Neuronal apoptosis and necrosis following spinal cord ischemia in the rat

Dietary restriction may attenuate the expression of cell death-related proteins in rats with acute spinal cord injury

OBJECTIVE

There is currently no effective treatment for spinal cord injuries (SCI). Previous studies have shown that every-other-day fasting (EODF), a dietary restriction method, can reduce SCI size and promote motor function recovery, making it a potential novel treatment. However, the mechanism that underlies the positive impact of EODF on SCI remains unclear. Caspase-dependent apoptosis and necroptosis, which involve receptor-interacting protein kinase (RIPK), drive the loss of nerve cells and restrict motor function recovery after SCI. Dietary restriction has a significant inhibitory effect on Caspase and RIPK expression. This study aimed to investigate whether the EODF diet achieves a neuroprotective effect by inhibiting Caspase-dependent apoptosis and RIPK-dependent necroptosis after SCI.

METHODS

The model rats underwent EODF for 4 weeks before SCI or started EODF diet immediately after SCI. Immunoblotting and immunohistochemical analyses were used to assess the impact of the intervention on protein expression. Apoptosis in the spinal cord was detected by TdT-mediated dUTP nick-end labeling (TUNEL).

RESULTS

Immunoblotting analysis results revealed that the levels of both RIPK1 and RIPK3 proteins in the injury zone were reduced at 6, 12, and 24 h, and at 3 and 7 days after SCI, respectively. Immunohistochemistry results showed that EODF reduced the expression of Caspase-3 and Bax proteins, while prophylactic EODF decreased the rate of apoptosis detected by TUNEL within 3 days after SCI.

CONCLUSIONS

These findings indicate that the mechanism by which EODF exerts neuroprotective effects may be related to the simultaneous inhibition of apoptosis and necroptosis in SCI.

Neurological safety of spinal surgery for nucleus pulposus removal under spinal endoscopic imaging guided by inter laminar spine

Objective

To explore the technical points, approach selection and short-term clinical efficacy of PELD through the intervertebral foramina or interlaminar approach in the treatment of highly shifted LDH.

Methods

From September 2018 to June 2020, 19 patients with highly shifted LDH were treated with PELD in The First Hospital of Yulin. It included, 10 males and 9 females; aged 34 to 69 years, with an average of 48 years. Thirteen cases were shifted to the caudal side, and six cases were shifted to the head side. The responsible segments included L3/41 cases, L4/511 cases, and L5/S17 cases. All patients had symptoms of low back and leg pain. The Sowerby dysfunction index (ODI) was 63.5%±10.7% before surgery. The visual analogue scale of pain (VAS) was low back pain (5.2±2.1) and leg pain (7.1±2.4). 14 cases used transforaminal approach, and 5 cases used translaminar approach.

Results

All cases completed the operation successfully, the operation time was 60~110min, with an average of 70 minutes. The follow-up time ranged from 6 to 42 months, with an average of 20.8 months. At the last follow-up, ODI was 10.8%±6.8%, VAS back pain score (2.1±1.1) and leg pain score (1.8±0.9). Compared with preoperative, ODI and VAS scores were significantly decreased (P<0.05). The results of Mac Nab method were 14 excellent, four good, and one fair. During the follow-up period, one patient's leg pain symptoms recurred seven days after operation. No further hernia was found under intervertebral foramen. The symptoms disappeared after two weeks of symptomatic treatment such as swelling and analgesia, and he was discharged. No perioperative complications such as infection and nerve root injury occurred.

Conclusion

When PELD is used to treat high-displacement LDH, the choice of transforaminal approach or interlaminar approach needs to be personalized according to the LDH segment and the direction of displacement.

Biochemical, pathological and ultrastructural investigation of whether lamotrigine has neuroprotective efficacy against spinal cord ischemia reperfusion injury

INTRODUCTION

Lamotrigine, an anticonvulsant drug with inhibition properties of multi-ion channels, has been shown to be able to attenuates secondary neuronal damage by influencing different pathways. The aim of this study was to look into whether lamotrigine treatment could protect the spinal cord from experimental spinal cord ischemia-reperfusion injury.

MATERIALS AND METHODS

Thirty-two rats, eight rats per group, were randomly assigned to the sham group in which only laparotomy was performed, and to the ischemia, methylprednisolone and lamotrigine groups, where the infrarenal aorta was clamped for thirty minutes to induce spinal cord ischemia-reperfusion injury. Tissue samples belonging to spinal cords were harvested from sacrificed animals twenty-four hours after reperfusion. Tumor necrosis factor-alpha levels, interleukin-1 beta levels, nitric oxide levels, superoxide dismutase activity, catalase activity, glutathione peroxidase activity, malondialdehyde levels and caspase-3 activity were studied. Light and electron microscopic evaluations were also performed to reveal the pathological alterations. Basso, Beattie, and Bresnahan locomotor scale and the inclined-plane test was used to evaluate neurofunctional status at the beginning of the study and just before the animals were sacrificed.

RESULTS

Lamotrigine treatment provided significant improvement in the neurofunctional status by preventing the increase in cytokine expression, increased lipid peroxidation and oxidative stress, depletion of antioxidant enzymes activity and increased apoptosis, all of which contributing to spinal cord damage through different paths after ischemia reperfusion injury. Furthermore, lamotrigine treatment has shown improved results concerning the histopathological and ultrastructural scores and the functional tests.

CONCLUSION

These results proposed that lamotrigine may be a useful therapeutic agent to prevent the neuronal damage developing after spinal cord ischemia-reperfusion injury.

Long non-coding RNA TUG1 knockdown prevents neurons from death to alleviate acute spinal cord injury via the microRNA-338/BIK axis

Taurine up-regulated gene 1 (TUG1) is a cancer-associated long noncoding RNA (lncRNA) and engages in the development of spinal cord injury (SCI), a suffering neuropathological disorder. However, the regulatory role of TUG1 in acute SCI (ASCI) is still underdetermined. RT-qPCR and western blot analysis were applied to measure the expression of TUG1, microRNA-338 (miR-338), Bcl2-interacting killer (BIK), cleaved caspase 3 (c-caspase 3) and hypoxia-inducible factor-1 alpha (HIF-1α) in ASCI rats and hypoxic cells. Cell death was evaluated using flow cytometric analysis. The relationships among miR-338, TUG1 or BIK were confirmed by luciferase reporter assay, RNA immunoprecipitation and RNA pull-down. Accordingly, we monitored higher expression of TUG1 and BIK, but lower expression of miR-338 in ASCI rats and hypoxic cells. In vitro, hypoxia expedited cell death and c-caspase 3 levels. In vivo, ASCI rats were successfully developed as evidenced by diminished Basso-Beattie-Bresnahan (BBB) locomotor score and enhanced c-caspase 3 and HIF-1α expression. Nevertheless, TUG1 knockdown mitigated the cell death in ASCI rats and hypoxic cells. Mechanically, TUG1 interacted with miR-338 to regulate the BIK expression. Together, TUG1 silencing could alleviate the death in neurons and ASCI models via modulating the miR-338/BIK axis.

Time-Course Changes and Role of Autophagy in Primary Spinal Motor Neurons Subjected to Oxygen-Glucose Deprivation: Insights Into Autophagy Changes in a Cellular Model of Spinal Cord Ischemia

Spinal cord ischemia is a severe clinical complication induced by thoracoabdominal aortic surgery, severe trauma, or compression to the spinal column. As one of the most important functional cells in the spinal cord, spinal motor neurons (SMNs) suffer most during the process since they are vulnerable to ischemic injury due to high demands of energy. Previous researches have tried various animal models or organotypic tissue experiments to mimic the process and get to know the pathogenesis and mechanism. However, little work has been performed on the cellular model of spinal cord ischemia, which has been hampered by the inability to obtain a sufficient number of pure primary SMNs for in vitro study. By optimizing the isolation and culture of SMNs, our laboratory has developed an improved culture system of primary SMNs, which allows cellular models and thus mechanism studies. In the present study, by establishing an in vitro model of spinal cord ischemia, we intended to observe the dynamic time-course changes of SMNs and investigate the role of autophagy in SMNs during the process. It was found that oxygen-glucose deprivation (OGD) resulted in destruction of neural networks and decreased cell viability of primary SMNs, and the severity increased with the prolonging of the OGD time. The OGD treatment enhanced autophagy, which reached a peak at 5 h. Further investigation demonstrated that inhibition of autophagy exacerbated the injury, evidencing that autophagy plays a protective role during the process.

Regional Hyperexcitability and Chronic Neuropathic Pain Following Spinal Cord Injury

Spinal cord injury (SCI) causes maladaptive changes to nociceptive synaptic circuits within the injured spinal cord. Changes also occur at remote regions including the brain stem, limbic system, cortex, and dorsal root ganglia. These maladaptive nociceptive synaptic circuits frequently cause neuronal hyperexcitability in the entire nervous system and enhance nociceptive transmission, resulting in chronic central neuropathic pain following SCI. The underlying mechanism of chronic neuropathic pain depends on the neuroanatomical structures and electrochemical communication between pre- and postsynaptic neuronal membranes, and propagation of synaptic transmission in the ascending pain pathways. In the nervous system, neurons are the only cell type that transmits nociceptive signals from peripheral receptors to supraspinal systems due to their neuroanatomical and electrophysiological properties. However, the entire range of nociceptive signaling is not mediated by any single neuron. Current literature describes regional studies of electrophysiological or neurochemical mechanisms for enhanced nociceptive transmission post-SCI, but few studies report the electrophysiological, neurochemical, and neuroanatomical changes across the entire nervous system following a regional SCI. We, along with others, have continuously described the enhanced nociceptive transmission in the spinal dorsal horn, brain stem, thalamus, and cortex in SCI-induced chronic central neuropathic pain condition, respectively. Thus, this review summarizes the current understanding of SCI-induced neuronal hyperexcitability and maladaptive nociceptive transmission in the entire nervous system that contributes to chronic central neuropathic pain.

A role for spinal cord hypoxia in neurodegeneration

The vascular system of the spinal cord is particularly complex and vulnerable. Damage to the main vessels or alterations to the regulation of blood flow will result in a reduction or temporary cessation of blood supply. The resulting tissue hypoxia may be brief: acute, or long lasting: chronic. Damage to the vascular system of the spinal cord will develop after a traumatic event or as a result of pathology. Traumatic events such as road traffic accidents, serious falls and surgical procedures, including aortic cross-clamping, will lead to an immediate cessation of perfusion, the result of which may not be evident for several days, but may have long-term consequences including neurodegeneration. Pathological events such as arterial sclerosis, venous occlusion and spinal cord compression will result in a progressive reduction of blood flow, leading to chronic hypoxia. While in some situations the initial pathology is exclusively vascular, recent research in neurodegenerative disease has drawn attention to concomitant vascular anomalies in disorders, including amyotrophic lateral sclerosis, spinal muscular atrophy and muscular sclerosis. Understanding the role of, and tissue response to, chronic hypoxia is particularly important in these cases, where inherent neural damage exacerbates the vulnerability of the nervous system to stressors including hypoxia.

The emerging role of long non-coding RNA in spinal cord injury

Spinal cord injury (SCI) is a significant health burden worldwide which causes permanent neurological deficits, and there are approximately 17,000 new cases each year. However, there are no effective and current treatments that lead to functional recovery because of the limited understanding of the pathogenic mechanism of SCI. In recent years, the biological roles of long non-coding RNAs (lncRNAs) in SCI have attracted great attention from the researchers all over the world, and an increasing number of studies have investigated the regulatory roles of lncRNAs in SCI. In this review, we summarized the biogenesis, classification and function of lncRNAs and focused on the investigations on the roles of lncRNAs involved in the pathogenic processes of SCI, including neuronal loss, astrocyte proliferation and activation, demyelination, microglia activation, inflammatory reaction and angiogenesis. This review will help understand the molecular mechanisms of SCI and facilitate the potential use of lncRNAs as diagnostic markers and therapeutic targets for SCI treatment.

Administration of low dose estrogen attenuates persistent inflammation, promotes angiogenesis, and improves locomotor function following chronic spinal cord injury in rats

Spinal cord injury (SCI) causes loss of neurological function and, depending upon the severity of injury, may lead to paralysis. Currently, no FDA-approved pharmacotherapy is available for SCI. High-dose methylprednisolone is widely used, but this treatment is controversial. We have previously shown that low doses of estrogen reduces inflammation, attenuates cell death, and protects axon and myelin in SCI rats, but its effectiveness in recovery of function is not known. Therefore, the goal of this study was to investigate whether low doses of estrogen in post-SCI would reduce inflammation, protect cells and axons, and improve locomotor function during the chronic phase of injury. Injury (40 g.cm force) was induced at thoracic 10 in young adult male rats. Rats were treated with 10 or 100 μg 17β-estradiol (estrogen) for 7 days following SCI and compared with vehicle-treated injury and laminectomy (sham) controls. Histology (H&E staining), immunohistofluorescence, Doppler laser technique, and Western blotting were used to monitor tissue integrity, gliosis, blood flow, angiogenesis, the expression of angiogenic factors, axonal degeneration, and locomotor function (Basso, Beattie, and Bresnahan rating) following injury. To assess the progression of recovery, rats were sacrificed at 7, 14, or 42 days post injury. A reduction in glial reactivity, attenuation of axonal and myelin damage, protection of cells, increased expression of angiogenic factors and microvessel growth, and improved locomotor function were found following estrogen treatment compared with vehicle-treated SCI rats. These results suggest that treatment with a very low dose of estrogen has significant therapeutic implications for the improvement of locomotor function in chronic SCI. Experimental studies with low dose estrogen therapy in chronic spinal cord injury (SCI) demonstrated the potential for multi-active beneficial outcomes that could ameliorate the degenerative pathways in chronic SCI as shown in (a). Furthermore, the alterations in local spinal blood flow could be significantly alleviated with low dose estrogen therapy. This therapy led to the preservation of the structural integrity of the spinal cord (b), which in turn led to the improved functional recovery as shown (c).

Comparison of Mechanical Allodynia and Recovery of Locomotion and Bladder Function by Different Parameters of Low Thoracic Spinal Contusion Injury in Rats

Background

The present study was designed to examine the functional recovery following spinal cord injury (SCI) by adjusting the parameters of impact force and dwell-time using the Infinite Horizon (IH) impactor device.

Methods

Sprague-Dawley rats (225–240 g) were divided into eight injury groups based on force of injury (Kdyn) and dwell time (seconds), indicated as Force-Dwell time: 150-4, 150-3, 150-2, 150-1, 150-0, 200-0, 90-2 and sham controls, respectively.

Results

After T10 SCI, higher injury force produced greater spinal cord displacement (P < 0.05) and showed a significant correlation (r = 0.813) between the displacement and the force (P < 0.05). In neuropathic pain-like behavior, the percent of paw withdrawals scores in the hindpaw for the 150-4, 150-3, 150-2, 150-1 and the 200-0 injury groups were significantly lowered compared with sham controls (P < 0.05). The recovery of locomotion had a significant within-subjects effect of time (P < 0.05) and the 150-0 group had increased recovery compared to other groups (P < 0.05). In addition, the 200-0 and the 90-2 recovered significantly better than all the 150 kdyn impact groups that included a dwell-time (P < 0.05). In recovery of spontaneous bladder function, the 150-4 injury group took significantly longer recovery time whereas the 150-0 and the 90-2 groups had the shortest recovery times.

Conclusions

The present study demonstrates SCI parameters optimize development of mechanical allodynia and other pathological outcomes.

Mechanical and cellular processes driving cervical myelopathy

Cervical myelopathy is a well-described clinical syndrome that may evolve from a combination of etiological mechanisms. It is traditionally classified by cervical spinal cord and/or nerve root compression which varies in severity and number of levels involved. The vast array of clinical manifestations of cervical myelopathy cannot fully be explained by the simple concept that a narrowed spinal canal causes compression of the cord, local tissue ischemia, injury and neurological impairment. Despite advances in surgical technology and treatment innovations, there are limited neuro-protective treatments for cervical myelopathy, which reflects an incomplete understanding of the pathophysiological processes involved in this disease. The aim of this review is to provide a comprehensive overview of the key pathophysiological processes at play in the development of cervical myelopathy.

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.

CCR5 blockade promotes M2 macrophage activation and improves locomotor recovery after spinal cord injury in mice

Spinal cord injury (SCI) is considered to be primarily associated with loss of motor function and leads to activate diverse cellular mechanisms in the central nervous system to attempt to repair the damaged spinal cord tissue. Chemokine Receptor 5 (CCR5), a major co-receptor for macrophage-tropic human immunodeficiency viruses, is expressed on the surface of monocytes/macrophages, dendritic cells, activated T cells, and NK cells. Recent papers have indicated the important role of CCR5 in SCI, but the mechanism is still unknown. In our current study, CCR5 blockade displayed increased myelin sparring and enhanced SC repair process. The number of CD4(+) T cells, CD8(+) T cells, Ly6G(+) neutrophils and CD11b(+) macrophages were all significantly lower in the anti-CCR5 group than that in the control group after SCI. The IL-4 and IL-13 levels in anti-CCR5 group were markedly higher than that in control group after SCI. Correspondingly, the anti-CCR5-treated group showed increased numbers of Arg1- or CD206-expressing macrophages compared with the control IgG group. Furthermore, CCR5 blockade promoted PPARγ activation, and the increased numbers of M2 macrophages induced by CCR5 blockade were both reversed with additional PPARγ antagonist treatment. In conclusion, our present work provides evidence to support the concept that CCR5 blockade promotes M2 macrophage activation and improves locomotor recovery after SCI in mice.

Minocycline Effectively Protects the Rabbit's Spinal Cord From Aortic Occlusion-Related Ischemia

OBJECTIVES

To identify the minocycline anti-inflammatory and antiapoptotic mechanisms through which it is believed to exert spinal cord protection during aortic occlusion in the rabbit model.

DESIGN

An animal model of aortic occlusion-related spinal cord ischemia. Randomized study with a control group and pre-ischemia and post-ischemia escalating doses of minocycline to high-dose minocycline in the presence of either hyperglycemia, a pro-apoptotic maneuver, or wortmannin, a specific phosphatidylinositol 3-kinase antagonist.

SETTING

Tertiary medical center and school of medicine laboratory.

PARTICIPANTS

Laboratory animals-rabbits.

INTERVENTIONS

Balloon obstruction of infrarenal aorta introduced via femoral artery incision.

RESULTS

Severe hindlimb paralysis (mean Tarlov score 0.36±0.81 out of 3) was observed in all the control group animals (9 of 11 with paraplegia and 2 of 11 with paraparesis) compared with 11 of 12 neurologically intact animals (mean Tarlov score 2.58±0.90 [p = 0.001 compared with control]) in the high-dose minocycline group. This protective effect was observed partially during a state of hyperglycemia and was completely abrogated by wortmannin. Minocycline administration resulted in higher neurologic scores (p = 0.003) and a shift to viable neurons and more apoptotic-stained nuclei resulting from reduced necrosis (p = 0.001).

CONCLUSIONS

In a rabbit model of infrarenal aortic occlusion, minocycline effectively reduced paraplegia by increasing the number of viable neurons in a dose-dependent manner. Its action was completely abrogated by inhibiting the phosphatidylinositol 3-kinase pathway and was inhibited partially by the pro-apoptotic hyperglycemia maneuver, indicating that the activation of cell salvage pathways and mitochondrial sites are possible targets of minocycline action in an ischemic spinal cord.

MicroRNA-155 Deficiency Suppresses Th17 Cell Differentiation and Improves Locomotor Recovery after Spinal Cord Injury

Spinal cord injury (SCI) is considered to be primarily associated with loss of motor function and leads to activate diverse cellular mechanisms in the central nervous system to attempt to repair the damaged spinal cord tissue. Mir-155 has been reported to be involved in both innate and adaptive immune responses. But the role of Mir-155 in spinal cord injury is still unknown. In our current study, Mir-155 deficiency displays increased myelin sparring and enhanced SC repair process. The number of T cells, B cells and neutrophils are all significantly lower in Mir-155(-/-) group than that in WT group after SCI. IL-17A-producing cells and the expression of IL-17A are markedly lower in Mir-155(-/-) mice than that in WT mice. We also found higher production of IL-17 by WT CD4(+) T cells than Mir-155(-/-) CD4(+) T cells in vitro. In our further DC-T cell coculture system, Mir-155 deficiency in DCs results in significantly less IL-17 production from T cells. Furthermore, the inhibited Th17 differentiation induced by Mir-155 deficiency is partly dependent on increased expression of SOCS1. In conclusion, our present work provides evidence to support the concept that Mir-155 deficiency suppresses Th17 cell differentiation and improves locomotor recovery after SCI.

Receptor for advanced glycation end products (RAGE) and its ligands: focus on spinal cord injury

Spinal cord injury (SCI) results in neuronal and glial death and the loss of axons at the injury site. Inflammation after SCI leads to the inhibition of tissue regeneration and reduced neuronal survival. In addition, the loss of axons after SCI results in functional loss below the site of injury accompanied by neuronal cell body’s damage. Consequently, reducing inflammation and promoting axonal regeneration after SCI is a worthy therapeutic goal. The receptor for advanced glycation end products (RAGE) is a transmembrane protein and receptor of the immunoglobulin superfamily. RAGE is implicated in inflammation and neurodegeneration. Several recent studies demonstrated an association between RAGE and central nervous system disorders through various mechanisms. However, the relationship between RAGE and SCI has not been shown. It is imperative to elucidate the association between RAGE and SCI, considering that RAGE relates to inflammation and axonal degeneration following SCI. Hence, the present review highlights recent research regarding RAGE as a compelling target for the treatment of SCI.

Conditioned medium from bone marrow-derived mesenchymal stem cells improves recovery after spinal cord injury in rats: an original strategy to avoid cell transplantation

Spinal cord injury triggers irreversible loss of motor and sensory functions. Numerous strategies aiming at repairing the injured spinal cord have been studied. Among them, the use of bone marrow-derived mesenchymal stem cells (BMSCs) is promising. Indeed, these cells possess interesting properties to modulate CNS environment and allow axon regeneration and functional recovery. Unfortunately, BMSC survival and differentiation within the host spinal cord remain poor, and these cells have been found to have various adverse effects when grafted in other pathological contexts. Moreover, paracrine-mediated actions have been proposed to explain the beneficial effects of BMSC transplantation after spinal cord injury. We thus decided to deliver BMSC-released factors to spinal cord injured rats and to study, in parallel, their properties in vitro. We show that, in vitro, BMSC-conditioned medium (BMSC-CM) protects neurons from apoptosis, activates macrophages and is pro-angiogenic. In vivo, BMSC-CM administered after spinal cord contusion improves motor recovery. Histological analysis confirms the pro-angiogenic action of BMSC-CM, as well as a tissue protection effect. Finally, the characterization of BMSC-CM by cytokine array and ELISA identified trophic factors as well as cytokines likely involved in the beneficial observed effects. In conclusion, our results support the paracrine-mediated mode of action of BMSCs and raise the possibility to develop a cell-free therapeutic approach.

Peroxisome proliferator-activated receptor-γ agonist rosiglitazone reduces secondary damage in experimental spinal cord injury

OBJECTIVE

To investigate the neuroprotective effects of rosiglitazone in a rat traumatic spinal cord injury (SCI) model.

METHODS

Adult Sprague-Dawley rats (n = 12/group) underwent laminectomy (sham), SCI, SCI and rosiglitazone treatment (2 mg/kg twice daily for 7 days), or SCI and saline injection (vehicle). SCI was induced via dural application of an aneurysm clip. Spinal cord apoptosis and levels of tumour necrosis factor-α (TNFα), interleukin (IL)-1β, myeloperoxidase (MPO) and the apoptosis-associated proteins B-cell leukaemia/lymphoma 2 (Bcl-2) and Bcl-2 associated X protein (Bax) were examined 24 h after SCI. Locomotor function was evaluated 3, 7, 10, 14 and 21 days after SCI.

RESULTS

At 24 h after SCI, apoptosis and TNFα, IL-1β and MPO concentrations were significantly lower in the rosiglitazone group than in the vehicle and SCI groups. SCI resulted in an increase in Bax and a decrease in Bcl-2, which was reversed by rosiglitazone treatment. Rats in the rosiglitazone group had significantly better functional recovery than those in the vehicle and SCI groups.

CONCLUSION

Rosiglitazone significantly improved functional recovery, probably via attenuation of the local inflammatory reaction and reduced apoptosis.

Citicoline and postconditioning provides neuroprotection in a rat model of ischemic spinal cord injury

BACKGROUND

Ischemic spinal cord injury is a chain of events caused by the reduction and/or cessation of spinal cord blood flow, which results in neuronal degeneration and loss. Ischemic postconditioning is defined as a series of intermittent interruptions of blood flow in the early phase of reperfusion and has been shown to reduce the infarct size in cerebral ischemia. Our study aimed to characterize the relationship between the neuronal injury-decreasing effects of citicoline and ischemic postconditioning, which were proven to be effective against the apoptotic process.

METHOD

Spinal cord ischemia was produced in rats using an intrathoracic approach to implement the synchronous arcus aorta and subclavian artery clipping method. In our study, 42 male Sprague-Dawley rats (309 +/- 27 g) were used. Animals were divided into sham operated, spinal ischemia, citicoline, postconditioning, and postconditioning citicoline groups. Postconditioning was generated by six cycles of 1 min occlusion/5 min reperfusion. A 600 mmol/kg dose of citicoline was given intraperitoneally before ischemia in the citicoline and postconditioning citicoline groups. All rats were sacrificed 96 h after reperfusion. For immunohistochemical analysis, bcl-2, caspase 3, caspase 9, and bax immune staining were performed. Caspase 3, caspase 9, bax, and bcl-2 were used as apoptotic and antiapoptotic markers, respectively.

FINDINGS

The blood pressure values obtained at the onset of reperfusion were significantly lower than the preischemic values. A difference in immunohistochemical scoring was detected between the caspase 3, caspase 9, bax, and bcl-2 groups. When comparisons between the ischemia (groups 2, 3, 4, and 5) and sham groups (group 1) were performed, a significant increase in caspase 3, caspase 9, bax, and bcl-2 was detected. When comparing the subgroups, the average score of caspase 9 was found to be significantly higher in ischemia group 2. The average score of bcl-2 was also found to be significantly higher in postconditioning and citicoline group 5.

CONCLUSIONS

It is thus thought that combining citicoline with postconditioning provides protection by inhibiting the caspase pathway and by increasing the antiapoptotic proteins.

High mobility group box 1 is upregulated after spinal cord injury and is associated with neuronal cell apoptosis

STUDY DESIGN

Cerebrocortical culture and rat spinal cord injury (SCI) model were used to examine the expression of high mobility group box 1 (HMGB1), TNF-alpha, and Rage by reverse transcription polymerase chain reaction (RT-PCR) and immunohistochemical examination. In addition, relationship between upregulation of HMGB1 and neural cells apoptosis was evaluated after SCI.

OBJECTIVE

To evaluate the upregulation of HMGB1, TNF-alpha, and Rage after SCI.

SUMMARY OF BACKGROUND DATA

It is known that the mode of delayed neuronal cell death after SCI is apoptosis. Apoptotic cell death is influenced by several injury-promoting factors which include pro-inflammatory cytokines. Inhibition of apoptosis promotes neurologic improvement following SCI. However, the factors which transmit inflammatory signaling following SCI have not yet been clarified in detail. HMGB1 was reported as an important mediator of inflammation. We examined the expression of HMGB1, TNF-alpha and Rage following acute SCI.

METHODS

Expression of HMGB1, TNF-alpha and Rage was examined by RT-PCR and immunohistochemical examination. Apoptotic cell death was evaluated by TUNEL methods.

RESULTS

HMGB1 was exported from nuclei to cytoplasm in active caspase-3 positive apoptotic cell in vitro. In addition, HMGB1, TNF-alpha, and Rage was expressed in same cell after NMDA treatment. RT-PCR revealed that expression of HMGB1 and TNF-alpha was upregulated following SCI. Immunohistochemical examination revealed that the numbers of HMGB1-, TNF-alpha-, and Rage-positive cells were increased following SCI. The number of TUNEL-positive cells was significantly increased at 12 hours after injury, and was maximal at 72 hours after injury. However, HMGB1- and TNF-alpha-positive cells were maximal in number 48 hours after injury, while Rage-positive cells were maximal in number at 24 hours after injury. These data suggest that HMGB1, TNF-alpha, and Rage were upregulated following SCI but preceding the apoptotic cell death.

CONCLUSION

Our findings suggest that HMGB1 play a role in the induction of apoptosis via inflammatory reaction.

Contribution of a mitochondrial pathway to excitotoxic neuronal necrosis

It is traditionally thought that excitotoxic necrosis is a passive mechanism that does not require the activation of a cell death program. In this study, we examined the contribution of the cytochrome c-dependent mitochondrial death pathway to excitotoxic neuronal necrosis, induced by exposing cultured cortical neurons to 1 mM glutamate for 6 hr and blocked by the NMDA antagonist, dizocilpine. Glutamate treatment induced early cytochrome c release, followed by activation of caspase-9 and caspase-3. Preincubation with the caspase-9 inhibitor z-LEHD-fmk, the caspase-3 inhibitor z-DEVD-fmk, or the specific pan-caspase inhibitor Q-VD-oph decreased the percentage of propidium iodide-positive neurons (52.5% +/- 3.1%, 39.4% +/- 3.5%, 44.6% +/- 3%, respectively, vs. 65% +/- 3% in glutamate + vehicle). EM studies showed mitochondrial release of cytochrome c in neurons in the early stages of necrosis and cleaved caspase-3 immunoreactivity in morphologically necrotic neurons. These results suggest that an active mechanism contributes to the demise of a subpopulation of excitotoxic necrotic neurons.

Expression of apoptosis signal-regulating kinase 1 in mouse spinal cord under chronic mechanical compression: possible involvement of the stress-activated mitogen-activated protein kinase pathways in spinal cord cell apoptosis

STUDY DESIGN

To examine apoptosis signal cascade in neurons and oligodendrocytes under the chronic spinal cord compression of tiptoe-walking Yoshimura (TWY) mouse, which is model of progressive cervical cord compression.

OBJECTIVE

To clarify the biologic mechanisms of apoptosis, which may produce destructive changes in the spinal cord under chronic mechanical compression, with a resulting irreversible neurologic deficit.

SUMMARY OF BACKGROUND DATA

The stress-activated mitogen-activated protein kinase pathways including ASK1 transmitted apoptosis signals after acute spinal cord injury. Apoptosis in acute spinal cord injury induced both secondary degeneration around the site of injury and chronic demyelination. Chronic spinal cord compression showed myelin destruction, loss of axons, and oligodendrocytes in white matter, and loss of neurons in gray matter. Apoptosis associated with chronic spinal cord compression contributes to these changes. However, the biologic mechanisms of apoptosis in the spinal cord under chronic mechanical compression remain unclear.

METHODS

We examined the expression of phosphorylated-apoptosis signal-regulating kinase 1 (ASK1), phosphorylated-c-Jun N-terminal kinase (JNK), phosphorylated-p38 mitogen-activated protein kinase (p38), and activated caspase-3 immunohistologically in TWY mice, an animal model of progressive cervical spinal cord compression, since the ASK1-JNK and -p38 signaling cascades participate in the signaling pathway leading to apoptosis in neural tissue and neuronal culture.

RESULTS

Double immunohistochemistry for phosphorylated-ASK1, phosphorylated-JNK, phosphorylated-p38, activated-caspase3, and cell-specific markers confirmed the presence of apoptosis signals in both neurons and oligodendrocytes in compressed spinal cord cells.

CONCLUSION

We found that mitogen-activated protein kinase pathways including ASK1, JNK, and p38 were activated in destructive spinal cord under chronic compression.

Therapeutic efficacy of Ac-DMQD-CHO, a caspase 3 inhibitor, for rat spinal cord injury

We investigated the therapeutic efficacy of Ac-DMQD-CHO, a caspase-3 inhibitor, and functional recovery in spinal cord injury in a rat model. Thirty rats were randomized into three groups of 10 each. In groups 2 and 3, spinal cord trauma was produced in the thoracic region. Group 3 rats were treated with Ac-DMQD-CHO. Treatment responses were evaluated based on histopathological and TUNEL staining findings at 24 h and 5 days post-injury. Neurologic performance was assessed during and following treatment. Twenty-four hours after injury, light microscopy examination revealed diffuse hemorrhagic necrosis, edema, vascular thrombi, and polymorphonuclear leukocyte infiltration in group 2 and 3 rats, but cavitation and demyelinization were less prominent in group 3. At this time point, treatment of the rats with Ac-DMQD-CHO significantly reduced the number of apoptotic cells. Traumatic injury to the spinal cord causes apoptosis and administration of Ac-DMQD-CHO decreases apoptosis and improves functional outcome.

Neuroprotective effects of Ac.YVAD.cmk on experimental spinal cord injury in rats

BACKGROUND

Apoptosis as a cell death mechanism is important in numerous diseases, including traumatic SCI. We evaluated the neuroprotective effects of Ac.YVAD.cmk and functional outcomes in a rat SCI model.

METHODS

Thirty rats were randomized into 3 groups of 10: sham-operated, trauma only, and trauma plus Ac.YVAD.cmk treatment. Trauma was produced in the thoracic region by a weight-drop technique. Group 3 rats received Ac.YVAD.cmk (1 mg/kg, ip) 1 minute after trauma. The rats were killed at 24 hours and 5 days after injury. Efficacy was evaluated with light microscopy and TUNEL staining. Functional outcomes were assessed with the inclined plane technique and a modified version of the Tarlov grading system.

RESULTS

At 24 hours postinjury, the respective mean number of apoptotic cells in groups 1, 2, and 3 were 0, 5.26 +/- 0.19, and 0.97 +/- 0.15. Microscopic examination of group 2 tissues showed widespread hemorrhage, edema, necrosis, and polymorphic nuclear leukocyte infiltration and vascular thrombi. Group 3 tissues revealed similar features, but cavitation and demyelination were less prominent than those in group 2 samples at this period. At 5 days postinjury, the respective mean inclined plane angles in groups 1, 2, and 3 were 65.5 +/- 2.09, 42.00 +/- 2.74, and 52.5 +/- 1.77. Motor grading of animals revealed a similar trend. These differences were statistically significant (P < .05).

CONCLUSIONS

Ac.YVAD.cmk inhibited posttraumatic apoptosis in a rat SCI model. This may provide the basis for development of new therapeutic strategies for the treatment of SCI.

Efficacy and vasodilatory benefit of magnesium prophylaxis for protection against spinal cord ischemia

Prevention of paraplegia remains an imperative issue in thoracoabdominal aortic surgery. The aim of this study was to assess the efficacy of a prophylactic magnesium infusion in a rat spinal cord ischemia model and to demonstrate spinal blood flow increase caused by the infusion. The study was conducted in two parts. Firstly, the neuroprotective effect of magnesium was assessed using a rat model with two different ischemic times: 10 min and 14 min. Spinal cord ischemia was induced by occlusion of the descending aorta. Rats in the treatment group were given a 100 mg/kg magnesium sulfate infusion before ischemia. Secondly, relative changes in spinal cord blood flow before and during ischemia were recorded using the laser Doppler flowmetry technique. Changes in blood flow were compared between the magnesium and control groups. Rats pretreated with magnesium showed good overall recovery after both 10 min (incidence of paraplegia 62.5% control vs. 37.5% Mg, n = 8 each) and 14 min (85.7% control vs. 57.1% Mg, n = 7 each) of ischemia, although the differences compared with controls were statistically insignificant. However, the magnesium group showed significantly better neurological performance during the early postischemic period. Comparison of changes in spinal circulation revealed less reduction in blood flow during ischemia in the magnesium-treated group. In conclusion, magnesium may have potential prophylactic benefits during ischemia by exerting a neuroprotective effect through vasodilation of the spinal cord vasculature. To our knowledge, this vasodilatory effect on the spinal cord has not previously been investigated. Optimization of the treatment regimen, however, is required.

The selective poly(ADP)ribose-polymerase 1 inhibitor INO1001 reduces spinal cord injury during porcine aortic cross-clamping-induced ischemia/reperfusion injury

OBJECTIVE

It is well-established that poly(ADP)ribose-polymerase (PARP) assumes major importance during ischemic brain damage, and the selective PARP-1 inhibitor PJ34 reduced spinal cord damage in murine aortic occlusion-induced ischemia/reperfusion injury. We investigated the effect of the PARP-1 inhibitor INO1001 on aortic-occlusion-related porcine spinal cord injury.

DESIGN AND SETTING

Prospective, randomized, controlled experimental study in an animal laboratory.

PATIENTS AND PARTICIPANTS

Ten anesthetized, mechanically ventilated, and instrumented pigs.

INTERVENTIONS

Animals underwent 45 min of thoracic aortic cross-clamping after receiving vehicle (n=5) or intravenous INO1001 (n=5, total dose 4 mg/kg administered both before clamping and during reperfusion). During reperfusion continuous intravenous norepinephrine was incrementally adjusted to maintain blood pressure at or above 80% of the preclamping level. Plasma INO1001 levels were analyzed by HPLC. After 4[Symbol: see text]h of reperfusion spinal cord biopsy samples were analyzed for neuronal damage (hematoxyline-eosine and Nissl staining), expression of the cyclin-dependent kinase inhibitor genes p21 and p27 (immunohistochemistry), and apoptosis (terminal deoxynucleotidyl transferase mediated nick end labeling assay).

MEASUREMENTS AND RESULTS

Plasma INO1001 levels were 0.8-2.3 and 0.30-0.76 mM before and after clamping, respectively. While 3-5% of the spinal cord neurons were irreversibly damaged in the INO1001 animals, the neuronal cell injury was three times higher in the control group. Neither p21 and p27 expression nor apoptosis showed any intergroup difference.

CONCLUSIONS

The selective PARP-1 inhibitor INO1001 markedly reduced aortic occlusion-induced spinal cord injury. Given the close correlation reported in the literature between morphological damage and impaired spinal cord function, INO1001 may improve spinal cord recovery after thoracic aortic cross-clamping.

Effects of intrathecal bupivacaine in conjunction with hypothermia on neuronal protection against transient spinal cord ischemia in rats

BACKGROUND

Excitotoxic neuronal injury from ischemia may be reduced by local anesthetics. We investigated the neuroprotective effects of intrathecally administered bupivacaine and hypothermia in a rat model of transient spinal cord ischemia.

METHODS

PE-10 intrathecal catheter-implanted male Sprague-Dawley rats were randomly assigned to one of four groups: normothermia (NT) and hypothermia (HT) groups (given 15 microl of normal saline) and bupivacaine (B) and bupivacaine-hypothermia (BHT) groups (given 15 mul of 0.5% bupivacaine). Transient spinal cord ischemia was induced by inflation of a 2F Fogarty catheter placed in the aortic arch for 12 min. The rectal temperature was maintained at 37.0 +/- 0.5 degrees C for the NT and B groups, and at 34.5 +/- 0.5 degrees C for the HT and BHT groups. Motor and sensory deficit scores were assessed 2 and 24 h after reperfusion. Lumbar spinal cords were harvested for histopathology and immunoreactivity of heat shock protein 70 (HSP70).

RESULTS

After reperfusion, the motor and sensory deficit scores of the NT group were significantly higher than those of the HT (P < 0.05) and BHT (P < 0.001) groups. Significant differences were evident in the motor and sensory deficit scores between the HT and BHT groups at 24 h (P < 0.05). Neuronal cell death and immunoreactivity of HSP70 were frequently observed in the NT and BT groups, but not in the HT and BHT groups.

CONCLUSIONS

These results collectively suggest that intrathecal bupivacaine does not provide neuroprotection during normothermic transient spinal cord ischemia in rats, but enhances the neuroprotective effects of hypothermia.

Neuronal damage in rat brain and spinal cord after cardiac arrest and massive hemorrhagic shock*

OBJECTIVE

Severe global ischemia often results in severe damage to the central nervous system of survivors. Hind-limb paralysis is a common deficit caused by global ischemia. Until recently, most studies of global ischemia of the central nervous system have examined either the brain or spinal cord, but not both. Spinal cord damage specifically after global ischemia has not been studied in detail. Because the exact nature of the neuronal damage to the spinal cord and the differences in neuronal damage between the brain and spinal cord after global ischemia are poorly understood, we developed a new global ischemia model in the rat and specifically studied spinal cord damage after global ischemia. Further, we compared the different forms of neuronal damage between the brain and spinal cord after global ischemia.

DESIGN

Randomized, controlled study using three different global ischemia models in the rat.

SETTING

University research laboratory.

SUBJECTS

Male, adult Sprague-Dawley rats (300 g).

INTERVENTIONS

Animals were divided into three experimental groups, group A (n = 6, survived for 7 days), 12 mins of hemorrhagic shock; group B (n = 6, survived for 7 days), 5 mins of cardiac arrest; or group C (n = 6, each for 6 hrs, 12 hrs, 1 day, 3 days, and 7 days), 7 mins of hemorrhagic shock and 5 mins of cardiac arrest. Motor deficit of the hind limbs was studied 6 hrs to 7 days after resuscitation. Also, nonoperated animals (n = 6) were used as the control. Histologic analysis (hematoxylin and eosin, Fluoro-Jade B, terminal deoxynucleotidyl transferase- mediated dUTP end-labeling [TUNEL], Klüver-Barrera) and ultrastructural analysis using electron microscopy were performed on samples from the CA1 region of the hippocampus and lumbar spinal cord. Demyelination of the white matter of the lumbar spinal cord was analyzed semiquantitatively using Scion Image software.

MAIN RESULTS

No paraplegic animals were observed in either group A or B. All group C animals showed severe hind-limb paralysis. Severe neuronal damage was found in the CA1 region of the hippocampus in all groups, and the state of delayed neuronal cell death was similar among the three groups. Neuronal damage in the lumbar spinal cord was detected only in group C animals, mainly in the dorsal horn and intermediate gray matter. Demyelination was prominent in the ventral and ventrolateral white matter in group C. A significant difference was observed between control and group C rats with Scion Image software. Ultrastructural analysis revealed extensive necrotic cell death in the intermediate gray matter in the lumbar spinal cord in group C rats.

CONCLUSION

The combination in the global ischemia model (i.e., hemorrhagic shock followed by cardiac arrest) caused severe neuronal damage in the central nervous system. Thereby, hind-limb paralysis after global ischemia might result from spinal cord damage. These results suggest that therapeutic strategies for preventing spinal cord injury are necessary when treating patients with severe global ischemia.

Inhibition of Fas-mediated apoptosis through administration of soluble Fas receptor improves functional outcome and reduces posttraumatic axonal degeneration after acute spinal cord injury

Fas receptor activation has been implicated in inflammatory responses, programmed cell death, Wallerian degeneration in neural injury and the axotomy induced death of motoneurons. Recent work using transection models of spinal cord injury (SCI) demonstrated that neutralization of Fas ligand with antibodies may promote axonal regeneration and functional recovery. Moreover, recent studies from our laboratory in mutant mice with deficient expression of Fas, show reduced cell death and enhanced behavioural recovery after SCI. The present paper examines the effects of soluble Fas receptor (sFasR) administration on inhibition of Fas receptor-Fas ligand interaction in the setting of acute SCI in vitro and in vivo. An in vitro model of SCI demonstrated that sFasR administration decreases cell death as assessed by propidium iodide fluorescence. Furthermore, in a moderately severe in vivo clip compression model of SCI at C7-T1, we demonstrate that subarachnoid infusion of sFasR results in increased neuron and oligodendrocyte survival, improved tissue and long tract axonal preservation, reduced apoptotic cell death and enhanced functional neurological outcome after acute SCI. These results strongly suggest that inhibiting Fas receptor activation is neuroprotective after acute SCI and that this strategy may have important translational significance.

Oxidative metabolism, apoptosis and perinatal brain injury

Perinatal hypoxic-ischaemic injury (HII) is a significant cause of neurodevelopmental impairment and disability. Studies employing 31P magnetic resonance spectroscopy to measure phosphorus metabolites in situ in the brains of newborn infants and animals have demonstrated that transient hypoxia-ischaemia leads to a delayed disruption in cerebral energy metabolism, the magnitude of which correlates with the subsequent neurodevelopmental impairment. Prominent among the biochemical features of HII is the loss of cellular ATP, resulting in increased intracellular Na+ and Ca2+, and decreased intracellular K+. These ionic imbalances, together with a breakdown in cellular defence systems following HII, can contribute to oxidative stress with a net increase in reactive oxygen species. Subsequent damage to lipids, proteins, and DNA and inactivation of key cellular enzymes leads ultimately to cell death. Although the precise mechanisms of neuronal loss are unclear, it is now clear both apoptosis and necrosis are the significant components of cell death following HII. A number of different factors influence whether a cell will undergo apoptosis or necrosis, including the stage of development, cell type, severity of mitochondrial injury and the availability of ATP for apoptotic execution. This review will focus on some pathological mechanisms of cell death in which there is a disruption to oxidative metabolism. The first sections will discuss the process of damage to oxidative metabolism, covering the data collected both from human infants and from animal models. Following sections will deal with the molecular mechanisms that may underlie cerebral energy failure and cell death in this form of brain injury, with a particular emphasis on the role of apoptosis and mitochondria.

Ischemia-induced disturbance of neuronal network function in the rat spinal cord analyzed by voltage-imaging

Using a voltage-imaging technique, we analyzed the acute effect of ischemia, hypoxia and hypoglycemia on the neuronal network function of the rat spinal cord. Ischemic, hypoxic, or hypoglycemic stress was loaded to spinal cord slices with an oxygen- and glucose-free, oxygen-free, or glucose-free mock cerebrospinal fluid, respectively. Depolarizing signals in the dorsal horn, induced by dorsal root stimulation, consisted of fast (pre-synaptic) and slow (post-synaptic) components. The slow component was attenuated much more than the fast component under an ischemic condition (P<0.0002). Post-synaptic neuronal activities in lamina III-IV were suppressed earlier than those in lamina I-II. The nerve fiber was relatively resistant to ischemia. As long as the fast component was preserved in the dorsal horn, the suppression of the fast and slow components was reversible. There was a significant difference (P<0.05) in the recovered slow component sizes between the group in which the fast component was suppressed by more than 20% by ischemia and the group in which the suppression was less than 20%. Further prolonged stress irreversibly eliminated most of the slow component, and attenuated the fast component (to 59+/-8%) accompanied by cellular damage in histology. Suppression of neural activity by hypoxic or hypoglycemic stress was less prominent than that by ischemia. Prolonged ischemic stress suddenly and irreversibly eliminated depolarizing signals in the ventral horn accompanied by morphological damage of motoneurons. Immunohistochemical staining was negative for apoptosis. We have, for the first time, analyzed the processes of spinal cord disturbance induced by ischemia, hypoxia and hypoglycemia at the neuronal network level by directly observing the regional neuronal network activities within the spinal cord. We conclude that synaptic transmission in the dorsal horn, especially in deep regions, is vulnerable and first affected by these stresses. Severe ischemic stress induces irreversible dysfunction of neurons accompanied by eventual cell death in both dorsal and ventral horns.

MK-801 improves neurological and histological outcomes after spinal cord ischemia induced by transient aortic cross-clipping in rats

BACKGROUND

Glutamergic excitotoxicity has been shown to play a deleterious role in the pathophysiology of ischemic spinal cord injury (ISCI). The aim of this study was to investigate the neuroprotective effect of a single dose of MK-801, an antiexcitotoxic drug, in a rat model of ISCI.

METHODS

Ischemic spinal cord injury was induced for 17 minutes in Sprague-Dawley rats using direct aortic arch, just proximal to the left common carotid artery, plus left subclavian artery cross-clamping through a left-sided limited thoracotomy. Study groups were as follows: control group (n = 8) receiving only vehicle and experimental group (n = 8) receiving a single dose of MK-801 (1 mg/kg IV) 10 minutes before aortic clamping. Neurological examination was performed at 6 hours, 24 hours, and daily up to 96 hours. Rats were sacrifice at methylprenisolone socium succinate 96 hours, and spinal cords were removed for histopathology.

RESULTS

All the control rats had severe permanent neurological deficits after ISCI, whereas the MK-801-treated rats had statistically (P < .05) better neurological outcome and good recovery. Histopathology revealed severe neuronal necrosis in the lumbar gray matter of control rats, whereas MK-801-treated rats showed mild injury.

CONCLUSION

These results demonstrate that combined temporary clipping of the aortic arch (just proximal to the left common carotid artery) plus left subclavian artery for 17 minutes reproduces reliable paraplegia, and a single dose of MK-801 given before ISCI provides significant neuroprotection.

The neuroprotective effects of z-DEVD.fmk, a caspase-3 inhibitor, on traumatic spinal cord injury in rats

BACKGROUND

Apoptosis is one of the most important forms of cell death seen in a variety of physiological and pathological conditions, including traumatic injuries. This type of cell death occurs via mediators known as caspases. Previous studies have investigated the roles that apoptosis and different caspases play in the pathogenesis of secondary damage after spinal cord injury (SCI). The aim of this research was to assess the neuroprotective effect of z-DEVD.fmk, a caspase-3 inhibitor, in a rat model of SCI.

METHODS

Forty-five Wistar albino rats were studied in 3 groups of 15 animals: sham-operated control animals (group 1); trauma-only control animals (group 2); and rats subjected to trauma + z-DEVD.fmk treatment (group 3). Spinal cord injury was produced at the thoracic level using the weight-drop technique. Responses to injury and the efficacy of z-DEVD.fmk were assessed by light microscopy and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining in cord tissues collected at 4 and 24 hours posttrauma. Five rats from each group were used to assess functional recovery at 7 days after SCI. The functional evaluations were done using the inclined-plane technique and a modified Tarlov motor grading scale.

RESULTS

At 4 hours postinjury, the mean apoptotic index in groups 1, 2, and 3 was 0, 33.01+/-6.62, and 16.40+/-4.91, respectively. The group 3 count was significantly lower than the group 2 count (P<.01). At 24 hours postinjury, light microscopic examination of group 2 tissues showed widespread hemorrhage, necrosis, polymorphonuclear leukocyte infiltration, and vascular thrombi. The group 3 tissues showed similar features. The prominent findings in group 2 were hemorrhage and necrosis, whereas the prominent findings in group 3 were focal hemorrhage and leukocyte infiltration. The mean inclined-plane angles in groups 1, 2, and 3 were 64.5 degrees+/-1.0 degrees, 41.5 degrees+/-1.3 degrees, and 47 degrees+/-2.0 degrees, respectively. Motor scale results in all groups showed a similar trend.

CONCLUSION

Local application of z-DEVD.fmk after SCI in rats reduces secondary tissue injury and helps preserve motor function. These effects can be explained by inhibition of apoptotic death in all cell types in the spinal cord.

Neuroprotection and functional recovery after application of the caspase-9 inhibitor z-LEHD-fmk in a rat model of traumatic spinal cord injury

OBJECT

Apoptosis is considered one of the most significant mechanisms in the pathogenesis of neuronal damage after spinal cord injury (SCI). This form of cell death occurs via mediators known as caspases. The aim of this study was to evaluate the neuroprotective effect of the caspase-9 inhibitor, z-LEHD-fmk, in a rat model of spinal cord trauma.

METHODS

Fifty-four Wistar albino rats were studied in the following three groups of 18 animals each: sham-operated controls (Group 1); trauma-only controls (Group 2); and trauma combined with z-LEHD-fmk-treated animals (0.8 microM/kg; Group 3). Spinal cord injury was produced at the thoracic level by using the weight-drop technique. Responses to SCI and the efficacy of z-LEHD-fmk treatment were determined on the basis of terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling staining and light and electron microscopy findings in cord tissue at 24 hours and 7 days posttrauma. Six rats from each group were also assessed for functional recovery at 3 and 7 days after SCI. This was conducted using the inclined-plane technique and a modified version of the Tarlov motor grading scale. At 24 hours postinjury, light microscopic examination of Group 2 tissue samples showed hemorrhage, edema, necrosis, polymorphonuclear leukocyte infiltration, and vascular thrombi. Those obtained in Group 3 rats at this stage showed similar features. At 24 hours postinjury, the mean apoptotic cell count in Group 2 was significantly higher than that in Group 3 (90.25 +/- 2.6 and 50.5 +/- 1.9, respectively; p < 0.05). At 7 days postinjury, the corresponding mean apoptotic cell counts were 49 +/- 2.1 and 17.7 +/- 2.6, also a significant difference (p < 0.05). Electron microscopy findings confirmed the occurrence of programmed cell death in different cell types in the spinal cord and showed that z-LEHD-fmk treatment protected neurons, glia, myelin, axons, and intracellular organelles.

CONCLUSIONS

Examination of the findings in this rat model of SCI revealed that apoptosis occurs not only in neurons and astrocytes but also in oligodendrocytes and microglia. Furthermore, immediate treatment with the caspase-9 inhibitor z-LEHD-fmk blocked apoptosis effectively and was associated with better functional outcome. More in-depth research of the role of programmed cell death in spinal cord trauma and further study of the ways in which caspases are involved in this process may lead to new strategies for treating SCI.

An Evaluation of White Matter Injury After Spinal Cord Ischemia in Rats: A Comparison with Gray Matter Injury

We quantitatively assessed both gray and white matter injury after spinal cord ischemia in rats, and the relationship between the magnitude of gray and white matter injury was determined. Twenty-five male rats were anesthetized with isoflurane, and spinal cord ischemia (SCI) was induced by balloon intraaortic occlusion combined with hypotension. The animals were randomly allocated to one of the following three groups: animals with SCI for 12 min (SCI-12; n = 8), 15 min (SCI-15; n = 9), or those with sham operation (n = 8). Twenty-four hours after reperfusion, hindlimb motor function was assessed using the Basso-Beattie-Bresnahan scale scoring. Gray matter damage was assessed on the basis of the number of normal neurons in the ventral horn. White matter damage was assessed on the basis of the extent of vacuolation and amyloid precursor protein immunoreactivity in the ventral and ventrolateral white matter. There were significantly less normal neurons in the SCI-15 group compared with those in the SCI-12 and sham groups (P < 0.05). There was a significant positive correlation between the Basso-Beattie-Bresnahan scores and the number of normal neurons. The percentages of vacuolation areas in the SCI-15 group were significantly larger compared with those in the SCI-12 and sham groups (30% +/- 10% versus 9% +/- 7%, 0% +/- 0%, P < 0.05). Immunohistochemical analysis revealed increased amyloid precursor protein immunoreactivity in the swollen axons, especially in the SCI-15 group. There was a significant negative correlation between the number of normal neurons and percentages of vacuolation areas. These results indicate that both gray and white matter were injured after SCI in rats and the degree of white mater injury was correlated with the severity of gray matter injury after a relatively short recovery period.

Morphological changes of the soleus motoneuron pool in chronic midthoracic contused rats

This study investigated the morphological features of the soleus motoneuron pool in rats with chronic (4 months), midthoracic (T8) contusions of moderate severity. Motoneurons were retrogradely labeled using unconjugated cholera toxin B (CTB) subunit solution injected directly into the soleus muscle of 10 contused and 6 age- and sex-matched, normal controls. Morphometric studies compared somal area, perimeter, diameter, dendritic length, and size distribution of labeled cells in normal and postcontusion animals. In normal animals, motoneurons with a mean of 110.4 +/- 5.2 were labeled on the toxin-injected side of the cord (left). By comparison, labeled cells with a mean of 93.0 +/- 8.4 (a 16% decrease, P = 0.006) were observed in the chronic spinal-injured animals. A significantly smaller frequency of very small (area, approximately 100 microm2) and medium (area, 545-914 microm2) neurons, and a significantly higher frequency of larger (area, >914 microm2) neurons was observed in the labeled soleus motoneuron pools of injured animals compared with the normal controls. Dendritic bundles in the contused animals were composed of thicker dendrites, were arranged in more closely aggregated bundles, and were organized in a longitudinal axis (rostrocaudal axis). Changes in soleus motoneuron dendritic morphology also included significant decrease of total number of dendrites, increased staining, hypertrophy of primary dendrites, and significant decreased primary, secondary, and tertiary branching. The changes in size distribution and dendritic morphology in the postcontusion animals possibly resulted from cell loss and transformation of medium cells to larger cells and/or injury-associated failure of medium cells to transport the immunolabel.

Gene expression profiling of cathepsin D, metallothioneins-1 and -2, osteopontin, and tenascin-C in a mouse spinal cord injury model by cDNA microarray analysis

The purpose of this study was to use a cDNA microarray to identify new genes involved in healing of spinal cord injury. C57BL/6 mice (7-8 weeks, male) were subjected to spinal cord compression injury (SCI) at the T7/8 level (20 g, 5 min; SCI group). For the control group, mice underwent only laminectomy. Mice were killed at 1, 3 and 7 days. cDNA transcribed from mRNA was hybridized to NIA mice 15K microarrays at each time point. We found 84 genes showing significant expressional changes, including higher and lower expression levels in the SCI groups than in the control [more than 1.0 or less than -1.0 using log ratio (base 2)]. Five genes were selected for further quantitative gene expression analysis by real-time reverse transcription (RT)-PCR. For histological examination, we applied in situ hybridization and fluorescence immunohistochemistry. Cathepsin D, metallothionein-1 (MT-1), metallothionein-2 (MT-2), osteopontin (OPN), and tenascin-C were selected for quantitative and histological analysis. Microarray analysis revealed that SCI led to the up-regulation of OPN and cathepsin D expression at 7 days and also of MT-1, MT-2, and tenascin-C expression at 1 day. Tenascin-C was re-up-regulated at 7 days. These values agreed with those of real-time RT-PCR analysis. By double labeling with in situ hybridization and fluorescence immunohistochemistry, MT-1, MT-2 and tenascin-C expression was observed in neurons and glial cells at 1 day, whereas at 7 days the main MT-2 and tenascin-C expression was found in fibronectin-positive fibroblasts. The main cathepsin D and OPN expression was observed in activated macrophages/microglia at 3 and 7 days. The five genes picked up by microarray gene expression profiling were shown to exhibit temporal and spatial changes of expression after SCI. This system is potentially useful for identifying genes that are involved in the response to SCI.

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

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

Injury in the spinal cord may produce cell death in the brain

Functional deficits after spinal cord injury have originated not only from the direct physical damage itself, but from the secondary biochemical and pathological changes. Apoptotic cell death has been seen around the periphery of an injured site and has been known to ultimately progress to necrosis and infarction. We have initiated the present study focusing on the role of apoptosis in the secondary injury of the brain after acute spinal cord injury (SCI), and conducted a series of experiments, the study examining the morphological changes in the brain following the spinal injury. Under pentobarbital anesthesia, male Sprague-Dawley rats were subjected to SCI model. Rats were laminectomized and SCI was induced using NYU spinal impactor at T9 segment. The behavioral test was performed. Electrophysiologically, motor evoked potentials (MEPs) were recorded. The animals were subjected to morphological study at 12, 24, 48, 72 h, and 1 week, postoperatively. Locomotor deficits were observed after SCI, and changes in the amplitudes and latencies of the MEPs were observed. The morphological changes were evidenced by terminal TUNEL staining and Calbindin-D(28K) immunohistochemistry. The TUNEL-positive cells were located at the brain motor cortex after SCI. TUNEL-positive cells were seldom found 4 h after injury. In addition, Calbindin-D28K immunoreactive neurons were observed in the motor cortex after injury. These results suggest that apoptosis may play an important role in the pathophysiology of the brain motor cortex following acute spinal cord injury and functions that were deteriorated after SCI may be related to these electrophysiological and morphological changes.

Injury severity and cell death mechanisms: effects of concomitant hypovolemic hypotension on spinal cord ischemia–reperfusion in rats

A number of previous studies indicated that ischemia-reperfusion injury causes two distinct types of cell death--necrosis and apoptosis--in the central nervous system. It was also implicated that the intensity of injury can somehow affect the cell death mechanisms. By occluding the descending thoracic aorta with or without simultaneously induced hypovolemic hypotension in rats, we established a model of experimental spinal cord ischemia-reperfusion (I/R) in which the injury severity can be controlled. Recordings of carotid blood pressure (CBP) and spinal cord blood flow (SCBF) showed that aortic occlusion induced dramatic CBP elevation but SCBF drop in both the normotensive (NT) and hypotensive (HT) groups of rats. However, the HT group demonstrated significantly lower SCBF during aortic occlusion, and much slower elevation of SCBF after reperfusion, and extremely poor neurological performance. Spinal cord lesions were characterized by infarction associated with extensive necrotic cell death, but little apoptosis and caspase-3 activity. In contrast, in the NT group, I/R injury resulted in minor tissue destruction associated with persistent abundant apoptosis, augmented caspase-3 activity, and favorable functional outcome. The relative sparing of motoneurons in the ventral horns from apoptosis might have accounted for the minor functional impairment in the NT group. The severity of I/R injury was found to have substantial impact on the histopathological changes and cell death mechanisms, which correlate with neurological performance. Our results implicate that injury severity and duration after injury are two critical factors to be considered in therapeutic intervention.

Regeneration of supraspinal axons after complete transection of the thoracic spinal cord in neonatal opossums (Monodelphis domestica)

These studies define the time table and origin of supraspinal axons regenerating across a complete spinal transection in postnatal Monodelphis domestica. After lumbar (L1) spinal cord injection of fluorophore-dextran amine conjugate on postnatal (P) day 4, a consistent number of neurons could be labeled. The numbers of labeled neurons remained stable for several weeks, but subsequently declined by P60 in control animals and by P35 in animals with complete spinal transection (T4-T6) performed at P7. In control animals, 25-40% of neurons labeled with a fluorophore injected (L1) at P4 could also be double-labeled by a second fluorophore injected (T8-T10) at different older ages. In spinally transected animals, total numbers of neurons labeled with the second marker were initially lower compared with age-matched controls, but were not significantly different by 3 weeks after injury. The proportion of double-labeled neurons in spinally transected animals increased from approximately 2% 1 week after injury (P14) to approximately 50% by P60, indicating that a substantial proportion of neurons with axons transected at P7 is able to regenerate and persist into adulthood. However, the proportion of axons originating from regenerating neurons made only a small contribution at older ages to total numbers of fibers growing through the injury site, because much of development of the spinal cord occurs after P7. Evidence was obtained that degenerating neurons with both apoptotic and necrotic morphologies were present in brainstem nuclei; the number of neurons with necrotic morphology was much greater in the brainstem of animals with spinal cords transected at P7.

Primary cortical motor neurons undergo apoptosis after axotomizing spinal cord injury

Spinal cord injury (SCI) results in loss of voluntary motor control followed by incomplete recovery, which is partly mediated by the descending corticospinal tract (CST). This system is an important target for therapeutic repair strategies after SCI; however, the question of whether apoptotic cell death occurs in these axotomized neurons remains unanswered. In this study, adult (150-175 g) male Sprague-Dawley rats underwent T9 transection of the dorsal funiculus, which axotomizes the dorsal CST, and introduction of the retrograde tracer Fluoro-Gold into the lesion site. Primary motor cortex (M1) was then examined for evidence of apoptosis weekly for 4 weeks after injury. Axotomized pyramidal cells, identified by retrograde transport of Fluoro-Gold, were found in M1 (57.5 +/- 9.6/median section, 6127 +/- 292 total), and a significant proportion were terminal deoxynucleotidyl transferase (TdT) -mediated deoxyuridine triphosphate (dUTP)-rhodamine nick end labeling (TUNEL) -positive at 1 week after injury (39.3 +/- 5.6%), compared with animals undergoing sham surgery (1.2 +/- 1.4%). At 2-4 weeks, fewer cells were Fluoro-Gold-positive (24.6 +/- 65.06 to 25.3 +/- 6.4/median section, 2338 +/- 233 to 2393 +/- 124 total), of which very few were TUNEL-positive. In TUNEL-positive cells, Hoechst 33342 staining revealed nuclear morphology consistent with apoptosis, chromatin condensation, and formation of apoptotic bodies. Fluoro-Gold-positive cells showed increased caspase-3 and Bax immunoreactivity. Hematoxylin and eosin staining revealed similar nuclear changes and dystrophic cells. Internucleosomal DNA fragmentation was detected by gel electrophoresis at the 1-week time point. Lesioned animals not receiving Fluoro-Gold exhibited the same markers of apoptosis. These results document, for the first time, features of apoptotic cell death in a proportion of axotomized cortical motor neurons after SCI, suggesting that protection from apoptosis may be a prerequisite for regenerative approaches to SCI.

Long-term assessment of hind limb motor function and neuronal injury following spinal cord ischemia in rats

Recent evidence suggests that brain injury caused by ischemia is a dynamic process characterized by ongoing neuronal loss for at least 14 days after ischemia. However, long-term outcome following spinal cord ischemia has not been extensively examined. Therefore, we investigated the changes of hind limb motor function and neuronal injury during a 14-day recovery period after spinal cord ischemia. Male Sprague-Dawley rats received spinal cord ischemia (n = 64) or sham operation (n = 21). Spinal cord ischemia was induced by inflation of a 2F Fogarty catheter placed into the thoracic aorta for 6, 8, or 10 minutes. The rats were killed 2, 7, or 14 days after reperfusion. Hind limb motor function was assessed with the 21-point Basso, Beattie, and Bresnahan (BBB) scale during the recovery period. The number of normal and necrotic neurons was counted in spinal cord sections stained with hematoxylin/eosin. Longer duration of spinal cord ischemia produced severer hind limb motor dysfunction at each time point. However, BBB scores gradually improved during the 14-day recovery period. Neurologic deterioration was not observed between 7 and 14 days after reperfusion. The number of necrotic neurons peaked 2 days after reperfusion and then decreased. A small number of necrotic neurons were still observed 7 and 14 days after reperfusion in some of the animals. These results indicate that, although hind limb motor function may gradually recover, neuronal loss can be ongoing for 14 days after spinal cord ischemia.

Neuroprotective synergy of N-methyl-D-aspartate receptor antagonist (MK801) and protein synthesis inhibitor (cycloheximide) on spinal cord ischemia-reperfusion injury in rats

Thoraco-abdominal aortic surgery requiring temporal cross clamping of the aorta results in a high incidence of paraplegia due to temporary ischemia of the spinal cord. Both excitotoxicity and apoptosis are implicated in the pathogenesis of spinal cord ischemia-reperfusion injury. We propose that the N-methyl-D-aspartate receptor antagonist dizocilpine maleate (MK801) and the protein synthesis inhibitor cycloheximide produce a synergic effect in a rodent model of spinal cord ischemia-reperfusion injury. Injury was induced by 20 min of temporal thoracic aorta occlusion and distal blood volume reduction. After injury, the animals were treated with vehicle, MK801, cycloheximide or MK801 and cycloheximide. Hind limb motor function recovery was better in the MK801 and combined therapy groups than in the control and cycloheximide groups. The mean neuronal survival rate of the control group was 45.3 +/- 3.2% on the 7(th) day after injury. In the MK801 and cycloheximide treatment groups, neuronal survival increased to 62.4 +/- 3.6% and 54.1 +/- 2.4%, respectively. For the combined therapy group, neuronal survival increased to 75.6 +/- 2.5%. The number of apoptotic cells in the control group was 211.4 +/- 8.8 per section on the 7th day after ischemic insult, while apoptosis was significantly reduced in the cycloheximide (96.8 +/- 6.7 cells) and combined (84.8 +/- 8.5 cells) groups. It was unchanged in the MK801 group (209.8 +/- 5.4 cells). These results suggest that combined treatments directed at blocking both N-methyl-D-aspartate receptor-mediated excitotoxic necrosis and caspase-mediated apoptosis might have synergic therapeutic potential in reducing spinal cord ischemia-reperfusion injury.

Exposure to short-lasting impulse noise causes neuronal c-Jun expression and induction of apoptosis in the adult rat brain

Exposure to impulse noise, above a certain intensity, is harmful to auditory function. Effects of impulse noise on the central nervous system (CNS) are largely unexplored, and there is little information on critical threshold values and time factors. We have recently shown that neurofilament proteins are affected in the cerebral cortex and the hippocampus. Now we show that impulse noise induces expression of the immediate early gene c-Jun products, proposed to play a role in the initiation of neuronal death, and apoptosis as revealed by TUNEL staining. Rat brains were investigated immunohistochemically 2 h to 21 days after exposure to impulse noise of 198 dB or 202 dB. c-Jun was expressed in neuronal perikarya in layers II-VI of the temporal cortex, the cingulate and the piriform cortices at 2 h to 21 days after both exposure levels. Granule neurons of the dentate gyrus and the CA1-3 in the hippocampus pyramidal neurons were similarly affected. The elevated expression of c-Jun products remained high at all postexposure times. TUNEL staining was positive among the same nerve cell populations 6 h after exposure and persisted even at 7 days at both exposure levels.