Isoprostanes as Biomarkers of Disease and Early Biological Effect

Nowadays, the relationship between environment and public health must be studied through molecular epidemiology techniques which needs of increasingly sensitive instruments able to detect the smaller exposure and the smaller biological effects. These instruments are the biomarkers, and each type of them indicates, for preventive purposes, a particular stage of the biochemical pathway that, from exposure, can lead to disease through absorption, metabolic activation, and possible covalent bonds with DNA and proteins. Oxidative stress is a typical condition that falls under the description of semispecific biomarkers of effect, highlighting, at the meantime, a prepathological condition. This last is due to a biological damage occurring when oxidants exceed the level of antioxidant defenses producing a physiological unbalance which is indicative of a risky condition. The resulting damage to cells and organs may activate and/or accelerate disease processes. Isoprostanes (IsoPs) are a group of prostaglandin-like compounds resulting from the peroxidation process of arachidonic acid induced by reactive oxygen species (ROS). These can contribute to the impairment of the chemical and physical properties of cell membranes that give rise to the oxidative damage. Isoprostanes can be grouped into four subfamilies, depending on where the radical link took place in the chain. Among all the isoprostanes, the F2-isoprostanes are the more stable molecules, detectable in all human tissues and biological fluids, including plasma, urine, bronchoalveolar lavage fluid, cerebrospinal fluid, and bile. The presence of isoprostanes in biological fluids and in human tissues is crucial because it describes a lipid peroxidation not completely contrasted by the antioxidant defenses. Due to their stability, the isoprostanes quantification, for example, in urine, can be adopted as a useful and sensitive marker of systemic oxidative stress resulting from an in flammatory response. The F2-isoprostanes allow to evaluate the oxidative lesions in a number of human diseases including atherosclerosis, Alzheimer, and lung disease. Oxidative stress increases in asthmatics and in subjects suffering from chronic obstructive pulmonary disease (COPD). Also for these reasons, isoprostanes have been proposed as a biomarker for in flammation of the airways and for the diagnosis of asthma. The 15-F2t-isoprostane is used also in epidemiological studies aiming to prove a relationship between the risk of developing chronic diseases and the action of free radicals arising from tobacco smoking and of occupational and environmental exposure to inhaled formaldehyde. The quantification of isoprostanes has opened up new areas of investigation regarding the role of free radicals in human physiology and pathology and in the strategies of primary prevention.