The presence of 4-hydroxynonenal/protein complex as an indicator of oxidative stress after experimental spinal cord contusion in a rat model

Thermosensitive hydrogel-based GPR124 delivery strategy for rebuilding blood-spinal cord barrier

Spinal cord injury (SCI) causes blood-spinal cord barrier (BSCB) disruption, leading to secondary damage, such as hemorrhagic infiltration, inflammatory response, and neuronal cell death. It is of great significance to rebuild the BSCB at the early stage of SCI to alleviate the secondary injury for better prognosis. Yet, current research involved in the reconstruction of BSCB is insufficient. Accordingly, we provide a thermosensitive hydrogel-based G protein-coupled receptor 124 (GPR124) delivery strategy for rebuilding BSCB. Herein, we firstly found that the expression of GPR124 decreased post-SCI and demonstrated that treatment with recombinant GPR124 could partially alleviate the disruption of BSCB post-SCI by restoring tight junctions (TJs) and promoting migration and tube formation of endothelial cells. Interestingly, GPR124 could also boost the energy metabolism of endothelial cells. However, the absence of physicochemical stability restricted the wide usage of GPR124. Hence, we fabricated a thermosensitive heparin-poloxamer (HP) hydrogel that demonstrated sustained GPR124 production and maintained the bioactivity of GPR124 (HP@124) for rebuilding the BSCB and eventually enhancing functional motor recovery post-SCI. HP@124 hydrogel can encapsulate GPR124 at the lesion site by injection, providing prolonged release, preserving wounded tissues, and filling injured tissue cavities. Consequently, it induces synergistically efficient integrated regulation by blocking BSCB rupture, decreasing fibrotic scar formation, minimizing inflammatory response, boosting remyelination, and regenerating axons. Mechanistically, giving GPR124 activates energy metabolism via elevating the expression of phosphoenolpyruvate carboxykinase 2 (PCK2), and eventually restores the poor state of endothelial cells. This research demonstrated that early intervention by combining GPR124 with bioactive multifunctional hydrogel may have tremendous promise for restoring locomotor recovery in patients with central nervous system disorders, in addition to a translational approach for the medical therapy of SCI.

Improved locomotor recovery after contusive spinal cord injury in Bmal1-/- mice is associated with protection of the blood spinal cord barrier

The transcription factor BMAL1/ARNTL is a non-redundant component of the clock pathway that regulates circadian oscillations of gene expression. Loss of BMAL1 perturbs organismal homeostasis and usually exacerbates pathological responses to many types of insults by enhancing oxidative stress and inflammation. Surprisingly, we observed improved locomotor recovery and spinal cord white matter sparing in Bmal1-/- mice after T9 contusive spinal cord injury (SCI). While acute loss of neurons and oligodendrocytes was unaffected, Bmal1 deficiency reduced the chronic loss of oligodendrocytes at the injury epicenter 6 weeks post SCI. At 3 days post-injury (dpi), decreased expression of genes associated with cell proliferation, neuroinflammation and disruption of the blood spinal cord barrier (BSCB) was also observed. Moreover, intraspinal extravasation of fibrinogen and immunoglobulins was decreased acutely at dpi 1 and subacutely at dpi 7. Subacute decrease of hemoglobin deposition was also observed. Finally, subacutely reduced levels of the leukocyte marker CD45 and even greater reduction of the pro-inflammatory macrophage receptor CD36 suggest not only lower numbers of those cells but also their reduced inflammatory potential. These data indicate that Bmal1 deficiency improves SCI outcome, in part by reducing BSCB disruption and hemorrhage decreasing cytotoxic neuroinflammation and attenuating the chronic loss of oligodendrocytes.

The Importance of Natural Antioxidants in the Treatment of Spinal Cord Injury in Animal Models: An Overview

Patients with spinal cord injury (SCI) face devastating health, social, and financial consequences, as well as their families and caregivers. Reducing the levels of reactive oxygen species (ROS) and oxidative stress are essential strategies for SCI treatment. Some compounds from traditional medicine could be useful to decrease ROS generated after SCI. This review is aimed at highlighting the importance of some natural compounds with antioxidant capacity used in traditional medicine to treat traumatic SCI. An electronic search of published articles describing animal models of SCI treated with natural compounds from traditional medicine was conducted using the following terms: Spinal Cord Injuries (MeSH terms) AND Models, Animal (MeSH terms) AND [Reactive Oxygen Species (MeSH terms) AND/OR Oxidative Stress (MeSH term)] AND Medicine, Traditional (MeSH terms). Articles reported from 2010 to 2018 were included. The results were further screened by title and abstract for studies performed in rats, mice, and nonhuman primates. The effects of these natural compounds are discussed, including their antioxidant, anti-inflammatory, and antiapoptotic properties. Moreover, the antioxidant properties of natural compounds were emphasized since oxidative stress has a fundamental role in the generation and progression of several pathologies of the nervous system. The use of these compounds diminishes toxic effects due to their high antioxidant capacity. These compounds have been tested in animal models with promising results; however, no clinical studies have been conducted in humans. Further research of these natural compounds is crucial to a better understanding of their effects in patients with SCI.

Carbonyl scavengers as pharmacotherapies in degenerative disease: Hydralazine repurposing and challenges in clinical translation

During cellular metabolism, spontaneous oxidative damage to unsaturated lipids generates many electrophilic carbonyl compounds that readily attack cell macromolecules, forming adducts that are potential drivers of tissue dysfunction. Since such damage is heightened in many degenerative conditions, researchers have assessed the efficacy of nucleophilic carbonyl-trapping drugs in animal models of such disorders, anticipating that they will protect tissues by intercepting toxic lipid-derived electrophiles (LDEs) within cells. This Commentary explores recent animal evidence for carbonyl scavenger efficacy in two disparate yet significant conditions known to involve LDE production, namely spinal cord injury (SCI) and alcoholic liver disease (ALD). Primary emphasis is placed on studies that utilised hydralazine, a clinically-approved "broad-spectrum" scavenger known to trap multiple LDEs. In addition to reviewing recent studies of hydralazine efficacy in animal SCI and ALD models, the Commentary reviews new insights concerning novel lifespan- and healthspan-extending properties of hydralazine obtained during studies in model invertebrate organisms, since the mechanisms involved seem of likely benefit during the treatment of degenerative disease. Finally, noting that human translation of the histoprotective properties of hydralazine have been limited, the final section of the Commentary will address two obstacles that hamper clinical translation of LDE-trapping therapies while also suggesting potential strategies for overcoming these problems.

Vincamine Alleviates Amyloid-β 25-35 Peptides-induced Cytotoxicity in PC12 Cells

Objective:

Vincamine is a plant alkaloid used clinically as a peripheral vasodilator that increases cerebral blood flow and oxygen and glucose utilization by neural tissue to combat the effect of aging. The main purpose of the present study is to investigate the influence of vincamine on amyloid-β 25–35 (Aβ25–35) induced cytotoxicity, to gain a better understanding of the neuroprotective effects of this clinically used anti-Alzheimer's disease drug.

Materials and Methods:

Oxidative stress was assessed by measuring malondialdehyde, glutathione, and superoxide dismutase (SOD) levels. Cell viability was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Cell apoptosis detection was performed using an Annexin-V-FITC Apoptosis Detection Kit. The production of reactive oxygen species (ROS) was determined using an ROS Assay Kit. Western blot detection was carried out to detect the protein expression.

Results:

Our studies showed that pretreatment with vincamine could reduce Aβ25–35 induced oxidative stress. Vincamine markedly inhibited cell apoptosis dose-dependently. More importantly, vincamine increased the phosphatidylinositol-3 kinase (PI3K)/Akt and Bcl-2 family protein ratios on preincubation with cells for 2 h.

Conclusion:

Above observation led us to assume that one possible mechanism of vincamine protects Aβ25-35-induced cell death could be through upregulation of SOD and activation of the PI3K/Akt pathway.

SUMMARY

Vincamine ameliorates amyloid-β 25–35 (Aβ25–35) peptides induced cytotoxicity in PC12 cells

Vincamine reduces Aβ 25–35 peptides induced apoptosis of PC12 cells

Vincamine activates the phosphatidylinositol-3 kinase/Akt pathway

Vincamine up-regulates the superoxide dismutase.

Abbreviation used: Aβ25-35: Amyloid-β 25-35; AD: Alzheimer's disease; BCA: Bicinchoninic acid; GSH: glutathione; PBS: Phosphate buffered solution; SDS: Sodium dodecylsulphate; SOD: Superoxide dismutase

Inflammogenesis of Secondary Spinal Cord Injury

Spinal cord injury (SCI) and spinal infarction lead to neurological complications and eventually to paraplegia or quadriplegia. These extremely debilitating conditions are major contributors to morbidity. Our understanding of SCI has certainly increased during the last decade, but remains far from clear. SCI consists of two defined phases: the initial impact causes primary injury, which is followed by a prolonged secondary injury consisting of evolving sub-phases that may last for years. The underlying pathophysiological mechanisms driving this condition are complex. Derangement of the vasculature is a notable feature of the pathology of SCI. In particular, an important component of SCI is the ischemia-reperfusion injury (IRI) that leads to endothelial dysfunction and changes in vascular permeability. Indeed, together with endothelial cell damage and failure in homeostasis, ischemia reperfusion injury triggers full-blown inflammatory cascades arising from activation of residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (neutrophils and macrophages). These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit. Therefore, our review considers the recent advances in SCI mechanisms, whereby it becomes clear that SCI is a heterogeneous condition. Hence, this leads towards evidence of a restorative approach based on monotherapy with multiple targets or combinatorial treatment. Moreover, from evaluation of the existing literature, it appears that there is an urgent requirement for multi-centered, randomized trials for a large patient population. These clinical studies would offer an opportunity in stratifying SCI patients at high risk and selecting appropriate, optimal therapeutic regimens for personalized medicine.

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

We previously demonstrated that hydrogen peroxide concentration ([H2O2]) significantly increases after spinal cord injury (SCI). The present study explored (1) whether SCI-elevated [H2O2] is sufficient to induce oxidation and cell death, (2) if apoptosis is a pathway of H2O2-induced cell death, and (3) whether H2O2-induced oxidation and cell death could be reversed by treatment with the catalytic antioxidant Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP). H2O2 was perfused through a microcannula into the uninjured rat spinal cord to mimic the conditions induced by SCI. Protein and DNA oxidation, membrane phospholipids peroxidation (MLP), cell death and apoptosis were characterized by histochemical and immunohistochemical staining with antibodies against markers of oxidation and apoptosis. Stained cells were quantified in sections of H2O2-, or artificial cerebrospinal fluid (ACSF)-exposed with vehicle-, or MnTBAP-treated groups. Compared with ACSF-exposed animals, SCI-elevated [H2O2] significantly increased intracellular protein and DNA oxidation by threefold and MLP by eightfold in neurons, respectively. H2O2-elevated extracellular malondialdehyde was measured by microdialysis sampling. We demonstrated that SCI-elevated [H2O2] significantly increased extracellular malondialdehyde above pre-injury levels. H2O2 also significantly increased cell loss and the numbers of terminal deoxynucleotidyl transferase (TdT)-mediated deoxyuridine triphosphate-(dUTP)-biotin nick end labeling (TUNEL)-positive and active caspase-3-positive neurons by 2.3-, 2.8-, and 5.6-fold compared to ACSF controls, respectively. Our results directly and unequivocally demonstrate that SCI-elevated [H2O2] contributes to post-SCI MLP, protein, and DNA oxidation to induce cell death. Therefore, we conclude that (1) the role of H2O2 in secondary SCI is pro-oxidation and pro-cell death, (2) apoptosis is a pathway for SCI-elevated [H2O2] to induce cell death, (3) caspase activation is a mechanism of H2O2-induced apoptosis after SCI, and (4) MnTBAP treatment significantly decreased H2O2-induced oxidation, cell loss, and apoptosis to the levels of ACSF controls, further supporting MnTBAP's ability to scavenge H2O2 by in vivo evidence.

Remote neurodegeneration: multiple actors for one play

Remote neurodegeneration significantly influences the clinical outcome in many central nervous system (CNS) pathologies, such as stroke, multiple sclerosis, and traumatic brain and spinal cord injuries. Because these processes develop days or months after injury, they are accompanied by a therapeutic window of opportunity. The complexity and clinical significance of remote damage is prompting many groups to examine the factors of remote degeneration. This research is providing insights into key unanswered questions, opening new avenues for innovative neuroprotective therapies. In this review, we evaluate data from various remote degeneration models to describe the complexity of the systems that are involved and the importance of their interactions in reducing damage and promoting recovery after brain lesions. Specifically, we recapitulate the current data on remote neuronal degeneration, focusing on molecular and cellular events, as studied in stroke and brain and spinal cord injury models. Remote damage is a multifactorial phenomenon in which many components become active in specific time frames. Days, weeks, or months after injury onset, the interplay between key effectors differentially affects neuronal survival and functional outcomes. In particular, we discuss apoptosis, inflammation, oxidative damage, and autophagy-all of which mediate remote degeneration at specific times. We also review current findings on the pharmacological manipulation of remote degeneration mechanisms in reducing damage and sustaining outcomes. These novel treatments differ from those that have been proposed to limit primary lesion site damage, representing new perspectives on neuroprotection.

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

BACKGROUND

Substantial experimental evidence supports that reactive species mediate secondary damage after traumatic spinal cord injury (SCI) by inducing oxidative stress. Removal of reactive species may reduce secondary damage following SCI. This study explored the effectiveness of a catalytic antioxidant - Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) - in removing reactive oxygen species (ROS), reducing oxidative stress, and improving functional recovery in vivo in a rat impact SCI model. The efficiency of MnTBAP was also compared with that of methylprednisolone - the only drug used clinically in treating acute SCI.

RESULTS

In vivo measurements of time courses of ROS production by microdialysis and microcannula sampling in MnTBAP, methylprednisolone, and saline (as vehicle control)-treated SCI rats showed that both agents significantly reduced the production of hydrogen peroxide, but only MnTBAP significantly reduced superoxide elevation after SCI. In vitro experiments further demonstrated that MnTBAP scavenged both of the preceding ROS, whereas methylprednisolone had no effect on either. By counting the immuno-positive neurons in the spinal cord sections immunohistochemically stained with anti-nitrotyrosine and anti-4-hydroxy-nonenal antibodies as the markers of protein nitration and membrane lipid peroxidation, we demonstrated that MnTBAP significantly reduced the numbers of 4-hydroxy-nonenal-positive and nitrotyrosine-positive neurons in the sections at 1.55 to 2.55 mm and 1.1 to 3.1 mm, respectively, rostral to the injury epicenter compared to the vehicle-treated animals. By behavioral tests (open field and inclined plane tests), we demonstrated that at 4 hours post-SCI treatment with MnTBAP and the standard methylprednisolone regimen both significantly increased test scores compared to those produced by vehicle treatment. However, the outcomes for MnTBAP-treated rats were significantly better than those for methylprednisolone-treated animals.

CONCLUSIONS

This study demonstrated for the first time in vivo and in vitro that MnTBAP significantly reduced the levels of SCI-elevated ROS and that MnTBAP is superior to methylprednisolone in removing ROS. Removal of ROS by MnTBAP significantly reduced protein nitration and membrane lipid peroxidation in neurons. MnTBAP more effectively reduced neurological deficits than did methylprednisolone after SCI - the first most important criterion for assessing SCI treatments. These results support the therapeutic potential of MnTBAP in treating SCI.

Acetyl-L-carnitine treatment following spinal cord injury improves mitochondrial function correlated with remarkable tissue sparing and functional recovery

We have recently documented that treatment with the alternative biofuel, acetyl-L-carnitine (ALC, 300 mg/kg), as late as 1 h after T10 contusion spinal cord injury (SCI), significantly maintained mitochondrial function 24 h after injury. Here we report that after more severe contusion SCI centered on the L1/L2 segments that are postulated to contain lamina X neurons critical for locomotion (the "central pattern generator"), ALC treatment resulted in significant improvements in acute mitochondrial bioenergetics and long-term hind limb function. Although control-injured rats were only able to achieve slight movements of hind limb joints, ALC-treated animals produced consistent weight-supported plantar steps 1 month after injury. Such landmark behavioral improvements were significantly correlated with increased tissue sparing of both gray and white matter proximal to the injury, as well as preservation of choline acetyltransferase (ChAT)-positive neurons in lamina X rostral to the injury site. These findings signify that functional improvements with ALC treatment are mediated, in part, by preserved locomotor circuitry rostral to upper lumbar contusion SCI. Based on beneficial effects of ALC on mitochondrial bioenergetics after injury, our collective evidence demonstrate that preventing mitochondrial dysfunction acutely "promotes" neuroprotection that may be associated with the milestone recovery of plantar, weight-supported stepping.

Antioxidant therapies in traumatic brain and spinal cord injury

Free radical formation and oxidative damage have been extensively investigated and validated as important contributors to the pathophysiology of acute central nervous system injury. The generation of reactive oxygen species (ROS) and reactive nitrogen species (RNS) is an early event following injury occurring within minutes of mechanical impact. A key component in this event is peroxynitrite-induced lipid peroxidation. As discussed in this review, peroxynitrite formation and lipid peroxidation irreversibly damages neuronal membrane lipids and protein function, which results in subsequent disruptions in ion homeostasis, glutamate-mediated excitotoxicity, mitochondrial respiratory failure and microvascular damage. Antioxidant approaches include the inhibition and/or scavenging of superoxide, peroxynitrite, or carbonyl compounds, the inhibition of lipid peroxidation and the targeting of the endogenous antioxidant defense system. This review covers the preclinical and clinical literature supporting the role of ROS and RNS and their derived oxygen free radicals in the secondary injury response following acute traumatic brain injury (TBI) and spinal cord injury (SCI) and reviews the past and current trends in the development of antioxidant therapeutic strategies. Combinatorial treatment with the suggested mechanistically complementary antioxidants will also be discussed as a promising neuroprotective approach in TBI and SCI therapeutic research. This article is part of a Special Issue entitled: Antioxidants and antioxidant treatment in disease.

Acrolein-mediated injury in nervous system trauma and diseases

Acrolein, an α,β-unsaturated aldehyde, is a ubiquitous pollutant that is also produced endogenously through lipid peroxidation. This compound is hundreds of times more reactive than other aldehydes such as 4-hydroxynonenal, is produced at much higher concentrations, and persists in solution for much longer than better known free radicals. It has been implicated in disease states known to involve chronic oxidative stress, particularly spinal cord injury and multiple sclerosis. Acrolein may overwhelm the anti-oxidative systems of any cell by depleting glutathione reserves, preventing glutathione regeneration, and inactivating protective enzymes. On the cellular level, acrolein exposure can cause membrane damage, mitochondrial dysfunction, and myelin disruption. Such pathologies can be exacerbated by increased concentrations or duration of exposure, and can occur in normal tissue incubated with injured spinal cord, showing that acrolein can act as a diffusive agent, spreading secondary injury. Several chemical species are capable of binding and inactivating acrolein. Hydralazine in particular can reduce acrolein concentrations and inhibit acrolein-mediated pathologies in vivo. Acrolein scavenging appears to be a novel effective treatment, which is primed for rapid translation to the clinic.

Antioxidant therapies for acute spinal cord injury

One of the most investigated molecular mechanisms involved in the secondary pathophysiology of acute spinal cord injury (SCI) is free radical-induced, iron-catalyzed lipid peroxidation (LP) and protein oxidative/nitrative damage to spinal neurons, glia, and microvascular cells. The reactive nitrogen species peroxynitrite and its highly reactive free radicals are key initiators of LP and protein nitration in the injured spinal cord, the biochemistry, and pathophysiology of which are first of all reviewed in this article. This is followed by a presentation of the antioxidant mechanistic approaches and pharmacological compounds that have been shown to have neuroprotective properties in preclinical SCI models. Two of these, which act by inhibition of LP, are high-dose treatment with the glucocorticoid steroid methylprednisolone (MP) and the nonglucocorticoid 21-aminosteroid tirilazad, have been demonstrated in the multicenter NASCIS clinical trials to produce at least a modest improvement in neurological recovery when administered within the first 8 hours after SCI. Although these results have provided considerable validation of oxidative damage as a clinically practical neuroprotective target, there is a need for the discovery of safer and more effective antioxidant compounds for acute SCI.

Temporal and spatial dynamics of peroxynitrite-induced oxidative damage after spinal cord contusion injury

The reactive nitrogen species peroxynitrite (PN) has been suggested to be an important mediator of the secondary oxidative damage that occurs following acute spinal cord injury (SCI). The PN decomposition products nitrogen dioxide (*NO(2)), hydroxyl radical (*OH), and carbonate radical (*CO(3)) are highly reactive with cellular lipids and proteins. In this immunohistochemical study, we examined the temporal (3, 24, and 72 h, and 1 and 2 weeks) and spatial relationships of PN-mediated oxidative damage in the contusion-injured rat thoracic spinal cord (IH device, 200 kdyn, T10) using 3-nitrotyrosine (3-NT), a marker for protein nitration by PN-derived *NO(2) and 4-hydroxynonenal (4-HNE), an indicator of lipid peroxidation (LP) initiated by any of the PN radicals. Minimal 3-NT or 4-HNE immunostaining was seen in sham, non-injured spinal cords. In contrast, both markers showed a substantial increase at 3 h post-injury at the epicenter, that extended throughout the gray matter and into the surrounding white matter. At 24 and 72 h, the oxidative damage expanded circumferentially to involve all but a small rim of white matter tissue at the injury site, and longitudinally as much as 6-9 mm in the rostral and caudal directions. The staining was observed in neuronal soma, axons, and microvessels. At all time points except 3 h, there was no significant difference in the mean rostral or caudal extent of 3-NT and 4-HNE staining. By 1, and more so at 2 weeks, the longitudinal extent of the oxidative damage staining was greatly decreased. The spatial and temporal overlap of 3-NT and 4-HNE staining supports the concept that PN is involved in both damage produced by lipid peroxidation and protein nitration, and that antioxidant agents that target PN or PN-derived radicals should be effective neuroprotectants for acute SCI if administered during the first post-injury hours.

Blood-spinal cord barrier permeability in experimental spinal cord injury: dynamic contrast-enhanced MRI

After a primary traumatic injury, spinal cord tissue undergoes a series of pathobiological changes, including compromised blood-spinal cord barrier (BSCB) integrity. These vascular changes occur over both time and space. In an experimental model of spinal cord injury (SCI), longitudinal dynamic contrast-enhanced MRI (DCE-MRI) studies were performed up to 56 days after SCI to quantify spatial and temporal changes in the BSCB permeability in tissue that did not show any visible enhancement on the post-contrast MRI (non-enhancing tissue). DCE-MRI data were analyzed using a two-compartment pharmacokinetic model. These studies demonstrate gradual restoration of BSCB with post-SCI time. However, on the basis of DCE-MRI, and confirmed by immunohistochemistry, the BSCB remained compromised even at 56 days after SCI. In addition, open-field locomotion was evaluated using the 21-point Basso-Beattie-Bresnahan scale. A significant correlation between decreased BSCB permeability and improved locomotor recovery was observed.

EGb761 protects hydrogen peroxide-induced death of spinal cord neurons through inhibition of intracellular ROS production and modulation of apoptotic regulating genes

The present study was conducted to investigate whether Ginkgo biloba extract (EGb) 761 could protect spinal cord neurons from H(2)O(2)-induced toxicity. In primary spinal cord neurons isolated from embryonic day 14 rats, H(2)O(2) administration resulted in a significant decrease in the survival of spinal cord neurons. Terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) and Hoechst 33342 nuclear staining showed that these cells die by apoptosis. Such neuronal death, however, was significantly reversed by EGb761 in a dose-dependent manner. Moreover, a marked increase in intracellular free radical generation was found after the H(2)O(2) administration which could be reversed almost completely by EGb761, indicating that inhibition of free radical generation is an important mechanism of the anti-apoptosis action of EGb761. Finally, treatment of cells with H(2)O(2) for 12 h reduced the expression of Bcl-2, an anti-apoptotic gene, by 70% but showed no effect on the level of Bax, a pro-apoptotic gene. EGb76 treatment, however, significantly reversed H(2)O(2)-induced reduction of Bcl-2 expression and inhibited Bax expression by 2.3-fold. Thus, our study provided evidence showing that the protective effect of EGb761 on spinal cord neuronal apoptosis after oxidative stress is mediated, at least in part, by its anti-oxidative action and regulation of apoptosis-related genes Bcl-2 and Bax.

Potentialities and pitfalls accompanying chemico-pharmacological strategies against endogenous electrophiles and carbonyl stress

The use of powerful analytical technologies to detect endogenous carbonyls formed as byproducts of oxidative cell injury has revealed that these species contribute to many human diseases. As electrophiles, they are attacked by reactive centers in cell macromolecules to form adducts, the levels of which serve as useful biomarkers of oxidative cell injury. Because the pathobiological significance of such damage is often unclear, the possibility of using low molecular weight drugs as exploratory sacrificial nucleophiles to intercept reactive carbonyls within cells and tissues is appealing. This perspective highlights the potential benefits of using carbonyl scavengers to evaluate the significance of endogenous carbonyls in particular diseases but also canvasses a number of challenges confronting this therapeutic strategy. Chief among the latter is the task of confirming that carbonyl sequestration underlies any suppression of disease symptoms elicited by these multipotent reagents, an issue needing clarification if these compounds are to command consideration as drug interventions in humans. Other problems include adverse consequences of reactions between carbonyl scavengers and important endogenous carbonyls (e.g., neurotoxicity due to pyridoxal depletion), as well as the potential for drugs to form ternary complexes with carbonylated cell proteins, raising the prospect of immunotoxicological outcomes. Strategies for moving carbonyl sequestering reagents from the laboratory bench to a clinical testing environment are discussed within the context of the search for new treatments for spinal cord injury, one of the most debilitating medical conditions sustainable by humans. This condition seems an appropriate test case for assessing carbonyl sequestering drugs given growing evidence for noxious carbonyls in the wave of neuronal cell death that follows traumatic injury to the spinal cord.

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

The metalloporphyrin Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP) is a cell-permeable superoxide dismutase mimetic and a broad-spectrum scavenger of reactive species. Since MnTBAP may not cross the blood-brain barrier, this study evaluated the therapeutic potential of MnTBAP to treat spinal cord injury (SCI; 25 g x cm) by directly administering it into the intrathecal space of the rat spinal cord. The cells in spinal sections removed at 24 h post-SCI were immunohistochemically stained with anti-4-hydroxynonenal (HNE), a marker of membrane lipid peroxidation (MLP); anti-nitrotyrosine (Ntyr), a marker of protein nitration; and anti-neuron-specific enolase (NSE) antibodies. Immunostained neurons were counted for quantitative evaluation. Pre-treatment 30 min before SCI with 1 mg/kg MnTBAP or 4-h post-SCI treatment with 2.5 mg/kg MnTBAP administered into the intrathecal space significantly reduced MLP and protein nitration, and increased the number of surviving neurons compared to vehicle controls. However, post-SCI treatment with a standard regimen of methylprednisolone sodium succinate (MPSS; 30 mg/kg followed by 5.4 mg/kg for maintenance, iv administration), the only drug used for clinical treatment of SCI, not only did not reduce MLP and neuron loss, it increased protein nitration compared with vehicle controls (two-way analysis of variance [ANOVA] followed by the Tukey test). These results demonstrate that pre- and post-intrathecal treatments with the low doses of MnTBAP provide sustained neuroprotection by preventing oxidative stress and that post-treatment with MnTBAP is superior to post-treatment with MPSS in preventing oxidative stress and resulting neuron loss.

Role of peroxynitrite in secondary oxidative damage after spinal cord injury

Peroxynitrite (PON, ONOO(-)), formed by nitric oxide synthase-generated nitric oxide radical ( NO) and superoxide radical (O(2) (-)), is a crucial player in post-traumatic oxidative damage. In the present study, we determined the spatial and temporal characteristics of PON-derived oxidative damage after a moderate contusion injury in rats. Our results showed that 3-nitrotyrosine (3-NT), a specific marker for PON, rapidly accumulated at early time points (1 and 3 h) and a significant increase compared with sham rats was sustained to 1 week after injury. Additionally, there was a coincident and maintained increase in the levels of protein oxidation-related protein carbonyl and lipid peroxidation-derived 4-hydroxynonenal (4-HNE). The peak increases of 3-NT and 4-HNE were observed at 24 h post-injury. In our immunohistochemical results, the co-localization of 3-NT and 4-HNE results indicates that PON is involved in lipid peroxidative as well as protein nitrative damage. One of the consequences of oxidative damage is an exacerbation of intracellular calcium overload, which activates the cysteine protease calpain leading to the degradation of several cellular targets including cytoskeletal protein (alpha-spectrin). Western blot analysis of alpha-spectrin breakdown products showed that the 145-kDa fragments of alpha-spectrin, which are specifically generated by calpain, were significantly increased as soon as 1 h following injury although the peak increase did not occur until 72 h post-injury. The later activation of calpain is most likely linked to PON-mediated secondary oxidative impairment of calcium homeostasis. Scavengers of PON, or its derived free radical species, may provide an improved antioxidant neuroprotective approach for the treatment of post-traumatic oxidative damage in the injured spinal cord.

Enzyme-linked immunosorbent assay for 4-hydroxynonenal-histidine conjugates

Highly reactive aldehyde 4-hydroxynonenal (HNE) is the final product of lipid peroxidation, known as a second messenger of free radicals and a signaling molecule. It forms protein conjugates involved in pathology of various diseases. To determine cellular HNE-protein conjugates we developed indirect ELISA based on well-known, monoclonal antibody against HNE-histidine (HNE-His) adducts. The method was calibrated using HNE-albumin conjugates as standards (R(2) = 0.999) and validated on human osteosarcoma cell cultures (HOS). The ELISA showed good sensitivity (8.1 pmol HNE-His/mg of protein), precision ( +/- 8% intra-assay and +/- 12% inter-assay) and spiking recovery ( +/- 9%). The assay revealed 60-fold increase of cellular HNE-His adducts upon copper-induced lipid peroxidation of HOS. The ELISA matched HNE-immunocytochemistry of HNE-treated HOS cells and quantified the increase of cellular HNE-His conjugates in parallel to the decrease of free HNE in culture medium. The ELISA was developed as ELISA Stress for severe lipid peroxidation and ELISA Fine for studies on HNE physiology.

Oxidative stress in head trauma in aging

Oxidative damage is proposed as a key mediator of exacerbated morphological responses and deficits in behavioral recovery in aged subjects with traumatic brain injury (TBI). In the present study, we show exacerbated loss of tissue in middle aged (12 months) and aged (22 months) Fisher-344 rats compared to young animals (3 months) subjected to moderate TBI. Analysis of 4-hydroxynonenal (4-HNE) and acrolein, neurotoxic by-products of lipid peroxidation, shows significant (P < 0.05) age-dependent increases in ipsilateral (IP) hippocampus 1 and 7 days post injury. In IP cortex, 4-HNE was significantly elevated 1 day post injury in all age groups, and both 4-HNE and acrolein were elevated in middle aged and aged animals 7 days post injury. Comparison of antioxidant enzyme activities shows significant (P < 0.05) age-dependent decreases of manganese superoxide dismutase in IP hippocampus and cortex 1 and 7 days post injury. Glutathione reductase activity also showed an age-dependent decrease. Overall, our data show increased levels of oxidative damage, diminished antioxidant capacities, and increased tissue loss in TBI in aging.

Acrolein-induced cell death in PC12 cells: role of mitochondria-mediated oxidative stress

Oxidative stress has been implicated in acrolein cytotoxicity in various cell types, including mammalian spinal cord tissue. In this study we report that acrolein also decreases PC12 cell viability in a reactive oxygen species (ROS)-dependent manner. Specifically, acrolein-induced cell death, mainly necrosis, is accompanied by the accumulation of cellular ROS. Elevating ROS scavengers can alleviate acrolein-induced cell death. Furthermore, we show that exposure to acrolein leads to mitochondrial dysfunction, denoted by the loss of mitochondrial transmembrane potential, reduction of cellular oxygen consumption, and decrease of ATP level. This raises the possibility that the cellular accumulation of ROS could result from the increased production of ROS in the mitochondria of PC12 cells as a result of exposure to acrolein. The acrolein-induced significant decrease of ATP production in mitochondria may also explain why necrosis, not apoptosis, is the dominant type of cell death. In conclusion, our data suggest that one possible mechanism of acrolein-induced cell death could be through mitochondria as its initial target. The subsequent increase of ROS then inflicts cell death and further worsens mitochondria function. Such mechanism may play an important role in CNS trauma and neurodegenerative diseases.

Distinct roles of oxidative stress and antioxidants in the nucleus dorsalis and red nucleus following spinal cord hemisection

Oxidative stress plays an important role in the pathogenesis of neurodegeneration after the acute central nervous system injury. We reported previously that increased nitric oxide (NO) production following spinal cord hemisection tends to lead to neurodegeneration in neurons of the nucleus dorsalis (ND) that normally lacks expression of neuronal NO synthase (nNOS) in opposition to those in the red nucleus (RN) that constitutively expresses nNOS. We wondered whether oxidative stress could be a mechanism underlying this NO involved neurodegeneration. In the present study, we examined oxidative damage evaluated by the presence of 4-hydroxynonenal (HNE) and iron accumulation and expression of putative antioxidant enzymes heme oxygenase-1 (HO-1) and superoxide dismutase (SOD) in neurons of the ND and RN after spinal cord hemisection. We found that HNE expression was induced in neurons of the ipsilateral ND from 1 to 14 days following spinal cord hemisection. Concomitantly, iron staining was seen from 7 to 14 days after lesion. HO-1, however, was only transiently induced in ipsilateral ND neurons between 3 and 7 days after lesion. In contrast to the ND neurons, HNE was undetectable and iron level was unaltered in the RN neurons after spinal cord hemisection. HO-1, SOD-Cu/Zn and SOD-Mn were constitutively expressed in RN neurons, and lesion to the spinal cord did not change their expression. These results suggest that oxidative stress is involved in the degeneration of the lesioned ND neurons; whereas constitutive antioxidant enzymes may protect the RN neurons from oxidative damage.

Accumulation of Acrolein–Protein Adducts after Traumatic Spinal Cord Injury

Reactive oxygen species and resultant lipid peroxidation (LPO) have been associated with central nervous system trauma. Acrolein (2-propenal) and 4-hydroxynonenal (HNE) are the most toxic byproducts of LPO, with detrimental effects in various types of cells. In this study, we used immunoblotting techniques to detect the accumulation of protein-bound acrolein and HNE. We report that protein-bound acrolein and HNE were significantly increased in guinea pig spinal cord following a controlled compression injury. The acrolein and HNE protein-adducts increased in the damaged spinal cord as early as 4 h after injury, reached a peak at 24 h after injury, and remained at a significantly high level up to 7 days after injury. Such increase of protein adducts was also observed in the adjacent segments of the injury site beginning at 24 h post injury. These results suggest that products of lipid peroxidation, especially acrolein, may play a critical role in the secondary neuronal degeneration, which follows mechanical insults.

Acrolein induces oxidative stress in brain mitochondria

Acrolein, a byproduct of lipid peroxidation, has been shown to inflict significant structural and functional damage to isolated guinea pig spinal cord. Reactive oxygen species (ROS) are thought to mediate such detrimental effects. The current study demonstrates that acrolein can directly stimulate mitochondrial oxidative stress. Specifically, exposure of purified brain mitochondria to acrolein resulted in a dose-dependent increase of ROS and decreases in glutathione content and aconitase activity. This effect was not accompanied by significant intramitochondrial calcium influx or mitochondrial permeability transition, but rather by impaired function of the mitochondrial electron transport system. As well, we detected a significant inhibition of mitochondrial adenine nucleotide translocase (ANT) in the presence of acrolein. This inhibition of ANT likely contributes to acrolein-induced ROS elevation since application of atractyloside, a specific ANT inhibitor, induced significant increase of ROS. We hypothesize that inhibition of ANT may mediate, in part, the acrolein-induced ROS increase in mitochondria.

Nicotine Attenuates Morphological Deficits in a Contusion Model of Spinal Cord Injury

Protection against the progression of secondary injury appears to be an effective therapeutic strategy in spinal cord injury (SCI). Evidence indicates that nicotine can induce potent neuroprotective effects against injury to spinal cord neurons. Therefore, the present study was focused on the effects of nicotine on the behavioral and morphological recovery associated with SCI. Adult male Long-Evans rats were subjected to a moderate contusion model of SCI and received subcutaneous injections of nicotine for 14 days at the dose of 0.35 or 7 mg/kg/day. The rats were examined using the BBB locomotor rating scale for 6 weeks. At the end of the BBB recording, spinal cords were examined for the volumetric tissue sparing of gray and white matters. All SCI rats demonstrated a loss of hindlimb function followed by a recovery phase that peaked at 2-3 weeks after the trauma. Compared to untreated SCI rats, chronic nicotine administration appeared to improve the recovery of the locomotor functions. Indeed, nicotine-treated animals scored consistently higher on the BBB scale indicating that the treatment altered animal behavior. However, when taking under consideration correction factors for multiple comparisons, these data did not reach significance at overall experimental levels of significance 0.05. Nevertheless, nicotine administration was effective in sparing tissue at injury epicenter and a lower dose of nicotine also resulted in significant sparing of white matter of the injured spinal cord. These results suggest that agonists of neuronal nicotinic receptors can be attractive candidates for SCI therapy.

Cataract formation in a strain of rats selected for high oxidative stress

The primary purpose of this study was to define the clinical and morphological features of cataractogenesis in the OXYS strain of rats that generate excess reactive oxygen species. Rats were sequentially examined from birth to the development of mature cataracts with slit lamp biomicroscopy. Morphology of selected stages of cataract development was studied using light and transmission electron microscopy (TEM), immunohistochemical localization of the lipid peroxidation product 4-hydroxynonenal (HNE) and fluorescent antibody labeling for DNA oxidation products. Lenses from age-matched normal rats were used as controls. OXYS rats developed cataracts as young as two weeks of age with progression to maturity by 1 year. Clinically, cataracts appeared initially either as nuclear or sub-capsular cortical changes and progressed to pronounced nuclear cataracts within months. TEM confirmed the light microscopic impression of region-specific alterations in both fiber cell cytoplasmic protein matrix and membrane structure. The outer adult nuclear region showed extensive cellular damage similar to osmotic cataracts, which is consistent with the postulated high uptake of glucose in the OXYS strain. The adult and outer fetal nuclear cells displayed several types of focal damage. The inner fetal and embryonic nuclear cells demonstrated textured cytoplasm, suggesting protein degradation or redistribution. Staining for HNE was increased in epithelium, cortex and nucleus compared to control lenses. Fluorescent antibody probes demonstrated increased levels of DNA oxidation products in OXYS rat lenses compared to age-matched controls. Fourier analysis of nuclear cytoplasm revealed significant components with corresponding sizes greater than 100 nm and, using a new theoretical approach, the texturing of the cytoplasm was shown to be sufficient to cause opacification of the nucleus. The OXYS rat appears to be an ideal model for oxidative stress cataractogenesis. The potential oxidative damage observed is extensive and characteristic of the developmental region. The source of oxidative damage may in part be a response to elevated levels of glucose. Because oxidative stress is thought to be a major factor in cataract formation in both diabetic and non-diabetic aging humans, this animal model may be a useful tool in assessing efficacy of antioxidant treatments that may slow or prevent cataract formation.

Polyethylene glycol improves function and reduces oxidative stress in synaptosomal preparations following spinal cord injury

Spinal cord injury (SCI) results in rapid and significant oxidative stress. We have previously demonstrated that administration of polyethylene glycol (PEG) inhibits oxidative stress using an in vitro model of SCI. In this study we tested the effects of PEG in vivo, to elucidate the mechanism of PEG-mediated neuroprotection. We show that a compression injury at T10-11 induced diffusive oxidative stress in crude synaptosomal preparations, correlated with synaptosomal dysfunction and increased intrasynaptosomal calcium. Administration of PEG immediately post-injury produced a marked decrease in synaptosomal oxidative stress and calcium, associated with an increase in synaptosomal function. Confocal microscopy using fluorescein conjugated PEG revealed that PEG entered the cells of the injured spinal cord, placing the polymer in a position to directly interact with cellular organelles. PEG attenuates calcium-induced functional compromise of normal spinal cord synaptosomes and mitochondria in vitro. These results indicate that PEG may exert its neuroprotective effect through direct interaction with mitochondria, besides its known ability to rescue neurons and their axons by repairing the plasma membranes. We submit that PEG is likely to interfere with the cascade of secondary injury by several mechanisms of action that in concert reduce oxidative stress.

Acrolein induces axolemmal disruption, oxidative stress, and mitochondrial impairment in spinal cord tissue

Acrolein, a byproduct of oxidative stress and lipid peroxidation, has been implicated in neurodegenerative disorders such as Alzheimer's disease, but not in spinal cord trauma, as a possible key factor in neuronal degeneration. Using an isolated guinea pig spinal cord model, we have found that acrolein, in a dose- and time-dependent manner, inflicts severe membrane disruption, a factor thought to be critical in triggering axonal deterioration and cell death. The concentration threshold of such detrimental effect is shown to be around 1 microM when acrolein was exposed for 4 h. The membrane damage is likely mediated in part by reactive oxygen species and lipid peroxidation, which were elevated in response to acrolein exposure. Antioxidants were able to significantly reduce acrolein-mediated membrane disruption which further supports the role of reactive oxygen species in the loss of membrane integrity. Mitochondrial function was also impaired after acrolein exposure which not only implicates but emphasizes the role of this organelle in reactive oxygen species generation. In summary, our data strongly suggest that at a clinically relevant concentration, acrolein can severely compromise membrane integrity and may further serve as an initiating toxin triggering secondary injury cascades following the initial physical insult to the spinal cord.

Nicotine attenuates oxidative stress, activation of redox-regulated transcription factors and induction of proinflammatory genes in compressive spinal cord trauma

Pathophysiology of neurodegeneration following spinal cord injury (SCI) involves alterations of cellular redox status, activation of transcription factors and induction of proinflammatory genes. In addition, recent evidence indicates that nicotine can induce potent neuroprotective effects. To study the influence of nicotine on the redox signaling pathways in relationship to SCI, moderate contusions of spinal cords at the level of T-10 were induced in rats treated or untreated with nicotine. Cellular oxidative stress, DNA binding activity of redox-responsive transcription factors (AP-1, NF-kappaB and CREB) as well as mRNA levels of inflammatory genes (MCP-1 and TNF-alpha) were determined in the thoracic and lumbar regions of the spinal cords. Nicotine was administrated 2 h after the SCI in a single i.p. injection at the dose of 0.35, 3.5 or 7 mg/kg, and rats were sacrificed 3 h following such an injection. Spinal cord trauma was associated with a significant increase in oxidative stress, and activation of NF-kappaB, AP-1 and CREB, as well as overexpression of MCP-1 and TNF-alpha in both the thoracic and lumbar regions. Nicotine administration following the SCI markedly attenuated, especially in the lumbar region, these oxidative and proinflammatory responses. These protective effects of nicotine were fully reversed by inhibition of neuronal nicotinic receptors by mecamylamine. The present results indicate that nicotine administration can attenuate the oxidative injury to spinal cords and suggest that neuronal nicotinic receptors can be attractive targets for neuroprotective therapy.

Diffusive oxidative stress following acute spinal cord injury in guinea pigs and its inhibition by polyethylene glycol

Spinal cord injury (SCI) results in rapid and significant oxidative stress. We have previously demonstrated that polyethylene glycol (PEG) repairs neuronal membrane and inhibits lipid peroxidation in an in vitro model of SCI. In this study we tested the effects of PEG on oxidative stress in guinea pigs after SCI. Oxidative stress was assessed by lipid peroxidation, protein carbonyl and glutathione content. A compression injury of spinal cord at T10-11 induced a rapid and diffusive oxidative stress. Administration of PEG immediately after injury resulted in a marked decrease in oxidative stress both at the injury site and in its adjacent segments. These results, along with our previous findings, suggest that an early application of PEG can effectively suppress oxidative stress after SCI in vivo.

Post-traumatic moderate systemic hypothermia reduces TUNEL positive cells following spinal cord injury in rat

STUDY DESIGN

A standardized animal model of contusive spinal cord injury (SCI) with incomplete paraplegia was used to test the hypothesis that moderate systemic hypothermia reduces neural cell death. Terminal deoxynucleotidyl transferase [TdT]-mediated deoxyuridine triphosphate [dUTP] nick-end labeling (TUNEL) staining was used as a marker of apoptosis or cell damage.

OBJECTIVE

To determine whether or not moderate hypothermia could have a neuroprotective effect in neural cell death following spinal cord injury in rats.

SETTING

Kagawa Medical University, Japan.

METHODS

Male Sprague-Dawley (SD) rats (n=39) weighing on average 300 g (280-320 g) were used to prepare SCI models. After receiving contusive injury at T11/12, rats were killed at 24 h, 72 h, or 7 days after injury. The spinal cord was removed en bloc and of examined at five segments: 5 and 10 mm rostral to the center of injury, center of injury, and 5 and 10 mm caudal to the center of injury. Rats that received hypothermia (32 degrees C/4 h) were killed at the same time points as those that received normothermia (37 degrees C/3 h). The specimens were stained with hematoxylin and eosin, and subjected to in situ nick-end labeling (TUNEL), a specific method for visualizing cell death in the spinal cord.

RESULTS

At 24 h postinjury, TUNEL positive cells (TPC) decreased significantly 10 mm rostral to center of injury in hypothermic animals compared to the normothermia group. At 72 h post-SCI, TPC also decreased significantly at 5 mm rostral, and 5 and 10 mm caudal to the lesion center compared to normothermic animals. At 7 days postinjury, a significant decrease of TPC was observed at the 5 mm rostral and 5 mm caudal sites compared to normothermic animals.

CONCLUSION

These results indicate that systemic hypothermia has a neuroprotective effect following SCI by attenuating post-traumatic TPC.

Ischemic insult exacerbates acrolein-induced conduction loss and axonal membrane disruption in guinea pig spinal cord white matter

Cellular destruction following ischemic insult may be due to secondary injury mechanisms, not the oxygen-glucose deprivation itself. We have examined the effect of acrolein, an aldehyde product of lipid peroxidation (LPO) and oxidative stress, on the axons in isolated guinea pig spinal cord white matter following ischemic insult. We have found that acrolein at 50 microM, which is unharmful to spinal cord when applied alone, causes action potential conduction failure and membrane disruption following 1 to 2 h of exposure when applied during the reperfusion period. Ischemic insult also exacerbates the effect of acrolein at 200 microM, which does inflict functional and anatomical damage when applied alone. Unlike metabolic poisoning, acrolein-mediated damage is not a function of axonal size and does not affect the refractoriness in response to dual and multiple stimuli. These results indicate that spinal cord axons, in addition to experiencing elevated free radicals, are more vulnerable to acrolein attack when the level of oxygen and glucose is low. We conclude that free radicals and lipid peroxidation in general, and acrolein in specific, may play a critical role in cellular destruction and functional loss in such injury.

4-hydroxynonenal as a bioactive marker of pathophysiological processes

The review is focused on the currently major aspect of 4-hydroxynonenal (HNE) research--studies that combine biological activities of the aldehyde together with the methods of its identification in cells and tissues. Because there were some excellent reviews on HNE published in recent years, starting in 1990 and 1991 with supreme reviews done by Hermann Esterbauer, who discovered the aldehyde, and colleagues from the Institute of Biochemistry in Graz, this article pays most of attention to the most recent articles, published in the last 15 months. Additionally, an overview on the relevance of HNE is given with respect to the research and publication trends in the period of 10 years (1993-2002) according to the data in the Current Contents and Medline data bases. It is obvious that HNE started in 1993 as a "toxic product of lipid peroxidation" and "second toxic messenger of free radicals", to become in 2002 a reliable marker of oxidative stress, a possible causative agent of several diseases (such as Alzheimer's disease), growth modulating factor and a signaling molecule. Novel analytical methods developed suitable pathways for HNE to become a clinically applicable marker of lipid peroxidation on one side and on the other a standardized parameter of food quality control. As it is also present physiologically in various cells and tissues, it is likely that HNE will soon become one of the most attractive factors for those who search for a small and reactive molecular link between genomics and proteomics.

Acrolein inflicts axonal membrane disruption and conduction loss in isolated guinea-pig spinal cord

We have examined the effect of acrolein, an aldehyde product of lipid peroxidation, on axons in isolated guinea-pig spinal cord white matter. We found that 200 microM acrolein, but not 50 microM, induced a time-dependent loss of compound action potential conduction. Such conduction loss was irreversible within 1 h after acrolein perfusion. Parallel anatomical assessment indicates membrane integrity breakdown based on a horseradish peroxidase-exclusion assay. This is the first report to suggest that acrolein inflicts severe axonal damage. Since axonal damage within white matter plays a key role in the pathology of traumatic spinal cord injury, we suggest that acrolein may be a critical factor in mediating secondary functional loss.

Spinal cord contusion models

Most human spinal cord injuries involve contusions of the spinal cord. Many investigators have long used weight-drop contusion animal models to study the pathophysiology and genetic responses of spinal cord injury. All spinal cord injury therapies tested to date in clinical trial were validated in such models. In recent years, the trend has been towards use of rats for spinal cord injury studies. The MASCIS Impactor is a well-standardized rat spinal cord contusion model that produces very consistent graded spinal cord damage that linearly predicts 24-h lesion volumes, 6-week white matter sparing, and locomotor recovery in rats. All aspects of the model, including anesthesia for male and female rats, age rather than body weight criteria, and arterial blood gases were empirically selected to enhance the consistency of injury.

Effect of glutathione augmentation on lipid peroxidation after spinal cord injury

Lipid peroxidation (LPO) is considered a major factor in damage spread after spinal cord injury (SCI). Therapies that limit LPO after SCI have demonstrated some utility in clinical trials, but more effective treatments are needed. In the present study the effects of augmenting SC levels of the endogenous antioxidant glutathione (GSH) on LPO after SCI were studied in a rat contusion injury model. A significant decrease in GSH occurred 1h after SCI which was paralleled by increases of 123% in malondialdehyde (MDA) and >500% in the 4-hydroxyalkenals (4-HA's), two LPO products. SC irrigation with gamma-glutamylcysteine (GC) preserved GSH and reduced 4-HA's below naive levels but had no effect on MDA. By 24 h after SCI, MDA returned to naive levels but 4-HA's were still elevated. Once again, GC treatment reduced 4-HA's. 4-HA's are much more reactive than MDA and are considered among the most toxic LPO products. These results suggest that (1) conditions after SCI may favor particular branches of the LPO pathway leading to differential LPO product levels, (2) MDA measurement is not by itself an adequate test for the presence or magnitude of LPO after SCI, (3) binding of GSH to 4-HA's may be an important mechanism by which the GSH system confers protection against LPO after SCI, and (4) SC GSH can be augmented after trauma by local irrigation with GC. These results also suggest that GSH augmentation may be an effective strategy for curtailment of LPO-mediated damage in acute phase SCI.

Cyclosporin A treatment following spinal cord injury to the rat: behavioral effects and stereological assessment of tissue sparing

The immunosuppressant drug cyclosporin A (CsA) has significant neuroprotective properties following CNS injury. In the present study, we assessed the efficacy of CsA therapy following a moderate spinal cord injury (SCI). Adult female rats were injured with the NYU impactor from a height of 12.5 mm, and CsA or vehicle therapy was initiated 15 min after the injury. All animals were behaviorally tested with the BBB locomotor rating scale prior to morphological assessment of changes in the spinal cord. CsA therapy failed to significantly improve the behavioral recovery following the injury. Using a unique stereological approach to assess tissue damage, it was determined that CsA did not alter the amount of spared tissue. The possible neuroprotective effects of CsA, observed in other models of CNS injury, do not appear to influence SCI pathology, perhaps reflecting both anatomical and physiological differences between these distinct regions of the CNS.

Contrasting antioxidant and cytotoxic effects of peroxiredoxin I and II in PC12 and NIH3T3 cells

We examined the impact of peroxiredoxin-I (Prx-I) and peroxiredoxin-II (Prx-II) stable transduction on oxidative stress in PC12 neurons and NIH3T3 fibroblasts and found variability depending on cell type and Prx subtype. In PC12 neurons, Prx-II suppressed reactive oxygen species (ROS) generation by 36% (p < 0.01) relative to vector-infected control cells. However, in NIH3T3 fibroblasts, Prx-II overexpression resulted in a 97% (p < 0.01) increase in ROS generation. Prx-I transduction elevated ROS generation in PC12 cells. The effect of Prx-I on PC12 cells was potentiated in the presence of menadione, and suppressed by an inhibitor of nitric oxide synthetase. Prx-II transduction resulted in 25-35% lower levels of glutathione (GSH) in both cell types, while Prx-I transduction increased GSH levels in neurons and decreased GSH and caspase-3 activity in fibroblasts. Prx-I and Prx-II also had differing effects on cell viability. These results suggest that Prx-I and Prx-II can either increase or decrease intracellular oxidative stress depending on cell type or experimental conditions, particularly conditions affecting nitric oxide levels.

Basic fibroblast growth factor (bFGF) enhances functional recovery following severe spinal cord injury to the rat

We have recently demonstrated that following a moderate contusion spinal cord injury (SCI) to rats, subsequent administration of basic fibroblast growth factor (bFGF) significantly enhances functional recovery and tissue sparing. To further characterize the effects of bFGF, we evaluated its efficacy after a more severe contusion injury at T(10) using the NYU impactor. Immediately after SCI, osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at 3 or 6 microg per day versus control vehicle for 1 week. Animals were behaviorally tested for 6 weeks before histological assessment of tissue sparing through the injured segment and glial reactivity distal to the lesion. Compared to moderate SCI, all rats had more prolonged and sustained functional deficits 6 weeks after severe contusion. Subjects treated with bFGF had pronounced recovery of hindlimb movements from 2 to 6 weeks compared to controls, manifested in significantly higher behavioral scores. Only marginal tissue sparing was seen rostral to the injury in bFGF-treated spinal cords versus controls. Optical density measurements of astrocyte and microglial cell immunoreactivity in bFGF-treated spinal cords showed that after 6 weeks they approximated controls, although astrocyte immunoreactivity remained higher in controls rostrally. In summary, intrathecal infusion of bFGF following severe SCI significantly restores gross hindlimb motor function that is not correlated with significant tissue sparing. In light of previous evidence that pharmacological intervention with bFGF after moderate SCI enhances tissue preservation, the current findings indicate that yet undefined mechanisms contribute to the enhanced functional recovery following bFGF treatment.

4-Hydroxynonenal induces oxidative stress and death of cultured spinal cord neurons

Primary spinal cord trauma can trigger a cascade of secondary processes leading to delayed and amplified injury to spinal cord neurons. Release of fatty acids, in particular arachidonic acid, from cell membranes is believed to contribute significantly to these events. Mechanisms of fatty acid-induced injury to spinal cord neurons may include lipid peroxidation. One of the major biologically active products of arachidonic acid peroxidation is 4-hydroxynonenal (HNE). The levels of HNE-protein conjugates in cultured spinal cord neurons increased in a dose-dependent manner after a 24-h exposure to arachidonic acid. To study cellular effects of HNE, spinal cord neurons were treated with different doses of HNE, and cellular oxidative stress, intracellular calcium, and cell viability were determined. A 3-h exposure to 10 microM HNE caused approximately 80% increase in oxidative stress and 30% elevation of intracellular calcium. Exposure of spinal cord neurons to HNE caused a dramatic loss of cellular viability, indicated by a dose-dependent decrease in MTS [3-(4, 5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-s ulfophenyl)- 2H-tetrazolium, inner salt] conversion. The cytotoxic effect of HNE was diminished by pretreating neurons with ebselen or N-acetylcysteine. These data support the hypothesis that formation of HNE may be responsible, at least in part, for the cytotoxic effects of membrane-released arachidonic acid to spinal cord neurons.

Distribution of hydroxynonenal-modified proteins in the kainate-lesioned rat hippocampus: evidence that hydroxynonenal formation precedes neuronal cell death

Decomposition of lipid peroxides gives rise to a wide range of aldehydes. 4-Hydroxyalkenals and in particular 4-hydroxynonenal (HNE) are often the most toxic products. Frequently, it is unclear at which stage in the tissue injury process HNE is formed, i.e., is it a late stage or an early stage in which HNE contributes to subsequent cell death? The present study was carried out using an antibody to HNE-modified proteins to elucidate the time course and distribution of HNE in the lesioned hippocampus after kainate injections. HNE was absent from normal neurons, but dense staining to HNE was observed in degenerating neurons after kainate injection. The increase in HNE staining occurred as early as 1 d postinjection, at a time when there was no histological evidence of cell death. HNE immunoreactivity was observed in the degenerating CA1 and CA3 fields at 3 d and 1 week postinjection, but was confined to a cluster of neurons at the edge of the degenerating CA fields, at 2 and 3 weeks postinjection. These observations suggest that HNE formation is an early event after this tissue injury, and may contribute to later cell death.

Propofol hemisuccinate protects neuronal cells from oxidative injury

Oxidative stress contributes to the neuronal death observed in neurodegenerative disorders and neurotrauma. Some antioxidants for CNS injuries, however, have yet to show mitigating effects in clinical trials, possibly due to the impermeability of antioxidants across the blood-brain barrier (BBB). Propofol (2,6-diisopropylphenol), the active ingredient of a commonly used anesthetic, acts as an antioxidant, but it is insoluble in water. Therefore, we synthesized its water-soluble prodrug, propofol hemisuccinate sodium salt (PHS), and tested for its protective efficacy in neuronal death caused by non-receptor-mediated, oxidative glutamate toxicity. Glutamate induces apoptotic death in rat cortical neurons and the mouse hippocampal cell line HT-22 by blocking cystine uptake and causing the depletion of intracellular glutathione, resulting in the accumulation of reactive oxygen species (ROS). PHS has minimal toxicity and protects both cortical neurons and HT-22 cells from glutamate. The mechanism of protection is attributable to the antioxidative property of PHS because PHS decreases the ROS accumulation caused by glutamate. Furthermore, PHS protects HT-22 cells from oxidative injury induced by homocysteic acid, buthionine sulfoximine, and hydrogen peroxide. For comparison, we also tested alpha-tocopherol succinate (TS) and methylprednisolone succinate (MPS) in the glutamate assay. Although TS is protective against glutamate at lower concentrations than PHS, TS is toxic to HT-22 cells. In contrast, MPS is nontoxic but also nonprotective against glutamate. Taken together, PHS, a water-soluble prodrug of propofol, is a candidate drug to treat CNS injuries owing to its antioxidative properties, low toxicity, and permeability across the BBB.

Basic fibroblast growth factor (bFGF) enhances tissue sparing and functional recovery following moderate spinal cord injury

The rapid increase in basic fibroblast growth factor (bFGF) production following spinal cord injury (SCI) in rats is thought to serve a role in the cellular processes responsible for the functional recovery often observed. In this study, bFGF was intrathecally administered continuously for 1 week beginning 30 min after a moderate (12.5 mm) spinal cord contusion in adult rats using the New York University impactor device. Osmotic minipumps were implanted into the lateral ventricle and lumbar thecal sac to deliver bFGF at a rate of 3 microg or 6 microg per day versus control vehicle. Animals were behaviorally tested for 6 weeks using the Basso, Beattie, Bresnahan locomotor rating scale and histologically assessed for both tissue sparing and glial reactivity rostral and caudal to the lesion. Rats treated with bFGF regained coordinated hindlimb movements earlier than controls and demonstrated consistent coordination from 4 to 6 weeks. Vehicle-treated rats showed only modest improvements in hindlimb function. The amount of spared tissue was significantly higher in bFGF-treated rats than in controls. Astrocyte and microglial reactivity was more pronounced in bFGF-treated animals versus controls. In summary, intrathecal infusion of exogenous bFGF following SCI significantly reduces tissue damage and enhances functional recovery. Early pharmacological intervention with bFGF following SCI may serve a neuroprotective role and/or create a proregenerative environment, possibly by modulating the neuroglial response.

Alterations in temporal/spatial distribution of GFAP- and vimentin-positive astrocytes after spinal cord contusion with the New York University spinal cord injury device

Astrocytes become reactive as a result of various types of lesions and upregulate 2 intermediate filaments, glial fibrillary acidic protein (GFAP), and the developmentally regulated protein vimentin. Young female Sprague-Dawley rats were subjected to a spinal cord contusion at segment T10 using the New York University injury device. Animals were killed at 1, 2, 7, 14, and 30 days postinjury. Horizontal spinal cord sections spanning segments T7-T13 were assessed with antibodies to both intermediate filament proteins. The number of gray matter GFAP-positive astrocytes increased by 2 days postinjury, with segments adjacent (proximal) to the injury site showing greater responses than areas several segments away (distal). By 30 days following injury, astroglial cell numbers returned to normal levels. Vimentin-positive astrocytes also showed a graded proximal/distal response by 2 days following injury. Proximal regions remained significantly higher at 30 days following injury than control animals. Rostral/caudal changes were also evident, with regions caudal to the injury showing significantly higher numbers of vimentin positive astrocytes than those rostral, indicating that gray matter areas caudal to spinal cord injury may undergo more stress following spinal cord injury.