This is the first submission of an application to investigate the mechanism of Zn2+ toxicity in the CNS. Recent findings indicate that this cation is elevated during stroke, traumatic brain injury, and oxidative stress, and that elevated intracellular Zn2+ is associated with the death of cultured neurons. Elevated Zn2+ is also associated with mitochondrial dysfunction, and with the death of cells by necrosis and apoptosis, although the mechanism of these effects is unknown. The investigator and his associates have recent findings that seem to bear upon the mechanism of Zn2+ toxicity at the cellular level. They have found that submicromolar concentrations of Zn2+ inhibit the mitochondrial alpha-ketoglutarate dehydrogenase and pyruvate dehydrogenase complexes, and that Zn2+ stimulates the mitochondrial permeability transition. They also note that oxidative stress can release Zn2+ from metallothioneins and that the metallothionein expressed in brain is associated with the mitochondrial outer membrane. Putting all of this together, the investigator hypothesizes that cell injury caused by oxidative stress arises, at least in part, because Zn2+ is released from metallothionein, inhibits the TCA cycle at the level of one or both of the dehydrogenases, and thereby, or through other mechanisms, provokes the permeability transition and subsequent cell death. To begin evaluating this hypothesis, Dr. Brown will investigate the mechanism by which Zn2+ inhibits the dehydrogenases using enzyme kinetics and the study of partial reactions. Mechanisms transporting Zn2+ in mitochondria will be determined, and respiration studies will be conducted to ascertain the relative importance of Zn2+ action on the dehydrogenases, compared to the electron transport chain, in producing mitochondrial dysfunction. Finally, the mechanism by which Zn2+ influences the permeability transition will be determined. In several cases data obtained from brain, heart, and liver mitochondria will be compared, to ascertain the generality of the findings, and to allow a cross comparisons of literature, which is developed to different extents for mitochondria from these various organs.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS038741-03
Application #
6394146
Study Section
Special Emphasis Panel (ZRG1-MDCN-2 (01))
Program Officer
Jacobs, Tom P
Project Start
1999-05-01
Project End
2003-04-30
Budget Start
2001-05-01
Budget End
2003-04-30
Support Year
3
Fiscal Year
2001
Total Cost
$284,416
Indirect Cost
Name
Winifred Masterson Burke Med Research Institute
Department
Type
DUNS #
780676131
City
White Plains
State
NY
Country
United States
Zip Code
10605
Gazaryan, Irina G; Krasinskaya, Inna P; Kristal, Bruce S et al. (2007) Zinc irreversibly damages major enzymes of energy production and antioxidant defense prior to mitochondrial permeability transition. J Biol Chem 282:24373-80
Gazaryan, Irina G; Brown, Abraham M (2007) Intersection between mitochondrial permeability pores and mitochondrial fusion/fission. Neurochem Res 32:917-29
Krasnikov, Boris F; Kim, Soo-Youl; McConoughey, Stephen J et al. (2005) Transglutaminase activity is present in highly purified nonsynaptosomal mouse brain and liver mitochondria. Biochemistry 44:7830-43
Krasnikov, Boris F; Zorov, Dmitry B; Antonenko, Yuri N et al. (2005) Comparative kinetic analysis reveals that inducer-specific ion release precedes the mitochondrial permeability transition. Biochim Biophys Acta 1708:375-92
Klyachko, Natalia L; Shchedrina, Valentina A; Efimov, Alexander V et al. (2005) pH-dependent substrate preference of pig heart lipoamide dehydrogenase varies with oligomeric state: response to mitochondrial matrix acidification. J Biol Chem 280:16106-14
Gazaryan, Irina G; Krasnikov, Boris F; Ashby, Gillian A et al. (2002) Zinc is a potent inhibitor of thiol oxidoreductase activity and stimulates reactive oxygen species production by lipoamide dehydrogenase. J Biol Chem 277:10064-72
Brown, A M; Kristal, B S; Effron, M S et al. (2000) Zn2+ inhibits alpha-ketoglutarate-stimulated mitochondrial respiration and the isolated alpha-ketoglutarate dehydrogenase complex. J Biol Chem 275:13441-7
Kristal, B S; Staats, P N; Shestopalov, A I (2000) Biochemical characterization of the mitochondrial permeability transition in isolated forebrain mitochondria. Dev Neurosci 22:376-83