Research Description

1. Free Radical Detection: Free radicals have been implicated in the pathogenesis of various diseases, or as mediators in a number of vital cellular functions.  One of my major research interests in the advancement of free radical detection and identification by electron paramagnetic resonance (EPR) spectroscopy focusing mainly on the development of new spin traps and probes for chemical, biological and biomedical imaging applications.  The spin trapping technique, using cyclic nitrone spin traps and electron paramagentic resonance (EPR) spectroscopy, has been widely employed for the identification of free radicals in chemical and biological systems.  We envision that molecules with improved properties will aid us in the detection and identification of free radicals in cellular and animal models, and ultimately contribute to the understanding of some of the fundamental mechanisms leading to oxidative stress or damage in biological systems.
2. Mechanisms of Oxidative Stress: Understanding the origin of radical production in cellular systems can lead to new therapeutic strategies for the reversal and prevention of oxidative stress, and for protection against environmental-induced cardiovascular injury.  Exogenously introduced chemical agents (toxins, particulates, metal ions) and ionizing radiation can attenuate or induce radical production in cells.  However, the mechanism of oxidative damage in the cell remains unclear.  The location of O2.-, i.e., whether extracellular versus intracellular, may have a significant pathophysiological affect.  Extracellularly generated O2.- may effect adjacent cells and inactivate NO in the vasculature.  On the other hand, intracellularly generated O2.- may cause dysfunction of the cells that produce it.  Moreover, although mitochondria are generally viewed as a major cellular source of O2.-, under both physiological and pathophysiological conditions (such as ischemia-reperfusion; hyperoxia), to date, it is not clear if O2.- is produced mainly from the mitochondrial electron transport chain (METC) in intact mitochondria during ischemia-reperfusion injury.  This is due to lack of techniques to directly measure intramitochondrial O2.- generation without disrupting the membrane integrity of the organelles and that of the cell.  Therefore, knowledge of the location of O2.- generation in cellular systems under pathophysiolgical conditions may help develop strategies to protect against O2.--mediated biological injury.
3. Design of Synthetic Antioxidants: The introduction of the nitrone-based, disodium 4-[(tert-butylimino)methyl]benzene-1,3-disulfonate N-oxide (NXY-059), the first drug that had reached phase III clinical trials in the US in the treatment of acute ischemic stroke, has provided opportunities for the development of new and more robust pharmacologic agents in the inhibition of neurodegenerative diseases and ischemia-reperfusion injuries.  However, the specific mechanism of nitrone activity remains obscure but current findings by others indicate that the pharmacological activity of NXY-059 involves modulation of the intracellular redox state, suppression of gene transcription (in particular that of NF-?B-regulated cytokines and iNOS), and prevention of mitochondrial dysfunction.  This research focus involves interdisciplinary approach to the development of novel synthetic antioxidants with improved pharmacological properties encompassing theoretical, synthetic, biochemical, and in-vitro/in-vivo studies.