Mst-1 deficiency promotes post-traumatic spinal motor neuron survival via enhancement of autophagy flux

The compensatory increase of Gli-similar 3 inhibited neuronal apoptosis through regulating Mps one binder kinase activator 1b (MOB1b): a possible strategy for the functional recovery after spinal cord injury

Spinal cord injury (SCI) is a devastating disease characterized by neuronal apoptosis. Gli-similar 3 (GLIS3), a transcriptional factor, was involved in cell apoptosis and associated with the transcription of downstream target genes related to neuronal function. However, the function of GLIS3 in SCI remains unknown. Therefore, we used the mouse model of SCI to explore the role of GLIS3 in SCI. The results showed that GLIS3 expression was significantly increased in spinal cord tissues of SCI mice, and GLIS3 overexpression promoted the functional recovery, reserved histological changes, and inhibited neuronal apoptosis after SCI. Through online tools, the potential target genes of GLIS3 were analyzed and we found that Mps one binder kinase activator 1b (Mob1b) had a strong association with SCI among these genes. MOB1b is a core component of Hippo signaling pathway, which was reported to inhibit cell apoptosis. MOB1b expression was significantly increased in mice at 7 days post-SCI and GLIS3 overexpression further increased its expression. Dual-luciferase reporter assay revealed that GLIS3 bound to the promoter of Mob1b and promoted its transcription. In conclusion, our findings reveal that the compensatory increase of GLIS3 promotes functional recovery after SCI through inhibiting neuronal apoptosis by transcriptionally regulating MOB1b. Our study provides a novel target for functional recovery after SCI.

Molecular mechanisms involved in regulating protein activity and biological function of MST3

Mammalian sterile 20-like (Ste20-like) protein kinase 3 (MST3) or serine/threonine-protein kinase 24 (STK24) is a serine/threonine protein kinase that belongs to the mammalian STE20-like protein kinase family. MST3 is a pleiotropic protein that plays a critical role in regulating a variety of events, including apoptosis, immune response, metabolism, hypertension, tumor progression, and development of the central nervous system. The MST3-mediated regulation is intricately related to protein activity, post-translational modification, and subcellular location. Here, we review the recent progress on the regulatory mechanisms against MST3 and its-mediated control of disease progression.

Low-frequency transcranial magnetic stimulation protects cognition in mice with chronic unpredictable mild stress through autophagy regulation

Although transcranial magnetic stimulation (TMS) has been approved for the treatment of major depression, few studies have analyzed the ability of low-frequency TMS (LF-TMS) to treat depressive symptoms. Our study confirmed that LF-TMS protects the cognitive function,which can play a certain reference role in the future clinical treatment. The effectiveness of high-frequency TMS therapy has been well documented. However, the use of low-frequency TMS (LF-TMS) in the treatment of depression is rarely reported. This study aims to evaluate whether LF-TMS can reverse depression-induced cognitive impairment. We created a mouse model of depression using the chronic unpredictable mild stress (CUMS) paradigm. Male C57BL/6J mice,6-8 weeks old,were randomly divided into four groups: a CON (control) group, a CUMS group, a CUMS+LF-TMS group, and a CUMS+LF-TMS+RAP (rapamycin) group. The CUMS was maintained for 28 days. LF-TMS (1 Hz) and Rap were administered for 28 days from the first day of CUMS. The mice in all groups except the control demonstrated evidence of anhedonia, anxiety, and cognitive decline on behavioral tests during the four weeks of CUMS.All the experiments were carried out under a 12-h light/dark cycle (lights on at 7 a.m.) except for the dark/light cycle reversal stimulation of CUMS. LF-TMS at 20 Mt, 1 Hz for 1 min alleviated damage to spatial cognition and synaptic plasticity in the hippocampus. Western blot analysis showed that LF-TMS reduced the down-regulation of autophagy signals in the CUMS+LF-TMS group, and enhanced the expression of synaptic plasticity-related factors, thereby improving the spatial cognitive impairment resulting from the CUMS. We concluded that LF-TMS can effectively relieve depressive behavior and cognitive dysfunction in mice subjected to CUMS by regulating autophagy signals and synaptic proteins.

The Proteostasis Network: A Global Therapeutic Target for Neuroprotection after Spinal Cord Injury

Proteostasis (protein homeostasis) is critical for cellular as well as organismal survival. It is strictly regulated by multiple conserved pathways including the ubiquitin-proteasome system, autophagy, the heat shock response, the integrated stress response, and the unfolded protein response. These overlapping proteostasis maintenance modules respond to various forms of cellular stress as well as organismal injury. While proteostasis restoration and ultimately organism survival is the main evolutionary driver of such a regulation, unresolved disruption of proteostasis may engage pro-apoptotic mediators of those pathways to eliminate defective cells. In this review, we discuss proteostasis contributions to the pathogenesis of traumatic spinal cord injury (SCI). Most published reports focused on the role of proteostasis networks in acute/sub-acute tissue damage post-SCI. Those reports reveal a complex picture with cell type- and/or proteostasis mediator-specific effects on loss of neurons and/or glia that often translate into the corresponding modulation of functional recovery. Effects of proteostasis networks on such phenomena as neuro-repair, post-injury plasticity, as well as systemic manifestations of SCI including dysregulation of the immune system, metabolism or cardiovascular function are currently understudied. However, as potential interventions that target the proteostasis networks are expected to impact many cell types across multiple organ systems that are compromised after SCI, such therapies could produce beneficial effects across the wide spectrum of highly variable human SCI.

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

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

TAZ Induces Migration of Microglia and Promotes Neurological Recovery After Spinal Cord Injury

Following spinal cord injury (SCI), microglia gradually migrate to the edge of the lesion, interweaving around the border of the lesion to form the microglial scar, which performs inflammatory limiting and neuroprotective functions. Recent reports showed that Yes-associated protein (YAP) was expressed in astrocytes and promoted the formation of astrocytic scars, while YAP was not expressed in microglia after SCI. YAP and its paralogue transcriptional coactivator with PDZ-binding motif (TAZ) are transcriptional coactivators, which have a similar functional role as both are negatively regulated by the Hippo signalling pathway. However, the expression and function of TAZ after SCI are unclear. Our research group previously found that Fascin-1 was highly expressed in microglia and promoted migration of microglia after SCI, and that, there was a close regulatory relationship between Fascin-1 and YAP/TAZ. In this study, we demonstrated that TAZ was significantly upregulated and mainly expressed in microglia after SCI, and accumulated in the nuclei of microglia in the spinal cord at 14 days post-SCI. Moreover, TAZ was upregulated and accumulated in the nuclei of anti-inflammatory M2-like (M2-L) polarized or myelin-treated microglia. Additionally, XMU-MP-1 (an inhibitor of the Hippo kinase MST1/2 to active TAZ) promoted the aggregation of microglia around the lesion core, resulting in the formation of microglial scars and the functional recovery of mice after SCI. Our findings also indicated that TAZ promoted microglial migration in vitro. Mechanistically, Fascin-1 interacted with TAZ, which upregulated TAZ expression and induced TAZ nuclear accumulation in microglia to promote microglial migration. These findings revealed that TAZ mediated microglial migration to the edge of the lesion core, promoting the formation of microglial scars and functional recovery after SCI. Moreover, TAZ was downstream of Fascin-1, which positively regulated microglial migration after SCI.

MST1 mediates the N-methyl-D-aspartate-induced excitotoxicity in mouse cortical neurons

Excessive activation of the ionotropic N-methyl-D-aspartate (NMDA) receptor has been shown to cause abnormally high levels of Ca2+ influx, thereby leading to excitotoxic neuronal death. In this study, exposure of mouse primary cortical neurons to NMDA resulted in the cleavage and activation of mammalian sterile 20-like kinase-1 (MST1), both of which were mediated by calpain 1. In vitro cleavage assay data indicated that calpain 1 cleaves out the autoinhibitory domain of MST1 to generate an active form of the kinase. Furthermore, calpain 1 mediated the cleavage and activation of wild-type MST1, but not of MST1 (G339A). Intriguingly, NMDA/calpain-induced MST1 activation promoted the nuclear translocation of the kinase and the phosphorylation of histone H2B in mouse cortical neurons, leading to excitotoxicity. Thus, we propose a previously unrecognized mechanism of MST1 activation associated with NMDA-induced excitotoxic neuronal death.

Valproic Acid Ameliorates Locomotor Function in the Rat Model of Contusion via Alteration of Mst1, Bcl-2, and Nrf2 Gene Expression

Background:

In animal models of inflammatory diseases, Mst1 facilitates the programmed cell death as a novel pro-apoptotic kinase. This research aimed to determine the expression level of Mst1 gene in a rat model of SCI treated with VPA.

Methods:

Severe rat model contusion was used for evaluation of the neuroprotective effect of valproic acid. The BBB test, was performed to determine locomotor functions. H&E staining and TUNEL assay were performed to detect cavity formation and apoptosis, respectively. The mRNA levels of the genes Mst1, Nrf2, and Bcl-2 were evaluated, using quantitative RT-PCR.

Results:

The results revealed that Mst1 gene expression and TUNEL-positive cells in the VPA-treated group were significantly reduced as compared to the untreated group (p ≤ 0.05).

Conclusion:

Our findings indicate that VPA has therapeutic potential and can be a candidate for the treatment of neurodegenerative disorders and traumatic injury as a promising drug.

MicroRNA-139-5p Promotes Functional Recovery and Reduces Pain Hypersensitivity in Mice with Spinal Cord Injury by Targeting Mammalian Sterile 20-like Kinase 1

Currently, there is no cure for spinal cord injury (SCI), a heavy burden on patients physiology and psychology. We found that microRNA-139-5p (miR-139-5p) expression was significantly downregulated in damaged spinal cords in mice. So, we aimed to test the effect of treatment with miR-139-5p on functional recovery and neuropathic pain in mice with SCI and investigate the underlying mechanism. The luciferase reporter assay revealed that miR-139-5p directly targeted mammalian sterile 20-like kinase 1 (Mst1), and miR-139-5p treatment suppressed Mst1 protein expression in damaged spinal cords of mice. Wild-type mice and Mst1(-/-) mice were exposed to SCI and treated with miR-139-5p agomir via intrathecal infusion. Treatment of SCI mice with miR-139-5p accelerated locomotor functional recovery, reduced hypersensitivities to mechanical and thermal stimulations, and promoted neuronal survival in damaged spinal cords. Treatment with miR-139-5p enhanced phosphorylation of adenosine monophosphate-activated protein kinase alpha (AMPKα), improved mitochondrial function, and suppressed NF-κB-related inflammation in damaged spinal cords. Deficiency of Mst1 had similar benefits in mice with SCI. Furthermore, miR-139-5p treatment did not provide further protection in Mst1(-/-) mice against SCI. In conclusion, miR-139-5p treatment enhanced functional recovery and reduced pain hypersensitivity in mice with SCI, possibly through targeting Mst1.

Local uncoordinated gene 5H2 contributes to nerve injury-induced mechanical allodynia associated to its role in autophagy

Lesions of the peripheral nerves can lead to lifelong neuropathic pain (NP). Autophagic deficiency in the Schwann cells (SCs) is an early event in the origin of NP chronification. Uncoordinated gene 5H2 (UNC5H2), one of the repulsive netrin receptors, mediated the effect of netrin-1 on autophagic activation and cell survival in endothelial cells. However, its role on autophagy regulation in peripheral nerves during NP process remains unidentified. Chronic constriction injury (CCI) of the left sciatic nerve was induced in Sprague-Dawley rats, and UNC5H2 small interfering RNA was transfected to the ipsilateral sciatic nerve immediately after injury. Mechanical allodynia was assessed. Sciatic UNC5H2 and netrin-1 protein levels were investigated. Autophagy in the ipsilateral sciatic nerves was evaluated by detecting punctate light chain 3(LC3) and autophagosomes, as well as the levels of LC3 II, p62 and phosphorylated UNC51-like kinase (ULK1). After CCI, UNC5H2 of the sciatic nerves was upregulated, exclusively expressed in SCs. Small interfering RNA transfection resulted in significant decrease of UNC5H2 and netrin-1 protein, leading to exaggeration of mechanical allodynia through 14 days after CCI. Autophagy was activated but autophagic influx was interfered within a week after CCI, shown by the elevated levels of both LC3II and p62, which was further deteriorated with UNC5H2 knockdown. In addition, the injury-induced augmentation of phosphorylated ULK1 was significantly diminished by UNC5H2 knockdown. Altogether, the results suggest that local UNC5H2 of the peripheral nerve plays a significant role in the process of injury-induced mechanical allodynia, probably associated to its contribution to autophagic regulation.

Emerging role of the Hippo pathway in autophagy

Autophagy is a dynamic circulatory system that occurs in all eukaryotic cells. Cytoplasmic material is transported to lysosomes for degradation and recovery through autophagy. This provides energy and macromolecular precursors for cell renewal and homeostasis. The Hippo-YAP pathway has significant biological properties in controlling organ size, tissue homeostasis, and regeneration. Recently, the Hippo-YAP axis has been extensively referred to as the pathophysiological processes regulating autophagy. Understanding the cellular and molecular basis of these processes is crucial for identifying disease pathogenesis and novel therapeutic targets. Here we review recent findings from Drosophila models to organisms. We particularly emphasize the regulation between Hippo core components and autophagy, which is involved in normal cellular regulation and the pathogenesis of human diseases, and its application to disease treatment.

STK4 Deficiency Impairs Innate Immunity and Interferon Production Through Negative Regulation of TBK1-IRF3 Signaling

BACKGROUND

STK4 deficiency due to homozygous mutations in the STK4 gene encoding the STK4/MST1 kinase was first described in 2012. STK4/MST1 kinase regulates cell proliferation, survival, differentiation, and immune responses through canonical and non-canonical Hippo signaling pathways.

OBJECTIVE

We describe an 11-year-old girl with a clinical presentation consisting of severe recurrent herpes zoster, chronic warts, and recurrent pneumonias, as well as a somatic phenotype with hypothyroidism and low stature. Whole exome sequencing revealed STK4 deficiency due to homozygosity for a novel frameshift variant in STK4, c.523dupA, p.(L174fsTer45), resulting in a premature stop codon within the kinase domain.

METHODS

We performed a thorough investigation of the genetics and innate and adaptive immunological abnormalities in STK4 deficiency.

RESULTS

We show significantly impaired type I, II, and III interferon (IFN) responses and partly reduced proinflammatory cytokine responses to ligands of Toll-like receptor (TLR)3, TLR9, and the cytosolic RNA and DNA sensors as well as to microorganisms. Impaired IFN responses could be attributed to reduced phosphorylation of TBK1 and IRF3. Moreover, virus infection induced enhanced cell death by apoptosis. Importantly, autophagy pathways were slightly disturbed, with enhanced LC3B-Ito LCB3-II conversion at the single cell level but normal overall formation of LCB3 punctae. Finally, the patient displayed some indicators of impaired adaptive immunity in the form of insufficient vaccination responses, T cell lymphopenia, and reduced Treg fractions, although with largely normal T cell proliferation and normal IFNg production.

CONCLUSION

Here, we demonstrate disturbances in various immune cell populations and pathways involved in innate immune responses, cell death, autophagy, and adaptive immunity in a patient homozygous for a novel STK4 frameshift mutation.

Astrocytic YAP Promotes the Formation of Glia Scars and Neural Regeneration after Spinal Cord Injury

Yes-associated protein (YAP) transcriptional coactivator is negatively regulated by the Hippo pathway and functions in controlling the size of multiple organs, such as liver during development. However, it is not clear whether YAP signaling participates in the process of the formation of glia scars after spinal cord injury (SCI). In this study, we found that YAP was upregulated and activated in astrocytes of C57BL/6 male mice after SCI in a Hippo pathway-dependent manner. Conditional knockout (KO) of yap in astrocytes significantly inhibited astrocytic proliferation, impaired the formation of glial scars, inhibited the axonal regeneration, and impaired the behavioral recovery of C57BL/6 male mice after SCI. Mechanistically, the bFGF was upregulated after SCI and induced the activation of YAP through RhoA pathways, thereby promoting the formation of glial scars. Additionally, YAP promoted bFGF-induced proliferation by negatively controlling nuclear distribution of p27^Kip1 mediated by CRM1. Finally, bFGF or XMU-MP-1 (an inhibitor of Hippo kinase MST1/2 to activate YAP) injection indeed activated YAP signaling and promoted the formation of glial scars and the functional recovery of mice after SCI. These findings suggest that YAP promotes the formation of glial scars and neural regeneration of mice after SCI, and that the bFGF-RhoA-YAP-p27^Kip1 pathway positively regulates astrocytic proliferation after SCI.SIGNIFICANCE STATEMENT Glial scars play critical roles in neuronal regeneration of CNS injury diseases, such as spinal cord injury (SCI). Here, we provide evidence for the function of Yes-associated protein (YAP) in the formation of glial scars after SCI through regulation of astrocyte proliferation. As a downstream of bFGF (which is upregulated after SCI), YAP promotes the proliferation of astrocytes through negatively controlling nuclear distribution of p27^Kip1 mediated by CRM1. Activation of YAP by bFGF or XMU-MP-1 injection promotes the formation of glial scar and the functional recovery of mice after SCI. These results suggest that the bFGF-RhoA-YAP-p27^Kip1 axis for the formation of glial scars may be a potential therapeutic strategy for SCI patients.

High-Frequency Repetitive Transcranial Magnetic Stimulation Mediates Autophagy Flux in Human Bone Mesenchymal Stromal Cells via NMDA Receptor-Ca2+-Extracellular Signal-Regulated Kinase-Mammalian Target of Rapamycin Signaling

Aim

Repetitive transcranial magnetic stimulation (rTMS) is a non-invasive and safe technique for treatment of central and peripheral nerve injury. In recent years, this technique has been widely used in clinic, and an increasing number of studies have reported its mechanisms. In this study, we investigated the mechanisms of rTMS-mediated autophagy flux in human bone mesenchymal stromal cells (BMSCs).

Methods

A frequency of 50 Hz was employed. Cells were divided into five groups: (1) normal, (2) sham, (3) 0.5 T, (4) 1.0 T, and (5) 1.5 T. Cells were stimulated for 20 min/day. The levels of p62, LC3-II/I, phosphorylated extracellular signal-regulated kinase (p-ERK), ERK, phosphorylated-AKT (p-AKT), AKT, phosphorylated mammalian target of rapamycin (p-mTOR), mTOR, phosphorylated protein kinase A (p-PKA), PKA, phosphorylated epidermal growth factor receptor (p-EGFR), EGFR, Nanog, Oct4, Sox2, and NMDA receptor (NMDAR1) were investigated by western blotting. Intracellular calcium (Ca²⁺) levels were quantified by flow cytometry. p62 and LC3 expression was also assessed by immunofluorescence analysis.

Results

In the 0.5 T group, rTMS increased the expression of LC3-II/I, p-ERK/ERK, and NMDAR1 and decreased the levels of p62 and p-mTOR/mTOR than in the normal group. The ratio of p-AKT/AKT, p-PKA/PKA, and p-EGFR/EGFR and the expression of Nanog, Oct4, and Sox2 remained unchanged. Immunofluorescence analysis revealed colocalization of p62 with LC3 puncta, and flow cytometry analysis displayed that Ca²⁺ levels were elevated. However, in the 1.0 and 1.5 T groups, no changes in the expression of these autophagy markers were observed.

Conclusion

In the 0.5 T group, high-frequency rTMS can induce autophagy through NMDAR–Ca²⁺–ERK–mTOR signaling in BMSCs. In the 1.0 and 1.5 T groups, autophagy is not activated.

The emerging role of Hippo signaling in neurodegeneration

Neurodegeneration refers to the complex process of progressive degeneration or neuronal apoptosis leading to a set of incurable and debilitating conditions. Physiologically, apoptosis is important in proper growth and development. However, aberrant and unrestricted apoptosis can lead to a variety of degenerative conditions including neurodegenerative diseases. Although dysregulated apoptosis has been implicated in various neurodegenerative disorders, the triggers and molecular mechanisms underlying such untimely and faulty apoptosis are still unknown. Hippo signaling pathway is one such apoptosis-regulating mechanism that has remained evolutionarily conserved from Drosophila to mammals. This pathway has gained a lot of attention for its tumor-suppressing task, but recent studies have emphasized the soaring role of this pathway in inflaming neurodegeneration. In addition, strategies promoting inactivation of this pathway have aided in the rescue of neurons from anomalous apoptosis. So, a thorough understanding of the relationship between the Hippo pathway and neurodegeneration may serve as a guide for the development of therapy for various degenerative diseases. The current review focuses on the mechanism of the Hippo signaling pathway, its upstream and downstream regulatory molecules, and its role in the genesis of numerous neurodegenerative diseases. The recent efforts employing the Hippo pathway components as targets for checking neurodegeneration have also been highlighted.

Dysregulation of the Hippo pathway signaling in aging and cancer

Human beings are facing emerging degenerative and cancer diseases, in large part, as a consequence of increased life expectancy. In the near future, researchers will have to put even more effort into fighting these new challenges, one of which will be prevention of cancer while continuing to improve the aging process through this increased life expectancy. In the last few decades, relevance of the Hippo pathway on cancer has become an important study since it is a major regulator of organ size control and proliferation. However, its deregulation can induce tumors throughout the body by regulating cell proliferation, disrupting cell polarity, releasing YAP and TAZ from the Scribble complexes and facilitating survival gene expression via activation of TEAD transcription factors. This pathway is also involved in some of the most important mechanisms that control the aging processes, such as the AMP-activated protein kinase and sirtuin pathways, along with autophagy and oxidative stress response/antioxidant defense. This could be the link between two tightly connected processes that could open a broader range of targeted molecular therapies to fight aging and cancer. Therefore, available knowledge of the processes involved in the Hippo pathway during aging and cancer must necessarily be well understood.

Loss-of-function mutation in Hippo suppressed enlargement of lysosomes and neurodegeneration caused by dFIG4 knockdown

Charcot–Marie–Tooth disease (CMT) is the most common hereditary neuropathy, and more than 80 CMT-causing genes have been identified to date. CMT4J is caused by a loss-of-function mutation in the Factor-Induced-Gene 4 (FIG4) gene, the product of which plays important roles in endosome–lysosome homeostasis. We hypothesized that Mammalian sterile 20-like kinase (MST) 1 and 2, tumor-suppressor genes, are candidate modifiers of CMT4J. We therefore examined the interaction between dFIG4 and Hippo (hpo), Drosophila counterparts of FIG4 and MSTs, respectively, using the Drosophila CMT4J model with the knockdown of dFIG4. The loss-of-function allele of hpo improved the rough eye morphology, locomotive dysfunction accompanied by structural defects in the presynaptic terminals of motoneurons, and the enlargement of lysosomes caused by the knockdown of dFIG4. Therefore, we identified hpo as a modifier of phenotypes induced by the knockdown of dFIG4. These results in Drosophila may provide an insight into the pathogenesis of CMT4J and contribute toward the development of disease-modifying therapy for CMT. We also identified the regulation of endosome–lysosome homeostasis as a novel probable function of Hippo/MST.

EPPS treatment attenuates traumatic brain injury in mice by reducing Aβ burden and ameliorating neuronal autophagic flux

Beta-amyloid (Aβ) burden and impaired neuronal autophagy contribute to secondary brain injury after traumatic brain injury (TBI). 4-(2-hydroxyethyl)-1-piperazinepropanesulphonic acid (EPPS) treatment has been reported to reduce Aβ aggregation and rescue behavioral deficits in Alzheimer's disease-like mice. Here, we investigated neuroprotective effects of EPPS in a mouse model of TBI. Mice subjected to controlled cortical impact (CCI) were treated with EPPS (120 mg/kg, orally) immediately after CCI and thereafter once daily for 3 or 7 days. We found that EPPS treatment profoundly reduced the accumulation of beta-amyloid precursor protein (β-APP) and Aβ over a widespread area detected in the pericontusional cortex, external capsule (EC), and hippocampal CA1 and CA3 at 3 days after TBI, accompanied by significant reduction in the TBI-induced diffuse axonal injury identified by increased immunoreactivity of SMI-32 (an indicator for axonal damage). We also found that EPPS treatment ameliorated the TBI-induced synaptic damage (as reflected by enhanced postsynaptic density 95, PSD-95), and impairment of autophagy flux in the neurons as reflected by reduced autophagy markers (LC3-II/LC3-I ratio and p62/SQSTM1) and increased lysosomal enzyme cathepsin D (CTSD) in neurons detected in the cortex and hippocampal CA1. As a result, EPPS treatment significantly reduced the TBI-induced early neuronal apoptosis (assessed by active caspase-3), and eventually prevented cortical tissue loss and hippocampal neuronal loss at 28 days after TBI. Additionally, we found that inhibition of autophagic flux with chloroquine by decreasing autophagosome-lysosome fusion significantly reversed the decreased expressions of neuronal p62/SQSTM1 and apoptosis by EPPS treatment. These data suggest that the neuroprotection by EPPS is, at least in part, related to improved autophagy flux. Finally, we found that EPPS treatment significantly improved the cortex-dependent motor and hippocampal-dependent cognitive deficits associated with TBI. Taken together, these findings support the further investigation of EPPS as a treatment for TBI.

Cell Specific Changes of Autophagy in a Mouse Model of Contusive Spinal Cord Injury

Autophagy is an essential process of cellular waist clearance that becomes altered following spinal cord injury (SCI). Details on these changes, including timing after injury, underlying mechanisms, and affected cells, remain controversial. Here we present a characterization of autophagy in the mice spinal cord before and after a contusive SCI. In the undamaged spinal cord, analysis of LC3 and Beclin 1 autophagic markers reveals important differences in basal autophagy between neurons, oligodendrocytes, and astrocytes and even within cell populations. Following moderate contusion, western blot analyses of LC3 indicates that autophagy increases to a maximum at 7 days post injury (dpi), whereas unaltered Beclin 1 expression and increase of p62 suggests a possible blockage of autophagosome clearance. Immunofluorescence analyses of LC3 and Beclin 1 provide additional details that reveal a complex, cell-specific scenario. Autophagy is first activated (1 dpi) in the severed axons, followed by a later (7 dpi) accumulation of phagophores and/or autophagosomes in the neuronal soma without signs of increased initiation. Oligodendrocytes and reactive astrocytes also accumulate phagophores and autophagosomes at 7 dpi, but whereas the accumulation in astrocytes is associated with an increased autophagy initiation, it seems to result from a blockage of the autophagic flux in oligodendrocytes. Comparison with previous studies highlights the complex and heterogeneous autophagic responses induced by the SCI, leading in many cases to contradictory results and interpretations. Future studies should consider this complexity in the design of therapeutic interventions based on the modulation of autophagy to treat SCI.

The role of S-nitrosylation of kainate-type of ionotropic glutamate receptor 2 in epilepsy induced by kainic acid

Epilepsy is a chronic brain disease affecting millions of individuals. Kainate receptors, especially kainate-type of ionotropic glutamate receptor 2 (GluK2), play an important role in epileptogenesis. Recent data showed that GluK2 could undergo post-translational modifications in terms of S-nitrosylation (SNO), and affect the signaling pathway of cell death in cerebral ischemia-reperfusion. However, it is unclear whether S-nitrosylation of GluK2 (SNO-GluK2) contributes to cell death induced by epilepsy. Here, we report that kainic acid-induced SNO-GluK2 is mediated by GluK2 itself, regulated by neuronal nitric oxide synthase (nNOS) and the level of cytoplasmic calcium in vivo and in vitro hippocampus neurons. The whole-cell patch clamp recordings showed the influence of SNO-GluK2 on ion channel characterization of GluK2-Kainate receptors. Moreover, immunohistochemistry staining results showed that inhibition of SNO-GluK2 by blocking nNOS or GluK2 or by reducing the level of cytoplasmic calcium-protected hippocampal neurons from kainic acid-induced injury. Finally, immunoprecipitation and western blotting data revealed the involvement of assembly of a GluK2-PSD95-nNOS signaling complex in epilepsy. Taken together, our results showed that the SNO-GluK2 plays an important role in neuronal injury of epileptic rats by forming GluK2-PSD95-nNOS signaling module in a cytoplasmic calcium-dependent way, suggesting a potential therapeutic target site for epilepsy.

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

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

ΔN-Bcl-xL, a therapeutic target for neuroprotection

The B-cell lymphoma-extra large (Bcl-xL) is a mitochondrial anti-apoptotic protein that plays a role in neuroprotection. However, during excitotoxic stimulation, Bcl-xL undergoes caspase-dependent cleavage and produces a fragmented form, ΔN-Bcl-xL. Accumulation of ΔN-Bcl-xL is associated with mitochondrial dysfunction and neuronal death. Therefore, strategies to inhibit the activity or formation of ΔN-Bcl-xL protect the brain against excitotoxic injuries. Our team found that the pharmacological inhibitor ABT-737 exerts dose dependent effects in primary neurons. When primary hippocampal neurons were treated with 1 μM ABT-737, glutamate-mediated mitochondrial damage and neuronal death were exacerbated, whereas 10 nM ABT-737, a 100-fold lower concentration, protected mitochondrial function and enhanced neuronal viability against glutamate toxicity. In addition, we suggested acute vs. prolonged formation of ΔN-Bcl-xL may have different effects on mitochondrial or neuronal functions. Unlike acute production of ΔN-Bcl-xL by glutamate, overexpression of ΔN-Bcl-xL did not cause drastic changes in neuronal viability. We predicted that neurons undergo adaptation and may activate altered metabolism to compensate for ΔN-Bcl-xL-mediated mitochondrial dysfunction. Although the detailed mechanism of ABT-mediated neurotoxicity neuroprotection is still unclear, our study shows that the mitochondrial membrane protein ΔN-Bcl-xL is a central target for interventions.