Cerebrospinal Fluid Of Alzheimer's Disease Patients Research Articles

Characteristics of T Cells in Single-Cell Datasets of Peripheral Blood and Cerebrospinal Fluid in Alzheimer's Disease Patients.

Alzheimer's disease (AD) is the most common type of dementia, causing a huge socioeconomic burden. In parallel with the widespread uptake of single-cell RNA sequencing (scRNA-seq) technology, there has been a rapid accumulation of data produced by researching AD at single-cell resolution, which is more conductive to explore the neuroimmune-related mechanism of AD. To explore the potential features of T cells in the peripheral blood and cerebrospinal fluid of AD patients. Two datasets, GSE181279 and GSE134578, were integrated from GEO database. Seurat, Monocle, CellChat, scRepertoire, and singleR packages were mainly employed for data analysis. Our analysis demonstrated that in peripheral blood, T cells were significantly expanded, and these expanded T cells were possessed effector function, such as CD8+TEMRA, CD4+TEMRA, and CD8+TEM. Interestingly, CD8+TEMRA and CD4+TEMRA cells positioned adjacently after dimensions reduction and clustering. Notably, we identified that the expanded T cells were developed from Naïve T cells and TCM cells, and TEM cells was in the intermediate state of this developing process. Additionally, in cerebrospinal fluid of AD patients, the amplified T cells were mainly CD8+TEMRA cells, and the number and strength of communication between CD4+TEM, CD8+TEM, and CD8+TEMRA were decreased in AD patients. Our comprehensive analyses identified the cells in cerebrospinal fluid from AD patients are expanded TEMRA or TEM cells and the TEMRA cells communicating with other immune cells is weakened, which may be an important immune feature that leads to AD.

Peripheral Blood and Cerebrospinal Fluid Levels of YKL-40 in Alzheimer's Disease: A Systematic Review and Meta-Analysis.

The pathogenesis associated with Alzheimer's disease (AD) is particularly complicated, and early diagnosis and course monitoring of the disease are not ideal based on the available core biomarkers. As a biomarker closely related to neuroinflammation, YKL-40 provides a potential scalable approach in AD, but its association remains controversial and inconclusive with AD. We conducted this study to assess the utility of YKL-40 levels in peripheral blood and cerebrospinal fluid (CSF) of AD patients and healthy controls (HCs) by meta-analysis. We systematically searched and screened relevant trials for comparing YKL-40 levels between AD patients and HCs in PubMed, Embase, Cochrane, and Web of Science, with a search deadline of 14 March 2023 for each database. A total of 17 eligible and relevant studies involving 1811 subjects, including 949 AD patients and 862 HCs, were included. The results showed that YKL-40 levels in the peripheral blood of AD patients and HCs did not possess significant differences. Subgroup analysis showed YKL-40 significantly differed in plasma (SMD = 0.527, 95%CI: [0.302, 0.752]; p = 0.000), but did not in serum. In the case of comparison with HCs, YKL-40 was significantly higher in CSF of AD patients (SMD = 0.893, 95%CI: [0.665, 1.121]; p = 0.000). Besides that, when we performed a combined analysis of total YKL-40 in both peripheral blood and CSF, overall YKL-40 concentrations were also significantly increased among AD patients (SMD = 0.608, 95%CI: [0.272, 0.943]; p = 0.000). YKL-40 provides support and rationale for the neuroinflammatory pathogenesis of AD. The significance of CSF levels of YKL-40 for early screening of AD is definite. Plasma levels of YKL-40 also appear to assist in discriminating AD patients from HCs, which facilitates early screening and monitoring of the natural course of AD.

Investigation for the involvement of microbial FliC and DING proteins in Alzheimer's Disease and Mild Cognitive Impairment and correlation with neurodegeneration and inflammation markers

The pathology of Alzheimer's Disease (AD) and Mild Cognitive Impairment (MCI) has been linked to inflammation attributed to the microbiome, mainly originating from the oral cavity and the intestine. The goal of this research was to estimate the levels of the bacterial proteins flagellin (FliC) and bacterial DING in cerebrospinal fluid (CSF) and their correlation with neurodegeneration and inflammation markers. FliC and DING levels were evaluated in CSF of 54 AD and 47 MCI patients compared to 23 cognitively healthy individuals, using indirect ELISA. Correlation and multilinear regression analyses with the inflammatory biomarkers COX-1 and COX-2, and with the AD hallmarks, Αβ42, and tau, were conducted as well. FliC and DING proteins were found increased in the CSF of AD patients compared to the control group, while FliC of MCI patients was also elevated in comparison with controls. In addition, FliC and DING levels correlate with each other, with tau and both COX-1/2. Also, multilinear regression analyses suggest that DING is a significant determinant of FliC in CSF and vice-versa, while COX-2 determines both FliC and DING levels and COX-1 only the levels of DING. Consequently, the increase of bacterial FliC and its possible translocation to the brain is an early event in dementia, reflected in dysbiosis events found in MCI and AD patients, and possibly neuroinflammation and neurodegeneration. Additionally, increased DING in AD patients seems to be a significant part of the inflammatory events and its correlation with FliC points to a possible link between these proteins.

The GABAergic system in Alzheimer's disease: a systematic review with meta-analysis.

The γ-aminobutyric acid (GABA)ergic system is the primary inhibitory neurotransmission system in the mammalian brain. Its dysregulation has been shown in multiple brain conditions, but in Alzheimer's disease (AD) studies have provided contradictory results. Here, we conducted a systematic review with meta-analysis to investigate whether the GABAergic system is altered in AD patients compared to healthy controls (HC), following the PRISMA 2020 Statement. We searched PubMed and Web of Science from database inception to March 18th, 2023 for studies reporting GABA, glutamate decarboxylase (GAD) 65/67, GABAA, GABAB, and GABAC receptors, GABA transporters (GAT) 1-3 and vesicular GAT in the brain, and GABA levels in the cerebrospinal fluid (CSF) and blood. Heterogeneity was estimated using the I2 index, and the risk of bias was assessed with an adapted questionnaire from the Joanna Briggs Institute Critical Appraisal Tools. The search identified 3631 articles, and 48 met the final inclusion criteria (518 HC, mean age 72.2, and 603 AD patients, mean age 75.6). Random-effects meta-analysis [standardized mean difference (SMD)] revealed that AD patients presented lower GABA levels in the brain (SMD = -0.48 [95% CI = -0.7, -0.27], adjusted p value (adj. p) < 0.001) and in the CSF (-0.41 [-0.72, -0.09], adj. p = 0.042), but not in the blood (-0.63 [-1.35, 0.1], adj. p = 0.176). In addition, GAD65/67 (-0.67 [-1.15, -0.2], adj. p = 0.006), GABAA receptor (-0.51 [-0.7, -0.33], adj. p < 0.001), and GABA transporters (-0.51 [-0.92, -0.09], adj. p = 0.016) were lower in the AD brain. Here, we showed a global reduction of GABAergic system components in the brain and lower GABA levels in the CSF of AD patients. Our findings suggest the GABAergic system is vulnerable to AD pathology and should be considered a potential target for developing pharmacological strategies and novel AD biomarkers.

Metals in Alzheimer's Disease.

The role of metals in the pathogenesis of Alzheimer's disease (AD) is still debated. Although previous research has linked changes in essential metal homeostasis and exposure to environmental heavy metals to the pathogenesis of AD, more research is needed to determine the relationship between metals and AD. In this review, we included human studies that (1) compared the metal concentrations between AD patients and healthy controls, (2) correlated concentrations of AD cerebrospinal fluid (CSF) biomarkers with metal concentrations, and (3) used Mendelian randomization (MR) to assess the potential metal contributions to AD risk. Although many studies have examined various metals in dementia patients, understanding the dynamics of metals in these patients remains difficult due to considerable inconsistencies among the results of individual studies. The most consistent findings were for Zn and Cu, with most studies observing a decrease in Zn levels and an increase in Cu levels in AD patients. However, several studies found no such relation. Because few studies have compared metal levels with biomarker levels in the CSF of AD patients, more research of this type is required. Given that MR is revolutionizing epidemiologic research, additional MR studies that include participants from diverse ethnic backgrounds to assess the causal relationship between metals and AD risk are critical.

Platelet Activating Factor Receptor Exaggerates Microglia-Mediated Microenvironment by IL10-STAT3 Signaling: A Novel Potential Biomarker and Target for Diagnosis and Treatment of Alzheimer’s Disease

BackgroundEarly diagnosis and effective intervention are the keys to delaying the progression of Alzheimer’s Disease (AD). Therefore, we aimed to identify new biomarkers for the early diagnosis of AD through bioinformatic analysis and elucidate the possible underlying mechanisms.Methods and ResultsGSE1297, GSE63063, and GSE110226 datasets from the GEO database were used to screen the highly differentially expressed genes. We identified a potential biomarker, Platelet activating factor receptor (PTAFR), significantly upregulated in the brain tissue, peripheral blood, and cerebrospinal fluid of AD patients. Furthermore, PTAFR levels in the plasma and brain tissues of APP/PS1 mice were significantly elevated. Simultaneously, PTAFR could mediate the inflammatory responses to exaggerate the microenvironment, particularly mediated by the microglia through the IL10-STAT3 pathway. In addition, PTAFR was a putative target of anti-AD compounds, including EGCG, donepezil, curcumin, memantine, and Huperzine A.ConclusionPTAFR was a potential biomarker for early AD diagnosis and treatment which correlated with the microglia-mediated microenvironment. It is an important putative target for the development of a novel strategy for clinical treatment and drug discovery for AD.

Degeneration of human orexinergic neurons across Braak stages of Alzheimer's disease: Implication for pathogenesis, sleep dysfunction, and therapy.

Sleep disturbances are common precognitive symptoms of Alzheimer's disease (AD). Wake-promoting orexinergic neurons (Oxe) in the lateral hypothalamic area (LHA) are key regulators of sleep-wake states. We recently reported a major loss of Oxe in the terminal stages of AD. This was unexpected, because clinical research shows elevated orexin levels in the cerebrospinal fluid (CSF) of AD patients. In line with this finding, suvorexant, an orexin receptor antagonist, was recently the first drug approved for insomnia in patients with mild-to-moderate AD. The aim of our current study was to understand the biological basis of these findings and elucidate the still unknown pattern of orexinergic neuron degeneration in the course of AD. We performed a postmortem study of 15 subjects with different AD stages and controls. Patients with contributing pathologies other than AD were excluded from the study. Using double immunohistochemistry and unbiased stereology, we estimated the number of total neurons, Oxe and tau-inclusions in the LHA along the Braak stages of AD. Examined participants' mean age was 70± 12 years, 47% female. Along AD progression, there was an increase of tau inclusions in Oxe, with 0.1% of tau-positive neurons at Braak stage 0 and 23% at stage 6 (Fig. 1). Further, we observed a substantial decrease of ONs from Braak stage 0 to stage 6 (Fig. 2). Along other Braak stages the decrease of orexinergic neuronal number was slower. We provide evidence of tau-accumulation in Oxe as early as Braak stage 0 and significant orexinergic neuronal loss from Braak 1. This correlates well with clinical data showing that in many patients sleep-wake disorders precede the cognitive symptoms, which typically emerge with Braak 3-4 stages. Further, we conclude that elevated orexin levels in the CSF of AD patients may represent a compensatory mechanism for the loss of Oxe in the early and middle disease stages, whereas in the terminal stage the compensatory capacity may be lost. The practical consequence is that during treatment, disease stages should be considered and symptomatic therapy should be adjusted accordingly. Further studies are necessary to develop better targeting / therapeutics for sleep disturbances in AD.

Simultaneous Detection of Six Isoforms of Tau Protein in Human Cerebrospinal Fluid by Multidimensional Mass Spectrometry-Based Targeted Proteomics

Abnormal expression of Tau protein can cause the development of Alzheimer's disease (AD). So far, much evidence has demonstrated that Tau has multiple isoforms. These isoforms are suggested to have distinct physiological roles and contribute unequally to the progress of AD. Thus, detection of individual Tau isoforms may be helpful to better understand the link between clinical outcome and Tau status and to further improve AD diagnosis and treatment. However, few studies have been conducted on absolute quantification of Tau isoforms, probably due to high sequence homology and also low abundance of these isoforms in biofluids such as cerebrospinal fluid (CSF). Therefore, mass spectrometry-based targeted proteomics was attempted here. This targeted proteomics approach can principally measure a protein of interest at the surrogate peptide level, yet little has been done to detect protein isoforms, probably due to lack of isoform-specific surrogate peptides in mass spectrometry. In this study, separations in more dimensions were added, including immunoprecipitation (IP) and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) for sample pretreatment and systems of linear equations for post-lab data extraction. Moreover, the reliability of the approach including IP enrichment, gel separation, and linear algebra algorithms was discussed. As a result, each isoform of Tau protein can be individually detected and quantified. Using IP enrichment, ∼250-fold enhancement of sensitivity was achieved. The ultimate LOQ was 0.50 nM. Finally, this multidimensional mass spectrometry-based targeted proteomics assay was validated and applied to simultaneous quantitative analysis of six Tau isoforms in CSF of AD patients.

New diagnostic method for Alzheimer's disease based on the toxic conformation theory of amyloid β.

Recent investigations suggest that soluble oligomeric amyloid β (Aβ) species may be involved in early onset of Alzheimer's disease (AD). Using systematic proline replacement, solid-state NMR, and ESR, we identified a toxic turn at position 22 and 23 of Aβ42, the most potent neurotoxic Aβ species. Through radicalization, the toxic turn can induce formation of the C-terminal hydrophobic core to obtain putative Aβ42 dimers and trimers. Synthesized dimer and trimer models showed that the C-terminal hydrophobic core plays a critical role in the formation of high molecular weight oligomers with neurotoxicity. Accordingly, an anti-toxic turn antibody (24B3) that selectively recognizes a toxic dimer model of E22P-Aβ42 was developed. Sandwich enzyme-linked immunosorbent assay with 24B3 and 82E1 detected a significantly higher ratio of Aβ42 with a toxic turn to total Aβ42 in cerebrospinal fluid of AD patients compared with controls, suggesting that 24B3 could be useful for early onset of AD diagnosis.

Thioredoxin-80 protects against amyloid-beta pathology through autophagic-lysosomal pathway regulation.

Aggregation and accumulation of amyloid beta (Aβ) are believed to play a key role in the pathogenesis of Alzheimer's disease (AD). We previously reported that Thioredoxin-80 (Trx80), a truncated form of Thioredoxin-1, prevents the toxic effects of Aβ and inhibits its aggregation in vitro. Trx80 levels were found to be dramatically reduced both in the human brain and cerebrospinal fluid of AD patients. In this study, we investigated the effect of Trx80 expression using in vivo and in vitro models of Aβ pathology. We developed Drosophila melanogaster models overexpressing either human Trx80, human Aβ42, or both Aβ42/Trx80 in the central nervous system. We found that Trx80 expression prevents Aβ42 accumulation in the brain and rescues the reduction in life span and locomotor impairments seen in Aβ42 expressing flies. Also, we show that Trx80 induces autophagosome formation and reverses the inhibition of Atg4b-Atg8a/b autophagosome formation pathway caused by Aβ42. These effects were also confirmed in human neuroblastoma cells. These results give insight into Trx80 function in vivo, suggesting its role in the autophagosome biogenesis and thus in Aβ42 degradation. Our findings put Trx80 on the spotlight as an endogenous agent against Aβ42-induced toxicity in the brain suggesting that strategies to enhance Trx80 levels in neurons could potentially be beneficial against AD pathology in humans.

Melatonin protective effect against amyloid β-induced neurotoxicity mediated by mitochondrial biogenesis; involvement of hippocampal Sirtuin-1 signaling pathway

Melatonin has a potential therapeutic value in Alzheimer's disease (AD), a disease that is associated with a dramatic decline in memory and cognitive abilities. The aggregation of the amyloid β (Aβ) peptide, a hallmark of AD, deactivates mitochondrial biogenesis and antioxidant defenses. Melatonin as an endogenous antioxidant, decreases in plasma and cerebrospinal fluid of AD patients. Even though several experimental studies have demonstrated the melatonin neuroprotection in AD, clinical trials of melatonin therapy have not yet confirmed outstanding results in AD patients. Better understanding of the molecular mechanisms involved in melatonin neuroprotective effects may pave the way for an efficient therapy. Hence, we investigated the involvement of silent information regulator 1 (SIRT1) signaling and mitochondrial biogenesis in melatonin neuroprotection in a rat model of cognitive impairment induced by intra-hippocampal Aβ injection. Animals assigned to melatonin treatment in the presence or absence of SIRT1 inhibitor (EX527), for 14 consecutive days. Spatial working memory and anxiety level were examined with Y-maze and elevated plus maze tests respectively. Hippocampal SIRT1, transcription factor-A mitochondrial (TFAM) and mitochondrial DNA (mtDNA) copy number were measured. We observed a decrease in hippocampal SIRT1, which accompanied with reduction in TFAM and mtDNA copy number in the Aβ-injected rats. Melatonin treatment increased hippocampal SIRT1 and TFAM expression and enhanced mtDNA copy number in the hippocampus. It also improved memory, ameliorated the anxiety, and attenuated hippocampal cell damage in the Aβ-injected animals. These effects were blocked by EX527 administration, suggesting SIRT1 signaling involvement in melatonin neuroprotective effect. This mechanism may introduce a new promising strategy in battle against AD.

Natriuretic Peptides in Post-mortem Brain Tissue and Cerebrospinal Fluid of Non-demented Humans and Alzheimer's Disease Patients.

Animal studies suggest the involvement of natriuretic peptides (NP) in several brain functions that are known to be disturbed during Alzheimer’s disease (AD). However, it remains unclear whether such findings extend to humans. In this study, we aimed to: (1) map the gene expression and localization of NP and their receptors (NPR) in human post-mortem brain tissue; (2) compare the relative amounts of NP and NPR between the brain tissue of AD patients and non-demented controls, and (3) compare the relative amounts of NP between the cerebrospinal fluid (CSF) of AD patients and non-demented controls. Using the publicly available Allen Human Brain Atlas dataset, we mapped the gene expression of NP and NPR in healthy humans. Using immunohistochemistry, we visualized the localization of NP and NPR in the frontal cortex of AD patients (n = 10, mean age 85.8 ± 6.2 years) and non-demented controls (mean age = 80.2 ± 9.1 years). Using Western blotting and ELISA, we quantified the relative amounts of NP and NPR in the brain tissue and CSF of these AD patients and non-demented controls. Our results showed that NP and NPR genes were ubiquitously expressed throughout the brain in healthy humans. NP and NPR were present in various cellular structures including in neurons, astrocyte-like structures, and cerebral vessels in both AD patients and non-demented controls. Furthermore, we found higher amounts of NPR type-A in the brain of AD patients (p = 0.045) and lower amounts of NP type-B in the CSF of AD patients (p = 0.029). In conclusion, this study shows the abundance of NP and NPR in the brain of humans suggesting involvement of NP in various brain functions. In addition, our findings suggest alterations of NP levels in the brain of AD patients. The role of NP in the development and progression of AD remains to be elucidated.

Recognition of Alzheimer’s Disease Related miRNAs Based on Genome-Wide Association Study Data

To analyze the mi RNA expression profile of patients with Alzheimer's disease (AD) in order to intensively study the relationship between mi RNA and the occurrence and development of AD, and to lay the foundations for the finding of new molecular markers. Use mi RNA chip to detect the mi RNA expression profiles of cerebrospinal fluid in AD patients and elderly people with normal cognition, and perform preliminary bioinformatics analysis. Real-time PCR was used to verify the results of mi RNA chip detection. The results of mi RNA chip analysis showed that there were many differentially expressed mi RNA in cerebrospinal fluid of AD patients and elderly people with normal cognition. Cerebrospinal fluid in AD patients has a specific mi RNA expression profile, suggesting that a new molecular marker for AD may be found in the expression of mi RNA.

Light-Up Nonthiolated Aptasensor for Low-Mass, Soluble Amyloid-β40 Oligomers at High Salt Concentrations.

Herein, a light-up nonthiolated aptasensor was developed for low-mass, soluble amyloid-β40 oligomers (LS-Aβ40-O). Au nanoparticles (AuNP) were employed as colorimetric probes, and the nonthiolated aptamers (Apt) were adsorbed on AuNP surfaces, acting as binding elements for LS-Aβ40-O. The aggregation of AuNPs was induced when Apt-modified AuNPs (Apt@AuNPs) were under high-salt conditions. However, upon the addition of LS-Aβ40-O into the Apt@AuNP solution, the salt tolerance of the AuNPs was greatly enhanced. Further studies confirmed that the formed LS-Aβ40-O-Apt complex attached onto the AuNP surfaces via interactions between LS-Aβ40-O and Au, which led to electrostatic and steric stabilization of the AuNPs under high-salt conditions. On the basis of this outcome, a sensitive light-up nonthiolated aptasensor for LS-Aβ40-O was achieved with a detection limit of 10.0 nM and a linear range from 35.0 to 700 nM in a 175 mM NaCl solution. Cerebrospinal-fluid (CSF) samples from healthy persons and Alzheimer's disease (AD) patients were successfully distinguished by using this proposed method. The concentrations of LS-Aβ40-O in the CSF of AD patients were of nanomolar grade, but there was no detectable LS-Aβ40-O in those of the healthy persons. This work provides a new insight into the interaction between Apt@AuNPs and Aβ40-O and also develops a simple, rapid, highly selective and sensitive, and applicable method for LS-Aβ40-O detection in real CSF samples, which is significant for the diagnosis of AD.

Reaction of Amyloid-β Peptide Antibody with Different Infectious Agents Involved in Alzheimer's Disease.

As early as the 1980s, molecular virologist Ruth Itzhaki began to investigate if there was a causal connection between infections and neurodegenerative disorder. Although the theory has yet to be universally embraced, in 2016 Itzhaki and 33 other scientists from all over the world published a review article in this very journal presenting evidence for the causal role of pathogens in Alzheimer's disease (AD). Exactly how and in what way pathogens affect the induction of AD has yet to be determined, but one possible answer may involve the cross-reactivity of different pathogens with amyloid-β (Aβ). Aβ autoantibodies have been detected in the serum and cerebrospinal fluid of AD patients and in some healthy individuals. In the present study our major goal was to investigate whether antibodies made against Aβ would react both with other brain proteins as well as pathogens associated with AD as a result of molecular mimicry or the binding of bacterial toxins to Aβ42. Our study used a specific monoclonal antibody made against Aβ42, which not only reacted strongly with Aβ42, tau protein, and α-synuclein, but also had from weak to strong reactions with 25 different pathogens or their molecules, some of which have been associated with AD. The homology between peptide stretches of microbial origin and proteins involved in AD could be a mechanism by which antibodies to homologous peptides mount attacks against autoantigens in AD. We concluded that bacterial molecules bind to Aβ protein, forming small oligomers, then encasing pathogens and their molecules to form amyloid plaques, the tell-tale markers of AD. Conversely, these same Aβ peptides induce the production of antibodies to both Aβ42 and bacterial molecules, which may inhibit bacterial pathogenesis, but in the process may promote amyloid plaque formation.

α-Melanocyte Stimulating Hormone as a Potential Therapy for Alzheimer`s Disease.

Alzheimer's disease (AD) is characterized by accumulation and aggregation of beta-amyloid peptide, neurofibrillary tangles of hyperphosphorylated tau, neuroinflammation, synaptic degeneration and eventual neuronal cell loss. Current treatment options for AD provide temporary symptomatic relief in a subset of patients. These drugs include cholinesterase inhibitors that improve cholinergic innervation such as rivastigmine, donepezil and galatamine. In addition, memantine, a Nmethyl- D-aspartate antagonist, is used to treat moderate to severe AD by reducing excitotoxicity. It has been proposed that increased excitation and decreased inhibition lead to aberrant excitatory neuronal activity and cognitive deficits in AD. We undertook a search of the literature using bibliographic databases to identify publications that were related to neuronal activity in Alzheimer's disease. We further delineated the publications to determine inclusion/exclusion criteria based on relevance to increased excitation or decreased inhibition of neuronal networks in both human patients and rodent models. The final criteria related to the potential use of α-Melanocyte stimulating hormone (α-MSH) as a potential treatment strategy for Alzheimer's disease. These data were utilized to obtain the content of this review. We identified 156 peer-reviewed publications that met our criteria and describe the findings here. Rodent models of AD and ageing both exhibit cognitive deficits and loss of inhibitory GABAerigc interneurons. α-Melanocyte stimulating hormone is a neuropeptide that is down-regulated in the brain and cerebrospinal fluid of AD patients. α-MSH has many functions in the central nervous system including neuroprotective and anti-inflammatory effects that target multiple aspects of the AD pathology. α-MSH treatment promoted the survival of GABAergic interneurons in the hippocampus and improved spatial memory as well as alterations in anxiety in a mouse model of AD. The somatostatin expressing subpopulation of GABAergic interneurons are particularly preserved by α-MSH treatment. Somatostatin has been implicated in hippocampal-dependent cognitive tasks. Somatostatin-expressing interneurons have also been shown to play an important role in maintaining excitatory-inhibitory balance. α-MSH preserved GABAergic interneurons and by preventing the loss of the somatostatin subpopulation, it improved cognitive function. α-MSH is a novel candidate for the treatment of AD but its therapeutic potential in AD patients remains to be investigated.

Increased PCSK9 Cerebrospinal Fluid Concentrations in Alzheimer's Disease.

Alzheimer's disease (AD) has been associated with dysregulation of brain cholesterol trafficking and abnormal production of apolipoprotein E isoform 4 (apoE4). Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a protein present in serum and cerebrospinal fluid (CSF) degrading the low-density lipoprotein receptor (LDLr) and other apoE-binding receptors involved in neuron cholesterol uptake. The role of PCSK9 in AD is controversial. We compared PCSK9 levels in CSF of AD patients and non-AD controls and looked at correlations with CSF total apoE and apoE4. CSF from AD (n = 30) and from age and sex-matched non-AD patients (n = 30) was collected by lumbar puncture for routine diagnosis. CSF PCSK9, total apoE, and apoE4 levels were measured by ELISA. AD patients showed the typical CSF neurobiomarker pattern (decreased Aβ42 and increased tau and phospho-tau) and impaired cognitive performances, as indicated by the scores of the Mini-Mental State Examination test. PCSK9 levels in CSF were higher in AD than in non-AD subjects (+1.45 fold; p = 0.0049). CSF total apoE concentrations did not differ between the two groups, while apoE4 levels were higher in AD subjects (+3.34 fold; p = 0.0068). Considering all samples, a significant positive correlation was found between PCSK9 and apoE4 (r = 0.4409; p = 0.0006). PCSK9 levels were higher in APOE ɛ4 carriers, reaching statistical significance in the AD group (+1.45 fold; p = 0.0454). These results report for the first time an alteration of CSF PCSK9 levels in AD and suggest a pathophysiological link between PCSK9, apoE4, and AD.

Seed-competent high-molecular-weight tau species accumulates in the cerebrospinal fluid of Alzheimer's disease mouse model and human patients.

Cerebrospinal fluid (CSF) tau is an excellent surrogate marker for assessing neuropathological changes that occur in Alzheimer's disease (AD) patients. However, whether the elevated tau in AD CSF is just a marker of neurodegeneration or, in fact, a part of the disease process is uncertain. Moreover, it is unknown how CSF tau relates to the recently described soluble high-molecular-weight (HMW) species that is found in the postmortem AD brain and can be taken up by neurons and seed aggregates. We have examined seeding and uptake properties of brain extracellular tau from various sources, including interstitial fluid (ISF) and CSF from an AD transgenic mouse model and postmortem ventricular and antemortem lumbar CSF from AD patients. We found that brain ISF and CSF tau from the AD mouse model can be taken up by cells and induce intracellular aggregates. Ventricular CSF from AD patients contained a rare HMW tau species that exerted a higher seeding activity. Notably, the HMW tau species was also detected in lumbar CSF from AD patients, and its levels were significantly elevated compared to control subjects. HMW tau derived from CSF of AD patients was seed competent in vitro. These findings suggest that CSF from an AD brain contains potentially bioactive HMW tau species, giving new insights into the role of CSF tau and biomarker development for AD. Ann Neurol 2016;80:355-367.

12/15-LIPOXYGENASE INHIBITION REVERSES COGNITIVE IMPAIRMENT, AMYLOIDOSIS, TAU AND SYNAPTIC PATHOLOGY BY STIMULATING AUTOPHAGY IN THE BRAIN OF AGED 3XTG MICE

Alzheimer's disease (AD) is the leading cause of dementia, afflicting 5 million Americans and costing over 200 billion dollars per year. The mechanisms involved in AD pathogenesis are still poorly understood. Moreover, no therapy is available to cure AD or to slow down its progression. The study of new pathways involved in AD pathogenesis is necessary to develop new therapeutic targets. The 12/15-lipoxygenase enzymatic pathway (12/15-LO) is upregulated in postmortem brain tissues and cerebrospinal fluid of AD patients. Its genetic absence or pharmacological inhibition prevents the development of the AD-like phenotype in transgenic mouse models of the disease. However, whether targeting pharmacologically this pathway after the neuropathological lesions and behavioral impairments are well established could be a viable therapeutic strategy against AD remain to be investigated. To this end, 12-month-old triple transgenic mice (3xTg) and their appropriate wild type controls were randomized to receive a specific and selective pharmacological inhibitor of 12/15-LO, PD146176, or placebo. After 3 months, when the animals were 15-month-old, treated and untreated groups were assessed for the effects of the drug on their behavioral impairments and neuropathology. While 15-month-old 3xTg mice on placebo by the end of the study showed a worsening of their memory and learning abilities, as assessed by the fear conditioning paradigms, mice at the same age receiving the PD146176 performed better than baseline in the same test. Compared with placebo, treated mice had significantly less Abeta levels and deposition, improved tau pathology as well as markers of synaptic integrity. Additionally, the same PD146176 treated animals showed a significant upregulation of autophagy markers, suggesting an involvement of this pathway in the pharmacological effect. In vitro experiments demonstrated that 12/15-LO effect on tau metabolism is mediated by modulating neuronal autophagy system. These studies provide new insights into the disease-modifying action of pharmacological inhibiting 12/15-LO as a viable therapeutic approach for AD treatment. They represent the successful completion of the preclinical studies for the development of this class of drug as clinically applicable therapy for the disease.

MiRNA expression profiles in cerebrospinal fluid and blood of patients with Alzheimer's disease and other types of dementia - an exploratory study.

BackgroundMicroRNAs (miRNAs) are small non-coding RNA molecules that function as posttranscriptional regulators of gene expression. Measurements of miRNAs in cerebrospinal fluid (CSF) and blood have just started gaining attention as a novel diagnostic tool for various neurological conditions. The purpose of this exploratory investigation was to analyze the expression of miRNAs in CSF and blood of patients with Alzheimer’s disease (AD) and other neurodegenerative disorders in order to identify potential miRNA biomarker candidates able to separate AD from other types of dementia.MethodsCSF was collected by lumbar puncture performed on 10 patients diagnosed with AD and 10 patients diagnosed with either vascular dementia, frontotemporal dementia or dementia with Lewy bodies. Blood samples were taken immediately after. Total RNA was extracted from cell free fractions of CSF and plasma, and a screening for 372 known miRNA sequences was carried out by real time quantitative polymerase chain reactions (miRCURY LNA™ Universal RT miRNA PCR, Polyadenylation and cDNA synthesis kit, Exiqon).ResultsFifty-two miRNAs were detected in CSF in at least nine out of ten patients in both groups. Among these, two miRNAs (let-7i-5p and miR-15a-5p) were found significantly up-regulated and one miRNA (miR-29c-3p) was found significantly down-regulated in patients with AD compared to controls. One hundred and sixty-eight miRNAs were frequently detected in the blood, among which miR-590-5p and miR-142-5p were significantly up-regulated and miR-194-5p was significantly down-regulated in AD patients compared to controls.ConclusionsDetection of miRNA expression profiles in blood and in particular CSF of patients diagnosed with different types of dementia is feasible and it seems that several expressional differences between AD and other dementia types do exist when measured in a clinically relevant setup. In this explorative pilot study, the deregulated miRNAs in CSF of AD patients may be associated with relevant target genes related to AD pathology, including APP and BACE1, which suggests that miRNAs are interesting candidates for AD biomarkers in the future.Electronic supplementary materialThe online version of this article (doi:10.1186/s40035-016-0053-5) contains supplementary material, which is available to authorized users.