Role of autophagy in the bimodal stage after spinal cord ischemia reperfusion injury in rats

Mesenchymal stem cell-derived exosomes as a new drug carrier for the treatment of spinal cord injury: A review

Spinal cord injury (SCI) is a devastating traumatic disease seriously impairing the quality of life in patients. Expectations to allow the hopeless central nervous system to repair itself after injury are unfeasible. Developing new approaches to regenerate the central nervous system is still the priority. Exosomes derived from mesenchymal stem cells (MSC-Exo) have been proven to robustly quench the inflammatory response or oxidative stress and curb neuronal apoptosis and autophagy following SCI, which are the key processes to rescue damaged spinal cord neurons and restore their functions. Nonetheless, MSC-Exo in SCI received scant attention. In this review, we reviewed our previous work and other studies to summarize the roles of MSC-Exo in SCI and its underlying mechanisms. Furthermore, we also focus on the application of exosomes as drug carrier in SCI. In particular, it combs the advantages of exosomes as a drug carrier for SCI, imaging advantages, drug types, loading methods, etc., which provides the latest progress for exosomes in the treatment of SCI, especially drug carrier.

The Temporal and Spatial Changes of Autophagy and PI3K Isoforms in Different Neural Cells After Hypoxia/Reoxygenation Injury

There are limited therapeutic options for patient with traumatic spinal cord injury (SCI). Phosphoinositide 3-kinase family (PI3Ks) are the key molecules for regulating cell autophagy, which is a possible way of treating SCI. As we know, PI3K family are composed of eight isoforms, which are distributed into three classes. While the role of PI3Ks in regulating autophagy is controversial and the effects may be in a cell-specific manner. Different isoforms do not distribute in neural cells consistently and it is not clear how the PI3K isoforms regulate and interact with autophagy. Therefore, we explored the distributions and expression of different PI3K isoforms in two key neural cells (PC12 cells and astrocytes). The results showed that the expression of LC3II/I and p62, which are the markers of autophagy, changed in different patterns in PC12 cells and astrocytes after hypoxia/reoxygenation injury (H/R). Furthermore, the mRNA level of eight PI3K isoforms did not change in the same way, and even for the same isoform the mRNA activities are different between PC12 cells and astrocytes. What is more, the results of western blot of PI3K isoforms after H/R were inconsistent with the relevant mRNA. Based on this study, the therapeutic effects of regulating autophagy on SCI are not confirmed definitely, and its molecular mechanisms may be related with different temporal and spatial patterns of activation and distributions of PI3K isoforms.

Ca2+ Regulates Autophagy Through CaMKKβ/AMPK/mTOR Signaling Pathway in Mechanical Spinal cord Injury: An in vitro Study

Spinal cord injury (SCI), resulting in damage of the normal structure and function of the spinal cord, would do great harm to patients, physically and psychologically. The mechanism of SCI is very complex. At present, lots of studies have reported that autophagy was involved in the secondary injury process of SCI, and several researchers also found that calcium ions (Ca²⁺) played an important role in SCI by regulating necrosis, autophagy, or apoptosis. However, to our best of knowledge, no studies have linked the spinal cord mechanical injury, intracellular Ca²⁺, and autophagy in series. In this study, we have established an in vitro model of SCI using neural cells from fetal rats to explore the relationship among them, and found that mechanical injury could promote the intracellular Ca²⁺ concentration, and the increased Ca²⁺ level activated autophagy through the CaMKKβ/AMPK/mTOR pathway. Additionally, we found that apoptosis was also involved in this pathway. Thus, our study provides new insights into the specific mechanisms of SCI and may open up new avenues for the treatment of SCI.

Targeting autophagy process in center nervous trauma

The central nervous system (CNS) is the primary regulator of physiological activity, and when CNS is compromised, its physical functions are affected. Spinal cord injury (SCI) and traumatic brain injury (TBI) are common trauma in CNS that are difficult to recover from, with a higher global disability and mortality rate. Autophagy is familiar to almost all researchers due to its role in regulating the degradation and recycling of cellular defective or incorrect proteins and toxic components, maintaining body balance and regulating cell health and function. Emerging evidence suggests it has a broad and long-lasting impact on pathophysiological process such as oxidative stress, inflammation, apoptosis, and angiogenesis, involving the alteration of autophagy marker expression and function recovery. Changes in autophagy level are considered a potential therapeutic strategy and have shown promising results in preclinical studies for neuroprotection following traumatic brain injury. However, the relationship between upward or downward autophagy and functional recovery following SCI or TBI is debatable. This article reviews the regulation and role of autophagy in repairing CNS trauma and the intervention effects of autophagy-targeted therapeutic agents to find more and better treatment options for SCI and TBI patients.

FDA-Approved Kinase Inhibitors in Preclinical and Clinical Trials for Neurological Disorders

Cancers and neurological disorders are two major types of diseases. We previously developed a new concept termed "Aberrant Cell Cycle Diseases" (ACCD), revealing that these two diseases share a common mechanism of aberrant cell cycle re-entry. The aberrant cell cycle re-entry is manifested as kinase/oncogene activation and tumor suppressor inactivation, which are hallmarks of both tumor growth in cancers and neuronal death in neurological disorders. Therefore, some cancer therapies (e.g., kinase inhibition, tumor suppressor elevation) can be leveraged for neurological treatments. The United States Food and Drug Administration (US FDA) has so far approved 74 kinase inhibitors, with numerous other kinase inhibitors in clinical trials, mostly for the treatment of cancers. In contrast, there are dire unmet needs of FDA-approved drugs for neurological treatments, such as Alzheimer's disease (AD), intracerebral hemorrhage (ICH), ischemic stroke (IS), traumatic brain injury (TBI), and others. In this review, we list these 74 FDA-approved kinase-targeted drugs and identify those that have been reported in preclinical and/or clinical trials for neurological disorders, with a purpose of discussing the feasibility and applicability of leveraging these cancer drugs (FDA-approved kinase inhibitors) for neurological treatments.

Dysregulated autophagic activity induced in response to chronic intermittent hypoxia contributes to the pathogenesis of NAFLD

Chronic intermittent hypoxia (CIH) is a pathological characteristic of obstructive sleep apnea (OSA) that has been linked to the pathogenesis of nonalcoholic fatty liver disease (NAFLD). The specific link between CIH, autophagic activity, and NAFLD, however, has not previously been characterized. The goal of this study was to assess the relationship between CIH-induced autophagy and the pathogenesis of OSA-associated NAFLD. Western blotting was used to assess the expression of proteins associated with lipid synthesis, endoplasmic reticulum (ER) stress, and autophagic activity. To establish an in vivo model system, C57BL/6 mice were subjected to CIH conditions for 8 h per day over a 12-week period, and were administered chloroquine (CQ) for 1 week prior to euthanization. Levels of serum and liver triglycerides in these animals were assessed, as were proteins related to hepatic autophagy, ER stress, and lipogenesis. qPCR was additionally used to assess hepatic inflammation-related gene expression, while transmission electron microscopy was used to monitor lipid droplet (LD) accumulation and ER morphology. OSA patients and CIH model mice exhibited increases in the expression of proteins associated with hepatic autophagy, ER stress, and lipogenesis. CIH was also associated with more pronounced LD accumulation, hepatic inflammation, and hepatic steatosis in these mice. While serum and hepatic TG and TC levels and serum ALT/AST were increased in response to CIH treatment, the administration of CQ to these mice led to reductions in ER stress-related proteins (XBP1, IRE1α, EIF2α) and lipogenesis-related proteins (ACC, SCD1, FASn), in addition to significantly reducing hepatic inflammation, steatosis, and LD accumulation in these animals. These results suggest that persistent CIH can drive dysregulated hepatic autophagic activity, hepatic steatosis, and ER stress, highlighting potential targets for therapeutic intervention aimed at preventing or treating OSA-associated NAFLD.

The PI3K/AKT signalling pathway in inflammation, cell death and glial scar formation after traumatic spinal cord injury: Mechanisms and therapeutic opportunities

Objects

Traumatic spinal cord injury (TSCI) causes neurological dysfunction below the injured segment of the spinal cord, which significantly impacts the quality of life in affected patients. The phosphoinositide 3kinase/serine‐threonine kinase (PI3K/AKT) signaling pathway offers a potential therapeutic target for the inhibition of secondary TSCI. This review summarizes updates concerning the role of the PI3K/AKT pathway in TSCI.

Materials and Methods

By searching articles related to the TSCI field and the PI3K/AKT signaling pathway, we summarized the mechanisms of secondary TSCI and the PI3K/AKT signaling pathway; we also discuss current and potential future treatment methods for TSCI based on the PI3K/AKT signaling pathway.

Results

Early apoptosis and autophagy after TSCI protect the body against injury; a prolonged inflammatory response leads to the accumulation of pro‐inflammatory factors and excessive apoptosis, as well as excessive autophagy in the surrounding normal nerve cells, thus aggravating TSCI in the subacute stage of secondary injury. Initial glial scar formation in the subacute phase is a protective mechanism for TSCI, which limits the spread of damage and inflammation. However, mature scar tissue in the chronic phase hinders axon regeneration and prevents the recovery of nerve function. Activation of PI3K/AKT signaling pathway can inhibit the inflammatory response and apoptosis in the subacute phase after secondary TSCI; inhibiting this pathway in the chronic phase can reduce the formation of glial scar.

Conclusion

The PI3K/AKT signaling pathway has an important role in the recovery of spinal cord function after secondary injury. Inducing the activation of PI3K/AKT signaling pathway in the subacute phase of secondary injury and inhibiting this pathway in the chronic phase may be one of the potential strategies for the treatment of TSCI.

Sulforaphane Ameliorates Limb Ischemia/Reperfusion-Induced Muscular Injury in Mice by Inhibiting Pyroptosis and Autophagy via the Nrf2-ARE Pathway

Background

Limb ischemia/reperfusion (I/R) injury, as a life-threatening syndrome, is commonly caused by skeletal muscle damage resulting from oxidative stress. Additionally, inflammation-induced pyroptosis and dysregulated autophagy are vital factors contributing to the aggravation of I/R injury. Of note, sulforaphane (SFN) is a natural antioxidant, but whether it worked in limb I/R injury and the possible mechanism behind its protection for skeletal muscle has not been clearly established.

Methods

Effects of SFN on limb I/R-injured skeletal muscle were assessed by HE staining, followed by assessment of wet weight/dry weight (W/D) ratio of muscle tissues. Next, ELISA and biochemical tests were used to measure the inflammatory cytokine production and oxidative stress. Immunofluorescent analysis and Western blot were adopted to examine the level of pyroptosis- and autophagy-related proteins in vivo. Moreover, protein levels of Nrf2-ARE pathway-related factors were also examined using Western blot.

Results

SFN treatment could protect skeletal muscle against limb I/R injury, as evidenced by diminished inflammation, pyroptosis, autophagy, and oxidative stress in skeletal muscles of mice. Further mechanistic exploration confirmed that antioxidative protection of SFN was associated with the Nrf2-ARE pathway activation.

Conclusions

SFN activates the Nrf2-ARE pathway, and thereby inhibits pyroptosis and autophagy and provides a novel therapeutic strategy for the limb I/R-induced muscle tissue damage.

Specific microRNAs for Modulation of Autophagy in Spinal Cord Injury

The treatment of spinal cord injury (SCI) is currently a major challenge, with a severe lack of effective therapies for yielding meaningful improvements in function. Therefore, there is a great opportunity for the development of novel treatment strategies for SCI. The modulation of autophagy, a process by which a cell degrades and recycles unnecessary or harmful components (protein aggregates, organelles, etc.) to maintain cellular homeostasis and respond to a changing microenvironment, is thought to have potential for treating many neurodegenerative conditions, including SCI. The discovery of microRNAs (miRNAs), which are short ribonucleotide transcripts for targeting of specific messenger RNAs (mRNAs) for silencing, shows prevention of the translation of mRNAs to the corresponding proteins affecting various cellular processes, including autophagy. The number of known miRNAs and their targets continues to grow rapidly. This review article aims to explore the relationship between autophagy and SCI, specifically with the intent of identifying specific miRNAs that can be useful to modulate autophagy for neuroprotection and the improvement of functional recovery in SCI.

Bone marrow mesenchymal stem cell derived exosomal miR-455-5p protects against spinal cord ischemia reperfusion injury

At present, much more studies have focused on the therapeutic effect of exosome-delivered microRNAs on diseases. Previous study has shown that miR-455-5p is downregulated in ischemic stroke, but little is known about the role of exosome-delivered miR-455-5p in spinal cord ischemia reperfusion (SCIR) injury. Herein, we isolated exosomes from bone marrow mesenchymal stem cells (BMSCs) transfected with lentivirus vectors containing miR-455-5p. SCIR rat model was established after the intrathecal injection of exosomes containing miR-455-5p. The expression level of miR-455-5p was downregulated after SCIR, administration of exosomal miR-455-5p enhanced the level of miR-455-5p in the injured spinal cord. Hind-limb motor function scores indicated that exosomal miR-455-5p improved the recovery of hind-limb function of SCIR rats. HE staining and Nissl staining showed that miR-455-5p enriched exosomes reduced histopathological abnormalities after SCIR. Double immunofluorescence staining revealed that exosomes containing miR-455-5p reduced apoptosis of neurons, and activated autophagy in neurons after SCIR. We observed that the expression of Nogo-A, a direct target of miR-455-5p, was decreased in the spinal cord of exosomal miR-455-5p administrated SCIR rats. Targeting relationship between miR-455-5p and Nogo-A was verified by dual-luciferase reporter assay. In summary, exosomes containing miR-455-5p had the neuroprotective effects on SCIR injury by promoting autophagy and inhibiting apoptosis of neurons.

The Potential Therapeutic Effects of Agmatine, Methylprednisolone, and Rapamycin on Experimental Spinal Cord Injury

OBJECTIVE

In spinal cord injury (SCI), the primary mechanical damage leads to a neuroinflammatory response and the secondary neuronal injury occurs in response to the release of reactive oxygen species (ROS). In addition to the suppression of inflammation, autophagy plays a significant role in the survival of neurons during secondary SCI. The present study aimed to examine the anti-inflammatory and autophagic effects of agmatine and rapamycin in SCI and to compare the results with methylprednisolone (MP) used in the clinic.

MATERIALS AND METHODS

In this animal-based experimental study, thirty adult male Sprague-Dawley rats were randomly divided into five groups as sham-control, injury, injury+MP, injury+rapamycin, injury+agmatine groups. SCI was induced by compressing the T7-8-9 segments of the spinal cord, using an aneurysm clip for one minute, and then rats were treated daily for 7 days. Seven days post-treatment, damaged spinal cord tissues of sacrificed rats were collected for microscopic and biochemical examinations using histopathologic and transmission electron microscope (TEM) scores. Malondialdehyde (MDA) and glutathione peroxidase (GPx) levels were spectrophotometrically measured.

RESULTS

The results of this study showed that the damaged area was smaller in the rapamycin group when compared to the MP group. Many autophagic vacuoles and macrophages were observed in the rapamycin group. Degeneration of axon, myelin, and wide edema was observed in SCI by electron microscopic observations. Fragmented myelin lamellae and contracted axons were also noted. While MDA and GPx levels were increased in the injury group, MDA levels were significantly decreased in the agmatine and MP groups, and GPx levels were decreased in the rapamycin group.

CONCLUSION

The results of our study confirmed that rapamycin and agmatine can be an effective treatment for secondary injury of SCI.

Insulin-like growth factor 1 promotes neurological functional recovery after spinal cord injury through inhibition of autophagy via the PI3K/Akt/mTOR signaling pathway

Spinal cord injury (SCI) is a serious trauma; however, the mechanisms underlying the role of insulin-like growth factor 1 (IGF-1) in autophagy following SCI remain to be elucidated. The present study aimed to investigate the therapeutic effect of IGF-1 on SCI and to determine whether IGF-1 regulates autophagy via the PI3K/Akt/mTOR signaling pathway. SH-SY5Y neuroblastoma cells were assigned to the H₂O₂, IGF-1 and control groups to investigate subsequent neuron injury in vitro. An MTT assay was performed to evaluate cell survival. In addition, Sprague-Dawley rats were randomly assigned to SCI, SCI + IGF-1 and sham groups, and Basso-Beatlie-Bresnahan scores were assessed to determine rat neurological function. Western blotting was used to analyze the autophagy level and the activation of the PI3K/Akt/mTOR signaling pathway. Cell survival was increased significantly in the IGF-1 group compared with the control group in vitro (P<0.05). Furthermore, neurological function was improved in the SCI + IGF-1 group compared with the control group in vivo (P<0.05). The western blotting results further demonstrated that LC3II/LC3I expression was increased in the IGF-1 group compared with the sham group in vivo and compared with the control group in vitro (both P<0.05). In the SCI + IGF-1 group, the expression levels of PI3K, phosphorylated (p)-Akt and p-mTOR were higher compared with those in the sham and SCI groups in vivo (P<0.05). Moreover, in the IGF-1 group, the expression levels of p-Akt and p-mTOR were higher compared with the control and the H₂O₂ groups in vitro (P<0.05). Collectively, the results of the present study suggested that IGF-1 promoted functional recovery in rats following SCI through neuroprotective effects. Furthermore, the underlying mechanism may involve activation of the PI3K/Akt/mTOR signaling pathway, followed by inhibition of autophagy. However, further investigation into the association between IGF-1-regulated autophagy and the activation of different subtypes of PI3K is required.

Induction of ischemic tolerance by remote perconditioning or postconditioning as neuroprotective strategy for spinal cord motor neurons

AIMS

The study is focused on the investigation of the mechanisms leading to ischemic tolerance acquisition in the spinal cord neurons via application of non-invasive method of remote conditioning.

MATERIAL AND METHODS

We have verified the possibility of neuroprotection of spinal cord in rabbit by using remote perconditioning (PerC) applied during last 12 min of spinal cord ischemia (SC-ischemia) or postconditioning (PostC) applied after 1st (early) or 3rd (late) h of reperfusion. Spinal cord ischemia was induced by occlusion of the aorta below the left renal artery for 20 min. Reperfusion period was 24 or 72 h. Remote conditioning was induced by compression of left forelimb with a tourniquet in 3 cycles of 2 min of ischemia, each followed by 2 min of reperfusion. Damaged neurons were detected by Fluoro Jade B method and the modified Tarlov score was used for functional assessment.

KEY FINDINGS

The remote conditioning significantly attenuated degeneration of motor neurons in all remote conditioned groups versus both SC-ischemia groups. We detected significant changes in number of Hsp70 positive motor neurons. At 72time point, in the group with remote late PostC we observed significant increase (p < 0.001) of Hsp70 positive motor neurons versus SC- ischemia group and sham control. There was a trend towards improvement of hindlimbs movement.

SIGNIFICANCE

This study showed the effectiveness of remote conditioning as a neuroprotective strategy, evidenced by induction of ischemic tolerance leading to decrease of motor neuron degeneration.

Bioinformatics-Based Analysis of the lncRNA-miRNA-mRNA Network and TF Regulatory Network to Explore the Regulation Mechanism in Spinal Cord Ischemia/Reperfusion Injury

Background

Spinal cord ischemia/reperfusion injury (SCII) is a catastrophic complication involved with cardiovascular, spine, and thoracic surgeries and can lead to paraplegia. Nevertheless, the molecular mechanism of SCII remain ill-defined.

Methods

Expression profiling (GSE138966) data were obtained from GEO database. Then, differentially expressed (DE) lncRNAs and DEmRNAs were screened out with p < 0.05, and | fold change| > 1.5. Aberrant miRNAs expression in SCII was obtained from PubMed. Functional enrichment analysis of overlapping DEmRNAs between predicted mRNAs in miRDB database and DEmRNAs obtained from GSE138966 was performed using cluster Profiler R package. The lncRNA-miRNA-mRNA competitive endogenous RNA (ceRNA) network was established in light of ceRNA theory. The key lncRNAs in the ceRNA network were identified by topological analysis. Subsequently, key lncRNAs related ceRNA-pathway network and transcription factors (TFs)-mRNAs network were constructed. Simultaneously, the expression levels of hub genes were measured via qRT-PCR.

Results

The results in this study indicated that 76 miRNAs, 1373 lncRNAs, and 4813 mRNAs were differentially expressed in SCII. A SCII-related ceRNA network was constructed with 154 ncRNAs, 139 mRNAs, and 51 miRNAs. According topological analysis, six lncRNAs (NONRATT019236.2, NONRATT009530.2, NONRATT026999.2, TCONS_00032391, NONRATT023112.2, and NONRATT021956.2) were selected to establish the ceRNA-pathway network, and then two candidate hub lncRNAs (NONRATT009530.2 and NONRATT026999.2) were identified. Subsequently, two lncRNA-miRNA-mRNA regulatory axes were identified. NONRATT026999.2 and NONRATT009530.2 might involve SCII via miR-20b-5p/Map3k8 axis based on the complex ceRNA network. SP1 and Hnf4a acting as important TFs might regulate Map3k8. Furthermore, qRT-PCR results showed that the NONRATT009530.2, NONRATT026999.2, Map3k8, Hfn4a, and SP1 were significantly upregulated in SCII of rats, while the miR-20b-5p was downregulated.

Conclusion

Our results offer a new insight to understand the ceRNA regulation mechanism in SCII and identify highlighted lncRNA-miRNA-mRNA axes and two key TFs as potential targets for prevention and treatment of SCII.

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.

Antibiotics with therapeutic effects on spinal cord injury: a review

Accumulating evidence indicates that a considerable number of antibiotics exert anti-inflammatory and neuroprotective effects in different central and peripheral nervous system diseases including spinal cord injury (SCI). Both clinical and preclinical studies on SCI have found therapeutic effects of antibiotics from different families on SCI. These include macrolides, minocycline, β-lactams, and dapsone, all of which have been found to improve SCI sequels and complications. These antibiotics may target similar signaling pathways such as reducing inflammatory microglial activity, promoting autophagy, inhibiting neuronal apoptosis, and modulating the SCI-related mitochondrial dysfunction. In this review paper, we will discuss the mechanisms underlying therapeutic effects of these antibiotics on SCI, which not only could supply vital information for investigators but also guide clinicians to consider administering these antibiotics as part of a multimodal therapeutic approach for management of SCI and its complications.

Therapeutic effects of rapamycin and surgical decompression in a rabbit spinal cord injury model

Surgical decompression after spinal cord injury (SCI) is a conventional treatment. Although it has been proven to have clinical effects, there are certain limitations, such as the surgical conditions that must be met and the invasive nature of the treatment. Therefore, there is an urgent need to develop a simple and maneuverable therapy for the emergency treatment of patients with SCI before surgery. Rapamycin (RAPA) has been reported to have potential as a therapeutic agent for SCI. In this study, we observed the therapeutic effects of rapamycin and surgical decompression, in combination or separately, on the histopathology in rabbits with SCI. After combination therapy, intramedullary pressure (IMP) decreased significantly, autophagic flux increased, and apoptosis and demyelination were significantly reduced. Compared with RAPA/surgical decompression alone, the combination therapy had a significantly better effect. In addition, we evaluated the effects of mechanical pressure on autophagy after SCI by assessing changes in autophagic initiation, degradation, and flux. Increased IMP after SCI inhibited autophagic degradation and impaired autophagic flux. Decompression improved autophagic flux after SCI. Our findings provide novel evidence of a promising strategy for the treatment of SCI in the future. The combination therapy may effectively improve emergency treatment after SCI and promote the therapeutic effect of decompression. This study also contributes to a better understanding of the effects of mechanical pressure on autophagy after neurotrauma.

Therapeutic effect of regulating autophagy in spinal cord injury: a network meta-analysis of direct and indirect comparisons

OBJECTIVE

An increasing number of studies indicate that autophagy plays an important role in the pathogenesis of spinal cord injury, and that regulating autophagy can enhance recovery from spinal cord injury. However, the effect of regulating autophagy and whether autophagy is detrimental or beneficial after spinal cord injury remain unclear. Therefore, in this study we evaluated the effects of autophagy regulation on spinal cord injury in rats by direct and indirect comparison, in an effort to provide a basis for further research.

DATA SOURCE

Relevant literature published from inception to February 1, 2018 were included by searching Wanfang, CNKI, Web of Science, MEDLINE (OvidSP), PubMed and Google Scholar in English and Chinese. The keywords included "autophagy", "spinal cord injury", and "rat".

DATA SELECTION

The literature included in vivo experimental studies on autophagy regulation in the treatment of spinal cord injury (including intervention pre- and post-spinal cord injury). Meta-analyses were conducted at different time points to compare the therapeutic effects of promoting or inhibiting autophagy, and subgroup analyses were also conducted.

OUTCOME MEASURE

Basso, Beattie, and Bresnahan scores.

RESULTS

Of the 622 studies, 33 studies of median quality were included in the analyses. Basso, Beattie, and Bresnahan scores were higher at 1 day (MD = 1.80, 95% CI: 0.81-2.79, P = 0.0004), 3 days (MD = 0.92, 95% CI: 0.72-1.13, P < 0.00001), 1 week (MD = 2.39, 95% CI: 1.85-2.92, P < 0.00001), 2 weeks (MD = 3.26, 95% CI: 2.40-4.13, P < 0.00001), 3 weeks (MD = 3.13, 95% CI: 2.51-3.75, P < 0.00001) and 4 weeks (MD = 3.18, 95% CI: 2.43-3.92, P < 0.00001) after spinal cord injury with upregulation of autophagy compared with the control group (drug solvent control, such as saline group). Basso, Beattie, and Bresnahan scores were higher at 1 day (MD = 6.48, 95% CI: 5.83-7.13, P < 0.00001), 2 weeks (MD = 2.43, 95% CI: 0.79-4.07, P = 0.004), 3 weeks (MD = 2.96, 95% CI: 0.09-5.84, P = 0.04) and 4 weeks (MD = 4.41, 95% CI: 1.08-7.75, P = 0.01) after spinal cord injury with downregulation of autophagy compared with the control group. Indirect comparison of upregulation and downregulation of autophagy showed no differences in Basso, Beattie, and Bresnahan scores at 1 day (MD = -4.68, 95% CI: -5.840 to -3.496, P = 0.94644), 3 days (MD = -0.28, 95% CI: -2.231-1.671, P = 0.99448), 1 week (MD = 1.83, 95% CI: 0.0076-3.584, P = 0.94588), 2 weeks (MD = 0.81, 95% CI: -0.850-2.470, P = 0.93055), 3 weeks (MD = 0.17, 95% CI: -2.771-3.111, P = 0.99546) or 4 weeks (MD = -1.23, 95% CI: -4.647-2.187, P = 0.98264) compared with the control group.

CONCLUSION

Regulation of autophagy improves neurological function, whether it is upregulated or downregulated. There was no difference between upregulation and downregulation of autophagy in the treatment of spinal cord injury. The variability in results among the studies may be associated with differences in research methods, the lack of clearly defined autophagy characteristics after spinal cord injury, and the limited autophagy monitoring techniques. Thus, methods should be standardized, and the dynamic regulation of autophagy should be examined in future studies.

Time-Course Changes and Role of Autophagy in Primary Spinal Motor Neurons Subjected to Oxygen-Glucose Deprivation: Insights Into Autophagy Changes in a Cellular Model of Spinal Cord Ischemia

Spinal cord ischemia is a severe clinical complication induced by thoracoabdominal aortic surgery, severe trauma, or compression to the spinal column. As one of the most important functional cells in the spinal cord, spinal motor neurons (SMNs) suffer most during the process since they are vulnerable to ischemic injury due to high demands of energy. Previous researches have tried various animal models or organotypic tissue experiments to mimic the process and get to know the pathogenesis and mechanism. However, little work has been performed on the cellular model of spinal cord ischemia, which has been hampered by the inability to obtain a sufficient number of pure primary SMNs for in vitro study. By optimizing the isolation and culture of SMNs, our laboratory has developed an improved culture system of primary SMNs, which allows cellular models and thus mechanism studies. In the present study, by establishing an in vitro model of spinal cord ischemia, we intended to observe the dynamic time-course changes of SMNs and investigate the role of autophagy in SMNs during the process. It was found that oxygen-glucose deprivation (OGD) resulted in destruction of neural networks and decreased cell viability of primary SMNs, and the severity increased with the prolonging of the OGD time. The OGD treatment enhanced autophagy, which reached a peak at 5 h. Further investigation demonstrated that inhibition of autophagy exacerbated the injury, evidencing that autophagy plays a protective role during the process.

Direct Peritoneal Resuscitation with Pyruvate Protects the Spinal Cord and Induces Autophagy via Regulating PHD2 in a Rat Model of Spinal Cord Ischemia-Reperfusion Injury

Direct peritoneal resuscitation with pyruvate (Pyr-PDS) has emerged as an interesting candidate to alleviate injury in diverse organs, while the potential mechanism has yet to be fully elucidated. To explore the effect of autophagy in the spinal cord ischemia-reperfusion (SCIR) injury and the underlying mechanism, we established a model of SCIR in vivo and in vitro. In vivo, male SD rats underwent aortic occlusion for 60 min and then followed by intraperitoneally infused with 20 mL of pyruvate or normal saline for 30 min, and the spinal cords were removed for analysis after 48 h of reperfusion. The functional and morphological results showed that Pyr-PDS alleviated SCIR injury; meanwhile, the expression of autophagy-related genes and transmission electron microscopy displayed autophagy was activated by SCIR injury, and Pyr-PDS treatment could further upregulate the degree of autophagy which plays a protective part in the SCIR injury, while there is no significant difference after treatment with saline. In addition, SCIR injury inhibited expression of PHD2, which results to activate its downstream HIF-1α/BNIP3 pathway to promote autophagy. In the Pyr-PDS, the results revealed PHD2 was further inhibited compared to the SCIR group, which could further activate the HIF-1α/BNIP3 signaling pathway. Additionally, oxygen-glucose deprivation and reoxygenation were applied to SH-SY5Y cells to mimic anoxic conditions in vitro, and the expression of autophagy-related genes, PHD2, and its downstream HIF-1α/BNIP3 pathway showed the same trend as the results in vivo. Besides, IOX2, a specific inhibitor of PHD2 was also treated to SH-SY5Y cells during reoxygenation, in which the result is as same as the pyruvate group. Then, we observed the expression of autophagy-related genes and the HIF-1α signal pathway in the process of reoxygenation; the results showed that as the reoxygenation goes, the expression of the HIF-1α signal pathway and degree of autophagy came to decrease gradually, while treated with pyruvate could maintain autophagy high and stable through keeping PHD2 at a lower level during reoxygenation, and the latter was observed downregulated during reoxygenation process from 0 to 24 hours in a time-effect way. The above results indicated that direct peritoneal resuscitation with pyruvate showed effective protection to ischemia-reperfusion of the spinal cord through activating autophagy via acting on PHD2 and its downstream HIF-1α/BNIP3 pathway.

Angiopoietin-1 Protects Spinal Cord Ischemia and Reperfusion Injury by Inhibiting Autophagy in Rats

Spinal cord ischemia and reperfusion (SCIR) injury can induce autophagy, which is involved in the survival of neurons. However, whether autophagy plays a neuroprotective or a detrimental role in SCIR injury remains controversial. Angiopoietin-1 (Ang-1), an endothelial growth factor, has been shown to have neuroprotective effects. The present study aimed to explore the neuroprotective mechanisms of Ang-1 in neuronal cells in a rat model of SCIR injury in vivo. Ang-1 protein and rapamycin were injected intrathecally. Basso Beattie Bresnahan (BBB) scoring and hematoxylin and eosin staining were used to assess the degree of SCIR injury. Proteins that reflected the level of autophagy expression, such as Beclin-1 and LC3, were evaluated by western blotting. The results indicated that SCIR injury resulted in loss in lower limb motor function. Ang-1 protein inhibited the expression of Beclin-1 and LC3, which improved the BBB score and alleviated spinal cord injury. In contrast, rapamycin, an autophagy activator, caused the opposite effect. This study provides evidence that Ang-1 plays a neuroprotective role by inhibiting of autophagy expression in SCIR injury. Overall, findings could be useful for the treatment of SCIR injury.

Emerging molecular therapeutic targets for spinal cord injury

Introduction: Spinal cord injury (SCI) is a complicated and devastating neurological disorder. Patients with SCI usually have dramatically reduced quality of life. In recent years, numerous studies have reported advances in understanding the pathophysiology of SCI and developing preclinical therapeutic strategies for SCI, including various molecular therapies, and yet there is still no cure. Areas covered: After SCI, tissue damage, responses and repair involve interactions among many cellular components, including neurons, axons, glia, leukocytes, and other cells. Accordingly, numerous cellular genes and molecules have become therapeutic targets for neural tissue repair, circuit reconstruction, and behavioral restoration. Here, we review the major recent advances in biological and molecular strategies to enhance neuroprotection, axon regeneration, remyelination, neuroplasticity and functional recovery in preclinical studies of SCI. Expert opinion: Researchers have made tremendous progress in identifying individual and combined molecular therapies in animal studies. It is very important to identify additional highly effective treatments for early neuroprotective intervention and for functionally meaningful axon regeneration and neuronal reconnections. Because multiple mechanisms contribute to the functional loss after SCI, combining the most promising approaches that target different pathophysiological and molecular mechanisms should exhibit synergistic actions for maximal functional restoration. [Databases searched: PubMed; inclusive dates: 6/27/2019].

MLN4924 Exerts a Neuroprotective Effect against Oxidative Stress via Sirt1 in Spinal Cord Ischemia-Reperfusion Injury

Oxidative stress is a leading contributor to spinal cord ischemia-reperfusion (SCIR) injury. Recently, MLN4924, a potent and selective inhibitor of the NEDD8-activating enzyme, was shown to exert a neuroprotective effect against oxidative stress in vitro. However, it is unknown whether MLN4924 plays a protective role against SCIR injury. In the present study, we found that MLN4924 treatment significantly attenuated oxidative stress and neuronal cell death induced by H₂O₂ in SH-SY-5Y neural cells and during rat SCIR injury. Furthermore, MLN4924 administration restored neurological and motor functions in rats with SCIR injury. Mechanistically, we found that MLN4924 protects against H₂O₂- and SCIR injury-induced neurodegeneration by regulating sirtuin 1 (Sirt1) expression. Collectively, these findings demonstrate the neuroprotective role of MLN4924 against oxidative stress in SCIR injury via Sirt1.

Hydrogen sulfide plays an important protective role by influencing autophagy in diseases

Autophagy can regulate cell growth, proliferation, and stability of cell environment. Its dysfunction can be involved in a variety of diseases. Hydrogen sulfide (H(2)S) is an important signaling molecule that regulates many physiological and pathological processes. Recent studies indicate that H(2)S plays an important protective role in many diseases through influencing autophagy, but its mechanism is not fully understood. This article reviewed the progress about the effect of H(2)S on autophagy in diseases in recent years in order to provide theoretical basis for the further research on the interaction of H(2)S and autophagy and the mechanisms involved.

Edaravone inhibits autophagy after neuronal oxygen-glucose deprivation/recovery injury

PURPOSE OF THE STUDY

Edaravone is an oxygen free radical scavenger that is widely used to treat ischemic injury to the nervous system. This study investigated the effect of edaravone pretreatment on neurons subjected to oxygen-glucose deprivation/recovery (OGD/R) injury.

MATERIALS AND METHODS

Common neurons were subjected to oxygen and glucose deprivation for 1 h, followed by oxygen and glucose recovery for 0.5, 2, 6 and 12 h to establish the OGD/R model. Autophagy was assessed by electron microscope observation of autophagosomes, cell immunofluorescence, mRFP-GFP-LC3 virus cell fluorescence and western blotting analyses of the autophagy-related proteins. The findings showed that at OGD/R 2 h autophagy was high. Next, neurons were pretreated with different concentrations of edaravone (0, 5, 10, 25, 50 and 100 μM) before establishing the OGD/R model. Western blotting was used to analyze the expression of autophagy-related proteins. The CCK-8 assay was used to analyze cell viability after pretreatment with different concentrations of edaravone. Optimal inhibition of autophagy was achieved with the concentration of edaravone 50 μM. Neurons pretreated with 50 μM edaravone and established OGD/R model were analyzed for autophagy levels.

RESULTS

At every OGD/R time point autophagy was lower in neurons pretreated with edaravone than in those not pretreated with the drug. The difference was statistically significant without OGD/R 12 h.

CONCLUSIONS

Pretreatment with edaravone may reduce the level of autophagy in neurons subjected to OGD/R injury.

The effect of lithium chloride on the motor function of spinal cord injury–controlled rat and the relevant mechanism

The objective of this study is to discuss the effect and mechanism of lithium chloride on the rehabilitation of locomotion post spinal cord injury (SCI) by observing the effect of lithium chloride on the expression of the brain-derived neurotrophic factor (BDNF)/tropomyosin receptor kinase B (TrkB) pathway. In total, 36 Sprague-Dawley (SD) rats were randomly divided into the sham operation group (n = 12), model group (n = 12), and lithium chloride group (n = 12). The sham operation group underwent laminectomy, while for the model group and the lithium chloride group with the NYU spinal cord impactor the SCI model was established. Basso, Beattie, and Bresnahan (BBB) score was used to evaluate locomotion after administration for 1, 3, 5, and 7 days, and the tissues were gathered for Nissl staining, transmission electron microscopy, immunofluorescence, and Western blot. With a statistical difference ( P < 0.05) on the 3rd day and significant difference ( P < 0.01) on the 5th day post administration, a higher BBB score was observed in the lithium chloride group indicating that lithium chloride improved the locomotion function after SCI. A better structure and morphology of neuron were observed by Nissl staining in the lithium chloride group. Lithium chloride promoted BDNF secretion from neurons in the spinal cord anterior horn with a significant difference compared to the model group ( P < 0.01). Compared with the model group, lithium chloride significantly promoted the expression of BDNF protein and phosphorylated TrkB protein ( P < 0.05), but no difference in the expression of TrkB was detected. Lithium chloride can alleviate the locomotion function after SCI with a mechanism that it can promote BDNF secretion from neurons in the spinal cord anterior horn and phosphorylation of TrkB to upregulate the BDNF/TrkB pathway supporting survival of neurons and regeneration and remyelination of axons.

Rapamycin Enhances Mitophagy and Attenuates Apoptosis After Spinal Ischemia-Reperfusion Injury

The spinal cord is extremely vulnerable to ischemia-reperfusion (I/R) injury, and the mitochondrion is the most crucial interventional target. Rapamycin can promote autophagy and exert neuroprotective effects in several diseases of the central nervous system. However, the impact of rapamycin via modulating mitophagy and apoptosis after spinal cord ischemia-reperfusion injury remains unclear. This study was undertaken to investigate the potential role of rapamycin in modulating mitophagy and mitochondria-dependent apoptosis using the spinal cord ischemia-reperfusion injury (SCIRI) mouse model. We found that rapamycin significantly (p < 0.05) enhanced mitophagy by increasing the translocation of p62 and Parkin to the damaged mitochondria in the mouse spinal cord injury model. At the same time, rapamycin significantly (p < 0.05) decreased mitochondrial apoptosis related protein (Apaf-1, Caspase-3, Caspase-9) expression by inhibiting Bax translocation to the mitochondria and the release of the cytochrome c from the mitochondria. After 24 h following SCIRI, rapamycin treatment reduced the TUNEL⁺ cells in the spinal cord ischemic tissue and improved the locomotor function in these mice. Our results therefore demonstrate that rapamycin can improve the locomotor function by promoting mitophagy and attenuating SCIRI -induced apoptosis, indicating its potential therapeutic application in a spinal cord injury.

Inhibition of MicroRNA-204 Conducts Neuroprotection Against Spinal Cord Ischemia

BACKGROUND

MicroRNA(miR)-204 is an autophagy- and apoptosis-related gene. Neuroprotection by the inhibition of miR-204 against spinal cord ischemia was evaluated, and the roles of neuronal autophagy and apoptosis were investigated.

METHODS

Spinal cord ischemia was conducted in rats by cross-clamping the descending aorta for 14 minutes. Inhibition of miR-204 was induced by intrathecal injection of lentivirus vectors containing antagomiR-204. Hind-limb motor function was assessed with the motor deficit index. Lumbar spinal cords were harvested for histologic examinations and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick-end labeling staining. Autophagy was evaluated by the LC3-II/LC3-I ratio and beclin-1 expression. Expressions of LC3-I, LC3-II, beclin-1, B-cell lymphoma-2 (BCL-2), caspase-3, and miR-204 were measured by Western blot and quantitative real-time polymerase chain reaction. Autophagy was blocked by 3-methyladenine.

RESULTS

Transient ischemia enhanced miR-204 expression and the LC3-II/LC3-I ratio and downregulated BCL-2 expression in spinal cords in a time-dependent manner. AntagomiR-204 significantly reduced expressions of miR-204 and caspase-3, dramatically upregulated expressions of beclin-1 and BCL-2 and the LC3-II/LC3-I ratio in spinal cords after reperfusion. Compared with controls, inhibition of miR-204 markedly decreased the motor deficit index scores at 6, 12, 24, and 48 hours after reperfusion; increased the number of viable motor neurons; and decreased the number of apoptotic neurons. 3-Methyladenine completely abolished enhancements of the LC3-II/LC3-I ratio and beclin-1 expression induced by antagomiR-204 and inhibited the protective effect on hind-limb motor function.

CONCLUSIONS

Inhibition of miR-204 exerts spinal cord protection against ischemia-reperfusion injury, possibly via promotion of autophagy and antiapoptotic effects.

Mitochondrial Autophagy and NLRP3 Inflammasome in Pulmonary Tissues from Severe Combined Immunodeficient Mice after Cardiac Arrest and Cardiopulmonary Resuscitation

Background:

The incidence of cancer, diabetes, and autoimmune diseases has been increasing. Furthermore, there are more and more patients with solid organ transplants. The survival rate of these immunocompromised individuals is extremely low when they are severely hit-on. In this study, we established cardiac arrest cardiopulmonary resuscitation (CPR) model in severe combined immunodeficient (SCID) mice, analyzed the expression and activation of mitochondrial autophagy and NLRP3 inflammasome/caspase-1, and explored mitochondrial repair and inflammatory injury in immunodeficiency individual during systemic ischemia-reperfusion injury.

Methods:

A potassium chloride-induced cardiac arrest model was established in C57BL/6 and nonobese diabetic/SCID (NOD/SCID) mice. One hundred male C57BL/6 mice and 100 male NOD/SCID mice were randomly divided into five groups (control, 2 h post-CPR, 12 h post-CPR, 24 h post-CPR, and 48 h post-CPR). A temporal dynamic view of alveolar epithelial cells, macrophages, and neutrophils from bronchoalveolar lavage fluid (BALF) was obtained using Giemsa staining. Spatial characterization of phenotypic analysis of macrophages in the lung interstitial tissue was analyzed by flow cytometry. The morphological changes of mitochondria 48 h after CPR were studied by transmission electron microscopy and quantified according to the Flameng grading system. Western blotting analysis was used to detect the expression and activation of the markers of mitochondrial autophagy, NLRP3 inflammasome, and caspase-1.

Results:

(1) In NOD/SCID mice, macrophages were disintegrated in BALF, and many alveolar epithelial cells were shed at 48 h after resuscitation. Compared with C57BL/6 mice, the ratio of macrophages/total cells peaked at 12 h and was significantly higher in NOD/SCID mice (31.17 ± 4.13 vs. 49.69 ± 2.43, t = 14.46, P = 0.001). After 24 h, the results showed a downward trend. Furthermore, a large number of macrophages were disintegrated in the BALF. (2) Mitochondrial autophagy was present in both C57BL/6 and NOD/SCID mice after CPR, but it began late in the NOD/SCID mice. Compared with C57BL/6 mice, phos-ULK1 (Ser³²⁷) expression was significantly lower at 2 h and 12 h after CPR (2 h after CPR: 1.88 ± 0.36 vs. 1.12 ± 0.11, t = −1.36, P < 0.01 and 12 h after CPR: 1.52 ± 0.16 vs. 1.05 ± 0.12, t = −0.33, P < 0.01), whereas phos-ULK1 (Ser⁷⁵⁷) expression was significantly higher at 2 h and 12 h after CPR in NOD/SCID mice (2 h after CPR: 1.28 ± 0.12 vs. 1.69 ± 0.14, t = 1.7, P < 0.01 and 12 h after CPR: 1.33 ± 0.10 vs. 1.94 ± 0.13, t = 2.75, P < 0.01). (3) Furthermore, NLRP3 inflammasome/caspase-1 activation in the pulmonary tissues occurred early and for only a short time in C57BL/6 mice, but this phenomenon was sustained in NOD/SCID mice. The expression of the NLRP3 inflammasome increased modestly in the C57 mice, but the increase was higher in the NOD/SCID mice than in the C57BL/6 mice, especially at 12, 24, 48 h after CPR (48 h after CPR: 1.46 ± 0.13 vs. 2.97 ± 0.19, t = 5.34, P = 0.001). The expression of caspase-1-20 generally followed the same pattern as the NLRP3 inflammasome.

Conclusions:

There is a regulatory relationship between the NLRP3 inflammasome and mitochondrial autophagy after CPR in the healthy mice. This regulatory relationship was disturbed in the NOD/SCID mice because the signals for mitochondrial autophagy occurred late, and NLRP3 inflammasome- and caspase-1-dependent cell injury was sustained.

B355252, A Novel Small Molecule, Confers Neuroprotection Against Cobalt Chloride Toxicity In Mouse Hippocampal Cells Through Altering Mitochondrial Dynamics And Limiting Autophagy Induction

Cerebral hypoxia as often occurs in cases of stroke, hemorrhage, or other traumatic brain injuries, is one of the leading causes of death worldwide and a main driver of disabilities in the elderly. Using a chemical mimetic of hypoxia, cobalt chloride (CoCl2), we tested the ability of a novel small molecule, 4-chloro-N-(naphthalen-1-ylmethyl)-5-(3-(piperazin-1-yl)phenoxy)thiophene-2-sulfonamide (B355252), to alleviate CoCl2-induced damage in mouse hippocampal HT22 cells. A dose-dependent decrease in cell viability was observed during CoCl2 treatment along with increases in mitochondrial membrane potential and generation of reactive oxygen species (ROS). B355252 conferred protection against these changes. We further found that mitochondrial dynamics, the balance between mitochondrial fusion and fission, were perturbed by CoCl2 treatment. Mitochondrial fusion, which was assessed by measuring the expression of proteins optic atrophy protein 1 (OPA1) and mitofusin 2 (Mfn2), declined due to CoCl2 exposure, but B355252 addition was able to elevate Mfn2 expression while OPA1 expression was unchanged. Mitochondrial fission, measured by phosphorylated dynamin-related protein 1 (p-DRP1) and fission protein 1 (FIS1) expression, also decreased following CoCl2 exposure, and was stabilized by B355252 addition. Finally, autophagy was assessed by measuring the conversion of cytosolic microtubule-associated protein 1A/1B-light chain three-I (LC3-I) to autophagosome-bound microtubule-associated protein 1A/1B-light chain three-II (LC3-II) and was found to be increased by CoCl2. B355252 addition significantly reduced autophagy induction. Taken together, our results indicate B355252 has therapeutic potential to reduce the damaging effects caused by CoCl2 and should be further evaluated for applications in cerebral ischemia therapy.

AMP-activated protein kinase-dependent induction of autophagy by erythropoietin protects against spinal cord injury in rats

AIMS

Autophagy has been regarded as a promising therapeutic target for spinal cord injury (SCI). Erythropoietin (EPO) has been demonstrated to exhibit neuroprotective effects in the central nervous system (CNS); however, the molecular mechanisms of its protection against SCI remain unknown. This study aims to investigate whether the neuroprotective effects of EPO on SCI are mediated by autophagy via AMP-activated protein kinase (AMPK) signaling pathways.

METHODS

Functional assessment and Nissl staining were used to investigate the effects of EPO on SCI. Expressions of proteins were detected by Western blot and immunohistochemistry.

RESULTS

Treatment with EPO significantly reduced the loss of motor neurons and improved the functional recovery following SCI. Erythropoietin significantly enhanced the SCI-induced autophagy through activating AMPK and inactivating mTOR signaling. The inhibitor of AMPK, compound C, could block the EPO-induced autophagy and beneficial action on SCI, whereas the activator of AMPK, metformin, could mimic the effects of EPO. In the in vitro studies, EPO enhanced the hypoxia-induced autophagy in an AMPK-dependent manner.

CONCLUSIONS

The AMPK-dependent induction of autophagy contributes to the neuroprotection of EPO on SCI.

Anti-Apoptotic Mechanisms of Acupuncture in Neurological Diseases: A Review

Apoptosis, known as programmed cell death, plays a significant role in the pathogenesis of neurological diseases. Most of these diseases can be obviously alleviated by means of acupuncture treatment. Current research studies have shown that the efficacy of acupuncture to these medical conditions is closely associated with the anti-apoptotic potentials. Mainly based on the acupuncture's anti-apoptotic efficacy in prevalent neurological disorders, including cerebral ischemia-reperfusion injury, Alzheimer's disease, depression or stress related-modes, spinal cord injuries, etc., this review comes to a conclusion that the anti-apoptotic effect of acupuncture treatment for neurological diseases, evidently reflected through Bcl-2, Bax or caspase expression change, results from regulating mitochondrial or autophagic dysfunction as well as reducing oxidative stress and inflammation. The possible mechanisms of acupuncture's anti-apoptotic effect are associated with a series of downstream signaling pathways and the up-regulated expression of neurotrophic factors. It is of great importance to illuminate the exact mechanisms of acupuncture treatment for neurological dysfunctions.

Lithium promotes recovery of neurological function after spinal cord injury by inducing autophagy

Lithium promotes autophagy and has a neuroprotective effect on spinal cord injury (SCI); however, the underlying mechanisms remain unclear. Therefore, in this study, we investigated the effects of lithium and the autophagy inhibitor 3-methyladenine (3-MA) in a rat model of SCI. The rats were randomly assigned to the SCI, lithium, 3-MA and sham groups. In the 3-MA group, rats were intraperitoneally injected with 3-MA (3 mg/kg) 2 hours before SCI. In the lithium and 3-MA groups, rats were intraperitoneally injected with lithium (LiCl; 30 mg/kg) 6 hours after SCI and thereafter once daily until sacrifice. At 2, 3 and 4 weeks after SCI, neurological function and diffusion tensor imaging indicators were remarkably improved in the lithium group compared with the SCI and 3-MA groups. The Basso, Beattie and Bresnahan locomotor rating scale score and fractional anisotropy values were increased, and the apparent diffusion coefficient value was decreased. Immunohistochemical staining showed that immunoreactivities for Beclin-1 and light-chain 3B peaked 1 day after SCI in the lithium and SCI groups. Immunoreactivities for Beclin-1 and light-chain 3B were weaker in the 3-MA group than in the SCI group, indicating that 3-MA inhibits lithium-induced autophagy. Furthermore, NeuN⁺ neurons were more numerous in the lithium group than in the SCI and 3-MA groups, with the fewest in the latter. Our findings show that lithium reduces neuronal damage after acute SCI and promotes neurological recovery by inducing autophagy. The neuroprotective mechanism of action may not be entirely dependent on the enhancement of autophagy, and furthermore, 3-MA might not completely inhibit all autophagy pathways.

Elevated microRNA-129-5p level ameliorates neuroinflammation and blood-spinal cord barrier damage after ischemia-reperfusion by inhibiting HMGB1 and the TLR3-cytokine pathway

Background

Ischemia-reperfusion (IR) affects microRNA (miR) expression and causes substantial inflammation. Multiple roles of the tumor suppressor miR-129-5p in cerebral IR have recently been reported, but its functions in the spinal cord are unclear. Here, we investigated the role of miR-129-5p after spinal cord IR, particularly in regulating high-mobility group box-1 (HMGB1) and the Toll-like receptor (TLR)-3 pathway.

Methods

Ischemia was induced via 5-min occlusion of the aortic arch. The relationship between miR-129-5p and HMGB1 was elucidated via RT-PCR, western blotting, and luciferase assays. The cellular distribution of HMGB1 was determined via double immunofluorescence. The effect of miR-129-5p on the expression of HMGB1, TLR3, and downstream cytokines was evaluated using synthetic miRs, rHMGB1, and the TLR3 agonist Poly(I:C). Blood-spinal cord barrier (BSCB) permeability was examined by measuring Evans blue (EB) dye extravasation and the water content.

Results

The temporal miR-129-5p and HMGB1 expression profiles and luciferase assay results indicated that miR-129-5p targeted HMGB1. Compared with the Sham group, the IR group had higher HMGB1 immunoreactivity, which was primarily distributed in neurons and microglia. Intrathecal injection of the miR-129-5p mimic significantly decreased the HMGB1, TLR3, interleukin (IL)-1β and tumor necrosis factor (TNF)-α levels and the double-labeled cell count 48 h post-surgery, whereas rHMGB1 and Poly(I:C) reversed these effects. Injection of miR-129-5p mimic preserved motor function and prevented BSCB leakage based on increased Basso Mouse Scale scores and decreased EB extravasation and water content, whereas injection rHMGB1 and Poly(I:C) aggravated these injuries.

Conclusions

Increasing miR-129-5p levels protect against IR by ameliorating inflammation-induced neuronal and BCSB damage by inhibiting HMGB1 and TLR3-associated cytokines.

Liraglutide activates autophagy via GLP-1R to improve functional recovery after spinal cord injury

Therapeutics used to treat central nervous system (CNS) injury are designed to promote axonal regeneration and inhibit cell death. Previous studies have shown that liraglutide exerts potent neuroprotective effects after brain injury. However, little is known if liraglutide treatment has neuroprotective effects after spinal cord injury (SCI). This study explores the neuroprotective effects of liraglutide and associated underlying mechanisms. Our results showed that liraglutide could improve recovery after injury by decreasing apoptosis as well as increasing microtubulin acetylation, and autophagy. Autophagy inhibition with 3-methyladenine (3-MA) partially reversed the preservation of spinal cord tissue and decreased microtubule acetylation and polymerization. Additionally, siRNA knockdown of GLP-1R suppressed autophagy and reversed mTOR inhibition induced by liraglutide in vitro, indicating that GLP-1R regulates autophagic flux. GLP-1R knockdown ameliorated the mTOR inhibition and autophagy induction seen with liraglutide treatment in PC12 cells under H₂O₂ stimulation. Taken together, our study demonstrated that liraglutide could reduce apoptosis, improve functional recovery, and increase microtubule acetylation via autophagy stimulation after SCI. GLP-1R was associated with both the induction of autophagy and suppression of apoptosis in neuronal cultures.

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.

CaSR and calpain contribute to the ischemia reperfusion injury of spinal cord

Spinal cord ischemia reperfusion injury (SCIRI) can cause spinal cord dysfunction and even devastating paraplegia. Calcium-sensing receptor (CaSR) and calpain are two calcium related molecules which have been reported to be involved in the ischemia reperfusion injury of cardiomyocytes and the subsequent apoptosis. Here, we studied the expression of CaSR and calpain in spinal cord neurons and tissues, followed by the further investigation of the role of CaSR/calpain axis in the cellular apoptosis process during SCIRI. The results of in vitro and in vivo studies showed that the expression of CaSR and calpain in spinal cord neurons increased during SCIRI. Moreover, the CaSR agonist GdCl₃ and antagonist NPS-2390 enhanced or decreased the expression of CaSR and calpain respectively. The expressions of CaSR and calpain were also consistent with the cellular apoptosis in spinal cord. Taken together, CaSR-calpain contributes to the SCIRI apoptosis, and CaSR antagonist might be a helpful drug for alleviating SCIRI.

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.

Transplantation and Damage-Associated Molecular Patterns (DAMPs)

Upon solid organ transplantation and during cancer immunotherapy, cellular stress responses result in the release of damage-associated molecular patterns (DAMPs). The various cellular stresses have been characterized in detail over the last decades, but a unifying classification based on clinically important aspects is lacking. Here, we provide an in-depth review of the most recent literature along with a unifying concept of the danger/injury model, suggest a classification of DAMPs, and review the recently elaborated mechanisms that result in the emission of such factors. We further point out the differences in DAMP responses including the release following a heat shock pattern, endoplasmic reticulum stress, DNA damage-mediated DAMP release, and discuss the diverse pathways of regulated necrosis in this respect. The understanding of various forms of DAMPs and the consequences of their different release patterns are prerequisite to associate serum markers of cellular stresses with clinical outcomes.