Hope on the Horizon For Alzheimer’s Disease Pathogenesisby Viatcheslav Wlassoff, PhD | August 23, 2015
Right now, there is only symptomatic treatment for Alzheimer’s disease, which does not stall the progress of the disease. Nor does this approach provide insights on the causes. But if findings from recent research studies are to be weighed upon, this is about to change.
Alzheimer’s disease (AD) is a curse, both for the person who has been afflicted with the condition and his loved ones. AD affects millions of elderly individuals all over the world and the number of cases is on the rise, as the quality of healthcare services improves, life expectancy increases and our population ages.
Scientists long believed that an abnormal level of beta-amyloid peptide (A?) production and accumulation is a probable cause of AD. This view is corroborated by a number of independent scientific studies.
However, scientists now believe that the A? peptides alone are not the culprits. These peptides provide some health benefits as well; it is only when they proliferate abnormally that they may trigger the development of AD. Too much of a good thing can be bad! These findings can help scientists as they tinker with therapeutic approaches that can keep A? peptide levels under control.
Beta amyloids: The double-edged sword
According to multiple research studies, individuals afflicted with AD tend to develop plaques in various areas of their brains in the early stages of the disease. These plaques are made up of A? peptides and are believed to hamper normal neural functions by disrupting synaptic connectivity. Scientists believe that these deposits trigger and worsen the symptoms related to neurodegeneration that are associated with AD. These findings have encouraged scientists to explore diagnostic approaches to detect AD early and treatment methodologies that would stem the progress of the disease by preventing A? peptide deposits from building up to alarming levels.
However, some more recent studies have hinted that the association between abnormal A? peptide deposits and the development and progress of AD is not so simple. Researchers found that not all individuals with neurodegeneration show abnormal A? peptide accumulation in their brains. What’s more, there is not always a positive correlation between A? peptides and neurodegeneration. In fact, AD-afflicted individuals with a high amount of a compound called PirB in their brains show poorer cognitive performance triggered by neural degeneration than individuals with just high levels of A? peptides.
These findings got scientists into thinking that A? deposits may not always trigger AD and that there could be other diagnostic tools, like the PirB level, to detect the disease earlier.
The confirmation came from another study that established the beneficial properties of A? peptide deposits. The A? protein occurs in two forms: a shorter and a longer form. The shorter form binds more readily to copper (about 1,000 times more strongly) than the longer form. Although copper is needed by the human body to function normally, abnormally high amounts of it causes adverse health effects. For instance, too much copper triggers formation of free radicals that are harmful for the body.
By binding copper, shorter form A? peptides reduce the amount of copper that would have gone on to generate harmful free radicals. This, in turn, reduces oxidative stress in the brain. However, as always, too much of a good thing is bad. Too many shorter A? peptides tend to cluster and absorb copper from other areas of the body where the metal is needed. What is more, an abnormally high amount of shorter form A? peptides in the brain increases the amount of copper.
These findings indicate that not all A? peptides are harmful and can lead to AD. Nor is the presence of A? peptides alone a cause for concern. The type of A? peptides present in the brain and the amount in which they are present should be taken into consideration before pronouncing an individual as a high-risk candidate for AD.
The above findings corroborate the results obtained in an earlier study, which demonstrated that neural damage starts to occur as soon as the A? peptides begin forming clumps. Scientists believe that the damage is greater in the early stages of clumping because these small clusters can move around the brain faster and thus kill more neural cells.
The abnormal accumulation of A? peptides in the brain triggers another development that is believed to lead to neural damage. The damage to the brain cells by the clumped A? peptides triggers inflammatory responses. This, in turn, leads to the production of another harmful cluster that is composed of tau protein. This new development aggravates neural degeneration and worsens the symptoms of AD.
The above findings have led scientists to explore another pharmacological approach to stem the progress of AD. They are now looking to develop drugs that will prevent the A? peptides from clumping together. Drug trials are on, and it is believed that among the current crop, Reminyl could be beneficial by treating the root cause of neural damage. However, scientists also need to concentrate on pharmacological approaches that will control the levels of both A? and tau protein.
The PirB angle in the development and progress of AD
Scientists have also discovered another element that they believe can increase the harmful effects of A? peptide clusters. The symptoms of AD are manifest even before the A? peptides accumulate to form plaques. This is because PirB, which is a powerful beta-amyloid receptor, attracts and binds the peptides — both the individual molecules and the clusters. This leads to the formation of bigger A? peptide clusters that go on to accelerate the neural degeneration process.
The slew of research to nail the pathogenesis of AD has laid bare several loopholes in the previously-held amyloid hypothesis. But this gives hope that scientists are now nearer to finding a cure for AD than ever before. More experiments have to be conducted, but the direction is clear.
Beckett TL, Webb RL, Niedowicz DM, Holler CJ, Matveev S, Baig I, LeVine H 3rd, Keller JN, & Murphy MP (2012). Postmortem Pittsburgh Compound B (PiB) binding increases with Alzheimer’s disease progression. Journal of Alzheimer’s disease : JAD, 32 (1), 127-38 PMID: 22766739
Gandy, S., & DeKosky, S. (2013). Toward the Treatment and Prevention of Alzheimer’s Disease: Rational Strategies and Recent Progress Annual Review of Medicine, 64 (1), 367-383 DOI: 10.1146/annurev-med-092611-084441
Goldsworthy, M., & Vallence, A. (2013). The Role of -Amyloid in Alzheimer’s Disease-Related Neurodegeneration Journal of Neuroscience, 33 (32), 12910-12911 DOI: 10.1523/JNEUROSCI.2252-13.2013
Hong-Qi, Y., Zhi-Kun, S., & Sheng-Di, C. (2012). Current advances in the treatment of Alzheimer’s disease: focused on considerations targeting A? and tau Translational Neurodegeneration, 1 (1) DOI: 10.1186/2047-9158-1-21
Kim, T., Vidal, G., Djurisic, M., William, C., Birnbaum, M., Garcia, K., Hyman, B., & Shatz, C. (2013). Human LilrB2 Is a -Amyloid Receptor and Its Murine Homolog PirB Regulates Synaptic Plasticity in an Alzheimer’s Model Science, 341 (6152), 1399-1404 DOI: 10.1126/science.1242077
Mokhtar, S., Bakhuraysah, M., Cram, D., & Petratos, S. (2013). The Beta-Amyloid Protein of Alzheimer’s Disease: Communication Breakdown by Modifying the Neuronal Cytoskeleton International Journal of Alzheimer’s Disease, 2013, 1-15 DOI: 10.1155/2013/910502
Mondragón-Rodríguez, S., Perry, G., Zhu, X., & Boehm, J. (2012). Amyloid Beta and Tau Proteins as Therapeutic Targets for Alzheimer’s Disease Treatment: Rethinking the Current Strategy International Journal of Alzheimer’s Disease, 2012, 1-7 DOI: 10.1155/2012/630182
Singh, I., Sagare, A., Coma, M., Perlmutter, D., Gelein, R., Bell, R., Deane, R., Zhong, E., Parisi, M., Ciszewski, J., Kasper, R., & Deane, R. (2013). Low levels of copper disrupt brain amyloid-? homeostasis by altering its production and clearance Proceedings of the National Academy of Sciences, 110 (36), 14771-14776 DOI: 10.1073/pnas.1302212110
Wirth, M., Madison, C., Rabinovici, G., Oh, H., Landau, S., & Jagust, W. (2013). Alzheimer’s Disease Neurodegenerative Biomarkers Are Associated with Decreased Cognitive Function but Not -Amyloid in Cognitively Normal Older Individuals Journal of Neuroscience, 33 (13), 5553-5563 DOI: 10.1523/JNEUROSCI.4409-12.2013
No future articles scheduled.
This Sunday February 14th (9 p.m. ET), the Emmy-nominated Brain Games tv-show is back! Wonder junkie Jason Silva returns to our screens, teaming up with... READ MORE →
Like what you read? Give to Brain Blogger sponsored by GNIF with a tax-deductible donation.Make A Donation