Neuroprotective Effect of Hydrogen-Rich Saline in Global Cerebral Ischemia/Reperfusion Rats: Up-Regulated Tregs and Down-Regulated miR-21, miR-210 and NF-κB Expression

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.

Research Progress of Hydrogen on Chronic Nasal Inflammation

Chronic nasal mucosal inflammatory disease is a common nasal disease, which is involved by inflammatory cells and a variety of cytokines. Its main pathological features are inflammatory reaction, increased secretion, mucosal swelling and thickening of nasal cavity or paranasal sinuses.It mainly includes chronic rhinitis (divided into allergic rhinitis, non-allergic rhinitis), chronic sinusitis (divided into with nasal polyps, without nasal polyps type), etc.The main symptoms of chronic rhinitis are nasal itching, sneezing, runny nose, and nasal congestion. The main symptoms of chronic sinusitis are nasal congestion, purulent or sticky nasal discharge, headache, and reduced sense of smell. They are a type of disease with a high incidence rate and seriously affect the quality of human life.Although the etiology and treatment of this type of disease have been extensively studied, there are still many aspects that are unclear.Currently, oxidative stress is believed to be an important link in the pathogenesis of chronic inflammatory diseases of the nasal mucosa. Therefore, anti-oxidative stress is a direction of research for the treatment of chronic nasal mucosal inflammatory diseases.Hydrogen, as a medically therapeutic gas, has been extensively studied for its antioxidant, anti-inflammatory, and anti-damage properties, and has been used in the treatment of various diseases.Although there are relatively few studies on the use of hydrogen for nasal inflammation, its positive effects have also been found. This article systematically summarizes the relevant research on the use of hydrogen to improve chronic nasal mucosal inflammation, with the aim of clarifying the ideas and indicating the direction for further research in the future.

Therapeutic Hypothermia Combined with Hydrogen Sulfide Treatment Attenuated Early Blood-Brain Barrier Disruption and Brain Edema Induced by Cardiac Arrest and Resuscitation in Rat Model

Brain injury remains a major problem in patients suffering cardiac arrest (CA). Disruption of the blood-brain barrier (BBB) is an important factor leading to brain injury. Therapeutic hypothermia is widely accepted to limit neurological impairment. However, the efficacy is incomplete. Hydrogen sulfide (H₂S), a signaling gas molecule, has protective effects after cerebral ischemia reperfusion injury. This study showed that combination of hypothermia and H₂S after resuscitation was more beneficial for attenuated BBB disruption and brain edema than that of hypothermia or H₂S treatment alone. CA was induced by ventricular fibrillation for 4 min. Hypothermia was performed by applying alcohol and ice bags to the body surface under anesthesia. We used sodium hydrosulphide (NaHS) as the H₂S donor. We found that global brain ischemia induced by CA and cardiopulmonary resuscitation (CPR) resulted in brain edema and BBB disruption; Hypothermia or H₂S treatment diminished brain edema, decreased the permeability and preserved the structure of BBB during the early period of CA and resuscitation, and more importantly, improved the neurologic function, increased the 7-day survival rate after resuscitation; the combination of hypothermia and H₂S treatment was more beneficial than that of hypothermia or H₂S treatment alone. The beneficial effects were associated with the inhibition of matrix metalloproteinase-9 expression, attenuated the degradation of the tight junction protein occludin, and subsequently protected the structure of BBB. These findings suggest that combined use of therapeutic hypothermia and hydrogen sulfide treatment during resuscitation of CA patients could be a potential strategy to improve clinical outcomes and survival rate.

Molecular Hydrogen Neuroprotection in Post-Ischemic Neurodegeneration in the Form of Alzheimer's Disease Proteinopathy: Underlying Mechanisms and Potential for Clinical Implementation-Fantasy or Reality?

Currently, there is a lot of public interest in naturally occurring substances with medicinal properties that are minimally toxic, readily available and have an impact on health. Over the past decade, molecular hydrogen has gained the attention of both preclinical and clinical researchers. The death of pyramidal neurons in especially the CA1 area of the hippocampus, increased permeability of the blood-brain barrier, neuroinflammation, amyloid accumulation, tau protein dysfunction, brain atrophy, cognitive deficits and dementia are considered an integral part of the phenomena occurring during brain neurodegeneration after ischemia. This review focuses on assessing the current state of knowledge about the neuroprotective effects of molecular hydrogen following ischemic brain injury. Recent studies in animal models of focal or global cerebral ischemia and cerebral ischemia in humans suggest that hydrogen has pleiotropic neuroprotective properties. One potential mechanism explaining some of the general health benefits of using hydrogen is that it may prevent aging-related changes in cellular proteins such as amyloid and tau protein. We also present evidence that, following ischemia, hydrogen improves cognitive and neurological deficits and prevents or delays the onset of neurodegenerative changes in the brain. The available evidence suggests that molecular hydrogen has neuroprotective properties and may be a new therapeutic agent in the treatment of neurodegenerative diseases such as neurodegeneration following cerebral ischemia with progressive dementia. We also present the experimental and clinical evidence for the efficacy and safety of hydrogen use after cerebral ischemia. The therapeutic benefits of gas therapy open up new promising directions in breaking the translational barrier in the treatment of ischemic stroke.

Medical Gas Therapy for Tissue, Organ, and CNS Protection: A Systematic Review of Effects, Mechanisms, and Challenges

Gaseous molecules have been increasingly explored for therapeutic development. Here, following an analytical background introduction, a systematic review of medical gas research is presented, focusing on tissue protections, mechanisms, data tangibility, and translational challenges. The pharmacological efficacies of carbon monoxide (CO) and xenon (Xe) are further examined with emphasis on intracellular messengers associated with cytoprotection and functional improvement for the CNS, heart, retina, liver, kidneys, lungs, etc. Overall, the outcome supports the hypothesis that readily deliverable "biological gas" (CO, H₂ , H₂ S, NO, O₂ , O₃ , and N₂ O) or "noble gas" (He, Ar, and Xe) treatment may preserve cells against common pathologies by regulating oxidative, inflammatory, apoptotic, survival, and/or repair processes. Specifically, CO, in safe dosages, elicits neurorestoration via igniting sGC/cGMP/MAPK signaling and crosstalk between HO-CO, HIF-1α/VEGF, and NOS pathways. Xe rescues neurons through NMDA antagonism and PI3K/Akt/HIF-1α/ERK activation. Primary findings also reveal that the need to utilize cutting-edge molecular and genetic tactics to validate mechanistic targets and optimize outcome consistency remains urgent; the number of neurotherapeutic investigations is limited, without published results from large in vivo models. Lastly, the broad-spectrum, concurrent multimodal homeostatic actions of medical gases may represent a novel pharmaceutical approach to treating critical organ failure and neurotrauma.

MicroRNA-21 Is a Versatile Regulator and Potential Treatment Target in Central Nervous System Disorders

MicroRNAs (miRNAs) are a class of endogenous, non-coding, single-stranded RNAs with a length of approximately 22 nucleotides that are found in eukaryotes. miRNAs are involved in the regulation of cell differentiation, proliferation, invasion, apoptosis, and metabolism by regulating the expression of their target genes. Emerging studies have suggested that various miRNAs play key roles in the pathogenesis of central nervous system (CNS) disorders and may be viable therapeutic targets. In particular, miR-21 has prominently emerged as a focus of increasing research on the mechanisms of its involvement in CNS disorders. Herein, we reviewed recent studies on the critical roles of miR-21, including its dysregulated expression and target genes, in the regulation of pathophysiological processes of CNS disorders, with a special focus on apoptosis and inflammation. Collectively, miR-21 is a versatile regulator in the progression of CNS disorders and could be a promising biomarker and therapeutic target for these diseases. An in-depth understanding of the mechanisms by which miR-21 affects the pathogenesis of CNS disorders could pave the way for miR-21 to serve as a therapeutic target for these conditions.

Hydrogen, a Novel Therapeutic Molecule, Regulates Oxidative Stress, Inflammation, and Apoptosis

Molecular hydrogen (H₂) is a colorless and odorless gas. Studies have shown that H₂ inhalation has the therapeutic effects in many animal studies and clinical trials, and its application is recommended in the novel coronavirus pneumonia treatment guidelines in China recently. H₂ has a relatively small molecular mass, which helps it quickly spread and penetrate cell membranes to exert a wide range of biological effects. It may play a role in the treatment and prevention of a variety of acute and chronic inflammatory diseases, such as acute pancreatitis, sepsis, respiratory disease, ischemia reperfusion injury diseases, autoimmunity diseases, etc.. H₂ is primarily administered via inhalation, drinking H₂-rich water, or injection of H₂ saline. It may participate in the anti-inflammatory and antioxidant activity (mitochondrial energy metabolism), immune system regulation, and cell death (apoptosis, autophagy, and pyroptosis) through annihilating excess reactive oxygen species production and modulating nuclear transcription factor. However, the underlying mechanism of H₂ has not yet been fully revealed. Owing to its safety and potential efficacy, H₂ has a promising potential for clinical use against many diseases. This review will demonstrate the role of H₂ in antioxidative, anti-inflammatory, and antiapoptotic effects and its underlying mechanism, particularly in coronavirus disease-2019 (COVID-19), providing strategies for the medical application of H₂ for various diseases.

Intelligent Nanomedicine Approaches Using Medical Gas-Mediated Multi-Therapeutic Modalities Against Cancer

The emerging area of gas-mediated cancer treatment has received widespread attention in the medical community. Featuring unique physical, chemical, and biological properties, nanomaterials can facilitate the delivery and controllable release of medicinal gases at tumor sites, and also serve as ideal platforms for the integration of other therapeutic modalities with gas therapy to augment cancer therapeutic efficacy. This review presents an overview of anti-cancer mechanisms of several therapeutic gases: nitric oxide (NO), hydrogen sulfide (H₂S), carbon monoxide (CO), oxygen (O₂), and hydrogen (H₂). Controlled release behaviors of gases under different endogenous and exogenous stimuli are also briefly discussed, followed by their synergistic effects with different therapeutic modes. Moreover, the potential challenges and future prospects regarding gas therapy based on nanomaterials are also described, aiming to facilitate the advancement of gas therapeutic nanomedicine in new frontiers for highly efficient cancer treatment.

The Protective Effects of miR-21-Mediated Fibroblast Growth Factor 1 in Rats with Coronary Heart Disease

Aim

The study is to verify the protective effects of miR-21-mediated fibroblast growth factor 1 (FGF1) against myocardial ischemia in rats with coronary heart disease.

Materials and Methods

Sprague-Dawley (SD) rat models of myocardial ischemia/reperfusion (MI/R) injury were constructed, and the expression of miR-21 and FGF1 in them was interfered through ischemic postconditioning. The protective effects of miR-21-mediated FGF1 on myocardium of the model rats were analyzed, and the targeted regulatory relationship between miR-21 and FGF1 was verified through myocardial cell experiments to find the mechanism of miR-21.

Results

MiR-21 and FGF1 with increased expression could protect the cardiac function of model rats and improve their diastolic blood pressure (DBP), systolic blood pressure (SBP), heart rate (HR), coronary flow (CF), bax, and bcl-2 levels, but it would also cause further increase of vascular endothelial growth factor (VEGF) and decreased infarct size (INF). In addition, intervention through both miR-21 mimics and recombinant human FGF1 could highlight the above changes. Pearson correlation analysis revealed that the expression of miR-21 was positively correlated with that of FGF1, and both miR-21 and FGF1 were significantly and linearly correlated with DBP, SBP, HR, CF, INF, bax, and bcl-2, but they were not significantly correlated with the VEGF level. The myocardial cell experiment results revealed that upregulation of miR-21 or FGF1 could alleviate apoptosis caused by hypoxia/reoxygenation of myocardial cells, and inhibition of the FGF1 expression could hinder the effect of miR-21 against apoptosis of myocardial cells. Dual luciferase reporter assay revealed that transfection of miR-21-mimics could effectively raise the fluorescence intensity of pmirGLO-FGF1-3′UTR Wt but had no significant effect on that of pmirGLO-FGF1-3′UTR Mut.

Conclusion

MiR-21 can specifically mediate the expression of FGF1 to relieve MI/R injury, protect the cardiac function, and resist apoptosis.

Neuroprotective effect of wild lowbush blueberry (Vaccinium angustifolium) on global cerebral ischemia/reperfusion injury in rats: Downregulation of iNOS/TNF-α and upregulation of miR-146a/miR-21 expression

This study aims to investigate the neuroprotective effect of wild lowbush blueberry on CIRI in rats. Accordingly, CIRI and reperfusion were induced in rats for 60 min and 24 h, respectively. Then, the mechanisms of the neuroprotective effects of BBE were investigated in the injury through evaluating miR-146a, miR-21, and their targets in a CIRI rat model. After that, the BBE (30, 60, and 120 mg/kg b.wt) was intraperitoneally injected for 14 days, then CIRI was induced by BCCAO for 60 min for ischemic stroke and reperfusion for 24 h. Several parameters including the oxidative stress levels in the hippocampus and serum were measured 24 h after the CIRI. The findings showed that the BBE significantly decreased the levels of malondialdehyde (MDA) and nitric oxide (NO) and increased ferric ion reducing antioxidant power (FRAP) levels in the hippocampus and serum following the stroke. The BBE also maximized the miR-146a and miR-21 expressions and moderated iNOS and TNF-α expressions in the hippocampus. Likewise, the BBE enlarged the CA1 and CA3 domains of the post-stroke pyramidal cell layers of the hippocampus. Overall, the results revealed that BBE had potent neuroprotective efficacy against CIRI via the effective modulation of neuroinflammatory cascades and protected neurons against ischemic death.

High-fat diet promotes epithelial-mesenchymal transition through enlarged growth of opportunistic pathogens and the intervention of saturated hydrogen

OBJECTIVES

This study investigated the effects and mechanism of high-fat diet on the epithelial-mesenchymal transition (EMT) of respiratory tract and the intervention of saturated hydrogen on it.

METHODS

80 five-week-old C57BL6/J male mice were randomly divided into normal control group, H₂ group, high-fat (HF) group and HF+H₂ group, making 20 mice in each group. The weights of the mice were measured on weekly basis. Six mice from each group were executed at every second week. Blood samples were collected for lipid testing. Lung tissues were collected for 16S rRNA gene sequencing, HE staining, immunofluorescence and quantitative real-time PCR (qPCR).

RESULTS

Compared with the control group, the mice in the HF group showed increased inflammatory cell infiltration, decreased expression of e-cadherin (E-cad) and increased expression of Twist. There were significant differences in the composition of bacteria in the lung, and the expression of isocitrate lyase (ICL) genes in Pseudomonas aeruginosa, Staphylococcus aureus and Acinetobacter baumannii, which were significantly associated with asthma were seen with a significant increasing trend. After the treatment of saturated hydrogen, the changes in lung microbial population, lung tissue infiltration of inflammatory cells and the transformation of epithelial stroma caused by high-fat diet were moderately alleviated.

CONCLUSION

High-fat diet can promote inflammation and EMT in the lung by enlarging the growth of glyoxylic acid cycle-dependent bacteria, and the pathological process are partly alleviated by saturated hydrogen.

miR-211 alleviates ischaemia/reperfusion-induced kidney injury by targeting TGFβR2/TGF-β/SMAD3 pathway

MicroRNA-211 (miR-211) is closely related to apoptosis and plays an important role in ischemia/reperfusion (I/R) injury. Whether miR-211 is involved in the protective effects in renal I/R injury is unknown. In this study, we evaluated the role of miR-211 in human tubular epithelial cells in response to hypoxia-reoxygenation (H/R) stimulation and I/R injury in vitro and in vivo. The results revealed that miR-211 was down-regulated and TGFβR2 was up-regulated in human kidney (HK-2) cells subjected to H/R. Luciferase reporter assay showed that TGFβR2 was a direct target of miR-211. Enforced miR-211 expression decreased H/R-induced HK-2 cell apoptosis and increased cell viability, and targeting miR-211 further increased H/R-induced HK-2 cell apoptosis and decreased cell viability. However, the effect of miR-211 was reversed by targeting TGFβR2 or enforced TGFβR2 expression in miR-211 overexpressing cells or miR-211 downexpressing cells. Moreover, we confirmed that miR-211 interacted with TGFβR2, and regulating TGF-β/SMAD3 signal. In vivo in mice, miR-211 overexpression ameliorates biochemical and histological kidney injury, reduces apoptosis in mice following I/R. On the contrary, miR-211 downexpressing promoted histological kidney injury and increased apoptosis in mice following I/R. Inhibition of miR-211 or miR-211 overexpression inhibited TGF-β/SMAD3 pathways or activated TGF-β/SMAD3 signal pathways in vitro and in vivo, which are critical for cell survival. Our findings suggested that miR-211 suppress apoptosis and relieve kidney injury following H/R or I/R via targeting TGFβR2/TGF-β/SMAD3 signals. Therefore, miR-211 may be as therapeutic potential for I/R- induced kidney injury.

Hydrogen Attenuates Endotoxin-Induced Lung Injury by Activating Thioredoxin 1 and Decreasing Tissue Factor Expression

Endotoxin-induced lung injury is one of the major causes of death induced by endotoxemia, however, few effective therapeutic options exist. Hydrogen inhalation has recently been shown to be an effective treatment for inflammatory lung injury, but the underlying mechanism is unknown. In the current study we aim to investigate how hydrogen attenuates endotoxin-induced lung injury and provide reference values for the clinical application of hydrogen. LPS was used to establish an endotoxin-induced lung injury mouse model. The survival rate and pulmonary pathologic changes were evaluated. THP-1 and HUVECC cells were cultured in vitro. The thioredoxin 1 (Trx1) inhibitor was used to evaluate the anti-inflammatory effects of hydrogen. Hydrogen significantly improved the survival rate of mice, reduced pulmonary edema and hemorrhage, infiltration of neutrophils, and IL-6 secretion. Inhalation of hydrogen decreased tissue factor (TF) expression and MMP-9 activity, while Trx1 expression was increased in the lungs and serum of endotoxemia mice. LPS-stimulated THP-1 and HUVEC-C cells in vitro and showed that hydrogen decreases TF expression and MMP-9 activity, which were abolished by the Trx1 inhibitor, PX12. Hydrogen attenuates endotoxin-induced lung injury by decreasing TF expression and MMP-9 activity via activating Trx1. Targeting Trx1 by hydrogen may be a potential treatment for endotoxin-induced lung injury.

Neuroprotective Effects of Molecular Hydrogen: A Critical Review

Molecular hydrogen (H2) is a physiologically inert gas. However, during the last 10 years, increasing evidence has revealed its biological functions under pathological conditions. More specifically, H2 has protective effects against a variety of diseases, particularly nervous system disorders, which include ischemia/reperfusion injury, traumatic injury, subarachnoid hemorrhage, neuropathic pain, neurodegenerative diseases, cognitive dysfunction induced by surgery and anesthesia, anxiety, and depression. In addition, H2 plays protective roles mainly through anti-oxidation, anti-inflammation, anti-apoptosis, the regulation of autophagy, and preservation of mitochondrial function and the blood-brain barrier. Further, H2 is easy to use and has neuroprotective effects with no major side-effects, indicating that H2 administration is a potential therapeutic strategy in clinical settings. Here we summarize the H2 donors and their pharmacokinetics. Meanwhile, we review the effectiveness and safety of H2 in the treatment of various nervous system diseases based on preclinical and clinical studies, leading to the conclusion that H2 can be a simple and effective clinical therapy for CNS diseases such as ischemia-reperfusion brain injury, Parkinson's disease, and diseases characterized by cognitive dysfunction. The potential mechanisms involved in the neuroprotective effect of H2 are also analyzed.

MicroRNA-26b-5p alleviates cerebral ischemia-reperfusion injury in rats via inhibiting the N-myc/PTEN axis by downregulating KLF10 expression

MicroRNAs plays important role in cerebral ischemia-reperfusion (CIR). However, the role of miR-26b-5p in CIR injury remains unclear. PC12 cells were treated with oxygen-glucose deprivation (OGD) for 0 h, 2 h, 4 h, 6 h, and then reoxygenated for 24 h to construct an in vitro I/R model. Then, miR-26b-5p mimic, small interfering RNA of KLF10 and KLF10 overexpression plasmid were transfected into cells respectively for mechanism study. Our results showed that miR-26b-5p was downregulated in OGD/R-induced PC12 cells. After overexpression of miR-26b-5p, cell proliferation ability was enhanced, apoptosis, ROS and inflammatory mediators were inhibited. Bioinformatics analysis indicated that miR-26b-5p was directly bound to the 3' UTR of KLF10, and downregulated the expression of KLF10. KLF10 was upregulated in OGD/R cells, and transfection with si-KLF10 promoted cell proliferation and reduced apoptosis, NO concentration and inflammatory factor secretion. Moreover, pcDNA-KLF10 reversed the inhibitory effects of miR-26b-5p mimic on apoptosis, NO content and inflammatory factor secretion, as well as the downregulation of N-myc and PTEN expression. Meanwhile, I/R rat models were constructed and divided into sham operation group (femoral artery isolation only), model group (middle cerebral artery occlusion model of rats was prepared by thread embolization), treatment group (200 µL of miR-26b-5p mimic was injected into the brain of model rats). We observed that the infarct size of brain tissue was reduced, KLF10 expression was downregulated, and apoptosis and inflammatory response were reduced. These results suggest that miR-26b-5p had protective effects on CIRI and it may be a potential treatment target.

Vitamin D Attenuates Ischemia/Reperfusion-Induced Cardiac Injury by Reducing Mitochondrial Fission and Mitophagy

Myocardial infarction is the leading cause of morbidity and mortality worldwide. Although myocardial reperfusion after ischemia (I/R) is an effective method to save ischemic myocardium, it can cause adverse reactions, including increased oxidative stress and cardiomyocyte apoptosis. Mitochondrial fission and mitophagy are essential factors for mitochondrial quality control, but whether they play key roles in cardiac I/R injury remains unknown. New pharmacological or molecular interventions to alleviate reperfusion injury are currently considered desirable therapies. Vitamin D₃ (Vit D₃) regulates cardiovascular function, but its physiological role in I/R-exposed hearts, especially its effects on mitochondrial homeostasis, remains unclear. An in vitro hypoxia/reoxygenation (H/R) model was established in H9c2 cells to simulate myocardial I/R injury. H/R treatment significantly reduced H9c2 cell viability, increased apoptosis, and activated caspase 3. In addition, H/R treatment increased mitochondrial fission, as manifested by increased expression of phosphorylated dynein-related protein 1 (p-Drp1) and mitochondrial fission factor (Mff) as well as increased mitochondrial translocation of Drp1. Treatment with the mitochondrial reactive oxygen species scavenger MitoTEMPO increased cell viability and decreased mitochondrial fission. H/R conditions elicited excessive mitophagy, as indicated by increased expression of BCL2-interacting protein 3 (BNIP3) and light chain (LC3BII/I) and increased formation of autolysosomes. In contrast, Vit D₃ reversed these effects. In a mouse model of I/R, apoptosis, mitochondrial fission, and mitophagy were induced. Vit D₃ treatment mitigated apoptosis, mitochondrial fission, mitophagy, and myocardial ultrastructural abnormalities. The results indicate that Vit D₃ exerts cardioprotective effects against I/R cardiac injury by protecting mitochondrial structural and functional integrity and reducing mitophagy.

Hydrogen: A Novel Option in Human Disease Treatment

H₂ has shown anti-inflammatory and antioxidant ability in many clinical trials, and its application is recommended in the latest Chinese novel coronavirus pneumonia (NCP) treatment guidelines. Clinical experiments have revealed the surprising finding that H₂ gas may protect the lungs and extrapulmonary organs from pathological stimuli in NCP patients. The potential mechanisms underlying the action of H₂ gas are not clear. H₂ gas may regulate the anti-inflammatory and antioxidant activity, mitochondrial energy metabolism, endoplasmic reticulum stress, the immune system, and cell death (apoptosis, autophagy, pyroptosis, ferroptosis, and circadian clock, among others) and has therapeutic potential for many systemic diseases. This paper reviews the basic research and the latest clinical applications of H₂ gas in multiorgan system diseases to establish strategies for the clinical treatment for various diseases.

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.

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.

Recent advances in the neuroprotective effects of medical gases

Central nervous system injuries are a leading cause of death and disability worldwide. Although the exact pathophysiological mechanisms of various brain injuries vary, central nervous system injuries often result in an inflammatory response, and subsequently lead to brain damage. This suggests that neuroprotection may be necessany in the treatment of multiple disease models. The use of medical gases as neuroprotective agents has gained great attention in the medical field. Medical gases include common gases, such as oxygen, hydrogen and carbon dioxide; hydrogen sulphide and nitric oxide that have been considered toxic; volatile anesthetic gases, such as isoflurane and sevoflurane; and inert gases like helium, argon, and xenon. The neuroprotection from these medical gases has been investigated in experimental animal models of various types of brain injuries, such as traumatic brain injury, stroke, subarachnoid hemorrhage, cerebral ischemic/reperfusion injury, and neurodegenerative diseases. Nevertheless, the transition into the clinical practice is still lagging. This delay could be attributed to the contradictory paradigms and the conflicting results that have been obtained from experimental models, as well as the presence of inconsistent reports regarding their safety. In this review, we summarize the potential mechanisms underlying the neuroprotective effects of medical gases and discuss possible candidates that could improve the outcomes of brain injury.

Effects of hypoxic-ischemic pre-treatment on microvesicles derived from endothelial progenitor cells

Endothelial progenitor cells (EPCs) have protective roles in ischemic injury due to their ability to improve endothelial function and modulate angiogenesis. Microvesicles (MVs) are small membrane particles released by various cell types, including EPCs, which affect various target cells by transferring carried genetic information, including microRNAs (miRNAs/miRs). Depending on the stimuli and cell types, MVs exert different functions. In the present study, oxygen-glucose deprivation (OGD) was used to mimic ischemic-hypoxic (HI) insult, where the effects of HI insult on EPC-derived MVs (EPC-MVs) were subsequently investigated. OGD induced Ca²⁺ influx in EPCs and increased the release of EPC-MVs compared with normoxic conditions. In addition, MVs prepared from EPCs cultured under normoxic conditions or OGD conditions (OGD-EMVs) had the ability to stimulate the proliferation of EPCs. Furthermore, OGD-EMVs induced stronger effects on proliferation, which may be associated with the upregulation of miR-210 in EPC-MVs. In conclusion, the present results indicated that HI insult promoted the release of MVs from EPCs and upregulated miR-210 in MVs, leading to positive modulation of the proliferation of EPCs cultured under normoxic conditions.

Effects of a high concentration of hydrogen on neurological function after traumatic brain injury in diabetic rats

Reactive oxygen species, inflammation, and apoptosis are major contributors to secondary injuries that follow traumatic brain injury (TBI) in diabetic patients. Hydrogen (H₂) can selectively neutralize reactive oxygen species and downregulate inflammatory and apoptotic factors. Therefore, we investigated the effects of inhaled high and low concentrations of hydrogen on neurological function after TBI in diabetic rats and the potential mechanism. We found that the inhalation of high concentrations of H₂ significantly improved outcomes following TBI in diabetic rats. The inhalation of 42% H₂ for one hour per day for 48 h significantly reduced brain edema, decreased the extravasation of sodium fluorescein, and reduced oxidative stress markers (p < 0.05). In addition, the inhalation of a high concentration of H₂ (42% for one hour per day for 7 days) improved neurological deficits (p < 0.05) and reduced the expression of apoptotic protein markers (p < 0.05). However, the inhalation of 3% H₂ did not yield significant effects. These results showed that the inhalation of 42% H₂ can alleviate nerve damage and improve neurological function after TBI in diabetic rats. Therefore, the inhalation of a high concentration of H₂ may be associated with the treatment of traumatic brain injuries.

Molecular hydrogen: current knowledge on mechanism in alleviating free radical damage and diseases

Ever since molecular hydrogen was first reported as a hydroxyl radical scavenger in 2007, the beneficial effect of hydrogen was documented in more than 170 disease models and human diseases including ischemia/reperfusion injury, metabolic syndrome, inflammation, and cancer. All these pathological damages are concomitant with overproduction of reactive oxygen species (ROS) where molecular hydrogen has been widely demonstrated as a selective antioxidant. Although it is difficult to construe the molecular mechanism of hydrogen's biomedical effect, an increasing number of studies have been helping us draw the picture clearer with days passing by. In this review, we summarized the current knowledge on systemic and cellular modulation by hydrogen treatment. We discussed the antioxidative, anti-inflammatory, and anti-apoptosis effects of hydrogen, as well as its protection on mitochondria and the endoplasmic reticulum, regulation of intracellular signaling pathways, and balancing of the immune cell subtypes. We hope that this review will provide organized information that prompts further investigation for in-depth studies of hydrogen effect.

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.

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 as a complementary therapy against ischemic stroke: A review of the evidence

Ischemic stroke is one of the most common sources of mortality in the world. Researchers have been trying to find a complementary therapy to treat ischemic stroke in order to improve its prognosis and expand the therapeutic window for reperfusion treatment. For this reason, many experimental and clinical trials studying the effects of hydrogen against ischemic stroke have been published. Hydrogen gas has been found to eliminate hydroxyl free radical and peroxynitrite anions as well as producing therapeutic effect in patients with ischemic stroke. Many studies have been published illustrating its anti-oxidative, anti-inflammatory and anti-apoptotic effects. The purpose of this article is to review the literature concerning treatment of cerebral I/R injury or ischemic stroke with hydrogen therapy. Specifically, we will examine the appropriate laboratory methods, mechanisms of hydrogen therapy, and outcomes of relevant clinical trials. We conclude this review with a discussion on future investigations of hydrogen therapy to treat ischemic stroke.

Hydrogen alleviates cellular senescence via regulation of ROS/p53/p21 pathway in bone marrow-derived mesenchymal stem cells in vivo

Senescence has become a hot point issue in recent decades and requires urgent attention. As a novel and effective antioxidant, hydrogen has been proved to alleviate cellular senescence in endothelial cells in vitro. However, the effects and mechanisms of hydrogen on senescence in vivo are still unclear. In the present study, 12-month-old Sprague Dawley (SD) rats were intraperitoneal administration of hydrogen-rich saline (HRS, 10 ml/kg). Subsequently, bone marrow-derived stem cells (BMSCs) were harvested for the detection of hydrogen antisenescence effects and mechanisms. The results showed that the number of senescence-associated β-galactosidase (SA-β-Gal) positive cells was reduced in BMSCs from rats treated with HRS. BMSCs in rats treated with HRS possessed a better proliferation ability, showed more effectively tri-lineage differentiation potential, and had less percentage of cells in G1 cell cycle arrest than the control cells. Additionally, HRS administration inhibited the production of intracellular reactive oxygen species (ROS) and decreased the expression of senescence-related proteins p53 and p21. Our results revealed that hydrogen could alleviate cellular senescence in vivo. And the underlying mechanism of antisenescence effects of hydrogen in BMSCs was via the ROS/p53/p21 signaling pathway. Thus, hydrogen could be a new and convenient strategy for alleviating senescence and for therapy of age-related diseases.

Effects of hydrogen-occluding-silica microparticles on wound repair and cell migratory behavior of normal human esophageal epitheliocytes

Many conventional studies on molecular hydrogen have not examined cell migration ability and the relationship between apoptosis and the cytoskeleton. Here we investigated the influence of hydrogen-occluding silica microparticles (H₂-silica) on cell migration motility and changes of the cytoskeleton (F-actin) in normal human esophageal epithelial cells (HEEpiCs). As the results, cell migration was promoted, and formation of microvilli was activated in the 100 ppm (low concentration) scratched group. After performing a wound healing assay, cells exhibited migration after 48 hours and 72 hours for both 10 ppm and 100 ppm groups, suggesting that the wound-repairing effects could be attributed to the antioxidant ability of H₂-silica. In scratched groups, high levels of activated caspase-3 were relatively expressed and presented a tendency to increase the observed Bax/Bcl-2 ratio at more than 300 ppm groups. The above-mentioned results show that H₂-silica induced apoptosis in HEEpiCs, especially in the scratched cells. Toxicity may cause an exaggerated apoptosis. Furthermore, since the ratio of fascin/tubulin in the 100, 300, and 600 ppm groups tended to increase in both the scratched and the non-scratched control groups, H₂-silica was thought to be able to promote fascin action on normal cells and may be have a proliferative effect.

MicroRNA-210 promotes angiogenesis in acute myocardial infarction

MicroRNA-210 (miRNA-210) has been reported to be associated with angiogenesis and may serve important roles in acute myocardial infarction (AMI), which remain unclear. The present study sought to evaluate the efficacy of miRNA‑210 in AMI and to examine the potential associated mechanisms. AMI models were established in Sprague‑Dawley rats. The expression of miRNA‑210 was upregulated via transfection with lentivirus‑mediated agonists and quantitative analysis was performed using the reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR). Immunoblotting and RT‑qPCR were separately used to detect the expression levels of hepatocyte growth factor (HGF) in heart samples, while only the protein expression level of β‑myosin heavy chain (β‑MHC) was assessed. The expression of HGF in human umbilical vein endothelial cells under hypoxic conditions was silenced by transfecting with small interfering RNA, as demonstrated by the determination of associated protein expression levels. The microvessel density (MVD) of the infarcted myocardium was selected to be the angiogenesis efficacy endpoint, which was evaluated by platelet endothelial cell adhesion molecule immunostaining. Markedly increased expression of HGF was observed among the AMI rats receiving miRNA‑210 agonists, demonstrated via quantitative analyses using RT‑qPCR or western blotting. Promotion of angiogenesis was observed with the increased MVD. Improved cardiac function in the rats was subsequently noted, as they exhibited improved left ventricular fractional shortening and left ventricular ejection fraction percentages, which may result from improved cardiac contractility indicated by attenuating the increase in β‑MHC protein expression. Overexpression of miRNA‑210 appeared to be an advantageous therapeutic tool for treating AMI, primarily due to its promoting effects on angiogenesis in the infarcted myocardium by stimulating HGF expression and inducing improved left ventricular remodeling, leading to improved cardiac function.

The microRNA miR-21 conditions the brain to protect against ischemic and traumatic injuries

Ischemic and traumatic injuries to CNS remain leading causes of death and disability worldwide, despite decades of research into risk factors, therapies, and preventative measures. Recent studies showed that CNS injuries significantly alter the cerebral microRNAome that impact the secondary brain damage as well as plasticity and recovery. Many microRNA based therapies are currently in various clinical trials for different pathologic conditions indicating their therapeutic potential. In the present review, we discuss the role of miR-21 in acute CNS injuries which is currently thought to be a potent neuroprotective microRNA. We emphasize on the potential of miR-21 in promoting cell and tissue survival and preventing inflammation and apoptosis. We also discussed the role of miR-21 in conditioning the brain to promote ischemic tolerance. Finally, we discussed some of the challenges and difficulties to develop miR-21 as a neuroprotective therapy in humans.

Hydrogen-Rich Saline Ameliorates Hepatic Ischemia-Reperfusion Injury Through Regulation of Endoplasmic Reticulum Stress and Apoptosis

OBJECTIVE

To evaluate the effect of hydrogen-rich saline (HS) on hepatic ischemia-reperfusion (I/R) injury.

METHODS

Forty rats were randomly allocated into five groups: one sham group (control group), one group treated with 20 min of ischemia and normal saline (NS; I/R1 + NS group), one group treated with 20 min of ischemia and HS (I/R1 + HS group), one group treated with 60 min of ischemia and NS (I/R2 + NS group), and one group treated with 60 min of ischemia and HS (I/R2 + HS group). After reperfusion for 6 h, hepatic function, oxidative stress, pathological changes, and apoptosis of hepatic cells were evaluated. Furthermore, the expression levels of endoplasmic reticulum (ER) stress-associated proteins were identified.

RESULTS

Serum ALT and AST levels and tissue MDA content in the I/R + HS groups were significantly lower than those in the I/R + NS groups. Pathological changes were also significantly ameliorated in the HS groups compared with those in the NS groups. Moreover, HS appeared to significantly attenuate hepatic I/R-induced ER stress responses, as indicated by the decreased expression of C/EBP homologous protein, protein-kinase-RNA-like ER kinase, and inositol-requiring protein-1α, as well as the increased expression of GRP78 proteins. Finally, the levels of apoptotic markers such as caspase-3 and TUNEL-positive cells were significantly lower in the HS groups than in the NS control groups, whereas the level of Bcl2 protein increased in the HS groups.

CONCLUSION

The protective effect of HS can be attributed to ER stress and apoptosis inhibition.

Molecular hydrogen: a preventive and therapeutic medical gas for various diseases

Since the 2007 discovery that molecular hydrogen (H2) has selective antioxidant properties, multiple studies have shown that H2 has beneficial effects in diverse animal models and human disease. This review discusses H2 biological effects and potential mechanisms of action in various diseases, including metabolic syndrome, organ injury, and cancer; describes effective H2 delivery approaches; and summarizes recent progress toward H2 applications in human medicine. We also discuss remaining questions in H2 therapy, and conclude with an appeal for a greater role for H2 in the prevention and treatment of human ailments that are currently major global health burdens. This review makes a case for supporting hydrogen medicine in human disease prevention and therapy.

Effects of hydrogen-rich saline on endotoxin-induced uveitis

The therapeutic effects of hydrogen-rich saline (HRS) have been reported for a wide range of diseases mainly via selectively reducing the amount of reactive oxygen species. Oxidative stress plays an important role in the pathogenesis of uveitis and endotoxin-induced uveitis (EIU). In this study, we investigated whether HRS can mitigate EIU in rats. Sprague-Dawley rats were randomly divided into Norm group, Model group, HRS group, dexamethasone (DEX) group, and rats in the latter three groups were injected with equal amount of lipopolysaccharide (LPS) to induce EIU of different severities (by 1 mg/kg of LPS, or 1/8 mg/kg of LPS). Rats in HRS group were injected with HRS intraperitoneally at three different modes to purse an ameliorating effect of EIU (10 mL/kg of HRS immediately after injection of 1 mg/kg of LPS, 20 mL/kg of HRS once a day for 1 week before injection of 1 mg/kg of LPS and at 0, 0.5, 1, 2, 6, 8, 12 hours after LPS administration, or 20 mL/kg of HRS once a day for 1 week before injection of 1/8 mg/kg of LPS, and at 0, 0.5, 1, 2, 6, 8, 12, 24 hours and once a day for 3 weeks after LPS administration). Rats of DEX group were injected with 1 mL/kg of DEX solution intraperitoneally immediately after LPS administration. Rats in Norm and Model groups did not receive any treatment. All rats were examined under slit lamp microscope and graded according to the clinical signs of uveitis. Electroretinogram, quantitative analysis of protein in aqueous humor (AqH) and histological examination of iris and ciliary body were also carried out. Our results showed that HRS did not obviously ameliorate the signs of uveitis under slit lamp examination and the inflammatory cells infiltration around iris and cilliary body of EIU induced by 1 mg/kg or 1/8 mg/kg of LPS (P > 0.05), while DEX significantly reduced the inflammation reflected by the above two indicators (P < 0.05). The impaired retinal function of mild EIU induced by 1/8 mg/kg of LPS, showed by delay of peak time of b-wave of Dark adapted 3.0 electroretinogram, was not significantly restored by HRS (P > 0.05), while DEX had an obvious therapeutic effect (P < 0.05). However, HRS exerted an inhibition trend on elevation of protein in AqH of EIU induced by 1 mg/kg of LPS, and significantly reduced the increasing amount of protein in AqH of mild EIU induced by 1/8 mg/kg of LPS (P < 0.05). In conclusion, HRS could not obviously mitigate EIU in rats, while it could inhibit the elevation of AqH protein.

Molecular hydrogen: a therapeutic antioxidant and beyond

Molecular hydrogen (H₂) medicine research has flourished since a landmark publication in Nature Medicine that revealed the antioxidant and cytoprotective effects of hydrogen gas in a focal stroke model. Emerging evidence has consistently demonstrated that molecular hydrogen is a promising therapeutic option for a variety of diseases and the underlying comprehensive mechanisms is beyond pure hydroxyl radicals scavenging. The non-toxicity at high concentrations and rapid cellular diffusion features of molecular hydrogen ensure the feasibility and readiness of its clinical translation to human patients.