Cigarette Smoke Radicals and the Role of Free Radicals in Chemical Carcinogenicity

Abstract

This article consists of two parts: a brief overview of the ways in which free radicals can be involved in chemical carcinogenesis, and a review of cigarette smoke chemistry. Carcinogenesis is generally agreed to involve at least three stages: initiation, promotion, and progression. It is suggested that radicals sometimes are involved in the initiation step, either in the oxidative activation of a procarcinogen (such as benzo[alpyrene) to its carcinogenic form or in the binding of the carcinogenic species to DNA, or both. The fraction of initiation events that involve radicals, as opposed to two-electron steps, is not known, but radicals probably are involved in a substantial number, although probably not a majority, of cancer initation reactions. Promotion always involves radicals, at least to some extent. Progression probably does not normally involve radicals. The second part of this article reviews the molecular mechanisms involved in cigarette-induced tumors, particularly by aqueous cigarette tar (ACT) extracts and by a model of these solutions, aged solutions of catechol. ACT solutions as well as aged solutions of catechol contain a quinone-hydroquinone-semiquinone system that can reduce oxygen to produce superoxide and hence hydrogen peroxide and the hydroxyl radical. Both the cigarette tar radical and the catecholderived radical can penetrate viable cells, bind to DNA, and cause nicks.Environ Health Perspect 1 05(Suppl 4): 875-882 (1997)

The effect of smoking on the ocular surface and the precorneal tear film

“…5 The ocular surface is exposed to over 1E+14 short-lived radicals in the gas phase per puff and even more in the tar phase during which the radicals are long lived. 6 Altinors et al 7 assessed the lipid layer of the tear film in smokers and reported damage in the lipid layer which prevents the even spreading of tear film over the corneal surface, rendering it unwettable. According to them, smoking damages the precorneal tear film lipid layer by lipid peroxidation process and causes dry eye symptoms.…”

“…7 Cigarette smokers also have higher levels of lipid peroxidation than non-smokers. 6 The chemical composition of cigarette smoke is complex, with many free radical species, aldehydes, peroxides, epoxides, nitrogen oxides, peroxyl radicals, and other pro-oxidants being present. 8 There is growing evidence that these oxidant species may contribute to the disease process associated with smoking.…”

Short-Term Effects of Nose-Only Cigarette Smoke Exposure on Glutathione Redox Homeostasis, Cytochrome P450 1A1/2 and Respiratory Enzyme Activities in Mice Tissues

“…Cigarette smoke is a complex mixture of thousands of constituents and induces the production of reactive oxygen species (ROS). Particulate tar and gas phase smoke component of CS also contain many semiquinone radicals, ROS and reactive nitrogen species (RNS) and carbon monoxide which have been associated with various chronic pulmonary and cardiovascular diseases ranging from inflammation to cancer [28]. GSH plays a major role in protecting biomolecules from oxidative damage caused by cigarette smoke.…”

Comparison of Peroxidase Response to Mental Arithmetic Stress in Saliva of Smokers and Non-Smokers

“…A fairly recent study demonstrated a sharp drop in OPO activity after smoking a single cigarette in both non-smokers and smokers and suggested that reactive oxygen species (ROS), such as the hydroxyl radical, might cause oxidative DNA damage to the surrounding tissues (Pryor, 1997). In this respect, the saliva antioxidative system also contributes to anticarcinogenic capability.…”