Constitutive and inducible nitric oxide synthase activities after spinal cord contusion in rats

Inhibition of Cytosolic Phospholipase A2 Has Neuroprotective Effects on Motoneuron and Muscle Atrophy after Spinal Cord Injury

Surviving motoneurons undergo dendritic atrophy after spinal cord injury (SCI), suggesting an important therapeutic target for neuroprotective strategies to improve recovery of function after SCI. Our previous studies showed that cytosolic phospholipase A₂ (PLA₂) may play an important role in the pathogenesis of SCI. In the present study, we investigated whether blocking cytosolic PLA₂ (cPLA₂) pharmacologically with arachidonyl trifluoromethyl ketone (ATK) or genetically using cPLA₂ knockout (KO) mice attenuates motoneuron atrophy after SCI. C57BL/6 mice received either sham or contusive SCI at the T10 level. At 30 min after SCI, mice were treated with ATK or vehicle. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. ATK administration reduced percent lesion volume and increased percent volume of spared white matter, compared to the vehicle-treated control animals. SCI with or without ATK treatment had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with ATK. Similarly, vastus lateralis muscle weights of untreated SCI animals were smaller than those of sham surgery controls, and these reductions were prevented by ATK treatment. No effects on fiber cross-sectional areas, motor endplate area, or density were observed across treatment groups. Remarkably, genetically deleting cPLA₂ in cPLA₂ KO mice attenuated dendritic atrophy after SCI. These findings suggest that, after SCI, cord tissue damage and regressive changes in motoneuron and muscle morphology can be reduced by inhibition of cPLA₂, further supporting a role for cPLA₂ as a neurotherapeutic target for SCI treatment.

Metallothionein-I + II Reduces Oxidative Damage and Apoptosis after Traumatic Spinal Cord Injury in Rats

After spinal cord injury (SCI), some self-destructive mechanisms start leading to irreversible neurological deficits. It is known that oxidative stress and apoptosis play a major role in increasing damage after SCI. Metallothioneins I and II (MT) are endogenous peptides with known antioxidant, neuroprotective capacities. Taking advantage of those capacities, we administered exogenous MT to rats after SCI in order to evaluate the protective effects of MT on the production of reactive oxygen species (ROS) and lipid peroxidation (LP), as markers of oxidative stress. The activities of caspases-9 and -3 and the number of annexin V and TUNEL-positive cells in the spinal cord tissue were also measured as markers of apoptosis. Rats were subjected to either sham surgery or SCI and received vehicle or two doses of MT (10 μg per rat) at 2 and 8 h after surgical procedure. The results showed a significant increase in levels of MT protein by effect of SCI and SCI plus treatment at 12 h, while at 24 h an increase of MT was observed only in the injury plus treatment group (p < 0.05). ROS production was decreased by effect of MT in lesioned tissue; likewise, we observed diminished LP levels by MT effect both in the sham group and in the group with SCI. Also, the results showed an increase in the activity of caspase-9 due to SCI, without changes by effect of MT, as compared to the sham group. Caspase-3 activity was increased by SCI, and again, MT treatment reduced this effect only at 24 h after injury. Finally, the results of the number of cells positive to annexin V and TUNEL showed a reduction due to MT treatment both at 24 and 72 h after the injury. With the findings of this work, we conclude that exogenously administered MT has antioxidant and antiapoptotic effects after SCI.

Effect evaluation of methylprednisolone plus mitochondrial division inhibitor-1 on spinal cord injury rats

PURPOSE

To investigate the combination effect of methylprednisolone (MP) and mitochondrial division inhibitor-1 (Mdivi-1) on the neurological function recovery of rat spinal cord injury (SCI) model.

METHODS

The weight-drop method was used to establish the rat SCI model; then, rats were randomized into sham group, SCI group, MP group, Mdivi-1 group and MP+Mdivi-1 group. Motor function scores were quantified to evaluate locomotor ability; HE staining was used to assess spinal cord histopathology; tissue water content, oxidative stress, tissue mitochondrial function, neurons apoptosis, and apoptosis-related protein expression were detected.

RESULTS

From the third day after SCI, BBB score of the MP+Mdivi-1 group was obviously higher than the other experimental groups (p < 0.05). Compared with the SCI group, tissue water content of the Mdivi-1 group and MP+Mdivi-1 group reduced obviously (p < 0.05), mitochondrial membrane potential (MMP) level and ATP content in the Mdivi-1 group and MP+Mdivi-1 group were both higher (p < 0.05). Meanwhile, three kinds of treatment all reduced apoptosis significantly, while MP plus Mdivi-1 exhibited the best inhibition effect on apoptosis (p < 0.05). The expression levels of Drp1, cytochrome c, and caspase-3 were all upregulated obviously; Mdivi-1 could inhibit Drp1 upregulation induced by SCI; for the upregulation of cytochrome c and caspase-3, the inhibition effect of Mdivi-1 approached MP. When MP combined with Mdivi-1, there was the best inhibition effect.

CONCLUSIONS

MP combined with Mdivi-1 may produce better neurological function recovery, through improving functional status of mitochondria and inhibiting lipid peroxidation in damaged tissue of SCI rats, and thus alleviating apoptosis.

Protective effects of gonadal hormones on spinal motoneurons following spinal cord injury

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. The majority of treatment strategies after SCI have concentrated on the damaged spinal cord, for example working to reduce lesion size or spread, or encouraging regrowth of severed descending axonal projections through the lesion, hoping to re-establish synaptic connectivity with caudal targets. In our work, we have focused on a novel target for treatment after SCI, surviving spinal motoneurons and their target musculature, with the hope of developing effective treatments to preserve or restore lost function following SCI. We previously demonstrated that motoneurons, and the muscles they innervate, show pronounced atrophy after SCI. Importantly, SCI-induced atrophy of motoneuron dendrites can be attenuated by treatment with gonadal hormones, testosterone and its active metabolites, estradiol and dihydrotestosterone. Similarly, SCI-induced reductions in muscle fiber cross-sectional areas can be prevented by treatment with androgens. Together, these findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be ameliorated by treatment with gonadal hormones, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

Protective Effects of Estradiol and Dihydrotestosterone following Spinal Cord Injury

Spinal cord injury (SCI) results in lesions that destroy tissue and disrupt spinal tracts, producing deficits in locomotor and autonomic function. We previously demonstrated that motoneurons and the muscles they innervate show pronounced atrophy after SCI, and these changes are prevented by treatment with testosterone. Here, we assessed whether the testosterone active metabolites estradiol and dihydrotestosterone have similar protective effects after SCI. Young adult female rats received either sham or T9 spinal cord contusion injuries and were treated with estradiol, dihydrotestosterone, both, or nothing via Silastic capsules. Basso-Beattie-Bresnahan locomotor testing was performed weekly and voiding behavior was assessed at 3 weeks post-injury. Four weeks after SCI, lesion volume and tissue sparing, quadriceps muscle fiber cross-sectional area, and motoneuron dendritic morphology were assessed. Spontaneous locomotor behavior improved after SCI, but hormone treatments had no effect. Voiding behavior was disrupted after SCI, but was significantly improved by treatment with either estradiol or dihydrotestosterone; combined treatment was maximally effective. Treatment with estradiol reduced lesion volume, but dihydrotestosterone alone and estradiol combined with dihydrotestosterone were ineffective. SCI-induced decreases in motoneuron dendritic length were attenuated by all hormone treatments. SCI-induced reductions in muscle fiber cross-sectional areas were prevented by treatment with either dihydrotestosterone or estradiol combined with dihydrotestosterone, but estradiol treatment was ineffective. These findings suggest that deficits in micturition and regressive changes in motoneuron and muscle morphology seen after SCI are ameliorated by treatment with estradiol or dihydrotestosterone, further supporting a role for steroid hormones as neurotherapeutic agents in the injured nervous system.

Identifying the Long-Term Role of Inducible Nitric Oxide Synthase after Contusive Spinal Cord Injury Using a Transgenic Mouse Model

Inducible nitric oxide synthase (iNOS) is a potent mediator of oxidative stress during neuroinflammation triggered by neurotrauma or neurodegeneration. We previously demonstrated that acute iNOS inhibition attenuated iNOS levels and promoted neuroprotection and functional recovery after spinal cord injury (SCI). The present study investigated the effects of chronic iNOS ablation after SCI using inos-null mice. iNOS^-/- knockout and wild-type (WT) control mice underwent a moderate thoracic (T8) contusive SCI. Locomotor function was assessed weekly, using the Basso Mouse Scale (BMS), and at the endpoint (six weeks), by footprint analysis. At the endpoint, the volume of preserved white and gray matter, as well as the number of dorsal column axons and perilesional blood vessels rostral to the injury, were quantified. At weeks two and three after SCI, iNOS^-/- mice exhibited a significant locomotor improvement compared to WT controls, although a sustained improvement was not observed during later weeks. At the endpoint, iNOS^-/- mice showed significantly less preserved white and gray matter, as well as fewer dorsal column axons and perilesional blood vessels, compared to WT controls. While short-term antagonism of iNOS provides histological and functional benefits, its long-term ablation after SCI may be deleterious, blocking protective or reparative processes important for angiogenesis and tissue preservation.

Identification of temporal genes involved in the mechanisms of spinal cord injury

OBJECTIVES

As a high-cost neurological disability, spinal cord injury (SCI) can result in permanent paralysis and loss of sensation. To identify the temporal genes involved in the pathogenesis of SCI, we analysed the expression profile of GSE45006.

METHODS

GSE45006 was downloaded from Gene Expression Omnibus, including 20 SCI samples (samples at 1 day, 3 days, 1 week, 2 weeks and 8 weeks after injury, four repetitions for each time point) and 4 normal samples. The Bayesian Estimation of Temporal Regulation (BETR) and randomForest packages were used to screen the temporal genes and the top 100 temporal genes, respectively. Then, the gplots package and Pearson correlation analysis separately were used to perform hot map analysis and expression pattern clustering for the top 100 temporal genes. Using the clusterProfiler package and TargetMine tool, their potential functions were analysed by enrichment analyses. Moreover, interaction relationships between these temporal genes and pathways were investigated by pathway-gene crosslinking networks.

RESULTS

In total, 1907 temporal genes were identified. The top 100 temporal genes were obtained and divided into six clusters. Most of the gene functions were enriched in biological process categories. ARG1 and NOS3 in cluster 4 were enriched in biological process of arginine catabolic process. TGFβ2, TGFβ3, ALDH2 and ALDH3A2 were correlated with numerous pathways in the pathway-gene crosslinking network. Pathways related to TGFβ2 and TGFβ3 were connected to pathways related to ARG1 and NOS3 via ARG1.

CONCLUSION

Several temporal genes, including TGFβ2, TGFβ3, ALDH2, ALDH3A2, ARG1 and NOS3, might be involved in SCI.

Combination of methylprednisolone and rosiglitazone promotes recovery of neurological function after spinal cord injury

Methylprednisolone exhibits anti-inflammatory antioxidant properties, and rosiglitazone acts as an anti-inflammatory and antioxidant by activating peroxisome proliferator-activated receptor-γ in the spinal cord. Methylprednisolone and rosiglitazone have been clinically used during the early stages of secondary spinal cord injury. Because of the complexity and diversity of the inflammatory process after spinal cord injury, a single drug cannot completely inhibit inflammation. Therefore, we assumed that a combination of methylprednisolone and rosiglitazone might promote recovery of neurological function after secondary spinal cord injury. In this study, rats were intraperitoneally injected with methylprednisolone (30 mg/kg) and rosiglitazone (2 mg/kg) at 1 hour after injury, and methylprednisolone (15 mg/kg) at 24 and 48 hours after injury. Rosiglitazone was then administered once every 12 hours for 7 consecutive days. Our results demonstrated that a combined treatment with methylprednisolone and rosiglitazone had a more pronounced effect on attenuation of inflammation and cell apoptosis, as well as increased functional recovery, compared with either single treatment alone, indicating that a combination better promoted recovery of neurological function after injury.

A modified compression model of spinal cord injury in rats: functional assessment and the expression of nitric oxide synthases

Study design:

Experimental study.

Objectives:

To investigate a modified compression model of spinal cord injury (SCI) in adult rats by using a room-air- inflated Fogarty balloon catheter.

Setting:

Kaohsiung, Taiwan.

Methods:

The rats were divided into injury, sham-operated and control groups. A 2-French Fogarty catheter was passed from the lumbar spine (L3–L4) epidurally, with a mini-laminectomy under the microscope, to the level of thoracic spine (T6–T7). The actual site of the catheter tip was confirmed with X-ray. The balloon of Fogarty catheter then was inflated with room air, 0.2 ml, for 10 min. Mini-laminectomy was performed without inserting the catheter in the sham-operated group. Quantitative neurological outcomes were evaluated with the Basso, Beattie and Bresnahan (BBB) locomotor rating scale daily. The gene expression of nitric oxide synthases (NOSs) of the spinal cord was investigated at the end of the functional assessment.

Results:

The mean BBB locomotor scores were 10±1.85 and 10±1.85, respectively, on days 1 and 3 in the injury group, and 21 and 20.29±0.69, respectively, in the sham-operated group. There was a significantly increased gene expression of inducible NOS in the SCI group compared with the sham-operated group and control group. Endothelial NOS gene expression was not significantly different among the groups.

Conclusion:

The functional and molecular assessments show that this modified balloon-compression technique is a reproducible, simple and inexpensive model of SCI in rats.

Hyperbaric oxygen treatment in the experimental spinal cord injury model

BACKGROUND CONTEXT

Spinal cord trauma is a major cause of mortality and morbidity. Although no known treatment for spinal cord injury exists, a limited number of effective treatment modalities and procedures are available that improve secondary injury. Hyperbaric oxygen (HBO) treatment has been used to assist in neurologic recovery after cranial injury or ischemic stroke.

PURPOSE

To report the findings on the effectiveness of HBO treatment on rats with experimental traumatic spinal cord injury. Improvement was evaluated through motor strength assessment and nitrite level assay testing.

STUDY DESIGN

We randomly distributed 40 rats among 5 groups of 8 rats each: sham incurable trauma, induced trauma, HBO treatment begun at the 1st hour, HBO treatment begun at the 6th hour, and HBO treatment begun at the 24th hour.

METHOD

The HBO treatment was administered to rats in three of the groups and conducted in two 90-minute sessions, under an absolute atmospheric pressure of 2.4 at 100% oxygen for 5 days. In the motor strength evaluations, all the rats were observed during the inclined plane test and clinical motor examination on the first, third, and fifth days. In addition, the nitrite levels of spinal cord tissues on the sixth day were also studied.

RESULTS

Results from the inclined plane levels and motor strength test from all the three groups undergoing HBO treatment were higher than those from Group 2. It was also determined that early HBO treatment resulted in higher recovery rates (groups 3 and 4). The highest levels were seen in the group in which the HBO treatments were started in the first hour (Group 3). It was noted that nitrite levels of rats in the group exposed to trauma increased, compared with the sham group, but increased levels also diminished after HBO treatments. Again, the greatest decrease in nitrite levels was evident in the group where the HBO treatment was started the earliest (Group 3).

CONCLUSIONS

Prompt HBO treatment after trauma significantly contributed to the clinical, histopathologic, and biochemical recovery of the rats.

Chrysin suppressed inflammatory responses and the inducible nitric oxide synthase pathway after spinal cord injury in rats

Chrysin (CH), a natural plant flavonoid, has shown a variety of beneficial effects. Our present study was conducted to evaluate the therapeutic potential of CH three days after spinal cord injury (SCI) in rats and to probe the underlying neuroprotective mechanisms. SCI was induced using the modified weight-drop method in Wistar rats. Then, they were treated with saline or CH by doses of 30 and 100 mg/kg for 26 days. Neuronal function was assessed with the Basso Beattle Bresnahan locomotor rating scale (BBB). The water content of spinal cord was determined after traumatic SCI. The NF-κB p65 unit, TNF-α, IL-1β and IL-6 in serums, as well as the apoptotic marker, caspase-3, of spinal cord tissues were measured using commercial kits. The protein level and activity of inducible nitric oxide synthase (iNOS) were detected by western blot and a commercial kit, respectively. NO (nitric oxide) production was evaluated by the determination of nitrite concentration. The rats with SCI showed marked reductions in BBB scores, coupled with increases in the water content of spinal cord, the NF-κB p65 unit, TNF-α, IL-1β, IL-6, iNOS, NO production and caspase-3. However, a CH supplement dramatically promoted the recovery of neuronal function and suppressed the inflammatory factors, as well as the iNOS pathway in rats with SCI. Our findings disclose that CH improved neural function after SCI in rats, which might be linked with suppressing inflammation and the iNOS pathway.

Activation of heme oxygenase recovers motor function after spinal cord injury in rats

Characterization of auto-destructive mechanisms, leading to cell death after spinal cord injury (SCI) is important to prevent further damage to tissue. Heme oxygenase (HO) catalyzes the oxidation of heme to biliverdin and carbon monoxide (CO), as a response to cell damage. Products of HO action have biological effects, as antioxidant biliverdin. We evaluated the changes of HO activity after injury, and the effect of pharmacological treatments with hemin (an inducer) and (Sn)-protoporphyrin (an inhibitor, Sn-PPIX) of HO, upon motor recovery after SCI. Female Wistar rats were submitted to SCI by trauma and sacrificed at several times (2, 4, 8, 12 and 24h) after injury to evaluate HO activity. Additional groups of rats were treated with either hemin or Sn-PPIX, to evaluate motor recovery, spared spinal cord tissue and HO activity. Results showed that HO control activity was increased by effect of SCI, at all times evaluated, as compared to sham group values. Twenty-four hours after injury, HO activity was increased 7.2-fold by hemin treatment, as compared to SCI plus vehicle group values. In addition, animals treated with hemin 2 and 8h after SCI, showed a better motor recovery and higher spared cord tissue, as compared to control group values. Our findings indicate that activation of HO is a beneficial mechanism when attained during the acute phase after SCI.

iNOS participates in apoptosis of spinal cord neurons via p-BAD dephosphorylation following ischemia/reperfusion (I/R) injury in rat spinal cord

The pro-apoptotic effect of nitric oxide (NO) has been reported both in vivo and in vitro. Previous studies have revealed that NO, especially which produced by inducible nitric oxide synthase (iNOS), has an important effect on apoptosis of neurons in spinal cord ischemia/reperfusion (I/R) injury. To investigate the role of iNOS in this process, a randomized, controlled study was designed using a classical rat model of ischemic spinal cord injury. Fifty-four male Sprague-Dawley rats were randomly divided into three different groups: a sham-operated group (n=6), a vehicle group (I/R, n=24), and an iNOS inhibitor (aminoguanidine: AG) group (I/R+AG, n=24). Rats were sacrificed 6, 12, 24 and 72 h after reperfusion. We examined neurological motor function evaluated by 'Tarlov's score', assessed alterations in the morphology of spinal cord neurons by transmission electron microscopy (TEM), analyzed expression of iNOS at the levels of mRNA and protein, evaluated local concentrations and cellular locations of other key regulatory proteins, and investigated protein-protein interactions. In the vehicle group, iNOS expression, dephosphorylation of p-BAD (Ser 136), disassociation of BAD from p-BAD/14-3-3 dimers, and release of cytochrome c were all increased compared with the sham group. But in the AG group, all the performances above were decreased compared with the vehicle group. Similarly, rats in the sham group got a maximum score of 5 by Tarlov's motor scores evaluation. While the scores were higher in the AG group compared to the vehicle group because iNOS was inhibited. These results indicate that the activity of iNOS plays a critical role in the apoptosis of spinal cord neurons by influencing the dephosphorylation of p-BAD (Ser 136) and the interaction between BAD and 14-3-3.

Effect of melatonin on the functional recovery from experimental traumatic compression of the spinal cord

Spinal cord injury is an extremely severe condition with no available effective therapies. We examined the effect of melatonin on traumatic compression of the spinal cord. Sixty male adult Wistar rats were divided into three groups: sham-operated animals and animals with 35 and 50% spinal cord compression with a polycarbonate rod spacer. Each group was divided into two subgroups, each receiving an injection of vehicle or melatonin (2.5 mg/kg, intraperitoneal) 5 min prior to and 1, 2, 3, and 4 h after injury. Functional recovery was monitored weekly by the open-field test, the Basso, Beattie and Bresnahan locomotor scale and the inclined plane test. Histological changes of the spinal cord were examined 35 days after injury. Motor scores were progressively lower as spacer size increased according to the motor scale and inclined plane test evaluation at all times of assessment. The results of the two tests were correlated. The open-field test presented similar results with a less pronounced difference between the 35 and 50% compression groups. The injured groups presented functional recovery that was more evident in the first and second weeks. Animals receiving melatonin treatment presented more pronounced functional recovery than vehicle-treated animals as measured by the motor scale or inclined plane. NADPH-d histochemistry revealed integrity of the spinal cord thoracic segment in sham-operated animals and confirmed the severity of the lesion after spinal cord narrowing. The results obtained after experimental compression of the spinal cord support the hypothesis that melatonin may be considered for use in clinical practice because of its protective effect on the secondary wave of neuronal death following the primary wave after spinal cord injury.

Beneficial effects of αB-crystallin in spinal cord contusion injury

αB-crystallin is a member of the heat shock protein family that exerts cell protection under several stress-related conditions. Recent studies have revealed that αB-crystallin plays a beneficial role in a mouse model of multiple sclerosis, brain ischemia, and Alexander disease. Whether αB-crystallin plays a role in modulating the secondary damage after CNS trauma is not known. We report here that αB-crystallin mediates protective effects after spinal cord injury. The levels of αB-crystallin are reduced in spinal cord tissue following contusion lesion. In addition, administration of recombinant human αB-crystallin for the first week after contusion injury leads to sustained improvement in locomotor skills and amelioration of secondary tissue damage. We also provide evidence that recombinant human αB-crystallin modulates the inflammatory response in the injured spinal cord, leading to increased infiltration of granulocytes and reduced recruitment of inflammatory macrophages. Furthermore, the delivery of recombinant human αB-crystallin promotes greater locomotor recovery even when the treatment is initiated 6 h after spinal cord injury. Our findings suggest that administration of recombinant human αB-crystallin may be a good therapeutic approach for treating acute spinal cord injury, for which there is currently no effective treatment.

Neuroprotective effects of testosterone on motoneuron and muscle morphology following spinal cord injury

Treatment with testosterone is neuroprotective/neurotherapeutic after a variety of motoneuron injuries. Here we assessed whether testosterone might have similar beneficial effects after spinal cord injury (SCI). Young adult female rats received either sham or T9 spinal cord contusion injuries and were implanted with blank or testosterone-filled Silastic capsules. Four weeks later, motoneurons innervating the vastus lateralis muscle of the quadriceps were labeled with cholera toxin-conjugated horseradish peroxidase, and dendritic arbors were reconstructed in three dimensions. Soma volume, motoneuron number, lesion volume, and tissue sparing were also assessed, as were muscle weight, fiber cross-sectional area, and motor endplate size and density. Contusion injury resulted in large lesions, with no significant differences in lesion volume, percent total volume of lesion, or spared white or gray matter between SCI groups. SCI with or without testosterone treatment also had no effect on the number or soma volume of quadriceps motoneurons. However, SCI resulted in a decrease in dendritic length of quadriceps motoneurons in untreated animals, and this decrease was completely prevented by treatment with testosterone. Similarly, the vastus lateralis muscle weights and fiber cross-sectional areas of untreated SCI animals were smaller than those of sham-surgery controls, and these reductions were both prevented by testosterone treatment. No effects on motor endplate area or density were observed across treatment groups. These findings suggest that regressive changes in motoneuron and muscle morphology seen after SCI can be prevented by testosterone treatment, further supporting a role for testosterone as a neurotherapeutic agent in the injured nervous system.

Harmful and beneficial effects of inflammation after spinal cord injury: potential therapeutic implications

Spinal cord injury (SCI) results in immediate damage followed by a secondary phase of tissue damage that occurs over a period of several weeks. The mechanisms underlying this secondary damage are multiple and not fully understood. A number of studies suggest that the local inflammatory response in the spinal cord that occurs after SCI contributes importantly to secondary damage. This response is mediated by cells normally found in the central nervous system (CNS) as well as infiltrating leukocytes. While the inflammatory response mediated by these cells is required for efficient clearance of tissue debris, and promotes wound healing and tissue repair, they also release various factors that can be detrimental to neurons, glia, axons, and myelin. In this chapter we provide an overview of the inflammatory response at the cell and molecular level after SCI, and review the current state of knowledge about its contribution to tissue damage and repair. Additionally, we discuss how some of this work is leading to the development and testing of drugs that modulate inflammation to treat acute SCI in humans.

Beneficial effects of endogenous and exogenous melatonin on neural reconstruction and functional recovery in an animal model of spinal cord injury

The purpose of this study was to investigate the beneficial effects of endogenous and exogenous melatonin on functional recovery in an animal model of spinal cord injury (SCI). Eight-week-old male Sprague-Dawley (SD, 250-260 g) rats were used for contusion SCI surgery. All experimental groups were maintained under one of the following conditions: 12/12-hr light/dark (L/D) or 24:0-hr constant light (LL). Melatonin (10 mg/kg) was injected subcutaneously for 4 wk, twice daily (07:00, 19:00). Locomotor recovery, inducible nitric oxide synthase (iNOS), glial fibrillary acidic protein gene expression, and muscle atrophy-related genes, including muscle atrophy F-box (MAFbx) and muscle-specific ring-finger protein 1 (MuRF1) gene expression were evaluated. Furthermore, autophagic signaling such as Beclin-1 and LC3 protein expression was examined in the spinal cord and in skeletal muscle. The melatonin treatment resulted in increased hind-limb motor function and decreased iNOS mRNA expression in the L/D condition compared with the LL condition (P < 0.05), indicating that endogenous melatonin had neuroprotective effects. Furthermore, the MAFbx, MuRF1 mRNA level, and converted LC3 II protein expression were decreased in the melatonin-treated SCI groups under the LL (P < 0.05), possibly in response to the exogenous melatonin treatment. Therefore, it seems that both endogenous and exogenous melatonin contribute to neural recovery and to the prevention of skeletal muscle atrophy, promoting functional recovery after SCI. Finally, this study supports the benefit of endogenous melatonin and use of exogenous melatonin as a therapeutic intervention for SCI.

Delayed administration of dapsone protects from tissue damage and improves recovery after spinal cord injury

After spinal cord injury (SCI), a complex cascade of pathophysiological processes increases the primary damage. The inflammatory response plays a key role in this pathology. Recent evidence suggests that myeloperoxidase (MPO), an enzyme produced and released by neutrophils, is of special importance in spreading tissue damage. Dapsone (4,4'-diaminodiphenylsulfone) is an irreversible inhibitor of MPO. Recently, we demonstrated, in a model of brain ischemia/reperfusion, that dapsone has antioxidant, antiinflammatory, and antiapoptotic effects. The effects of dapsone on MPO activity, lipid peroxidation (LP) processes, motor function recovery, and the amount of spared tissue were evaluated in a rat model of SCI. MPO activity had increased 24.5-fold 24 hr after SCI vs. the sham group, and it had diminished by 38% and 19% in the groups treated with dapsone at 3 and 5 hr after SCI, respectively. SCI increased LP by 45%, and this increase was blocked by dapsone. In rats treated with dapsone, a significant motor function recovery (Basso-Beattie-Bresnahan score, BBB) was observed beginning during the first week of evaluation and continuing until the end of the study. Spontaneous recovery 8 weeks after SCI was 9.2 ± 1.12, whereas, in the dapsone-treated groups, it reached 13.6 ± 1.04 and 12.9 ± 1.17. Spared tissue increased by 42% and 33% in the dapsone-treated groups (3 and 5 hr after SCI, respectively) vs. SCI without treatment. Dapsone significantly prevented mortality. The results show that inhibition of MPO by dapsone significantly protected the spinal cord from tissue damage and enhanced motor recovery after SCI.

Melatonin plus exercise-based neurorehabilitative therapy for spinal cord injury

Spinal cord injury (SCI) is damage to the spinal cord caused by the trauma or disease that results in compromised or loss of body function. Subsequent to SCI in humans, many individuals have residual motor and sensory deficits that impair functional performance and quality of life. The available treatments for SCI are rehabilitation therapy, activity-based therapies, and pharmacological treatment using antioxidants and their agonists. Among pharmacological treatments, the most efficient and commonly used antioxidant for experimental SCI treatment is melatonin, an indolamine secreted by pineal gland at night. Melatonin's receptor-independent free radical scavenging action and its broad-spectrum antioxidant activity makes it an ideal antioxidant to protect tissue from oxidative stress-induced secondary damage after SCI. Owing to the limitations of an activity-based therapy and antioxidant treatment singly on the functional recovery and oxidative stress-induced secondary damages after SCI, a melatonin plus exercise treatment may be a more effective therapy for SCI. As suggested herein, supplementation with melatonin in conjunction with exercise not only would improve the functional recovery by enhancing the beneficial effects of exercise but would reduce the secondary tissue damage simultaneously. Finally, melatonin may protect against exercise-induced fatigue and impairments. In this review, based on the documented evidence regarding the beneficial effects of melatonin, activity-based therapy and the combination of both on functional recovery, as well as reduction of secondary damage caused by oxidative stress after SCI, we suggest the melatonin combined with exercise would be a novel neurorehabilitative strategy for the faster recovery after SCI.

Synergistic effect of melatonin on exercise-induced neuronal reconstruction and functional recovery in a spinal cord injury animal model

Nitric oxide (NO) may aggravate neuronal damage after spinal cord injury (SCI). We hypothesized that NO produced by inducible nitric oxide synthase (iNOS) accelerates secondary damage to spinal tissue, which may be reversed by the neuroprotectant, melatonin. This study investigated the effects of combination therapy with melatonin (10 mg/kg) and exercise (10 m/min) on recovery from SCI caused by contusion. We examined locomotor recovery, iNOS gene expression, autophagic and apoptotic signaling, including Beclin-1, LC3, p53 and IKKalpha protein expression and histological alterations in the ventral horn of the spinal cord. Melatonin in combination with exercise resulted in significantly increased hindlimb movement (P < 0.05), a reduced level of iNOS mRNA (P < 0.05) and more motor neurons in the ventral horn, versus control SCI and SCI plus exercise alone, with no effect on the other signaling molecules examined. This study shows that combined therapy with melatonin and exercise reduces the degree of secondary damage associated with SCI in rats and supports the possible use of melatonin in combination with exercise to reduce the side effects related to exercise-induced fatigue and impairment.

Blockade of peroxynitrite-induced neural stem cell death in the acutely injured spinal cord by drug-releasing polymer

Therapeutic impact of neural stem cells (NSCs) for acute spinal cord injury (SCI) has been limited by the rapid loss of donor cells. Neuroinflammation is likely the cause. As there are close temporal-spatial correlations between the inducible nitric oxide (NO) synthase expression and the donor NSC death after neurotrauma, we reasoned that NO-associated radical species might be the inflammatory effectors which eliminate NSC grafts and kill host neurons. To test this hypothesis, human NSCs (hNSCs: 5 x 10(4) to 2 x 10(6) per milliliter) were treated in vitro with "plain" medium, 20 microM glutamate, or donors of NO and peroxynitrite (ONOO(-); 100 and 400 microM of spermine or DETA NONOate, and SIN-1, respectively). hNSC apoptosis primarily resulted from SIN-1 treatment, showing ONOO(-)-triggered protein nitration and the activation of p38 MAPK, cytochrome c release, and caspases. Therefore, cell death following post-SCI (p.i.) NO surge may be mediated through conversion of NO into ONOO(-). We subsequently examined such causal relationship in a rat model of dual penetrating SCI using a retrievable design of poly-lactic-co-glycolic acid (PLGA) scaffold seeded with hNSCs that was shielded by drug-releasing polymer. Besides confirming the ONOO(-)-induced cell death signaling, we demonstrated that cotransplantation of PLGA film embedded with ONOO(-) scavenger, manganese (III) tetrakis (4-benzoic acid) porphyrin, or uric acid (1 micromol per film), markedly protected hNSCs 24 hours p.i. (total: n = 10). Our findings may provide a bioengineering approach for investigating mechanisms underlying the host microenvironment and donor NSC interaction and help formulate strategies for enhancing graft and host cell survival after SCI.

Expression of CAPON after spinal cord injury in rats

The adaptor protein, carboxy-terminal PDZ ligand of nNOS (CAPON), regulates the distribution of neuronal nitric oxide synthase (nNOS) that increased after spinal cord injury (SCI) and produces the key signaling molecule nitric oxide (NO). But little is known about the role of CAPON in the pathological process of SCI. The main objective of the present study was to investigate expression of CAPON and nNOS in a spinal cord contusion model in adult rats. Real time-polymerase chain reaction (PCR) and Western blot analysis revealed that mRNA and protein for CAPON increased at 2 h after SCI and reached the peak at 8 h, gradually recovered to the baseline level at 14 days. The expression of nNOS mRNA and protein was similar to that of CAPON. During the peak expression, CAPON mRNA was found in the ventral horn, mediate zone, dorsal horn, and white matter by in situ hybridization. Immunofluorescence showed that CAPON was colocalized with nNOS in neurons, oligodendrocytes, and some astrocytes of spinal cord tissues within 5 mm from the epicenter. Interaction between CAPON and nNOS was also detected by co-immunoprecipitation. Thus, the transient expression of high levels of CAPON may provide new insight into the secondary response after SCI.

Spatiotemporal patterns of postsynaptic density (PSD)-95 expression after rat spinal cord injury

AIMS

Postsynaptic density (PSD)-95 is a scaffolding protein linking the N-methyl-D-aspartate receptor with neuronal nitric oxide synthase (nNOS), which contributes to many physiological and pathological actions. We here investigated whether PSD-95 was involved in the secondary response following spinal cord injury (SCI).

METHODS

Spinal cord contusion (SCC) and spinal cord transection (SCT) models at thoracic (T) segment 9 (T(9)) were established in adults rats. Real-time polymerase chain reaction, Western blot, immunohistochemistry and immunofluorescence were used to detect the temporal profile and spatial distribution of PSD-95 after SCI. The association between PSD-95 and nNOS in the injured cords was also assessed by coimmmunoprecipation and double immunofluorescent staining.

RESULTS

The mRNA and protein for PSD-95 expression were significantly increased at 2 h or 8 h, and then gradually declined to the baseline level, ultimately up-regulated again from 5 days to 7 days for its mRNA level and at 7 days or 14 days for its protein level after either SCC or SCT. PSD-95 immunoreactivity was found in neurones, oligodendrocytes and synaptic puncta of spinal cord tissues within 5 mm from the lesion site. Importantly, injury-induced expression of PSD-95 was colabelled by active caspase-3 (apoptotic marker), Tau-1 (the marker for pathological oligodendrocytes) and nNOS.

CONCLUSIONS

Accompanied by the spatio-temporal changes for PSD-95 expression, the association between PSD-95 and nNOS undergoes substantial alteration after SCI. These two molecules are likely to form a complex on apoptotic neurones and pathological oligodendrocytes, which may in turn be involved in the secondary response after SCI.

Nitric oxide in the injured spinal cord: synthases cross-talk, oxidative stress and inflammation

Nitric oxide (NO) is a unique informational molecule involved in a variety of physiological processes in the central nervous system (SNS). It has been demonstrated that it can exert both protective and detrimental effects in several diseases states of the CNS, including spinal cord injury (SCI). The effects of NO on the spinal cord depend on several factors such as: concentration of produced NO, activity of different synthase isoforms, cellular source of production and time of release. Basically, it has been shown that low NO concentrations may play a role in physiologic processes, whereas large amounts of NO may be detrimental by increasing oxidative stress. However, this does not explain all the discrepancies evidenced studying the effects of NO in SCI models. The analysis of the different synthase isoforms, of their temporal profile of activation and cellular source has shed light on this topic. Two post-injury time intervals can be defined with reference to the NO production: immediately after injury and several hours-to-days later. The initial immediate peak of NO production after injury is due to the up-regulation of the neuronal NO synthase (nNOS) in resident spinal cord cells. The late peak is due primarily to the activity of inducible NOS (nNOS) produced by inflammatory infiltrating cells. High NO levels produced by up-regulated nNOS and iNOS are neurotoxic; the down-regulation of nNOS corresponds temporally to the expression of iNOS. On the bases of the evidence, therapeutic approaches should be aimed: (1) to reduce the NO-elicited damage by inhibition of specific synthases according to the temporal profile of activation; (2) by maintaining physiologic amount of NO to keep the induction of iNOS.

The correlation between nitric oxide and vascular endothelial growth factor in spinal cord injury

STUDY DESIGN

Prospective, randomized, placebo-controlled, experimental study.

OBJECTIVES

The issue of whether nitric oxide (NO) production is beneficial or deleterious on ischemic injuries of the central nervous system still remains doubtful. Vascular endothelial growth factor (VEGF) is known to induce the release of NO from endothelial cells. However, the effect of NO on VEGF synthesis is not clear. We aimed to determine the effects of L-arginine and NG-nitro-L-arginine methyl ester (L-NAME) on VEGF synthesis and free radicals in a rat model of spinal cord ischemia-reperfusion (IR) injury.

SETTING

Surgical Research Laboratory of a Medical School.

MATERIAL AND METHODS

Twenty-eight Wistar rats were divided into four groups as follows (n=7): Sham, IR injury, L-arginine, and L-NAME. Infrarenal abdominal aorta was occluded to induce spinal cord ischemia. L-Arginine (100 mg/kg) and L-NAME (10 mg/kg) were given before aortic occlusion. Biochemical assays of malondialdehyde (MDA), NO and VEGF were carried out in spinal cord specimens.

RESULTS

L-Arginine treatment significantly increased MDA and NO, but decreased VEGF levels in spinal cord. However, nonselective inhibition of NOS with L-NAME significantly decreased MDA and NO, but increased VEGF levels. Besides, the positive linear correlation between MDA and NO, and negative linear correlations between MDA, NO and VEGF levels have also been demonstrated.

CONCLUSION

Nonselective inhibition of NO synthase activity with L-NAME attenuated free radical formation and increased VEGF level when compared with NO precursor L-arginine in a rat model of spinal cord ischemia. We suggest that inhibition of NO synthase, as well as induction of VEGF, may be a therapeutic option in spinal cord IR injury.

Changes in nitric oxide synthase expression in young and adult rats after spinal cord injury

OBJECTIVE

To examine the clinical meaning of the changes in nitric oxide synthase (NOS) expression and activity after spinal cord injury (SCI) according to the age of the experiment animal.

MATERIAL AND METHOD

Ten 5- and 16-week-old Sprague-Dawley rats were laminectomized at T10 and SCI induced at this level using a New York impactor. Outcome measures to assess SCI utilized the Basso-Beatti-Bresnahan scale to quantitate hind limb motor dysfunction as a functional outcome measure. NOS isoforms (nNOS, neuronal NOS; iNOS, inducible NOS; and eNOS, endothelial NOS) were also immunolocalized in sections of control and spinal cord injury in the two sample groups using specific monoclonal antibodies. Student's t-test evaluated the difference between the young and adult rats, and P<0.05 was considered as significant value.

RESULT

As the expression of nNOS on the spinal gray matter of the adult rat decreased, eNOS activity increased. Different from the adult rat, expression of the nNOS in the young rat was maintained until 1 day after SCI, and compared with the adult rat; eNOS activity was increased in the vessels from the damaged gray matter area after 7 days of SCI. iNOS expression was maintained until the 7th day of SCI on the adult rat, but iNOS expression after 7 days of SCI on young rat decreased. The young rat showed relatively less motor disability on the hind limb when compared with the adult rat, and had a rapid recovery.

CONCLUSION

Neural protective eNOS activity increased after SCI in the young rat, and neural destructive iNOS expression was more remarkable in the adult rat.

Phosphorylation of neuronal nitric oxide synthase at Ser847 in the nucleus intermediolateralis after spinal cord injury in mice

We previously demonstrated that Ca2+/calmodulin (CaM)-dependent protein kinase IIalpha (CaM-KIIalpha) can phosphorylate neuronal nitric oxide synthase (nNOS) at Ser847 and attenuate NOS activity in neuronal cells. In the present study we focused on chronological alteration in levels and cellular location of nNOS, phosphorylated (p)-Ser847-nNOS (NP847), CaM-KII and p-Thr286-CaM-KIIalpha following spinal cord injury (SCI) in mice. Western blot analysis showed nNOS to be significantly phosphorylated at Ser847 from 3 h after SCI, peaking at 24 h and gradually decreasing thereafter, and CaM-KII to be colocalized with nNOS after SCI. Immunohistochemical analysis revealed that SCI causes an increase in both NP847 and p-Thr286-CaM-KIIalpha in the nucleus intermediolateralis. These findings suggest that SCI induces p-Thr286-CaM-KIIalpha, which phosphorylates the nNOS at Ser847 in the nucleus intermediolateralis where NO is thought to play a role as a neurotransmitter in autonomic preganglionic neurons. Thus, the NP847 signaling pathway might be involved in the autonomic failure which occurs immediately after SCI.

Traumatic injury of the spinal cord and nitric oxide

In the current report, we summarize our findings related to the involvement of nitric oxide (NO) in the pathology of spinal cord trauma. We initially studied the distribution of nitric oxide synthase (NOS)-immunolabeled and/or nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd; which is highly colocalized with NOS)-stained somata and fibers in the spinal cord of the rabbit. Segmental and laminar distribution of NADPHd-stained neurons in the rabbit revealed a large number of NADPHd-stained neurons in the spinal cord falling into six categories, N1-N6, while others could not be classified. Large numbers of NADPHd-stained neurons were identified in the superficial dorsal horn and around the central canal. Four morphologically distinct kinds of NADPHd-stained axons 2.5-3.5 microm in diameter were identified throughout the white matter in the spinal cord. Moreover, a massive occurrence of axonal NADPHd-staining was detected in the juxtagriseal layer of the ventral funiculus along the rostrocaudal axis. The prominent NADPHd-stained fiber bundles were identified in the mediobasal and central portion of the ventral funiculus. The sulcomarginal fasciculus was found in the basal and medial portion of the ventral funiculus in all cervical and thoracic segments. Since the discovery that NO may act as a neuronal transmitter, an increasing interest has focused on its ability to modulate synaptic function. NO passes through cell membranes without specific release or uptake mechanisms inducing changes in signal-related functions by several means. In particular, the activation of the soluble guanylyl cyclases (sGC), the formation of cyclic guanosine 3',5'-monophosphate (cGMP) and the action of cGMP-dependent protein kinases has been identified as the main signal transduction pathways of NO in the nervous system including spinal cord. It is known that the intracellular level of cGMP is strictly controlled by its rate of synthesis via guanylyl cyclases (GC) and/or by the rate of its degradation via 3',5'-cyclic nucleotide phosphodiesterases (PDE). GC can be divided into two main groups, i.e., the membrane-bound or particular guanylyl cyclase (pGC) and the cytosolic or sGC. In the spinal cord, the activation of pGC has only been demonstrated for natriuretic peptides, which stimulate cGMP accumulation in GABA-ergic structures in laminae I-III of the rat cervical spinal cord. These neurons are involved in controlling the action of the locomotor circuit. In view of the abundance of NO-responsive structures in the brain, it is proposed that NO-cGMP signaling will be part of neuronal information processing at many levels. In relation to this, we found that surgically induced Th7 constriction of 24 h duration stimulated both the constitutive NOS activity and cGMP level by 120 and 131%, respectively, in non-compartmentalized white matter of Th8-Th9 segments, located just caudally to the site of injury. NO-mediated cGMP formation was only slightly increased in the dorsal funiculus of Th5-Th9 segments. There are some other sources that may influence the NO-mediated cGMP formation in spinal cord. A high level of glutamate produced at the site of the lesion and an excessive accumulation of intracellular Ca2+ may stimulate NOS activity and create suitable conditions for NO synthesis and its adverse effect on white matter. An increased interest has focused on the role of NO at the site of injury and in areas located close to the epicenter of the impact site and, in these connections an upregulation of NOS was noted in neurons and interneurons. However, the upregulation of NOS expression was also seen in interneurons located just rostrally and caudally to the lesion. A quantitative analysis of laminar distribution of multiple cauda equina constriction (MCEC) induced NADPHd-stained neurons revealed a considerable increase in these neurons in laminae VIII-IX 8h postconstriction, and a highly statistically significant increase of such neurons in laminae VII-X 5 days postconstriction in the lumbosacral segments. Concurrently, the number of NADPHd-stained neurons on laminae I-II in LS segments was greatly reduced. It is concluded that a greater understanding of NO changes after spinal cord trauma is essential for the possibility of targeting this pathway therapeutically.

Acute alterations of glutamate, glutamine, GABA, and other amino acids after spinal cord contusion in rats

Spinal cord injury (SCI) leads to an alteration of energetic metabolism. As a consequence, glutamate, glutamine, aspartate and other important amino acids are altered after damage, leading to important disregulation of the neurochemical pathways. In the present study, we characterized the acute-phase changes in tissue concentration of amino acids involved in neurotransmitter and non-neurotransmitter actions after SCI by contusion in rats. Animals were submitted to either laminectomy or SCI by contusion and sacrificed at 2, 4, 8, and 12 h after lesion, for the analysis of tissue amino acids by HPLC. Results showed that both aspartate and glutamate contents diminished after SCI, while glutamine concentrations raised, however, the sum of molar concentrations of glutamate plus glutamine remained unchanged at all time points. GABA concentrations increased versus control group, while glycine remained unchanged. Finally, citrulline levels increased by effect of SCI, while taurine-increased only 4 h after lesion. Results indicate complex acute-phase changes in amino acids concentrations after SCI, reflecting the different damaging processes unchained after lesion.

The Effect of a Spinal Cord Hemisection on Changes in Nitric Oxide Synthase Pools in the Site of Injury and in Regions Located Far Away from the Injured Site

1. The present study was designed to examine the nitric oxide synthase activities (constitutive and inducible) in the site of injury in response to Th10-Th11 spinal cord hemisection and, to determine whether unilateral disconnection of the spinal cord influences the NOS pools on the contra- and ipsilateral sides in segments located far away from the epicentre of injury. 2. A radioassay detection was used to determine Ca(2+)-dependent and inducible nitric oxide synthase activities. Somal, axonal and neuropil neuronal nitric oxide synthase was assessed by immunocytochemical study. A quantitative assessment of neuronal nitric oxide synthase immunoreactivity was made by an image analyser. The level of neuronal nitric oxide synthase protein was measured by the Western blot analysis. 3. Our data show the increase of inducible nitric oxide synthase activity and a decrease of Ca(2+)-dependent nitric oxide synthase activity in the injured site analysed 1 and 7 days after surgery. In segments remote from the epicentre of injury the inducible nitric oxide synthase activity was increased at both time points. Ca(2+)-dependent nitric oxide synthase activity had decreased in L5-S1 segments in a group of animals surviving for 7 days. A hemisection performed at thoracic level did not cause significant difference in the nitric oxide synthase activities and in the level of neuronal nitric oxide synthase protein between the contra- and ipsilateral sides in C6-Th1 and L5-S1 segments taken as a whole. Significant differences were observed, but only when the spinal cord was analysed segment by segment, and/or was divided into dorsal and ventral parts. The cell counts in the cervicothoracic (C7-Th1) and lumbosacral (L5-S1) enlargements revealed changes in neuronal nitric oxide synthase immunoreactivity on the ipsilateral side of the injury. The densitometric area measurements confirmed the reduction of somal, neuropil and axonal neuronal nitric oxide synthase immunoreactive staining in the ventral part of rostrally oriented segments. 4. Our findings provide evidence that the changes in nitric oxide synthase pools are limited not only to impact zone, but spread outside the original lesion. The regional distribution of nitric oxide synthase activity and neuronal nitric oxide synthase immunoreactivity, measured segment by segment shows that nitric oxide may play a significant role in the stepping cycle in the quadrupeds.

Early nuclear factor–κB activation and inducible nitric oxide synthase expression in injured spinal cord neurons correlating with a diffuse reduction of constitutive nitric oxide synthase activity

Object

Because of toxicity at high concentrations, nitric oxide (NO) contributes to spinal cord injury (SCI) secondary lesions. At low concentrations NO modulates nuclear factor–κB (NF-κB) activation. The authors investigated the activity of neuronal and endothelial NO synthase (nNOS and eNOS) to determine correlations with NF-κB activation and inducible NOS (iNOS) expression soon after SCI.

Methods

In 48 adult male Wistar rats clip-based (50 g/mm2/10 seconds) SCI was induced, and spinal cords were removed at different intervals for the following evaluations: 1) assaying specific activity of nNOS and eNOS; 2) electrophoresis mobility shift assay for activated NF-κB; 3) Northern blotting for iNOS; 4) immunohistochemistry for iNOS and NF-κB; and 5) immunofluorescence for iNOS and NF-κB.

At 15 minutes postinjury, eNOS activity decreased significantly (p < 0.001), as did nNOS activity at 1 hour compared with these levels in control animals and rats killed at 15 and 30 minutes after SCI (p < 0.001). Basal NF-κB levels were variable in controls and at 15 and 30 minutes after injury. One hour postinjury, NF-κB activation was diffuse. Inducible NOS messenger RNA localized diffusely, peaking 6 hours after injury and remaining stable until 24 hours postinjury. Immunohistochemical analysis showed diffuse iNOS and NF-κB staining, especially in neurons inside and around the lesion. Immunofluorescence demonstrated that injured neurons were a source of NF-κB and iNOS soon after injury.

Conclusions

Both nNOS and eNOS exhibited different regulation and roles soon after injury: nNOS correlated with NF-κB activation, whereas eNOS may have participated in vascular changes of the injured spinal cord. Neurons seemed to play a pivotal role in modulating and amplifying the inflammatory response in the injured spinal cord.

Investigation of the dose-dependent neuroprotective effects of agmatine in experimental spinal cord injury: a prospective randomized and placebo-control trial

OBJECT

No definitive treatment for spinal cord injuries (SCIs) exists, and more research is required. The use of agmatine [4-(aminobutyl)-guanidine-NH2-CH2-CH2-CH2-CH2-NH-C(-NH2)(=NH)], a guanidinium compound formed by decarboxylation of L-arginine by arginine decarboxylase, is a neurotransmitter-neuromodulator with both N-methyl-D-aspartate receptor (NMDAR)-antagonizing and nitric oxide synthase (NOS)-inhibiting activities. The purpose of this study was to demonstrate the dose-dependent activity of agmatine, an inducible NOS (iNOS) inhibitor and selective NMDAR antagonist, on biochemical and functional recovery in an experimental rat SCI model.

METHODS

This study involved 40 Wistar albino male rats. The rats were subjected to sleep-awake cycles for 7 days before surgery. In each group, general anesthesia was induced by a 60-mg/kg ketamine injection. For the surgical SCI model, a Yaşargil aneurysm clip was placed in the spinal cord. The study was conducted in the following four main groups: Group I (control group) laminectomy only; Group II, trauma-only group and SCI; Group III, laminectomy, SCI and agmatine 50 mg/kg for 10 days; and Group IV, laminectomy, SCI, and agmatine 100 mg/kg for 10 days. On Day 1, no statistical difference was observed in any group (p < 0.005, analysis of variance [ANOVA] and the Fisher protected least significant difference [PLSD]). On Day 2, no statistical difference was noted among Groups II, III, and IV (p = 0.27, p = 0.42, and p = 0.76, respectively; ANOVA and Fisher PLSD). Beginning on Day 3, recovery in Groups III and IV differed significantly from that in Group II (p < 0.005, ANOVA and Fisher PLSD), and a statistically significant difference between Groups III and IV was observed, which also was present on Days 5, 7, and 10 (p = 0.003, p = 0.0024, and p = 0.0036, respectively; ANOVA and Fisher PLSD). Several observations were noteworthy: motor function scores were reduced significantly in the spinal cord-injured rats compared with the controls (p < 0.005); on Day 1, the agreement of motor function scores in rats in each SCI group indicated that the traumatic event had been replicated equally across all groups (p = 0.59, p = 0.59, and p = 0.28); a statistically significant difference in motor function scores developed on Day 3 between the rats subjected to trauma alone (Group II) and those treated with agmatine (Groups III and IV) (p < 0.005); and no statistically significant intergroup difference in motor function existed at any postinjury interval between the 50- and 100-mg/kg/day agmatine-treated rats (p > 0.005).

CONCLUSIONS

Agmatine administration following SCI was shown to reduce NO levels significantly. No statistically significant intergroup difference in the reduction of NO levels was found between rats treated with 50- and 100-mg/kg/day doses of agmatine. Administration of a 100-mg/kg/day dose of agmatine reduced the NO levels to those measured in controls. The authors conclude that with additional studies into the role of agmatine, this drug may be helpful in the treatment of patients with SCIs.

Signaling pathways mediating a selective induction of nitric oxide synthase II by tumor necrosis factor alpha in nerve growth factor-responsive cells

Background

Inflammation and oxidative stress play a critical role in neurodegeneration associated with acute and chronic insults of the nervous system. Notably, affected neurons are often responsive to and dependent on trophic factors such as nerve growth factor (NGF). We previously showed in NGF-responsive PC12 cells that tumor necrosis factor alpha (TNFα) and NGF synergistically induce the expression of the free-radical producing enzyme inducible nitric oxide synthase (iNOS). We proposed that NGF-responsive neurons might be selectively exposed to iNOS-mediated oxidative damage as a consequence of elevated TNFα levels. With the aim of identifying possible therapeutic targets, in the present study we investigated the signaling pathways involved in NGF/TNFα-promoted iNOS induction.

Methods

Western blotting, RT-PCR, transcription factor-specific reporter gene systems, mutant cells lacking the low affinity p75NTR NGF receptor and transfections of TNFα/NGF chimeric receptors were used to investigate signalling events associated with NGF/TNFα-promoted iNOS induction in PC12 cells.

Results

Our results show that iNOS expression resulting from NGF/TNFα combined treatment can be elicited in PC12 cells. Mutant PC12 cells lacking p75NTR did not respond, suggesting that p75NTR is required to mediate iNOS expression. Furthermore, cells transfected with chimeric TNFα/NGF receptors demonstrated that the simultaneous presence of both p75NTR and TrkA signaling is necessary to synergize with TNFα to mediate iNOS expression. Lastly, our data show that NGF/TNFα-promoted iNOS induction requires activation of the transcription factor nuclear factor kappa B (NF-κB).

Conclusion

Collectively, our in vitro model suggests that cells bearing both the high and low affinity NGF receptors may display increased sensitivity to TNFα in terms of iNOS expression and therefore be selectively at risk during acute (e.g. neurotrauma) or chronic (e.g. neurodegenerative diseases) conditions where high levels of pro-inflammatory cytokines in the nervous system occur pathologically. Our results also suggest that modulation of NFκB-promoted transcription of selective genes could serve as a potential therapeutic target to prevent neuroinflammation-induced neuronal damage.

Cyclosporin-A Inhibits Constitutive Nitric Oxide Synthase Activity and Neuronal and Endothelial Nitric Oxide Synthase Expressions after Spinal Cord Injury in Rats

Nitric oxide (NO) plays a role in the pathophysiology of spinal cord injury (SCI). NO is produced by three types of nitric oxide synthase (NOS) enzymes: The constitutive Ca2+/calmodulin-dependent neuronal NOS (nNOS) and endothelial NOS (eNOS) isoforms, and the inducible calcium-independent isoform (iNOS). During the early stages of SCI, nNOS and eNOS produce significant amounts of NO, therefore, the regulation of their activity and expression may participate in the damage after SCI. In the present study, we used Cyclosporin-A (CsA) to further substantiate the role of Ca-dependent NOS in neural responses associated to SCI. Female Wistar rats were subjected to SCI by contusion, and killed 4 h after lesion. Results showed an increase in the activity of constitutive NOS (cNOS) after lesion, inhibited by CsA (2.5 mg/kg i.p.). Western blot assays showed an increased expression of both nNOS and eNOS after trauma, also antagonized by CsA administration.