Another reason for senile dementia
Immune protein spoils memory
In their article in Nature Medicine, Saul Villeda and colleagues talk about the immune protein beta2-microglobulin, which, as it turned out, begins to have a bad effect on the brain with age (Smith et al., [beta]2-microglobulin is a systemic pro-aging factor that impairs cognitive function and neurogenesis).
All cells have this small protein – it is part of a large complex that helps the immune system distinguish "its own" from "strangers". Its level usually increases with an increase in the activity of the immune system: in autoimmune diseases, in inflammation, in infections, in malignant diseases associated with immune cells (myelomas and lymphomas). But, in addition, the synthesis of microglobulin is also enhanced in Alzheimer's syndrome and in general in cognitive disorders.
When the protein level was checked in people of different ages and mice, they found that with age it becomes more. If microglobulin was injected into young three-month-old mice, they began to have memory problems. When the animals were placed in a water maze, where they had to find a platform to get to, even after learning the right way, they were twice as likely to forget it and make twice as many mistakes – compared to those who were not injected with protein.
And most importantly, after microglobulin injection, neurogenesis weakened in mice, that is, the appearance of new neurons. (As you know, new nerve cells can appear in the hippocampus, the main memory center of the brain.) After 30 days, the excess protein from the animals' body disappeared, their mental abilities returned to normal, and the growth of new cells became normal for their age.
The fact that microglobulin can have a bad effect on memory was confirmed by additional experiments with mice in which the corresponding gene was simply turned off. Elderly genetically modified mice remembered new things better than ordinary mice with the microglobulin gene turned on.
A few years ago, Sol Villeda, who was then working at Stanford, together with colleagues set up an experiment in which they combined the blood flow in mice of different ages. In that work, it was possible to show that young blood stimulates neurogenesis in old individuals, and old, on the contrary, suppresses it in young individuals, and memory and learning ability deteriorated at the same time in the young, while the number of new cells increased in the old, but also the number of connections-synapses between them (respectively, memory improved). At the same time, it turned out to determine 17 blood components, the concentration of which increased with age.
Now, as we can see, it has come to the study of specific proteins that, accumulating in the "old" blood, may be responsible for brain aging. It is not yet clear exactly how microglobulin can affect nerve cells. Perhaps when we learn more about this, it will be possible to create drugs that reduce the level of microglobulin in the elderly and thereby help at least a little to protect memory from aging.
However, it should be noted that, although the effect of rejuvenating or aging blood itself is confirmed in many experiments, specific causes and factors often cause heated discussions. For example, let's recall the history of a protein called tissue differentiation factor 11 (GDF-11), which we recently wrote about. In 2014, a similar experiment with the unification of circulatory systems was done at Harvard under the leadership of Amy Wagers and Richard Lee, and as a result, 13 potential anti-aging blood factors were identified, among which was the protein GDF-11, which had a beneficial effect on the heart muscle.
Diagram from the article by Bitto et al., “Rejuvenation: it's in our blood.,” Cell Metab., 2014 – WM.
But when later, in another laboratory, they tried to repeat the experiment with GDF-11 itself, it turned out that no muscle regeneration took place – moreover, under the influence of protein, muscles recovered even more slowly after damage than without it. We can only hope that microglobulin will not present such surprises, and we will really become one step closer to creating a means to slow down aging.
Portal "Eternal youth" http://vechnayamolodost.ru
08.07.2015