Pot may hold Alzheimer's promise

Published: Monday, October 09, 2006
THC, the active component in marijuana, may protect the brain from the ravages of Alzheimer's disease, U.S. scientists reported.

In lab experiments, investigators from Scripps Research Institute in La Jolla, Calif., found THC appears to block an enzyme in the brain that causes plaques to form better than currently approved drugs.

Alzheimer's is the leading cause of dementia among the elderly. An estimated 290,000 Canadians over 65 have the disease -- a number expected to double over the next two decades. Women account for more than two-thirds of cases, according to the Alzheimer Society of Canada. The progressive, degenerative brain disease has no cure.

"I'm not at all suggesting you smoke pot," said Kim Janda, a professor of chemistry and immunology at Scripps, who is working on developing vaccines against cocaine, nicotine and other drugs of abuse.

But his team's work may provide a lead for new and more effective medications, he said.

"I think it could have strong implications that molecules like THC could prevent fibrils or plaque formation."

It's the latest study to suggest the compound that produces a high might also be protective to the brain. Marijuana-like compounds are already being tested in mice against the fatal brain disease ALS, or Lou Gehrig's disease.

People with Alzheimer's have low levels of acetylcholine, a brain chemical believed to be important for learning and memory.

Existing drugs help ease symptoms of the disease by blocking an enzyme that breaks down acetylcholine.

Janda's team found THC (delta-9-tetrahydrocannabinol) did the same but at lower concentrations. It also "blunted" the formation of fibrils, or long, thread-like fibers that get woven into healthy brain cells, eventually choking them.

The researchers believe they've found a way THC "can directly impact Alzheimer's disease pathology." Their work is published in Molecular Pharmaceutics.

There are important limitations to the study. The experiments didn't involve tests on human cells, or even mice (it's one of the reasons why Janda said they were turned down by several other bigger journals.) Instead, they used synthetic versions of a peptide that causes brain plaques to form.

"The definitive study would be to get animals that have been bred to have early-onset Alzheimer's and look at the long-term effects of chronic THC administration," Janda said.

As well, there is still debate over what causes Alzheimer's, and just how important plaques are in causing the disease.

"I think most people believe it is a key component," Janda said.

According to the Alzheimer Society of Canada, symptoms of the illness including forgetting simple words, forgetting things more often, especially things that have happened recently, and trouble performing familiar tasks.

skirkey@canwest.com

http://www.canada.com/vancouversun/n...75ee39&k=33721