Effect of Chronic Smoking on Antioxidants in Normal Healthy Persons and Gastric Carcinoma

Abstract

Cigarette smoking is a serious health problem worldwide. Smoking has been strongly implicated as a risk factor for human diseases including cancer because cigarette smoke is known to contain a large number of oxidants. It has been hypothesized that many of the adverse effects of smoking may result from oxidative damage to critical biologic substances. Such damage could result both from oxidants present in cigarette smoke and from the activation of phagocytic cells that generate reactive oxygen species. Two major phases were identified in cigarette smoke: a tar phase and a gas phase. Both phases are rich in oxygen-centered, carboncentered and nitrogen-centered free radicals as well as non-radical oxidants. From the analysis of each phase, it was estimated that a single cigarette puff contains approximately 1014 free radicals in the tar phase and 1015 radicals in the gas phase. Cigarette smoke-induced oxidants include nitric oxide (NO), an air pollutant, which is capable of reacting with superoxide anion radical (O2.-) to form peroxynitrite (ONOO.-) and with organic peroxyl radicals to form alkyl peroxynitrites (ONOOR). In addition to free radicals, cigarette smoke is also rich in toxic gases that which are involved in more radical formation. Tobacco smoke contains some deadly carcinogenic chemicals. Some of these cancer-causing chemicals, such as the tobacco-specific nittosamines N-Nitrosomorpholine N -Nitrosonornicotine (NNN), 4- (Methylnitrosamino)-1- (3-pyridyl)-1-butanone (NNK), N -Nitrosoanatabine (NAT) and N -Nitrosoanabasine (NAB), are formed from natural components of the tobacco plants. Cigarette smoke is a main source of free radicals and can activate endogenous ROS-related enzymes. These reactive oxygen species in turn are capable of initiating and promoting oxidative damage in the form of lipid peroxidation. The enhanced lipid peroxidation have been found to be associated with an increased risk of cancer. Adeno carcinoma of the stomach remains a major cause of mortality world wide.