Smoking and Saliva ... a Deadly Combo

Newswise — What do you get when you mix cigarette smoke and healthy saliva? According to researchers at the Technion-Israel Institute of Technology, the answer is very likely to be mouth cancer. The findings were published in the May 25, 2004 online edition of British Journal of Cancer.

Normally, saliva provides a protective buffer between toxins and the lining of the mouth because it contains enzymes that neutralize harmful substances. But the researchers found that the chemicals in tobacco smoke, when combined with saliva, destroy saliva's protective components, leaving a corrosive mix that damages cells in the mouth and eventually turn them cancerous.

"Cigarette smoke is damaging on its own, but when mixed with saliva it turns the body against itself," says co-lead researcher Dr. Raphael Nagler of the Technion Faculty of Medicine. "Our study shows that when exposed to cigarette smoke, normally healthy saliva loses its beneficial qualities, turns traitor and actually aids in destroying the cells of the mouth and oral cavity."

The study recreated the effects of cigarette smoke on cancerous cells of the mouth. Half the cells were exposed to cigarette smoke only, while the other half were exposed to a saliva and cigarette smoke mixture. The researchers then studied the cells to assess whether the saliva and smoke mixture would speed up the cancer's development.

The longer the mouth cells were exposed to the contaminated saliva, the more they were damaged. The researchers also found that the cigarette smoke destroyed various salivary components, including protective ones such as peroxidase, the most important antioxidant contained in saliva. Antioxidants are molecules that help protect the body against cancer. According to Nagler, the reaction between certain components of saliva and the low reactive free radicals contained in cigarette smoke results in the production of highly active hydroxyl free radicals. Free radicals, oxygen by-products created by normal cell metabolism, possess unpaired electrons. In a process called oxidation, they cause cellular damage by taking electrons from molecules in healthy cells.

"These hydroxyl radicals are dangerous and lethal," notes Nagler. "They attack biological molecules in a tenth of a second."

Smoking and drinking are the leading causes of head, neck and oral cancer " also known as Oropharyngeal (OP) cancer, which includes cancer of the mouth, lip, tongue gums, larynx and pharynx. Nearly 400,000 new cases are diagnosed worldwide each year, with the majority in developing countries. The five-year survival rates are less than 50 percent.

Nagler and his colleagues believe this research could open new avenues for developing better ways to prevent oral cancer.

Nagler and co-lead researcher Dr. Abraham Reznick have also studied the effects of cigarette smoke and vitamin C. In a previous study (Archives of Biochemistry and Biophysics, July 2000), they found that vitamin C, an essential antioxidant, becomes a harmful oxidizing substance in the presence of cigarette smoke, speeding up the degenerative changes that come with aging.

The Technion-Israel Institute of Technology is Israel's leading science and technology university. It commands a worldwide reputation for its pioneering work in computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine. The majority of the founders and managers of Israel's high-tech companies are alumni. Based in New York City, the American Technion Society is the leading American organization supporting higher education in Israel, with more than 20,000 supporters and 17 offices around the country.