Prostaglandin release by spinal cord injury mediates production of hydroxyl radical, malondialdehyde and cell death: a site of the neuroprotective action of methylprednisolone

Prognostic Value of Malondialdehyde (MDA) in the Temporal Progression of Chronic Spinal Cord Injury

Background: Oxidative stress is a major signature of spinal cord injury (SCI). The altered levels of various oxidative stress markers have been demonstrated in acute and chronic SCI. However, the variation of these markers in patients with chronic SCI depending on the time since the initial injury has not been explored yet. Objective: Our aim was to measure plasma levels of malondialdehyde (MDA), a marker of lipid peroxidation in patients with SCI stratified in different periods of suffering the injury (0–5 years, 5–10 years, and more than 10 years). Patients and methods: This cross-sectional study enrolled patients with SCI (N = 105) from different periods of the lesion and healthy control (HC) subjects (N = 38): short period (SCI SP, N = 31, time of evolution less than 5 years); early chronic (SCI ECP, N = 32, time of evolution 5–15 years); and late chronic (SCI LCP, N = 42, time of evolution more than 15 years). The plasma levels of MDA were measured using a commercially available colorimetric assay. Results: Patients with SCI had significantly higher plasma levels of MDA than HC subjects. Receiver operating characteristic (ROC) curve analysis for plasma MDA levels in patients with SCI demonstrated areas under the curve (AUC) of 1 (HC vs. SCI-SP); 0.998 (HC vs. SCI-ECP); and 0.964 (HC vs. SCI-LCP). Additionally, three ROC curves were used to compare the different concentrations of MDA between the subgroups of patients with SCI, and the resulting AUCs were: 0.896 (SCI-SP vs. SCI-ECP); 0.840 (SCI-ECP vs. SCI-LCP); and 0.979 (SCI-SP vs. SCI-LCP). Conclusion: Plasma concentration of MDA can be considered as an oxidative stress biomarker to assess the prognosis of SCI in chronic stages.

Early Targeting of L-Selectin on Leukocytes Promotes Recovery after Spinal Cord Injury, Implicating Novel Mechanisms of Pathogenesis

L-selectin, a lectin-like receptor on all leukocyte classes, functions in adhesive and signaling roles in the recruitment of myeloid cells from the blood to sites of inflammation. Here, we consider L-selectin as a determinant of neurological recovery in a murine model of spinal cord injury (SCI). Spinal cord-injured, L-selectin knock-out (KO) mice (male) showed improved long-term recovery with greater white matter sparing relative to wild-type (WT) mice and reduced oxidative stress in the injured cord at 72 h post-SCI. There was a partial and transient reduction in accumulation of neutrophils in the injured spinal cords of KOs at 24 h post-injury. To complement these findings with KO mice, we sought a pharmacologic means for lowering L-selectin levels. We found that diclofenac, a nonsteroidal anti-inflammatory drug (NSAID), induced the shedding of L-selectin from the cell surface of myeloid subsets, specifically neutrophils and non-classical monocytes, in the blood and the injured spinal cord. Diclofenac administration to injured WT mice enhanced neurological recovery to a level comparable to that of KOs but did not improve recovery in KOs. While diclofenac treatment had no effect on myeloid cell accumulation, there was a reduction in oxidative stress at 72 h post-SCI. These findings implicate L-selectin in secondary pathogenesis beyond a role in leukocyte recruitment and raise the possibility of repurposing diclofenac for the treatment of SCI.

Phospholipase A₂-Generated Lipid Mediators in the Brain: The Good, the Bad, and the Ugly

Phospholipase A2 (PLA2) generates arachidonic acid, docosahexaenoic acid, and lysophospholipids from neural membrane phospholipids. These metabolites have a variety of physiological effects by themselves and also are substrates for the synthesis of more potent lipid mediators such as eicosanoids, platelet activating factor, and 4-hydroxynonenal (4-HNE). At low concentrations, these mediators act as second messengers. They affect and modulate several cell functions, including signal transduction, gene expression, and cell proliferation, but at high concentrations, these lipid mediators cause neurotoxicity. Among the metabolites generated by PLA2, 4-HNE is the most cytotoxic metabolite and is associated with the apoptotic type of neural cell death. Levels of 4-HNE are markedly increased in neurological disorders such as Alzheimer disease, Parkinson disease, ischemia, spinal cord trauma, and head injury. The purpose of this review is to summarize and integrate the vast literature on metabolites generated by PLA2 for a wider audience. The authors hope that this discussion will jump-start more studies not only on the involvement of PLA2 in neurological disorders but also on the importance of PLA2-generated lipid mediators in physiological and pathological processes.

Neuroprotective effect of hydrogen sulfide on acute cauda equina injury in rats

BACKGROUND

Hydrogen sulfide (H2S), as a novel gaseous messenger molecule, plays an important role in signal transduction and biological modulation.

PURPOSE

In the present study the effect of H2S after compression injury of cauda equina was studied.

STUDY DESIGN

The setting of this study is the laboratory investigation.

METHODS

A total of 162 rats were randomly allocated into three groups: sham group, compression group, and H2S group. Cauda equina compression (CEC) injury in rats was induced by implanting silicone gels (10×1×1 mm) into the epidural spaces L5 and L6; laminectomy was performed at the L4 level of the vertebra in the sham-operated group. The experimental group was treated with sodium hydrosulfide intraperitoneally (20 µmol/kg body weight), whereas the compression and sham groups received equal volumes of physiological saline. Levels of malonaldehyde (MDA) and glutathione (GSH) were determined immediately before CEC surgery, 12 h, 24 h, 48 h, and 72 h after CEC surgery. Furthermore, hematoxylin and eosin (H&E) staining and terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick-end labeling (TUNEL) assay were performed 48 h after CEC.

RESULTS

Hematoxylin and eosin staining showed that myelin sheath and the cauda equina fibers in the compression group were less compact and highly degenerated compared with the sham group, and that H2S treatment could improve the status. Terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick-end labeling staining exhibited that decreased number of TUNEL positive cells was found in the H2S group than in the compression group. The level of MDA was increased in the sham and H2S groups compared with the compression group (p<.05, p<.01), whereas the level of GSH was decreased (p<.05, p<.01).

CONCLUSIONS

With the above data, we conclude that H2S could reduce the oxidative stress and has neuroprotective effect in acute cauda equina syndrome.

A functional progesterone receptor is required for immunomodulation, reduction of reactive gliosis and survival of oligodendrocyte precursors in the injured spinal cord

The anti-inflammatory effects of progesterone have been increasingly recognized in several neuropathological models, including spinal cord inflammation. In the present investigation, we explored the regulation of proinflammatory factors and enzymes by progesterone at several time points after spinal cord injury (SCI) in male rats. We also demonstrated the role of the progesterone receptor (PR) in inhibiting inflammation and reactive gliosis, and in enhancing the survival of oligodendrocyte progenitors cells (OPC) in injured PR knockout (PRKO) mice receiving progesterone. First, after SCI in rats, progesterone greatly attenuated the injury-induced hyperexpression of the mRNAs of interleukin 1β (IL1β), IL6, tumor necrosis factor alpha (TNFα), inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX-2), all involved in oligodendrocyte damage. Second, the role of the PR was investigated in PRKO mice after SCI, in which progesterone failed to reduce the high expression of IL1β, IL6, TNFα and IκB-α mRNAs, the latter being considered an index of reduced NF-κB transactivation. These effects occurred in a time framework coincident with a reduction in the astrocyte and microglial responses. In contrast to wild-type mice, progesterone did not increase the density of OPC and did not prevent apoptotic death of these cells in PRKO mice. Our results support a role of PR in: (a) the anti-inflammatory effects of progesterone; (b) the modulation of astrocyte and microglial responses and (c) the prevention of OPC apoptosis, a mechanism that would enhance the commitment of progenitors to the remyelination pathway in the injured spinal cord.

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.

Targeting endothelin receptors A and B attenuates the inflammatory response and improves locomotor function following spinal cord injury in mice

After spinal cord injury (SCI), the disruption of blood-spinal cord barrier by activation of the endothelin (ET) system is a critical event leading to leukocyte infiltration, inflammatory response and oxidative stress, contributing to neurological disability. In the present study, we showed that blockade of ET receptor A (ETAR) and/or ET receptor B (ETBR) prevented early inflammatory responses directly via the inhibition of neutrophil and monocyte diapedesis and inflammatory mediator production following traumatic SCI in mice. Long-term neurological improvement, based on a series of tests of locomotor performance, occurred only in the spinal cord‑injured mice following blockade of ETAR and ETBR. We also examined the post‑traumatic changes of the micro-environment within the injured spinal cord of mice following blockade of ET receptors. Oxidative stress reflects an imbalance between malondialdehyde and superoxide dismutase in spinal cord‑injured mice treated with vehicle, whereas blockade of ETAR and ETBR reversed the oxidation state imbalance. In addition, hemeoxygenase-1, a protective protease involved in early SCI, was increased in spinal cord‑injured mice following the blockade of ETAR and ETBR, or only ETBR. Matrix metalloproteinase-9, a tissue-destructive protease involved in early damage, was decreased in the injured spinal cord of mice following blockade of ETAR, ETBR or a combination thereof. The findings of the present study therefore suggested an association between ETAR and ETBR in regulating early pathogenesis of SCI and determining the outcomes of long‑term neurological recovery.

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.

Prevention of both neutrophil and monocyte recruitment promotes recovery after spinal cord injury

Strategies that block infiltration of leukocytes into the injured spinal cord improve sparing of white matter and neurological recovery. In this article, we examine the dependency of recovery on hematogenous depletion of neutrophils and monocytes. Mice were depleted of neutrophils or monocytes by systemic administration of anti-Ly6G or clodronate-liposomes. A third group was depleted of both subsets. Neurological improvement, based on a battery of tests of performance, and white matter sparing, occurred only in animals depleted of both neutrophils and monocytes. We also attempted to define the nature of the environment that was favorable to recovery. Hemeoxygenase-1 and malondialdehyde, markers of oxidative stress and lipid peroxidation, respectively, were reduced to similar levels in animals depleted of both neutrophils and monocytes, or only monocytes, but remained elevated in the group only depleted of neutrophils. Matrix metalloproteinase-9, a protease involved in early damage, was most strongly reduced in animals depleted of both leukocyte subsets. Finally, disruption of the blood-spinal cord barrier and abnormal nonheme iron accumulation were reduced only in animals depleted of both neutrophils and monocytes. Together, these findings indicate cooperation between neutrophils and monocytes in mediating early pathogenesis in the contused spinal cord and defining long-term neurological recovery.

Early metabolic reactivation versus antioxidant therapy after a traumatic spinal cord injury in adult rats

Disability after traumatic spinal cord injury (TSCI) results from physical trauma and from "secondary mechanisms of injury" such as low metabolic energy levels, oxidative damage and lipid peroxidation. In order to prove if early metabolic reactivation is a better therapeutic option than antioxidant therapy in the acute phase of TSCI, spinal cord contusions were performed in adult rats using a well-characterized weight drop technique at thoracic 9 level. After TSCI, pyrophosphate of thiamine or non-degradable cocarboxylase (NDC) enzyme was used to maintain energy levels, antioxidants such as superoxide dismutase and catalase (ANT) were used to decrease oxidative damage and methylprednisolone (MP), which has both therapeutic properties, was used as a control. Rats were divided into one sham group and six with TSCI; one of them received no treatment, and the rest were treated with NDC, MP, NDC + MP, NDC + ANT or ANT. The ANT group decreased lactate and creatine phosphokinase levels and increased the amount of preserved tissue (morphometric analysis) as well as functional recovery (Basso, Beattie and Bresnahan or BBB motor scale). In contrast, NDC treatment increased lipid peroxidation, measured through thiobarbituric acid reactive substances (TBARS) levels, as well as spinal cord tissue destruction and functional deficit. Early metabolic reactivation after a TSCI may be deleterious, while natural early metabolic inhibition may not be a "secondary mechanism of injury" but a "secondary neuroprotective response". While increased antioxidant defence after a TSCI may currently be an ideal therapeutic strategy, the usefulness of metabolic reactivation should be tested in the sub-acute or chronic phases of TSCI and new strategies must continue to be tested for the early ones.

Colocalization of prostaglandin F(2alpha) receptor FP and prostaglandin F synthase-I in the spinal cord

Prostaglandin F(2alpha) is synthesized by prostaglandin F synthase, which exists in two types, prostaglandin F synthase I (PGFS I) and prostaglandin F synthase II (PGFS II). Prostaglandin F(2alpha) binds to its specific receptor, FP. Our previous immunohistochemical study showed the distinct localization of prostaglandin F synthases in rat spinal cord. PGFS I exists in neuronal somata and dendrites in the gray substance, and PGFS II exists in ependymal cells and tanycytes surrounding the central canal. Both enzymes are also present in endothelial cells of blood vessels in the white and gray substances of the spinal cord. In this study, we found that FP localizes in neuronal somata and dendrites but not in ependymal cells, tanycytes, or endothelial cells. Immunohistochemical analysis of serial sections showed the colocalization of FP and PGFS I. FP immunoreactivity was intense in spinal laminae I and II of the dorsal horn, a connection site of pain transmission, and was similar to that of PGFS I in neuronal elements. These findings suggest that prostaglandin F(2alpha) synthesized in the neuronal somata and dendrites exert an autocrine action there.

Duration of lipid peroxidation after acute spinal cord injury in rats and the effect of methylprednisolone

OBJECT

Oxidative stress leading to lipid peroxidation is a major cause of secondary injury following spinal cord injury (SCI). The objectives of this study were to determine the duration of lipid peroxidation following acute SCI and the efficacy of short-and long-term administration of methylprednisolone on decreasing lipid peroxidation.

METHODS

A total of 226 female Wistar rats underwent clip-compression induced SCI. In the first part of the study, spinal cords of untreated rats were assayed colorimetrically for malondialdehyde (MDA) to determine lipid peroxidation levels at various time points between 0 and 10 days. In the second part of the study, animals were treated with methylprednisolone for either 24 hours or 7 days. Control animals received equal volumes of normal saline. Treated and control rats were killed at various time points between 0 and 7 days.

RESULTS

The MDA levels initially peaked 4 hours postinjury. By 12 hours, the MDA levels returned to baseline. A second increase was observed from 24 hours to 5 days. Both peak values differed statistically from the trough values (p < 0.008). The methylprednisolone reduced MDA levels (p < 0.04) within 12 hours of injury. No effect was seen at 24 hours or later.

CONCLUSIONS

The results of this study indicate that oxidative stress persists for 5 days following SCI in rats, and although methylprednisolone reduces MDA levels within the first 12 hours, it has no effect on the second lipid peroxidation peak.

Role of secretory phospholipase a(2) in CNS inflammation: implications in traumatic spinal cord injury

Secretory phospholipases A(2) (sPLA(2)s) are a subfamily of lipolytic enzymes which hydrolyze the acyl bond at the sn-2 position of glycerophospholipids to produce free fatty acids and lysophospholipids. These products are precursors of bioactive eicosanoids and platelet-activating factor (PAF). The hydrolysis of membrane phospholipids by PLA(2) is a rate-limiting step for generation of eicosanoids and PAF. To date, more than 10 isozymes of sPLA(2) have been found in the mammalian central nervous system (CNS). Under physiological conditions, sPLA(2)s are involved in diverse cellular responses, including host defense, phospholipid digestion and metabolism. However, under pathological situations, increased sPLA(2) activity and excessive production of free fatty acids and their metabolites may lead to inflammation, loss of membrane integrity, oxidative stress, and subsequent tissue injury. Emerging evidence suggests that sPLA(2) plays a role in the secondary injury process after traumatic or ischemic injuries in the brain and spinal cord. Importantly, sPLA(2) may act as a convergence molecule that mediates multiple key mechanisms involved in the secondary injury since it can be induced by multiple toxic factors such as inflammatory cytokines, free radicals, and excitatory amino acids, and its activation and metabolites can exacerbate the secondary injury. Blocking sPLA(2) action may represent a novel and efficient strategy to block multiple injury pathways associated with the CNS secondary injury. This review outlines the current knowledge of sPLA(2) in the CNS with emphasis placed on the possible roles of sPLA(2) in mediating CNS injuries, particularly the traumatic and ischemic injuries in the brain and spinal cord.

Nuclear factor-kappaB decoy amelioration of spinal cord injury-induced inflammation and behavior outcomes

Spinal cord injury (SCI) results in a pathophysiology characterized by multiple locomotor and sensory deficits, resulting in altered nociception and hyperalgesia. SCI triggers an early and prolonged inflammatory response, with increased interleukin-1beta levels. Transient changes are observed in subunit populations of the transcription factor nuclear factor-kappaB (NF-kappaB). There were decreases in neuronal c-Rel levels and inverse increases in p65 and p50 levels. There were no changes in neuronal p52 or RelB subunits after SCI at any time point tested. Similarly, SCI had no effect on oligodendroglial levels of any NF-kappaB subunit. There were significant early increases in COX-2 and inducible nitric oxide synthase mRNA and protein levels after SCI. We used synthetic double-stranded "decoy" deoxyoligonucleotides containing selective NF-kappaB protein dimer binding consensus sequences. Decoys targeting the p65/p50 binding site on the COX-2 promoter decreased SCI-induced cell losses, NF-kappaB p65/p50 DNA-binding activity, and COX-2 and iNOS protein levels. NF-kappaB p65/p50 targeted decoys improved early locomotor recovery after moderate but not severe SCI, yet ameliorated SCI-induced hypersensitization after both moderate and severe SCI. To determine whether changes in GABA activity played a role in decreased hypersensitivity after SCI and p65/p50 targeted decoy, we counted gamma-aminobutyric acid (GABA)-containing neurons in laminae 1-3. There were significantly more GABAergic neurons in the p65/p50 targeted decoy-treated group at the level of injury.

Temporal and spatial profiles of cell loss after spinal cord injury: Reduction by a metalloporphyrin

This study presents quantitative temporal and spatial profiles of neuronal loss and apoptosis following a contusion spinal cord injury (50 g . cm). The profiles were evaluated by counting the cresol violet-stained surviving cells and the total number of TUNEL-positive cells and of TUNEL-positive neurons in sections 0- 4 mm from the epicenter and 1, 6, 12, 24, 48, and 72 hr and 1 week postinjury. We demonstrated that neurons continue to disappear over 1 week postinjury and that neuronal loss shifts to areas longer distances from the epicenter over time. TUNEL-positive cells in both gray and white matter appeared after 6 hr, gradually increased to a peak level after 48 hr, and declined by 72 hr postinjury. TUNEL-positive neurons peaked earlier and were present for 1 week, although the total number of neurons was reduced significantly by the end of the week. The neuronal loss and apoptosis were partially prevented by a metalloporphyrin [Mn(III) tetrakis (4-benzoic acid) porphyrin (MnTBAP)]. We demonstrated that MnTBAP (10 and 50 mg/kg, given intraperitoneally) significantly reduced neuronal death in the sections 1-2.5 mm rostral and 1 mm caudal from the epicenter compared with that in the vehicle-treated group, suggesting MnTBAP is more effective in the sections rostral than in those caudal to the epicenter. MnTBAP (10 mg/kg) significantly reduced the number of TUNEL-positive neurons in the sections 1 mm caudal from the epicenter. Our profiles provide a database for pharmacological intervention, and our results on MnTBAP treatment support an important role for antioxidant therapy in spinal cord injury.

Mutation of superoxide dismutase elevates reactive species: comparison of nitration and oxidation of proteins in different brain regions of transgenic mice with amyotrophic lateral sclerosis

As part of our effort to study the role of reactive species in amyotrophic lateral sclerosis (ALS), the goal of this work is to explore the correlation between nitration and oxidation of proteins and mutation of Cu, Zn-superoxide dismutase (SOD1) in ALS. Transgenic mice overexpressing the mutant Cu, Zn-superoxide dismutase (mSOD1) gene from humans with familial ALS, wild-type mice overexpressing the normal human SOD1 gene and normal mice without gene overexpression were used. Brain sections from different regions of three groups of mice were double immunohistochemically stained with anti-neurofilament plus anti-nitrotyrosine or treated with 2,4-dinitrophenylhydrazine to label protein carbonyls, then double stained with anti-neurofilament plus anti-2,4-dinitrophenyl (anti-DNP). Neurons containing nitrated and oxidized proteins were visualized only in mSOD1 mice in the motor cortex, the cerebellar cortex and nucleus of hypoglossal nerves (regions related with movement). This correlates mutation of SOD1 to nitration and oxidation of neurons in the movement regions. By counting double-stained neurons, we demonstrated that the number of nitrotyrosine- and DNP-positive neurons was significantly higher in the brain sections of both motor and sensory cortex in mSOD1 mice than in the corresponding regions of control mice (P=0.005 to <0.001), further correlating nitration and oxidation of proteins to SOD1 mutation. Neurons underwent significantly more nitration and oxidation in the motor cortex than in the sensory cortex in mSOD1 mice (P=0.002 and 0.02 respectively), indicating enhanced susceptibility of the motor cortex to nitration and oxidation of proteins and thereby targeting oxidation and nitration of proteins in neurons of the motor cortex in ALS. Significantly elevated protein nitration and nitric oxide synthesis were also demonstrated biochemically in the brain tissues and in cerebrospinal fluid of mutant SOD1 mice. Our in vivo evidence correlates mutation of the SOD1 gene to increased nitric oxide, nitration and oxidation of proteins in ALS.

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.

Microsomal prostaglandin E synthase-1 is a critical factor of stroke-reperfusion injury

Although augmented prostaglandin E(2) (PGE(2)) synthesis and accumulation have been demonstrated in the lesion sites of rodent transient focal ischemia models, the role of PGE(2) in neuronal survival has been controversial, showing both protective and toxic effects. Here we demonstrate the induction of microsomal PGE synthase 1 (mPGES-1), an inducible terminal enzyme for PGE(2) synthesis, in neurons, microglia, and endothelial cells in the cerebral cortex after transient focal ischemia. In mPGES-1 knockout (KO) mice, in which the postischemic PGE(2) production in the cortex was completely absent, the infarction, edema, apoptotic cell death, and caspase-3 activation in the cortex after ischemia were all reduced compared with those in wild-type (WT) mice. Furthermore, the behavioral neurological dysfunctions observed after ischemia in WT mice were significantly ameliorated in KO mice. The ameliorated symptoms observed in KO mice after ischemia were reversed to almost the same severity as WT mice by intracerebroventricular injection of PGE(2) into KO mice. Our observations suggest that mPGES-1 may be a critical determinant of postischemic neurological dysfunctions and a valuable therapeutic target for treatment of human stroke.

Effect of postinjury intravenous or intrathecal methylprednisolone on spinal cord excitatory amino-acid release, nitric oxide generation, PGE2 synthesis, and myeloperoxidase content in a pig model of acute spinal cord injury

STUDY DESIGN

Prospective, randomized, in vivo acute spinal cord injury in pigs.

SETTING

Department of Anesthesiology, University of Washington, Seattle, WA, USA.

OBJECTIVES

To determine whether postinjury methylprednisolone could reduce the generation of known mediators of secondary neurological injury.

METHODS

Intrathecal microdialysis probes were used to sample cerebrospinal fluid (CSF) for measurement of PGE(2), glutamate, and citrulline (a byproduct of nitric oxide generation), before and after spinal cord injury in anesthetized pigs. The spinal cord was removed at the end of the study for measurement of myeloperoxidase and methylprednisolone concentrations. Animals were randomly allocated to receive intravenous methylprednisolone (30 mg/kg bolus then 3.4 mg/kg/h), intrathecal methylprednisolone (5 mg bolus then 5 mg/h), or saline, beginning 30 min after the spinal cord was injured by using a modification of the Allen weight drop technique.

RESULTS

Spinal cord injury significantly increased the amount of glutamate, PGE(2), myeloperoxidase, and citrulline, recovered from the CSF dialysates. However, neither intravenous nor intrathecal methylprednisolone administered after injury had any effect on the magnitude of the increase in any of the measured biochemicals. Intrathecal methylprednisolone administration produced a spinal cord methylprednisolone concentration that was eight times greater, and a plasma concentration that was 32 times less, than that achieved with intravenous administration.

CONCLUSIONS

Contrary to earlier animal studies in which methylprednisolone was administered either before or immediately after spinal cord injury, we found no effect of intravenous or intrathecal methylprednisolone on any of the parameters measured when administered 30 min postinjury.

Peroxynitrite Generated at the Level Produced by Spinal Cord Injury Induces Peroxidation of Membrane Phospholipids in Normal Rat Cord: Reduction by a Metalloporphyrin

The goal of the present study was to determine in vivo whether peroxynitrite, at the concentration and duration produced by SCI, contributes to membrane lipid peroxidation (MLP) after traumatic spinal cord injury (SCI) and the capability of a broad spectrum scavenger of reactive species, Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP), to reduce MLP. This was accomplished by administering a peroxynitrite donor 3-morpholinosydnonimine (SIN-1) into the gray matter of an uninjured rat spinal cord through a microdialysis fiber to generate ONOO at the SCI-elevated levels. The resulting MLP was characterized by measuring the productions of extracellular malondialdehyde and of intracellular 4-hydroxynonenal. We demonstrated that extracellular SIN- 1 administration significantly increased the concentration of malondialdehyde (p < 0.001) and the numbers of hydroxynonenal-positive cells (p < 0.001) as compared to a control group in which ACSF was administered. Simultaneous administration of MnTBAP through a second microdialysis fiber significantly reduced SIN-1-induced malondialdehyde production (p < 0.001) and the numbers of HNE-positive cells (p < 0.001). There was no significant difference between MnTBAP-treated and ACSF-controls (p = 0.3). These results demonstrate in vivo that (1) SCI-produced levels of peroxynitrite sufficient to cause MLP, and therefore that peroxynitrite is an agent of secondary damage after acute SCI; (2) MnTBAP can efficiently reduce SIN-1-induced MLP.

Systemic Treatment of Cerebral Cortex Lesions in Rats with a New Secreted Phospholipase A2 Inhibitor

An internal fragment of the human neuroprotective polypeptide DSEP (Diffusible Survival Evasion Peptide) was delivered at 0.4 mg/kg (subcutaneously) 20-30 min after stab wound lesions in the parietal cortex of anesthetized rats. The peptide, CHEASAAQC or CHEC-9, inhibited the inflammatory response to the lesion and the degeneration of neurons adjacent to the wound. Four days after surgery, peptide-treated animals (n = 6) had 75% fewer reactive ameboid microglia/brain macrophages in the cortical parenchyma surrounding the lesion compared to vehicle-injected control rats (n = 6, p = 0.004). The cortical laminae in area 2 adjacent to the lesion were completely obscured in controls because of the increase in inflammatory cells and frank degeneration of neurons, while there was preservation of the neurons and cytoarchitecture after peptide treatment. In parallel experiments, CHEC-9 was found to inhibit the enzymatic activity of secreted phospholipase A2 (sPLA2), including activity present in the serum of peptide-injected rats. Kinetic analysis revealed the peptide increased the average Km for serum by 318% when tested 45 min after treatment (peptide-treated, n = 6; control-treated, n = 6; p = 0.0087), suggesting the principal effect of the peptide was to lower the affinity of serum sPLA2 for substrate. The sPLA2 inhibition by this particular peptide sequence appeared to be highly specific since inversion of a single pair of amino acids eliminated the inhibitory effect. Phorbol-12-myristate-13-acetate stimulated platelet aggregation, a PLA2-regulated activity, was also inhibited by the peptide. The discovery of CHEC-9 makes it possible to study in vivo the long appreciated contribution made by PLA2-directed inflammation to both acute and chronic neurodegeneration and may be helpful in designing therapies to limit neuron death in these conditions.

The Time Course of Hydroxyl Radical Formation following Spinal Cord Injury: The Possible Role of the Iron-Catalyzed Haber-Weiss Reaction

This study explores whether the hydroxyl radical (*OH)-one of the most destructive reactive oxygen species-plays a role in secondary spinal cord injury (SCI). First, we measured the time course of *OH formation in rat spinal tissue after impact SCI by administering salicylate as a trapping agent into the intrathecal space of the cord and measuring the hydroxylation products of salicylate, 2,3- and 2,5-dihydroxybenzoic acid (2,3- and 2,5-DHBA) by HPLC. The 2,3-DHBA concentration was significantly higher in injured spinal tissue than in sham controls at 5 min, 1 and 3 h, but not at 5 h post-injury. Second, we generated *OH by administering H(2)O(2) and FeCl(2)/EDTA (Fenton's reagents) at the concentrations produced by SCI into the gray matter of the cord for 4 h and found that it induced significant cell loss at 24 h post-*OH exposure. Mn (III) tetrakis (4-benzoic acid) porphyrin(MnTBAP)-a broad spectrum reactive species scavenger-significantly reduced *OH-induced cell death. Finally, we generated superoxide and administered FeCl(3)/EDTA in the intrathecal space of the cord at the concentration produced by SCI and measured extracellular *OH formation in the gray matter of the cord by microdialysis sampling. We found that the levels of *OH significantly increased compared to the pre-administration level, indicating that *OH can be produced in vivo by the iron-catalyzed Haber-Weiss reaction. All together, we demonstrated that *OH is an endogenous secondary damaging agent following SCI and the metal-catalyzed Haber-Weiss reaction may contribute to early *OH formation after SCI.

Screening anti-inflammatory compounds in injured spinal cord with microarrays: a comparison of bioinformatics analysis approaches

Inflammatory responses contribute to secondary tissue damage following spinal cord injury (SCI). A potent anti-inflammatory glucocorticoid, methylprednisolone (MP), is the only currently accepted therapy for acute SCI but its efficacy has been questioned. To search for additional anti-inflammatory compounds, we combined microarray analysis with an explanted spinal cord slice culture injury model. We compared gene expression profiles after treatment with MP, acetaminophen, indomethacin, NS398, and combined cytokine inhibitors (IL-1ra and soluble TNFR). Multiple gene filtering methods and statistical clustering analyses were applied to the multi-dimensional data set and results were compared. Our analysis showed a consistent and unique gene expression profile associated with NS398, the selective cyclooxygenase-2 (COX-2) inhibitor, in which the overall effect of these upregulated genes could be interpreted as neuroprotective. In vivo testing demonstrated that NS398 reduced lesion volumes, unlike MP or acetaminophen, consistent with a predicted physiological effect in spinal cord. Combining explanted spinal cultures, microarrays, and flexible clustering algorithms allows us to accelerate selection of compounds for in vivo testing.

Neuroprotective function of the PGE2 EP2 receptor in cerebral ischemia

The cyclooxygenases COX-1 and COX-2 catalyze the first committed step of prostaglandin synthesis from arachidonic acid. Previous studies in rodent stroke models have shown that the inducible COX-2 isoform promotes neuronal injury, and the administration of COX-2 inhibitors reduces infarct volume. We investigated the function of PGE2, a principal prostaglandin product of COX-2 enzymatic activity, in neuronal survival in cerebral ischemia. PGE2 exerts its downstream effects by signaling through a class of four distinct G-protein-coupled EP receptors (for E-prostanoid: EP1, EP2, EP3, and EP4) that have divergent effects on cAMP and phosphoinositol turnover and different anatomical distributions in brain. The EP2 receptor subtype is abundantly expressed in cerebral cortex, striatum, and hippocampus, and is positively coupled to cAMP production. In vitro studies of dispersed neurons and organotypic hippocampal cultures demonstrated that activation of the EP2 receptor was neuroprotective in paradigms of NMDA toxicity and oxygen glucose deprivation. Pharmacologic blockade of EP2 signaling by inhibition of protein kinase A activation reversed this protective effect, suggesting that EP2-mediated neuroprotection is dependent on cAMP signaling. In the middle cerebral artery occlusion-reperfusion model of transient forebrain ischemia, genetic deletion of the EP2 receptor significantly increased cerebral infarction in cerebral cortex and subcortical structures. These studies indicate that activation of the PGE2 EP2 receptor can protect against excitotoxic and anoxic injury in a cAMP-dependent manner. Taken together, these data suggest a novel mechanism of neuroprotection mediated by a dominant PGE2 receptor subtype in brain that may provide a target for therapeutic intervention.

Peroxynitrite generated in the rat spinal cord induces apoptotic cell death and activates caspase-3

We previously demonstrated that the peroxynitrite concentration increases after impact spinal cord injury. This study tests whether spinal cord injury-elevated peroxynitrite induces apoptotic cell death. Peroxynitrite was generated at the concentration and duration produced by spinal cord injury by administering S-morpholinosydnonimine through a microdialysis fiber into the gray matter of the rat spinal cord. Fragmented DNA was visualized by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling. Transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling-positive neurons were quantitated by counting the transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling and neuron-specific enolase double-stained neurons along the fiber track in the sections removed at 6, 12, 24 and 48 h post-peroxynitrite exposure. Peroxynitrite significantly increased transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling-positive neurons at all time points examined (P< or =0.001) compared with artificial cerebrospinal fluid controls (Two-way analysis of variance followed by Tukey test), peaking at 24 h post-exposure. Electron microscopic observation of characteristic features of apoptosis confirmed peroxynitrite-induced neuronal apoptosis. Total transferase-mediated deoxyuridine triphosphate-biotin nick end-labeling-positive cells were counted in areas near and 0.2 mm away from the fiber track. The counts both peaked at 24 h with no significant difference between the two areas. However, at 6 and 12 h post-exposure the counts were significantly higher near than away from the fiber track (P=0.03 and P=0.007 respectively, paired t test). Immunohistochemical staining indicates caspase-3 was activated by peroxynitrite; this activation peaked at 6 h post-exposure, suggesting that activation of caspase-3 might be an early event in the apoptotic cell death cascade. We conclude that 1) peroxynitrite generated in the cord at the level produced by spinal cord injury induces neuronal apoptosis, indicating a role for peroxynitrite in secondary spinal cord injury; 2) caspase activation might be involved in peroxynitrite-induced neuronal apoptosis; 3) therefore removal of peroxynitrite should reduce secondary cell death after spinal cord injury.

Peroxynitrite generated in the rat spinal cord induces neuron death and neurological deficits

We previously demonstrated that the concentration of peroxynitrite significantly increases following impact spinal cord injury (SCI). The aim of this study was to test whether the SCI-induced elevation of peroxynitrite induces neuronal death and consequent neurological deficits. Peroxynitrite was generated by administering 5 mM S-morpholinosydnonimine, a donor of peroxynitrite, through a microdialysis fiber into the gray matter of the rat spinal cord for 5 h. This mimics the concentration and duration of peroxynitrite elevation after SCI. Neuron death was assessed by counting the neurons along the fiber track in Cresyl Violet-stained sections removed at different times post-peroxynitrite exposure. Peroxynitrite induced significantly more neuron death than did the artificial cerebrospinal fluid (ACSF) control, with the percentage of neuronal loss being 17+/-2%, 28+/-2%, 39+/-3%, and 43+/-4% at 6, 12, 24 and 48 h post-peroxynitrite exposure (P=0.01-<0.001). The losses of total neurons or motoneurons immuno-stained with anti-neuron-specific enolase or anti-choline acetyltransferase antibodies was significantly higher in the peroxynitrate-exposed group than in ACSF controls at 24 h post-exposure, further confirming peroxynitrate damage to neurons. The susceptibility to oxidative damage in motoneurons was similar to that of other neurons characterized at 24 h post-peroxynitrite exposure. Peroxynitrite-induced neurological deficits were examined by the Basso-Beattie-Bresnahan test (BBB test), the inclined-plane test and footprint analysis. Peroxynitrite significantly (P<0.001) reduced the locomotor rating score (BBB test) and the maximum angle of inclined plane compared to sham and ACSF-exposed animals (repeated measures analysis of variance). The footprint analysis revealed that peroxynitrite significantly increased the distance between the feet and the angle of hindlimb rotation compared to sham (P=0.01 and P<0.001) or ACSF controls (P=0.01 and P=0.005) and significantly shortened the stride length compared to sham (P<0.001) and ACSF control (P=0.005) treatments. Therefore the SCI-produced level of peroxynitrite induced neuron loss and neurological dysfunction, strong evidence that peroxynitrite is a secondary damage agent in SCI.

Determination of thiobarbituric acid adduct of malondialdehyde using on-line microdialysis coupled with high-performance liquid chromatography

An on-line analytical system for the continuous monitoring of malondialdehyde (MDA) was developed. This method involves the use of microdialysis perfusion, on-line derivatization and on-line HPLC analysis. This method gave a linear response for MDA concentrations and HPLC peak areas in the range from 0.051 microM to 2.43 microM. The intra-day (RSD = 1.6-10.5%) and inter-day (RSD = 1.1-9.3%) precisions were acceptable. The average in vitro probe recovery of MDA standard was 18.4 +/- 1.0%. The detection limit was 0.03 microM, corresponding to 0.6 pmol for an injection volume of 20 microl. This method was used for in vitro peroxidation investigations, which provided evidence for elevated MDA levels following the incubation of metal ions to a linoleic acid solution.

The effects of prednisolone and serum malondialdehyde levels in puppies with experimentally induced meconium aspiration syndrome

The aim of this study was to investigate the effect of different doses of prednisolone in puppies experimentally induced with meconium aspiration syndrome (MAS). Meconium was collected from human babies in the first day of life and was released into the trachea of 11 newborn puppies to induce MAS. Puppies were treated with 2 mg/kg prednisolone (standard dose), 30 mg/kg prednisolone (megadose) or 0.9% saline, all administered intravenously. The study ended 20 h after meconium aspiration and the lungs were then scored for histopathology. Animals not treated with prednisolone deteriorated after 8 h while respiration rate, oxygenation, pH and partial pressure of carbon dioxide values were better in the prednisolone-treated groups. Histopathology scores were better in the treatment groups compared with the control group, with megadose giving the best result. At the end of the study, serum malondialdehyde levels were significantly higher in the megadose prednisolone group compared with the other two groups. In conclusion, we determined that prednisolone reduced physiological and histological changes in puppies with MAS and that a 30 mg/kg dose was more effective than 2 mg/kg.

Peroxynitrite generated in the rat spinal cord induces oxidation and nitration of proteins: reduction by Mn (III) tetrakis (4-benzoic acid) porphyrin

To determine whether peroxynitrite at the concentration and duration present after spinal cord injury induces protein oxidation and nitration in vivo, the peroxynitrite donor 3-morpholinosydnonimine (SIN-1) was administered into the gray matter of the rat spinal cord for 5 hr. The cords were removed at 6, 12, 24, and 48 hr after SIN-1 exposure, immunohistochemically stained with antibodies to dinitrophenyl (DNP) and nitrotyrosine (Ntyr), markers of protein oxidation and nitration, respectively, and the immunostained neurons were counted. The percentages of DNP-positive (P = 0.023-0.002) and Ntyr-positive (P < 0.001 for all) neurons were significantly higher in the SIN-1-exposed groups than in the ACSF controls at each time, suggesting that peroxynitrite induced intracellular oxidation and nitration of proteins. The percentages of DNP- and Ntyr-positive neurons were not significantly different over time in either SIN-1- or ACSF-exposed groups (P = 0.20-1.00). The percentage of DNP-positive neurons was 7.6 +/- 3% to 12 +/- 4.2% at 6-24 hr, and it was 14 +/- 2% to 19 +/- 2% at 6-24 hr for Ntyr-positive neurons after SIN-1-exposure, whereas both ranged over 2-3% in ACSF controls. Mn (III) tetrakis (4-benzoic acid) porphyrin (MnTBAP, a broad-spectrum scavenger of reactive species) significantly reduced the percentages of DNP- and Ntyr-positive neurons (P = 0.04 and 0.002, respectively) compared to a SIN-1-exposed, untreated group at 24 hr after SIN-1 exposure. There were no significant differences between MnTBAP-treated and ACSF controls (P = 0.7 for DNP and 0.2 for Ntyr). These results further demonstrate peroxynitrite-induced protein oxidation and nitration and the efficiency of MnTBAP in scavenging peroxynitrite.

Spinal cord injury increases iron levels: catalytic production of hydroxyl radicals

This study used a weight drop impact injury model to explore the role of iron and the reality of iron-catalyzed hydroxyl radical ((*)OH) formation in secondary spinal cord injury (SCI). The time course of total extracellular iron was measured following SCI by microcannula sampling and atomic absorption spectrophotometry analysis. Immediately following SCI, the total iron concentration increased from an undetectable level to an average of 1.32 microM. The time course of SCI-induced (*)OH-generating catalytic activity in the cord was obtained by determining the ability of tissue homogenate to convert hydrogen peroxide to (*)OH and then measuring 2,3-dihydroxybenzoic acid, a hydroxylation product of salicylate. The concentration of 2,3-DHBA quickly and significantly increased (p <.001) and returned to sham level (p = 1) by 30 min post-SCI. Desferrioxamine (80 and 800 mg/kg body weight) significantly (p <.001) reduced the catalytic activity, suggesting that iron is the major contributor of the activity. Administering FeCl(3) (100 microM)/EDTA (0.5 mM) in ACSF into the cord through a dialysis fiber significantly increased SCI-induced (*)OH production in the extracellular space, demonstrating that Fe(3+) can catalyze (*)OH production in vivo. Our results support that iron-catalyzed (*)OH formation plays a role in the early stage of secondary SCI.

Dietary intakes and serum concentrations of vitamin E and total carotenoids of healthy adults with severe physical disabilities are lower than matched controls

Millions of people worldwide have severe chronic physical disabilities (e.g., polio, spinal cord injury). We hypothesized that these people are at risk for poor antioxidant nutrient intakes and status, because of their typically low energy expenditures and low socioeconomic status. We surveyed antioxidant nutrient intakes and concentrations in subjects with physical disabilities and age matched non-disabled controls. Only one subject with physical disabilities ate five or more servings of vegetables per day. The group had low intakes of vegetables (minus potatoes) and citrus fruits, and trends for low intakes of all antioxidant nutrients. Serum a-tocopherol and total carotenoid concentrations were lower in subjects with physical disabilities, while retinol and individual carotenoids showed non-significant lower trends. Since adequate antioxidant nutrients are associated with decreased chronic disease risk, nutrition professionals might improve the health of patients with physical disabilities by periodically monitoring their intakes and status of antioxidant nutrients.

Selective cyclooxygenase 2 inhibition lowers spinal cord prostaglandin concentrations after injury

BACKGROUND CONTEXT

Prostaglandin E2 (PGE2) and thromboxane B2 (TxB2) concentrations are elevated in the injured spinal cord for hours to days after injury. Treatment of animals with a selective cyclooxygenase-2 (COX-2) inhibitor has been shown to improve functional outcome in an animal model.

PURPOSE

We sought to characterize the effects of COX-2 inhibition on prostaglandin concentrations in the spinal cord after injury.

STUDY DESIGN/SETTING

A drug study was performed using 76 male Long Evans rats.

OUTCOME MEASURES

PGE2 and TxB2 concentrations were measured by enzyme immune assay.

METHODS

Fifty-six rats were subject to spinal cord injury, and 4 rats served as sham controls. Twenty eight rats received 3 mg/kg of celebocid by means of an orogastric tube within 20 minutes after injury, and 28 received vehicle alone. The animals were sacrificed at time points between 2 and 72 hours after injury, and PGE2 and TxB2 levels were measured. A second study was performed using transcardiac saline perfusion in order to reduce intragroup variance in measured PGE2 and TxB2 levels. Sixteen animals underwent spinal cord injury. Animals were sacrificed at 4 and 24 hours after injury, and PGE2 and TxB2 levels were measured.

RESULTS

PGE2 and TxB2 concentrations were elevated after injury in all animals. Administration of celebocid resulted in a delayed reduction of PGE2 and TxB2 concentrations in the initial drug study. These results were not statistically significant. Transcardiac perfusion with normal saline reduced the intragroup variance. Using this technique, administration of celebocid resulted in a statistically significant reduction in PGE2 and TxB2 concentrations in the injured cord segment 4 and 24 hours after injury.

CONCLUSION

Administration of a selective COX-2 inhibitor after injury results in a decrease of PGE2 and TxB2 concentrations in the injured spinal cord. Transcardiac perfusion after sacrifice reduces measured variance, probably through reducing the contribution of blood-borne prostaglandins.