Research reveals some of Alzheimer's secrets

By Julie Steenhuysen

CHICAGO (Reuters) - Scientists are unraveling some of the mechanisms behind the plaques in the brain that are a hallmark of Alzheimer's disease, offering new leads for drugs to treat the fatal brain-wasting disease.

A team at Massachusetts General Hospital and Harvard Medical School in Boston reported on Thursday in the journal Science that amyloid plaques agitate a type of brain cell called an astrocyte needed for normal brain function.

On Wednesday, a team at Yale University in New Haven, Connecticut, reported in the journal Nature that prions -- proteins known to wreak havoc on the brain in mad cow and Creutzfeldt-Jakob diseases -- appear to kick-start the toxic effects of amyloid plaques in Alzheimer's disease.

The findings shed new light on the complex brain mechanisms behind Alzheimer's, which is marked by memory loss, confusion and eventually the inability to care for oneself.

"Alzheimer's disease is probably a very complex disease with many things happening simultaneously," Kishore Kuchibhotla of Harvard said in a telephone interview.

Kuchibhotla's team used an advanced optical imaging technique to study the brains of live mice with Alzheimer's-like plaques. They found astrocytes, a star-shaped type of brain cell needed to support normal brain function, become hyperactive in the presence of amyloid plaques.

"It supports the idea that somehow amyloid beta does something that alters brain function," Kuchibhotla said.

Astrocytes are known to proliferate around injury sites, but in Alzheimer's, astrocytes appear to share this information with other astrocytes in far-flung parts of the brain using a communications pathway known as a calcium-signaling network.