BioChemistry&Molecular Biology, Pharmacology
Education and Training
1969‑1973: B.A., U.C.L.A., Zoology
1973‑1978: Ph.D., St. Louis University, Biochemistry (Dr. Ronald Cockrell, Advisor)
Post Graduate Education and Training:
1978‑1981: Postdoctoral Fellow, Department of Physiological Chemistry, Johns Hopkins University School of Medicine (Dr. Albert L. Lehninger, Advisor)
My current, primary mechanistic research goal is to identify the molecular causes of bioenergetic dysfunction in acute neurologic disorders, e.g., stroke and head trauma. My translational research goal is to demonstrate clinically realistic approaches to reducing primary and secondary oxidative stress and metabolic failure. Our demonstration that exposure of animals to unnecessary hyperoxia following brain ischemia is just as damaging as hypoxia led to a fundamental change in the Advanced Cardiac Life Support Resuscitation guidelines.
Since 1987, my research has focused on mitochondrial metabolic dysfunction, oxidative stress, and apoptotic pathways in acute brain injury. These studies were performed primarily with animal models; however, we have also published several studies with human brain, including a detailed analysis of mitochondrial ultrastructural alterations following severe traumatic brain injury. Many of my 185 peer-reviewed research articles have described the complex interactions between oxidative stress and mitochondrial bioenergetics and development of therapeutic interventions that target these interactions. For example, we were the first to demonstrate that pharmacologic activation of the Nrf2 pathway of antioxidant gene expression protects mitochondria from stress-induced dysfunction.
Most recently, we identified sexually dimorphic differences in mitochondrial antioxidant molecules and changes in morphology that may be responsible for the relative resistance of female rat pups to brain injury caused by hypoxia. I have also have published over 30 articles on mitochondria and cancer cells, including a group of papers that differentiated between the inhibition by Bcl-2 on Bax-induced apoptosis and inhibition by Bcl-2 on the mitochondrial membrane permeability transition. In summary, I have over 40 yr of experience in mitochondrial research applied to a wide variety of diseases and disorders ranging from cancer to traumatic brain injury.
Adult and pediatric traumatic and ischemic brain injury; Mitochondrial bioenergetics; Cerebral energy metabolism; Oxidative stress; Apoptosis; Neuroprotection
Demarest, TG, Waite, DL, Kristian, T, Puche, AC, Waddell, J, McKenna, MC, and Fiskum, G. Sex dependent mitophagy and neuronal death following rat neonatal hypoxic-ischemia, Neuroscience (2016 in press)
Demarest, T.G., Schuh, R.A., Waddell, J., McKenna, M.C. and Fiskum, G., Sex dependent mitochondrial respiratory impairment and oxidative stress in a rat model of neonatal hypoxic-ischemic encephalopathy, J. Neurochem. 137:714-29 (2016) (PMID: 27197831)
Skovira, JW, Kabadi, SV, Wu, J, Zhao, Z, DuBose, J, Rosenthal, RE, Fiskum, G, and Faden, AI, Simulated aeromedical evacuation exacerbates experimental brain injury, J. Neurotrauma 33:1292-302 (2016) (PMID: 26593382)
Mazzeffi M, Lund L, Wallace K, Herrera AV, Tanaka K, Odonkor P, Strauss E, Rock P, Fiskum G. Effect of cardiopulmonary bypass on platelet mitochondrial respiration and correlation with aggregation and bleeding: a pilot study. Perfusion (2016 in press) (PMID:26916901)
Proctor, JL, Scutella, D, Pan, Y, Vaughan, J. Rosenthal, RE, Puche, A, and Fiskum, G., Hyperoxic resuscitation improves survival but worsens neurologic outcome in a rat polytrauma model of traumatic brain injury plus hemorrhagic shock, J Trauma Acute Care Surgery 79(4 Suppl 2):S101-109
The following link provides access to all of Dr. Fiskum’s pubmed cited publications:
1. Basic Research on Mitochondrial Bioenergetics
As a postdoctoral fellow in the laboratory of Dr. Albert L. Lehninger, I established the stoichiometric relationships between mitochondrial oxygen consumption, proton efflux, phosphate influx and ATP formation. These experiments taken together with those measuring rates of respiration-dependent calcium influx provided critical detailed information that fine-tuned the chemiosmotic coupling hypothesis of oxidative phosphorylation (1).The most physiologically important discovery I made during this period was that physiological levels of cytosolic calcium are buffered primarily by endoplasmic reticulum and plasma membrane calcium-ATPases and that mitochondrial calcium uptake is important for stimulating oxidative phosphorylation and for buffering pathologic increases in cytosolic calcium. These measurements were the first to utilize digitonin-permeabilized cells (2), obviating the isolation of organelles and increasing their physiological significance. Since then, over 1000 published studies have employed the digitonin permeabilization technique (see e.g., 3)
- Fiskum, G., Reynafarje, B. and Lehninger, A.L. (1979) The electric charge stoichiometry of respiration-dependent Ca2+ uptake by mitochondria, J. Biol. Chem. 254:6288-6295. (PMID: 36391)
- Becker, G., Fiskum, G. and Lehninger, A.L. (1980) Regulation of free Ca2+ by mitochondria, endoplasmic reticulum, and digitonin-treated cells, J. Biol. Chem. 255, 9009-9012 (PMID: 7410406)
- Fiskum, G. (1985) Intracellular levels and distribution of Ca2+ in digitonin-permeabilized cells, Cell Calcium 6, 25-37. (PMID:4016893)
2. Bioenergetics Pathobiology Research
I was also one of the first researchers to study what was eventually termed the mitochondrial inner membrane permeability transition pore (PTP) (1), which is now known to be a very important mediator of necrotic cell death in ischemic and traumatic injury to all vital organs, including the heart and brain. My major contributions to this field were the demonstration that oxidized mitochondrial redox state promotes permeability transition pore opening and that the anti-death protein Bcl2 inhibits pore opening by conferring resistance to oxidized shifts in redox state (2, 3). This finding provides an explanation why Bcl2 overexpression protects against both necrotic and apoptotic cell death.
My lab also contributed significantly to understanding the mitochondrial pathway of apoptosis. We demonstrated that cytochrome c release occurs as a consequence of Bax binding to the outer membrane and subsequent mega-pore formation rather than activation of the inner membrane permeability transition pore (4). This finding is very important since it explains why drugs, e.g., cyclosporin A, inhibit necrotic but not apoptotic cell death in paradigms, e.g., ischemia/reperfusion, where both forms of cell death occur. My lab also made a substantial impact in understanding mitochondrial formation and detoxification of reactive oxygen species (ROS), which can trigger both necrosis and apoptosis. Our most highly cited publication demonstrated that ROS production by specific enzymes present in the Kreb’s cycle are as or more important than the ROS generated by reactions that occur in the electron transport chain (5).
We have applied this knowledge of normal and pathogenic mitochondrial bioenergetics to a large variety of both in vitro and in vivo models of cell injury and death. For instance, we have shown that mitochondrial respiratory impairment occurs rapidly following both cerebral ischemia and traumatic brain injury and that the degree of bioenergetic impairment is directly related to the extent of subsequent neuronal death and neurologic impairment. Oxidative modification of important mitochondrial metabolic proteins, e.g., the pyruvate dehydrogenase complex (PDHC), is a primary mechanism responsible the death of neurons caused by toxins, excitotoxicity, and acute ischemic or traumatic brain injury. As described below, this knowledge led to the successful design of several neuroprotective interventions, including at least one that was translated into a change in clinical practice.
- Fiskum, G. and Lehninger, A.L., Regulated release of Ca2+ from respiring mitochondria by Ca2+/2H+ antiport, J. Biol. Chem.254, 6236-6239 (1979). (PMID: 36390)
- Murphy, A.N., Bredesen, D.E., Cortopassi, G., Wang, E., and Fiskum, G. (1996) Bcl-2 potentiates the maximal calcium uptake capacity of neural cell mitochondria, Proc. Natl. Acad. Sci., USA 93:9893-9898 (PMID: 8790427)
- Kowaltowski, A.J., Vercesi, A.E. and Fiskum, G. (2000) Bcl-2 prevents mitochondrial permeability transition and cytochrome c release via maintenance of reduced pyridine nucleotides, Cell Death Diff. 7, 207-214 (PMID:16120274)
- 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). (PMID:11483608)
- Starkov, A.A., Fiskum, G., Chinopoulos, C., Lorenzo, B.J., Browne, S.E., Patel, M.S., and Beal, M.F. (2004) Mitochondrial alpha-ketoglutarate dehydrogenase complex generates reactive oxygen species, J. Neurosci. 24: 7779-7788. (PMID:15356189)
3. Translational Neuroprotection Research
Our approach to neuroprotection has been based primarily on bioenergetics dysfunction hypotheses but tested using highly clinically relevant models of acute brain injury, using both small and large laboratory animals. Knowing that reduced PDHC activity can explain reduced aerobic energy metabolism following brain injury (1), we initially hypothesized that another source of fuel that bypasses the PDHC step can improve cerebral energy metabolism and protect against impaired neurobehavioral outcomes. Based on this hypothesis, we found that administration of acetyl-L-carnitine (ALCAR) provided significant neuroprotection in both a rat model of focal cerebral ischemia (stroke) and a canine model of cardiac arrest and resuscitation (2). We also more recently observed neuroprotection by ALCAR in a rat pediatric traumatic brain injury model. Moreover, using 13C NMR spectroscopy, we obtained the first direct evidence that the acetyl carbons in ALCAR are used for both cerebral energy production and the biosynthesis of the neurotransmitter GABA (3). Based on the proven safety of carnitine administration in neonates with failure to thrive and the numerous other labs that have documented neuroprotection by ALCAR, we are striving to translate these findings into a neuroprotection clinical trial for ischemic or traumatic brain injury.
During our ALCAR research, we measured levels of oxidized lipids and proteins as biomarkers of oxidative stress. We found that ALCAR reduced the extent of oxidative stress early during reperfusion, probably due to increased reducing power for ROS detoxification. At that time, we routinely used 100% inspired oxygen both during and after resuscitation, per standard American Heart Association (AHA) Advanced Cardiac Life Support (ACLS) guidelines. In light of the extensive oxidative molecular modifications we observed in the brain within even 30 min of reperfusion, we questioned the advisability of using such high levels of oxygen. Since ventilation on pure oxygen resulted in systemic hyperoxia, we hypothesized that abnormally high levels of oxygen also occur in the brain, thereby increasing ROS production. The ensuing experiments led in some of our most important publications (1,4). These articles described rigorous quantitative evidence that in comparison to hyperoxic reperfusion, normoxic reperfusion reduces oxidative protein alterations, improves pyruvate dehydrogenase activity, reduces brain lactate levels, improves hippocampal neuronal survival, and, most importantly, improves neurologic outcome. We published at least 16 articles on this topic, using both large and small animal models and in vitro models of oxygen toxicity to neurons and astrocytes. In 2010, the ACLS guidelines were changed dramatically from indiscriminately using oxygen to using the minimum oxygen necessary to achieve systemic normoxia. These guidelines were reaffirmed in 2013 but still await prospective clinical studies to confirm their validity.
- Vereczki, V., Martin, E., Rosenthal, R.E., Hof, P.R., Hoffman, G.E., and Fiskum, G. (2006) Normoxic resuscitation after cardiac arrest protects against hippocampal oxidative stress, metabolic dysfunction, and neuronal death, J. Cereb. Blood Flow Metab., 26: 821-35. (PMID:16251887)
- Rosenthal, R.E., Williams, R.M., Getson, P., Bogaert, Y.E. and Fiskum, G. *1992) Post-ischemic administration of acetyl-L-carnitine improves neurological outcome and lowers cerebral cortex lactate/pyruvate ratios following cardiac arrest in dogs, Stroke 23:1312-1318. (PMID:1519288
- Scafidi, S., Fiskum, G., Lindauer, S.L., Bamford, P., Shi, D., Hopkins, I., and McKenna, M.C. (2010) Metabolism of acetyl-L-carnitine for energy and neurotransmitter synthesis in the immature rat brain. J. Neurochem. 114:820-831 (PMID:20477950)
- Balan, I.S., Fiskum, G., Hazelton, J., Cotto-Cumba, C., and Rosenthal, R.E. (2006) Oximetry-guided reoxygenation improves neurologic outcome after experimental cardiac arrest, Stroke 37: 3008-3013 (PMID:17068310)
Current Research Directions
Our recently awarded NIH R01 grant tests the hypothesis that both oxygen and specific agents, e.g., sulforaphane, can be used following resuscitation from cardiac arrest to stimulate the expression of antioxidant gene products, resulting in protection against mitochondrial oxidative stress, reduced brain inflammation, and improved neurologic outcome. The Air Force funded “polytrauma” grant focuses on the effects of exposure to aeromedical evacuation-relevant hypobaria on survival and brain injury following impact traumatic brain injury plus hemorrhagic shock (1). This animal model is highly clinically relevant but rarely reported due to the difficult critical care procedures that are required. The Aims addressed by these two projects, together with those for the Air Force funded “sepsis hypobaria” grant include measurements of respiration and ROS production by isolated brain mitochondria. Therefore, resources and expertise associated with these three ongoing projects will definitely benefit this current application studying the role of mitochondrial dysfunction in renal cystogenesis. The proposed R01 project will also benefit from the results obtained during the recently expired NIH P01 grant, highlighting the sexually dimorphic responses of brain mitochondria to cerebral ischemia (2). We will therefore apply this knowledge to the new experiments that will utilize both male and female mice.
- Proctor, JL, Scutella, D, Pan, Y, Vaughan, J. Rosenthal, RE, Puche, A, and Fiskum, G. (2015) Hyperoxic resuscitation improves survival but worsens neurologic outcome in a rat polytrauma model of traumatic brain injury plus hemorrhagic shock, J Trauma Acute Care Surgery 79(4 Suppl 2):S101-109 (PMID: 26406421)
- Demarest, T.G., Schuh, R.A., Waddell, J., McKenna, M.C. and Fiskum, G., Sex dependent mitochondrial respiratory impairment and oxidative stress in a rat model of neonatal hypoxic-ischemic encephalopathy, J. Neurochem. (2016, in press)
2011 University of Maryland Baltimore Campus Researcher of the Year
Current Research Support
US Air Force FA8650-14-2-6D17 (07/21/14 – 05/20/16)
Prolongation of Platelet Storage Time by Protection against Mitochondrial Energy Failure
This project tests the hypothesis that platelet storage time can be extended by the addition of different energy-metabolism supplements to the storage solution.
NIH 1 R01 NS091099-01A1 (09/30/15 – 09/29/20)
Optimal Oxygenation and Gene Expression During Critical Care after Cardiac Arrest
This large R01 grant is an extension of our highly translation neuroprotection research using animal models of cardiac arrest and resuscitation. This project also includes mechanistic studies focusing on mitochondrial mechanisms of reperfusion brain injury.
US Air Force FA8650-15-2-6D27 (08/01/15 – 07/31/16)
Effect of Hypobaria during Sepsis on Survival, Encephalopathy, and Energy Metabolism
This grant focuses on the effects of aeromedical evacuation-relevant hypobaria during early sepsis, with emphasis on exacerbation of brain and liver mitochondrial bioenergetics dysfunction.
US Army W81XWH-13-1-0016 (01/06/13 – 01/05/17)
Underbody Blast Models of TBI Caused by Hyperacceleration and Secondary Head Impact
This project focuses on a rodent model of TBI induced by blasts, as occurs with occupants of vehicles targeted by improvised explosive devices.
US Air Force FA8650-15-2-6D21 (06/22/15 – 06/21/18)
Effects of Hypobaria on Brain Injury and Mortality Following Head Trauma Combined with Hemorrhagic Shock
This project tests the hypothesis that exposure to air evacuation-relevant hypobaria worsens mortality and neurologic outcome following an animal model of polytrauma consisting of impact traumatic brain injury plus hemorrhagic shock.
US Air Force FA8650-15-2-6D20 (12/01/14 – 06/30/16)
Changes in Gene Expression following Exposure to Different Durations and Levels of Hypobaria
This project characterizes changes in gene expression in the brains of normal rats following exposure of different levels and durations of hypobaria.
Completed Research Support
NIH 2P01 1HD16596-26 A1 (01/20/11 – 01/19/16)
Metabolic & Developmental Aspects of Intellectual Disability
This program project represents a multidisciplinary approach to determine the pathophysiology of neonatal hypoxic ischemic encephalopathy. Project 1 focuses on mitochondrial bioenergetics dysfunction, using both a neonatal rat model of hypoxic ischemia and cell culture models.
Role: Co-PI of P01 and PI of Project 1
US Air Force FA8650-11-2-6D04 (10/24/11 – 10/23/14)
Animal Models of Traumatic Brain Injury with Aerial Evacuation
This project studied the effects of hypobaria associated with aerial evacuation on traumatic brain injury
US Army W81XWH-13-1-0016 (10/01/09 – 09/30/13)
The Effects of Systemic Hyperoxia and/or Hyperventilation on the Oxidative Injury and Cerebral Perfusion after TBI and Hemorrhage
The goal of this grant was to optimize neuroprotective critical care in a rat model of polytrauma consisting of traumatic brain injury and hemorrhagic shock.
- Clinically relevant small and large animal models of acute brain injury
- Respirometry for isolated mitochondria and cells
- Primary culture of neurons and astrocytes using an environmental chamber precisely controling ambient oxygen concentrations
- Fluorescent measurements of cell death
- Development of transgenic animals
- Fluorescent live cell imaging of intracellular NAD(P)H, calcium, mitochondrial membrane potential and superoxide
- Stereologic histology and immunohistochemistry
- 13C NMR spectroscopy of brain energy metabolites
- Rodent behavorial tests
- Enzyme activity measurements
- Quantative rtPCR
- Southern and Western blots
- ELISA Spectrofluorometry
- 09/81 Asst. Professor of Biochemistry, George Washington Univ. School of Medicine
- 07/87 Tenured Associate Professor of Biochemistry and of Emergency Medicine, GWUMC successful design of several neuroprotective interventions, including at least one that was translated into a change in clinical practice.
- 07/91 Professor of Biochemistry and Molecular Biology and of Emergency Medicine, GWUMC
- 10/97 Professor and Research Director of Anesthesiology, Professor of Biochemistry and MolecularBiology, Professor of Pharmacology, Univ. of Maryland School of Medicine (UMSOM)
- 03/03 Vice-Chair for Research, Department of Anesthesiology, UMSOM
- 10/10 M. Jane Matjasko Professor for Research, Dept. of Anesthesiology, UMSOM