- The Washington Times - Wednesday, April 6, 2005

ASSOCIATED PRESS

Low doses of the main active ingredient in marijuana slowed hardening of the arteries in mice, suggesting a hint for developing a new therapy in people.

Experts stressed that the finding does not mean people should smoke marijuana in the hope of getting the same benefit.

“To extrapolate this to ‘a joint a day will keep the doctor away’ I think is premature,” said Dr. Peter Libby, chief of cardiovascular medicine at Boston’s Brigham and Women’s Hospital.

The mouse work is presented in today’s issue of the journal Nature by Dr. Francois Mach of Geneva University Hospital in Switzerland, and colleagues. He said in an e-mail message that future work will focus on finding drugs that mimic the benefit without producing marijuana’s effects on the brain.

Hardening of the arteries sets the stage for heart attacks. Inflammation plays a key role in the condition, characterized by a buildup on the inside walls of blood vessels. So Dr. Mach and colleagues explored the anti-inflammatory effects of marijuana’s main active ingredient, delta-9-tetrahydrocannabinol, or THC.

They fed mice a high-cholesterol diet for 11 weeks. About halfway through that period, they started giving some of the mice very low, daily oral doses of THC — too low to produce any marijuanalike changes in behavior. At the end of the experiment, mice given the THC showed less blood vessel clogging than did mice given no THC.

Related work showed no additional benefit from higher THC doses, such as that a person would get from smoking marijuana, Dr. Mach said.

Researchers found that the benefit came from THC’s effect on immune-system cells. It reduced their secretion of an inflammation-promoting substance and their migration to the vessel wall.

THC apparently did that by binding to proteins called CB2 receptors, which are found mostly on immune-system cells. THC also targets CB1 receptors, found mostly in the brain. So the work suggests that scientists should try to develop a drug that works on CB2 receptors but ignores the brain receptors, Dr. Mach said.

Dr. Libby, who did not participate in the study, said the work was valuable for identifying the CB2 receptor as a potential target for treatment in hardening of the arteries and showing that a natural substance could help.

But he said controlling one’s weight, exercising and eating right already have been proven to reduce a person’s risk of heart attacks and strokes from clogged arteries.

Dr. Edward A. Fisher of the New York University School of Medicine said that THC’s impact on artery-clogging in the experiment was relatively modest and that it’s not clear that results would apply to people.

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