endothelin-1 and Alzheimer-Disease

In brain disorders, reactive astrocytes, which are characterized by hypertrophy of the cell body and proliferative properties, are commonly observed. As reactive astrocytes are involved in the pathogenesis of several brain disorders, the control of astrocytic function has been proposed as a therapeutic strategy, and target molecules to effectively control astrocytic functions have been investigated. The production of brain endothelin-1 (ET-1), which increases in brain disorders, is involved in the pathophysiological response of the nervous system. Endothelin B (ET

Topics: Alzheimer Disease; Animals; Astrocytes; Brain Diseases; Brain Injuries; Brain Ischemia; Endothelin-1; Humans; Neuralgia; Receptor, Endothelin B

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.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Astrocytes; Brain; Brain Ischemia; Dementia, Vascular; Endothelin-1; Humans

Endothelin Converting Enzyme-1 (ECE-1) plays a significant role in the regulation of vascular tone and hence blood pressure. It has also been implicated in the pathogenesis of cardiovascular diseases, female malignancies and Alzheimer's disease. Four different isoforms of ECE-1 exist and have varying degrees of distribution throughout the cell. Production of ET-1 by ECE-1 occurs at the cell surface and the expression and localisation of ECE-1 is the rate limiting step in the production of ET-1. This review looks at the current knowledge on ECE-1 phosphorylation and other stimuli which act induce trafficking of ECE-1 to the cell surface.

Topics: Alzheimer Disease; Amino Acid Sequence; Animals; Aspartic Acid Endopeptidases; Biological Transport; Cell Membrane; CHO Cells; Cricetinae; Cricetulus; Endothelin-1; Endothelin-Converting Enzymes; Female; Humans; Metalloendopeptidases; Models, Biological; Molecular Sequence Data; Neoplasms; Phosphorylation; Protein Isoforms

The steady-state level of peptide hormones represents a balance between their biosynthesis and proteolytic processing by convertases and their catabolism by proteolytic enzymes. Low levels of neuropeptide Y, somatostatin and corticotropin-releasing factor, described in Alzheimer disease (AD), were related to a defect in proteolytic processing of their protein precursors. In contrast the abundance of beta-amyloid peptides, the major protein constituents of senile plaques is likely related to inefficient catabolism. Therefore, attention is mainly focused on convertases that generate active peptides and counter-regulatory proteases that are involved in their catabolism. Some well-described proteases such as NEP are thought to be involved in beta-amyloid catabolism. The search of other possible candidates represents a primary effort in the field. A variety of vascular risk factors such as diabetes, hypertension and arteriosclerosis suggest that the functional vascular defect contributes to AD pathology. It has also been described that beta-amyloid peptides potentiate endothelin-1 induced vasoconstriction. In this review, we will critically evaluate evidence relating proteases implicated in amyloid protein precursor proteolytic processing and beta-amyloid catabolism.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Amyloid Precursor Protein Secretases; Animals; Aspartic Acid Endopeptidases; Endopeptidases; Endothelin-1; Humans; Models, Biological; Peptide Hydrolases; Peptides

Cerebral blood flow is reduced early in the onset of Alzheimer's disease (AD). Because most of the vascular resistance within the brain is in capillaries, this could reflect dysfunction of contractile pericytes on capillary walls. We used live and rapidly fixed biopsied human tissue to establish disease relevance, and rodent experiments to define mechanism. We found that in humans with cognitive decline, amyloid β (Aβ) constricts brain capillaries at pericyte locations. This was caused by Aβ generating reactive oxygen species, which evoked the release of endothelin-1 (ET) that activated pericyte ET

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Biopsy; Capillaries; Cerebral Cortex; Cerebrovascular Circulation; Constriction, Pathologic; Endothelin-1; Humans; Hypoxia; Mice; Pericytes; Protein Multimerization; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin A; Signal Transduction; Vascular Resistance

Endothelin-1 (ET-1) is a neuroactive peptide produced by neurons, reactive astrocytes, and endothelial cells in the brain. Elevated levels of ET-1 have been detected in the post-mortem brains of individuals with Alzheimer's disease (AD). We have previously demonstrated that overexpression of astrocytic ET-1 exacerbates memory deficits in aged mice or in APP

Topics: Actin Depolymerizing Factors; Alzheimer Disease; Animals; Dendrites; Endothelin B Receptor Antagonists; Endothelin-1; Endothelins; Mice; Oxidative Stress; Peptide Fragments; Receptor, Endothelin B

The pathophysiology of sporadic Alzheimer's disease (AD) remains uncertain. Along with brain amyloid-β (Aβ) deposits and neurofibrillary tangles, cerebrovascular dysfunction is increasingly recognized as fundamental to the pathogenesis of AD. Using an experimental model of limb ischemia in transgenic APPPS1 mice, a model of AD (AD mice), we showed that microvascular impairment also extends to the peripheral vasculature in AD. At D70 following femoral ligation, we evidenced a significant decrease in cutaneous blood flow (- 29%, P < 0.001), collateral recruitment (- 24%, P < 0.001), capillary density (- 22%; P < 0.01) and arteriole density (- 28%; P < 0.05) in hind limbs of AD mice compared to control WT littermates. The reactivity of large arteries was not affected in AD mice, as confirmed by unaltered size, and vasoactive responses to pharmacological stimuli of the femoral artery. We identified blood as the only source of Aβ in the hind limb; thus, circulating Aβ is likely responsible for the impairment of peripheral vasculature repair mechanisms. The levels of the majority of pro-angiogenic mediators were not significantly modified in AD mice compared to WT mice, except for TGF-β1 and PlGF-2, both of which are involved in vessel stabilization and decreased in AD mice (P = 0.025 and 0.019, respectively). Importantly, endothelin-1 levels were significantly increased, while those of nitric oxide were decreased in the hind limb of AD mice (P < 0.05). Our results suggest that vascular dysfunction is a systemic disorder in AD mice. Assessment of peripheral vascular function may therefore provide additional tools for early diagnosis and management of AD.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Arterioles; Capillaries; Disease Models, Animal; Endothelin-1; Femoral Artery; Hindlimb; Humans; Ischemia; Mice; Mice, Transgenic; Microcirculation; Nitric Oxide; Peripheral Vascular Diseases; Placenta Growth Factor; Transforming Growth Factor beta1

Alzheimer's disease is a progressive neurodegenerative disease characterized by loss of hippocampal neurons leading to memory deficits and cognitive decline. Studies suggest that levels of the vasoactive peptide endothelin-1 (ET-1) are increased in the brain tissue of Alzheimer's patients. Curcumin, the main ingredient of the spice turmeric, has been shown to have anti-inflammatory, anti-cancer, and neuroprotective effects. However, the mechanisms underlying some of these beneficial effects are not completely understood. The objective of this study was to determine if curcumin could protect hippocampal neurons from ET-1 mediated cell death and examine the involvement of c-Jun in this pathway.. Primary hippocampal neurons from rat pups were isolated using a previously published protocol. Viability of the cells was measured by the live/dead assay. Immunoblot and immunohistochemical analyses were performed to analyze c-Jun levels in hippocampal neurons treated with either ET-1 or a combination of ET-1 and curcumin. Apoptotic changes were evaluated by immunoblot detection of cleaved caspase-3, cleaved fodrin, and a caspase 3/7 activation assay.. ET-1 treatment produced a 2-fold increase in the levels of c-Jun as determined by an immunoblot analysis in hippocampal neurons. Co-treatment with curcumin significantly attenuated the ET-1 mediated increase in c-Jun levels. ET-1 caused increased neuronal cell death of hippocampal neurons indicated by elevation of cleaved caspase-3, cleaved fodrin and an increased activity of caspases 3 and 7 which was attenuated by co-treatment with curcumin. Blockade of JNK, an upstream effector of c-Jun by specific inhibitor SP600125 did not fully protect from ET-1 mediated activation of pro-apoptotic enzymes in primary hippocampal cells.. Our data suggests that one mechanism by which curcumin protects against ET-1-mediated cell death is through blocking an increase in c-Jun levels. Other possible mechanisms include decreasing pro-apoptotic signaling activated by ET-1 in primary hippocampal neurons.

Topics: Alzheimer Disease; Animals; Apoptosis; Carrier Proteins; Caspase 3; Caspase 7; Cell Death; Cells, Cultured; Curcumin; Endothelin-1; Hippocampus; Microfilament Proteins; Neurons; Neuroprotective Agents; Proto-Oncogene Proteins c-jun; Rats; Rats, Sprague-Dawley; Signal Transduction

Vascular risk factors are associated with a higher incidence of dementia. In fact, diabetes mellitus is considered a main risk factor for Alzheimer's disease (AD) and both diseases are characterized by vascular dysfunction. However, the underlying mechanisms remain largely unknown. Here, the effects of high-sucrose-induced type 2 diabetes (T2D) in the aorta of wild type (WT) and triple-transgenic AD (3xTg-AD) mice were investigated. 3xTg-AD mice showed a significant decrease in body weight and an increase in postprandial glycemia, glycated hemoglobin (HbA1c), and vascular nitrotyrosine, superoxide anion (O2•-), receptor for the advanced glycation end products (RAGE) protein, and monocyte chemoattractant protein-1 (MCP-1) levels when compared to WT mice. High-sucrose intake caused a significant increase in body weight, postprandial glycemia, HbA1c, triglycerides, plasma vascular cell adhesion molecule 1 (VCAM-1), and vascular nitrotyrosine, O2•-, RAGE, and MCP-1 levels in both WT and 3xTg-AD mice when compared to the respective control group. Also, a significant decrease in nitric oxide-dependent vasorelaxation was observed in 3xTg-AD and sucrose-treated WT mice. In conclusion, AD and T2D promote similar vascular dysfunction of the aorta, this effect being associated with elevated oxidative and nitrosative stress and inflammation. Also, AD-associated vascular alterations are potentiated by T2D. These findings support the idea that metabolic alterations predispose to the onset and progression of dementia.

Topics: Acetylcholine; Alzheimer Disease; Amyloid beta-Protein Precursor; Analysis of Variance; Animals; Aorta; Diabetes Mellitus, Type 2; Disease Models, Animal; Endothelin-1; Humans; Mice; Mice, Inbred C57BL; Mice, Transgenic; Mutation; Nitroprusside; Presenilin-1; Superoxide Dismutase; tau Proteins; Vasodilator Agents

Sporadic Alzheimer's disease (AD) accounts for a high proportion of AD cases. Therefore, it is of importance to investigate other factors that contribute to the etiology and progression of AD. AD is characterized by decreased cholinergic tone, tau hyperphosphorylation and beta-amyloid (Aβ) accumulation. In addition to the hallmark pathology, other factors have been identified that increase the risk of AD, including stroke. This study examined the combined effects of beta-amyloid administration and unilateral stroke in an animal model of AD. Adult rats were given a sham surgery, bilateral intraventricular infusion of 10 μL of 50n mol Aβ(25-35), a unilateral injection of endothelin-1 into the right striatum, or Aβ and endothelin-1 administration in combination. Following a recovery period, rats were tested in the 1-trial place learning variant of the Morris water task followed by an ambiguous discriminative fear-conditioning to context task. After behavioural assessment, rats were euthanized, and representative sections of the medial septum were analyzed for differences in choline-acetyltransferase (ChAT) immunohistochemistry. No differences were observed in spatial working memory, but the combined effect of Aβ and stroke resulted in deficits in the discriminative fear-conditioning to context task. A trend towards decreased ChAT-positive staining in the medial septum was observed. This study indicates that Aβ and stroke in combination produce worse functional consequences than when experienced alone, furthering the concept of AD as a disease with multiple and complex etiologies.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Choline O-Acetyltransferase; Conditioning, Psychological; Disease Models, Animal; Endothelin-1; Fear; Infusions, Intraventricular; Learning; Male; Memory, Short-Term; Rats; Rats, Wistar; Septal Nuclei; Spatial Memory; Stroke

Millions of Mexico, US and across the world children are overweight and obese. Exposure to fossil-fuel combustion sources increases the risk for obesity and diabetes, while long-term exposure to fine particulate matter (PM2.5) and ozone (O3) above US EPA standards is associated with increased risk of Alzheimer's disease (AD). Mexico City Metropolitan Area children are chronically exposed to PM2.5 and O3 concentrations above the standards and exhibit systemic, brain and intrathecal inflammation, cognitive deficits, and Alzheimer disease neuropathology. We investigated adipokines, food reward hormones, endothelial dysfunction, vitamin D and apolipoprotein E (APOE) relationships in 80 healthy, normal weight 11.1±3.2 year olds matched by age, gender, BMI and SES, low (n: 26) versus high (n:54) PM2.5 exposures. Mexico City children had higher leptin and endothelin-1 (p<0.01 and p<0.000), and decreases in glucagon-like peptide-1 (GLP 1), ghrelin, and glucagon (<0.02) versus controls. BMI and leptin relationships were significantly different in low versus high PM2.5 exposed children. Mexico City APOE 4 versus 3 children had higher glucose (p=0.009). Serum 25-hydroxyvitamin D<30 ng/mL was documented in 87% of Mexico City children. Leptin is strongly positively associated to PM 2.5 cumulative exposures. Residing in a high PM2.5 and O3 environment is associated with 12h fasting hyperleptinemia, altered appetite-regulating peptides, vitamin D deficiency, and increases in ET-1 in clinically healthy children. These changes could signal the future trajectory of urban children towards the development of insulin resistance, obesity, type II diabetes, premature cardiovascular disease, addiction-like behavior, cognitive impairment and Alzheimer's disease. Increased efforts should be made to decrease pediatric PM2.5 exposures, to deliver health interventions prior to the development of obesity and to identify and mitigate environmental factors influencing obesity and Alzheimer disease.

Topics: Adolescent; Alzheimer Disease; Body Weight; Case-Control Studies; Child; Cohort Studies; Endothelin-1; Hormones; Humans; Leptin; Mexico; Obesity; Particulate Matter; Vitamin D Deficiency

Numerous clinical and epidemiological reports indicate that patients with history of vascular illness such as stroke are more likely to develop dementia as the clinical manifestation of Alzheimer's disease. However, there are little data regarding the pathologic mechanisms that link vascular risk factors to the factors associated with dementia onset. We provide evidence that suggests intriguing detrimental interactions between stroke and β-amyloid (Aβ) toxicity in the hippocampus. Stroke was induced by unilateral striatal injection of endothelin-1, the potent vasoconstrictor. Aβ toxicity was modeled by bilateral intracerebroventricular injections of the toxic fragment Aβ. Gross morphologic changes in comorbid Aβ and stroke rats were enlargement of the lateral ventricles with concomitant shrinkage of the hippocampus. The hippocampus displayed a series of synergistic biochemical alterations, including microgliosis, deposition of Aβ precursor protein fragments, and cellular degeneration. In addition, there was bilateral induction of connexin43, reduced neuronal survival, and impaired dendritic development of adult-born immature neurons in the dentate gyrus of these rats compared with either rats alone. Behaviorally, there was impairment in the hippocampal-based discriminative fear-conditioning to context task indicating learning and memory deficit. These results suggest an insight into the relationship between hippocampal atrophy, pathology, and functional impairment. Our work not only highlights the exacerbated pathology that emerges when Aβ toxicity and stroke occur comorbidly but also demonstrates that this comorbid rat model exhibits physiopathology that is highly characteristic of the human condition.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Amyloid beta-Protein Precursor; Animals; Atrophy; Connexin 43; Dementia; Disease Models, Animal; Endothelin-1; Hippocampus; Humans; Injections, Intraventricular; Male; Stroke; Vasoconstrictor Agents

Little is known about the contributors and physiological responses to white matter hypoperfusion in the human brain. We previously showed the ratio of myelin-associated glycoprotein to proteolipid protein 1 in post-mortem human brain tissue correlates with the degree of ante-mortem ischaemia. In age-matched post-mortem cohorts of Alzheimer's disease (n = 49), vascular dementia (n = 17) and control brains (n = 33) from the South West Dementia Brain Bank (Bristol), we have now examined the relationship between the ratio of myelin-associated glycoprotein to proteolipid protein 1 and several other proteins involved in regulating white matter vascularity and blood flow. Across the three cohorts, white matter perfusion, indicated by the ratio of myelin-associated glycoprotein to proteolipid protein 1, correlated positively with the concentration of the vasoconstrictor, endothelin 1 (P = 0.0005), and negatively with the concentration of the pro-angiogenic protein, vascular endothelial growth factor (P = 0.0015). The activity of angiotensin-converting enzyme, which catalyses production of the vasoconstrictor angiotensin II was not altered. In samples of frontal white matter from an independent (Oxford, UK) cohort of post-mortem brains (n = 74), we confirmed the significant correlations between the ratio of myelin-associated glycoprotein to proteolipid protein 1 and both endothelin 1 and vascular endothelial growth factor. We also assessed microvessel density in the Bristol (UK) samples, by measurement of factor VIII-related antigen, which we showed to correlate with immunohistochemical measurements of vessel density, and found factor VIII-related antigen levels to correlate with the level of vascular endothelial growth factor (P = 0.0487), suggesting that upregulation of vascular endothelial growth factor tends to increase vessel density in the white matter. We propose that downregulation of endothelin 1 and upregulation of vascular endothelial growth factor in the context of reduced ratio of myelin-associated glycoprotein to proteolipid protein 1 are likely to be protective physiological responses to reduced white matter perfusion. Further analysis of the Bristol cohort showed that endothelin 1 was reduced in the white matter in Alzheimer's disease (P < 0.05) compared with control subjects, but not in vascular dementia, in which endothelin 1 tended to be elevated, perhaps reflecting abnormal regulation of white matter perfusion in vascular dementia. Our findings

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Brain; Cohort Studies; Dementia, Vascular; Endothelin-1; Factor VIII; Female; Humans; Male; Middle Aged; Myelin-Associated Glycoprotein; Nerve Fibers, Myelinated; Peptidyl-Dipeptidase A; Vascular Endothelial Growth Factor A

Angiotensin II (AngII) receptor blockers that bind selectively AngII type 1 (AT1) receptors may protect from Alzheimer's disease (AD). We studied the ability of the AT1 receptor antagonist losartan to cure or prevent AD hallmarks in aged (~18months at endpoint, 3months treatment) or adult (~12months at endpoint, 10months treatment) human amyloid precursor protein (APP) transgenic mice. We tested learning and memory with the Morris water maze, and evaluated neurometabolic and neurovascular coupling using [(18)F]fluoro-2-deoxy-D-glucose-PET and laser Doppler flowmetry responses to whisker stimulation. Cerebrovascular reactivity was assessed with on-line videomicroscopy. We measured protein levels of oxidative stress enzymes (superoxide dismutases SOD1, SOD2 and NADPH oxidase subunit p67phox), and quantified soluble and deposited amyloid-β (Aβ) peptide, glial fibrillary acidic protein (GFAP), AngII receptors AT1 and AT2, angiotensin IV receptor AT4, and cortical cholinergic innervation. In aged APP mice, losartan did not improve learning but it consolidated memory acquisition and recall, and rescued neurovascular and neurometabolic coupling and cerebrovascular dilatory capacity. Losartan normalized cerebrovascular p67phox and SOD2 protein levels and up-regulated those of SOD1. Losartan attenuated astrogliosis, normalized AT1 and AT4 receptor levels, but failed to rescue the cholinergic deficit and the Aβ pathology. Given preventively, losartan protected cognitive function, cerebrovascular reactivity, and AT4 receptor levels. Like in aged APP mice, these benefits occurred without a decrease in soluble Aβ species or plaque load. We conclude that losartan exerts potent preventive and restorative effects on AD hallmarks, possibly by mitigating AT1-initiated oxidative stress and normalizing memory-related AT4 receptors.

Topics: Alzheimer Disease; Amyloid beta-Protein Precursor; Angiotensin II Type 1 Receptor Blockers; Animals; Arginine; Blood Pressure; Brain; Cerebrovascular Circulation; Cognition Disorders; Disease Models, Animal; Endothelin-1; Enzyme Inhibitors; Female; Gene Expression Regulation; Humans; Losartan; Male; Mice; Mice, Transgenic; Mutation

Alzheimer's disease (AD) patients have reduced cerebral blood flow. This precedes dementia and may contribute to its progression. In mice that overexpress amyloid-β protein precursor, cerebral blood flow declines before the development of plaques or cognitive abnormalities. In the brain, endothelin-1 (ET-1) is a locally acting vasoconstrictor, produced in neurons by endothelin-converting enzyme (ECE)-2 and in endothelial cells by ECE-1. Both ECEs are also capable of cleaving amyloid-β (Aβ). We previously showed ECE-2 and ET-1 to be elevated in postmortem temporal cortex from AD patients, and ECE-2 expression and ET-1 release to be upregulated by Aβ42 in vitro. We have now studied isolated leptomeningeal blood vessels from postmortem brains and found that although ECE-1 level is reduced, ECE-1 activity and ET-1 level are significantly elevated in AD vessels. This is specific to AD as there is no specific change in vascular dementia vessels. In primary cultures of human brain endothelial cells, both Aβ40 and Aβ42 caused a significant increase in ET-1 release, the increase being particularly pronounced with Aβ40. In view of previous studies implicating free radicals in the endothelial dysfunction caused by Aβ40, we examined whether Aβ-mediated ET-1 release could be prevented by the antioxidant superoxide dismutase. Addition of superoxide dismutase to cells exposed to Aβ40 prevented the increase in the concentration of ET-1. Our findings indicate that cerebral vasoconstriction induced by Aβ results in part from a free radical-mediated increase in ECE-1 activity and ET-1 production.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Aspartic Acid Endopeptidases; Brain; Endothelial Cells; Endothelin-1; Endothelin-Converting Enzymes; Endothelium, Vascular; Female; Humans; Male; Metalloendopeptidases; Middle Aged; Neurons; Peptide Fragments; Vasoconstriction

Vascular dysfunction and lowered cerebral blood flow are thought to contribute to the development and progression of Alzheimer's disease (AD). Endothelin-1 (ET-1) is a potent vasoconstrictor, the production of which is mainly catalyzed by endothelin-converting enzymes (ECEs). We previously showed that ECE-2 is upregulated by amyloid-β (Aβ), and its expression elevated in AD postmortem brain tissue. We have now investigated whether there is a concomitant increase in ET-1. We studied temporal cortex from 20 cases of sporadic AD and 20 matched controls. The cellular distribution of ET-1 was assessed immunohistochemically in paraffin sections. PreproET-1 (EDN1) mRNA and ET-1 protein were measured in homogenates of superior temporal cortex by real-time PCR and sandwich ELISA respectively. Cultured SH-SY5Y human neuroblastoma cells were incubated with 10 μM oligomeric Aβ42 for 24 h, and ET-1 protein level was measured in cell culture supernatants by sandwich ELISA. Antibody to ET-1 labeled neurons throughout the temporal cortex, and the walls of some cerebral blood vessels. ET-1 mRNA measured in the temporal neocortex was significantly elevated in AD when normalized for expression of GAPDH (p = 0.0256) or the neuronal marker neuron-specific enolase (NSE, p = 0.0001). ET-1 protein was also significantly higher in AD than in control tissue, when adjusted for neuronal content by measurement of NSE (p = 0.0275). ET-1 protein in SH-SY5Y cell supernatant rose 1.7-fold after exposure to 10 μM oligomeric Aβ (p = 0.024). These findings provide evidence of overactivity of the endothelin system in AD, further supporting the suggestion that endothelin receptor antagonists may be of value for the treatment of this disease.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Amyloid beta-Peptides; Aspartic Acid Endopeptidases; Case-Control Studies; Cell Line, Tumor; Endothelin-1; Endothelin-Converting Enzymes; Enzyme-Linked Immunosorbent Assay; Female; Humans; Male; Metalloendopeptidases; Middle Aged; Neuroblastoma; Neurons; Peptide Fragments; Phosphopyruvate Hydratase; Postmortem Changes; RNA, Messenger; Temporal Lobe; Up-Regulation

Recent studies have suggested that β-asarone have neuroprotective and cardiovascular protective effects in animal model. However, the influence of β-asarone on cerebrovascular system has not been explored so far. Therefore, present study was designed to determine whether repeated exposures to β-asarone resulted in positive effects on cerebrovascular function in AD rats.. Alzheimer's disease induced rats was established by injecting both D-galactose (D-gal) and aluminum chloride (AlCl(3)) into abdominal cavity for 42 days. After injection of AlCl(3) and D-gal or saline for 28 days, the rats were treated with volume-matched vehicle or β-asarone (25mg/kg, 50mg/kg or 100mg/kg, i.h.) or Nimodipine (40mg/kg, i.g) once daily for consecutive 14 days, respectively. Behavioral responses of animals were assessed in a Morris water maze. CBF was measured by laser Doppler flowmetry. At the end of this period all rats were sacrificed, lactic acid, pyruvic acid content, Na+K+ATPase activity were determined in brain tissue homogenate to estimate the brain biochemical changes and mRNA expression of ET-1, eNOS and APP was measured with real-time RT-PCR method.. The spatial navigation task latencies, the times through platform zone and the time for the first through platform zone in the target quadrant in probe task, rCBF of right parietal lobe, the contents of lactic acid, pyruvic acid, and the activity of Na-K-ATP of cortex, and ET-1 and eNOS mRNA expression in hippocampus of AG rats were different from those of BG, P<0.05; The level of APP mRNA expression in model control group rats was higher than that in BG, though there was not a statistically significant difference, P>0.05; Compared with AG, HG rats spatial navigation task latencies were shorter, in probe task the times through platform zone in the target quadrant were bigger, rCBF and blood cell concentration of right parietal lobe were higher, the contents of pyruvic acid was lower, the activity of Na-K-ATP was higher, and ET-1 mRNA expression in hippocampus was lower, P<0.05; The level of eNOS and APP mRNA expression in HG rats was lower than that in AG, though there was not a statistically significant difference, P>0.05;. The present results suggested that β-asarone may be useful in memory impairment due to its cerebrovascular protection in AD rats and may develop as a therapeutic drug for treatment of AD patients.

Topics: Allylbenzene Derivatives; Aluminum Chloride; Aluminum Compounds; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Anisoles; Behavior, Animal; Cerebrovascular Circulation; Chlorides; Endothelin-1; Female; Galactose; Maze Learning; Memory; Nitric Oxide Synthase Type III; Phytotherapy; Protective Agents; Rats; Rats, Wistar; RNA, Messenger

Autopsy evidence suggests that the presence of both Alzheimer(')s disease (AD) and cerebral infarction pathology is associated with more severe cognitive impairment than that produced by AD pathology alone. This study aims to investigate the effect of cerebral ischemia on cognitive function in rats with AD constructed by hippocampal injection and to determine its underlying mechanism, which is proposed to be of significance to the treatment of AD.. AD was modeled by injection of aggregated Aβ(1-40), either alone or followed by hippocampal endothelin-1 injection to mimic cerebral ischemia in hippocampus, into the right dentate gyrus (DG) of rats. The Morris water maze was used to evaluate cognitive function. Aβ deposition, neuronal loss and phosphorylated tau expression in hippocampus were examined by Congo red staining, Nissl's staining and immunohistochemistry, respectively. Reactive astrocytes, IL-1β and TNF-α expressions were measured by immunohistochemistry, in situ hybridization and reverse transcription-polymerase chain reaction.. Compared with rats treated with either Aβ or endothelin alone, rats treated with both Aβ and endothelin showed more aggravated cognitive impairment and more Aβ deposits, neuron loss, phosphorylated tau expression, reactive astrocytes, IL-1β and TNF-α expressions in hippocampus.. Hippocampal ischemia aggravates cognitive impairment of AD rats by increasing Aβ deposits, neuron loss and tau phosphorylation in hippocampus. The enhanced inflammatory response may be responsible for cerebral ischemia-induced aggravation of cognitive impairment in AD rats. Based on these findings, prevention and treatment of cerebral ischemia may improve clinical symptoms of AD and suppress the progression of AD.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Astrocytes; Brain Ischemia; Cognition Disorders; Disease Models, Animal; Drug Therapy, Combination; Endothelin-1; Hippocampus; Interleukin-1beta; Male; Maze Learning; Memory; Neurons; NF-kappa B; Peptide Fragments; Phosphorylation; Rats; Rats, Sprague-Dawley; tau Proteins; Tumor Necrosis Factor-alpha

Increased levels of transforming growth factor-beta1 (TGF-beta1) induce a vascular pathology that shares similarities with that seen in Alzheimer's disease, and which possibly contributes to the cognitive decline. In aged transgenic mice that overexpress TGF-beta1 (TGF mice), we previously found reduced dilatory function and selectively impaired endothelin-1 (ET-1)-induced contraction. Here we studied the effects of chronic treatments with selective ETA (ABT-627) or ETB (A-192621) receptor antagonist on cerebrovascular reactivity, cerebral perfusion, or memory performance. The dilatory deficit of TGF mice was not improved by either treatment, but both ET-1 contraction and basal nitric oxide (NO) production were distinctly altered. Although ABT-627 was devoid of any effect in TGF mice, it virtually abolished the ET-1-induced contraction and NO release in wild-type (WT) littermates. In contrast, A-192621 only acted upon TGF mice with full recovery of ET-1 contraction and baseline NO synthesis. TGF mice, treated or not, had no cognitive deficit in the Morris water maze, nor did ABT-627-treated WT controls despite severely impaired vasoreactivity. These findings confirm that ETA receptors primarily mediate the ET-1-induced contraction. Further, they suggest that ETB receptors play a detrimental role in conditions of increased TGF-beta1 and that vascular dysfunction does not inevitably lead to cognitive deficit.

Topics: Aging; Alzheimer Disease; Animals; Atrasentan; Blood Vessels; Brain; Cerebral Arteries; Cerebrovascular Circulation; Endothelin A Receptor Antagonists; Endothelin B Receptor Antagonists; Endothelin Receptor Antagonists; Endothelin-1; Female; Male; Maze Learning; Mice; Mice, Inbred C57BL; Mice, Transgenic; Nitric Oxide; Nitroarginine; Pyrrolidines; Transforming Growth Factor beta1; Vasoconstriction; Vasodilation; Vasodilator Agents; Vibrissae

The vasoactive protein endothelin-1 (ET-1) is produced by vascular endothelial cells and participates in the regulation of vascular inflammation. We have previously documented that the cerebral microvasculature is a source of inflammatory proteins and a likely contributor to the pathogenesis of Alzheimer's disease (AD). In this study, we (a) compare expression of ET-1 in brain microvessels isolated from AD and control brains; (b) determine thrombin regulation of ET-1 synthesis and release in brain endothelial cells; and (c) assess the effects of ET-1 on neuronal viability in vitro. Western blot analysis indicates a significantly higher level of ET-1 in AD vessels compared to vessels from age-matched controls. ET-1 expression and secretion are both induced by the inflammatory and neurotoxic protein thrombin. Pretreatment of neuronal cultures with ET-1 significantly increases neuronal survival when cells are challenged with oxidative stress (H2O2) or thrombin. The protective effect of ET-1 is blocked by incubation with an inhibitor of the c-Jun kinase (JNK) cascade. These data demonstrate that in the brain microvasculature dysfunctional or stressed endothelial cells express ET-1 and that this protein promotes the survival of brain neurons exposed to injury.

Topics: Alzheimer Disease; Analysis of Variance; Animals; Blotting, Western; Brain; Cells, Cultured; Endothelial Cells; Endothelin-1; Endothelium, Vascular; Enzyme-Linked Immunosorbent Assay; Humans; Microvessels; Neurons; Oxidative Stress; Rats; Reverse Transcriptase Polymerase Chain Reaction; Thrombin

Clinical data has shown that stroke exacerbates dementia in Alzheimer's disease (AD) patients. Previous work, combining rat models of AD and stroke have shown that neuroinflammation may be the common mediator between AD and stroke toxicity. This study examined the effects of triflusal (2-acetoxy-4-trifluoromethylbenzoic acid) in APP(23) transgenic mice receiving strokes. Six month-old APP(23) mice over-expressing mutant human amyloid precursor protein (APP) were used to model AD in this study. Unilateral injections of a potent vasoconstrictor, endothelin-1, into the striatum were used to mimic small lacunar infarcts. Immunohistochemical analysis was performed to examine AD-like pathology and inflammatory correlates of stroke and AD. APP(23) mice showed increases in AD-like pathology and inflammatory markers of AD in the cortex and hippocampus. Endothelin-induced ischemia triggered an inflammatory response along with increases in AD pathological markers in the region of the infarct. Triflusal reduced inflammation surrounding the endothelin-induced infarct only. At the dose used, anti-inflammatory treatment may be beneficial in reducing the AD and inflammatory correlates of stroke in a combined AD-stroke mouse model.

Topics: Administration, Oral; Alzheimer Disease; Amyloid beta-Protein Precursor; Animals; Antigens, CD; Brain Ischemia; Disease Models, Animal; Endothelin-1; Humans; Inflammation; Mice; Mice, Inbred C57BL; Mice, Transgenic; NF-kappa B; Platelet Aggregation Inhibitors; Salicylates; Stroke; tau Proteins; Tumor Necrosis Factor-alpha

There is evidence that vascular factors contribute substantially to Alzheimer's disease (AD). We have developed assays to reliably detect the circulation and microcirculation regulating factors C-terminal endothelin-1 precursor fragment (CT-proET-1), midregional pro-adrenomedullin (MR-proADM), and midregional pro-atrial natriuretic peptide (MR-proANP). We hypothesized that this set of blood-based (micro)circulation parameters is altered in AD.. Prospectively recruited volunteer cohort (94 patients with probable AD, 53 healthy control subjects [HC]). In plasma, CT-proET-1, MR-proADM, and MR-proANP were analyzed using sandwich luminescence immunoassays. Concentrations of plasma markers and their ratios (MR-proANP/CT-proET-1 and MR-proADM/CT-proET-1) were compared between groups. Diagnostic accuracy of the vasodilator/vasoconstrictor ratios were calculated in the training set (half of AD and HC groups, respectively) and the optimal cutoff was then applied to the test set (remaining half of the study population).. In AD patients, concentrations of MR-proADM and MR-proANP were significantly increased and levels of CT-proET-1 were significantly decreased compared with HC subjects. The ratios MR-proANP/CT-proET-1 and MR-proADM/CT-proET-1 improved group separation compared with the single markers. In a logistic regression analysis, the ratios of vasodilator/vasoconstrictor significantly contributed to group separation. The highest diagnostic accuracy was found for the MR-proANP/CT-proET-1 ratio. When applied to the training (test) set, specificity was 82% (80) and sensitivity was 81% (72).. This indicates altered expression of microcirculation parameters and supports the hypothesis of a disturbed microvascular homeostasis in AD. We generated the hypothesis that the vasodilator/vasoconstrictor ratios hold promise as a diagnostic marker of AD. The best diagnostic accuracy was achieved for the MR-proANP/CT-proET-1 ratio.

Topics: Aged; Aged, 80 and over; Alzheimer Disease; Analysis of Variance; Apolipoproteins E; Atrial Natriuretic Factor; Biomarkers; Endothelin-1; Female; Humans; Male; Microcirculation; Middle Aged; Peptide Fragments; ROC Curve; Vasoconstriction; Vasodilation

Nitric oxide (NO) is an important regulatory molecule for the host defense that plays a fundamental role in the cardiovascular, immune, and nervous systems. NO is synthesized through the conversion of L-arginine to L-citrulline by the enzyme NO synthase (NOS), which is found in three isoforms classified as neuronal (nNOS), inducible (iNOS), and endothelial (eNOS). Recent evidence supports the theory that this bioactive molecule has an influential role in the disruption of normal brain and vascular homeostasis, a condition known to elucidate chronic hypoperfusion which ultimately causes the development of brain lesions and the pathology that typify Alzheimer disease (AD). In addition, vascular NO activity appears to be a major contributor to this pathology before any overexpression of NOS isoforms is observed in the neuron, glia, and microglia of the brain tree, where the overexpression the NOS isoforms causes the formation of a large amount of NO. We hypothesize that since an imbalance between the NOS isoforms and endothelin-1 (ET-1), a human gene that encodes for blood vessel constriction, can cause antioxidant system insufficiency; by using pharmacological intervention with NO donors and/or NO suppressors, the brain lesions and the downstream progression of brain pathology and dementia in AD should be delayed or minimized.

Topics: Alzheimer Disease; Animals; Brain; Brain Injuries; Cardiovascular Diseases; Disease Progression; Endothelin-1; Humans; Nitric Oxide; Nitric Oxide Synthase; Oxidative Stress; Protein Isoforms

A beta peptides are the major protein constituents of Alzheimer's disease (AD) senile plaques and also form some deposits in the cerebrovasculature leading to cerebral amyloid angiopathy and hemorrhagic stroke. Functional vascular abnormalities are one of the earlier clinical manifestations in both sporadic and familial forms of AD. Most of the cardiovascular risk factors (for instance, diabetes, hypertension, high cholesterol levels, atherosclerosis and smoking) constitute risk factors for AD as well, suggesting that functional vascular abnormalities may contribute to AD pathology. We studied the effect of A beta on endothelin-1 induced vasoconstriction in isolated human cerebral arteries collected following rapid autopsies. We report that freshly solubilized A beta enhances endothelin-1 induced vasoconstriction in isolated human middle cerebral and basilar arteries. The vasoactive effect of A beta in these large human cerebral arteries is inhibited by NS-398, a selective cyclooxygenase-2 inhibitor and by SB202190, a specific p38 Mitogen Activated Protein Kinase inhibitor suggesting the involvement of a pro-inflammatory pathway. Using a scanner laser Doppler imager, we observed that cerebral blood flow is decreased in the double transgenic APPsw Alzheimer mouse (PS1/APPsw) compared to PS1 littermates and can be improved by chronic treatment with either NS-398 or SB202190. Altogether, our data suggest a link between inflammation and the compromised cerebral hemodynamics in AD.

Topics: Aged; Alzheimer Disease; Amyloid beta-Peptides; Animals; Cerebral Arteries; Cerebrovascular Circulation; Cerebrovascular Disorders; Cyclooxygenase 2; Disease Models, Animal; Dose-Response Relationship, Drug; Encephalitis; Endothelin-1; Endothelium, Vascular; Enzyme Inhibitors; Female; Humans; Isoenzymes; Male; Membrane Proteins; Mice; Mice, Transgenic; Mitogen-Activated Protein Kinases; p38 Mitogen-Activated Protein Kinases; Prostaglandin-Endoperoxide Synthases; Vasoconstriction

Freshly prepared soluble amyloid (Abeta) peptide has been reported to have vascular actions both in vitro and in vivo. This study was designed to examine the in vivo microvascular effects of beta in two skin microvascular model systems that might reflect possible short and long-term vascular effects of this peptide. Short-term vascular effects were examined using freshly prepared soluble Abeta(1-40) peptide superfused over naive rat skin microvasculature for 15 min. Peripheral microvascular functional changes in 9-months-old transgenic (Tg) mice overexpressing soluble beta in the brain, peripheral circulation and other tissues, were also examined. Microvascular responses were monitored using laser Doppler flowmetry from the base of a blister raised on the hind footpad of the animals. Endothelial-dependent and independent vasodilatation responses (VD) were examined using acetylcholine (ACh) and sodium nitroprusside (SNP) respectively. The exposure of naïve rat skin microvasculature to Abeta(1-40) resulted in an immediate vasoconstriction (VC) that prevented ACh but not SNP from inducing a subsequent VD response. The vascular effects of Abeta(1-40) were reversed by antioxidants (superoxide dismutase and catalase) and an endothelin A (ETA) receptor antagonist (BQ-123). Tg mice overexpressing soluble Abeta and C100 showed significant reductions in both endothelial-dependent and endothelial-independent VD that were also reversed by antioxidants and BQ-123. In conclusion, this study provided evidence to support the notion of peripheral vascular effects of Abeta in vivo and present novel evidence for alterations in endothelial and smooth muscle cell function in peripheral skin microvasculature in Tg mice overexpressing Abeta and C100. We suggest that skin microvasculature is a useful model to examine the mechanisms underlying the vascular actions of the Abeta protein.

Topics: Acetylcholine; Alzheimer Disease; Amyloid beta-Peptides; Animals; Antioxidants; Cerebral Amyloid Angiopathy; Endothelin Receptor Antagonists; Endothelin-1; Endothelium, Vascular; Humans; Laser-Doppler Flowmetry; Mice; Mice, Transgenic; Microcirculation; Nitroprusside; Peptide Fragments; Peptides, Cyclic; Rats; Rats, Sprague-Dawley; Reactive Oxygen Species; Receptor, Endothelin A; Receptors, Endothelin; Skin; Vasodilation

Topics: Alzheimer Disease; Brain; Dementia, Vascular; Endothelin-1; Humans; Nitric Oxide; Nitric Oxide Synthase; Nitric Oxide Synthase Type II; Regional Blood Flow; Risk Factors; Up-Regulation

Mounting evidence from in vitro and in vivo studies in transgenic mice overproducing beta-amyloid peptides (A beta) suggests that A beta can induce vasoconstriction and decrease cerebral blood flow. In this report, we describe the vasoactive properties of A beta, in particular the enhancement of endothelin-1-induced vasoconstriction and A beta's induction of a long-lasting vasoconstrictive event. Furthermore, we show that low doses (as low as 50 nM) of freshly solubilized A beta similar to those observed in the plasma of patients suffering from Alzheimer's disease are vasoactive. By using various inhibitors and activators of the phospholipase A2 (PLA2)/arachidonic acid (AA) cascade, we demonstrate that A beta vasoactivity is dependent on activation of this intracellular signaling pathway, resulting in stimulation of downstream cyclooxygenase-2 and 5-lipoxygenase, which mediate production of proinflammatory eicosanoids. Taken together, our data show that A beta directly activates an intracellular proinflammatory pathway, which is responsible for its vasoactive properties.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Analysis of Variance; Animals; Aorta; Cyclooxygenase Inhibitors; Endothelin-1; Humans; In Vitro Techniques; Inflammation; Lipoxygenase Inhibitors; Male; Mice; Mice, Transgenic; Muscle, Smooth, Vascular; Peptide Fragments; Rats; Rats, Sprague-Dawley; Signal Transduction; Vasoconstriction; Vasodilation

The beta-amyloid (A beta 1-40) peptide has previously been shown to enhance phenylephrine contraction of aortic rings in vitro. We have employed a novel observation, that A beta peptides enhance endothelin-1 (ET-1) contraction, to examine the relationship between vasoactivity and potential amyloidogenicity of A beta peptides, the role played by free radicals and calcium in the vasoactive mechanism, and the requirement of an intact endothelial layer for enhancement of vasoactivity. Rings of rat aortae were constricted with ET-1 before and after addition of amyloid peptide and/or other compounds, and a comparison was made between post- and pre-treatment contractions. In this system, vessel constriction is consistently dramatically enhanced by A beta 1-40, is enhanced less so by A beta 1-42, and is not enhanced by A beta 25-35. The endothelium is not required for A beta vasoactivity, and calcium channel blockers have a greater effect than antioxidants in blocking enhancement of vasoconstriction by A beta peptides. In contrast to A beta-induced cytotoxicity, A beta-induced vasoactivity is immediate, occurs in response to low doses of freshly solubilized peptide, and appears to be inversely related to the amyloidogenic potential of the A beta peptides. We conclude that the mechanism of A beta vasoactivity is distinct from that of A beta cytotoxicity. Although free radicals appear to modulate the vasoactive effects, the lack of requirement for endothelium suggests that loss of the free radical balance (between NO and O2-) may be a secondary influence on A beta enhancement of vasoconstriction. These effects of A beta on isolated vessels, and reported effects of A beta in cells of the vasculature, suggest that A beta-induced disruption of vascular tone may be a factor in the pathogenesis of cerebral amyloid angiopathy and Alzheimer's disease. Although the mechanism of enhanced vasoconstriction is unknown, it is reasonable to propose that in vivo contact of A beta peptides with small cerebral vessels may increase their tendency to constrict and oppose their tendency to relax. The subclinical ischemia resulting from this would be expected to up-regulate beta APP production in and around the vasculature with further increase in A beta formation and deposition. The disruptive and degenerative effects of such a cycle would lead to the complete destruction of cerebral vessels and consequently neuronal degeneration in the affected areas.

Topics: Alzheimer Disease; Amyloid beta-Peptides; Animals; Aorta; Calcimycin; Calcium Channel Blockers; Calcium Channels; Calcium Channels, L-Type; Cerebral Amyloid Angiopathy; Drug Synergism; Endothelin-1; Endothelium, Vascular; Ionophores; Male; Peptide Fragments; Rats; Rats, Sprague-Dawley; Vasoconstriction; Vasoconstrictor Agents; Verapamil