Molecular insights of the injured lesions of rat spinal cords: Inflammation, apoptosis, and cell survival

Neuroprotective effects of lovastatin against traumatic spinal cord injury in rats

BACKGROUND

Lovastatin, as a drug of statins subgroup, has been conceptualized to have anti-inflammatory, antioxidant, and anti-apoptotic properties. Accordingly, the present study aimed to investigate the neuroprotective ramification of lovastatin on spinal cord injury (SCI).

MATERIAL AND METHODS

Seventy-five female adult Wistar rats were divided into five groups (n = 15). In addition to non-treated (Control group) and laminectomy alone (Sham group), SCI animals were randomly assigned to non-treated spinal cord injury (SCI group), treated with 2 mg/kg of lovastatin (Lova 2 group), and treated with 5 mg/kg of lovastatin (Lova 5 group). At the end of the study, to evaluate the treatments, MDA, CAT, SOD, and GSH factors were evaluated biochemically, apoptosis and gliosis were assessed by immunohistochemical while measuring caspase-3 and GFAP antibodies, and inflammation was estimated by examining the expression of IL-10, TNF-α, and IL-1β genes. The stereological method was used to appraise the total volume of the spinal cord at the site of injury, the volume of the central cavity created, and the density of neurons and glial cells in the traumatic area. In addition, Basso-Beattie-Bresnehan (BBB) and narrow beam test (NBT) were utilized to rate neurological functions.

RESULTS

Our results exposed the fact that biochemical factors (except MDA), stereological parameters, and neurological functions were significantly ameliorated in both lovastatin-treated groups, especially in Lova 5 ones, compared to the SCI group. The expression of the IL-10 gene was significantly upregulated in both lovastatin-treated groups compared to the SCI group and was considerably heighten in Lova 5 group. Expression of TNF-α and IL-1β, as well as the rate of apoptosis and GFAP positive cells significantly decreased in both lovastatin treated groups compared to the SCI group, and it was more pronounced in the Lova 5 ones.

CONCLUSION

Overall, using lovastatin, especially at a dose of 5 mg/kg, has a dramatic neuroprotective impact on SCI treatment.

Investigation into the potential mechanism and molecular targets of Fufang Xueshuantong capsule for the treatment of ischemic stroke based on network pharmacology and molecular docking

Fufang Xueshuantong (FFXST) capsule is a traditional Chinese medicine (TCM) preparation used to activate blood circulation, resolve stasis, benefit qi, and nourish yin in clinical practice. However, its potential mechanism and molecular targets after ischemic stroke (IS) have not been investigated. The aim of this research was to investigate the molecular mechanisms of FFXST in the treatment of IS based on network pharmacology and molecular docking. We used the Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform (TCMSP) to collect candidate compounds of four herbs in FFXST; disease-related differential genes were screened using the Gene Expression Omnibus (GEO) database, and a compound–disease network was created using Cytoscape 3.8.2 software. The topological analysis of the protein–protein interaction (PPI) network was then created to determine the candidate targets of FFXST against IS. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses were conducted using the clusterProfiler package in R. The gene–pathway network of FFXST against IS was created to obtain the key target genes. Molecular docking was used to validate the core targets using AutoDock Vina 1.1.2. A total of 455 candidate compounds of FFXST and 18,544 disease-related differential genes were screened. Among them, FFXST targets for IS treatment had 67 active compounds and 10 targets in the PPI network related to STAT1, STAT3, and HIF1A. The biological processes of GO analysis included the regulation of reactive oxygen species metabolic process, cellular response to chemical stress, regulation of angiogenesis, regulation of vasculature development, positive regulation of cytokine production, and response to oxidative stress. The KEGG enrichment analysis showed that Kaposi sarcoma-associated herpesvirus infection, microRNAs in the cancer signaling pathway, Th17 cell differentiation, and HIF-1 signaling pathway were significantly enriched. The network pharmacology outcomes were further verified by molecular docking. We demonstrated that FFXST protection against IS may relate to the regulation of oxidative stress, immune inflammatory response, and angiogenesis through the relevant signaling pathways. Our study systematically illustrated the application of network pharmacology and molecular docking in evaluating characteristics of multi-component, multi-target, and multi-pathway of FFXST for IS.

Neurological recovery and antioxidant effect of erythropoietin for spinal cord injury: A systematic review and meta-analysis

Background

To critically evaluate the neurological recovery effects and antioxidant effects of erythropoietin (EPO) in rat models of spinal cord injury (SCI).

Methods

The PubMed, EMBASE, MEDLINE, ScienceDirect, and Web of Science were searched for animal experiments applying EPO to treat SCI to January 2022. We included studies which examined neurological function by the Basso, Beattie, and Bresnahan (BBB) scale, as well as cavity area and spared area, and determining the molecular-biological analysis of antioxidative effects by malondialdehyde (MDA) levels in spinal cord tissues. Meta-analysis were performed with Review Manager 5.4 software.

Results

A total of 33 studies were included in this review. The results of the meta-analysis showed that SCI rats receiving EPO therapy showed a significant locomotor function recovery after 14 days compared with control, then the superiority of EPO therapy maintained to 28 days from BBB scale. Compared with the control group, the cavity area was reduced [4 studies, weighted mean difference (WMD) = −16.65, 95% CI (−30.74 to −2.55), P = 0.02] and spared area was increased [3 studies, WMD =11.53, 95% CI (1.34 to 21.72), P = 0.03] by EPO. Meanwhile, MDA levels [2 studies, WMD = −0.63 (−1.09 to −0.18), P = 0.007] were improved in the EPO treatment group compared with control, which indicated its antioxidant effect. The subgroup analysis recommended 5,000 UI/kg is the most effective dose [WMD = 4.05 (2.23, 5.88), P < 0.0001], although its effect was not statistically different from that of 1,000 UI/kg. Meanwhile, the different rat strains (Sprague-Dawley vs. Wistar), and models of animals, as well as administration method (single or multiple administration) of EPO did not affect the neuroprotective effect of EPO for SCI.

Conclusions

This systematic review indicated that EPO can promote the recovery of the locomotor function of SCI rats. The mechanism exploration of EPO needs to be verified by experiments, and then carefully designed randomized controlled trials are needed to explore its neural recovery effects.

MicroRNA-138-5p Targets Pro-Apoptotic Factors and Favors Neural Cell Survival: Analysis in the Injured Spinal Cord

The central nervous system microRNA miR-138-5p has attracted much attention in cancer research because it inhibits pro-apoptotic genes including CASP3. We hypothesize that miR-138-5p downregulation after SCI leads to overexpression of pro-apoptotic genes, sensitizing neural cells to noxious stimuli. This study aimed to identify miR-138-5p targets among pro-apoptotic genes overexpressed following SCI and to confirm that miR-138-5p modulates cell death in neural cells. Gene expression and histological analyses revealed that the drop in miR-138-5p expression after SCI is due to the massive loss of neurons and oligodendrocytes and its downregulation in neurons. Computational analyses identified 176 potential targets of miR-138-5p becoming dysregulated after SCI, including apoptotic proteins CASP-3 and CASP-7, and BAK. Reporter, RT-qPCR, and immunoblot assays in neural cell cultures confirmed that miR-138-5p targets their 3′UTRs, reduces their expression and the enzymatic activity of CASP-3 and CASP-7, and protects cells from apoptotic stimuli. Subsequent RT-qPCR and histological analyses in a rat model of SCI revealed that miR-138-5p downregulation correlates with the overexpression of its pro-apoptotic targets. Our results suggest that the downregulation of miR-138-5p after SCI may have deleterious effects on neural cells, particularly on spinal neurons.

EGF signaling promotes the lineage conversion of astrocytes into oligodendrocytes

Background

The conversion of astrocytes activated by nerve injuries to oligodendrocytes is not only beneficial to axonal remyelination, but also helpful for reversal of glial scar. Recent studies have shown that pathological niche promoted the Sox10-mediated astrocytic transdifferentiation to oligodendrocytes. The extracellular factors underlying the cell fate switching are not known.

Methods

Astrocytes were obtained from mouse spinal cord dissociation culture and purified by differential adherent properties. The lineage conversion of astrocytes into oligodendrocyte lineage cells was carried out by Sox10-expressing virus infection both in vitro and in vivo, meanwhile, epidermal growth factor (EGF) and epidermal growth factor receptor (EGFR) inhibitor Gefitinib were adopted to investigate the function of EGF signaling in this fate transition process. Pharmacological inhibition analyses were performed to examine the pathway connecting the EGF with the expression of oligodendrogenic genes and cell fate transdifferentiation.

Results

EGF treatment facilitated the Sox10-induced transformation of astrocytes to O4⁺ induced oligodendrocyte precursor cells (iOPCs) in vitro. The transdifferentiation of astrocytes to iOPCs went through two distinct but interconnected processes: (1) dedifferentiation of astrocytes to astrocyte precursor cells (APCs); (2) transformation of APCs to iOPCs, EGF signaling was involved in both processes. And EGF triggered astrocytes to express oligodendrogenic genes Olig1 and Olig2 by activating extracellular signal-regulated kinase 1 and 2 (Erk1/2) pathway. In addition, we discovered that EGF can enhance astrocyte transdifferentiation in injured spinal cord tissues.

Conclusions

These findings provide strong evidence that EGF facilitates the transdifferentiation of astrocytes to oligodendrocytes, and suggest that targeting the EGF-EGFR-Erk1/2 signaling axis may represent a novel therapeutic strategy for myelin repair in injured central nervous system (CNS) tissues.

Supplementary Information

The online version contains supplementary material available at 10.1186/s10020-022-00478-5.

PEITC promotes neurite growth in primary sensory neurons via the miR-17-5p/STAT3/GAP-43 axis

The present study explored a key miRNA that plays a vital role in sciatic nerve conditioning injury promoting repair of injured dorsal column, and validated its function. Microarray analysis revealed miR-17-5p expression decreased sharply at 3, 7 and 14 days in the sciatic nerve conditioning injury group compared with the simple dorsal column lesion group. After miR-17-5p inhibition in DRG neurons, GAP-43 expression was upregulated and neurite growth was increased. STAT3 together with p-STAT3 showed opposite trends with miR-17-5p. MiR-17-5p inhibition extended neurite and upregulated STAT3, p-STAT3 and GAP-43. To further determine a substitution therapy for sciatic nerve conditioning injury, beta-phenethyl isothiocyanate (PEITC), which downregulates miR-17-5p, was assessed. The results showed that treatment with 10 µM PEITC resulted in longest neurite length. Further experiments demonstrated PEITC induced neurite growth by inhibiting miR-17-5p and further upregulating STAT3, p-STAT3 and GAP-43. The somatosensory evoked potential test confirmed similar treatment effects for PEITC, Ad-miRNA-17-5p inhibitor, and sciatic nerve conditioning injury on the dorsal column lesion. In conclusion, the miR-17-5p/STAT3/GAP-43 axis is an indispensable component of sciatic nerve conditioning injury promoting repair of injured dorsal column. PEITC could promote repair of injured dorsal column via the miR-17-5p/STAT3/GAP-43 axis, and could mimic the treatment effect of sciatic nerve conditioning injury.

Baicalein alleviates tubular-interstitial nephritis in vivo and in vitro by down-regulating NF-κB and MAPK pathways

Tubular-interstitial nephritis (TIN) is characterized by tubular cell damage and inflammatory lesions of kidneys. Baicalein (BAI) is a flavonoid compound found in the roots of Scutellaria baicalensis Georgi. The present study was undertaken to explore the anti-inflammatory and anti-oxidative effects of BAI on TIN patients and a lipopolysaccharide (LPS)-induced TIN cell model. The expression levels of interleukin-6 (IL-6), IL-10, and tumor necrosis factor α in serum samples of TIN patients and culture supernatants of renal proximal tubular epithelial cells (RPTECs) were evaluated using enzyme-linked immunosorbent assay. Creatinine clearance was calculated using the Cockcroft-Gault equation. Activities of malondialdehyde, superoxide dismutase, and glutathione peroxidase were also determined. Viability and apoptosis of RPTECs were measured using MTT assay and Guava Nexin assay, respectively. qRT-PCR was performed to determine the expressions of Bax, Bcl-2, nuclear factor kappa B (IκBα), and p65. Protein levels of Bax, Bcl-2, IκBα, p65, c-Jun N-terminal kinase, extracellular regulated protein kinases, and p38 were analyzed using western blotting. We found that BAI reduced inflammation and oxidative stress in vivo and in vitro. Moreover, BAI alleviated the LPS-induced RPTECs viability inhibition and apoptosis enhancement, as well as nuclear factor kappa B (NF-κB), and mitogen-activated protein kinase (MAPK) activation. Phorbol ester, an activator of NF-κB, attenuated the effects of BAI on LPS-induced inflammatory cytokine expressions in RPTECs. In conclusion, BAI had anti-inflammatory and anti-oxidative effects on TIN patients and LPS-induced RPTECs by down-regulating NF-κB and MAPK pathways.

Tauroursodeoxycholic acid alleviates secondary injury in the spinal cord via up-regulation of CIBZ gene

Spinal cord injury (SCI) is generally divided into primary and secondary injuries, and apoptosis is an important event of the secondary injury. As an endogenous bile acid and recognized endoplasmic reticulum (ER) stress inhibitor, tauroursodeoxycholic acid (TUDCA) administration has been reported to have a potentially therapeutic effect on neurodegenerative diseases, but its real mechanism is still unclear. In this study, we evaluated whether TUDCA could alleviate traumatic damage of the spinal cord and improve locomotion function in a mouse model of SCI. Traumatic SCI mice were intraperitoneally injected with TUDCA, and the effects were evaluated based on motor function assessment, histopathology, apoptosis detection, qRT-PCR, and western blot at different time periods. TUDCA administration can improve motor function and reduce secondary injury and lesion area after SCI. Furthermore, the apoptotic ratios were significantly reduced; Grp78, Erdj4, and CHOP were attenuated by the treatment. Unexpectedly, the levels of CIBZ, a novel therapeutic target for SCI, were specifically up-regulated. Taken together, it is suggested that TUDCA effectively suppressed ER stress through targeted up-regulation of CIBZ. This study also provides a new strategy for relieving secondary damage by inhibiting apoptosis in the early treatment of spinal cord injury.

Biochemical events related to glial response in spinal cord injury

Introducción. La lesión de la médula espinal (LME) es un evento devastador con implicaciones físicas, psicológicas y socioeconómicas. En el tejido cercano a la lesión se instauran cambios morfofisiológicos que determinan la recuperación funcional del segmento medular y de los órganos efectores dependientes de los tractos axonales lesionados.Objetivo. Describir los eventos bioquímicos secuenciales más relevantes de la respuesta de las células gliales posterior a la LME.Materiales y métodos. Se realizó una búsqueda de publicaciones científicas de los últimos 18 años en las bases de datos PubMed y ScienceDirect, bajo los términos en inglés spinal cord injury (SCI), SCI pathophysiology, SCI inflammation, microglia in SCI, glial scar y chondroitin sulfate proteoglycans (CSPG).Resultados. Los procesos fisiopatológicos que se producen después de la LME determinan la recuperación neurológica de los pacientes. La activación de las células gliales juega un papel importante, ya que promueve la producción de moléculas bioactivas y la formación de barreras físicas que inhiben la regeneración neural.Conclusión. El conocimiento de los cambios neurobiológicos ocurridos tras la LME permite una mayor comprensión de la fisiopatología y favorece la búsqueda de nuevas alternativas terapéuticas que limiten la progresión de la lesión primaria y que minimicen el daño secundario responsable de la disfunción neurológica.

A Novel Five-Node Feed-Forward Loop Unravels miRNA-Gene-TF Regulatory Relationships in Ischemic Stroke

The complex and interlinked cascade of events regulated by microRNAs (miRNAs), transcription factors (TF), and target genes highlight the multifactorial nature of ischemic stroke pathology. The complexity of ischemic stroke requires a wider assessment than the existing experimental research that deals with only a few regulatory components. Here, we assessed a massive set of genes, miRNAs, and transcription factors to build a miRNA-gene-transcription factor regulatory network to elucidate the underlying post-transcriptional mechanisms in ischemic stroke. Feed-forward loops (three-node, four-node, and novel five-node) were converged to establish regulatory relationships between miRNAs, TFs, and genes. The synergistic function of miRNAs in ischemic stroke was predicted and incorporated into a novel five-node feed-forward loop. Significant miRNA-TF pairs were identified using cumulative hypergeometric distribution. Two subnetworks were derived from the extensive miRNA-TF regulatory network and analyzed to predict the molecular mechanism relating the regulatory components. NFKB and STAT were identified to be the chief regulators of innate inflammatory and neuronal survival mechanisms, respectively. Exclusive novel interactions between miR-9 and miR-124 with TLX, BCL2, and HDAC4 were identified to explain the post-stroke induced neurogenesis mechanism. Therefore, this network-based approach to delineate miRNA, TF, and gene interactions might promote the development of effective therapeutics against ischemic stroke.

Mechanisms underlying the promotion of functional recovery by deferoxamine after spinal cord injury in rats

Deferoxamine, a clinically safe drug used for treating iron overload, also repairs spinal cord injury although the mechanism for this action remains unknown. Here, we determined whether deferoxamine was therapeutic in a rat model of spinal cord injury and explored potential mechanisms for this effect. Spinal cord injury was induced by impacting the spinal cord at the thoracic T10 vertebra level. One group of injured rats received deferoxamine, a second injured group received saline, and a third group was sham operated. Both 2 days and 2 weeks after spinal cord injury, total iron ion levels and protein expression levels of the proinflammatory cytokines tumor necrosis factor-α and interleukin-1β and the pro-apoptotic protein caspase-3 in the spinal cords of the injured deferoxamine-treated rats were significantly lower than those in the injured saline-treated group. The percentage of the area positive for glial fibrillary acidic protein immunoreactivity and the number of terminal deoxynucleotidyl transferase dUTP nick end labeling-positive cells were also significantly decreased both 2 days and 2 weeks post injury, while the number of NeuN-positive cells and the percentage of the area positive for the oligodendrocyte marker CNPase were increased in the injured deferoxamine-treated rats. At 14–56 days post injury, hind limb motor function in the deferoxamine-treated rats was superior to that in the saline-treated rats. These results suggest that deferoxamine decreases total iron ion, tumor necrosis factor-α, interleukin-1β, and caspase-3 expression levels after spinal cord injury and inhibits apoptosis and glial scar formation to promote motor function recovery.

Cytokine and Growth Factor Activation In Vivo and In Vitro after Spinal Cord Injury

Spinal cord injury results in a life-disrupting series of deleterious interconnected mechanisms encompassed by the primary and secondary injury. These events are mediated by the upregulation of genes with roles in inflammation, transcription, and signaling proteins. In particular, cytokines and growth factors are signaling proteins that have important roles in the pathophysiology of SCI. The balance between the proinflammatory and anti-inflammatory effects of these molecules plays a critical role in the progression and outcome of the lesion. The excessive inflammatory Th1 and Th17 phenotypes observed after SCI tilt the scale towards a proinflammatory environment, which exacerbates the deleterious mechanisms present after the injury. These mechanisms include the disruption of the spinal cord blood barrier, edema and ion imbalance, in particular intracellular calcium and sodium concentrations, glutamate excitotoxicity, free radicals, and the inflammatory response contributing to the neurodegenerative process which is characterized by demyelination and apoptosis of neuronal tissue.

Evidence for proangiogenic cellular and humoral systemic response in patients with acute onset of spinal cord injury

CONTEXT/OBJECTIVE

Traumatic spinal cord injury (SCI) leads to disruption of local vasculature inducing secondary damage of neural tissue. Circulating endothelial progenitor cells (EPCs) play an important role in post-injury regeneration of vasculature, whereas endothelial cells (ECs) reflect endothelial damage.

METHODS

Twenty patients with SCI were assessed during the first 24 hours, at day 3, and day 7 post-injury and compared to 25 healthy subjects. We herein investigated EPC and EC counts by flow cytometry as well as the levels of soluble factors (SDF-1, HGF, VEGF, Ang2, EGF, endoglin, PLGF, FGF-2, ET-1, BDNF, IGF-1) regulating their migration and proangiogenic function. To better characterize peripheral blood (PB) cells, global gene expression profiles of PB-derived cells were determined using genome-wide RNA microarray technology.

RESULTS

We found significantly higher EPC (CD34(+)/CD133(+)/VEGFR2(+)) as well as EC (VEGFR2(+)) count in PB of patients with SCI within 7 days post-injury and the increased HGF, ET-1, Ang2, EGF, and PLGF plasma levels. Global gene expression analysis revealed considerably lower expression of genes associated with both innate and adaptive immune response in PB cells in patients.

CONCLUSION

Collectively, our findings demonstrate that SCI triggers bone marrow-derived EPC mobilization accompanied by increased circulating EC numbers. Significant changes in both chemoattractive and proangiogenic cytokines plasma levels occurring rapidly after SCI suggest their role in SCI-related regenerative responses to injury. Broadened knowledge concerning the mechanisms governing of human organism response to the SCI might be helpful in developing effective therapeutic strategies.

Acute administration of ucf-101 ameliorates the locomotor impairments induced by a traumatic spinal cord injury

Secondary death of neural cells plays a key role in the physiopathology and the functional consequences of traumatic spinal cord injury (SCI). Pharmacological manipulation of cell death pathways leading to the preservation of neural cells is acknowledged as a main therapeutic goal in SCI. In the present work, we hypothesize that administration of the neuroprotective cell-permeable compound ucf-101 will reduce neural cell death during the secondary damage of SCI, increasing tissue preservation and reducing the functional deficits. To test this hypothesis, we treated mice with ucf-101 during the first week after a moderate contusive SCI. Our results reveal that ucf-101 administration protects neural cells from the deleterious secondary mechanisms triggered by the trauma, reducing the extension of tissue damage and improving motor function recovery. Our studies also suggest that the effects of ucf-101 may be mediated through the inhibition of HtrA2/OMI and the concomitant increase of inhibitor of apoptosis protein XIAP, as well as the induction of ERK1/2 activation and/or expression. In vitro assays confirm the effects of ucf-101 on both pathways as well as on the reduction of caspase cascade activation and apoptotic cell death in a neuroblastoma cell line. These results suggest that ucf-101 can be a promising therapeutic tool for SCI that deserves more detailed analyses.

The role of the JAK-STAT pathway in neural stem cells, neural progenitor cells and reactive astrocytes after spinal cord injury

Patients with spinal cord injuries can develop severe neurological damage and dysfunction, which is not only induced by primary but also by secondary injuries. As an evolutionarily conserved pathway of eukaryotes, the JAK-STAT pathway is associated with cell growth, survival, development and differentiation; activation of the JAK-STAT pathway has been previously reported in central nervous system injury. The JAK-STAT pathway is directly associated with neurogenesis and glia scar formation in the injury region. Following injury of the axon, the overexpression and activation of STAT3 is exhibited specifically in protecting neurons. To investigate the role of the JAK-STAT pathway in neuroprotection, we summarized the effect of JAK-STAT pathway in the following three sections: Firstly, the modulation of JAK-STAT pathway in proliferation and differentiation of neural stem cells and neural progenitor cells is discussed; secondly, the time-dependent effect of JAK-STAT pathway in reactive astrocytes to reveal their capability of neuroprotection is revealed and lastly, we focus on how the astrocyte-secretory polypeptides (astrocyte-derived cytokines and trophic factors) accomplish neuroprotection via the JAK-STAT pathway.

Prolonged electrical stimulation causes no damage to sacral nerve roots in rabbits

Previous studies have shown that, anode block electrical stimulation of the sacral nerve root can produce physiological urination and reconstruct urinary bladder function in rabbits. However, whether long-term anode block electrical stimulation causes damage to the sacral nerve root remains unclear, and needs further investigation. In this study, a complete spinal cord injury model was established in New Zealand white rabbits through T9-10 segment transection. Rabbits were given continuous electrical stimulation for a short period and then chronic stimulation for a longer period. Results showed that compared with normal rabbits, the structure of nerve cells in the anterior sacral nerve roots was unchanged in spinal cord injury rabbits after electrical stimulation. There was no significant difference in the expression of apoptosis-related proteins such as Bax, Caspase-3, and Bcl-2. Experimental findings indicate that neurons in the rabbit sacral nerve roots tolerate electrical stimulation, even after long-term anode block electrical stimulation.

Ginsenoside Rd attenuates mitochondrial permeability transition and cytochrome C release in isolated spinal cord mitochondria: involvement of kinase-mediated pathways

Ginsenoside Rd (Rd), one of the main active ingredients in Panax ginseng, has multifunctional activity via different mechanisms and neuroprotective effects that are exerted probably via its antioxidant or free radical scavenger action. However, the effects of Rd on spinal cord mitochondrial dysfunction and underlying mechanisms are still obscure. In this study, we sought to investigate the in vitro effects of Rd on mitochondrial integrity and redox balance in isolated spinal cord mitochondria. We verified that Ca²⁺ dissipated the membrane potential, provoked mitochondrial swelling and decreased NAD(P)H matrix content, which were all attenuated by Rd pretreatment in a dose-dependent manner. In contrast, Rd was not able to inhibit Ca²⁺ induced mitochondrial hydrogen peroxide generation. The results of Western blot showed that Rd significantly increased the expression of p-Akt and p-ERK, but had no effects on phosphorylation of PKC and p38. In addition, Rd treatment significantly attenuated Ca²⁺ induced cytochrome c release, which was partly reversed by antagonists of Akt and ERK, but not p-38 inhibitor. The effects of bisindolylmaleimide, a PKC inhibitor, on Rd-induced inhibition of cytochrome c release seem to be at the level of its own detrimental activity on mitochondrial function. Furthermore, we also found that pretreatment with Rd in vivo (10 and 50 mg/kg) protected spinal cord mitochondria against Ca²⁺ induced mitochondrial membrane potential dissipation and cytochrome c release. It is concluded that Rd regulate mitochondrial permeability transition pore formation and cytochrome c release through protein kinases dependent mechanism involving activation of intramitochondrial Akt and ERK pathways.

Say "no" to spinal cord injury: is nitric oxide an option for therapeutic strategies?

PURPOSE

a literature review was made to investigate the role of nitric oxide (NO) in spinal cord injury, a pathological condition that leads to motor, sensory, and autonomic deficit. Besides, we were interested in potential therapeutic strategies interfering with NO mechanism of secondary damage.

MATERIALS

A literature search using PubMed Medline database has been performed.

RESULTS

excessive NO production after spinal cord injury promotes oxidative damage perpetuating the injury causing neuronal loss at the injured site and in the surrounding area.

CONCLUSION

different therapeutic approaches for contrasting or avoiding NO secondary damage have been studied, these include nitric oxide synthase inhibitors, compounds that interfere with inducible NO synthase expression, and molecules working as antioxidant. Further studies are needed to explain the neuroprotective or cytotoxic role of the different isoforms of NO synthase and the other mediators that take part or influence the NO cascade. In this way, it would be possible to find new therapeutic targets and furthermore to extend the experimentation to humans.

Spatial and temporal expression levels of specific microRNAs in a spinal cord injury mouse model and their relationship to the duration of compression

BACKGROUND CONTEXT

MicroRNAs, a class of small nonprotein-coding RNAs, are thought to control gene translation into proteins. The latter are the ultimate effectors of the biochemical cascade occurring in any physiological and pathological process. MicroRNAs have been shown to change their expression levels during injury of spinal cord in contusion rodent models. Compression is the most frequent mode of damage of neural elements in spinal cord injury. The cellular and molecular changes occurring in the spinal cord during prolonged compression are not very well elucidated. Understanding the underlying molecular events that occur during sustained compression is paramount in building new therapeutic strategies.

PURPOSE

The purpose of our study was to probe the relationship between the expression level changes of different miRNAs and the timing of spinal cord decompression in a mouse model.

STUDY DESIGN

A compression spinal cord injury mouse model was used for the study.

METHODS

A laminectomy was performed in the thoracic spine of C57BL/6 mice. Then, the thecal sac was compressed to create the injury. Decompression was performed early for one group and it was delayed in the second group. The spinal cord at the epicenter of the injury and one level rostral to it were removed at 3, 6, and 24 hours after trauma, and RNA was extracted. Expression levels of six different microRNAs and the relationship to the duration of compression were analyzed. This work was supported in part by the University Research Council Grants Program at the University of Texas Health Science Center San Antonio (Grant 130267). There are no specific conflicts of interest to be disclosed for this work.

RESULTS

Expression levels of microRNAs in the prolonged compression of spinal cord model were significantly different compared with the expression levels in the short duration of compression spinal cord injury model. Furthermore, microRNAs show a different expression pattern in different regions of the injured spinal cord.

CONCLUSIONS

Our findings demonstrate that spinal cord compression causes alterations in the expression of different miRNAs in the acute phase of injury. Their expression is related to the duration of the compression of the spinal cord. These findings suggest that early decompression of the spinal cord may have an important modulating effect on the molecular cascade triggered during secondary injury through the changes in expression levels of specific microRNAs.

Genome wide expression profiling during spinal cord regeneration identifies comprehensive cellular responses in zebrafish

BACKGROUND

Among the vertebrates, teleost and urodele amphibians are capable of regenerating their central nervous system. We have used zebrafish as a model to study spinal cord injury and regeneration. Relatively little is known about the molecular mechanisms underlying spinal cord regeneration and information based on high density oligonucleotide microarray was not available. We have used a high density microarray to profile the temporal transcriptome dynamics during the entire phenomenon.

RESULTS

A total of 3842 genes expressed differentially with significant fold changes during spinal cord regeneration. Cluster analysis revealed event specific dynamic expression of genes related to inflammation, cell death, cell migration, cell proliferation, neurogenesis, neural patterning and axonal regrowth. Spatio-temporal analysis of stat3 expression suggested its possible function in controlling inflammation and cell proliferation. Genes involved in neurogenesis and their dorso-ventral patterning (sox2 and dbx2) are differentially expressed. Injury induced cell proliferation is controlled by many cell cycle regulators and some are commonly expressed in regenerating fin, heart and retina. Expression pattern of certain pathway genes are identified for the first time during regeneration of spinal cord. Several genes involved in PNS regeneration in mammals like stat3, socs3, atf3, mmp9 and sox11 are upregulated in zebrafish SCI thus creating PNS like environment after injury.

CONCLUSION

Our study provides a comprehensive genetic blue print of diverse cellular response(s) during regeneration of zebrafish spinal cord. The data highlights the importance of different event specific gene expression that could be better understood and manipulated further to induce successful regeneration in mammals.

Eph/Ephrin signaling in injury and inflammation

The Eph/ephrin receptor-ligand system plays an important role in embryogenesis and adult life, principally by influencing cell behavior through signaling pathways, resulting in modification of the cell cytoskeleton and cell adhesion. There are 10 EphA receptors, and six EphB receptors, distinguished on sequence difference and binding preferences, that interact with the six glycosylphosphatidylinositol-linked ephrin-A ligands and the three transmembrane ephrin-B ligands, respectively. The Eph/ephrin proteins, originally described as developmental regulators that are expressed at low levels postembryonically, are re-expressed after injury to the optic nerve, spinal cord, and brain in fish, amphibians, rodents, and humans. In rodent spinal cord injury, the up-regulation of EphA4 prevents recovery by inhibiting axons from crossing the injury site. Eph/ephrin proteins may be partly responsible for the phenotypic changes to the vascular endothelium in inflammation, which allows fluid and inflammatory cells to pass from the vascular space into the interstitial tissues. Specifically, EphA2/ephrin-A1 signaling in the lung may be responsible for pulmonary inflammation in acute lung injury. A role in T-cell maturation and chronic inflammation (heart failure, inflammatory bowel disease, and rheumatoid arthritis) is also reported. Although there remains much to learn about Eph/ephrin signaling in human disease, and specifically in injury and inflammation, this area of research raises the exciting prospect that novel therapies will be developed that precisely target these pathways.

Contribution of bone marrow-derived endothelial progenitor cells to neovascularization and astrogliosis following spinal cord injury

Spinal cord injury causes initial mechanical damage, followed by ischemia-induced, secondary degeneration, worsening the tissue damage. Although endothelial progenitor cells (EPCs) have been reported to play an important role for pathophysiological neovascularization in various ischemic tissues, the EPC kinetics following spinal cord injury have never been elucidated. In this study, we therefore assessed the in vivo kinetics of bone marrow-derived EPCs by EPC colony-forming assay and bone marrow transplantation from Tie2/lacZ transgenic mice into wild-type mice with spinal cord injury. The number of circulating mononuclear cells and EPC colonies formed by the mononuclear cells peaked at day 3 postspinal cord injury. Bone marrow transplantation study revealed that bone marrow-derived EPCs recruited into the injured spinal cord markedly increased at day 7, when neovascularization and astrogliosis drastically occurred in parallel with axon growth in the damaged tissue. To elucidate further the contribution of EPCs to recovery after spinal cord injury, exogenous EPCs were systemically infused immediately after the injury. The administered EPCs were incorporated into the injured spinal cord and accelerated neovascularization and astrogliosis. These findings suggest that bone marrow-derived EPCs may contribute to the tissue repair by augmenting neovascularization and astrogliosis following spinal cord injury.

CIBZ, a novel BTB domain-containing protein, is involved in mouse spinal cord injury via mitochondrial pathway independent of p53 gene

Spinal cord injury (SCI) induces both primary uncontrollable mechanical injury and secondary controllable degeneration, which further results in the activation of cell death cascades that mediate delayed tissue damage. To alleviate its impairments and seek for an effective remedy, mRNA differential display was used to investigate gene mRNA expression profiling in mice following SCI. A specific Zinc finger and BTB domain-containing protein, CIBZ, was discovered to implicate in the SCI process for the first time. Further researches indicated that CIBZ was extensively distributed in various tissues, and the expression level was highest in muscle, followed by spinal cord, large intestine, kidney, spleen, thymus, lung, cerebrum, stomach, ovary and heart, respectively. After injury, the CIBZ expression decreased dramatically and reached the lowest level at 8 h, but it gradually increased to the maximal level at 7 d. Caspase-3 and C-terminal-binding protein (CtBP), two CIBZ-related proteins, showed similar tendency. Interestingly, p53 expression remained constant in all groups. Via flow cytometry (FCM) analysis, it was found that the cell death rate in SCI group markedly increased and reached the highest value 1 d after surgery and the mitochondrial transmembrane potential (ΔΨm) at 1 d was the lowest in all groups. Taken together, it is suggested that: (i) in the presence of CtBP, CIBZ gene is involved in secondary injury process and trigger the activation of apoptotic caspase-3 and bax genes independent of p53; (ii) abrupt down-regulation of CtBP at 8 h is a sign of mitochondria dysfunction and the onset of cell death; (iii) it could be used as an inhibitor or target drug of caspase-3 gene to improve spinal cord function.

Evaluation of the effects of hyperbaric oxygen therapy for spinal cord lesion in correlation with the moment of intervention

STUDY DESIGN

Experimental, controlled, animal study.

OBJECTIVES

To evaluate the functional effect of hyperbaric oxygen therapy administered shortly, one day after, and no intervention (control) in standardized experimental spinal cord lesions in Wistar rats.

SETTING

São Paulo, Brazil.

METHODS

In all, 30 Wistar rats with spinal cord lesions were divided into three groups: one group was submitted to hyperbaric oxygen therapy beginning half an hour after the lesion and with a total of 10 one-hour sessions, one session per day, at 2 atm; the second received the same treatment, but beginning on the day after the lesion; and the third received no treatment (control). The Basso, Beattie and Bresnahan scales were used for functional evaluation on the second day after the lesion and then weekly, until being killed 1 month later.

RESULTS

There were no significant differences between the groups in the functional analysis on the second day after the lesion. There was no functional difference comparing Groups 1 and 2 (treated shortly after or one day after) in any evaluation moment. On the 7th day, as well as on the 21st and 28th postoperative days, the evaluation showed that groups 1 and 2 performed significantly better than the control group (receiving no therapy).

CONCLUSION

Hyperbaric chamber therapy is beneficial in the functional recovery of spinal cord lesions in rats, if it is first administered just after spinal cord injury or within 24 h.

Glucocorticoid-induced leucine zipper (GILZ) over-expression in T lymphocytes inhibits inflammation and tissue damage in spinal cord injury

Spinal cord injury (SCI) is a traumatic event that causes a secondary and extended inflammation characterized by infiltration of immune cells, including T lymphocytes, release of pro-inflammatory mediators in the lesion site, and tissue degeneration. Current therapeutic approaches for SCI are limited to glucocorticoids (GC) due to their potent anti-inflammatory activity. GC efficacy resides, in part, in the capability to inhibit NF-κB, T lymphocyte activation, and the consequent cytokine production. In this study, we performed experiments aimed to test the susceptibility of glucocorticoid-induced leucine zipper (GILZ) transgenic (GILZ(TG)) mice, in which GILZ is selectively over-expressed in T lymphocytes, to SCI induction. Consistent with a decreased inflammatory response, GILZ(TG) were less susceptible to SCI as compared to wild-type littermates. Notably, inhibition of NF-κB activation and nuclear translocation, diminished T lymphocytes activation and tissue infiltration, as well as decreased release of cytokines were evident in GILZ(TG) as compared to wild-type mice. Moreover, GILZ(TG) showed a reduced tumor necrosis factor-α, IL-1β, Inductible nitric oxide synthase (iNOS) and nytrotyrosine production, apoptosis, and neuronal tissue damage. Together these results indicate that GILZ mimics the anti-inflammatory effect of GC and represents a potential pharmacological target for modulation of T lymphocyte-mediated immune response in inflammatory disorders, such as SCI.

Signal transducers and activators of transcription: STATs-mediated mitochondrial neuroprotection

Cerebral ischemia is defined as little or no blood flow in cerebral circulation, characterized by low tissue oxygen and glucose levels, which promotes neuronal mitochondria dysfunction leading to cell death. A strategy to counteract cerebral ischemia-induced neuronal cell death is ischemic preconditioning (IPC). IPC results in neuroprotection, which is conferred by a mild ischemic challenge prior to a normally lethal ischemic insult. Although many IPC-induced mechanisms have been described, many cellular and subcellular mechanisms remain undefined. Some reports have suggested key signal transduction pathways of IPC, such as activation of protein kinase C epsilon, mitogen-activated protein kinase, and hypoxia-inducible factors, that are likely involved in IPC-induced mitochondria mediated-neuroprotection. Moreover, recent findings suggest that signal transducers and activators of transcription (STATs), a family of transcription factors involved in many cellular activities, may be intimately involved in IPC-induced ischemic tolerance. In this review, we explore current signal transduction pathways involved in IPC-induced mitochondria mediated-neuroprotection, STAT activation in the mitochondria as it relates to IPC, and functional significance of STATs in cerebral ischemia.

Targeting mitochondrial function for the treatment of acute spinal cord injury

Traumatic injury to the mammalian spinal cord is a highly dynamic process characterized by a complex pattern of pervasive and destructive biochemical and pathophysiological events that limit the potential for functional recovery. Currently, there are no effective therapies for the treatment of spinal cord injury (SCI) and this is due, in part, to the widespread impact of the secondary injury cascades, including edema, ischemia, excitotoxicity, inflammation, oxidative damage, and activation of necrotic and apoptotic cell death signaling events. In addition, many of the signaling pathways associated with these cascades intersect and initiate other secondary injury events. Therefore, it can be argued that therapeutic strategies targeting a specific biochemical cascade may not provide the best approach for promoting functional recovery. A "systems approach" at the subcellular level may provide a better strategy for promoting cell survival and function and, as a consequence, improve functional outcomes following SCI. One such approach is to study the impact of SCI on the biology and function of mitochondria, which serve a major role in cellular bioenergetics, function, and survival. In this review, we will briefly describe the importance and unique properties of mitochondria in the spinal cord, and what is known about the response of mitochondria to SCI. We will also discuss a number of strategies with the potential to promote mitochondrial function following SCI.

Stem cells for spinal cord regeneration: Current status

Background:

Nearly 11,000 cases of spinal cord injury (SCI) are reported in the United States annually. Current management options give a median survival time of 38 years; however, no rehabilitative measures are available. Stem cells have been under constant research given their ability to differentiate into neural cell lines replacing non functional tissue. Efforts have been made to establish new synapses and provide a conducive environment, by grafting cells from autologous and fetal sources; including embryonic or adult stem cells, Schwann cells, genetically modified fibroblasts, bone stromal cells, and olfactory ensheathing cells and combinations/ variants thereof.

Methods:

In order to discuss the underlying mechanism of SCI along with the previously mentioned sources of stem cells in context to SCI, a simple review of literature was conducted. An extensive literature search was conducted using the PubMed data base and online search engines and articles published in the last 15 years were considered along with some historical articles where a background was required.

Results:

Stem cell transplantation for SCI is at the forefront with animal and in vitro studies providing a solid platform to enable well-designed human studies. Olfactory ensheathing cells seem to be the most promising; whilst bone marrow stromal cells appear as strong candidates for an adjunctive role.

Conclusion:

The key strategy in developing the therapeutic basis of stem cell transplantation for spinal cord regeneration is to weed out the pseudo-science and opportunism. All the trials should be based on stringent scientific criteria and effort to bypass that should be strongly discouraged at the international level.

Anti-TNF therapy in the injured spinal cord

Spinal cord injury (SCI) has a significant impact on the quality and expectancy of life. It also carries a heavy economic burden, with considerable costs associated with primary care and loss of income. The normal architecture of the spinal cord is radically disrupted by injury. After the initial insult, structure and function are lost through active secondary processes that involve reactive astrocytes, glial progenitors, microglia, macrophages, fibroblasts and Schwann cells. These cells produce chemokines and cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β, which mediate the recruitment of inflammatory cells to the injury site. Targeting of these cytokines represents a potential strategy to reduce the secondary damage in SCI. In this review, we focus on several emerging strategies to neutralize TNF-α, including antibodies, soluble receptors, recombinant TNF-binding proteins, TNF receptor fusion proteins, and non-specific agents (e.g. thalidomide) and discuss their potential as therapy for SCI.

Early events of secondary degeneration after partial optic nerve transection: an immunohistochemical study

Secondary degeneration in the central nervous system involves indirect damage to neurons and glia away from the initial injury. Partial transection of the dorsal optic nerve (ON) results in precise spatial separation of the primary trauma from delayed degenerative events in ventrally placed axons and parent somata. Here we conduct an immunohistochemical survey of secondary cellular changes in and around axons and their parent retinal ganglion cell (RGC) somata during the first 3 days after a restricted, dorsal ON transection. This is before the secondary loss of RGCs and axons projecting through the uninjured, ventral portion of the ON. Within 5 min, manganese superoxide dismutase (MnSOD; a marker of oxidative stress) co-localizes within the astrocytic network across the entire profile of the ON. Secondary astrocyte hypertrophy of immunofluorescent labeling was evident from 3 h, with sustained increases in myelin basic protein immunoreactivity across the nerve by 24 h. Increases in NG-2-positive oligodendrocyte precursor cells, ED-1-positive activated microglia/macrophages, and Iba1-positive reactive resident microglia/macrophage numbers were only seen in ON vulnerable to secondary degeneration by 3 days. Changes within RGC somata exclusively vulnerable to secondary degeneration were detected at 24 h, as evidenced by increases in MnSOD immunoreactivity, followed by increases in c-jun immunoreactivity at 3 days. Treatment with the voltage-gated calcium channel blocker lomerizine did not alter any measured outcome. We conclude that oxidative stress spreading via the astrocytic network and from injured axons to parent RGC somata is an early event during secondary degeneration, and containment is likely to be required in order to prevent further damage to the nerve.

Proteomic and phosphoproteomic analyses of the soluble fraction following acute spinal cord contusion in rats

Traumatic spinal cord injury (SCI) causes marked neuropathological changes in the spinal cord, resulting in limited functional recovery. Currently, there are no effective treatments, and the mechanisms underlying these neuropathological changes are not completely understood. In this study, two-dimensional gel electrophoresis coupled with mass spectrometry was used to investigate injury-related changes in the abundance (SYPRO Ruby stain) and phosphorylation (Pro-Q Diamond stain) of proteins from the soluble fraction of the lesion epicenter at 24 h following SCI. Over 1500 SYPRO Ruby-stained spots and 100 Pro-Q Diamond-stained spots were examined. We identified 26 unique proteins within 38 gel spots that differentially changed in abundance, phosphorylation, or both in response to SCI. Protein redundancies among the gel spots were likely due to differences in proteolysis, post-translational modifications, and the existence of isoforms. The proteins affected were blood-related proteins, heat-shock proteins, glycolytic enzymes, antioxidants, and proteins that function in cell structure, cell signaling, DNA damage, and protein degradation. These protein changes post injury may suggest additional avenues of investigation into the underlying molecular mechanisms responsible for the pathophysiological consequences of SCI.

Bone morphogenetic protein-2 used in spinal fusion with spinal cord injury penetrates intrathecally and elicits a functional signaling cascade

BACKGROUND CONTEXT

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) and its indications for spinal fusion continue to be expanded with recent reports citing spinal trauma application. However, there are no data establishing the effects of rhBMP-2 on the injured spinal cord.

PURPOSE

The purpose of this study was to evaluate the extent of bone morphogenetic protein (BMP)-specific intrathecal signaling after application to the spine at various time points after a spinal cord injury (SCI).

STUDY DESIGN

This is an in vivo rat study using a combination of the dorsal hemisection SCI and the posterolateral arthrodesis animal models.

METHODS

Sixty-five female Sprague-Dawley rats underwent either a T9-T10 dorsal hemisection SCI (n=52) or laminectomy only (n=13). Spinal cord injury animals were further subdivided into four follow-up groups (n=13/group): 30 minutes, 24 hours, 7 days, and 21 days, at which time one of two secondary surgeries were performed: Eight rats per time point received either 43 microg of rhBMP-2 per side or sterile water control over T9-T11 on absorbable collagen sponges (ACSs). Animals were perfused after 24 hours, and spinal cords were immunohistochemically analyzed. Sections of the lesion were stained with BMP-specific pSmad 1, 5, 8 antibody and costained with cell-specific markers. pSmad-positive cells were then counted around the lesion. The remaining five rats (n=5/time point) had luciferase (blood spinal cord barrier [BSCB] permeability marker) injected through the jugular vein. Subsequently, spinal cords were collected and luciferase activity was quantified around the lesion and in the cervical samples (controls) using a luminometer.

RESULTS

After injury, a significant increase in the number of pSmad-positive cells was observed when rhBMP-2 was implanted at the 30-minute, 24-hour, and 7-day time points (p<.05). Costaining revealed BMP-specific signaling activation in neurons, glial cells, macrophages, and fibroblasts. Spinal cord permeability to luciferase was significantly increased at 30 minutes, 24 hours, and 7 days post lesion (p<.05). A significant linear regression was established between the extent of BSCB permeability and pSmad signaling (r(2)=0.66, p=.000).

CONCLUSIONS

Our results indicate that rhBMP-2 use around a spinal cord lesion elicits a robust signaling response within the spinal cord parenchyma. All CNS cell types and the invading fibroblasts are activated to the extent dependent on the integrity of the meningeal and BSCB barriers. Therefore, in the presence of a SCI and/or dural tear, rhBMP-2 diffuses intrathecally and activates a signaling cascade in all major CNS cell types, which may increase glial scarring and impact neurologic recovery.

Role of signal transducer and activator of transcription 3 in neuronal survival and regeneration

Signal Transducers and Activators of Transcription (STATs) comprise a family of transcription factors that mediate a wide variety of biological functions in the central and peripheral nervous systems. Injury to neural tissue induces STAT activation, and STATs are increasingly recognized for their role in neuronal survival. In this review, we discuss the role of STAT3 during neural development and following ischemic and traumatic injury in brain, spinal cord and peripheral nerves. We focus on STAT3 because of the expanding body of literature that investigates protective and regenerative effects of growth factors, hormones and cytokines that use STAT3 to mediate their effect, in part through transcriptional upregulation of neuroprotective and neurotrophic genes. Defining the endogenous molecular mechanisms that lead to neuroprotection by STAT3 after injury might identify novel therapeutic targets against acute neural tissue damage as well as chronic neurodegenerative disorders.

Tamoxifen attenuates inflammatory-mediated damage and improves functional outcome after spinal cord injury in rats

Tamoxifen has been found to be neuroprotective in both transient and permanent experimental ischemic stroke. However, it remains unknown whether this agent shows a similar beneficial effect after spinal cord injury (SCI), and what are its underlying mechanisms. In this study, we investigated the efficacy of tamoxifen treatment in attenuating SCI-induced pathology. Blood-spinal cord barrier (BSCB) permeability, tissue edema formation, microglial activation, neuronal cell death and myelin loss were determined in rats subjected to spinal cord contusion. The results showed that tamoxifen, administered at 30 min post-injury, significantly decreased interleukin-1beta (IL-1beta) production induced by microglial activation, alleviated the amount of Evans blue leakage and edema formation. In addition, tamoxifen treatment clearly reduced the number of apoptotic neurons post-SCI. The myelin loss and the increase in production of myelin-associated axonal growth inhibitors were also found to be significantly attenuated at day 3 post-injury. Furthermore, rats treated with tamoxifen scored much higher on the locomotor rating scale after SCI than did vehicle-treated rats, suggesting improved functional outcome after SCI. Together, these results demonstrate that tamoxifen provides neuroprotective effects for treatment of SCI-related pathology and disability, and is therefore a potential neuroprotectant for human spinal cord injury therapy.

Neuroproteomic methods in spinal cord injury

Spinal cord injury (SCI) is a major public health problem with no known effective treatment. Traumatic injury to the spinal cord initiates a host of pathophysiological events that are secondary to the initial insult leading to neuronal dysfunction and death; yet, the molecular mechanisms underlying its dysfunction are poorly understood. Furthermore, while use of imaging methods (e.g., computed tomography scans and magnetic resonance imaging) may help define injury severity and location, they do not elucidate biological mechanisms of SCI progression. The lack of comparable biomarkers for monitoring SCI makes accurate diagnosis and evaluation of SCI progression difficult. Spinal cord contusion is an extensively used SCI model in rats that best represents the etiology of SCI in humans. In this chapter, we describe a two-dimensional (2D) gel electrophoresis-based proteomic approach to investigate the injury-related differences in the proteome and phosphoproteome of spinal cord lesion epicenter at 24 h after spinal cord contusion in rats. The purpose of this study is to elucidate the mechanisms of acute spinal cord dysfunction, as well as discover novel biomarker candidates to evaluate the biological mechanisms of SCI progression and the injury severity.

Secondary degeneration of the optic nerve following partial transection: the benefits of lomerizine

Secondary degeneration is a form of 'bystander' damage that can affect neural tissue both nearby and remote from an initial injury. Partial optic nerve transection is an excellent model in which to unequivocally differentiate events occurring during secondary degeneration from those resulting from primary CNS injury. We analysed the primary injury site within the optic nerve (ON) and intact areas vulnerable to secondary degeneration. Areas affected by the primary injury showed morphological disruption, loss of beta-III tubulin axonal staining, reduced myelinated axon density, greater proteoglycan expression (phosphacan), increased microglia and macrophage numbers and increased oxidative stress. Similar, but less extreme, changes were seen in areas of the optic nerve undergoing secondary degeneration. The CNS-specific L- and T-type calcium channel blocker lomerizine alleviated some of the changes in areas vulnerable to secondary degeneration. Lomerizine reduced morphological disruption, oxidative stress and phosphacan expression, and limited early increases in macrophage numbers. However, lomerizine failed to prevent progressive de-myelination of ON axons. Within the retina, secondary retinal ganglion cell (RGC) death was significant in areas vulnerable to secondary degeneration. Lomerizine protected RGCs from secondary death at 4 weeks but did not fully restore behavioural function (optokinetic nystagmus). We conclude that blockade of calcium channels is neuroprotective and limits secondary degenerative changes following CNS injury. However such an approach may need to be combined with other treatments to ensure long-term maintenance of full visual function.

Interleukin-6 induces proliferation in adult spinal cord-derived neural progenitors via the JAK2/STAT3 pathway with EGF-induced MAPK phosphorylation

INTRODUCTION

In a previous study, we observed cell proliferation 3 days after spinal cord injury, and levels of interleukin-6 (IL-6) and epidermal growth factor (EGF) had significantly increased in the region of the injury.

OBJECTIVES

The purpose of the new study described here was to evaluate the roles of IL-6 and EGF after traumatic damage to the spinal cord having isolated neural progenitor cells (NPC) from adult mice.

METHODS AND RESULTS

Evidence provided by the trypan blue dye exclusion assay, 5-bromodeoxyuridine immunoreactivity and Western blot analysis indicated that IL-6 and EGF induced proliferation of these spinal cord-derived NPCs via phosphorylation of Janus-activated kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and mitogen-activated protein kinases (MAPK), respectively. Combined treatment with IL-6 and EGF accelerated proliferation of cells synergistically and phosphorylation of STAT3 and extracellular signal-regulated kinase 1/2 (Erk1/2). Furthermore, AG490 and AG1478, JAK2 inhibitor and EGFR inhibitor, respectively, prevented the IL-6- and EGF-induced proliferation of the cells. Interestingly, IL-6-activated MAPKs but EGF did not influence JAK2/STAT3 activation; AG490 specifically inhibited IL-6-induced Erk1/2 phosphorylation without affecting IL-6-induced phosphorylation of Raf and MEK1/2. These results indicate that IL-6 is directly involved in Erk1/2 activation via JAK2 and that Erk1/2 provides a signal bridge between the IL-6-induced JAK2/STAT3 pathway and EGF-induced MAPK pathway.

CONCLUSIONS

Our study is the first demonstration of IL-6- and EGF-stimulated proliferation of spinal cord progenitor cells via JAK2/STAT3 and MAPK signalling pathways. These pathways play key roles in repopulation and regeneration of spinal cord tissue after injury. It may represent novel therapeutic targets for pharmacological intervention in central nervous system disease, including spinal cord injury.

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.

Antiapoptotic therapies in the treatment of spinal cord injury

Mechanical trauma to the spinal cord triggers events resulting in the death of neurons and glia over several weeks following the initial injury. It has been suggested that the prevention of delayed apoptosis after spinal cord injury (SCI) is likely to have a beneficial effect by reducing the extent of neuronal and oligodendroglial death, which would translate into better functional outcomes. Drugs acting at different levels in the apoptotic cascade (i.e., caspase inhibitors and antiapoptotic Bcl-xL) have been shown to decrease apoptotic cell death, but benefits in functional outcomes result only when inflammation is also decreased. Furthermore, long-term antiapoptotic therapy can result in nonapoptotic death with necrotic features, which will further increase inflammation and worsen outcome. Even though neuroprotective therapies are one of the targets for the promotion of functional recovery after SCI, targeting only post-SCI apoptosis is unlikely to be as successful as more integrated interventions that also target inflammation.

Detrimental effects of antiapoptotic treatments in spinal cord injury

Long-term functional impairments due to spinal cord injury (SCI) in the rat result from secondary apoptotic death regulated, in part, by SCI-induced decreases in protein levels of the antiapoptotic protein Bcl-xL. We have shown that exogenous administration of Bcl-xL spares neurons 24 h after SCI. However, long-term effects of chronic application of Bcl-xL have not been characterized. To counteract SCI-induced decreases in Bcl-xL and resulting apoptosis, we used the TAT protein transduction domain fused to the Bcl-xL protein (Tat-Bcl-xL), or its antiapoptotic domain BH4 (Tat-BH4). We used intrathecal delivery of Tat-Bcl-xL, or Tat-BH4, into injured spinal cords for 24 h or 7 days, and apoptosis, neuronal death and locomotor recovery were assessed up to 2 months after injury. Both, Tat-Bcl-xL and Tat-BH4, significantly decreased SCI-induced apoptosis in thoracic segments containing the site of injury (T10) at 24 h or 7 days after SCI. However, the 7-day delivery of Tat-Bcl-xL, or Tat-BH4, also induced a significant impairment of locomotor recovery that lasted beyond the drug delivery time. We found that the 7-day administration of Tat-Bcl-xL, or Tat-BH4, significantly increased non-apoptotic neuronal loss and robustly augmented microglia/macrophage activation. These results indicate that the antiapoptotic treatment targeting Bcl-xL shifts neuronal apoptosis to necrosis, increases the inflammatory response and impairs locomotor recovery. Our results suggest that a combinatorial treatment consisting of antiapoptotic and anti-inflammatory agents may be necessary to achieve tissue preservation and significant improvement in functional recovery after SCI.

Cell cycle inhibition attenuates microglia induced inflammatory response and alleviates neuronal cell death after spinal cord injury in rats

The spinal cord is well known to undergo inflammatory reactions in response to traumatic injury. Activation and proliferation of microglial cells, with associated proinflammatory cytokines expression, plays an important role in the secondary damage following spinal cord injury. It is likely that microglial cells are at the center of injury cascade and are targets for treatments of CNS traumatic diseases. Recently, we have demonstrated that the cell cycle inhibitor olomoucine attenuates astroglial proliferation and glial scar formation, decreases lesion cavity and mitigates functional deficits after spinal cord injury (SCI) in rats [Tian, D.S., Yu, Z.Y., Xie, M.J., Bu, B.T., Witte, O.W., Wang, W., 2006. Suppression of astroglial scar formation and enhanced axonal regeneration associated with functional recovery in a spinal cord injury rat model by the cell cycle inhibitor olomoucine. J. Neurosci. Res. 84, 1053-1063]. Whether neuroprotective effects of cell cycle inhibition are involved in attenuation of microglial induced inflammation awaits to be elucidated. In the present study, we sought to determine the influence of olomoucine on microglial proliferation with associated inflammatory response after spinal cord injury. Tissue edema formation, microglial response and neuronal cell death were quantified in rats subjected to spinal cord hemisection. Microglial proliferation and neuronal apoptosis were observed by immunofluorescence. Level of the proinflammatory cytokine interleukin-1beta (IL-1beta) expression in the injured cord was determined by Western blot analysis. Our results showed that the cell cycle inhibitor olomoucine, administered at 1 h post injury, significantly suppressed microglial proliferation and produced a remarkable reduction of tissue edema formation. In the olomoucine-treated group, a significant reduction of activated and/or proliferated microglial induced IL-1beta expression was observed 24 h after SCI. Moreover, olomoucine evidently attenuated the number of apoptotic neurons after SCI. Our findings suggest that modulation of microglial proliferation with associated proinflammatory cytokine expression may be a mechanism of cell cycle inhibition-mediated neuroprotections in the CNS trauma.