Trash-collecting cells in the brain called microglia were believed to fuel the progress of Alzheimer's disease. A new study published in the May issue of the journal Nature Medicine, however, finds that they can actually help fight the condition. All it takes is a little extra Transforming Growth Factor Beta-1 (TGF-b1). Indeed, Tony Wyss-Coray of the Gladstone Institute of Neurological Disease and his colleagues from the University of California at San Francisco found that increased concentrations of this signaling molecule stimulate microglial cells to clear away b-amyloida substance that accumulates in the brains of Alzheimer's patients and creates harmful plaques. "People always thought that the inflammation and microglial activation were bad," Wyss-Coray explains. "But we showed that, when stimulated by TGF-b1, microglial activities can be beneficial."

The researchers studied mice genetically engineered to produce both b-amyloid and extra TGF-b1. Compared with mice with normal TGF-b1 levels, these animals had 75 percent fewer plaques and 60 percent lower b-amyloid levels. To investigate the correlation further, the team put microglial cells, b-amyloid and TGF-b1 into petri dishes and found that after 18 hours the microglia had destroyed most of the b-amyloid. Because TGF-b1 has many effects in the body, it cannot be used to treat Alzheimer's, Wyss-Coray says. Instead the molecules that microglia produce in response to TGF-b1 may prove more viable drug target