Subcortical vascular dementia

Brain-derived neurotrophic factor gene polymorphism affects cognitive function and neurofilament light chain level in patients with subcortical ischaemic vascular dementia

Objective

To investigate the effects of brain-derived neurotrophic factor (BDNF) gene polymorphism on cognitive function, neuroimaging and blood biological markers in patients with subcortical ischaemic vascular dementia (SIVD).

Methods

A total of 81 patients with SIVD were included. According to their BDNF gene polymorphism, the participants were divided into the Val/Val (n = 26), Val/Met (n = 35), and Met/Met (n = 20) groups. A comprehensive neuropsychological evaluation and multimodal brain MRI scan were performed. MRI markers for small vessel disease were visually rated or quantitatively analysed. Moreover, 52 patients were further evaluated with blood marker assays, including amyloid beta (Aβ), phosphorylated tau at threonine-181 (P-tau181), glial fibrillary acidic protein (GFAP), total tau (T-tau) and neurofilament light chain (NfL).

Results

There were no significant differences in demographics, disease duration or MRI markers of small vessel disease between the three groups. Compared with the Val/Val and Val/Met groups, the Met/Met group showed worse performance in the verbal fluency test and higher levels of plasma NfL.

Conclusion

The rs6265 polymorphism of the BDNF gene is associated with semantic language fluency in patients with SIVD. The Met genotype may be a risk factor for cognitive impairment and neuronal injury.

Vascular dementia subtypes, pathophysiology, genetics, neuroimaging, biomarkers, and treatment updates along with its association with Alzheimer's dementia and diabetes mellitus

Dementia is a chronic progressive cognitive decline illness that results in functional impairment. Vascular dementia (VaD), second only to Alzheimer's disease (AD), is one of the most prevalent forms of dementia in the elderly (aged over 65 years), with a varied presentation and unpredictable disease development caused by cerebrovascular or cardiovascular illness. To get a better understanding of the changes occurring in the brain and to drive therapy efforts, new biomarkers for early and precise diagnosis of AD and VaD are required. In this review, Firstly, we describe the subtypes of vascular dementia, their clinical features, pathogenesis, genetics implemented, and their associated neuroimaging and biomarkers, while describing extensively the recent biomarkers discovered in the literature. Secondly, we describe some of the well-documented and other less-defined risk factors and their association and pathophysiology in relation to vascular dementia. Finally, we follow recent updates in the management of vascular dementia along with its association and differentiation from Alzheimer's disease. The aim of this review is to gather the scattered updates and the most recent changes in blood, CSF, and neuroimaging biomarkers related to the multiple subtypes of vascular dementia along with its association with Alzheimer's dementia and diabetes mellitus.

Willis Lecture: Biomarkers for Inflammatory White Matter Injury in Binswanger Disease Provide Pathways to Precision Medicine

Binswanger disease is the small vessel form of vascular cognitive impairment and dementia. Deposition of Alzheimer disease proteins can begin in midlife and progress slowly, whereas aging of the vasculature also can begin in midlife, continuing to progress into old age, making mixed dementia the most common type of dementia. Biomarkers facilitate the early diagnosis of dementias. It is possible to diagnose mixed dementia before autopsy with biomarkers for vascular disease derived from diffusor tensor images on magnetic resonance imaging and Alzheimer disease proteins, Aβ (amyloid β), and phosphorylated tau, in cerebrospinal fluid or in brain with positron emission tomography. The presence of vascular disease accelerates cognitive decline. Both misfolded proteins and vascular disease promote inflammation, which can be detected in cerebrospinal fluid by the presence of MMPs (matrix metalloproteinases), angiogenic growth factors, and cytokines. MMPs disrupt the blood-brain barrier and break down myelin, producing Binswanger disease's 2 main pathological features. Advances in detecting biomarkers in plasma will provide early detection of dementia and aided by machine learning and artificial intelligence, will enhance diagnosis and form the basis for early treatments.

Cognitive Decline in Older People with Multiple Sclerosis—A Narrative Review of the Literature

Several important questions regarding cognitive aging and dementia in older people with multiple sclerosis (PwMS) are the focus of this narrative review: Do older PwMS have worse cognitive decline compared to older people without MS? Can older PwMS develop dementia or other neurodegenerative diseases such as Alzheimer’s disease (AD) that may be accelerated due to MS? Are there any potential biomarkers that can help to determine the etiology of cognitive decline in older PwMS? What are the neural and cellular bases of cognitive aging and neurodegeneration in MS? Current evidence suggests that cognitive impairment in MS is distinguishable from that due to other neurodegenerative diseases, although older PwMS may present with accelerated cognitive decline. While dementia is prevalent in PwMS, there is currently no consensus on defining it. Cerebrospinal fluid and imaging biomarkers have the potential to identify disease processes linked to MS and other comorbidities—such as AD and vascular disease—in older PwMS, although more research is required. In conclusion, one should be aware that multiple underlying pathologies can coexist in older PwMS and cause cognitive decline. Future basic and clinical research will need to consider these complex factors to better understand the underlying pathophysiology, and to improve diagnostic accuracy.

Inflammatory Biomarkers Aid in Diagnosis of Dementia

Dual pathology of Alzheimer's disease (AD) and vascular cognitive impairment and dementia (VCID) commonly are found together at autopsy, but mixed dementia (MX) is difficult to diagnose during life. Biological criteria to diagnose AD have been defined, but are not available for vascular disease. We used the biological criteria for AD and white matter injury based on MRI to diagnose MX. Then we measured multiple biomarkers in CSF and blood with multiplex biomarker kits for proteases, angiogenic factors, and cytokines to explore pathophysiology in each group. Finally, we used machine learning with the Random forest algorithm to select the biomarkers of maximal importance; that analysis identified three proteases, matrix metalloproteinase-10 (MMP-10), MMP-3 and MMP-1; three angiogenic factors, VEGF-C, Tie-2 and PLGF, and three cytokines interleukin-2 (IL-2), IL-6, IL-13. To confirm the clinical importance of the variables, we showed that they correlated with results of neuropsychological testing.

Vascular Dementia and Underlying Sex Differences

Vascular dementia (VaD) is the second most common form of dementia after Alzheimer's disease (AD); where Alzheimer's accounts for 60-70% of cases of dementia and VaD accounts for 20% of all dementia cases. VaD is defined as a reduced or lack of blood flow to the brain that causes dementia. VaD is also known occasionally as vascular contributions to cognitive impairment and dementia (VCID) or multi-infarct dementia (MID). VCID is the condition arising from stroke and other vascular brain injuries that cause significant changes to memory, thinking, and behavior, and VaD is the most severe stage while MID is produced by the synergistic effects caused by multiple mini strokes in the brain irrespective of specific location or volume. There are also subtle differences in the presentation of VaD in males and females, but they are often overlooked. Since 1672 when the first case of VaD was reported until now, sex and gender differences have had little to no research done when it comes to the umbrella term of dementia in general. This review summarizes the fundamentals of VaD followed by a focus on the differences between sex and gender when an individual is diagnosed. In addition, we provide critical evidence concerning sex and gender differences with a few of the main risk factors of VaD including pre-existing health conditions and family history, gene variants, aging, hormone fluctuations, and environmental risk factors. Additionally, the pharmaceutical treatments and possible mitigation of risk factors is explored.

Shared and oppositely regulated transcriptomic signatures in Huntington's disease and brain ischemia confirm known and unveil novel potential neuroprotective genes

Huntington's disease and subcortical vascular dementia display similar dementing features, shaped by different degrees of striatal atrophy, deep white matter degeneration and tau pathology. To investigate the hypothesis that Huntington's disease transcriptomic hallmarks may provide a window into potential protective genes upregulated during brain acute and subacute ischemia, we compared RNA sequencing signatures in the most affected brain areas of 2 widely used experimental mouse models: Huntington's disease, (R6/2, striatum and cortex and Q175, hippocampus) and brain ischemia-subcortical vascular dementia (BCCAS, striatum, cortex and hippocampus). We identified a cluster of 55 shared genes significantly differentially regulated in both models and we screened these in 2 different mouse models of Alzheimer's disease, and 96 early-onset familial and apparently sporadic small vessel ischemic disease patients. Our data support the prevalent role of transcriptional regulation upon genetic coding variability of known neuroprotective genes (Egr2, Fos, Ptgs2, Itga5, Cdkn1a, Gsn, Npas4, Btg2, Cebpb) and provide a list of potential additional ones likely implicated in different dementing disorders and worth further investigation.

Investigation of hypertensive arteriopathy-related and cerebral amyloid angiopathy-related small vessel disease scores in patients from a memory clinic: a prospective single-centre study

Objective

The severity of cerebral small vessel disease (SVD) is assessed through neuroimaging findings, including hypertensive arteriopathy (HA)-SVD and cerebral amyloid angiopathy (CAA)-SVD. HA-SVD and CAA-SVD have been collectively estimated as total scores: the HA-SVD and CAA-SVD scores, respectively. Previous reports suggest that HA-SVD scores are associated with cognitive function; however, the relationship between CAA-SVD scores and cognitive function remains unclear. Therefore, we examined the association between CAA-SVD scores and cognitive function. Furthermore, we developed a modified CAA-SVD score considering cortical microinfarcts and posterior dominant white matter hyperintensities, which are imaging findings of CAA, and examined the association between these scores and cognitive function in the same patient group.

Design

Prospective study.

Setting

Single centre study from a memory clinic.

Participants

Subjects were diagnosed with mild cognitive impairment (MCI) or mild dementia in our memory clinic between February 2017 and July 2019 and underwent clinical dementia rating scale and brain MRI assessment. A total of 42 patients (aged 75.3±9.12 years) were registered prospectively.

Primary and secondary outcome measures

We evaluated intellectual function, memory, frontal lobe function and constructional ability. Furthermore, the relationship between each score and cognitive function was examined.

Results

The CAA-SVD score showed significant associations with cognitive function (R²=0.63, p=0.016), but the HA-SVD score did not (R²=0.41, p=0.35). The modified CAA-SVD score was also significantly associated with cognitive function (R²=0.65, p=0.008).

Conclusion

Cognitive function is associated with the CAA-SVD score, and more efficiently with the modified CAA-SVD score, in memory clinic patients. Although we have not validated the weighting of the modified CAA-SVD score, these scores can be a predictor of cognitive deterioration in patients with MCI and mild dementia.

Clinical Features and Experimental Models of Cerebral Small Vessel Disease

Cerebral small vessel disease (SVD) refers to a group of disease conditions affecting the cerebral small vessels, which include the small arteries, arterioles, capillaries, and postcapillary venules in the brain. SVD is the primary cause of vascular cognitive impairment and gait disturbances in aged people. There are several types of SVD, though arteriolosclerosis, which is mainly associated with hypertension, aging, and diabetes mellitus, and cerebral amyloid angiopathy (CAA) comprise most SVD cases. The pathology of arteriolosclerosis-induced SVD is characterized by fibrinoid necrosis and lipohyalinosis, while CAA-associated SVD is characterized by progressive deposition of amyloid beta (Aβ) protein in the cerebral vessels. Brain magnetic resonance imaging (MRI) has been used for examination of SVD lesions; typical lesions are characterized by white matter hyperintensity, lacunar infarcts, enlargement of perivascular spaces (EPVS), microbleeds, cortical superficial siderosis (cSS), and cortical microinfarcts. The microvascular changes that occur in the small vessels are difficult to identify clearly; however, these consequent image findings can represent the SVD. There are two main strategies for prevention and treatment of SVD, i.e., pharmacotherapy and lifestyle modification. In this review, we discuss clinical features of SVD, experimental models replicating SVD, and treatments to further understand the pathological and clinical features of SVD.

Intracerebral Transcatheter Laser Photobiomodulation Therapy in the Treatment of Binswanger's Disease and Vascular Parkinsonism: Research and Clinical Experience

Objective: This research is devoted to intracerebral transcatheter laser photobiomodulation therapy (PBMT) in the treatment of ischemic and neurodegenerative lesions of cerebral white matter in patients with Binswanger's disease (BD) and vascular parkinsonism (VP) in comparison with conservative treatment methods. Background: Recent studies have shown PBMT high potential in the treatment of various cerebral lesions. Materials and methods: Twenty-seven patients with BD, 58-81 years of age (mean age 78), 17 (62.96%) men, and 10 (27.04%) women. Of these, test group 1-14 (51.85%) patients-underwent intracerebral transcatheter laser PBMT, and control group 1-13 (48.15%) patients-had conservative treatment. Besides, 62 patients with VP, 52-80 years of age (mean age 77), 48 (77.42%) men, and 14 (22.58%) women. Of these, test group 2-37 (59.68%) patients-underwent intracerebral transcatheter laser PBMT, and control group 2-25 (40.32%) patients-had conservative treatment. Results: Good and satisfactory clinical results were obtained in Test group 1 and Test group 2 patients in 49 (92.45%) cases, with a persistent decrease of dementia and motor impairment, and recovery of cognitive functions and daily life activity. Control group 1 and Control group 2 patients showed a satisfactory clinical result in 6 (15.79%) cases. Persistent positive dynamics was not observed. Conclusions: Intracerebral transcatheter laser PBMT is a pathogenetically justified, effective treatment for BD and VP; it restores cerebral collateral and capillary blood supply, improves microcirculation, restores cellular and tissue metabolism, stimulates neurogenesis, and causes regenerative processes in the brain.

Small vessel disease to subcortical dementia: a dynamic model, which interfaces aging, cholinergic dysregulation and the neurovascular unit

Background

Small vessels have the pivotal role for the brain’s autoregulation. The arteriosclerosis-dependent alteration of the brain perfusion is one of the major determinants in small vessel disease. Endothelium distress can potentiate the flow dysregulation and lead to subcortical vascular dementia (sVAD). sVAD increases morbidity and disability. Epidemiological studies have shown that sVAD shares with cerebrovascular disease most of the common risk factors. The molecular basis of this pathology remains controversial.

Purpose

To detect the possible mechanisms between small vessel disease and sVAD, giving a broad vision on the topic, including pathological aspects, clinical and laboratory findings, metabolic process and cholinergic dysfunction.

Methods

We searched MEDLINE using different search terms (“vascular dementia”, “subcortical vascular dementia”, “small vessel disease”, “cholinergic afferents”, etc). Publications were selected from the past 20 years. Searches were extended to Embase, Cochrane Library, and LILIACS databases. All searches were done from January 1, 1998 up to January 31, 2018.

Results

A total of 560 studies showed up, and appropriate studies were included. Associations between traditional vascular risk factors have been isolated. We remarked that SVD and white matter abnormalities are seen frequently with aging and also that vascular and endothelium changes are related with age; the changes can be accelerated by different vascular risk factors. Vascular function changes can be heavily influenced by genetic and epigenetic factors.

Conclusion

Small vessel disease and the related dementia are two pathologies that deserve attention for their relevance and impact in clinical practice. Hypertension might be a historical problem for SVD and SVAD, but low pressure might be even more dangerous; CBF regional selective decrease seems to be a critical factor for small vessel disease-related dementia. In those patients, endothelium damage is a super-imposed condition. Several issues are still debatable, and more research is needed.

A mouse model of subcortical vascular dementia reflecting degeneration of cerebral white matter and microcirculation

Subcortical vascular dementia(SVaD) is associated with white matter damage, lacunar infarction, and degeneration of cerebral microcirculation. Currently available mouse models can mimic only partial aspects of human SVaD features. Here, we combined bilateral common carotid artery stenosis (BCAS) with a hyperlipidaemia model in order to develop a mouse model of SVaD; 10- to 12-week-old apolipoprotein E (ApoE)-deficient or wild-type C57BL/6J mice were subjected to sham operation or chronic cerebral hypoperfusion with BCAS using micro-coils. Behavioural performance (locomotion, spatial working memory, and recognition memory), histopathological findings (white matter damage, microinfarctions, astrogliosis), and cerebral microcirculation (microvascular density and blood-brain barrier (BBB) integrity) were investigated. ApoE-deficient mice subjected to BCAS showed impaired locomotion, spatial working memory, and recognition memory. They also showed white matter damage, multiple microinfarctions, astrogliosis, reduction in microvascular density, and BBB breakdown. The combination of chronic cerebral hypoperfusion and ApoE deficiency induced cognitive decline and cerebrovascular pathology, including white matter damage, multiple microinfarctions, and degeneration of cerebral microcirculation. Together, these features are all compatible with those of patients with SVaD. Thus, the proposed animal model is plausible for investigating SVaD pathophysiology and for application in preclinical drug studies.

Vascular cognitive impairment: A preventable component of dementia

For many decades during the 20th century, the common belief was that the slow strangulation of the brains' blood supply from hardening of the brain arteries led to chronic brain ischemia and neuronal death. Not surprisingly, to counter this, vasodilators rapidly became one of the most commonly used and profitable medications worldwide; however, no clinical benefits were ever proven. In the 1970s and early 1980s cerebral blood flow studies strongly disproved the idea of brain failure due to chronic ischemia. It was also shown that infarcts and not chronic ischemia caused dementia, leading to the concept of multiinfarct dementia. In addition to infarcts, it was then realized that other vascular lesions can also cause cognitive decline. Gradually, as "atherosclerotic dementia" lost ground, Alzheimer's disease (AD) that once had been considered a presenile dementia and rare, became almost synonymous with dementia. Subsequent memory-based definitions and evaluations of dementia led to a bias in favor of diagnosing AD, overshadowing vascular contributions. The widespread use of brain imaging in the 1980s and 1990s contributed to the resurgence of evidence of cerebrovascular diseases. Moreover, it was shown that most cognitive impairment of the elderly results from mixed pathologies, emphasizing the need for a change in the traditional categorical diagnosis of dementia, e.g., AD vs vascular dementia. The alternative diagnostic method was named the vascular cognitive impairment approach, meaning identifying any impairment caused by or associated with vascular factors. The importance of this approach is that vascular lesions are currently the most important treatable and preventable components of dementia, even before any symptoms manifest, i.e., at the brain at risk stage. This chapter provides a summary of the vascular cognitive impairment approach to diagnosis, treatment, and prevention of cognitive decline.

Chronic neurological disorders and related comorbidities: Role of age-associated physiological changes

Current knowledge indicates that the physiological aging process starts with subclinical changes at the molecular and cellular level, which affect nearly all physiological systems. For example, the age-associated remodeling of the immune system (i.e., immunosenescence) and vascular aging per se can contribute to frailty and vulnerability among older adults. They are also described as being implicated in the pathophysiology of some major chronic comorbid conditions such as age-associated diseases of the central (e.g., stroke, Parkinson's disease, Alzheimer's disease, and related disorders) and peripheral (e.g., polyneuropathy) nervous systems. These neurologic disorders are also among the greatest contributors to geriatric syndromes, which refer to highly prevalent and chronic conditions among aged people of multifactorial origin, such as delirium, falls, incontinence, and frailty. Neurologic disorders can also occur in patients with one or more geriatric syndromes and thus further interfere with the quality of life, physical function, morbidity, and mortality. This chapter presents and discusses in three sections the complex interrelationships between the main determinants of aging with a specific focus on vascular aging, chronic neurologic disorders, and the specific clinical presentation of geriatric syndromes in older people.

Mapping water exchange across the blood-brain barrier using 3D diffusion-prepared arterial spin labeled perfusion MRI

PURPOSE

To present a novel MR pulse sequence and modeling algorithm to quantify the water exchange rate (k_w ) across the blood-brain barrier (BBB) without contrast, and to evaluate its clinical utility in a cohort of elderly subjects at risk of cerebral small vessel disease (SVD).

METHODS

A diffusion preparation module with spoiling of non-Carr-Purcell-Meiboom-Gill signals was integrated with pseudo-continuous arterial spin labeling (pCASL) and 3D gradient and spin echo (GRASE) readout. The tissue/capillary fraction of the arterial spin labeling (ASL) signal was separated by appropriate diffusion weighting (b = 50 s/mm² ). k_w was quantified using a single-pass approximation (SPA) model with total generalized variation (TGV) regularization. Nineteen elderly subjects were recruited and underwent 2 MRIs to evaluate the reproducibility of the proposed technique. Correlation analysis was performed between k_w and vascular risk factors, Clinical Dementia Rating (CDR) scale, neurocognitive assessments, and white matter hyperintensity (WMH).

RESULTS

The capillary/tissue fraction of ASL signal can be reliably differentiated with the diffusion weighting of b = 50 s/mm² , given ~100-fold difference between the (pseudo-)diffusion coefficients of the 2 compartments. Good reproducibility of k_w measurements (intraclass correlation coefficient = 0.75) was achieved. Average k_w was 105.0 ± 20.6, 109.6 ± 18.9, and 94.1 ± 19.6 min^-1 for whole brain, gray and white matter. k_w was increased by 28.2%/19.5% in subjects with diabetes/hypercholesterolemia. Significant correlations between k_w and vascular risk factors, CDR, executive/memory function, and the Fazekas scale of WMH were observed.

CONCLUSION

A diffusion prepared 3D GRASE pCASL sequence with TGV regularized SPA modeling was proposed to measure BBB water permeability noninvasively with good reproducibility. k_w may serve as an imaging marker of cerebral SVD and associated cognitive impairment.

Neuropsychological Features of Microbleeds and Cortical Microinfarct Detected by High Resolution Magnetic Resonance Imaging

BACKGROUND

Lobar microbleeds (MBs) and cortical microinfarct (CMI) are caused by cerebral amyloid angiopathy in the elderly and increase in number in Alzheimer's disease.

OBJECTIVE

The aim of this study is to elucidate the effects of lobar MBs and CMIs on cognitive function.

METHODS

The subjects were outpatients who visited the memory clinic of Mie University Hospital. Among 120 subjects, 109 patients fulfilled the inclusion criteria. We quantitatively estimated MBs and CMIs using double inversion recovery and 3D FLAIR images of 3T MRI. Neuropsychological assessments included intellectual, memory, constructional, and frontal lobe function.

RESULTS

Of the 109 patients, MBs and CMIs were observed in 68 (62%) and 17 (16%) subjects, respectively. Of the 68 patients with MBs, lobar MBs were found in 28, deep MBs in 8 and mixed MBs in 31. In each age group, the number of MBs increased in patients with CMI (CMI+ group) than those without CMI (CMI- group), and MBs and CMIs additively decreased MMSE scores. In psychological screens, the MBs+ group with more than 10 MBs showed significantly lower scores of category- and letter-WF than MB- group. The CMI+ group showed significantly worse scores than CMI- group in Japanese Raven's coloured progressive matrices, Trail Making Test-A, category- and letter-word fluency and copy and drawing of figures.

CONCLUSION

Lobar MBs and CMIs in the elderly frequently coexisted with each other and additively contributed to cognitive impairment, which is mainly predisposed to frontal lobe function.

Cerebral gray matter volume reduction in subcortical vascular mild cognitive impairment patients and subcortical vascular dementia patients, and its relation with cognitive deficits

INTRODUCTION

Subcortical vascular mild cognitive impairment (svMCI) is the predementia stage of subcortical vascular dementia (SVaD). The aim of this research is to explore and compare cerebral gray matter (GM) volume reduction in svMCI patients and SVaD patients, and to investigate the relationship between cerebral GM volume reduction and cognitive deficits.

METHODS

Thirty one svMCI patients, 29 SVaD patients, and 31 healthy controls were recruited in our research. They conducted neuropsychological tests and brain structural magnetic resonance imaging (MRI) examination. To detect cerebral GM volume reduction in svMCI patients and SVaD patients, we used statistical parametric mapping 8-voxel-based morphometry 8 (SPM8-VBM8) method to analyze MRI data. To detect the relationship between cerebral GM volume reduction and cognitive deficits, multiple linear regression analysis was used.

RESULTS

Compared with healthy controls, svMCI patients showed cerebral GM volume reduction in hippocampus and parahippocampal gyrus, insula and superior temporal gyrus. Compared with healthy controls, SVaD patients exhibited more atrophy which encompasses all of these areas plus anterior and middle cingulate, inferior temporal gyrus, orbitofrontal cortex, and superior frontal gyrus. In svMCI patients, cerebral GM volume reduction correlated with memory loss, attention dysfunction, and language dysfunction; in SVaD patients, besides those cognitive deficits, cerebral GM volume reduction correlated with more cognitive impairments, including executive dysfunction, neuropsychiatric symptom, and depression.

CONCLUSIONS

Our findings prove that both svMCI patients and SVaD patients exhibit cerebral GM volume reduction and there may exist a hierarchy between svMCI and SVaD, and cerebral GM volume reduction in both svMCI patients and SVaD patients correlates with cognitive deficits, which can help us understand the mechanism of cognitive impairments in svMCI patients and SVaD patients, and diagnose SVaD at its early stage.

Arterial stiffness and cognitive impairment

BACKGROUND

Arterial stiffness is one of the earliest indicators of changes in vascular wall structure and function and may be assessed using various indicators, such as pulse-wave velocity (PWV), the cardio-ankle vascular index (CAVI), the ankle-brachial index (ABI), pulse pressure (PP), the augmentation index (AI), flow-mediated dilation (FMD), carotid intima media thickness (IMT) and arterial stiffness index-β. Arterial stiffness is generally considered an independent predictor of cardiovascular and cerebrovascular diseases. To date, a significant number of studies have focused on the relationship between arterial stiffness and cognitive impairment.

OBJECTIVES AND METHODS

To investigate the relationships between specific arterial stiffness parameters and cognitive impairment, elucidate the pathophysiological mechanisms underlying the relationship between arterial stiffness and cognitive impairment and determine how to interfere with arterial stiffness to prevent cognitive impairment, we searched PUBMED for studies regarding the relationship between arterial stiffness and cognitive impairment that were published from 2000 to 2017. We used the following key words in our search: "arterial stiffness and cognitive impairment" and "arterial stiffness and cognitive impairment mechanism". Studies involving human subjects older than 30years were included in the review, while irrelevant studies (i.e., studies involving subjects with comorbid kidney disease, diabetes and cardiac disease) were excluded from the review.

RESULTS

We determined that arterial stiffness severity was positively correlated with cognitive impairment. Of the markers used to assess arterial stiffness, a higher PWV, CAVI, AI, IMT and index-β and a lower ABI and FMD were related to cognitive impairment. However, the relationship between PP and cognitive impairment remained controversial. The potential mechanisms linking arterial stiffness and cognitive impairment may be associated with arterial pulsatility, as greater arterial pulsatility damages the cerebral microcirculation, which causes various phenomena associated with cerebral small vessel diseases (CSVDs), such as white matter hyperintensities (WMHs), cerebral microbleeds (CMBs), and lacunar infarctions (LIs). The mechanisms underlying the relationship between arterial stiffness and cognitive impairment may also be associated with reductions in white matter and gray matter integrity, medial temporal lobe atrophy and Aβ protein deposition. Engaging in more frequent physical exercise; increasing flavonoid and long-chain n-3 polyunsaturated fatty acid consumption; increasing tea, nitrite, dietary calcium and vitamin D intake; losing weight and taking medications intended to improve insulin sensitivity; quitting smoking; and using antihypertensive drugs and statins are early interventions and lifestyle changes that may be effective in preventing arterial stiffness and thus preventing cognitive impairment.

CONCLUSION

Arterial stiffness is a sensitive predictor of cognitive impairment, and arterial stiffness severity has the potential to serve as an indicator used to facilitate treatments designed to prevent or delay the onset and progression of dementia in elderly individuals. Early treatment of arterial stiffness is beneficial and recommended.

Rivastigmine: the advantages of dual inhibition of acetylcholinesterase and butyrylcholinesterase and its role in subcortical vascular dementia and Parkinson's disease dementia

Several studies have demonstrated clinical benefits of sustained cholinesterase inhibition with rivastigmine in Alzheimer's disease (AD) and Parkinson's disease dementia (PDD). Unlike donepezil and galantamine that selectively inhibit acetylcholinesterase (AChE; EC 3.1.1.7), rivastigmine is a unique cholinesterase inhibitor with both AChE and butyrylcholinesterase (BuChE; EC 3.1.1.8) inhibitory activity. Rivastigmine is also available as transdermal patch that has been approved by the US Food and Drug Administration for the treatment of mild, moderate, and severe AD as well as mild-to-moderate PDD. In this review, we explore the role of BuChE inhibition in addition to AChE inhibition with rivastigmine in the outcomes of cognition, global function, behavioral symptoms, and activities of daily living. Additionally, we review the evidence supporting the use of dual AChE-BuChE inhibitory activity of rivastigmine as a therapeutic strategy in the treatment of neurological disorders, with a focus on the role of rivastigmine in subcortical dementias such as vascular dementia (VaD) and PDD. Toward this objective, we performed a literature search in PubMed and Ovid with limits to articles published in the English language before June 2016. The available evidence from the literature suggests that the dual inhibition of AChE and BuChE may afford additional therapeutic potential of rivastigmine in subcortical dementias (subcortical VaD and PDD) with benefits on cognition and behavioral symptoms. Rivastigmine was found to specifically benefit executive dysfunction frequently observed in subcortical dementias; however, large randomized clinical studies are warranted to support these observations.

Elucidation of mechanism of blood-brain barrier damage for prevention and treatment of vascular dementia

It is well-known that the blood-brain barrier (BBB) plays significant roles in transporting intravascular substances into the brain. The BBB in cerebral capillaries essentially impedes the influx of intravascular compounds from the blood to the brain, while nutritive substances, such as glucose, can be selectively transported through several types of influx transporters in endothelial cells. In the choroid plexus, intravascular substances can invade the parenchyma as fenestrations exist in endothelial cells of capillaries. However, the substances cannot invade the ventricles easily as there are tight junctions between epithelial cells in the choroid plexus. This restricted movement of the substances across the cytoplasm of the epithelial cells constitutes a blood-cerebrospinal fluid barrier (BCSFB). In the brain, there are circumventricular organs, in which the barrier function is imperfect in capillaries. Accordingly, it is reasonable to consider that intravascular substances can move in and around the parenchyma of the organs. Actually, it was reported in mice that intravascular substances moved in the corpus callosum, medial portions of the hippocampus, and periventricular areas via the subfornical organs or the choroid plexus. Regarding pathways of intracerebral interstitial and cerebrospinal fluids to the outside of the brain, two representative drainage pathways, or perivascular drainage and glymphatic pathways, are being established. The first is the pathway in a retrograde direction to the blood flow through the basement membrane in walls of cerebral capillaries, the tunica media of arteries, and the vessels walls of the internal carotid artery. The second is in an anterograde direction to blood flow through the para-arterial routes, aquaporin 4-dependent transport through the astroglial cytoplasm, and para-venous routes, and then the fluids drain into the subarachnoid CSF. These fluids are finally considered to drain into the cervical lymph nodes or veins. These clearance pathways may play a role in maintenance of the barrier in the entire brain. Obstruction of the passage of fluids through the perivascular drainage and glymphatic pathways as well as damage of the BBB and BCSFB may induce several kinds of brain disorders, such as vascular dementia. In this review, we focus on the relationship between damage of the barriers and the pathogenesis of vascular dementia and introduce recent findings including our experimental data using animal models.

White matter hyperintensities and geriatric syndrome: An important role of arterial stiffness

White matter hyperintensities (WMH) are defined as cerebral white matter changes presumed to be of vascular origin, bilateral and mostly symmetrical. They can appear as hyperintense on T2-weighted and fluid-attenuated inversion recovery sequences, and as isointense or hypointense on T1-weighted magnetic resonance imaging of the brain. WMH have been focused on because of their clinical importance as a risk factor for cerebrovascular diseases and cognitive impairment. WMH are associated with geriatric syndrome, which is defined by clinical symptoms characteristic of older adults, including cognitive and functional impairment and falls. Cerebral small vessel diseases, such as WMH, might play an important role as risk factors for cerebrovascular diseases, cognitive impairment and geriatric syndrome through the mechanism of arterial stiffness. However, the vascular, physiological and metabolic roles of arterial stiffness remain unclear. Basically, arterial stiffness indicates microvessel arteriosclerosis presenting with vascular endothelial dysfunction. These changes might arise from hemodynamic stress as a result of a "tsunami effect" on cerebral parenchyma. In the present article, we review the clinical characteristics of WMH, focusing particularly on two associations: (i) those between cerebral small vessel diseases including WMH and arterial stiffness; and (ii) those between WMH and geriatric syndrome.

Hippocampal subfield volumetry in patients with subcortical vascular mild cognitive impairment

Memory impairment is a typical characteristic of patients with subcortical vascular mild cognitive impairment (svMCI) or with amnestic mild cognitive impairment (aMCI). The hippocampus, which plays an important role in the consolidation of information from short-term memory to long-term memory, is a heterogeneous structure that consists of several anatomically and functionally distinct subfields. However, whether distinct hippocampal subfields are differentially and selectively affected by svMCI pathology and whether these abnormal changes in hippocampal subfields are different between svMCI and aMCI patients are largely unknown. A total of 26 svMCI patients, 26 aMCI patients and 26 healthy controls matched according to age, gender and years of education were enrolled in this study. We utilized an automated hippocampal subfield segmentation method provided by FreeSurfer to estimate the volume of several hippocampal subfields, including the cornu ammonis (CA) areas, the dentate gyrus (DG), the subiculum and the presubiculum. Compared with controls, the left subiculum and presubiculum and the right CA4/DG displayed significant atrophy in patients with svMCI. Interestingly, we also found significant differences in the volume of the right CA1 between the svMCI and aMCI groups. Taken together, our results reveal region-specific vulnerability of hippocampal subfields to svMCI pathology and identify distinct hippocampal subfield atrophy patterns between svMCI and aMCI patients.

Cerebral Small Vessel Disease and Arterial Stiffness: Tsunami Effect in the Brain?

BACKGROUND

Cerebral small vessel diseases, including silent lacunar infarcts, white matter hyperintensities, and microbleeds, pose a risk for cerebrovascular disease, cognitive impairment, and the geriatric syndrome via effects on arterial stiffness. However, the vascular, physiological, and metabolic roles of arterial stiffness in cerebral small vessel diseases remain unclear.

SUMMARY

Arterial stiffness can be assessed using various indicators such as the ankle-brachial index, pulse wave velocity, cardio-ankle vascular index, and augmentation index. Arterial stiffness is independently associated with all components of cerebral small vessel disease including silent lacunar infarcts, white matter hyperintensities, and microbleeds, although there are some methodological differences between the various surrogate markers. Evidence of arterial stiffness indicates microvessel arteriosclerosis presenting with vascular endothelial dysfunction. Further, vascular narrowing due to atherosclerosis and vascular stiffness due to lipohyalinosis can accelerate the pulse waves. This hemodynamic stress, pulsatile pressure, or blood pressure variability can cause a 'tsunami effect' towards the cerebral parenchyma and lead to cerebral small vessel disease. Previous studies have shown that silent lacunar infarcts and white matter hyperintensities are strongly associated with arterial stiffness. However, the association between microbleeds and arterial stiffness remains controversial, as there are two vessel mechanisms related to microbleeds: cerebral amyloid angiopathy and hypertensive small vessel disease.

KEY MESSAGES

Cerebral small vessel disease with associated arterial stiffness is a risk factor for silent cerebral lesions, stroke, and cognitive impairment. Improvement of the living environment, management of risk factors, and innovation and development of novel drugs that improve arterial stiffness may suppress the progression of cerebral small vessel disease, and may reduce the risk for stroke and dementia.

Consensus statement for diagnosis of subcortical small vessel disease

Vascular cognitive impairment (VCI) is the diagnostic term used to describe a heterogeneous group of sporadic and hereditary diseases of the large and small blood vessels. Subcortical small vessel disease (SVD) leads to lacunar infarcts and progressive damage to the white matter. Patients with progressive damage to the white matter, referred to as Binswanger's disease (BD), constitute a spectrum from pure vascular disease to a mixture with neurodegenerative changes. Binswanger's disease patients are a relatively homogeneous subgroup with hypoxic hypoperfusion, lacunar infarcts, and inflammation that act synergistically to disrupt the blood-brain barrier (BBB) and break down myelin. Identification of this subgroup can be facilitated by multimodal disease markers obtained from clinical, cerebrospinal fluid, neuropsychological, and imaging studies. This consensus statement identifies a potential set of biomarkers based on underlying pathologic changes that could facilitate diagnosis and aid patient selection for future collaborative treatment trials.

Protective effects of carnosine on white matter damage induced by chronic cerebral hypoperfusion

Carnosine is a dipeptide that scavenges free radicals, inhibits inflammation in the central nervous system, and protects against ischemic and hypoxic brain damage through its anti-oxidative and anti-apoptotic actions. Therefore, we hypothesized that carnosine would also protect against white matter damage caused by subcortical ischemic injury. White matter damage was induced by right unilateral common carotid artery occlusion in mice. The animals were treated with 200, 500 or 750 mg/kg carnosine by intraperitoneal injection 30 minutes before injury and every other day after injury. Then, 37 days later, Klüver-Barrera staining, toluidine blue staining and immunofluorescence staining were performed. Carnosine (200, 500 mg/kg) substantially reduced damage to the white matter in the corpus callosum, internal capsule and optic tract, and it rescued expression of myelin basic protein, and alleviated the loss of oligodendrocytes. However, carnosine at the higher dose of 750 mg/kg did not have the same effects as the 200 and 500 mg/kg doses. These findings show that carnosine, at a particular dose range, protects against white matter damage caused by chronic cerebral ischemia in mice, likely by reducing oligodendroglial cell loss.

MMP-9 gene ablation mitigates hyperhomocystenemia-induced cognition and hearing dysfunction

Hyperhomocysteinemia (HHcy) is associated with cognitive decline and hearing loss due to vascular dysfunction. Although we have shown that HHcy-induced increased expression of matrix metalloproteinase-9 (MMP-9) is associated with cochlear pathology in cystathionine-β-synthase heterozygous (CBS(+/-)) mice, it is still unclear whether MMP-9 contributes to functional deficit in cognition and hearing. Therefore, we hypothesize that HHcy-induced MMP-9 activation causes vascular, cerebral and cochlear remodeling resulting in diminished cognition and hearing. Wildtype (WT), CBS(+/-), MMP-9(-/-) and CBS(+/-)/MMP-9(-/-) double knock-out (DKO) mice were genotyped and used. Doppler flowmetry of internal carotid artery (ICA) was performed for peak systolic velocity [PSV], pulsatility index [PI] and resistive index [RI]. Cognitive functions were assessed by Novel Object Recognition Test (NORT) and for cochlear function Auditory brainstem response (ABR) was elicited. Peak systolic velocity, pulsatility and resistive indices of ICA were decreased in CBS(+/-) mice, indicating reduced perfusion. ABR threshold was increased and maximum ABR amplitude and NORT indices (recognition, discrimination) were decreased in CBS(+/-) mice compared to WT and MMP-9(-/-). All these parameters were attenuated in DKO mice suggesting a significant role of MMP-9 in HHcy-induced vascular, neural and cochlear pathophysiology. Regression analysis of PSV with ABR and cognitive parameters revealed significant correlation (0.44-0.58). For the first time, MMP-9 has been correlated directly to functional deficits of brain and cochlea, and found to have a significant role. Our data suggests a dual pathology of HHcy occurring due to a decrease in blood supply (vasculo-neural and vasculo-cochlear) and direct tissue remodeling.

Clinical Neuropathological Analysis of 10 Cases of Cerebral Amyloid Angiopathy-Related Cerebral Lobar Hemorrhage

Objective

The clinical and pathological characteristics of 10 cases of cerebral amyloid angiopathy (CAA)-related cerebral lobar hemorrhage (CLH) that was diagnosed at autopsy were investigated to facilitate the diagnosis of this condition.

Methods

The clinical characteristics of 10 cases of CAA-related CLH were retrospectively reviewed, and a neuropathological examination was performed on autopsy samples.

Results

The 10 cases included two with a single lobar hemorrhage and eight with multifocal lobar hemorrhages. In all of the cases, the hemorrhage bled into the subarachnoid space. Pathological examinations of the 10 cases revealed microaneurysms in two, double barrel-like changes in four, multifocal arteriolar clusters in five, obliterative onion skin-like intimal changes in four, fibrinoid necrosis of the vessels in seven, neurofibrillary tangles in eight, and senile plaques in five cases.

Conclusion

CAA-related CLHs were located primarily in the parietal, temporal, and occipital lobes. These hemorrhages normally consisted of multiple repeated CLHs that frequently bled into the subarachnoid space. CAA-associated microvascular lesions may be the pathological factor underlying CLH.

Pathogenesis and treatment of vascular cognitive impairment

SUMMARY 

Vascular cognitive impairment (VCI) defines a continuum of disorders ranging from mild cognitive impairment to full-blown dementia, attributable to cerebrovascular causes. Major morphological types – multi-infarct encephalopathy, strategic infarct type, subcortical arteriosclerotic leukoencephalopathy, multilacunar state, postischemic encephalopathy – result from systemic, cardiac and local large or small vessel disease. Cognitive decline is commonly caused by widespread small cerebrovascular lesions (CVLs) affecting regions/networks essential for cognition, memory and behavior. CVLs often coexist with Alzheimer-type and other pathologies, which interact in promoting dementia, but in many nondemented elderly individuals, mixed brain pathologies are also present. Due to the high variability of CVLs, no validated clinical and neuropathological criteria for VCI are available. Cholinesterase inhibitors and memantine produce small cognitive improvement but without essential effect. Antihypertensive treatment, cardiovascular control and lifestyle modifications reducing vascular risk factors are essential. Given its growing health, social and economic burden, prevention and treatment of VCI are a major challenge of neuroscience.

Hot water extract of wheat bran attenuates white matter injury in a rat model of vascular dementia

Vascular dementia is characterized by white matter lesions involving the demyelination and activation of astrocytes and microglia. In a previous study, we showed that the supernatant of a laboratory-scale, hot water extract of ground whole wheat (TALE) attenuated white matter injury and astrocytic activation in a rat model of bilateral common carotid artery occlusion (BCCAO). In the present study, we made several modifications to the hot water extraction process to remove starch and enable large-scale production. We used wheat bran (WB), which contains less starch, instead of ground whole wheat. In addition, we removed starch granules with a decanter before hot water extraction. The final product, wheat bran extract (WBE), contained 2.42% arabinose, a surrogate marker of arabinoxylan, which is an active constituent of WBE. Supplementation of the rat model of BCCAO with WBE (400 mg/kg/day) for 33 days attenuated white matter injury, which was assessed by Luxol Fast Blue staining, in the corpus callosum (cc) and optic tract (opt) regions. Attenuation of white matter injury in the opt region was accompanied by improvement of the pupillary light reflex. Immunochemical staining revealed that supplementation with WBE reduced astrocytic activation in the cc and opt regions and reduced microglial activation in the opt region. These findings indicate that supplementation with WBE is effective at attenuating white matter injury accompanied by the inhibition of astrocytic and microglial activation. Therefore, extracts from WB, a cheap by-product of wheat milling, can be developed as a nutraceutical to prevent vascular dementia, a disease for which there is no approved pharmaceutical treatment.

Binswanger's disease: toward a diagnosis agreement and therapeutic approach

Binswanger's disease (BD) is a progressive form of cerebral small vessel disease affecting the white matter and other subcortical structures. Clinical and imaging characteristics, neuropsychological profile and cerebrospinal fluid analysis aid in making the diagnosis. BD shares features of other small vessel diseases and degenerative neurological conditions, which makes diagnosis difficult. However, with recent developments in MRI methods and serum/cerebrospinal fluid biomarkers, we have gained a greater understanding of the complex pathophysiology of the disease that will guide us to a more certain diagnosis. There is growing evidence that the white matter injury in BD is related to endothelial dysfunction with a secondary inflammatory response leading to breakdown of the neurovascular unit. This review summarizes current and future research directions, including pathophysiological mechanisms and potential therapeutic approaches.

Brain lipidomes of subcortical ischemic vascular dementia and mixed dementia

Despite its importance as the leading cause of vascular dementia, the primary pathogenic mechanisms in subcortical ischemic vascular dementia (SIVD) have remained elusive. Because of the lack of approved therapeutic agents for SIVD, there is a pressing need to identify novel therapeutic targets. Comparative lipidomic analyses of SIVD and mixed dementia (i.e., SIVD and Alzheimer's disease, MixD) may also confer new insights pertaining to the possible interaction between neurodegenerative and vascular mechanisms in the pathogenesis of dementia. Liquid chromatography coupled to mass spectrometry was used to comprehensively analyze the lipidomes of white and gray matter from the temporal cortex of nondemented controls, SIVD, and MixD subjects. Detailed molecular profiles highlighted the pathologic relevance of gray matter sphingolipid fatty acyl chain heterogeneity in dementia. In addition, the levels of sulfatides and lysobisphosphatidic acids were progressively increased in the temporal cortex gray matter from control to SIVD to MixD. White matter phospholipid profiles indicated possible adaptive mechanisms (i.e., increased unsaturation) to chronic ischemia in SIVD and elevated membrane degradation in MixD.

Assessment and management of pain, with particular emphasis on central neuropathic pain, in moderate to severe dementia

In patients with dementia, undertreatment of pain, irrespective of its aetiology, is widely recognized; the risk for undertreatment increases with the severity of dementia. We argue, however, that central neuropathic pain is by far the most undertreated type of pain in patients with dementia. Central pain is a type of neuropathic pain that is known to occur in stroke patients and is caused by white matter lesions. Although white matter lesions are also a neuropathological hallmark of dementia, central neuropathic pain has hardly been described in dementia. Therefore, the goal of this review was to address assessment and management of pain, with particular emphasis on central neuropathic pain, in moderate to severe dementia. Concerning pain assessment, the findings of this review suggest that self-report pain rating scales, in particular the Verbal Rating Scale, the Horizontal Visual Analogue Scale and the Faces Pain Scale can be administered to patients in a more advanced stage of dementia. For those who are no longer able to communicate pain, pain observation scales are most appropriate. Self-report and pain observation should be combined, if possible. For an overview of assessment tools to measure pain with older people unable to verbally communicate, we refer readers to the City of Hope Pain and Palliative Care Resource Center ( http://prc.coh.org/PAIN-NOA.htm ). The review further highlights that behavioural disturbances, e.g. agitation and physical inactivity, as well as autonomic responses, e.g. an increase in blood pressure and heart rate, may contribute to a more reliable assessment of pain. With respect to central neuropathic pain in particular, assessment of sensory abilities (touch, pinprick, temperature and vibration), mood (e.g. anxiety) and determination of the presence of a Babinsky reflex, accelerated tendon reflexes, and spasticity may contribute to reliable assessment. Management of pain, not of a central origin, starts with paracetamol (acetaminophen), which, together with opioids, is the most frequently prescribed analgesic drug in dementia. Non-steroidal anti-inflammatory drugs are hardly prescribed in a residential setting. Some authors advise starting treatment with a low dose of opioids. Antidepressants and antiepileptic drugs appear to have a positive effect on central neuropathic pain. In the review, advantages and disadvantages of amitriptyline, carbamazepine, lamotrigine, gabapentin and pregabalin are discussed; a negative effect of these drugs on liver and kidney functions, as well as on cognitive functions in patients who already suffer from cognitive impairment is highlighted. Next to pharmacotherapy, non-pharmacological treatment strategies such as transcutaneous electrical nerve stimulation may be effective as long as afferent pathways transmitting the electrical stimulus are still intact.

Pathology and pathogenesis of vascular cognitive impairment-a critical update

Vascular cognitive impairment (VCI) [vascular cognitive disorder (VCD), vascular dementia] describes a continuum of cognitive disorders ranging from mild cognitive impairment (MCI) to dementia, in which vascular brain injury involving regions important for memory, cognition and behavior plays an important role. Clinical diagnostic criteria show moderate sensitivity (ca 50%) and variable specificity (range 64-98%). In Western clinical series, VaD is suggested in 8-10% of cognitively impaired elderly subjects. Its prevalence in autopsy series varies from 0.03 to 58%, with means of 8 to 15% (in Japan 22-35%). Major types of sporadic VaD are multi-infarct encephalopathy, small vessel and strategic infarct type dementias, subcortical arteriosclerotic leukoencephalopathy (SAE) (Binswanger), multilacunar state, mixed cortico-subcortical type, granular cortical atrophy (rare), postischemic encephalopathy, and a mixture of cerebrovascular lesions (CVLs). They result from systemic, cardiac and local large or small vessel disease (SVD); their pathogenesis is multifactorial. Hereditary forms of VaD caused by gene mutations are rare. Cognitive decline is commonly associated with widespread small ischemic vascular lesions involving subcortical brain areas (basal ganglia and hemispheral white matter). The lesions affect neuronal networks involved in cognition, memory, and behavior (thalamo-cortical, striato-subfrontal, cortico-subcortical, limbic systems). CVLs often coexist with Alzheimer-type lesions and other pathologies; 25-80% of elderly demented show mixed pathologies. The lesion pattern of "pure" VaD differs from that in mixed dementia (AD + CVLs) suggesting different pathogenesis of both phenotypes. Minor CVLs, except for severe amyloid angiopathy, appear not essential for cognitive impairment in full-blown AD, while both mild AD-type pathology and SVD may interact synergistically in promoting dementia. However, in a large percentage of non-demented elderly individuals, both AD-related and vascular brain pathologies have been reported. Despite recent suggestions for staging and grading CVLs in specific brain areas, due to the high variability of CVLs associated with cognitive impairment, no validated neuropathological criteria are currently available for VaD and mixed dementia. Further clinico-pathological studies and harmonization of neuropathological procedures are needed to validate the diagnostic criteria for VaD and mixed dementia in order to clarify the impact of CVLs and other coexistent pathologies on cognitive impairment as a basis for further successful therapeutic options.

Protective effect of carnosine on subcortical ischemic vascular dementia in mice

AIMS

Recently, we found carnosine protects against N-Methyl-D-Aspartate (NMDA) induced excitotoxicity through a histaminergic pathway. The aim of this study was to determine whether the carnosine-histidine-histamine pathway also played a protective role in subcortical ischemic vascular dementia (SIVD).

METHODS

Adult male mice (C57BL/6 strain) were subjected to right unilateral common carotid arteries occlusion (rUCCAO) and treated with carnosine or histidine. Object recognition test, passive avoidance task, Morris water maze, and immunohistochemical analyses were performed after rUCCAO.

RESULTS

We found that carnosine (200, 500 mg/kg) ameliorated white matter lesion and cognitive impairment evaluated by object recognition test, passive avoidance task, and Morris water maze test after rUCCAO in both wide-type mice and histidine decarboxylase knockout mice, which are lack of endogenous histamine. However, administration of histidine did not show the same effect. The myelin basic protein in the corpus callosum decreased obviously at day 37 after rUCCAO, which was largely reversed by carnosine (200, 500 mg/kg). Carnosine (200, 500 mg/kg) suppressed the activation of microglia and astrocyte as attenuating the elevation of glial fibrillary acidic protein (GFAP) and Iba-1 fluorescent intensity. Moreover, carnosine (200, 500 mg/kg) significantly attenuated the increase in reactive oxygen species generation after rUCCAO.

CONCLUSION

These data suggest that the neuroprotective effect of carnosine on rUCCAO in mice is not dependent on the histaminergic pathway, but may be due to a suppression of reactive oxygen species generation, glia activation, and myelin degeneration.

[Differential diagnosis and common pathology between Alzheimer's disease and vascular dementia]

Dementia due to both Alzheimer's disease (AD) and cerebrovascular disease (CVD) is designated as mixed dementia, or alternatively, AD with CVD. Cerebral amyloid angiopathy almost always accompanies AD, and causes lobar microbleeds, cortical subarachnoid hemorrhage and cortical microinfarctions. Dementia exclusively with cerebral amyloid angiopathy is a form of vascular dementia, while it is classified to AD when significant Alzheimer's pathology coexists. Between AD and vascular dementia there are common and overlapping pathologies, which is important for differential diagnosis of these diseases.

Pre-clinical models of human cerebral small vessel disease: utility for clinical application

Small vessel disease (SVD) is a frequent cause of vascular cognitive impairment (VCI), encompassing vascular dementia. SVD is characterised by vasculopathy in deep penetrating arteries, diffuse white matter lesions (seen radiologically as leukoaraiosis) and focal, lacunar infarcts. Risk factors are age and hypertension but the pathogenic mechanism is unknown. Recent systematic reviews assessed experimental models of SVD or VCI. Chronically hypertensive animals (e.g. stroke-prone spontaneously hypertensive rats) display some features of SVD vasculopathy, such as vessel wall thickening. White matter lesions are seen in chronic hypoperfusion states (e.g. carotid occlusion/stenosis models). Small focal infarcts are induced by targeted ischemic challenge (surgical occlusion of a small artery, or stereotaxic endothelin-1 injection). Some degree of cognitive impairment is detectable in most cerebrovascular models, probably reflecting the broad neuroanatomical mapping of cognitive function. Important confounds to be considered in animal models of VCI are somatosensory impairment and hippocampal damage. Advances in clinical understanding will come from targeting specific questions on some aspect of SVD (e.g. vasculopathy, white matter damage) to the appropriate model in vivo. In vivo models of SVD are likely to benefit experimental studies of pathological processes, interactions with other brain disease states (such as Alzheimer disease), and therapeutic strategies.