The dose-dependent neuroprotective effect of alpha-lipoic acid in experimental spinal cord injury

Background and purposeFree radical production after spinal cord injury (SCI) plays an important role in secondary damage. The aim of this study was to investigate neuroprotective effects of the powerful antioxidant alpha-lipoic acid (ALA) in a spinal cord clip compression injury model.Material and methodsFifty-six Sprague-Dawley rats, weighing between 210 and 300 g, were randomly divided into seven groups. Spinal cord injury was performed by an aneurysm clip placed extradurally at the level of T9. Group 1 (sham) received laminectomy only. Group 2 (control) received SCI; Group 3 received 30 mg/kg of methylprednisolone sodium succinate (MPSS); Groups 4, 5, 6 and 7 received ALA at doses of 50, 100, 150, 200 mg/kg, respectively, via the intraperitoneal route immediately after SCI. The rats were neurologically tested 24 hours after trauma. Spinal cord samples from injury sites were harvested for measurement of lipid peroxidation products and histopathological evaluation.ResultsSpinal cord malonyldialdehyde levels of rats in treatment groups decreased after administration of ALA. The difference between the trauma group and groups receiving MPSS-ALA was statistically significant. The difference between the ALA (50, 100, 150 mg/kg) and MPSS groups was insignificant. Group 7 (ALA 200 mg/kg) was excluded from the study because of the possible toxic effect. Alpha lipoic acid and MPSS had similar effects on spinal cord injury in terms of lipid peroxidation, neurological recovery and histopathological changes.ConclusionsAlpha lipoic acid at a dose range of 50–150 mg/kg is as effective as MPSS (30 mg/kg) in neuroprotection after SCI. Further, more detailed experimental studies are needed to determine the effects of ALA on the detrimental results of secondary SCI before its use in humans.     

Comparative neuroprotective effect of sodium channel blockers after experimental spinal cord injury.

Spinal cord injury (SCI) results in loss of function below the lesion. Secondary injury following the primary impact includes a number of biochemical and cellular alterations leading to tissue necrosis and cell death. Influx of Na(+) ions into cells has been postulated to be a key early event in the pathogenesis of secondary traumatic and ischemic central nervous system injury. Previous studies have shown that some voltage-sensitive sodium channel blockers provide powerful neuroprotection. The purpose of the present study was to compare the neuroprotective effect of three sodium channel blockers-mexiletine, phenytoin and riluzole--after SCI. Ninety rats were randomly and blindly divided into five groups of 18 rats each: sham-operated group, trauma group (bolus injection of 1 mL physiological saline intraperiteonally [i.p.]), mexiletine treatment group (80 mg/kg, i.p.), phenytoin treatment group (200 mg/kg, i.p.) and riluzole treatment group (8 mg/kg, i.p.). Twenty-four hours after injury, the rats were killed for determination of spinal cord water content and malondialdehyde (MDA) levels. Motor function scores of six rats from each group were evaluated weekly for six weeks. Then the rats were killed for histopathological assessment. Although all the treatment groups revealed significantly lower MDA levels and spinal cord edema than the trauma group (p<0.05), the riluzole and mexiletine treatment groups were better than the phenytoin treatment group. In the chronic stage, riluzole and mexiletine treatment achieved better results for neurobehavioral and histopathological recovery than phenytoin treatment. In conclusion, all the tested Na(+) blockers had a neuroprotective effect after SCI; riluzole and mexiletine were superior to phenytoin.     

Lampreys as an animal model in regeneration studies after spinal cord injury

Spinal cord injuries are an important sanitary and economical problem for the society. In mammals, including humans, a traumatic injury to the spinal cord leads to a loss of motor and sensorial function, which is irreversible due to the low regenerative ability of the central nervous system. In contrast to mammals, functional recovery occurs spontaneously after a complete spinal cord transection in lampreys. Functional recovery occurs because in these animals about 50% of the reticulospinal axons regenerate after injury and also because of the occurrence of processes of reorganization and plasticity of the spinal circuits. In this review, we first analyze the characteristics and regeneration ability of lampreys as compared to mammals. Then, we compile the knowledge about the process of recovery after a spinal cord injury acquired in studies using the lampreys as animal model and finally we provide some general perspectives about the molecular processes implicated in regeneration that can be investigated in a very advantageous way in this animal model and which knowledge could allow to develop new therapies for patients suffering spinal cord injury.     

MK-801在脊髓缺血中的神经保护作用

目的地佐环平(MK-801)对脊髓缺血中神经保护作用的研究。方法建立新西兰兔脊髓缺血模型,利用HE染色、原位末端转移酶标记技术(TUNEL)、免疫组化、逆转录反应系统(RT-PCR)等技术检测N-甲基-D-天门冬氨酸受体(N-methyl-D-aspartate receptor,NMDAR)、诱导型一氧化氮合酶(inducible Nitric Oxide Synthase,iNOS)、半胱氨酸天冬氨酸蛋白酶3(Caspase-3)的表达水平,观察不同剂量MK-801在脊髓缺血中的神经保护作用。结果对照组脊髓结构完全消失,低剂量组结构较完整,高剂量组缺血损害程度最轻,假手术组脊髓结构正常。NMDAR、iNOS、Caspase-3等蛋白在神经元中有明确表达。凋亡指数、NMDAR、iNOS、Caspase-3 mRNA表达水平在对照组最高,低剂量组、高剂量组,假手术组则逐渐降低,差别具有统计学意义(P<0.05)。结论 MK-801能抑制神经细胞凋亡,对脊髓缺血具有神经保护作用。     

The neuroprotective effect of treatment of valproic Acid in acute spinal cord injury

Objective

Valproic acid (VPA), as known as histone deacetylase inhibitor, has neuroprotective effects. This study investigated the histological changes and functional recovery from spinal cord injury (SCI) associated with VPA treatment in a rat model.

Methods

Locomotor function was assessed according to the Basso-Beattie-Bresnahan scale for 2 weeks in rats after receiving twice daily intraperitoneal injections of 200 mg/kg VPA or the equivalent volume of normal saline for 7 days following SCI. The injured spinal cord was then examined histologically, including quantification of cavitation.

Results

Basso-Beattie-Bresnahan scale scores in rats receiving VPA were significantly higher than in the saline group (p<0.05). The cavity volume in the VPA group was significantly reduced compared with the control (saline-injected) group (p<0.05). The level of histone acetylation recovered in the VPA group, while it was significantly decreased in the control rats (p<0.05). The macrophage level was significantly decreased in the VPA group (p<0.05).

Conclusion

VPA influences the restoration of hyperacetylation and reduction of the inflammatory reaction resulting from SCI, and is effective for histology and motor function recovery.     

Topiramate as a neuroprotective agent in a rat model of spinal cord injury

Topiramate(TPM) is a widely used antiepileptic and antimigraine agent which has been shown to exert neuroprotective effects in various experimental traumatic brain injury and stroke models. However, its utility in spinal cord injury has not been studied extensively. Thus, we evaluated effects of TPM on secondary cellular injury mechanisms in an experimental rat model of traumatic spinal cord injury(SCI). After rat models of thoracic contusive SCI were established by free weight-drop method, TPM(40 mg/kg) was given at 12-hour intervals for four times orally. Post TPM treatment, malondialdehyde and protein carbonyl levels were significantly reduced and reduced glutathione levels were increased, while immunoreactivity for endothelial nitric oxide synthase, inducible nitric oxide synthase, and apoptotic peptidase activating factor 1 was diminished in SCI rats. In addition, TPM treatment improved the functional recovery of SCI rats. This study suggests that administration of TPM exerts neuroprotective effects on SCI.     

Strapping the spinal cord: an innovative experimental model of CNS injury in rats

Experimental models of spinal cord (SC) lesion are essential for understanding a few of the primary and secondary mechanisms of injury and functional recovery of the central nervous system (CNS). We have developed an experimental model of SC injury in adult rats (n=32), that involves the use of a device (SC-STRAPPER) that straps the SC and promotes gradual and controlled SC injury similar to clinical compressive SC injuries. SC strapping is a less-invasive procedure in comparison to other SC injury models, and it performs compression with smaller infection risk and undetectable paravertebral or vertebral lesions. The survival of the rats was 100%, minimizing the suffering of the animals. We have analyzed the histopathological changes that occur during experimental SC compression, as well as the immunohistochemical labeling for glial fibrillary acidic protein (GFAP). Animals survived for 21 days being thereafter anesthetized and perfused with aldehydes. SC lesions were associated with motor deficits and local increase in GFAP immunolabeling proportionate to the severity of the compression. This experimental model represents a potential contribution for neuroscientific research, providing a low-cost and rather simple system of controllable and reproducible SC experimental damage.     

In vivo serial diffusion tensor imaging of experimental spinal cord injury

In vivo longitudinal diffusion tensor imaging (DTI) of rodent spinal cord injury (SCI) was carried out over a period of eight weeks post-injury. A balanced, rotationally invariant, alternating gradient polarity icosahedral diffusion encoding scheme was used for an unbiased estimation of the DTI metrics. The fractional anisotropy (FA), diffusivities along (longitudinal), and perpendicular (transverse) to the fiber tracts, were estimated for the ventral, dorsal, and lateral white matter. In all the three regions, the DTI metrics were observed to be significantly different in injured cords relative to the uninjured controls close to the epicenter of the injury. However, these differences gradually disappeared away from the epicenter. The spatio-temporal changes in the DTI metrics showed a recovery pattern that is region specific. Although the temporal trends in the tissue recovery in rostral and caudal sections seem to be similar, overall the DTI metrics were observed to be closer to the normal tissue values in the caudal relative to the rostral sections (rostral-caudal asymmetry).     

Characterization of a novel bidirectional distraction spinal cord injury animal model

Scoliosis corrective surgery requires the application of significant multidirectional stress forces, including distraction, for correction of the curved spine deformity and the application of fixation rods. If excessive, spine distraction may result in the development of new neurological deficits, some as severe as permanent paralysis. Current animal models of spinal cord injury, however, are limited to contusion, transection, or unidirectional distraction injuries, which fail to replicate the multidirectional forces that occur during spine corrective surgery. To address such limitation, we designed a novel device that relies on intervertebral grip fixation and linear actuators to induce controllable bidirectional distraction injuries to the spine. The device was tested in three (i.e., 3, 5, and 7 mm) distention paradigms of the rat T9-T11 vertebra, and the resulting injuries were evaluated through electrophysiological, behavioral, and histological analysis. As expected, 3mm bilateral spine distractions showed no neurological deficit. In contrast, those with 5 and 7 mm showed partial and complete paralysis, respectively. The relationship between the severity of the spine distraction and injury to the spinal cord tissue was determined using glial fibrillary acidic protein immunocytochemistry for visualization of reactive astrocytes and labeling of ED1-positive activated macrophages/microglia. Our results demonstrate that this device can produce bidirectional spine distraction injuries with high precision and control and, thus, may be valuable in contributing to the testing of neuroprotective strategies aimed at preventing unintended new neurological damage during corrective spine surgery.     

Evaluation of spinal cord injury animal models

Because there is no curative treatment for spinal cord injury, establishing an ideal animal model is important to identify injury mechanisms and develop therapies for individuals suffering from spinal cord injuries. In this article, we systematically review and analyze various kinds of animal models of spinal cord injury and assess their advantages and disadvantages for further studies.     

Immunomodulation as a neuroprotective strategy after spinal cord injury

正The initial trauma to the spinal cord is just the starting point for a cascade of endogenous events that will collectively determine the injury extension.These secondary events include,but are not limited to:glutamate excitoxicity,induction of apoptotic pathways,ionic imbalances and the development of a strong and dysfunctional inflammatory response.The secondary injury is associated to an aggravation of neuronal damage increasing the extent of neurological deficits(Ek et al.,2010).     

脊髓损伤大鼠损伤早期电位变化与损伤程度的关系

To investigate characteristics of injury potentials after different degrees of spinal cord injury in rats,the present study established models of spinal cord contusion with severe,moderate,and mild degrees of injury.Injury potential was measured in vivo using a direct current voltage amplification system.Results revealed that in the first 4 hours after acute spinal cord injury,initial amplitude of injury potential was greatest after severe injury,followed by moderate and mild injuries.Amplitude of injury potential decreased gradually with injury time,and the recession curve was logarithmic.Under the same degree of injuries,amplitude of rostral injury potential was generally less than caudal injury potential.Results suggested that injury potential reflected injury severity,because large initial amplitude of injury potential during the early injury stage implied severe injury.     

Hemodynamic parameters and neurogenic pulmonary edema following spinal cord injury: an experimental model

Neurogenic pulmonary edema is a serious and always life-threatening complication following several lesions of the central nervous system. We report an experiment with 58 Wistar-Hanover adult male rats. Two groups were formed: control (n=4) and experimental (n=54). The experimental group sustained acute midthoracic spinal cord injury by Fogarty's balloon-compression technique containing 20 microL of saline for 5, 15, 30 or 60 seconds. The rats were anesthetized by intraperitoneal (i.p.) sodium pentobarbital (s.p.) 60 mg/Kg. The quantitative neurological outcome was presented at 4, 24 and 48 hours from compression to characterize the injury graduation in different groups. Poor outcome occurred with 60 seconds of compression. Six animals died suddenly with pulmonary edema. Using the procedure to investigate the pulmonary edema during 60 seconds of compression, followed by decompression and time-course of 60 seconds, 20 rats were randomly assigned to one of the following groups: control (1, n=4, anesthetized by i.p. s.p., 60 mg/Kg but without compression) and experimental (2, n=7, anesthetized by i.p. xylazine 10 mg/Kg and ketamine 75 mg/Kg) and (3, n=9, anesthetized by i.p. s.p., 60 mg/Kg). The pulmonary index (100 x wet lung weight/body weight) was 0.395 +/- 0.018 in control group, rose to 0.499 +/- 0.060 in group 2, and was 0.639 +/- 0.14 in group 3. Histologic examination of the spinal cord showed parenchymal ruptures and acute hemorrhage. Comparison of the pulmonary index with morphometric evaluation of edema fluid-filled alveoli by light microscopy showed that relevant intra-alveolar edema occurred only for index values above 0.55. The results suggest that the pulmonary edema induced by spinal compression is of neurogenic nature and that the type of anesthesia used might be important for the genesis of lung edema.     

Antioxidant therapy in experimental spinal cord injury

We have tested the capacity of several compounds with in vitro and/or in vivo antioxidant or antilipolytic activity to ameliorate locomotor function in cats subjected to static loading (i.e. compression) injury of the spinal cord. These include the synthetic glucocorticoid, methylprednisolone sodium succinate (MP), and the new 21-aminosteroid antioxidant, U74006F. Treatment of spinal cord-injured cats with high doses of MP promoted or spared locomotor function and preserved spinal cord tissue. Extending these findings in cats to humans, it was recently demonstrated that high doses of MP administered within 8 h of injury significantly improved neurologic recovery in human spinal cord-injured patients. The compound U74006F is one of a series of 21-aminosteroids that, unlike MP, lack glucocorticoid, mineralocorticoid or other hormonal activity yet are potent inhibitors of lipid perioxidation. Over a 100-fold range of doses, U74006F promoted recovery of locomotor function in spinal cord-injured cats. The lowest effective dose for U74006F was 100 times lower than the maximally effective dose for MP. The efficacy of U74006F is unchanged if treatment is initiated within 4 h of injury. However, if treatment is delayed for 8 h, the therapeutic potency of U74006F is substantially reduced. These findings suggest that antioxidant therapy can successfully limit the effects of both experimental and clinical spinal cord injury especially if the treatment is initiated shortly after injury.     

Vascular permeability in experimental spinal cord injury

Following spinal cord injury in rats there was a time-dependent change of vascular permeability as reflected by extravasation of ¹²⁵I-labelled serum albumin. The change of vascular permeability correlated with tissue calcium and water accumulation suggesting that cord exposure to plasma calcium as a consequence of vascular injury may contribute to the progressive post-traumatic cord necrosis.     

Proteolytic enzymes in experimental spinal cord injury

Experimental spinal cord injury was produced in rats by dropping a 10 g weight from 30 cm upon dura-invested exposed spinal cord. Proteolytic activities at neutral (pH 7.6) and acid (pH 5.5 and 3.6) pH were determined in whole homogenate and the cytosolic fraction of the lesion (lumbar) and cervical control segments. The enzyme activity was monitored by SDS-PAGE analysis of the extent of substrate myelin basic protein (MBP) degradation. Activities (neutral and cathepsin B-like) in the sham-operated spinal cord were lower than those of cervical autologous control at 24 h after injury. The increase in neutral proteinase activity was progressive and greater in the lesion than the autologous control. A 61.5% +/- 3.5 loss of MBP was observed at 2 h following injury and increased at 24 h (78.2% +/- 3.4). The loss of MBP coincided with the appearance of several low molecular weight peptides. The cathepsin B-like and cathepsin D activities were also increased in the lesion but to a lesser extent than the neutral proteinase. The neutral proteinase and cathepsin B-like activity were inhibited by leupeptin and not by pepstatin while the converse obtained for cathepsin D activity. The release of neutral proteolytic activity which is nonlysosomal in origin suggests a novel hypothesis for the mechanism of traumatic axon-myelin injury.     

Induced hypothermia in experimental traumatic spinal cord injury: an update

The use of induced hypothermia in the treatment of traumatic spinal cord injury (SCI) has been studied extensively between the 1960s and 1970s. Although the treatment showed some promise, it became less popular by the 1980s, mainly because of its adverse effects. However, a revival of hypothermia in the treatment of traumatic brain injury (TBI) in the last decade has encouraged neuroscientists to conduct experiments to reevaluate the potential benefits of hypothermia in traumatic SCI. All laboratory investigations studying the mechanisms of action and/or the efficacy of induced hypothermia in treating experimental traumatic SCI published in the last decade were reviewed. Although efficacy of hypothermia in improving functional outcome of mild to moderate traumatic SCI has been demonstrated, hypothermia may not be protective against severe traumatic SCI. At present, induced hypothermia has yet to be recognized or approved as a potential treatment having therapeutic value for traumatic SCI in humans. The continued search for a possible synergistic effect of induced hypothermia and pharmacological therapy may yield some promise. It has also been deduced from these laboratory studies that hyperthermia is deleterious and rigorous measures to prevent hyperthermia should be taken to minimize the propagation of secondary neuronal damage after traumatic SCI.     

Neuroprotective effect of etomidate on functional recovery in experimental spinal cord injury

OBJECTIVE: Primary impact to the spinal cord causes rapid oxidative stress after injury. To protect neural tissue, it is important to prevent secondary pathophysiological mechanisms. Etomidate, a strong antiexcitotoxic agent, stimulates the gamma aminobutyric acid (GABA) receptors. The purpose of this study was to investigate neurobehavioral and histological recovery and to evaluate the biochemical responses to treatment of experimental spinal cord injury (SCI) in rats with etomidate or methylprednisolone (MP) or both etomidate and MP. MATERIAL AND METHODS: Seventy-two rats were randomly allocated into six groups: a control group (laminectomy alone), a trauma group (laminectomy+trauma), a methylprednisolone group (30 mg/kg MP), an etomidate group (2 mg/kg), a methylprednisolone and etomidate combined treatment group (30 mg/kg MP and 2 mg/kg etomidate) and a vehicle group. Six rats from each group were killed at the 24th hour after the injury. Malondialdehyde, glutathione, nitric oxide and xanthine oxidase levels were measured. Neurological functions of the remaining rats were recorded weekly. Six weeks after injury, all of those rats were killed for histopathological assessment. RESULTS: Etomidate treatment revealed similar neurobehavioral and histopathological recovery to MP treatment 6 weeks after injury. Combined treatment did not provide additional neuroprotection. CONCLUSION: Etomidate treatment immediately after spinal cord injury has similar neuroprotection to MP. In spite of different neuroprotection mechanisms, combined treatment with MP and etomidate does not provide extra protection.     

Hemorrhagic changes in experimental spinal cord injury models

Early hemorrhagic changes in the spinal cord were compared in three experimental spinal cord injury models in the rat in order to determine the nature and consistency of spinal cord hemorrhage following specific and quantitated forces of injury. The spinal cords were injured by weight-dropping, aneurysm clip and extradural balloon compression techniques. Hemorrhagic changes were assessed quantitatively by the image analyser at 1 and 3 hours after injury. Tissue damage was assessed by determining the percentage of total cross sectional area containing hemorrhage. The extent of hemorrhage at site of injury in the clip and balloon preparations was equal, but several times lower in the weight-drop induced injury. Within each experimental group no appreciable differences were observed at the site of injury between the 1 and 3 hours preparations. The variability of damage within experimental groups was most in the weight-dropping and balloon and least in the clip preparations. Differences were also indicated with respect to the distribution of hemorrhage in grey versus white matter. These findings may be of significance when functional recovery is considered in various experimental acute spinal cord injury models.