Alzheimer’s disease is characterised by two types of lesions, amyloid plaques and degenerated tau protein. Cholesterol plays an important role in the physiopathology of this disease. Two research teams have shown, in a rodent model, that overexpressing an enzyme that can eliminate excess cholesterol from the brain may have a beneficial action on the tau component of the disease, and completely correct it. This is the first time that a direct relationship has been shown between the tau component of Alzheimer’s disease and cholesterol. This work is published in Human Molecular Genetics.
The first step in this work made it possible to show that injecting a viral vector, AAV-CYP46A1, effectively corrects a mouse model of amyloid pathology of the disease, the APP23 mouse. CYP46A1 thus appears to be a therapeutic target for Alzheimer’s disease.
Conversely, in vivo inhibition of CYP46A1 in the mice, using antisense RNA molecules delivered by an AAV vector administered to the hippocampus, induces an increase in the production of Aß peptides, abnormal tau protein, neuronal death and hippocampal atrophy, leading to memory problems. Together these elements reproduce a phenotype mimicking Alzheimer’s disease.
These results demonstrate the key role of cholesterol in the disease, and confirm the relevance of CYP46A1 as a potential therapeutic target (work published in Brain on 3 July 2015).
Taken together, this work now enables the research team to propose a gene therapy approach for Alzheimer’s disease: intracerebral administration of a vector, AAV-CYP46A1, in patients with early and severe forms (1% of patients, familial forms) for whom there is no available treatment.