Functional recovery in rat spinal cord injury induced by hyperbaric oxygen preconditioning

Upregulation of miR‑128 inhibits neuronal cell apoptosis following spinal cord injury via FasL downregulation by repressing ULK1

Spinal cord injury (SCI) is characterized by permanent motor deficits followed by inflammation and oxidative stress, causing neuronal cell death. The present study aimed to investigate the role of microRNA (miR)‑128 in neuronal cell apoptosis and its underlying mechanism. Targeting relationships among miR‑128 and Unc‑51 like autophagy activating kinase 1 (ULK1) and Fas ligand (FasL) were verified using dual‑luciferase reporter assay and ChIP assays. Loss‑ and gain‑of‑function assays were conducted in rat models of SCI to determine the roles of miR‑128 and ULK1 in neuronal cell apoptosis, inflammation, and motor function. Apoptosis, motor function and expression of inflammatory factors were respectively determined by Terminal deoxynucleotidyl transferase‑mediated dUTp nick end‑labeling, Basso, Beattie and Bresnahan (BBB) score and enzyme‑linked immunosorbent assay. Hematoxylin and eosin staining, Nissl staining and immunofluorescence were respectively performed to observe morphological changes and number of neurons and nestin‑positive cells. The neuronal cells were isolated from neuron injury models and cultured in vitro. MTT and flow cytometry was conducted to determine the neuronal cell viability and apoptosis respectively. miR‑128 was downregulated whereas ULK1 was upregulated in rats with SCI. Overexpression of miR‑128 or downregulation of ULK1 inhibited neuronal cell apoptosis and inflammation as evidenced by an increased BBB score and more neurons and nestin‑positive cells, but reduced expression of inflammatory and apoptosis‑related factors. ULK1 was negatively regulated by miR‑128, whereas FasL was positively regulated by ULK1. In vitro experiments validated the roles of miR‑128 and ULK1 in neuronal cell differentiation and apoptosis. In conclusion, the upregulation of miR‑128 depresses neuronal cell apoptosis by downregulating ULK1, thereby attenuating SCI via the downregulation of FasL.

An Extra Breath of Fresh Air: Hyperbaric Oxygenation as a Stroke Therapeutic

Stroke serves as a life-threatening disease and continues to face many challenges in the development of safe and effective therapeutic options. The use of hyperbaric oxygen therapy (HBOT) demonstrates pre-clinical effectiveness for the treatment of acute ischemic stroke and reports reductions in oxidative stress, inflammation, and neural apoptosis. These pathophysiological benefits contribute to improved functional recovery. Current pre-clinical and clinical studies are testing the applications of HBOT for stroke neuroprotection, including its use as a preconditioning regimen. Mild oxidative stress may be able to prime the brain to tolerate full extensive oxidative stress that occurs during a stroke, and HBOT preconditioning has displayed efficacy in establishing such ischemic tolerance. In this review, evidence on the use of HBOT following an ischemic stroke is examined, and the potential for HBOT preconditioning as a neuroprotective strategy. Additionally, HBOT as a stem cell preconditioning is also discussed as a promising strategy, thus maximizing the use of HBOT for ischemic stroke.

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.

Hyperbaric oxygen preconditioning improves postoperative cognitive dysfunction by reducing oxidant stress and inflammation

Postoperative cognitive dysfunction is a crucial public health issue that has been increasingly studied in efforts to reduce symptoms or prevent its occurrence. However, effective advances remain lacking. Hyperbaric oxygen preconditioning has proved to protect vital organs, such as the heart, liver, and brain. Recently, it has been introduced and widely studied in the prevention of postoperative cognitive dysfunction, with promising results. However, the neuroprotective mechanisms underlying this phenomenon remain controversial. This review summarizes and highlights the definition and application of hyperbaric oxygen preconditioning, the perniciousness and pathogenetic mechanism underlying postoperative cognitive dysfunction, and the effects that hyperbaric oxygen preconditioning has on postoperative cognitive dysfunction. Finally, we conclude that hyperbaric oxygen preconditioning is an effective and feasible method to prevent, alleviate, and improve postoperative cognitive dysfunction, and that its mechanism of action is very complex, involving the stimulation of endogenous antioxidant and anti-inflammation defense systems.

Hyperbaric oxygen therapy and preconditioning for ischemic and hemorrhagic stroke

To date, the therapeutic methods for ischemic and hemorrhagic stroke are still limited. The lack of oxygen supply is critical for brain injury following stroke. Hyperbaric oxygen (HBO), an approach through a process in which patients breathe in 100% pure oxygen at over 101 kPa, has been shown to facilitate oxygen delivery and increase oxygen supply. Hence, HBO possesses the potentials to produce beneficial effects on stroke. Actually, accumulated basic and clinical evidences have demonstrated that HBO therapy and preconditioning could induce neuroprotective functions via different mechanisms. Nevertheless, the lack of clinical translational study limits the application of HBO. More translational studies and clinical trials are needed in the future to develop effective HBO protocols.

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.

Transplantation of erythropoietin gene-modified neural stem cells improves the repair of injured spinal cord

The protective effects of erythropoietin on spinal cord injury have not been well described. Here, the eukaryotic expression plasmid pcDNA3.1 human erythropoietin was transfected into rat neural stem cells cultured in vitro. A rat model of spinal cord injury was established using a free falling object. In the human erythropoietin-neural stem cells group, transfected neural stem cells were injected into the rat subarachnoid cavity, while the neural stem cells group was injected with non-transfected neural stem cells. Dulbecco's modified Eagle's medium/F12 medium was injected into the rats in the spinal cord injury group as a control. At 1–4 weeks post injury, the motor function in the rat lower limbs was best in the human erythropoietin-neural stem cells group, followed by the neural stem cells group, and lastly the spinal cord injury group. At 72 hours, compared with the spinal cord injury group, the apoptotic index and Caspase-3 gene and protein expressions were apparently decreased, and the bcl-2 gene and protein expressions were noticeably increased, in the tissues surrounding the injured region in the human erythropoietin-neural stem cells group. At 4 weeks, the cavities were clearly smaller and the motor and somatosensory evoked potential latencies were remarkably shorter in the human erythropoietin-neural stem cells group and neural stem cells group than those in the spinal cord injury group. These differences were particularly obvious in the human erythropoietin-neural stem cells group. More CM-Dil-positive cells and horseradish peroxidase-positive nerve fibers and larger amplitude motor and somatosensory evoked potentials were found in the human erythropoietin-neural stem cells group and neural stem cells group than in the spinal cord injury group. Again, these differences were particularly obvious in the human erythropoietin-neural stem cells group. These data indicate that transplantation of erythropoietin gene-modified neural stem cells into the subarachnoid cavity to help repair spinal cord injury and promote the recovery of spinal cord function better than neural stem cell transplantation alone. These findings may lead to significant improvements in the clinical treatment of spinal cord injuries.

Hyperbaric oxygen preconditioning attenuates neuroinflammation after intracerebral hemorrhage in rats by regulating microglia characteristics

Intracerebral Hemorrhage (ICH) results in a detrimental neurologic disorder with complicated secondary brain injury. Hyperbaric oxygen preconditioning (HBOP) may be a safe and effective therapeutic method for ICH victims. Our previous studies have demonstrated that HBOP induces neuroprotection in cerebral ischemia and traumatic brain injury. This study aimed to investigate whether HBOP could alleviate neuroinflammation by regulating changes in microglia characteristics in a rat model of ICH. ICH was induced by autologous arterial blood injection, and animals were sacrificed at 12, 24, and 72 h post injury. We measured motor function and brain water content to evaluate the extent of inflammation. Fluoro-Jade C and TNF-α staining was used to characterize neuronal degeneration and neuroinflammatory cytokines, and immunofluorescence staining was performed for CD11b to show activated microglia and Iba-1 to show microglia. Our results indicate that motor dysfunction and brain water content are alleviated by HBOP, and Fluoro-Jade C staining demonstrates that neuron degeneration decreased in the HBOP group. The growth of Iba-1-positive microglia decreased in the HBOP group. Moreover, TNF-α was dynamically reduced in the HBOP group compared with the ICH group. CD11b-Iba-1 double staining demonstrated that the ratio of CD11b and Iba-1 was significantly decreased in the HBOP group. Overall, the data demonstrated that HBOP could significantly alleviate the ICH-induced neuroinflammation by regulating microglia characteristics changing. The phenomenon may propel the progress of the relation between microglia and HBOP and represent a novel target for ICH treatment.

Effect of hyperbaric oxygen preconditioning on peri-hemorrhagic focal edema and aquaporin-4 expression

The aim of the present study was to investigate the effect of hyperbaric oxygen preconditioning (HBO-PC) on peri-hemorrhagic focal edema and aquaporin-4 (AQP-4) expression in an experimental intracerebral hemorrhage (ICH) rat model. Sixty-six Sprague Dawley® rats were divided into three groups: The sham-surgery group (SHG; n=6); the control group (A-ICH; n=30), in which the rats were injected with autologous blood; and the experimental HBO-PC group (P-HBO; n=30). The rats underwent brain edema and AQP-4 detection at 5 postoperative time-points (24, 48 and 72 h and 5 and 7 days). The water content in the brain tissues of the A-ICH animals was higher than that in the brain tissues of the SHG rats at each time-point (P<0.05), and the edema in the P-HBO was significantly more severe 24 and 48 h postoperatively than that at 7 days postoperatively (P<0.05). The difference between the P-HBO and A-ICH was significant at 48 and 72 h postoperatively (P<0.05). AQP-4 was expressed in the post-hemorrhagic rat brains of all groups; the SHG animals exhibited low expression, while the A-ICH animals exhibited an increased expression 24 h postoperatively. In the A-ICH, expression peaked at 48 h postoperatively and began to decrease gradually after 72 h. At the 7-day time-point, the expression level in the A-ICH was closer to but still higher than that of the SHG animals (P<0.05). The differences between the P-HBO and A-ICH animals at the postoperative 24-h, 48-h and 7-day time-points were statistically significant (P<0.05). In conclusion, HBO-PC may downregulate AQP-4 expression to reduce the intracerebral edema, thus strengthening tolerance to ICH and protecting the nerves.

Hyperbaric oxygen therapy in China

Hyperbaric oxygen therapy (HBOT) is defined as a treatment in which a patient intermittently breathes 100% oxygen while the treatment chamber is pressurized to a pressure greater than sea level (1.0 atmosphere absolute, ATA). In China, for nearly 50 years, HBOT has been used as a primary or adjuvant therapy to treat a variety of diseases. This article mainly reviewed the indications and contraindications of HBOT, as well as the status of clinical and experimental HBOT research in China. At the same time, there is a brief introduction of hyperbaric oxygen preconditioning (HBO-PC) in China.

Hyperbaric oxygen preconditioning induces tolerance against oxidative injury and oxygen-glucose deprivation by up-regulating heat shock protein 32 in rat spinal neurons

OBJECTIVE

Hyperbaric oxygen (HBO) preconditioning (HBO-PC) has been testified to have protective effects on spinal cord injury (SCI). However, the mechanisms remain enigmatic. The present study aimed to explore the effects of HBO-PC on primary rat spinal neurons against oxidative injury and oxygen-glucose deprivation (OGD) and the relationship with heat shock proteins (HSPs).

METHODS

Primary rat spinal neurons after 7 days of culture were used in this study. HSPs were detected in rat spinal neurons following a single exposure to HBO at different time points by Western blot. Using lactate dehydrogenase release assay and cell counting kit-8 assay, the injuries induced by hydrogen peroxide (H2O2) insult or OGD were determined and compared among neurons treated with HBO-PC with or without HSP inhibitors.

RESULTS

The results of Western blot showed that HSP27, HSP70 and HSP90 have a slight but not significant increase in primary neurons following HBO exposure. However, HSP32 expression significantly increased and reached highest at 12 h following HBO exposure. HBO-PC significantly increased the cell viability and decreased the medium lactate dehydrogenase content in cultures treated with H2O2 or OGD. Pretreatment with zinc protoporphyrin IX, a specific inhibitor of HSP32, significantly blocked the protective effects of HBO-PC.

CONCLUSIONS

These results suggest that HBO-PC could protect rat spinal neurons in vitro against oxidative injury and OGD mostly by up-regulating of HSP32 expression.

Reduced apoptosis by combining normobaric oxygenation with ethanol in transient ischemic stroke

BACKGROUND AND PURPOSE

The effect of normobaric oxygen (NBO) on apoptosis remains controversial. The present study evaluated the effect of NBO on ischemia-induced apoptosis and assessed the potential for improved outcomes by combining NBO administration with another neuroprotective agent, ethanol, in a rat stroke model.

METHODS

Rats were subjected to right middle cerebral artery occlusion (MCAO) for 2h. At the onset of reperfusion, ischemic animals received either NBO (2h duration), an intraperitoneal injection of ethanol (1.0g/kg), or both NBO and ethanol. Extent of brain injury was determined by infarct volume, neurological deficit, and apoptotic cell death. Expression of pro- and anti-apoptotic proteins was evaluated through Western immunoblotting.

RESULTS

Given alone, NBO and ethanol each slightly (p<0.05) reduced infarct volume to 38% and 37%, respectively, as compared to the impressive reduction of 51% (p<0.01) seen with combined NBO-ethanol administration. Neurologic deficits were also significantly reduced by 48% with combined NBO-ethanol therapy, as compared to lesser reductions of 24% and 23% with NBO or ethanol, respectively. Combined NBO-ethanol therapy decreased apoptotic cell death by 49%, as compared to 31% with NBO and 30% with ethanol. Similarly, combination therapy significantly increased expression of anti-apoptotic factors (Bcl-2 and Bcl-xL) and significantly reduced expression of pro-apoptotic proteins (BAX, Caspase-3, and AIF), as compared to the minimal or nil protein expression changes elicited by NBO or ethanol alone.

CONCLUSIONS

In rats subjected to ischemic stroke, NBO administration salvages ischemic brain tissue through evidenced decrease in apoptotic cell death. Combined NBO therapy with ethanol administration greatly improves both degree of neuroprotection and associated apoptosis.