Preventive and therapeutic application of molecular hydrogen in situations with excessive production of free radicals

Navigating nonalcoholic fatty liver disease (NAFLD): Exploring the roles of estrogens, pharmacological and medical interventions, and life style

The pursuit of studying this subject is driven by the urgency to address the increasing global prevalence of Non-Alcoholic Fatty Liver Disease (NAFLD) and its profound health implications. NAFLD represents a significant public health concern due to its association with metabolic disorders, cardiovascular complications, and the potential progression to more severe conditions like non-alcoholic steatohepatitis (NASH), fibrosis, and cirrhosis. Liver estrogen signaling is important for maintaining liver function, and loss of estrogens increases the likelihood of NAFLD in postmenopausal women. Understanding the multifaceted mechanisms underlying NAFLD pathogenesis, its varied treatment strategies, and their effectiveness is crucial for devising comprehensive and targeted interventions. By unraveling the intricate interplay between genetics, lifestyle, hormonal regulation, and gut microbiota, we can unlock insights into risk stratification, early detection, and personalized therapeutic approaches. Furthermore, investigating the emerging pharmaceutical interventions and dietary modifications offers the potential to revolutionize disease management. This review reinforces the role of collaboration in refining NAFLD comprehension, unveiling novel therapeutic pathways, and ultimately improving patient outcomes for this intricate hepatic condition.

Antioxidation activity of molecular hydrogen via protoheme catalysis in vivo: an insight from ab initio calculations

Recently, molecular hydrogen has been found to exhibit antioxidation activity through many clinical experiments, but the mechanism has not been fully understandable at atomic level. In this work, we perform systematic ab initio calculations of protoheme-hydrogen complexes to clarify the antioxidation mechanism of molecular hydrogen. We make molecular modeling of iron-protoporphyrin coordinated by imidazole, FeP(Im), and its hydrogen as well as dihydrogen complexes, together with reactive oxygen/nitrogen species (RONS). We carry out structural optimization and Mulliken charge analysis, revealing the two kinds of bonding characteristics between FeP(Im) and H[Formula: see text]: dihydrogen bonding in the end-on asymmetric configuration and Kubas bonding in the side-on symmetric configuration of H[Formula: see text] molecule. The activation barriers for adsorption and dissociation of H[Formula: see text] on and further desorption of H atom from FeP(Im) are found to be below 2.78 eV at most, which is remarkably lower than the H-H bond breaking energy of 4.64 eV in free H[Formula: see text] molecule. We find that the hydrogen bond dissociation energies of FeP(Im)-H[Formula: see text] and -H complexes are lower than those of RONS-H complexes, indicating the decisive role of protoheme as an effective catalyst in RONS antioxidation by molecular hydrogen in vivo.

Role of Molecular Hydrogen in Ageing and Ageing-Related Diseases

Ageing is a physiological process of progressive decline in the organism function over time. It affects every organ in the body and is a significant risk for chronic diseases. Molecular hydrogen has therapeutic and preventive effects on various organs. It has antioxidative properties as it directly neutralizes hydroxyl radicals and reduces peroxynitrite level. It also activates Nrf2 and HO-1, which regulate many antioxidant enzymes and proteasomes. Through its antioxidative effect, hydrogen maintains genomic stability, mitigates cellular senescence, and takes part in histone modification, telomere maintenance, and proteostasis. In addition, hydrogen may prevent inflammation and regulate the nutrient-sensing mTOR system, autophagy, apoptosis, and mitochondria, which are all factors related to ageing. Hydrogen can also be used for prevention and treatment of various ageing-related diseases, such as neurodegenerative disorders, cardiovascular disease, pulmonary disease, diabetes, and cancer. This paper reviews the basic research and recent application of hydrogen in order to support hydrogen use in medicine for ageing prevention and ageing-related disease therapy.

Evaluation of the hydrogen-rich water alleviation potential on mercury toxicity in earthworms using ATR-FTIR and LC-ESI-MS/MS spectroscopy

The toxic effects of mercury in earthworms and the potential alleviation effect of hydrogen-rich water (HRW) using ATR-FTIR and LC-MS analysis methods were investigated. Different concentrations of mercury chloride (H1: 5 µg/mL, H2: 10 µg/mL, H3: 20 µg/mL, H4: 40 µg/mL, and C1: control) and mercury chloride prepared in hydrogen-rich water (H5: 5 µg/mL, H6: 10 µg/mL, H7: 20 µg/mL, H8: 40 µg/mL, and C2: control) were injected into earthworms. The changes and reductions in some bands representing proteins, lipids, and polysaccharides (3280 cm^-1, 2922 cm^-1, 2855 cm^-1, 1170 cm^-1, and 1047 cm^-1) showed that protective effects could occur in groups prepared with hydrogen-rich water. In the FTIR results, it was found that these bands in the H3 group were more affected and decreased by the influence of mercury on earthworms than the H7 group prepared with hydrogen. LC-MS analysis showed that the changes in some ions of the highest dose groups (H4 and H8) were different, and mercury caused oxidative DNA damage in earthworms. When the high-level application groups of mercury, i.e., H4 and H8 were compared with the controls, the ion exchange ([M + H] + ; m/z 283.1) representing the 8-Oxo-dG level in earthworms was higher in the H4 group than the H8 group. This reveals that HRW exhibited the potential ability to alleviate the toxic effects of mercury; however, a longer period of HRW treatment may be necessary to distinguish an obvious effect. The ATR-FTIR spectroscopy provided a rapid and precise method for monitoring the changes in biological tissues caused by a toxic compound at the molecular level.

Antioxidants in Alzheimer's Disease: Current Therapeutic Significance and Future Prospects

Alzheimer's disease (AD) rate is accelerating with the increasing aging of the world's population. The World Health Organization (WHO) stated AD as a global health priority. According to the WHO report, around 82 million people in 2030 and 152 million in 2050 will develop dementia (AD contributes 60% to 70% of cases), considering the current scenario. AD is the most common neurodegenerative disease, intensifying impairments in cognition, behavior, and memory. Histopathological AD variations include extracellular senile plaques' formation, tangling of intracellular neurofibrils, and synaptic and neuronal loss in the brain. Multiple evidence directly indicates that oxidative stress participates in an early phase of AD before cytopathology. Moreover, oxidative stress is induced by almost all misfolded protein lumps like α-synuclein, amyloid-β, and others. Oxidative stress plays a crucial role in activating and causing various cell signaling pathways that result in lesion formations of toxic substances, which foster the development of the disease. Antioxidants are widely preferred to combat oxidative stress, and those derived from natural sources, which are often incorporated into dietary habits, can play an important role in delaying the onset as well as reducing the progression of AD. However, this approach has not been extensively explored yet. Moreover, there has been growing evidence that a combination of antioxidants in conjugation with a nutrient-rich diet might be more effective in tackling AD pathogenesis. Thus, considering the above-stated fact, this comprehensive review aims to elaborate the basics of AD and antioxidants, including the vitality of antioxidants in AD. Moreover, this review may help researchers to develop effectively and potentially improved antioxidant therapeutic strategies for this disease as it also deals with the clinical trials in the stated field.

Oxidative Stress and Pathways of Molecular Hydrogen Effects in Medicine

There are many situations of excessive production of reactive oxygen species (ROS) such as radiation, ischemia/reperfusion (I/R), and inflammation. ROS contribute to and arises from numerous cellular pathologies, diseases, and aging. ROS can cause direct deleterious effects by damaging proteins, lipids, and nucleic acids as well as exert detrimental effects on several cell signaling pathways. However, ROS are important in many cellular functions. The injurious effect of excessive ROS can hypothetically be mitigated by exogenous antioxidants, but clinically this intervention is often not favorable. In contrast, molecular hydrogen provides a variety of advantages for mitigating oxidative stress due to its unique physical and chemical properties. H₂ may be superior to conventional antioxidants, since it can selectively reduce ●OH radicals while preserving important ROS that are otherwise used for normal cellular signaling. Additionally, H₂ exerts many biological effects, including antioxidation, anti-inflammation, anti-apoptosis, and anti-shock. H₂ accomplishes these effects by indirectly regulating signal transduction and gene expression, each of which involves multiple signaling pathways and crosstalk. The Keap1-Nrf2-ARE signaling pathway, which can be activated by H₂, plays a critical role in regulating cellular redox balance, metabolism, and inducing adaptive responses against cellular stress. H₂ also influences the crosstalk among the regulatory mechanisms of autophagy and apoptosis, which involve MAPKs, p53, Nrf2, NF-κB, p38 MAPK, mTOR, etc. The pleiotropic effects of molecular hydrogen on various proteins, molecules and signaling pathways can at least partly explain its almost universal pluripotent therapeutic potential.

Review article: FODMAPS, prebiotics and gut health-the FODMAP hypothesis revisited

BACKGROUND

Restriction of dietary FODMAP intake can alleviate symptoms in patients with irritable bowel syndrome. Because many FODMAPs have prebiotic actions, there is concern that their dietary restriction leads to dysbiosis with health consequences, and their intake is being encouraged by addition to foods and via supplements.

AIMS

To examine the hazards and benefits of high and low FODMAP intake.

METHODS

Current literature was reviewed and alternative hypotheses formulated.

RESULTS

Low FODMAP intake reduces abundance of faecal Bifidobacteria without known adverse outcomes and has no effect on diversity, but the reduction in bacterial density may potentially be beneficial to gut health. Supplementary prebiotics can markedly elevate the intake of FODMAPs over levels consumed in the background diet. While this increases the abundance of Bifidobacteria, it adversely affects gut health in animal studies by inducing colonic mucosal barrier dysfunction, mucosal inflammation and visceral hypersensitivity. Rapid colonic fermentation is central to the identified mechanisms that include injury from high luminal concentrations of short-chain fatty acids and low pH, and inflammatory effects of increased endotoxin load and glycation of macromolecules. Whether these observations translate into humans requires further study. Opposing hypotheses are presented whereby excessive intake of FODMAPs might have health benefits via prebiotic effects, but might also be injurious and contribute to the apparent increase in functional intestinal disorders.

CONCLUSIONS

Reduced FODMAP intake has few deleterious effects on gut microbiota. Consequences (both positive and negative) of excessive carbohydrate fermentation in the human intestines from elevated FODMAP intake require more attention.

Role of antioxidants and a nutrient rich diet in Alzheimer's disease

The joint attack on the body by metabolic acidosis and oxidative stress suggests that treatment in degenerative diseases, including Alzheimer's disease (AD), may require a normalizing of extracellular and intracellular pH with simultaneous supplementation of an antioxidant combination cocktail at a sufficiently high dose. Evidence is also accumulating that combinations of antioxidants may be more effective, taking advantage of synergistic effects of appropriate antioxidants as well as a nutrient-rich diet to prevent and reverse AD. This review focuses on nutritional, nutraceutical and antioxidant treatments of AD, although they can also be used in other chronic degenerative and neurodegenerative diseases.

The role of medical gas in stroke: an updated review

Medical gas is a large class of bioactive gases used in clinical medicine and basic scientific research. At present, the role of medical gas in neuroprotection has received growing attention. Stroke is a leading cause of death and disability in adults worldwide, but current treatment is still very limited. The common pathological changes of these two types of stroke may include excitotoxicity, free radical release, inflammation, cell death, mitochondrial disorder, and blood-brain barrier disruption. In this review, we will discuss the pathological mechanisms of stroke and the role of two medical gases (hydrogen and hydrogen sulfide) in stroke, which may potentially provide a new insight into the treatment of stroke.

Molecular hydrogen attenuates methamphetamine-induced behavioral sensitization and activation of ERK-ΔFosB signaling in the mouse nucleus accumbens

Methamphetamine (METH) is one of the most prevalently used illegal psychostimulants in many countries. Continuous exposure to METH leads to behavioral sensitization in animals, which can be used as a behavioral model with many mechanisms in common with relapse in humans. Molecular hydrogen has recently gained attention for its potential as a novel healthcare product with preventive and therapeutic applicability to a wide range of pathological conditions. However, it remains unclear whether and, if so, how hydrogen regulates METH-induced behavioral abnormalities. In the present study, we investigated the roles of molecular hydrogen on the acquisition and transfer of METH-induced behavioral sensitization and the accompanying changes in ERK phosphorylation and ΔFosB activation in the nucleus accumbens (NAc) of mice. To this end, male C57BL/6 mice received METH (0.1, 0.5 and 1.0 mg/kg, i.p.) injections for 7 days followed by a METH challenge (0.1, 0.5 and 1.0 mg/kg, i.p.) after a 7-day transfer period. Molecular hydrogen, delivered through a hydrogen-rich saline (HRS) injection (10 mL/kg, i.p., 3-h interval), was administered during the acquisition and transfer periods. We found that HRS administration was able to inhibit the acquisition and transfer of 0.1 and 0.5 mg/kg METH-induced behavioral sensitization to a certain extent, thereby attenuating the expression of behavioral sensitization. The HRS injections alone did not induce any obvious changes in locomotor activity in mice. Intriguingly, the increases in pERK and ΔFosB in the NAc, which accompanied the METH-induced behavioral sensitization, were also attenuated by the HRS treatments. Due to the anti-oxidative function of molecular hydrogen, the HRS injections reduced METH-induced reactive oxygen species and malondialdehyde generation in the NAc. These results suggest that molecular hydrogen serves as an anti-oxidative agent with potentially therapeutic applicability to the treatment of METH addicts.

Hydrogen-rich water alleviates cyclosporine A-induced nephrotoxicity via the Keap1/Nrf2 signaling pathway

Oxidative stress induced by long-term cyclosporine A (CsA) administration is a major cause of chronic nephrotoxicity, which is characterized by tubular atrophy, tubular cell apoptosis, and interstitial fibrosis in the progression of organ transplantation. Although hydrogen-rich water (HRW) has been used to prevent various oxidative stress-related diseases, its underlying mechanisms remain unclear. This study investigated the effects of HRW on CsA-induced nephrotoxicity and its potential mechanisms. After administration of CsA (25 mg/kg/day), rats were treated with or without HRW (12 mL/kg) for 4 weeks. Renal function and vascular activity were investigated. Histological changes in kidney tissues were analyzed using Masson's trichrome and terminal deoxynucleotidyl transferase dUTP nick-end labeling stains. Oxidative stress markers and the activation of the Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway were also measured. We found that CsA increased the levels of reactive oxygen species (ROS) and malonaldehyde (MDA), but it reduced glutathione (GSH) and superoxide dismutase (SOD) levels. Such alterations induced vascular dysfunction, tubular atrophy, interstitial fibrosis, and tubular apoptosis. This was evident secondary to an increase in urinary protein, serum creatinine, and blood urea nitrogen, ultimately leading to renal dysfunction. Conversely, HRW decreased levels of ROS and MDA while increasing the activity of GSH and SOD. This was accompanied by an improvement in vascular and renal function. Moreover, HRW significantly decreased the level of Keap1 and increased the expression of Nrf2, NADPH dehydrogenase quinone 1, and heme oxygenase 1. In conclusion, HRW restored the balance of redox status, suppressed oxidative stress damage, and improved kidney function induced by CsA via activation of the Keap1/Nrf2 signaling pathway.

Circulating messenger for neuroprotection induced by molecular hydrogen

Molecular hydrogen (H2) showed protection against various kinds of oxidative-stress-related diseases. First, it was reported that the mechanism of therapeutic effects of H2was antioxidative effect due to inhibition of the most cytotoxic reactive oxygen species, hydroxy radical (•OH). However, after chronic administration of H2in drinking water, oxidative-stress-induced nerve injury is significantly attenuated even in the absence of H2. It suggests indirect signaling of H2and gastrointestinal tract is involved. Indirect effects of H2could be tested by giving H2water only before nerve injury, as preconditioning. For example, preconditioning of H2for certain a period (∼7 days) in Parkinson’s disease model mice shows significant neuroprotection. As the mechanism of indirect effect, H2in drinking water induces ghrelin production and release from the stomach via β1-adrenergic receptor stimulation. Released ghrelin circulates in the body, being transported across the blood–brain barrier, activates its receptor, growth-hormone secretagogue receptor. H2-induced upregulation of ghrelin mRNA is also shown in ghrelin-producing cell line, SG-1. These observations help with understanding the chronic effects of H2and raise intriguing preventive and therapeutic options using H2.

A new insight into the molecular hydrogen effect on coenzyme Q and mitochondrial function of rats

Mitochondria are the major source of cellular energy metabolism. In the cardiac cells, mitochondria produce by way of the oxidative phosphorylation more than 90% of the energy supply in the form of ATP, which is utilized in many ATP-dependent processes, like cycling of the contractile proteins or maintaining ion gradients. Reactive oxygen species (ROS) are by-products of cellular metabolism and their levels are controlled by intracellular antioxidant systems. Imbalance between ROS and the antioxidant defense leads to oxidative stress and oxidative changes to cellular biomolecules. Molecular hydrogen (H₂) has been proved as beneficial in the prevention and therapy of various diseases including cardiovascular disorders. It selectively scavenges hydroxyl radical and peroxynitrite, reduces oxidative stress, and has anti-inflammatory and anti-apoptotic effects. The effect of H₂ on the myocardial mitochondrial function and coenzyme Q levels is not well known. In this paper, we demonstrated that consumption of H₂-rich water (HRW) resulted in stimulated rat cardiac mitochondrial electron respiratory chain function and increased levels of ATP production by Complex I and Complex II substrates. Similarly, coenzyme Q₉ levels in the rat plasma, myocardial tissue, and mitochondria were increased and malondialdehyde level in plasma was reduced after HRW administration. Based on obtained data, we hypothesize a new metabolic pathway of the H₂ effect in mitochondria on the Q-cycle and in mitochondrial respiratory chain function. The Q-cycle contains three coenzyme Q forms: coenzyme Q in oxidized form (ubiquinone), radical form (semiquinone), or reduced form (ubiquinol). H₂ may be a donor of both electron and proton in the Q-cycle and thus we can suppose stimulation of coenzyme Q production. When ubiquinone is reduced to ubiquinol, lipid peroxidation is reduced. Increased CoQ₉ concentration can stimulate electron transport from Complex I and Complex II to Complex III and increase ATP production via mitochondrial oxidative phosphorylation. Our results indicate that H₂ may function to prevent/treat disease states with disrupted myocardial mitochondrial function.

Myalgic encephalomyelitis/chronic fatigue syndrome: From pathophysiological insights to novel therapeutic opportunities

Myalgic encephalomyelitis (ME) or chronic fatigue syndrome (CFS) is a common and disabling condition with a paucity of effective and evidence-based therapies, reflecting a major unmet need. Cognitive behavioural therapy and graded exercise are of modest benefit for only some ME/CFS patients, and many sufferers report aggravation of symptoms of fatigue with exercise. The presence of a multiplicity of pathophysiological abnormalities in at least the subgroup of people with ME/CFS diagnosed with the current international consensus "Fukuda" criteria, points to numerous potential therapeutic targets. Such abnormalities include extensive data showing that at least a subgroup has a pro-inflammatory state, increased oxidative and nitrosative stress, disruption of gut mucosal barriers and mitochondrial dysfunction together with dysregulated bioenergetics. In this paper, these pathways are summarised, and data regarding promising therapeutic options that target these pathways are highlighted; they include coenzyme Q₁₀, melatonin, curcumin, molecular hydrogen and N-acetylcysteine. These data are promising yet preliminary, suggesting hopeful avenues to address this major unmet burden of illness.

Acid-Responsive H2 -Releasing 2D MgB2 Nanosheet for Therapeutic Synergy and Side Effect Attenuation of Gastric Cancer Chemotherapy

The hydrogen molecule is recognized as a high potential to attenuate toxic side effects of chemotherapy and also enhance chemotherapeutic efficacy, and the development of a novel hydrogen-generating prodrug for facile, safe, and efficient hydrogen delivery is vitally important for combined hydrogenochemotherapy but is still challenging. Here, targeting gastric cancer, a 2D magnesium boride nanosheet (MBN) is synthesized as a new type of acid-responsive hydrogen-releasing prodrug by an ultrasound-assisted chemical etching route, which is used to realize hydrogenochemotherapy by combination of facile oral administration of polyvinylpyrrolidone (PVP)-encapsulating MBN (MBN@PVP) pills with routine intravenous injection of doxorubicin (DOX). The MBN@PVP pill has high stability in normal tissues/blood environments as well as high gastric acid-responsiveness with sustained release behavior, which matches well with its metabolism rate in the stomach in great favor of continuous and long-term hydrogen administration. Hydrogenochemotherapy with DOX+MBN@PVP has remarkably prolonged the survival time of gastric tumor-bearing mice by reducing the toxic side effects of chemotherapy. The mechanism for therapeutic synergy and side effect attenuation of hydrogenochemotherapy is discovered to be derived from the selectivity of hydrogen molecules in inhibiting aerobic respiration of gastric cells but activating aerobic respiration of normal cells including marrow mesenchymal stem cells and cardiac, hepatic, and splenic cells.

Molecular hydrogen attenuates gefitinib-induced exacerbation of naphthalene-evoked acute lung injury through a reduction in oxidative stress and inflammation

Although inhibition of epidermal growth factor receptor (EGFR)-mediated cell signaling by the EGFR tyrosine kinase inhibitor gefitinib is highly effective against advanced non-small cell lung cancer, this drug might promote severe acute interstitial pneumonia. We previously reported that molecular hydrogen (H₂) acts as a therapeutic and preventive anti-oxidant. Here, we show that treatment with H₂ effectively protects the lungs of mice from severe damage caused by oral administration of gefitinib after intraperitoneal injection of naphthalene, the toxicity of which is related to oxidative stress. Drinking H₂-rich water ad libitum mitigated naphthalene/gefitinib-induced weight loss and significantly improved survival, which was associated with a decrease in lung inflammation and inflammatory cytokines in the bronchoalveolar lavage fluid. Naphthalene decreased glutathione in the lung, increased malondialdehyde in the plasma, and increased 4-hydroxy-2-nonenal production in airway cells, all of which were mitigated by H₂-rich water, indicating that the H₂-rich water reverses cellular damage to the bronchial wall caused by oxidative stress. Finally, treatment with H₂ did not interfere with the anti-tumor effects of gefitinib on a lung cancer cell line in vitro or on tumor-bearing mice in vivo. These results indicate that H₂-rich water has the potential to improve quality of life during gefitinib therapy by mitigating lung injury without impairing anti-tumor activity.

A New Approach for the Prevention and Treatment of Cardiovascular Disorders. Molecular Hydrogen Significantly Reduces the Effects of Oxidative Stress

Cardiovascular diseases are the most common causes of morbidity and mortality worldwide. Redox dysregulation and a dyshomeostasis of inflammation arise from, and result in, cellular aberrations and pathological conditions, which lead to cardiovascular diseases. Despite years of intensive research, there is still no safe and effective method for their prevention and treatment. Recently, molecular hydrogen has been investigated in preclinical and clinical studies on various diseases associated with oxidative and inflammatory stress such as radiation-induced heart disease, ischemia-reperfusion injury, myocardial and brain infarction, storage of the heart, heart transplantation, etc. Hydrogen is primarily administered via inhalation, drinking hydrogen-rich water, or injection of hydrogen-rich saline. It favorably modulates signal transduction and gene expression resulting in suppression of proinflammatory cytokines, excess ROS production, and in the activation of the Nrf2 antioxidant transcription factor. Although H2 appears to be an important biological molecule with anti-oxidant, anti-inflammatory, and anti-apoptotic effects, the exact mechanisms of action remain elusive. There is no reported clinical toxicity; however, some data suggests that H2 has a mild hormetic-like effect, which likely mediate some of its benefits. The mechanistic data, coupled with the pre-clinical and clinical studies, suggest that H2 may be useful for ROS/inflammation-induced cardiotoxicity and other conditions.

Hydrogen gas: from clinical medicine to an emerging ergogenic molecule for sports athletes 1

H₂ has been clinically demonstrated to provide antioxidant and anti-inflammatory effects, which makes it an attractive agent in exercise medicine. Although exercise provides a multiplicity of benefits including decreased risk of disease, it can also have detrimental effects. For example, chronic high-intensity exercise in elite athletes, or sporadic bouts of exercise (i.e., noxious exercise) in untrained individuals, result in similar pathological factors such as inflammation, oxidation, and cellular damage that arise from and result in disease. Paradoxically, exercise-induced pro-inflammatory cytokines and reactive oxygen species largely mediate the benefits of exercise. Ingestion of conventional antioxidants and anti-inflammatories often impairs exercise-induced training adaptations. Disease and noxious forms of exercise promote redox dysregulation and chronic inflammation, changes that are mitigated by H₂ administration. Beneficial exercise and H₂ administration promote cytoprotective hormesis, mitochondrial biogenesis, ATP production, increased NAD⁺/NADH ratio, cytoprotective phase II enzymes, heat-shock proteins, sirtuins, etc. We review the biomedical effects of exercise and those of H₂, and we propose that hydrogen may act as an exercise mimetic and redox adaptogen, potentiate the benefits from beneficial exercise, and reduce the harm from noxious exercise. However, more research is warranted to elucidate the potential ergogenic and therapeutic effects of H₂ in exercise medicine.

Molecular hydrogen: potential in mitigating oxidative-stress-induced radiation injury

Uncontrolled production of oxygen and nitrogen radicals results in oxidative and nitrosative stresses that impair cellular functions and have been regarded as causative common denominators of many pathological processes. In this review, we report on the beneficial effects of molecular hydrogen in scavenging radicals in an artificial system of•OH formation. As a proof of principle, we also demonstrate that in rat hearts in vivo, administration of molecular hydrogen led to a significant increase in superoxide dismutase as well as pAKT, a cell survival signaling molecule. Irradiation of the rats caused a significant increase in lipid peroxidation, which was mitigated by pre-treatment of the animals with molecular hydrogen. The nuclear factor erythroid 2-related factor 2 is regarded as an important regulator of oxyradical homeostasis, as well as it supports the functional integrity of cells, particularly under conditions of oxidative stress. We suggest that the beneficial effects of molecular hydrogen may be through the activation of nuclear factor erythroid 2-related factor 2 pathway that promotes innate antioxidants and reduction of apoptosis, as well as inflammation.

The neuroprotective effect of hyperoxygenate hydrogen-rich saline on CO-induced brain injury in rats

This study was designed to investigate the neuroprotective effect of hyperoxygenate hydrogen-rich saline (HOHS) against brain injury induced by carbon monoxide (CO) poisoning in rats. A rat model of CO poisoning was established by administering CO via intraperitoneal injection to male Sprague-Dawley rats. Forty-eight adult male rats were randomly divided into the following groups: normal control group (NG), CO poisoning group (CO), HOS treatment group (hyperoxygenated solution, HOS) and HOHS treatment group (HOHS). After CO poisoning, the carboxyhemoglobin (COHb) contents in the blood of rats in all the CO poisoning groups were increased significantly. However, HOS and HOHS significantly decreased COHb contents, furthermore, the HOHS group had lower COHb contents than the HOS group. Arterial oxygen partial pressure (PaO₂) and arterial oxygen saturation (SaO₂) results showed that HOS and HOHS could improve the oxygenation of the rats with CO poisoning. Compared with the CO group, the HOS group and the HOHS group had persistently neuroprotective effect on CO-induced brain injury, as assessed by modified neurological severity score (mNSS), furthermore, the HOHS group had better neurological functional recovery than the HOS group. The neuronal apoptosis induced by CO was also evaluated. Except the NG group, all the CO-poisoning groups had varying degrees of neuronal apoptosis. There was lesser degree of neuronal apoptosis in both the HOS group and the HOHS group than that in the CO group. Moreover, the HOHS group had more minor degree of neuronal apoptosis than the HOS group. Compared with the CO group, the free radicals production in the HOS group and the HOHS group were significantly inhibited. In addition, there were significantly difference in the free radicals production between the HOS group and the HOHS group. We could conclude that HOHS exerted a stronger neuroprotective effect against CO-induced brain injury than HOS, and the neuroprotective mechanism of HOHS may be related with inhibition of both neuronal apoptosis and free radicals.

Regulation of microRNAs by molecular hydrogen contributes to the prevention of radiation-induced damage in the rat myocardium

microRNAs (miRNAs) constitute a large class of post-transcriptional regulators of gene expression. It has been estimated that miRNAs regulate up to 30% of the protein-coding genes in humans. They are implicated in many physiological and pathological processes, including those involved in radiation-induced heart damage. Biomedical studies indicate that molecular hydrogen has potential as a radioprotective agent due to its antioxidant, anti-inflammatory, and signal-modulating effects. However, the impact of molecular hydrogen on the expression of miRNAs in the heart after irradiation has not been investigated. This study aimed to explore the involvement of miRNA-1, -15b, and -21 in the protective action of molecular hydrogen on rat myocardium damaged by irradiation. The results showed that the levels of malondialdehyde (MDA) and tumor necrosis factor alpha (TNF-α) increased in the rat myocardium after irradiation. Treatment with molecular hydrogen-rich water (HRW) reduced these values to the level of non-irradiated controls. miRNA-1 is known to be involved in cardiac hypertrophy, and was significantly decreased in the rat myocardium after irradiation. Application of HRW attenuated this decrease in all evaluated time periods. miRNA-15b is considered to be anti-fibrotic, anti-hypertrophic, and anti-oxidative. Irradiation downregulated miRNA-15b, whereas administration of HRW restored these values. miRNA-21 is connected with cardiac fibrosis. We observed significant increase in miRNA-21 expression in the irradiated rat hearts. Molecular hydrogen lowered myocardial miRNA-21 levels after irradiation. This study revealed for the first time that the protective effects of molecular hydrogen on irradiation-induced heart damage may be mediated by regulating miRNA-1, -15b, and -21.

Hydrogen-Rich Water Ameliorates Autistic-Like Behavioral Abnormalities in Valproic Acid-Treated Adolescent Mice Offspring

Due to its anti-inflammatory and anti-oxidative effects, recent research has demonstrated that molecular hydrogen can serve as a new medical approach for depression, anxiety and traumatic brain injury. However, its potential effects on neurodevelopmental diseases, such as autism are still elusive. The present study aims to investigate the potential effects of hydrogen-rich water (HRW) administration on valproic acid (VPA)-induced autistic-like behavioral deficits, and the associated underlying mechanism in adolescent mice offspring. Pregnant ICR mice were randomly divided into five groups (n = 6). One group was injected with saline (NAV group) and provided hydrogen-free water. The other four groups were injected with VPA (600 mg/kg, intraperitoneally, i.p.) on pregnant day (PND) 12.5. One group was provided with hydrogen-free water (VEH group) and the other three groups were provided HRW at different segments, postnatal day 1 (PND 1) to PND 21 (PHV group), PND 13 to PND 21 (PVS group) or from PND 13 to postnatal day 42 (PVL group). Behavioral tests, including open field, novelty suppressed feeding (NSF), hot plate, social interaction (SI) and contextual fear memory tests were conducted between postnatal day 35–42. We found that HRW administration significantly reversed the autistic-like behaviors induced by maternal VPA exposure in the adolescent offspring of both male and female adolescent offspring. Furthermore, HRW administration significantly reversed the alternation of serum levels of interleukin 6 (IL-6) and tumor necrosis factor-α (TNF-α), but without any effects on the BDNF levels in maternal VPA-exposed mice offspring. These data suggest the need for additional research on HRW as a potential preventive strategy for autism and related disorders.

Lay Summary: Maternal VPA injection induces autistic-like behavioral deficits in adolescent mice offspring. HRW administration ameliorates autistic-like behavioral deficits. HRW administration reverses the alternation of serum levels of IL-6 and TNF-α induced by VPA.

Therapeutic effect of molecular hydrogen in corneal UVB-induced oxidative stress and corneal photodamage

The aim of this study is to examine whether molecular hydrogen (H₂) is able to reduce oxidative stress after corneal damage induced by UVB irradiation. We previously found that UVB irradiation of the cornea caused the imbalance between the antioxidant and prooxidant enzymes in the corneal epithelium, followed by the imbalance between metalloproteinases and their physiological inhibitors (imbalances in favour of prooxidants and metalloproteinases) contributing to oxidative stress and development of the intracorneal inflammation. Here we investigate the effect of H₂ dissolved in PBS in the concentration 0.5 ppm wt/vol, applied on rabbit corneas during UVB irradiation and healing (UVB doses 1.01 J/cm² once daily for four days). Some irradiated corneas remained untreated or buffer treated. In these corneas the oxidative stress appeared, followed by the excessive inflammation. Malondiladehyde and peroxynitrite expressions were present. The corneas healed with scar formation and neovascularization. In contrast, in H₂ treated irradiated corneas oxidative stress was suppressed and malondiladehyde and peroxynitrite expressions were absent. The corneas healed with the restoration of transparency. The study provides the first evidence of the role of H₂ in prevention of oxidative and nitrosative stress in UVB irradiated corneas, which may represent a novel prophylactic approach to corneal photodamage.

The Comparative Efficiency of Intraperitoneal and Intravitreous Injection of Hydrogen Rich Saline against N-Methyl-N-Nitrosourea Induced Retinal Degeneration: A Topographic Study

Retinitis pigmentosa (RP) comprises a heterogeneous group of inherited retinal diseases leading to blindness. The present study explored the protective effects of hydrogen rich saline (HRS) against the photoreceptor degeneration in the N-Methyl-N-nitrosourea (MNU) administrated rat, a pharmacologically induced RP model. The therapeutic effects of intraperitoneal (IP) and intravitreous (IV) injections of HRS on regional retina was quantified via topographic measurements. The MNU administrated rats received IV or IP injections of HRS, and then they were subjected to electroretinography, multi electrode array, histological and immunohistochemistry examinations. The concentrations of the retinal malondialdehyde (MDA), superoxide dismutase (SOD), as well as the mRNA levels of apoptotic-associated genes were quantified. The IP and IV delivery pathways of HRS were both effective to ameliorate MNU induced photoreceptor degeneration. Moreover, the IV acted as a more efficient delivery method than the IP in terms of therapeutic effects. Particularly, the topographic measurements suggested that the IV delivery of HRS could alleviate MNU induced photoreceptor degeneration in the posterior retina. The immunostaining experiments also verified the comparative efficiency between IV and IP delivery of HRS on regional cone photoreceptors. Focal cone photoreceptors showed different susceptibilities to HRS and exhibited as a distinct spatial disequilibrium: cone photoreceptors in the ST quadrant were preferentially rescued; meanwhile, HRS induced protection was feeblest in the IN quadrant. Furthermore, the HRS treatment increased the level of retinal SOD, while reduce the level of retinal MDA in MNU administered rats. The expression levels of sever apoptotic -associated genes were significantly altered by HRS treatment. Collectively, these findings suggest that the IV space is an excellent target for HRS delivery. The IV delivery of HRS can efficiently alleviate the photoreceptors (especially these locate at the posterior retina) from MNU toxicity and act as a candidate treatment for RP.

Potential markers and metabolic processes involved in the mechanism of radiation-induced heart injury

Irradiation of normal tissues leads to acute increase in reactive oxygen/nitrogen species that serve as intra- and inter-cellular signaling to alter cell and tissue function. In the case of chest irradiation, it can affect the heart, blood vessels, and lungs, with consequent tissue remodelation and adverse side effects and symptoms. This complex process is orchestrated by a large number of interacting molecular signals, including cytokines, chemokines, and growth factors. Inflammation, endothelial cell dysfunction, thrombogenesis, organ dysfunction, and ultimate failing of the heart occur as a pathological entity - "radiation-induced heart disease" (RIHD) that is major source of morbidity and mortality. The purpose of this review is to bring insights into the basic mechanisms of RIHD that may lead to the identification of targets for intervention in the radiotherapy side effect. Studies of authors also provide knowledge about how to select targeted drugs or biological molecules to modify the progression of radiation damage in the heart. New prospective studies are needed to validate that assessed factors and changes are useful as early markers of cardiac damage.

Molecular hydrogen potentiates beneficial anti-infarct effect of hypoxic postconditioning in isolated rat hearts: a novel cardioprotective intervention

Generation of free radicals through incomplete reduction of oxygen during ischemia-reperfusion (I/R) is well described. On the other hand, molecular hydrogen (H₂) reduces oxidative stress due to its ability to react with strong oxidants and easily penetrate cells by diffusion, without disturbing metabolic redox reactions. This study was designed to explore cardioprotective potential of hypoxic postconditioning (HpostC) against I/R (30 min global I - 120 min R) in isolated rat hearts using oxygen-free Krebs-Henseleit buffer (KHB). Furthermore, the possibility to potentiate the effect of HpostC by H₂ using oxygen-free KHB saturated with H₂ (H₂ + HpostC) was tested. HPostC was induced by 4 cycles of 1-minute perfusion with oxygen-free KHB intercepted by 1-minute perfusion with normal KHB, at the onset of reperfusion. H₂ + HPostC was applied in a similar manner using H₂-enriched oxygen-free KHB. Cardioprotective effects were evaluated on the basis of infarct size (IS, in % of area at risk, AR) reduction, post-I/R recovery of heart function, and occurrence of reperfusion arrhythmias. HPostC significantly reduced IS/AR compared with non-conditioned controls. H₂ present in KHB during HPostC further decreased IS/AR compared with the effect of HPostC, attenuated severe arrhythmias, and significantly restored heart function (vs. controls). Cardioprotection by HpostC can be augmented by molecular hydrogen infusion.