Autophagy is activated in injured neurons and inhibited by methylprednisolone after experimental spinal cord injury

Identification of key autophagy-related genes and pathways in spinal cord injury

Spinal cord injury (SCI) can cause a range of functional impairments, and patients with SCI have limited potential for functional recovery. Previous studies have demonstrated that autophagy plays a role in the pathological process of SCI, but the specific mechanism of autophagy in this context remains unclear. Therefore, we explored the role of autophagy in SCI by identifying key autophagy-related genes and pathways. This study utilized the GSE132242 expression profile dataset, which consists of four control samples and four SCI samples; autophagy-related genes were sourced from GeneCards. R software was used to screen differentially expressed genes (DEGs) in the GSE132242 dataset, which were then intersected with autophagy-related genes to identify autophagy-related DEGs in SCI. Subsequently, the expression levels of these genes were confirmed and analyzed with gene ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG). A protein-protein interaction (PPI) analysis was conducted to identify interaction genes, and the resulting network was visualized with Cytoscape. The MCODE plug-in was used to build gene cluster modules, and the cytoHubba plug-in was applied to screen for hub genes. Finally, the GSE5296 dataset was used to verify the reliability of the hub genes. We screened 129 autophagy-related DEGs, including 126 up-regulated and 3 down-regulated genes. GO and KEGG pathway enrichment analysis showed that these 129 genes were mainly involved in the process of cell apoptosis, angiogenesis, IL-1 production, and inflammatory reactions, the TNF signaling pathway and the p53 signaling pathway. PPI identified 10 hub genes, including CCL2, TGFB1, PTGS2, FN1, HGF, MYC, IGF1, CD44, CXCR4, and SERPINEL1. The GSE5296 dataset revealed that the control group exhibited lower expression levels than the SCI group, although only CD44 and TGFB1 showed significant differences. This study identified 129 autophagy-related genes that might play a role in SCI. CD44 and TGFB1 were identified as potentially important genes in the autophagy process after SCI. These findings provide new targets for future research and offer new perspectives on the pathogenesis of SCI.

Micro electrical fields induced MSC-sEVs attenuate neuronal cell apoptosis by activating autophagy via lncRNA MALAT1/miR-22-3p/SIRT1/AMPK axis in spinal cord injury

Spinal cord injury (SCI) is a traumatic condition of the central nervous system that causes paralysis of the limbs. Micro electric fields (EF) have been implicated in a novel therapeutic approach for nerve injury repair and regeneration, but the effects of human umbilical cord mesenchymal stem cell-derived small extracellular vesicles that are induced by micro electric fields (EF-sEVs) stimulation on SCI remain unknown. The aim of the present study was to investigate whether EF-sEVs have therapeutic effects a rat model of SCI. EF-sEVs and normally conditioned human umbilical cord mesenchymal stem cells-derived small extracellular vesicles (CON-sEVs) were collected and injected intralesionally into SCI model rats to evaluate the therapeutic effects. We detect the expression of candidate long noncoding RNA metastasis-associated lung adenocarcinoma transcript 1 (lncRNA-MALAT1) in EF-sEVs and CON-sEVs. The targets and downstream effectors of lncRNA-MALAT1 were investigated using luciferase reporter assays. Using both in vivo and in vitro experiments, we demonstrated that EF-sEVs increased autophagy and decreased apoptosis after SCI, which promoted the recovery of motor function. We further confirmed that the neuroprotective effects of EF-sEVs in vitro and in vivo correlated with the presence of encapsulated lncRNA-MALAT1 in sEVs. lncRNA-MALAT1 targeted miR-22-3p via sponging, reducing miR-22-3p's suppressive effects on its target, SIRT1, and this translated into AMPK phosphorylation and increased levels of the antiapoptotic protein Bcl-2. Collectively, the present study identified that the lncRNA-MALAT1 in EF-sEVs plays a neuroprotective role via the miRNA-22-3p/SIRT1/AMPK axis and offers a fresh perspective and a potential therapeutic approach using sEVs to improve SCI.

Functional State of the Motor Centers of the Lumbar Spine after Contusion (Th8-Th9) with Application of Methylprednisolone-Copolymer at the Site of Injury

Spinal cord injuries must be treated as soon as possible. Studies of NASCIS protocols have questioned the use of methylprednisolone therapy. This study aimed to evaluate the effect of local delivery of methylprednisolone succinate in combination with a tri-block copolymer in rats with spinal cord injury. The experiments were conducted in accordance with the bioethical guidelines. We evaluated the state of the motor centers below the level of injury by assessing the amplitude of evoked motor responses in the hind limb muscles of rats during epidural stimulation. Kinematic analysis was performed to examine the stepping cycle in each rat. Trajectories of foot movements were plotted to determine the range of limb motion, maximum foot lift height, and lateral deviation of the foot in rats on the 21st day after spinal cord injury. We have shown that the local application of methylprednisolone succinate in combination with block copolymer leads to recovery of center excitability by 21 days after injury. In rats, they recovered weight-supported locomotion, directional control of walking, and balance. The proposed assessment method provides valuable information on gait disturbances following injury and can be utilized to evaluate the quality of therapeutic interventions.

All-Trans Retinoic Acid-Preconditioned Mesenchymal Stem Cells Improve Motor Function and Alleviate Tissue Damage After Spinal Cord Injury by Inhibition of HMGB1/NF-κB/NLRP3 Pathway Through Autophagy Activation

Spinal cord injury (SCI) is a significant public health issue that imposes numerous burdens on patients and society. Uncontrolled excessive inflammation in the second pathological phase of SCI can aggravate the injury. In this paper, we hypothesized that suppressing inflammatory pathways via autophagy could aid functional recovery, and prevent spinal cord tissue degeneration following SCI. To this end, we examined the effects of intrathecal injection of all-trans retinoic acid (ATRA)-preconditioned bone marrow mesenchymal stem cells (BM-MSCs) (ATRA-MSCs) on autophagy activity and the HMGB1/NF-κB/NLRP3 inflammatory pathway in an SCI rat model. This study demonstrated that SCI increased the expression of Beclin-1 (an autophagy-related gene) and NLRP3 inflammasome components such as NLRP3, ASC, Caspase-1, and pro-inflammatory cytokines IL-1β, IL-18, IL-6, and TNF-α. Additionally, following SCI, the protein levels of key autophagy factors (Beclin-1 and LC3-II) and HMGB1/NF-κB/NLRP3 pathway factors (HMGB1, p-NF-κB, NLRP3, IL-1β, and TNF-α) increased. Our findings indicated that ATRA-MSCs enhanced Beclin-1 and LC3-II levels, regulated the HMGB1/NF-κB/NLRP3 pathway, and inhibited pro-inflammatory cytokines. These factors improved hind limb motor activity and aided in the survival of neurons. Furthermore, ATRA-MSCs demonstrated greater beneficial effects than MSCs in treating spinal cord injury. Overall, ATRA-MSC treatment revealed beneficial effects on the damaged spinal cord by suppressing excessive inflammation and activating autophagy. Further research and investigation of the pathways involved in SCI and the use of amplified stem cells may be beneficial for future clinical use.

Biological Functions and Therapeutic Potential of Autophagy in Spinal Cord Injury

Autophagy is an evolutionarily conserved lysosomal degradation pathway that maintains metabolism and homeostasis by eliminating protein aggregates and damaged organelles. Many studies have reported that autophagy plays an important role in spinal cord injury (SCI). However, the spatiotemporal patterns of autophagy activation after traumatic SCI are contradictory. Most studies show that the activation of autophagy and inhibition of apoptosis have neuroprotective effects on traumatic SCI. However, reports demonstrate that autophagy is strongly associated with distal neuronal death and the impaired functional recovery following traumatic SCI. This article introduces SCI pathophysiology, the physiology and mechanism of autophagy, and our current review on its role in traumatic SCI. We also discuss the interaction between autophagy and apoptosis and the therapeutic effect of activating or inhibiting autophagy in promoting functional recovery. Thus, we aim to provide a theoretical basis for the biological therapy of SCI.

Involvement of mTOR Pathways in Recovery from Spinal Cord Injury by Modulation of Autophagy and Immune Response

Traumatic spinal cord injury (SCI) is untreatable and remains the leading cause of disability. Neuroprotection and recovery after SCI can be partially achieved by rapamycin (RAPA) treatment, an inhibitor of mTORC1, complex 1 of the mammalian target of rapamycin (mTOR) pathway. However, mechanisms regulated by the mTOR pathway are not only controlled by mTORC1, but also by a second mTOR complex (mTORC2). Second-generation inhibitor, pp242, inhibits both mTORC1 and mtORC2, which led us to explore its therapeutic potential after SCI and compare it to RAPA treatment. In a rat balloon-compression model of SCI, the effect of daily RAPA (5 mg/kg; IP) and pp242 (5 mg/kg; IP) treatment on inflammatory responses and autophagy was observed. We demonstrated inhibition of the mTOR pathway after SCI through analysis of p-S6, p-Akt, and p-4E-BP1 levels. Several proinflammatory cytokines were elevated in pp242-treated rats, while RAPA treatment led to a decrease in proinflammatory cytokines. Both RAPA and pp242 treatments caused an upregulation of LC3B and led to improved functional and structural recovery in acute SCI compared to the controls, however, a greater axonal sprouting was seen following RAPA treatment. These results suggest that dual mTOR inhibition by pp242 after SCI induces distinct mechanisms and leads to recovery somewhat inferior to that following RAPA treatment.

AAV2-mediated and hypoxia response element-directed expression of bFGF in neural stem cells showed therapeutic effects on spinal cord injury in rats

Neural stem cell (NSCs) transplantation has been one of the hot topics in the repair of spinal cord injury (SCI). Fibroblast growth factor (FGF) is considered a promising nerve injury therapy after SCI. However, owing to a hostile hypoxia condition in SCI, there remains a challenging issue in implementing these tactics to repair SCI. In this report, we used adeno-associated virus 2 (AAV2), a prototype AAV used in clinical trials for human neuron disorders, basic FGF (bFGF) gene under the regulation of hypoxia response element (HRE) was constructed and transduced into NSCs to yield AAV2-5HRE-bFGF-NSCs. Our results showed that its treatment yielded temporally increased expression of bFGF in SCI, and improved scores of functional recovery after SCI compared to vehicle control (AAV2-5HRE-NSCs) based on the analyses of the inclined plane test, Basso-Beattie-Bresnahan (BBB) scale and footprint analysis. Mechanistic studies showed that AAV2-5HRE-bFGF-NSCs treatment increased the expression of neuron-specific neuronal nuclei protein (NeuN), neuromodulin GAP43, and neurofilament protein NF200 while decreased the expression of glial fibrillary acidic protein (GFAP) as compared to the control group. Further, the expressions of autophagy-associated proteins LC3-II and Beclin 1 were decreased, whereas the expression of P62 protein was increased in AAV2-5HRE-bFGF-NSCs treatment group. Taken together, our data indicate that AAV2-5HRE-bFGF-NSCs treatment improved the recovery of SCI rats, which is accompanied by evidence of nerve regeneration, and inhibition of SCI-induced glial scar formation and cell autophagy. Thus, this study represents a step forward towards the potential use of AAV2-5HRE-bFGF-NSCs for future clinical trials of SCI repair.

Role of ABT888, a Novel Poly(ADP-Ribose) Polymerase (PARP) Inhibitor in Countering Autophagy and Apoptotic Processes Associated to Spinal Cord Injury

Accidents are the cause of some 50 deaths per 100,000 population each year; some 3% of these are from traumatic spinal cord injury (SCI), a damage that causes temporary or permanent motor deficits, often leading to permanent neurological alterations. The activation of poly(ADP-ribose) polymerase (PARP) as DNA damage response, together with autophagy and apoptosis processes contributes to the secondary injury processes seen after SCI. Thus, in the present study, a mouse compression model of SCI was used to determine whether the treatment with ABT888, as PARP-1/2 inhibitor, could restore the neuronal damage induced by SCI. Mice were orally administered with ABT888 (at a dose of 25 mg/kg) 1 h and 6 h after SCI induction. Histological analysis, myeloperoxidase (MPO) activity, and Basso Mouse scale (BMS) were performed. The expression of autophagy-related proteins and apoptosis-inducing factors was quantified in the cytosolic fraction from spinal cord tissue collected after 24 h after SCI. TUNEL assay was performed in SCI-tissues 24 h after damage. ABT888 treatment significantly reduced histological damage and neutrophilic infiltration, improving motor skills. PARP-1/2 inhibition by ABT888 slowed cell death, decreasing autophagy-activation proteins. These results showed that ABT888, inhibiting PARP-1/2 activity, through a reduction in the apoptosis-autophagy machinery, plays a protective role after SCI, suggesting a new insight into the potential application of ABT888 as novel candidate in SCI therapies.

Neuroprotection of melatonin on spinal cord injury by activating autophagy and inhibiting apoptosis via SIRT1/AMPK signaling pathway

The effect of melatonin (MT) on spinal cord injury (SCI) has attracted increasing research attention. However, the specific role and molecular mechanism of MT on SCI have not been elucidated. An experiment was performed to investigate the effect and molecular mechanism of MT on the neuronal autophagy after SCI and its effect on the recovery of nerve function. The rats were randomly divided into four treatment groups: the SCI+MT+EX527 (SIRT1 inhibitor), SCI+MT, SCI, and sham operation groups. On the 14th day after SCI, MT significantly promoted the recovery of motor function in the hind limbs according to the results of Basso, Beattie, and Bresnahan scores. At the same time, MT treatment resulted in reduced activation of cleaved-caspase-3, cleaved-caspase-9, and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive neurons and increased the survival of motoneurons in the anterior horn of the spinal cord on the 14th day after SCI, which exerted its neuroprotection. Furthermore, western blot and immunofluorescence double staining were performed to verify the molecular mechanism of effect of MT on SCI, and results showed the significantly upregulated expressions of Beclin-1, light chain-3B, SIRT1, p-AMPK proteins in the spinal cord tissue of MT-treated rats on the 14th day after SCI, however, the effect of MT on autophagy was reversed by EX527 (SIRT1 inhibitor), which implied that MT activated autophagy via SIRT1/AMPK signaling pathway after SCI. Similarly, the neuroprotective effects of MT on SCI were also inhibited after the SIRT1/AMPK signaling pathway was suppressed by EX527. Taken together, these results suggest that MT inhibits the apoptosis and activates autophagy of nerve cells after SCI and ultimately exerts the neuroprotective effect by SIRT1/AMPK signaling pathway.

Modulation of autophagy for neuroprotection and functional recovery in traumatic spinal cord injury

Spinal cord injury (SCI) is a serious central nervous system trauma that leads to loss of motor and sensory functions in the SCI patients. One of the cell death mechanisms is autophagy, which is 'self-eating' of the damaged and misfolded proteins and nucleic acids, damaged mitochondria, and other impaired organelles for recycling of cellular building blocks. Autophagy is different from all other cell death mechanisms in one important aspect that it gives the cells an opportunity to survive or demise depending on the circumstances. Autophagy is a therapeutic target for alleviation of pathogenesis in traumatic SCI. However, functions of autophagy in traumatic SCI remain controversial. Spatial and temporal patterns of activation of autophagy after traumatic SCI have been reported to be contradictory. Formation of autophagosomes following therapeutic activation or inhibition of autophagy flux is ambiguous in traumatic SCI studies. Both beneficial and harmful outcomes due to enhancement autophagy have been reported in traumatic SCI studies in preclinical models. Only further studies will make it clear whether therapeutic activation or inhibition of autophagy is beneficial in overall outcomes in preclinical models of traumatic SCI. Therapeutic enhancement of autophagy flux may digest the damaged components of the central nervous system cells for recycling and thereby facilitating functional recovery. Many studies demonstrated activation of autophagy flux and inhibition of apoptosis for neuroprotective effects in traumatic SCI. Therapeutic induction of autophagy in traumatic SCI promotes axonal regeneration, supporting another beneficial role of autophagy in traumatic SCI. In contrast, some other studies demonstrated that disruption of autophagy flux in traumatic SCI strongly correlated with neuronal death at remote location and impaired functional recovery. This article describes our current understanding of roles of autophagy in acute and chronic traumatic SCI, cross-talk between autophagy and apoptosis, therapeutic activation or inhibition of autophagy for promoting functional recovery, and future of autophagy in traumatic SCI.

Naringin inhibits autophagy mediated by PI3K-Akt-mTOR pathway to ameliorate endothelial cell dysfunction induced by high glucose/high fat stress

As a flavonoid, naringin (Nar) has been shown to have multiple pharmacological effects including lowering blood cholesterol, reducing thrombus formation and improving microcirculation. However, effects of Nar on function and autophagy of vascular endothelial cells under high glucose and high fat (HG/HF) stress are largely unclear. This study was designed to investigate such effects of Nar in human umbilical vein endothelial cells (HUVECs) and to determine whether such effects are related to autophagy. Our present results show that 86 μM of Nar inhibits the autophagy levels and protects the cells against the dysfunction induced by HG/HF stress. Moreover, Nar increases the phosphorylation levels of phosphatidylinositol-3-kinase (PI3K), protein kinase B (Akt) and mammalian rapamycin target protein (mTOR). However, pretreatment with rapamycin (RAPA, 5 μM, autophagy inducer), LY294002(10 μM, PI3K inhibitor) and Akt inhibitor Ⅳ (0.5 μM, Akt inhibitor) partially abrogates the protective effects of Nar, suggesting that the protective effects of Nar are achieved by activating the PI3K-Akt-mTOR pathway to inhibit autophagy. In conclusion, Nar improves the function of HUVECs under HG/HF stress through activating the PI3K-Akt-mTOR pathway to inhibit autophagy. The findings offer an insight into HG/HF stress-induced autophagy and indicate that Nar might have potential to prevent and treat the diabetic angiopathy.

NT-3 Promotes Oligodendrocyte Proliferation and Nerve Function Recovery After Spinal Cord Injury by Inhibiting Autophagy Pathway

BACKGROUND

Spinal cord injury (SCI) is a serious medical problem, leading to lifelong disability and increasing the health burden worldwide. Traditional treatments have limited effects on neuronal function recovery. Previous studies showed that neurotrophin-3 (NT-3) promoted oligodendrocyte survival and improved neuronal functional recovery after SCI. However, the mechanism by which NT-3 promotes oligodendrocyte survival after SCI remains unclear, which limits its application.

MATERIALS AND METHODS

A total of 75 female Sprague-Dawley rats were randomly divided into three groups: the NS group, NT-3 group, and NT-3 + rapamycin group. After successful modeling, the spinal cord specimens were taken at the corresponding time points. Western blot was used to detect autophagy-related proteins and Olig1 protein expression and combined with pathology, immunohistochemistry, flow cytometry, and other methods to detect the proliferation of oligodendrocytes after NT-3 application.

RESULTS

NT-3 was found to significantly promote the recovery of motor function by Basso-Beattie-Bresnahan scores analysis in the rat SCI model. Furthermore, intraspinal administration of NT-3 could downregulate the expression of Beclin-1 in oligodendrocytes, indicating that NT-3 could inhibit excessive autophagy of oligodendrocytes after SCI. The effects of NT-3 on oligodendrocyte survival could be blocked by an autophagy activator rapamycin.

CONCLUSIONS

This study found that NT-3 could promote the recovery of motor function after SCI in rats. The underlying reason may be that NT-3 inhibits the expression of autophagy proteins in oligodendrocytes and promotes oligodendrocyte proliferation. This study provided evidence for the future clinical application of NT-3 in SCI patients.

Autophagy in Neurotrauma: Good, Bad, or Dysregulated

Autophagy is a physiological process that helps maintain a balance between the manufacture of cellular components and breakdown of damaged organelles and other toxic cellular constituents. Changes in autophagic markers are readily detectable in the spinal cord and brain following neurotrauma, including traumatic spinal cord and brain injury (SCI/TBI). However, the role of autophagy in neurotrauma remains less clear. Whether autophagy is good or bad is under debate, with strong support for both a beneficial and detrimental role for autophagy in experimental models of neurotrauma. Emerging data suggest that autophagic flux, a measure of autophagic degradation activity, is impaired in injured central nervous systems (CNS), and interventions that stimulate autophagic flux may provide neuroprotection in SCI/TBI models. Recent data demonstrating that neurotrauma can cause lysosomal membrane damage resulting in pathological autophagosome accumulation in the spinal cord and brain further supports the idea that the impairment of the autophagy-lysosome pathway may be a part of secondary injury processes of SCI/TBI. Here, we review experimental work on the complex and varied responses of autophagy in terms of both the beneficial and detrimental effects in SCI and TBI models. We also discuss the existing and developing therapeutic options aimed at reducing the disruption of autophagy to protect the CNS after injuries.

Effects of dexamethasone on autophagy and apoptosis in acute spinal cord injury

Previous studies have indicated that spinal cord injury can induce autophagy. To a certain extent, increased autophagy has a protective effect on neurons. Early hormone therapy is well recognized as a treatment for spinal cord injury. However, whether the protective effect of autophagy is important in recovery from spinal cord injury remains unclear. In this study, we established an in-vitro model of spinal cord injury to study the effects of dexamethasone on mechanical injury, autophagy, and apoptosis in spinal cord neurons. The results showed that dexamethasone inhibited the level of autophagy in the injured nerve cells in a dose-dependent manner. High doses of dexamethasone protected the damaged spinal cord neurons by inhibiting apoptosis, but a protective effect from low hormone concentrations was not obvious. When autophagy was inhibited in damaged spinal cord neurons, apoptosis decreased significantly; in contrast, impairment of autophagy-induced activation of spinal cord neurons and apoptosis levels were significantly increased.

NEP1-40-modified human serum albumin nanoparticles enhance the therapeutic effect of methylprednisolone against spinal cord injury

Background

Frequent injection of high-dose methylprednisolone (MP) is used to treat spinal cord injury (SCI), but free MP is associated with various side effects and its water solubility is low, limiting potential dosing regimes and administration routes. Albumin-based nanoparticles, which can encapsulate therapeutic drugs and release cargo in a controlled pattern, show high biocompatibility and low toxicity. The Nogo protein, expressed on the surface of oligodendrocytes, can inhibit axonal growth by binding with the axonal Nogo receptor (NgR). Peptide NEP_1-40, an NgR antagonist, can bind specifically to Nogo, significantly improving functional recovery and axon growth in the corticospinal tract. Therefore, we hypothesized that delivering MP within nanoparticles decorated with NEP_1-40 could avoid the disadvantages of free MP and enhance its therapeutic efficacy against SCI.

Results

We used human serum albumin to prepare MP-loaded NPs (MP-NPs), to whose surface we conjugated NEP_1-40 to form NEP_1-40-MP-NPs. Transmission electron microscopy indicated successful formation of nanoparticles. NEP_1-40-MP-NPs were taken up significantly better than MP-NPs by the Nogo-positive cell line RSC-96 and were associated with significantly higher Basso–Beattie–Bresnahan locomotor scores in rats recovering from SCI. Micro-computed tomography assay showed that NEP_1-40-MP-NPs mitigated SCI-associated loss of bone mineral density and accelerated spinal cord repair.

Conclusions

NEP_1-40-MP-NPs can enhance the therapeutic effects of MP against SCI. This novel platform may also be useful for delivering other types of drugs.

Electronic supplementary material

The online version of this article (10.1186/s12951-019-0449-3) contains supplementary material, which is available to authorized users.

Neuroprotective effects of rapamycin on spinal cord injury in rats by increasing autophagy and Akt signaling

Rapamycin treatment has been shown to increase autophagy activity and activate Akt phosphorylation, suppressing apoptosis in several models of ischemia reperfusion injury. However, little has been studied on the neuroprotective effects on spinal cord injury by activating Akt phosphorylation. We hypothesized that both effects of rapamycin, the increased autophagy activity and Akt signaling, would contribute to its neuroprotective properties. In this study, a compressive spinal cord injury model of rat was created by an aneurysm clip with a 30 g closing force. Rat models were intraperitoneally injected with rapamycin 1 mg/kg, followed by autophagy inhibitor 3-methyladenine 2.5 mg/kg and Akt inhibitor IV 1 µg/kg. Western blot assay, immunofluorescence staining and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay were used to observe the expression of neuronal autophagy molecule Beclin 1, apoptosis-related molecules Bcl-2, Bax, cytochrome c, caspase-3 and Akt signaling. Our results demonstrated that rapamycin inhibited the expression of mTOR in injured spinal cord tissue and up-regulated the expression of Beclin 1 and phosphorylated-Akt. Rapamycin prevented the decrease of bcl-2 expression in injured spinal cord tissue, reduced Bax, cytochrome c and caspase-3 expression levels and reduced the number of apoptotic neurons in injured spinal cord tissue 24 hours after spinal cord injury. 3-Methyladenine and Akt inhibitor IV intervention suppressed the expression of Beclin-1 and phosphorylated-Akt in injured spinal cord tissue and reduced the protective effect of rapamycin on apoptotic neurons. The above results indicate that the neuroprotective effect of rapamycin on spinal cord injury rats can be achieved by activating autophagy and the Akt signaling pathway.

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

INTRODUCTION

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSIONS

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

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.

Epidermal growth factor regulates apoptosis and oxidative stress in a rat model of spinal cord injury

Spinal cord injury (SCI) leads to vascular damage and disruption of blood-spinal cord barrier which participates in secondary nerve injury. Epidermal growth factor (EGF) is an endogenous protein which regulates cell proliferation, growth and differention. Previous studies reported that EGF exerts neuroprotective effect in spinal cord after SCI. However, the molecular mechanisms underlying EGF-mediated protection in different regions of nervous system have not shown yet. In this study, we aimed to examine possible anti-apoptotic and protective roles of EGF not only in spinal cord but also in brain following SCI. Twenty-eight adult rats were divided into four groups of seven animals each as follows: sham, trauma (SCI), SCI + EGF and SCI + methylprednisolone (MP) groups. The functional neurological deficits due to the SCI were assessed by behavioral analysis using the Basso, Beattie and Bresnahan (BBB) open-field locomotor test. The alterations in pro-/anti-apoptotic protein levels and antioxidant enzyme activities were measured in spinal cord and frontal cortex. In our study, EGF promoted locomotor recovery and motor neuron survival of SCI rats. EGF treatment significantly decreased Bax and increased Bcl-2 protein expressions both in spinal cord and brain when compared to SCI group. Moreover, antioxidant enzyme activities including catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPx) were increased following EGF treatment similar to MP treatment. Our experiment also suggests that alteration of the ratio of Bcl-2 to Bax may result from decreased apoptosis following EGF treatment. As a conclusion, these results show, for the first time, that administration of EGF exerts its protection via regulating apoptotic and oxidative pathways in response to spinal cord injury in different regions of central nervous system.

Chloroquine Promotes the Recovery of Acute Spinal Cord Injury by Inhibiting Autophagy-Associated Inflammation and Endoplasmic Reticulum Stress

Spinal cord injury (SCI) is a severe nervous system disease that may lead to lifelong disability. Studies have shown that autophagy plays a key role in various diseases; however, the mechanisms regulating cross-talk between autophagy, inflammation, and endoplasmic reticulum (ER) stress during SCI recovery remain unclear. This study was designed to investigate the mechanism by which chloroquine (CQ) inhibits autophagy-associated inflammation and ER stress in rats during their recovery from acute SCI. We evaluated the locomotor function, level of autophagy, and levels of inflammatory cytokines and ER-stress-associated proteins and examined the degradation of the key regulator of inflammation inhibitor of kappa B alpha (I-κBα) through autophagy by analyzing the colocalization of I-κBα, p62, and microtubule-associated protein 1 light chain 3-II. In addition, overexpression of the p62 and activating transcription factor 4 (ATF4) silencing plasmids was used to verify the important roles for autophagic degradation and ER stress. In this study, locomotor function is improved, and autophagy and inflammation are significantly inhibited by, CQ treatment in the model rats. In addition, CQ significantly inhibits the degradation of ubiquitinated I-κBα and blocks the nuclear translocation of nuclear factor kappa B p65 and expression of inflammatory factors. Overexpression of p62 increases I-κBα degradation and improves inflammatory responses. Moreover, CQ treatment also inhibits the activation of ER stress in the rat SCI model, and the ATF4 signaling pathway is required for ER-stress-induced activation of autophagy. These findings reveal a novel mechanism underlying the beneficial effects of CQ on the recovery of SCI, particularly the mechanisms regulating cross-talk between autophagy, inflammation, and ER stress.

Neuroprotective Effects of C-terminal Domain of Tetanus Toxin on Rat Brain Against Motorneuron Damages After Experimental Spinal Cord Injury

STUDY DESIGN

Experimental animal study investigating the efficacy of C-terminal domain of tetanus toxin application as neuroprotective effects on rat brain in a model of spinal cord injury (SCI).

OBJECTIVE

The aim of the present study was to investigate the possible role of C-terminal domain of tetanus toxin (Hc-TeTx) on cell death mechanisms including apoptosis and autophagy following SCI.

SUMMARY OF BACKGROUND DATA

Traumatic SCI can lead to posttraumatic inflammation, oxidative stress, motor neuron apoptosis, necrosis, and autophagy of tissue. To promote and enhance recovery after SCI, recent development of devices and therapeutic interventions are needed.

METHODS

Twenty-eight adult rats were divided into four groups (n = 7 each) as follows: sham, trauma (SCI), SCI + Hc-TeTx, and SCI + methylprednisolone groups. The functional neurological deficits due to the SCI were assessed by behavioral analysis using the Basso, Beattie and Bresnahan (BBB) open-field locomotor test. The alterations in pro-/anti-apoptotic and autophagy related-protein levels were measured by Western blotting technique.

RESULTS

In this study, Hc-TeTx promotes locomotor recovery and motor neuron survival of SCI rats. Hc-TeTx also decreased expression of bax, bad, bak, cleaved caspase-3, Ask1, and autophagy-related proteins including Atg5 and LC3II in brain. Our study provides an evidence that cell death mechanisms play critical roles in SCI and that the nontoxic peptides including Hc-TeTx may exert protective effect and decrease cell death following SCI.

CONCLUSION

Our preliminary findings suggest a possible therapeutic agent to improve survival after spinal cord trauma, but further analysis are still needed to evaluate the difference between acute and chronic injuries.

LEVEL OF EVIDENCE

N/A.

Autophagy-independent increase of ATG5 expression in T cells of multiple sclerosis patients

Autophagy, a process of controlled self-digestion which regulates cell homeostasis, is involved in innate and adaptive immunity. We investigated the expression of autophagy genes and autophagic activity in distinct lymphocyte populations in treatment-naive MS patients. The mRNA and protein levels of autophagy-related (ATG)5, required for autophagosome formation, were increased in CD4⁺ and CD4^- T cells, but not B cells of MS patients compared to control subjects. The expression of other investigated autophagy genes, as well as the autophagic activity, did not significantly differ between the two groups. ATG5 mRNA levels in CD4⁺ T cells from MS patients were positively correlated with those of the proinflammatory cytokine tumor necrosis factor. These data suggest that autophagy-independent increase in ATG5 expression might be associated with the proinflammatory capacity of T cells in multiple sclerosis.

Neuroserpin restores autophagy and promotes functional recovery after acute spinal cord injury in rats

This study is to reveal the characteristics of autophagy and the effect of neuroserpin (NSP) treatment on autophagy during the process of functional recovery following spinal cord injury (SCI). After the clip compress rat model of SCI had been made, autophagy‑associated proteins, including LC3‑II, beclin‑1 and p62, were evaluated at 2, 4, 24, 72 h, and 168 h in the experimental group, and the sham group as control. Transmission electron microscopy (TEM) was further used for autophagy detection at 4 and 72 h. All the male rats were randomly divided into three groups: Sham, vehicle and NSP group. NSP or an equal volume of saline vehicle was administered via intrathecal injection immediately after SCI. Each group was further divided into subgroups for the following experiments: i)Western blot (LC3‑II and p62); ii) Immunofluorescent double staining (LC3/MAP‑2/DAPI); iii) Nissl staining and Basso Beattie Bresnahan (BBB score) for NSP neuroprotection evaluation. Our results revealed both LC3‑II and p62 expression trended upward at 24, 72 and 168 h after SCI. The LC3‑II peaked at 72 h, while p62 peaked at 24 h. Beclin‑1 dropped significantly at 72 and 168 h. TEM results showed that autophagosomes largely accumulated at 72 h after SCI when compared with the sham group. Western blot analysis showed that LC3‑II and p62 were markedly decreased with NSP treatment at 72 h after injury compared with that of the vehicle‑group. Immunofluorescent double labeling indicated that accumulation of autophagosomes was reduced in the NSP group. Further, post‑SCI treatment with NSP improved the BBB scale and increased the number of anterior horn motor neurons. Together, this study demonstrates that autophagic flux is impaired, meanwhile NSP restores autophagic flux and promotes functional recovery after SCI in rats.

Pterostilbene inhibits reactive oxygen species production and apoptosis in primary spinal cord neurons by activating autophagy via the mechanistic target of rapamycin signaling pathway

Autophagy is an important self-adaptive mechanism that is involved in inhibiting reactive oxygen species (ROS) in spinal cord neurons. Pterostilbene, a natural plant extract, has been demonstrated to possess antioxidant effects; however, it has not yet been investigated whether pterostilbene could activate autophagy and protect spinal cord neurons from oxidative stress. In the present study, primary spinal cord neurons of Sprague Dawley rats were cultured. Cell counting kit‑8 analysis was used to detect cytotoxicity of pterostilbene. Cells were treated with various doses of pterostilbene for 24 and 48 h, respectively, and H2O2 was used to induce ROS production. Western blot analysis was performed to assess the protein expression of microtubule‑associated protein 1 light chain 3 (LC3)‑II, Beclin‑1, p62, p‑p70S6K and p‑mechanistic target of rapamycin (mTOR). Furthermore, the green fluorescent protein (GFP)‑LC3 assay was used to detect the level of autophagy level and activation mechanism. 2',7'‑Dichlorofluorescin diacetate and MitoSOX Red staining were used to detect ROS production, and Terminal deoxynucleotidyl‑transferase‑mediated dUTP nick end labelling assay was used to analyze apoptosis percentage. ATG5 small interfering (si)RNA transfection was used to analyze the involvement of autophagy. A dose‑dependent increase in the expression of LC3‑II and Beclin‑1, as well as the p62 decline, were observed in the pterostilbene‑treated neurons; however, p‑p70S6K and p‑mTOR expression was inhibited by pterostilbene. Pterostilbene increased the expression of LC3‑II in H2O2‑treated cells, and GFP‑LC3 analysis demonstrated an increased number of autophagosomes. Furthermore, pterostilbene significantly inhibited the ROS production and apoptosis induced by H2O2; however, ATG5 siRNA transfection significantly reversed the protection of pterostilbene. These results indicate that pterostilbene may inhibit the ROS production and apoptosis in spinal cord neurons by activating autophagy via the mTOR signaling pathway.

Resveratrol ameliorates autophagic flux to promote functional recovery in rats after spinal cord injury

Resveratrol is known to improve functional recovery after spinal cord injury, but the exact mechanism involved is yet unclear. The aim of this study was to clarify whether resveratrol can exert neuroprotective effects via activating neuronal autophagic flux, in view of the underlying role of the autophagic flux mediated by resveratrol on neuronal apoptosis after spinal cord injury, and identify the role of the liver kinase B1(LKB1)/adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR)/ p70 ribosomal protein S6 kinase (p70s6k) signal pathway in the autophagic flux mediated by resveratrol. The results obtained strongly indicate that resveratrol improved functional recovery in Sprague–Dawley rats after acute spinal cord injury, preserved their motor neurons, alleviated the neuronal apoptosis, and ameliorated neuronal autophagic flux. After blocking the autophagic flux, the neuroprotective effects of resveratrol were eliminated. Furthermore, it was proved that resveratrol can activate the LKB1/AMPK/mTOR/p70s6k pathway in vivo and in vitro, and the LKB1/AMPK/mTOR/p70s6k pathway plays a vital role in activating the autophagic flux mediated by resveratrol in PC12 cells. Thus, resveratrol enables to ameliorate neuronal autophagic flux via the LKB1/AMPK/mTOR/p70s6k pathway to alleviate apoptosis, and finally ameliorating functional recovery after acute SCI in SD rats.

Inhibition of Autophagy is Involved in the Protective Effects of Ginsenoside Rb1 on Spinal Cord Injury

Spinal cord injury (SCI) is a devastating neurological disorder. Autophagy is induced and plays a crucial role in SCI. Ginsenoside Rb1 (Rb1), one of the major active components extracted from Panax Ginseng CA Meyer, has exhibited neuroprotective effects in various neurodegenerative diseases. However, it remains unknown whether autophagy is involved in the neuroprotection of Rb1 on SCI. In this study, we examined the regulation of autophagy following Rb1 treatment and its involvement in the Rb1-induced neuroprotection in SCI and in vitro injury model. Firstly, we found that Rb1 treatment decreased the loss of motor neurons and promoted function recovery in the SCI model. Furthermore, we found that Rb1 treatment inhibited autophagy in neurons, and suppressed neuronal apoptosis and autophagic cell death in the SCI model. Finally, in the in vitro injury model, Rb1 treatment increased the viability of PC12 cells and suppressed apoptosis by inhibiting excessive autophagy, whereas stimulation of autophagy by rapamycin abolished the anti-apoptosis effect of Rb1. Taken together, these findings suggest that the inhibition of autophagy is involved in the neuroprotective effects of Rb1 on SCI.

Hydrogen Sulfide Inhibits Autophagic Neuronal Cell Death by Reducing Oxidative Stress in Spinal Cord Ischemia Reperfusion Injury

Autophagy is upregulated in spinal cord ischemia reperfusion (SCIR) injury; however, its expression mechanism is largely unknown; moreover, whether autophagy plays a neuroprotective or neurodegenerative role in SCIR injury remains controversial. To explore these issues, we created an SCIR injury rat model via aortic arch occlusion. Compared with normal controls, autophagic cell death was upregulated in neurons after SCIR injury. We found that autophagy promoted neuronal cell death during SCIR, shown by a significant number of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling- (TUNEL-) positive cells colabeled with the autophagy marker microtubule-associated protein 1 light chain 3, while the autophagy inhibitor 3-methyladenine reduced the number of TUNEL-positive cells and restored neurological and motor function. Additionally, we showed that oxidative stress was the main trigger of autophagic neuronal cell death after SCIR injury and N-acetylcysteine inhibited autophagic cell death and restored neurological and motor function in SCIR injury. Finally, we found that hydrogen sulfide (H₂S) inhibited autophagic cell death significantly by reducing oxidative stress in SCIR injury via the AKT-the mammalian target of rapamycin (mTOR) pathway. These findings reveal that oxidative stress induces autophagic cell death and that H₂S plays a neuroprotective role by reducing oxidative stress in SCIR.

PPAR-γ agonist rosiglitazone reduces autophagy and promotes functional recovery in experimental traumaticspinal cord injury

BACKGROUND

Secondary damage is often more important in determining the functional outcome and provides a practical target for therapeutic intervention. Rosiglitazone (ROSG) is a potent PPAR-γ agonist and has been shown to induce neuroprotection in animal models of spinal cord injury (SCI). However, it is still unclear whether this PPAR-γ agonist can mediate neuronal autophagy after SCI.

METHODS

SCI was induced by application of vascular clips (force of 24g) to the dura via a four-level T5-T8 laminectomy. The role of the PPAR-γ agonist ROSG on neuronal autophagy induced by SCI was investigated.

RESULTS

The expression of autophagy-related proteins, including microtubule-associated protein 1 light chain 3 type II (LC3-II), beclin-1, and cathepsin D, increased significantly after SCI. ROSG downregulated autophagy-related protein expression and improved the locomotor function after SCI. GW9662 (a PPAR-γ inhibitor) significantly antagonized the effect of ROSG and abolished the protective effect on SCI.

CONCLUSIONS

Our results clearly demonstrated that the administration of ROSG after SCI reduced autophagy and promoted functional recovery after SCI in rats.

The Temporal Pattern, Flux, and Function of Autophagy in Spinal Cord Injury

Previous studies have indicated that autophagy plays a critical role in spinal cord injury (SCI), including traumatic spinal cord injury (TSCI) and ischemia-reperfusion spinal cord injury (IRSCI). However, while the understanding of mechanisms underlying autophagy in SCI has progressed, there remain several controversial points: (1) temporal pattern results of autophagic activation after SCI are not consistent across studies; (2) effect of accumulation of autophagosomes due to the blockade or enhancement of autophagic flux is uncertain; (3) overall effect of enhanced autophagy remains undefined, with both beneficial and detrimental outcomes reported in SCI literature. In this review, the temporal pattern of autophagic activation, autophagic flux, autophagic cell death, relationship between autophagy and apoptosis, and pharmacological intervention of autophagy in TSCI (contusion injury, compression injury and hemisection injury) and IRSCI are discussed. Types of SCI and severity appear to contribute to differences in outcomes regarding temporal pattern, flux, and function of autophagy. With future development of specific strategies on autophagy intervention, autophagy may play an important role in improving functional recovery in patients with SCI.

Netrin-1 Improves Functional Recovery through Autophagy Regulation by Activating the AMPK/mTOR Signaling Pathway in Rats with Spinal Cord Injury

Autophagy is an process for the degradation of cytoplasmic aggregated proteins and damaged organelles and plays an important role in the development of SCI. In this study, we investigated the therapeutic effect of Netrin-1 and its potential mechanism for autophagy regulation after SCI. A rat model of SCI was established and used for analysis. Results showed that administration of Netrin-1 not only significantly enhanced the phosphorylation of AMP-activated protein kinase (AMPK) but also reduced the phosphorylation of mammalian target of rapamycin (mTOR) and P70S6K. In addition, the expression of Beclin-1 and the ratio of the light-chain 3B-II (LC3B-II)/LC3B-I in the injured spinal cord significantly increased in Netrin-1 group than those in SCI group. Moreover, the ratio of apoptotic neurons in the anterior horn of the spinal cord and the cavity area of spinal cord significantly decreased in Netrin-1 group compared with those in SCI group. In addition, Netrin-1 not only preserved motor neurons but also significantly improved motor fuction of injured rats. These results suggest that Netrin-1 improved functional recovery through autophagy stimulation by activating the AMPK/mTOR signaling pathway in rats with SCI. Thus, Netrin-1 treatment could be a novel therapeutic strategy for SCI.

Intrathecal Injection of 3-Methyladenine Reduces Neuronal Damage and Promotes Functional Recovery via Autophagy Attenuation after Spinal Cord Ischemia/Reperfusion Injury in Rats

The present study aimed to determine the occurrence of autophagy following ischemia/reperfusion (I/R) injury in the rat spinal cord and whether autophagy inhibition contributes to neural tissue damage and locomotor impairment. A spinal cord I/R model was induced via descending thoracic aorta occlusion for 10 min using systemic hypotension (40 mmHg) in adult male Sprague-Dawley rats. Then, 600 nmol 3-methyladenine (3-MA) or vehicle was intrathecally administered. Ultrastructural spinal cord changes were observed via transmission electron microscopy (TEM) and immunofluorescent double-labeling. Western blots were used to determine the protein expression of microtubule-associated protein light chain 3 (LC3) and Beclin 1. Autophagy was activated after spinal cord I/R injury as demonstrated by significantly increased LC3 and Beclin 1 expression at 3-48 h after injury. Furthermore, TEM images indicated the presence of autophagosomes and autolysosomes in the injured spinal cord. 3-MA significantly decreased LC3 and Beclin 1 expression and the number of LC3-positive cells in spinal cord of I/R versus vehicle groups. Moreover, the 3-MA-treated rats exhibited better neurobehavioral scores compared with control rats. These findings suggest activation of autophagy leading to neuronal cell death in the I/R injured spinal cord. These effects were significantly inhibited by intrathecal 3-MA administration. Thus intrathecal 3-MA administration may represent a novel treatment target following spinal cord I/R injury.

Inflammatory Bowel Disease Drugs: A Focus on Autophagy

Inflammatory bowel disease [IBD] is characterized by chronic inflammation of the gastrointestinal tract. Medications such as corticosteroids, thiopurines, immunomodulators and biologic agents are used to induce and maintain remission; however, response to these drugs is variable and can diminish over time. Defective autophagy has been strongly linked to IBD pathogenesis, with evidence showing that enhancing autophagy may be therapeutically beneficial by regulating inflammation and clearing intestinal pathogens. It is plausible that the therapeutic effects of some IBD drugs are mediated in part through modulation of the autophagy pathway, with studies investigating a wide range of diseases and cell types demonstrating autophagy pathway regulation by these agents. This review will highlight the current evidence, both in vitro and in vivo, for the modulation of autophagy by drugs routinely used in IBD. A clearer understanding of their mechanisms of action will be invaluable to utilize these drugs in a more targeted and personalized manner in this diverse and often complex group of patients.

Reduction of neuronal damage and promotion of locomotor recovery after spinal cord injury by early administration of methylprednisolone: possible involvement of autophagy pathway

Interaction between autophagy and apoptosis participates in the neuroprotective effect of methylprednisolone on spinal cord injury.

Autophagy Inhibition Favors Survival of Rubrospinal Neurons After Spinal Cord Hemisection

Spinal cord injuries (SCIs) are devastating conditions of the central nervous system (CNS) for which there are no restorative therapies. Neuronal death at the primary lesion site and in remote regions that are functionally connected to it is one of the major contributors to neurological deficits following SCI.Disruption of autophagic flux induces neuronal death in many CNS injuries, but its mechanism and relationship with remote cell death after SCI are unknown. We examined the function and effects of the modulation of autophagy on the fate of axotomized rubrospinal neurons in a rat model of spinal cord dorsal hemisection (SCH) at the cervical level. Following SCH, we observed an accumulation of LC3-positive autophagosomes (APs) in the axotomized neurons 1 and 5 days after injury. Furthermore, this accumulation was not attributed to greater initiation of autophagy but was caused by a decrease in AP clearance, as demonstrated by the build-up of p62, a widely used marker of the induction of autophagy. In axotomized rubrospinal neurons, the disruption of autophagic flux correlated strongly with remote neuronal death and worse functional recovery. Inhibition of AP biogenesis by 3-methyladenine (3-MA) significantly attenuated remote degeneration and improved spontaneous functional recovery, consistent with the detrimental effects of autophagy in remote damage after SCH. Collectively, our results demonstrate that autophagic flux is blocked in axotomized neurons on SCI and that the inhibition of AP formation improves their survival. Thus, autophagy is a promising target for the development of therapeutic interventions in the treatment of SCIs.

Atorvastatin activates autophagy and promotes neurological function recovery after spinal cord injury

Atorvastatin, a lipid-lowering medication, provides neuroprotective effects, although the precise mechanisms of action remain unclear. Our previous studies confirmed activated autophagy following spinal cord injury, which was conducive to recovery of neurological functions. We hypothesized that atorvastatin could also activate autophagy after spinal cord injury, and subsequently improve recovery of neurological functions. A rat model of spinal cord injury was established based on the Allen method. Atorvastatin (5 mg/kg) was intraperitoneally injected at 1 and 2 days after spinal cord injury. At 7 days post-injury, western blot assay, reverse transcription-polymerase chain reaction, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) staining results showed increased Beclin-1 and light chain 3B gene and protein expressions in the spinal cord injury + atorvastatin group. Additionally, caspase-9 and caspase-3 expression was decreased, and the number of TUNEL-positive cells was reduced. Compared with the spinal cord injury + saline group, Basso, Beattie, and Bresnahan locomotor rating scale scores significantly increased in the spinal cord injury + atorvastatin group at 14-42 days post-injury. These findings suggest that atorvastatin activated autophagy after spinal cord injury, inhibited apoptosis, and promoted recovery of neurological function.

The Association of Palmitoylethanolamide with Luteolin Decreases Autophagy in Spinal Cord Injury

Spinal cord injury (SCI) is a devastating condition of the central nervous system (CNS) often resulting in severe functional impairment and for which there are not yet restorative therapies. In the present study, we performed a widely used model of SCI to determine the neuroprotective propriety of palmitoylethanolamide (PEA) and the antioxidant effect of a flavonoid luteolin (Lut), given as a co-ultramicronized compound co-ultraPEALut. In particular, by western blot analysis and immunofluorescence staining, we investigated whether this compound (at the dose of 1 mg/kg) was able to modulate autophagy. Our results showed that treatment with co-ultraPEALut after SCI reduced the expression of proteins promoter of autophagy such as Beclin-1 and microtubule-associated protein 1A/1B-light chain 3 (MAP-LC3). In contrast, this compound decreased the levels of mammalian target of rapamycin (mTOR), p-Akt, and p-70S6K which are proteins that inhibit autophagy. These data confirmed that the protective role of co-ultraPEALut is associated with inhibition of excessive autophagy and regulation of protein degradation. Therefore, treatment with co-ultraPEALut could be considered as a possible therapeutic approach in an acute traumatic lesion like SCI.

Methylprednisolone exerts neuroprotective effects by regulating autophagy and apoptosis

Methylprednisolone markedly reduces autophagy and apoptosis after secondary spinal cord injury. Here, we investigated whether pretreatment of cells with methylprednisolone would protect neuron-like cells from subsequent oxidative damage via suppression of autophagy and apoptosis. Cultured N2a cells were pretreated with 10 µM methylprednisolone for 30 minutes, then exposed to 100 µM H₂O₂ for 24 hours. Inverted phase contrast microscope images, MTT assay, flow cytometry and western blot results showed that, compared to cells exposed to 100 µM H₂O₂ alone, cells pretreated with methylprednisolone had a significantly lower percentage of apoptotic cells, maintained a healthy morphology, and showed downregulation of autophagic protein light chain 3B and Beclin-1 protein expression. These findings indicate that methylprednisolone exerted neuroprotective effects against oxidative damage by suppressing autophagy and apoptosis.

Probucol inhibits neural cell apoptosis via inhibition of mTOR signaling pathway after spinal cord injury

Autophagy plays an essential role in neurodevelopment, axonal guidance, neuropathic pain remission, and neuronal survival. Inhibiting the mammalian target of rapamycin (mTOR) signaling pathway can induce the occurrence of autophagy. In this study, we initially detected the effect of probucol on autophagy after spinal cord injury (SCI) by intraperitoneally injecting spinal cord-injured rats with probucol for 7days. The levels of Beclin1 and LC3B were evidently enhanced at 7days post-operation. However, the increase in the phosphorylated AMP-activated protein kinase (AMPK) protein and the decrease in ribosomal protein S6 kinase p70 subtype (p70S6K) phosphorylation level simultaneously occurred after SCI. Moreover, the expression levels of apoptosis-related proteins of Caspase-3, Caspase-9, and Bax were significantly reduced. Immunofluorescence results indicated that the expression of Caspase-3 protein was evidently decreased and that of Beclin-1 protein was increased by probucol. Nissl staining and Basso, Beattie, and Bresnahan scores showed that the quantity and function of motor neurons were visibly preserved by probucol after SCI. This study showed that probucol inhibited the mTOR signaling pathway to induce autophagy, reduce neural cell apoptosis and promote recovery of neurological function after SCI.

Metformin Improves Functional Recovery After Spinal Cord Injury via Autophagy Flux Stimulation

Spinal cord injury (SCI) is a severe neurological disease with few efficacious drugs. Autophagy is a cellular process to confront with stress after SCI and considered to be a therapeutic target of SCI. In this study, we investigated the therapeutic effect of metformin on functional recovery after SCI and its underlying mechanism of autophagy regulation. Using a rat model of traumatic SCI, we found improved function recovery which was paralleled by a reduction of apoptosis after metformin treatment. We further examined autophagy via detecting autophagosomes by transmission electron microscopy and immunofluorescence, as well as autophagy markers by western blot in each groups. The results showed that the number of autophagosomes and expression of autophagy markers such as LC3 and beclin1 were increased in SCI group, while autophagy substrate protein p62 as well as ubiquitinated proteins were found to accumulate in SCI group, indicating an impaired autophagy flux in SCI. But, metformin treatment attenuated the accumulation of p62 and ubiquitinated proteins, suggesting a stimulative effect of autophagy flux by metformin. Blockage of autophagy flux by chloroquine partially abolished the apoptosis inhibition and functional recovery effect of metformin on SCI, which suggested that the protective effect of metformin on SCI was through autophagy flux stimulation. Activation of AMPK as well as inhibition of its downstream mTOR signaling were detected under metformin treatment in vivo and in vitro; inhibition of AMPK signaling by compound C suppressed autophagy flux induced by metformin in vitro, indicating that AMPK signaling was involved in the effect of metformin on autophagy flux regulation. Together, these results illustrated that metformin improved functional recovery effect through autophagy flux stimulation and implied metformin to be a potential drug for SCI therapy.

Methylprednisolone promotes recovery of neurological function after spinal cord injury: association with Wnt/β-catenin signaling pathway activation

Some studies have indicated that the Wnt/β-catenin signaling pathway is activated following spinal cord injury, and expression levels of specific proteins, including low-density lipoprotein receptor related protein-6 phosphorylation, β-catenin, and glycogen synthase kinase-3β, are significantly altered. We hypothesized that methylprednisolone treatment contributes to functional recovery after spinal cord injury by inhibiting apoptosis and activating the Wnt/β-catenin signaling pathway. In the current study, 30 mg/kg methylprednisolone was injected into rats with spinal cord injury immediately post-injury and at 1 and 2 days post-injury. Basso, Beattie, and Bresnahan scores showed that methylprednisolone treatment significantly promoted locomotor functional recovery between 2 and 6 weeks post-injury. The number of surviving motor neurons increased, whereas the lesion size significantly decreased following methylprednisolone treatment at 7 days post-injury. Additionally, caspase-3, caspase-9, and Bax protein expression levels and the number of apoptotic cells were reduced at 3 and 7 days post-injury, while Bcl-2 levels at 7 days post-injury were higher in methylprednisolone-treated rats compared with saline-treated rats. At 3 and 7 days post-injury, methylprednisolone up-regulated expression and activation of the Wnt/β-catenin signaling pathway, including low-density lipoprotein receptor related protein-6 phosphorylation, β-catenin, and glycogen synthase kinase-3β phosphorylation. These results indicate that methylprednisolone-induced neuroprotection may correlate with activation of the Wnt/β-catenin signaling pathway.

High-mobility group box 1 induces neuron autophagy in a rat spinal root avulsion model

Autophagy, a tightly regulated lysosome-dependent catabolic pathway, is implicated in various pathological states in the nervous system. High-mobility group box 1 (HMGB1) is an inflammatory mediator known to be released into the local microenvironment from damaged cells. However, whether autophagy is induced and exogenous HMGB1 is involved in the process of spinal root avulsion remain unclear. Here, we investigated the induction effect of autophagy and the possible role of HMGB1 during spinal root avulsion. It was found that autophagy was activated in the anterior horn of the spinal cord as represented by the increased expression of the autophagic marker microtubule-associated protein light chain 3-II (LC3-II), degradation of sequestosome 1 (p62), and formation of autophagosomes, and that autophagy was inhibited after intraperitoneal injection of anti-HMGB1-neutralizing antibodies in the rat spinal root avulsion model. In addition, HMGB1-induced autophagy and activated mitogen-activated protein kinases (MAPKs) in primary spinal neurons, including c-Jun N-terminal kinase (JNK), extracellular-signal-regulated kinase (ERK), and p38MAPK. Inhibition of JNK or ERK activity significantly blocked the effect of HMGB1-induced autophagy in primary spinal neurons. Finally, HMGB1-induced autophagy increased cell viability in primary spinal neurons under oxygen-glucose deprivation conditions. The above results suggest that HMGB1 is a critical regulator of autophagy and HMGB1-induced autophagy plays an important role in protecting spinal neurons against injury, which may provide new insights into the pathophysiological process of spinal root avulsion.

G-CSF promotes autophagy and reduces neural tissue damage after spinal cord injury in mice

Granulocyte colony-stimulating factor (G-CSF) was investigated for its capacity to induce autophagy and related neuroprotective mechanisms in an acute spinal cord injury model. To accomplish this goal, we established a mouse spinal cord hemisection model to test the effects of recombinant human G-CSF. The results showed that autophagy was activated after spinal cord injury and G-CSF appears to induce a more rapid activation of autophagy within injured spinal cords as compared with that of non-treated animals. Apoptosis as induced in mechanically injured neurons with G-CSF treatment was enhanced after inhibiting autophagy by 3-methyladenine (3-MA), which partially blocked the neuroprotective effect of autophagy as induced by G-CSF. In addition, G-CSF inhibited the activity of the NF-κB signal pathway in neurons after mechanical injury. We conclude that G-CSF promotes autophagy by inhibiting the NF-κB signal pathway and protects neuronal structure after spinal cord injury. We therefore suggest that G-CSF, which rapidly induces autophagy after spinal cord injury to inhibit neuronal apoptosis, may thus provide an effective auxiliary therapeutic intervention for spinal cord injury.

HDAC6 Regulates the Chaperone-Mediated Autophagy to Prevent Oxidative Damage in Injured Neurons after Experimental Spinal Cord Injury

Hypoxia-ischemia- (HI-) induced oxidative stress plays a role in secondary pathocellular processes of acute spinal cord injury (SCI) due to HI from many kinds of mechanical trauma. Increasing evidence suggests that the histone deacetylase-6 (HDAC6) plays an important role in cell homeostasis in both physiological and abnormal, stressful, pathological conditions. This paper found that inhibition of HDAC6 accelerated reactive oxygen species (ROS) generation and cell apoptosis in response to the HI. Deficiency of HDAC6 hindered the chaperone-mediated autophagy (CMA) activity to resistance of HI-induced oxidative stress. Furthermore, this study provided the experimental evidence for the potential role of HDAC6 in the regulation of CMA by affecting HSP90 acetylation. Therefore, HDAC6 plays an important role in the function of CMA pathway under the HI stress induced by SCI and it may be a potential therapeutic target in acute SCI model.

Neuroprotective effects of Ganoderma lucidum polysaccharides against traumatic spinal cord injury in rats

INTRODUCTION

Ganoderma lucidum (G. lucidum) is a mushroom belonging to the polyporaceae family of Basidiomycota and has widely been used as a traditional medicine for thousands of years. G. lucidum has never been studied in traumatic spinal cord injury. The aim of this study is to investigate whether G. lucidum polysaccharides (GLPS) can protect the spinal cord after experimental spinal cord injury.

MATERIALS AND METHODS

Rats were randomized into five groups of eight animals each: control, sham, trauma, GLPS, and methylprednisolone. In the control group, no surgical intervention was performed. In the sham group, only a laminectomy was performed. In all the other groups, the spinal cord trauma model was created by the occlusion of the spinal cord with an aneurysm clip. In the spinal cord tissue, caspase-3 activity, tumour necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, nitric oxide levels, and superoxide dismutase levels were analysed. Histopathological and ultrastructural evaluations were also performed. Neurological evaluation was performed using the Basso, Beattie, and Bresnahan locomotor scale and the inclined-plane test.

RESULTS

After traumatic spinal cord injury, increases in caspase-3 activity, tumour necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, and nitric oxide levels were detected. After the administration of GLPS, decreases were observed in tissue caspase-3 activity, tumour necrosis factor-alpha levels, myeloperoxidase activity, malondialdehyde levels, and nitric oxide levels. Furthermore, GLPS treatment showed improved results in histopathological scores, ultrastructural scores, and functional tests.

CONCLUSIONS

Biochemical, histopathological, and ultrastructural analyses and functional tests reveal that GLPS exhibits meaningful neuroprotective effects against spinal cord injury.

Neuroprotective Effect of Simvastatin via Inducing the Autophagy on Spinal Cord Injury in the Rat Model

Simvastatin, an inhibitor of 3-hydroxy-3-methylglutaryl-coenzyme A reductase, is invariably used to treat cardiovascular diseases. Simvastatin has been recently demonstrated to have a neuroprotective effect in nervous system diseases. The present study aimed to further verify the neuroprotection and molecular mechanism of simvastatin on rats after spinal cord injury (SCI). The expression of Beclin-1 and LC3-B was evidently enhanced at postoperation days 3 and 5, respectively. However, the reduction of the mTOR protein and ribosomal protein S6 kinase p70 subtype (p70S6K) phosphorylation level occurred at the same time after SCI. Simvastatin significantly increased the expression of brain-derived neurotrophic factor (BDNF) and glial cell line-derived neurotrophic factor (GDNF). Meanwhile, immunofluorescence results indicated that the expression of chondroitin sulfate proteoglycan (CSPG) and caspase-3 protein was obviously reduced by simvastatin. Furthermore, Nissl staining and Basso, Beattie, and Bresnahan (BBB) scores showed that the quantity and function of motor neurons were visibly preserved by simvastatin after SCI. The findings of this study showed that simvastatin induced autophagy by inhibiting the mTOR signaling pathway and contributed to neuroprotection after SCI.

Autophagy and the Kidney: Implications for Ischemia-Reperfusion Injury and Therapy

Autophagy, an evolutionary conserved intracellular lysosome-dependent catabolic process, is an important mechanism for cellular homeostasis and survival during pathologic stress conditions in the kidney, such as ischemia-reperfusion injury (IRI). However, stimulation of autophagy has been described to both improve and exacerbate IRI in the kidney. We summarize the current understanding of autophagy in renal IRI and discuss possible reasons for these contradictory findings. Furthermore, we hypothesize that autophagy plays a dual role in renal IRI, having both protective and detrimental properties, depending on the duration of the ischemic period and the phase of the IRI process. Finally, we discuss the influence of currently used diuretics and immunosuppressive drugs on autophagy, underscoring the need to clarify the puzzling role of autophagy in renal IRI.