Antioxidants Defend Against Environmental Pollutants that Cause Oxidative Stress
Throughout the beginning of this semester, MCDB 4422 has begun to distinguish the origin, importance, and consequences of reactive oxygen and nitrogen species while observed through the lens of molecular complexity. So far, the focus of this course has been on the conditions resulting in conception and subsequent ramifications of free radicals within the cell: particularly the mitochondrial respiration chain and the damage of mitochondrial DNA respectively, under conditions of differing oxygen concentration for specific tissues. Native, cellular antioxidants like glutathione play an important role in maintaining ROS/RNS homeostasis within the cell. However, the peptides and DNA sequences that provide the mechanisms for maintaining free radical equilibrium can and will be damaged by the presence of free radicals within the cell due to the profusion of reactive oxygen and nitrogen species provided by environmental toxins like “ionising and nonionising radiation, ultraviolet radiation, elevated concentrations of ozone, nitrogen oxides, sulphur dioxide, cigarette smoke, asbestos, particulate matter, pesticides, dioxins and furans, polycyclic aromatic hydrocarbons” (Poljšak B). Research is now being conducted to measure the effectiveness of dietary supplements and “exogenous antioxidants” in an attempt to reduce the consequences of, or protect against, oxidative stress caused by pollutants.
Many researchers have shown that air contaminates can cause oxidative stress in mucosal surfaces or the respiratory tract. Oxygen itself, as well as other air pollutants: ozone, sulfur dioxide, cigarette smoke, nitrogen oxides, and particulate matter, have all been shown to cause oxidative stress in more than one way in eukaryotes (Poljšak B). A study done by the Shenyang Normal University in the People's Republic of China investigated oxidative stress induced by high doses of sulfur dioxide in rat brains and livers. In their study, they showed that “exposure to SO2 caused significant elevation of…TBARS levels and reduction of enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT)” in those tissues. (Zhao H.) Lipid peroxidation—a free radical reaction that results in the formation of a fatty acid radical and the consequent formation of a lipid peroxide in the presence of molecular oxygen—results in the formation of TBARS. However, the Shenyang Normal University went on to demonstrate the effects of moderate concentrations of two well studied antioxidants: salicylic acid (SA) and Vitamin C (Vit C). Their results indicated that administration of either SA or Vit C resulted in reduction of “SO2-induced elevation of TBARS levels," as well as “SOD, POD, and CAT in liver and brain” levels increasing relative to controls. (Zhao, H.) This research could provide evidence for the benefit of auxiliary antioxidants being used to reduce oxidative stress caused by airborne pollutants.
Domestic environments are capable of releasing toxic chemicals through “wood products, pulp products, paper products, plastics, synthetic fibres, and in textile finishing” that contain industrial resigns as adhesives or binders. (Poljšak B) Formaldehyde was “demonstrated to exert increased oxidative stress formation, primarily as lipid peroxidation, as found in a study performed by Chang and Xu” from the Chinese Center for Disease Control and Prevention. (Poljšak B). In a study conducted by İnönü University in Malatya, Turkey by Dr. Evren Köse, while studying rat testes, formaldehyde was shown to decrease testosterone, epididymal sperm concentration and progressive motility and increasing the amount of abnormal sperm. Inhalation of rose oil indicated protection against all damages presented by formaldehyde. (Köse, E.) Rose oil, and various other essential oils were shown to inhibit the formation of malonaldehyde—a reactive aldehyde formed from oxidation of polyunsaturated fats—by Department of Environmental Toxicology at the University of California. (Wei A.) The implications of essential oils being capable of acting as antioxidants to defend against cellular damaged cause by oxidation are significant: exogenous supplementation could help protect against diseases caused by oxidative stress.
Based on research done by the Department of Physiology of Suleyman Demirel University in Isparta, Turkey,“mechanisms of adverse effects of EMR [electromagnetic radiation] indicate that reactive oxygen species may play a role in the biological effects of this radiation” and “melatonin and caffeic acid phenethyl ester (CAPE), a component of honeybee propolis, were recently found to be potent free radical scavengers and antioxidants.” (Ozguner F.) The research exhibited that 900 MHz EMR emitting mobile phones resulted in increased the levels of oxidation products: NO and malondialdehyde, while decreasing native antioxidant activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px). Theses findings coincide with the premise of mobile phone EMR capability of causing retinal oxidative stress. Daily melatonin and CAPE administration for sixty days prior to EMR exposure demonstrated significant reduction of NO and MDA levels while also increasing antioxidant enzymatic activity to higher stages than in control rats. (Ozguner F.) These findings are particularly remarkable. Not only does this research complement the previous findings that dietary antioxidant intake can protect against oxidative stress while increasing native antioxidant enzymatic activity, but also reveals that oxidative stress can be induced by non-physical medium: emission of radiation from an increasingly prominent instrument in modern society: the mobile phone.
Overall, even though the research is relatively new, the developing field on studies of free radicals, oxidative stress, and the effects of diet and antioxidant supplementation on cellular oxidative damage imperative and influential. Protection from and/or termination of excess reactive oxygen/nitrogen species resulting from excess environmental oxidizing agents has far-reaching, positive consequences. Studying antioxidant supplementation may produce therapies that could effectively treat, at some level, exacerbated oxidative injury (Poljšak B.) resulting from environmentally induced oxidative stress.
Köse, E., Sarsılmaz, M., Taş, U., Kavaklı, A., Türk, G., Özlem Dabak, D., Sapmaz, H. and Ögetürk, M. (2012), Rose oil inhalation protects against formaldehyde-induced testicular damage in rats. Andrologia, 44: 342–348. doi: 10.1111/j.1439-0272.2011.01187.
Ozguner F., Bardak Y., Comlekci S. Protective effects of melatonin and caffeic acid phenethyl ester against retinal oxidative stress in long-term use of mobile phone: a comparative study. Mol Cell Biochem. 2006;282(1-2):83-8.
Poljšak B., Fink R. The protective role of antioxidants in the defence against ROS/RNS- mediated environmental pollution. Oxid Med Cell Longev. 2014;2014:671539.
Wei A., Shibamoto T. Antioxidant activities and volatile constituents of various essential oils. J Agric Food Chem. 2007;55(5):1737-42.
Zhao H, Xu X, Na J, et al. Protective effects of salicylic acid and vitamin C on sulfur dioxide- induced lipid peroxidation in mice. Inhal Toxicol. 2008;20(9):865-71.
