Dose-Dependent Effect of Hyperbaric Oxygen Treatment on Burn-Induced Neuropathic Pain in Rats

Complex Hippocampal Response to Thermal Skin Injury and Protocols with Hyperbaric Oxygen Therapy and Filipendula ulmaria Extract in Rats

The aim of this study was to evaluate the alterations of the hippocampal function that may be related to anxiogenic response to thermal skin injury, including the morpho-functional alterations, and the effects of hyperbaric oxygen (HBO) and Filipendula ulmaria (FU) extract in the treatment of anxiety-like behavior that coincides with thermal skin injury. A rat thermal skin injury experimental model was performed on 2-month-old male Wistar albino rats. The evaluated therapeutic protocols included HBO and/or antioxidant supplementation. HBO was applied for 7 days in the hyperbaric chamber (100% O2, 2.5 ATA, 60 min). Oral administration of FU extract (final concentration of 100 mg/kg b.w.) to achieve antioxidant supplementation was also applied for 7 days. Anxiety level was estimated in the open field and elevated plus-maze test, which was followed by anesthesia, sacrifice, and collection of hippocampal tissue samples. HBO treatment and FU supplementation significantly abolished anxiogenic response to thermal skin injury. This beneficial effect was accompanied by the reduction in hippocampal pro-inflammatory and pro-apoptotic indicators, and enhanced BDNF and GABA-ARα2S gene expression, previously observed in untreated burns. The hippocampal relative gene expression of melatonin receptors and NPY positively responded to the applied protocols, in the same manner as µ and δ opioid receptors, while the opposite response was observed for κ receptors. The results of this study provide some confirmations that adjuvant strategies, such as HBO and antioxidant supplementation, may be simultaneously applied in the treatment of the anxiety-like behavior that coincides with thermal skin injury.

Evaluation of Melatonin and its Nanostructures Effects on Skin Disorders Focused on Wound Healing

Skin is the largest organ of the human body functioning as a great primitive defensive barrier against different harmful environmental factors. However, it is damaged through varying injuries such as different wounds, burns, and skin cancers that cause disruption in internal organs and essential mechanisms of the body through inflammation, oxidation, coagulation problems, infection, etc. Melatonin is the major hormone of the pineal gland that is also effective in skin disorders due to strong antioxidant and anti-inflammatory features with additional desirable antiapoptotic, anti-cancer, and antibiotic properties. However, melatonin characteristics require improvements due to its limited water solubility, halflife and stability. The application of nanocarrier systems can improve its solubility, permeability, and efficiency, as well as inhibit its degradation and promote photostability. Our main purpose in the current review is to explore the possible role of melatonin and melatonin-containing nanocarriers in skin disorders focused on wounds. Additionally, melatonin's effect in regenerative medicine and its structures as a wound dressing in skin damage has been considered.

Simultaneous Administration of Hyperbaric Oxygen Therapy and Antioxidant Supplementation with Filipendula ulmaria Extract in the Treatment of Thermal Skin Injuries Alters Nociceptive Signalling and Wound Healing

Background and Objectives: Thermal skin injuries are a prevalent cause of skin damage, potentially leading to severe morbidity and significant mortality. In this study, we intended to estimate the effects of HBO (hyperbaric oxygen treatment) and antioxidant supplementation with Filipendula ulmaria extract, individually and simultaneously, in the treatment of thermal skin injuries. Materials and Methods: As a thermal skin injury experimental model, we used two-month-old male Wistar albino rats. Thermal injuries were made with a solid aluminium bar at a constant temperature of 75 °C for 15 s. Hyperbaric oxygen treatment was performed in a specially constructed hyperbaric chamber for rats (HYB-C 300) for seven consecutive days (100% O2 at 2.5 ATA for 60 min). Antioxidant supplementation was performed with oral administration of Filipendula ulmaria extract dissolved in tap water to reach a final concentration of 100 mg/kg b.w. for seven consecutive days. Results: Simultaneous administration of hyperbaric oxygen therapy and antioxidant supplementation with Filipendula ulmaria extract significantly ameliorated the macroscopic and histopathological characteristics of the wound area and healing. Also, this therapeutic approach decreased the local expression of genes for proinflammatory mediators and increased the expression of the μ-opioid receptor and the MT1 and MT2 receptors in the wound area and spinal cord, with a consequent increase in reaction times in behavioural testing. Conclusions: In conclusion, the presented results of our study allow evidence for the advantages of the simultaneous employment of HBO and antioxidant supplementation in the treatment of thermal skin injuries, with special reference to the attenuation of painful sensations accompanied by this type of trauma.

The role of hyperbaric oxygen therapy in the management of perioperative peripheral nerve injury: a scoping review of the literature

Background/importance

Peripheral nerve injury is an uncommon but potentially catastrophic complication of anesthesia and surgery, for which there are limited effective treatment options. Hyperbaric oxygen therapy is a unique medical intervention which improves tissue oxygen delivery and reduces ischemia via exposure to oxygen at supra-atmospheric partial pressures. While the application of hyperbaric oxygen therapy has been evidenced for other medical conditions involving relative tissue ischemia, its role in the management of peripheral nerve injury remains unclear.

Objective

This scoping review seeks to characterize rehabilitative outcomes when hyperbaric oxygen therapy is applied as an adjunct therapy in the treatment of perioperative peripheral nerve injury.

Evidence review

The review was conducted according to Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines for scoping reviews, using a systematic screening and extraction process. The search included articles published from database inception until June 11, 2022, which reported clinical outcomes (in both human and non-human models) of peripheral nerve injury treated with hyperbaric oxygen therapy.

Findings

A total of 51 studies were included in the narrative synthesis. These consisted of animal (40) and human studies (11) treating peripheral nerve injury due to various physiological insults. Hyperbaric oxygen therapy protocols were highly heterogenous and applied at both early and late intervals relative to the time of peripheral nerve injury. Overall, hyperbaric oxygen therapy was reported as beneficial in 88% (45/51) of included studies (82% of human studies and 90% of animal studies), improving nerve regeneration and/or time to recovery with no reported major adverse events.

Conclusions

Existing data suggest that hyperbaric oxygen therapy is a promising intervention in the management of perioperative peripheral nerve injury, in which tissue ischemia is the most common underlying mechanism of injury, neurological deficits are severe, and treatment options are sparse. This positive signal should be further investigated in prospective randomized clinical trials.

Is There a Place for Hyperbaric Oxygen Therapy?

Hyperbaric oxygen therapy (HBOT) involves treating patients by providing 100% oxygen through inhalation while inside a treatment pressurized chamber. The oxygen acts as a drug and the hyperbaric chamber as the dosing device. The effect of hyperbaric hyperoxia is dose dependent and, therefore, treatment depth and duration are important when considering its use. HBOT can either be the primary method of treatment or used adjunctively to medications or surgical techniques. The underpinning physiology is to bring oxygen-rich plasma to hypoxic tissue, preventing reperfusion injury, strengthening immune responsiveness, and encouraging new collagen deposition as well as endothelial cell formation.

Simultaneous hyperbaric oxygen therapy during systemic chemotherapy reverses chemotherapy-induced peripheral neuropathy by inhibiting TLR4 and TRPV1 activation in the central and peripheral nervous system

BACKGROUND AND OBJECTIVES

Chemotherapy-induced peripheral neuropathy (CIPN) is considered one of the most common sequelae in patients with cancer who experience consistent abnormal sensations or pain symptoms during or after paclitaxel (PAC) chemotherapy. Transient receptor potential vanilloid 1 (TRPV1) and toll-like receptor 4 (TLR4) have been reported to interact in the nervous system in patients with CIPN. The antinociceptive effects of hyperbaric oxygen therapy (HBOT) on CIPN was demonstrated in this study through behavior tests. Using a CIPN rat model, we examined the effects of simultaneous HBOT (SHBOT) administration during chemotherapy and discovered that SHBOT achieved better reversal effects than chemotherapy alone.

MATERIALS AND METHODS

Twenty-four rats were randomly allocated to four groups: control, PAC, SHBOT, and HBOT after PAC groups. Behavior tests were performed to evaluate mechanical allodynia and thermal hyperalgesia status. Tissues from the spinal cord and dorsal root ganglions were collected, and TLR4 and TRPV1 expression and microglial activation were investigated through immunofluorescence (IF) staining.

RESULTS

The mechanical and thermal behavior tests revealed that HBOT intervention during PAC treatment led to the early alleviation of CIPN symptoms and inhibited CIPN deterioration. IF staining revealed that TLR4, TRPV1, and microglial activation were all upregulated in PAC-injected rats and exhibited early and significant downregulation in SHBOT-treated rats.

CONCLUSION

This study is the first to demonstrate that the use of SHBOT during PAC treatment has potential for the early suppression of CIPN initiation and deterioration, indicating that it can alleviate CIPN symptoms and may reverse CIPN in patients undergoing systemic chemotherapy.

Hyperbaric oxygen therapy effectively alleviates D-galactose-induced-age-related cardiac dysfunction via attenuating mitochondrial dysfunction in pre-diabetic rats

Currently, the prevalence of obesity in aging populations is fast growing worldwide. Aging induced by D-galactose (D-gal) is proven to cause the worsening of cardiac dysfunction in pre-diabetic rats via deteriorating cardiac mitochondrial function. Hyperbaric oxygen therapy (HBOT) has been shown to attenuate D-gal-induced cognitive deterioration through decreased inflammation and apoptosis. We tested the hypothesis that HBOT alleviates D-gal induced cardiac dysfunction via improving mitochondrial function in pre-diabetic rats. Wistar rats (n=56) were fed normal diet or high-fat diet for 12 weeks. For subsequent 8 weeks, they were subcutaneously injected either vehicle (0.9% normal saline) or D-gal (150mg/kg/day). Rats were randomly subdivided into 7 groups at week 21: sham-treated (normal diet fed rats with vehicle (NDV), high-fat diet fed rats with vehicle (HFV), normal diet fed rats with D-gal (NDDg), high-fat diet fed rats with D-gal (HFDg)) and HBOT-treated (HFV, NDDg, HFDg). Sham rats received ambient pressure of oxygen while HBOT-treated ones received 100% oxygen given once daily for 60 minutes at 2 atmosphere absolute. HBOT reduced metabolic impairments, mitochondrial dysfunction and increased autophagy, resulting in an improvement of cardiac function in aged pre-diabetic rats.

The History and Development of Hyperbaric Oxygenation (HBO) in Thermal Burn Injury

Background and Objectives: Hyperbaric oxygenation (HBO) denotes breathing of 100% oxygen under elevated ambient pressure. Since the initiation of HBO for burns in 1965, abundant experimental and clinical work has been done. Despite many undisputedly positive and only a few controversial results on the efficacy of adjunctive HBO for burn injury, the method has not yet been established in clinical routine. Materials and Methods: We did a retrospective analysis of the literature according to PRISMA-guidelines, from the very beginning of HBO for burns up to present, trying to elucidate the question why HBO is still sidelined in the treatment of burn injury. Results: Forty-seven publications (32 animal experiments, four trials in human volunteers and 11 clinical studies) fulfilled the inclusion criteria. Except four investigators who found little or no beneficial action, all were able to demonstrate positive effects of HBO, most of them describing less edema, improved healing, less infection or bacterial growth and most recently, reduction of post-burn pain. Secondary enlargement of burn was prevented, as microvascular perfusion could be preserved, and cells were kept viable. The application of HBO, however, concerning pressure, duration, frequency and number of treatment sessions, varied considerably. Authors of large clinical studies underscored the intricate measures required when administering HBO in severe burns. Conclusions: HBO unquestionably has a positive impact on the pathophysiological mechanisms, and hence on the healing and course of burns. The few negative results are most likely due to peculiarities in the administration of HBO and possibly also to interactions when delivering the treatment to severely ill patients. Well-designed studies are needed to definitively assess its clinical value as an adjunctive treatment focusing on relevant outcome criteria such as wound healing time, complications, length of hospital stay, mortality and scar quality, while also defining optimal HBO dosage and timing.

Hyperbaric Oxygen Therapy Attenuates Burn-Induced Denervated Muscle Atrophy

Background: Neuronal apoptosis and inflammation in the ventral horn of the spinal cord contribute to denervated muscle atrophy post-burn. Hyperbaric oxygen therapy (HBOT) exerts anti-inflammation and neuroprotection. Furthermore, hypoxia-inducible factor (HIF)-1α has been reported to promote inflammation and apoptosis. We investigated the therapeutic potential of HBOT and the role of HIF-1α post-burn. Methods: Sprague-Dawley rats were divided into three groups: a control group, an untreated burn group receiving burn and sham treatment, and a HBOT group receiving burn injury and HBOT. The burn injury was induced with 75ºC ± 5ºC at the right hindpaw. HBOT (100% oxygen at 2.5 atmosphere, 90 min/day) and sham HBOT (21% oxygen at 1 atmosphere, 90 min/day) was started on day 28 after burn injury and continued for 14 treatments (days 28-41). Incapacitance (hind limb weight bearing) testing was conducted before burn and weekly after burn. At day 42 post-burn, the gastrocnemius muscle and the spinal cord ventral horn were analyzed. Results: HBOT improved burn-induced weight bearing imbalance. At day 42 post-burn, less gastrocnemius muscle atrophy and fibrosis were noted in the HBOT group than in the untreated burn group. In the ventral horn, HBOT attenuated the neuronal apoptosis and glial activation post-burn. The increases in phosphorylated AKT/mTOR post-burn were reduced after HBOT. HBOT also inhibited HIF-1α signaling, as determined by immunofluorescence and western blot. Conclusions: HBOT reduces burn-induced neuronal apoptosis in the ventral horn, possibly through HIF-1α signaling.

Role of Melatonin in the Regulation of Pain

Melatonin is a pleiotropic hormone synthesized and secreted mainly by the pineal gland in vertebrates. Melatonin is an endogenous regulator of circadian and seasonal rhythms. Melatonin is involved in many physiological and pathophysiological processes demonstrating antioxidant, antineoplastic, anti-inflammatory, and immunomodulatory properties. Accumulating evidence has revealed that melatonin plays an important role in pain modulation through multiple mechanisms. In this review, we examine recent evidence for melatonin on pain regulation in various animal models and patients with pain syndromes, and the potential cellular mechanisms.