Inhibition of mTOR protects the blood-brain barrier in models of Alzheimer's disease and vascular cognitive impairment

An intact blood-brain barrier (BBB) limits entry of proinflammatory and neurotoxic blood-derived factors into the brain parenchyma. The BBB is damaged in Alzheimer's disease (AD), which contributes significantly to the progression of AD pathologies and cognitive decline. However, the mechanisms underlying BBB breakdown in AD remain elusive, and no interventions are available for treatment or prevention. We and others recently established that inhibition of the mammalian/mechanistic target of rapamycin (mTOR) pathway with rapamycin yields significant neuroprotective effects, improving cerebrovascular and cognitive function in mouse models of AD. To test whether mTOR inhibition protects the BBB in neurological diseases of aging, we treated hAPP(J20) mice modeling AD and low-density lipoprotein receptor-null (LDLR-/-) mice modeling vascular cognitive impairment with rapamycin. We found that inhibition of mTOR abrogates BBB breakdown in hAPP(J20) and LDLR-/- mice. Experiments using an in vitro BBB model indicated that mTOR attenuation preserves BBB integrity through upregulation of specific tight junction proteins and downregulation of matrix metalloproteinase-9 activity. Together, our data establish mTOR activity as a critical mediator of BBB breakdown in AD and, potentially, vascular cognitive impairment and suggest that rapamycin and/or rapalogs could be used for the restoration of BBB integrity. NEW & NOTEWORTHY This report establishes mammalian/mechanistic target of rapamycin as a critical mediator of blood-brain barrier breakdown in models of Alzheimer's disease and vascular cognitive impairment and suggests that drugs targeting the target of rapamycin pathway could be used for the restoration of blood-brain barrier integrity in disease states.

Molecular Pharmacology of Rosmarinic and Salvianolic Acids: Potential Seeds for Alzheimer's and Vascular Dementia Drugs

Both caffeic acid and 3,4-dihydroxyphenyllactic acid (danshensu) are synthesized through two distinct routs of the shikimic acid biosynthesis pathway. In many plants, especially the rosemary and sage family of Lamiaceae, these two compounds are joined through an ester linkage to form rosmarinic acid (RA). A further structural diversity of RA derivatives in some plants such as Salvia miltiorrhiza Bunge is a form of RA dimer, salvianolic acid-B (SA-B), that further give rise to diverse salvianolic acid derivatives. This review provides a comprehensive perspective on the chemistry and pharmacology of these compounds related to their potential therapeutic applications to dementia. The two common causes of dementia, Alzheimer's disease (AD) and stroke, are employed to scrutinize the effects of these compounds in vitro and in animal models of dementia. Key pharmacological mechanisms beyond the common antioxidant and anti-inflammatory effects of polyphenols are highlighted with emphasis given to amyloid beta (Aβ) pathologies among others and neuronal regeneration from stem cells.

Person-specific contribution of neuropathologies to cognitive loss in old age

OBJECTIVE

Mixed neuropathologies are the most common cause of dementia at the population level, but how different neuropathologies contribute to cognitive decline at the individual level remains unknown. We quantified the contribution of 9 neuropathologies to cognitive loss at an individual level.

METHODS

Participants (n = 1,079) came from 2 longitudinal clinical-pathologic studies of aging. All completed 2 + cognitive evaluations (maximum = 22), died, and underwent neuropathologic examinations to identify Alzheimer disease (AD), other neurodegenerative diseases, and vascular pathologies. Linear mixed models examined associations of neuropathologies with cognitive decline and estimated the proportion of cognitive loss accounted for by each neuropathology at a person-specific level.

RESULTS

Neuropathology was ubiquitous, with 94% of participants having 1+, 78% having 2+, 58% having 3+, and 35% having 4+. AD was most frequent (65%) but rarely occurred in isolation (9%). Remarkably, >230 different neuropathologic combinations were observed, each of which occurred in <6% of the cohort. The relative contributions of specific neuropathologies to cognitive loss varied widely across individuals. Although AD accounted for an average of about 50% of the observed cognitive loss, the proportion accounted for at the individual level ranged widely from 22% to 100%. Lewy bodies and hippocampal sclerosis also had potent effects, but again their impacts varied at the person-specific level.

INTERPRETATION

There is much greater heterogeneity in the comorbidity and cognitive impact of age-related neuropathologies than currently appreciated, suggesting an urgent need for novel therapeutic approaches that embrace the complexity of disease to combat cognitive decline in old age. Ann Neurol 2018;83:74-83.

Correlations between Gray Matter and White Matter Degeneration in Pure Alzheimer's Disease, Pure Subcortical Vascular Dementia, and Mixed Dementia

Alzheimer's disease dementia (ADD) and subcortical vascular dementia (SVaD) both show cortical thinning and white matter (WM) microstructural changes. We evaluated different patterns of correlation between gray matter (GM) and WM microstructural changes in pure ADD, pure SVaD, and mixed dementia. We enrolled 40 Pittsburgh compound B (PiB) positive ADD patients without WM hyperintensities (pure ADD), 32 PiB negative SVaD patients (pure SVaD), 23 PiB positive SVaD patients (mixed dementia), and 56 normal controls. WM microstructural integrity was quantified using fractional anisotropy (FA), axial diffusivity (DA), and radial diffusivity (DR) values. We used sparse canonical correlation analysis to show correlated regions of cortical thinning and WM microstructural changes. In pure ADD patients, lower FA in the frontoparietal area correlated with cortical thinning in the left inferior parietal lobule and bilateral paracentral lobules. In pure SVaD patients, lower FA and higher DR across extensive WM regions correlated with cortical thinning in bilateral fronto-temporo-parietal regions. In mixed dementia patients, DR and DA changes across extensive WM regions correlated with cortical thinning in the bilateral fronto-temporo-parietal regions. Our findings showed that the relationships between GM and WM degeneration are distinct in pure ADD, pure SVaD, and mixed dementia, suggesting that different pathomechanisms underlie their correlations.

Small vessel disease, neurovascular regulation and cognitive impairment: post-mortem studies reveal a complex relationship, still poorly understood

The contribution of vascular disease to cognitive impairment is under-recognized and the pathogenesis is poorly understood. This information gap has multiple causes, including a lack of post-mortem validation of clinical diagnoses of vascular cognitive impairment (VCI) or vascular dementia (VaD), the exclusion of cases with concomitant neurodegenerative disease when diagnosing VCI/VaD, and a lack of standardization of neuropathological assessment protocols for vascular disease. Other contributors include a focus on end-stage destructive lesions to the exclusion of more subtle types of diffuse brain injury, on structural abnormalities of arteries and arterioles to the exclusion of non-structural abnormalities and capillary damage, and the use of post-mortem sampling strategies that are biased towards the identification of neurodegenerative pathologies. Recent studies have demonstrated the value of detailed neuropathology in characterizing vascular contributions to cognitive impairment (e.g. in diabetes), and highlight the importance of diffuse white matter changes, capillary damage and vasoregulatory abnormalities in VCI/VaD. The use of standardized, evidence-based post-mortem assessment protocols and the inclusion of biochemical as well as morphological methods in neuropathological studies should improve the accuracy of determination of the contribution of vascular disease to cognitive impairment and clarify the relative contribution of different pathogenic processes to the tissue damage.

Milder Alzheimer's disease pathology in heart failure and atrial fibrillation

INTRODUCTION

Heart failure (HF) and atrial fibrillation (AF) have been associated with a higher risk of Alzheimer's disease (AD). Whether HF and AF are related to AD by enhancing AD neuropathological changes is unknown.

METHODS

We applied network analyses and multiple logistic regression models to assess the association between HF and AF with severity of AD neuropathology in patients from the National Alzheimer's Coordinating Center database with primary neuropathological diagnosis of AD.

RESULTS

We included 1593 patients, of whom 129 had HF and 250 had AF. HF and AF patients were older and had milder AD pathology. In the network analyses, HF and AF were associated with milder AD neuropathology. In the regression analyses, age (odds ratio [OR] 0.94, 95% confidence interval [CI] 0.93-0.95 per 1-year increase in age, P < .001) and the interaction term HF × AF (OR 0.61, 95% CI 0.40-0.91, P = .014) were inversely related to severe AD pathology, whereas APOE ε4 genotype showed a direct association (OR 1.68, 95% CI 1.31-2.16). Vascular neuropathology was more frequent in patient with HF and AF patients than in those without.

DISCUSSION

HF and AF had milder AD neuropathology. Patients with milder AD lived longer and had more exposure to vascular risk factors. HF and AF patients showed a higher frequency of vascular neuropathology, which could have contributed to lower the threshold for clinically evident dementia.

Paving the Way Toward Complex Blood-Brain Barrier Models Using Pluripotent Stem Cells

A tissue with great need to be modeled in vitro is the blood-brain barrier (BBB). The BBB is a tight barrier that covers all blood vessels in the brain and separates the brain microenvironment from the blood system. It consists of three cell types [neurovascular unit (NVU)] that contribute to the unique tightness and selective permeability of the BBB and has been shown to be disrupted in many diseases and brain disorders, such as vascular dementia, stroke, multiple sclerosis, and Alzheimer's disease. Given the progress that pluripotent stem cells (PSCs) have made in the past two decades, it is now possible to produce many cell types from the BBB and even partially recapitulate this complex tissue in vitro. In this review, we summarize the most recent developments in PSC differentiation and modeling of the BBB. We also suggest how patient-specific human-induced PSCs could be used to model BBB dysfunction in the future. Lastly, we provide perspectives on how to improve production of the BBB in vitro, for example by improving pericyte differentiation protocols and by better modeling the NVU in the dish.

Neuropathological diagnoses and clinical correlates in older adults in Brazil: A cross-sectional study

BACKGROUND

Clinicopathological studies are important in determining the brain lesions underlying dementia. Although almost 60% of individuals with dementia live in developing countries, few clinicopathological studies focus on these individuals. We investigated the frequency of neurodegenerative and vascular-related neuropathological lesions in 1,092 Brazilian admixed older adults, their correlation with cognitive and neuropsychiatric symptoms, and the accuracy of dementia subtype diagnosis.

METHODS AND FINDINGS

In this cross-sectional study, we describe clinical and neuropathological variables related to cognitive impairment in 1,092 participants (mean age = 74 y, 49% male, 69% white, and mean education = 4 y). Cognitive function was investigated using the Clinical Dementia Rating (CDR) and the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE); neuropsychiatric symptoms were evaluated using the Neuropsychiatric Inventory (NPI). Associations between neuropathological lesions and cognitive impairment were investigated using ordinal logistic regression. We developed a neuropathological comorbidity (NPC) score and compared it to CDR, IQCODE, and NPI scores. We also described and compared the frequency of neuropathological diagnosis to clinical diagnosis of dementia subtype. Forty-four percent of the sample met criteria for neuropathological diagnosis. Among these participants, 50% had neuropathological diagnoses of Alzheimer disease (AD), and 35% of vascular dementia (VaD). Neurofibrillary tangles (NFTs), hippocampal sclerosis, lacunar infarcts, hyaline atherosclerosis, siderocalcinosis, and Lewy body disease were independently associated with cognitive impairment. Higher NPC scores were associated with worse scores in the CDR sum of boxes (β = 1.33, 95% CI 1.20-1.46), IQCODE (β = 0.14, 95% CI 0.13-0.16), and NPI (β = 1.74, 95% CI = 1.33-2.16). Compared to neuropathological diagnoses, clinical diagnosis had high sensitivity to AD and high specificity to dementia with Lewy body/Parkinson dementia. The major limitation of our study is the lack of clinical follow-up of participants during life.

CONCLUSIONS

NFT deposition, vascular lesions, and high NPC scorewere associated with cognitive impairment in a unique Brazilian sample with low education. Our results confirm the high prevalence of neuropathological diagnosis in older adults and the mismatch between clinical and neuropathological diagnoses.

Use of the Ten-Point Clock Test to Compare Executive Functioning across 24 Months in Patients with Subcortical Vascular Dementia

The Ten-point Clock Test can be used to identify early forms of Alzheimer's disease because it is reliable, well accepted, and easily administered at the bedside. Nevertheless, its clinical role in the detection of early dementia and its correlations with other cognitive processes is still under investigation. Vascular dementia is an uncertain nosological entity, in which unevenly distributed patterns of cognitive deficits comprising slowing of cognitive processing and impairment of executive function occur. The present study assessed how the Clock Test scores correlated with a number of other neuropsychological and functional tests in a sample of 144 patients with vascular dementia, who were followed for a period of 24 mo. At baseline, at 12 mo. and at 24 mo. subjects were administered a battery of tests, including the Mini-Mental State Examination, word fluency, visuospatial skills, an evaluation of hetero- and autotopognosia (knowledge of self), the Proverbs Test, and the Ten-point Clock Test. For these patients scores on the Clock Test correlated significantly with semantic abilities, with abstract reasoning capacities, visuospatial perception, and with right and left recognition.

Macrophages come to mind as keys to cognitive decline

Cognitive impairment, an underappreciated consequence of hypertension, is linked to cerebral arteriolar disease through poorly defined mechanisms. A study by Faraco et al. in this issue of the JCI points to perturbations of neurovascular unit coupling caused by perivascular macrophages (PVMs) as a cause of hypertension-related cognitive impairment. Angiotensin II (Ang II) was shown to activate PVMs, causing them to produce superoxide and thereby alter the proper functioning of the adjacent arterioles. Faraco and colleagues also show that disruption of the blood-brain barrier occurs in hypertension, allowing circulating Ang II to access PVMs. This study provides important new insight into the role of inflammatory cells in the genesis of vascular dementia.

Impact of Alzheimer's Disease, Lewy Body and Vascular Co-Pathologies on Clinical Transition to Dementia in a National Autopsy Cohort

AIMS

We examined the effect of vascular or Lewy body co-pathologies in subjects with autopsy-confirmed Alzheimer's disease (AD) on the rate of cognitive and functional decline and transition to dementia.

METHODS

In an autopsy sample of prospectively characterized subjects from the National Alzheimer's Coordinating Center database, neuropathology diagnosis was used to define the groups of pure AD (pAD, n = 84), mixed vascular and AD (ADV, n = 54), and mixed Lewy body disease and AD (ADLBD, n = 31). Subjects had an initial Clinical Dementia Rating-Global (CDR-G) score <1, Mini-Mental State Examination ≥15, a final visit CDR-G >1, ≥3 evaluations, and Braak tangle stage ≥III. We compared the rate of cognitive and functional decline between the groups.

RESULTS

The rate of functional and cognitive decline was lower for ADV, and ADV patients had less severe deficits on CDR-G and the CDR-Sum of Boxes scores at the last visit than pAD and ADLBD patients. No significant differences were noted between ADLBD and pAD patients. After controlling for age at death, the odds of reaching CDR ≥1 at the last visit were lower in the ADV subjects compared to the pAD subjects.

CONCLUSIONS

The mean rate of functional and cognitive decline among ADV subjects was slower than among either pAD or ADLBD patients. Vascular pathology did not increase the odds of attaining CDR ≥1 when occurring with AD in this national cohort.

Frontal Lobe Dementia and Subcortical Vascular Dementia: A Neuropsychological Comparison

We compared the performance of 40 patients with frontal lobe dementia to that of 40 patients with subcortical vascular dementia (80 patients including, 46 men and 34 women) in a set of tasks assessing attentional, executive, and behavioural tasks. The frontal lobe dementia represents an important cause for degenerative disruption and is increasingly recognised as an important form (up to 25%) of degenerative dementia among individuals of late-middle-age. The main involvement is the frontal-subcortical pathway, which is the final target of impairment even in subcortical vascular dementia. A wider involvement of the cortical (decisional) layers in frontal dementia, in contrast with the prominent and widespread involvement of the subcortical pathways (refinement and corrections programs) creates the different profiles of the two groups. Frontal patients have more difficulties in abstract reasoning, focusing attention, and implementing strategies to solve problems. They exhibit more profound behavioural alterations in personality and social conduct and show only moderate depression, and a total lack of insight concerning their clinical condition. In contrast, the patients with subcortical vascular dementia have poor general cognitive functions, high insight, and important depression and apathy as the principal and most salient characteristic of their behavioral conduct.

The Cognition and Affect after Stroke - a Prospective Evaluation of Risks (CASPER) study: rationale and design

BACKGROUND

Cognitive impairment and neuropsychiatric syndromes, like depression and apathy, are frequent residual consequences of stroke. These have a large impact on quality of life and long-term prognosis. Several factors are involved in the development of these residual syndromes, although their exact role and their interrelationships remain still rather unclear. The Cognition and Affect after Stroke: a Prospective Evaluation of Risks (CASPER) study has been primarily designed to examine whether stroke-specific (e.g. lesion location, volume, type, severity), cerebrovascular and neurodegenerative (e.g. white matter changes, atrophy, microbleeds, perivascular spaces), inflammatory, endothelial, and (epi)genetic markers are associated with cognitive impairment, post-stroke depression, and post-stroke apathy, and whether they predict their course over 12 months. The secondary aims are to investigate how the above-mentioned markers interact with each other, and to determine if patients with apathy and depression after stroke differ in pathogenesis, course, and outcome (e.g. functional outcome, neurocognitive performance, quality of life).

METHODS/DESIGN

CASPER is a 1-year prospective clinical cohort follow-up study in 250 stroke patients recruited at the neurological in- and outpatient services at Maastricht University Medical Center (MUMC+, Maastricht, The Netherlands), and Zuyderland Medical Center (Sittard and Heerlen, The Netherlands). At baseline (3 months post-stroke), a neuropsychological assessment, neuropsychiatric interview, blood sample, and brain magnetic resonance imaging (MRI) scan are conducted. Assessment of neuropsychiatric and neurocognitive status are repeated 6 and 12 months later.

DISCUSSION

The CASPER study investigates stroke-specific, vascular, neurodegenerative, inflammatory, and genetic markers of the development of vascular cognitive impairment, depression, and apathy after stroke. This creates the possibility to study not only the contribution of these individual markers but also their joint contribution, which differentiates this study from earlier stroke cohorts who lacked long-term follow-up data, a large sample size, an extensive MRI protocol, and markers from the blood. The knowledge we derive from this study might help in identifying markers that are associated with, or can predict the onset, maintenance, and progression of vascular cognitive impairment, depression, and apathy after stroke, and could provide new insights into possibilities for treatment and rehabilitation that result in better functional outcome after stroke.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02585349.

Vascular cognitive impairment and dementia

Vascular contributions to cognitive impairment are receiving heightened attention as potentially modifiable factors for dementias of later life. These factors have now been linked not only to vascular cognitive disorders but also Alzheimer's disease. In this chapter we review 3 related topics that address vascular contributions to cognitive impairment: 1. vascular pathogenesis and mechanisms; 2. neuropsychological and neuroimaging phenotypic manifestations of cerebrovascular disease; and 3. prospects for prevention of cognitive impairment of later life based on cardiovascular and stroke risk modification. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Animal Models of Vascular Cognitive Impairment and Dementia (VCID)

Vascular cognitive impairment and dementia (VCID) is the most common etiology of dementia in the elderly. Both, vascular and Alzheimer's disease, pathologies work synergistically to create neurodegeneration and cognitive impairments. The main causes of VCID include hemorrhage/microbleed (i.e., hyperhomocysteinemia), cerebral small vessel disease, multi-infarct dementia, severe hypoperfusion (i.e., bilateral common carotid artery stenosis), strategic infarct, angiopathy (i.e., cerebral angiopathy), and hereditary vasculopathy (i.e., cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy). In this review, we will discuss the experimental animal models that have been developed to study these pathologies. We will discuss the limitations and strengths of these models and the important research findings that have advanced the field through the use of the models.

Subcortical ischemic vascular disease: Roles of oligodendrocyte function in experimental models of subcortical white-matter injury

Oligodendrocytes are one of the major cell types in cerebral white matter. Under normal conditions, they form myelin sheaths that encircle axons to support fast nerve conduction. Under conditions of cerebral ischemia, oligodendrocytes tend to die, resulting in white-matter dysfunction. Repair of white matter involves the ability of oligodendrocyte precursors to proliferate and mature. However, replacement of lost oligodendrocytes may not be the only mechanism for white-matter recovery. Emerging data now suggest that coordinated signaling between neural, glial, and vascular cells in the entire neurovascular unit may be required. In this mini-review, we discuss how oligodendrocyte lineage cells participate in signaling and crosstalk with other cell types to underlie function and recovery in various experimental models of subcortical white-matter injury.

Effect of Melatonin and Resveratrol against Memory Impairment and Hippocampal Damage in a Rat Model of Vascular Dementia

OBJECTIVES

This study was intended to investigate whether treatment with resveratrol and melatonin alone or in combination can exert neurorestorative effects in a rat model of vascular dementia.

METHODS

Briefly, male Wistar rats were subjected to permanent bilateral common carotid artery occlusion (BCCAO) by surgery. After 4 weeks, the cognitive deficits were assessed using the Morris water maze and novel object recognition tests. The biochemical parameters of oxidative stress and inflammation were also assessed.

RESULTS

Rats in the BCCAO group showed cognitive deficits, accompanied by oxidonitrosative stress, neuroinflammation, and a reduction in brain-derived neurotrophic factor (BDNF) in the hippocampus region. Moreover, the acetylcholinesterase activity in the hippocampus was found to be increased in the BCCAO group compared to the sham group. The 4-week treatment with melatonin (10 mg/kg) and resveratrol (20 mg/kg) alone and in combination (melatonin 5 mg/kg and reseveratrol 10 mg/kg) caused a significant improvement in the cognitive deficits induced by BCCAO, accompanied by a reversal of oxidonitrosative stress, neuroinflammation, and BDNF depletion in the hippocampus region. Additionally, the treatment with melatonin and resveratrol significantly decreased acetylcholinesterase activity compared to in the BCCAO group. Melatonin and resveratrol ameliorated the BDNF expression of hippocampal protein.

CONCLUSION

These results emphasize that coadministration of melatonin and resveratrol can be beneficial in BCCAO-induced vascular dementia through changes in BDNF expressions.

Vascular cognitive impairment: Modeling a critical neurologic disease in vitro and in vivo

BACKGROUND

Vascular contributions to cognitive impairment and dementia (VCID) is a complex form of dementia, combining aspects of vascular disease and other forms of dementia, such as Alzheimer's disease. VCID encompasses a wide spectrum of cerebrovascular-driven cognitive impairment, from mild cognitive impairment to fully developed dementia. This disease state is further complicated by metabolic disorders, such as type 2 diabetes and hypertension, and lifestyle factors, like obesity and high fat diets.

SCOPE OF REVIEW

This manuscript is meant to both define VCID and review the in vitro and in vivo models of the disease state. This includes in vitro models of the neurovascular unit, models of chronic cerebral hypoperfusion, animals with NOTCH3 mutations as a model of small vessel disease, large animals with cerebral amyloid angiopathy (CAA), and animal models of mixed dementia.

MAJOR CONCLUSIONS

Synthetic microvessels are a promising technique to study the neurovascular unit and canines, despite the cost, are an excellent model to study CAA. While there are several good models of individual aspects of VCID, the heterogeneity of the disease states prevents them from being a model of all aspects of the disease. Therefore, VCID needs to be further defined into disease states that exist within this umbrella term. This includes specific guidelines for stroke counts and stroke locations and further categorization of overlapping cerebrovascular and AD pathologies that contribute to dementia. This will allow for better models and a more thorough understanding of how vascular disease contributes to dementia.

GENERAL SIGNIFICANCE

VCID is the second most common form of dementia and is expected to increase in coming years. The heterogeneity of VCID makes it difficult to study, but without better definitions and models, VCID presents a major public health problem for our aging population. This article is part of a Special Issue entitled: Vascular Contributions to Cognitive Impairment and Dementia, edited by M. Paul Murphy, Roderick A. Corriveau and Donna M. Wilcock.

Acupuncture ameliorates cognitive impairment and hippocampus neuronal loss in experimental vascular dementia through Nrf2-mediated antioxidant response

Emerging evidence suggests acupuncture could exert neuroprotection in the vascular dementia via anti-oxidative effects. However, the involvement of Nrf2, a master regulator of antioxidant defense, in acupuncture-induced neuroprotection in vascular dementia remains undetermined. The goal of our study was to investigate the contribution of Nrf2 in acupuncture and its effects on vascular dementia. Morris water maze and Nissl staining were used to assess the effect of acupuncture on cognitive function and hippocampal neurodegeneration in experimental vascular dementia. The distribution of Nrf2 in neurons in hippocampus, the protein expression of Nrf2 in both cytosol and nucleus, and the protein and mRNA levels of its downstream target genes NQO1 and HO-1 were detected by double immunofluorescent staining, Western blotting and realtime PCR analysis respectively. Cognitive function and microglia activation were measured in both wild-type and Nrf2 gene knockout mice after acupuncture treatment. We found that acupuncture could remarkably reverse the cognitive deficits, neuron cell loss, reactive oxygen species production, and decreased cerebral blood flow. It was notable that acupuncture enhanced nuclear translocation of Nrf2 in neurons and up-regulate the protein and mRNA levels of Nrf2 and its target genes HO-1 and NQO1. Moreover, acupuncture could significantly down-regulated the over-activation of microglia after common carotid artery occlusion surgery. However, the reversed cognitive deficits, neuron cell loss and microglia activation by acupuncture were abolished in Nrf2 gene knockout mice. In conclusion, these findings provide evidence that the neuroprotection of acupuncture in models of vascular dementia was via the Nrf2 activation and Nrf2-dependent microglia activation.

Hippocampal diffusion tensor imaging microstructural changes in vascular dementia

To explore microstructural integrity of hippocampus in vascular dementia (VD) using DTI. Twenty-five individuals with VD, without magnetic resonance imaging (MRI) evidence of gray matter pathology, and 25 matched healthy control (HC) individuals underwent a 3T MRI protocol including T2, FLAIR, and PD in the axial plane, 3D whole-brain T1-weighted with an isotropic resolution of 1 mm, and DTI acquired using 64 diffusion sensitizing directions, b value of 1,500 s/mm(2), 65 axial slices, isotropic resolution of 1.8 mm. Images were processed to obtain indices of microstructural variations of bilateral hippocampi. Mean diffusivity (MD) in the hippocampus of patients with VD was significantly increased (p < 0.05) bilaterally with respect to that of the group of HC examinees. In VD group left hippocampal MD (10(-6 )× mm(2)/s) was 833.4 ± 92.8; in HC group left MD was 699.8 ± 56. In VD group, right hippocampal MD was 859.1 ± 69.8; in HC group right MD was 730.4 ± 40.2. No group differences were found in hippocampal FA. DTI shows microstructural hippocampal damage in VD in patients with normal appearing gray matter structures on conventional MRI, indicating the need for further research on the link between VD and AD.

Gastrodin improves cognitive dysfunction and decreases oxidative stress in vascular dementia rats induced by chronic ischemia

OBJECTIVE

To study the potential protective effects of gastrodin on reducing tissue oxidative stress and attenuating cognitive deficits in vascular dementia induced by cerebral chronic hyperfusion. To explore the detailed molecular mechanisms.

METHODS

6 to 8 week old male Wistar rats were adopted as experimental animals. Animals were divided into the following groups: Group 1 (sham group with no occlusion), Group 2 (control group with 2VO procedure), Group 3 (sham group with gastrodin administration), Group 4 (2VO group with gastrodin administration). Morris water maze (MWM) test was adopted to test the learning and memory function of rats within different groups. MDA, glutathione peroxidase and total thiol assessment was done to reflect the oxidative stress in the brain tissue. Cell counting kit-8 (CCK8) and flow cytometry (FCM) were performed to examine the cell viability and apoptosis rate of SH-SY5Y cells induced by hydrogen peroxide and rescued by gastrodin treatments. Reactive oxygen species (ROS) generation was determined by the 2', 7'-dichlorofluorescein diacetate (DCFH-DA) assay. qPCR and Western blot (WB) were adopted to detect the molecular mechanisms related to the anti-apoptosis and ROS scavenging effects of gastrodin.

RESULTS

Our results indicated an obvious protective effect of gastrodin on vascular dementia induced brain ischemia. Administration of gastrodin could improve the impaired learning and memory function induced by 2VO procedure in rats. The levels of MDA were partially decreased by the administration of gastrodin. The levels of glutathione peroxidase and total thiol were partially restored by the administration of gastrodin. Cell viability was improved by gastrodin in a dose-dependent pattern on SH-SY5Y cells induced by hydrogen peroxide (P < 0.05). Cell apoptosis rate was reduced by gastrodin in a dose-dependent pattern on SH-SY5Y cells induced by hydrogen peroxide (P < 0.05). Gastrodin could scavenge ROS generation induced by pre-treatment of hydrogen peroxide. Both qPCR and WB results showed significant enhancements on the expression levels of NFE2L2, ADH7, GPX2 and GPX3 (P < 0.05).

CONCLUSION

Gastrodin administration is protective on the learning and memory functions that might be affected by vascular dementia induced oxidative stress due to brain ischemia. On the molecular level, NFE2L2, ADH7, GPX2 and GPX3 were up regulated by gastrodin.

Long-Term Blood-Brain Barrier Permeability Changes in Binswanger Disease

BACKGROUND AND PURPOSE

The blood-brain barrier (BBB) is disrupted in small vessel disease patients with lacunes and white matter hyperintensities (WMHs). The relationship of WMHs and regional BBB permeability changes has not been studied. We hypothesized that BBB disruption occurs in normal appearing WM and regions near the WMHs. To test the hypothesis, we repeated BBB permeability measurements in patients with extensive WMHs related to Binswanger disease.

METHODS

We selected a subset of 22 Binswanger disease subjects from a well-characterized larger prospective vascular cognitive impairment cohort. We used 16 age-matched controls for comparison. The abnormal WM permeability (WMP) was measured twice for several years using dynamic contrast-enhanced magnetic resonance imaging. WMP maps were constructed from voxels above a predetermined threshold. Scans from first and second visits were coregistered. WM was divided into 3 regions: normal appearing WM, WMH ring, and WMH core. The ring was defined as 2 mm on each side of the WMH border. WMP was calculated in each of the 3 specific regions. We used paired t test, ANOVA, and Fisher exact test to compare individual changes.

RESULTS

WMP was significantly higher in subjects than in controls (P<0.001). There was no correlation between WMH load and WMP. High permeability regions had minimal overlap between first and second scans. Nine percent of WMP was within the WMHs, 49% within the normal appearing WM, and 52% within the WMH ring (P<0.001; ANOVA).

CONCLUSIONS

Increased BBB permeability in normal appearing WM and close to the WMH borders supports a relationship between BBB disruption and the development of WMHs.

Caspase-Cleaved Tau Co-Localizes with Early Tangle Markers in the Human Vascular Dementia Brain

Vascular dementia (VaD) is the second most common form of dementia in the United States and is characterized as a cerebral vessel vascular disease that leads to ischemic episodes. Whereas the relationship between caspase-cleaved tau and neurofibrillary tangles (NFTs) in Alzheimer's disease (AD) has been previously described, whether caspase activation and cleavage of tau occurs in VaD is presently unknown. To investigate a potential role for caspase-cleaved tau in VaD, we analyzed seven confirmed cases of VaD by immunohistochemistry utilizing a well-characterized antibody that specifically detects caspase-cleaved tau truncated at Asp421. Application of this antibody (TauC3) revealed consistent labeling within NFTs, dystrophic neurites within plaque-rich regions and corpora amylacea (CA) in the human VaD brain. Labeling of CA by the TauC3 antibody was widespread throughout the hippocampus proper, was significantly higher compared to age matched controls, and co-localized with ubiquitin. Staining of the TauC3 antibody co-localized with MC-1, AT8, and PHF-1 within NFTs. Quantitative analysis indicated that roughly 90% of PHF-1-labeled NFTs contained caspase-cleaved tau. In addition, we documented the presence of active caspase-3 within plaques, blood vessels and pretangle neurons that co-localized with TauC3. Collectively, these data support a role for the activation of caspase-3 and proteolytic cleavage of TauC3 in VaD providing further support for the involvement of this family of proteases in NFT pathology.

Interaction between hypertension and cerebral hypoperfusion in the development of cognitive dysfunction and white matter pathology in rats

Hypertension is the most significant modifiable risk factor for vascular cognitive impairment. However, influence of hypertension on the development of ischemic white matter injury and cognitive dysfunction is not fully understood. We compared cognitive functions and neuropathological outcomes of chronic cerebral hypoperfusion induced by bilateral common carotid artery occlusion (BCCAO) between normotensive rats (NRs) and spontaneously hypertensive rats (SHRs). SHRs developed earlier and more severe deficits in spatial memory performance than NRs following BCCAO. Although no significant changes in the gross structure of myelinated white matter or oligodendrocyte number were noted, BCCAO resulted in subtle myelin degeneration and paranodal structural alterations at the nodes of Ranvier, regardless of hypertension. Disruption of the blood-brain barrier (BBB) was predominantly observed in the white matter of SHRs following BCCAO, implying a role of hypertension in BBB dysfunction in chronic cerebral hypoperfusion. In chronic cerebral ischemia, long-standing hypertension may aggravate impairment of BBB integrity, and the leaky BBB may in turn exacerbate dysfunction in the white matter leading to worsening of spatial cognitive performance.