In this blog post, we will examine the role of β-amyloid, which is believed to be the cause of Alzheimer’s disease, and the current state of neuroscientific research to understand why a cure is so difficult to find.

What is neuroscience?

Many people today do not know what neuroscience is. In a nutshell, neuroscience is the study of the anatomy, physiology, biochemistry, and pharmacology of the nervous system. The benefits of neuroscience to our lives are enormous. In this article, we will introduce Alzheimer’s disease, which is currently a hot topic in neuroscience. I think most people have heard the word ‘Alzheimer’s’ at least once in their lives. In fact, there have been many dramas and films on the subject of Alzheimer’s disease recently. However, few people know what Alzheimer’s disease actually is. Due to the ageing population, the treatment of dementia is becoming the focus of more and more scientists, and investment in this field is also increasing. Despite this interest, dementia remains a widespread disease with no known cure. In Japan, there are approximately 1 million people suffering from dementia, and in the United States, that number is four times higher. Statistically, about one in five people over the age of 85 will develop the disease.

What is dementia?

So what is dementia? According to reports, the causes of dementia can be divided into two categories. One is the death of nerve cells called neurons, which occurs when the blood vessels leading to the brain become blocked. In most cases, this is caused by excessive cholesterol intake. However, since diseases caused by blockages in blood vessels can occur not only in the brain but also throughout the body, it is more accurate to consider this cause as a disease related to blood vessels rather than a brain disease.
Another category is Alzheimer’s disease, which is the subject of this article. The name Alzheimer’s was named after a doctor named Alzheimer who discovered dementia in 1906. The symptoms of Alzheimer’s disease appear over a long period of time, and the process is as follows. First, slight memory loss occurs. Then, as the disease progresses, confusion about one’s identity begins. They do not know where they are, whether it is morning or evening, and in more severe cases, they do not even know who they are. As the disease progresses, they eventually become unable to walk on their own and even wander around the hallway making strange noises. Therefore, we decided to learn about the characteristics and causes of Alzheimer’s disease.

Characteristics of Alzheimer’s disease

One of the characteristics of Alzheimer’s disease is brain shrinkage. As you can see in the photo above, the brain of a patient with Alzheimer’s disease is about half the size of a normal brain. When viewed under a microscope, the number of nerve cells is also reduced by about half. Of course, it is natural for the number of nerve cells to decrease with age, but in Alzheimer’s patients, the rate of decline is abnormally fast. Another characteristic of Alzheimer’s disease is senile plaques. Senile plaques are found only in patients with Alzheimer’s disease, and many scientists predict that these plaques are the cause of Alzheimer’s disease. So what exactly are these senile plaques, and what causes them?

β-amyloid, the component of senile plaques

According to scientific reports, senile plaques cause the destruction of nerve cells. As a result of studying these senile plaques, it was discovered that they are composed of a substance called β-amyloid. This β-amyloid is toxic, and this toxicity kills nerve cells. So how is this β-amyloid produced?
In the process of searching for the cause of β-amyloid, scientists accidentally discovered a family tree in which Alzheimer’s disease was genetically transmitted. This led scientists to focus on the brains of members of this family, and in 1991, they discovered a gene associated with the disease. The protein associated with this gene is called amyloid precursor protein (APP), which is located on human chromosome 21. APP is a protein that forms the basis of β-amyloid. In other words, when APP is cut, what remains is β-amyloid. In Alzheimer’s patients, this cutting of APP occurs much faster than in normal people. So what are the ‘scissors’ that cut β-amyloid?
The scissors that scientists have discovered that cut APP are a substance called ‘proteasome,’ a protein produced by the 14th gene. In fact, there are two types of scissors that cut β-amyloid, and one of them is a substance called proteasome. In the case of genetic Alzheimer’s disease, it appears due to the abnormal expression of this proteasome. Perhaps the action of proteasome occurs much faster than in normal people.

The process by which β-amyloid causes Alzheimer’s disease

So what does β-amyloid do? Until now, scientists believed that β-amyloid killed nerve cells. However, further research has shown that the amount of β-amyloid required to kill cells is quite high. In other words, only when β-amyloid levels are very high do they cause cell death, but even small amounts of β-amyloid can cause Alzheimer’s disease. Therefore, scientists came to believe that β-amyloid is not a direct cause of Alzheimer’s disease.
This led to further research, and scientists have now discovered that β-amyloid acts on the synapses of neurons and interferes with the activity of neurotransmitters. The best-known neurotransmitter is glutamate, which is secreted from the secretory vesicles of neurons and detected by receptors on other neurons, where it transmits stimuli. These neurotransmitters are then recovered by glial cells, where β-amyloid acts. β-amyloid is involved in the recovery action of these glial cells, and when the amount of β-amyloid increases, this recovery action accelerates and the transmission of stimuli is disrupted. This leads to a decline in neurotransmission, and this mechanism acts as a cause of dementia.

Is Alzheimer’s disease treatable?

Based on this scientific knowledge, scientists are currently working hard to develop a cure for Alzheimer’s disease. By tracing the causes of the disease, they have established a theoretical basis for treatment at many stages, and many drugs are currently in the development stage. However, no drug that is 100% effective has been developed yet, and even now, many elderly people are suffering from dementia.
Of course, there will inevitably be social problems that arise when dementia is cured. However, from the perspective of scientists and medical professionals, this disease is a target for treatment and a challenge that must be solved through significant investment. The efforts of scientists will undoubtedly continue until the day when elderly people are freed from the suffering of dementia.