin-6 production in cultured pericytes and astrocytes, which could be antagonized by dexamethasone, whereas other sHsps and A beta were inactive, suggesting that sHsps may be among the key mediators of the local inflammatory response associated with HCHWA-D and AD lesions.

Variability in longitudinal cerebrospinal fluid tau and phosphorylated tau measurements.

BACKGROUND: The influence of assay variation and duration of storage on changes in cerebrospinal fluid (CSF) levels of tau and phosphorylated (P)-tau with time was evaluated in 112 patients with various neurological disorders. METHODS: These patients (aged 66+/-9 years, 52% male), referred to our memory clinic, underwent two spinal taps (mean interval 19 months) and the baseline samples were assayed twice in a sandwich enzyme-linked immunosorbent assay (ELISA): once after the first spinal tap (A1) and once in a separately stored aliquot (A2) simultaneous with the follow-up sample (B). RESULTS: Coefficients of variances (CVs) of tau and P-tau levels determined in repeated spinal taps (DeltaB-A2) measured in one assay (10.9% and 7.6%) were lower (p<0.01) than the CVs observed in two different (DeltaB-A1) assays (16.5% and 11.7%). The CVs of tau and P-tau measurement of one CSF sample repeated on two occasions (DeltaA1-A2) were 12.3% and 8.6%. A difference in mean P-tau level was found if the same CSF samples were repeatedly measured in two different ELISAs (A1-A2). CONCLUSIONS: Longitudinal CSF tau and P-tau are best measured in one assay resulting in a lower variability compared to measurement in two different assays. The within person variability in levels of these markers currently limits the use of these ELISAs in a longitudinal clinical setting.

Neuroinflammation in plaque and vascular beta-amyloid disorders: clinical and therapeutic implications.

BACKGROUND: The cerebral beta-amyloid (Abeta) disorders show a great variability in the distribution of parenchymal and vascular amyloid deposits. OBJECTIVE: To study the relationship between amyloid deposition and inflammatory responses in three distinct subtypes of cerebral Abeta disorders. METHODS: The distribution of inflammatory proteins and cells in vascular and plaque amyloid deposits was evaluated in postmortem brain tissue using immunohistochemistry. The effects of a mixture of Abeta peptides and inflammation-related Abeta-associated proteins were studied in postmortem obtained human microglia cell cultures. RESULTS: The chronic inflammatory response is associated with amyloid plaques (but not with amyloid in the walls of larger vessels) in Alzheimer's disease (AD), with amyloid in cerebral arteries in hereditary cerebral hemorrhage with amyloidosis-Dutch type and with amyloid microangiopathy in the vascular variant of AD. Abeta(1-42) fibrils complexed with complement factor C1q and serum amyloid P component (the relevant amyloid-associated proteins) stimulate the production of proinflammatory cytokines in human microglia cell cultures and this production is attenuated by minocycline. CONCLUSION: The pattern of the chronic inflammatory response associated with fibrillar Abeta is strikingly different in the three studied types of Abeta disorders. The site of the fibrillar Abeta-induced chronic inflammatory response is closely related to clinical symptoms. Minocycline is a drug of interest to inhibit microglia-mediated neuroinflammatory response in Abeta brain disorders.

Homogeneity of active demyelinating lesions in established multiple sclerosis.

OBJECTIVE: Four different patterns of demyelination have been described in active demyelinating lesions of multiple sclerosis (MS) patients that were biopsied shortly after disease onset. These patterns were suggested to represent heterogeneity of the underlying pathogenesis. The aim of this study was to determine whether lesion heterogeneity also exists in an unselected collection of autopsy material from patients with established MS. METHODS: All MS brain tissue available in the VU Medical Center was assessed for the presence of active demyelinating lesions using magnetic resonance imaging-guided sampling and immunohistochemistry. Tissue blocks containing active demyelinating lesions were evaluated for the presence of complement and antibody deposition, oligodendrocyte apoptosis, differential loss of myelin proteins, and hypoxia-like damage using histology, immunohistochemistry, and confocal microscopy. Blocks with active demyelinating lesions were compared with blocks with active (nondemyelinating) and inactive lesions. RESULTS: Complement and antibodies were consistently associated with macrophages in areas of active demyelination. Preferential loss of myelin proteins, extensive hypoxia-like damage, and oligodendrocyte apoptosis were absent or rare. This pattern was observed in all tissue blocks containing active demyelinating lesions; lesion heterogeneity between patients was not found. INTERPRETATION: The immunopathological appearance of active demyelinating lesions in established MS is uniform. Initial heterogeneity of demyelinating lesions in the earliest phase of MS lesion formation may disappear over time as different pathways converge in one general mechanism of demyelination. Consistent presence of complement, antibodies, and Fcgamma receptors in phagocytic macrophages suggests that antibody- and complement-mediated myelin phagocytosis is the dominant mechanism of demyelination in established MS.