azulenyl-nitrone and Amyotrophic-Lateral-Sclerosis

Azulenyl nitrones have been recently demonstrated to constitute a new class of nitrone-based spin traps with the unprecedented capacity to tag free radicals by yielding characteristically colored and highly visible diamagnetic (and paramagnetic) spin adducts. In addition, a comparison of the oxidation potentials of azulenyl nitrones such as 1 and congeners to those of conventional nitrone spin traps previously investigated as potential antioxidant therapeutics such as N-tert-butyl-alpha-phenylnitrone and its related ortho-sodium sulfonate reveals that the azulene-derived spin traps are far more readily oxidized. These special features render azulenyl nitrones of interest with regard to both their distinct ability to engender the convenient use of colorimetric detection to monitor free radical-mediated oxidative stress in biological systems, and to their potentially enhanced efficacy as neuroprotective antioxidants vs. those conventional nitrone spin traps earlier examined as such. Herein is reported an overview of recent developments pertaining to the use of azulenyl nitrones in the detection of oxidative stress in animal models of amyotrophic lateral sclerosis and stroke, and to their neuroprotective activity in animal models of Parkinson's disease, stroke and neurodegeneration within the retina.

Topics: Amyotrophic Lateral Sclerosis; Animals; Antioxidants; Azulenes; Brain Ischemia; Disease Models, Animal; Dopamine; Humans; Neuroprotective Agents; Nitrogen Oxides; Oxidative Stress; Parkinson Disease; Retinal Ganglion Cells; Sesquiterpenes; Spin Trapping; Stroke; Superoxide Dismutase

Much evidence exists for the increased peroxidase activity of copper, zinc superoxide dismutase (SOD1) in oxidant-induced diseases. In this study, we measured the peroxidase activity of SOD1 by monitoring the oxidation of dichlorodihydrofluorescein (DCFH) to dichlorofluorescein (DCF). Bicarbonate dramatically enhanced DCFH oxidation to DCF in a SOD1/H(2)O(2)/DCFH system. Peroxidase activity could be measured at a lower H(2)O(2) concentration ( approximately 1 microm). We propose that DCFH oxidation to DCF is a sensitive index for measuring the peroxidase activity of SOD1 and familial amyotrophic lateral sclerosis SOD1 mutants and that the carbonate radical anion (CO(3)) is responsible for oxidation of DCFH to DCF in the SOD1/H(2)O(2)/bicarbonate system. Bicarbonate enhanced H(2)O(2)-dependent oxidation of DCFH to DCF by spinal cord extracts of transgenic mice expressing SOD1(G93A). The SOD1/H(2)O(2)/HCO(3)(-)-dependent oxidation was mimicked by photolysis of an inorganic cobalt carbonato complex that generates CO(3). Metalloporphyrin antioxidants that are usually considered as SOD1 mimetic or peroxynitrite dismutase effectively scavenged the CO(3) radical. Implications of this reaction as a plausible protective mechanism in inflammatory cellular damage induced by peroxynitrite are discussed.

Topics: Amino Acids, Aromatic; Amyotrophic Lateral Sclerosis; Animals; Azulenes; Bicarbonates; Electron Spin Resonance Spectroscopy; Fluoresceins; Free Radical Scavengers; Hydrogen Peroxide; Metalloporphyrins; Mice; Mice, Transgenic; Molecular Structure; Neuroprotective Agents; Nitrogen Oxides; Oxidants; Oxidation-Reduction; Peroxidase; Sesquiterpenes; Spin Trapping; Spinal Cord; Superoxide Dismutase

Mutations of the SOD1 gene encoding copper/zinc superoxide dismutase (CuZnSOD) cause an inherited form of amyotrophic lateral sclerosis. When expressed in transgenic mice, the same SOD1 mutations cause progressive loss of spinal motor neurons with consequent paralysis and death. In vitro biochemical studies indicate that SOD1 mutations enhance free radical generation by the mutant enzyme. We investigated those findings in vivo by using a novel, brain-permeable spin trap, azulenyl nitrone. Reaction of azulenyl nitrone with a free radical forms a nitroxide adduct that then fragments to yield the corresponding azulenyl aldehyde. Transgenic mice expressing mutant SOD1-G93A show enhanced free radical content in spinal cord but not brain. This correlates with tissue-specific differences in the level of transgene expression. In spinal cord, the increase in free radical content is in direct proportion to the age-dependent increase in mutant human CuZnSOD expression. This increase precedes motor neuron degeneration. The higher level of human CuZnSOD expression seen in spinal cord compared with brain, and consequent difference in free radical generation, provides a basis for understanding the selective vulnerability of the spinal cord in this disease model.

Topics: Aging; Amyotrophic Lateral Sclerosis; Animals; Azulenes; Brain; Disease Models, Animal; Free Radicals; Gene Expression Regulation, Developmental; Gene Expression Regulation, Enzymologic; Humans; Mice; Mice, Transgenic; Nitrogen Oxides; Point Mutation; Sesquiterpenes; Spin Labels; Spinal Cord; Superoxide Dismutase; Superoxides