"This is surprising, because similar protein aggregate spheres called amyloid oligomers can be highly toxic to neurons and synapses," Cole said. "It will be important for the authors to prove that the EGCG-directed proteins also lack toxicity to synapses which were not present in the systems used to test toxicity," he said.
Assuming that the green tea compound has a stable effect and chronically blocks toxicity to real neurons and synapses, it could have genuine potential for Alzheimer's patients, Cole said.
"The major caveat is the very poor absorption and delivery of EGCG seen in some studies," Cole said. The fact that EGCG isn't available for patenting by pharmaceutical companies might be a problem, too, he said, since it could "limit the investment needed for clinical trials of sufficient size to prove that it really works."
In related research, a team of American scientists said that interrupting a key signaling pathway in immune system cells allowed those cells to enter the brain and attack and remove amyloid plaque.
Reporting May 30 in Nature Medicine, a team led by research scientist Terrence Town, of Cedars-Sinai Medical Center, Los Angeles, conducted their study in genetically engineered mice. The group blocked a molecule that typically suppresses a portion of the immune response. Once the system was freed up, immune cells called macrophages made their way to the brains and devoured up to 90 percent of amyloid plaques, the team said.
"If these experimental animals are representative of the clinical syndrome of Alzheimer's disease, we may have a therapeutic target that we did not have before," study co-author Dr. Jun Tan, of the University of South Florida, said in a statement.
For more about Alzheimer's disease, visit the Alzheimer's Association.
SOURCES: Erich Wanker, Ph.D., Max Delbrueck Center for Molecular Medicine, Berlin, Germany; Greg M. Cole, Ph.D., neuroscientist, Greater Los Angeles VA Healthcare System, and associate director, Alzheimer's Disease Research Center, UCLA David Geffen School of Medicine; May 30, 2008, online edition, Nature Structural & Molecular Biology; May 30, 2008, statement, Cedars-Sinai Medical Center, Los Angeles