Alzheimer’s Drugs Linked to a Reduced Risk of Heart Attacks

The European Heart Journal, an online publication, looked at a study from Sweden involving Alzheimer’s medication and heart attacks.  The research, which had a testing base of 7,000 people with Alzheimer’s disease, showed that drugs typically administered in the early stages of Alzheimer’s reduced patient risk of heart attack and death by any means.

The study looked at cholinesterase inhibitors (ChEIs), including donepezil, rivastigmine, and galantamine, which aid in the treatment of moderate Alzheimer’s disease.  Scientists became interested in the possible effect of this drug on the heart because it is targeted at reducing the chronic inflammation seen in Alzheimer’s patients, and a side effect of ChEls is the calming of the vagus nerve, which is responsible for controlling the heartbeat.  At Umea University in Sweden, Professor Peter Nordstrom and his colleagues followed 7,073 people with Alzheimer’s disease who appeared on the Swedish Dementia Registry for an average of two years. They found that those individuals who were on ChEIs had a 36 percent reduced risk of death in general, a 38 percent reduced risk of a myocardial infarction (heart-attack), and a 26 percent reduction in the risk of any cardiovascular-related death, such as stroke, compared to those not on the ChEIs. Professor Nordstrom remarked the results if translated into absolute figures representing the data of one year for a group of 100,000 individuals with Alzheimer’s disease on ChEls; there would be 180 fewer heart attacks (295 compared to 475), and 1,125 fewer deaths overall (2000 cases versus 3,125).  It was also recorded that patients who took the highest levels possible of ChEIs while remaining safe had a 65% lower risk of heart attack and a 46 % lower risk of death than those who did not take the anti-inflammatory.  As a control, scientists tested other types of medication commonly administered to Alzheimer’s and dementia patients, and the research found no change or significant results. The study holds scientific uncertainty, for while it yields promising data, the scientists cannot say that ChEls are responsible for the lowering the risks, only that is in some way related to said reduction.  However, the strong results hold promise, and Professor Nordstrom said that further experimentation and trials involving the anti-inflammatory drug could bring forth more information regarding its role in the reduction of risk of myocardial infarction and death.

1) P. Nordstrom, D. Religa, A. Wimo, B. Winblad, M. Eriksdotter. The use of cholinesterase inhibitors and the risk of myocardial infarction and death: a nationwide cohort study in subjects with Alzheimer’s disease. European Heart Journal, 2013; DOI: 10.1093/eurheartj/eht182

2) European Society of Cardiology (ESC) (2013, June 5). Alzheimer’s disease drugs linked to reduced risk of heart attacks. ScienceDaily. Retrieved June 7, 2013, from http://www.sciencedaily.com/releases/2013/06/130605090257.htm

By Lauren Horne

The Roskamp Institute is a 501(c)3 research facility dedicated to translating the efforts of its qualified research staff into real-world results for those suffering from neurological diseases. To learn more about our programs and to get information about donating, visit http://www.rfdn.org.

Alzheimer’s disease: Molecular Trigger Found?

Scientists at Cambridge’s Department of Chemistry have been able to construct a detailed map that shows how the formation of aberrant proteins in the brain can lead to a build-up so massive that it causes the development of numerous brain-damaging diseases, chief among them being Alzheimer’s.

In 2010, the Alzheimer’s Research Trust found that dementia alone cost the UK economy 23 billion euros, more than the costs of cancer and heart disease combined. Normally, proteins are made up of chemical building blocks known as amino acids, which are joined together in a code ordered by our DNA. New proteins appear as long, thin strips, which are then intricately folded to properly carry out their designated biological function. However, there are points at which the amyloid-beta protein misfolds or unfolds and gets tangled with other newly-made proteins. The tangles stick to one another until they number in the millions, known as amyloid fibrils, and they start the huge deposits of proteins known as plaque, which are so large, they become insoluble.

When the plaque in the brain reaches a critical level, a chain reaction is set off, and new focal points of tendrils form. From these tendrils, a smaller number of proteins, known as toxic oligomers, can easily diffuse through membranes, effectively killing neurons and causing memory loss as well as other dementia symptoms. This new groundbreaking information required scientists to come together, using kinetic experiments with a framework of theory. Master equations, more commonly used in the fields of chemistry and physics, aided researchers in their efforts to better understand Alzheimer’s, and how effectively to fight it.

 

Sources:

 

Source 1)

University of Cambridge (2013, May 20). Molecular trigger for Alzheimer’s disease identified. ScienceDaily. Retrieved May 22, 2013,

 

Source 2)

Samuel I. A. Cohen, Sara Linse, Leila M. Luheshi, Erik Hellstrand, Duncan A. White, Luke Rajah, Daniel E. Otzen, Michele Vendruscolo, Christopher M. Dobson, and Tuomas P. J. Knowles. Proliferation of amyloid-β42 aggregates occurs through a secondary nucleation mechanism. Proceedings of the National Academy of Sciences, 2013; DOI: 10.1073/pnas.1218402110

 

By Lauren Horne

The Roskamp Institute is a 501(c)3 research facility dedicated to translating the efforts of its qualified research staff into real-world results for those suffering from neurological diseases. To learn more about our programs and to get information about donating, visit http://www.rfdn.org.

Anti-Tumoral Activity of a Short Decapeptide Fragment of the Alzheimer’s Abeta Peptide.

The inhibition of angiogenesis is regarded as a promising avenue for cancer treatment. Although some antiangiogenic compounds are in the process of development and testing, these often prove ineffective in vivo, therefore the search for new inhibitors is critical. We have recently identified a ten amino acid fragment of the Alzheimer Abeta peptide that is anti-angiogenic both in vitro and in vivo. In the present study, we investigated the antitumoral potential of this decapeptide using human MCF-7 breast carcinoma xenografts nude mice. We observed that this decapeptide was able to suppress MCF-7 tumor growth more potently than the antiestrogen tamoxifen. Inhibition of tumor vascularization as determined by PECAM-1 immunostaining and decreased tumor cell proliferation as determined by Ki67 immunostaining were observed following treatment with the Abeta fragment. In vitro, this peptide had no direct impact on MCF-7 tumor cell proliferation and survival suggesting that the inhibition of tumor growth and tumor cell proliferation observed in vivo is related to the antiangiogenic activity of the peptide. Taken together these data suggest that this short Abeta derivative peptide may constitute a new antitumoral agent.

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Impaired orthotopic glioma growth and vascularization in transgenic mouse models of Alzheimer’s disease.

Alzheimer’s disease (AD) is the most common form of dementia among the aging population and is characterized pathologically by the progressive intracerebral accumulation of beta-amyloid (Abeta) peptides and neurofibrillary tangles. The level of proangiogenic growth factors and inflammatory mediators with proangiogenic activity is known to be elevated in AD brains which has led to the supposition that the cerebrovasculature of AD patients is in a proangiogenic state. However, angiogenesis depends on the balance between proangiogenic and antiangiogenic factors and the brains of AD patients also show an accumulation of endostatin and Abeta peptides which have been shown to be antiangiogenic. To determine whether angiogenesis is compromised in the brains of two transgenic mouse models of AD overproducing Abeta peptides (Tg APPsw and Tg PS1/APPsw mice), we assessed the growth and vascularization of orthotopically implanted murine gliomas since they require a high degree of angiogenesis to sustain their growth. Our data reveal that intracranial tumor growth and angiogenesis is significantly reduced in Tg APPsw and Tg PS1/APPsw mice compared with their wild-type littermates. In addition, we show that Abeta inhibits the angiogenesis stimulated by glioma cells when cocultured with human brain microvascular cells on a Matrigel layer. Altogether our data suggest that the brain of transgenic mouse models of AD does not constitute a favorable environment to support neoangiogenesis and may explain why vascular insults synergistically precipitate the cognitive presentation of AD.

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Characterization and use of human brain microvascular endothelial cells to examine β-amyloid exchange in the blood-brain barrier. Bachmeier C, Mullan M, Paris D.

Alzheimer’s disease (AD) is characterized by excessive cerebrovascular deposition of the β-amyloid peptide (Aβ). The investigation of Aβ transport across the blood-brain barrier (BBB) has been hindered by inherent limitations in the cellular systems currently used to model the BBB, such as insufficient barrier properties and poor reproducibility. In addition, many of the existing models are not of human or brain origin and are often arduous to establish and maintain. Thus, we characterized an in vitro model of the BBB employing human brain microvascular endothelial cells (HBMEC) and evaluated its utility to investigate Aβ exchange at the blood-brain interface. Our HBMEC model offers an ease of culture compared with primary isolated or coculture BBB models and is more representative of the human brain endothelium than many of the cell lines currently used to study the BBB. In our studies, the HBMEC model exhibited barrier properties comparable to existing BBB models as evidenced by the restricted permeability of a known paracellular marker. In addition, using a simple and rapid fluormetric assay, we showed that antagonism of key Aβ transport proteins significantly altered the bi-directional transcytosis of fluorescein-Aβ (1-42) across the HBMEC model. Moreover, the magnitude of these effects was consistent with reports in the literature using the same ligands in existing in vitro models of the BBB. These studies establish the HBMEC as a representative in vitro model of the BBB and offer a rapid fluorometric method of assessing Aβ exchange between the periphery and the brain.

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Depletion of CXCR2 inhibits γ-secretase activity and amyloid-β production in a murine model of Alzheimer’s disease.

Alzheimer’s disease (AD) is a neurodegenerative disorder that leads to progressive cognitive decline. Recent studies from our group and others have suggested that certain G-protein coupled receptors (GPCRs) can influence the processing of the amyloid precursor protein (APP). Earlier, we demonstrated that stimulation of a chemokine receptor, CXCR2, results in enhanced γ-secretase activity and in increased amyloid-beta (Aβ) production. Taken together, results obtained from in vitro studies indicate that therapeutic targeting of CXCR2 might aid in lowering Aβ levels in the AD brain. To better understand the precise function and to predict the consequences of CXCR2 depletion in the AD brain, we have crossed CXCR2 knockout mice with mice expressing presenilin (PS1 M146L) and APPsw mutations (PSAPP). Our present study confirms that CXCR2 depletion results in reduction of Aβ with concurrent increases of γ-secretase substrates. At the mechanistic level, the effect of CXCR2 on γ-secretase was not found to occur via their direct interaction. Furthermore, we provide evidence that Aβ promotes endocytosis of CXCR2 via increasing levels of CXCR2 ligands. In conclusion, our current study confirms the regulatory role of CXCR2 in APP processing, and poses it as a potential target for developing novel therapeutics for intervention in AD.

For more information on the Roskamp Institute and Alzheimer’s please visit:

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Induction of drug efflux protein expression by venlafaxine but not desvenlafaxine.

Venlafaxine and its metabolite desvenlafaxine are serotonin-norepinephrine reuptake inhibitors currently prescribed for the treatment of depression. Previously, it was reported that venlafaxine is an inducer of MDR1, the gene responsible for P-glycoprotein (P-gp). The present study expanded upon these findings by examining the effect of venlafaxine and desvenlafaxine on the expression of both P-gp and the breast cancer resistance protein (BCRP) in human brain endothelial cells (HBMEC), an in vitro model of the blood-brain barrier (BBB). The HBMEC were treated for 1 h with various concentrations (500 nM to 50 µM) of venlafaxine and desvenlafaxine. Western blot analysis revealed treatment with venlafaxine significantly induced the expression of P-gp (2-fold) and BCRP (1.75-fold) in a dose-dependent manner, while treatment with desvenlafaxine had no effect on drug efflux transporter expression. To determine the functional significance of this effect, the permeability of a known drug efflux probe, rhodamine 123, across the BBB model and Caco-2 cells, a model of intestinal absorption, were examined. Treatment with venlafaxine (1-50 µM) for 1 h significantly reduced the apical-to-basolateral permeability of R123 across the BBB model (30%) and Caco-2 cell monolayers (25%), indicative of increased drug efflux transporter expression at the apical membrane. Conversely, desvenlafaxine had no effect on R123 permeability in either cellular model. These studies indicate that venlafaxine, but not desvenlafaxine is an inducer of drug efflux transporter expression, which consequently increases the potential for clinical drug-drug interactions. Therefore, based on these preliminary results, caution should be taken when prescribing venlafaxine with other P-gp substrates.

for more information on the Roskamp Institute and Alzheimer’s please visit:

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