Increased intrathecal TGF-beta1, but not IL-12, IFN-gamma and IL-10 levels in Alzheimer's disease patients

Transforming growth factor-beta 1 enhances discharge activity of cortical neurons

JOURNAL/nrgr/04.03/01300535-202502000-00031/figure1/v/2024-05-28T214302Z/r/image-tiff Transforming growth factor-beta 1 (TGF-β1) has been extensively studied for its pleiotropic effects on central nervous system diseases. The neuroprotective or neurotoxic effects of TGF-β1 in specific brain areas may depend on the pathological process and cell types involved. Voltage-gated sodium channels (VGSCs) are essential ion channels for the generation of action potentials in neurons, and are involved in various neuroexcitation-related diseases. However, the effects of TGF-β1 on the functional properties of VGSCs and firing properties in cortical neurons remain unclear. In this study, we investigated the effects of TGF-β1 on VGSC function and firing properties in primary cortical neurons from mice. We found that TGF-β1 increased VGSC current density in a dose- and time-dependent manner, which was attributable to the upregulation of Nav1.3 expression. Increased VGSC current density and Nav1.3 expression were significantly abolished by preincubation with inhibitors of mitogen-activated protein kinase kinase (PD98059), p38 mitogen-activated protein kinase (SB203580), and Jun NH2-terminal kinase 1/2 inhibitor (SP600125). Interestingly, TGF-β1 significantly increased the firing threshold of action potentials but did not change their firing rate in cortical neurons. These findings suggest that TGF-β1 can increase Nav1.3 expression through activation of the ERK1/2-JNK-MAPK pathway, which leads to a decrease in the firing threshold of action potentials in cortical neurons under pathological conditions. Thus, this contributes to the occurrence and progression of neuroexcitatory-related diseases of the central nervous system.

CSF Biomarkers in the Early Diagnosis of Mild Cognitive Impairment and Alzheimer's Disease

Alzheimer's disease (AD) is a rapidly growing disease that affects millions of people worldwide, therefore there is an urgent need for its early diagnosis and treatment. A huge amount of research studies are performed on possible accurate and reliable diagnostic biomarkers of AD. Due to its direct contact with extracellular space of the brain, cerebrospinal fluid (CSF) is the most useful biological fluid reflecting molecular events in the brain. Proteins and molecules that reflect the pathogenesis of the disease, e.g., neurodegeneration, accumulation of Abeta, hyperphosphorylation of tau protein and apoptosis may be used as biomarkers. The aim of the current manuscript is to present the most commonly used CSF biomarkers for AD as well as novel biomarkers. Three CSF biomarkers, namely total tau, phospho-tau and Abeta42, are believed to have the highest diagnostic accuracy for early AD diagnosis and the ability to predict AD development in mild cognitive impairment (MCI) patients. Moreover, other biomarkers such as soluble amyloid precursor protein (APP), apoptotic proteins, secretases and inflammatory and oxidation markers are believed to have increased future prospects.

The association between inflammatory markers in blood and cerebrospinal fluid: a systematic review and meta-analysis

BACKGROUND

Neuroinflammatory processes have been hypothesized to play a role in the pathogenesis of psychiatric and neurological diseases. Studies on this topic often rely on analysis of inflammatory biomarkers in peripheral blood. Unfortunately, the extent to which these peripheral markers reflect inflammatory processes in the central nervous system (CNS) is unclear.

METHODS

We performed a systematic review and found 29 studies examining the association between inflammatory marker levels in blood and cerebrospinal (CSF) samples. We performed a random effects meta-analysis of 21 studies (pooled n = 1679 paired samples) that reported the correlation of inflammatory markers in paired blood-CSF samples.

RESULTS

A qualitative review revealed moderate to high quality of included studies with the majority of studies reporting no significant correlation of inflammatory markers between paired blood-CSF. Meta-analyses revealed a significant low pooled correlation between peripheral and CSF biomarkers (r = 0.21). Meta-analyses of individual cytokines revealed a significant pooled correlation for IL-6 (r = 0.26) and TNFα (r = 0.3) after excluding outlier studies, but not for other cytokines. Sensitivity analyses showed that correlations were highest among participants with a median age above 50 (r = 0.46) and among autoimmune disorder patients (r = 0.35).

CONCLUSION

This systematic review and meta-analysis revealed poor correlation between peripheral and central inflammatory markers in paired blood-CSF samples, with increased correlations in certain study populations. Based on the current findings, peripheral inflammatory markers are a poor reflection of the neuroinflammatory profile.

Relationships between Inflammation and Age-Related Neurocognitive Changes

The relationship between inflammation and age-related neurocognitive changes is significant, which may relate to the age-related immune dysfunctions characterized by the senescence of immune cells and elevated inflammatory markers in the peripheral circulation and the central nervous system. In this review, we discuss the potential mechanisms, including the development of vascular inflammation, neuroinflammation, organelle dysfunctions, abnormal cholesterol metabolism, and glymphatic dysfunctions as well as the role that the key molecules play in the immune-cognition interplay. We propose potential therapeutic pharmacological and behavioral strategies for ameliorating age-related neurocognitive changes associated with inflammation. Further research to decipher the multidimensional roles of chronic inflammation in normal and pathological aging processes will help unfold the pathophysiological mechanisms underpinning neurocognitive disorders. The insight gained will lay the path for developing cost-effective preventative measures and the buffering or delaying of age-related neurocognitive decline.

Biomarker of Neuroinflammation in Parkinson's Disease

Parkinson's disease (PD) is caused by abnormal accumulation of α-synuclein in dopaminergic neurons of the substantia nigra, which subsequently causes motor symptoms. Neuroinflammation plays a vital role in the pathogenesis of neurodegeneration in PD. This neuroinflammatory neurodegeneration involves the activation of microglia, upregulation of proinflammatory factors, and gut microbiota. In this review, we summarized the recent findings on detection of PD by using inflammatory biomarkers, such as interleukin (IL)-1β, IL-2, IL-6, IL-10, tumor necrosis factor (TNF)-α; regulated upon activation, normal T cell expressed and presumably secreted (RANTES) and high-sensitivity c-reactive protein (hsCRP); and radiotracers such as [11C]PK11195 and [18F]-FEPPA, as well as by monitoring disease progression and the treatment response. Many PD-causing mutations in SNCA, LRRK2, PRKN, PINK1, and DJ-1 are also associated with neuroinflammation. Several anti-inflammatory medications, including nonsteroidal anti-inflammatory drugs (NSAID), inhibitors of TNF-α and NLR family pyrin domain containing 3 (NLRP3), agonists of nuclear factor erythroid 2-related factor 2 (NRF2), peroxisome proliferator-activated receptor gamma (PPAR-γ), and steroids, have demonstrated neuroprotective effects in in vivo or in vitro PD models. Clinical trials applying objective biomarkers are required to investigate the therapeutic potential of anti-inflammatory medications for PD.

Cerebrospinal fluid biomarkers and genetic factors associated with normal pressure hydrocephalus and Alzheimer’s disease: a narrative review

Background

Normal pressure hydrocephalus is a neurologic disease leading to enlargement of ventricles which is presented with gait and balance disturbance, cognitive decline, and urinary incontinence. Diagnosis of normal pressure hydrocephalus is challenging due to the late onset of signs and symptoms. In this review, we summarize the cerebrospinal fluid, plasma, pathology, and genetic biomarkers of normal pressure hydrocephalus and related disorders.

Body

Recently, cerebrospinal fluid and serum biomarkers analysis alongside gene analysis has received a lot of attention. Interpreting a set of serum and cerebrospinal fluid biomarkers along with genetic testing for candidate genes could differentiate NPH from other neurological diseases such as Alzheimer's disease, Parkinson's disease with dementia, and other types of dementia.

Conclusion

Better understanding the pathophysiology of normal pressure hydrocephalus through genetic studies can aid in evolving preventative measures and the early treatment of normal pressure hydrocephalus patients.

Inflammatory Markers in Cerebrospinal Fluid from Patients with Hydrocephalus: A Systematic Literature Review

OBJECTIVE

The aim of this systematic review was to evaluate existing literature on inflammatory markers in CSF from patients with hydrocephalus and identify potential markers capable of promoting hydrocephalus development and progression.

METHODS

Relevant studies published before December 3rd 2020 were identified from PubMed, Embase, and reference lists. Studies were screened for eligibility using the predefined inclusion and exclusion criteria. Data from eligible studies were extracted, and sources of bias were evaluated. We included articles written in English investigating inflammatory markers in CSF from patients with hydrocephalus and control subjects. The review was conducted according to the PRISMA guidelines by three independent reviewers.

RESULTS

Twenty-two studies analyzed CSF from 311 patients with idiopathic normal pressure hydrocephalus (iNPH), 178 with posthemorrhagic hydrocephalus (PHH), 151 with other hydrocephalus diagnoses, and 394 control subjects. Fifty-eight inflammatory markers were investigated. The CSF of iNPH patients had increased CSF levels of IL-6, IL-1β, and LRG compared with control subjects, whereas the CSF of PHH patients had increased levels of IL-6, IL-18, and VEGF. CSF from patients with "other hydrocephalus diagnoses" had elevated IFN-γ compared to control subjects, and VEGF was increased in congenital hydrocephalus, spina bifida, and hydrocephalus associated with tuberculous meningitis compared with controls.

CONCLUSION

IL-6, IL-1β, LRG, IL-18, VEGF, and IFN-γ are elevated in CSF from patients with hydrocephalus and may be involved in promotion of hydrocephalus development and progression. They may serve as novel disease biomarkers, and their signaling pathways may represent targets for pharmacological management of hydrocephalus.

Characterization of the chromatin accessibility in an Alzheimer's disease (AD) mouse model

Background

The pathological hallmarks of Alzheimer’s disease (AD) involve alterations in the expression of numerous genes associated with transcriptional levels, which are determined by chromatin accessibility. Here, the landscape of chromatin accessibility was studied to understand the outline of the transcription and expression of AD-associated metabolism genes in an AD mouse model.

Methods

The assay for transposase-accessible chromatin by sequencing (ATAC-seq) was used to investigate the AD-associated chromatin reshaping in the APPswe/PS1dE9 (APP/PS1) mouse model. ATAC-seq data in the hippocampus of 8-month-old APP/PS1 mice were generated, and the relationship between chromatin accessibility and gene expression was analyzed in combination with RNA sequencing. Gene ontology (GO) analysis was applied to elucidate biological processes and signaling pathways altered in APP/PS1 mice. Critical transcription factors were identified; alterations in chromatin accessibility were further confirmed using chromatin immunoprecipitation assays.

Results

We identified 1690 increased AD-associated chromatin-accessible regions in the hippocampal tissues of APP/PS1 mice. These regions were enriched in genes related to diverse signaling pathways, including the PI3K-Akt, Hippo, TGF-β, and Jak-Stat signaling pathways, which play essential roles in regulating cell proliferation, apoptosis, and inflammatory responses. A total of 1003 decreased chromatin-accessible regions were considered to be related with declined AD-associated biological processes including cellular response to hyperoxia and insulin stimulus, synaptic transmission, and positive regulation of autophagy. In the APP/PS1 hippocampus, 1090 genes were found to be upregulated and 1081 downregulated. Interestingly, enhanced ATAC-seq signal was found in approximately 740 genes, with 43 exhibiting upregulated mRNA levels. Several genes involved in AD development were found to have a significantly increased expression in APP/PS1 mice compared to controls, including Sele, Clec7a, Cst7, and Ccr6. The signatures of numerous transcription factors, including Olig2, NeuroD1, TCF4, and NeuroG2, were found enriched in the AD-associated accessible chromatin regions. The transcription-activating marks of H3K4me3 and H3K27ac were also found increased in the promoters of these genes. These results indicate that the mechanism for the upregulation of genes could be attributed to the enrichment of open chromatin regions with transcription factors motifs and the histone marks H3K4me3 and H3K27ac.

Conclusion

Our study reveals that alterations in chromatin accessibility may be an initial mechanism in AD pathogenesis.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s13195-020-00598-2.

Alzheimer's disease: microglia targets and their modulation to promote amyloid phagocytosis and mitigate neuroinflammation

Introduction: Despite the revolutionary progress in neurodegenerative disease research, there is no cure for Alzheimer's disease (AD). This is a chronic progressive neurodegenerative disease affecting aged people and is associated with chronic neuroinflammation and amyloid-beta (Aβ) deposition in the brain parenchyma. Microglia, the resident myeloid cells in the central nervous system, are critically involved in the pathogenesis of AD and have emerged as a potential therapeutic target for treating or preventing AD. The failure of microglia to keep up with persistent amyloid-beta development along with secretion of inflammatory cytokines is detrimental to neurons and favors Aβ accumulation.Areas covered: This review illuminates the latest research that is focused on molecules and their intracellular targets that promote microglial phagocytosis and /or its polarization to an anti-inflammatory state.Expert opinion: A robust inflammatory response of microglia is not necessary to improve their efficiency of Aβ clearance. The challenge is to master inflammatory/anti-inflammatory phenotypes depending on the stage of AD and to maintain efficient responses to remove Aβ. Therefore, promoting microglia phagocytosis without a persistent excessive inflammatory response could be a potential therapeutic strategy.

Early intraneuronal amyloid triggers neuron-derived inflammatory signaling in APP transgenic rats and human brain

This work provides evidence that soluble and oligomeric amyloid protein stokes neuronal inflammation during the earliest stages of Alzheimer’s disease. Identifying neuron-derived factors that engage the brain’s immune system will provide insight into how vulnerable neurons might interact with other immune cells to propagate cytotoxic signaling cascades and cellular dysfunction during disease development.

Chronic inflammation during Alzheimer’s disease (AD) is most often attributed to sustained microglial activation in response to amyloid-β (Aβ) plaque deposits and cell death. However, cytokine release and microgliosis are consistently observed in AD transgenic animal models devoid of such pathologies, bringing into question the underlying processes that may be at play during the earliest AD-related immune response. We propose that this plaque-independent inflammatory reaction originates from neurons burdened with increasing levels of soluble and oligomeric Aβ, which are known to be the most toxic amyloid species within the brain. Laser microdissected neurons extracted from preplaque amyloid precursor protein (APP) transgenic rats were found to produce a variety of potent immune factors, both at the transcript and protein levels. Neuron-derived cytokines correlated with the extent of microglial activation and mobilization, even in the absence of extracellular plaques and cell death. Importantly, we identified an inflammatory profile unique to Aβ-burdened neurons, since neighboring glial cells did not express similar molecules. Moreover, we demonstrate within disease-vulnerable regions of the human brain that a neuron-specific inflammatory response may precede insoluble Aβ plaque and tau tangle formation. Thus, we reveal the Aβ-burdened neuron as a primary proinflammatory agent, implicating the intraneuronal accumulation of Aβ as a significant immunological component in the AD pathogenesis.

Ineffective levels of transforming growth factors and their receptor account for old age being a risk factor for Alzheimer's disease

After the midninth decade of age, the incidence rates of Alzheimer's disease (AD) and the presence of active TGF-β1 show comparable increases. The hypothesis is proposed that the reason why advanced age is a major risk factor for AD is a progressive decrease with advancing age in the numbers of TGFR2 receptors in the brain, with the consequence of a decline in the neurotrophic efficacy of TGF-β1 and 2 despite their already increased levels in older persons. Alternative, possible reasons are discussed but rejected because either those reasons may also affect young persons or because they cannot be validated in a clinical trial. The proposed hypothesis may be validated in persons with aMCI after raising their brain levels of TGF-β1 and 2 by using a combination of three drugs, lithium, memantine, plus either glatiramer or venlafaxine, and then assessing their progression to AD.

Intra- and extracellular β-amyloid overexpression via adeno-associated virus-mediated gene transfer impairs memory and synaptic plasticity in the hippocampus

Alzheimer's disease (AD), the most common age-related neurodegenerative disorder, is currently conceptualized as a disease of synaptic failure. Synaptic impairments are robust within the AD brain and better correlate with dementia severity when compared with other pathological features of the disease. Nevertheless, the series of events that promote synaptic failure still remain under debate, as potential triggers such as β-amyloid (Aβ) can vary in size, configuration and cellular location, challenging data interpretation in causation studies. Here we present data obtained using adeno-associated viral (AAV) constructs that drive the expression of oligomeric Aβ either intra or extracellularly. We observed that expression of Aβ in both cellular compartments affect learning and memory, reduce the number of synapses and the expression of synaptic-related proteins, and disrupt chemical long-term potentiation (cLTP). Together, these findings indicate that during the progression AD the early accumulation of Aβ inside neurons is sufficient to promote morphological and functional cellular toxicity, a phenomenon that can be exacerbated by the buildup of Aβ in the brain parenchyma. Moreover, our AAV constructs represent a valuable tool in the investigation of the pathological properties of Aβ oligomers both in vivo and in vitro.

TGF-β Signaling in Cellular Senescence and Aging-Related Pathology

Aging is broadly defined as the functional decline that occurs in all body systems. The accumulation of senescent cells is considered a hallmark of aging and thought to contribute to the aging pathologies. Transforming growth factor-β (TGF-β) is a pleiotropic cytokine that regulates a myriad of cellular processes and has important roles in embryonic development, physiological tissue homeostasis, and various pathological conditions. TGF-β exerts potent growth inhibitory activities in various cell types, and multiple growth regulatory mechanisms have reportedly been linked to the phenotypes of cellular senescence and stem cell aging in previous studies. In addition, accumulated evidence has indicated a multifaceted association between TGF-β signaling and aging-associated disorders, including Alzheimer’s disease, muscle atrophy, and obesity. The findings regarding these diseases suggest that the impairment of TGF-β signaling in certain cell types and the upregulation of TGF-β ligands contribute to cell degeneration, tissue fibrosis, inflammation, decreased regeneration capacity, and metabolic malfunction. While the biological roles of TGF-β depend highly on cell types and cellular contexts, aging-associated changes are an important additional context which warrants further investigation to better understand the involvement in various diseases and develop therapeutic options. The present review summarizes the relationships between TGF-β signaling and cellular senescence, stem cell aging, and aging-related diseases.

Inflammation in mild cognitive impairment due to Parkinson's disease, Lewy body disease, and Alzheimer's disease

BACKGROUND

Inflammation appears to play a role in the progression of neurodegenerative diseases. However, little is known about inflammation during early stages of cognitive decline or whether this differs in different disease groups. We sought to investigate this by assessing the inflammatory profile in patients with Parkinson disease with the early stages of cognitive impairment (PD-MCI), patients with prodromal Alzheimer disease (MCI-AD), prodromal Lewy body disease (MCI-LB), and controls.

METHODS

We obtained venous blood samples from participants with PD-MCI (n = 44), PD-normal cognition (n = 112), MCI-LB (n = 38), MCI-AD (n = 21), and controls (n = 84). We measured 10 cytokines using Meso Scale Discovery V-Plex Plus including interferon gamma, interleukin (IL)-10, IL-12p70, IL-13, IL-1beta, IL-2, IL-4, IL-6, IL-8, and tumour necrosis factor alpha. High-sensitivity C-reactive protein was measured.

RESULTS

There was a higher level of inflammation in patients with MCI-AD and MCI-LB compared with controls. PD noncognitively impaired had higher inflammatory markers than controls, but there was no difference between PD-MCI and controls. There was a decrease in inflammatory markers with increasing motor severity based on the Unified Parkinson's Disease Rating Scale.

CONCLUSIONS

Inflammation may be involved in the onset of cognitive decline in patients with MCI-AD and MCI-LB but appears to be less prominent PD-MCI albeit in a small data set. This suggests that anti-inflammatory medications may have most benefit at the earliest stages of neurodegenerative diseases. For PD cases, this might be in advance of the development of MCI.

Bi-directional Association of Cerebrospinal Fluid Immune Markers with Stage of Alzheimer's Disease Pathogenesis

Immune mechanisms may be important in the pathogenesis of Alzheimer’s disease (AD). Yet, studies comparing cerebrospinal fluid (CSF) and plasma immune marker levels of healthy and demented individuals have yielded conflicting results. We analyzed CSF from 101 members of the parental history-positive PREVENT-AD cohort of healthy aging adults, and 237 participants without dementia from the initial cohort of the Alzheimer’s Disease Neuroimaging Initiative (ADNI-1). Following recent practice, we used the biomarkers total-tau and amyloid-β_1-42 to allocate participants from each study into four stages of AD pathogenesis: Stage 0 (no abnormality), Stage 1 (reduced amyloid-β_1-42), Stage 2 (reduced amyloid-β_1-42 and increased total-tau), or “Suspected Non-Alzheimer Pathology” (elevated total-tau only). Investigating the PREVENT-AD participants’ CSF assay results for 19 immune/inflammatory markers, we found six that showed a distinct bi-directional relationship with pathogenetic stage. Relative to Stage 0, these were diminished at Stage 1 but strongly increased at Stage 2. Among the ADNI participants (90 healthy controls and 147 with mild cognitive impairment), we found that 23 of 83 available CSF markers also showed this distinct pattern. These results support recent observations that immune activation may become apparent only after the onset of both amyloid and tau pathologies. Unexpectedly, they also suggest that immune marker activity may diminish along with earliest appearance of amyloid-β plaque pathology. These findings may explain discordant results from past studies, and suggest the importance of characterizing the extent of AD pathology when comparing clinical groups.

Serum Inflammatory Profile for the Discrimination of Clinical Subtypes in Parkinson's Disease

Background: Blood levels of immune markers have been proposed to discriminate patients with Parkinson's disease (PD) from controls. However, differences between clinical PD subgroups regarding these markers still need to be identified.

Objective: To investigate whether clinical phenotypes can be predicted by the assessment of immune marker profiles in the serum of PD patients.

Methods: Phenotypes of clinical PD from Tübingen, Germany (n = 145) and Toronto, Canada (n = 90) were defined regarding clinical subtype, disease onset, severity, and progression as well as presence of cognitive and/or autonomic dysfunction. A panel of serum immune markers was assessed using principal component analysis (PCA) and regression models to define the marker(s) that were associated with clinical phenotypes after adjusting for potential confounders. Findings of both centers were compared for validation. Further, a [18F] FEPPA-PET was performed in a group of patients with high and low values of candidate markers for the assessment of in vivo brain microglial activation.

Results: Overall, serum immune markers did not cluster to define a pro/anti-inflammatory profile in PCA. Out of 25 markers only IL-12p40 showed a trend to discriminate between PD subgroups in both cohorts which could not be replicated by [18F] FEPPA-PET.

Conclusions: Assessment of cytokines in serum does not reliably differentiate clinical PD subtypes. Accompanying subtype-irrelevant inflammation in PD, dual activity, and lack of specificity of the immune markers, the complex function of microglia, probable effects of treatment, disease stage, and progression on inflammation as well as current technical limitations may limit the usefulness of serum immune markers for the differentiation of subtypes.

Impact of Aging in Microglia-Mediated D-Serine Balance in the CNS

A mild chronic inflammatory state, like that observed in aged individuals, affects microglial function, inducing a dysfunctional phenotype that potentiates neuroinflammation and cytotoxicity instead of neuroprotection in response to additional challenges. Given that inflammatory activation of microglia promotes increased release of D-serine, we postulate that age-dependent inflammatory brain environment leads to microglia-mediated changes on the D-serine-regulated glutamatergic transmission. Furthermore, D-serine dysregulation, in addition to affecting synaptogenesis and synaptic plasticity, appears also to potentiate NMDAR-dependent excitotoxicity, promoting neurodegeneration and cognitive impairment. D-serine dysregulation promoted by microglia could have a role in age-related cognitive impairment and in the induction and progression of neurodegenerative processes like Alzheimer's disease.

Systemic Inflammation in Lewy Body Diseases: A Systematic Review

Few studies have investigated the role of inflammation in Lewy body dementia (LBD) and variable results have been found. We systematically reviewed the literature for evidence of systemic inflammatory changes in dementia with Lewy bodies and Parkinson disease dementia. Owing to the low number of studies we also included Parkinson disease. Key terms were used to search the relevant databases. Titles and abstracts were screened and potentially relevant articles were reviewed in full. References of included studies and relevant reviews were searched. The database search returned 2166 results, 46 of which were finally included in the systematic review. These studies showed a general increase in inflammatory markers in the peripheral blood, most notably interleukin-1β (IL-1β), tumor necrosis factor-α, IL-6, and IL-10. Studies examining cerebrospinal fluid found IL-1β, IL-6, and transforming growth factor-β1 to be particularly increased, and interferon-γ decreased. C-reactive protein levels were increased, particularly in Parkinson disease dementia. These results provide evidence that LBD is associated with an increased inflammatory response. Furthermore, there may be a stronger general inflammatory response in LBD than in Parkinson disease, while complex changes occur in the individual cytokines.

Cellular Senescence, Neurological Function, and Redox State

SIGNIFICANCE

Cellular senescence, characterized by permanent cell cycle arrest, has been extensively studied in mitotic cells such as fibroblasts. However, senescent cells have also been observed in the brain. Even though it is recognized that cellular energetic metabolism and redox homeostasis are perturbed in the aged brain and neurodegenerative diseases (NDDs), it is still unknown which alterations in the overall physiology can stimulate cellular senescence induction and their relationship with the former events. Recent Advances: Recent findings have shown that during prolonged inflammatory and pathologic events, the blood-brain barrier could be compromised and immune cells might enter the brain; this fact along with the brain's high oxygen dependence might result in oxidative damage to macromolecules and therefore senescence induction. Thus, cellular senescence in different brain cell types is revised here.

CRITICAL ISSUES

Most information related to cellular senescence in the brain has been obtained from research in glial cells since it has been assumed that the senescent phenotype is a feature exclusive to mitotic cells. Nevertheless, neurons with senescence hallmarks have been observed in old mouse brains. Therefore, although this is a controversial topic in the field, here we summarize and integrate the observations from several studies and propose that neurons indeed senesce.

FUTURE DIRECTIONS

It is still unknown which alterations in the overall metabolism can stimulate senescence induction in the aged brain, what are the mechanisms and signaling pathways, and what is their relationship to NDD development. The understanding of these processes will expose new targets to intervene age-associated pathologies.-Antioxid. Redox Signal. 28, 1704-1723.

Acetyl Cholinesterase Inhibitors and Cell-Derived Peripheral Inflammatory Cytokines in Early Stages of Alzheimer's Disease

BACKGROUND

Clinical and preclinical studies firmly support the involvement of the inflammation in the pathogenesis of Alzheimer's disease (AD). Despite acetylcholinesterase inhibitors (AChEI) being widely used in AD patients, there is no conclusive evidence about their impact on the inflammatory response.

METHODS

This study investigates peripheral proinflammatory cytokines (interferon gamma [IFN-γ], tumor necrosis factor alpha [TNF-α], and interleukins 1β [IL-1β] and 6 [IL-6]) by firstly comparing peripheral blood mononuclear cell (PBMC)-derived secretion in drug-naïve and AChEI-treated AD patients versus healthy controls. A subset of those drug-naïve AD patients, who were prescribed the AChEI donepezil, was followed-up for 6 months to investigate if donepezil suppresses proinflammatory cell-derived cytokine secretion.

RESULTS

Patients with AD showed higher levels of PBMC-derived proinflammatory cytokines (IFN-γ, TNF-α, IL-1β, and IL-6) in comparison with healthy controls. On reexamination, previously drug-naïve AD patients who received donepezil treatment for 6 months displayed a decrease in cell-derived IFN-γ, TNF-α, IL-1β, and IL-6.

CONCLUSIONS

Proinflammatory PBMC-derived cytokines were increased in patients with AD in comparison with healthy controls and donepezil-reduced proinflammatory cytokines when examining drug-naïve AD patients before and after AChEI treatment.

Peripheral inflammation in prodromal Alzheimer's and Lewy body dementias

OBJECTIVES

There is growing evidence for the role of systemic inflammation in Alzheimer's disease (AD) and other neurodegenerative diseases; however the systemic inflammatory profile in dementia with Lewy bodies (DLB) has never before been investigated. This study aimed to characterise systemic inflammatory mediators in established DLB and AD, as well as in their prodromal, mild cognitive impairment (MCI) phases.

METHODS

We obtained plasma samples from patients with DLB (n=37), AD (n=20), MCI with DLB profile (n=38), MCI with AD profile (n=20) and healthy control subjects (n=20). The following inflammatory biomarkers were measured using Roche cobas c702 and Meso Scale Discovery V-Plex Plus: high-sensitivity C-reactive protein, interferon-gamma, interleukin (IL)-10, IL-12p70, IL-13, IL-1beta, IL-2, IL-4, IL-6, IL-8 and tumour necrosis factor-alpha.

RESULTS

We found significantly higher levels of IL-10, IL-1beta, IL-4 and IL-2 in both MCI groups (P<0.001), while there was no significant difference in inflammatory markers between dementia groups and controls. Furthermore, increased disease severity was associated with lower levels of IL-1beta, IL-2 and IL-4 (P<0.05).

INTERPRETATION

We have shown for the first time that in both DLB and AD, increased peripheral inflammation occurs early at the MCI disease stages. These data support a role for inflammation early in the disease process, and have important implications for the stage of disease where trials of anti-inflammatory medication should be focused.

U1 snRNP Alteration and Neuronal Cell Cycle Reentry in Alzheimer Disease

The aberrancy of U1 small nuclear ribonucleoprotein (snRNP) complex and RNA splicing has been demonstrated in Alzheimer’s disease (AD). Importantly, the U1 proteopathy is AD-specific, widespread and early-occurring, thus providing a very unique clue to the AD pathogenesis. The prominent feature of U1 histopathology is its nuclear depletion and redistribution in the neuronal cytoplasm. According to the preliminary data, the initial U1 cytoplasmic distribution pattern is similar to the subcellular translocation of the spliceosome in cells undergoing mitosis. This implies that the U1 mislocalization might reflect the neuronal cell cycle-reentry (CCR) which has been extensively evidenced in AD brains. The CCR phenomenon explains the major molecular and cellular events in AD brains, such as Tau and amyloid precursor protein (APP) phosphorylation, and the possible neuronal death through mitotic catastrophe (MC). Furthermore, the CCR might be mechanistically linked to inflammation, a critical factor in the AD etiology according to the genetic evidence. Therefore, the discovery of U1 aberrancy might strengthen the involvement of CCR in the AD neuronal degeneration.

TGF-β1 Regulation of P-JNK and L-Type Calcium Channel Cav1.2 in Cortical Neurons

Central nervous system (CNS) diseases can cause a series of neuronal lesions, which may be improved by the anti-apoptotic neuroprotection of transforming growth factor-beta 1 (TGF-β1). In neurons, L-type Ca²⁺ channels (LTCC) are mainly composed of Cav1.2 subunits. Given the implication of TGF-β1 in numerous CNS diseases, we examined the neuroprotective effects of TGF-β1 on the Cav1.2 channel in the CNS. To simulate acute mechanical traumatic brain injury (TBI), we used a needle to create parallel scratches across plates, which were cultured for 9 h. Meanwhile, Fluo4-AM-loaded laser scanning confocal microscopy with a dual wavelength of 488 nm/530 nm was employed to determine intracellular calcium concentrations ([Ca²⁺]_i). We found that MAPK inhibitors impede TGF-β1-induced cell viability and that TGF-β1 recovered from the trauma-induced cell viability in neurons. Cav1.2 production was significantly decreased in the TGF-β1-treated (10 ng/mL) neurons. At this TGF-β1 concentration, Cav1.2 was significantly down-regulated in a time-dependent manner after 12 h. Moreover, TGF-β1 partially recovered the protein levels of Cav1.2 that were reduced by TBI. TGF-β1 significantly inhibited the fluorescence intensity of [Ca²⁺]_i increased by KCl and delayed the time of the peak [Ca²⁺]_i. The observed effects of TGF-β1 on Cav1.2 were regulated by MAPK inhibitors. The observed effects of TGF-β1 on P-JNK were also impeded by pre-incubation with the LTCC inhibitor (10 μM) nimodipine in trauma-injured neurons. Altogether, TGF-β1 regulated LTCCs through a mechanism dependent on MEK, JNK1/2 and p38 MAPK signal pathways in cortical neurons. Thus, we suggest the involvement of this mechanism in cell viability.

Single-Base Resolution Mapping of 5-Hydroxymethylcytosine Modifications in Hippocampus of Alzheimer's Disease Subjects

Epigenetic modifications to cytosine have been shown to regulate transcription in cancer, embryonic development, and recently neurodegeneration. While cytosine methylation studies are now common in neurodegenerative research, hydroxymethylation studies are rare, particularly genome-wide mapping studies. As an initial study to analyze 5-hydroxymethylcytosine (5-hmC) in the Alzheimer's disease (AD) genome, reduced representation hydroxymethylation profiling (RRHP) was used to analyze more than 2 million sites of possible modification in hippocampal DNA of sporadic AD and normal control subjects. Genes with differentially hydroxymethylated regions were filtered based on previously published microarray data for altered gene expression in hippocampal DNA of AD subjects. Our data show significant pathways for altered levels of 5-hmC in the hippocampus of AD subjects compared to age-matched normal controls involved in signaling, energy metabolism, cell function, gene expression, protein degradation, and cell structure and stabilization. Overall, our data suggest a possible role for the dysregulation of epigenetic modifications to cytosine in late stage AD.

Alzheimer’s disease and cytokine IL-10 gene polymorphisms: is there an association?

ABSTRACT Alzheimer’s disease (AD) is the most common form of dementia. In the last 15 years, a new theory has proposed the autoimmune mechanism as a trigger for AD. Studies on the association between AD and inflammatory biomarkers have yielded controversial results. Interleukin-10 (IL-10), an anti-inflammatory mediator, has been pointed out as one of the main cytokines associated with the occurrence of AD. Moreover, treatment that increases IL-10 levels could be a potential therapy for AD, since this cytokine acts on amyloid and pro-inflammatory molecule reduction. Based on the current literature, this study reviews evidence regarding the role of IL-10 polymorphisms in the context of AD, which has been shown to be of paramount importance for attenuating neuroinflammation, cognitive dysfunction and neurodegeneration.

Blood–Brain Barrier Pathology in Alzheimer's and Parkinson's Disease: Implications for Drug Therapy

The blood–brain barrier (BBB) is a tightly regulated barrier in the central nervous system. Though the BBB is thought to be intact during neurodegenerative diseases such as Alzheimer's (AD) and Parkinson's disease (PD), recent evidence argues otherwise. Dysfunction of the BBB may be involved in disease progression, eliciting of peripheral immune response, and, most importantly, altered drug efficacy. In this review, we will give a brief overview of the BBB, its components, and their functions. We will critically evaluate the current literature in AD and PD BBB pathology resulting from insult, neuroinflammation, and neurodegeneration. Specifically, we will discuss alterations in tight junction, transport and endothelial cell surface proteins, and vascular density changes, all of which result in altered permeability. Finally, we will discuss the implications of BBB dysfunction in current and future therapeutics. Developing a better appreciation of BBB dysfunction in AD and PD may not only provide novel strategies in treatment, but will prove an interesting milestone in understanding neurodegenerative disease etiology and progression.

Reduced cerebrospinal fluid concentration of interleukin-12/23 subunit p40 in patients with cognitive impairment

Background

The role of inflammation in Alzheimer’s disease (AD) and other cognitive disorders is unclear. In a well-defined mono-center population, we measured cytokines and chemokines in paired serum and cerebrospinal fluid (CSF) samples.

Methods

Consecutive patients with AD (n = 30), stable mild cognitive impairment (SMCI, n = 11), other dementias (n = 11), and healthy controls (n = 18) were included. None of the subjects was treated with glucocorticoids, cholinesterase inhibitors, or non-steroidal anti-inflammatory drugs. Serum and CSF concentrations of interleukin-6 (IL-6), IL-8, IL-12/23 p40, IL-15, IL-16, vascular endothelial growth factor-A (VEGF-A), and three chemokines were measured using a multiplex panel.

Results

After correction for multiple comparisons, only CSF IL-12/23 p40 concentration differed significantly between the total patient group (n = 52) and controls (n = 18; p = 0.002). Further analyses showed that CSF IL-12/23 p40 concentration was decreased in all patient subgroups (AD, other dementias, and SMCI) compared to healthy controls (p < 0.01, p < 0.05, and p < 0.05, respectively). In the total study population (n = 70), CSF IL-12/23 p40 concentrations correlated positively with CSF concentrations of β-amyloid_1-42 (Aβ_1–42) and phosphorylated tau protein (P-tau) whereas in AD patients (n = 30), CSF IL-12/23 p40 only correlated positively with CSF P-Tau (r = 0.46, p = 0.01).

Conclusions

Most cytokines and chemokines were similar in patients and controls, but CSF IL-12/23 subunit p40 concentration was decreased in patients with cognitive impairment, and correlated with markers of AD disease status. Further studies are needed to evaluate the role of CSF IL-12/23 p40 in other dementias and SMCI.

The impact of selected cytokines in the follow-up of normal pressure hydrocephalus

Cytokines are widely known mediators of inflammation accompanying many neurodegenerative disorders including normal pressure hydrocephalus (NPH). NPH is caused by impaired cerebrospinal fluid (CSF) reabsorption and treated by surgical shunt insertion. The diagnostics is still complicated and the shunt effect is not durable; after several years, dementia may develop. In the clinical practice, biomarkers support the diagnostics as well as the further time course of many neurodegenerative diseases. Until recently, no reliable biomarker for NPH was evaluated. The attempt of this review was to make a survey concerning cytokines as possible NPH markers. Among all reviewed cytokines, the most promising are CSF IL-10 and IL-33, enabling to follow-up the disease progression and monitoring the effectiveness of the shunt insertion.

Increased serum concentrations of transforming growth factor-β1 (TGF-β1) in patients with Guillain-Barré syndrome

BACKGROUND

Guillain-Barré syndrome (GBS) is an acquired demyelinating peripheral neuropathy. It has shown that macrophage activation contribute to the pathogenesis of GBS. Therefore macrophage-mediated factors could be the potential markers for disease diagnosis and status of GBS.

METHODS

We measured serum concentrations of 4 macrophage-mediated factors, including interleukin-6 (IL-6), transforming growth factor-β1 (TGF-β1), vascular cell adhesion protein 1 (VCAM-1) and vascular endothelial growth factor (VEGF), in 23 chronic inflammatory demyelinating polyradiculoneuropathy (CIDP), 28 GBS, 11 Miller-Fisher syndrome (MFS), 40 multiple sclerosis (MS), and 12 Alzheimer's disease (AD) patients, as well as 15 healthy controls.

RESULTS

Serum TGF-β1 concentration of GBS patients (35.94±2.55ng/ml) was significantly higher compared with CIDP (25.46±1.40ng/ml, P<0.001), MFS (25.32±2.31ng/ml, P=0.010), MS (21.35±0.90ng/ml, P<0.001) and AD patients (22.92±1.82ng/ml, P<0.001), as well as healthy controls (23.12±1.67ng/ml, P<0.001). A positive correlation between serum TGF-β1 concentrations and Hughes' functional grading scales was observed in GBS patients. Serum concentrations of IL-6, VCAM-1 and VEGF were similar between the studied groups.

CONCLUSION

The high serum concentrations of TGF-β1 and the correlation between serum TGF-β1 concentration and disease severity highlight the potential of TGF-β1 as a biomarker of GBS.

Smad3 deficiency inhibits dentate gyrus LTP by enhancing GABAA neurotransmission

Transforming growth factor-β signaling through intracellular Smad3 has been implicated in Parkinson's disease (PD) and it fulfills an important role in the neurogenesis and synaptic plasticity that occurs in the adult dentate gyrus (DG). The long-term potentiation (LTP) induced in the DG by high-frequency stimulation of the medial perforant pathway is abolished in the DG of Smad3-deficient mice, but not in the CA1 hippocampal region. Here, we show that NMDA- and AMPA-type glutamate receptors do not participate in the inhibition of LTP associated with Smad3 deficiency. Moreover, there is no difference in the hippocampal GAD65 and GAD67 content, suggesting that GABA biosynthesis remains unaffected. Increased conductance and higher action potential firing thresholds were evident in intracellular recordings of granule cells from Smad3 deficient mice. Interestingly, phasic and tonic GABAA receptor (GABAA R)-mediated neurotransmission is enhanced in the DG of Smad3-deficient mice, and LTP induction can be rescued by inhibiting GABAA R with picrotoxin. Hence, Smad3 signaling in the DG appears to be necessary to induce LTP by regulating GABAA neurotransmission, suggesting a central role of this intracellular signaling pathway in the hippocampal brain plasticity related to learning and memory. Smad3 deficient mice represent a new and interesting model of Parkinson's disease, displaying hippocampal dysfunctions that include decreased neurogenesis and the failure to induce LTP in the dentate gyrus. Here we show that Smad3 deficiency inhibits LTP induction by enhancing phasic and tonic GABAA receptor-mediated neurotransmission, while LTP induction can be rescued with a GABAA receptor antagonist. Alteration of GABA neurotransmission is thought to produce hippocampal cognitive dysfunction in Down's syndrome or Alzheimer's disease, and here we provide new insights into the hippocampal changes in an animal model of Parkinson's disease.

Insight into the Molecular Imaging of Alzheimer's Disease

Alzheimer's disease is a complex neurodegenerative disease affecting millions of individuals worldwide. Earlier it was diagnosed only via clinical assessments and confirmed by postmortem brain histopathology. The development of validated biomarkers for Alzheimer's disease has given impetus to improve diagnostics and accelerate the development of new therapies. Functional imaging like positron emission tomography (PET), single photon emission computed tomography (SPECT), functional magnetic resonance imaging (fMRI), and proton magnetic resonance spectroscopy provides a means of detecting and characterising the regional changes in brain blood flow, metabolism, and receptor binding sites that are associated with Alzheimer's disease. Multimodal neuroimaging techniques have indicated changes in brain structure and metabolic activity, and an array of neurochemical variations that are associated with neurodegenerative diseases. Radiotracer-based PET and SPECT potentially provide sensitive, accurate methods for the early detection of disease. This paper presents a review of neuroimaging modalities like PET, SPECT, and selected imaging biomarkers/tracers used for the early diagnosis of AD. Neuroimaging with such biomarkers and tracers could achieve a much higher diagnostic accuracy for AD and related disorders in the future.

Analysis of Differentially Expressed Genes Associated With Alzheimer's Disease Based on Bioinformatics Methods

OBJECTIVE

To screen differentially expressed genes (DEGs) of Alzheimer's disease (AD).

METHODS

The gene expression profile (GSE26972) of AD was downloaded from Gene Expression Omnibus database. The DEGs were mapped to protein-protein interaction (PPI) data for acquiring the potential PPI relationship. The coexpressed significance of a gene pair in AD was determined. Then significantly enriched Gene Ontology (GO) terms and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of DEGs were analyzed based on database for annotation visualization and integrated discovery tool.

RESULTS

The PPI network showed 7 upregulated genes and 4 downregulated genes that might play meaningful functional roles in AD. Meanwhile, 3 significantly enriched KEGG pathways as well as several significant GO terms (included α-actinin binding, interleukin 33 receptor activity, and telethonin binding) were identified.

CONCLUSIONS

The screened DEGs have the potential to become candidate target molecules to monitor, diagnose, and treat AD.

Distinctive RNA expression profiles in blood associated with Alzheimer disease after accounting for white matter hyperintensities

BACKGROUND

Defining the RNA transcriptome in Alzheimer Disease (AD) will help understand the disease mechanisms and provide biomarkers. Though the AD blood transcriptome has been studied, effects of white matter hyperintensities (WMH) were not considered. This study investigated the AD blood transcriptome and accounted for WMH.

METHODS

RNA from whole blood was processed on whole-genome microarrays.

RESULTS

A total of 293 probe sets were differentially expressed in AD versus controls, 5 of which were significant for WMH status. The 288 AD-specific probe sets classified subjects with 87.5% sensitivity and 90.5% specificity. They represented 188 genes of which 29 have been reported in prior AD blood and 89 in AD brain studies. Regulated blood genes included MMP9, MME (Neprilysin), TGFβ1, CA4, OCLN, ATM, TGM3, IGFR2, NOV, RNF213, BMX, LRRN1, CAMK2G, INSR, CTSD, SORCS1, SORL1, and TANC2.

CONCLUSIONS

RNA expression is altered in AD blood irrespective of WMH status. Some genes are shared with AD brain.

Amyloid-β Activates Microglia and Regulates Protein Expression in a Manner Similar to Prions

Prions are the only convincingly demonstrated proteinaceous infectious particle, yet recent studies find that amyloid-β peptide (Aβ) aggregates are capable of self-propagation, which induces amyloidosis pathology in Alzheimer's disease (AD) model mice that is similar to the self-propagation phenomenon of prions in neurons. Gliosis is a common hallmark of AD and prion diseases, in which activated microglia accumulate around abnormal protein deposits. Analyses of the characteristics of activated microglia induced by Aβ in comparison with those induced by prions will provide new insight into the pathogenesis of AD. Therefore, we compared the characteristics of BV-2 cells (model microglia) activated by Aβ fibrillar peptides (Aβ1-42) and prions (PrP106-126). Aβ1-42 and PrP106-126, as well as the supernatants of the media collected from BV-2 cells cocultured with Aβ1-42 and PrP106-126, were potent activators of BV-2 microglial activity, but the chemotaxis index (CI) induced by Aβ1-42 was significantly higher than that induced by PrP106-126 at each concentration. Aβ1-42 and PrP106-126 increased the proliferation index (PI) and upregulated monocyte chemoattractant protein-1 (MCP-1) and transforming growth factor beta 1 (TGF-β1) expression after 12 h of exposure. Our results show that Aβ activates microglia and regulates microglial protein expression in a manner similar to prions and, thus, provide new insight into the pathogenesis of AD.

Plasma inflammatory biomarkers for Huntington's disease patients and mouse model

Huntington's disease (HD), caused by expanded CAG repeats encoding a polyglutamine tract in the huntingtin (HTT) protein, presents with a predominant degeneration of neurons in the striatum and cortex. Lines of evidence have observed neuroinflammation, particularly microglial activation, is involved in the pathogenesis of HD. Given that HTT is also expressed in peripheral inflammatory cells, it is possible that inflammatory changes detected in peripheral plasma may be biologically relevant and parallel the neuroinflammatory process of HD patients. By examining the expression levels of 13 microglia-derived inflammatory markers in the plasma of 5 PreHD carriers, 15 HD patients and 16 healthy controls, we found plasma levels of IL-6, MMP-9, VEGF and TGF-β1 were significantly increased in HD patients when compared with the controls, while plasma level of IL-18 were significantly reduced in HD patients compared with controls. Plasma level of IL-6 was reversely correlated with the UHDRS independence scale and functional capacity. To understand the temporal correlation between these inflammatory markers and HD progression, their levels were further tested in plasma from R6/2 mouse HD model at different ages. In rotarod test, R6/2 HD mice started to manifest HD phenotype at 7.5 weeks of age. Higher plasma VEGF levels of R6/2 mice than those of age-matched wild-type (WT) littermates were noted from 7 (presymptomatic stage) to 13 weeks of age (late symptomatic stage). The plasma IL-6 levels of R6/2 mice were higher than those of the WT littermates from 9 (early symptomatic stage) to 13 weeks of age. R6/2 mice demonstrated higher MMP-9 and TGF-β1 levels than their WT littermates from 11 (middle symptomatic stage) to 13 weeks of age. In contrast, the plasma IL-18 level was lower than those in WT littermates since 11 weeks of age. These altered expressions of inflammatory markers may serve as the potential biomarkers for HD onset and progression. Specific inhibition/activation of these inflammatory markers may be the targets of HD drug development.

Neuroinflammation in Alzheimer's disease

Amyloid-β plaques and neurofibrillary tangles are the main neuropathological hallmarks in Alzheimer's disease (AD), the most common cause of dementia in the elderly. However, it has become increasingly apparent that neuroinflammation plays a significant role in the pathophysiology of AD. This review summarizes the current status of neuroinflammation research related to AD, focusing on the connections between neuroinflammation and some inflammation factors in AD. Among these connections, we discuss the dysfunctional blood-brain barrier and alterations in the functional responses of microglia and astrocytes in this process. In addition, we summarize and discuss the role of intracellular signaling pathways involved in inflammatory responses in astrocytes and microglia, including the mitogen-activated protein kinase pathways, nuclear factor-kappa B cascade, and peroxisome proliferator-activated receptor-gamma transcription factors. Finally, the dysregulation of the control and release of pro- and anti-inflammatory cytokines and classic AD pathology (amyloid plaques and neurofibrillary tangles) in AD is also reviewed.

Interleukin 10 Level in the Cerebrospinal Fluid as a Possible Biomarker for Lymphomatosis Cerebri

A 71-year-old immunocompetent man developed cognitive decline and gait disturbance. Brain magnetic resonance imaging (MRI) revealed bilateral diffuse leukoencephalopathy without a mass lesion. An analysis of the cerebrospinal fluid (CSF) showed elevated levels of interleukin (IL)-10. The condition of the patient progressively deteriorated, and intravenous high-dose steroids proved ineffective. Detection of non-destructive, diffusely infiltrating, large B-cell lymphoma in biopsy and autopsy specimens led to a diagnosis of lymphomatosis cerebri (LC). On serial MRI, the basal ganglia and white matter lesions increased in parallel with the levels of IL-10. These findings suggest that the IL-10 level in the CSF may represent a potentially useful biomarker for the early diagnosis and monitoring of the disease progression in LC.

Cerebrospinal fluid biochemical studies in patients with Parkinson's disease: toward a potential search for biomarkers for this disease

The blood-brain barrier supplies brain tissues with nutrients and filters certain compounds from the brain back to the bloodstream. In several neurodegenerative diseases, including Parkinson's disease (PD), there are disruptions of the blood-brain barrier. Cerebrospinal fluid (CSF) has been widely investigated in PD and in other parkinsonian syndromes with the aim of establishing useful biomarkers for an accurate differential diagnosis among these syndromes. This review article summarizes the studies reported on CSF levels of many potential biomarkers of PD. The most consistent findings are: (a) the possible role of CSF urate on the progression of the disease; (b) the possible relations of CSF total tau and phosphotau protein with the progression of PD and with the preservation of cognitive function in PD patients; (c) the possible value of CSF beta-amyloid 1-42 as a useful marker of further cognitive decline in PD patients, and (d) the potential usefulness of CSF neurofilament (NFL) protein levels in the differential diagnosis between PD and other parkinsonian syndromes. Future multicentric, longitudinal, prospective studies with long-term follow-up and neuropathological confirmation would be useful in establishing appropriate biomarkers for PD.

Inflammatory response in Parkinson's disease (Review)

Parkinson's disease (PD) is one of the most common age‑related neurodegenerative diseases, which results from a number of environmental and inherited factors. PD is characterized by the slow progressive degeneration of dopaminergic (DA) neurons in the substantia nigra. The nigrostriatal DA neurons are particularly vulnerable to inflammatory attack. Neuroinflammation is an important contributor to the pathogenesis of age‑related neurodegenerative disorders, such as PD, and as such anti‑inflammatory agents are becoming a novel therapeutic focus. This review will discuss the current knowledge regarding inflammation and review the roles of intracellular inflammatory signaling pathways, which are specific inflammatory mediators in PD. Finally, possible therapeutic strategies are proposed, which may downregulate inflammatory processes and inhibit the progression of PD.

Cerebrospinal fluid markers of neuroinflammation in delirium: a role for interleukin-1β in delirium after hip fracture

OBJECTIVE

Exaggerated central nervous system (CNS) inflammatory responses to peripheral stressors may be implicated in delirium. This study hypothesised that the IL-1β family is involved in delirium, predicting increased levels of interleukin-1β (IL-1β) and decreased IL-1 receptor antagonist (IL-1ra) in the cerebrospinal fluid (CSF) of elderly patients with acute hip fracture. We also hypothesised that Glial Fibrillary Acidic Protein (GFAP) and interferon-γ (IFN-γ) would be increased, and insulin-like growth factor 1 (IGF-1) would be decreased.

METHODS

Participants with acute hip fracture aged >60 (N=43) were assessed for delirium before and 3-4 days after surgery. CSF samples were taken at induction of spinal anaesthesia. Enzyme-linked immunosorbent assays (ELISA) were used for protein concentrations.

RESULTS

Prevalent delirium was diagnosed in eight patients and incident delirium in 17 patients. CSF IL-1β was higher in patients with incident delirium compared to never delirium (incident delirium 1.74 pg/ml (1.02-1.74) vs. prevalent 0.84 pg/ml (0.49-1.57) vs. never 0.66 pg/ml (0-1.02), Kruskal-Wallis p=0.03). CSF:serum IL-1β ratios were higher in delirious than non-delirious patients. CSF IL-1ra was higher in prevalent delirium compared to incident delirium (prevalent delirium 70.75 pg/ml (65.63-73.01) vs. incident 31.06 pg/ml (28.12-35.15) vs. never 33.98 pg/ml (28.71-43.28), Kruskal-Wallis p=0.04). GFAP was not increased in delirium. IFN-γ and IGF-1 were below the detection limit in CSF.

CONCLUSION

This study provides novel evidence of CNS inflammation involving the IL-1β family in delirium and suggests a rise in CSF IL-1β early in delirium pathogenesis. Future larger CSF studies should examine the role of CNS inflammation in delirium and its sequelae.

Cerebrospinal fluid biomarker and brain biopsy findings in idiopathic normal pressure hydrocephalus

Background

The significance of amyloid precursor protein (APP) and neuroinflammation in idiopathic normal pressure hydrocephalus (iNPH) and Alzheimer's disease (AD) is unknown.

Objective

To investigate the role of soluble APP (sAPP) and amyloid beta (Aβ) isoforms, proinflammatory cytokines, and biomarkers of neuronal damage in the cerebrospinal fluid (CSF) in relation to brain biopsy Aβ and hyperphosphorylated tau (HPτ) findings.

Methods

The study population comprised 102 patients with possible NPH with cortical brain biopsies, ventricular and lumbar CSF samples, and DNA available. The final clinical diagnoses were: 53 iNPH (91% shunt-responders), 26 AD (10 mixed iNPH+AD), and 23 others. Biopsy samples were immunostained against Aβ and HPτ. CSF levels of AD-related biomarkers (Aβ42, p-tau, total tau), non-AD-related Aβ isoforms (Aβ38, Aβ40), sAPP isoforms (sAPPα, sAPPβ), proinflammatory cytokines (several interleukins (IL), interferon-gamma, monocyte chemoattractant protein-1, tumor necrosis factor-alpha) and biomarkers of neuronal damage (neurofilament light and myelin basic protein) were measured. All patients were genotyped for APOE.

Results

Lumbar CSF levels of sAPPα were lower (p<0.05) in patients with shunt-responsive iNPH compared to non-iNPH patients. sAPPβ showed a similar trend (p = 0.06). CSF sAPP isoform levels showed no association to Aβ or HPτ in the brain biopsy. Quantified Aβ load in the brain biopsy showed a negative correlation with CSF levels of Aβ42 in ventricular (r = −0.295, p = 0.003) and lumbar (r = −0.356, p = 0.01) samples, while the levels of Aβ38 and Aβ40 showed no correlation. CSF levels of proinflammatory cytokines and biomarkers of neuronal damage did not associate to the brain biopsy findings, diagnosis, or shunt response. Higher lumbar/ventricular CSF IL-8 ratios (p<0.001) were seen in lumbar samples collected after ventriculostomy compared to the samples collected before the procedure.

Conclusions

The role of sAPP isoforms in iNPH seems to be independent from the amyloid cascade. No neuroinflammatory background was observed in iNPH or AD.

Age-dependent changes on TGFβ1 Smad3 pathway modify the pattern of microglial cell activation

Aging is the main risk factor for Alzheimer's disease. Among other characteristics, it shows changes in inflammatory signaling that could affect the regulation of glial cell activation. We have shown that astrocytes prevent microglial cell cytotoxicity by mechanisms mediated by TGFβ1. However, whereas TGFβ1 is increased, glial cell activation persists in aging. To understand this apparent contradiction, we studied TGFβ1-Smad3 signaling during aging and their effect on microglial cell function. TGFβ1 induction and activation of Smad3 signaling in the hippocampus by inflammatory stimulation was greatly reduced in adult mice. We evaluated the effect of TGFβ1-Smad3 pathway on the regulation of nitric oxide (NO) and reactive oxygen species (ROS) secretion, and phagocytosis of microglia from mice at different ages with and without in vivo treatment with lipopolysaccharide (LPS) to induce an inflammatory status. NO secretion was only induced on microglia from young mice exposed to LPS, and was potentiated by inflammatory preconditioning, whereas in adult mice the induction of ROS was predominant. TGFβ1 modulated induction of NO and ROS production in young and adult microglia, respectively. Modulation was partially dependent on Smad3 pathway and was impaired by inflammatory preconditioning. Phagocytosis was induced by inflammation and TGFβ1 only in microglia cultures from young mice. Induction by TGFβ1 was also prevented by Smad3 inhibition. Our findings suggest that activation of the TGFβ1-Smad3 pathway is impaired in aging. Age-related impairment of TGFβ1-Smad3 can reduce protective activation while facilitating cytotoxic activation of microglia, potentiating microglia-mediated neurodegeneration.

Body fluid cytokine levels in mild cognitive impairment and Alzheimer's disease: a comparative overview

This article gives a comprehensive overview of cytokine and other inflammation associated protein levels in plasma, serum and cerebrospinal fluid (CSF) of patients with Alzheimer's disease (AD) and mild cognitive impairment (MCI). We reviewed 118 research articles published between 1989 and 2013 to compare the reported levels of 66 cytokines and other proteins related to regulation and signaling in inflammation in the blood or CSF obtained from MCI and AD patients. Several cytokines are evidently regulated in (neuro-) inflammatory processes associated with neurodegenerative disorders. Others do not display changes in the blood or CSF during disease progression. However, many reports on cytokine levels in MCI or AD are controversial or inconclusive, particularly those which provide data on frequently investigated cytokines like tumor necrosis factor alpha (TNF-α) or interleukin-6 (IL-6). The levels of several cytokines are possible indicators of neuroinflammation in AD. Some of them might increase steadily during disease progression or temporarily at the time of MCI to AD conversion. Furthermore, elevated body fluid cytokine levels may correlate with an increased risk of conversion from MCI to AD. Yet, research results are conflicting. To overcome interindividual variances and to obtain a more definite description of cytokine regulation and function in neurodegeneration, a high degree of methodical standardization and patients collective characterization, together with longitudinal sampling over years is essential.

The Postprandial Effects of a Moderately High-Fat Meal on Lipid Profiles and Vascular Inflammation in Alzheimer's Disease Patients: A Pilot Study

Objective

Alzheimer’s disease (AD) is a neurodegenerative disease of aging with unknown causative factors. Accumulating evidence suggests that inflammation and neurovascular dysfunction play important roles in AD. The postprandial period following a moderately high-fat meal is associated with vascular inflammation in young, healthy individuals; however, this relationship has not been investigated in Alzheimer’s patients despite their exaggerated inflammatory state.

Methods

Patients with AD and age-matched control subjects were recruited through the UC Davis Alzheimer’s Disease Center. All subjects consumed a moderately high-fat breakfast meal. Fasting and postprandial blood samples were collected for lipid, lipoprotein, and oxylipin analyses, as well as assays for cytokine levels and monocyte activation.

Results

The plasma lipid analyses revealed similar levels of triglycerides and esterified oxylipins between groups, but there was an interaction between postprandial non-esterified fatty acid (NEFA) levels and body mass index in the AD group compared to the control subjects. The AD group also had increased behenic acid and decreased linoleic and oleic acids in the postprandial period; however, these were not significantly different. Inflammatory assays revealed elevated fasting levels of interleukin (IL)-10 and IL-12 p70, but no change in monocyte activation in the AD group.

Conclusion

The postprandial period following a moderately high-fat meal is not associated with an exaggerated inflammatory state in Alzheimer’s patients, and basal esterified oxylipin profiles do not indicate elevated oxidative stress. However, the baseline inflammatory state during fasting in AD patients includes elevated levels of plasma IL-10 and IL-12 p70, which may indicate a balance between immune responses mediated by these interleukins.

Differential effects of duration and age on the consequences of neuroinflammation in the hippocampus

The current study investigated the hypothesis that the duration of the proinflammatory environment plays a critical role in the brain's response that results in negative consequences on cognition, biochemistry, and pathology. Lipopolysaccharide or artificial cerebrospinal fluid was slowly (250 ηg/h) infused into the fourth ventricle of young (3-month-old), adult (9-month-old), or aged (23-month-old) male F-344 rats for 21 or 56 days. The rats were then tested in the water pool task and endogenous hippocampal levels of pro- and anti-inflammatory proteins and genes and indicators of glutamatergic function were determined. The duration of the lipopolysaccharide infusion, compared with the age of the rat, had the greatest effect on (1) spatial working memory; (2) the density and distribution of activated microglia within the hippocampus; and (3) the cytokine protein and gene expression profiles within the hippocampus. The duration- and age-dependent consequences of neuroinflammation might explain why human adults respond positively to anti-inflammatory therapies and aged humans do not.

Alzheimer's disease biomarkers: correspondence between human studies and animal models

Alzheimer's disease (AD) represents an escalating global threat as life expectancy and disease prevalence continue to increase. There is a considerable need for earlier diagnoses to improve clinical outcomes. Fluid biomarkers measured from cerebrospinal fluid (CSF) and blood, or imaging biomarkers have considerable potential to assist in the diagnosis and management of AD. An additional important utility of biomarkers is in novel therapeutic development and clinical trials to assess efficacy and side effects of therapeutic interventions. Because many biomarkers are initially examined in animal models, the extent to which markers translate from animals to humans is an important issue. The current review highlights many existing and pipeline biomarker approaches, focusing on the degree of correspondence between AD patients and animal models. The review also highlights the need for greater translational correspondence between human and animal biomarkers.

Inhibition of IL-12/IL-23 signaling reduces Alzheimer's disease-like pathology and cognitive decline

The pathology of Alzheimer's disease has an inflammatory component that is characterized by upregulation of proinflammatory cytokines, particularly in response to amyloid-β (Aβ). Using the APPPS1 Alzheimer's disease mouse model, we found increased production of the common interleukin-12 (IL-12) and IL-23 subunit p40 by microglia. Genetic ablation of the IL-12/IL-23 signaling molecules p40, p35 or p19, in which deficiency of p40 or its receptor complex had the strongest effect, resulted in decreased cerebral amyloid load. Although deletion of IL-12/IL-23 signaling from the radiation-resistant glial compartment of the brain was most efficient in mitigating cerebral amyloidosis, peripheral administration of a neutralizing p40-specific antibody likewise resulted in a reduction of cerebral amyloid load in APPPS1 mice. Furthermore, intracerebroventricular delivery of antibodies to p40 significantly reduced the concentration of soluble Aβ species and reversed cognitive deficits in aged APPPS1 mice. The concentration of p40 was also increased in the cerebrospinal fluid of subjects with Alzheimer's disease, which suggests that inhibition of the IL-12/IL-23 pathway may attenuate Alzheimer's disease pathology and cognitive deficits.

Transforming growth factor-beta inhibits the expression of clock genes

Disturbances of sleep-wake rhythms are an important problem in Alzheimer's disease (AD). Circadian rhythms are regulated by clock genes. Transforming growth factor-beta (TGF-β) is overexpressed in neurons in AD and is the only cytokine that is increased in cerebrospinal fluid (CSF). Our data show that TGF-β2 inhibits the expression of the clock genes Period (Per)1, Per2, and Rev-erbα, and of the clock-controlled genes D-site albumin promoter binding protein (Dbp) and thyrotroph embryonic factor (Tef). However, our results showed that TGF-β2 did not alter the expression of brain and muscle Arnt-like protein-1 (Bmal1). The concentrations of TGF-β2 in the CSF of 2 of 16 AD patients and of 1 of 7 patients with mild cognitive impairment were in the dose range required to suppress the expression of clock genes. TGF-β2-induced dysregulation of clock genes may alter neuronal pathways, which may be causally related to abnormal sleep-wake rhythms in AD patients.