By Will Dunham

WASHINGTON (Reuters) - An enzyme that helps the body break down alcohol also works to limit damage during a heart attack, and an experimental drug can crank up this protective role, scientists said on Thursday.

They expressed hope these findings in rat studies may lead to a drug that would protect people with chest pain that often precedes a heart attack or during coronary bypass surgery and other events in which the heart does not receive enough blood.

The enzyme, which is controlled by a gene called ALDH2, was previously known for its role in allowing the body to metabolize alcoholic beverages.

Researchers led by Daria Mochly-Rosen of Stanford University Medical Center in California observed that rats with higher levels of the enzyme suffered less damage when they had heart attacks.

When they lowered levels of the ALDH2 enzyme in rats and caused heart attacks, the animals sustained more heart damage.

Giving a chemical compound called Alda-1 to the rats greatly turned up the activity of the enzyme to protect against heart damage, the researchers wrote in the journal Science. The drug helped protect cells that would otherwise die because of reduced blood flow, they said.

The enzyme gets rid of toxins that accumulate when the heart is not getting enough oxygen and nutrients.

"This enzyme is central to a number of cellular processes that are related to how the body deals with toxic compounds," Thomas Hurley of Indiana University School of Medicine, who took part in the research, said in a telephone interview.

There is a lot of interest in finding drugs that limit damage caused by heart attack or by certain surgical procedures, the researchers noted. A drug like Alda-1 may be able to do this.

Mochly-Rosen said such a drug, if it worked in people, may be useful for those with angina, the chest pain that occurs when the heart muscle does not get enough oxygen-rich blood and that can signal an impending heart attack.

But it is unclear if it could be given to people shortly after they have a heart attack to minimize the cardiac damage.

"We're really clueless about that at the moment," Mochly-Rosen said in a telephone interview.

Such a drug could particularly help the roughly 40 percent of people of East Asian descent who have a mutated form of ALDH2 that may put them at increased risk of cardiovascular damage, the researchers said.

It also might be useful in other conditions involving so-called oxidative stress including Alzheimer's and Parkinson's disease, Mochly-Rosen said.

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