Memory's Armageddon: the Brain Fights Back Alzheimer's Disease and a Research for Development
of Innovative Treatment
"… no remembrance among those that will be afterwards."
"For there is no remembrance forever… in the coming days, all is forgotten."
Researcher: Erez Podoly
Advisers: Prof. Hermona Soreq, Prof. Oded Livnah
The Department of Biochemistry and the Wolfson Center for Applied Structural Biology, Hebrew University of Jerusalem
Background Alzheimer's Disease General: Alzheimer's disease (AD) is an incurable brain disorder characterized by a gradual decline in brain activity leading to a progressive loss of memory, reasoning ability, and personality and, eventually, to death.
Causes: One of the key pathological changes in AD is the accumulation of microscopic neuro-toxic elements that contain an insoluble protein called ß-amyloid (Aß). Aß is produced by the body from another protein which is abnormally processed in AD. Aß fragments clump together to form the neuro-toxic elements: insoluble long, spaghetti-like fibrils and toxic deposits (plaque) that fill the spaces between cells and cause the surrounding nerve cells to die. The first area affected is the hippocampus, a part of the brain that is crucial for learning and memory. The result is a reduction in the amount of acetylcholine (ACh, a neurotransmitter) secreted by the cells, which disrupts the message transmitted to other nerves and to muscles and glands.
Treatment: The most widely used treatment for AD suppresses proteins that break down ACh in an attempt to restore the quantity of this neurotransmitter to its normal level. However, this method treats the symptoms and not the cause of the disease. While it slows down patients' deterioration and improves their quality of life slightly, it does nothing to arrest or cure the disease.
There are two proteins in the family of "ACh breakers": Acetylcholinesterase (AChE) and Butyrylcholinesterase (BChE), here referred to as A and B, respectively. Both proteins chemically break down ACh in the space between two nerve cells so the next nerve impulse can be transmitted. These two proteins resemble each other very closely, both in their chemical composition and their physical structure. Researchers have shown that A is present in plaques and accelerates their production. Although protein B is also presents in plaques, its influence there was unknown. Misinterpreted findings misled researchers to assume that B has no affect on plaque production in AD.
In scientific research, a single finding is often the catalyst for new research questions. Just as castles cannot be built in the air, research questions cannot be examined without first analyzing previous findings. This was true in the case of our research as well.
Research Question 1: Do the ACh-breaking proteins A and B differ in their effect on plaque production in cases of AD?
Research Question 2: If so, what makes two similar proteins act in different ways?
Monitoring amyloid beta production in a test tube using fluorescent techniques. In this way, substances coming into contact with amyloid fibers emit fluorescent light. The light intensity measured indicates the amount of fibers produced in the test tube.
Examination of amyloid beta fibers through an electron microscope.
Construction of a computer model of the proteins' three-dimensional structure.
Synthesis of short segments of proteins - a and b - according the sequence derived from A and B, respectively.
Genetic engineering: Initially, the source of the protein was human blood, which is medically problematic due its high level of health risk and the relatively poor supply capacities. An alternative method to produce protein B at a low level of risk and in unlimited quantities utilized the advances in genetic engineering: an insertion of the human gene encoding protein B into a goat genome, so that the goat secreted B into its own milk.
Result 1: Proteins A and B have the opposite effect on the production of fibrils.
The fluorescent technique and the electron microscopic observations indicated that A accelerates the pace of fiber production when it is added to the amyloid beta test tube, while the same concentration of B slows down the process.
Result 2: The segment of protein B that is responsible for slowing down amyloid beta fiber production was identified and characterized.
Our structural analysis of the computer models of the two proteins led us to hypothesize that the ends of the proteins had the potential to produce the different effects. We therefore reexamined the rate of amyloid fiber production in the presence of the short protein segments we created (a and b), which included the ends of the whole proteins, and we arrived at the same results.
A second structural analysis revealed that one amino acid impaired the solubility properties of protein segment b but caused no such damage to protein segment a.
Discussion and Conclusions
We found, surprisingly, that the plaque formed in the brains of AD patients contains a protein that slows down the plaque's production. Even though this protein is very similar to a protein that accelerates the plaque's production, a relatively slight change in its structure possibly allows it to come into contact with the fundamental building block of the fibers and plaque, neutralizing its toxic effect. This protein, which is a natural part of our brains, is a defense against the toxicity of the plaque. It may be the brain's way of fighting AD.
Intensive research on cell cultures and laboratory mice is now in progress. If the results are consistent with those of the test tube experiments, the research might then move on to the clinical stages in which patients are tested. The aim will be to determine if BChE (B) or segments of it can be used as a form of medication for AD. If so, it would be the key to treating the destructive agent itself - the disease - and not its symptoms.
"The happiest moment in my life."
Albert Einstein, on discovering the equivalency principle, the basis for his theory of general relativity.
The Results - A scientific finding, as represented in a graph or described in several lines of an article, is most often the result of long and hard work. That "eureka" moment of achieving results is often the happiest and most satisfying of a scientist's life. Nevertheless, scientists need to view their findings critically and verify their reliability before the entire scientific community can accept them as valid. Since results can depend on the particular research method used or the way the findings were analyzed, scientists verify what they discover by repeating their experiments or conducting them in different ways, in the hope of achieving identical results; eliminating intervening variables, which can produce results but do not answer the fundamental research question; or analyzing the findings in several different ways. Scientists must also present their results straightforwardly and clearly, without casting them in the light of any interpretation they believe is correct. In reality, though, researchers adopt different scientific points of view, and a single finding can sometimes produce a number of interpretations that are not necessarily compatible. Different interpretations of the same result often lead to new research questions, which inspire new experimentation, which, in turn, promotes scientific advancement. Even though experiments are designed to answer predefined research questions, it is sometimes the findings that are not consistent with the hypothesis-or were totally unexpected-that are most interesting and have the most to contribute to scientific advancement.