Rejuvenation Through Oxygen, More or Less

A Review of Emerging Evidence and Clinical Applications of Hyperbaric Oxygen Therapy

Background: Hyperbaric Oxygen Therapy (HBOT) is a medical treatment that involves administering 100% oxygen at increased atmospheric pressure to enhance oxygen delivery to tissues. Initially developed for decompression sickness, HBOT has since been utilized for a wide range of medical conditions, including severe infections, non-healing wounds, and, more recently, COVID-19. Objective: This review explores the historical development of HBOT, its principles, its emerging role in the management of and its outcome as treatment in COVID-19, particularly in mitigating inflammation, hypoxemia, and oxidative stress. Methods: A comprehensive review of the literature was conducted, analyzing case reports and case series that examined the effectiveness of HBOT in various clinical scenarios, with a focus on COVID-19. Results: HBOT has been shown to enhance tissue oxygenation, reduce inflammation, and modulate oxidative stress, thereby improving clinical outcomes in patients with severe COVID-19. The therapy's ability to increase dissolved oxygen levels in blood and tissues, independent of hemoglobin, makes it particularly beneficial in conditions like COVID-19, where hypoxemia and inflammation are prominent. Conclusion: HBOT offers a promising adjunctive treatment for severe COVID-19, with the potential to reduce mortality and improve recovery by targeting key pathophysiological processes such as hypoxemia, inflammation, and oxidative stress. Further research is warranted to optimize treatment protocols and confirm long-term benefits.

A Hypoxia-Inflammation Cycle and Multiple Sclerosis: Mechanisms and Therapeutic Implications

Purpose of Review

Multiple sclerosis (MS) is a complex neurodegenerative disease characterized by inflammation, demyelination, and neurodegeneration. Significant hypoxia exists in brain of people with MS (pwMS), likely contributing to inflammatory, neurodegenerative, and vascular impairments. In this review, we explore the concept of a negative feedback loop between hypoxia and inflammation, discussing its potential role in disease progression based on evidence of hypoxia, and its implications for therapeutic targets.

Recent Findings

In the experimental autoimmune encephalomyelitis (EAE) model, hypoxia has been detected in gray matter (GM) using histological stains, susceptibility MRI and implanted oxygen sensitive probes. In pwMS, hypoxia has been quantified using near-infrared spectroscopy (NIRS) to measure cortical tissue oxygen saturation (StO2), as well as through blood-based biomarkers such as Glucose Transporter-1 (GLUT-1). We outline the potential for the hypoxia-inflammation cycle to drive tissue damage even in the absence of plaques. Inflammation can drive hypoxia through blood-brain barrier (BBB) disruption and edema, mitochondrial dysfunction, oxidative stress, vessel blockage and vascular abnormalities. The hypoxia can, in turn, drive more inflammation.

Summary

The hypoxia-inflammation cycle could exacerbate neuroinflammation and disease progression. We explore therapeutic approaches that target this cycle, providing information about potential treatments in MS. There are many therapeutic approaches that could block this cycle, including inhibiting hypoxia-inducible factor 1-α (HIF-1α), blocking cell adhesion or using vasodilators or oxygen, which could reduce either inflammation or hypoxia. This review highlights the potential significance of the hypoxia-inflammation pathway in MS and suggests strategies to break the cycle. Such treatments could improve quality of life or reduce rates of progression.

Hyperbaric oxygen therapy suppresses hypoxia and reoxygenation injury to retinal pigment epithelial cells through activating peroxisome proliferator activator receptor-alpha signalling

Retinal ischemia followed by reperfusion (IR) is a common cause of many ocular disorders, such as age-related macular degeneration (AMD), which leads to blindness in the elderly population, and proper therapies remain unavailable. Retinal pigment epithelial (RPE) cell death is a hallmark of AMD. Hyperbaric oxygen (HBO) therapy can improve IR tissue survival by inducing ischemic preconditioning responses. We conducted an in vitro study to examine the effects of HBO preconditioning on oxygen-glucose deprivation (OGD)-induced IR-injured RPE cells. RPE cells were treated with HBO (100% O2 at 3 atmospheres absolute for 90 min) once a day for three consecutive days before retinal IR onset. Compared with normal cells, the IR-injured RPE cells had lower cell viability, lower peroxisome proliferator activator receptor-alpha (PPAR-α) expression, more severe oxidation status, higher blood-retinal barrier disruption and more elevated apoptosis and autophagy rates. HBO preconditioning increased PPAR-α expression, improved cell viability, decreased oxidative stress, blood-retinal barrier disruption and cellular apoptosis and autophagy. A specific PPAR-α antagonist, GW6471, antagonized all the protective effects of HBO preconditioning in IR-injured RPE cells. Combining these observations, HBO therapy can reverse OGD-induced RPE cell injury by activating PPAR-α signalling.

Understanding human aging and the fundamental cell signaling link in age-related diseases: the middle-aging hypovascularity hypoxia hypothesis

Aging-related hypoxia, oxidative stress, and inflammation pathophysiology are closely associated with human age-related carcinogenesis and chronic diseases. However, the connection between hypoxia and hormonal cell signaling pathways is unclear, but such human age-related comorbid diseases do coincide with the middle-aging period of declining sex hormonal signaling. This scoping review evaluates the relevant interdisciplinary evidence to assess the systems biology of function, regulation, and homeostasis in order to discern and decipher the etiology of the connection between hypoxia and hormonal signaling in human age-related comorbid diseases. The hypothesis charts the accumulating evidence to support the development of a hypoxic milieu and oxidative stress-inflammation pathophysiology in middle-aged individuals, as well as the induction of amyloidosis, autophagy, and epithelial-to-mesenchymal transition in aging-related degeneration. Taken together, this new approach and strategy can provide the clarity of concepts and patterns to determine the causes of declining vascularity hemodynamics (blood flow) and physiological oxygenation perfusion (oxygen bioavailability) in relation to oxygen homeostasis and vascularity that cause hypoxia (hypovascularity hypoxia). The middle-aging hypovascularity hypoxia hypothesis could provide the mechanistic interface connecting the endocrine, nitric oxide, and oxygen homeostasis signaling that is closely linked to the progressive conditions of degenerative hypertrophy, atrophy, fibrosis, and neoplasm. An in-depth understanding of these intrinsic biological processes of the developing middle-aged hypoxia could provide potential new strategies for time-dependent therapies in maintaining healthspan for healthy lifestyle aging, medical cost savings, and health system sustainability.

Hyperbaric oxygen therapy for healthy aging: From mechanisms to therapeutics

Hyperbaric oxygen therapy (HBOT), a technique through which 100% oxygen is provided at a pressure higher than 1 atm absolute (ATA), has become a well-established treatment modality for multiple conditions. The noninvasive nature, favorable safety profile, and common clinical application of HBOT make it a competitive candidate for several new indications, one of them being aging and age-related diseases. In fact, despite the conventional wisdom that excessive oxygen accelerates aging, appropriate HBOT protocols without exceeding the toxicity threshold have shown great promise in therapies against aging. For one thing, an extensive body of basic research has expanded our mechanistic understanding of HBOT. Interestingly, the therapeutic targets of HBOT overlap considerably with those of aging and age-related diseases. For another, pre-clinical and small-scale clinical investigations have provided validated information on the efficacy of HBOT against aging from various aspects. However, a generally applicable protocol for HBOT to be utilized in therapies against aging needs to be defined as a subsequent step. It is high time to look back and summarize the recent advances concerning biological mechanisms and therapeutic implications of HBOT in promoting healthy aging and shed light on prospective directions. Here we provide the first comprehensive overview of HBOT in the field of aging and geriatric research, which allows the scientific community to be aware of the emerging tendency and move beyond conventional wisdom to scientific findings of translational value.

Hyperbaric oxygen therapy improves age induced bone dyshomeostasis in non-obese and obese conditions

AIMS

To investigate the effects of hyperbaric oxygen therapy (HBOT) on metabolic disturbance, aging and bone remodeling in D-galactose-induced aging rats with and without obesity by determining the metabolic parameters, aging and oxidative stress markers, bone turnover markers, bone microarchitecture, and bone biomechanical strength.

MATERIALS AND METHODS

Male Wistar rats were fed either a normal diet (ND; n = 18) or a HFD (n = 12) for 22 weeks. At week 13, vehicle (0.9% NaCl) was injected into ND-fed rats (NDV; n = 6), while 150 mg/kg/day of D-galactose was injected into 12 ND-fed rats (NDD) and 12 HFD-fed rats (HFDD) for 10 weeks. At week 21, rats were treated with either sham (NDVS, NDDS, or HFDDS; n = 6/ group) or HBOT (NDDH, or HFDDH; n = 6/group) for 14 days. Rats were then euthanized. Blood samples, femora, and tibiae were collected.

KEY FINDINGS

Both NDD and HFDD groups developed aging as indicated by increased AGE level, increased inflammation and oxidative stress as shown by raised serum TNF-α and MDA levels, impaired bone remodeling as indicated by an increase in levels of CTX-1, TRACP-5b, and impaired bone structure/strength, when compared with those of the NDVS group. HFD aggravated these indicators of bone dyshomeostasis in D-galactose-treated rats. HBOT restored bone remodeling and bone structure/strength in the NDD group, however HBOT ameliorated bone dyshomeostasis in the HFDD group.

SIGNIFICANCE

HBOT is a potential intervention to decrease the risk of osteoporosis and bone fracture in aging with or without obesity.

Hyperbaric Oxygen Treatment: Effects on Mitochondrial Function and Oxidative Stress

Hyperbaric oxygen treatment (HBOT)—the administration of 100% oxygen at atmospheric pressure (ATA) greater than 1 ATA—increases the proportion of dissolved oxygen in the blood five- to twenty-fold. This increase in accessible oxygen places the mitochondrion—the organelle that consumes most of the oxygen that we breathe—at the epicenter of HBOT’s effects. As the mitochondrion is also a major site for the production of reactive oxygen species (ROS), it is possible that HBOT will increase also oxidative stress. Depending on the conditions of the HBO treatment (duration, pressure, umber of treatments), short-term treatments have been shown to have deleterious effects on both mitochondrial activity and production of ROS. Long-term treatment, on the other hand, improves mitochondrial activity and leads to a decrease in ROS levels, partially due to the effects of HBOT, which increases antioxidant defense mechanisms. Many diseases and conditions are characterized by mitochondrial dysfunction and imbalance between ROS and antioxidant scavengers, suggesting potential therapeutic intervention for HBOT. In the present review, we will present current views on the effects of HBOT on mitochondrial function and oxidative stress, the interplay between them and the implications for several diseases.

Hyperbaric Oxygen Treatment-From Mechanisms to Cognitive Improvement

Hyperbaric oxygen treatment (HBOT)—the medical use of oxygen at environmental pressure greater than one atmosphere absolute—is a very effective therapy for several approved clinical situations, such as carbon monoxide intoxication, incurable diabetes or radiation-injury wounds, and smoke inhalation. In recent years, it has also been used to improve cognition, neuro-wellness, and quality of life following brain trauma and stroke. This opens new avenues for the elderly, including the treatment of neurological and neurodegenerative diseases and improvement of cognition and brain metabolism in cases of mild cognitive impairment. Alongside its integration into clinics, basic research studies have elucidated HBOT’s mechanisms of action and its effects on cellular processes, transcription factors, mitochondrial function, oxidative stress, and inflammation. Therefore, HBOT is becoming a major player in 21st century research and clinical treatments. The following review will discuss the basic mechanisms of HBOT, and its effects on cellular processes, cognition, and brain disorders.

Response to Hypoxia in Cognitive Decline

Inflammaging, the increase of proinflammatory processes with increasing age, has multiple mechanisms from increasing numbers of senescent cells secreting cytokines to changes in metabolic processes. Alterations of oxygen metabolism with aging, especially decreased levels of O₂ with age resulting from endocrine and cardiovascular dysfunction as well as desensitization of cellular response to hypoxia, may exacerbate inflammaging, which in turn creates further oxygen metabolic dysfunction. During aging, decline in levels of erythrocyte 2,3-bisphosphoglycerate (2,3-BPG), BPG mutase, and adenosine A2B receptor, a key adenosine signaling receptor that can augment 2,3-BPG expression, may fail to protect sensitive brain tissue from subtly reduced O₂ levels, in turn resulting in increased numbers of activated microglia and secretion of proinflammatory cytokines, ultimately promoting inflammaging and senescence of endothelial cells. Interventions to restore O₂ levels directly or via increasing 2,3-BPG may help promote cognitive health in old age, but significant work to quantify the degree of reduced O₂ during aging in mammals, and especially humans, needs to be pursued.