Alzheimer's may be caused by anti-cancer defence

by Nick Collins for The Telegraph:American researchers found for the first time that as brain cells age and the quality of their DNA deteriorates, they stop dividing and begin releasing harmful proteins.

Scientists believe the process, which also happens elsewhere in the body, may have evolved to protect our organs against cancer because it prompts the immune system to attack faulty cells which are at risk of becoming tumours.

But now that people are living longer lives the cell transition, known as "senescence," could be responsible for one of the world's most costly diseases. As our brains age larger numbers of cells begin to senesce, meaning there is no longer enough healthy matter to clear away the plaque which collects in the brains of Alzheimer's patients.

The plaque itself seems to cause even more cells to stop dividing, causing a vicious cycle which results in the rapid deterioration of the brain, the scientists explained.Dr Claudio Torres of Drexel University College of Medicine in Philadelphia exposed brain cells to hydrogen peroxide to simulate the effects of ageing, and found that they stopped dividing and began releasing large amounts of inflammatory protein.The study showed that in healthy 80 and 90 year olds up to 30 per cent of astrocytes, a type of brain cell, had senesced but in people with Alzheimer's the figure was 10 per cent higher.He told New Scientist magazine the finding provided a "new way to look at the disease", and said it could also explain why other degenerative brain conditions become more common as we grow older.Dr Torres said trying to prevent senescence from ever happening would be risky as it could lead to cancer, but removing the faulty cells could help block the disease.He said: "If we can clear senescent cells, then we can probably clear Alzheimer's ... this finding opens up a new window that could be very important."