Astrocytic CCAAT/Enhancer-Binding Protein Delta Contributes to Glial Scar Formation and Impairs Functional Recovery After Spinal Cord Injury

Effects of latroeggtoxin-VI on dopamine and α-synuclein in PC12 cells and the implications for Parkinson's disease

BACKGROUND

Parkinson's disease (PD) is characterized by death of dopaminergic neurons leading to dopamine deficiency, excessive α-synuclein facilitating Lewy body formation, etc. Latroeggtoxin-VI (LETX-VI), a proteinaceous neurotoxin discovered from the eggs of spider L. tredecimguttatus, was previously found to promote the synthesis and release of PC12 cells, showing a great potential as a drug candidate for PD. However, the relevant mechanisms have not been understood completely. The present study explored the mechanism underlying the effects of LETX-VI on dopamine and α-synuclein of PC12 cells and the implications for PD.

RESULTS

After PC12 cells were treated with LETX-VI, the level of dopamine was significantly increased in a dose-dependent way within a certain range of concentrations. Further mechanism analysis showed that LETX-VI upregulated the expression of tyrosine hydroxylase (TH) and L-dopa decarboxylase to enhance the biosynthesis of dopamine, and downregulated that of monoamine oxidase B to reduce the degradation of dopamine. At the same time, LETX-VI promoted the transport and release of dopamine through modulating the abundance and/or posttranslational modification of vesicular monoamine transporter 2 (VMAT2) and dopamine transporter (DAT). While the level of dopamine was increased by LETX-VI treatment, α-synuclein content was reduced by the spider toxin. α-Synuclein overexpression significantly decreased the dopamine level and LETX-VI efficiently alleviated the inhibitory action of excessive α-synuclein on dopamine. In the MPTP-induced mouse model of PD, application of LETX-VI ameliorated parkinsonian behaviors of the mice, and reduced the magnitude of MPTP-induced α-synuclein upregulation and TH downregulation. In addition, LETX-VI displayed neuroprotective effects by inhibiting MPTP-induced decrease in the numbers of TH-positive and Nissl-stained neurons in mouse brain tissues.

CONCLUSIONS

All the results demonstrate that LETX-VI promotes the synthesis and release of dopamine in PC12 cells via multiple mechanisms including preventing abnormal α-synuclein accumulation, showing implications in the prevention and treatment of PD.

Inhibition of MMP8 effectively alleviates manic-like behavior and reduces neuroinflammation by modulating astrocytic CEBPD

There is an intrinsic relationship between psychiatric disorders and neuroinflammation, including bipolar disorder. Ouabain, an inhibitor of Na+/K+-ATPase, has been implicated in the mouse model with manic-like behavior. However, the molecular mechanisms linking neuroinflammation and manic-like behavior require further investigation. CCAAT/Enhancer-Binding Protein Delta (CEBPD) is an inflammatory transcription factor that contributes to neurological disease progression. In this study, we demonstrated that the expression of CEBPD in astrocytes was increased in ouabain-treated mice. Furthermore, we observed an increase in the expression and transcript levels of CEBPD in human primary astrocytes following ouabain treatment. Transcriptome analysis revealed high MMP8 expression in human primary astrocytes following CEBPD overexpression and ouabain treatment. We confirmed that MMP8 is a CEBPD-regulated gene that mediates ouabain-induced neuroinflammation. In our animal model, treatment of ouabain-injected mice with M8I (an inhibitor of MMP8) resulted in the inhibition of manic-like behavior compared to ouabain-injected mice that were not treated with M8I. Additionally, the reduction in the activation of astrocytes and microglia was observed, particularly in the hippocampal CA1 region. Excessive reactive oxygen species formation was observed in ouabain-injected mice, and treating these mice with M8I resulted in the reduction of oxidative stress, as indicated by nitrotyrosine staining. These findings suggest that MMP8 inhibitors may serve as therapeutic agents in mitigating manic symptoms in bipolar disorder.

Agomir-331 Suppresses Reactive Gliosis and Neuroinflammation after Traumatic Brain Injury

Traumatic brain injury usually triggers glial scar formation, neuroinflammation, and neurodegeneration. However, the molecular mechanisms underlying these pathological features are largely unknown. Using a mouse model of hippocampal stab injury (HSI), we observed that miR-331, a brain-enriched microRNA, was significantly downregulated in the early stage (0-7 days) of HSI. Intranasal administration of agomir-331, an upgraded product of miR-331 mimics, suppressed reactive gliosis and neuronal apoptosis and improved cognitive function in HSI mice. Finally, we identified IL-1β as a direct downstream target of miR-331, and agomir-331 treatment significantly reduced IL-1β levels in the hippocampus after acute injury. Our findings highlight, for the first time, agomir-331 as a pivotal neuroprotective agent for early rehabilitation of HSI.

Heterogeneity in quiescent Müller glia in the uninjured zebrafish retina drive differential responses following photoreceptor ablation

Introduction

Loss of neurons in the neural retina is a leading cause of vision loss. While humans do not possess the capacity for retinal regeneration, zebrafish can achieve this through activation of resident Müller glia. Remarkably, despite the presence of Müller glia in humans and other mammalian vertebrates, these cells lack an intrinsic ability to contribute to regeneration. Upon activation, zebrafish Müller glia can adopt a stem cell-like state, undergo proliferation and generate new neurons. However, the underlying molecular mechanisms of this activation subsequent retinal regeneration remains unclear.

Methods/Results

To address this, we performed single-cell RNA sequencing (scRNA-seq) and report remarkable heterogeneity in gene expression within quiescent Müller glia across distinct dorsal, central and ventral retina pools of such cells. Next, we utilized a genetically driven, chemically inducible nitroreductase approach to study Müller glia activation following selective ablation of three distinct photoreceptor subtypes: long wavelength sensitive cones, short wavelength sensitive cones, and rods. There, our data revealed that a region-specific bias in activation of Müller glia exists in the zebrafish retina, and this is independent of the distribution of the ablated cell type across retinal regions. Notably, gene ontology analysis revealed that injury-responsive dorsal and central Müller glia express genes related to dorsal/ventral pattern formation, growth factor activity, and regulation of developmental process. Through scRNA-seq analysis, we identify a shared genetic program underlying initial Müller glia activation and cell cycle entry, followed by differences that drive the fate of regenerating neurons. We observed an initial expression of AP-1 and injury-responsive transcription factors, followed by genes involved in Notch signaling, ribosome biogenesis and gliogenesis, and finally expression of cell cycle, chromatin remodeling and microtubule-associated genes.

Discussion

Taken together, our findings document the regional specificity of gene expression within quiescent Müller glia and demonstrate unique Müller glia activation and regeneration features following neural ablation. These findings will improve our understanding of the molecular pathways relevant to neural regeneration in the retina.

Astrocytic Cebpd Regulates Pentraxin 3 Expression to Promote Fibrotic Scar Formation After Spinal Cord Injury

Astroglial-fibrotic scars resulted from spinal cord injury affect motor and sensory function, leading to paralysis. In particular, the fibrotic scar is a main barrier that disrupts neuronal regeneration after spinal cord injury. However, the association between astrocytes and fibrotic scar formation is not yet understood. We have previously demonstrated that the transcriptional factor Cebpd contributes to astrogliosis, which promotes glial scar formation after spinal cord injury. Herein, we show that fibrotic scar formation was decreased in the epicenter region in Cebpd^-/- mice after contusive spinal cord injury and astrocytic Cebpd promoted fibroblast migration through secretion of Ptx3. Furthermore, the expression of Mmp3 was increased under recombinant protein Ptx3 treatment in fibroblasts by observing microarray data, resulting in fibroblast migration. In addition, regulation of Mmp3 occurs through the NFκB signaling pathway by using an irreversible inhibitor of IκBα phosphorylation in pretreated fibroblasts. Of note, we used the synthetic peptide RI37, which blocks fibroblast migration and decreases fibroblast Mmp3 expression in IL-1β-treated astrocyte conditioned media. Collectively, our data suggest that fibroblast migration can be affected by astrocytic Cebpd through the Ptx3/NFκB/Mmp3 axis pathway and that the RI37 peptide may act as a therapeutic medicine to inhibit fibrotic scar formation after spinal cord injury.

CCAAT/Enhancer-Binding Proteins in Fibrosis: Complex Roles Beyond Conventional Understanding

CCAAT/enhancer-binding proteins (C/EBPs) are a family of at least six identified transcription factors that contain a highly conserved basic leucine zipper domain and interact selectively with duplex DNA to regulate target gene expression. C/EBPs play important roles in various physiological processes, and their abnormal function can lead to various diseases. Recently, accumulating evidence has demonstrated that aberrant C/EBP expression or activity is closely associated with the onset and progression of fibrosis in several organs and tissues. During fibrosis, various C/EBPs can exert distinct functions in the same organ, while the same C/EBP can exert distinct functions in different organs. Modulating C/EBP expression or activity could regulate various molecular processes to alleviate fibrosis in multiple organs; therefore, novel C/EBPs-based therapeutic methods for treating fibrosis have attracted considerable attention. In this review, we will explore the features of C/EBPs and their critical functions in fibrosis in order to highlight new avenues for the development of novel therapies targeting C/EBPs.

Protein post-translational modifications after spinal cord injury

Deficits in intrinsic neuronal capacities in the spinal cord, a lack of growth support, and suppression of axonal outgrowth by inhibitory molecules mean that spinal cord injury almost always has devastating consequences. As such, one of the primary targets for the treatment of spinal cord injury is to develop strategies to antagonize extrinsic or intrinsic axonal growth-inhibitory factors or enhance the factors that support axonal growth. Among these factors, a series of individual protein level disorders have been identified during the generation of axons following spinal cord injury. Moreover, an increasing number of studies have indicated that post-translational modifications of these proteins have important implications for axonal growth. Some researchers have discovered a variety of post-translational modifications after spinal cord injury, such as tyrosination, acetylation, and phosphorylation. In this review, we reviewed the post-translational modifications for axonal growth, functional recovery, and neuropathic pain after spinal cord injury, a better understanding of which may elucidate the dynamic change of spinal cord injury-related molecules and facilitate the development of a new therapeutic strategy for spinal cord injury.

Expression and Functional Characterization of c-Fos Gene in Chinese Fire-Bellied Newt Cynops Orientalis

c-Fos is an immediate-early gene that modulates cellular responses to a wide variety of stimuli and also plays an important role in tissue regeneration. However, the sequence and functions of c-Fos are still poorly understood in newts. This study describes the molecular cloning and characterization of the c-Fos gene (Co-c-Fos) of the Chinese fire-bellied newt, Cynops orientalis. The full-length Co-c-Fos cDNA sequence consists of a 1290 bp coding sequence that encoded 429 amino acids. The alignment and phylogenetic analyses reveal that the amino acid sequence of Co-c-Fos shared a conserved basic leucine zipper domain, including a nuclear localization sequence and a leucine heptad repeat. The Co-c-Fos mRNA is widely expressed in various tissues and is highly and uniformly expressed along the newt limb. After limb amputation, the expression of Co-c-Fos mRNA was immediately upregulated, but rapidly declined. However, the significant upregulation of Co-c-Fos protein expression was sustained for 24 h, overlapping with the wound healing stage of C. orientalis limb regeneration. To investigate if Co-c-Fos participate in newt wound healing, a skin wound healing model is employed. The results show that the treatment of T-5224, a selective c-Fos inhibitor, could largely impair the healing process of newt’s skin wound, as well as the injury-induced matrix metalloproteinase-3 upregulation, which is fundamental to wound epithelium formation. These data suggest that Co-c-Fos might participate in wound healing by modulating the expression of its potential target gene matrix metalloproteinase-3. Our study provides important insights into mechanisms that are responsible for the initiation of newt limb regeneration.

CCAAT/Enhancer-binding protein delta mediates glioma stem-like cell enrichment and ATP-binding cassette transporter ABCA1 activation for temozolomide resistance in glioblastoma

Glioblastoma (GBM) is the most aggressive brain tumor and relapses after chemo- or radiotherapy in a short time. The anticancer drug temozolamide (TMZ) is commonly used for GBM treatment, but glioma stem-like cells (GSCs) often lead to drug resistance and therapeutic failure. To date, the mechanism of GSC formation in TMZ-treated GBM remains largely unknown. CCAAT/Enhancer-binding protein delta (CEBPD) is an inflammation-responsive transcription factor and is proposed to be oncogenic in the context of drug resistance, prompting us to clarify its role in TMZ-resistant GBM. In this study, we first found that the CEBPD protein levels in GBM patients were significantly increased and further contributed to TMZ resistance by promoting GSC formation. Accordingly, the protein levels of stemness transcription factors, namely, SRY-box transcription factor 2 (SOX2), octamer-binding transcription factor 4 (OCT4), NANOG, and ATP-binding cassette subfamily A member 1 (ABCA1), were increased in GSCs and TMZ-treated GBM cells. Increased binding of CEBPD to promoter regions was observed in GSCs, indicating the direct regulation of these GSC-related genes by CEBPD. In addition, an ABCA1 inhibitor increased the caspase 3/7 activity of TMZ-treated GSCs, suggesting that TMZ efflux is controlled by ABCA1 activity and that the expression levels of the ABCA1 gene are an indicator of the efficiency of TMZ treatment. Together, we revealed the mechanism of CEBPD-mediated GSC drug resistance and proposed ABCA1 inhibition as a potential strategy for the treatment of TMZ-resistant GBM.

Decoding the role of zebrafish neuroglia in CNS disease modeling

Neuroglia, including microglia and astrocytes, is a critical component of the central nervous system (CNS) that interacts with neurons to modulate brain activity, development, metabolism and signaling pathways. Thus, a better understanding of the role of neuroglia in the brain is critical. Complementing clinical and rodent data, the zebrafish (Danio rerio) is rapidly becoming an important model organism to probe the role of neuroglia in brain disorders. With high genetic and physiological similarity to humans and rodents, zebrafish possess some common (shared), as well as some specific molecular biomarkers and features of neuroglia development and functioning. Studying these common and zebrafish-specific aspects of neuroglia may generate important insights into key brain mechanisms, including neurodevelopmental, neurodegenerative, neuroregenerative and neurological processes. Here, we discuss the biology of neuroglia in humans, rodents and fish, its role in various CNS functions, and further directions of translational research into the role of neuroglia in CNS disorders using zebrafish models.

A novel model of acute closed ventral spinal cord injury and its pathological changes in rats

OBJECTIVE

To establish a spinal cord injury (SCI) model by ventral violence and explore its pathological changes.

METHODS

We first designed and made a shape-suitable impinger. SD rats were divided into 4 groups according to force momentum calculated by weight and height: Group A (350 g*28 cm), Group B (280 g*28 cm), Group C (210 g*28 cm), and Group D (sham, 0 g*0 cm). Then the anterior border of the rat's T11 centrum was hit by the by impinger via a free-falling method. Locomotor functional (Basso, Beattie and Bresnahan scale-BBB scale), GFAP expression and pathological changes, complications, and mortality were observed.

RESULTS

The BBB scale scores were significantly different among all groups. Contusion, hematoma, and subarachnoid hemorrhage appeared at 1-6 h after injury in group A and B. Edema was obvious and the inflammatory cell infiltrated at the time of 6-48 h. Cicatricial contracture and porosis formed at 3-4 weeks, while group C only showed sporadic punctate hemorrhage. GFAP expression changed by time and location dynamically compared with group D. Various complications appeared in the experimental groups. Intestinal obstruction was the main cause of death. The mortality was significantly different among the groups (P<0.05).

CONCLUSION

The acute ventral closing SCI model could be set up successfully by a shape-suitable impinger. The procedure was simple and repetitive. Neural function deficiency, pathological changes, and mortality were consistent with the injury controlled by coup momentum. Under the condition of this model, astrocytes went through an acute damage period and continued in the further hyperplasia stage.

Glial Scar-a Promising Target for Improving Outcomes After CNS Injury

After central nervous system (CNS) injury, a series of stress responses induce astrocytes activation. Reactive astrocytes, which are typically different from astrocytes in normal conditions in altered morphology and gene expression, combine with extracellular matrix (ECM) components to form a glial scar at the lesion site, which walls of the injured region from neighboring healthier tissue. However, as a physical and molecular barrier, glial scar can impede patients' functional recovery in the late period of CNS injury. Thus, inhibiting glial scar formation in the chronic stage after CNS injury may be a promising target to improve outcomes. Since the therapeutic strategies targeting on mediating glial scar formation are regarded as an important part on improving functional recovery after CNS injury, in this review, we focus on the regulating effects of related signaling pathways and other molecules on glial scar, and the process of glial scar formation and the roles that it plays during the acute and chronic stages are also expounded in this article. We hope to get a comprehensive understanding of glial scar during CNS injury based on current researches and to open new perspectives for the therapies to promote functional recovery after CNS injury.

CCAAT/enhancer-binding protein delta regulates the stemness of glioma stem-like cells through activating PDGFA expression upon inflammatory stimulation

Background

The small population of glioma stem-like cells (GSCs) contributes to tumor initiation, malignancy, and recurrence in glioblastoma. However, the maintenance of GSC properties in the tumor microenvironment remains unclear. In glioma, non-neoplastic cells create an inflammatory environment and subsequently mediate tumor progression and maintenance. Transcriptional factor CCAAT/enhancer-binding protein delta (CEBPD) is suggested to regulate various genes responsive to inflammatory cytokines, thus prompting us to investigate its role in regulating GSCs stemness after inflammatory stimulation.

Methods

Stemness properties were analyzed by using spheroid formation. Oncomine and TCGA bioinformatic databases were used to analyze gene expression. Western blotting, quantitative real-time polymerase chain reaction, luciferase reporter assay, and chromatin immunoprecipitation assay were used to analyze proteins and gene transcript levels. The glioma tissue microarrays were used for CEBPD and PDGFA expression by immunohistochemistry staining.

Results

We first found that IL-1β promotes glioma spheroid formation and is associated with elevated CEBPD expression. Using microarray analysis, platelet-derived growth factor subunit A (PDGFA) was confirmed as a CEBPD-regulated gene that mediates IL-1β-enhanced GSCs self-renewal. Further analysis of the genomic database and tissue array revealed that the expression levels between CEBPD and PDGFA were coincident in glioma patient samples.

Conclusion

This is the first report showing the activation of PDGFA expression by CEBPD through IL-1β treatment and a novel CEBPD function in maintaining the self-renewal feature of GSCs.

Electronic supplementary material

The online version of this article (10.1186/s12974-019-1535-z) contains supplementary material, which is available to authorized users.

Secukinumab attenuates reactive astrogliosis via IL-17RA/(C/EBPβ)/SIRT1 pathway in a rat model of germinal matrix hemorrhage

Aims

Reactive astrogliosis plays a critical role in neurological deficits after germinal matrix hemorrhage (GMH). It has been reported that interleukin‐17A and IL‐17A receptor IL‐17RA/(C/EBPβ)/SIRT1 signaling pathway enhances reactive astrogliosis after brain injuries. We evaluated the effects of secukinumab on reactive astrogliosis in a rat pup model of GMH.

Methods

A total of 146 Sprague Dawley P7 rat pups were used. GMH was induced by intraparenchymal injection of collagenase. Secukinumab was administered intranasally 1 hour post‐GMH. C/EBPβ CRISPR or SIRT1 antagonist EX527 was administrated intracerebroventricularly (icv) 48 hours and 1 hour before GMH induction, respectively. Neurobehavior, Western blot, histology, and immunohistochemistry were used to assess treatment regiments in the short term and long term.

Results

The endogenous IL‐17A, IL‐17RA, C/EBPβ, and GFAP and proliferation marker CyclinD1 were increased, while SIRT1 expression was decreased after GMH. Secukinumab treatment improved neurological deficits, reduced ventriculomegaly, and increased cortical thickness. Additionally, treatment increased SIRT1 expression and lowered proliferation proteins PCNA and CyclinD1 as well as GFAP expression. C/EBPβ CRISPR activation plasmid and EX527 reversed the antireactive astrogliosis effects of secukinumab.

Conclusion

Secukinumab attenuated reactive astrogliosis and reduced neurological deficits after GMH, partly by regulating IL‐17RA/(C/EBPβ)/SIRT1 pathways. Secukinumab may provide a promising therapeutic strategy for GMH patients.

Snx27 Deletion Promotes Recovery From Spinal Cord Injury by Neuroprotection and Reduces Macrophage/Microglia Proliferation

Sorting nexin 27 (SNX27) is an endosome-associated cargo adaptor that is involved in various pathologies and development of neurological diseases. However, the role of SNX27 in spinal cord injury (SCI) remains unclear. In this study, we found that SNX27 was up-regulated in injured mice spinal cords by western blot and immunofluorescence. A comparative analysis of Basso mouse scale (BMS), footprint test and corticospinal tract (CST) tracing in Snx27 ^+/+ and Snx27 ^+/- mice revealed that haploinsufficiency of SNX27 ameliorated the clinical symptoms of SCI. Based on the results of western blot and immunofluorescence, mechanistically, we found that SNX27 deficiency suppresses apoptotic caspase-3 induced neuronal death. In addition, SNX27 haploinsufficiency lowers the infiltration and activation of macrophage/microglia by suppressing their proliferation at the SCI lesion site. Together, these results suggest that down-regulation of SNX27 is a potential therapy targeting both acute neuronal death and chronic neuroinflammation, and promoting nerve repair after SCI.

Astrocytic CCAAT/Enhancer-binding protein delta contributes to reactive oxygen species formation in neuroinflammation

Excessive reactive oxygen species (ROS) can form an oxidative stress and an associated neuroinflammation. However, the contribution of astrocytes to ROS formation, the cause of the resistance of astrocytes to oxidative stress, and the consequences on neurons remain largely uninvestigated. The transcription factor CCAAT/enhancer-binding protein delta (CEBPD) is highly expressed in astrocytes and has been suggested to contribute to the progress of Alzheimer's disease (AD). In this study, we found that ROS formation and expression of p47^phox and p67^phox, subunits of NADPH oxidase, were increased in AppTg mice but attenuated in AppTg/Cebpd^-/- mice. Cebpd can up-regulate p47^phox and p67^phox transcription via a direct binding on their promoters, which results in an increase in intracellular oxidative stress. In addition, Cebpd also up-regulated Cu/Zn superoxide dismutase (Sod1) in astrocytes. Inactivation of Sod1 increased the sensitization to oxidative stress, which provides a reason for the resistance of astrocytes in an oxidative stress environment. Taken together, the study first revealed and dissected the involvement of astrocytic Cebpd in the promotion of oxidative stress and the contribution of CEBPD to the resistance of astrocytes in an oxidative stress environment.

Transcriptome Analysis Reveals Neuroprotective aspects of Human Reactive Astrocytes induced by Interleukin 1β

Reactive astrogliosis is a critical process in neuropathological conditions and neurotrauma. Although it has been suggested that it confers neuroprotective effects, the exact genomic mechanism has not been explored. The prevailing dogma of the role of astrogliosis in inhibition of axonal regeneration has been challenged by recent findings in rodent model’s spinal cord injury, demonstrating its neuroprotection and axonal regeneration properties. We examined whether their neuroprotective and axonal regeneration potentials can be identify in human spinal cord reactive astrocytes in vitro. Here, reactive astrogliosis was induced with IL1β. Within 24 hours of IL1β induction, astrocytes acquired reactive characteristics. Transcriptome analysis of over 40000 transcripts of genes and analysis with PFSnet subnetwork revealed upregulation of chemokines and axonal permissive factors including FGF2, BDNF, and NGF. In addition, most genes regulating axonal inhibitory molecules, including ROBO1 and ROBO2 were downregulated. There was no increase in the gene expression of “Chondroitin Sulfate Proteoglycans” (CSPGs’) clusters. This suggests that reactive astrocytes may not be the main CSPG contributory factor in glial scar. PFSnet analysis also indicated an upregulation of “Axonal Guidance Signaling” pathway. Our result suggests that human spinal cord reactive astrocytes is potentially neuroprotective at an early onset of reactive astrogliosis.