The temporal profile of the reaction of microglia, astrocytes, and macrophages in the delayed onset paraplegia after transient spinal cord ischemia in rabbits

A new method for primary culture of microglia in rats with spinal cord injury

At present, the primary culture method of microglia is complicated, and the culture of spinal cord microglia is rare, so we will explore to establish a new and efficient primary culture method of microglia in rats with spinal cord injury (SCI). The SCI model of SD rats was established by modified A11en's method, and the model of SCI was performed on 1 d, 3 d, 7 d and 14 d respectively. Then the injured spinal cord was removed, mechanically separated and filtered. The morphology of microglia was observed the next day and its purity was identified by CD11b and Iba1 immunofluorescence labeling. According to the above results, the morphological changes of microglia after 3 d of SCI were observed at 1 d, 2 d and 4 d. The results showed that the purity of microglia was 98%. The number of microglia after 3 d of SCI was the most. After SCI, the migration ability of microglia was enhanced, the number of microglia in the injured area increased, and the number was the highest at 3 d, then gradually decreased. In addition, the microglia after SCI would gradually change from active state to resting state with the passage of time. Therefore, we can use a simple and efficient mechanical separation method to extract primary microglia, which provides the basis for the study of microglia.

Lidocaine relieves spinal cord ischemia-reperfusion injury via long non-coding RNA MIAT-mediated Notch1 downregulation

Microglial activation and inflammatory response play a critical role in spinal cord ischemia-reperfusion injury (SCIRI). This study aimed to investigate whether lidocaine relieves SCIRI via modulating MIAT-mediated Notch1 downregulation. Mouse SCIRI was induced by the obstruction of the aortic arch. Lidocaine was injected after reperfusion. Microglial activation and inflammatory response were assessed by Iba1, interleukin 1 beta (IL-1β), and tumor necrosis factor alpha (TNF-α) levels. The interaction between MIAT and Notch1 was assessed by RNA pull-down and RNA immunoprecipitation assays. Lidocaine treatment relieved SCIRI by reducing Iba1 and serum TNF-α and IL-1β levels. After lidocaine treatment, MIAT expression was elevated in lipopolysaccharide- (LPS-) induced BV2 cells. The interference of MIAT and the overexpression of MIAT and Notch1 restored TNF-α and IL-1β levels in supernatants. Notch1 protein was existent in MIAT-pull-down compounds, and the expression of MIAT was markedly elevated in Notch1-immunoprecipitants. The overexpression of MIAT markedly promoted the degradation of Notch1 and increased the level of ubiquitin-bound Notch1 complex. The therapeutic effect of lidocaine on SCIRI mice could be reversed by adeno-associated virus-mediated MIAT knockdown. In conclusion, lidocaine treatment relieved SCIRI via inhibiting microglial activation and reducing the inflammatory response. The molecular mechanism was partly through MIAT-mediated Notch1 downregulation.

Autophagy of Spinal Microglia Affects the Activation of Microglia through the PI3K/AKT/mTOR Signaling Pathway

Delayed paralysis occurs within some patients suffered from ischemic spinal cord injury (ISCI) due to the aorta occlusion during the repair surgery of thoracic and thoracoabdominal aortic aneurysms. Although mild hypothermia has been reported to improve ISCI and prolong the tolerance of rats to ISCI without inducing immediate paralysis, the mechanism remains unclear. Herein, the study revealed that the mild hypothermia treatment indeed partially improved the ISCI in rats caused by cross-clamping at the descending aorta. ISCI induced the excessive activation of microglia and moderate autophagy in the spinal cord tissues of rats, while mild hypothermia significantly induced autophagy and reversed the excessive activation of microglia in the spinal cord tissues of rats. In OGD-stimulated mouse microglia BV-2 cells, the excessive activation of microglia and moderate autophagy were also observed; in the rapamycin-treated OGD model in BV-2 cells, autophagy was significantly enhanced whereas the excessive activation of microglia was reversed. In both in vivo ISCI model in rats and in vitro OGD model in BV-2 cells, the PI3K/AKT/mTOR pathway showed to be inhibited, whereas the PI3K/AKT/mTOR pathway was further inhibited by mild hypothermia in ISCI rats or rapamycin treatment in OGD-stimulated BV-2 cells. In conclusion, enhanced autophagy might be the mechanism of inhibited microglia activation by hypothermia treatment in ISCI rats and by rapamycin treatment in OGD-stimulated BV-2 cells. Autophagy could be enhanced through inhibiting the PI3K/AKT/mTOR pathway.

Non-Coding RNAs: Emerging Therapeutic Targets in Spinal Cord Ischemia-Reperfusion Injury

Paralysis or paraplegia caused by transient or permanent spinal cord ischemia–reperfusion injury (SCIRI) remains one of the most devastating post-operative complications after thoracoabdominal aortic surgery, even though perioperative strategies and surgical techniques continue to improve. Uncovering the molecular and cellular pathophysiological processes in SCIRI has become a top priority. Recently, the expression, function, and mechanism of non-coding RNAs (ncRNAs) in various diseases have drawn wide attention. Non-coding RNAs contain a variety of biological functions but do not code for proteins. Previous studies have shown that ncRNAs play a critical role in SCIRI. However, the character of ncRNAs in attenuating SCIRI has not been systematically summarized. This review article will be the first time to assemble the knowledge of ncRNAs regulating apoptosis, inflammation, autophagy, and oxidative stress to attenuate SCIRI. A better understanding of the functional significance of ncRNAs following SCIRI could help us to identify novel therapeutic targets and develop potential therapeutic strategies. All the current research about the function of nRNAs in SCIRI will be summarized one by one in this review.

Inhibition of MALT1 Alleviates Spinal Ischemia/Reperfusion Injury-Induced Neuroinflammation by Modulating Glial Endoplasmic Reticulum Stress in Rats

PURPOSE

Glial activation and the disorders of cytokine secretion induced by endoplasmic reticulum stress (ERS) are crucial pathogenic processes in establishing ischemia/reperfusion (I/R) injury of the brain and spinal cord. This present study aimed to investigate the effects of mucous-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) on spinal cord ischemia/reperfusion (SCI/R) injury via regulating glial ERS.

METHODS

SCI/R was induced by thoracic aorta occlusion-reperfusion in rats. The MALT1-specific inhibitor MI-2 or human recombinant MALT1 protein (hrMALT1) was administrated for three consecutive days after the surgery. Immunofluorescent staining was used to detect the localization of MALT1 and ERS profiles in activated astrocyte and microglia of spinal cord. The ultrastructure of endoplasmic reticulum (ER) was examined by transmission electron microscopy. Blood-spinal cord barrier (BSCB) disruption and noninflammatory status were assessed. The neuron loss and demyelination in the spinal cord were monitored, and the hindlimb motor function was evaluated in SCI/R rats.

RESULTS

Intraperitoneally postoperative MI-2 treatment down-regulated phos-NF-κB (p65) and Bip (ERS marker protein) expression in the spinal cord after SCI/R in rats. Intraperitoneal injection MI-2 attenuated the swelling/dilation of ER of the glia in SCI/R rats. Furthermore, MI-2 attenuated I/R-induced Evans blue (EB) leakage and microglia M1 polarization in spinal cord, implying a role for MALT1 in the BSCB destruction and neuroinflammation after SCI/R in rats. Furthermore, intrathecal injection of hrMALT1 aggravated the fragmentation of neuron, loss of neurofibrils and demyelination caused by I/R, while 4-PBA, an ERS inhibitor, co-treatment with hrMALT1 reversed these effects in SCI/R rats. hrMALT1 administration aggravated the motor deficit index (MDI) scoring, while 4-PBA co-treatment improved SCI/R-induced motor deficits in rats.

CONCLUSION

Inhibition of MALT1 alleviates SCI/R injury-induced neuroinflammation by modulating glial endoplasmic reticulum stress in rats.

The influence of ApoE4 on the clinical outcomes and pathophysiology of degenerative cervical myelopathy

Degenerative cervical myelopathy (DCM) is the most common cause of nontraumatic spinal cord injury in adults worldwide. Surgical decompression is generally effective in improving neurological outcomes and halting progression of myelopathic deterioration. However, a subset of patients experience suboptimal neurological outcomes. Given the emerging evidence that apolipoprotein E4 (ApoE4) allelic status influences neurodegenerative conditions, we examined whether the presence of the ApoE4 allele may account for the clinical heterogeneity of treatment outcomes in patients with DCM. Our results demonstrate that human ApoE4⁺ DCM patients have a significantly lower extent of improvement after decompression surgery. Functional analysis of our DCM mouse model in targeted-replacement mice expressing human ApoE4 revealed delayed gait recovery, forelimb grip strength, and hind limb mechanical sensitivity after decompression surgery, compared with their ApoE3 counterparts. This was accompanied by an exacerbated proinflammatory response resulting in higher concentrations of TNF-α, IL-6, CCL3, and CXCL9. At the site of injury, there was a significant decrease in gray matter area, an increase in the activation of microglia/macrophages, and increased astrogliosis after decompression surgery in the ApoE4 mice. Our study is the first to our knowledge to investigate the pathophysiological underpinnings of ApoE4 in DCM, which suggests a possible personalized medicine approach for the treatment of DCM in ApoE4 carriers.

Ischemic spinal cord injury - experimental evidence and evolution of protective measures

BACKGROUND

Paraplegia remains one of the most devastating complications of descending and thoracoabdominal aortic repair. The aim of this review is to outline the current state of art in the rapidly developing field of spinal cord injury (SCI) research.

METHODS

A review of PubMed and Web of Science databases was performed using the following terms and their combinations: spinal cord, injury, ischemia, ischemia-reperfusion, ischemic spinal cord injury, paraplegia, paraparesis. Articles published before July 2019 were screened and included if considered relevant.

RESULTS

The review focuses on the topic of SCI and the developments concerning methods of monitoring, diagnostics and prevention of SCI.

CONCLUSIONS

Translation of novel technologies from bench to bedside and into everyday clinical practice is challenging, however each of the developing areas hold great promise in SCI prevention.

Chronic constriction injury of the sciatic nerve in rats causes different activation modes of microglia between the anterior and posterior horns of the spinal cord

Chronic constriction injury of the sciatic nerve is frequently considered as a cause of chronic neuropathic pain. Marked activation of microglia in the posterior horn (PH) has been well established with regard to this pain. However, microglial activation in the anterior horn (AH) is also strongly induced in this process. Therefore, in this study, we compared the differential activation modes of microglia in the AH and PH of the lumbar cord 7 days after chronic constriction injury of the left sciatic nerve in Wistar rats. Microglia in both the ipsilateral AH and PH demonstrated increased immunoreactivity of the microglial markers Iba1 and CD11b. Moreover, abundant CD68⁺ phagosomes were observed in the cytoplasm. Microglia in the AH displayed elongated somata with tightly surrounding motoneurons, whereas cells in the PH displayed a rather ameboid morphology and were attached to myelin sheaths rather than to neurons. Microglia in the AH strongly expressed NG2 chondroitin sulfate proteoglycan. Despite the tight attachment to neurons in the AH, a reduction in synaptic proteins was not evident, suggesting engagement of the activated microglia in synaptic stripping. Myelin basic protein immunoreactivity was observed in the phagosomes of activated microglia in the PH, suggesting the phagocytic removal of myelin. CCI caused both motor deficit and hyperalgesia that were evaluated by applying BBB locomotor rating scale and von Frey test, respectively. Motor defict was the most evident at postoperative day1, and that became less significant thereafter. By contrast, hyperalgesia was not severe at day 1 but it became worse at least by day 7. Collectively, the activation modes of microglia were different between the AH and PH, which may be associated with the difference in the course of motor and sensory symptoms.

Knockdown of the AIM2 molecule attenuates ischemia-reperfusion-induced spinal neuronal pyroptosis by inhibiting AIM2 inflammasome activation and subsequent release of cleaved caspase-1 and IL-1β

Ischemia-reperfusion (IR) injury induces activation of several inflammasomes that widely affect neuroinflammation and, subsequently, neuronal viability. The absent in melanoma 2 (AIM2) inflammasome is highly expressed in neurons after traumatic injury. This study was performed to investigate whether the AIM2 molecule acts as an initiator to trigger AIM2 inflammasome activation and regulate neuronal pyroptosis in a mouse IR model. The early motor dysfunction that occurred within the first 8 h post-IR injury was closely associated with a massive increase in dsDNA in serum and cerebrospinal fluid (CSF) at the same observed timepoints. However, the subsequent persistent dysfunction was consistent with the continuously increasing protein levels of apoptosis-associated speck-like protein containing a caspase-recruitment domain (ASC), cleaved caspase-1 and IL-1β with time. Upregulated AIM2 immunoreactivity was primarily visualized in neurons. The si-AIM2 treatment in vivo preserved part of motor function, accompanied by decreased protein levels of AIM2, ASC, cleaved caspase-1 and IL-1β. In vitro, the direct interactions between the AIM2 molecule and caspase-1 were demonstrated by immunofluorescence staining and coimmunoprecipitation. In this context, both si-AIM2 and Ac-YVAD-CMK treatments effectively maintained neuronal viability, as demonstrated by the decreased percentage of cells with pyroptosis and release of lactate dehydrogenase (LDH), accompanied by weak immunoreactivity and a decreased number of AIM2-caspase-1 positive neurons. By contrast, poly(dA-dT) treatment exacerbated neuronal pyroptosis by reversing the above-mentioned effects. However, no significant differences were observed after si-Con treatment. These results suggest AIM2 molecule played an important role in initiating AIM2 inflammasome activation through IR-induced release of ectopic dsDNA.

Neuroprotective mechanism involved in spinal cord stimulation postconditioning

OBJECTIVES

Delayed paraplegia developed postoperatively after thoracoabdominal aneurysm surgery is primarily associated with spinal cord ischemia/reperfusion injury. Our previous study suggested that spinal cord stimulation postconditioning protected the spinal cord from ischemia/reperfusion injury through microglia inhibition. In this study, we further investigated whether α7 nicotinic acetylcholine receptors were involved in the neuroprotective mechanism of spinal cord stimulation.

METHODS

Rabbits were randomly assigned to sham, control, 2 Hz, α-bungarotoxin, and 2 Hz-α-bungarotoxin groups (n = 24/group). Transient spinal cord ischemia was performed on all rabbits except rabbits in the sham group. Rabbits in the control group received no further intervention, rabbits in the 2 Hz group were given 2 Hz spinal cord stimulation, rabbits in the α-bungarotoxin group received prescribed intrathecal α-bungarotoxin (α-bungarotoxin, a specific α7 nicotinic acetylcholine receptor antagonist) injections, and rabbits in the 2 Hz-α-bungarotoxin group received both α-bungarotoxin injections and 2 Hz spinal cord stimulation. Hind-limb neurologic function was assessed, and spinal cord histologic examination, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining, and microglia staining were performed at 8 hours, 1 day, 3 days, and 7 days of reperfusion.

RESULTS

Rabbits in the 2 Hz group had significantly better neurologic functions, more α-motor neurons, and lower terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive neuron rates and microglia area/anterior horn area ratios (microglia area ratios) than the control group. The neurologic functions of the α-bungarotoxin group were significantly worse than those of the control group, whereas other results were not significantly different from the control group. The results of the 2 Hz-α-bungarotoxin group were insignificant to the control group except for the terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive neuron rates, which were significantly lower than in the control group.

CONCLUSIONS

The neuroprotective effects of spinal cord stimulation postconditioning against spinal cord ischemia/reperfusion injury were partially mediated by activating α7 nicotinic acetylcholine receptors.

Spinal cord stimulation postconditioning reduces microglial activation through down-regulation of ERK1/2 phosphorylation during spinal cord ischemic reperfusion in rabbits

Microglial activation plays a critical role in spinal cord ischemic reperfusion injury. Spinal cord stimulation preconditioning and postconditioning has shown spinal cord protection in ischemic reperfusion injury in animal studies. However, whether spinal cord stimulation could reduce microglial activation is still unclear. In this study, rabbits experienced 28-min infrarenal aorta occlusion and reperfusion for 8 h, 1, 3, and 7 days correspondingly. Immediately after reperfusion, rabbits received spinal cord stimulation of 2 or 50 Hz for 30 min and daily for a week. The results showed that spinal cord stimulation of 2 Hz reduced microglial activation. Microglial activation was accompanied with up-regulated p-ERK1/2, and microglial inhibition by 2 Hz spinal cord stimulation was associated with down-regulated p-ERK1/2. Spinal cord stimulation increased the expression of IL-1β. Our results revealed, for the first time, that spinal cord stimulation postconditioning suppresses microglial activation during spinal cord ischemic reperfusion by down-regulation of p-ERK1/2, which may be the protective mechanism of spinal cord stimulation.

Anti-Inflammatory Effect of Lycopene on Experimental Spinal Cord Ischemia Injury via Cyclooxygenase-2 Suppression

OBJECTIVE

Spinal cord ischemia/reperfusion injury (SCII) is a devastating complication following thoracoabdominal aortic surgeries, often leading to severe neurological deficits. We sought to examine the effects of lycopene, a naturally existing carotenoid with anti-inflammatory properties, in the treatment against SCII.

METHODS

Rats were assigned into four treatment groups: Sham (sham operation), SCII (SCII-induction), LY25, and LY50 (lycopene treatment at 25 or 50 mg/kg following SCII induction, respectively).

RESULTS

Lycopene treatment improved the recovery of neurological functions following SCII and suppressed the neuronal cell death and neuroinflammation at 14 days after SCII. Furthermore, Western blot assay revealed that lycopene treatment attenuated the SCII-induced increase in the protein levels of cyclooxygenase-2 (COX-2), nuclear factor-κB, and activate protein-1, as well as the reduction of heme oxygenase-1.

CONCLUSION

Lycopene exerted neuroprotective functions in SCII and inhibited SCII-elicited neuroinflammation via COX-2 suppression.

MicroRNA-125b mimic inhibits ischemia reperfusion-induced neuroinflammation and aberrant p53 apoptotic signalling activation through targeting TP53INP1

BACKGROUND

Ischemia reperfusion (IR) injury affects neuronal function through multiple pathogeneses that induce neuroinflammation and cellular apoptosis. The important roles of microRNAs (miRs) in the regulation of spinal cord IR have been recently reported. Among these roles, we investigated whether miR-125b and its downstream targets regulated the p53 signalling network and participated in both inflammation and apoptosis.

METHODS

An IR model was established via 12-min occlusion of the aortic arch. The direct interaction between miR-125b and TP53INP1 was demonstrated by Western blotting and luciferase assays. The cellular distributions of TP53INP1 were visualised by double immunofluorescence labelling. The effects of miR-125b on the expression of TP53INP1, p53 and release of proinflammatory cytokines were evaluated by synthetic miRs. Additionally, the detection of hind-limb motor function in vivo and motor neuronal apoptosis in vitro were evaluated to explore the potential mechanisms.

RESULTS

IR-induced alterations in hind-limb motor function were closely related to the temporal changes in miR-125b and TP53INP1 expression. The miR-125b/TP53INP1 gene pair was confirmed by luciferase assay. Compared with Sham controls, IR treatment resulted in increased TP53INP1 immunoreactivity that was primarily distributed in neurons. Treatment with miR-125b mimic markedly decreased the protein levels of TP53INP1, p53 and cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, whereas miR-125b control or inhibitor did not have the above-mentioned effects. Moreover, miR-125b mimic improved motor function in vivo and attenuated neuronal apoptosis in vitro, as demonstrated by the increased average Tarlov scores in lower limbs and lower percentages of neurons in the A4 and A2 quadrants of flow cytometry. Fluorescent staining and quantification further indicated that miR-125b mimic decreased the immunoreactivities of p53 and cleaved caspase 3 in neurons and simultaneously reduced the number of double-labelled cells with TP53INP1.

CONCLUSIONS

miR-125b mimic partially protected neurons against neuroinflammation and aberrant p53 network activation-induced apoptosis during IR injury through downregulation of TP53INP1.

Comparative effects of methylprednisolone and tetracosactide (ACTH1-24) on ischemia/reperfusion injury of the rabbit spinal cord

INTRODUCTION

Tetracosactide is an engineered peptide that applies the same biological impacts as the endogenous adrenocorticotropic hormone. Previous studies indicated that tetracosactide has anti-inflammatory, antioxidant and neurotrophic activity. In this study, we hypothesized that tetracosactide may have protective effects in spinal cord ischemia-reperfusion injury.

MATERIAL AND METHODS

Rabbits were randomized into the accompanying four groups of eight animals each: group 1 (control), group 2 (ischemia), group 3 (methylprednisolone) and group 4 (tetracosactide). In the control group, just a laparotomy was performed. In the various groups, the spinal cord ischemia model was made by the impediment of the aorta only caudal to the renal vein. Neurological assessment was conducted with the Tarlov scoring system. Levels of myeloperoxidase, malondialdehyde and catalase were analyzed, similar to the activities of xanthine oxidase and caspase-3. Histopathological and ultrastructural assessments were additionally performed.

RESULTS

After ischemia-reperfusion injury, increments were found in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p < 0.001), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both serum and tissue catalase levels were diminished (p < 0.001 for both). After the administration of tetracosactide, declines were seen in the tissue myeloperoxidase levels (p < 0.001), malondialdehyde levels (p = 0.003), xanthine oxidase action (p < 0.001) and caspase-3 movement (p < 0.001). Conversely, both the serum and tissue catalase levels were expanded (p < 0.001). Besides, tetracosactide treatment indicated enhanced results related to the histopathological scores (p < 0.001), the ultra-structural score (p = 0.008) and the Tarlov scores (p < 0.001).

CONCLUSIONS

The findings showed for the first time that tetracosactide shows significant neuroprotective activity against ischemia-reperfusion injury of the spinal cord.

Morphological characterization of NG2 glia and their association with neuroglial cells in the 3-nitropropionic acid-lesioned striatum of rat

Our aim was to examine the spatiotemporal profiles and phenotypic characteristics of neuron-glia antigen 2 (NG2) glia and their associations with neuroglial cells in striatal lesions due to the mitochondrial toxin 3-nitropropionic acid (3-NP). In control striatum, weak NG2 immunoreactivity was restricted to resting NG2 glia with thin processes, but prominent NG2 expression was noted on activated microglia/macrophages, and reactive NG2 glia in the lesion core after 3-NP injection. Activation of NG2 glia, including enhanced proliferation and morphological changes, had a close spatiotemporal relationship with infiltration of activated microglia into the lesion core. Thick and highly branched processes of reactive NG2 glia formed a cellular network in the astrocyte-free lesion core and primarily surrounded developing cavities 2–4 weeks post-lesion. NG2 glia became associated with astrocytes in the lesion core and the border of cavities over the chronic interval of 4–8 weeks. Immunoelectron microscopy indicated that reactive NG2 glia had large euchromatic nuclei with prominent nucleoli and thick and branched processes that ramified distally. Thus, our data provide detailed information regarding the morphologies of NG2 glia in the lesion core, and support the link between transformation of NG2 glia to the reactive form and microglial activation/recruitment in response to brain insults.

Delayed xenon post-conditioning mitigates spinal cord ischemia/reperfusion injury in rabbits by regulating microglial activation and inflammatory factors

The neuroprotective effect against spinal cord ischemia/reperfusion injury in rats exerted by delayed xenon post-conditioning is stronger than that produced by immediate xenon post-conditioning. However, the mechanisms underlying this process remain unclear. Activated microglia are the main inflammatory cell type in the nervous system. The release of pro-inflammatory factors following microglial activation can lead to spinal cord damage, and inhibition of microglial activation can relieve spinal cord ischemia/reperfusion injury. To investigate how xenon regulates microglial activation and the release of inflammatory factors, a rabbit model of spinal cord ischemia/reperfusion injury was induced by balloon occlusion of the infrarenal aorta. After establishment of the model, two interventions were given: (1) immediate xenon post-conditioning—after reperfusion, inhalation of 50% xenon for 1 hour, 50% N₂/50%O₂ for 2 hours; (2) delayed xenon post-conditioning—after reperfusion, inhalation of 50% N₂/50%O₂ for 2 hours, 50% xenon for 1 hour. At 4, 8, 24, 48 and 72 hours after reperfusion, hindlimb locomotor function was scored using the Jacobs locomotor scale. At 72 hours after reperfusion, interleukin 6 and interleukin 10 levels in the spinal cord of each group were measured using western blot assays. Iba1 levels were determined using immunohistochemistry and a western blot assay. The number of normal neurons at the injury site was quantified using hematoxylin-eosin staining. At 72 hours after reperfusion, delayed xenon post-conditioning remarkably enhanced hindlimb motor function, increased the number of normal neurons at the injury site, decreased Iba1 levels, and inhibited interleukin-6 and interleukin-10 levels in the spinal cord. Immediate xenon post-conditioning did not noticeably affect the above-mentioned indexes. These findings indicate that delayed xenon post-conditioning after spinal cord injury improves the recovery of neurological function by reducing microglial activation and the release of interleukin-6 and interleukin-10.

Phosphodiesterase inhibitor ameliorates neuronal injury in spinal cord ischemia/reperfusion injured rat model

This study investigated the mechanisms responsible for the neuroprotective effect of sildenafil citrate (SFC) on ischemia-reperfusion spinal cord (SC) injuries. Balloon occlusion of the thoracic aorta was used to induce SC ischemia. The animals (n=30) were separated into three groups: sham, SC injury with saline, and SC injury with 5mg/kg i.p. SFC treatment (SFC). The Basso, Beattie, and Bresnahan (BBB) score was determined to assess neurological function at different time intervals after reperfusion. After 48h, histopathology of the SC was assessed by triphenyltetrazolium chloride (TTC) and Nissl staining. Myeloperoxidase (MPO) activity was estimated using an MPO assay kit. Western blot and ELISA assays were performed to estimate interleukin 1 & 10 (IL-1 & IL-10), tumour necrosis factor α (TNF-α), and nuclear factor (NF-kB) levels in SC tissue homogenates. The study results suggest that treatment with SFC significantly increased neurological function compared with the SC group. In addition, SFC treatment reduced MPO activity compared with the SC group, which subsequently inhibited the infiltration of neutrophils into the SC. There was a significant (p<0.01) decrease in the expression of IL-1 and TNF-α, and an increase in the expression of IL-10 in SFC tissue homogenates compared with SC tissues. Moreover, SFC treatment inhibited the activation of NF-kB in the SC after injury. This study shows that SFC exerts a neuroprotective effect on the SC after ischemia/reperfusion injury by attenuating inflammatory mediators.

Methane ameliorates spinal cord ischemia-reperfusion injury in rats: Antioxidant, anti-inflammatory and anti-apoptotic activity mediated by Nrf2 activation

Methane is reported to have antioxidant, anti-inflammatory and anti-apoptotic properties. We investigated the potential neuroprotective effects of methane-rich saline (MS) on spinal cord ischemia-reperfusion injury and determined that its therapeutic benefits are associated with the activation of nuclear factor erythroid 2-related factor 2 (Nrf2). Rats received 9min of spinal cord ischemia induced by occlusion of the descending thoracic aorta plus systemic hypotension followed by a single MS treatment (10ml/kg, ip) and 72h reperfusion. MS treatment attenuated motor sensory deficits and produced high concentrations of methane in spinal cords during reperfusion, which increased Nrf2 expression and transcriptional activity in neurons, microglia and astrocytes in the ventral, intermediate and dorsal gray matter of lumbar segments. Heme oxygenase-1, superoxide dismutase, catalase and glutathione were upregulated; and glutathione disulfide, superoxide, hydrogen peroxide, malondialdehyde, 8-hydroxy-2-deoxyguanosine and 3-nitrotyrosine were downregulated in MS-treated spinal cords. MS treatment reduced neuronal apoptosis in gray matter zones, which was consistent with the suppression of cytochrome c release to the cytosol from the mitochondria and the activation of caspase-9 and -3. Throughout the gray matter, the activation of microglia and astrocytes was inhibited; the nuclear accumulation of phosphorylated nuclear factor-kappa B p65 was reduced; and tumor necrosis factor α, interleukin 1β, chemokine (C-X-C motif) ligand 1, intercellular adhesion molecule 1 and myeloperoxidase were decreased. MS treatment attenuated blood-spinal cord barrier dysfunction by preventing the expression and activity of matrix metallopeptidase-9 and disrupting tight junction proteins. Consecutive intrathecal injection of specific siRNAs targeting Nrf2 at 24-h intervals 3 days before ischemia reduced the beneficial effects of MS. Our data indicate that MS treatment prevents IR-induced spinal cord damage via antioxidant, anti-inflammatory and anti-apoptotic activities that involve the activation of Nrf2 signaling. Thus, methane may serve as a novel promising therapeutic agent for treating ischemic spinal cord injury.

Role of HMGB1 translocation to neuronal nucleus in rat model with septic brain injury

High-mobility Group Box-1 (HMGB1) is a central late proinflammatory cytokine that triggers the inflammatory response during sepsis. However, whether HMGB1 is involved in the pathogenesis of septic brain damage is unknown. In this study, we investigated the role of HMGB1 in regulating brain injury in a rat model of sepsis. Wistar rats were subjected to cecal ligation and puncture (CLP) to induce septic brain injury. Hematoxylin and eosin staining was used to detect pathological changes in the cortex. The cellular localization of HMGB1 was determined using immunostaining. Cortical levels of HMGB1, its receptor for advanced glycation end-products (RAGE), and downstream effecter, nuclear factor kappa-B (NF-κB) subunit p65, were detected via western blot.HMGB1was increased in the cytoplasm via translocation from the nucleus predominantly in neurons. Moreover, RAGE and NF-κB p65 were upregulated after septic brain injury. Ethyl pyruvate, an inhibitor of HMGB1, down-regulated the expression of RAGE and NF-κB p65via inhibiting HMGB1 expression in the cytoplasm. Collectively, our findings suggest that HMGB1 and its signaling transduction have critical roles in the pathogenesis of septic brain injury. HMGB1 inhibition might be a potential new therapeutic target for septic brain injury.

Moderate hypothermia increased the incidence of delayed paralysis through activation of the spinal microglia in an aortic cross-clamping rat model

BACKGROUND

Hypothermia reduces immediate paralysis during surgical repair of aortic aneurysms. However, it is unknown what the impact of hypothermia is on delayed paralysis, a serious complication of this type of surgery.

METHODS

Sprague-Dawley rats were subjected to occlusion of the descending aorta at different duration under normothermia (38.0±0.5) or hypothermia (33.0±0.5°). Neurologic function was assessed. Motor neuron number, glial activation, and cytokine expression in the spinal cord were examined. Minocycline was administered perioperatively by intraperitoneal injection in the rats subjected to the aorta occlusion.

RESULTS

In contrast to normothermia conditions at which immediate paralysis occurred when the duration of aorta occlusion exceeded 11.5min, hypothermia did not induce immediate paralysis if the duration of aorta occlusion was less than 41min. However, delayed paralysis was developed when the duration of aorta occlusion exceeded 18min, and reached peak level when the duration of aorta occlusion was 40min at hypothermia condition. The number of motoneurons was significantly decreased (P<0.05) at 30h postoperation. In addition, microglia was activated, and interleukin-1β and interleukin-6 levels were upregulated, both of which were co-localized in microglia at 24h postoperation in the hypothermia group. Minocycline treatment attenuated the incidence and degree of paralysis but did not decrease the mortality.

CONCLUSIONS

Hypothermia, a neuroprotective strategy in cardiothoracic surgery, increased the incidence of delayed paralysis through activation of spinal microglia and cytokines. Blocking the activated microglia may be a potential intervention to prevent the incidence of delayed paralysis.

Inflammatory mechanisms involved in brain injury following cardiac arrest and cardiopulmonary resuscitation

Cardiac arrest (CA) is a leading cause of fatality and long-term disability worldwide. Recent advances in cardiopulmonary resuscitation (CPR) have improved survival rates; however, the survivors are prone to severe neurological injury subsequent to successful CPR following CA. Effective therapeutic options to protect the brain from CA remain limited, due to the complexities of the injury cascades caused by global cerebral ischemia/reperfusion (I/R). Although the precise mechanisms of neurological impairment following CA-initiated I/R injury require further clarification, evidence supports that one of the key cellular pathways of cerebral injury is inflammation. The inflammatory response is orchestrated by activated glial cells in response to I/R injury. Increased release of danger-associated molecular pattern molecules and cellular dysfunction in activated microglia and astrocytes contribute to ischemia-induced cytotoxic and pro-inflammatory cytokines generation, and ultimately to delayed death of neurons. Furthermore, cytokines and adhesion molecules generated within activated microglia, as well as astrocytes, are involved in the innate immune response; modulate influx of peripheral immune and inflammatory cells into the brain, resulting in neurological injury. The present review discusses the molecular aspects of immune and inflammatory mechanisms in global cerebral I/R injury following CA and CPR, and the potential therapeutic strategies that target neuroinflammation and the innate immune system.

Inflammation Level after Decompression Surgery for a Rat Model of Chronic Severe Spinal Cord Compression and Effects on Ischemia-Reperfusion Injury

Delayed neurological deterioration in the absence of direct spinal cord insult following surgical decompression is a severe postoperative complication in patients with chronic severe spinal cord compression (SCC). The spinal cord ischemia-reperfusion injury (IRI) has been verified as a potential etiology of the complication. However, the exact pathophysiologic mechanisms of the decompression-related IRI remain to be defined. In this study, we developed a practical rat model of chronic severe SCC. To explore the underlying role of inflammation in decompression-related IRI, immunoreactivity of pro-inflammatory cytokines including tumor necrosis factor-alpha (TNF-α) and interleukin-1β (IL-1β) before and after decompression were measured. In addition, expression level of TNF-α and IL-1β was examined with Western blot. Immunohistochemical staining showed negative result in gray matters in the sham group and sham-decompression group. In the severe compression group, strong positive staining of TNF-α and IL-1β were found, suggesting a dramatic infiltration of inflammatory cells in gray matters. Furthermore, the severe compression group showed a significant increase in expression level of TNF-α and IL-1β as compared with the sham group (p < 0.05). In the severe compression-decompression group, both immunostaining and Western blot showed significant increase of TNF-α and IL-1β levels in the spinal cord compared with the severe compression group (p < 0.05). The results demonstrated that surgical decompression plays a stimulative role in inflammation through increasing the expression of inflammatory cytokines in the rat model of chronic severe SCC injury. Inflammation may be one of the important pathological mechanisms of decompression-related IRI of chronic ischemia.

Sevoflurane preconditioning ameliorates neuronal deficits by inhibiting microglial MMP-9 expression after spinal cord ischemia/reperfusion in rats

Background

Microglia are the primary immune cells of the spinal cord that are activated in response to ischemia/reperfusion (IR) injury and release various neurotrophic and/or neurotoxic factors to determine neuronal survival. Among them, matrix metalloproteinase-9 (MMP-9), which cleaves various components of the extracellular matrix in the basal lamina and functions as part of the blood spinal cord barrier (BSCB), is considered important for regulating inflammatory responses and microenvironmental homeostasis of the BSCB in the pathology of ischemia. Sevoflurane has been reported to protect against neuronal apoptosis during cerebral IR. However, the effects of sevoflurane preconditioning on spinal cord IR injury remain unclear. In this study, we investigated the role of sevoflurane on potential genetic roles of microglial MMP-9 in tight junction protein breakdown, opening of the BSCB, and subsequent recruitment of microglia to apoptotic spinal cord neurons.

Results

The results showed significant upregulation of MMP-9 in rats with IR-induced inflammation of the BSCB compared to that of the sham group, manifested as dysfunctional BSCB with increased Evans blue extravasation and reduced expression of occludin protein. Increased MMP-9 expression was also observed to facilitate invasion and migration of activated microglia, imaging as high Iba-1 expression, clustered to neurons in the injured spinal cord, as shown by double immunofluorescence, and increased proinflammatory chemokine production (CXCL10, CCL2). Further, sevoflurane preconditioning markedly improved motor function by ameliorating neuronal apoptosis, as shown by reduced TUNEL-positive cell counts and expression of cleaved caspase-3. These protective effects were probably responsible for downregulation of MMP-9 and maintenance of normal expression of occludin protein indicating BSCB integrity from inflammatory damage, which was confirmed by decreased protein levels of Iba-1 and MMP-9, as well as reduced production of proinflammatory chemokines (CXCL10, CCL2) and proinflammatory cytokines (IL-1β). Intrathecal injection of specific siRNAs targeting MMP-9 had similar protective effects to those of sevoflurane preconditioning.

Conclusions

Preconditioning with 2.4% sevoflurane attenuated spinal cord IR injury by inhibiting recruitment of microglia and secretion of MMP-9; thus inhibiting downstream effects on inflammatory damage to BSCB integrity and neuronal apoptosis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13041-014-0069-7) contains supplementary material, which is available to authorized users.

Role of the TLR4 pathway in blood-spinal cord barrier dysfunction during the bimodal stage after ischemia/reperfusion injury in rats

Background

Spinal cord ischemia-reperfusion (I/R) involves two-phase injury, including an initial acute ischemic insult and subsequent inflammatory reperfusion injury, resulting in blood-spinal cord barrier (BSCB) dysfunction involving the TLR₄ pathway. However, the correlation between TLR₄/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in BSCB dysfunction is not fully understood. The aim of this study is to characterize inflammatory responses in spinal cord I/R and the events that define its clinical progression with delayed neurological deficits, supporting a bimodal mechanism of injury.

Methods

Rats were intrathecally pretreated with TAK-242, MyD₈₈ inhibitory peptide, or Resveratrol at a 12 h interval for 3 days before undergoing 14-minute occlusion of aortic arch. Evan’s Blue (EB) extravasation and water content were detected at 6, 12, 18, 24, 36, 48, and 72 h after reperfusion. EB extravasation, water content, and NF-κB activation were increased with time after reperfusion, suggesting a bimodal distribution, as maximal increasing were detected at both 12 and 48 h after reperfusion. The changes were directly proportional to TLR₄ levels determined by Western blot. Double-labeled immunohistochemical analysis was also used to detect the relationship between different cell types of BSCB with TLR₄. Furthermore, NF-κB and IL-1β were analyzed at 12 and 48 h to identify the correlation between MyD₈₈-dependent and TRIF-dependent pathways.

Results

Rats without functional TLR₄ and MyD₈₈ attenuated BSCB leakage and inflammatory responses at 12 h, suggesting the ischemic event was largely mediated by MyD₈₈-dependent pathway. Similar protective effects observed in rats with depleted TLR₄, MyD₈₈, and TRIF receptor at 48 h infer that the ongoing inflammation which occurred in late phase was mainly initiated by TRIF-dependent pathway and such inflammatory response could be further amplified by MyD₈₈-dependent pathway. Additionally, microglia appeared to play a major role in early phase of inflammation after I/R injury, while in late responding phase both microglia and astrocytes were necessary.

Conclusions

These findings indicate the relevance of TLR₄/MyD₈₈-dependent and TLR₄/TRIF-dependent pathways in bimodal phases of inflammatory responses after I/R injury, corresponding with the clinical progression of injury and delayed onset of symptoms. The clinical usage of TLR₄ signaling inhibitors at different phases may be a therapeutic option for the prevention of delayed injury.

Glycyrrhizin protects spinal cord and reduces inflammation in spinal cord ischemia-reperfusion injury

OBJECTIVE

Inflammation, which is detrimental to the neurologic defect after ischemia-reperfusion, provides a potential target for therapeutic approach for spinal cord ischemia-reperfusion injury. High mobility group box 1 (HMGB-1) was recently discovered to be a crucial cytokine that mediates the response to infection, injury and inflammation. The present study aimed to gain a deep insight into the neuroprotective effect of glycyrrhizin in the process of ischemia and reperfusion injury in spinal cord of mice.

METHODS

Spinal cord ischemia was induced in male C57BL/6 mice by occlusion of the thoracic aorta. The experimental groups (n = 6 per group) included sham operation, control (receiving phosphate buffered saline (PBS)) and glycyrrhizin (10 mg/kg, when cross-clamped). Neurologic function was assessed by the motor function score of the hind limbs at 72 hours after reperfusion. Histologic changes were studied using hematoxylin and eosin staining. Expression changes of inflammatory cytokines or their receptors at messenger RNA level or protein level were determined by real-time transcription polymerase chain reaction or enzyme-linked immunosorbent assay at different time points post reperfusion. Nuclear factor κB (NF-κB) activity was examined with Western blotting.

RESULTS

Compared with the control group, the glycyrrhizin group showed significantly improved neurologic outcome, reduced apoptosis of motoneurons of spinal anterior horn, decreased the activation of NF-κB and subsequent inflammatory cytokines expression [tumor necrosis factor (TNF) and interleukin 1β (IL-1β)], and alleviated neutrophil infiltration in ischemic spinal cord. HMGB-1 treatment also reduced the expressions of itself.

CONCLUSIONS

Treatment with glycyrrhizin exerted a neuroprotective effect against spinal cord ischemia-reperfusion injury. The anti-inflammatory effect was believed to be one of the contributing mechanisms. Our findings provided experimental and therapeutic options for the treatment of spinal cord ischemia-reperfusion injury.

Development and treatments of inflammatory cells and cytokines in spinal cord ischemia-reperfusion injury

During aortic surgery, interruption of spinal cord blood flow might cause spinal cord ischemia-reperfusion injury (IRI). The incidence of spinal cord IRI after aortic surgery is up to 28%, and patients with spinal cord IRI might suffer from postoperative paraplegia or paraparesis. Spinal cord IRI includes two phases. The immediate spinal cord injury is related to acute ischemia. And the delayed spinal cord injury involves both ischemic cellular death and reperfusion injury. Inflammation is a subsequent event of spinal cord ischemia and possibly a major contributor to spinal cord IRI. However, the development of inflammatory mediators is incompletely demonstrated. And treatments available for inflammation in spinal cord IRI are insufficient. Improved understanding about spinal cord IRI and the development of inflammatory cells and cytokines in this process will provide novel therapeutic strategies for spinal cord IRI. Inflammatory cytokines (e.g., TNF-α and IL-1) may play an important role in spinal cord IRI. For treatment of several intractable autoimmune diseases (e.g., rheumatoid arthritis), where inflammatory cytokines are involved in disease progression, anti-inflammatory cytokine antagonist is now available. Hence, there is great potential of anti-inflammatory cytokine antagonist for therapeutic use of spinal cord IRI. We here review the mediators and several possibilities of treatment in spinal cord IRI.

The effect of ribavirin on reactive astrogliosis in experimental autoimmune encephalomyelitis

Experimental autoimmune encephalomyelitis (EAE) is an animal model of CNS inflammatory and demyelinating disease multiple sclerosis. Microglia and astrocytes represent two related cell types involved in the brain pathology in EAE. Accumulations of hypertrophic reactive astrocytes, intensely stained with glial fibrillary acidic protein (GFAP), which also expressed vimentin, are prominent features of EAE lesions. Recent studies from our laboratory reported that ribavirin attenuated the disease process in EAE by reducing clinical and histological manifestations. EAE was induced in genetically susceptible Dark Agouti rats with syngeneic spinal cord homogenate in complete Freund's adjuvant. Real time PCR and immunohistochemistry were used for determination of GFAP and vimentin gene and tissue expression. We have observed the increased gene and tissue expression of GFAP and vimentin in EAE rats. Ribavirin treatment significantly decreased the number of reactive astrocytes at the peak of disease. At the end of the disease, we have observed reactive GFAP(+) and vimentin(+) astrocytes in both immunized and ribavirin-treated groups, accompanied by increased level of GFAP mRNA. The present study indicates that ribavirin may have the ability to attenuate astrocyte proliferation and glial scaring at the peak of the disease and modulate the astroglial response to EAE during the time-course of the disease.

Development of AMPA receptor and GABA B receptor-sensitive spinal hyper-reflexia after spinal air embolism in rat: a systematic neurological, electrophysiological and qualitative histopathological study

Decompression sickness results from formation of bubbles in the arterial and venous system, resulting in spinal disseminated neurodegenerative changes and may clinically be presented by motor dysfunction, spinal segmental stretch hyper-reflexia (i.e., spasticity) and muscle rigidity. In our current study, we describe a rat model of spinal air embolism characterized by the development of similar spinal disseminated neurodegenerative changes and functional deficit. In addition, the anti-spastic potency of systemic AMPA receptor antagonist (NGX424) or GABA B receptor agonist (baclofen) treatment was studied. To induce spinal air embolism, animals received an intra-aortic injection of air (50-200 μl/kg). After embolism, the development of spasticity was measured using computer-controlled ankle rotation. Animals receiving 150 or 200 μl of intra-aortic air injections displayed motor dysfunction with developed spastic (50-60% of animals) or flaccid (25-35% of animals) paraplegia at 5-7 days. MRI and spinal histopathological analysis showed disseminated spinal cord infarcts in the lower thoracic to sacral spinal segments. Treatment with NGX424 or baclofen provided a potent anti-spasticity effect (i.e., stretch hyper-reflexia inhibition). This model appears to provide a valuable experimental tool to study the pathophysiology of air embolism-induced spinal injury and permits the assessment of new treatment efficacy targeted to modulate neurological symptoms resulting from spinal air embolism.

Spatial and temporal activation of spinal glial cells: role of gliopathy in central neuropathic pain following spinal cord injury in rats

In the spinal cord, neuron and glial cells actively interact and contribute to neurofunction. Surprisingly, both cell types have similar receptors, transporters and ion channels and also produce similar neurotransmitters and cytokines. The neuroanatomical and neurochemical similarities work synergistically to maintain physiological homeostasis in the normal spinal cord. However, in trauma or disease states, spinal glia become activated, dorsal horn neurons become hyperexcitable contributing to sensitized neuronal-glial circuits. The maladaptive spinal circuits directly affect synaptic excitability, including activation of intracellular downstream cascades that result in enhanced evoked and spontaneous activity in dorsal horn neurons with the result that abnormal pain syndromes develop. Recent literature reported that spinal cord injury produces glial activation in the dorsal horn; however, the majority of glial activation studies after SCI have focused on transient and/or acute time points, from a few hours to 1 month, and peri-lesion sites, a few millimeters rostral and caudal to the lesion site. In addition, thoracic spinal cord injury produces activation of astrocytes and microglia that contributes to dorsal horn neuronal hyperexcitability and central neuropathic pain in above-level, at-level and below-level segments remote from the lesion in the spinal cord. The cellular and molecular events of glial activation are not simple events, rather they are the consequence of a combination of several neurochemical and neurophysiological changes following SCI. The ionic imbalances, neuroinflammation and alterations of cell cycle proteins after SCI are predominant components for neuroanatomical and neurochemical changes that result in glial activation. More importantly, SCI induced release of glutamate, proinflammatory cytokines, ATP, reactive oxygen species (ROS) and neurotrophic factors trigger activation of postsynaptic neuron and glial cells via their own receptors and channels that, in turn, contribute to neuronal-neuronal and neuronal-glial interaction as well as microglia-astrocytic interactions. However, a systematic review of temporal and spatial glial activation following SCI has not been done. In this review, we describe time and regional dependence of glial activation and describe activation mechanisms in various SCI models in rats. These data are placed in the broader context of glial activation mechanisms and chronic pain states. Our work in the context of work by others in SCI models demonstrates that dysfunctional glia, a condition called "gliopathy", is a key contributor in the underlying cellular mechanisms contributing to neuropathic pain.

The blood-spinal cord barrier: morphology and clinical implications

The blood-spinal cord barrier (BSCB) is the functional equivalent of the blood-brain barrier (BBB) in the sense of providing a specialized microenvironment for the cellular constituents of the spinal cord. Even if intuitively the BSCB could be considered as the morphological extension of the BBB into the spinal cord, evidence suggests that this is not so. The BSCB shares the same principal building blocks with the BBB; nevertheless, it seems that morphological and functional differences may exist between them. Dysfunction of the BSCB plays a fundamental role in the etiology or progression of several pathological conditions of the spinal cord, such as spinal cord injury, amyotrophic lateral sclerosis, and radiation-induced myelopathy. This review summarizes current knowledge of the morphology of the BSCB, the methodology of studying the BSCB, and the potential role of BSCB dysfunction in selected disorders of the spinal cord, and finally summarizes therapeutic approaches to the BSCB.

A mouse model of ischemic spinal cord injury with delayed paralysis caused by aortic cross-clamping

BACKGROUND

Spinal cord ischemia and paralysis are devastating perioperative complications that can accompany open or endovascular repair surgery for aortic aneurysms. Here, we report on the development of a new mouse model of spinal cord ischemia with delayed paralysis induced by cross-clamping the descending aorta.

METHODS

Transient aortic occlusion was produced in mice by cross-clamping the descending aorta through a lateral thoracotomy. To establish an optimal surgical procedure with limited mortality, variable cross-clamp times and core temperatures were tested between experiments.

RESULTS

The onset of paresis or paralysis and postsurgical mortality varied as a function of cross-clamp time and core temperature that was maintained during the period of cross-clamp. Using optimal surgical parameters (7.5-min cross-clamp duration at 33°C core temperature), the onset of paralysis is delayed 24-36 h after reperfusion, and more than 95% of mice survive through 9 weeks after surgery. These mice are further stratified into two groups, 70% (n = 19/27) of mice developing severe hind limb paralysis and the remaining mice showing mild, though still permanent, behavioral deficits.

CONCLUSION

This new model should prove useful as a preclinical tool for screening neuroprotective therapeutics and for defining the basic biologic mechanisms that cause delayed paralysis and neurodegeneration after transient spinal cord ischemia.

Does high-dose opioid anesthesia exacerbate ischemic spinal cord injury in rabbits?

PURPOSE

Intrathecal morphine given during a post-ischemic period has been reported to have the potential to exacerbate ischemic spinal cord injury. However, it remains unknown whether synthetic opioids administered systemically exacerbate ischemic injury. We sought to compare the damage of the spinal cord after transient spinal cord ischemia in rabbits anesthetized with three different regimens; isoflurane, fentanyl with isoflurane, and remifentanil with isoflurane.

METHODS

We assigned rabbits to three groups (n = 9 in each); an isoflurane group (isoflurane 1 minimum alveolar concentration [MAC]), a fentanyl group (isoflurane 0.5 MAC + 100 microg x kg(-1) i.v. fentanyl given over 30 min before aortic occlusion), and a remifentanil group (isoflurane 0.5 MAC + 1 microg x kg(-1) x min(-1) i.v. remifentanil started 30 min before aortic occlusion and maintained until 1 h after reperfusion). Spinal cord ischemia was produced by occluding the abdominal aorta for 13 min. Hindlimb motor function (score range: 4, normal to 0, paraplegia) was assessed daily for 7 days, and then the number of normal neurons in the anterior spinal cord was counted.

RESULTS

Severe motor dysfunction (score < or = 1) was observed in seven, four, and five animals in the isoflurane, fentanyl, and remifentanil groups, respectively. There were no significant intergroup differences in neurological scores. There were no differences in the numbers of normal neurons among the three groups (22 +/- 22, 42 +/- 30, 33 +/- 28, respectively).

CONCLUSION

Our results suggest that neither i.v. fentanyl nor i.v. remifentanil added to 0.5 MAC isoflurane exacerbated ischemic spinal cord injury in rabbits when compared to 1 MAC isoflurane.

Tight glycemic control by insulin, started in the preischemic, but not postischemic, period, protects against ischemic spinal cord injury in rabbits

BACKGROUND

It is not well established whether insulin protects against ischemic spinal cord injury. We examined the effects of a single dose of insulin that corrects mild hyperglycemia on the outcome after transient spinal cord ischemia in rabbits.

METHODS

We assigned rabbits to four groups (n = 8 in each); untreated control (C) group, preischemic insulin (Pre-I) group, preischemic insulin with glucose (GI) group (glucose concentrations were maintained at levels similar to the C group by the administration of glucose), and postischemic insulin (Post-I) group. Insulin (0.5 IU/kg) was administered 30 min before ischemia in the Pre-I and GI groups, and just after reperfusion in the Post-I group. Spinal cord ischemia was produced by occluding the abdominal aorta for 13 min. Neurologic and histopathologic evaluations were performed 7 days after ischemia.

RESULTS

The mean blood glucose concentration before ischemia in the Pre-I group (118 mg/dL) was significantly lower than in the other three groups (158-180 mg/dL) and those of 30 min after reperfusion in the Pre-I (92 mg/dL) and Post-I (100 mg/dL) groups were significantly lower than in the C (148 mg/dL) and GI (140 mg/dL) groups. The motor function score and number of normal neurons in the anterior lumbar spinal cord in the Pre-I group were significantly greater than in the other three groups.

CONCLUSIONS

These results suggest that a relatively small dose of preischemic insulin protects against ischemic spinal cord injury, and that the protective effects result from tight glycemic control before ischemia.

Real-time direct measurement of spinal cord blood flow at the site of compression: relationship between blood flow recovery and motor deficiency in spinal cord injury

STUDY DESIGN

An in vivo study to measure rat spinal cord blood flow in real-time at the site of compression using a newly developed device.

OBJECTIVES

To evaluate the change in thoracic spinal cord blood flow by compression force and to clarify the association between blood flow recovery and motor deficiency after a spinal cord compression injury.

SUMMARY OF BACKGROUND DATA

Until now, no real-time measurement of spinal cord blood flow at the site of compression has been conducted. In addition, it has not been clearly determined whether blood flow recovery is related to motor function after a spinal cord injury.

METHODS

Our blood flow measurement system was a combination of a noncontact type laser Doppler system and a spinal cord compression device. The rat thoracic spinal cord was exposed at the 11th vertebra and spinal cord blood flow at the site of compression was continuously measured before, during, and after the compression. The functioning of the animal's hind-limbs was evaluated by the Basso, Beattie and Bresnahan scoring scale and the frequency of voluntary standing. Histologic changes such as permeability of blood-spinal cord barrier, microglia proliferation, and apoptotic cell death were examined in compressed spinal cord tissue.

RESULTS

The spinal blood flow decreased on each increase in the compression force. After applying a 5-g weight, the blood flow decreased to <40% of the precompression level. Complete ischemia was reached using a 20-g weight. After decompression, the blood flow level in the 20-minute complete ischemia group was significantly higher than that in the 40-minute complete ischemia group. The hind-limb motor function in the 40-minute complete ischemia group was significantly less than that in the sham group (without compression), while no significant difference was observed between the 20-minute ischemia group and the sham group. In the 20-minute ischemia group, the rats whose spinal cord blood flow recovery was incomplete showed significant motor function loss compared with rats that completely recovered blood flow. Extensive breakdown of blood-spinal cord barrier integrity and the following microglia proliferation and apoptotic cell death were detected in the 40-minute complete ischemia group.

CONCLUSION

Duration of ischemia/compression and blood flow recovery of the spinal cord are important factors in the recovery of motor function after a spinal cord injury.

Multilevel somatosensory evoked potentials and cerebrospinal proteins: indicators of spinal cord injury in thoracoabdominal aortic aneurysm surgery

OBJECTIVE

Multilevel somatosensory evoked potentials (SSEP) and the release of biochemical markers in cerebrospinal fluid (CSF) were investigated to identify patients with spinal cord ischemia during thoracoabdominal aortic repair and/or a vulnerable spinal cord during the postoperative period.

METHODS

Thirty-nine consecutive patients undergoing elective aneurysm repair using distal aortic perfusion and cerebrospinal fluid drainage were studied. Continuous SSEP were monitored using nerve stimulation of the right and left posterior tibial nerves with signal recording at the level of both common peroneal nerves, the cervical cord and at the cortical level. CSF concentrations of the markers glial fibrillary acidic protein (GFAp), the light subunit of neurofilament triplet protein (NFL), and S100B were determined at different time points from before surgery until 3 days postoperatively.

RESULTS

SSEP indicated spinal cord ischemia in two patients leading to additional intercostal artery reattachments. In one of them the signal loss was permanent and the patient woke up with paraplegia. In the other the signal returned but the patient later developed delayed paraplegia. Three patients without SSEP indications of spinal cord ischemia during surgery later developed delayed paraplegia. The patients with spinal cord symptoms had significant increases, during the postoperative period of CSF biomarkers GFAp (571-fold), NFL (14-fold) and S100B (18-fold) compared to asymptomatic patients. GFAp increased before or in parallel to onset of symptoms in the patients with delayed paraplegia.

CONCLUSIONS

Peroperative multilevel SSEP has a high specificity in detecting spinal cord ischemia but does not identify all patients with a postoperative vulnerable spinal cord. Biochemical markers in CSF increase too late for intraoperative monitoring but GFAp is promising for identifying patients at risk for postoperative delayed paraplegia.

Inhibition of macrophage activation and phagocytosis by a novel NF-κB inhibitor, dehydroxymethylepoxyquinomicin

Previously, we designed and synthesized a new NF-kappaB inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ). In the present research we looked into the effect of DHMEQ on the activation of macrophages, especially on the phagocytotic activity of cells of the mouse macrophage-like cell line RAW264.7. DHMEQ inhibited lipopolysaccharide (LPS)-induced NF-kappaB activation by inhibiting its nuclear translocation from the cytoplasm. It also inhibited the expression of inducible NO synthase (iNOS) and nitric oxide (NO) production induced by LPS and interferon-gamma. Using enzyme-linked immunosorbent assays (ELISAs) we showed DHMEQ to inhibit LPS-induced secretion of IL-6, IL-12, interleukin-1beta (IL-1beta), and TNF-alpha. Furthermore, DHMEQ also inhibited the phagocytosis of fluorescently labeled Escherichia coli by RAW264.7 cells treated with LPS or IL-1beta, thus being the first evidence for the involvement of NF-kappaB in the regulation of phagocytosis by use of this inhibitor. Deletion of p65 by siRNA also inhibited the phagocytosis. DHMEQ inhibited the LPS-induced but not IL-1beta-induced phagocytosis of glass beads, indicating that activation of not only NF-kappaB but also Toll-like receptor 4 (TLR-4) is essential for the phagocytosis of E. coli. Previously we found that DHMEQ inhibited type 2 collagen-induced rheumatoid arthritis and the growth of various human carcinomas in mice. It is thus likely that inhibition of macrophage activation is involved in the mechanism of these anti-inflammatory and antitumor activities of DHMEQ in mice.

The effect of thalidomide on spinal cord ischemia/reperfusion injury in a rabbit model

STUDY DESIGN

Randomized study.

OBJECTIVES

To evaluate the effects of thalidomide on spinal cord ischemia/reperfusion injury via reduced TNF-alpha production.

SETTING

Animal experimental laboratory, Clinical Research Institute of Seoul National University Hospital, Seoul, Korea.

METHODS

Spinal cord ischemia was induced in rabbits by occluding the infrarenal aorta. Rabbits in group N did not undergo ischemic insult, but rabbits in groups C (the untreated group), THA, and THB underwent ischemic insult for 15 min. The THA and THB groups received thalidomide (20 mg/kg) intraperitoneally (i.p.) before ischemia, but only the THB group received thalidomide (i.p., 20 mg/kg) after 24 and 48 h of reperfusion. After evaluating neurologic functions at 1.5 h, 3, and 5 days of reperfusion, rabbits were killed for histopathologic examination and Western blot analysis of TNF-alpha.

RESULTS

The THA and THB groups showed significantly less neurologic dysfunction than the C group at 1.5 h, 3, and 5 days of reperfusion. The number of normal spinal motor neurons in ventral gray matter was higher in THA and THB than in C, but no difference was observed between THA and THB. Western blot analysis showed a significantly higher level of TNF-alpha in C than in THA and THB at 1.5 h of reperfusion, but no difference was observed between C, THA, or THB at 3 or 5 days of reperfusion.

CONCLUSION

Thalidomide treatment before ischemic insult reduces early phase ischemia/reperfusion injury of the spinal cord in rabbits.

Expression and changes of calbindin D-28k immunoreactivity in the ventral horn after transient spinal cord ischemia in rabbits

We examined ischemia-related changes of calbindin D-28k (CB) immunoreactivity in L(7) of the spinal ventral horn after transient spinal cord ischemia in rabbits. In the sham-operated group, CB immunoreactivity was not present in the spinal ventral horn, but CB immunoreactivity was detectable in the dorsal horn. CB immunoreactivity was detectable in the ventral horn at 30 min after ischemia: the CB immunoreactivity was found in glial cells identified as astrocytes. At 1 h after ischemia, CB immunoreactivity was highest and present at a few somata located in the lamina VII as well as many glial cells. CB immunoreactivity was lower in the lamina VII at 3 h after ischemia compared to 1 h post-ischemic group. By 2 days after ischemia, CB immunoreactivity was decreased in this region. In addition, the result of Western blot result showed the pattern of CB expression similar to that of immunohistochemistry. In conclusion, the ischemia-related changes of CB immunoreactivity in neurons and glial cells in the ischemic spinal ventral horn in rabbits may be related to modulation of intracellular calcium following transient ischemia.