Washington ? Scientists have discovered molecular janitors that clear away a sticky gunk blamed for Alzheimer’s disease – until they get old and quit sweeping.

The finding helps explain why Alzheimer’s is a disease of aging. More importantly, it suggests a new weapon: drugs that give nature’s cleanup crews a boost.

“It’s a whole new way of thinking in the Alzheimer’s field,” said Dr. Andrew Dillin, a biologist at California’s Salk Institute for Biological Studies who led the new research.

The discovery, published Thursday by the journal Science, was made in a tiny roundworm called C. elegans.

What do worms have to do with people? They’re commonly used in age-related genetics research, and the new work involves a collection of genes that people harbor, too. Dillin’s team from Salk and the neighboring Scripps Research Institute already is on the trail of potential drug candidates.

About 4.5 million Americans have Alzheimer’s, a toll expected to more than triple by 2050 as the population grays. The creeping brain disease gradually robs sufferers of their memories and ability to care for themselves, eventually killing them. There is no known cure; today’s drugs only temporarily alleviate symptoms.

Nor does anyone know what causes Alzheimer’s. The lead suspect is a gooey protein called beta-amyloid. All brains contain it, although healthy cells somehow get rid of excess amounts. But beta-amyloid builds up in Alzheimer’s patients, both inside their brain cells and forming clumps that coat the cells – plaque that is the disease’s hallmark.

Thursday’s study reveals one way that cells fend off amyloid buildup, and that natural aging gradually erodes that detoxification process.

Worms can’t get Alzheimer’s. So Dillin’s team used roundworms that produce human beta-amyloid in the muscles of the body wall. As the worms age, amyloid builds up until it eventually paralyzes them; they can wiggle only their heads.

Scientists already are creating drugs to try to rid the brain of amyloid. These cleanup proteins point to a novel way to do that. The hope: Create drugs that boost their effects, and amyloid might not build up in the first place. Dillin said some initial drug attempts are showing promise in his worms.