Regulation of Cigarette Smoke-Triggered Nitrative Stress by Gamma-Tocopherol
Cigarette smoking has been well established to increase the risk for cardiovascular disease (CVD). Each puff of cigarette smoke contains high concentrations of reactive oxygen species and reactive nitrogen species (ROS/RNS) which can react to form peroxynitrite or induce an inflammatory response within the body. The formation of peroxynitrite is responsible for the nitration of various biomolecules (e.g. tyrosine) that results in the presence of dysfunctional proteins which raise cardiovascular disease risk. γ-tocopherol, a subclass of vitamin E with an unsubstituted position on its chromanol head, can terminate lipid peroxidation and react with peroxynitrite to form 5-nitro-γ-tocopherol, thus protecting target biomolecules from nitration and reducing risk of CVD. The Bruno laboratory has been conducting a human intervention study to determine the mechanism by which γ-tocopherol regulates cigarette smoke-triggered nitrative stress. Subjects were asked to donate blood samples and 3-day food records on two occasions (pre-and post-supplementation with γ-tocopherol ) separated by one week. Plasma obtained from the blood samples was exposed to air and smoke ex vivo for a maximum of 6 hours.
Aliquots of plasma were removed during the exposure period for further analysis. Following the collection phase, plasma samples were analyzed for cholesterol, nitrotyrosine, reactive nitrogen species, malondialdehyde (lipid oxidation product) and α-, γ-, and nitro-γ tocopherol. A statistical difference was found between the formation of malondialdehyde and RNS in smoke-exposed versus air-exposed plasma (p<0.05). No statistical difference was found between the concentrations of malondialdehyde and RNS in non-supplemented versus supplemented plasma samples (p>0.05). A significant correlation was found between RNS concentration and lipid peroxidation for cigarette smoke exposure but not air exposure. Further analysis is required to determine plasma concentrations of nitrotyrosine and tocopherol levels and to correlate tocopherol status with plasma concentrations of oxidative/nitrative stress biomarkers.