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

Proteomics in orthopedic research: Recent studies and their translational implications

Proteomics is a growing field that offers insights into various aspects of disease processes and therapy responses. Within the field of orthopedics, there are a variety of diseases that have a poor prognosis due to a lack of targeted curative therapy or disease modifying therapy. Other diseases have been difficult to manage in part due to lack of clinical biomarkers that offer meaningful insight into disease progression or severity. As an emerging technology, proteomics has been increasingly applied in studying bone biology and an assortment of orthopedics related diseases, such as osteoarthritis, osteosarcoma and bone tumors, osteoporosis, traumatic bone injury, spinal cord injury, hip and knee arthroplasty, and fragile healing. These efforts range from mechanistic studies for elucidating novel insights in tissue activity and metabolism to identification of candidate biomarkers for diagnosis, prognosis, and targeted treatment. The knowledge gained from these proteomic and functional studies has provided unique perspectives in studying orthopedic diseases. In this review, we seek to report on the current state of the proteomic study in the field of orthopedics, overview the advances in clinically applicable discoveries, and discuss the opportunities that may guide us for future research.

Hyperbaric Oxygen Treatment in Spinal Cord Injury Recovery: Profiling Long Noncoding RNAs

STUDY DESIGN

A functional, transcriptome, and long noncoding RNAs (lncRNAs) expression analysis in the spinal cord of mice after hyperbaric oxygen (HBO) treatment.

OBJECTIVE

We aimed to explore the mechanism by which HBO treats spinal cord injury (SCI) at the level of lncRNAs.

SUMMARY OF BACKGROUND DATA

Immense amounts of research have established that HBO treatment promotes the recovery of neurological function after SCI. The mechanism of action remains to be clarified.

METHODS

High-throughput RNA sequencing, Gene Ontology, and Kyoto Encyclopedia of Genes and Genomes enrichment analysis were used to profile lncRNA expression and analyze biological function in the spinal cords of mice from sham-operated, SCI, and HBO-treated groups. The differential expression of lncRNA between the groups was assessed using real-time quantitative polymerase chain reaction.

RESULTS

Differential expression across 577 lncRNAs was identified among the three groups. GO analysis showed that free ubiquitin chain polymerization, ubiquitin homeostasis, DNA replication, synthesis of RNA primer, single-stranded telomeric DNA binding, and alpha-amylase activity were significantly enriched. Kyoto Encyclopedia of Genes and Genomes enrichment analysis displayed that vitamin B6 metabolism, one carbon pool by folate, DNA replication, lysine degradation, beta-alanine metabolism, fanconi anemia pathway, and Notch signal pathway were the main pathways with enrichment significance. LncRNAs NONMMUT 092674.1, NONMMUT042986.2, and NONMMUT018850.2 showed significantly different expression between the SCI and the other two groups (P<0.05, <0.01).

CONCLUSIONS

This study is the first to determine the expression profiles of lncRNAs in the injured spinal cord after HBO treatment. We identified several important dysregulated lncRNAs in this setting. These results help us better understand the mechanism by which HBO treats SCI and provide new potential therapeutic targets for SCI.

Synergistic neuroprotective effects of hyperbaric oxygen and methylprednisolone following contusive spinal cord injury in rat

OBJECTIVE

Recent studies revealed the neuroprotective effects of hyperbaric oxygen (HBO) on spinal cord injury (SCI). Meanwhile, the use of methylprednisolone (MP) is one of the current protocols with limited effects in SCI patients. Accordingly, the aim of the present study was to investigate the effect of combined HBO and MP treatment on SCI.

DESIGN

The present study was conducted on five groups of rats each as follows: Sham group (underwent laminectomy alone at T9 level vertebra); SCI group (underwent moderate contusive SCI); MP group (underwent SCI and received MP); HBO group (underwent SCI and received HBO); HBO + MP group (underwent SCI and simultaneously received MP and HBO). Blood serum and Spinal cord tissue samples were taken 48 h after SCI for analysis of serum ferric reducing antioxidant power (FRAP) and tissue malodialdehyde (MDA) levels as well as immunohistochemistry of caspase-3 and tumor necrosis factor-alpha (TNF-α). Neurological function was evaluated by the Basso-Beattie-Bresnehan (BBB) locomotion scores until the end of experiments. Additionally, histopathology was assessed at the end of the study.

SETTING

Mazandaran University of Medical Sciences, Sari, Iran.

RESULTS

Combination therapy with HBO and MP in the HBO + MP group significantly decreased MDA as well as increased FRAP levels compared to other treatment groups. Meanwhile, attenuated TNF-α and Caspase-3 expression could be significantly detected in the HBO + MP group. At the end of treatment, the neurological outcome was significantly improved and the extent of injured spinal tissue was also significantly reduced in the HBO + MP compared to other treatment groups.

CONCLUSION

The results suggest that combined therapy with MP and HBO has synergistic effects on SCI treatment.

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

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

Hyperbaric Oxygen Therapy-Induced Molecular and Pathway Changes in a Rat Model of Spinal Cord Injury: A Proteomic Analysis

Hyperbaric Oxygen Therapy (HBOT) has definitive therapeutic effects on spinal cord injury (SCI), but its mechanism of action is still unclear. Here, we've conducted a systemic proteomic analysis to identify differentially expressed proteins (DEPs) between SCI rats and HBOT + SCI rats. The function clustering analysis showed that the top enriched pathways of DEPs include oxygen transport activity, oxygen binding, and regulation of T cell proliferation. The results of functional and signal pathway analyses indicated that metabolic pathways, thermogenesis, LXR/RXR activation, acute phase response signaling, and the intrinsic prothrombin pathway in the SCI + HBOT group was higher than SCI group.

Synergistic neuroprotective effects of hyperbaric oxygen and N-acetylcysteine against traumatic spinal cord injury in rat

BACKGROUND

The mitochondrial dysfunction and following oxidative stress, as well as the spread of inflammation plays major roles in the failure to regenerate following severe spinal cord injury (SCI). In this regard, we investigated the neuroprotective effects of hyperbaric oxygen (HBO), as an anti-apoptotic and anti-inflammatory agent, and N-acetylcysteine (NAC), as a mitochondrial enhancer, in SCI.

MATERIAL AND METHODS

Seventy-five female adult Wistar rats divided into five groups (n = 15): laminectomy alone (Sham) group, SCI group, HBO group (underwent SCI and received HBO), NAC group (underwent SCI and received NAC), and HBO+NAC group (underwent SCI and simultaneously received NAC and HBO). At the end of study, spinal cord tissue samples were taken for evaluation of biochemical profiles including malondialdehyde (MDA), catalase (CAT), superoxide dismutase (SOD) and glutathione (GSH) levels, immunohistochemistry for caspase-3 as well as gene expressions of interleukin (IL)-10, tumor necrosis factor alpha (TNF-α), and IL-1β. Stereological assessments were performed to determine the total volumes, central cavity volumes and as well as numerical density of the neural and glial cells in traumatic area. Moreover, neurological functions were evaluated by the Basso-Beattie-Bresnehan (BBB) and electromyography (EMG).

RESULTS

Our results showed that the stereological parameters, biochemical profiles (except MDA) and neurological function were significantly higher in each HBO, NAC and HBO+NAC groups compared to the SCI group, and were highest in HBO+NAC ones. The transcript for IL-10 gene was significantly upregulated in all treatment regimens compared to SCI group, and was highest in HBO+NAC ones. While expression of TNF-α and IL-1β, latency, as well as density of apoptosis cells in caspase-3 evaluation significantly more decreased in HBO+NAC group compared to other groups.

CONCLUSION

Overall, using combined therapy with HBO and NAC has synergistic neuroprotective effects in SCI treatment.

HBO-PC Promotes Locomotor Recovery by Reducing Apoptosis and Inflammation in SCI Rats: The Role of the mTOR Signaling Pathway

Hyperbaric oxygen preconditioning (HBO-PC) has beneficial effects on the promotion of locomotor recovery by reducing apoptosis and inflammation after traumatic spinal cord injury (SCI). The mammalian target of rapamycin (mTOR) signaling pathway has been implicated in apoptosis and inflammation in many pathophysiological conditions. However, whether HBO-PC improves traumatic SCI-induced locomotor dysfunction by regulating the mTOR signaling pathway and its downstream molecules remains unknown. In the present study, we found that HBO-PC significantly promoted SCI-induced hind-limb locomotor recovery and increased the amplitude and potential of motor evoked potential. Magnetic resonance imaging showed that spinal cavitation or atrophy caused by SCI was obviously alleviated by HBO-PC therapy. Histological analysis showed that the changes in spinal cord neural structure in SCI rats were markedly restored by HBO-PC treatment. Western blot analysis showed that the SCI-induced enhanced levels of p-mTOR, inflammatory cytokines and apoptosis in the spinal cord were abrogated after administration of HBO-PC. Furthermore, intrathecal administration of an mTOR agonist reversed the effects of HBO-PC on locomotor function recovery, p-NF-κB p65 and p-p70S6K levels, inflammation and apoptosis. These findings indicated a new mechanism by which HBO-PC therapy suppressed inflammation and apoptosis through inactivation of the mTOR signaling pathway, which contributed to motor disability in SCI rats.

Effect of Nrf2 signaling pathway on the improvement of intestinal epithelial barrier dysfunction by hyperbaric oxygen treatment after spinal cord injury

Disruption of the intestinal epithelial barrier following spinal cord injury (SCI) seriously affect long-term quality of life. Oxidative stress-induced epithelial cells' injury contributes to the epithelial barrier dysfunction. Hyperbaric oxygen (HBO) treatment has been proved to alleviate SCI. However, it is unclear whether or not HBO treatment affects intestinal barrier function following SCI. In this study, our purpose was to explore the impact of HBO treatment on intestinal epithelial barrier function and underlying mechanisms following SCI. An SCI model was established in rats, and the rats received HBO treatment. Intestinal injury, mucosal permeability, intercellular junction proteins, and oxidative stress indicators were evaluated in our study. We found that HBO treatment significantly alleviated intestinal histological damage, reduced mucosal permeability, and markedly prevented bacterial translocation. Furthermore, HBO treatment significantly increased the expression of Claudin-1 and E-cadherin, inhibited intestinal tissue oxidative stress as demonstrated by upregulation of superoxide dismutase and glutathione, and HBO downregulated malondialdehyde. Mechanically, we demonstrated that HBO treatment ameliorated intestinal oxidative stress possibly through upregulating nuclear factor E2-related factor 2 (Nrf2) and its downstream targets, Heme oxygenase-1(HO-1), NADH-quinone oxidoreductase-1(NQO-1), and glutamate cysteine ligase catalytic subunit (GCLC). These results suggested that HBO treatment triggered antioxidative effects against intestinal epithelial barrier dysfunction by promoting Nrf2 signaling pathway after SCI.

A review on the neuroprotective effects of hyperbaric oxygen therapy

Hyperbaric oxygen therapy, intermittent breathing of 100% oxygen at a pressure upper than sea level, has been shown to be some of the neuroprotective effects and used therapeutically in a wide range of neurological disorders. This review summarizes current knowledge about the neuroprotective effects of hyperbaric oxygen therapy with their molecular mechanisms in different models of neurological disorders.

Knockdown of long noncoding RNA XIST mitigates the apoptosis and inflammatory injury of microglia cells after spinal cord injury through miR-27a/Smurf1 axis

Spinal cord injury (SCI) is a devastating neuropathological condition. Long noncoding RNA X-inactive specific transcript (XIST) is an acknowledged cancer-related gene and participates in the development of SCI. However, role of XIST in SCI remains to be well revealed. Expression of XIST, miRNA-27a-3p (miR-27a) and smad ubiquitination regulatory factor 1 (Smurf1) was detected using RT-qPCR and western blotting. Cell apoptosis and inflammatory injury were assessed by sulforhodamine B (SRB) assay, flow cytometry, western blotting and enzyme-linked immunosorbent assay. The relationship among miR-27a, XIST and Smurf1 was confirmed by dual-luciferase reporter assay, RNA immunoprecipitation and RNA pull-down assay. As a result, we observed higher level of XIST and Smurf1, but lower level of miR-27a in SCI rats and lipopolysaccharide (LPS)-induced primary microglial cells. in vitro, LPS induced SCI microglia cells as described by decreased cell viability and B cell lymphoma 2 (Bcl-2) expression, and increased cell apoptosis rate, Bax and cleaved caspase 3 levels, and tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) secretions. in vivo, a T10 laminectomy caused SCI rats as evidenced by decreased Basso-Beattie-Bresnahan Locomotor Rating Scale (BBB) score and induced expression of Bax, cleaved caspase 3, TNF-α and IL-6. However, silencing of XIST could mitigate the apoptosis and inflammatory injury in LPS-induced microglia and SCI rats. Mechanically, miR-27a interacted with XIST and Smurf1 via target binding. Either miR-27a downregulation or Smurf1 overexpression partially reversed the role of XIST deletion in LPS-treated microglial cells. Collectively, knockdown of XIST could alleviate the apoptosis and inflammatory injury of SCI models in vitro and in vivo through directly modulating miR-27a/Smurf1 axis.

Methotrexate remediates spinal cord injury in vivo and in vitro via suppression of endoplasmic reticulum stress-induced apoptosis

It has been suggested that endoplasmic reticulum stress (ERS) may induce apoptosis following spinal cord injury (SCI). Methotrexate (MTX) has been used as a long-term therapy regimen for rheumatoid arthritis. However, it is not clear whether MTX remediates SCI by inhibiting ERS. In the present study, to establish an in vitro ERS cell model, PC12 cells were pre-incubated with triglycerides (TG). MTT assays revealed that treatment with 1, 2.5, 5 and 10 µM TG decreased PC12 cell viability in a dose-dependent manner. Additionally, MTX treatment significantly reversed the TG-induced decrease in cell viability and increased apoptosis according to the flow cytometry assay (P<0.05). Notably, western blotting indicated that MTX significantly decreased levels of glucose-regulated protein (GRP)78, CCAAT-enhancer-binding protein homologous protein (CHOP) and caspase-12 expression (P<0.05), which were increased following treatment with TG. Furthermore, the in vivo role of MTX in a rat model of SCI was evaluated. The motor behavioral function of rats was improved following treatment with MTX according to Basso, Beattie and Bresnahan scoring (P<0.05). Terminal deoxynucleotidyl-transferase-mediated dUTP nick end staining indicated that there were no apoptotic cells present in sham rats. In the SCI model group, apoptotic cells were observed at day 7; however, the number of apoptotic cells was reduced following an additional 7 days of MTX administration. Furthermore, levels of ERS-associated proteins, including caspase-3, activating transcription factor 6, serine/threonine-protein kinase/endoribonuclease inositol-requiring enzyme 1 α, eukaryotic initiation factor 2 α and GRP78, were significantly increased following SCI; however, administration of MTX for 7 days significantly reversed this effect (P<0.05, P<0.01 and P<0.001). Therefore, MTX may improve SCI by suppressing ERS-induced apoptosis in vitro and in vivo.

Neuroprotective effects of hyperbaric oxygen (HBO) therapy on neuronal death induced by sciatic nerve transection in rat

Background

Recent studies shows that hyperbaric oxygen (HBO) therapy exerts some protective effects against neural injuries. The purpose of this study was to determine the neuroprotective effects of HBO following sciatic nerve transection (SNT).

Methods

Rats were randomly divided into five groups (n = 14 per group): Sham-operated (SH) group, SH + HBO group, SNT group, and SNT + pre- and SNT + post-HBO groups (100% oxygen at 2.0 atm absolute, 60 min/day for five consecutive days beginning on 1 day before and immediately after nerve transaction, respectively). Spinal cord segments of the sciatic nerve and related dorsal root ganglions (DRGs) were removed 4 weeks after nerve transection for biochemical assessment of malodialdehyde (MDA) levels in spinal cord, biochemical assessment of superoxide dismutase (SOD) and catalse (CAT) activities in spinal cord, immunohistochemistry of caspase-3, cyclooxigenase-2 (COX-2), S100beta (S100ß), and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) in spinal cord and DRG.

Results

The results revealed that MDA levels were significantly decreased in the SNT + pre-HBO group, while SOD and CAT activities were significantly increased in SNT + pre- and SNT + post-HBO treated rats. Attenuated caspase-3 and COX-2 expression, and TUNEL reaction could be significantly detected in the HBO-treated rats after nerve transection. Also, HBO significantly increased S100ß expression.

Conclusions

Based on these results, we can conclude that pre- and post-HBO therapy had neuroprotective effects against sciatic nerve transection-induced degeneration.

Hyperbaric oxygen therapy of spinal cord injury

Spinal cord injury (SCI) is a complex disease process that involves both primary and secondary mechanisms of injury and can leave patients with devastating functional impairment as well as psychological debilitation. While no curative treatment is available for spinal cord injury, current therapeutic approaches focus on reducing the secondary injury that follows SCI. Hyperbaric oxygen (HBO) therapy has shown promising neuroprotective effects in several experimental studies, but the limited number of clinical reports have shown mixed findings. This review will provide an overview of the potential mechanisms by which HBO therapy may exert neuroprotection, provide a summary of the clinical application of HBO therapy in patients with SCI, and discuss avenues for future studies.

Macrophage polarization: a key event in the secondary phase of acute spinal cord injury

Acute spinal cord injury (SCI) has become epidemic in modern society. Despite advances made in the understanding of the pathogenesis and improvements in early recognition and treatment, it remains a devastating event, often producing severe and permanent disability. SCI has two phases: acute and secondary. Although the acute phase is marked by severe local and systemic events such as tissue contusion, ischaemia, haemorrhage and vascular damage, the outcome of SCI are mainly influenced by the secondary phase. SCI causes inflammatory responses through the activation of innate immune responses that contribute to secondary injury, in which polarization‐based macrophage activation is a hallmarker. Macrophages accumulated within the epicentre and the haematoma of the injured spinal cord play a significant role in this inflammation. Depending on their phenotype and activation status, macrophages may initiate secondary injury mechanisms and/or promote CNS regeneration and repair. When it comes to therapies for SCI, very few can be performed in the acute phase. However, as macrophage activation and polarization switch are exquisitely sensitive to changes in microenvironment, some trials have been conducted to modulate macrophage polarization towards benefiting the recovery of SCI. Given this, it is important to understand how macrophages and SCI interrelate and interact on a molecular pathophysiological level. This review provides a comprehensive overview of the immuno‐pathophysiological features of acute SCI mainly from the following perspectives: (i) the overview of the pathophysiology of acute SCI, (ii) the roles of macrophage, especially its polarization switch in acute SCI, and (iii) newly developed neuroprotective therapies modulating macrophage polarization in acute SCI.

Hyperbaric oxygen therapy as a potential treatment for post-traumatic stress disorder associated with traumatic brain injury

Traumatic brain injury (TBI) describes the presence of physical damage to the brain as a consequence of an insult and frequently possesses psychological and neurological symptoms depending on the severity of the injury. The recent increased military presence of US troops in Iraq and Afghanistan has coincided with greater use of improvised exploding devices, resulting in many returning soldiers suffering from some degree of TBI. A biphasic response is observed which is first directly injury-related, and second due to hypoxia, increased oxidative stress, and inflammation. A proportion of the returning soldiers also suffer from post-traumatic stress disorder (PTSD), and in some cases, this may be a consequence of TBI. Effective treatments are still being identified, and a possible therapeutic candidate is hyperbaric oxygen therapy (HBOT). Some clinical trials have been performed which suggest benefits with regard to survival and disease severity of TBI and/or PTSD, while several other studies do not see any improvement compared to a possibly poorly controlled sham. HBOT has been shown to reduce apoptosis, upregulate growth factors, promote antioxidant levels, and inhibit inflammatory cytokines in animal models, and hence, it is likely that HBOT could be advantageous in treating at least the secondary phase of TBI and PTSD. There is some evidence of a putative prophylactic or preconditioning benefit of HBOT exposure in animal models of brain injury, and the optimal time frame for treatment is yet to be determined. HBOT has potential side effects such as acute cerebral toxicity and more reactive oxygen species with long-term use, and therefore, optimizing exposure duration to maximize the reward and decrease the detrimental effects of HBOT is necessary. This review provides a summary of the current understanding of HBOT as well as suggests future directions including prophylactic use and chronic treatment.