WEDNESDAY, Feb. 23, 2005 (HealthDay News) -- By suppressing inflammation in the brain, a synthetic marijuana compound could potentially offer some protection against Alzheimer's disease, Spanish scientists report.
The researchers, who studied the brain tissue of deceased Alzheimer's patients, discovered that many of these patients lose the function of important cannabinoid brain receptors, which seem to guard against cognitive decline.
They further discovered in a rat study involving synthetic marijuana that when these brain receptors were working, they reduced the brain inflammation that is associated with Alzheimer's.
"This is the first time the effects of such damage have been found in Alzheimer's patients," said study co-author Maria de Ceballos, head of the neurodegeneration group at the Cajal Institute, Spain's largest neuroscience research center, in Madrid. "Previously, it has been known only in those with acute brain damage from trauma."
The findings appear in the Feb. 23 issue of The Journal of Neuroscience.
The researchers studied cannabinoid receptors called CB1 and CB2, which are proteins that bind with cannabinoids, the active ingredients of marijuana. The synergy between these receptors and cannabinoids are known to provide protective effects against inflammation in the brain.
In the first part of their study, they compared the brain tissue of deceased Alzheimer's patients to similar tissue from healthy people who had died at the same age. Those who suffered from Alzheimer's had significantly reduced functioning of their cannabinoid receptors compared to the healthy group, which meant those with the disease had lost the capacity to experience the protective effects of cannabinoids.
Then, in a series of rat experiments, the scientists found cannabinoids reduced inflammation in the brain and prevented cognitive decline.
To find this, the researchers injected amyloid, a protein that activates immune cells and leads to cognitive decline, into the brains of one group of rats. Another group of rats received injections of a control protein. A third group of rats were injected with cannabinoids along with amyloid, and a last group received cannabinoids with the control protein.
After two months, the researchers trained the rats over five days to find a platform hidden underwater. Rats treated with the control protein -- with or without the cannabinoids -- and those treated with the amyloid protein and the cannabinoids were able to find the platform. The rats treated with the amyloid protein alone did not learn how to find the platform.
The scientists further confirmed that the amyloid protein activated the rats' brains' immune cells, causing inflammation, but that the cannabinoids counteracted this effect and reduced the inflammation.
de Ceballos said the findings suggest that those who are known to be at risk for Alzheimer's could benefit from using cannabinoids to slow the progression of the disease.
But she added that much work remains to be done before this can be put to clinical use.
Alzheimer's experts also warned this is very preliminary work because it only studied tissue in animals to find the beneficial effects of the cannabinoids, and, as such, is far from an endorsement of marijuana use in preventing Alzheimer's.
"The paper doesn't reflect any thought that people should use marijuana as any kind of therapeutic agent for Alzheimer's. It would be irresponsible to suggest that," said William Thies, vice president of medical and scientific affairs for the Alzheimer's Association.
By looking at a new possible agent that could be useful in moderating the pathology of Alzheimer's, he said, the study joins others examining the possible ways that the disease advances, including the effects of cholesterol, inflammation and the presence of amyloid proteins.
"Certainly every one of these papers that gives us new possibilities to explore is welcome," he said.
Information about the amyloid protein that is a part of Alzheimer's disease can be found at The National Institute of Aging.