Contributions of Aging to Cerebral Small Vessel Disease

Linking peripheral atherosclerosis to blood-brain barrier disruption: elucidating its role as a manifestation of cerebral small vessel disease in vascular cognitive impairment

Aging plays a pivotal role in the pathogenesis of cerebral small vessel disease (CSVD), contributing to the onset and progression of vascular cognitive impairment and dementia (VCID). In older adults, CSVD often leads to significant pathological outcomes, including blood-brain barrier (BBB) disruption, which in turn triggers neuroinflammation and white matter damage. This damage is frequently observed as white matter hyperintensities (WMHs) in neuroimaging studies. There is mounting evidence that older adults with atherosclerotic vascular diseases, such as peripheral artery disease, ischemic heart disease, and carotid artery stenosis, face a heightened risk of developing CSVD and VCID. This review explores the complex relationship between peripheral atherosclerosis, the pathogenesis of CSVD, and BBB disruption. It explores the continuum of vascular aging, emphasizing the shared pathomechanisms that underlie atherosclerosis in large arteries and BBB disruption in the cerebral microcirculation, exacerbating both CSVD and VCID. By reviewing current evidence, this paper discusses the impact of endothelial dysfunction, cellular senescence, inflammation, and oxidative stress on vascular and neurovascular health. This review aims to enhance understanding of these complex interactions and advocate for integrated approaches to manage vascular health, thereby mitigating the risk and progression of CSVD and VCID.

Blood-brain barrier pathology in cerebral small vessel disease

ABSTRACT

Cerebral small vessel disease is a neurological disease that affects the brain microvasculature and which is commonly observed among the elderly. Although at first it was considered innocuous, small vessel disease is nowadays regarded as one of the major vascular causes of dementia. Radiological signs of small vessel disease include small subcortical infarcts, white matter magnetic resonance imaging hyperintensities, lacunes, enlarged perivascular spaces, cerebral microbleeds, and brain atrophy; however, great heterogeneity in clinical symptoms is observed in small vessel disease patients. The pathophysiology of these lesions has been linked to multiple processes, such as hypoperfusion, defective cerebrovascular reactivity, and blood-brain barrier dysfunction. Notably, studies on small vessel disease suggest that blood-brain barrier dysfunction is among the earliest mechanisms in small vessel disease and might contribute to the development of the hallmarks of small vessel disease. Therefore, the purpose of this review is to provide a new foundation in the study of small vessel disease pathology. First, we discuss the main structural domains and functions of the blood-brain barrier. Secondly, we review the most recent evidence on blood-brain barrier dysfunction linked to small vessel disease. Finally, we conclude with a discussion on future perspectives and propose potential treatment targets and interventions.

Advanced age and female sex protect cerebral arteries from mitochondrial depolarization and apoptosis during acute oxidative stress

Aging increases reactive oxygen species (ROS) which can impair vascular function and contribute to brain injury. However, aging can also promote resilience to acute oxidative stress. Therefore, we tested the hypothesis that advanced age protects smooth muscle cells (SMCs) and endothelial cells (ECs) of posterior cerebral arteries (PCAs; diameter, ∼80 μm) during exposure to H2O2. PCAs from young (4-6 months) and old (20-26 months) male and female C57BL/6 mice were isolated and pressurized (~70 mm Hg) to evaluate cell death, mitochondrial membrane potential (ΔΨm), ROS production, and [Ca2+]i in response to H2O2 (200 μM, 50 min). SMC death and ΔΨm depolarization were greater in PCAs from males vs. females. Aging increased ROS in PCAs from both sexes but increased SMC resilience to death only in males. Inhibiting TRPV4 channels with HC-067047 (1 μM) or Src kinases with SU6656 (10 μM) reduced Ca2+ entry and SMC death to H2O2 most effectively in PCAs from young males. Activating TRPV4 channels with GSK1016790A (50 nM) evoked greater Ca2+ influx in SMCs and ECs of PCAs from young vs. old mice but did not induce cell death. However, when combined with H2O2, TRPV4 activation exacerbated EC death. Activating Src kinases with spermidine (100 μM) increased Ca2+ influx in PCAs from males vs. females with minimal cell death. We conclude that in males, chronic oxidative stress during aging increases the resilience of cerebral arteries, which contrasts with inherent protection in females. Findings implicate TRP channels and Src kinases as targets to limit vascular damage to acute oxidative injury.

Chronological vs Biological Age in Interventional Cardiology: A Comprehensive Approach to Care for Older Adults: JACC Family Series

Aging is the gradual decline in physical and physiological functioning leading to increased susceptibility to stressors and chronic illnesses, including cardiovascular disease. With an aging global population, in which 1 in 6 individuals will be older than 60 years by 2030, interventional cardiologists are increasingly involved in providing complex care for older individuals. Although procedural aspects remain their main clinical focus, interventionalists frequently encounter age-associated risks that influence eligibility for invasive care, decision making during the intervention, procedural adverse events, and long-term management decisions. The unprecedented growth in transcatheter interventions, especially for structural heart diseases at extremes of age, have pushed age-related risks and implications for cardiovascular care to the forefront. In this JACC state-of-the-art review, the authors provide a comprehensive overview of the aging process as it relates to cardiovascular interventions, with special emphasis on the difference between chronological and biological aging. The authors also address key considerations to improve health outcomes for older patients during and after their invasive cardiovascular care. The role of "gerotherapeutics" in interventional cardiology, technological innovation in measuring biological aging, and the integration of patient-centered outcomes in the older adult population are also discussed.

Atherosclerotic burden and cerebral small vessel disease: exploring the link through microvascular aging and cerebral microhemorrhages

Cerebral microhemorrhages (CMHs, also known as cerebral microbleeds) are a critical but frequently underestimated aspect of cerebral small vessel disease (CSVD), bearing substantial clinical consequences. Detectable through sensitive neuroimaging techniques, CMHs reveal an extensive pathological landscape. They are prevalent in the aging population, with multiple CMHs often being observed in a given individual. CMHs are closely associated with accelerated cognitive decline and are increasingly recognized as key contributors to the pathogenesis of vascular cognitive impairment and dementia (VCID) and Alzheimer's disease (AD). This review paper delves into the hypothesis that atherosclerosis, a prevalent age-related large vessel disease, extends its pathological influence into the cerebral microcirculation, thereby contributing to the development and progression of CSVD, with a specific focus on CMHs. We explore the concept of vascular aging as a continuum, bridging macrovascular pathologies like atherosclerosis with microvascular abnormalities characteristic of CSVD. We posit that the same risk factors precipitating accelerated aging in large vessels (i.e., atherogenesis), primarily through oxidative stress and inflammatory pathways, similarly instigate accelerated microvascular aging. Accelerated microvascular aging leads to increased microvascular fragility, which in turn predisposes to the formation of CMHs. The presence of hypertension and amyloid pathology further intensifies this process. We comprehensively overview the current body of evidence supporting this interconnected vascular hypothesis. Our review includes an examination of epidemiological data, which provides insights into the prevalence and impact of CMHs in the context of atherosclerosis and CSVD. Furthermore, we explore the shared mechanisms between large vessel aging, atherogenesis, microvascular aging, and CSVD, particularly focusing on how these intertwined processes contribute to the genesis of CMHs. By highlighting the role of vascular aging in the pathophysiology of CMHs, this review seeks to enhance the understanding of CSVD and its links to systemic vascular disorders. Our aim is to provide insights that could inform future therapeutic approaches and research directions in the realm of neurovascular health.

Aging in Ocular Blood Vessels: Molecular Insights and the Role of Oxidative Stress

Acknowledged as a significant pathogenetic driver for numerous diseases, aging has become a focal point in addressing the profound changes associated with increasing human life expectancy, posing a critical concern for global public health. Emerging evidence suggests that factors influencing vascular aging extend their impact to choroidal and retinal blood vessels. The objective of this work is to provide a comprehensive overview of the impact of vascular aging on ocular blood vessels and related diseases. Additionally, this study aims to illuminate molecular insights contributing to vascular cell aging, with a particular emphasis on the choroid and retina. Moreover, innovative molecular targets operating within the domain of ocular vascular aging are presented and discussed.

Angiography-based hemodynamic features predict recurrent ischemic events after angioplasty and stenting of intracranial vertebrobasilar atherosclerotic stenosis

OBJECTIVES

To assess the predictive value of hemodynamic features for stroke relapse in patients with intracranial vertebrobasilar atherosclerotic stenosis treated with percutaneous transluminal angioplasty and stenting (PTAS) using quantitative digital subtraction angiography (q-DSA).

METHODS

In this retrospective longitudinal study, patients with intracranial vertebrobasilar atherosclerotic stenosis and who underwent PTAS treatment between January 2012 and May 2020 were enrolled. The q-DSA assessment was performed before and after PTAS. ROIs 1-4 were placed along the vertebral artery, proximal and distal basilar artery, and posterior cerebral artery; ROIs 5-8 were in 5 mm and 10 mm proximal and distal to the lesion, respectively. Relative time to peak (rTTP) was defined as the difference in TTP between ROIs. Cox regression analyses were performed to determine risk factors for recurrent stroke.

RESULTS

A total of 137 patients (mean age, 62 years ± 10 [standard deviation], 83.2% males) were included, and 26 (19.0%) patients had stroke relapse during follow-up (median time of 42.6 months [interquartile range, 19.7-60.7]). Preprocedural rTTP4-1 (adjusted hazard ratio (HR) = 2.270; 95% CI 1.371-3.758; p = 0.001) and preprocedural rTTP8-5 (adjusted HR = 0.240; 95% CI 0.088-0.658; p = 0.006) were independently associated with the recurrent stroke. These hemodynamic parameters provided an incremental prognostic value for stroke relapse (AUC, 0.817 [0.704-0.931]; the net reclassification index, 0.431 [0.057-0.625]; and the integrated discrimination index, 0.140 [0.035-0.292]).

CONCLUSIONS

In patients with intracranial vertebrobasilar atherosclerosis treated with PTAS, preprocedural prolonged TTP of the target vessel and shortened trans-stenotic TTP difference were associated with stroke relapse. Q-DSA-defined hemodynamic parameters provided incremental predictive value over conventional parameters for stroke recurrence.

CLINICAL RELEVANCE STATEMENT

Quantitative DSA analysis enables intuitive observation and semi-quantitative evaluation of peri-therapeutic cerebral blood flow. More importantly, quantitative DSA-defined hemodynamic parameters have the potential for risk stratification of patients with intracranial atherosclerotic stenosis.

KEY POINTS

Semi-quantitative angiography-based parameters can reflect pre- and postprocedural subtle changes in blood flow in patients with intracranial atherosclerotic stenosis. Although angioplasty procedures can significantly improve blood flow status, patients with more restricted baseline blood flow still show a higher risk of stroke recurrence. Angiography-based hemodynamic features possess prognostic value and can serve as clinical markers to assess stroke risk of patients with intracranial atherosclerotic stenosis.

Hypertension: Causes and Consequences of Circadian Rhythms in Blood Pressure

Hypertension is extremely common, affecting approximately 1 in every 2 adults globally. Chronic hypertension is the leading modifiable risk factor for cardiovascular disease and premature mortality worldwide. Despite considerable efforts to define mechanisms that underlie hypertension, a potentially major component of the disease, the role of circadian biology has been relatively overlooked in both preclinical models and humans. Although the presence of daily and circadian patterns has been observed from the level of the genome to the whole organism, the functional and structural impact of biological rhythms, including mechanisms such as circadian misalignment, remains relatively poorly defined. Here, we review the impact of daily rhythms and circadian systems in regulating blood pressure and the onset, progression, and consequences of hypertension. There is an emphasis on the impact of circadian biology in relation to vascular disease and end-organ effects that, individually or in combination, contribute to complex phenotypes such as cognitive decline and the loss of cardiac and brain health. Despite effective treatment options for some individuals, control of blood pressure remains inadequate in a substantial portion of the hypertensive population. Greater insight into circadian biology may form a foundation for novel and more widely effective molecular therapies or interventions to help in the prevention, treatment, and management of hypertension and its related pathophysiology.

Salidroside promotes pro-angiogenesis and repair of blood brain barrier via Notch/ITGB1 signal path in CSVD Model

INTRODUCTION

Salidroside (SAL), extracted from Rhodiola rosea, has been widely used in coronary heart disease and myocardial ischemia for decades. Previous studies have demonstrated that SAL could reduce arteriosclerosis, and thus combat ischemic brain damage. However, the in-depth function of the salidroside in Cerebral Small Vascular Disease (CSVD) has not been discovered, and related molecular mechanism is still unclear.

OBJECTIVES

The present study aims to explore the effects of salidroside in angiogenesis as well as repair of blood brain barrier (BBB) and its possible mechanisms.

METHODS

We established a rat model of SHR via 2-vessel gradual occlusion (SHR-2VGO) to mimic the CSVD. Subsequently, the MRI, pathomorphism, as well as Morriss water maze test were conducted to determine CSVD-related indicators. 8 weeks post-surgery, animals were randomly administered SAL, DAPT, ATN161 or saline.The aim was to explore the protective effects of SAL in CSVD as well as its possible mechanism.

RESULTS

Here we found that SAL could attenuate cerebral hypoperfusion-induced BBB disruption, promote the pro-angiogenesis through enhancing the cell budding. Further investigations demonstrated that SAL could significantly increase the expression of Notch1, Hes1, Hes5, and ITGB1. In addition, we confirmed that SAL could activate Notch signal path, and then up-regulate ITGB1 to promote pro-angiogenesis and thus protect BBB from disruption.

CONCLUSION

The aforementioned findings demonstrated that SAL could protect BBB integrity through Notch-ITGB1 signaling path in CSVD, which indicated that SAL could be a potential medicine candidate for CSVD treatment.

Deep medullary vein damage correlates with small vessel disease in small vessel occlusion acute ischemic stroke

OBJECTIVES

We aim to investigate whether cerebral small vessel disease (cSVD) imaging markers correlate with deep medullary vein (DMV) damage in small vessel occlusion acute ischemic stroke (SVO-AIS) patients.

METHODS

The DMV was divided into six segments according to the regional anatomy. The total DMV score (0-18) was calculated based on segmental continuity and visibility. The damage of DMV was grouped according to the quartiles of the total DMV score. Neuroimaging biomarkers of cSVD including white matter hyperintensity (WMH), cerebral microbleed (CMB), perivascular space (PVS), and lacune were identified. The cSVD score were further analyzed.

RESULTS

We included 229 SVO-AIS patients, the mean age was 63.7 ± 23.1 years, the median NIHSS score was 3 (IQR, 2-6). In the severe DMV burden group (the 4th quartile), the NIHSS score grade (6 (3-9)) was significantly higher than other groups (p < 0.01). The grade scores for basal ganglia PVS (BG-PVS) were positively correlated with the degree of DMV (R = 0.67, p < 0.01), rather than centrum semivole PVS (CS-PVS) (R = 0.17, p = 0.1). In multivariate analysis, high CMB burden (adjusted odds ratio [aOR], 25.38; 95% confidence interval [CI], 1.87-345.23) was associated with severe DMV scores. In addition, BG-PVS was related to severe DMV burden in a dose-dependent manner: when BG-PVS score was 3 and 4, the aORs of severe DMV burden were 18.5 and 12.19, respectively.

CONCLUSION

The DMV impairment was associated with the severity of cSVD, which suggests that DMV burden may be used for risk stratification in SVO-AIS patients.

CLINICAL RELEVANCE STATEMENT

The DMV damage score, based on the association between small vessel disease and the deep medullary veins impairment, is a potential new imaging biomarker for the prognosis of small vessel occlusion acute ischemic stroke, with clinical management implications.

KEY POINTS

• The damage to the deep medullary vein may be one mechanism of cerebral small vessel disease. • Severe burden of the basal ganglia perivascular space and cerebral microbleed is closely associated with significant impairment to the deep medullary vein. • The deep medullary vein damage score may reflect a risk of added vascular damage in small vessel occlusion acute ischemic stroke patients.

Identification of differentially expressed exosome proteins in serum as potential biomarkers for cognitive impairments in cerebral small vessel disease

BACKGROUND

Cognitive impairment arising from cerebral small vessel disease (CSVD) represents a critical subtype of vascular cognitive impairments (VCI) and is the primary cause of vascular dementia. However, identifying reliable clinical and laboratory indicators for this disease remain elusive. We hypothesize that plasma exosome proteins hold the potential to serve as biomarkers for the onset of cognitive dysfunction associated with cerebrovascular diseases.

METHODS

We employed TMT-based proteomics to discern variations in serum exosome proteomes between individuals with cognitive impairments due to CSVD and healthy volunteers.

RESULTS

Each group comprised 18 subjects, and through differential expression analysis, we identified 22 down-regulated and 8 up-regulated proteins between the two groups. Our research revealed 30 differentially expressed plasma exosome proteins, including histone, proteasome, clusterin and coagulation factor XIII, in individuals with cognitive impairments caused by CSVD.

CONCLUSION

The 30 differentially expressed plasma exosome proteins identified in our study are promising as biomarkers for diagnosing cognitive impairments resulting from CSVD. These findings may help us better understand the underlying pathological mechanisms involved in the diseases.

Association Between Head Computed Tomography Findings and In-Hospital Mortality in COVID-19 Patients

OBJECTIVE

The present study investigated the association between head computed tomography (CT) findings and mortality in patients with COVID-19. Specifically, we focused on low-density lesions identified on head CT screenings.

MATERIALS AND METHODS

We performed a single-center, retrospective cohort study based on data obtained from the medical charts of inpatients admitted to the Tokyo Metropolitan Hiroo Hospital between January 1 and December 31, 2021. We focused on the basal ganglia--a representative anatomical region for assessing routine head CT in patients with COVID-19. Patients were divided into two groups based on the presence or absence of low-density lesions in the basal ganglia. The primary outcome was all-cause in-hospital mortality, and the secondary outcome was the length of hospital stay. We performed multivariable regression analyses for outcomes to adjust for patients' background and disease severity.

RESULTS

During the study period, 1,906 COVID-19 patients were admitted to our facility. Among them, 1,203 patients underwent head CT evaluations and were included in this study. The median age was 56 years (interquartile range: 43-76 years) and 725 patients (60.3%) were male. A total of 235 (19.5%) patients required oxygen therapy on admission and 1,051 (87.4%) patients had pneumonia. Crude in-hospital mortality was 6.1% and the median length of hospital stay was 10 days (interquartile range: 8-14 days). The multivariate regression analyses showed that low-density lesions in the basal ganglia were significantly associated with increased in-hospital mortality and prolonged hospital stay.

CONCLUSIONS

The presence of ischemic changes in the basal ganglia denoted by low-density findings may be a promising prognostic factor in patients with COVID-19.

Cortical microvascular raspberries and ageing: an independent but not exclusive relationship

INTRODUCTION

Raspberries are cerebral microvascular formations of unknown origin, defined as three or more transversally sectioned vascular lumina surrounded by a common perivascular space. We have previously demonstrated an increased raspberry density in the cortex of patients with vascular dementia and cerebral atherosclerosis, while studies by other authors on overlapping and synonymously defined vascular entities mainly associate them with advancing age. The aim of the present study was to examine the relationship between raspberries and age in a large study sample while including multiple potential confounding factors in the analysis.

MATERIALS AND METHODS

Our study sample consisted of 263 individuals aged 20-97 years who had undergone a clinical autopsy including a neuropathological examination. The cortical raspberry density had either been quantified as part of a previous study or was examined de novo in a uniform manner on haematoxylin- and eosin-stained tissue sections from the frontal lobe. The medical records and autopsy reports were assessed regarding neurodegeneration, cerebral infarcts, cerebral atherosclerosis and small vessel disease, cardiac hypertrophy, nephrosclerosis, hypertension, and diabetes mellitus. With the patients grouped according to 10-year age interval, non-parametric tests (the Kruskal-Wallis test, followed by pairwise testing with Bonferroni-corrected P values) and multiple linear regression models (not corrected for multiple tests) were performed.

RESULTS

The average raspberry density increased with advancing age. The non-parametric tests demonstrated statistically significant differences in raspberry density when comparing the groups aged 60-99 years and 70-99 years to those aged 20-29 years (P < 0.012) and 30-59 years (P < 0.011), respectively. The multiple linear regression models demonstrated positive associations with age interval (P < 0.001), cerebral atherosclerosis (P = 0.024), cardiac hypertrophy (P = 0.021), hypertension subgrouped for organ damage (P = 0.006), and female sex (P = 0.004), and a tendency towards a negative association with Alzheimer's disease neuropathologic change (P = 0.048).

CONCLUSION

The raspberry density of the frontal cortex increases with advancing age, but our results also indicate associations with acquired pathologies. Awareness of the biological and pathological context where raspberries occur can guide further research on their origin.

Maintaining brain health across the lifespan

Across the lifespan, the human body and brain endure the impact of a plethora of exogenous and endogenous factors that determine the health outcome in old age. The overwhelming inter-individual variance spans between progressive frailty with loss of autonomy to largely preserved physical, cognitive, and social functions. Understanding the mechanisms underlying the diverse aging trajectories can inform future strategies to maintain a healthy body and brain. Here we provide a comprehensive overview of the current literature on lifetime factors governing brain health. We present the growing body of evidence that unhealthy alimentary regime, sedentary behaviour, sleep pathologies, cardio-vascular risk factors, and chronic inflammation exert their harmful effects in a cumulative and gradual manner, and that timely and efficient intervention could promote healthy and successful aging. We discuss the main effects and interactions between these risk factors and the resulting brain health outcomes to follow with a description of current strategies aiming to eliminate, treat, or counteract the risk factors. We conclude that the detailed insights about modifiable risk factors could inform personalized multi-domain strategies for brain health maintenance on the background of increased longevity.

Correlation between lenticulostriate arteries and white matter microstructure changes in patients with cerebral small vessel disease

To explore the correlation between the number of lenticulostriate arteries (LSAs) and the white matter features in cerebral small vessel diseases (CSVD) by 3T magnetic resonance imaging (MRI). Seventy-one patients with diagnoses of CSVD were prospectively enrolled to undergo 3T MRI examination, including high-resolution vascular wall imaging (VWI) and diffusion tensor imaging (DTI). The LSAs were observed and counted on VWI, and the patients were divided into three groups according to the LSA counts. The presence of white matter hyperintensities (WMHs), lacunes, cerebral microbleeds (CMBs), and enlarged perivascular spaces (EPVS) was assessed in each patient, and a composite CSVD score was calculated. Periventricular and deep white matter hyperintensity (PVWMH, DWMH) volume ratios were obtained based on automatic segmentation. Fractional anisotropy (FA) and mean diffusivity (MD) were processed by using tract-based spatial statistics (TBSS) analysis. These parameters were compared among the three groups. Correlations between the LSA counts and white matter features were also analyzed. There were differences in WMHs (P = 0.001), CMBs (P < 0.001), EPVS (P = 0.017), composite CSVD scores (P < 0.001), PVWMH volume ratios (P = 0.001), DWMH volume ratios (P < 0.001), global FA (P = 0.001), and global MD (P = 0.002) among the three groups. There were correlations between the LSA counts and WMHs (r = -0.45, P < 0.001), CMBs (r = -0.44, P < 0.001), EPVS (r = -0.28, P = 0.020), the composite CSVD score (r = -0.52, P < 0.001), DWMH volume ratio (r = -0.47, P < 0.001), PWMH volume ratio (r = -0.34, P = 0.004), global FA (r = 0.36, P = 0.002), and global MD (r = -0.33, P = 0.005). Diabetes mellitus (OR 3.36, 95% CI 1.06-10.63; P = 0.039) and increased DWMH volume ratios (OR 1.04, 95% CI 1.00-1.08; P = 0.048) were independent risk factors for a decrease in LSA counts. TBSS analysis showed differences among the three groups in global FA and MD after adjusting for age and sex (P < 0.05). The LSA counts was associated with white matter microstructure changes in CSVD and has the potential to represent the extent of subcortical microvascular damage in CSVD patients.

Correlation between obstructive sleep apnea and cerebral small vessel disease: a mendelian randomization study

BACKGROUND

Whether obstructive sleep apnea (OSA) is causally associated with an increased risk of cerebral small vessel disease (CSVD) remains controversial. We conducted a two-sample Mendelian randomization (MR) study to clarify the causal relationship between OSA and CSVD risk.

METHODS

Single-nucleotide polymorphisms associated with OSA at the genome-wide significance level (P < 5 × 10- 8) in the FinnGen consortium were selected as instrumental variables. Summary-level data for white matter hyperintensities (WMHs), lacunar infarctions (LIs), cerebral microbleeds (CMBs), fractional anisotropy (FA), and mean diffusivity (MD) were obtained from three meta-analyses of genome-wide association studies (GWASs). The random-effects inverse-variance weighted (IVW) method was selected for the major analysis. Weighted-median, MR-Egger, MR pleiotropy residual sum and outlier (MR-PRESSO), and leave-one-out analysis methods were implemented for the sensitivity analyses.

RESULTS

Genetically predicted OSA was not associated with LIs (odds ratio [OR] = 1.10, 95% confidence interval [CI] = 0.86-1.40), WMHs (OR = 0.94, 95% CI = 0.83-1.07), FA (OR = 1.33, 95% CI = 0.75-2.33), MD (OR = 0.93, 95% CI = 0.58-1.47), CMBs (OR = 1.29, 95% CI = 0.86-1.94), mixed CMBs (OR = 1.17, 95% CI = 0.63-2.17), and lobar CMBs (OR = 1.15, 95% CI = 0.75-1.76) in IVW method. The results of the sensitivity analyses were generally consistent with the major analyses.

CONCLUSIONS

This MR study does not support causal associations between OSA and the risk of CSVD in individuals of European ancestry. These findings need to be further validated in randomized controlled trials, larger cohort studies, and MR studies based on larger GWASs.

Ceramide in cerebrovascular diseases

Ceramide, a bioactive sphingolipid, serves as an important second messenger in cell signal transduction. Under stressful conditions, it can be generated from de novo synthesis, sphingomyelin hydrolysis, and/or the salvage pathway. The brain is rich in lipids, and abnormal lipid levels are associated with a variety of brain disorders. Cerebrovascular diseases, which are mainly caused by abnormal cerebral blood flow and secondary neurological injury, are the leading causes of death and disability worldwide. There is a growing body of evidence for a close connection between elevated ceramide levels and cerebrovascular diseases, especially stroke and cerebral small vessel disease (CSVD). The increased ceramide has broad effects on different types of brain cells, including endothelial cells, microglia, and neurons. Therefore, strategies that reduce ceramide synthesis, such as modifying sphingomyelinase activity or the rate-limiting enzyme of the de novo synthesis pathway, serine palmitoyltransferase, may represent novel and promising therapeutic approaches to prevent or treat cerebrovascular injury-related diseases.

The vasculature of neurogenic niches: Properties and function

In the adult rodent brain, neural stem cells (NSCs) reside in the subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the hippocampus. In these areas, NSCs and their progeny integrate intrinsic signals and extrinsic cues provided by their microenvironment that control their behavior. The vasculature in the SVZ and SGZ, and the choroid plexus (ChP) in the SVZ, have emerged as critical compartments of the neurogenic niches as they provide a rich repertoire of cues to regulate NSC quiescence, proliferation, self-renewal and differentiation. Physical contact between NSCs and blood vessels is also a feature within the niches and supports different processes such as quiescence, migration and vesicle transport. In this review, we provide a description of the brain and choroid plexus vasculature in both stem cell niches, highlighting the main properties and role of the vasculature in each niche. We also summarize the current understanding of how blood vessel- and ChP-derived signals influence the behavior of NSCs in physiological adulthood, as well as upon aging.

Emerging Roles of Endothelial Nitric Oxide in Preservation of Cognitive Health

eNOS (endothelial nitric oxide synthase) is critically important enzyme responsible for regulation of cardiovascular homeostasis. Under physiological conditions, constitutive eNOS activity and production of endothelial nitric oxide (NO) exert essential neurovascular protective functions. In this review, we first discuss the roles of endothelial NO in prevention of neuronal amyloid accumulation and formation of neurofibrillary tangles, hallmarks of Alzheimer disease pathology. Next, we review existing evidence suggesting that NO released from endothelium prevents activation of microglia, stimulates glycolysis in astrocytes, and increases biogenesis of mitochondria. We also address major risk factors for cognitive impairment including aging and ApoE4 (apolipoprotein 4) genotype with focus on their detrimental effects on eNOS/NO signaling. Relevant to this review, recent studies suggested that aged eNOS heterozygous mice are unique model of spontaneous cerebral small vessel disease. In this regard, we review contribution of dysfunctional eNOS to deposition of Aβ (amyloid-β) into blood vessel wall leading to development of cerebral amyloid angiopathy. We conclude that endothelial dysfunction manifested by the loss of neurovascular protective functions of NO may significantly contribute to development of cognitive impairment.

Blood-to-brain communication in aging and rejuvenation

Aging induces molecular, cellular and functional changes in the adult brain that drive cognitive decline and increase vulnerability to dementia-related neurodegenerative diseases. Leveraging systemic and lifestyle interventions, such as heterochronic parabiosis, administration of 'young blood', exercise and caloric restriction, has challenged prevalent views of brain aging as a rigid process and has demonstrated that aging-associated cognitive and cellular impairments can be restored to more youthful levels. Technological advances in proteomic and transcriptomic analyses have further facilitated investigations into the functional impact of intertissue communication on brain aging and have led to the identification of a growing number of pro-aging and pro-youthful factors in blood. In this review, we discuss blood-to-brain communication from a systems physiology perspective with an emphasis on blood-derived signals as potent drivers of both age-related brain dysfunction and brain rejuvenation.

The relevance of serum macrophage migratory inhibitory factor and cognitive dysfunction in patients with cerebral small vascular disease

Cerebral small vascular disease (CSVD) is a common type of cerebrovascular disease, and an important cause of vascular cognitive impairment (VCI) and stroke. The disease burden is expected to increase further as a result of population aging, an ongoing high prevalence of risk factors (e.g., hypertension), and inadequate management. Due to the poor understanding of pathophysiology in CSVD, there is no effective preventive or therapeutic approach for CSVD. Macrophage migration inhibitory factor (MIF) is a multifunctional cytokine that is related to the occurrence and development of vascular dysfunction diseases. Therefore, MIF may contribute to the pathogenesis of CSVD and VCI. Here, reviewed MIF participation in chronic cerebral ischemia-hypoperfusion and neurodegeneration pathology, including new evidence for CSVD, and its potential role in protection against VCI.

Negative correlation between serum pyruvate kinase M2 and cognitive function in patients with cerebral small vessel disease

OBJECTIVE

Cerebral small vessel disease (CSVD) is one of the main contributing factors to vascular cognitive impairment (VCI), with an increasing incidence rate. However, the genesis of CSVD cognitive impairment remains unknown. Inflammation and metabolic disorders are considered important pathogenesis of CSVD. In addition to acting as the key regulator of aerobic glycolysis, pyruvate kinase muscle isozyme 2 (PKM2) is a proinflammatory mediator transcriptional activator that can promote an inflammatory response. This study explored whether serum PKM2 is associated with cognitive impairment in CSVD patients.

METHODS

The demographic data, history of risk factors, laboratory data, and cognitive function scale assessment of 219 CSVD patients were analyzed, and the correlation between the CSVD clinical data and neuroimaging parameters with serum PKM2 was further explored. The serum PKM2 level was determined by enzyme-linked immunosorbent assay using the collected serum samples. Insulin resistance (IR) was assessed with reference to the Homeostasis Model Assessment of Insulin Resistance (HOMA-IR). HOMA-IR was calculated using the formula HOMA-IR = fasting plasma glucose (FPG, mmol/L) × fasting insulin (FINS, μU/mL)/22.5. A binomial logistic regression model was referred to infer the risk factors for VCI, and the ability of serum PKM2 to diagnose VCI was assessed by using a ROC curve.

RESULTS

Serum PKM2 level was positively correlated with HOMA-IR (r = 0.206, P = 0.002), negatively correlated with MMSE and MOCA on the cognitive scale in CSVD patients, and higher in CSVD patients with white matter hyperintensities (WMH) (P < 0.001). When compared with patients without cognitive impairment, the serum PKM2 levels were elevated in cases with suspected dementia, mild dementia, mild to moderate dementia, and moderate to severe dementia, and the differences were statistically significant (P < 0.05). Serum PKM2 levels were correlated with cognitive screening test scores in CSVD.

CONCLUSION

The present findings indicated that the serum PKM2 level was positively correlated with HOMA-IR, WMH, and enlarged perivascular spaces and negatively correlated with cognitive function in CSVD patients.

Impaired dynamics of precapillary sphincters and pericytes at first-order capillaries predict reduced neurovascular function in the aging mouse brain

The microvascular inflow tract, comprising the penetrating arterioles, precapillary sphincters and first-order capillaries, is the bottleneck for brain blood flow and energy supply. Exactly how aging alters the structure and function of the microvascular inflow tract remains unclear. By in vivo four-dimensional two-photon imaging, we reveal an age-dependent decrease in vaso-responsivity accompanied by a decrease in vessel density close to the arterioles and loss of vascular mural cell processes, although the number of mural cell somas and their alpha smooth muscle actin density were preserved. The age-related reduction in vascular reactivity was mostly pronounced at precapillary sphincters, highlighting their crucial role in capillary blood flow regulation. Mathematical modeling revealed impaired pressure and flow control in aged mice during vasoconstriction. Interventions that preserve dynamics of cerebral blood vessels may ameliorate age-related decreases in blood flow and prevent brain frailty.

Accelerated brain aging with opioid misuse and HIV: New insights on the role of glially derived pro-inflammation mediators and neuronal chloride homeostasis

Opioid use disorder (OUD) has become a national crisis and contributes to the spread of human immunodeficiency virus (HIV) infection. Emerging evidence and advances in experimental models, methodology, and our understanding of disease processes at the molecular and cellular levels reveal that opioids per se can directly exacerbate the pathophysiology of neuroHIV. Despite substantial inroads, the impact of OUD on the severity, development, and prognosis of neuroHIV and HIV-associated neurocognitive disorders is not fully understood. In this review, we explore current evidence that OUD and neuroHIV interact to accelerate cognitive deficits and enhance the neurodegenerative changes typically seen with aging, through their effects on neuroinflammation. We suggest new thoughts on the processes that may underlie accelerated brain aging, including dysregulation of neuronal inhibition, and highlight findings suggesting that opioids, through actions at the μ-opioid receptor, interact with HIV in the central nervous system to promote unique structural and functional comorbid deficits not seen in either OUD or neuroHIV alone.

Sex differences in frontotemporal atrophy in CADASIL revealed by 7-Tesla MRI

Brain damage caused by small vessel disease (SVD) differs between males and females. We aimed to examine the pure sex-specific neuroanatomical mechanisms of SVD adjusted for voxel-based expected effects of age and sex on healthy brain volume. Thirty-one female and 32 male genetic SVD (cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, CADASIL) patients and 55 sex- and age-matched healthy controls (HCs) underwent 7-Tesla MRI examinations. Voxel-based W-score maps were calculated from volumes and deformations of brain tissues, controlling for the expected effects of age and sex in HCs. Significant cognitive declines in working memory and executive function were identified in male CADASIL patients compared to female patients. Greater gray matter (GM) atrophy was found in the bilateral orbitofrontal cortex (OFC), left anterior cingulate cortex (ACC), left entorhinal cortex (EC), and right temporooccipital cortex in male CADASIL patients than in females. Working memory was associated with volumes in the right OFC specific to female CADASIL patients, whereas visuospatial ability was associated with the right hOcl (primary visual area, BA 17) volume specific to males. The current findings indicate that sex affects the pathogenesis of CADASIL, ranging from differences in neuroanatomy to those in behavioral performance, which may facilitate the development of more effective sex-specific therapeutic strategies for CADASIL and SVD.

Brain microvascular disease and functional network connectivity-a call for a stage-based approach

This scientific commentary refers to 'Functional connectivity in older adults-the effect of cerebral small vessel disease' by Drenth et al. (https://doi.org/10.1093/braincomms/fcad126).

The global burden of cerebral small vessel disease in low- and middle-income countries: A systematic review and meta-analysis

BACKGROUND

Cerebral small vessel disease (cSVD) is a major cause of stroke and dementia. Previous studies on the prevalence of cSVD are mostly based on single geographically defined cohorts in high-income countries. Studies investigating the prevalence of cSVD in low- and middle-income countries (LMICs) are expanding but have not been systematically assessed.

AIM

This study aims to systematically review the prevalence of cSVD in LMICs.

RESULTS

Articles were searched from the Ovid MEDLINE and EMBASE databases from 1 January 2000 to 31 March 2022, without language restrictions. Title/abstract screening, full-text review, and data extraction were performed by two to seven independent reviewers. The prevalence of cSVD and study sample size were extracted by pre-defined world regions and health status. The Risk of Bias for Non-randomized Studies tool was used. The protocol was registered on PROSPERO (CRD42022311133). A meta-analysis of proportion was performed to assess the prevalence of different magnetic resonance imaging markers of cSVD, and a meta-regression was performed to investigate associations between cSVD prevalence and type of study, age, and male: female ratio. Of 2743 studies identified, 42 studies spanning 12 global regions were included in the systematic review. Most of the identified studies were from China (n = 23). The median prevalence of moderate-to-severe white matter hyperintensities (WMHs) was 20.5%, 40.5%, and 58.4% in the community, stroke, and dementia groups, respectively. The median prevalence of lacunes was 0.8% and 33.5% in the community and stroke groups. The median prevalence of cerebral microbleeds (CMBs) was 10.7% and 22.4% in the community and stroke groups. The median prevalence of moderate-to-severe perivascular spaces was 25.0% in the community. Meta-regression analyses showed that the weighted median age (51.4 ± 0.0 years old; range: 36.3-80.2) was a significant predictor of the prevalence of moderate-to-severe WMH and lacunes, while the type of study was a significant predictor of the prevalence of CMB. The heterogeneity of studies was high (>95%). Male participants were overrepresented.

CONCLUSIONS

This systematic review and meta-analysis provide data on cSVD prevalence in LMICs and demonstrated the high prevalence of the condition. cSVD research in LMICs is being published at an increasing rate, especially between 2010 and 2022. More data are particularly needed from Sub-Saharan Africa and Central Europe, Eastern Europe, and Central Asia.

Association of deep medullary veins with the neuroimaging burden of cerebral small vessel disease

Background

This study aimed to explore the association between deep medullary veins (DMVs) and the neuroimaging burden of cerebral small vessel disease (CSVD).

Methods

In this cross-sectional study based on a retrospective analysis, a total of 248 patients (183 males and 65 females; mean age ± standard deviation, 69.5±14.8 years) diagnosed with CSVD with complete imaging and clinical data were enrolled. Neuroimaging markers of CSVD, including white matter hyperintensities, lacunes, prominent perivascular spaces (PVSs), and cerebral microbleeds (CMBs), were identified, and the total burden of CSVD was scored. Both DMV number and DMV score were used for assessment using susceptibility-weighted imaging (SWI).

Results

With the exception of perivascular spaces, more severe neuroimaging markers were observed in patients with a higher DMV score. After adjustments were made for age and body mass index (BMI), a higher DMV score (β=1.39; P<0.001) and smaller DMV number (β=-2.55; P=0.001) were associated with an increased CSVD burden. The degree of CMBs was independently correlated with both DMV score (β=1.60; P<0.001) and DMV number (β=-2.27; P=0.009). The association between lacunes and DMV score was also significant (β=0.97; P=0.026).

Conclusions

Both DMV score and DMV number are potential imaging indicators of CSVD.

Plasticity of cerebral microvascular structure and mechanics during hypertension and following recovery of arterial pressure

Changes in vascular structure contribute to vascular events and loss of brain health. We examined changes in cerebral arterioles at the onset of hypertension and the hypothesis that alterations during hypertension would recover with the return of mean arterial pressure (MAP) to normal. MAP was measured with radiotelemetry in awake male C57BL/6J mice at baseline and during infusion of vehicle or angiotensin II (ANG II, 1.4 mg/kg/day using osmotic pumps) for 28 days, followed by a 28-day recovery. With ANG II treatment, MAP increased through day 28. On day 30, MAP began to recover, reaching levels not different from vehicle on day 37. We measured intravascular pressure, diameter, wall thickness (WT), wall:lumen ratio (W:L), cross-sectional area (CSA), and slope of the tangential elastic modulus (ET) in maximally dilated arterioles. Variables were similar in both groups at day 1, with no significant change with vehicle treatment. With ANG II treatment, CSA, WT, and W:L increased on days 7-28. Internal and external diameter was reduced at 14 and 28 days. ET versus wall stress was reduced on days 7-28. During recovery, the diameter remained at days 14 and 28 values, whereas other variables returned partly or completely to normal. Thus, CSA, WT, W:L, and ET versus wall stress changed rapidly during hypertension and recovered with MAP. In contrast, inward remodeling developed slowly and did not recover. This lack of recovery has mechanistic implications for the long-term impact of hypertension on vascular determinants of brain health.NEW & NOTEWORTHY Changes in vascular structure contribute to vascular events and loss of brain health. We examined the inherent structural plasticity of cerebral arterioles during and after a period of hypertension. Arteriolar wall thickness, diameter, wall-to-lumen ratio, and biological stiffness changed rapidly during hypertension and recovered with blood pressure. In contrast, inward remodeling developed slowly and did not recover. This lack of recovery of arteriolar diameter has implications for the long-term impact of hypertension on vascular determinants of brain health.

Mechanisms Underlying Brain Aging Under Normal and Pathological Conditions

Aging is a major risk factor for many human diseases, including cognitive impairment, which affects a large population of the elderly. In the past few decades, our understanding of the molecular and cellular mechanisms underlying the changes associated with aging and age-related diseases has expanded greatly, shedding light on the potential role of these changes in cognitive impairment. In this article, we review recent advances in understanding of the mechanisms underlying brain aging under normal and pathological conditions, compare their similarities and differences, discuss the causative and adaptive mechanisms of brain aging, and finally attempt to find some rules to guide us on how to promote healthy aging and prevent age-related diseases.

Magnetic resonance imaging reveals microemboli-mediated pathological changes in brain microstructure in diabetic rats: relevance to vascular cognitive impairment/dementia

Diabetes doubles the risk of vascular cognitive impairment, but the underlying reasons remain unclear. In the present study, we determined the temporal and spatial changes in the brain structure after microemboli (ME) injection using diffusion MRI (dMRI). Control and diabetic rats received cholesterol crystal ME (40-70 µm) injections. Cognitive tests were followed up to 16 weeks, while dMRI scans were performed at baseline and 12 weeks post-ME. The novel object recognition test had a lower d2 recognition index along with a decrease in spontaneous alternations in the Y maze test in diabetic rats with ME. dMRI showed that ME injection caused infarction in two diabetic animals (n=5) but none in controls (n=6). In diabetes, radial diffusivity (DR) was increased while fractional anisotropy (FA) was decreased in the cortex, indicating loss of tissue integrity and edema. In the dorsal hippocampus, mean diffusivity (MD), axial diffusivity (DA), and DR were significantly increased, indicating loss of axons and myelin damage. Histological analyses confirmed more tissue damage and microglial activation in diabetic rats with ME. These results suggest that ME injury and associated cerebrovascular dysfunction are greater in diabetes, which may cause cognitive deficits. Strategies to improve vascular function can be a preventive and therapeutic approach for vascular cognitive impairment.

Brain Metabolic Network Redistribution in Patients with White Matter Hyperintensities on MRI Analyzed with an Individualized Index Derived from 18F-FDG-PET/MRI

OBJECTIVE

Whether metabolic redistribution occurs in patients with white matter hyperintensities (WMHs) on magnetic resonance imaging (MRI) is unknown. This study aimed 1) to propose a measure of the brain metabolic network for an individual patient and preliminarily apply it to identify impaired metabolic networks in patients with WMHs, and 2) to explore the clinical and imaging features of metabolic redistribution in patients with WMHs.

MATERIALS AND METHODS

This study included 50 patients with WMHs and 70 healthy controls (HCs) who underwent 18F-fluorodeoxyglucose-positron emission tomography/MRI. Various global property parameters according to graph theory and an individual parameter of brain metabolic network called "individual contribution index" were obtained. Parameter values were compared between the WMH and HC groups. The performance of the parameters in discriminating between the two groups was assessed using the area under the receiver operating characteristic curve (AUC). The correlation between the individual contribution index and Fazekas score was assessed, and the interaction between age and individual contribution index was determined. A generalized linear model was fitted with the individual contribution index as the dependent variable and the mean standardized uptake value (SUVmean) of nodes in the whole-brain network or seven classic functional networks as independent variables to determine their association.

RESULTS

The means ± standard deviations of the individual contribution index were (0.697 ± 10.9) × 10-3 and (0.0967 ± 0.0545) × 10-3 in the WMH and HC groups, respectively (p < 0.001). The AUC of the individual contribution index was 0.864 (95% confidence interval, 0.785-0.943). A positive correlation was identified between the individual contribution index and the Fazekas scores in patients with WMHs (r = 0.57, p < 0.001). Age and individual contribution index demonstrated a significant interaction effect on the Fazekas score. A significant direct association was observed between the individual contribution index and the SUVmean of the limbic network (p < 0.001).

CONCLUSION

The individual contribution index may demonstrate the redistribution of the brain metabolic network in patients with WMHs.

Cerebral small vessel disease: Pathological mechanisms and potential therapeutic targets

Cerebral small vessel disease (CSVD) represents a diverse cluster of cerebrovascular diseases primarily affecting small arteries, capillaries, arterioles and venules. The diagnosis of CSVD relies on the identification of small subcortical infarcts, lacunes, white matter hyperintensities, perivascular spaces, and microbleeds using neuroimaging. CSVD is observed in 25% of strokes worldwide and is the most common pathology of cognitive decline and dementia in the elderly. Still, due to the poor understanding of pathophysiology in CSVD, there is not an effective preventative or therapeutic approach for CSVD. The most widely accepted approach to CSVD treatment is to mitigate vascular risk factors and adopt a healthier lifestyle. Thus, a deeper understanding of pathogenesis may foster more specific therapies. Here, we review the underlying mechanisms of pathological characteristics in CSVD development, with a focus on endothelial dysfunction, blood-brain barrier impairment and white matter change. We also describe inflammation in CSVD, whose role in contributing to CSVD pathology is gaining interest. Finally, we update the current treatments and preventative measures of CSVD, as well as discuss potential targets and novel strategies for CSVD treatment.

Endothelial Cells and the Cerebral Circulation

Endothelial cells form the innermost layer of all blood vessels and are the only vascular component that remains throughout all vascular segments. The cerebral vasculature has several unique properties not found in the peripheral circulation; this requires that the cerebral endothelium be considered as a unique entity. Cerebral endothelial cells perform several functions vital for brain health. The cerebral vasculature is responsible for protecting the brain from external threats carried in the blood. The endothelial cells are central to this requirement as they form the basis of the blood-brain barrier. The endothelium also regulates fibrinolysis, thrombosis, platelet activation, vascular permeability, metabolism, catabolism, inflammation, and white cell trafficking. Endothelial cells regulate the changes in vascular structure caused by angiogenesis and artery remodeling. Further, the endothelium contributes to vascular tone, allowing proper perfusion of the brain which has high energy demands and no energy stores. In this article, we discuss the basic anatomy and physiology of the cerebral endothelium. Where appropriate, we discuss the detrimental effects of high blood pressure on the cerebral endothelium and the contribution of cerebrovascular disease endothelial dysfunction and dementia. © 2022 American Physiological Society. Compr Physiol 12:3449-3508, 2022.

Angiotensin II-induced endothelial dysfunction: Impact of sex, genetic background, and rho kinase

The renin-angiotensin system (RAS) contributes to vascular disease with multiple cardiovascular risk factors including hypertension. As a major effector within the RAS, angiotensin II (Ang II) activates diverse signaling mechanisms that affect vascular biology. Despite the impact of such vascular pathophysiology, our understanding of the effects of Ang II in relation to the function of endothelial cells is incomplete. Because genetic background and biological sex can be determinants of vascular disease, we performed studies examining the direct effects of Ang II using carotid arteries from male and female mice on two genetic backgrounds, C57BL/6J and FVB/NJ. Although FVB/NJ mice are much less susceptible to atherosclerosis than C57BL/6J, the effects of Ang II on endothelial cells in FVB/NJ are poorly defined. Overnight incubation of isolated arteries with Ang II (10 nmol/L), impaired endothelial function in both strains and sexes by approximately one-half (p < 0.05). To examine the potential mechanistic contribution of Rho kinase (ROCK), we treated arteries with SLX-2119, an inhibitor with high selectivity for ROCK2. In both male and female mice of both strains, SLX-2119 largely restored endothelial function to normal, compared to vessels treated with vehicle. Thus, Ang II-induced endothelial dysfunction was observed in both FVB/NJ and C57BL/6J mice. This effect was sex-independent. In all groups, effects of Ang II were reversed by inhibition of ROCK2 with SLX-2119. These studies provide the first evidence that ROCK2 may be a key contributor to Ang II-induced endothelial dysfunction in both sexes and in mouse strains that differ in relation to other major aspects of vascular disease.

Advances in the Role of Endothelial Cells in Cerebral Small Vessel Disease

Cerebral small vessel disease (CSVD) poses a serious socio-economic burden due to its high prevalence and severe impact on the quality of life of elderly patients. Pathological changes in CSVD mainly influence small cerebral arteries, microarteries, capillaries, and small veins, which are usually caused by multiple vascular risk factors. CSVD is often identified on brain magnetic resonance imaging (MRI) by recent small subcortical infarcts, white matter hyperintensities, lacune, cerebral microbleeds (CMBs), enlarged perivascular spaces (ePVSs), and brain atrophy. Endothelial cell (EC) dysfunction is earlier than clinical symptoms. Immune activation, inflammation, and oxidative stress may be potential mechanisms of EC injury. ECs of the blood–brain–barrier (BBB) are the most important part of the neurovascular unit (NVU) that ensures constant blood flow to the brain. Impaired cerebral vascular autoregulation and disrupted BBB cause cumulative brain damage. This review will focus on the role of EC injury in CSVD. Furthermore, several specific biomarkers will be discussed, which may be useful for us to assess the endothelial dysfunction and explore new therapeutic directions.

Usefulness of arterial spin labeling perfusion as an initial evaluation of status epilepticus

This study aimed to evaluate the sensitivity and prognostic value of arterial spin labeling (ASL) in a large group of status epilepticus (SE) patients and compare them with those of other magnetic resonance (MR) sequences, including dynamic susceptibility contrast (DSC) perfusion imaging. We retrospectively collected data of patients with SE in a tertiary center between September 2016 and March 2020. MR images were visually assessed, and the sensitivity for the detection of SE and prognostication was compared among multi-delay ASL, DSC, fluid-attenuated inversion recovery (FLAIR), and diffusion-weighted imaging (DWI). We included 51 SE patients and 46 patients with self-limiting seizures for comparison. Relevant changes in ASL were observed in 90.2% (46/51) of SE patients, a percentage higher than those for DSC, FLAIR, and DWI. ASL was the most sensitive method for initial differentiation between SE and self-limiting seizures. The sensitivity of ASL for detecting refractory SE (89.5%) or estimating poor outcomes (100%) was higher than those of other MR protocols or electroencephalography and comparable to those of clinical prognostic scores, although the specificity of ASL was very low as 9.4% and 15.6%, respectively. ASL showed a better ability to detect SE and predict the prognosis than other MR sequences, therefore it can be valuable for the initial evaluation of patients with SE.

Endothelial Dysfunction and Hyperhomocysteinemia-Linked Cerebral Small Vessel Disease: Underlying Mechanisms and Treatment Timing

Cerebral small vessel disease (cSVD)—a common cause of stroke and vascular dementia—is a group of clinical syndromes that affects the brain's small vessels, including arterioles, capillaries, and venules. Its pathogenesis is not fully understood, and effective treatments are limited. Increasing evidence indicates that an elevated total serum homocysteine level is directly and indirectly associated with cSVD, and endothelial dysfunction plays an active role in this association. Hyperhomocysteinemia affects endothelial function through oxidative stress, inflammatory pathways, and epigenetic alterations at an early stage, even before the onset of small vessel injuries and the disease. Therefore, hyperhomocysteinemia is potentially an important therapeutic target for cSVD. However, decreasing the homocysteine level is not sufficiently effective, possibly due to delayed treatment, which underlying reason remains unclear. In this review, we examined endothelial dysfunction to understand the close relationship between hyperhomocysteinemia and cSVD and identify the optimal timing for the therapy.

GPR39 localization in the aging human brain and correlation of expression and polymorphism with vascular cognitive impairment

INTRODUCTION

The pathogenesis of vascular cognitive impairment (VCI) is not fully understood. GPR39, an orphan G-protein coupled receptor, is implicated in neurological disorders but its role in VCI is unknown.

METHODS

We performed GPR39 immunohistochemical analysis in post mortem brain samples from mild cognitive impairment (MCI) and control subjects. DNA was analyzed for GPR39 single nucleotide polymorphisms (SNPs), and correlated with white matter hyperintensity (WMH) burden on pre mortem magnetic resonance imaging.

RESULTS

GPR39 is expressed in aged human dorsolateral prefrontal cortex, localized to microglia and peri-capillary cells resembling pericytes. GPR39-capillary colocalization, and density of GPR39-expressing microglia was increased in aged brains compared to young. SNP distribution was equivalent between groups; however, homozygous SNP carriers were present only in the MCI group, and had higher WMH volume than wild-type or heterozygous SNP carriers.

DISCUSSION

GPR39 may play a role in aging-related VCI, and may serve as a therapeutic target and biomarker for the risk of developing VCI.

Regulation of cerebral blood flow in humans: physiology and clinical implications of autoregulation

Brain function critically depends on a close matching between metabolic demands, appropriate delivery of oxygen and nutrients, and removal of cellular waste. This matching requires continuous regulation of cerebral blood flow (CBF), which can be categorized into four broad topics: 1) autoregulation, which describes the response of the cerebrovasculature to changes in perfusion pressure; 2) vascular reactivity to vasoactive stimuli [including carbon dioxide (CO2)]; 3) neurovascular coupling (NVC), i.e., the CBF response to local changes in neural activity (often standardized cognitive stimuli in humans); and 4) endothelium-dependent responses. This review focuses primarily on autoregulation and its clinical implications. To place autoregulation in a more precise context, and to better understand integrated approaches in the cerebral circulation, we also briefly address reactivity to CO2 and NVC. In addition to our focus on effects of perfusion pressure (or blood pressure), we describe the impact of select stimuli on regulation of CBF (i.e., arterial blood gases, cerebral metabolism, neural mechanisms, and specific vascular cells), the interrelationships between these stimuli, and implications for regulation of CBF at the level of large arteries and the microcirculation. We review clinical implications of autoregulation in aging, hypertension, stroke, mild cognitive impairment, anesthesia, and dementias. Finally, we discuss autoregulation in the context of common daily physiological challenges, including changes in posture (e.g., orthostatic hypotension, syncope) and physical activity.

Microvascular changes that stagger the mind

Hypertension is a leading cause of cognitive impairment and dementias. Such loss of brain health has a vascular component, but the mechanisms involved are poorly defined. In this issue of the JCI, Koide et al. provide evidence that end-organ effects of hypertension on capillary endothelium and inward-rectifier K+ channels (Kir2.1) impair integrated propagation of electrical signals and vasodilation upstream, resulting in reduced neurovascular coupling (NVC) despite neural activation. NVC was partly restored by amlodipine, but not losartan. Moreover, NVC was improved by eplerenone in the presence of losartan, suggesting a role for aldosterone. These findings support the concept that endothelial cells and Kir2.1 are potential therapeutic targets to prevent or reverse the loss of NVC and the vascular component of cognitive deficits that occur with increased frequency during hypertension.

Indexing cerebrovascular health using near-infrared spectroscopy

Near-infrared spectroscopy (NiRS) is a relatively new technology of brain imaging with its potential in the assessment of cerebrovascular health only recently discovered. Encouraging early results suggest that NiRS can be used as an inexpensive and portable cerebrovascular health tracking device using a recently proposed pulse relaxation function (PReFx). 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PReFx, however, did not have significant correlations with any of the vascular health factors. The proposed timing index is a reliable indicator of cerebrovascular aging factors in the NiRS waveform.

Roles and Mechanisms of DNA Methylation in Vascular Aging and Related Diseases

Vascular aging is a pivotal risk factor promoting vascular dysfunction, the development and progression of vascular aging-related diseases. The structure and function of endothelial cells (ECs), vascular smooth muscle cells (VSMCs), fibroblasts, and macrophages are disrupted during the aging process, causing vascular cell senescence as well as vascular dysfunction. DNA methylation, an epigenetic mechanism, involves the alteration of gene transcription without changing the DNA sequence. It is a dynamically reversible process modulated by methyltransferases and demethyltransferases. Emerging evidence reveals that DNA methylation is implicated in the vascular aging process and plays a central role in regulating vascular aging-related diseases. In this review, we seek to clarify the mechanisms of DNA methylation in modulating ECs, VSMCs, fibroblasts, and macrophages functions and primarily focus on the connection between DNA methylation and vascular aging-related diseases. Therefore, we represent many vascular aging-related genes which are modulated by DNA methylation. Besides, we concentrate on the potential clinical application of DNA methylation to serve as a reliable diagnostic tool and DNA methylation-based therapeutic drugs for vascular aging-related diseases.

Activation of the Central Renin-Angiotensin System Causes Local Cerebrovascular Dysfunction

[Figure: see text].

Effects of cardiorespiratory fitness and exercise training on cerebrovascular blood flow and reactivity: a systematic review with meta-analyses

We address two aims: Aim 1 (Fitness Review) compares the effect of higher cardiorespiratory fitness (CRF) (e.g., endurance athletes) with lower CRF (e.g., sedentary adults) on cerebrovascular outcomes, including middle cerebral artery velocity (MCAv), cerebrovascular reactivity and resistance, and global cerebral blood flow, as assessed by transcranial Doppler (TCD) or magnetic resonance imaging (MRI). Aim 2 (Exercise Training Review) determines the effect of exercise training on cerebrovascular outcomes. Systematic review of studies with meta-analyses where appropriate. Certainty of evidence was assessed by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE). Twenty studies (18 using TCD) met the eligibility criteria for Aim 1, and 14 studies (8 by TCD) were included for Aim 2. There was a significant effect of higher CRF compared with lower CRF on cerebrovascular resistance (effect size = -0.54, 95% confidence interval = -0.91 to -0.16) and cerebrovascular reactivity (0.98, 0.41-1.55). Studies including males only demonstrated a greater effect of higher CRF on cerebrovascular resistance than mixed or female studies (male only: -0.69, -1.06 to -0.32; mixed and female studies: 0.10, -0.28 to 0.49). Exercise training did not increase MCAv (0.05, -0.21 to 0.31) but showed a small nonsignificant improvement in cerebrovascular reactivity (0.60, -0.08 to 1.28; P = 0.09). Exercise training showed heterogeneous effects on regional but little effect on global cerebral blood flow as measured by MRI. High CRF positively effects cerebrovascular function, including decreased cerebrovascular resistance and increased cerebrovascular reactivity; however, global cerebral blood flow and MCAv are primarily unchanged following an exercise intervention in healthy and clinical populations.NEW & NOTEWORTHY Higher cardiorespiratory fitness is associated with lower cerebrovascular resistance and elevated cerebrovascular reactivity at rest. Only adults with a true-high fitness based on normative data exhibited elevated middle cerebral artery velocity. The positive effect of higher compared with lower cardiorespiratory fitness on resting cerebrovascular resistance was more evident in male-only studies when compared with mixed or female-only studies. A period of exercise training resulted in negligible changes in middle cerebral artery velocity and global cerebral blood flow, with potential for improvements in cerebrovascular reactivity.