Inhibition of E2F1/CDK1 pathway attenuates neuronal apoptosis in vitro and confers neuroprotection after spinal cord injury in vivo

The role of apoptosis in spinal cord injury: a bibliometric analysis from 1994 to 2023

Background

Apoptosis after spinal cord injury (SCI) plays a pivotal role in the secondary injury mechanisms, which cause the ultimate neurologic insults. A better understanding of the molecular and cellular basis of apoptosis in SCI allows for improved glial and neuronal survival via the administrations of anti-apoptotic biomarkers. The knowledge structure, development trends, and research hotspots of apoptosis and SCI have not yet been systematically investigated.

Methods

Articles and reviews on apoptosis and SCI, published from 1st January 1994 to 1st Oct 2023, were retrieved from the Web of Science™. Bibliometrix in R was used to evaluate annual publications, countries, affiliations, authors, sources, documents, key words, and hot topics.

Results

A total of 3,359 publications in accordance with the criterions were obtained, which exhibited an ascending trend in annual publications. The most productive countries were the USA and China. Journal of Neurotrauma was the most impactive journal; Wenzhou Medical University was the most prolific affiliation; Cuzzocrea S was the most productive and influential author. "Apoptosis," "spinal-cord-injury," "expression," "activation," and "functional recovery" were the most frequent key words. Additionally, "transplantation," "mesenchymal stemness-cells," "therapies," "activation," "regeneration," "repair," "autophagy," "exosomes," "nlrp3 inflammasome," "neuroinflammation," and "knockdown" were the latest emerging key words, which may inform the hottest themes.

Conclusions

Apoptosis after SCI may cause the ultimate neurological damages. Development of novel treatments for secondary SCI mainly depends on a better understanding of apoptosis-related mechanisms in molecular and cellular levels. Such therapeutic interventions involve the application of anti-apoptotic agents, free radical scavengers, as well as anti-inflammatory drugs, which can be targeted to inhibit core events in cellular and molecular injury cascades pathway.

HIV-1 gp120 Protein Activates Cyclin-Dependent Kinase 1, a Possible Link to Central Nervous System Cell Death

Human immunodeficiency virus-1 (HIV-1)-associated neurodegenerative disorder (HAND) is frequently reported in HIV-infected individuals. The gp120 envelope viral protein has been implicated in the pathogenesis of HAND in HIV-1-infected patients; however, its pathogenic mechanism remains unclear. In this study, we first overexpressed gp120 proteins in pc12 cells and used PI staining, a CCK8 assay, a TUNEL assay, and caspase-9/caspase-3-induced apoptosis to ascertain the mediated cell death. Subsequently, the gp120-overexpressed cells were subjected to RNA transcriptomics and mass spectrometry. The obtained results were integrated and validated using a quantitative polymerase chain reaction (qPCR) and the postmortem brain samples with HIV-associated dementia were analyzed against the normal control (using the GSE35864 data set on gene ontology omnibus repository). Upon the integration of the RNA transcriptomic and proteomic results, 78 upregulated genes were revealed. Fut8, Unc13c, Cdk1, Loc100359539, and Hspa2 were the top five upregulated genes. Upon the analysis of the GSE35864 data set, the results indicate that Cdk1 was upregulated in HIV-associated dementia in comparison to the normal control. Moreover, the protein expression of Cdk1 was significantly higher in the gp120 transfected group compared to the normal control and decreased significantly upon inhibition using Roscovitine (a known Cdk1 inhibitor). Taken together, our results provide a possible molecular signature of the neurological impairment secondary to HIV glycoprotein 120.

The Role of Pink1-Mediated Mitochondrial Pathway in Propofol-Induced Developmental Neurotoxicity

The mechanisms underlying propofol-induced toxicity in developing neurons are still unclear. The aim of present study was to explore the role of Pink1 mediated mitochondria pathway in propofol-induced developmental neurotoxicity. The primary Neural Stem Cells (NSCs) were isolated from the hippocampus of E15.5 mice embryos and then treated with propofol. The effects of propofol on proliferation, differentiation, apoptosis, mitochondria ultrastructure and MMP of NSCs were investigated. In addition, the abundance of Pink1 and a group of mitochondria related proteins in the cytoplasm and/or mitochondria were investigated, which mainly included CDK1, Drp1, Parkin1, DJ-1, Mfn1, Mfn2 and OPA1. Moreover, the relationship between Pink1 and these molecules was explored using gene silencing, or pretreatment with protein inhibitors. Finally, the NSCs were pretreated with mitochondrial specific antioxidant (MitoQ) or Drp1 inhibitor (Mdivi-1), and then the toxic effects of propofol on NSCs were investigated. Our results indicated that propofol treatment inhibited NSCs proliferation and division, and promoted NSCs apoptosis. Propofol induced significant NSCs mitochondria deformation, vacuolization and swelling, and decreased MMP. Additional studies showed that propofol affected a group of mitochondria related proteins via Pink1 inhibition, and CDK1, Drp1, Parkin1 and DJ-1 are the important downstream proteins of Pink1. Finally, the effects of propofol on proliferation, differentiation, apoptosis, mitochondrial ultrastructure and MMP of NSCs were significantly attenuated by MitoQ or Mdivi-1 pretreatment. The present study demonstrated that propofol regulates the proliferation, differentiation and apoptosis of NSCs via Pink1mediated mitochondria pathway.

When Good Kinases Go Rogue: GSK3, p38 MAPK and CDKs as Therapeutic Targets for Alzheimer's and Huntington's Disease

Alzheimer's disease (AD) is a mostly sporadic brain disorder characterized by cognitive decline resulting from selective neurodegeneration in the hippocampus and cerebral cortex whereas Huntington's disease (HD) is a monogenic inherited disorder characterized by motor abnormalities and psychiatric disturbances resulting from selective neurodegeneration in the striatum. Although there have been numerous clinical trials for these diseases, they have been unsuccessful. Research conducted over the past three decades by a large number of laboratories has demonstrated that abnormal actions of common kinases play a key role in the pathogenesis of both AD and HD as well as several other neurodegenerative diseases. Prominent among these kinases are glycogen synthase kinase (GSK3), p38 mitogen-activated protein kinase (MAPK) and some of the cyclin-dependent kinases (CDKs). After a brief summary of the molecular and cell biology of AD and HD this review covers what is known about the role of these three groups of kinases in the brain and in the pathogenesis of the two neurodegenerative disorders. The potential of targeting GSK3, p38 MAPK and CDKS as effective therapeutics is also discussed as is a brief discussion on the utilization of recently developed drugs that simultaneously target two or all three of these groups of kinases. Multi-kinase inhibitors either by themselves or in combination with strategies currently being used such as immunotherapy or secretase inhibitors for AD and knockdown for HD could represent a more effective therapeutic approach for these fatal neurodegenerative diseases.

Programmed cell death in spinal cord injury pathogenesis and therapy

Spinal cord injury (SCI) always leads to functional deterioration due to a series of processes including cell death. In recent years, programmed cell death (PCD) is considered to be a critical process after SCI, and various forms of PCD were discovered in recent years, including apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis. Unlike necrosis, PCD is known as an active cell death mediated by a cascade of gene expression events, and it is crucial for elimination unnecessary and damaged cells, as well as a defence mechanism. Therefore, it would be meaningful to characterize the roles of PCD to not only enhance our understanding of the pathophysiological processes, but also improve functional recovery after SCI. This review will summarize and explore the most recent advances on how apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis are involved in SCI. This review can help us to understand the various functions of PCD in the pathological processes of SCI, and contribute to our novel understanding of SCI of unknown aetiology in the near future.

MiR-495 regulates cell proliferation and apoptosis in H2O2 stimulated rat spinal cord neurons through targeting signal transducer and activator of transcription 3 (STAT3)

Background

MicroRNA-495 (miR-495) is a post-translational modulator that performs several functions, and it is involved in several disease states. On the other hand, the physiological functions of miR-495 in H₂O₂ stimulated mouse spinal cord neuronal dysfunction have not yet been fully understood.

Methods

In this study, we speculated that miR-495 may regulate the expression of STAT3 in the processes of neuronal proliferation and apoptosis following spinal cord injury (SCI). Cell viability was assessed with methyl thiazolyl tetrazolium (MTT) assay. Caspase-3 activity was assayed with ELISA. Cellular apoptotic changes were measured with TUNEL assay. Intracellular ROS production was determined by measuring uptake of dichlorodihydrofluorescein diacetate (DCFH-DA; PCR was used to assay the mRNA expression of STAT3 gene bearing predicted targeting positions for miR-495, while qRT-PCR was used to measure miR-495 mRNA.

Results

The results demonstrated that treatment of SCNs with H₂O₂ led to a significant decrease in cell survival, while it enhanced apoptosis. The H₂O₂ treatment induced cell membrane dysfunction, and increased ROS levels and DNA damage. Interestingly, the expression of miR-495 was markedly suppressed when SCNs were exposed to H₂O₂. However, miR-495 overexpression reversed H₂O₂-induced cytotoxicity and apoptosis in SCNs. Moreover, H₂O₂ exposure elevated protein and mRNA concentrations of STAT3 in SCNs. Bioinformatics analysis showed likely binding domains of miR-495 in the 3'-untranslated regions of STAT3 in SCNs. MiR-495 loss-of-function and gain-of-function significantly up-regulated and down-regulated both STAT3 mRNA and protein expressions, respectively, in SCNs.

Conclusions

miR-495 overexpression inhibited H₂O₂-induced SCN dysfunction. This mechanism was mediated through the down-regulation of STAT3 expression.

Programmed cell death in spinal cord injury pathogenesis and therapy

Spinal cord injury (SCI) always leads to functional deterioration due to a series of processes including cell death. In recent years, programmed cell death (PCD) is considered to be a critical process after SCI, and various forms of PCD were discovered in recent years, including apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis. Unlike necrosis, PCD is known as an active cell death mediated by a cascade of gene expression events, and it is crucial for elimination unnecessary and damaged cells, as well as a defence mechanism. Therefore, it would be meaningful to characterize the roles of PCD to not only enhance our understanding of the pathophysiological processes, but also improve functional recovery after SCI. This review will summarize and explore the most recent advances on how apoptosis, necroptosis, autophagy, ferroptosis, pyroptosis and paraptosis are involved in SCI. This review can help us to understand the various functions of PCD in the pathological processes of SCI, and contribute to our novel understanding of SCI of unknown aetiology in the near future.

Dementia, Depression, and Associated Brain Inflammatory Mechanisms after Spinal Cord Injury

Evaluation of the chronic effects of spinal cord injury (SCI) has long focused on sensorimotor deficits, neuropathic pain, bladder/bowel dysfunction, loss of sexual function, and emotional distress. Although not well appreciated clinically, SCI can cause cognitive impairment including deficits in learning and memory, executive function, attention, and processing speed; it also commonly leads to depression. Recent large-scale longitudinal population-based studies indicate that patients with isolated SCI (without concurrent brain injury) are at a high risk of dementia associated with substantial cognitive impairments. Yet, little basic research has addressed potential mechanisms for cognitive impairment and depression after injury. In addition to contributing to disability in their own right, these changes can adversely affect rehabilitation and recovery and reduce quality of life. Here, we review clinical and experimental work on the complex and varied responses in the brain following SCI. We also discuss potential mechanisms responsible for these less well-examined, important SCI consequences. In addition, we outline the existing and developing therapeutic options aimed at reducing SCI-induced brain neuroinflammation and post-injury cognitive and emotional impairments.

Pharmacological Inhibition of Cyclin-Dependent Kinases Triggers Anti-Fibrotic Effects in Hepatic Stellate Cells In Vitro

Liver fibrosis is a wound healing process in response to chronic liver injury, which is characterized by the accumulation of extracellular collagen produced by Hepatic Stellate Cells (HSCs). This process involves cell cycle re-entry and proliferation of normally quiescent HSCs controlled by cyclins and associated cyclin-dependent kinases (Cdks). Cdk2 mediates the entry and progression through S-phase in complex with E-and A-type cyclins. We have demonstrated that cyclin E1 is essential for liver fibrogenesis in mice, but it is not known if this is dependent on Cdk2 or related Cdks. Here, we aimed to evaluate the benefit of the pan-Cdk inhibitor CR8 for treatment of liver fibrosis in vitro. CR8-treatment reduced proliferation and survival in immortalized HSC lines and in addition attenuated pro-fibrotic properties in primary murine HSCs. Importantly, primary murine hepatocytes were much more tolerant against the cytotoxic and anti-proliferative effects of CR8. We identified CR8 dosages mediating anti-fibrotic effects in primary HSCs without affecting cell cycle activity and survival in primary hepatocytes. In conclusion, the pharmacological pan-Cdk inhibitor CR8 restricts the pro-fibrotic properties of HSCs, while preserving proliferation and viability of hepatocytes at least in vitro. Therefore, CR8 and related drugs might be beneficial for the treatment of liver fibrosis.

Cell Cycle Proteins as Key Regulators of Postmitotic Cell Death

Cell cycle progression in dividing cells, characterized by faithful replication of the genomic materials and duplication of the original cell, is fundamental for growth and reproduction of all mammalian organisms. Functional maturation of postmitotic cells, however, requires cell cycle exit and terminal differentiation. In mature postmitotic cells, many cell cycle proteins remain to be expressed, or can be induced and reactivated in pathological conditions such as traumatic injury and degenerative diseases. Interestingly, elevated levels of cell cycle proteins in postmitotic cells often do not induce proliferation, but result in aberrant cell cycle reentry and cell death. At present, the cell cycle machinery is known predominantly for regulating cell cycle progression and cell proliferation, albeit accumulating evidence indicates that cell cycle proteins may also control cell death, especially in postmitotic tissues. Herein, we provide a brief summary of these findings and hope to highlight the connection between cell cycle reentry and postmitotic cell death. In addition, we also outline the signaling pathways that have been identified in cell cycle-related cell death. Advanced understanding of the molecular mechanisms underlying cell cycle-related death is of paramount importance because this knowledge can be applied to develop protective strategies against pathologies in postmitotic tissues. Moreover, a full-scope understanding of the cell cycle machinery will allow fine tuning to favor cell proliferation over cell death, thereby potentially promoting tissue regeneration.

cPLA2 activation contributes to lysosomal defects leading to impairment of autophagy after spinal cord injury

The autophagy–lysosomal pathway plays an essential role in cellular homeostasis as well as a protective function against a variety of diseases including neurodegeneration. Conversely, inhibition of autophagy, for example due to lysosomal dysfunction, can lead to pathological accumulation of dysfunctional autophagosomes and consequent neuronal cell death. We previously reported that autophagy is inhibited and contributes to neuronal cell death following spinal cord injury (SCI). In this study, we examined lysosomal function and explored the mechanism of lysosomal defects following SCI. Our data demonstrated that expression levels and processing of the lysosomal enzyme cathepsin D (CTSD) are decreased by 2 h after SCI. Enzymatic activity levels of CTSD and another lysosomal enzyme, N-acetyl-alpha-glucosaminidase, are both decreased 24 h post injury, indicating general lysosomal dysfunction. Subcellular fractionation and immunohistochemistry analysis demonstrated that this dysfunction is due to lysosomal membrane permeabilization and leakage of lysosomal contents into the cytosol. To directly assess extent and mechanisms of damage to lysosomal membranes, we performed mass spectrometry-based lipidomic analysis of lysosomes purified from SCI and control spinal cord. At 2 h post injury our data demonstrated increase in several classes of lysosophospholipids, the products of phospholipases (PLAs), as well as accumulation of PLA activators, ceramides. Phospholipase cPLA2, the main PLA species expressed in the CNS, has been previously implicated in mediation of secondary injury after SCI, but the mechanisms of its involvement remain unclear. Our data demonstrate that cPLA2 is activated within 2 h after SCI preferentially in the lysosomal fraction, where it colocalizes with lysosomal-associated membrane protein 2 in neurons. Inhibition of cPLA2 in vivo decreased lysosomal damage, restored autophagy flux, and reduced neuronal cell damage. Taken together our data implicate lysosomal defects in pathophysiology of SCI and for the first time indicate that cPLA2 activation leads to lysosomal damage causing neuronal autophagosome accumulation associated with neuronal cell death.

Screening the Action Targets of Enterovirus 71 in Human SH-SY5Y Cells Using RNA Sequencing Data

Hand, foot, and mouth disease (HFMD) is a common infection for children younger than the age of five. HFMD is mainly induced by coxsackievirus A16 and enterovirus 71 (EV71). EV71-associated HFMD often has serious neurological disease complications. The purpose of this study was to reveal the mechanisms of action of EV71 on neurons. SH-SY5Y cells transfected or untransfected with EV71 were sequenced. After data preprocessing, differentially expressed genes (DEGs) were screened using the limma package in R, and clustering analysis was then performed using the ComplexHeatmap package in R. The DAVID tool was used for EDG enrichment analysis. Protein-protein interactions (PPIs) were predicted using the STRING database and PPI networks were then constructed using Cytoscape software. After pathways involved in the key PPI network nodes were enriched, pathway deviation scores were calculated. Clustering analysis was also conducted for these pathways. There were 978 DEGs in the transfected samples. Upregulated TNF was enriched in NF-kappa B signaling pathway. Among the top 20 nodes in the PPI network, CDK1, STAT3, CCND1, TNF, and MYC had the highest degrees. A total of 28 pathways were enriched for the top 20 nodes, including Epstein-Barr virus infection (p = 3.78E-06), proteoglycans in cancer (p = 4.96E-06), and melanoma (p = 1.99E-05). In addition, clustering analysis showed that these pathways could clearly differentiate the two groups of samples. EV71 may affect neurons by mediating CDK1, STAT3, CCND1, TNF, and MYC, indicating that these genes are promising targets for preventing the neuronal complications of HFMD.

Comparing effects of CDK inhibition and E2F1/2 ablation on neuronal cell death pathways in vitro and after traumatic brain injury

Traumatic brain injury (TBI) activates multiple neuronal cell death mechanisms, leading to post-traumatic neuronal loss and neurological deficits. TBI-induced cell cycle activation (CCA) in post-mitotic neurons causes regulated cell death involving cyclin-dependent kinase (CDK) activation and initiation of an E2F transcription factor-mediated pro-apoptotic program. Here we examine the mechanisms of CCA-dependent neuronal apoptosis in primary neurons in vitro and in mice exposed to controlled cortical impact (CCI). In contrast to our prior work demonstrating robust neuroprotective effects by CDK inhibitors after TBI, examination of neuronal apoptotic mechanisms in E2F1^−/−/E2F2^−/− or E2F2^−/− transgenic mice following CCI suggests that E2F1 and/or E2F2 likely play only a modest role in neuronal cell loss after brain trauma. To elucidate more critical CCA molecular pathways involved in post-traumatic neuronal cell death, we investigated the neuroprotective effects and mechanisms of the potent CDK inhibitor CR8 in a DNA damage model of cell death in primary cortical neurons. CR8 treatment significantly reduced caspase activation and cleavage of caspase substrates, attenuating neuronal cell death. CR8 neuroprotective effects appeared to reflect inhibition of multiple pathways converging on the mitochondrion, including injury-induced elevation of pro-apoptotic Bcl-2 homology region 3 (BH3)-only proteins Puma and Noxa, thereby attenuating mitochondrial permeabilization and release of cytochrome c and AIF, with reduction of both caspase-dependent and -independent apoptosis. CR8 administration also limited injury-induced deficits in mitochondrial respiration. These neuroprotective effects may be explained by CR8-mediated inhibition of key upstream injury responses, including attenuation of c-Jun phosphorylation/activation as well as inhibition of p53 transactivation of BH3-only targets.

Signatures of altered long noncoding RNAs and messenger RNAs expression in the early acute phase of spinal cord injury

Spinal cord injury (SCI) is a highly severe disease and it can lead to the destruction of the motor and sensory function resulting in temporary or permanent disability. Long noncoding RNAs (lncRNAs) are transcripts longer than 200 nt that play a critical role in central nervous system (CNS) injury. However, the exact roles of lncRNAs and messenger RNAs (mRNAs) in the early acute phase of SCI remain to be elucidated. We examined the expression of mRNAs and lncRNAs in a rat model at 2 days after SCI and identified the differentially expressed lncRNAs (DE lncRNAs) and differentially expressed mRNAs (DE mRNAs) using microarray analysis. Subsequently, a comprehensive bioinformatics analysis was also performed to clarify the interaction between DE mRNAs. A total of 3,193 DE lncRNAs and 4,308 DE mRNAs were identified between the injured group and control group. Classification, length distribution, and chromosomal distribution of the dysregulated lncRNAs were also performed. The gene ontology analysis and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were performed to identify the critical biological processes and pathways. A protein-protein interaction (PPI) network indicated that IL6, TOP2A, CDK1, POLE, CCNB1, TNF, CCNA2, CDC20, ITGAM, and MYC were the top 10 core genes. The subnetworks from the PPI network were identified to further elucidate the most significant functional modules of the DE mRNAs. These data may provide novel insights into the molecular mechanism of the early acute phase of SCI. The identification of lncRNAs and mRNAs may offer potential diagnostic and therapeutic targets for SCI.

Complement After Trauma: Suturing Innate and Adaptive Immunity

The overpowering effect of trauma on the immune system is undisputed. Severe trauma is characterized by systemic cytokine generation, activation and dysregulation of systemic inflammatory response complementopathy and coagulopathy, has been immensely instrumental in understanding the underlying mechanisms of the innate immune system during systemic inflammation. The compartmentalized functions of the innate and adaptive immune systems are being gradually recognized as an overlapping, interactive and dynamic system of responsive elements. Nonetheless the current knowledge of the complement cascade and its interaction with adaptive immune response mediators and cells, including T- and B-cells, is limited. In this review, we discuss what is known about the bridging effects of the complement system on the adaptive immune system and which unexplored areas could be crucial in understanding how the complement and adaptive immune systems interact following trauma.

HAX1 is associated with neuronal apoptosis and astrocyte proliferation after spinal cord injury

HS1-associated protein X-1 (HAX1) is a class of multifunctional protein, participated in various physiological processes such as cell apoptosis, proliferation and motility. However, the HAX1 expression and function in the spinal cord injury (SCI) pathological process have not been investigated. In our current research, the rat model of SCI was established, and then we explored the possible role of HAX1 after SCI. The results of western blot indicated that HAX1 was present in sham operated control group and significantly elevated at 3 days post SCI, then declined gradually. Immunohistochemical studies indicated HAX1 expression was enhanced significantly in white and gray matter at 3 days post SCI compared with sham operated group. Double immunofluorescence staining showed the proportion of cells, double-labeled HAX1 and neurons, astrocytes, increased significantly at 3 days post SCI. In addition, co-localization of HAX1/active caspase-3 and HAX1/PCNA was tested in cells. Furthermore, over-expression of HAX1 inhibited neuronal apoptosis in vitro, and in astrocytes HAX1 silencing could down-regulate PCNA expression post LPS treatment. Meanwhile, CCK8 assay showed that knockdown of HAX1 could inhibit the astrocyte proliferation. In summary, our data indicated that HAX1 might play significant roles in pathological process of neuronal apoptosis and astrocyte proliferation during SCI.

Genetic and pharmacological inhibition of Cdk1 provides neuroprotection towards ischemic neuronal death

Cell cycle proteins are mainly expressed by dividing cells. However, it is well established that these molecules play additional non-canonical activities in several cell death contexts. Increasing evidence shows expression of cell cycle regulating proteins in post-mitotic cells, including mature neurons, following neuronal insult. Several cyclin-dependent kinases (Cdks) have already been shown to mediate ischemic neuronal death but Cdk1, a major cell cycle G2/M regulator, has not been investigated in this context. We therefore examined the role of Cdk1 in neuronal cell death following cerebral ischemia, using both in vitro and in vivo genetic and pharmacological approaches. Exposure of primary cortical neurons cultures to 4 h of oxygen–glucose deprivation (OGD) resulted in neuronal cell death and induced Cdk1 expression. Neurons from Cdk1-cKO mice showed partial resistance to OGD-induced neuronal cell death. Addition of R-roscovitine to the culture medium conferred neuroprotection against OGD-induced neuronal death. Transient 1-h occlusion of the cerebral artery (MCAO) also leads to Cdk1 expression and activation. Cdk1-cKO mice displayed partial resistance to transient 1-h MCAO. Moreover, systemic delivery of R-roscovitine was neuroprotective following transient 1-h MCAO. This study demonstrates that promising neuroprotective therapies can be considered through inhibition of the cell cycle machinery and particularly through pharmacological inhibition of Cdk1.

Cell cycle inhibition limits development and maintenance of neuropathic pain following spinal cord injury

Chronic pain after spinal cord injury (SCI) may present as hyperalgesia, allodynia, and/or spontaneous pain and is often resistant to conventional pain medications. Identifying more effective interventions to manage SCI pain requires improved understanding of the pathophysiological mechanisms involved. Cell cycle activation (CCA) has been implicated as a key pathophysiological event following SCI. We have shown that early central or systemic administration of a cell cycle inhibitor reduces CCA, prevents glial changes, and limits SCI-induced hyperesthesia. Here, we compared the effects of early vs late treatment with the pan-cyclin-dependent kinase inhibitor flavopiridol on allodynia as well as spontaneous pain. Adult C57BL/6 male mice subjected to moderate SCI were treated with intraperitoneal injections of flavopiridol (1 mg/kg), daily for 7 days beginning either 3 hours or 5 weeks after injury. Mechanical/thermal allodynia was evaluated, as well as spontaneous pain using the mouse grimace scale (MGS). We show that sensitivity to mechanical and thermal stimulation, and locomotor dysfunction were significantly reduced by early flavopiridol treatment compared with vehicle-treated controls. Spinal cord injury caused robust and extended increases of MGS up to 3 weeks after trauma. Early administration of flavopiridol significantly shortened duration of MGS changes. Late flavopiridol intervention significantly limited hyperesthesia at 7 days after treatment, associated with reduced glial changes, but without effect on locomotion. Thus, our data suggest that cell cycle modulation may provide an effective therapeutic strategy to reduce hyperesthesia after SCI, with a prolonged therapeutic window.

Ablation of the transcription factors E2F1-2 limits neuroinflammation and associated neurological deficits after contusive spinal cord injury

Traumatic spinal cord injury (SCI) induces cell cycle activation (CCA) that contributes to secondary injury and related functional impairments such as motor deficits and hyperpathia. E2F1 and E2F2 are members of the activator sub-family of E2F transcription factors that play an important role in proliferating cells and in cell cycle-related neuronal death, but no comprehensive study have been performed in SCI to determine the relative importance of these factors. Here we examined the temporal distribution and cell-type specificity of E2F1 and E2F2 expression following mouse SCI, as well as the effects of genetic deletion of E2F1-2 on neuronal cell death, neuroinflammation and associated neurological dysfunction. SCI significantly increased E2F1 and E2F2 expression in active caspase-3(+) neurons/oligodendrocytes as well as in activated microglia/astrocytes. Injury-induced up-regulation of cell cycle-related genes and protein was significantly reduced by intrathecal injection of high specificity E2F decoy oligodeoxynucleotides against the E2F-binding site or in E2F1-2 null mice. Combined E2F1+2 siRNA treatment show greater neuroprotection in vivo than E2F1 or E2F2 single siRNA treatment. Knockout of both E2F1 and E2F2 genes (E2Fdko) significantly reduced neuronal death, neuroinflammation, and tissue damage, as well as limiting motor dysfunction and hyperpathia after SCI. Both CCA reduction and functional improvement in E2Fdko mice were greater than those in E2F2ko model. These studies demonstrate that SCI-induced activation of E2F1-2 mediates CCA, contributing to gliopathy and neuronal/tissue loss associated with motor impairments and post-traumatic hyperesthesia. Thus, E2F1-2 provide a therapeutic target for decreasing secondary tissue damage and promoting recovery of function after SCI.

The Expression of VHL (Von Hippel-Lindau) After Traumatic Spinal Cord Injury and Its Role in Neuronal Apoptosis

The VHL (Von Hippel-Lindau) gene is a tumor suppressor gene, which is best known as an E3 ubiquitin ligase that negatively regulates the hypoxia inducible factor. The inactivation of VHL gene could result in the abnormal synthesis of VHL protein, which is in contact with the development and occurrence of renal clear cell carcinoma. However, the expression and possible function of VHL in central nervous system (CNS) is still unclear. To examine the function of VHL in CNS injury and repair, we used an acute spinal cord injury (SCI) model in adult rats. Western blot analysis showed an important upregulation of VHL protein, reaching a peak at day 3 and then declined during the following days. Double immunofluorescence staining showed that VHL was co-expressed with neurons, but not with astrocytes and microglia. Moreover, we detected that active caspase-3 had co-localized with VHL in neurons after SCI. Additionally in vitro, VHL depletion, by short interfering RNA, significantly reduced neuronal apoptosis. In conclusion, these data suggested that the change of VHL protein expression was related to neuronal apoptosis after SCI.

The feasibility of in vivo imaging of infiltrating blood cells for predicting the functional prognosis after spinal cord injury

After a spinal cord injury (SCI), a reliable prediction of the potential functional outcome is essential for determining the optimal treatment strategy. Despite recent advances in the field of neurological assessment, there is still no satisfactory methodology for predicting the functional outcome after SCI. We herein describe a novel method to predict the functional outcome at 12 hours after SCI using in vivo bioluminescence imaging. We produced three groups of SCI mice with different functional prognoses: 50 kdyn (mild), 70 kdyn (moderate) and 90 kdyn (severe). Only the locomotor function within 24 hours after SCI was unable to predict subsequent functional recovery. However, both the number of infiltrating neutrophils and the bioluminescence signal intensity from infiltrating blood cells were found to correlate with the severity of the injury at 12 hours after SCI. Furthermore, a strong linear relationship was observed among the number of infiltrating neutrophils, the bioluminescence signal intensity, and the severity of the injury. Our findings thus indicate that in vivo bioluminescence imaging is able to accurately predict the long-term functional outcome in the hyperacute phase of SCI, thereby providing evidence that this imaging modality could positively contribute to the future development of tailored therapeutic approaches for SCI.

E2F4 Promotes Neuronal Regeneration and Functional Recovery after Spinal Cord Injury in Zebrafish

Mammals exhibit poor recovery after spinal cord injury (SCI), whereas non-mammalian vertebrates exhibit significant spontaneous recovery after SCI. The mechanisms underlying this difference have not been fully elucidated; therefore, the purpose of this study was to investigate these mechanisms. Using comparative transcriptome analysis, we demonstrated that genes related to cell cycle were significantly enriched in the genes specifically dysregulated in zebrafish SCI. Most of the cell cycle-related genes dysregulated in zebrafish SCI were down-regulated, possibly through activation of e2f4. Using a larval zebrafish model of SCI, we demonstrated that the recovery of locomotive function and neuronal regeneration after SCI were significantly inhibited in zebrafish treated with an E2F4 inhibitor. These results suggest that activation of e2f4 after SCI may be responsible, at least in part, for the significant recovery in zebrafish. This provides novel insight into the lack of recovery after SCI in mammals and informs potential therapeutic strategies.

Altered Mitochondrial Dynamics Contributes to Propofol-induced Cell Death in Human Stem Cell-derived Neurons

BACKGROUND

Studies in developing animals have shown that anesthetic agents can lead to neuronal cell death and learning disabilities when administered early in life. Development of human embryonic stem cell-derived neurons has provided a valuable tool for understanding the effects of anesthetics on developing human neurons. Unbalanced mitochondrial fusion and fission lead to various pathological conditions including neurodegeneration. The aim of this study was to dissect the role of mitochondrial dynamics in propofol-induced neurotoxicity.

METHODS

Terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate in situ nick-end labeling staining was used to assess cell death in human embryonic stem cell-derived neurons. Mitochondrial fission was assessed using TOM20 staining and electron microscopy. Expression of mitochondrial fission-related proteins was assessed by Western blot, and confocal microscopy was used to assess opening time of the mitochondrial permeability transition pore (mPTP).

RESULTS

Exposure to 6 h of 20 μg/ml propofol increased cell death from 3.18 ± 0.17% in the control-treated group to 9.6 ± 0.95% and led to detrimental increases in mitochondrial fission (n = 5 coverslips per group) accompanied by increased expression of activated dynamin-related protein 1 and cyclin-dependent kinase 1, key proteins responsible for mitochondrial fission. Propofol exposure also induced earlier opening of the mPTP from 118.9 ± 3.1 s in the control-treated group to 73.3 ± 1.6 s. Pretreatment of the cells with mdivi-1, a mitochondrial fission blocker rescued the propofol-induced toxicity, mitochondrial fission, and mPTP opening time (n = 75 cells per group). Inhibiting cyclin-dependent kinase 1 attenuated the increase in cell death and fission and the increase in expression of activated dynamin-related protein 1.

CONCLUSION

These data demonstrate for the first time that propofol-induced neurotoxicity occurs through a mitochondrial fission/mPTP-mediated pathway.

The role of pharmacotherapy in modifying the neurological status of patients with spinal and spinal cord injuries

The aim here was to conduct a review of the literature on pharmacological therapies for modifying the neurological status of patients with spinal cord injuries. The PubMed database was searched for articles with the terms "spinal cord injury AND methylprednisolone/GM1/apoptosis inhibitor/calpain inhibitor/naloxone/tempol/tirilazad", in Portuguese or in English, published over the last five years. Older studies were included because of their historical importance. The pharmacological groups were divided according to their capacity to interfere with the physiopathological mechanisms of secondary injuries. Use of methylprednisolone needs to be carefully weighed up: other anti-inflammatory agents have shown benefits in humans or in animals. GM1 does not seem to have greater efficacy than methylprednisolone, but longer-term studies are needed. Many inhibitors of apoptosis have shown benefits in in vitro studies or in animals. Naloxone has not shown benefits. Tempol inhibits the main consequences of oxidation at the level of the spinal cord and other antioxidant drugs seem to have an effect superior to that of methylprednisolone. There is an urgent need to find new treatments that improve the neurological status of patients with spinal cord injuries. The benefits from treatment with methylprednisolone have been questioned, with concerns regarding its safety. Other drugs have been studied, and some of these may provide promising alternatives. Additional studies are needed in order to reach conclusions regarding the benefits of these agents in clinical practice.

Regulation of Bim in Health and Disease

The BH3-only Bim protein is a major determinant for initiating the intrinsic apoptotic pathway under both physiological and pathophysiological conditions. Tight regulation of its expression and activity at the transcriptional, translational and post-translational levels together with the induction of alternatively spliced isoforms with different pro-apoptotic potential, ensure timely activation of Bim. Under physiological conditions, Bim is essential for shaping immune responses where its absence promotes autoimmunity, while too early Bim induction eliminates cytotoxic T cells prematurely, resulting in chronic inflammation and tumor progression. Enhanced Bim induction in neurons causes neurodegenerative disorders including Alzheimer's, Parkinson's and Huntington's diseases. Moreover, type I diabetes is promoted by genetically predisposed elevation of Bim in β-cells. On the contrary, cancer cells have developed mechanisms that suppress Bim expression necessary for tumor progression and metastasis. This review focuses on the intricate network regulating Bim activity and its involvement in physiological and pathophysiological processes.

An Up-regulation of IRF-1 After a Spinal Cord Injury: Implications for Neuronal Apoptosis

IRF-1, a kind of transcription factor, is expressed in many cell types, except in early embryonal cells. IRF-1 has played an essential role in various physiological and pathological processes, including tumor immune surveillance, viral infection, development of immunity system and pro-inflammatory injury. However, the expression and function of IRF-1 in spinal cord injury (SCI) are still unknown. In this study, we have performed an acute SCI model in adult rats and investigated the dynamic changes of IRF-1 expression in the spinal cord. Western blot have shown that IRF-1 protein levels gradually increased, reaching a peak at day 3 and then gradually declined to a normal level at day 14 after SCI. Double immunofluorescence staining showed that IRF-1 immunoreactivity was found in neurons, but not in astrocytes and microglia. Additionally, colocalization of IRF-1/active caspase-3 was detected in neurons. In vitro, IRF-1 depletion, by short interfering RNA, obviously decreases neuronal apoptosis. In conclusion, this is the first description of IRF-1 expression in spinal cord injury. Our results suggested that IRF-1 might play crucial roles in CNS pathophysiology after SCI.

Isolated spinal cord contusion in rats induces chronic brain neuroinflammation, neurodegeneration, and cognitive impairment. Involvement of cell cycle activation

Cognitive dysfunction has been reported in patients with spinal cord injury (SCI), but it has been questioned whether such changes may reflect concurrent head injury, and the issue has not been addressed mechanistically or in a well-controlled experimental model. Our recent rodent studies examining SCI-induced hyperesthesia revealed neuroinflammatory changes not only in supratentorial pain-regulatory sites, but also in other brain regions, suggesting that additional brain functions may be impacted following SCI. Here we examined effects of isolated thoracic SCI in rats on cognition, brain inflammation, and neurodegeneration. We show for the first time that SCI causes widespread microglial activation in the brain, with increased expression of markers for activated microglia/macrophages, including translocator protein and chemokine ligand 21 (C-C motif). Stereological analysis demonstrated significant neuronal loss in the cortex, thalamus, and hippocampus. SCI caused chronic impairment in spatial, retention, contextual, and fear-related emotional memory-evidenced by poor performance in the Morris water maze, novel objective recognition, and passive avoidance tests. Based on our prior work implicating cell cycle activation (CCA) in chronic neuroinflammation after SCI or traumatic brain injury, we evaluated whether CCA contributed to the observed changes. Increased expression of cell cycle-related genes and proteins was found in hippocampus and cortex after SCI. Posttraumatic brain inflammation, neuronal loss, and cognitive changes were attenuated by systemic post-injury administration of a selective cyclin-dependent kinase inhibitor. These studies demonstrate that chronic brain neurodegeneration occurs after isolated SCI, likely related to sustained microglial activation mediated by cell cycle activation.

Gene expression profiling for human iPS-derived motor neurons from sporadic ALS patients reveals a strong association between mitochondrial functions and neurodegeneration

Amyotrophic Lateral Sclerosis (ALS) is a fatal neurodegenerative disease that leads to widespread motor neuron death, general palsy and respiratory failure. The most prevalent sporadic ALS form is not genetically inherited. Attempts to translate therapeutic strategies have failed because the described mechanisms of disease are based on animal models carrying specific gene mutations and thus do not address sporadic ALS. In order to achieve a better approach to study the human disease, human induced pluripotent stem cell (hiPSC)-differentiated motor neurons were obtained from motor nerve fibroblasts of sporadic ALS and non-ALS subjects using the STEMCCA Cre-Excisable Constitutive Polycistronic Lentivirus system and submitted to microarray analyses using a whole human genome platform. DAVID analyses of differentially expressed genes identified molecular function and biological process-related genes through Gene Ontology. REVIGO highlighted the related functions mRNA and DNA binding, GTP binding, transcription (co)-repressor activity, lipoprotein receptor binding, synapse organization, intracellular transport, mitotic cell cycle and cell death. KEGG showed pathways associated with Parkinson's disease and oxidative phosphorylation, highlighting iron homeostasis, neurotrophic functions, endosomal trafficking and ERK signaling. The analysis of most dysregulated genes and those representative of the majority of categorized genes indicates a strong association between mitochondrial function and cellular processes possibly related to motor neuron degeneration. In conclusion, iPSC-derived motor neurons from motor nerve fibroblasts of sporadic ALS patients may recapitulate key mechanisms of neurodegeneration and may offer an opportunity for translational investigation of sporadic ALS. Large gene profiling of differentiated motor neurons from sporadic ALS patients highlights mitochondrial participation in the establishment of autonomous mechanisms associated with sporadic ALS.

HEDGEHOG/GLI-E2F1 axis modulates iASPP expression and function and regulates melanoma cell growth

HEDGEHOG (HH) signaling is a key regulator of tissue development and its aberrant activation is involved in several cancer types, including melanoma. We and others have shown a reciprocal cross talk between HH signaling and p53, whose function is often impaired in melanoma. Here we present evidence that both GLI1 and GLI2, the final effectors of HH signaling, regulate the transcription factor E2F1 in melanoma cells, by binding to a functional non-canonical GLI consensus sequence. Consistently, we find a significant correlation between E2F1 and PATCHED1 (PTCH1), GLI1 and GLI2 expression in human melanomas. Functionally, we find that E2F1 is a crucial mediator of HH signaling and it is required for melanoma cell proliferation and xenograft growth induced by activation of the HH pathway. Interestingly, we present evidence that the HH/GLI-E2F1 axis positively modulates the inhibitor of apoptosis-stimulating protein of p53 (iASPP) at multiple levels. HH activation induces iASPP expression through E2F1, which directly binds to iASPP promoter. HH pathway also contributes to iASPP function, by the induction of Cyclin B1 and by the E2F1-dependent regulation of CDK1, which are both involved in iASPP activation. Our data show that activation of HH signaling enhances proliferation in presence of E2F1 and promotes apoptosis in its absence or upon CDK1 inhibition, suggesting that E2F1/iASPP dictates the outcome of HH signaling in melanoma. Together, these findings identify a novel HH/GLI-E2F1-iASPP axis that regulates melanoma cell growth and survival, providing an additional mechanism through which HH signaling restrains p53 proapoptotic function.

What's New in Traumatic Brain Injury: Update on Tracking, Monitoring and Treatment

Traumatic brain injury (TBI), defined as an alteration in brain functions caused by an external force, is responsible for high morbidity and mortality around the world. It is important to identify and treat TBI victims as early as possible. Tracking and monitoring TBI with neuroimaging technologies, including functional magnetic resonance imaging (fMRI), diffusion tensor imaging (DTI), positron emission tomography (PET), and high definition fiber tracking (HDFT) show increasing sensitivity and specificity. Classical electrophysiological monitoring, together with newly established brain-on-chip, cerebral microdialysis techniques, both benefit TBI. First generation molecular biomarkers, based on genomic and proteomic changes following TBI, have proven effective and economical. It is conceivable that TBI-specific biomarkers will be developed with the combination of systems biology and bioinformation strategies. Advances in treatment of TBI include stem cell-based and nanotechnology-based therapy, physical and pharmaceutical interventions and also new use in TBI for approved drugs which all present favorable promise in preventing and reversing TBI.

Spinal cord injury causes brain inflammation associated with cognitive and affective changes: role of cell cycle pathways

Experimental spinal cord injury (SCI) causes chronic neuropathic pain associated with inflammatory changes in thalamic pain regulatory sites. Our recent studies examining chronic pain mechanisms after rodent SCI showed chronic inflammatory changes not only in thalamus, but also in other regions including hippocampus and cerebral cortex. Because changes appeared similar to those in our rodent TBI models that are associated with neurodegeneration and neurobehavioral dysfunction, we examined effects of mouse SCI on cognition, depressive-like behavior, and brain inflammation. SCI caused spatial and retention memory impairment and depressive-like behavior, as evidenced by poor performance in the Morris water maze, Y-maze, novel objective recognition, step-down passive avoidance, tail suspension, and sucrose preference tests. SCI caused chronic microglial activation in the hippocampus and cerebral cortex, where microglia with hypertrophic morphologies and M1 phenotype predominated. Stereological analyses showed significant neuronal loss in the hippocampus at 12 weeks but not 8 d after injury. Increased cell-cycle-related gene (cyclins A1, A2, D1, E2F1, and PCNA) and protein (cyclin D1 and CDK4) expression were found chronically in hippocampus and cerebral cortex. Systemic administration of the selective cyclin-dependent kinase inhibitor CR8 after SCI significantly reduced cell cycle gene and protein expression, microglial activation and neurodegeneration in the brain, cognitive decline, and depression. These studies indicate that SCI can initiate a chronic brain neurodegenerative response, likely related to delayed, sustained induction of M1-type microglia and related cell cycle activation, which result in cognitive deficits and physiological depression.

Decreased GFAP expression and improved functional recovery in contused spinal cord of rats following valproic acid therapy

Many studies have illustrated that much of the post-traumatic degeneration of the spinal cord cells is caused by the secondary mechanism. The aim of this study is to evaluate the effect of the anti-inflammatory property of valproic acid (VPA) on injured spinal cords (SC). The rats with the contused SC received intraperitoneal single injection of VPA (150, 200, 300, 400 or 500 mg/kg) at 2, 6, 12 and 24 h post-injury. Basso-Beattie-Bresnahan (BBB) test and H-reflex evaluated the functional outcome for 12 weeks. The SC were investigated 3 months post-injury using morphometry and glial fibrillary acid protein (GFAP) expression. Reduction in cavitation, H/M ratio, BBB scores and GFAP expression in the treatment groups were significantly more than that of the untreated one (P < 0.05). The optimal improvement in the condition of the contused rats was in the ones treated at the acute phase of injury with 300 mg/kg of VPA at 12 h post-injury, they had the highest increase in BBB score and decrease in astrogliosis and axonal loss. We conclude that treating the contused rats with 300 mg/kg of VPA at 12 h post-injury improves the functional outcome and reduces the traumatized SC gliosis.

Cyclin-dependent kinases regulate apoptosis of intestinal epithelial cells

Homeostasis of the gastrointestinal epithelium is dependent upon a balance between cell proliferation and apoptosis. Cyclin-dependent kinases (Cdks) are well known for their role in cell proliferation. Previous studies from our group have shown that polyamine-depletion of intestinal epithelial cells (IEC-6) decreases cyclin-dependent kinase 2 (Cdk2) activity, increases p53 and p21Cip1 protein levels, induces G1 arrest, and protects cells from camptothecin (CPT)-induced apoptosis. Although emerging evidence suggests that members of the Cdk family are involved in the regulation of apoptosis, their roles directing apoptosis of IEC-6 cells are not known. In this study, we report that inhibition of Cdk1, 2, and 9 (with the broad range Cdk inhibitor, AZD5438) in proliferating IEC-6 cells triggered DNA damage, activated p53 signaling, inhibited proliferation, and induced apoptosis. By contrast, inhibition of Cdk2 (with NU6140) increased p53 protein and activity, inhibited proliferation, but had no effect on apoptosis. Notably, AZD5438 sensitized, whereas, NU6140 rescued proliferating IEC-6 cells from CPT-induced apoptosis. However, in colon carcinoma (Caco-2) cells with mutant p53, treatment with either AZD5438 or NU6140 blocked proliferation, albeit more robustly with AZD5438. Both Cdk inhibitors induced apoptosis in Caco-2 cells in a p53-independent manner. In serum starved quiescent IEC-6 cells, both AZD5438 and NU6140 decreased TNF-α/CPT-induced activation of p53 and, consequently, rescued cells from apoptosis, indicating that sustained Cdk activity is required for apoptosis of quiescent cells. Furthermore, AZD5438 partially reversed the protective effect of polyamine depletion whereas NU6140 had no effect. Together, these results demonstrate that Cdks possess opposing roles in the control of apoptosis in quiescent and proliferating cells. In addition, Cdk inhibitors uncouple proliferation from apoptosis in a p53-dependent manner.

CR8, a novel inhibitor of CDK, limits microglial activation, astrocytosis, neuronal loss, and neurologic dysfunction after experimental traumatic brain injury

Central nervous system injury causes a marked increase in the expression of cell cycle-related proteins. In this study, we show that cell cycle activation (CCA) is detected in mature neurons at 24 hours after rat lateral fluid percussion (LFP)-induced traumatic brain injury (TBI), as reflected by increased expression of cyclin G1, phosphorylated retinoblastoma (phospho-Rb), E2F1 and proliferating cell nuclear antigen (PCNA). These changes were associated with progressive cortical, hippocampal, and thalamic neuronal loss and microglial and astrocyte activation. Notably, we detected 5-bromo-2'-deoxyuridine (BrdU)-positive neurons, microglia, and astrocytes at 7 days, but not at 24 hours, suggesting that cell cycle reaches the S phase in these cell types at the latter time point. A delayed systemic post-LFP administration at 3 hours of CR8--a potent second-generation cyclin-dependent kinase (CDK) inhibitor--reduced CCA; cortical, hippocampal, and thalamic neuronal loss; and cortical microglial and astrocyte activation. Furthermore, CR8 treatment attenuated sensorimotor and cognitive deficits, alleviated depressive-like symptoms, and decreased lesion volume. These findings underscore the contribution of CCA to progressive neurodegeneration and chronic neuroinflammation following TBI, and demonstrate the neuroprotective potential of cell cycle inhibition in a clinically relevant experimental TBI model.

Supplement zinc as an effective treatment for spinal cord ischemia/reperfusion injury in rats

OBJECTIVE

Brain-derived neurotrophic factor (BDNF) plays a key role in the pathophysiology process and therapy of spinal cord injury (SCI). Accordingly, zinc regulates the expression of BDNF and its receptor in the central nervous system, the mechanism of which is still unknown. The present study investigates whether supplement zinc could reduce neurological damage in a rat model, with spinal cord ischemia-reperfusion (I/R) injury and how the effect of zinc transporter 1(ZnT-1) was involved.

METHODS

100 Sprague-Dawley male rats were randomly and evenly divided into four groups. They were subjected to spinal cord ischemia by clamping the abdominal aorta for 45 min. Rats in the zinc-deficient dietary model group (ZD), zinc-adequate dietary model group (ZA), and zinc-high dietary model group (ZH) were given free access to purified diet, containing 5, 30, or 180 mg Zn/kg. Sham operation rats were subjected to laparotomy without clamping of the aorta and were fed by ZA diet (30 mg Zn/kg). Neurological function was scored by Tarlov's score. The spinal cord segments (L5) were harvested for histological examination, auto-metallographic (AMG) analysis, myeloperoxidase (MPO) activity analysis, expression of ZnT-1 and BDNF.

RESULTS

The rats in the ZH group have shown the higher neurological scores, slighter histological changes and the attenuated MPO activity, compared with those in the ZD and ZA groups at the four observation time points (p<0.05). The AMG staining density in the ZH group was significantly higher than that of ZD group in 14 days later after the operation. Compared with other groups, ZH group's expression of Zn-T1 and BDNF were significantly increased, and was positively correlated with the same time points after surgery (Spearman rho=0.403, p=0.0152.)

CONCLUSION

These findings suggest that zinc supplement can significantly reduce the spinal cord I/R injury in rats. The mechanism may be related with restraining the MPO activity and increasing of ZnT-1, which promoted the synthesis and release of BDNF.

Propofol Limits Microglial Activation after Experimental Brain Trauma through Inhibition of Nicotinamide Adenine Dinucleotide Phosphate Oxidase

Background:

Microglial activation is implicated in delayed tissue damage after traumatic brain injury (TBI). Activation of microglia causes up-regulation of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, with the release of reactive oxygen species and cytotoxicity. Propofol appears to have antiinflammatory actions. The authors evaluated the neuroprotective effects of propofol after TBI and examined in vivo and in vitro whether such actions reflected modulation of NADPH oxidase.

Methods:

Adult male rats were subjected to moderate lateral fluid percussion TBI. Effect of propofol on brain microglial activation and functional recovery was assessed up to 28 days postinjury. By using primary microglial and BV2 cell cultures, the authors examined propofol modulation of lipopolysaccharide and interferon-γ–induced microglial reactivity and neurotoxicity.

Results:

Propofol improved cognitive recovery after TBI in novel object recognition test (48 ± 6% for propofol [n = 15] vs. 30 ± 4% for isoflurane [n = 14]; P = 0.005). The functional improvement with propofol was associated with limited microglial activation and decreased cortical lesion volume and neuronal loss. Propofol also attenuated lipopolysaccharide- and interferon-γ–induced microglial activation in vitro, with reduced expression of inducible nitric oxide synthase, nitric oxide, tumor necrosis factor-α, interlukin-1β, reactive oxygen species, and NADPH oxidase. Microglial-induced neurotoxicity in vitro was also markedly reduced by propofol. The protective effect of propofol was attenuated when the NADPH oxidase subunit p22phox was knocked down by small interfering RNA. Moreover, propofol reduced the expression of p22phox and gp91phox, two key components of NADPH oxidase, after TBI.

Conclusion:

The neuroprotective effects of propofol after TBI appear to be mediated, in part, through the inhibition of NADPH oxidase.

TrkB.T1 contributes to neuropathic pain after spinal cord injury through regulation of cell cycle pathways

Spinal cord injury (SCI) frequently causes severe, persistent central neuropathic pain that responds poorly to conventional pain treatments. Brain-derived neurotrophic factor (BDNF) signaling appears to contribute to central sensitization and nocifensive behaviors in certain animal models of chronic pain through effects mediated in part by the alternatively spliced truncated isoform of the BDNF receptor tropomyosin-related kinase B.T1 (trkB.T1). Mechanisms linking trkB.T1 to SCI-induced chronic central pain are unknown. Here, we examined the role of trkB.T1 in central neuropathic pain after spinal cord contusion. Genetic deletion of trkB.T1 in mice significantly reduced post-SCI mechanical hyperesthesia, locomotor dysfunction, lesion volumes, and white matter loss. Whole genome analysis, confirmed at the protein level, revealed that cell cycle genes were upregulated in trkB.T1(+/+) but not trkB.T1(-/-) spinal cord after SCI. TGFβ-induced reactive astrocytes from WT mice showed increased cell cycle protein expression that was significantly reduced in astrocytes from trkB.T1(-/-) mice that express neither full-length trkB nor trkB.T1. Administration of CR8, which selectively inhibits cyclin-dependent kinases, reduced hyperesthesia, locomotor deficits, and dorsal horn (SDH) glial changes after SCI, similar to trkB.T1 deletion, without altering trkB.T1 protein expression. In trkB.T1(-/-) mice, CR8 had no effect. These data indicate that trkB.T1 contributes to the pathobiology of SCI and SCI pain through modulation of cell cycle pathways and suggest new therapeutic targets.

Pharmacokinetics and biodistribution of the cyclin-dependent kinase inhibitor -CR8- in mice

BACKGROUND

CR8 is a second generation inhibitor of cyclin-dependent kinases derived from roscovitine. CR8 was shown to be 50-100 fold more potent than roscovitine in inducing apoptosis in different tumor cell lines. In the present investigation, we have established an analytical method for the quantification of CR8 in biological samples and evaluated its bioavailability, biodistribution and pharmacokinetics in mice.

METHODS

A liquid chromatography method utilizing UV-detection was used for the determination of CR8. CR8 was administered either orally (100 mg/kg) or i.v. (50 mg/kg) and the animals were sacrificed at different time points. Blood samples and organs were collected, after which the pharmacokinetic parameters were calculated for plasma and organs.

RESULTS

CR8 was eluted at 5 minutes in the high performance liquid chromatography system used. The LLOQ detection was 0.10 μg/ml and linearity was observed within the 0.10-10 μg/ml range (r² > 0.998). The accuracy and precision were >86%, while the recovery from plasma was >95%. CR8 was stable for 2 months at room temperature in both solution and plasma. CR8 pharmacokinetics was fitted to a two-compartment open model after oral administration and to a one compartment model after i.v. injection. The elimination half-life was about 3 hours. Organ exposure to CR8 (expressed as % AUC organ vs. AUC plasma) was highest in liver (205%), adipose tissue (188%) and kidney (150%) and low in bone marrow (30%) and brain (15%) as compared to plasma. The oral bioavailability of CR8 was found to be essentially 100%.

CONCLUSIONS

We have developed a rapid and simple method for the analysis of CR8. CR8 pharmacokinetics pattern showed 100% bioavailability, long half-life and limited distribution to brain and bone marrow, which may allow systemic exposure higher than the IC₅₀ reported for cell death in tumor cell lines. CR8 displays favorable pharmacological properties and is therefore a good candidate for future clinical studies.

Cell cycle activation contributes to increased neuronal activity in the posterior thalamic nucleus and associated chronic hyperesthesia after rat spinal cord contusion

Spinal cord injury (SCI) causes not only sensorimotor and cognitive deficits, but frequently also severe chronic pain that is difficult to treat (SCI pain). We previously showed that hyperesthesia, as well as spontaneous pain induced by electrolytic lesions in the rat spinothalamic tract, is associated with increased spontaneous and sensory-evoked activity in the posterior thalamic nucleus (PO). We have also demonstrated that rodent impact SCI increases cell cycle activation (CCA) in the injury region and that post-traumatic treatment with cyclin dependent kinase inhibitors reduces lesion volume and motor dysfunction. Here we examined whether CCA contributes to neuronal hyperexcitability of PO and hyperpathia after rat contusion SCI, as well as to microglial and astroglial activation (gliopathy) that has been implicated in delayed SCI pain. Trauma caused enhanced pain sensitivity, which developed weeks after injury and was correlated with increased PO neuronal activity. Increased CCA was found at the thoracic spinal lesion site, the lumbar dorsal horn, and the PO. Increased microglial activation and cysteine-cysteine chemokine ligand 21 expression was also observed in the PO after SCI. In vitro, neurons co-cultured with activated microglia showed up-regulation of cyclin D1 and cysteine-cysteine chemokine ligand 21 expression. In vivo, post-injury treatment with a selective cyclin dependent kinase inhibitor (CR8) significantly reduced cell cycle protein induction, microglial activation, and neuronal activity in the PO nucleus, as well as limiting chronic SCI-induced hyperpathia. These results suggest a mechanistic role for CCA in the development of SCI pain, through effects mediated in part by the PO nucleus. Moreover, cell cycle modulation may provide an effective therapeutic strategy to improve reduce both hyperpathia and motor dysfunction after SCI.