Research paper Exogenous markers for the characterization of human diseases associated with oxidative stress Jacob Vaya * Oxidative Stress Research Laboratory, MIGAL e Galilee Technology Center, Kiryat Shmona and Tel Hai College, P.O. Box 831, 11016 Kiryat Shmona, Israel article info Article history: Received 15 January 2012 Accepted 2 March 2012 Available online 10 March 2012 Keywords: Biomarker Oxidative stress Oxysterol Parkinson’s disease abstract Many human conditions, including neurological diseases, atherosclerosis, cancer, diabetic complications and aging, are thought to be associated with oxidative stress (OS). The development of reliable and informative markers for the characterization of OS in humans is thus highly important. Various endogenous markers are known, but their accumulation with increasing OS and with time is not certain, and most of them do not provide information on the type or source of the stress, or on the kinetics of their formation. The aim of the present overview is to present exogenous markers, designed and synthesized by our group, which are sensitive to OS and can identify its presence, the type of reactive oxygen and nitrogen species involved ex vivo, and potential damage incurred by bio-macromolecules, in real time. A microdialysis technique is used in animals for evaluation of OS in vivo. The designed probes are composed of several endogenous subunits, attached together covalently to form molecules that do not exist as such in humans. The subunits include an amino acid (tyrosine), an unsaturated fatty acid (linoleic acid), a nucleic acid (2 0 -deoxyribose guanosine) and cholesterol, representing the major macromolecules of the body, i.e. proteins, lipids, DNA and sterols, respectively. Incubation of these markers in a biological sample ex vivo, such as blood/serum, urine, saliva, cells or tissues under OS, alters their subunits, which are then analyzed and identified by LC/MS. This review demonstrates the potential of these markers to identify OS in samples taken from humans and animals suffering from, for example, atherosclerosis, hypertension, or Alzheimer’s or Parkinson’s disease. Ó 2012 Elsevier Masson SAS. All rights reserved. 1. Introduction Reactive oxygen and nitrogen species (ROS and RNS, respec- tively) and thiol homeostasis are essential elements and pathways in cells, tissues and organs: they serve as signaling species, deliv- ering messages to cellular compartments in response to physio- logical variations and they assist in maintaining normal organ activities [1]. Fibroblasts, endothelial cells and smooth muscle cells have been shown to produce ROS, upregulate protein expression, and regulate cell-proliferation genes. As such, ROS/RNS may play a role as secondary messengers, regulating signal-transduction pathways that ultimately control gene expression [2]. At the same time, a high excess of ROS/RNS generated from endogenous sour- ces, for example mitochondria in response to inflammatory conditions, upregulation of various enzymes (NADPH oxidase, hemoxygenase1, xanthine oxidase, nitric oxide synthase), or from the environment (smoking, radiation, industrial pollution) may damage macromolecules such as lipids, proteins and DNA and induce neurological disorders (such as Alzheimer’s or Parkinson’s disease), atherosclerosis, diabetic complications or aging [3e7]. The identification of reliable biomarkers of stress is thus essential for characterizing the stress and for early identification of the disease development which might follow [6]. Many endogenous biomarkers are known, such as modified endogenous compounds formed in cells and organs as a result of oxidative stress (OS), and many methods have been proposed for their detection [8]. Among well-known biomarkers and methods are peroxide value (PV), which measures the levels of various hydroperoxides, thio- barbituric reactive substances (TBARS), which measures the levels of malondialdehydes and other aldehydes, isoprostanes, which result from arachidonic acid oxidation and are among the most reliable in vivo markers of OS, and oxysterols, which are the oxidized products of cholesterol: all of these represent biomarkers of lipid oxidation. Other known biomarkers are the keto proteins chloro- and nitro-tyrosine for protein damage and 8-oxo-2 0 -deox- yguanosine (8-oxodG) for DNA. Despite the large number of endogenous biomarkers known, most of them bear some limitations. Some are not specific, * Tel.: þ972 4 6953512; fax: þ972 4 6944980. E-mail addresses: vaya@migal.org.il, vered.michal@gmail.com. Contents lists available at SciVerse ScienceDirect Biochimie journal homepage: www.elsevier.com/locate/biochi 0300-9084/$ e see front matter Ó 2012 Elsevier Masson SAS. All rights reserved. doi:10.1016/j.biochi.2012.03.005 Biochimie 95 (2013) 578e584