Alzheimer's disease and endothelial dysfunction

Phytomolecules as Alzheimer's therapeutics: A comprehensive review

Alzheimer's disease (AD) is a leading neurodegenerative disorder recognized by progressive cognitive decline and behavioral changes. The pathology of AD is characterized by the accumulation of amyloid-β (Aβ) plaques and the hyperphosphorylation of tau protein, which leads to synaptic loss and subsequent neurodegeneration. Additional contributors to disease progression include metabolic, vascular, and inflammatory factors. Glycogen synthase kinase-3β (GSK-3β) is also implicated, as it plays a crucial role in tau phosphorylation and the progression of neurodegeneration. This review provides a comprehensive analysis of various phytomolecules and their potential to target multiple aspects of AD pathology. We examined natural products from diverse classes, including stilbenes, flavonoids, phenolic acids, alkaloids, coumarins, terpenoids, chromenes, cannabinoids, chalcones, phloroglucinols, and polycyclic polyprenylated acylphloroglucinols (PPAPs). The key mechanisms of action of these phytomolecules include modulating tau protein dynamics to reduce aggregation, inhibiting acetylcholinesterase (AChE) to maintain neurotransmitter levels and enhance cognitive function, and inhibiting β-secretase (BACE1) to decrease Aβ production. Additionally, some phytomolecules were found to influence GSK-3β activity, thereby impacting tau phosphorylation and neurodegeneration. By addressing multiple targets, Aβ production, tau hyperphosphorylation, AChE activity, and GSK-3β, these natural products offer a promising multi-targeted approach to AD therapy. This review highlights their potential to develop effective treatments that not only mitigate core pathological features but also manage the complex, multifactorial aspects of AD progression.

Potential Roles of Hypoxia-Inducible Factor-1 in Alzheimer's Disease: Beneficial or Detrimental?

The major pathological characteristics of Alzheimer's disease (AD) include senile plaques and neurofibrillary tangles (NFTs), which are mainly composed of aggregated amyloid-beta (Aβ) peptide and hyperphosphorylated tau protein, respectively. The excessive production of reactive oxygen species (ROS) and neuroinflammation are crucial contributing factors to the pathological mechanisms of AD. Hypoxia-inducible factor-1 (HIF-1) is a transcription factor critical for tissue adaption to low-oxygen tension. Growing evidence has suggested HIF-1 as a potential therapeutic target for AD; conversely, other experimental findings indicate that HIF-1 induction contributes to AD pathogenesis. These previous findings thus point to the complex, even contradictory, roles of HIF-1 in AD. In this review, we first introduce the general pathogenic mechanisms of AD as well as the potential pathophysiological roles of HIF-1 in cancer, immunity, and oxidative stress. Based on current experimental evidence in the literature, we then discuss the possible beneficial as well as detrimental mechanisms of HIF-1 in AD; these sections also include the summaries of multiple chemical reagents and proteins that have been shown to exert beneficial effects in AD via either the induction or inhibition of HIF-1.

High Behavioral Reactivity to Novelty as a Susceptibility Factor for Memory and Anxiety Disorders in Streptozotocin-Induced Neuroinflammation as a Rat Model of Alzheimer's Disease

Individual differences in responsiveness to environmental factors, including stress reactivity and anxiety levels, which differ between high (HR) and low (LR) responders to novelty, might be risk factors for development of memory and anxiety disorders in sporadic Alzheimer's disease (sAD). In the present study, we investigated whether behavioral characteristics of the HR and LR rats, influence the progression of sAD (neuroinflammation, β-amyloid peptide, behavioral activity related to memory (Morris water maze) and anxiety (elevated plus maze, white and illuminated open field test) in streptozotocin (STZ)-induced neuroinflammation as a model of early pathophysiological alterations in sAD. Early (45 days) in disease progression, there was a more severe impairment of reference memory and higher levels of anxiety in HRs compared with LRs. Behavioral depression in HRs was associated with higher expression of β-amyloid deposits, particularly in the NAcS, and activation of microglia (CD68+ cells) in the hypothalamus, as opposed to less inflammation in the hippocampus, particularly in CA1, compared with LRs in late (90 days) sAD progression. Our findings suggest that rats with higher behavioral activity and increased responsivity to stressors show more rapid progression of disease and anxiety disorders compared with low responders to novelty in the STZ-induced sAD model.

Senolytics and Senomorphics Targeting p38MAPK/NF-κB Pathway Protect Endothelial Cells from Oxidative Stress-Mediated Premature Senescence

Oxidative stress is a prominent causal factor in the premature senescence of microvascular endothelial cells and the ensuing blood-brain barrier (BBB) dysfunction. Through the exposure of an in vitro model of human BBB, composed of brain microvascular endothelial cells (BMECs), astrocytes, and pericytes to H2O2, this study examined whether a specific targeting of the p38MAPK/NF-κB pathway and/or senescent cells could delay oxidative stress-mediated EC senescence and protect the BBB. Enlarged BMECs, displaying higher β-galactosidase activity, γH2AX staining, p16 expression, and impaired tubulogenic capacity, were regarded as senescent. The BBB established with senescent BMECs had reduced transendothelial electrical resistance and increased paracellular flux, which are markers of BBB integrity and function, respectively. Premature senescence disrupted plasma-membrane localization of the tight junction protein, zonula occludens-1, and elevated basement membrane-degrading matrix metalloproteinase-2 activity and pro-inflammatory cytokine release. Inhibition of p38MAPK by BIRB796 and NF-κB by QNZ and the elimination of senescent cells by a combination of dasatinib and quercetin attenuated the effects of H2O2 on senescence markers; suppressed release of the pro-inflammatory cytokines interleukin-8, monocyte chemoattractant protein-1, and intercellular adhesion molecule-1; restored tight junctional unity; and improved BBB function. In conclusion, therapeutic approaches that mitigate p38MAPK/NF-κB activity and senescent cell accumulation in the cerebrovasculature may successfully protect BBB from oxidative stress-induced BBB dysfunction.

Endothelial Dysfunction and Pre-Existing Cognitive Disorders in Stroke Patients

BACKGROUND

The origin of pre-existing cognitive impairment in stroke patients remains controversial, with a vascular or a degenerative hypothesis.

OBJECTIVE

To determine whether endothelial dysfunction is associated with pre-existing cognitive problems, lesion load and biological anomalies in stroke patients.

METHODS

Patients originated from the prospective STROKDEM study. The baseline cognitive state, assessed using the IQ-CODE, and risk factors for stroke were recorded at inclusion. Patients with an IQ-CODE score >64 were excluded. Endothelial function was determined 72 h after stroke symptom onset by non-invasive digital measurement of endothelium-dependent flow-mediated dilation and calculation of the reactive hyperemia index (RHI). RHI ≤ 1.67 indicated endothelial dysfunction. Different biomarkers of endothelial dysfunction were analysed in blood or plasma. All patients underwent MRI 72 h after stroke symptom onset.

RESULTS

A total of 86 patients were included (52 males; mean age 63.5 ± 11.5 years). Patients with abnormal RHI have hypertension or antihypertensive treatment more often. The baseline IQ-CODE was abnormal in 33 (38.4%) patients, indicating a pre-existing cognitive problem. Baseline IQ-CODE > 48 was observed in 15 patients (28.3%) with normal RHI and in 18 patients (54.6%) with abnormal RHI (p = 0.016). The RHI median was significantly lower in patients with abnormal IQ-CODE. Abnormal RHI was associated with a significantly higher median FAZEKAS score (2.5 vs. 2; p = 0.008), a significantly higher frequency of periventricular lesions (p = 0.015), more white matter lesions (p = 0.007) and a significantly higher cerebral atrophy score (p < 0.001) on MRI. Vascular biomarkers significantly associated with abnormal RHI were MCP-1 (p = 0.009), MIP_1a (p = 0.042), and homocysteinemia (p < 0.05).

CONCLUSIONS

A vascular mechanism may be responsible for cognitive problems pre-existing stroke. The measurement of endothelial dysfunction after stroke could become an important element of follow-up, providing an indication of the functional and cognitive prognosis of stroke patients.

Vascular Ageing: Mechanisms, Risk Factors, and Treatment Strategies

Ageing constitutes the biggest risk factor for poor health and adversely affects the integrity and function of all the cells, tissues, and organs in the human body. Vascular ageing, characterised by vascular stiffness, endothelial dysfunction, increased oxidative stress, chronic low-grade inflammation, and early-stage atherosclerosis, may trigger or exacerbate the development of age-related vascular diseases, which each year contribute to more than 3.8 million deaths in Europe alone and necessitate a better understanding of the mechanisms involved. To this end, a large number of recent preclinical and clinical studies have focused on the exponential accumulation of senescent cells in the vascular system and paid particular attention to the specific roles of senescence-associated secretory phenotype, proteostasis dysfunction, age-mediated modulation of certain microRNA (miRNAs), and the contribution of other major vascular risk factors, notably diabetes, hypertension, or smoking, to vascular ageing in the elderly. The data generated paved the way for the development of various senotherapeutic interventions, ranging from the application of synthetic or natural senolytics and senomorphics to attempt to modify lifestyle, control diet, and restrict calorie intake. However, specific guidelines, considering the severity and characteristics of vascular ageing, need to be established before widespread use of these agents. This review briefly discusses the molecular and cellular mechanisms of vascular ageing and summarises the efficacy of widely studied senotherapeutics in the context of vascular ageing.

Endothelial dysfunction predicts bleeding and cardiovascular death in acute coronary syndrome

BACKGROUNDS

Recently, there has been increasing awareness that bleeding may lead to adverse outcomes. Endothelial dysfunction is associated with increased risk of cardiovascular and bleeding events. This study aimed to investigate the association of endothelial dysfunction with major bleeding and specific causes of death in addition to major adverse cardiovascular events in patients with acute coronary syndrome.

METHODS

This single-centre retrospective observational study was conducted at a tertiary-care hospital; patients with acute coronary syndrome were included between June 2010 and November 2014 (median follow-up, 6.1 years). The reactive hyperaemia index was assessed before their discharge; reactive hyperaemia index <1.67 was defined as endothelial dysfunction. The main outcomes were the incidence of major bleeding, all-cause death, cardiovascular death, non-cardiovascular death, resuscitated cardiac arrest, non-fatal myocardial infarction, non-fatal stroke, and hospitalisation for heart failure.

RESULTS

Among the included 674 patients with acute coronary syndrome, 264 (39.2%) had endothelial dysfunction. Multivariable Cox-hazard analyses revealed an independent predictive value of endothelial dysfunction for major bleeding (hazard ratio 2.29, 95% confidence interval 1.17-4.48, P = 0.016) and major adverse cardiovascular events (hazard ratio 2.04, 95% confidence interval 1.43-2.89, P < 0.001). The endothelial dysfunction group patients had a 2.5-fold greater risk of cardiovascular death; however, no association was found with non-cardiovascular death.

CONCLUSION

Endothelial dysfunction assessed using reactive hyperaemia index predicted future major cardiovascular event as well as major bleeding and cardiovascular death in patients with acute coronary syndrome.

Therapeutic potential of intranasal photobiomodulation therapy for neurological and neuropsychiatric disorders: a narrative review

The application of photobiomodulation therapy (PBMT) for neuronal stimulation is studied in different animal models and in humans, and has shown to improve cerebral metabolic activity and blood flow, and provide neuroprotection via anti-inflammatory and antioxidant pathways. Recently, intranasal PBMT (i-PBMT) has become an attractive and potential method for the treatment of brain conditions. Herein, we provide a summary of different intranasal light delivery approaches including a nostril-based portable method and implanted deep-nasal methods for the effective systemic or direct irradiation of the brain. Nostril-based i-PBMT devices are available, using either lasers or light emitting diodes (LEDs), and can be applied either alone or in combination to transcranial devices (the latter applied directly to the scalp) to treat a wide range of brain conditions such as mild cognitive impairment, Alzheimer's disease, Parkinson's disease, cerebrovascular diseases, depression and anxiety as well as insomnia. Evidence shows that nostril-based i-PBMT improves blood rheology and cerebral blood flow, so that, without needing to puncture blood vessels, i-PBMT may have equivalent results to a peripheral intravenous laser irradiation procedure. Up to now, no studies were conducted to implant PBMT light sources deep within the nose in a clinical setting, but simulation studies suggest that deep-nasal PBMT via cribriform plate and sphenoid sinus might be an effective method to deliver light to the ventromedial part of the prefrontal and orbitofrontal cortex. Home-based i-PBMT, using inexpensive LED applicators, has potential as a novel approach for neurorehabilitation; comparative studies also testing sham, and transcranial PBMT are warranted.

Brachial Flow-mediated Dilation and Risk of Dementia: The Cardiovascular Health Study

INTRODUCTION

Brachial flow-mediated dilation (FMD) is a physiologic measure of endothelial function. We determined the prospective association of brachial FMD with incident dementia among older adults.

METHODS

We included 2777 Cardiovascular Health Study participants who underwent brachial FMD measurement. Incident dementia was ascertained by medication use, International Classification of Diseases-9 codes, requirement for a proxy, and death certificates and calibrated to gold-standard assessments performed in a subset of the cohort.

RESULTS

Mean participant age at time of brachial FMD measurement was 77.9 years. We identified 1650 incident dementia cases (median follow-up=10.5 y). After adjusting for age, race, sex, education, clinic site, and baseline arterial diameter, risk of dementia for participants in the highest quartile of percent brachial FMD did not differ from those in lowest quartile (hazard ratio=0.89, 95% confidence interval: 0.77, 1.03).

CONCLUSIONS

Brachial FMD, measured late in life, is not associated with an increased risk of incident dementia.

CHA2DS2-VASc scores and Intermountain Mortality Risk Scores for the joint risk stratification of dementia among patients with atrial fibrillation

BACKGROUND

High CHA₂DS₂-VASc scores in atrial fibrillation (AF) patients are generally associated with increased risks of stroke and dementia. At lower CHA₂DS₂-VASc scores, there remains an unquantifiable cranial injury risk, necessitating an improved risk assessment method within these lower-risk groups.

OBJECTIVE

The purpose of this study was to determine whether sex-specific Intermountain Mortality Risk Scores (IMRS), a dynamic measures of systemic health that comprises commonly performed blood tests, can stratify dementia risk overall and among CHA₂DS₂-VASc score strata in AF patients.

METHODS

Female (n = 34,083) and male (n = 39,998) AF patients with no history of dementia were studied. CHA₂DS₂-VASc scores were assessed at the time of AF diagnosis and were stratified into scores of 0-1, 2, and ≥3. Within each CHA₂DS₂-VASc score stratum, patients were further stratified by IMRS categories of low, moderate, and high. Multivariable Cox hazard regression was used to determine dementia risk.

RESULTS

High-risk IMRS patients were generally older and had higher rates of hypertension, diabetes, heart failure, and prior stroke. Higher CHA₂DS₂-VASc score strata (≥3 vs ≤1: women, hazard ratio [HR] 7.77, 95% confidence interval [CI] 5.94-10.17, P < .001; men: HR 4.75, 95% CI 4.15-5.44, P < .001) and IMRS categories (high vs low: women, HR 3.09, 95% CI 2.71-3.51, P < .001; men, HR 2.70, 95% CI 2.39-3.06, P < .001) were predictive of dementia. When stratified by CHA₂DS₂-VASc scores, IMRS further identified risk in each stratum.

CONCLUSION

Both CHA₂DS₂-VASc scores and IMRS were independently associated with dementia incidence among AF patients. IMRS further stratified dementia risk among CHA₂DS₂-VASc score strata, particularly among those with lower CHA₂DS₂-VASc scores.

Alterations of transcriptome signatures in head trauma-related neurodegenerative disorders

Chronic traumatic encephalopathy (CTE) is a neurodegenerative disease that is associated with repetitive traumatic brain injury (TBI). CTE is known to share similar neuropathological features with Alzheimer’s disease (AD), but little is known about the molecular properties in CTE. To better understand the neuropathological mechanism of TBI-related disorders, we conducted transcriptome sequencing analysis of CTE including AD and CTE with AD (CTE/AD) post-mortem human brain samples. Through weighted gene co-expression network analysis (WGCNA) and principal component analysis (PCA), we characterized common and unique transcriptome signatures among CTE, CTE/AD, and AD. Interestingly, synapse signaling-associated gene signatures (such as synaptotagmins) were commonly down-regulated in CTE, CTE/AD, and AD. Quantitative real-time PCR (qPCR) and Western blot analyses confirmed that the levels of synaptotagmin 1 (SYT1) were markedly decreased in CTE and AD compared to normal. In addition, calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase A (PKA), protein kinase C (PKC), and AMPA receptor genes that play a pivotal role in memory function, were down-regulated in head trauma-related disorders. On the other hand, up-regulation of cell adhesion molecules (CAMs) associated genes was only found in CTE. Our results indicate that dysregulation of synaptic transmission- and memory function-related genes are closely linked to the pathology of head injury-related disorder and AD. Alteration of CAMs-related genes may be specific pathological markers for the CTE pathology.

Chronic cerebral hypoperfusion: An undefined, relevant entity

Despite the large body of data available, chronic cerebral hypoperfusion lacks an operative definition. In a tautological way, the term hypoperfusion is being referred to conditions of "inadequate blood flow", "defects of perfusion" or "dysfunction of autoregulation". The chronicity refers to sustained conditions or wavering states characterized by repeated phases of inefficient functional hyperemia. The phenomenon may affect the whole brain or defined areas. A few defined clinical disorders, including heart failure, hypotension, atherosclerosis of large or small vessels and carotid stenosis are thought to cause progressive brain disorders due to chronic hypoperfusion. The clinical relevance manifests mostly as neurocognitive disorders associated with neuroimaging changes.The available data support a conceptual framework that considerschronic cerebral hypoperfusiona likely, relevant pathogenic mechanism for the neurodegeneration-like progression of the neurocognitive disorders. The relationship between neuropathology, cerebral perfusion, and symptoms progression is, however, elusive for several aspects. Typical microangiopathy findings, such as MRI white matter hyperintensities, may appear in individuals without any cerebrovascular risk or vascular lesions. Pathology features of the MRI changes, such as demyelination and gliosis, may result from dysfunction of the neuro-vascular unit not directly associated withvascular mechanisms. In this review, we aim to overview the most common clinical conditions thought to reflect chronic hypoperfusion.

Acute Intake of a Grape and Blueberry Polyphenol-Rich Extract Ameliorates Cognitive Performance in Healthy Young Adults During a Sustained Cognitive Effort

Despite an increasing level of evidence supporting the individual beneficial effect of polyphenols on cognitive performance, information related to the potential synergistic action of these phytonutrients on cognitive performance during a prolonged cognitive effort is currently lacking. This study investigated the acute and sustained action of a polyphenols-rich extract from grape and blueberry (PEGB), on working memory and attention in healthy students during a prolonged and intensive cognitive effort. In this randomised, cross-over, double blind study, 30 healthy students consumed 600 mg of PEGB or a placebo. Ninety minutes after product intake, cognitive functions were assessed for one hour using a cognitive demand battery including serial subtraction tasks, a rapid visual information processing (RVIP) task and a visual analogical scale. Flow-mediated dilation (FMD) and plasma flavan-3-ols metabolites quantification were also performed. A 2.5-fold increase in serial three subtraction variation net scores was observed following PEGB consumption versus placebo (p < 0.001). A trend towards significance was also observed with RVIP percentage of correct answers (p = 0.058). No treatment effect was observed on FMD. Our findings suggest that consumption of PEGB coupled with a healthy lifestyle may be a safe alternative to acutely improve working memory and attention during a sustained cognitive effort.

Factors associated with the onset of Alzheimer's disease: Data mining in the French nationwide discharge summary database between 2008 and 2014

INTRODUCTION

Identifying modifiable risk factors for Alzheimer's disease (AD) is critical for research. Data mining may be a useful tool for finding new AD associated factors.

METHODS

We included all patients over 49 years of age, hospitalized in France in 2008 (without dementia) and in 2014. Dependent variable was AD or AD dementia diagnosis in 2014. We recoded the diagnoses of hospital stays (in ICD-10) into 137 explanatory variables.To avoid overweighting the "age" variable, we divided the population into 7 sub-populations of 5 years.

RESULTS

We analyzed 1,390,307 patients in the PMSI in 2008 and 2014: 55,997 patients had coding for AD or AD dementia in 2014 (4.04%). We associated Alzheimer disease in 2014 with about 20 variables including male sex, stroke, diabetes mellitus, mental retardation, bipolar disorder, intoxication, Parkinson disease, depression, anxiety disorders, alcohol, undernutrition, fall and 3 less explored variables: intracranial hypertension (odd radio [95% confidence interval]: 1.16 [1.12-1.20] in 70-80 years group), psychotic disorder (OR: 1.09 [1.07-1.11] in 70-75 years group) and epilepsy (OR: 1.06 [1.05-1.07] after 70 years).

DISCUSSION

We analyzed 137 variables in the PMSI identified some well-known risk factors for AD, and highlighted a possible association with intracranial hypertension, which merits further investigation. Better knowledge of associations could lead to better targeting (identifying) at-risk patients, and better prevention of AD, in order to reduce its impact.

Age-related changes in cerebrovascular reactivity and their relationship to cognition: A four-year longitudinal study

Although cerebrovascular factors are the second leading cause of cognitive impairment and dementia in elderly, the precise spatial and temporal trajectories of vascular decline in aging have not been fully characterized. With an advanced cerebrovascular reactivity (CVR) MRI technique that specifically informs vascular stiffness and dilatory ability of cerebral vessels, we present four-year longitudinal CVR data measured in 116 healthy individuals (20-88 years of age). Our data revealed a spatial heterogeneity in vascular decline in aging (p = 0.003), in that temporal lobe showed the fastest rate of longitudinal CVR decline, followed by parietal and frontal lobes. The rate of CVR decline was also age-dependent. Middle age, not older age, manifested the fastest rate of longitudinal CVR decline (p < 0.05). Longitudinal changes in CVR were associated with changes in processing speed (p = 0.031) and episodic memory (p = 0.022), but not with working memory or reasoning. The rate of longitudinal CVR change was not different between hypertensive and normotensive participants. However, cross-sectionally, individuals with hypertension revealed in a lower CVR compared to normotensive participants (p = 0.016). These findings help elucidate age-related decline in brain hemodynamics and support CVR as a non-invasive biomarker in evaluating cerebrovascular conditions in elderly individuals.

Vitamin C, Aging and Alzheimer's Disease

Accumulating evidence in mice models of accelerated senescence indicates a rescuing role of ascorbic acid in premature aging. Supplementation of ascorbic acid appeared to halt cell growth, oxidative stress, telomere attrition, disorganization of chromatin, and excessive secretion of inflammatory factors, and extend lifespan. Interestingly, ascorbic acid (AA) was also found to positively modulate inflamm-aging and immunosenescence, two hallmarks of biological aging. Moreover, ascorbic acid has been shown to epigenetically regulate genome integrity and stability, indicating a key role of targeted nutrition in healthy aging. Growing in vivo evidence supports the role of ascorbic acid in ameliorating factors linked to Alzheimer’s disease (AD) pathogenesis, although evidence in humans yielded equivocal results. The neuroprotective role of ascorbic acid not only relies on the general free radical trapping, but also on the suppression of pro-inflammatory genes, mitigating neuroinflammation, on the chelation of iron, copper, and zinc, and on the suppression of amyloid-beta peptide (Aβ) fibrillogenesis. Epidemiological evidence linking diet, one of the most important modifiable lifestyle factors, and risk of Alzheimer's disease is rapidly increasing. Thus, dietary interventions, as a way to epigenetically modulate the human genome, may play a role in the prevention of AD. The present review is aimed at providing an up to date overview of the main biological mechanisms that are associated with ascorbic acid supplementation/bioavailability in the process of aging and Alzheimer’s disease. In addition, we will address new fields of research and future directions.

Possible role of endothelin receptor against hyperhomocysteinemia and β-amyloid induced AD type of vascular dementia in rats

Vascular dementia (VaD) is considered as the second commonest form of dementia after Alzheimer's disease (AD). The study was designed to investigate the effect of endothelin receptor against β-amyloid induced AD type of vascular dementia. This disease was induced by combine administration of single ICV (intracerebroventricle) infusion of β-amyloid (Aβ) once and chronic oral administration of l-Methionine for 21 days. Bosentan (dual endothelin receptor antagonist) was administered for 21 days. Behavioral alterations were observed during different time interval of the study. Animals were killed immediately following the last behavior session. Oxidative parameters, acetylcholinesterase activity, neuro-inflammatory markers, amyloid beta levels were determined in hippocampus and cortex while serum homocysteine, serum nitrite carotid artery superoxide anion level were also determined. Endothelial function was measured on isolated carotid artery using myograph instrument. Aβ+l-Methionine showed more significant development of cognitive and vascular endothelial deficits, manifested in terms of increase in serum homocysteine level, endothelial dysfunction, impairment of learning and memory, enhanced brain acetylcholinesterase activity, marked mito-oxidative damage in rats. We have observed that l-Methionine and combination of Aβ+l-Methionine significantly enhanced Aβ level both in cortex as well as hippocampus. Treatment of bosentan attenuated Aβ+l-Methionine induced impairment of learning and memory, enhanced Aβ level, mitochondrial and endothelial dysfunction. The results of present study concluded that bosentan offers protection against β-amyloid-induced vascular dementia in rats. Endothelin receptor may be considered as a potential pharmacological target for the management of AD type of vascular dementia.

Examination of candidate exonic variants for association to Alzheimer disease in the Amish

Alzheimer disease (AD) is the most common cause of dementia. As with many complex diseases, the identified variants do not explain the total expected genetic risk that is based on heritability estimates for AD. Isolated founder populations, such as the Amish, are advantageous for genetic studies as they overcome heterogeneity limitations associated with complex population studies. We determined that Amish AD cases harbored a significantly higher burden of the known risk alleles compared to Amish cognitively normal controls, but a significantly lower burden when compared to cases from a dataset of unrelated individuals. Whole-exome sequencing of a selected subset of the overall study population was used as a screening tool to identify variants located in the regions of the genome that are most likely to contribute risk. By then genotyping the top candidate variants from the known AD genes and from linkage regions implicated previous studies in the full dataset, new associations could be confirmed. The most significant result (p = 0.0012) was for rs73938538, a synonymous variant in LAMA1 within the previously identified linkage peak on chromosome 18. However, this association is specific to the Amish and did not generalize when tested in a dataset of unrelated individuals. These results suggest that additional risk variation in the Amish remains to be identified and likely resides outside of the classical protein coding gene regions.

Nut consumption for vascular health and cognitive function

Nuts are rich in many nutrients that can benefit multiple cardiometabolic functions, including arterial compliance, blood pressure, inflammation, glucoregulation and endothelial vasodilatation. Impaired vasodilatation may contribute to impaired cognitive performance due to poor cerebral perfusion. The present narrative review examines associations between nut consumption, vascular health and cognitive function. It includes a systematic search which identified seventy-one epidemiological or intervention studies in which effects of chronic nut consumption on blood pressure, glucoregulation, endothelial vasodilator function, arterial compliance, inflammatory biomarkers and cognitive performance were evaluated. Weighted mean changes were estimated where data were available; they indicate that nut consumption reduces blood pressure and improves glucoregulation, endothelial vasodilator function and inflammation, whilst a limited number of studies suggest that nut consumption may also improve cognitive performance. Further clinical trials are warranted to explore relationships between nut consumption, endothelial function and cognitive function.

The impact of hypertension on cerebral perfusion and cortical thickness in older adults

Hypertension may increase risk for dementia possibly because of its association with decreased cortical thickness. Disturbed cerebral autoregulation is one plausible mechanism by which hypertension impacts the cerebral structure, but the associations among hypertension, brain perfusion, and cortical thickness are poorly understood. The current sample consisted of 58 older adults with varying levels of vascular disease. Diagnostic history of hypertension and antihypertensive medication status was ascertained through self-report, and when available, confirmed by medical record review. All participants underwent arterial spin labeling and T1-weighted magnetic resonance imaging to quantify total and regional cortical perfusion and thickness. Analysis of covariance adjusting for medical variables showed that participants with hypertension exhibited reduced temporal and occipital brain perfusion and total and regional cortical thickness relative to those without hypertension. The effects of hypertension on total brain perfusion remained unchanged even after adjustment for age, although no such pattern emerged for cortical thickness. Decreased total brain perfusion predicted reduced thickness of the total brain and of the frontal, temporal, and parietal lobe cortices. Antihypertensive treatment was not associated with total cerebral perfusion or cortical thickness. This study provides initial evidence for the adverse effects of a diagnostic history of hypertension on brain hypoperfusion and reduced cortical thickness. Longitudinal studies are needed to investigate the role of hypertension and its interaction with other contributing factors (e.g., age) in the manifestation of cerebral hypoperfusion and reduced cortical thickness.

The neglected co-star in the dementia drama: the putative roles of astrocytes in the pathogeneses of major neurocognitive disorders

Alzheimer's disease (AD) and vascular dementia are the major causes of cognitive disorders worldwide. They are characterized by cognitive impairments along with neuropsychiatric symptoms, and that their pathogeneses show overlapping multifactorial mechanisms. Although AD has long been considered the most common cause of dementia, individuals afflicted with AD commonly exhibit cerebral vascular abnormalities. The concept of mixed dementia has emerged to more clearly identify patients with neurodegenerative phenomena exhibiting both AD and cerebral vascular pathologies-vascular damage along with β-amyloid (Aβ)-associated neurotoxicity and τ-hyperphosphorylation. Cognitive impairment has long been commonly explained through a 'neuro-centric' perspective, but emerging evidence has shed light over the important roles that neurovascular unit dysfunction could have in neuronal death. Moreover, accumulating data have been demonstrating astrocytes being the essential cell type in maintaining proper central nervous system functioning. In relation to dementia, the roles of astrocytes in Aβ deposition and clearance are unclear. This article emphasizes the multiple events triggered by ischemia and the cytotoxicity exerted by Aβ either alone or in association with endothelin-1 and receptor for advanced glycation end products, thereby leading to neurodegeneration in an 'astroglio-centric' perspective.

Cardiorenal metabolic syndrome and diabetic cognopathy

The prevalence of the cardiorenal metabolic syndrome (CRS) is increasing in parallel with obesity, type 2 diabetes mellitus, Alzheimer's disease, and other forms of dementia. Along with metabolic, inflammatory, and immunological abnormalities, there is maladaptive structural remodeling of the heart, kidney, and brain. The term 'diabetic cognopathy' (DC) may be used when discussing functional and structural changes in the brain of the diabetic patient. DC likely represents an advanced form of these changes in the brain that evolve with increasing duration of the CRS and subsequent clinical diabetes. We posit that DC develops due to a convergence of aging, genetic and lifestyle abnormalities (overnutrition and lack of exercise), which result in multiple injurious metabolic and immunologic toxicities such as dysfunctional immune responses, oxidative stress, inflammation, insulin resistance, and dysglycemia (systemically and in the brain). These converging abnormalities may lead to endothelial blood-brain barrier tight junction/adherens junction (TJ/AJ) complex remodeling and microglia activation, which may result in neurodegeneration, impaired cognition, and dementia. Herein, we describe the brain ultrastructural changes evolving from a normal state to maladaptive remodeling in rodent models of CRS including microglia activation/polarization and attenuation and/or loss of the TJ/AJ complexes, pericytes and astrocytes of the neurovascular unit. Further, we discuss the potential relationship between these structural changes and the development of DC, potential therapeutic strategies, and future directions.

Alzheimer's disease treated patients showed different patterns for oxidative stress and inflammation markers

Alzheimer's disease (AD) is the most common type of dementia accounting for 60-80% of the reported cases. The aim of this study was to evaluate levels of certain parameters of oxidative stress and markers of endothelial dysfunction in the blood of 21 AD patients under standard treatment compared with 10 controls, in an attempt to elucidate the contribution of AD to the total oxidative stress status of the patients. Results indicate that IL-6, TNF-α, ADMA and homocysteine levels were significantly elevated in AD patients. Protein carbonyls levels were higher in AD group, while glutathione reductase and total antioxidant capacity were lower, depicting decreased defense ability against reactive oxygen species. Besides, a higher level of advanced glycation end-products was observed in AD patients. Depending on the treatment received, a distinct inflammatory and oxidative stress profile was observed: in Rivastigmine-treated group, IL6 levels were 47% lower than the average value of the remaining AD patients; homocysteine and glutathione reductase were statistically unchanged in the Rivastigmine and Donepezil-Memantine, respectively Donepezil group. Although the study is based on a limited population, the results could constitute the basis for further studies regarding the effect of medication and diet on AD patients.

The possible role of antioxidant vitamin C in Alzheimer's disease treatment and prevention

Oxidative stress is suggested to play a major role in the pathogenesis of Alzheimer's disease (AD). Among the antioxidants, vitamin C has been regarded as the most important one in neural tissue. It also decreases β-amyloid generation and acetylcholinesterase activity and prevents endothelial dysfunction by regulating nitric oxide, a newly discovered factor in the pathogenesis and progression of AD. However, clinical trials using antioxidants, including vitamin C, in patients with AD yielded equivocal results. The current article discusses the relevance of vitamin C in the cellular and molecular pathogenesis of AD and explores its therapeutic potential against this neurodegenerative disorder.

Pharmacological inhibition of inducible nitric oxide synthase (iNOS) and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, convalesce behavior and biochemistry of hypertension induced vascular dementia in rats

Cognitive disorders are likely to increase over the coming years (5-10). Vascular dementia (VaD) has heterogeneous pathology and is a challenge for clinicians. Current Alzheimer's disease drugs have had limited clinical efficacy in treating VaD and none have been approved by major regulatory authorities specifically for this disease. Role of iNOS and NADPH-oxidase has been reported in various pathological conditions but there role in hypertension (Hypt) induced VaD is still unclear. This research work investigates the salutiferous effect of aminoguanidine (AG), an iNOS inhibitor and 4'-hydroxy-3'-methoxyacetophenone (HMAP), a NADPH oxidase inhibitor in Hypt induced VaD in rats. Deoxycorticosterone acetate-salt (DOCA-S) hypertension has been used for development of VaD in rats. Morris water-maze was used for testing learning and memory. Vascular system assessment was done by testing endothelial function. Mean arterial blood pressure (MABP), oxidative stress [aortic superoxide anion, serum and brain thiobarbituric acid reactive species (TBARS) and brain glutathione (GSH)], nitric oxide levels (serum nitrite/nitrate) and cholinergic activity (brain acetyl cholinesterase activity-AChE) were also measured. DOCA-S treated rats have shown increased MABP with impairment of endothelial function, learning and memory, reduction in serum nitrite/nitrate & brain GSH levels along with increase in serum & brain TBARS, and brain AChE activity. AG as well as HMAP significantly convalesce Hypt induced impairment of learning, memory, endothelial function, and alterations in various biochemical parameters. It may be concluded that AG, an iNOS inhibitor and HMAP, a NADPH-oxidase inhibitor may be considered as potential agents for the management of Hypt induced VaD.

Activation of PARP by oxidative stress induced by β-amyloid: implications for Alzheimer's disease

Alzheimer's disease (AD) is a major neurodegenerative disease of old age, characterised by progressive cognitive impairment, dementia and atrophy of the central nervous system. The pathological hallmarks include the accumulation of the peptide β-amyloid (Aβ) which itself is toxic to neurons in culture. Recently, it has been discovered that Aβ activates the protein poly(ADP-ribosyl) polymerase-1 (PARP-1) specifically in astrocytes, leading indirectly to neuronal cell death. PARP-1 is a DNA repair enzyme, normally activated by single strand breaks associated with oxidative stress, which catalyses the formation of poly ADP-ribose polymers from nicotinamide adenine dinucleotide (NAD(+)). The pathological over activation of PARP-1 causes depletion of NAD(+) and leads to cell death. Here we review the relationship between AD and PARP-1, and explore the role played by astrocytes in neuronal death. AD has so far proven refractory to any effective treatment. Identification of these pathways represents a step towards a greater understanding of the pathophysiology of this devastating disease with the potential to explore novel therapeutic targets.

Attenuation of vascular dementia by sodium butyrate in streptozotocin diabetic rats

RATIONALE

Vascular dementia is the second leading cause of dementia, which is strongly associated with diabetes. Diabetes and dementia have become a major public health concern worldwide. At this point of time, it is very important to find the possible pharmacological agents which may be useful in management and therapy of dementia including Alzheimer's disease, vascular dementia, etc.

OBJECTIVES

To investigate the effect of sodium butyrate on streptozotocin (STZ) diabetes induced vascular dementia in rats.

METHODS

Diabetes and subsequent endothelial dysfunction and dementia were induced in rats by administration of single dose of STZ. Drug treatment was started after 1 month of STZ administration and treatment was continued until the end of the study. Morris water maze (MWM) test was employed for testing learning and memory. Endothelial function was measured on isolated aortic rings using student physiograph. Serum glucose, body weight, serum nitrite/nitrate, aortic superoxide anion generation, brain thiobarbituric acid reactive species (TBARS), reduced glutathione (GSH) levels, and acetylcholinesterase activity were also tested.

RESULTS

STZ treatment produced endothelial dysfunction, impairment of learning and memory, reduction in body weight and serum nitrite/nitrate, and increase in serum glucose, aortic and brain oxidative stress (increased superoxide anion, TBARS, and decreased GSH levels), and brain acetylcholinesterase activity. Treatment of sodium butyrate attenuated diabetes induced impairment of learning, memory, endothelial function, and various biochemical parameters.

CONCLUSIONS

Sodium butyrate may be considered as potential pharmacological agent for the management of diabetes induced vascular dementia.

Neurovascular dysfunction, inflammation and endothelial activation: implications for the pathogenesis of Alzheimer's disease

Alzheimer's disease (AD) is an age-related disorder characterized by progressive cognitive decline and dementia. Alzheimer's disease is an increasingly prevalent disease with 5.3 million people in the United States currently affected. This number is a 10 percent increase from previous estimates and is projected to sharply increase to 8 million by 2030; it is the sixth-leading cause of death. In the United States the direct and indirect costs of Alzheimer's and other dementias to Medicare, Medicaid and businesses amount to more than $172 billion each year. Despite intense research efforts, effective disease-modifying therapies for this devastating disease remain elusive. At present, the few agents that are FDA-approved for the treatment of AD have demonstrated only modest effects in modifying clinical symptoms for relatively short periods and none has shown a clear effect on disease progression. New therapeutic approaches are desperately needed. Although the idea that vascular defects are present in AD and may be important in disease pathogenesis was suggested over 25 years ago, little work has focused on an active role for cerebrovascular mechanisms in the pathogenesis of AD. Nevertheless, increasing literature supports a vascular-neuronal axis in AD as shared risk factors for both AD and atherosclerotic cardiovascular disease implicate vascular mechanisms in the development and/or progression of AD. Also, chronic inflammation is closely associated with cardiovascular disease, as well as a broad spectrum of neurodegenerative diseases of aging including AD. In this review we summarize data regarding, cardiovascular risk factors and vascular abnormalities, neuro- and vascular-inflammation, and brain endothelial dysfunction in AD. We conclude that the endothelial interface, a highly synthetic bioreactor that produces a large number of soluble factors, is functionally altered in AD and contributes to a noxious CNS milieu by releasing inflammatory and neurotoxic species.

Type 1 diabetes predisposes to enhanced gingival leukocyte margination and macromolecule extravasation in vivo

BACKGROUND AND OBJECTIVE

Diabetes predisposes to periodontal disease. However, the cellular and molecular mechanisms linking the two conditions are not clear. The impact of chronic hyperglycemia on leukocyte margination and macromolecule extravasation was determined in gingival vessels in vivo.

MATERIALS AND METHODS

Gingival intravital microscopy was employed to measure extravasation of fluorescein isothiocyanate (FITC)-dextran in diabetic Akita and healthy wild-type (WT) mice. Rhodamine 6G and FITC-LY6G were injected for nonspecific and polymorphonuclear-specific leukocyte labeling, respectively. Surface expression of leukocyte adhesion molecules was determined with flow cytometry and western blotting.

RESULTS

Vascular permeability was significantly increased in Akita gingival vessels compared with WT [permeability index (PI): WT, 0.75 ± 0.05; Akita, 1.1 ± 0.03: p < 0.05). Wild-type gingival vessels reached comparable permeability 2 h after intragingival injection of tumor necrosis factor α (TNFα), used here as positive control (PI, 1.17 ± 0.16). The number of rolling leukocytes was significantly elevated in diabetic gingiva (WT, 25 ± 3.7 cells/min; Akita, 42 ± 8.5 cells/min; p < 0.03). Similar rolling cell counts were obtained in WT after intragingival injection of TNFα (10 ng TNFα, 47 ± 1.3 cells/min; 100 ng TNFα, 57.5 ± 5.85 cells/min). The number of leukocytes firmly attached to the endothelium was similar in WT and Akita mice. Leukocyte cell-surface expression of P-selectin glycoprotein ligand-1 and CD11a was increased in Akita mice, while L-selectin remained unchanged when compared with WT. Moreover, P-selectin expression in Akita gingival tissues was elevated compared with that of WT.

CONCLUSION

Chronic hyperglycemia induces a proinflammatory state in the gingival microcirculation characterized by increased vascular permeability, and leukocyte and endothelial cell activation. Leukocyte-induced microvascular damage, in turn, may contribute to periodontal tissue damage in diabetes.

[Cognitive impairment and chronic kidney disease: which links?]

Ageing of the population leads to an increase of cognitive disorders and chronic renal failure incidence. Compared to the general population, prevalence of cognitive impairment is more important in renal failure patients, especially in dialyzed patients. No direct link has been established between renal failure and cognitive impairment. The care of older and older patients and the high frequency of vascular risk factors, in particular hypertension and diabetes, partially explain the prevalence of vascular dementia and Alzheimer disease in this population. Other factors as the anemia, phosphocalcic metabolism disorders facilitate the cognitive impairment. The present work reviews the links existing between chronic renal failure and cognitive impairment.