Spinal cord injury (SCI) is a major health care issue, causing immense hardships to its victims and their families. The initial injury is worsened by secondary """"""""autodestructive"""""""" processes caused by over production of harmful substances by injured cells. The PI's long-term focus in studying SCI is to identify endogenous toxic substances that cause secondary damage and to explore the pathways by which they cause cell death in order to develop therapeutic strategies to prevent such death. Methylprednisolone (MP) is the only drug approved for SCI treatment;however side effects limit its utility. Therefore it is urgent to discover more effective, less toxic therapeutic agents to reduce secondary injury. Reactive species (RS) identified as mediators of secondary injury after SCI induce cell death by two hypothesized pathways: 1) SCI-induced RS initiate oxidation of major cellular components, thereby destroying cells;2) Other SCI-induced toxic agents (e.g. glutamate) induce RS formation, which in turn potentiate toxicity of non-RS toxins. Due to this feedback amplification mechanism, RS are produced longer after SCI than are some non-RS toxins;this provides a longer therapeutic window for scavenging RS. Mn (III) tetrakis (benzoic acid) porphyrin (MnTBAP), a novel superoxide dismutase mimetic and a broad spectrum RS scavenger, is cell permeable, active, stable, nontoxic, and scavenges superoxide anion, hydrogen peroxide, and peroxynitrite. It appears significantly superior to MP. The goal of this project is thus to explore the therapeutic potential of MnTBAP for SCI treatment and its mechanism of action in vivo.
Specific Aim 1 is to explore the therapeutic potential and action site of MnTBAP to reduce secondary injury using a standard mechanical SCI model. The effect of MnTBAP will be compared with that of MP. The PI's group has demonstrated RS as initiators to induce oxidative damage and cell death.
Specific Aims 2 and 3 will explore the role of RS as death signaling messengers to potentiate toxicity of non-RS toxins and the action site of MnTBAP in this hypothesized pathway. A novel overall secondary chemical injury model will be used. It separates secondary chemical events from initial mechanical injury by sampling extracellular death signals in the extracellular fluid of an injured rat spinal cord and administering them directly into the cord of an uninjured rat by a microcannula inserted laterally through the cords of both rats to induce secondary cell death. To explore the role of RS and effect of MnTBAP in delayed Glu toxicity, Glu will be administered at the SCI-induced concentration and duration into the rat spinal cord through a microdialysis fiber to induce cell death. The ability of MnTBAP to scavenge RS, prevent oxidation of proteins, DNA and membrane lipids, reduce activation of caspases and death of different types of cells, particularly by apoptosis, and ameliorate neurological dysfunction will be assessed by comparing the results of MnTBAP- and saline-treated experiments. Production of RS and biomarkers of oxidation will be measured by HPLC, visualized by fluorescent probes and specific antibodies. Apoptosis of each cell type will be characterized by double staining with TUNEL and cell specific antibodies, Hoechst 33342 staining and electron microscopy. Activation of caspases in each cell types will be characterized by double staining. The immunohistochemical stained cells will be counted to determine the effect of MnTBAP on cell death. The therapeutic potential of MnTBAP will be assessed by behavioral tests.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
3R01NS044324-05S1
Application #
7778681
Study Section
Special Emphasis Panel (ZRG1-BDCN-1 (01))
Program Officer
Kleitman, Naomi
Project Start
2003-04-01
Project End
2011-03-31
Budget Start
2007-04-01
Budget End
2011-03-31
Support Year
5
Fiscal Year
2009
Total Cost
$50,000
Indirect Cost
Name
University of Texas Medical Br Galveston
Department
Neurology
Type
Schools of Medicine
DUNS #
800771149
City
Galveston
State
TX
Country
United States
Zip Code
77555
Liu, D; Bao, F (2015) Hydrogen peroxide administered into the rat spinal cord at the level elevated by contusion spinal cord injury oxidizes proteins, DNA and membrane phospholipids, and induces cell death: attenuation by a metalloporphyrin. Neuroscience 285:81-96
Ling, Xiang; Bao, Feng; Qian, Hao et al. (2013) The temporal and spatial profiles of cell loss following experimental spinal cord injury: effect of antioxidant therapy on cell death and functional recovery. BMC Neurosci 14:146
Liu, Danxia; Shan, Yichu; Valluru, Lokanatha et al. (2013) Mn (III) tetrakis (4-benzoic acid) porphyrin scavenges reactive species, reduces oxidative stress, and improves functional recovery after experimental spinal cord injury in rats: comparison with methylprednisolone. BMC Neurosci 14:23
Valluru, Lokanatha; Diao, Yao; Hachmeister, Jorge E et al. (2012) Mn (III) tetrakis (4-benzoic acid) porphyrin protects against neuronal and glial oxidative stress and death after spinal cord injury. CNS Neurol Disord Drug Targets 11:774-90
Wu, Liqin; Shan, Yichu; Liu, Danxia (2012) Stability, disposition, and penetration of catalytic antioxidants Mn-porphyrin and Mn-salen and of methylprednisolone in spinal cord injury. Cent Nerv Syst Agents Med Chem 12:122-30
Hachmeister, Jorge E; Valluru, Lokanatha; Bao, Feng et al. (2006) Mn (III) tetrakis (4-benzoic acid) porphyrin administered into the intrathecal space reduces oxidative damage and neuron death after spinal cord injury: a comparison with methylprednisolone. J Neurotrauma 23:1766-78
Liu, Danxia; Bao, Feng; Prough, Donald S et al. (2005) Peroxynitrite generated at the level produced by spinal cord injury induces peroxidation of membrane phospholipids in normal rat cord: reduction by a metalloporphyrin. J Neurotrauma 22:1123-33
Bao, F; Liu, D (2004) Hydroxyl radicals generated in the rat spinal cord at the level produced by impact injury induce cell death by necrosis and apoptosis: protection by a metalloporphyrin. Neuroscience 126:285-95
Liu, Danxia; Liu, Jing; Sun, Dachuan et al. (2004) The time course of hydroxyl radical formation following spinal cord injury: the possible role of the iron-catalyzed Haber-Weiss reaction. J Neurotrauma 21:805-16