Frederick A. Villamena
Department of Pharmacology, Biomedical Research Tower, R390 460 W. 12th Ave., Columbus, OH 43210, USA,

Abstract:

Over the past 2 decades, it has become clear that reactive oxygen species (ROS) plays a major role in the initiation of oxidative damage to biomolecular systems and in the pathogenesis of various diseases. Nitrone spin traps have been employed as reagents for the detection of radicals in chemical and biological systems using electron paramagnetic resonance spectroscopy and as therapeutic agent against oxidative stress-mediated injuries. Nitrones such as 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), tert-butyl-a-phenyl nitrone (PBN) and its di-sulfonylated derivative, NXY-059 have shown pharmacological activity against I/R injury in the heart and brain, neurodegeneration and cancer. However, other than its free radical trapping properties, experimental evidence suggests other mechanisms for its protection being involved such as suppression of gene induction and signal transduction process leading to apoptosis. Although cyclic nitrones are structurally simple molecules, they posses rich chemistries and biological properties that make them relevant pharmacological agents. For example, nitrones 1) can act as oxidizing and reducing agents by virtue of their oxidation state; 2) react with a variety of free radicals; 3) decompose to NO after addition to O2•– ; 4) produce NO3– after reaction with CO3•– ; 5) O2•– adduct can be oxidized and reduced by O2•– itself to form biologically relevant species such as hydroxamic acid, aldehydes, and nitrous acid; and 6) prevent ROS-mediated pro-apoptotic signal transduction and gene induction processes. Based on our preliminary results, the non-target specific DMPO showed cardioprotective property in isolated rat heart during I/R. Our goal is to understand the mechanisms of nitrone cardioprotective effect. We found that nitrone-based antioxidants can reverse eNOS uncoupling, modulate antioxidant enzyme activities and increase endogenous GSH levels and improves contractile dysfunction in nNOS knockout myocytes due to increased NO bioavailability.

Our efforts on optimizing nitrone pharmacological activity will also be presented through application of a systematic approach to spin trap development that encompasses computational studies, design, synthesis, kinetics and in vitro applications. New advancements in spin trap development will be presented which include the synthesis of newly conceptualized nitrones showing improved efficiency for O2•– trapping, longer O2•– half-life and target specificity via bi-conjugation of the spin traps.