Amyloid burden, neuroinflammation, and links to cognitive decline after ischemic stroke

CCN1 Is a Therapeutic Target for Reperfused Ischemic Brain Injury

Ischemic stroke can lead to systemic inflammation, which can activate peripheral immune cells, causing neuroinflammation and brain injury. Meningeal lymphatics play a crucial role in transporting solutes and immune cells out of the brain and draining them into cervical lymph nodes (CLNs). However, the role of meningeal lymphatics in regulating systemic inflammation during the reperfusion stage after ischemia is not well understood. In this study, we demonstrated that brain infarct size, neuronal loss, and the effector function of inflammatory macrophage subsets were reduced after ischemia-reperfusion and disruption of meningeal lymphatics. Spatial memory function was improved in the late stage of ischemic stroke following meningeal lymphatic disruption. Brain-infiltrating immune cells, including neutrophils, monocytes, and T and natural killer cells, were reduced after cerebral ischemia-reperfusion and meningeal lymphatic disruption. Single-cell RNA sequencing analysis revealed that meningeal lymphatic disruption reprogrammed the transcriptome profile related to chemotaxis and leukocyte migration in CLN lymphatic endothelial cells (LECs), and it also decreased chemotactic CCN1 expression in floor LECs. Replenishment of CCN1 through intraventricular injection increased brain infarct size and neuronal loss, while restoring numbers of macrophages/microglia in the brains of meningeal lymphatic-disrupted mice after ischemic stroke. Blocking CCN1 in cerebrospinal fluid reduced brain infarcts and improves spatial memory function after ischemia-reperfusion injury. In summary, this study indicates that CCN1-mediated detrimental inflammation was alleviated after cerebral ischemia-reperfusion injury and meningeal lymphatic disruption. CCN1 represents a novel therapeutic target for inhibiting systemic inflammation in the brain-CLN axis after ischemia-reperfusion injury.

Systemic immune-inflammation index upon admission correlates to post-stroke cognitive impairment in patients with acute ischemic stroke

BACKGROUND

The purpose of this prospective study was to evaluate the association of systemic immune-inflammation index (SII) and systemic inflammation response index (SIRI), with PSCI in patients with acute ischemic stroke (AIS).

METHODS

First-onset AIS patients were consecutively included from January 1, 2022 to March 1, 2023. The baseline information was collected at admission. Fasting blood was drawn the next morning. Cognitive function was assessed by the Montreal Cognitive Assessment (MoCA) 3 months after onset. Logistic regression analysis was performed to explore the correlation between SII, SIRI, and PSCI. Receiver operating characteristic (ROC) was conducted to evaluate the predictive ability of SII.

RESULTS

332 participants were recruited, and 193 developed PSCI. Compared with patients without PSCI, the patients with PSCI had higher SII (587.75 (337.42, 988.95) vs. 345.66 (248.44, 572.89), P<0.001) and SIRI (1.59 (0.95, 2.84) vs. 1.02 (0.63, 1.55), P=0.007). SII and SIRI negatively correlated with MoCA scores (both P<0.05). The multivariable logistic regression analysis indicated that SII was independently associated with PSCI (P<0.001), while SIRI was not. The optimal cutoff for SII to predict PSCI was 676.83×109/L.

CONCLUSIONS

A higher level of SII upon admission was independently correlated to PSCI three months later in AIS patients.

Ion transporter cascade, reactive astrogliosis and cerebrovascular diseases

Cerebrovascular diseases and their sequalae, such as ischemic stroke, chronic cerebral hypoperfusion, and vascular dementia are significant contributors to adult disability and cognitive impairment in the modern world. Astrocytes are an integral part of the neurovascular unit in the CNS and play a pivotal role in CNS homeostasis, including ionic and pH balance, neurotransmission, cerebral blood flow, and metabolism. Astrocytes respond to cerebral insults, inflammation, and diseases through unique molecular, morphological, and functional changes, collectively known as reactive astrogliosis. The function of reactive astrocytes has been a subject of debate. Initially, astrocytes were thought to primarily play a supportive role in maintaining the structure and function of the nervous system. However, recent studies suggest that reactive astrocytes may have both beneficial and detrimental effects. For example, in chronic cerebral hypoperfusion, reactive astrocytes can cause oligodendrocyte death and demyelination. In this review, we will summarize the (1) roles of ion transporter cascade in reactive astrogliosis, (2) role of reactive astrocytes in vascular dementia and related dementias, and (3) potential therapeutic approaches for dementing disorders targeting reactive astrocytes. Understanding the relationship between ion transporter cascade, reactive astrogliosis, and cerebrovascular diseases may reveal mechanisms and targets for the development of therapies for brain diseases associated with reactive astrogliosis.

Looking Upstream to Understand Race/Ethnicity as a Moderator for Poststroke Neuroinflammation and a Social Determinant for Poststroke Aphasia Outcomes

INTRODUCTION

Over the past decade, the stroke literature has begun to acknowledge and explore explanations for longstanding racial/ethnic differences in stroke outcomes. Poststroke cognitive impairment (PSCI) and poststroke aphasia are two such negative poststroke outcomes where racial/ethnic differences exist. Physiological differences, such as stroke type and lesion size, have been used to partially explain the variation in PSCI and aphasia. However, there is some evidence, although limited, that suggests neuroinflammatory processes as part of allostatic load may be a key contributor to the observed disparities.

METHOD

In this tutorial, we explore the influence of race differences in inflammation on poststroke cognitive outcomes. We suggest lifetime stress and other external determinants of health such as neighborhood environment and discriminatory practices through "weathering" explain differences in inflammation. While using an allostatic load framework, we explore the literature focusing specifically on the role of neuroinflammation on poststroke outcomes.

CONCLUSIONS

Examination of the immune response poststroke provides a foundation for understanding the mechanisms of PSCI and poststroke aphasia and the potential contributions of neuroinflammatory processes on poststroke cognitive outcomes. Furthermore, understanding of racial differences in those processes may contribute to a better understanding of racial disparities in general stroke outcomes as well as poststroke aphasia.

Metabolic Syndrome: A Narrative Review from the Oxidative Stress to the Management of Related Diseases

Metabolic syndrome (MS) is a growing disorder affecting thousands of people worldwide, especially in industrialised countries, increasing mortality. Oxidative stress, hyperglycaemia, insulin resistance, inflammation, dysbiosis, abdominal obesity, atherogenic dyslipidaemia and hypertension are important factors linked to MS clusters of different pathologies, such as diabesity, cardiovascular diseases and neurological disorders. All biochemical changes observed in MS, such as dysregulation in the glucose and lipid metabolism, immune response, endothelial cell function and intestinal microbiota, promote pathological bridges between metabolic syndrome, diabesity and cardiovascular and neurodegenerative disorders. This review aims to summarise metabolic syndrome's involvement in diabesity and highlight the link between MS and cardiovascular and neurological diseases. A better understanding of MS could promote a novel strategic approach to reduce MS comorbidities.

White matter hyperintensities influence distal cortical β-amyloid accumulation in default mode network pathways

BACKGROUND AND PURPOSE

Cerebral small vessel disease (SVD) has been suggested to contribute to the pathogenesis of Alzheimer's disease (AD). Yet, the role of SVD in potentially contributing to AD pathology is unclear. The main objective of this study was to test the hypothesis that WMHs influence amyloid β (Aβ) levels within connected default mode network (DMN) tracts and cortical regions in cognitively unimpaired older adults.

METHODS

Regional standard uptake value ratios (SUVr) from Aβ-PET and white matter hyperintensity (WMH) volumes from three-dimensional magnetic resonance imaging FLAIR images were analyzed across a sample of 72 clinically unimpaired (mini-mental state examination ≥26), older adults (mean age 74.96 and standard deviation 8.13) from the Alzheimer's Disease Neuroimaging Initiative (ADNI3). The association of WMH volumes in major fiber tracts projecting from cortical DMN regions and Aβ-PET SUVr in the connected cortical DMN regions was analyzed using linear regression models adjusted for age, sex, ApoE, and total brain volumes.

RESULTS

The regression analyses demonstrate that increased WMH volumes in the superior longitudinal fasciculus were associated with increased regional SUVr in the inferior parietal lobule (p = .011).

CONCLUSION

The findings suggest that the relation between Aβ in parietal cortex is associated with SVD in downstream white matter (WM) pathways in preclinical AD. The biological relationships and interplay between Aβ and WM microstructure alterations that precede overt WMH development across the continuum of AD progression warrant further study.

Genes Involved by Dexamethasone in Prevention of Long-Term Memory Impairment Caused by Lipopolysaccharide-Induced Neuroinflammation

Inflammatory activation within the brain is linked to a decrease in cognitive abilities; however, the molecular mechanisms implicated in the development of inflammatory-related cognitive dysfunction and its prevention are poorly understood. This study compared the responses of hippocampal transcriptomes 3 months after the striatal infusion of lipopolysaccharide (LPS; 30 µg), resulting in memory loss, or with dexamethasone (DEX; 5 mg/kg intraperitoneal) pretreatment, which abolished the long-term LPS-induced memory impairment. After LPS treatment, a significant elevation in the expression of immunity/inflammatory-linked genes, including chemokines (Cxcl13), cytokines (Il1b and Tnfsf13b), and major histocompatibility complex (MHC) class II members (Cd74, RT1-Ba, RT1-Bb, RT1-Da, and RT1-Db1) was observed. DEX pretreatment did not change the expression of these genes, but significantly affected the expression of genes encoding ion channels, primarily calcium and potassium channels, regulators of glutamate (Slc1a2, Grm5, Grin2a), and GABA (Gabrr2, Gabrb2) neurotransmission, which enriched in such GO biological processes as "Regulation of transmembrane transport", "Cognition", "Learning", "Neurogenesis", and "Nervous system development". Taken together, these data suggest that (1) pretreatment with DEX did not markedly affect LPS-induced prolonged inflammatory response; (2) DEX pretreatment can affect processes associated with glutamatergic signaling and nervous system development, possibly involved in the recovery of memory impairment induced by LPS.

Implication of the cooking oil-peroxidation product "hydroxynonenal" for Alzheimer's disease

Aldehyde dehydrogenase 2 (ALDH2) is a mitochondrial enzyme that reduces cell injuries via detoxification of lipid-peroxidation product, 4-hydroxy-2-nonenal (hydroxynonenal). It is generated exogenously via deep-frying of linoleic acid-rich cooking oils and/or endogenously via oxidation of fatty acids involved in biomembranes. Although its toxicity for human health is widely accepted, the underlying mechanism long remained unknown. In 1998, Yamashima et al. have formulated the "calpain-cathepsin hypothesis" as a molecular mechanism of ischemic neuronal death. Subsequently, they found that calpain cleaves Hsp70.1 which became vulnerable after the hydroxynonenal-induced carbonylation at the key site Arg469. Since it is the pivotal aberration that induces lysosomal membrane rupture, they suggested that neuronal death in Alzheimer's disease similarly occurs by chronic ischemia via the calpain-cathepsin cascade triggered by hydroxynonenal. For nearly three decades, amyloid β (Aβ) peptide was thought to be a root substance of Alzheimer's disease. However, because of both the insignificant correlations between Aβ depositions and occurrence of neuronal death or dementia, and the negative results of anti-Aβ medicines tested so far in the patients with Alzheimer's disease, the strength of the "amyloid cascade hypothesis" has been weakened. Recent works have suggested that hydroxynonenal is a mediator of programmed cell death not only in the brain, but also in the liver, pancreas, heart, etc. Increment of hydroxynonenal was considered an early event in the development of Alzheimer's disease. This review aims at suggesting ways out of the tunnel, focusing on the implication of hydroxynonenal in this disease. Herein, the mechanism of Alzheimer neuronal death is discussed by focusing on Hsp70.1 with a dual function as chaperone protein and lysosomal stabilizer. We suggest that Aβ is not a culprit of Alzheimer's disease, but merely a byproduct of autophagy/lysosomal failure resulting from hydroxynonenal-induced Hsp70.1 disorder. Enhancing ALDH2 activity to detoxify hydroxynonenal emerges as a promising strategy for preventing and treating Alzheimer's disease.

Changes in gene expression and neuroinflammation in the hippocampus of rats with poststroke cognitive impairment

Poststroke cognitive impairment (PSCI) often occurs during the stroke recovery period and greatly increases the difficulty of rehabilitation. Activation of neuroinflammation and long-term changes in gene expression patterns in the hippocampus could be essential in the development of PSCI. Therefore, this study aimed to identify neuroinflammation and changes in gene expression patterns in the hippocampus in rats with PSCI. Rats underwent transient middle cerebral artery occlusion (tMCAO) or sham surgery. The infarct volume was measured on day 3 after surgery. The Morris water maze (MWM) test was used to assess cognitive function. Microglial activation and white matter (WM) lesions in the hippocampus were evaluated on day 28 after surgery. In addition, we compared differentially expressed genes (DEGs) in the hippocampus between tMCAO group rats and sham group rats by RNA sequencing. Then, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) network analyses were conducted to investigate these DEGs. The results showed that the tMCAO group rats showed extensive infarction and cognitive dysfunction compared with the sham group rats. Microglial activation and WM damage were obvious in the hippocampus of tMCAO group rats. We found 43 DEGs by RNA sequencing: 29 genes with upregulated expression and 14 genes with downregulated expression. The GO analysis indicated that DEGs were mainly involved in cell proliferation and differentiation, cholesterol synthesis, and metabolism. The KEGG pathway analysis suggested that the DEGs were significantly enriched in intestinal immune network for IgA production and steroid biosynthesis. Acta2, Calb2, and Cxcl12 were notable in the PPI analysis. Our results suggest that microglial activation and WM damage are maintained in rats with PSCI. The mechanism may be related to the regulation of steroid biosynthesis, intestinal immunity, and potential key genes such as Acta2, Calb2, and Cxcl12 in the hippocampus.

The Associations Between Intracranial Stenosis, Brain Amyloid-beta, and Cognition in a Memory Clinic Sample

BACKGROUND

Intracranial stenosis (ICS) and brain amyloid-beta (Aβ) have been associated with cognition and dementia. We aimed to investigate the association between ICS and brain Aβ and their independent and joint associations with cognition.

METHODS

We conducted a cross-sectional study of 185 patients recruited from a memory clinic. ICS was measured on 3-dimensional time-of-flight magnetic resonance angiography and defined as stenosis ≥50%. Brain Aβ was measured with [ 11 C] Pittsburgh compound B-positron emission tomography imaging. Cognition was assessed with a locally validated neuropsychological battery.

RESULTS

A total of 17 (9.2%) patients had ICS, and the mean standardized uptake value ratio was 1.4 (±0.4 SD). ICS was not significantly associated with brain Aβ deposition. ICS was significantly associated with worse global cognition (β: -1.26, 95% CI: -2.25; -0.28, P =0.013), executive function (β: -1.04, 95% CI: -1.86; -0.22, P =0.015) and visuospatial function (β: -1.29, 95% CI: -2.30; -0.27, P =0.015). Moreover, in ICS patients without dementia (n=8), the presence of Aβ was associated with worse performance on visuomotor speed.

CONCLUSIONS

ICS was significantly associated with worse cognition and showed interaction with brain Aβ such that patients with both pathologies performed worse on visuomotor speed specifically in those without dementia. Further studies may clarify if ICS and brain Aβ deposition indeed have a synergistic association with cognition.

Present and future avenues of cell-based therapy for brain injury: The enteric nervous system as a potential cell source

Cell therapy is a promising strategy in the field of regenerative medicine; however, several concerns limit the effective clinical use, namely a valid cell source. The gastrointestinal tract, which contains a highly organized network of nerves called the enteric nervous system (ENS), is a valuable reservoir of nerve cells. Together with neurons and neuronal precursor cells, it contains glial cells with a well described neurotrophic potential and a newly identified neurogenic one. Recently, enteric glia is looked at as a candidate for cell therapy in intestinal neuropathies. Here, we present the therapeutic potential of the ENS as cell source for brain repair, too. The example of stroke is introduced as a brain injury where cell therapy appears promising. This disease is the first cause of handicap in adults. The therapies developed in recent years allow a partial response to the consequences of the disease. The only prospect of recovery in the chronic phase is currently based on rehabilitation. The urgency to offer other treatments is therefore tangible. In the first part of the review, some elements of stroke pathophysiology are presented. An update on the available therapeutic strategies is provided, focusing on cell‐ and biomaterial‐based approaches. Following, the ENS is presented with its anatomical and functional characteristics, focusing on glial cells. The properties of these cells are depicted, with particular attention to their neurotrophic and, recently identified, neurogenic properties. Finally, preliminary data on a possible therapeutic approach combining ENS‐derived cells and a biomaterial are presented.

Association of Blood Amyloid Beta-Protein 1-42 with Poststroke Cognitive Impairment: A Systematic Review and Meta-Analysis

Background

Increases in blood of amyloid beta-protein (Aβ) have been noted in patients with Alzheimer's dementia (AD). Recent studies have shown that blood amyloid beta-protein 1-42 (Aβ1-42) level is closely related to poststroke cognitive impairment (PSCI), which may be the influencing factor and even a predictor of PSCI. The aim of this systematic review was to synthesize the evidence for the association of cognitive impairment among PSCI.

Methods

PubMed (MEDLINE), EMBASE, Cochrane Library, the Cochrane Central Register of Controlled Trial (CENTRAL), CNKI, and WanFang data were searched. Case-control, cohort, and cross-sectional studies that evaluated the association between blood Aβ1-42 and PSCI were included irrespective of language and date of publication. The outcomes of this review consisted of (1) any dementia, (2) any cognitive impairment, and (3) any cognitive impairment no dementia, which were assessed at least 3 months (90 days) after stroke. Exposure of interest was blood Aβ1-42 level (including serum and plasma).

Results

Of 617 records retrieved, 8 studies (6 case-control and 2 cohort studies) involving 931 stroke patients were included for further analysis. 8 studies with 931 subjects explored the correlation between Aβ1-42 and PSCI. PSCI was reported in 457 patients, and the pooled SMD of amyloid beta-protein 1-42 was -0.96 (95% CI -1.10~-0.82, I² = 15%, P < 0.01). The results remained robust in sensitivity analysis adjusting for study quality, sample source, and cognitive scale score in analysis of studies, as well as in analysis adjusted for publication bias.

Conclusions

Blood Aβ1-42 level was significantly negatively related to the risk for PSCI, and more prospective studies with large sample size are needed to define a precise threshold value of blood Aβ1-42 level to predict PSCI in the future. This study is registered with PROSPERO, registration number: CRD42021246165.

A High Neutrophil-to-Lymphocyte Ratio Predicts Higher Risk of Poststroke Cognitive Impairment: Development and Validation of a Clinical Prediction Model

Objective

Poststroke cognitive impairment (PSCI) is a serious complication of stroke. The neutrophil-to-lymphocyte ratio (NLR) is a marker of peripheral inflammation. The relationship between the NLR and PSCI is far from well studied, and the thesis of this study was to assess the predictive value of the NLR in patients with PSCI, and establish and verify the corresponding prediction model based on this relationship.

Methods

A total of 367 stroke patients were included in this study. Neutrophils, lymphocytes, and NLRs were measured at baseline, and clinical and neuropsychological assessments were conducted 3 months after stroke. The National Institutes of Health Scale (NIHSS) was used to assess the severity of stroke. A Chinese version of the Mini Mental State Examination (MMSE) was used for the assessment of cognitive function.

Results

After three months of follow-up, 87 (23.7%) patients were diagnosed with PSCI. The NLR was significantly higher in PSCI patients than in non-PSCI patients (P &lt; 0.001). Patient age, sex, body mass index, NIHSS scores, and high-density lipoprotein levels also differed in the univariate analysis. In the logistic regression analysis, the NLR was an independent risk factor associated with the patients with PSCI after adjustment for potential confounders (OR = 1.67, 95%CI: 1.21–2.29, P = 0.002). The nomogram based on patient sex, age, NIHSS score, and NLR had good predictive power with an AUC of 0.807. In the validation group, the AUC was 0.816.

Conclusion

An increased NLR at admission is associated with PSCI, and the model built with NLR as one of the predictors can increase prognostic information for the early detection of PSCI.

Neurodegeneration and Vascular Burden on Cognition After Midlife: A Plasma and Neuroimaging Biomarker Study

Background and Objectives: Neurodegeneration and vascular burden are the two most common causes of post-stroke cognitive impairment. However, the interrelationship between the plasma beta-amyloid (Aβ) and tau protein, cortical atrophy and brain amyloid accumulation on PET imaging in stroke patients is undetermined. We aimed to explore: (1) the relationships of cortical thickness and amyloid burden on PET with plasma Aβ40, Aβ42, tau protein and their composite scores in stroke patients; and (2) the associations of post-stroke cognitive presentations with these plasma and neuroimaging biomarkers.

Methods: The prospective project recruited first-ever ischemic stroke patients around 3 months after stroke onset. The plasma Aβ40, Aβ42, and total tau protein were measured with the immunomagnetic reduction method. Cortical thickness was evaluated on MRI, and cortical amyloid plaque deposition was evaluated by ¹⁸F-florbetapir PET. Cognition was evaluated with Mini-Mental State Examination (MMSE), Geriatric Depression Scale (GDS), Dementia Rating Scale-2 (DRS-2).

Results: The study recruited 24 stroke patients and 13 normal controls. The plasma tau and tau*Aβ42 levels were correlated with mean cortical thickness after age adjustment. The Aβ42/Aβ40 ratio was correlated with global cortical ¹⁸F-florbetapir uptake value. The DRS-2 and GDS scores were associated with mean cortical thickness and plasma biomarkers, including Aβ42/Aβ40, tau, tau*Aβ42, tau/Aβ42, and tau/Aβ40 levels, in stroke patients.

Conclusion: Plasma Aβ, tau, and their composite scores were associated with cognitive performance 3 months after stroke, and these plasma biomarkers were correlated with corresponding imaging biomarkers of neurodegeneration. Further longitudinal studies with a larger sample size are warranted to replicate the study results.

Microglia and Macrophages in Neuroprotection, Neurogenesis, and Emerging Therapies for Stroke

Stroke remains the number one cause of morbidity in the United States. Within weeks to months after an ischemic event, there is a resolution of inflammation and evidence of neurogenesis; however, years following a stroke, there is evidence of chronic inflammation in the central nervous system, possibly by the persistence of an autoimmune response to brain antigens as a result of ischemia. The mechanisms underlying the involvement of macrophage and microglial activation after stroke are widely acknowledged as having a role in ischemic stroke pathology; thus, modulating inflammation and neurological recovery is a hopeful strategy for treating the long-term outcomes after ischemic injury. Current treatments fail to provide neuroprotective or neurorestorative benefits after stroke; therefore, to ameliorate brain injury-induced deficits, therapies must alter both the initial response to injury and the subsequent inflammatory process. This review will address differences in macrophage and microglia nomenclature and summarize recent work in elucidating the mechanisms of macrophage and microglial participation in antigen presentation, neuroprotection, angiogenesis, neurogenesis, synaptic remodeling, and immune modulating strategies for treating the long-term outcomes after ischemic injury.

Prestroke cognitive decline in africans: Prevalence, predictors and association with poststroke dementia

OBJECTIVES

Pre-existing cognitive decline is a risk factor for stroke onset and poststroke dementia. There is a knowledge gap on prestroke cognitive decline in indigenous Africans. We estimated prevalence and predictors of prestroke cognitive decline, as well as its association with poststroke dementia at one year in Nigerian survivors of a first ever stroke.

METHODS

Prospective observational study. Prestroke cognitive decline was ascertained using an average score > 3.31 on the 16-item Informant Questionnaire for Cognitive Decline in the Elderly (IQ-CODE). Poststroke dementia was ascertained according to the 'National Institute of Neurological Disorders and Stroke and the Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN) criteria'. Associations were investigated using multivariate logistic regression models and presented as odds ratios (O.R) within 95% confidence intervals (C.I).

RESULTS

Among 150 stroke survivors, prestroke cognitive decline was found in 25 (16.7%, 95% C.I = 11.5%-23.6%). In analyses adjusting for the effect of age, education and stroke severity, prestroke cognitive decline was associated with diabetes mellitus (O.R = 3.0, 95% C.I = 1.2-7.6). Ten (62.5%) survivors in the prestroke cognitive decline sub-sample developed dementia at one-year poststroke. In analyses adjusting for the effects of age, education, stroke severity and comorbid diabetes mellitus, survivors with prestroke cognitive decline had six times the odds of dementia at one year poststroke (O.R = 6.2, 95% C.I = 1.3-30.4).

CONCLUSION

Prestroke cognitive decline is common, assessment is feasible and identifying pre-stroke problems has prognostic implications.

Neurovascular Alterations in Vascular Dementia: Emphasis on Risk Factors

Vascular dementia (VaD) constitutes the second most prevalent cause of dementia in the world after Alzheimer’s disease (AD). VaD regroups heterogeneous neurological conditions in which the decline of cognitive functions, including executive functions, is associated with structural and functional alterations in the cerebral vasculature. Among these cerebrovascular disorders, major stroke, and cerebral small vessel disease (cSVD) constitute the major risk factors for VaD. These conditions alter neurovascular functions leading to blood-brain barrier (BBB) deregulation, neurovascular coupling dysfunction, and inflammation. Accumulation of neurovascular impairments over time underlies the cognitive function decline associated with VaD. Furthermore, several vascular risk factors, such as hypertension, obesity, and diabetes have been shown to exacerbate neurovascular impairments and thus increase VaD prevalence. Importantly, air pollution constitutes an underestimated risk factor that triggers vascular dysfunction via inflammation and oxidative stress. The review summarizes the current knowledge related to the pathological mechanisms linking neurovascular impairments associated with stroke, cSVD, and vascular risk factors with a particular emphasis on air pollution, to VaD etiology and progression. Furthermore, the review discusses the major challenges to fully elucidate the pathobiology of VaD, as well as research directions to outline new therapeutic interventions.

Predicting the Emergence of Major Neurocognitive Disorder Within Three Months After a Stroke

Background: Neurocognitive disorder (NCD) is common after stroke, with major NCD appearing in about 10% of survivors of a first-ever stroke. We aimed to classify clinical- and imaging factors related to rapid development of major NCD 3 months after a stroke, so as to examine the optimal composition of factors for predicting rapid development of the disorder. We hypothesized that the prediction would mainly be driven by neurodegenerative as opposed to vascular brain changes. Methods: Stroke survivors from five Norwegian hospitals were included from the "Norwegian COgnitive Impairment After STroke" (Nor-COAST) study. A support vector machine (SVM) classifier was trained to distinguish between patients who developed major NCD 3 months after the stroke and those who did not. Potential predictor factors were based on previous literature and included both vascular and neurodegenerative factors from clinical and structural magnetic resonance imaging findings. Cortical thickness was obtained via FreeSurfer segmentations, and volumes of white matter hyperintensities (WMH) and stroke lesions were semi-automatically gathered using FSL BIANCA and ITK-SNAP, respectively. The predictive value of the classifier was measured, compared between classifier models and cross-validated. Results: Findings from 227 stroke survivors [age = 71.7 (11.3), males = (56.4%), stroke severity NIHSS = 3.8 (4.8)] were included. The best predictive accuracy (AUC = 0.876) was achieved by an SVM classifier with 19 features. The model with the fewest number of features that achieved statistically comparable accuracy (AUC = 0.850) was the 8-feature model. These features ranked by their weighting were; stroke lesion volume, WMH volume, left occipital and temporal cortical thickness, right cingulate cortical thickness, stroke severity (NIHSS), antiplatelet medication intake, and education. Conclusion: The rapid (<3 months) development of major NCD after stroke is possible to predict with an 87.6% accuracy and seems dependent on both neurodegenerative and vascular factors, as well as aspects of the stroke itself. In contrast to previous literature, we also found that vascular changes are more important than neurodegenerative ones. Although possible to predict with relatively high accuracy, our findings indicate that the development of rapid onset post-stroke NCD may be more complex than earlier suggested.

Dementia Prevalence, Comorbidities, and Lifestyle Among Jatinangor Elders

Introduction: Research on dementia prevalence and the potentially related risk factors from Indonesia is scarce. We sought to identify the prevalence of dementia, health risk factors, and lifestyle in Jatinangor elders.

Methods: A total of 686 participants completed questionnaires on lifestyle, health risk factors, and cognitive and functional tests from September 2013 to December 2013. We determined the prevalence of dementia; and the associations between health, leisure activities, dietary pattern, and dementia were analyzed using logistic regression.

Results: The prevalence of dementia was 29.15%. The risk factors differed between age groups. Those aged 60–74 years and who have a lower education level, lower occupational attainment, and less active intellectual and recreational activities were associated with higher dementia risk. Those aged > 75 years living in a rural area and who take less fruit were associated with a higher risk of dementia.

Conclusions: The prevalence of dementia in Jatinangor is high. The identified modifiable risk factors are a potential target for intervention and valuable for designing public health policies.

Association between Blood Pressure, Blood Pressure Variability, and Post-Stroke Cognitive Impairment

After stroke, dynamic changes take place from necrotic-apoptotic continuum, inflammatory response to poststroke neurogenesis, and remodeling of the network. These changes and baseline brain pathology such as small vessel disease (SVD) and amyloid burden may be associated with the occurrence of early or late poststroke cognitive impairment (PSCI) or dementia (PSD), which affect not only stroke victims but also their families and even society. We reviewed the current concepts and understanding of the pathophysiology for PSCI/PSD and identified useful tools for the diagnosis and the prediction of PSCI in serological, CSF, and image characteristics. Then, we untangled their relationships with blood pressure (BP) and blood pressure variability (BPV), important but often overlooked risk factors for PSCI/PSD. Finally, we provided evidence for the modifying effects of BP and BPV on PSCI as well as pharmacological and non-pharmacological interventions and life style modification for PSCI/PSD prevention and treatment.

Is Cerebral Amyloid-β Deposition Related to Post-stroke Cognitive Impairment?

Approximately two-thirds of ischemic stroke patients suffer from different levels of post-stroke cognitive impairment (PSCI), but the underlying mechanisms of PSCI remain unclear. Cerebral amyloid-β (Aβ) deposition, a pathological hallmark of Alzheimer's disease, has been discovered in the brains of stroke patients in some autopsy studies. However, less is known about the role of Aβ pathology in the development of PSCI. It is hypothesized that cerebral ischemic injury may lead to neurotoxic Aβ accumulation in the brain, which further induces secondary neurodegeneration and progressive cognitive decline after stroke onset. In this review, we summarized available evidence from pre-clinical and clinical studies relevant to the aforementioned hypothesis. We found inconsistency in the results obtained from studies in rodents, nonhuman primates, and stroke patients. Moreover, the causal relationship between post-stroke cerebral Aβ deposition and PSCI has been uncertain and controversial. Taken together, evidence supporting the hypothesis that brain ischemia induces cerebral Aβ deposition has been insufficient so far. And, there is still no consensus regarding the contribution of cerebral amyloid pathology to PSCI. Other non-amyloid neurodegenerative mechanisms might be involved and remain to be fully elucidated.

The Role of Inflammation and Infection in Age-Related Neurodegenerative Diseases: Lessons From Bacterial Meningitis Applied to Alzheimer Disease and Age-Related Macular Degeneration

Age-related neurodegenerative diseases, such as Alzheimer disease (AD) and age-related macular degeneration (AMD), are multifactorial and have diverse genetic and environmental risk factors. Despite the complex nature of the diseases, there is long-standing, and growing, evidence linking microbial infection to the development of AD dementia, which we summarize in this article. Also, we highlight emerging research findings that support a role for parainfection in the pathophysiology of AMD, a disease of the neurosensory retina that has been shown to share risk factors and pathological features with AD. Acute neurological infections, such as Bacterial Meningitis (BM), trigger inflammatory events that permanently change how the brain functions, leading to lasting cognitive impairment. Neuroinflammation likewise is a known pathological event that occurs in the early stages of chronic age-related neurodegenerative diseases AD and AMD and might be triggered as a parainfectious event. To date, at least 16 microbial pathogens have been linked to the development of AD; on the other hand, investigation of a microbe-AMD relationship is in its infancy. This mini-review article provides a synthesis of existing evidence indicating a contribution of parainfection in the aetiology of AD and of emerging findings that support a similar process in AMD. Subsequently, it describes the major immunopathological mechanisms that are common to BM and AD/AMD. Together, this evidence leads to our proposal that both AD and AMD may have an infectious aetiology that operates through a dysregulated inflammatory response, leading to deleterious outcomes. Last, it draws fresh insights from the existing literature about potential therapeutic options for BM that might alleviate neurological disruption associated with infections, and which could, by extension, be explored in the context of AD and AMD.

CD36 deficiency reduces chronic BBB dysfunction and scar formation and improves activity, hedonic and memory deficits in ischemic stroke

Ameliorating blood-brain barrier disruption and altering scar formation dynamics are potential strategies that may improve post-stroke recovery. CD36 is a class B scavenger receptor that plays a role in innate immunity, inflammation and vascular dysfunction and regulates post-stroke injury, neovascularization, reactive astrogliosis and scar formation. By subjecting WT and CD36KO mice to different MCAo occlusion durations to generate comparable acute lesion sizes, we addressed the role of CD36 in BBB dysfunction, scar formation and recovery. The majority of stroke recovery studies primarily focus on motor function. Here, we employed an extensive behavioral test arsenal to evaluate psychological and cognitive endpoints. While not evident during the acute phase, CD36 deficient mice displayed significantly attenuated BBB leakage and scar formation at three months after stroke compared to wild-type littermates. Assessment of motor (open field, rotarod), anxiety (plus maze, light-dark box), depression (forced swim, sucrose preference) and memory tests (water maze) revealed that CD36 deficiency ameliorated stroke-induced behavioral impairments in activity, hedonic responses and spatial learning and strategy switching. Our findings indicate that CD36 contributes to stroke-induced BBB dysfunction and scar formation in an injury-independent manner, as well as to the chronic motor and neurophysiological deficits in chronic stroke.

Rates, risks and routes to reduce vascular dementia (R4vad), a UK-wide multicentre prospective observational cohort study of cognition after stroke: Protocol

BACKGROUND

Stroke commonly affects cognition and, by definition, much vascular dementia follows stroke. However, there are fundamental limitations in our understanding of vascular cognitive impairment, restricting understanding of prevalence, trajectories, mechanisms, prevention, treatment and patient-service needs.

AIMS

Rates, Risks and Routes to Reduce Vascular Dementia (R4VaD) is an observational cohort study of post-stroke cognition. We aim to recruit a wide range of patients with stroke, presenting to geographically diverse UK hospitals, into a longitudinal study to determine rates of, and risk factors for, cognitive and related impairments after stroke, to assess potential mechanisms and improve prediction models.

METHODS

We will recruit at least 2000 patients within six weeks of stroke with or without capacity to consent and collect baseline demographic, clinical, socioeconomic, lifestyle, cognitive, neuropsychiatric and informant data using streamlined patient-centred methods appropriate to the stage after stroke. We will obtain more detailed assessments at four to eight weeks after the baseline assessment and follow-up by phone and post yearly to at least two years. We will assess diagnostic neuroimaging in all and high-sensitivity inflammatory markers, genetics, blood pressure and diffusion tensor imaging in mechanistic sub-studies.Planned outputs: R4VaD will provide reliable data on long-term cognitive function after stroke, stratified by prior cognition, stroke- and patient-related variables and improved risk prediction. It will create a platform enabling sharing of data, imaging and samples. Participants will be consented for re-contact, facilitating future clinical trials and providing a resource for the stroke and dementia research communities.

Lack of association between acute stroke, post-stroke dementia, race, and β-amyloid status

INTRODUCTION

Stroke and Alzheimer disease share risk factors and often co-occur, and both have been reported to have a higher prevalence in African Americans as compared to non-Hispanic whites. However, their interaction has not been established. The objective of this study was to determine if preclinical Alzheimer disease is a risk factor for stroke and post-stroke dementia and whether racial differences moderate this relationship.

METHODS

This case-control study was analyzed in 2019 using retrospective data from 2007 to 2013. Participants were adults age 65 and older with and without acute ischemic stroke. Recruitment included word of mouth and referrals in Saint Louis, MO, with stroke participants recruited from acutely hospitalized patients and non-stroke participants from community living older adults who were research volunteers. Our assessment included radiologic reads of infarcts, microbleeds, and white matter hyperintensitites (WMH); a Pittsburgh Compound B PET measure of cortical β-amyloid binding; quantitative measures of hippocampal and WMH volume; longitudinal Mini Mental State Examination (MMSE) scores; and Clinical Dementia Rating (CDR) 1 year post-stroke.

RESULTS

A total of 243 participants were enrolled, 81 of which had a recent ischemic stroke. Participants had a mean age of 75, 57% were women, and 52% were African American. Cortical amyloid did not differ significantly by race, stroke status, or CDR post-stroke. There were racial differences in MMSE scores at baseline (mean 26.8 for African Americans, 27.9 for non-Hispanic whites, p = 0.03), but not longitudinally. African Americans were more likely to have microbleeds (32.8% vs 22.6%, p = 0.04), and within the acute stroke group, African Americans were more likely to have small infarcts (75.6% vs 56.8%, p = 0.049).

CONCLUSION

Preclinical Alzheimer disease did not show evidence of being a risk factor for stroke nor predictive of post-stroke dementia. We did not observe racial differences in β-amyloid levels. However, even after controlling for several vascular risk factors, African Americans with clinical stroke presentations had greater levels of vascular pathology on MRI.

Measurement of carotid plaque burden: A tool for predicting and preventing dementia?

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Strokes markedly increase the risk of dementia from Alzheimer disease, and preventing strokes reduces the risk of dementia. Delaying dementia by 5 years nearly halves the incidence of dementia, because old patients often die before dementia is expressed.

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Carotid plaque burden is a strong predictor of the risk of stroke, and measurement of plaque burden has also been used to treat atherosclerosis. In high-risk patients with asymptomatic carotid stenosis, doing so was associated with a >80% reduction of the 2-year risk of stroke and myocardial infarction compared to usual therapy.

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We found that high plaque burden was significantly associated with impairment of cognitive function.

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We suggest that measurement of carotid plaque burden may be a powerful tool not only for predicting risk of dementia, but also for preventing dementia.

Introduction

Carotid plaque burden is a strong predictor of stroke risk, and preventing stroke reduces the risk of dementia. Treating carotid plaque burden markedly reduces the risk of stroke.

Methods

Among patients age 65–80 years attending a stroke prevention clinic, we identified those with a carotid plaque burden in the top 20% of Total Plaque Area (High TPA) and the bottom 20% (Low TPA) and performed cognitive tests: The Montreal Cognitive Assessment test (MoCA), the WAIS-III Digit Symbol-Coding Test (DSST) and Trail-Making Test (TMT) part A and B.

Results

There were 31 patients recruited; 11 Low TPA (5 men) and 20 High TPA (17 men), p = 0.04. TPA was 35 ± 25 mm² in the Low TPA vs.392 ± 169 mm² in the High TPA group (0.0001). Patients with a high plaque burden had significantly worse performance on all the cognitive tests, all p< 0.05

Discussion

A high carotid plaque burden identifies patients at risk of cognitive impairment. Because carotid plaque burden is treatable, and treating it markedly reduces the risk of stroke, we suggest that measurement of plaque burden is a useful tool for both prediction of cognitive impairment, and prevention of dementia.

The Role of Cilostazol and Inflammation in Cognitive Impairment After Ischemic Stroke

PURPOSE

The aim of this study is to examine the potential effect of cilostazol and inflammation on cognitive impairment after stroke in an Asian population.

METHODS

Forty-five patients with cognitive impairment after ischemic stroke using cilostazol were enrolled as the study group and 45 patients using aspirin or clopidogrel were enrolled as the control group. Neuropsychiatric assessments were administered at the start of the study and after 6 months. Multiple logistic regression analysis was used to estimate the association between the cognitive change and cilostazol use. Macrophage polarization were assessed using flow cytometry in 7 patients.

RESULTS

There were a significantly higher number of patients with peripheral arterial occlusive disease in the cilostazol group. No significant differences were observed in the cognitive change between the cilostazol and control groups. M1 macrophage subset increment were observed in the patient having a declined cognitive change.

CONCLUSION

Cilostazol did not make a significant difference in cognitive change after ischemic stroke. M1 macrophage subset increment may indicate post stroke cognitive decline. Due to limited number of subjects, these findings should be examined further in large-scale randomized clinical trials.

Immunomagnetic Reduction Detects Plasma Aβ1-42 Levels as a Potential Dominant Indicator Predicting Cognitive Decline

Although the concentrations of Alzheimer’s disease (AD) biomarkers Aβ_1–40, Aβ_1–42 and tau protein are very low in human plasma, ultrasensitive assays such as immunomagnetic reduction (IMR) are able to precisely quantify them. Review articles have described the detailed working mechanism of IMR and revealed the feasibility of detecting early-stage AD by assaying these plasma biomarkers with IMR. In this review, we aimed to compare the significance of these plasma biomarkers in predicting cognitive decline in patients with Down syndrome, stroke, or amnestic mild cognitive impairment based on findings in the literature. We found that plasma Aβ_1–42 might play the predominant role in predicting cognitive decline in these patients.

Investigation of reactive astrogliosis effect on post-stroke cognitive impairment

BACKGROUND

The aim of this study is to investigate the associations between post-stroke cognitive impairment (PSCI) severity and reactive astrogliosis (RA) extent on normalized ¹⁸F-THK-5351 positron-emission tomography (PET) imaging in amyloid-negative patients with first-ever stroke.

METHODS

We prospectively enrolled 63 amyloid-negative patients with first-ever stroke. Neurocognitive evaluation, MRI, ¹⁸F-THK-5351, and ¹⁸F-florbetapir PET were performed around 3 months after stroke. The ¹⁸F-THK-5351 uptake intensity was normalized using a signal distribution template to obtain the Z-SUM scores as the RA extent in the whole brain and cerebral hemisphere ipsilateral to stroke lesion. We evaluated stroke volume, leukoaraiosis, and brain atrophy on MRI. We used a comprehensive neurocognitive battery to obtain composite cognitive scores, and defined PSCI as a general cognitive function score < - 1. We analyzed the influence of Z-SUM scores on PSCI severity after adjusting for demographic, vascular, and neurodegenerative variables.

RESULTS

Twenty-five of 63 stroke patients had PSCI. Patients with PSCI had older age, lower education, and more severe cortical atrophy and total Z-SUM scores. Total Z-SUM scores were significantly associated with general cognitive and executive functions at multiple regression models. Path analyses showed that stroke can exert cognitive influence directly by stroke itself as well as indirectly through RA, including total and ipsilateral Z-SUM scores, in patients with either right or left hemisphere stroke.

CONCLUSION

The patterns and intensity of ¹⁸F-THK-5351 uptake in amyloid-negative patients with first-ever stroke were associated with PSCI manifestations, which suggests that RA presents a modulating effect in PSCI development.

Heterogeneity in brain distribution of activated microglia and astrocytes in a rat ischemic model of Alzheimer's disease after 2 years of survival

The present study was designed to follow neuroinflammation after ischemic brain injury in the long-term survival rat model. Immunohistochemistry was performed 2 years after 10 min global brain ischemia due to cardiac arrest. For the visualization of the cellular inflammatory reaction microglial marker Iba1 and astrocyte marker GFAP were used. In post-ischemic animals our study revealed significant activation of astrocytes in all tested brain regions (hippocampal CA1 and CA3 areas and dentate gyrus, motor and somatosensory cortex, striatum and thalamus), while microglial activation was only found in CA1 and CA3 areas, and the motor cortex. In the specifically sensitive brain areas microglia and astrocytes showed simultaneously significant activation, while in the resistant brain areas only astrocytes were activated. Thus, there was clear evidence of less intensive neuroinflammation in brain areas resistant to ischemia. Such neuroinflammatory processes are backed by microglia and astrocytes activity even up to 2 years after ischemia-reperfusion brain injury. Our study thus revealed a chronic effect of global cerebral ischemia on the neuroinflammatory reaction in the rat brain even 2 years after the insult.

No evidence for amyloid pathology as a key mediator of neurodegeneration post-stroke - a seven-year follow-up study

Background

Cognitive impairment (CI) with mixed vascular and neurodegenerative pathologies after stroke is common. The role of amyloid pathology in post-stroke CI is unclear. We hypothesize that amyloid deposition, measured with Flutemetamol (¹⁸F-Flut) positron emission tomography (PET), is common in seven-year stroke survivors diagnosed with CI and, further, that quantitatively assessed ¹⁸F-Flut-PET uptake after 7 years correlates with amyloid-β peptide (Aβ₄₂) levels in cerebrospinal fluid (CSF) at 1 year, and with measures of neurodegeneration and cognition at 7 years post-stroke.

Methods

208 patients with first-ever stroke or transient Ischemic Attack (TIA) without pre-existing CI were included during 2007 and 2008. At one- and seven-years post-stroke, cognitive status was assessed, and categorized into dementia, mild cognitive impairment or normal. Etiologic sub-classification was based on magnetic resonance imaging (MRI) findings, CSF biomarkers and clinical cognitive profile. At 7 years, patients were offered ¹⁸F-Flut-PET, and amyloid-positivity was assessed visually and semi-quantitatively. The associations between ¹⁸F-Flut-PET standardized uptake value ratios (SUVr) and measures of neurodegeneration (medial temporal lobe atrophy (MTLA), global cortical atrophy (GCA)) and cognition (Mini-Mental State Exam (MMSE), Trail-making test A (TMT-A)) and CSF Aβ₄₂ levels were assessed using linear regression.

Results

In total, 111 patients completed 7-year follow-up, and 26 patients agreed to PET imaging, of whom 13 had CSF biomarkers from 1 year. Thirteen out of 26 patients were diagnosed with CI 7 years post-stroke, but only one had visually assessed amyloid positivity. CSF Aβ₄₂ levels at 1 year, MTA grade, GCA scale, MMSE score or TMT-A at 7 years did not correlate with ¹⁸F-Flut-PET SUVr in this cohort.

Conclusions

Amyloid binding was not common in 7-year stroke survivors diagnosed with CI. Quantitatively assessed, cortical amyloid deposition did not correlate with other measures related to neurodegeneration or cognition. Therefore, amyloid pathology may not be a key mediator of neurodegeneration 7 years post-stroke.

Trial registration

Clinicaltrials.gov (NCT00506818). July 23, 2007. Inclusion from February 2007, randomization and intervention from May 2007 and trial registration in July 2007.

HDAC inhibitor protects chronic cerebral hypoperfusion and oxygen-glucose deprivation injuries via H3K14 and H4K5 acetylation-mediated BDNF expression

Vascular dementia (VaD) is the second most common cause of dementia, but the treatment is still lacking. Although many studies have reported that histone deacetylase inhibitors (HDACis) confer protective effects against ischemic and hypoxic injuries, their role in VaD is still uncertain. Previous studies shown, one HDACi protected against cognitive decline in animals with chronic cerebral hypoperfusion (CCH). However, the underlying mechanisms remain elusive. In this study, we tested several 10,11‐dihydro‐5H‐dibenzo[b,f]azepine hydroxamates, which act as HDACis in the CCH model (in vivo), and SH‐SY5Y (neuroblastoma cells) with oxygen‐glucose deprivation (OGD, in vitro). We identified a compound 13, which exhibited the best cell viability under OGD. The compound 13 could increase, in part, the protein levels of brain‐derived neurotrophic factor (BDNF). It increased acetylation status on lysine 14 residue of histone 3 (H3K14) and lysine 5 of histone 4 (H4K5). We further clarified which promoters (I, II, III, IV or IX) could be affected by histone acetylation altered by compound 13. The results of chromatin immunoprecipitation and Q‐PCR analysis indicate that an increase in H3K14 acetylation leads to an increase in the expression of BDNF promoter II, while an increase in H4K5 acetylation results in an increase in the activity of BDNF promoter II and III. Afterwards, these cause an increase in the expression of BDNF exon II, III and coding exon IX. In summary, the HDACi compound 13 may increase BDNF specific isoforms expression to rescue the ischemic and hypoxic injuries through changes of acetylation on histones.

Framework of treating Alzheimer’s dementia

Current treatment paradigm in Alzheimer’s disease (AD) involves multiple approaches combining pharmacological and nonpharmacological intervention to mitigate the clinical symptoms, slow the progressive loss of cognitive and functional abilities, or modify the disease course. So far, beyond anti-cholinesterase inhibitors (AChEIs), donepezil, rivastigmine, galantamine, and antagonist of N-methyl-D-aspartic acid (NMDA) receptor, there are no newly approved medicines to treat AD. Under pharmacological treatment, the personal characteristic and the intra-individual therapeutic evaluations to examine various cognitive domains, behavioral and psychological problems, and global function should be considered when choosing any of AChEIs. The use of optimal dosage referring to the expected clinical outcomes and currently reported deficits from patient with AD has become an important issue in clinical treatment. Establishing and maintaining a strong therapeutic alliance to physician, patient, and caregiver is crucial and central to the comprehensive care in AD.

Post-stroke remodeling processes in animal models and humans

After cerebral ischemia, events like neural plasticity and tissue reorganization intervene in lesioned and non-lesioned areas of the brain. These processes are tightly related to functional improvement and successful rehabilitation in patients. Plastic remodeling in the brain is associated with limited spontaneous functional recovery in patients. Improvement depends on the initial deficit, size, nature and localization of the infarction, together with the sex and age of the patient, all of them affecting the favorable outcome of reorganization and repair of damaged areas. A better understanding of cerebral plasticity is pivotal to design effective therapeutic strategies. Experimental models and clinical studies have fueled the current understanding of the cellular and molecular processes responsible for plastic remodeling. In this review, we describe the known mechanisms, in patients and animal models, underlying cerebral reorganization and contributing to functional recovery after ischemic stroke. We also discuss the manipulations and therapies that can stimulate neural plasticity. We finally explore a new topic in the field of ischemic stroke pathophysiology, namely the brain-gut axis.

EphrinB2 activation enhances angiogenesis, reduces amyloid-β deposits and secondary damage in thalamus at the early stage after cortical infarction in hypertensive rats

Cerebral infarction causes secondary neurodegeneration and angiogenesis in thalamus, which impacts functional recovery after stroke. Here, we hypothesize that activation of ephrinB2 could stimulate angiogenesis and restore the secondary neurodegeneration in thalamus after cerebral infarction. Focal cerebral infarction was induced by middle cerebral artery occlusion (MCAO). Secondary damage, angiogenesis, amyloid-β (Aβ) deposits, levels of ephrinB2 and receptor for advanced glycation end product (RAGE) in the ipsilateral thalamus were determined by immunofluorescence and immunoblot. The contribution of ephrinB2 to angiogenesis was determined by siRNA-mediated knockdown of ephrinB2 and pharmacological activation of ephrinB2. The results showed that formation of new vessels and ephrinB2 expression was markedly increased in the ipsilateral thalamus at seven days after MCAO. EphrinB2 knockdown markedly suppressed angiogenesis coinciding with increased Aβ accumulation, neuronal loss and gliosis in the ipsilateral thalamus. In contrast, clustered EphB2-Fc significantly enhanced angiogenesis, alleviated Aβ accumulation and the secondary thalamic damage, which was accompanied by accelerated function recovery. Additionally, activation of ephrinB2 significantly reduced RAGE levels in the ipsilateral thalamus. Our findings suggest that activation of ephrinB2 promotes angiogenesis, ameliorates Aβ accumulation and the secondary thalamic damage after cerebral infarction. Additionally, RAGE might be involved in Aβ clearance by activating ephrinB2 in the thalamus.

Implementing the Proclamation of Stroke and Potentially Preventable Dementias

Brain health plays a central role in wellbeing and in the management of chronic diseases. Stroke and dementia pose the two greatest threats to brain health, but recent developments suggest the possibility that preventing stroke may also prevent some dementias: 1. A large population study showed a 32% decrease in the incidence of stroke and a concomitant 7% reduction in the incidence of dementia; 2. Treatment of atrial fibrillation resulted not only in stroke reduction, but a 48% decrease in dementia; 3. A hypothesis free analyses has shown that the first phase of Alzheimer disease involves vascular dysregulation, opening the door to new therapeutic approaches; 4. Cognitive impairment, often treatable and reversible, accompanies heart and kidney failure. These developments, combined with the knowledge that stroke, dementia and heart disease share the same major treatable risk factors, particularly hypertension, offers an opportunity for their joint prevention. This aspiration is expressed by a Proclamation of the World Stroke Organization on Stroke and Potentially Preventable Dementias and endorsed by the World Heart Federation, the World Hypertension League, Alzheimer Disease International and 18 other international, regional and national organizations as a call for action.

Plasma Amyloid Beta and Tau Levels Are Predictors of Post-stroke Cognitive Impairment: A Longitudinal Study

Objectives: Post-stroke cognitive impairment (PSCI) is a common disease that may occur within 3 months after a stroke or even later. However, the mechanism of PSCI development is unclear. The present study investigated whether the levels of plasma amyloid beta-42 (Aβ42) and tau are associated with the onset of PSCI. Methods: Fifty-five patients admitted within 7 days of acute ischemic stroke were enrolled and followed up for 1 year. Montreal Cognitive Assessment (MoCA) was administered at 3 months and 1 year, and plasma Aβ42 and tau levels were determined using an ultrasensitive immunoassay (immunomagnetic reduction) within 7 days of the stroke event and 3 months later. Results: In this study, 13 of 55 patients developed PSCI (MoCA score <23) at 3 months. Seven patients with PSCI at 3 months recovered to a cognitively normal state at 1 year, whereas seven cognitively normal patients developed PSCI at 1 year. The patients with PSCI at 1 year had a higher incidence of cognitive function deterioration between 3 months and 1 year compared with those without PSCI at 1 year. Plasma Aβ42 and tau levels at 3 months were lower in the patients with PSCI at 1 year than in those without PSCI (Aβ42: 15.1 vs. 17.2 pg/mL, P = 0.013; tau: 16.7 vs. 19.9 pg/mL, P = 0.018). Low education levels and pre-existing white matter disease were the most significant predictors of PSCI at 3 months, and poor cognitive performance at 3 months and low plasma Aβ42 and tau levels at 3 months were the most significant predictors of PSCI at 1 year. Conclusion: The pathogenesis of PSCI is complex and changes with time. Ischemia-induced Aβ42/tau pathology might be involved in PSCI development.

Can Disease-Modifying Anti-Rheumatic Drugs Reduce the Risk of Developing Dementia in Patients with Rheumatoid Arthritis?

Disease-modifying anti-rheumatic drugs (DMARDs) can reduce inflammation and slow progression of rheumatoid arthritis (RA). It remains unknown what impact DMARDs may have on dementia, where inflammation also plays a critical role in pathogenesis. Patients without a prior history of dementia who were newly diagnosed with RA between 2000 and 2005 were identified from Taiwan's National Health Insurance Research Database. The participants were stratified by age and gender. The outcome of interest was all-cause dementia, and Cox regression models were used to estimate the hazard ratio (HR) of dementia. The cumulative DMARD dosage was stratified by quartiles of defined daily doses. A total of 20,707 patients were diagnosed with RA, and 62,121 non-RA individuals aged 20 years or older were included. Cox proportional hazard regression analysis revealed that the RA cohort was 37% less likely to develop dementia compared with the non-RA cohort [adjusted HR 0.63, 95% confidence interval (CI) 0.55-0.72]. Further decreased risk was noted in DMARD users (adjusted HR 0.48, 95% CI 0.39-0.58) with dose-dependent effect. Subgroup analysis identified DMARD use as having a protective effect against developing dementia in female and younger patients. Also, in male and older patients, DMARD use further reduced the risk. These observations suggest that DMARDs may reduce the risk of developing dementia, and its effect is further increased at high cumulative dosages. These findings warrant further examination in randomized control trials.

On frail minds: addressing and assessing age-related neural decline and disease

The terminology surrounding frailty is used in clinical settings, and in research and development for identifying processes of, and patients in, age-related physical decline. However, a framework suitable for age-related neurodegenerative diseases needs to (1) adequately account for the effects that the processes of aging have on neural decline and disease, and (2) be helpful in identifying relevant groups of users and patients. This is becoming increasingly necessary due to emerging possibilities to detect, prevent, and treat age-related neural decline and disease. Based on a number of relevant criteria, I distinguish four groups of patients and users: robust, non-frail, pre-frail, and frail. With the four groups defined, ethical assessments can be made on an individual basis regarding which medical technologies are best suited for a person who risks, or suffers from, age-related neurodegenerative disease.

Misery perfusion and amyloid deposition in atherosclerotic major cerebral artery disease

Although experimental studies have shown that global cerebral hypoperfusion leads to amyloid deposition in the hemisphere with carotid artery occlusion in rodents, the results of such occurrence are controversial in humans. Hence, we aim to determine whether global cerebral hypoperfusion leading to decreased blood flow relative to metabolic demand [increased oxygen extraction fraction (OEF), misery perfusion] is associated with increases in amyloid deposition in the hemisphere with atherosclerotic major cerebral artery disease in patients. We evaluated the distribution of β-amyloid plaques using positron emission tomography and a [18F]-pyridylbenzofuran derivative (¹⁸F-FPYBF-2) in 13 patients with unilateral atherosclerotic disease of the internal carotid artery (ICA) or middle cerebral artery (MCA) disease and no cortical infarction. The distribution volume ratio (DVR) of ¹⁸F- FPYBF-2 was calculated using dynamic data and Logan graphical analysis with reference tissue and was correlated with the cerebral blood flow (CBF), cerebral metabolic rate of oxygen (CMRO₂), and OEF, obtained from ¹⁵O-gas PET. The mean cortical value was calculated as the mean value within the frontal, posterior cingulate, precuneus, parietal, and lateral temporal cortical regions. Significant reductions in CBF and CMRO₂ and increases in OEF were found in the hemisphere ipsilateral to the arterial lesion compared with the contralateral hemisphere. There was no significant difference for ¹⁸F-FPYBF-2 DVR between hemispheres. The ipsilateral to contralateral ratio of the ¹⁸F- FPYBF-2 DVR was increased in 3 patients, while the ipsilateral to contralateral OEF ratio was increased in 4 patients. The incidence of an increased hemispheric DVR ratio was significantly higher in patients with an increased hemispheric OEF ratio (3/4) than in patients without (0/9) (p < 0.02). Although the ¹⁸F- FPYBF-2 DVR in the ipsilateral hemisphere was positively correlated with OEF after adjustment for the ¹⁸F- FPYBF-2 DVR in the contralateral hemisphere using multiple regression analysis (p < 0.05), the contribution rate of OEF was small (R² = 5.5%). Only one of the 4 patients with an increased hemispheric OEF ratio showed amyloid positivity based on the DVR value. In atherosclerotic major cerebral artery disease, misery perfusion accompanied only small increases of amyloid deposition at best. Misery perfusion was not associated with amyloid positivity.

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Misery perfusion accompanied only small increases of amyloid deposition at best.

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Relative oxygen extraction fraction correlated with relative amyloid deposition.

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Misery perfusion was not associated with amyloid positivity.

Blood Pressure Gradients in the Brain: Their Importance to Understanding Pathogenesis of Cerebral Small Vessel Disease

The term "lacunar infarction" referred to small infarctions in the basal ganglia, internal capsule, thalamus, and brainstem, due to hypertensive small vessel disease. However, it has become common to refer to all small infarctions as "vascular centrencephalon", where short straight arteries with few branches transmit high blood pressure straight through to end-arterioles. The cortex is supplied by long arteries with many branches, so there is a very large blood pressure gradient in the brain. When blood pressure in the brachial artery is 117/75 mmHg, the pressure in the lenticulostriate artery would be 113/73, and the pressure in small parietal arterioles would be only 59/38 mmHg. Recent studies have reported that patients with a pulse pressure >60 mmHg and diastolic pressure <60 mmHg have a doubling of coronary risk and a 5.85-fold increase in stroke risk. This means that new low systolic targets being proposed will probably decrease the incidence of true lacunes, but increase small subcortical infarctions in the hemispheres. The pathogenesis of small vessel disease should be interpreted in the light of these blood pressure gradients.

Dementia: new vistas and opportunities

Over the past four decades, Alzheimer disease has become near synonymous with dementia and the amyloid/tau hypothesis as its dominant explanation. However, this monorail approach to etiology has failed to yield a single disease-modifying drug. Part of the explanation stems from the fact that most dementias in the elderly result from interactive Alzheimer and cerebrovascular pathologies. Stroke and dementia share the same risk factors and their control is associated with a decrease in stroke and some dementias. Additionally, intensive control of risk factors and enhancement of protective factors improve cognition. Moreover, anticoagulation of atrial fibrillation patients decreases their chance of developing dementia by 48%. Preliminary data suggest that treating blood pressure to a target of 120 mmHg systolic compared to a target of 140 mmHg decreases the chances of mild cognitive impairment by 19%. The Berlin Manifesto establishes the scientific bases of "preventing dementia by preventing stroke." Enlarging our vista of dementia to include cerebrovascular disease offers the opportunity of preventing not only stroke, but some dementias, beginning now.

The Norwegian Cognitive impairment after stroke study (Nor-COAST): study protocol of a multicentre, prospective cohort study

BACKGROUND

Early and late onset post-stroke cognitive impairment (PCI) contributes substantially to disability following stroke, and is a high priority within stroke research. The aetiology for PCI is complex and related to the stroke itself, brain resilience, comorbid brain diseases, prestroke vulnerability and complications during the hospital stay. The aim of the Norwegian Cognitive Impairment After Stroke study (Nor-COAST) is to quantify and measure levels of cognitive impairments in a general Norwegian stroke population and to identify biological and clinical markers associated with prognosis for cognitive disorders following incident stroke. The study will be organised within five work packages: 1) Incidence and trajectories 2) Pathological mechanisms 3) Development of a risk score 4) Impact of physical activity and 5) Adherence to secondary prevention.

METHODS

Nor-COAST is an ongoing multicentre (five participating hospitals), prospective, cohort study with consecutive inclusion during the acute phase and with follow-up at three and 18 months, and at three years. Inclusion criteria are stroke defined according to the WHO criteria. During the recruitment period from 18.05.2015 to 31.03.2017, 816 participants have been included. Cognitive impairment will be classified according to the DSM-5 criteria using a consensus group. Cognitive function is assessed by a standardised neuropsychological test battery, the Montreal Cognitive Assessment, Trail making A and B, ten-word immediate and delayed recall test, the Controlled Oral Word Association, Global Deterioration Scale and proxy based information by and the Ascertain Dementia 8 item informant questionnaire. Biomarkers include magnetic resonance imaging, routine blood samples and bio-banking. Clinical assessments include characteristics of the stroke, comorbidity, delirium, frailty and tests for cognitive and physical function, sensor based activity monitoring and adherence to secondary prophylaxis.

DISCUSSION

Nor-COAST is the first Norwegian multicentre study to quantify burden of PCI that will provide reliable estimates in a general stroke population. A multidisciplinary approach aiming to identify biomarkers and clinical markers of overall prognosis will add new knowledge about risk profiles, including pre-stroke vulnerability and modifiable factors such as physical activity and secondary prophylaxis of relevance for clinical practice and later intervention studies.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT02650531 . Retrospectively registered January 8, 2016. First participant included May 18, 2015.

Questions concerning the role of amyloid-β in the definition, aetiology and diagnosis of Alzheimer's disease

The dominant hypothesis of Alzheimer’s disease (AD) aetiology, the neuropathological guidelines for diagnosing AD and the majority of high-profile therapeutic efforts, in both research and in clinical practice, have been built around one possible causal factor, amyloid-β (Aβ). However, the causal link between Aβ and AD remains unproven. Here, in the context of a detailed assessment of historical and contemporary studies, we raise critical questions regarding the role of Aβ in the definition, diagnosis and aetiology of AD. We illustrate that a holistic view of the available data does not support an unequivocal conclusion that Aβ has a central or unique role in AD. Instead, the data suggest alternative views of AD aetiology are potentially valid, at this time. We propose that an unbiased way forward for the field, beyond the current Aβ-centric approach, without excluding a role for Aβ, is required to come to an accurate understanding of AD dementia and, ultimately, an effective treatment.

Implementing the proclamation of stroke and potentially preventable dementias

Brain health plays a central role in well-being and in the management of chronic diseases. Stroke and dementia pose the two greatest threats to brain health, but recent developments suggest the possibility that preventing stroke may also prevent some dementias: (a) A large population study showed a 32% decrease in the incidence of stroke and a concomitant 7% reduction in the incidence of dementia; (b) the treatment of atrial fibrillation resulted not only in stroke reduction, but also a 48% decrease in dementia; (c) the hypothesis-free analyses have shown that the first phase of Alzheimer disease involves vascular dysregulation, opening the door to new therapeutic approaches; (d) cognitive impairment, often treatable and reversible, accompanies heart and kidney failure. These developments, combined with the knowledge that stroke, dementia, and heart disease share the same major treatable risk factors, particularly hypertension, offer an opportunity for their joint prevention. This aspiration is expressed by a Proclamation of the World Stroke Organization on Stroke and Potentially Preventable Dementias and endorsed by the World Heart Federation, the World Hypertension League, Alzheimer Disease International, and 18 other international, regional, and national organizations as a call for action.