Chronic alcohol abuse has been found to not only damage the liver, but also result in increased susceptibility to lung disease, according to research at Emory University School of Medicine and the Atlanta Veterans Affairs Medical Center.
The effects of the alcohol lead to a severe deficiency of the antioxidant glutathione in the lungs, bringing about the heightened risk of being infected by serious lung diseases.
Lowered glutathione levels can be as deadly to the lungs of alcohol abusers as alcohol itself can be to their livers and other organs, said Dr David Guidot, associate professor of medicine at Emory University School of Medicine. Dr. Guidot explained the effects of glutathione depletion on the lungs at a symposium on the cellular effects of chronic alcohol abuse at the Experimental Biology 2002 meeting in New Orleans last week.
Scientists first connected the alcohol abuse and lung damage six years ago, when Dr Marc Moss at Emory University reported on the link.
Dr. Guidot said: "We now know that as many deaths occur every year from alcohol abuse related to lung injury as occur from alcohol abuse and liver disease or alcohol abuse and traffic accidents."
Even though alcohol's ill effects on the liver, brain and other organs was well recognised, scientists had not focused on the connection between alcohol and lung disease because the cause-and-effect relationship is indirect, unlike the direct effect of alcohol on the liver, explained Dr Guidot.
Guidot began studying the effects of glutathione depletion on the lungs while reviewing the mechanisms of alcohol toxicity in other organs. The body manufactures glutathione - a strong antioxidant molecule - from amino acids, which are the building blocks of proteins. Individuals with reasonably good diets maintain an adequate supply of glutathione, which is constantly being used up and replenished.
Although glutathione is manufactured in a variety of organs and tissues, including the liver, the lungs are particularly dependent on glutathione for protection from oxidative damage, especially in the small airways where breathing takes place.
The lack of glutathione in the lungs leads to a variety of abnormalities, said Guidot, including damage to the epithelial cells and fluid that lines the lungs, changes in the barrier function of lung cells and increased susceptibility to apoptosis, or cell death in the lungs.
These abnormal cell changes in the lung caused by chronic alcohol abuse leave the lung vulnerable to injury when a serious illness such as sepsis or pneumonia occurs.
"Heavy drinking and its relationship to lung disease is like driving on the highway without a seat belt," said the scientist. "It's risky behaviour, but it doesn't cause injury unless you get in an accident. Alcohol doesn't cause lung disease unless you get sick, then the lungs are less able to respond to the challenges of infection," he added.
However the cure for alcohol-induced lung damage is not as simple as just taking extra doses of glutathione, because an acute lung infection often is the first sign of damage, noted Guidot.
"If your house is on fire, it's too late to install a smoke detector," he said. Glutathione depletion cannot be quickly reversed. Only after the immediate illness is addressed can physicians consider treating a patient for alcoholism and consider long-term glutathione therapy.
By studying the mechanisms of glutathione damage, Dr Guidot and his colleagues hope to design more effective therapies for preventing and treating the effects of chronic alcohol abuse.