Inhaled Hydrogen Gas Therapy for Prevention of Lung Transplant-Induced Ischemia/Reperfusion Injury in Rats

Molecular Hydrogen Therapy: Mechanisms, Delivery Methods, Preventive, and Therapeutic Application

Molecular hydrogen (H2), recognized as the smallest gas molecule, is capable of permeating cellular membranes and diffusing throughout the body. Due to its high bioavailability, H2 is considered a therapeutic gas for the treatment of various diseases. The therapeutic efficacy of hydrogen is contingent upon factors such as the administration method, duration of contact with diseased tissue, and concentration at targeted sites. H2 can be administered exogenously and is also produced endogenously within the intestinal tract. A comprehensive understanding of its delivery mechanisms and modes of action is crucial for advancing hydrogen medicine. This review highlights H₂'s mechanisms of action, summarizes its administration methods, and explores advancements in treating intestinal diseases (e.g., inflammatory bowel disease, intestinal ischemia-reperfusion, colorectal cancer). Additionally, its applications in managing other diseases are discussed. Finally, the challenges associated with its clinical application and potential solutions are explored. We propose that current delivery challenges faced by H2 can be effectively addressed through the use of nanoplatforms; furthermore, interactions between hydrogen and gut microbiota may provide insights into its mechanisms for treating intestinal diseases. Future research should explore the synergistic effects of H2 in conjunction with conventional therapies and develop personalized treatment plans to achieve precision medicine.

Molecular Hydrogen in the Treatment of Respiratory Diseases

Molecular hydrogen is gaining increasing attention as an antioxidant, anti-inflammatory, and antiapoptotic agent. Once considered an inert gas, it reveals current therapeutic potential among others in inflammatory diseases, cancer, and sports medicine, among others. The present review aims to provide a consistent summary of the findings of the last twenty years on the use of molecular hydrogen in major respiratory diseases, including allergies, asthma, COPD, pulmonary fibrosis, lung injury of various origins, as well as cancer and infections of the respiratory tract. In addition, the basic mechanisms through which molecular hydrogen exercises its biological activity on the respiratory system are described.

Hydrogen gas inhalation ameliorates glomerular enlargement after hypoxic-ischemic insult in asphyxiated piglet model

Acute kidney injury (AKI) has been reported to occur in 30-70% of asphyxiated neonates. Hydrogen (H2) gas became a major research focus in neonatal medicine after the identification of its robust antioxidative properties. However, the ability of H2 gas to ameliorate AKI is unknown. We examined histopathological injuries in the piglet renal cortex on day 5 after a hypoxic-ischemic (HI) insult and if H2 gas can alleviate kidney injuries. Twenty piglets were divided into three groups: no insult (Control, n = 6), HI insult alone (HI, n = 8), and HI insult with H2 gas ventilation (HI-H2, 2.1-2.7% for 24 h, n = 6). The total glomerular cell count was significantly higher in the HI group than in the other groups, with no difference between the HI-H2 and control groups. Proximal tubular lumen narrowing was significantly increased in the HI group versus control, but not in the HI-H2 group. In this piglet model, glomerular enlargement with an increase in glomerular cell number due to tubular lumen narrowing was observed on day 5 after HI insult. H2 gas effectively suppressed this glomerular cell increase and tubular lumen narrowing.

Plasma brain-related biomarkers and potential therapeutic targets in pediatric ECMO

Extracorporeal membrane oxygenation (ECMO) is a technique used to support severe cardiopulmonary failure. Its potential life-saving benefits are tempered by the significant risk for acute brain injury (ABI), from both primary pathophysiologic factors and ECMO-related complications through central nervous system cellular injury, blood-brain barrier dysfunction (BBB), systemic inflammation and neuroinflammation, and coagulopathy. Plasma biomarkers are an emerging tool used to stratify risk for and diagnose ABI, and prognosticate neurofunctional outcomes. Components of the neurovascular unit have been rational targets for this inquiry in ECMO. Central nervous system (CNS) neuronal and astroglial cellular-derived neuron-specific enolase (NSE), tau, glial fibrillary acidic protein (GFAP) and S100β elevations have been detected in ABI and are associated with poorer outcomes. Evidence of BBB breakdown through peripheral blood detection of CNS cellular components NSE, GFAP, and S100β, as well as evidence of elevated BBB components vWF and PDGFRβ are associated with higher mortality and worse neurofunctional outcomes. Higher concentrations of pro-inflammatory cytokines (IL-1β, IL-6, IFN-γ, TNF-α) are associated with abnormal neuroimaging, and proteomic expression panels reveal different coagulation and inflammatory responses. Abnormal coagulation profiles are common in ECMO with ongoing studies attempting to describe specific abnormalities either being causal or associated with neurologic outcomes; vWF has shown some promise. Understanding these mechanisms of injury through biomarker analysis supports potential neuroprotective strategies such as individualized blood pressure targets, judicious hypercarbia and hypoxemia correction, and immunomodulation (inhaled hydrogen and N-acetylcysteine). Further research continues to elucidate the role of biomarkers as predictors, prognosticators, and therapeutic targets.

Hydrogen-rich water alleviates asthma airway inflammation by modulating tryptophan metabolism and activating aryl hydrocarbon receptor via gut microbiota regulation

Hydrogen-rich water (HRW) is a beverage containing a high concentration of hydrogen that has been researched for its antioxidant, anti-apoptotic, and anti-inflammatory properties in asthma. This study investigates the potential therapeutic impact of HRW on the gut-lung axis. Using 16S rRNA and serum metabolomics, we examined changes in gut microbiota and serum metabolites in asthmatic mice after HRW intervention, followed by validation experiments. The findings revealed that HRW influenced gut microbiota by increasing Ligilactobacillus and Bifidobacterium abundance and enhancing the presence of indole-3-acetic acid (IAA), a microbially derived serum metabolite. Both in vivo and in vitro experiments showed that HRW's protective effects against airway inflammation in asthmatic mice may be linked to the gut microbiota, with IAA potentially playing a role in reducing asthmatic airway inflammation through the aryl hydrocarbon receptors (AhR) signaling pathway. In summary, HRW can modify gut microbiota, increase Bifidobacterium abundance, elevate microbial-derived IAA levels, and activate AhR, which could potentially alleviate inflammation in asthma.

Hydrogen Protects Mitochondrial Function by Increasing the Expression of PGC-1α and Ameliorating Myocardial Ischaemia-Reperfusion Injury

To investigate the application of H2 to alleviate cardiac ischaemia-reperfusion (I/R) injury in a PGC-1α-dependent manner. A rat in vitro myocardial I/R injury model was used, Western blot was used to detect the expression levels of apoptosis markers (Bax, cleaved caspase-3, Bcl2), inflammatory factors (IL-1β, TNF-α), mitochondrial fission (DRP1, MFF) and mitochondrial fusion (MFN1, MFN2, OPA1). HE staining was used to observe the effect of H2 on the myocardial tissue structure injured by I/R. Transmission electron microscopy (TEM) was used to observe the changes in the mitochondrial structure of myocardial tissue after I/R injury. Real-time quantitative PCR (qPCR) was used to detect the expression of PGC-1α in the myocardial tissue of rats after I/R injury and H2 treatment. H2 increases the expression level of PGC-1α, while the deletion of PGC-1α inhibited the therapeutic effect of H2. H2 can improve the changes of the myocardial tissue and mitochondrial structure caused by I/R injury. H2 treatment effectively inhibited the inflammatory response, and the loss of PGC-1α could inhibit the therapeutic effect of H2. The application of H2 can alleviate myocardial I/R injury, and the loss of PGC-1α weakens the protective effect of H2 on the I/R heart.

The Landscape of Smart Biomaterial-Based Hydrogen Therapy

Hydrogen (H2) therapy is an emerging, novel, and safe therapeutic modality that uses molecular hydrogen for effective treatment. However, the impact of H2 therapy is limited because hydrogen molecules predominantly depend on the systemic administration of H2 gas, which cannot accumulate at the lesion site with high concentration, thus leading to limited targeting and utilization. Biomaterials are developed to specifically deliver H2 and control its release. In this review, the development process, stimuli-responsive release strategies, and potential therapeutic mechanisms of biomaterial-based H2 therapy are summarized. H2 therapy. Specifically, the produced H2 from biomaterials not only can scavenge free radicals, such as reactive oxygen species (ROS) and lipid peroxidation (LPO), but also can inhibit the danger factors of initiating diseases, including pro-inflammatory cytokines, adenosine triphosphate (ATP), and heat shock protein (HSP). In addition, the released H2 can further act as signal molecules to regulate key pathways for disease treatment. The current opportunities and challenges of H2-based therapy are discussed, and the future research directions of biomaterial-based H2 therapy for clinical applications are emphasized.

The Protective Role of Molecular Hydrogen in Ischemia/Reperfusion Injury

Ischemia/reperfusion injury (IRI) represents a significant contributor to morbidity and mortality associated with various clinical conditions, including acute coronary syndrome, stroke, and organ transplantation. During ischemia, a profound hypoxic insult develops, resulting in cellular dysfunction and tissue damage. Paradoxically, reperfusion can exacerbate this injury through the generation of reactive oxygen species and the induction of inflammatory cascades. The extensive clinical sequelae of IRI necessitate the development of therapeutic strategies to mitigate its deleterious effects. This has become a cornerstone of ongoing research efforts in both basic and translational science. This review examines the use of molecular hydrogen for IRI in different organs and explores the underlying mechanisms of its action. Molecular hydrogen is a selective antioxidant with anti-inflammatory, cytoprotective, and signal-modulatory properties. It has been shown to be effective at mitigating IRI in different models, including heart failure, cerebral stroke, transplantation, and surgical interventions. Hydrogen reduces IRI via different mechanisms, like the suppression of oxidative stress and inflammation, the enhancement of ATP production, decreasing calcium overload, regulating cell death, etc. Further research is still needed to integrate the use of molecular hydrogen into clinical practice.

Protective Effects of Hydrogen Gas Inhalation for Hindlimb Ischaemia-Reperfusion Injury in a Mouse Model

OBJECTIVE

Ischaemia-reperfusion (I/R) injury is a severe post-operative complication that triggers an inflammatory response and causes severe damage. Hydrogen gas has anti-oxidant and anti-apoptotic properties and has been shown to be safe in humans. The study aimed to investigate whether hydrogen gas protects against skeletal muscle I/R injury.

METHODS

Experimental basic research using mice. A total of 160 eight to 10 week old albino laboratory bred strain of house mice (25.8 ± 0.68 g) were used in this study. The mice were cable tied to the hindlimb under anaesthesia and then placed in an anaesthesia box filled with air and 2% isoflurane (control group); 80 mice were additionally subjected to 1.3% hydrogen gas in this mix (hydrogen group). After two hours, the cable ties were removed to initiate reperfusion, and hydrogen inhalation lasted for six hours in the hydrogen group. After six hours, the mice were taken out of the box and kept in cages under standard conditions until time for observation at 16 different time points after reperfusion: zero, two, four, six, eight, and 10 hours and one, two, three, four, five, six, seven, 14, 21, and 28 days. Five mice were sacrificed using excess anaesthesia at each time point, and the bilateral hindlimb tissues were harvested. The inflammatory effects of the I/R injury were assessed by evaluating serum interleukin-6 concentrations using enzyme linked immunosorbent assay, as well as histological and immunohistochemical analyses. Untreated mice with I/R injury were used as controls.

RESULTS

Hydrogen gas showed protective effects associated with a reduction in inflammatory cell infiltration (neutrophils, macrophages, and lymphocytes), a reduced area of damaged muscle, maintenance of normal muscle cells, and replacement of damaged muscle cells with neoplastic myocytes.

CONCLUSION

Inhalation of hydrogen gas had a protective effect against hindlimb I/R injury in mice, in part by reducing inflammatory cell infiltration and in part by preserving normal muscle cells.

Pyroptosis in myocardial ischemia/reperfusion and its therapeutic implications

Ischemic heart disease, a prevalent cardiovascular disease with global significance, is associated with substantial morbidity. Timely and successful reperfusion is crucial for reducing infarct size and enhancing clinical outcomes. However, reperfusion may induce additional myocardium injury, manifesting as myocardial ischemia/reperfusion (MI/R) injury. Pyroptosis is a regulated cell death pathway, the signaling pathway of which is activated during MI/R injury. In this process, the inflammasomes are triggered, initiating the cleavage of gasdermin proteins and pro-interleukins, which results in the formation of membrane pores and the maturation and secretion of inflammatory cytokines. Numerous preclinical evidence underscores the pivotal role of pyroptosis in MI/R injury. Inhibiting pyroptosis is cardioprotective against MI/R injury. Although certain agents exhibiting promise in preclinical studies for attenuating MI/R injury through inhibiting pyroptosis have been identified, the suitability of these compounds for clinical trials remains untested. This review comprehensively summarizes the recent developments in this field, with a specific emphasis on the impact of pyroptosis on MI/R injury. Deciphering these findings not only sheds light on new disease mechanisms but also paves the way for innovative treatments. And then the exploration of the latest advances in compounds that inhibit pyroptosis in MI/R is discussed, which aims to provide insights into potential therapeutic strategies and identify avenues for future research in the pursuit of effective clinical interventions.

Hydrogen treatment reduces electroencephalographic activity and neuronal death in rats with refractory status epilepticus by inhibiting membrane NR2B phosphorylation and oxidative stress

OBJECTIVE

To investigate the effects of hydrogen therapy on epileptic seizures in rats with refractory status epilepticus and the underlying mechanisms.

METHODS

Status epilepticus was induced using pilocarpine. The effects of hydrogen treatment on epilepsy severity in model rats were then monitored using Racine scores and electroencephalography (EEG), followed by western blot of plasma membrane N-methyl-D-aspartate receptor subtype 2B (NR2B) and phosphorylated NR2B expression. We also generated a cellular epilepsy model using Mg2+-free medium and used polymerase chain reaction to investigate the neuroprotective effects of hydrogen.

RESULTS

There were no significant differences in Racine scores between the hydrogen and control groups. EEG amplitudes were lower in the hydrogen treatment group than in the control group. In epilepsy model rats, hippocampal cell membrane NR2B expression and phosphorylation increased gradually over time. Although hippocampal cell membrane NR2B expression was not significantly different between the two groups, NR2B phosphorylation levels were significantly lower in the hydrogen group. Hydrogen treatment also increased superoxide dismutase, mitochondrial (SOD2) expression.

CONCLUSIONS

Hydrogen treatment reduced EEG amplitudes and NR2B phosphorylation; it also decreased neuronal death by reducing oxidative stress. Hydrogen may thus be a potential treatment for refractory status epilepticus by inhibiting membrane NR2B phosphorylation and oxidative stress.

Hydrogen in Transplantation: Potential Applications and Therapeutic Implications

Hydrogen gas, renowned for its antioxidant properties, has emerged as a novel therapeutic agent with applications across various medical domains, positioning it as a potential adjunct therapy in transplantation. Beyond its antioxidative properties, hydrogen also exerts anti-inflammatory effects by modulating pro-inflammatory cytokines and signaling pathways. Furthermore, hydrogen's capacity to activate cytoprotective pathways bolsters cellular resilience against stressors. In recent decades, significant advancements have been made in the critical medical procedure of transplantation. However, persistent challenges such as ischemia-reperfusion injury (IRI) and graft rejection continue to hinder transplant success rates. This comprehensive review explores the potential applications and therapeutic implications of hydrogen in transplantation, shedding light on its role in mitigating IRI, improving graft survival, and modulating immune responses. Through a meticulous analysis encompassing both preclinical and clinical studies, we aim to provide valuable insights into the promising utility of hydrogen as a complementary therapy in transplantation.

Hydrogen attenuates endothelial glycocalyx damage associated with partial cardiopulmonary bypass in rats

Cardiopulmonary bypass (CPB) causes systemic inflammation and endothelial glycocalyx damage. Hydrogen has anti-oxidant and anti-inflammatory properties; therefore, we hypothesized that hydrogen would alleviate endothelial glycocalyx damage caused by CPB. Twenty-eight male Sprague-Dawley rats were randomly divided into four groups (n = 7 per group), as follows: sham, control, 2% hydrogen, and 4% hydrogen. The rats were subjected to 90 minutes of partial CPB followed by 120 minutes of observation. In the hydrogen groups, hydrogen was administered via the ventilator and artificial lung during CPB, and via the ventilator for 60 minutes after CPB. After observation, blood collection, lung extraction, and perfusion fixation were performed, and the heart, lung, and brain endothelial glycocalyx thickness was measured by electron microscopy. The serum syndecan-1 concentration, a glycocalyx component, in the 4% hydrogen group (5.7 ± 4.4 pg/mL) was lower than in the control (19.5 ± 6.6 pg/mL) and 2% hydrogen (19.8 ± 5.0 pg/mL) groups (P < 0.001 for each), but it was not significantly different from the sham group (6.2 ± 4.0 pg/mL, P = 0.999). The endothelial glycocalyces of the heart and lung in the 4% hydrogen group were thicker than in the control group. The 4% hydrogen group had lower inflammatory cytokine concentrations (interleukin-1β and tumor necrosis factor-α) in serum and lung tissue, as well as a lower serum malondialdehyde concentration, than the control group. The 2% hydrogen group showed no significant difference in the serum syndecan-1 concentration compared with the control group. However, non-significant decreases in serum and lung tissue inflammatory cytokine concentrations, as well as in serum malondialdehyde concentration, were observed. Administration of 4% hydrogen via artificial and autologous lungs attenuated endothelial glycocalyx damage caused by partial CPB in rats, which might be mediated by the anti-inflammatory and anti-oxidant properties of hydrogen.

Hydrogen Attenuates Chronic Intermittent Hypoxia-Induced Cardiac Hypertrophy by Regulating Iron Metabolism

The present study aimed to investigate the impact of hydrogen (H2) on chronic intermittent hypoxia (CIH)-induced cardiac hypertrophy in mice by modulating iron metabolism. C57BL/6N mice were randomly allocated into four groups: control (Con), CIH, CIH + H2, and H2. The mice were exposed to CIH (21-5% FiO2, 3 min/cycle, 8 h/d), and received inhalation of a hydrogen-oxygen mixture (2 h/d) for 5 weeks. Cardiac and mitochondrial function, levels of reactive oxygen species (ROS), and iron levels were evaluated. The H9C2 cell line was subjected to intermittent hypoxia (IH) and treated with H2. Firstly, we found H2 had a notable impact on cardiac hypertrophy, ameliorated pathological alterations and mitochondrial morphology induced by CIH (p < 0.05). Secondly, H2 exhibited a suppressive effect on oxidative injury by decreasing levels of inducible nitric oxide synthase (i-NOS) (p < 0.05) and 4-hydroxynonenal (4-HNE) (p < 0.01). Thirdly, H2 demonstrated a significant reduction in iron levels within myocardial cells through the upregulation of ferroportin 1 (FPN1) proteins (p < 0.01) and the downregulation of transferrin receptor 1 (TfR1), divalent metal transporter 1 with iron-responsive element (DMT1(+ire)), and ferritin light chain (FTL) mRNA or proteins (p < 0.05). Simultaneously, H2 exhibited the ability to decrease the levels of Fe2+ and ROS in H9C2 cells exposed to IH (p < 0.05). Moreover, H2 mediated the expression of hepcidin, hypoxia-inducible factor-1α (HIF-1α) (p < 0.01), and iron regulatory proteins (IRPs), which might be involved in the regulation of iron-related transporter proteins. These results suggested that H2 may be beneficial in preventing cardiac hypertrophy, a condition associated with reduced iron toxicity.

Hydrogen: A Rising Star in Gas Medicine as a Mitochondria-Targeting Nutrient via Activating Keap1-Nrf2 Antioxidant System

The gas molecules O2, NO, H2S, CO, and CH4, have been increasingly used for medical purposes. Other than these gas molecules, H2 is the smallest diatomic molecule in nature and has become a rising star in gas medicine in the past few decades. As a non-toxic and easily accessible gas, H2 has shown preventive and therapeutic effects on various diseases of the respiratory, cardiovascular, central nervous system, and other systems, but the mechanisms are still unclear and even controversial, especially the mechanism of H2 as a selective radical scavenger. Mitochondria are the main organelles regulating energy metabolism in living organisms as well as the main organelle of reactive oxygen species' generation and targeting. We propose that the protective role of H2 may be mainly dependent on its unique ability to penetrate every aspect of cells to regulate mitochondrial homeostasis by activating the Keap1-Nrf2 phase II antioxidant system rather than its direct free radical scavenging activity. In this review, we summarize the protective effects and focus on the mechanism of H2 as a mitochondria-targeting nutrient by activating the Keap1-Nrf2 system in different disease models. In addition, we wish to provide a more rational theoretical support for the medical applications of hydrogen.

Protective Effect of Calpain Inhibition During Cold Ischemia on Ischemia-reperfusion Injury After Lung Transplantation

BACKGROUND

Necroptosis, one of the types of regulated necrosis, causes ischemia-reperfusion (IR) lung injury. N-acetyl-leucyl-leucyl-norleucinal (ALLN), a calpain inhibitor, is known to attenuate necroptosis and apoptosis, and the purpose of this study was to evaluate the protective effect of ALLN during cold ischemia against IR injury in a rat lung transplant model.

METHODS

Male Lewis rats (250-350 g) were divided into 3 groups: sham group (n = 4), nontransplantation; control group (n = 8), transplantation with IR lung injury; and ALLN group (n = 8), transplantation with IR lung injury/ALLN. Rats in the sham group underwent a simple thoracotomy, and the remaining 2 groups of rats underwent an orthotopic left lung transplant. Cold ischemic time was 15 h. After 2 h of reperfusion, physiological function, inflammatory cytokine expression, pathway activation, and the degrees of necroptosis and apoptosis were evaluated.

RESULTS

Lung gas exchange (PaO 2 /FiO 2 ) was significantly better, and pulmonary edema was significantly improved in the ALLN group compared with the control group ( P = 0.0009, P = 0.0014). Plasma expression of interleukin-1β was significantly lower in the ALLN group than in the control group ( P = 0.0313). The proportion of necroptotic and apoptotic cells was significantly lower in the ALLN group than in the control group ( P = 0.0009), whereas the proportion of apoptotic cells remained unchanged ( P = 0.372); therefore, the calpain inhibitor was thought to suppress necroptosis.

CONCLUSIONS

The administration of ALLN during cold ischemia appears to improve IR lung injury in a lung transplant animal model via the inhibition of necroptosis.

Hydrogen inhalation attenuates lung contusion after blunt chest trauma in mice

BACKGROUND

Lung contusion caused by blunt chest trauma evokes a severe inflammatory reaction in the pulmonary parenchyma that may be associated with acute respiratory distress syndrome. Although hydrogen gas has antioxidant and anti-inflammatory effects and is protective against multiple types of lung injury at safe concentrations, the effects of inhaled hydrogen gas on blunt lung injury have not been previously investigated. Therefore, using a mouse model, we tested the hypothesis that hydrogen inhalation after chest trauma would reduce pulmonary inflammation and acute lung injury associated with lung contusion.

METHODS

Inbred male C57BL/6 mice were randomly divided into 3 groups: sham with air inhalation, lung contusion with air inhalation, and lung contusion with 1.3% hydrogen inhalation. Experimental lung contusion was induced using a highly reproducible and standardized apparatus. Immediately after induction of lung contusion, mice were placed in a chamber exposed to 1.3% hydrogen gas in the air. Histopathological analysis and real-time polymerase chain reaction in lung tissue and blood gas analysis were performed 6 hours after contusion.

RESULTS

Histopathological examination of the lung tissue after contusion revealed perivascular/intra-alveolar hemorrhage, perivascular/interstitial leukocyte infiltration, and interstitial/intra-alveolar edema. These histological changes and the extent of lung contusion, as determined by computed tomography, were significantly mitigated by hydrogen inhalation. Hydrogen inhalation also significantly reduced inflammatory cytokine and chemokine mRNA levels and improved oxygenation.

CONCLUSION

Hydrogen inhalation therapy significantly mitigated inflammatory responses associated with lung contusion in mice. Hydrogen inhalation therapy may be a supplemental therapeutic strategy for treating lung contusion.

Hydrogen inhalation enhances autophagy via the AMPK/mTOR pathway, thereby attenuating doxorubicin-induced cardiac injury

AIMS

Doxorubicin is a drug widely used in clinical cancer treatment, but severe cardiotoxicity limits its clinical application. Autophagy disorder is an important factor in the mechanism of doxorubicin-induced cardiac injury. As the smallest molecule in nature, hydrogen has various biological effects such as anti-oxidation, anti-apoptosis and regulation of autophagy. Hydrogen therapy is currently considered to be an emerging therapeutic method, but the effect and mechanism of hydrogen on doxorubicin-induced myocardial injury have not been determined. The purpose of this study was to investigate the protective effect of hydrogen inhalation on doxorubicin-induced chronic myocardial injury and its effect and mechanism on autophagy.

METHODS

In this study, we established a chronic heart injury model by intraperitoneal injection of doxorubicin in rats for 30 days, accumulating 20 mg/kg. The effect of hydrogen inhalation on the cardiac function in rats was explored by echocardiography, Elisa, and H&E staining. To clarify the influence of autophagy, we detected the expression of LC3 and related autophagy proteins in vivo and in vitro by immunofluorescence and western blot.In order to further explore the mechanism of autophagy, we added pathway inhibitors and used western blot to preliminarily investigate the protective effect of hydrogen inhalation on myocardial injury caused by doxorubicin.

RESULTS

Hydrogen inhalation can improve doxorubicin-induced cardiac function decline and pathological structural abnormalities in rats. It was confirmed by immunofluorescence that hydrogen treatment could restore the expression of autophagy marker protein LC3 (microtubule-associated protein 1 light chain 3) in cardiomyocytes reduced by doxorubicin, while reducing cardiomyocyte apoptosis. Mechanistically, Western blot results consistently showed that hydrogen treatment up-regulated the ratio of p-AMPK (phosphorylated AMP-dependent protein kinase) to AMPK and down-regulated p-mTOR (phosphorylated mammalian target of rapamycin) and mTOR ratio.

CONCLUSIONS

These results suggest that hydrogen inhalation can activate autophagy through the AMPK/mTOR pathway and protect against myocardial injury induced by doxorubicin. Hydrogen inhalation therapy may be a potential treatment for doxorubicin-induced myocardial injury.

Neonatal asphyxia as an inflammatory disease: Reactive oxygen species and cytokines

Neonatologists resuscitate asphyxiated neonates by every available means, including positive ventilation, oxygen therapy, and drugs. Asphyxiated neonates sometimes present symptoms that mimic those of inflammation, such as fever and edema. The main pathophysiology of the asphyxia is inflammation caused by hypoxic-ischemic reperfusion. At birth or in the perinatal period, neonates may suffer several, hypoxic insults, which can activate inflammatory cells and inflammatory mediator production leading to the release of larger quantities of reactive oxygen species (ROS). This in turn triggers the production of oxygen stress-induced high mobility group box-1 (HMGB-1), an endogenous damage-associated molecular patterns (DAMPs) protein bound to toll-like receptor (TLR) -4, which activates nuclear factor-kappa B (NF-κB), resulting in the production of excess inflammatory mediators. ROS and inflammatory mediators are produced not only in activated inflammatory cells but also in non-immune cells, such as endothelial cells. Hypothermia inhibits pro-inflammatory mediators. A combination therapy of hypothermia and medications, such as erythropoietin and melatonin, is attracting attention now. These medications have both anti-oxidant and anti-inflammatory effects. As the inflammatory response and oxidative stress play a critical role in the pathophysiology of neonatal asphyxia, these drugs may contribute to improving patient outcomes.

Research Progress on the Role of Pyroptosis in Myocardial Ischemia-Reperfusion Injury

Myocardial ischemia-reperfusion injury (MIRI) results in the aggravation of myocardial injury caused by rapid recanalization of the ischemic myocardium. In the past few years, there is a growing interest in investigating the complex pathophysiological mechanism of MIRI for the identification of effective targets and drugs to alleviate MIRI. Currently, pyroptosis, a type of inflammatory programmed death, has received greater attention. It is involved in the MIRI development in combination with other mechanisms of MIRI, such as oxidative stress, calcium overload, necroptosis, and apoptosis, thereby forming an intertwined association between different pathways that affect MIRI by regulating common pathway molecules. This review describes the pyroptosis mechanism in MIRI and its relationship with other mechanisms, and also highlights non-coding RNAs and non-cardiomyocytes as regulators of cardiomyocyte pyroptosis by mediating associated pathways or proteins to participate in the initiation and development of MIRI. The research progress on novel small molecule drugs, clinical drugs, traditional Chinese medicine, etc. for regulating pyroptosis can play a crucial role in effective MIRI alleviation. When compared to research on other mature mechanisms, the research studies on pyroptosis in MIRI are inadequate. Although many related protective drugs have been identified, these drugs generally lack clinical applications. It is necessary to further explore and verify these drugs to expand their applications in clinical setting. Early inhibition of MIRI by targeted regulation of pyroptosis is a key concern that needs to be addressed in future studies.

Hydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response in mice

Background

Chronic inflammation and oxidant/antioxidant imbalance are two main pathological features associated with lipopolysaccharide (LPS)-induced acute lung injury (ALI). The following study investigated the protective role of hydrogen (H₂), a gaseous molecule without known toxicity, in LPS-induced lung injury in mice and explored its potential molecular mechanisms.

Methods

Mice were randomly divided into three groups: H₂ control group, LPS group, and LPS + H₂ group. The mice were euthanized at the indicated time points, and the specimens were collected. The 72 h survival rates, cytokines contents, pathological changes, expression of Toll-like receptor 4 (TLR4), and oxidative stress indicators were analyzed. Moreover, under different culture conditions, RAW 264.7 mouse macrophages were used to investigate the potential molecular mechanisms of H₂ in vitro. Cells were divided into the following groups: PBS group, LPS group, and LPS + H₂ group. The cell viability, intracellular ROS, cytokines, and expression of TLR4 and nuclear factor kappa-B (NF-κB) were observed.

Results

Hydrogen inhalation increased the survival rate to 80%, reduced LPS-induced lung damage, and decreased inflammatory cytokine release in LPS mice. Besides, H₂ showed remarked anti-oxidative activity to reduce the MDA and NO contents in the lung. In vitro data further indicated that H₂ down-regulates the levels of ROS, NO, TNF-α, IL-6, and IL-1β in LPS-stimulated macrophages and inhibits the expression of TLR4 and the activation of nuclear factor kappa-B (NF-κB).

Conclusion

Hydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response most probably through the TLR4-NF-κB pathway.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12950-022-00314-x.

Luminal Administration of a Water-soluble Carbon Monoxide-releasing Molecule (CORM-3) Mitigates Ischemia/Reperfusion Injury in Rats Following Intestinal Transplantation

BACKGROUND

The protective effects of carbon monoxide (CO) against ischemia/reperfusion (IR) injury during organ transplantation have been extensively investigated. Likewise, CO-releasing molecules (CORMs) are known to exert a variety of pharmacological activities via liberation of controlled amounts of CO in organs. Therefore, we hypothesized that intraluminal administration of water-soluble CORM-3 during cold storage of intestinal grafts would provide protective effects against IR injury.

METHODS

Orthotopic syngeneic intestinal transplantation was performed in Lewis rats following 6 h of cold preservation in Ringer solution or University of Wisconsin solution. Saline containing CORM-3 (100 µmol/L) or its inactive counterpart (iCORM-3) was intraluminally introduced in the intestinal graft before cold preservation.

RESULTS

Histopathological analysis of untreated and iCORM-3-treated grafts revealed a similar erosion and blunting of the intestinal villi. These changes in the mucosa structure were significantly attenuated by intraluminal administration of CORM-3. Intestinal mucosa damage caused by IR injury led to considerable deterioration of gut barrier function 3 h postreperfusion. CORM-3 significantly inhibited upregulation of proinflammatory mRNA levels, ameliorated intestinal morphological changes, and improved graft blood flow and mucosal barrier function. Additionally, CORM-3-treated grafts increased recipient survival rates. Pharmacological blockade of soluble guanylyl cyclase activity significantly reversed the protective effects conferred by CORM-3, indicating that CO partially mediates its therapeutic actions via soluble guanylyl cyclase activation.

CONCLUSIONS

Our study demonstrates that luminally delivered CORM-3 provides beneficial effects in cold-stored rat small intestinal grafts and could be an attractive therapeutic application of CO in the clinical setting of organ preservation and transplantation.

Hydrogen Repairs LPS-Induced Endothelial Progenitor Cells Injury via PI3K/AKT/eNOS Pathway

Endotoxins and other harmful substances may cause an increase in permeability in endothelial cells (ECs) monolayers, as well as ECs shrinkage and death to induce lung damage. Lipopolysaccharide (LPS) can impair endothelial progenitor cells (EPCs) functions, including proliferation, migration, and tube formation. EPCs can migrate to the damaged area, differentiate into ECs, and participate in vascular repair, which improves pulmonary capillary endothelial dysfunction and maintains the integrity of the endothelial barrier. Hydrogen (H2) contributes to the repairment of lung injury and the damage of ECs. We therefore speculate that H2 protects the EPCs against LPS-induced damage, and it's mechanism will be explored. The bone marrow-derived EPCs from ICR Mice were treated with LPS to establish a damaged model. Then EPCs were incubated with H2, and treated with PI3K inhibitor LY294002 and endothelial nitric oxide synthase (eNOS) inhibitor L-NAME. MTT assay, transwell assay and tube formation assay were used to detect the proliferation, migration and angiogenesis of EPCs. The expression levels of target proteins were detected by Western blot. Results found that H2 repaired EPCs proliferation, migration and tube formation functions damaged by LPS. LY294002 and L-NAME significantly inhibited the repaired effect of H2 on LPS-induced dysfunctions of EPCs. H2 also restored levels of phosphor-AKT (p-AKT), eNOS and phosphor-eNOS (p-eNOS) suppressed by LPS. LY294002 significantly inhibited the increase of p-AKT and eNOS and p-eNOS expression exposed by H2. L-NAME significantly inhibited the increase of eNOS and p-eNOS expression induced by H2. H2 repairs the dysfunctions of EPCs induced by LPS, which is mediated by PI3K/AKT/eNOS signaling pathway.

Co-administration of hydrogen and metformin exerts cardioprotective effects by inhibiting pyroptosis and fibrosis in diabetic cardiomyopathy

Hydrogen is a novel medical gas with several properties, including anti-oxidative, anti-inflammatory, anti-apoptotic, anti-allergic, and energy metabolism stimulating properties. Hydrogen therapy has been proven effective in the treatment of myocardial ischemia, myocardial infarction, and ischemia-reperfusion injury. Diabetic cardiomyopathy (DCM) is a serious cardiovascular complication of long-term chronic diabetes that is linked to increased heart failure and arrhythmia morbidity. The effect of hydrogen on the pathogenesis of DCM is yet to be determined. Metformin is a well-known pharmacological agent for the treatment of diabetes; however, the application of large doses of the drug is limited by its side effects. Therefore, this highlights the importance of developing novel therapies against DCM. In this regard, we investigated the effect of hydrogen on DCM and the mechanisms that underlie it. Furthermore, we also assessed the efficacy of co-administration of metformin and hydrogen. In this study, we found that hydrogen improved cardiac dysfunction and abnormal morphological structure in streptozotocin-induced diabetic mice. As a mechanism, it was confirmed that hydrogen mediated its action by reducing pyroptosis via inhibition of the AMPK/mTOR/NLRP3 signaling pathway and ameliorating fibrosis via inhibition of the TGF-β1/Smad signaling pathway. Furthermore, our findings suggested that co-administration of hydrogen and metformin shows potent protective effects, as evidenced by increased survival rates, reduced fasting blood glucose, and decreased cell injury when compared to a single application of metformin. In conclusion, our study demonstrated that hydrogen inhalation attenuates DCM by reducing pyroptosis and fibrosis and that hydrogen can be combined with metformin to exhibit a more potent cardioprotective effect in DCM.

Molecular hydrogen is a potential protective agent in the management of acute lung injury

Acute lung injury (ALI) and acute respiratory distress syndrome, which is a more severe form of ALI, are life-threatening clinical syndromes observed in critically ill patients. Treatment methods to alleviate the pathogenesis of ALI have improved to a great extent at present. Although the efficacy of these therapies is limited, their relevance has increased remarkably with the ongoing pandemic caused by the novel coronavirus disease 2019 (COVID-19), which causes severe respiratory distress syndrome. Several studies have demonstrated the preventive and therapeutic effects of molecular hydrogen in the various diseases. The biological effects of molecular hydrogen mainly involve anti-inflammation, antioxidation, and autophagy and cell death modulation. This review focuses on the potential therapeutic effects of molecular hydrogen on ALI and its underlying mechanisms and aims to provide a theoretical basis for the clinical treatment of ALI and COVID-19.

Molecular hydrogen is a promising therapeutic agent for pulmonary disease

Molecular hydrogen exerts biological effects on nearly all organs. It has anti-oxidative, anti-inflammatory, and anti-aging effects and contributes to the regulation of autophagy and cell death. As the primary organ for gas exchange, the lungs are constantly exposed to various harmful environmental irritants. Short- or long-term exposure to these harmful substances often results in lung injury, causing respiratory and lung diseases. Acute and chronic respiratory diseases have high rates of morbidity and mortality and have become a major public health concern worldwide. For example, coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic. An increasing number of studies have revealed that hydrogen may protect the lungs from diverse diseases, including acute lung injury, chronic obstructive pulmonary disease, asthma, lung cancer, pulmonary arterial hypertension, and pulmonary fibrosis. In this review, we highlight the multiple functions of hydrogen and the mechanisms underlying its protective effects in various lung diseases, with a focus on its roles in disease pathogenesis and clinical significance.

Hydrogen: Potential Applications in Solid Organ Transplantation

Ischemia reperfusion injury (IRI) in organ transplantation has always been an important hotspot in organ protection. Hydrogen, as an antioxidant, has been shown to have anti-inflammatory, antioxidant, and antiapoptotic effects. In this paper, the protective effect of hydrogen against IRI in organ transplantation has been reviewed to provide clues for future clinical studies.

Hydrogen inhalation in rehabilitation program of the medical staff recovered from COVID-19

Active hydrogen inhalation (H(H2O)m) has powerful antioxidant and antiapoptotic effects. In recent years, it has been used in a number of experimental and clinical studies.

Aim. To study the safety and effectiveness of inhalation of the “active form of hydrogen” (AFV;(H(H2O)m)) in the rehabilitation program of coronavirus disease 2019 (COVID-19) survivors during the recovery period.

Material and methods. This randomized controlled parallel prospective study included 60 COVID-19 survivors with post-COVID-19 syndrome (ICD-10: U09.9) during the recovery period, with clinical manifestations of chronic fatigue syndrome (CFS), who received standard therapy in accordance with the management protocol of patients with CFS (ICD-10: G93.3): physiotherapy and medication therapy with drugs containing magnesium, B vitamins and L-carnitine. The patients were divided into 2 groups. The experimental group (n=30) included patients who received hydrogen inhalation for 90 minutes every day during 10 days (SUISONIA hydrogen inhalation device, Japan). The control group (n=30) consisted of patients who received standard therapy. In both groups, patients were comparable in sex and mean age: in the experimental group — 53 (22; 70) years, in the control group — 51 (25; 70) years. Biological markers of systemic inflammation, oxygen transport, lactate metabolism, intrapulmonary shunting, 6-minute walk test, and vascular endothelial function were determined in all patients on the 1st and 10th days of follow-up.

Results. In the experimental group, a decrease in following parameters was revealed: stiffness index (SI), from 8,8±1,8 to 6,8±1,5 (p<0,0001); ALT, from 24,0±12,7 to 20,22±10,61 U/L (p<0,001); venous blood lactate, from 2,5±0,8 to 1,5±1,0 mmol/L (p<0,001); capillary blood lactate, from 2,9±0,8 to 2,0±0,8 mmol/L (p<0,0001); estimated pulmonary shunt fraction (Qs/Qt, Berggren equation, 1942) from 8,98±5,7 to 5,34±3,2 (p<0,01); white blood cells, from 6,64±1,57 to 5,92±1,32 109/L. In addition, we revealed an increase in the refractive index (RI) from 46,67±13,26% to 63,32±13,44% (p<0,0001), minimum blood oxygen saturation (SpO2) from 92,25±2,9 to 94,25±1, 56% (p<0,05), direct bilirubin from 2,99±1,41 to 3,39±1,34 pmol/L (p<0,01), partial oxygen tension (PvO2) from 26,9±5,0 to 34,8±5,6 mm Hg (p<0,0001), venous oxygen saturation (SvO2) from 51,8±020,6 to 61,1±018,1% (p<0,05), partial capillary oxygen tension (PcO2) from 48,7±15,4 to 63,8±21,2 mm Hg (p<0,01), capillary oxygen saturation (ScO2) from 82,2±4,2 to 86,2±4,8% (p<0,01), distance in 6 minute walk test from 429±45,0 to 569±60 m.

Conclusion. Inhalation therapy with H(H2O)m in the rehabilitation program of COVID-19 survivors during the recovery period is a safe and highly effective method. Manifestations of silent hypoxemia and endothelial dysfunction decreased, while exercise tolerance increased. As for laboratory tests, a decrease in the white blood cell count, estimated pulmonary shunt fraction and lactate content parameters was revealed.

Lung Inflation With Hydrogen During the Cold Ischemia Phase Alleviates Lung Ischemia-Reperfusion Injury by Inhibiting Pyroptosis in Rats

Background: Lung inflation with hydrogen is an effective method to protect donor lungs from lung ischemia-reperfusion injury (IRI). This study aimed to examine the effect of lung inflation with 3% hydrogen during the cold ischemia phase on pyroptosis in lung grafts of rats.

Methods: Adult male Wistar rats were randomly divided into the sham group, the control group, the oxygen (O₂) group, and the hydrogen (H₂) group. The sham group underwent thoracotomy but no lung transplantation. In the control group, the donor lungs were deflated for 2 h. In the O₂ and H₂ groups, the donor lungs were inflated with 40% O₂ + 60% N₂ and 3% H₂ + 40% O₂ + 57% N₂, respectively, at 10 ml/kg, and the gas was replaced every 20 min during the cold ischemia phase for 2 h. Two hours after orthotopic lung transplantation, the recipients were euthanized.

Results: Compared with the control group, the O₂ and H₂ groups improved oxygenation indices, decreases the inflammatory response and oxidative stress, reduced lung injury, and improved pressure-volume (P-V) curves. H₂ had a better protective effect than O₂. Furthermore, the levels of the pyroptosis-related proteins selective nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), cysteinyl aspartate specific proteinase (caspase)-1 p20, and the N-terminal of gasdermin D (GSDMD-N) were decreased in the H₂ group.

Conclusion: Lung inflation with 3% hydrogen during the cold ischemia phase inhibited the inflammatory response, oxidative stress, and pyroptosis and improved the function of the graft. Inhibiting reactive oxygen species (ROS) production may be the main mechanism of the antipyroptotic effect of hydrogen.

Rat model of smoke inhalation-induced acute lung injury

BACKGROUND

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is a lethal disease with limited therapeutic options and an unacceptably high mortality rate. Understanding the complex pathophysiological processes involved in the development of ALI/ARDS is critical for developing novel therapeutic strategies. Smoke inhalation (SI) injury is the leading cause of morbidity and mortality in patients with burn-associated ALI/ARDS; however, to our knowledge few reliable, reproducible models are available for pure SI animal model to investigate therapeutic options for ALI/ARDS without the confounding variables introduced by cutaneous burn or other pathology.

OBJECTIVE

To develop a small animal model of pure SI-induced ALI and to use this model for eventual testing of novel therapeutics for ALI.

METHODS

Rats were exposed to smoke using a custom-made smoke generator. Peripheral oxygen saturation (SpO₂), heart rate, arterial blood gas, and chest X-ray (CXR) were measured before and after SI. Wet/dry weight (W/D) ratio, lung injury score and immunohistochemical staining of cleaved caspase 3 were performed on harvested lung tissues of healthy and SI animals.

RESULTS

The current study demonstrates the induction of ALI in rats after SI as reflected by a significant, sustained decrease in SpO₂ and the development of diffuse bilateral pulmonary infiltrates on CXR. Lung tissue of animals exposed to SI showed increased inflammation, oedema and apoptosis as reflected by the increase in W/D ratio, injury score and cleaved caspase 3 level of the harvested tissues compared with healthy animals.

CONCLUSION

We have successfully developed a small animal model of pure SI-induced ALI. This model is offered to the scientific community as a reliable model of isolated pulmonary SI-induced injury without the confounding variables of cutaneous injury or other systemic pathology to be used for study of novel therapeutics or other investigation.

Hydrogen regulates the M1/M2 polarization of alveolar macrophages in a rat model of chronic obstructive pulmonary disease

OBJECTIVE

Chronic obstructive pulmonary disease (COPD) is a respiratory disease with high morbidity and mortality worldwide, so far there is no ideal treatment method. Previous studies have shown that hydrogen (H₂) is involved in the treatment of COPD as an antioxidant. In this study, the effect of H₂ on M1/M2 polarization of alveolar macrophages in COPD rats was observed, and its anti-inflammatory mechanism was further elucidated. Methods: Twenty-four Sprague-Dawley rats were randomly divided into three groups including the control, COPD and H₂ group. A rat model of COPD was established by cigarette exposure combined with lipopolysaccharide (LPS) induction. H₂ therapy was administered 2 hours per day for 14 days. Lung function and pathology were assessed. The levels of interleukin (IL)-6, tumor necrosis factor (TNF)-α, transforming growth factor (TGF)-β1 and IL-10 in bronchoalveolar lavage fluid (BALF) and lung tissue were measured by enzyme-linked immunosorbent assay. The mRNA, protein expression and immunoreactivity of inducible nitric oxide synthase (iNOS) and arginase (Arg)-1 in lung were observed by quantitative real-time PCR, western blot and immunohistochemistry. Results: Compared with the control rats, there were a significant decline in lung function, a marked inflammatory infiltration and pulmonary parenchymal remodeling and the increases of IL-6, TNF-α and TGF-β1 levels in BALF and lung tissue, but a lower expression of IL-10 in COPD rats. The iNOS mRNA and protein expression, as well as its optical density (OD), were increased significantly in lung tissue, while those of Arg-1 decreased significantly. H₂ treatment improved the lung function and the parenchymal inflammation, reversed the increased levels of IL-6, TNF-α and TGF-β1, and the lower IL-10. Meanwhile, H₂ also down-regulated the expression of iNOS, but up-regulated expression of Arg-1 in lung tissue. Conclusion: H₂ reduces inflammation in the lung of COPD, which may be related to its inhibition of M1 type polarization and activation of M2 type polarization of alveolar macrophage.

Role of Molecular Hydrogen in Skin Diseases and its Impact in Beauty

In today's society, healthy skin and a beautiful appearance are considered the foundation of general well-being. The skin is the largest organ of the body and plays an important role in protecting it against various hazards such as environmental, physical, chemical, and biological hazards. These factors include mediators that lead to oxidation reactions that produce reactive oxygen/nitrogen species and additional oxidants in the skin cells. An increase in oxidants beyond the antioxidant capacity of its defense system causes oxidative stress and chronic inflammation in the body. This response can cause further disruption of collagen fibers and hinder the functioning of skin cells that may result in the development of various skin diseases including psoriasis, atopic dermatitis, and aging. In this review, we summarized the present information related to the role of oxidative stress in the pathogenesis of dermatological disorders, and its impact on physical beauty and the daily lives of patients. We also discussed how molecular hydrogen exhibits a therapeutic effect against skin diseases via its effects on oxidative stress. Furthermore, findings from this summary review indicate that molecular hydrogen might be an effective treatment modality for the prevention and treatment of skin-related illnesses.

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.

Protective effects of molecular hydrogen on lung injury from lung transplantation

Lung grafts may experience multiple injuries during lung transplantation, such as warm ischaemia, cold ischaemia, and reperfusion injury. These injuries all contribute to primary graft dysfunction, which is a major cause of morbidity and mortality after lung transplantation. As a potential selective antioxidant, hydrogen molecule (H₂) protects against post-transplant complications in animal models of multiple organ transplantation. Herein, the authors review the current literature regarding the effects of H₂ on lung injury from lung transplantation. The reviewed studies showed that H₂ improved the outcomes of lung transplantation by decreasing oxidative stress and inflammation at the donor and recipient phases. H₂ is primarily administered via inhalation, drinking hydrogen-rich water, hydrogen-rich saline injection, or a hydrogen-rich water bath. H₂ favorably modulates signal transduction and gene expression, resulting in the suppression of pro-inflammatory cytokines and excess reactive oxygen species production. Although H₂ appears to be a physiological regulatory molecule with antioxidant, anti-inflammatory and anti-apoptotic properties, its exact mechanisms of action remain elusive. Taken together, accumulating experimental evidence indicates that H₂ can significantly alleviate transplantation-related lung injury, mainly via inhibition of inflammatory cytokine secretion and reduction in oxidative stress through several underlying mechanisms. Further animal experiments and preliminary human clinical trials will lay the foundation for the use of H₂ as a treatment in the clinic.

State-of-the-art methods for the treatment of severe hemorrhagic trauma: selective aortic arch perfusion and emergency preservation and resuscitation-what is next?

Trauma is a primary cause of death globally, with non‐compressible torso hemorrhage constituting an important part of “potentially survivable trauma death.” Resuscitative endovascular balloon occlusion of the aorta has become a popular alternative to aortic cross‐clamping under emergent thoracotomy for non‐compressible torso hemorrhage in recent years, however, it alone does not improve the survival rate of patients with severe shock or traumatic cardiac arrest from non‐compressible torso hemorrhage. Development of novel advanced maneuvers is essential to improve these patients’ survival, and research on promising methods such as selective aortic arch perfusion and emergency preservation and resuscitation is ongoing. This review aimed to provide physicians in charge of severe trauma cases with a broad understanding of these novel therapeutic approaches to manage patients with severe hemorrhagic trauma, which may allow them to develop lifesaving strategies for exsanguinating trauma patients. Although there are still hurdles to overcome before their clinical application, promising research on these novel strategies is in progress, and ongoing development of synthetic red blood cells and techniques that reduce ischemia‐reperfusion injury may further maximize their effects. Both continuous proof‐of‐concept studies and translational clinical evaluations are necessary to clinically apply these hemostasis approaches to trauma patients.

New Approaches for Hydrogen Therapy of Various Diseases

Hydrogen therapy has recently received increasing attention as an emerging and promising therapeutic technology due to its selective antioxidant property and cell energy regulatory capability in vivo. To solve the low solubility issue of hydrogen, a variety of nanomaterials and devices for hydrogen supply have recently been developed, aiming to increase the concentration of hydrogen in the specific disease site and realize controlled hydrogen release and combined treatment. In this review, we mainly focus on the latest advances in using hydrogen-generating devices and nanomaterials for hydrogen therapy. These developments include sustained release of H2, controlled release of H2, versatile modalities of synergistic therapy, etc. Also, bio-safety issues and challenges are discussed to further promote the clinical applications of hydrogen therapy and the development of hydrogen medicine.

Hydrogen gas inhalation alleviates myocardial ischemia-reperfusion injury by the inhibition of oxidative stress and NLRP3-mediated pyroptosis in rats

AIMS

Reperfusion therapy is the most common and effective treatment against ischemic heart disease (IHD), but the process inflicts massive ischemia/reperfusion (I/R) injury for which no treatment exists. Notably, reperfusion after ischemia causes ischemia/reperfusion injury (IR injury) and the "no-reflow" phenomenon seriously affecting the therapeutic effects in clinical practice. The principle purpose of this study is to validate the effect of hydrogen gas on IHD and further explore the mechanism of hydrogen gas in alleviating myocardial I/R injury and no-reflow phenomenon.

MATERIALS AND METHODS

The rat model of myocardial ischemia-reperfusion was well established. Myocardial infarct size was evaluated by TTC & Evans blue staining. The no-reflow area and the cardiac function were assessed by thioflavin-S staining and echocardiography respectively. Microstructure and mitochondria of myocardial tissue were assessed by transmission electron microscope. Western blot and immunohistochemistry were used to evaluate the expression of NLRP3 mediated pyroptosis related proteins. The 8-OHdG, MDA and serum total ROS were used to evaluate the degree of oxidative stress.

KEY FINDINGS

The myocardial infarct size, no-reflow area, cardiac function, microstructure and mitochondrial morphology of I/R model rats were significantly improved after hydrogen inhalation. In addition, the expression of 8-OHdG, MDA, ROS and NLRP3 mediated pyroptosis related proteins were significantly decreased.

SIGNIFICANCE

We found that oxidative stress and NLRP3 mediated pyroptosis are the important mechanisms for hydrogen to alleviate myocardial I/R injury, and we also confirmed that hydrogen can significantly improve no reflow phenomenon caused by ischemia-reperfusion.

Molecular and Cellular Mechanisms Associated with Effects of Molecular Hydrogen in Cardiovascular and Central Nervous Systems

The increased production of reactive oxygen species and oxidative stress are important factors contributing to the development of diseases of the cardiovascular and central nervous systems. Molecular hydrogen is recognized as an emerging therapeutic, and its positive effects in the treatment of pathologies have been documented in both experimental and clinical studies. The therapeutic potential of hydrogen is attributed to several major molecular mechanisms. This review focuses on the effects of hydrogen on the cardiovascular and central nervous systems, and summarizes current knowledge about its actions, including the regulation of redox and intracellular signaling, alterations in gene expressions, and modulation of cellular responses (e.g., autophagy, apoptosis, and tissue remodeling). We summarize the functions of hydrogen as a regulator of nuclear factor erythroid 2-related factor 2 (Nrf2)-mediated redox signaling and the association of hydrogen with mitochondria as an important target of its therapeutic action. The antioxidant functions of hydrogen are closely associated with protein kinase signaling pathways, and we discuss possible roles of the phosphoinositide 3-kinase/protein kinase B (PI3K/Akt) and Wnt/β-catenin pathways, which are mediated through glycogen synthase kinase 3β and its involvement in the regulation of cellular apoptosis. Additionally, current knowledge about the role of molecular hydrogen in the modulation of autophagy and matrix metalloproteinases-mediated tissue remodeling, which are other responses to cellular stress, is summarized in this review.

Luminal preloading with hydrogen-rich saline ameliorates ischemia-reperfusion injury following intestinal transplantation in rats

Prolonged intestinal cold storage causes considerable mucosal breakdown, which could bolster bacterial translocation and cause life-threatening infection for the transplant recipient. The intestine has an intraluminal compartment, which could be a target for intervention, but has not yet been fully investigated. Hydrogen gas exerts organ protection and has used been recently in several clinical and basic research studies on topics including intestinal transplantation. In this study, we aimed to investigate the cytoprotective efficacy of intraluminally administered hydrogen-rich saline on cold IR injury in intestinal transplantation. Isogeneic intestinal transplantation with 6 hours of cold ischemia was performed on Lewis rats. Hydrogen-rich saline (H₂ concentration at 5 ppm) or normal saline was intraluminally introduced immediately before preservation. Graft intestine was excised 3 hours after reperfusion and analyzed. Histopathological analysis of control grafts revealed blunting of the villi and erosion. These mucosal changes were notably attenuated by intraluminal hydrogen. Intestinal mucosa damage caused by IR injury led to considerable deterioration of gut barrier function 3 h post-reperfusion. However, this decline in permeability was critically prevented by hydrogen treatment. IR-induced upregulation of proinflammatory cytokine mRNAs such as IL-6 was mitigated by hydrogen treatment. Western blot revealed that hydrogen treatment regulated loss of the transmembrane protein ZO-1. Hydrogen-rich saline intraluminally administered in the graft intestine modulated IR injury to transplanted intestine in rats. Successful abrogation of intestinal IR injury with a novel strategy using intraluminal hydrogen may be easily clinically applicable and will compellingly improve patient care after transplantation.

Protective Mechanism and Clinical Application of Hydrogen in Myocardial Ischemia-reperfusion Injury

Cardiovascular disease accounts for one-third of all deaths, with ischemic heart disease as the main cause of death. Under pathological conditions, ischemia-reperfusion injury (IRI) often occurs in tissues. Ischemic injury is mainly caused by anaerobic cell death and reperfusion which results in a wide range of inflammatory responses. These responses are able to increase tissue damage and even damage to the whole body. IRI can also aggravate the original cardiovascular disease during the treatment of cardiovascular disease. Therefore, it is particularly important to understand the mechanism of myocardial ischemia-reperfusion injury (MIRI) for clinical treatment and application. At the same time, it is necessary to find a safe, reliable and feasible method for treating MIRI to reduce the incidence of complications and mortality as well as improve the prognosis and quality of life of patients. As a selective antioxidant, hydrogen can neutralize excessive free radicals, has certain anti-apoptotic and anti-inflammatory effects and it has gradually become a focus and hotspot of preclinical and clinical research. Hydrogen has been shown to have a certain therapeutic effect on MIRI, which can provide a new therapeutic direction for the clinical treatment of myocardial ischemia-reperfusion injury. In this review, the protective mechanism and clinical application of hydrogen in myocardial ischemia-reperfusion injury is discussed.

Prospects of molecular hydrogen in perioperative neuroprotection from basic research to clinical application

PURPOSE OF REVIEW

The current systematic review summarizes recent, basic clinical achievements regarding the neuroprotective effects of molecular hydrogen in distinct central nervous system conditions.

RECENT FINDINGS

Perioperative neuroprotection remains a major topic of clinical anesthesia. Various gaseous molecules have previously been explored as a feasible therapeutic option in neurological disorders. Among them, molecular hydrogen, which has emerged as a novel and potential therapy for perioperative neuroprotection, has received much attention.

SUMMARY

Fundamental and clinical evidence supports the antioxidant, antiinflammation, antiapoptosis and mitochondrial protective effects of hydrogen in the pathophysiology of nervous system diseases. The clinically preventive and therapeutic effects of hydrogen on different neural diseases, however, remain uncertain, and the lack of support by large randomized controlled trials has delayed its clinical application.

Molecular hydrogen: A potential radioprotective agent

In recent years, many studies have shown that hydrogen has therapeutic and preventive effects on various diseases. Its selective antioxidant properties were well noticed. Most of the ionizing radiation-induced damage is caused by hydroxyl radicals (OH) from radiolysis of H₂O. Since hydrogen can mitigate such damage through multiple mechanisms, it presents noteworthy potential as a novel radio-protective agent. This review analyses possible mechanisms for hydrogen's radioprotective properties and effective delivery methods. We also look into details of vitro and vivo studies for hydrogen's radioprotective effects, and clinical practices. We conclude that hydrogen has good potential in radio-protection, with evidence that warrants greater research efforts in this field.

Hydrogen-rich water reduces inflammatory responses and prevents apoptosis of peripheral blood cells in healthy adults: a randomized, double-blind, controlled trial

The evidence for the beneficial effects of drinking hydrogen-water (HW) is rare. We aimed to investigate the effects of HW consumption on oxidative stress and immune functions in healthy adults using systemic approaches of biochemical, cellular, and molecular nutrition. In a randomized, double-blind, placebo-controlled study, healthy adults (20–59 y) consumed either 1.5 L/d of HW (n = 20) or plain water (PW, n = 18) for 4 weeks. The changes from baseline to the 4th week in serum biological antioxidant potential (BAP), derivatives of reactive oxygen, and 8-Oxo-2′-deoxyguanosine did not differ between groups; however, in those aged ≥ 30 y, BAP increased greater in the HW group than the PW group. Apoptosis of peripheral blood mononuclear cells (PBMCs) was significantly less in the HW group. Flow cytometry analysis of CD4⁺, CD8⁺, CD20⁺, CD14⁺ and CD11b⁺ cells showed that the frequency of CD14⁺ cells decreased in the HW group. RNA-sequencing analysis of PBMCs demonstrated that the transcriptomes of the HW group were clearly distinguished from those of the PW group. Most notably, transcriptional networks of inflammatory responses and NF-κB signaling were significantly down-regulated in the HW group. These finding suggest HW increases antioxidant capacity thereby reducing inflammatory responses in healthy adults.

Therapeutic strategies for ischemia reperfusion injury in emergency medicine

Ischemia reperfusion (IR) injury occurs when blood supply, perfusion, and concomitant reoxygenation is restored to an organ or area following an initial poor blood supply after a critical time period. Ischemia reperfusion injury contributes to mortality and morbidity in many pathological conditions in emergency medicine clinical practice, including trauma, ischemic stroke, myocardial infarction, and post‐cardiac arrest syndrome. The process of IR is multifactorial, and its pathogenesis involves several mechanisms. Reactive oxygen species are considered key molecules in reperfusion injury due to their potent oxidizing and reducing effects that directly damage cellular membranes by lipid peroxidation. In general, IR injury to an individual organ causes various pro‐inflammatory mediators to be released, which could then induce inflammation in remote organs, thereby possibly advancing the dysfunction of multiple organs. In this review, we summarize IR injury in emergency medicine. Potential therapies include pharmacological treatment, ischemic preconditioning, and the use of medical gases or vitamin therapy, which could significantly help experts develop strategies to inhibit IR injury.

Hydrogen Attenuates Allergic Inflammation by Reversing Energy Metabolic Pathway Switch

Mechanisms mediating the protective effects of molecular hydrogen (H₂) are not well understood. This study explored the possibility that H₂ exerts its anti-inflammatory effect by modulating energy metabolic pathway switch. Activities of glycolytic and mitochondrial oxidative phosphorylation systems were assessed in asthmatic patients and in mouse model of allergic airway inflammation. The effects of hydrogen treatment on airway inflammation and on changes in activities of these two pathways were evaluated. Monocytes from asthmatic patients and lungs from ovalbumin-sensitized and challenged mice had increased lactate production and glycolytic enzyme activities (enhanced glycolysis), accompanied by decreased ATP production and mitochondrial respiratory chain complex I and III activities (suppressed mitochondrial oxidative phosphorylation), indicating an energy metabolic pathway switch. Treatment of ovalbumin-sensitized and challenged mice with hydrogen reversed the energy metabolic pathway switch, and mitigated airway inflammation. Hydrogen abrogated ovalbumin sensitization and challenge-induced upregulation of glycolytic enzymes and hypoxia-inducible factor-1α, and downregulation of mitochondrial respiratory chain complexes and peroxisome proliferator activated receptor-γ coactivator-1α. Hydrogen abrogated ovalbumin sensitization and challenge-induced sirtuins 1, 3, 5 and 6 downregulation. Our data demonstrates that allergic airway inflammation is associated with an energy metabolic pathway switch from oxidative phosphorylation to aerobic glycolysis. Hydrogen inhibits airway inflammation by reversing this switch. Hydrogen regulates energy metabolic reprogramming by acting at multiple levels in the energy metabolism regulation pathways.

Organ preservation solution containing dissolved hydrogen gas from a hydrogen-absorbing alloy canister improves function of transplanted ischemic kidneys in miniature pigs

Various methods have been devised to dissolve hydrogen gas in organ preservation solutions, including use of a hydrogen gas cylinder, electrolysis, or a hydrogen-generating agent. However, these methods require considerable time and effort for preparation. We investigated a practical technique for rapidly dissolving hydrogen gas in organ preservation solutions by using a canister containing hydrogen-absorbing alloy. The efficacy of hydrogen-containing organ preservation solution created by this method was tested in a miniature pig model of kidney transplantation from donors with circulatory arrest. The time required for dissolution of hydrogen gas was only 2–3 minutes. When hydrogen gas was infused into a bag containing cold ETK organ preservation solution at a pressure of 0.06 MPa and the bag was subsequently opened to the air, the dissolved hydrogen concentration remained at 1.0 mg/L or more for 4 hours. After warm ischemic injury was induced by circulatory arrest for 30 minutes, donor kidneys were harvested and perfused for 5 minutes with hydrogen-containing cold ETK solution or hydrogen-free cold ETK solution. The perfusion rate was faster from the initial stage with hydrogen-containing cold ETK solution than with hydrogen-free ETK solution. After storage of the kidney in hydrogen-free preservation solution for 1 hour before transplantation, no urine production was observed and blood flow was not detected in the transplanted kidney at sacrifice on postoperative day 6. In contrast, after storage in hydrogen-containing preservation solution for either 1 or 4 hours, urine was detected in the bladder and blood flow was confirmed in the transplanted kidney. This method of dissolving hydrogen gas in organ preservation solution is a practical technique for potentially converting damaged organs to transplantable organs that can be used safely in any clinical setting where organs are removed from donors.