Hyperbaric oxygen treatment in the experimental spinal cord injury model

Acute Hyperoxia Improves Spinal Cord Oxygenation and Circulatory Function Following Cervical Spinal Cord Injury in Rats

Spinal cord injury is associated with spinal vascular disruptions that result in spinal ischemia and tissue hypoxia. This study evaluated the therapeutic efficacy of normobaric hyperoxia on spinal cord oxygenation and circulatory function at the acute stage of cervical spinal cord injury. Adult male Sprague Dawley rats underwent dorsal cervical laminectomy or cervical spinal cord contusion. At 1-2 days after spinal surgery, spinal cord oxygenation was monitored in anesthetized and spontaneously breathing rats through optical recording of oxygen sensor foils placed on the cervical spinal cord and pulse oximetry. The arterial blood pressure, heart rate, blood gases, and peripheral oxyhemoglobin saturation were also measured under hyperoxic (50% O2) and normoxic (21% O2) conditions. The results showed that contused animals had significantly lower spinal cord oxygenation levels than uninjured animals during normoxia. Peripheral oxyhemoglobin saturation, arterial oxygen partial pressure, and mean arterial blood pressure are significantly reduced following cervical spinal cord contusion. Notably, spinal oxygenation of contused rats could be improved to a level comparable to uninjured animals under hyperoxia. Furthermore, acute hyperoxia elevated blood pressure, arterial oxygen partial pressure, and peripheral oxyhemoglobin saturation. These results suggest that normobaric hyperoxia can significantly improve spinal cord oxygenation and circulatory function in the acute phase after cervical spinal cord injury. We propose that adjuvant normobaric hyperoxia combined with other hemodynamic optimization strategies may prevent secondary damage after spinal cord injury and improve functional recovery.

Activation of SIRT1 by hyperbaric oxygenation promotes recovery of motor dysfunction in spinal cord injury rats

BACKGROUND

Hyperbaric oxygenation (HBO) therapy can improve locomotor dysfunction following spinal cord injury (SCI). Emerging evidence has demonstrated that sirtuin1 (SIRT1) exerts protective effects on neurons. However, whether HBO alleviates locomotor dysfunction by regulating SIRT1 is unclear.

METHODS

The traumatic SCI animal model was performed on the adult Sprague-Dawley rats. The Basso, Beattie Bresnahan (BBB) locomotor rating scale was used to evaluate the open-field locomotor function. Western blot, real-time quantitative reverse transcription polymerase chain reaction, SIRT1 activity assay, and enzyme-linked immunosorbent assays were performed to explore the molecular mechanisms.

RESULTS

We found that series HBO therapy significantly improved locomotor dysfunction and ameliorated the decreased mRNA, protein, and activity of spinal cord SIRT1 induced by traumatic SCI injury in rats. In addition, intraperitoneal injection of SIRT1 inhibitor EX-527 abolished the beneficial effects of series HBO treatment on locomotor deficits. Importantly, series HBO treatment following the traumatic SCI injury inhibited the inflammatory cascade and apoptosis-related protein, which was retained by EX-527 and enhanced by SRT1720. Furthermore, EX-527 blocked the enhanced induction of autophagy series with the HBO application.

CONCLUSION

These findings demonstrated a new mechanism for series HBO therapy involving activation of SIRT1 and subsequent modulation of the inflammatory cascade, apoptosis, and autophagy, which contributed to the recovery of motor dysfunction.

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.

Evaluation of the neuroprotective effects of ozone in an experimental spine injury model

OBJECTIVE

The pathophysiology of spine injury consists of primary and secondary damage mechanisms. The vast majority of treatments aim to prevent or at least stop the progression of secondary neurotoxic events during the acute period. Ozone has been found to have potent antiinflammatory effects, to activate the immune system, and to have a substantial impact on the antioxidant system. In this study the authors aimed to evaluate the neuroprotective effects of ozone and their possible roles in recovery from spine injury, assessed based on biochemical, histological, and neurological parameters using an experimental spine injury model in rats.

METHODS

The study included 31 female Wistar albino rats. The rats were divided randomly into 5 groups, with 7 rats in each group except the sham group, which contained 3 rats, as follows: group 1 (sham), laminectomy; group 2 (control), laminectomy and spinal trauma with no medical treatment (0.5 ml isotonic saline applied 1 hour postsurgery); group 3, single medical treatment with 30 mg/kg methylprednisolone applied intraperitoneally 1 hour after laminectomy and trauma; group 4, single medical treatment with 60 μg/ml ozone at 0.7 mg/kg applied intraperitoneally 1 hour after laminectomy and trauma; and group 5, double medical treatment with 30 mg/kg methylprednisolone and 60 μg/ml ozone at 0.7 mg/kg applied intraperitoneally 1 hour after laminectomy and trauma. After neurosurgery, neurobehavioral tests were performed in all groups. After 7 days of follow-up, all the rats were killed. Biopsy specimens obtained from trauma sites were examined using H & E, cresyl violet, immunohistochemical (anticonnexin-43), and TUNEL staining processes. Levels of interleukin (IL)-1β, IL-6, and tumor necrosis factor-α (TNF-α) and total oxidant status (TOS) and total antioxidant status (TAS) were measured in blood samples.

RESULTS

The level of neurobehavioral healing was the highest in the double-treatment group (group 5), and the difference between the groups was significant. The minimum IL-6 level was found in group 5, indicating that the antiinflammatory impact was the most significant in this group (p = 0.01). Additionally, ozone was found to reduce oxidant stress more effectively than methylprednisolone (p = 0.03). Although methylprednisolone was superior to ozone in terms of the antiinflammatory effect, this effect was greater in group 5. Nevertheless, the number of neurons in group 5 was close to that of the control group, and the number of apoptotic cells was the least in group 5 (p < 0.001).

CONCLUSIONS

In acute spinal injury, the combined application of methylprednisolone and ozone was found to have a greater antiinflammatory effect, hasten clinical recovery, and increase histological recovery compared with methylprednisolone therapy alone. This study showed that this combination therapy of methylprednisolone with the addition of ozone might have a more beneficial effect in the treatment of spinal injury than methylprednisolone therapy alone.

Effects of heparin and hyperbaric oxygenation on necrosis reduction in an animal model for degloving injuries

Objective:

to evaluate the efficacy of the treatment with hyperbaric oxygen therapy or with topical and intralesional heparin in an animal model of degloving lesions.

Methods:

we conducted an experimental study with adult, male Wistar rats submitted to degloving of the left hind limb and divided into four groups according to the treatment: Group 1 (control) - without treatment; Group 2 (Heparin) - intralesional application at the time of surgery and topically, in the postoperative period, with heparin spray 10,000IU/mL; Group 3 (hyperbaric oxygenation) - daily sessions of 30 minutes in a hyperbaric chamber with 100% oxygen and 2 ATA pressure; Group 4 (positive control) - administration of a single dose of 45 mg/kg of intraperitoneal allopurinol. On the seventh day, we killed the animals, removed the cutaneous flaps and measured the total and necrotic areas, as well as computed the percentage of necrotic area.

Results:

the mean percentage of necrosis in the control group was 56.03%; in the positive control group it was 51.36% (p<0.45); in the heparin group, 42.10% (p<0.07); and in the hyperbaric oxygen therapy group, 31.58% (p<0.01) .

Conclusion:

both hyperbaric oxygen and heparin therapies were effective in reducing the percentage of necrosis in the model studied, although only the hyperbaric oxygenation showed statistical significance.

Objetivos:

avaliar a eficácia do tratamento com oxigenoterapia hiperbárica ou com heparina tópica e intralesional em modelo animal de desluvamentos.

Métodos:

estudo experimental, com ratos adultos machos Wistar, submetidos a desluvamento do membro posterior esquerdo e divididos em quatro grupos, de acordo com o tratamento: Grupo 1 (controle) - sem tratamento; Grupo 2 (Heparina) - aplicação intralesional no momento da cirurgia e tópica, no pós operatório, com spray de heparina 10.000UI/mL; Grupo 3 (oxigenação hiperbárica) - sessões diárias de 30 minutos em câmara hiperbárica com 100% de oxigênio e 2 ATA de pressão; Grupo 4 (controle positivo) - administração de dose única de 45mg/kg de alopurionol intraperitoneal. No sétimo dia os animais foram mortos e os retalhos cutâneos foram retirados e realizadas medidas das áreas total e necrótica, bem como cálculo da porcentagem da área de necrose.

Resultados:

a média da porcentagem de necrose do grupo controle foi 56,03%; no grupo controle positivo, 51,36% (p≤0,45); no grupo da heparina, 42,10% (p≤0,07) e no grupo da oxigenoterapia hiperbárica, 31,58% (p≤0,01).

Conclusão:

tanto a oxigenoterapia hiperbárica quanto a terapia com heparina mostraram-se eficazes na redução do percentual de necrose no modelo estudado, embora neste trabalho apenas a oxigenação hiperbárica tenha demonstrado significância estatística.

Hyperbaric oxygen treatment of spinal cord injury in rat model

Background

The purpose of this study was to investigate the therapeutic effects and mechanisms of hyperbaric oxygen (HBO) treatment on rats following spinal cord injury (SCI).

Methods

A total of 45 Sprague-Dawley (SD) rats were randomly divided into three groups. Sham-SCI group was surgically exposed but not subjected to the SCI procedure. SCI-control group was administered SCI and treated with regular air. SCI-HBO group was administered SCI and HBO treatment. Neuromotor functions were examined using the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale and the inclined plane assessment at before SCI (baseline) and after SCI. Superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels were measured.

Results

Starting from Day 1 after SCI but except Day 2, the SCI-HBO group has significantly higher BBB scores than the SCI-control group. After SCI, the maximum inclination angles at which rats could maintain were significantly lower in both SCI groups. But the maximum angles were significantly bigger for the rats in the SCI-HBO group than those on the SCI-control group at 5, 10 and 20 days after SCI. SOD activities in SCI-HBO rats were significantly higher and MDA levels were significantly lower than in SCI-control rats, at two and five days after SCI. There was also less cystic degeneration of spinal cord in SCI-HBO rats, compared to SCI-control rats.

Conclusions

These results suggest that HBO treatment has a therapeutic value in treating SCI. Increased oxygen free radical scavenging and reduced lipid oxidation may be one of the mechanisms.

Simvastatin protects ischemic spinal cord injury from cell death and cytotoxicity through decreasing oxidative stress: in vitro primary cultured rat spinal cord model under oxygen and glucose deprivation-reoxygenation conditions

Background

Ischemia and the following reperfusion damage are critical mechanisms of spinal cord injury. Statins have been reported to decrease ischemia–reperfusion injury in many organs including the spinal cord. Anti-oxidative effect is one of the main protective mechanisms of statin against neuronal death and cytotoxicity. We hypothesized that statins’ anti-oxidative property would yield neuroprotective effects on spinal cord ischemia–reperfusion injury

Methods

Primary cultured spinal cord motor neurons were isolated from Sprague–Dawley rat fetuses. Ischemia–reperfusion injury model was induced by 60 min of oxygen and glucose deprivation (OGD) and 24 h of reoxygenation. Healthy and OGD cells were treated with simvastatin at concentrations of 0.1, 1, and 10 μM for 24 h. Cell viability was assessed using water-soluble tetrazolium salt (WST)-8, cytotoxicity with LDH, and production of free radicals with DCFDA (2′,7′-dichlorofluorescein diacetate).

Results

OGD reduced neuronal viability compared to normoxic control by 35.3%; however, 0.1–10 μM of simvastatin treatment following OGD improved cell survival. OGD increased LDH release up to 214%; however, simvastatin treatment attenuated its cytotoxicity at concentrations of 0.1–10 μM (p < 0.001 and p = 0.001). Simvastatin also reduced deteriorated morphological changes of motor neurons following OGD. Oxidative stress was reduced by simvastatin (0.1–10 μM) compared to untreated cells exposed to OGD (p < 0.001).

Conclusions

Simvastatin effectively reduced spinal cord neuronal death and cytotoxicity against ischemia–reperfusion injury, probably via modification of oxidative stress.

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.

Changes in autophagy in rats after spinal cord injury and the effect of hyperbaric oxygen on autophagy

The purpose of this study was to explore the effects of Hyperbaric oxygen (HBO) on the autophagic changes after induction of spinal cord injury (SCI) in rats. A total of 75 rats were randomly divided into the sham-operated group, the spinal cord injury group, and the SCI+HBO group. We found that at 7 d and 14 d after surgery, the BBB scores were higher in the SCI+HBO group in comparison to the SCI group. The expression of Beclin-1 and LC3II was upregulated in the SCI and SCI+HBO groups after SCI. Fluorescently stained Beclin-1 and LC3II proteins were barely detectable in the sham group. In contrast, Beclin-l and LC3II expression was observed in neurons and glial cells from the SCI and SCI+HBO groups. Beclin-1 and LC3II expression appeared at 6h after SCI. At each time point, Beclin-1 and LC3II expression was significantly higher in the SCI+HBO group compared to the SCI group. These results suggest that autophagy is activated in rats after SCI and sustained over a period of time. HBO treatment enhances autophagy expression in rats after SCI and accelerates cell repair rate, which may represent one of the mechanisms of action of HBO in the treatment of SCI.

Effects of hyperbaric oxygen therapy on NACHT domain-leucine-rich-repeat- and pyrin domain-containing protein 3 inflammasome expression in rats following spinal cord injury

The clinical application of hyperbaric oxygen therapy (HBOT) in spinal cord injury (SCI) has been reported, however the mechanism underlying its therapeutic effects remains to be elucidated. In the present study, SCI was modeled in male Sprague‑Dawley rats. A total of 120 rats were randomly divided into four groups: Sham‑operated group (SH); sham‑operated and hyperbaric oxygen group (SH+HBO); spinal cord injury group (SCI) and spinal cord injury and hyperbaric oxygen treatment group (SCI+HBO). The rats in each group were randomly divided into five smaller groups (12 h, 1, 3, 7 and 14 days after surgery). The mRNA and protein expression levels of NACHT domain‑, leucine‑rich‑repeat‑ and pyrin domain‑containing protein 3 (NALP3) inflammasome, including NALP3, adaptor molecule apoptosis‑associated speck‑like protein (ASC) and caspase‑1 were determined at several time points following injury. The results of the present study demonstrated that HBOT compromised the mRNA and protein expression levels of NALP3, ASC and caspase‑1 in the SCI model rats and HBOT mitigated SCI‑induced interleukin 1β release in the injured spinal cord tissue. It was concluded that HBOT is an effective approach, which can prevent against spinal cord injury, likely by inactivating NALP3 inflammasome.