Main theory about Alzheimer’s increasingly questioned

The main hypothesis about the development of Alzheimer’s is increasingly criticized, to the point that scientists wonder if they followed a false lead in the search for a drug in recent decades.

The “amyloid cascade” theory has served as the basis for the last 20 years of research into this degenerative disease, but without any tangible results.

Despite being the best known and most common dementia, the causes and its development remain unknown.

One of the few certainties is that people with Alzheimer’s have plaques of proteins, called amyloids, that form around neurons and destroy them.

But do these plaques represent the main cause? Or would it be the consequence of another pathology? This is the main question of scientists.

According to the “cascade” theory, Alzheimer’s is due to the formation of these plaques. However, this hypothesis raises more and more doubts, three decades after it was formulated by the British biologist John Hardy.

A study published this Thursday (2) by the journal Nature Neuroscience casts doubt on the role of protein plaques and supports the hypothesis that, in reality, Alzheimer’s would arise inside neurons, not outside.

This publication, based on analyzes in genetically modified mice, points to a possible dysfunction of lysosomes, cellular organelles that serve to “digest” these useless or degraded components.

“These new elements undermine the beliefs we had about how Alzheimer’s disease works,” said American biologist Ralph Nixon, who supervised the study carried out at New York University.

This research does not in itself alter the scientific consensus on Alzheimer’s disease, as the hypothesis needs to be confirmed in humans. However, it is part of a general questioning of the “waterfall” theory, which has guided the efforts of the pharmaceutical industry in vain.

The American laboratory Biogen has developed the only authorized drug against this degenerative disease, but its effectiveness is questioned by the scientific community.