C/EBP homologous protein (CHOP) mediates neuronal apoptosis in rats with spinal cord injury

Isoliquiritigenin from licorice flavonoids attenuates NLRP3-mediated pyroptosis by SIRT6 in vascular endothelial cells

ETHNOPHARMACOLOGIC RELEVANCE

Licorice is a traditional Chinese medicine that has been used for cardiovascular diseases. Recent studies found that supplementation with licorice extracts attenuated the development of atherosclerosis (AS) in hypercholesterolemic patients. Many studies have shown that licorice flavonoids, the main active components of licorice, have a variety of pharmacological effects, including anti-inflammation, regulation of lipid metabolism, and antioxidation. However, the key active components against AS in licorice flavonoids are still unclear.

AIM OF THE STUDY

The aim of this paper is to investigate the active components of licorice flavonoids that exert anti-atherosclerotic effects and the underlying mechanisms.

MATERIALS AND METHODS

Network pharmacology was used to screen the active components of licorice flavonoids that have anti-atherosclerotic effects. Combining bioinformatics analysis and in vitro studies, the effects and underlying mechanisms of the active component isoliquiritigenin (ISL) on cell pyroptosis were further investigated in tumor necrosis factor (TNF)-α-treated human umbilical vein endothelial cells (HUVECs).

RESULTS

We constructed a compound-target network and screened 3 active components, namely, ISL, glabridin, and naringenin in licorice flavonoids. The half maximal effective concentration values of these 3 components suggested that ISL was the key active component against TNF-α-induced endothelial cell injury. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis showed that ISL could potentially treat AS via the nucleotide-binding and oligomerization domain (NOD)-like receptor signaling pathway. An in vitro study verified that ISL suppressed TNF-α-induced NLRP3 activation and pyroptosis in HUVECs. The molecular docking and cellular thermal shift assay showed good compatibility between ISL and class III histone deacetylase sirtuin 6 (SIRT6). Moreover, we found that ISL upregulated the expression of SIRT6 in TNF-α-treated HUVECs. Further study found that SIRT6 knockdown reduced the inhibitory effect of ISL on pyroptosis, whereas the NLRP3 inhibitor reversed this process in TNF-α-treated HUVECs.

CONCLUSIONS

Our results demonstrate that ISL is a key active component of licorice flavonoids. ISL attenuates NLRP3-mediated vascular endothelial cell pyroptosis via SIRT6, and SIRT6 may be a potential target of ISL for the treatment of AS.

Circulating Ubiquitin Carboxyl Terminal Hydrolase L1 and Neuroglobin Levels in Traumatic Spinal Cord Injuries: Relation to Severity and Outcomes

Introduction

Traumatic spinal cord injury (TSCI) is a life-threatening neurological disorder and there is a lack of biomarker research, particularly human studies that could help to categorize the severity and predict the outcome. We aimed to assess the role of serum Ubiquitin C-terminal hydrolase L1 (UCH-L1) and Neuroglobin (NGB) in predicting severity and outcome of TSCI.

Methods

This prospective study included 63 participants categorized into 33 patients with various types of TSCI and 30 unrelated healthy volunteers. Neurosurgical [American spinal injury association (ASIA) impairment score (AIS)] and radiological [using spine computed tomography (CT) and magnetic resonance imaging (MRI)] assessments were performed on the included patients to determine the severity and the level of injury with neurological follow-up of patients within 6 months post-injury. Serum UCH-L1 and NGB were measured for all participants using commercially available ELISA assay kits.

Results

Of the included patients, 20 (60.60%) had partial SCI and the remaining 13 patients (39.39%) had complete SCI. On follow-up, 19 patients (57.57%) showed improved AIS, while 14 cases (42.42%) did not show any improvement in their AIS scores. There was significantly higher median serum UCHL1 value among cases compared to controls (1723 pg/mL and 657 pg/mL, respectively), p ˂ 0.05. There was an insignificant rise of serum NGB levels among cases in comparison with the controls (15.2pg/mL and 7.52pg/mL, respectively, p ˃ 0.05). Significantly lower initial median serum UCHL1 levels (pg/mL) were observed in patients with improved AIS during the neurological follow-up compared with those who did not show any improvement in their AIS score (1723, and 4700 respectively, p ˂ 0.05), with lack of significant difference in the initial median serum NGB levels, p ˃ 0.05.

Conclusion

Initial serum UCHL1 assay could be a helpful marker in reflecting the degree of TSCI and predicting its outcome, though NGB needs further assessment.

Endoplasmic Reticulum Stress and the Unfolded Protein Response in Cerebral Ischemia/Reperfusion Injury

Ischemic stroke is an acute cerebrovascular disease characterized by sudden interruption of blood flow in a certain part of the brain, leading to serious disability and death. At present, treatment methods for ischemic stroke are limited to thrombolysis or thrombus removal, but the treatment window is very narrow. However, recovery of cerebral blood circulation further causes cerebral ischemia/reperfusion injury (CIRI). The endoplasmic reticulum (ER) plays an important role in protein secretion, membrane protein folding, transportation, and maintenance of intracellular calcium homeostasis. Endoplasmic reticulum stress (ERS) plays a crucial role in cerebral ischemia pathophysiology. Mild ERS helps improve cell tolerance and restore cell homeostasis; however, excessive or long-term ERS causes apoptotic pathway activation. Specifically, the protein kinase R-like endoplasmic reticulum kinase (PERK), activating transcription factor 6 (ATF6), and inositol-requiring enzyme 1 (IRE1) pathways are significantly activated following initiation of the unfolded protein response (UPR). CIRI-induced apoptosis leads to nerve cell death, which ultimately aggravates neurological deficits in patients. Therefore, it is necessary and important to comprehensively explore the mechanism of ERS in CIRI to identify methods for preserving brain cells and neuronal function after ischemia.

Recent efforts in drug discovery on vascular inflammation and consequent atherosclerosis

Introduction: Preservation of vascular endothelium integrity and maintenance of its full functionality are fundamental aspects in order to avoid both cardiovascular and non-cardiovascular diseases.Areas covered: Although a massive endothelial disruption is a rare condition, caused by acute and uncontrolled inflammatory responses (e.g. the cytokine storm induced by SARS-CoV-2 infection), more frequently the vascular tree is the first target of slowly progressive inflammatory processes which affect the integrity of endothelium and its 'barrier' function, supporting the onset of atherosclerotic plaque and spreading inflammation. This endothelial dysfunction leads to decrease NO biosynthesis, impaired regulation of vascular tone, and increased platelet aggregation. Such chronic subclinic inflammation leads to macrophage infiltration in atherosclerotic lesions. Therefore, many efforts should be addressed to find useful approaches to preserve vascular endothelium from inflammation. In this review, the authors have evaluated the most recent strategies to counteract this pathological condition.Expert opinion: The therapeutic and nutraceutical approaches represent useful tools to treat or prevent different phases of vascular inflammation. In particular, the pharmacological approach should be used in advanced phases characterized by clinical signs of vascular disease, whilst the nutraceutical approach may represent a promising preventive strategy to preserve the integrity of the endothelial tissue.

TFE3, a potential therapeutic target for Spinal Cord Injury via augmenting autophagy flux and alleviating ER stress

Background and Aim: Increasing evidence suggests that spinal cord injury (SCI)-induced defects in autophagic flux may contribute to an impaired ability for neurological repair following injury. Transcription factor E3 (TFE3) plays a crucial role in oxidative metabolism, lysosomal homeostasis, and autophagy induction. Here, we investigated the role of TFE3 in modulating autophagy following SCI and explored its impact on neurological recovery.

Methods: Histological analysis via HE, Nissl and Mason staining, survival rate analysis, and behavioral testing via BMS and footprint analysis were used to determine functional recovery after SCI. Quantitative real-time polymerase chain reaction, Western blotting, immunofluorescence, TUNEL staining, enzyme-linked immunosorbent assays, and immunoprecipitation were applied to examine levels of autophagy flux, ER-stress-induced apoptosis, oxidative stress, and AMPK related signaling pathways. In vitro studies using PC12 cells were performed to discern the relationship between ROS accumulation and autophagy flux blockade.

Results: Our results showed that in SCI, defects in autophagy flux contributes to ER stress, leading to neuronal death. Furthermore, SCI enhances the production of reactive oxygen species (ROS) that induce lysosomal dysfunction to impair autophagy flux. We also showed that TFE3 levels are inversely correlated with ROS levels, and increased TFE3 levels can lead to improved outcomes. Finally, we showed that activation of TFE3 after SCI is partly regulated by AMPK-mTOR and AMPK-SKP2-CARM1 signaling pathways.

Conclusions: TFE3 is an important regulator in ROS-mediated autophagy dysfunction following SCI, and TFE3 may serve as a promising target for developing treatments for SCI.

Inhibition of microRNA-103 attenuates inflammation and endoplasmic reticulum stress in atherosclerosis through disrupting the PTEN-mediated MAPK signaling

Atherosclerosis (AS), a chronic disorder of large arteries, is the underlying pathological process of heart disease and stroke. Former researchers have found that microRNAs (miRs) are involved in the several key processes of AS. Apolipoprotein E knockout (ApoE^-/- ) mice fed a high-fat-diet (HFD) to establish AS model. The expression of miR-103 was characterized in the mice model. The effects of miR-103 on inflammation and endoplasmic reticulum stress (ERS) were analyzed when the expression of miR-103 was inhibited in ApoE ^-/- mice fed an HFD and human aortic endothelial cells (HAECs) exposed to oxidized low-density lipoprotein (ox-LDL). The relationship between miR-103 and phosphatase and tensin homolog (PTEN) was identified by luciferase activity detection and real-time quantitative polymerase chain reaction (RT-qPCR). Gain- and loss-function approaches were further applied for investigating the regulatory effects of miR-103 and PTEN on ERS. Role of MAPK signaling was then analyzed using PD98059 to block this pathway. miR-103 was highly expressed in the ApoEApoE ^-/- mice fed an HFD. Downregulation of miR-103 suppressed inflammation and ERS in endothelial cells isolated from ApoE ^-/- mice fed a HFD and ox-LDL-exposed HAECs. In addition, miR-103 can target PTEN and downregulate its expression. Overexpression of PTEN reversed the miR-103-induced activation of MAPK signaling. Moreover, PTEN upregulation or MAPK signaling inhibition ease miR-103-induced inflammation and ERS in vivo and in vitro. Thus, miR-103 depletion restrains the progression of AS through blocking PTEN-mediated MAPK signaling.

Traumatic Spinal Cord Injury: An Overview of Pathophysiology, Models and Acute Injury Mechanisms

Traumatic spinal cord injury (SCI) is a life changing neurological condition with substantial socioeconomic implications for patients and their care-givers. Recent advances in medical management of SCI has significantly improved diagnosis, stabilization, survival rate and well-being of SCI patients. However, there has been small progress on treatment options for improving the neurological outcomes of SCI patients. This incremental success mainly reflects the complexity of SCI pathophysiology and the diverse biochemical and physiological changes that occur in the injured spinal cord. Therefore, in the past few decades, considerable efforts have been made by SCI researchers to elucidate the pathophysiology of SCI and unravel the underlying cellular and molecular mechanisms of tissue degeneration and repair in the injured spinal cord. To this end, a number of preclinical animal and injury models have been developed to more closely recapitulate the primary and secondary injury processes of SCI. In this review, we will provide a comprehensive overview of the recent advances in our understanding of the pathophysiology of SCI. We will also discuss the neurological outcomes of human SCI and the available experimental model systems that have been employed to identify SCI mechanisms and develop therapeutic strategies for this condition.

ZBTB38, a novel regulator of autophagy initiation targeted by RB1CC1/FIP200 in spinal cord injury

Apoptosis is an important contributing factor in spinal cord injury (SCI). ZBTB38 is involved in the transcriptional regulation of multiple signaling pathways, is differentially expressed at different SCI stages, and may provide a therapeutic strategy for the treatment of patients with SCI. In this study, we found that autophagy is blocked in ZBTB38 knockdown SH-SY5Y cells and that the expression levels of LC3B II/I decreased and P62 increased. We used transcriptome high-throughput sequencing to identify the target in ZBTB38 knockdown cells. From the transcriptome profile, RB1CC1 (i.e., FIP200), a key component of the initiation machinery of autophagy (FIP200-ATG13-ULK1-ATG101), was found to decrease 4.2-fold following ZBTB38 knockdown. When RB1CC1-overexpressed plasmids were transfected into ZBTB38 knockdown cells, they rescued the phenotype of ZBTB38 knockdown cells. Cell proliferation and viability were significantly enhanced by RB1CC1 overexpression, and LC3B and P62 expression returned to their original levels. We also injected ZBTB38-overexpressed lentivirus into the injured center of the spinal cord and detected significant upregulation of RB1CC1 in the spinal cord. ZBTB38 overexpression can promote autophagy and partly rescue the secondary damage of SCI. Therefore, our findings provide a new strategy for the treatment of SCI.

Tauroursodeoxycholic acid alleviates secondary injury in the spinal cord via up-regulation of CIBZ gene

Spinal cord injury (SCI) is generally divided into primary and secondary injuries, and apoptosis is an important event of the secondary injury. As an endogenous bile acid and recognized endoplasmic reticulum (ER) stress inhibitor, tauroursodeoxycholic acid (TUDCA) administration has been reported to have a potentially therapeutic effect on neurodegenerative diseases, but its real mechanism is still unclear. In this study, we evaluated whether TUDCA could alleviate traumatic damage of the spinal cord and improve locomotion function in a mouse model of SCI. Traumatic SCI mice were intraperitoneally injected with TUDCA, and the effects were evaluated based on motor function assessment, histopathology, apoptosis detection, qRT-PCR, and western blot at different time periods. TUDCA administration can improve motor function and reduce secondary injury and lesion area after SCI. Furthermore, the apoptotic ratios were significantly reduced; Grp78, Erdj4, and CHOP were attenuated by the treatment. Unexpectedly, the levels of CIBZ, a novel therapeutic target for SCI, were specifically up-regulated. Taken together, it is suggested that TUDCA effectively suppressed ER stress through targeted up-regulation of CIBZ. This study also provides a new strategy for relieving secondary damage by inhibiting apoptosis in the early treatment of spinal cord injury.

Zbtb38 is a novel target for spinal cord injury

Spinal cord injury (SCI) is currently incurable since treatments applied to clinic are limited to minimizing secondary complications and the mechanisms of injury-induced spinal cord damage are poorly understood. Zbtb38, also called CIBZ, is highly expressed in spinal cord and it functions as a negative regulator in SCI-induced apoptosis. We show here that Zbtb38 is downregulated under endoplasmic reticulum (ER) stress, which promotes ER stress-associated apoptosis in human bone marrow neuroblastoma cells. In the traumatic SCI mice, ER stress presented in injured spinal cord induced repression of Zbtb38 expression and triggered Zbtb38-mediated apoptosis. ChIP-QPCR analysis revealed that ATF4, an ER-stress inducible transcription factor, directly activated Zbtb38 transcription by binding to the Zbtb38 promoter. However, this binding was significantly reduced following SCI, leading to a sharp decrease in Zbtb38 expression. Restoring Zbtb38 function in injured spinal cord by injection of lentivirus containing Zbtb38 into SCI mice, significantly alleviated secondary damage of spinal cord with decreased ER stress-associated apoptosis and partially recovered spinal cord functions. These findings demonstrate that restoration of Zbtb38 expression can reduce secondary tissue damage after SCI, and suggest that a therapeutic strategy for targeting Zbtb38 may promote functional recovery of spinal cord for patients with SCI.

Sustained-release of FGF-2 from a hybrid hydrogel of heparin-poloxamer and decellular matrix promotes the neuroprotective effects of proteins after spinal injury

Introduction

The short lifetime of protein-based therapies has largely limited their therapeutic efficacy in injured nervous post-spinal cord injury (post-SCI).

Methods

In this study, an affinity-based hydrogel delivery system provided sustained-release of proteins, thereby extending the efficacy of such therapies. The affinity-based hydrogel was constructed using a novel polymer, heparin-poloxamer (HP), as a temperature-sensitive bulk matrix and decellular spinal cord extracellular matrix (dscECM) as an affinity depot of drug. By tuning the concentration of HP in formulation, the cold ternary fibroblast growth factor-2 (FGF2)-dscECM-HP solution could rapidly gelatinize into a hydrogel at body temperature. Due to the strong affinity for FGF2, hybrid FGF2-dscECM-HP hydrogel enabled sustained-release of encapsulated FGF2 over an extended period in vitro.

Results

Compared to free FGF2, it was observed that both neuron functions and tissue morphology after SCI were clearly recovered in rats treated with FGF2-dscECM-HP hydrogel. Moreover, the expression of neurofilament protein and the density of axons were increased after treatment with hybrid FGF2-dscECM-HP. In addition, the neuroprotective effects of FGF2-dscECM-HP were related to inhibition of chronic endoplasmic reticulum stress-induced apoptosis.

Conclusion

The results revealed that a hybrid hydrogel system may be a potential carrier to deliver macromolecular proteins to the injured site and enhance the therapeutic effects of proteins.

Daidzein ameliorates spinal cord ischemia/reperfusion injury-induced neurological function deficits in Sprague-Dawley rats through PI3K/Akt signaling pathway

Daidzein (DZ) has a broad spectrum of biological activities, including antioxidant, anti-inflammatory and anticancer as well as cardio- and hepatoprotective properties. The present study was designed to elucidate the in-depth mechanism underlying the neuroprotective efficacy of DZ against spinal cord ischemic/reperfusion injury (SCII) in a rat model by comparison with the standard neuroprotective agent methylprednisolone (MP). A total of 48 rats were divided into four groups of twelve rats in each (n=12). In sham-operated group (Control) group, rats received only saline (Fogarty catheter was inserted without balloon inflation), whereas rats in the SCII induction group (SCII) were subjected to SCII insult by insertion of a Fogarty balloon catheter, which was inflated in the descending thoracic aorta to cause an occlusion. A proportion of rats was treated with DZ (20 mg/kg; DZ+SCII group) or MP (50 mg/kg; MP+SCII group) for seven days prior to and after SCII. The locomotor function (neurological activity) and antioxidant levels (superoxide dismutase and catalase) levels were significantly improved upon treatment with DZ and MP in comparison with those in the SCII group. A concomitant decline in edema, inflammatory markers (myeloperoxidase, tumor necrosis factor-α and nuclear factor κB p65), the apoptotic marker caspase-3 and the number of cells with terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling was also observed in the DZ and MP groups. The protein levels of phosphoinositide-3 kinase (PI3K), the phosphorylated Akt/Akt ratio and B-cell lymphoma 2 (Bcl-2) were substantially downregulated, while Bcl-2-associated X protein levels were upregulated SCII insult group, which was inhibited by treatment with DZ. To conclude, pre-treatment with DZ significantly improved the neurological function by upregulating PI3K/Akt signaling and thereby considerably attenuating the inflammatory response and apoptosis, thus maintaining the neuronal count in an SCII-induced rat model.

Upregulation of PTP1B After Rat Spinal Cord Injury

Protein tyrosine phosphatase 1B (PTP1B), a member of the protein tyrosine phosphatase family, attaches to the endoplasmic reticulum (ER) via its C-terminal tail. Previous studies have reported that PTP1B participates in various signal transduction pathways in many human diseases, including diabetes, cancers, osteoporosis, and obesity. It also plays an important role in the ER stress. ER stress induced by spinal cord injury (SCI) was reported to result in cell apoptosis. Till now, the role of PTP1B in the injury of the central nervous system remains unknown. In the present study, we built an adult rat SCI model to investigate the potential role of PTP1B in SCI. Western blot analysis detected a notable alteration of PTP1B expression after SCI. Immunohistochemistry indicated that PTP1B expressed at a low level in the normal spinal cord and greatly increased after SCI. Double immunofluorescence staining revealed that PTP1B immunoreactivity was predominantly increased in neurons following SCI. In addition, SCI resulted in a significant alteration in the level of active caspase-3, caspase-12, and 153/C/EBP homologous transcription factor protein, which were correlated with the upregulation of PTP1B. Co-localization of PTP1B/active caspase-3 was also detected in neurons. Taken together, our findings elucidated the PTP1B expression in the SCI for the first time. These results suggested that PTP1B might be deeply involved in the injury response and probably played an important role in the neuro-pathological process of SCI.

The critical role of oxidative stress in the toxicity and metabolism of quinoxaline 1,4-di-N-oxides in vitro and in vivo

Quinoxaline 1,4-dioxide derivatives (QdNOs) have been widely used as growth promoters and antibacterial agents. Carbadox (CBX), olaquindox (OLA), quinocetone (QCT), cyadox (CYA) and mequindox (MEQ) are the classical members of QdNOs. Some members of QdNOs are known to cause a variety of toxic effects. To date, however, almost no review has addressed the toxicity and metabolism of QdNOs in relation to oxidative stress. This review focused on the research progress associated with oxidative stress as a plausible mechanism for QdNO-induced toxicity and metabolism. The present review documented that the studies were performed over the past 10 years to interpret the generation of reactive oxygen species (ROS) and oxidative stress as the results of QdNO treatment and have correlated them with various types of QdNO toxicity, suggesting that oxidative stress plays critical roles in their toxicities. The major metabolic pathways of QdNOs are N→O group reduction and hydroxylation. Xanthine oxidoreductase (XOR), aldehyde oxidase (SsAOX1), carbonyl reductase (CBR1) and cytochrome P450 (CYP) enzymes were involved in the QdNOs metabolism. Further understanding the role of oxidative stress in QdNOs-induced toxicity will throw new light onto the use of antioxidants and scavengers of ROS as well as onto the blind spots of metabolism and the metabolizing enzymes of QdNOs. The present review might contribute to revealing the QdNOs toxicity, protecting against oxidative damage and helping to improve the rational use of concurrent drugs, while developing novel QdNO compounds with more efficient potentials and less toxic effects.

Reduced AKT phosphorylation contributes to endoplasmic reticulum stress-mediated hippocampal neuronal apoptosis in rat recurrent febrile seizure

AIMS

Febrile seizure (FS) is one of the most common types of seizures in childhood. Recurrent FS can result in hippocampus injury and thus impair learning capacity and memory, while the underlying molecular mechanisms are still elusive. Studies indicated that endoplasmic reticulum stress (ERS), involved in many diseases including some neurodegenerative diseases, can increase the expression of tribbles-related protein 3 (TRIB3), which thus inhibits the activity of AKT. The current study assessed whether ERS, TRIB3 and AKT signalling is involved in the hippocampus injury following recurrent FS.

MAIN METHODS

Recurrent FS was induced in Sprague-Dawley (SD) rats by using a heated water-bath. TdT-mediated dUTP nick-end labeling (TUNEL) assay was performed to assess hippocampus apoptosis, and electron microscopy was used to examine ultrastructural changes. Protein expression and localization of TRIB3, glucose-regulated protein 78(GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) as well as AKT were examined by using western blot and double immunofluorescence staining. Knockdown of TRIB3 was studied in primary cultured neurons treated with hyperthermia.

KEY FINDINGS

As compared with control, apoptosis of hippocampus was significantly induced in FS group. Abundance of TRIB3, GRP78 and CHOP was remarkably elevated, while phosphor-AKT decreased significantly in hippocampus of rats with recurrent FS. Double immunofluorescence indicated that phosphor-AKT was not detected in cells with induction of TRIB3 in FS rats. Hyperthermia-treated cells showed up-regulates TRIB3 expression and that TRIB3 reduces AKT phosphorylation.

SIGNIFICANCE

These results show that recurrent FS may induce injury of hippocampal cell by interfering with AKT activation through ERS-mediated up-regulation of TRIB3.

Hyperbaric Oxygen Treatment Protects Against Spinal Cord Injury by Inhibiting Endoplasmic Reticulum Stress in Rats

STUDY DESIGN

Experimental animal study of treatment of SCI.

OBJECTIVE

To explore whether HBO treatment protects against secondary SCI by inhibiting the ER stress response.

SUMMARY OF BACKGROUND DATA

SCI is a neurological disorder that can severely limit the execution of the simplest day-to-day functions. ER stress plays an important role in the induction of neuronal apoptosis after SCI. HBO treatment can alleviate secondary injury and benefit neurological recovery after SCI, but the effect of HBO on ER stress response after SCI is yet to be characterized.

METHODS

The spinal cord of rats was injured via T10 laminectomy. Experimental animals were randomly assigned to 1 of 3 groups: sham-operated, SCI, and SCI+HBO. Each group was analyzed 1, 2, 3, 7, and 14 days after injury. Neurological recovery was evaluated using the Basso-Beattie-Bresnahan (BBB) scoring system and the TdT-mediated dUTP nick-end labeling reaction was carried out to visualize apoptotic cells. The expression of ER stress-related factors was evaluated by immunohistochemical, western blot, and real-time reverse transcription-polymerase chain reaction analyses.

RESULTS

SCI-induced apoptosis and an increase in the levels of CCAAT-enhancer-binding protein homologous protein (CHOP), and caspase-12 and caspase-3 compared with the sham-operated group. HBO treatment decreased CHOP and caspase-12 and caspase-3 expression as well as apoptosis compared with the SCI group. In addition, BBB scores were improved in the SCI+HBO relative to the SCI group at 7 and 14 days.

CONCLUSION

These results suggest that HBO treatment alleviates secondary injury to the spinal cord by inhibiting ER stress induced apoptosis, thereby promoting the recovery of neurological function.

LEVEL OF EVIDENCE

N/A.

Necroptosis, a novel type of programmed cell death, contributes to early neural cells damage after spinal cord injury in adult mice

BACKGROUND

Necroptosis is an emerging programmed necrosis other than traditional necrosis and apoptosis. Until recently, there have not been studies that have investigated a relationship between necroptosis and pathogenesis of cell death after spinal cord injury (SCI).

OBJECTIVE

To investigate whether necroptosis takes part in the early pathophysiological processes of traumatic SCI in mice.

METHODS

Female ICR mice were randomized equally into three groups: the sham, the vehicle-treated + SCI group, and the Nec-1-treated + SCI group. To induce SCI, the mice were subjected to a laminectomy at T9 and compression with a vascular clip. After mice were sacrificed 24 hours post-SCI, propidium iodide (PI)-positive cells were detected using in vivo PI labeling. Morphological analyses were performed by hematoxylin and eosin staining and Nissl staining. The samples were evaluated for apoptosis by the in situ TUNEL assay. The expression of caspase-3 was assessed by western blot. Locomotor behavior of hindlimb was evaluated by BMS (Basso mouse scale) score at 1, 3, 5, 7, and 14 days post-injury.

RESULTS

Compared with dimethyl sulfoxide -treated mice, necrostatin-1-treated mice showed decreased PI-positive cells (P < 0.05), alleviated tissue damage, more surviving neuron at 24 hours after SCI (P < 0.05), and improved functional recovery from days 7 to 14 (P < 0.05). Necrostatin-1 did not reduce the expression of caspase-3 and the number of TUNEL-positive cells at 24 hours after SCI (P > 0.05).

CONCLUSIONS

Necroptosis contributes to necroptotic cell death and influences functional outcome after SCI in adult mice. The inhibition of necroptosis by necrostatin-1 may have therapeutic potential for patients with SCI.

Involvement of endoplasmic reticulum stress in optic nerve degeneration after chronic high intraocular pressure in DBA/2J mice

DBA/2J mice are one of several animal strains used for experimental models of both intraocular hypertension and glaucoma. This study investigates the relationship between endoplasmic reticulum (ER) stress and optic nerve degeneration in DBA/2J mice. Intraocular pressure (IOP) was measured in DBA/2J mice between the ages of 6 and 15 months. Optic nerve damage was assessed at 15 months of age. The nerve was immunostained with antibodies to either neurofilament heavy chain (NFH) or phosphorylated NFH (pNFH), and optic nerve damage was assessed by performing NFH- and pNFH-positive axon counts. Expression levels of the ER stress proteins 78-kDa glucose-regulated protein, also known as binding immunoglobulin protein, and C/EBP homologous protein were assayed with Western blotting. We also investigated ER stress localization in the optic nerve by double immunostaining with antibodies to ionized calcium-binding adaptor molecule 1, myelin basic protein, and glial fibrillary acidic protein (GFAP). In DBA/2J mice, IOP began to rise at 8 months of age, and retinal degeneration was detected at 15 months of age. DBA/2J mice had fewer axons than controls at 15 months of age. ER stress-related protein levels were higher in the optic nerves of DBA/2J mice and were colocalized with GFAP-positive astrocytes. Our findings suggest that ER stress plays a role in optic nerve degeneration during chronic ocular hypertension. Furthermore, ER stress may be related in some way to astrocyte activation.

Region-specific vulnerability to endoplasmic reticulum stress-induced neuronal death in rat brain after status epilepticus

We sought to clarify the involvement and the intra-cerebral distribution variability of C/EBP homologous protein (CHOP), a representative molecule related to endoplasmic reticulum (ER) stress-induced cell death signalling pathways, in neuronal death resulting from status epilepticus in rats. The expression patterns of CHOP and glucose-regulated protein (GRP) 78, a good marker of ER stress, were assessed by Western blotting, real-time PCR, Hoechst and immunohistochemistry in the hippocampus, cortex and striatum on a status epilepticus (SE) model. Double-fluorescent staining of CHOP and the terminal deoxynucleotidyl transferase-mediated DNA nick-end labelling (TUNEL) method were performed to clarify the involvement of CHOP in cell death. SE resulted in a timedependent increase in the expression of GRP78 and CHOP. The expression of GRP78 protein was increased at 3, 6 and 12 h after SE and no brain region variability was found. The expression of CHOP protein was also increased, reached its peak at 24 h and remained high at 48 h. CHOP protein expression, however, showed brain region variability with highest expression noted in the hippocampus followed by the striatum, and lowest in the cortex. The up-regulation of CHOP occurring at the transcriptional level was demonstrated by real-time PCR. Double fluorescence showed that CHOP expression strongly correlated with neurons undergoing apoptosis. The results indicated that SE compromises the function of the ER and that the hippocampus is more vulnerable than the cortex and the striatum.

Nerve growth factor improves functional recovery by inhibiting endoplasmic reticulum stress-induced neuronal apoptosis in rats with spinal cord injury

Background

Endoplasmic reticulum (ER) stress-induced apoptosis plays a major role in various diseases, including spinal cord injury (SCI). Nerve growth factor (NGF) show neuroprotective effect and improve the recovery of SCI, but the relations of ER stress-induced apoptosis and the NGF therapeutic effect in SCI still unclear.

Methods

Young adult female Sprague-Dawley rats’s vertebral column was exposed and a laminectomy was done at T9 vertebrae and moderate contusion injuries were performed using a vascular clip. NGF stock solution was diluted with 0.9% NaCl and administered intravenously at a dose of 20 μg/kg/day after SCI and then once per day until they were executed. Subsequently, the rats were executed at 1d, 3 d, 7d and 14d. The locomotor activities of SCI model rats were tested by the 21-point Basso-Beattie-Bresnahan (BBB) locomotion scale, inclined plane test and footprint analysis. In addition, Western blot analysis was performed to identify the expression of ER-stress related proteins including CHOP, GRP78 and caspase-12 both in vivo and in vitro. The level of cell apoptosis was determined by TUNEL in vivo and Flow cytometry in vitro. Relative downstream signals Akt/GSK-3β and ERK1/2were also analyzed with or without inhibitors in vitro.

Results

Our results demonstrated that ER stress-induced apoptosis was involved in the injury of SCI model rats. NGF administration improved the motor function recovery and increased the neurons survival in the spinal cord lesions of the model rats. NGF decreases neuron apoptosis which measured by TUNEL and inhibits the activation of caspase-3 cascade. The ER stress-induced apoptosis response proteins CHOP, GRP78 and caspase-12 are inhibited by NGF treatment. Meanwhile, NGF administration also increased expression of growth-associated protein 43 (GAP43). The administration of NGF activated downstream signals Akt/GSK-3β and ERK1/2 in ER stress cell model in vitro.

Conclusion

The neuroprotective role of NGF in the recovery of SCI is related to the inhibition of ER stress-induced cell death via the activation of downstream signals, also suggested a new trend of NGF translational drug development in the central neural system injuries which involved in the regulation of chronic ER stress.

Disturbance of endoplasmic reticulum proteostasis in neurodegenerative diseases

The unfolded protein response (UPR) is a homeostatic mechanism by which cells regulate levels of misfolded proteins in the endoplasmic reticulum (ER). Although it is well characterized in non-neuronal cells, a proliferation of papers over the past few years has revealed a key role for the UPR in normal neuronal function and as an important driver of neurodegenerative diseases. A complex scenario is emerging in which distinct UPR signalling modules have specific and even opposite effects on neurodegeneration depending on the disease context. Here, we provide an overview of the most recent findings addressing the biological relevance of ER stress in the nervous system.

Inhibition of serine/threonine protein phosphatase PP1 protects cardiomyocytes from tunicamycin-induced apoptosis and I/R through the upregulation of p-eIF2α

The serine/threonine protein phosphatase PP1 mediates the dephosphorylation of phosphorylated eukaryotic translation initiation factor 2 subunit α (p-eIF2α), which is a central regulator of protein synthesis. In the present study, we examined the protective effects of PP1-12 (an inhibitor of the serine/threonine protein phosphatase PP1) against tunicamycin (TM)-induced apoptosis in cultured cardiomyocytes in vitro, as well as in an in vivo model of ischemia/reperfusion (I/R) injury in rat hearts. Neonatal cardiomyocytes cultured from the ventricles of the hearts of 1-day-old Wistar rats were exposed to various concentrations of PP1-12 (0.3, 1 and 3 µmol/l) for 30 min, followed by treatment with TM for 36 h. Cell viability was assessed by adenosine triphosphate (ATP) bioluminescence, and the results revealed that pre-treatment with PP1-12 protected cell viability. Western blot analysis revealed that PP1-12 induced eIF2α phosphorylation and immuncytochemistry indicated that PP1-12 downregulated the expression of C/EBP homologous protein (CHOP), which is related to apoptosis. PP1-12 suppressed cell apoptosis, with maximum protective effects displayed at the concentration of 3 µmol/l. For the in vivo experiments, male Sprague-Dawley rats were randomly divided into 5 groups: i) sham-operated; ii) vehicle (I/R + DMSO); iii) I/R + 1 mg/kg/day PP1-12; iv) I/R + 3 mg/kg/day PP1-12; and v) I/R + 10 mg/kg/day PP1-12. PP1-12 reduced the expression of cleaved caspase-12 and increased the phosphorylation of eIF2α, as revealed by western blot analysis. By calculating the apoptotic index (AI), we found that 10 mg/kg/day PP1-12 exerted the most pronounced anti-apoptotic effect. The infarction area was significantly decreased following treatment with this concentration of PP1-12, as revealed by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Taken together, these data suggest that PP1-12 protects cardiomyocytes from TM- and I/R-induced apoptosis, and this effect is achieved at least in part through the inhibition of cell apoptosis and the induction of eIF2α phosphorylation.

Cardiac ablation of Rheb1 induces impaired heart growth, endoplasmic reticulum-associated apoptosis and heart failure in infant mice

Ras homologue enriched in brain 1 (Rheb1) plays an important role in a variety of cellular processes. In this study, we investigate the role of Rheb1 in the post-natal heart. We found that deletion of the gene responsible for production of Rheb1 from cardiomyocytes of post-natal mice resulted in malignant arrhythmias, heart failure, and premature death of these mice. In addition, heart growth impairment, aberrant metabolism relative gene expression, and increased cardiomyocyte apoptosis were observed in Rheb1-knockout mice prior to the development of heart failure and arrhythmias. Also, protein kinase B (PKB/Akt) signaling was enhanced in Rheb1-knockout mice, and removal of phosphatase and tensin homolog (Pten) significantly prolonged the survival of Rheb1-knockouts. Furthermore, signaling via the mammalian target of rapamycin complex 1 (mTORC1) was abolished and C/EBP homologous protein (CHOP) and phosphorylation levels of c-Jun N-terminal kinase (JNK) were increased in Rheb1 mutant mice. In conclusion, this study demonstrates that Rheb1 is important for maintaining cardiac function in post-natal mice via regulation of mTORC1 activity and stress on the endoplasmic reticulum. Moreover, activation of Akt signaling helps to improve the survival of mice with advanced heart failure. Thus, this study provides direct evidence that Rheb1 performs multiple important functions in the heart of the post-natal mouse. Enhancing Akt activity improves the survival of infant mice with advanced heart failure.

ER stress and effects of DHA as an ER stress inhibitor

The endoplasmic reticulum (ER) functions in the synthesis, folding, modification, and transport of newly synthesized transmembrane and secretory proteins. The ER also has important roles in the storage of intracellular Ca(2+) and regulation of Ca(2+) homeostasis. The integrity of the Ca(2+) homeostasis in the ER lumen is vital for proper folding of proteins. Dysregulation of ER Ca(2+) could result in an increase in unfolded or misfolded proteins and ER stress. ER stress triggers activation of the unfolded protein response (UPR), which is a fundamentally adaptive cell response and functions as a cytoprotective mechanism by over-expression of relevant chaperones and the global shutdown of protein synthesis. UPR activation occurs when three key ER membrane-sensor proteins detect an accumulation of aberrant proteins. The UPR acts to alleviate ER stress, but if the stress is too severe or prolonged, apoptosis will be triggered. In this review, we focused on ER stress and the effects of docosahexaenoic acid (DHA) on ER stress. DHA and its bioactive compounds, such as protectins and resolvins, provide neuroprotection against oxidative stress and apoptosis and have the ability to resolve inflammation in neurological diseases. New studies reveal that DHA blocks inositol trisphosphate receptor (IP3R)-mediated ER Ca(2+) depletion and ER stress. The administration of DHA post-traumatic brain injury (TBI) reduces ER stress, aberrant protein accumulation, and neurological deficits. Therefore, DHA presents therapeutic potentials for TBI via its pleiotropic effects including inhibition of ER stress.

Endoplasmic reticulum stress response in the rat contusive spinal cord injury model-susceptibility in specific cell types

STUDY DESIGN

Focus group study.

OBJECTIVE

To investigate cell-specific endoplasmic reticulum (ER) stress reactions in contusive spinal cord by evaluating the expression of the glucose-regulated protein 78 (GRP78) and C/EBP homologous transcription factor protein (CHOP) using immunohistochemical staining.

SETTING

Data were analysed at Tokai University School of Medicine in Japan.

METHODS

The authors generated rat spinal cord injury (SCI) models using an IH-Impactor (100 kdyne(LI), 200 kdyne (HI)). Rats were killed at 1, 3, 5, 7 and 14 days post operation (dpo). Spinal cord sections were prepared and the expression ratio of GRP78 and CHOP was evaluated in oligodendrocyte precursor cells (OPCs) (NG2+), oligodendrocytes (OLs) (APC+), neurons (NeuN+) and astrocytes (GFAP+) using double immunohistochemical staining. We examined an area 8 mm distal from SCI-epicenter.

RESULTS

Compared with the sham group, both injured groups had higher GRP78 expression ratio in contused spinal cord at 1 dpo. GRP78 expression ratio was highest in GFAP+ cells of both groups, and lowest in NG2+ cells. Although GRP78 was expressed strongly immediately after SCI in the both groups, increased CHOP expression was observed only in the HI group. The CHOP expression in NG2+ cells was significantly higher than that observed in GFAP+ cells at 5 dpo.

CONCLUSION

Although the ER stress response contributes to cell survival in the low-stress SCI conditions, the ER stress response induces an apoptotic cascade in high-stress SCI conditions. The ER response varies according to cell type, with the highest observed in astrocytes, and the lowest observed in oligodendrocyte precursor cells.

Bone marrow stromal cells inhibit caspase-12 expression in rats with spinal cord injury

The mechanisms underlying the potentially beneficial effect of bone marrow stem cells (BMSCs) on spinal cord injury (SCI) are unknown. Therefore, the aim of the present study was to explore the protective effect of BMSCs in rats with SCI. A total of 45 adult male Sprague-Dawley rats were randomly divided into three groups; the SCI group (n=15), the BMSC group (n=15) and the sham-operation group (n=15). In the SCI and BMSC treatment groups, a modified Allen’s weight-drop technique was used to induce SCI. The BMSC treatment group received an injection of BMSCs using a microneedle into the epicenter of the spinal cord 24 h after injury. Rats in the sham-operation group were not subjected to SCI; however, the corresponding vertebral laminae were removed. Seven days after transplantation, a rapid recovery was observed in the Basso, Beattie and Bresnahan (BBB) scores of the BMSC treatment group, whereas the BBB scores in the SCI group remained low (P<0.05). Caspase-12 expression in the SCI group was increased compared with that in the sham-operation group, whereas caspase-12 expression was attenuated 24 h after transplantation in the BMSC treatment group (P<0.05). In conclusion, the transplantation of BMSCs may improve locomotor function and attenuate caspase-12 expression following SCI. Therefore, it is likely to be an effective strategy for preventing severe injury of the spinal cord.