Methods for Measurements of Oxidized LDL, Homocysteine and Nitric Oxide as Clinical Parameters of Oxidative Stress and Endothelial Dysfunction

Abstract: Timely and accurate evaluation of clinical parameters associated with endothelial dysfunction is critical in diagnosing and treating atherosclerosis, which represents a severe health problem, accounting for at least 30% of deaths globally. A critical early event in the pathogenesis of atherosclerosis is the oxidative modification of low-density lipoprotein [LDL]. Oxidized LDL [OxLDL] represents numerous changes in lipid and apolipoprotein B [apo B] fractions of LDLs generated by lipid peroxidation. Another critical indicator of perturbed vascular homeostasis is homocysteine [Hcy], an amino acid containing sulfhydryl-group, an intermediate methionine and cysteine biosynthesis product. The total level of Hcy in plasma correlates better than cholesterol with the risk of cardiovascular disease. In addition, nitric oxide [NO] plays an essential role in regulating vascular physiological homeostasis due to its involvement in intravascular free radical and oxidant reactions. Reduced NO decreases oxidative stress in the vascular wall, which reduces the rate of LDL oxidation and the expression of redox-sensitive genes involved in atherogenesis. Endothelial dysfunction is typically associated with increased levels of OxLDL, decreased nitric oxide [NO], and hyperhomocysteinemia. Thus, OxLDL, Hcy, and NO are representative parameters of oxidative stress and endothelial dysfunction. Considering the important role of oxLDL, Hcy and NO in oxidative stress, atherogenesis and accompanying endothelial dysfunction, the challenge of the present work was to systematically present available methods for reliable measurement of these parameters and assess their potential for the use in the clinical setting. Here we present a comprehensive overview of analytical methods for measuring OxLDL, HCy, and NO in biological samples and discuss their advantages and potential problems regarding their application in clinical settings.