 | Gary Fiskum,
Ph.D.
Professor
Vice-Chair, Research
Departments of Anesthesiology, Biochemistry & Molecular Biology, and Pharmacology & Experimental Therapeutics
School of Medicine
410-706-4711
gfisk001@umaryland.edu
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ResearchOur research focuses on the molecular mechanisms responsible for neurodegeneration with emphasis on ischemic and traumatic brain injury and Parkinson's Disease. We are particularly interested in the relationships between increased intracellular calcium, free radical-dependent alterations to macromolecules, mitochondrial dysfunction and altered cerebral energy metabolism. Hypotheses concerning these relationships are being tested in animal models of global and focal cerebral ischemia and with neural cell culture systems. These models are also being used to develop clinically-feasible neuroprotective interventions. The success of these investigations is largely due to our interdisciplinary approach made possible through close collaboration with many researchers in basic science and clinical departments.
The animal studies are designed to closely simulate true clinical scenarios and involve comparisons of biochemical, histological and neurological outcome. These studies have demonstrated that postischemic intravenous administration of acetyl-L-carnitine promotes aerobic cerebral energy metabolism, protects against free radical-dependent protein and lipid oxidation, inhibits delayed neuronal death and improves neurological outcome following both cardiac arrest (global ischemia) and stroke (focal ischemia).
Acetyl-L-carnitine is now being tested in clinical trials for neuroprotection following cerebral ischemia. Other postischemic treatment protocols have focused on the effects of different concentrations of inspired oxygen and the relationships between metabolic failure and oxidative stress. Results demonstrating improved neurochemical, histological and neurological outcomes with normoxic (room air) vs. hyperoxic (100% O2) resuscitation support our hypothesis that mitochondrial injury during ischemia and early reperfusion limits the usefulness and increases the toxicity of high tissue oxygen concentrations. In contrast, when animals are exposed to hyperbaric oxygen treatment several hours following resuscitation, neurological outcome is improved. Thus, the delivery of high levels of O2 to the postischemic brain can either exacerbate or alleviate brain injury, depending on when the O2 is administered. Experiments performed with neural cell cultures have been very important in our ability to test specific cause-and-effect molecular relationships. The results of these experiments support the critical role that mitochondrial injury plays in delayed neuronal death. Mitochondrial injury involves calcium-mediated membrane permeability alterations, oxidative damage to macromolecules, including the key metabolic enzyme pyruvate dehydrogenase, and altered mitochondrial gene expression. One exciting aspect of our current research involves elucidation of the mechanism by which mitochondria release cytochrome c, a component of the electron transport chain, into the cytosol following events that trigger apoptotic cell death. Cytochrome c is an important intracellular signal that activates the latter steps of apoptosis. The release of cytochrome c is inhibited by the mitochondrial protein Bcl-2, a potent inhibitor of apoptosis. Our use of neural cells transfected with the human bcl-2 gene provided the first demonstration that it protects against mitochondrial injury, oxidative stress, and both apoptotic and necrotic cell death following transient severe hypoxia and glucose deprivation. Additional findings indicating that Bcl-2 dramatically increases the calcium buffering capacity of mitochondria and protects mitochondria from calcium-induced damage represent the first demonstration of a specific subcellular activity for this powerful anti-death gene product. This information is applicable to the understanding and, ultimately, the treatment of many neurodegenerative disorders including those caused by ischemia and trauma as well as Alzheimer's and Parkinson's diseases, and amyotrophic lateral sclerosis.
Our future work will utilize human studies as well as our animal and cell culture systems. Previous results obtained by a new member of our group, Dr. Chandrasekaran, demonstrated a close relationship between depressed mitochondrial gene expression and neuronal death in Alzheimer's autopsy material. We will pursue this avenue of molecular biological research using cell and animal models of ischemic and excitotoxic neuronal death and with biopsy material obtained from head trauma patients. We are also working with trauma and emergency medicine physicians at the University of Maryland Medical System to implement clinical trials for stroke, trauma and cardiac arrest based on results obtained with our animal neuroprotection studies. Our work is supported by grants from the NIH (NINDS, NIEHS, NICHD), the U.S. Army, the American Heart Association, and from the pharmaceutical industry.
http://gpilsinside.umaryland.edu/Web%20files/Neuroscience/gfiskum1.gif |
Lab TechniquesMitochondrial and cellular O2 consumption, fluorescent and electrode measurements of mitochondrial membrane potential, immunoblot and ELISA assays for apoptosis-related proteins, mitochondrial gene expression, measurements of necrotic and apoptotic cell death, biochemical assays of enzyme activities and metabolite levels, fluorescent microscopy of intracellular Ca2+, reactive oxygen species and mitochondrial membrane potential, immunohistochemistry, transmission electron microscopy, primary cultures of neurons and astrocytes, cultures of wild-type and gene-transfected cell lines, animal model of cardiac arrest and resuscitation, animal models of focal and global cerebral ischemia, adult and immature animal models of traumatic brain injury.
PublicationsMurphy, A.N., Bredesen, D.E., Cortopassi, G., Wang, E., and Fiskum, G., Bcl-2 potentiates the maximal calcium uptake capacity of neural cell mitochondria, Proc. Natl. Acad. Sci., USA 3:9893-9898 (1996).
Miljkovic Lolic, M., Fiskum, G. and Rosenthal, R.E., Neuroprotective effects of acetyl-L-carnitine after stroke in rats, Ann. Emerg. Med. 29:758-765 (1997).
Liu, Y., Rosenthal, R.E., Haywood, Y., Miljkovic Lolic, M., Vanderhoek, J.Y. and Fiskum, G., Normoxic ventilation following cardiac arrest reduces oxidation of brain lipids and improves neurological outcome, Stroke 29:1679-1686 (1998).
Andreyev, A.Y., Fahy, B. and Fiskum, G., Cytochrome c release from brain mitochondria is independent of the mitochondrial permeability transition. FEBS Letts. 439:373-376 (1998).
Murphy, A.N., Fiskum, G., and Beal, M.F., Mitochondria in neurodegeneration: Bioenergetic function in cell life and death. J. Cereb. Blood Flow Metab. 19:231-245 (1999).
Fiskum, G., Murphy, A.N., and Beal, M.F., Mitochondria in neurodegeneration: Acute ischemia and chronic neurodegenerative disease. J. Cereb. Blood Flow Metab. 19:351-369 (1999).
Bogaert, Y.E., Rex-Sheu, K.-F., Hof, P.R., Brown, A.M., Blass, J.P., Rosenthal, R.E. and Fiskum, G., Neuronal subclass-selective loss of pyruvate dehydrogenase immunoreactivity following canine cardiac arrest and resuscitation. Exp. Neurology 161: 115-125 (2000).
Buee, L., Mailliot, C., Podevin-Dimster, V., Rosenthal, R.E., Delacourte, A. and Fiskum, G., Rapid tau protein dephosphorylation and differential rephosphorylation during cardiac arrest-induced cerebral ischemia and reperfusion, J. Cereb. Blood Flow Metab. 20: 543-549 (2000).
Fiskum, G., Kowaltowksi, A.J., Andreyev, A.Y., Kushnareva, Y.E. and Starkov, A.A., Apoptosis-related activities measured with isolated mitochondria and digitonin-permeabilized cells, Meth. Enzymol. 322: 222-234 (2000).
Kowaltowski, A.J., Smaili, S.S., Russell, J.T. and Fiskum, G., Elevation of the resting mitochondrial membrane potential of neural cells by cyclosporin A, BAPTA-AM and Bcl-2 overexpression. Am. J. Physiol. 48: 852-859 (2000).
Fiskum, G., Polster, B.M., and Kowaltowski, A.J., Mitochondria as targets of neuroprotection by Bcl-2 family proteins, In: "Pharmacology of Cerebral Ischemia 2000" (J. Krieglstein and S. Klumpp, eds.) Medpharm Publisher, Stuttgart, Germany, pp. 177-188 (2000).
Kowaltowski, A.J., Vercesi, A.E. and Fiskum, G., Bcl-2 prevents mitochondrial permeability transition and cytochrome c release via maintenance of reduced pyridine nucleotides, Cell Death Diff. 7, 207-214 (2000).
Fiskum, G., Mitochondrial participation in ischemic and traumatic neural cell death, J. Neurotrauma 17, 843-855 (2000).
Kushnareva, Y.E., Polster, B.M., Sokolove, P.M., Kinnally, K.W. and Fiskum, G., Mitochondrial precursor signal peptide induces a unique permeability transition and release of cytochrome c from liver and brain mitochondria, Arch. Biochem. Biophys. 386, 144-154 (2001).
Starkov, A.A. and Fiskum, G., Myxothiazol induces H2O2 production from mitochondrial respiratory chain, Biochem. Biophys. Res. Commun. 281, 645-650 (2001).
Chandrasekaran, K., Mehrabyan, Z., Murray, P., and Fiskum, G., Chronic exposure of neural cells to elevated intracellular sodium decreases mitochondrial mRNA expression, Mitochondrion 1, 141-150 (2001).
DasGupta, S.F., Rapoport, S.I., Gerschenson, M., Murphy, E., Fiskum, G., Russell, S.J. and Chandrasekaran K., ATP synthesis is coupled to rat liver mitochondrial RNA synthesis, Mol Cell Biochem 221, 3-10 (2001).
37. Polster, B.M., Kinnally, K.W. and Fiskum, G., BH3 domain peptide induces cell-type selective mitochondrial outer membrane permeability, J. Biol. Chem. 276, 37887-37894 (2001).
Chandrasekaran, K., Mehrabian, Z., Spinnewyn, B., Drieu, K., and Fiskum, G., Neuroprotective effects of bilobalide, a component of the Ginkgo biloba extract (EGb 761), in gerbil global brain ischemia. Brain Res. 922, 282-292 (2001).
Liu, Y., Fiskum, G., and Schubert, D., Generation of reactive oxygen species by the mitochondrial electron transport chain, J. Neurochem. 80, 780-787 (2002).
Qiu, J., Whalen, M.J., Lowenstein, P., Fiskum, G., Fahy, B., Darwish, R., Aarabi, B., Yuan, J., and Moskowitz, M.A., Upregulation of the Fas receptor death inducing signaling complex after traumatic brain injury in mice and humans, J. Neurosci. 22, 3504-3511(2002).
Rosen GM, Tsai P, Weaver JM, Porasuphatana S, Roman LJ, Starkov AA, Fiskum G, Pou S., Tetrahydrobiopterin: Its role in the regulation of neuronal nitric oxide synthase-generated superoxide, J. Biol. Chem. 277, 40275-40280.
Starkov, A.A., Polster, B.M., and Fiskum, G., Regulation of mitochondrial reactive oxygen species generation by calcium and Bax., J. Neurochem. 83, 220-228 (2002).
Kowaltowski, A.J., Cosso, R.G., Campos, C.B., and Fiskum, G., Effect of Bcl-2 overexpression on mitochondrial structure and function, J. Biol. Chem. 277, 42802-42807 (2002).
Personal HistoryDr. Fiskum received his B.A. degree from U.C.L.A. in 1973 and his Ph.D. in Biochemistry from St. Louis University in 1978. He then spent three years as a postdoctoral fellow with Dr. Albert L. Lehninger at the Johns Hopkins University. In 1981, he joined the faculty at George Washington University and was promoted to Professor of Biochemistry and Molecular Biology in 1991. He moved to the University of Maryland School of Medicine in 1997 where he serves as Professor and Vice-Chair for Research in the Department of Anesthesiology. He also serves as the organizer of the Program in Neuroscience Neuroprotection Research Focus Group. His areas of research interest include molecular mechanisms of neurodegeneration and neuroprotection, mitochondrial bioenergetics, cerebral energy metabolism, cell calcium homeostasis, oxidative stress, and apoptosis Laboratory PersonnelKrish Chandrasekaran, Ph.D., Assistant Professor Linda Bambrick, Ph.D., Assistant Professor Tibor Kristian, Ph.D., Assistant Professor Lucian Soane, Ph.D., Research Associate Zara Mehryaban, Ph.D. Back to All Faculty |