Amyloid Plaques Produce Natural "Bleach" Toxic to Brain Cells
Harvard Medical School researchers say they have found a "completely new" mechanism for explaining how Alzheimer's disease damages the brain. They say a chemical reaction, involving proteins that accumulate in Alzheimer's patients' brains, produces a bleaching agent that is toxic to cells there. The scientists [U1]think the discovery could provide a unique target for new drugs to treat Alzheimer's, which causes dementia in at least four million Americans.
The findings will be in the June 15 print edition of the peer-reviewed journal Biochemistry, which is published by the American Chemical Society (ACS), the world's largest scientific society. The paper was published on the ACS Web May 27.
Currently incurable, Alzheimer's disease is the fourth leading cause of death in Western countries. Those over 85 years of age, the fastest growing portion of the U.S. population, have a 50-50 chance of developing the disease. Upon autopsy, patients' brains are typically found to be riddled with deposits of amyloid protein plaques.
Though the amyloid plaques have long been an obvious suspect as a cause of the disease pathology, exactly how they might do it has been a mystery. "We have found that the amyloid protein...binds copper and iron and produces hydrogen peroxide (H2O2) out of oxygen when doing so. Yes, bleach," says co-author Ashley I. Bush, M.D., Ph.D., who directs the Laboratory for Oxidation Biology in Massachusetts General Hospital's Psychiatry Department, a part of Harvard Medical School.
While H2O2 has previously been detected in laboratory cell cultures exposed to
synthetic amyloid, researchers thought that some reaction within dying cells
produced the substance. The new study is the first indication that a
substantial portion of the H2O2 is being made by the plaques themselves, adding
that "previously it was not shown that amyloid could produce any new chemic
Contact: Julie Malveaux
American Chemical Society