Hydrogen-rich saline reduces delayed neurologic sequelae in experimental carbon monoxide toxicity:

Mechanisms and therapeutic targets of carbon monoxide poisoning: A focus on reactive oxygen species

Carbon monoxide (CO) poisoning presents a substantial public health challenge that necessitates the identification of its pathological mechanisms and therapeutic targets. CO toxicity arises from tissue hypoxia-ischemia secondary to carboxyhemoglobin formation, and cellular damage mediated by CO at the cellular level. The mitochondria are the major targets of neuronal damage caused by CO. Under normal physiological conditions, mitochondria produce reactive oxygen species (ROS), which are byproducts of aerobic metabolism. While low ROS levels are crucial for essential cellular functions, including signal transduction, differentiation, responses to hypoxia and immunity, transcriptional regulation, and autophagy, excess ROS become pathological and exacerbate CO poisoning. This review presents the evidence of elevated ROS being associated with the progression of CO poisoning. Antioxidant treatments targeting ROS removal have been proven effective in mitigating CO poisoning, underscoring their therapeutic potential. In this review, we highlight the latest advances in the understanding of the role and the clinical implications of ROS in CO poisoning. We focus on cellular sources of ROS, the molecular mechanisms underlying mitochondrial oxidative stress, and potential therapeutic strategies for targeting ROS in CO poisoning.

NADPH Oxidase 3: Beyond the Inner Ear

Reactive oxygen species (ROS) were formerly known as mere byproducts of metabolism with damaging effects on cellular structures. The discovery and description of NADPH oxidases (Nox) as a whole enzyme family that only produce this harmful group of molecules was surprising. After intensive research, seven Nox isoforms were discovered, described and extensively studied. Among them, the NADPH oxidase 3 is the perhaps most underrated Nox isoform, since it was firstly discovered in the inner ear. This stigma of Nox3 as "being only expressed in the inner ear" was also used by me several times. Therefore, the question arose whether this sentence is still valid or even usable. To this end, this review solely focuses on Nox3 and summarizes its discovery, the structural components, the activating and regulating factors, the expression in cells, tissues and organs, as well as the beneficial and detrimental effects of Nox3-mediated ROS production on body functions. Furthermore, the involvement of Nox3-derived ROS in diseases progression and, accordingly, as a potential target for disease treatment, will be discussed.

The effect of preconditioning agents on cardiotoxicity and neurotoxicity of carbon monoxide poisoning in animal studies: a systematic review

BACKGROUND

Carbon monoxide (CO) poisoning is a common intoxication and many people die yearly due to CO poisoning and preconditioning agents attenuate brain and cardiac injury caused by intoxication. It is critical to fully understand the efficacy of new methods to directly target the toxic effect of CO, such as conditioning agents, which are currently under development. This study aims to systematically investigate current evidence from animal experiments and the effects of administration preconditions in acute and late phases after CO poisoning on cardiotoxicity and neurotoxicity.

METHODS

Four databases (PubMed, Embase, Scopus, and Web of Science) were systematically searched without language restrictions, and hand searching was conducted until November 2021. We included studies that compare preconditioning agents with the control group after CO poisoning in animals. The SYRCLE RoB tool was used for risk of bias assessments.

RESULTS

Thirty-seven studies were included in the study. Erythropoietin, granulocyte colony-stimulating factor (GCSF), hydrogen-rich saline, and N-butylphthalide (NBP) were found to have positive effects on reducing neurotoxicity and cardiotoxicity. As other preconditions have fewer studies, no valuable results can be deduced. Most of the studies were unclear for sources of bias.

DISCUSSION

Administration of the examined preconditioning agents including NBP, hydrogen-rich saline, and GCSF in acute and late phases could attenuate neurotoxicity and cardiotoxicity of CO poisoned animals. For a better understanding of mechanisms and activities, and finding new and effective preconditioning agents, further preclinical and clinical studies should be performed to analyze the effects of preconditioning agents.

Pediatric Carbon Monoxide Poisoning: Effects of Hyperbaric Oxygen Therapy on Thiol/Disulfide Balance

OBJECTIVES

Carbon monoxide (CO) poisoning remains the foremost cause of poisoning worldwide. This study aimed to investigate the effects of hyperbaric oxygen therapy (HBOT) and normobaric oxygen therapy (NBOT) on thiol/disulfide homeostasis in children with CO intoxication.

METHODS

Eighty-one children aged 0 to 18 years with CO intoxication were included in this cross-sectional study. No changes were made in the routine clinical evaluation and treatment practices of the patients. Thirty-two children who received HBOT and 49 children who received NBOT were compared for serum native thiol, disulfide, and total thiol levels, as well as for the changes in disulfide/native thiol, disulfide/total thiol, and native thiol/total thiol ratios before and after treatment.

RESULTS

Antioxidant levels, such as native thiol and total thiol, were significantly decreased in patients who received HBOT and increased in those who received NBOT (P = 0.02 and P = 0.01, respectively). There was no statistically significant difference between the 2 groups concerning the change of native thiol/total thiol ratios (P = 0.07). In addition, there was no significant difference regarding changes in disulfide, disulfide/native thiol, and disulfide/total thiol levels before and after treatment (P = 0.39, P = 0.07, and P = 0.07, respectively).

CONCLUSIONS

Although thiol-disulfide balance is maintained in patients treated with HBOT, antioxidant levels decrease significantly compared with NBOT. Despite efficiency of HBOT in CO intoxication, oxidative stress and reperfusion injury due to hyperoxygenation should be considered in the treatment of HBOT.

Neurocognitive sequelae after carbon monoxide poisoning and hyperbaric oxygen therapy

Carbon monoxide (CO) has been the leading cause of poisoning mortality in many countries and hyperbaric oxygen (HBO) is a widely accepted treatment for CO poisoning. However, some patients with CO poisoning will still develop neurocognitive sequelae regardless of HBO therapy, which can persist since CO poisoning or be present days to weeks after a recovery from CO poisoning. HBO has been used in the prevention and treatment of neurocognitive sequelae after CO poisoning, and some mechanisms are also proposed for the potential neuroprotective effects of HBO on the neurocognitive impairment after CO poisoning, but there is still controversy on the effectiveness of HBO on neurocognitive sequelae after CO poisoning. In this paper, we briefly introduce the neurocognitive sequelae after CO poisoning, summarize the potential predictive factors of neurocognitive sequelae, and discuss the use of HBO in the treatment and prevention of neurocognitive sequelae after CO poisoning.

Mitochondrial toxins potentiate hydroxyl radical production in rat striatum during carbon monoxide poisoning

Hydroxyl radical (•OH) production in the rat striatum during carbon monoxide (CO) poisoning, which inhibits complex IV, was enhanced synergistically by malonate, a mitochondrial complex II inhibitor, but not N-methyl-4-phenylpyridinium or NaCN, complex I and IV inhibitors, respectively. No such enhancement appeared in the case of NaCN combined with malonate. Intrastriatal dopamine, which is involved in •OH production by malonate, did not synergistically enhance CO-induced •OH production. Diphenyleneiodonium, a nonselective NADPH oxidase inhibitor, partly suppressed the potentiation of CO-induced •OH production by malonate. Impairment of mitochondrial functions might potentiate oxidative stress and intensify CO toxicity in the brain.

TDZD-8 alleviates delayed neurological sequelae following acute carbon monoxide poisoning involving tau protein phosphorylation

Objective: Acute carbon monoxide （CO）poisoning can cause delayed neurological sequelae (DNS). Glycogen synthase kinase 3β (GSK-3β) /Tau protein pathway is reported to play a key role in neurological abnormalities. In the present study, we aimed to determine the role of GSK-3β/Tau in DNS following acute CO poisoning.Methods: 4-benzyl-2-methyl-1,2,4-thiadiazolidine-3,5-dione (TDZD-8), a specific non-competitive inhibitor of GSK-3β, was used to inhibit GSK-3β. Twenty-four male Sprague-Dawley rats were randomly assigned to the three groups: Control group, CO group and CO-TDZD-8 group. Rats breathed 1000 ppm CO for 40 minutes and then 3000 ppm for up to 20 minutes until they lost consciousness. TDZD-8 (1 mg/kg) was administered intravenously three times after the end of CO exposure at 0, 24, 48 hours late. Learning and memory abilities were observed using the Morris Water Maze (MWM). Brain histological changes were evaluated by hematoxylin-eosin staining. Moreover, the expression levels of Tau and GSK-3β were detected after acute carbon monoxide poisoning.Results: TDZD-8 significantly attenuated the learning and memory dysfunction induced by acute CO poisoning, ameliorated the histology structure of damaged neural cells in cortex and hippocampus CA1 area. TDZD-8 clearly decreased p-Tau expression, reversed the reduction of p-GSK-3β induced by acute CO poisoning.Conclusions: The therapeutic effect of TDZD-8 in alleviating DNS caused by acute CO poisoning is related to the inactivation of Tau by intensifying the level of GSK-3β phosphorylation.

Blockade of the renin-angiotensin system suppresses hydroxyl radical production in the rat striatum during carbon monoxide poisoning

Oxidative stress has been suggested to play a role in brain damage during carbon monoxide (CO) poisoning. Severe poisoning induced by CO at 3000 ppm, but not 1000 ppm, enhances hydroxyl radical (˙OH) production in the rat striatum, which might be mediated by NADPH oxidase (NOX) activation associated with Ras-related C3 botulinum toxin substrate (Rac) via cAMP signaling pathway activation. CO-induced ˙OH production was suppressed by antagonists of angiotensin II (AngII) type 1 receptor (AT1R) and type 2 receptor (AT2R) but not an antagonist of the Mas receptor. Suppression by an AT1R antagonist was unrelated to peroxisome proliferator-activated receptor γ. Angiotensin-converting enzyme inhibitors also suppressed CO-induced ˙OH production. Intrastriatal AngII at high concentrations enhanced ˙OH production. However, the enhancement of ˙OH production was resistant to inhibitors selective for NOX and Rac and to AT1R and AT2R antagonists. This indicates a different mechanism for ˙OH production induced by AngII than for that induced by CO poisoning. AT1R and AT2R antagonists had no significant effects on CO-induced cAMP production or ˙OH production induced by forskolin, which stimulates cAMP production. These findings suggest that the renin-angiotensin system might be involved in CO-induced ˙OH production in a manner independent of cAMP signaling pathways.

Current and research therapies for the prevention and treatment of delayed neurological syndrome associated with carbon monoxide poisoning: A narrative review

Severe carbon monoxide (CO) poisoning causes fulminant deaths in common environment as well as neurological sequelae to survivors. Prevention of delayed neurological syndrome (DNS) after exposure to CO, the most important sequela, is based up to date on hyperbaric oxygen administration. Nevertheless, its use remains controversial due to the lack of evidence regarding its efficacy. The aim of this review is to report therapies under investigation for preventing or improving DNS, some of them with promising results in humans.

Hydrogen gas protects against delayed encephalopathy after acute carbon monoxide poisoning in a rat model

Objective: The protective effects of 2%-4% hydrogen gas in delayed encephalopathy after acute carbon monoxide poisoning (DEACMP) have been previously reported. This study aimed to assess the neuroprotective effects of high concentration hydrogen (HCH) on DEACMP.Methods: A total of 36 male Sprague-Dawley rats were divided into 3 groups. In the DEACMP group, rats were exposed to CO to induce CO poisoning; in the HCH group, the animals were exposed to 67% H₂ and 33% O₂ at 3,000 mL/min for 90 min immediately after CO poisoning. Neurological function was evaluated at 1 and 9 days after poisoning. Then, the contents of malondialdehyde, 3-nitrotyrosine and 8-hydroxy-2-deoxyguanosine, as well as superoxide dismutase activity in the serum, cortex and hippocampus were detected by ELISA. Additionally, the mRNA and protein expression levels of Nrf2 and downstream genes were detected by RT-PCR and Western blotting, respectively.Results: Our results showed that CO poisoning significantly impaired neurological function which was improved over time, and HCH markedly attenuated neurological impairment following CO poisoning. In addition, CO poisoning resulted in increased levels of malondialdehyde, 3-nitrotyrosine and 8-hydroxy-2-deoxyguanosine and markedly reduced superoxide dismutase activity at 1 and 9 days, which were significantly inhibited by HCH at 9 days. Finally, CO poisoning increased the mRNA and protein levels of Nrf2 and downstream genes, and HCH further induced the anti-oxidative capability.Conclusion: These findings indicate the neuroprotective effects of HCH on DEACMP, which are related to the activation of Nrf2 signaling pathway.

Hydrogen-Rich Saline Ameliorates Experimental Autoimmune Encephalomyelitis in C57BL/6 Mice Via the Nrf2-ARE Signaling Pathway

Multiple sclerosis (MS) is a chronic and inflammatory disease of the central nervous system that is associated with demyelination, neurodegeneration, and sensitivity to oxidative stress. Hydrogen-rich saline (HRS) is efficacious in preventive and therapeutic applications for many disorders because of its antioxidant and anti-inflammatory properties. Here, we determined the effect of HRS in experimental autoimmune encephalomyelitis (EAE), which is a generally accepted model of the immuno-pathogenic mechanisms underlying MS. We found that HRS reduced the severity of EAE in mice and alleviated inflammation and demyelination. Furthermore, treatment with HRS attenuated oxidative stress in EAE mice. Finally, the results of our study suggest that activation of the Nrf2-ARE pathway plays a critical role in the protective effects of HRS in EAE mice.

Hydrogen Alleviates Necroptosis and Cognitive Deficits in Lithium-Pilocarpine Model of Status Epilepticus

Status epilepticus without prompt seizure control always leads to neuronal death and long-term cognitive deficits, but effective intervention is still absent. Here, we found that hydrogen could alleviate the hippocampus-dependent spatial learning and memory deficit in lithium-pilocarpine model of status epilepticus in rats, as evidenced by the results in Morris water maze test. Hydrogen treatment downregulated the expression of necroptosis-related proteins, such as MLKL, phosphorylated-MLKL, and RIPK3 in hippocampus, and further protected neurons and astrocytes from necroptosis which was here first verified to occur in status epilepticus. Hydrogen also protected cells from apoptosis, which was indicated by the decreased cleaved-Caspase 3 expression. Meanwhile, Iba1+ microglial activation by status epilepticus was reduced by hydrogen treatment. These findings confirm the utility of hydrogen treatment in averting cell death including necroptosis and alleviating cognitive deficits caused by status epilepticus. Therefore, hydrogen may provide a potential and powerful clinical treatment for status epilepticus-related cognitive deficits.

Hydrogen-rich saline ameliorated LPS-induced acute lung injury via autophagy inhibition through the ROS/AMPK/mTOR pathway in mice

IMPACT STATEMENT

Acute lung injury (ALI), a common complication of many serious health issues, such as serious infection, burns, and shock, is one of the most common critical illnesses in clinical practice with a high mortality rate of 30-40%. There are still short of effective prevention and treatment measures. Evidence is growing that hydrogen-rich saline (HRS) may be an effective drug for the prevention and treatment of ALI. However, the mechanisms involved in have not been clearly understood. In this study, we investigated the underling mechanisms by focusing on autophagy regulation. The results showed that HRS ameliorated lipopolysaccharide-induced ALI in mice by inhibiting autophagy over-activation through ROS/AMPK/mTOR pathway. HRS may be a new therapeutic strategy for ALI prevention and treatment in the future.

The Role of Gaseous Molecules in Traumatic Brain Injury: An Updated Review

Traumatic brain injury (TBI) affects millions of people in China each year. TBI has a high mortality and often times a serious prognosis. The causative mechanisms of TBI during development and recovery from an injury remain vague, leaving challenges for the medical community to provide treatment options that improve prognosis and provide an optimal recovery. Biological gaseous molecules including nitric oxide (NO), carbon monoxide (CO), hydrogen sulfide (H₂S), and molecular hydrogen (H₂) have been found to play critical roles in physiological and pathological conditions in mammals. Accumulating evidence has found that these gaseous molecules can execute neuroprotection in many central nervous system (CNS) conditions due to their highly permeable properties allowing them to enter the brain. Considering the complicated mechanisms and the serious prognosis of TBI, effective and adequate therapeutic approaches are urgently needed. These four gaseous molecules can be potential attractive therapeutic intervention on TBI. In this review, we will present a comprehensive overview on the role of these four biological gasses in the development of TBI and their potential therapeutic applications.

Structural and lipid peroxidation effects of lead on rat hippocampus and its attenuation by hydrogen rich water

Despite the well-known toxicity and the efforts to control its exposure, lead still has a serious health concern, particularly in young ages. Chelation therapy cannot correct the neurocognitive effects of chronic exposure. So, there is a requirement to test different protective agents for lead intoxication. Hydrogen-rich water (HRW) has gained attraction recently as an antioxidant. Four groups of rats received sodium acetate, HRW, lead acetate (LA), or LA plus HRW for 8 weeks. Oxidative stress, histological and immunohistochemistry using p53 antibody were used to investigate the toxic effect of lead and the possible HRW protective effect in rat hippocampus. Results showed that HRW corrected the elevated malondialdehyde levels (MDA) and restore the lead-induced depletion of antioxidant enzymes; glutathione reductase (GR), catalase (CAT) and superoxide dismutase (SOD). HRW does not affect the diminished nitric oxide (NO) level in the LA-treated group. Moreover, HRW reversed the LA-induced histological and immunohistochemical changes. It significantly decreased the percentage of the apoptotic index. We concluded that HRW protects the neurons against lead-induced oxidative stress and has anti-apoptotic effects without a noticeable change in NO level which already was diminished by LA.

Delayed neurologic sequelae of carbon monoxide intoxication

Altered consciousness and accompanying neurological symptoms are both complex and challenging cases for emergency physicians. These are not specific and may be a sign of a variety of medical conditions including stroke and delayed neurological sequelae (DNS) is a recurrent transient neuropsychiatric consequence of CO intoxication. DNS produces a spectrum of varying symptoms and the diagnosis is primarily made on the basis of clinical features and radiological findings from CT and conventional MRI. In clinical practice, serious CO intoxication is treated only with oxygen therapy although no effective treatment exists. Emergency physicians play a major role in managing patients presenting with CO intoxication and preventing DNS.

Molecular hydrogen in the treatment of acute and chronic neurological conditions: mechanisms of protection and routes of administration

Oxidative stress caused by reactive oxygen species is considered a major mediator of tissue and cell injuries in various neuronal conditions, including neurological emergencies and neurodegenerative diseases. Molecular hydrogen is well characterized as a scavenger of hydroxyl radicals and peroxynitrite. Recently, the neuroprotective effects of treatment with molecular hydrogen have been reported in both basic and clinical settings. Here, we review the effects of hydrogen therapy in acute neuronal conditions and neurodegenerative diseases. Hydrogen therapy administered in drinking water may be useful for the prevention of neurodegenerative diseases and for reducing the symptoms of acute neuronal conditions.

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

Excessive production of oxygen free radicals has been regarded as a causative common denominator of many pathological processes in the animal kingdom. Hydroxyl and nitrosyl radicals represent the major cause of the destruction of biomolecules either by a direct reaction or by triggering a chain reaction of free radicals. Scavenging of free radicals may act preventively or therapeutically. A number of substances that preferentially react with free radicals can serve as scavengers, thus increasing the internal capacity/activity of endogenous antioxidants and protecting cells and tissues against oxidative damage. Molecular hydrogen (H(2)) reacts with strong oxidants, such as hydroxyl and nitrosyl radicals, in the cells, that enables utilization of its potential for preventive and therapeutic applications. H(2) rapidly diffuses into tissues and cells without affecting metabolic redox reactions and signaling reactive species. H(2) reduces oxidative stress also by regulating gene expression, and functions as an anti-inflammatory and anti-apoptotic agent. There is a growing body of evidence based on the results of animal experiments and clinical observations that H(2) may represent an effective antioxidant for the prevention of oxidative stress-related diseases. Application of molecular hydrogen in situations with excessive production of free radicals, in particular, hydroxyl and nitrosyl radicals is relatively simple and effective, therefore, it deserves special attention.

Gene expression in rat striatum following carbon monoxide poisoning

Carbon monoxide (CO) poisoning causes brain damage, which is attenuated by treatment with hydrogen [1], [2], a scavenger selective to hydroxyl radical (•OH) [3]. This suggests a role of •OH in brain damage due to CO poisoning. Studies have shown strong enhancement of •OH production in rat striatum by severe CO poisoning with a blood carboxyhemoglobin (COHb) level > 70% due to 3000 ppm CO, but not less severe CO poisoning with a blood COHb level at approximately 50% due to 1000 ppm CO [4]. Interestingly, 5% O₂ causes hypoxia comparable with that by 3000 ppm CO and produces much less ^•OH than 3000 ppm CO does [4]. In addition, cAMP production in parallel with •OH production [5] might contribute to •OH production [6]. It is likely that mechanisms other than hypoxia contribute to brain damage due to CO poisoning [7]. To search for the mechanisms, we examined the effects of 1000 ppm CO, 3000 ppm CO and 5% O₂ on gene expression in rat striatum. All array data have been deposited in the Gene Expression Omnibus (GEO) database under accession number GSE94780.

Molecular Hydrogen as a Neuroprotective Agent

Oxidative stress and neuroinflammation cause many neurological disorders. Recently, it has been reported that molecular hydrogen (H2) functions as an antioxidant and anti-inflammatory agent. The routes of H2 administration in animal model and human clinical studies are roughly classified into three types, inhalation of H2 gas, drinking H2-dissolved water, and injection of H2-dissolved saline. This review discusses some of the remarkable progress that has been made in the research of H2 use for neurological disorders, such as cerebrovascular diseases, neurodegenerative disorders, and neonatal brain disorders. Although most neurological disorders are currently incurable, these studies suggest the clinical potential of H2 administration for their prevention, treatment, and mitigation. Several of the potential effectors of H2 will also be discussed, including cell signaling molecules and hormones that are responsible for preventing oxidative stress and inflammation. Nevertheless, further investigation will be required to determine the direct target molecule of H2.

G-CSF administration attenuates brain injury in rats following carbon monoxide poisoning via different mechanisms

Acute severe carbon monoxide (CO) poisoning induces hypoxia that leads to cardiovascular and nervous systems disturbances. Different complex mechanisms lead to CO neurotoxicity including lipid peroxidation, inflammatory and immune-mediated reactions, myelin degeneration and finally neuronal apoptosis and necrosis. Granulocyte colony-stimulating factor (G-CSF) is considered to be a novel neuroprotective agent. In this study, we evaluated the efficacy of G-CSF therapy on CO neurotoxicity in rats with acute CO poisoning. Rats were exposed to 3000 ppm CO in air (0.3%) for 1 h, and then different doses (50,100, and 150 µg/kg) of G-CSF or normal saline were administrated intraperitoneally. Water content of brain as an indicator for total edema and blood brain barrier integrity (Evans blue extravasation) were evaluated. Malondialydehyde was determined in order to evaluate the effect of G-CSF on CO-induced lipid peroxidation in brain tissues. Also, the effect of G-CSF on myeloperoxidase activity in the brain tissue was evaluated. The effect of G-CSF administration on induced apoptosis in the brain was measured using TUNEL method. To evaluate the level of MBP, STAT3 and pSTAT3 and HO-1 proteins and the effect of G-CSF on these proteins Western blotting was carried out. G-CSF reduced water content of the edematous poisoned brains (100 µg/kg) and BBB permeability (100 and 150 µg/kg) (P < 0.05). G-CSF (150 µg/kg) reduced the MDA level in the brain tissues (P < 0.05 as compared to CO poisoned animals). G-CSF did not decrease the MPO activity after CO poisoning in any doses. G-CSF significantly reduced the number of apoptotic neurons and Caspase 3 protein levels in the brain. Western blotting results showed that G-CSF treatment enhanced expression of HO-1 and MBP, STAT3 and pSTAT3 proteins in the brain tissues. Based on our results, a single dose of G-CSF immediately after CO poisoning significantly attenuates CO neurotoxicity via different mechanisms. © 2015 Wiley Periodicals, Inc. Environ Toxicol 32: 37-47, 2017.

Hydrogen therapy: from mechanism to cerebral diseases

The medicinal value of hydrogen (H₂) was ignored prior to research illustrating that inhalation of 2% H₂ can significantly decrease the damage of cerebral ischemia/reperfusion caused by oxidative stress via selective elimination of hydroxyl freebase (OH) and peroxynitrite anion (ONOOˉ). Subsequently, there have been numerous experiments on H₂. Most research and trials involving the mechanisms underlying H₂ therapy show the effects of antioxygenation, anti-inflammation, and anti-apoptosis. Among quantities of diseases related with H₂ therapy, the brain disease is a hotspot as brain tissue and cell damage are easier to be induced by oxidative stress and other stimulations. In this review, emphasis is on stroke, traumatic brain injuries, and degenerative diseases, such as Alzheimer's disease and Parkinson's disease. Taking into account the blood-brain barrier, penetrability, possible side effects, and the molecular properties of H₂ within a single comprehensive review should contribute to advancing both clinical and non-clinical research and therapies. A systematic introduction of H₂ therapy with regards to mechanisms and cerebral diseases both in animal and human subjects can make it easier to comprehend H₂ therapy and therefore provide the basis for further clinical strategy.

Hydrogen-rich water attenuates brain damage and inflammation after traumatic brain injury in rats

Inflammation and oxidative stress are the two major causes of apoptosis after traumatic brain injury (TBI). Most previous studies of the neuroprotective effects of hydrogen-rich water on TBI primarily focused on antioxidant effects. The present study investigated whether hydrogen-rich water (HRW) could attenuate brain damage and inflammation after traumatic brain injury in rats. A TBI model was induced using a controlled cortical impact injury. HRW or distilled water was injected intraperitoneally daily following surgery. We measured survival rate, brain edema, blood-brain barrier (BBB) breakdown and neurological dysfunction in all animals. Changes in inflammatory cytokines, inflammatory cells and Cho/Cr metabolites in brain tissues were also detected. Our results demonstrated that TBI-challenged rats exhibited significant brain injuries that were characterized by decreased survival rate and increased BBB permeability, brain edema, and neurological dysfunction, while HRW treatment ameliorated the consequences of TBI. HRW treatment also decreased the levels of pro-inflammatory cytokines (TNF-α, IL-1β and HMGB1), inflammatory cell number (Iba1) and inflammatory metabolites (Cho) and increased the levels of an anti-inflammatory cytokine (IL-10) in the brain tissues of TBI-challenged rats. In conclusion, HRW could exert a neuroprotective effect against TBI and attenuate inflammation, which suggests HRW as an effective therapeutic strategy for TBI patients.

MAPKs and Hsc70 are critical to the protective effect of molecular hydrogen during the early phase of acute pancreatitis

Molecular hydrogen (H2 ) has been proven to be an effective agent that can cure multiple organ diseases by reducing oxidative stress. Although the protective effect of hydrogen on acute pancreatitis (AP) has been confirmed, its molecular mechanism is still unclear. In this article, we aimed to investigate the changes in pancreatic cell protein expression associated with the protective effect of H2 against AP and attempted to uncover the molecular mechanism underlying this process. A proteomic analysis identified 73 differentially expressed proteins and generated the protein-protein interaction networks of these proteins. The results triggered our interest in mitogen-activated protein kinase (MAPK) and heat shock cognate 71 kDa protein (Hsc70). The subsequent in vitro experiments showed that H2 treatment inhibited the phosphorylation of extracellular signal-regulated kinase (ERK), c-jun N-terminal kinase (JNK), and p38 MAPK, and activated NF-κB and the expression of tumor necrosis factor α and interleukin-1β, while simultaneously preventing the translocation of phospho-ERK, phospho-JNK, and phospho-p38 from the cytoplasm to the nucleus. Furthermore, Hsc70 expression was upregulated by H2 administration. The animal experimental results were consistent with those of the in vitro experiments. In conclusion, H2 treatment can ameliorate the inflammatory response and reduce the expression of inflammatory mediators during the early phase of AP by inhibiting the MAPK pathways and increasing Hsc70 expression.

Beneficial biological effects and the underlying mechanisms of molecular hydrogen - comprehensive review of 321 original articles

Therapeutic effects of molecular hydrogen for a wide range of disease models and human diseases have been investigated since 2007. A total of 321 original articles have been published from 2007 to June 2015. Most studies have been conducted in Japan, China, and the USA. About three-quarters of the articles show the effects in mice and rats. The number of clinical trials is increasing every year. In most diseases, the effect of hydrogen has been reported with hydrogen water or hydrogen gas, which was followed by confirmation of the effect with hydrogen-rich saline. Hydrogen water is mostly given ad libitum. Hydrogen gas of less than 4 % is given by inhalation. The effects have been reported in essentially all organs covering 31 disease categories that can be subdivided into 166 disease models, human diseases, treatment-associated pathologies, and pathophysiological conditions of plants with a predominance of oxidative stress-mediated diseases and inflammatory diseases. Specific extinctions of hydroxyl radical and peroxynitrite were initially presented, but the radical-scavenging effect of hydrogen cannot be held solely accountable for its drastic effects. We and others have shown that the effects can be mediated by modulating activities and expressions of various molecules such as Lyn, ERK, p38, JNK, ASK1, Akt, GTP-Rac1, iNOS, Nox1, NF-κB p65, IκBα, STAT3, NFATc1, c-Fos, and ghrelin. Master regulator(s) that drive these modifications, however, remain to be elucidated and are currently being extensively investigated.

Hydrogen-rich saline injection into the subarachnoid cavity within 2 weeks promotes recovery after acute spinal cord injury

Hydrogen can relieve tissue-damaging oxidative stress, inflammation and apoptosis. Injection of hydrogen-rich saline is an effective method for transporting molecular hydrogen. We hypothesized that hydrogen-rich saline would promote the repair of spinal cord injury induced by Allen's method in rats. At 0.5, 1, 2, 4, 8, 12 and 24 hours after injury, then once daily for 2 weeks, 0.25 mL/kg hydrogen-rich saline was infused into the subarachnoid space through a catheter. Results at 24 hours, 48 hours, 1 week and 2 weeks after injury showed that hydrogen-rich saline markedly reduced cell death, inflammatory cell infiltration, serum malondialdehyde content, and caspase-3 immunoreactivity, elevated serum superoxide dismutase activity and calcitonin gene-related peptide immunoreactivity, and improved motor function in the hindlimb. The present study confirms that hydrogen-rich saline injected within 2 weeks of injury effectively contributes to the repair of spinal cord injury in the acute stage.

Hydrogen-Rich Saline Attenuated Subarachnoid Hemorrhage-Induced Early Brain Injury in Rats by Suppressing Inflammatory Response: Possible Involvement of NF-κB Pathway and NLRP3 Inflammasome

Early brain injury (EBI), highlighted with inflammation and apoptosis, occurring within 72 h after subarachnoid hemorrhage (SAH), is associated with the prognosis of SAH. Recent studies have revealed that hydrogen-rich saline (HS) exerted multiple neuroprotective properties in many neurological diseases including SAH, involved to anti-oxidative and anti-apoptotic effect. We have previously reported that HS could attenuate neuronal apoptosis as well as vasospasm. However, the underlying mechanism of HS on inflammation in SAH-induced EBI remains unclear. In this study, we explored the influence of HS on nuclear factor-κB (NF-κB) pathway and nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome at early stage after SAH, by injecting HS intraperitoneally to SAH rats. One hundred and twenty-nine SD rats were randomly divided into four groups: sham group, SAH group, SAH+vehicle group, and SAH+HS group. SAH model was conducted using endovascular perforation method; all rats were sacrificed at 24 h after SAH. Protein level of pIκBα, cytosolic and nuclear p65, NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), caspase-1, interleukin-1β (IL-1β), and cleaved caspase-3 were measured by western blot. mRNA level of IL-1β, interleukin-6 (IL-6), tumor necrosis factor-c (TNF-α) were evaluated by RT-PCR. Cellular injury and death was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and Nissl staining, respectively. Our results showed that pIκBα, nuclear p65, NLRP3, ASC, caspase-1, IL-1β, cleaved caspase-3 proteins, as well as the mRNA of IL-1β, IL-6, and TNF-ɑ increased at 24 h after SAH, while cytosolic p65 decreased. TUNEL and Nissl staining presented severe cellular injury at 24 h post-SAH. However, after HS administration, the changes mentioned above were reversed. In conclusion, HS may inhibit inflammation in EBI and improve neurobehavioral outcome after SAH, partially via inactivation of NF-κB pathway and NLRP3 inflammasome. Graphical Abstract Schematic representation of the mechanism of HS-mediated anti-inflammatory effect in EBI after SAH. The NF-κB inflammatory pathway and NLRP3 inflammasome are involved in the anti-neuroinflammatory effect of HS post-SAH. SAH-induced oxidative stress enhances the activation of NF-κB, thus promoting the translocation of p65 subunit into nucleus and increasing the mRNA level of its downstream proinflammatory cytokines (IL-1β, IN-6, TNF-α) and NLRP3. Elevated expression of NLRP3 mRNA increases the assembly of NLRP3 inflammasome. In addition, oxidative stress after SAH stimulates the activation of NLRP3 inflammasome, therefore, promoting caspase-1 activation and the cleavage of pro-IL-1β into mature IL-1β. Finally, activation of NF-κB pathway and NLRP3 inflammasome contribute to the inflammation response and cellular injury in EBI after SAH. HS treatment reversed the detrimental effect mentioned above via inactivation of NF-κB pathway and NLRP3 inflammasome. NF-κB nuclear factor-κB, IκB inhibitor of NF-κB, IKK Iκ kinase, NLRP3 nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3, ASC apoptosis-associated speck-like protein containing a caspase recruitment domain.

A modern literature review of carbon monoxide poisoning theories, therapies, and potential targets for therapy advancement

The first descriptions of carbon monoxide (CO) and its toxic nature appeared in the literature over 100 years ago in separate publications by Drs. Douglas and Haldane. Both men ascribed the deleterious effects of this newly discovered gas to its strong interaction with hemoglobin. Since then the adverse sequelae of CO poisoning has been almost universally attributed to hypoxic injury secondary to CO occupation of oxygen binding sites on hemoglobin. Despite a mounting body of literature suggesting other mechanisms of injury, this pathophysiology and its associated oxygen centric therapies persists. This review attempts to elucidate the remarkably complex nature of CO as a gasotransmitter. While CO's affinity for hemoglobin remains undisputed, new research suggests that its role in nitric oxide release, reactive oxygen species formation, and its direct action on ion channels is much more significant. In the course of understanding the multifaceted character of this simple molecule it becomes apparent that current oxygen based therapies meant to displace CO from hemoglobin may be insufficient and possibly harmful. Approaching CO as a complex gasotransmitter will help guide understanding of the complex and poorly understood sequelae and illuminate potentials for new treatment modalities.

Allopurinol reduces severity of delayed neurologic sequelae in experimental carbon monoxide toxicity in rats

Approximately half of those who survive severe carbon monoxide (CO) poisoning develop delayed neurologic sequelae. Growing evidence supports the crucial role of free radicals in delayed brain injury associated with CO toxicity. Xanthine oxidase (XO) has been reported to play a pivotal role in the generation of reactive oxygen species (ROS) in CO poisoning. A recent report indicates that allopurinol both attenuated oxidative stress and possessed anti-inflammatory properties in an animal model of acute liver failure. In this study, we aimed to explore the potential of allopurinol to reduce the severity of delayed neurologic sequelae. The rats were first exposed to 1000 ppm CO for 40 min and then to 3000 ppm CO for another 20 min. Following CO poisoning, the rats were injected with allopurinol (50 mg/kg, i.p.) six times. Results showed that allopurinol significantly reduced neuronal death and suppressed expression of pro-inflammatory factors, including tumor necrosis factor-α, intercellular adhesion molecule-1, ionized calcium-binding adapter molecule 1, and degraded myelin basic protein. Furthermore, behavioral studies revealed an improved performance in the Morris water maze test. Our findings indicated that allopurinol may have protective effects against delayed neurologic sequelae caused by CO toxicity.

Hydrogen-rich saline ameliorates lung injury associated with cecal ligation and puncture-induced sepsis in rats

AIMS

Although hydrogen has been proved to be a novel therapeutic medical gas in several lung injury animal models, to our knowledge, it has not been tested yet in acute lung injury (ALI) induced by cecal ligation and puncture (CLP). This study was to investigate the hypothesis that hydrogen could ameliorate CLP-induced lung injury in rats.

METHODS AND RESULTS

Our experiments exhibited that gas exchange dysfunction and lung tissue inflammation were observed in animals exposed to CLP. Hydrogen-rich saline treatment significantly attenuated lung injury as indicated by significantly improved gas exchange and histological changes in the lung and significantly reduced lung water content (LWC) and neutrophil infiltration 8h after CLP. Lipid peroxidation and DNA oxidation in the lung tissue were significantly reduced along with a decreased nitrotyrosine content and maintained superoxide dismutase activity in the presence of hydrogen, demonstrating antioxidant role of hydrogen in CLP-induced ALI. Importantly, hydrogen-rich saline treatment significantly inhibited the activation of p-p38 and NF-κB while suppressing the production of several proinflammatory mediators.

CONCLUSIONS

This observation indicated that hydrogen-rich saline peritoneal injection improves histological and functional assessment in rat model of CLP-induced ALI. The therapeutic effects of hydrogen-rich saline may be related to antioxidant and anti-inflammatory actions.

A review of experimental studies of hydrogen as a new therapeutic agent in emergency and critical care medicine

Hydrogen is the most abundant chemical element in the Universe, but is seldom regarded as a therapeutic agent. Recent evidence has shown that hydrogen is a potent antioxidative, antiapoptotic and anti-inflammatory agent and so may have potential medical applications in cells, tissues and organs. There are several methods to administer hydrogen, such as inhalation of hydrogen gas, aerosol inhalation of a hydrogen-rich solution, drinking hydrogen dissolved in water, injecting hydrogen-rich saline (HRS) and taking a hydrogen bath. Drinking hydrogen solution (saline/pure water/other solutions saturated with hydrogen) may be more practical in daily life and more suitable for daily consumption. This review summarizes the findings of recent studies on the use of hydrogen in emergency and critical care medicine using different disease models.

Different mechanisms of hydroxyl radical production susceptible to purine P2 receptor antagonists between carbon monoxide poisoning and exogenous ATP in rat striatum

Previous studies have suggested that carbon monoxide (CO) poisoning stimulates cAMP production via purine P2Y11-like receptors in the rat striatum, activating cAMP signaling pathways, resulting in hydroxyl radical ((•)OH) production. Extracellular ATP was thought likely to trigger the cascade, but the present study has failed to demonstrate a clear increase in the extracellular ATP due to CO poisoning. The CO-induced (•)OH production was attenuated by the P2Y11 receptor antagonist NF157, in parallel with its abilities to suppress the CO-induced cAMP production. The (•)OH production was more strongly suppressed by a non-selective P2 receptor antagonist, PPADS, which had no effect on cAMP production. More selective antagonists toward the respective P2 receptors susceptible to PPADS, including NF279, had little or no effect on the CO-induced (•)OH production. The intrastriatal administration of exogenous ATP dose-dependently stimulated (•)OH production, which was dose-dependently antagonized by PPADS and NF279 but not by NF157. Exogenous GTP and CTP dose-dependently stimulated (•)OH production, though less potently. The GTP-induced (•)OH production was susceptible to both of NF279 and PPADS, but the CTP-induced (•)OH production was resistant to PPADS. The mechanism of (•)OH production may differ between CO poisoning and exogenous ATP, while multiple P2 receptors could participate in (•)OH production. The CO-induced (•)OH production was susceptible to the inhibition of NADPH oxidase, but not xanthine oxidase. Also, the NADPH oxidase inhibition suppressed (•)OH production induced by forskolin, a stimulator of intracellular cAMP formation. It is likely that (•)OH is produced by NADPH oxidase activation via cAMP signaling pathways during CO poisoning.

The role of reactive oxygen species and oxidative stress in carbon monoxide toxicity: an in-depth analysis

The underlying mechanism of the central nervous system (CNS) injury after acute carbon monoxide (CO) poisoning is interlaced with multiple factors including apoptosis, abnormal inflammatory responses, hypoxia, and ischemia/reperfusion-like problems. One of the current hypotheses with regard to the molecular mechanism of CO poisoning is the oxidative injury induced by reactive oxygen species, free radicals, and neuronal nitric oxide. Up to now, the relevant mechanism of this injury remains poorly understood. The weakening of antioxidant systems and the increase of lipid peroxidation in the CNS have been implicated, however. Accordingly, in this review, we will highlight the relationship between oxidative stress and CO poisoning from the perspective of forensic toxicology and molecular toxicology.

Molecular hydrogen as a preventive and therapeutic medical gas: initiation, development and potential of hydrogen medicine

Molecular hydrogen (H2) has been accepted to be an inert and nonfunctional molecule in our body. We have turned this concept by demonstrating that H2 reacts with strong oxidants such as hydroxyl radical in cells, and proposed its potential for preventive and therapeutic applications. H2 has a number of advantages exhibiting extensive effects: H2 rapidly diffuses into tissues and cells, and it is mild enough neither to disturb metabolic redox reactions nor to affect signaling reactive oxygen species; therefore, there should be no or little adverse effects of H2. There are several methods to ingest or consume H2; inhaling H2 gas, drinking H2-dissolved water (H2-water), injecting H2-dissolved saline (H2-saline), taking an H2 bath, or dropping H2-saline into the eyes. The numerous publications on its biological and medical benefits revealed that H2 reduces oxidative stress not only by direct reactions with strong oxidants, but also indirectly by regulating various gene expressions. Moreover, by regulating the gene expressions, H2 functions as an anti-inflammatory and anti-apoptotic, and stimulates energy metabolism. In addition to growing evidence obtained by model animal experiments, extensive clinical examinations were performed or are under investigation. Since most drugs specifically act to their targets, H2 seems to differ from conventional pharmaceutical drugs. Owing to its great efficacy and lack of adverse effects, H2 has promising potential for clinical use against many diseases.

Carbon monoxide poisoning in the 21st century

The world has experienced some very large shifts in the epidemiology of carbon monoxide poisoning, but it remains one of the most important toxicological global causes of morbidity and mortality. The diagnosis can be quickly confirmed with blood gases (pulse oximeters lack both sensitivity and specificity). Several strong predictors for serious neurological sequelae (prolonged loss of consciousness and elevated S100B) and reduced life expectancy (elevated troponin) are now reasonably well established. Despite this clearly defined high-risk group and extensive research into the pathophysiology, there has been little translation into better treatment. Much of the pathophysiological research has focused on hyperbaric oxygen. Yet it is apparent that clinical trials show little evidence for benefit from hyperbaric oxygen, and the most recent even raises the possibility of harm for repeated courses. More logical and promising potential antidotes have been under-researched, although recently both animal and small human studies suggest that erythropoietin may reduce S100B and prevent neurological sequelae. Major breakthroughs are likely to require further research on this and other treatments that may inhibit post-hypoxic inflammatory responses and apoptosis.

Neuropeptides, trophic factors, and other substances providing morphofunctional and metabolic protection in experimental models of diabetic retinopathy

Vision is the most important sensory modality for many species, including humans. Damage to the retina results in vision loss or even blindness. One of the most serious complications of diabetes, a disease that has seen a worldwide increase in prevalence, is diabetic retinopathy. This condition stems from consequences of pathological metabolism and develops in 75% of patients with type 1 and 50% with type 2 diabetes. The development of novel protective drugs is essential. In this review we provide a description of the disease and conclude that type 1 diabetes and type 2 diabetes lead to the same retinopathy. We evaluate existing experimental models and recent developments in finding effective compounds against this disorder. In our opinion, the best models are the long-term streptozotocin-induced diabetes and Otsuka Long-Evans Tokushima Fatty and spontaneously diabetic Torii rats, while the most promising substances are topically administered somatostatin and pigment epithelium-derived factor analogs, antivasculogenic substances, and systemic antioxidants. Future drug development should focus on these.

Hydrogen rich saline reduces immune-mediated brain injury in rats with acute carbon monoxide poisoning

OBJECTIVES

This experiment was designed to determine whether hydrogen (H(2)) rich saline can ameliorate brain abnormalities in a rat model with acute carbon monoxide (CO) poisoning.

METHODS

Sprague-Dawley male rats were used for CO poisoning and H(2) rich saline treatment. Changes in neurons, microglias, and myelin sheath were observed by electron microscope. Neuron loss was assessed by Nissl staining. Antioxidant capacities were evaluated by studying superoxide dismutase activities and malondialdehyde concentration in the brain and serum. Infiltration of macrophages, expression of immune-associated cytokines (MIP-1-alpha and ICAM-1), and changes in myelin basic protein (MBP) were monitored by immunohistochemical staining and western blotting.

RESULTS

CO-exposed rats showed the increase in neuron loss and the decrease in antioxidant capacities. And H(2) rich saline given after CO poisoning can prevent the alterations mentioned above. CO-mediated oxidative stress caused alterations in MBP, which initiated an adaptive immunological response that led to brain injury. MBP from H(2) rich saline-treated, CO-exposed rats was recognized normally by immunohistochemical staining and western blotting. Electron microscope observation from CO-exposed rats showed an apparent aggregation of microglias. Macrophages from CO-exposed rats were significantly more than those from H(2) rich saline-treated and control rats, and the immunofluorescence observation showed that macrophages were similar to microglias in type. Expression levels of MIP-1-alpha and ICAM-1 increased in the brains of CO-poisoned rats and H(2) rich saline treatment decreased the levels.

DISCUSSION

The results indicate that H(2) rich saline prevents immune-mediated brain injury after CO poisoning.

Hydrogen therapy may be an effective and specific novel treatment for acute graft-versus-host disease (GVHD)

Allogeneic haematopoietic stem cell transplantation (HSCT) has been widely used for the treatment of haematological malignant and non-malignant haematologic diseases. However, acute graft-versus-host disease (aGVHD) is a kind of severe complication of HSCT limiting its application. Cytokines such as tumour necrosis factor-α (TNF-α), IL-6 play an extremely important role in the formation and development of aGVHD. Besides, the oxidation phenomena and/or the formation of free radicals have been suggested to be causally related to various haematological disorders including aGVHD. Reactive oxygen species (ROS), such as hydroxyl radicals, play an important role in the formation and development of aGVHD. Hydrogen has been reported to have the ability to inhibit levels of cytokines such as TNF, IL-6 in vivo. Our recent studies provided evidence that hydrogen inhalation can selectively reduce cytotoxic oxygen radicals and exert antioxidant effects. Therefore, we suggested that hydrogen may have therapeutic effects on aGVHD. This hypothesis entails many experimentally testable predictions. We propose the experimental study by detecting complete blood counts (CBC) and Clinic signs of aGVHD mice. We also propose to detect the levels of TNF-α, IL-2, IL-1β, IL-6 which play important roles in the pathogenesis of aGVHD. To discover potential mechanisms of the therapeutic effects of hydrogen on the aGVHD model, we will examine gene-expression profiles. This study will open a new therapeutic avenue combining the field of therapeutic medical gases and aGVHD. This theory is original and probably of importance, because therapeutic medical gases have never been used for aGVHD previously.

Hydrogen-rich medium suppresses the generation of reactive oxygen species, elevates the Bcl-2/Bax ratio and inhibits advanced glycation end product-induced apoptosis

The purpose of the present study was to determine whether using hydrogen-rich medium (HRM) to increase hydrogen levels in endothelial cells (ECs) protects ECs from apoptosis induced by advanced glycation end products (AGEs). The thoracic aorta was removed from 2-3-year-old Sprague-Dawley rats, and ECs were isolated and cultured. After culturing ECs in the presence of AGEs and/or with HRM for 24 h, Annexin V/7-AAD and TUNEL staining were carried out to detect apoptosis. Intracellular ROS were detected by fluorescent probe and quantified by flow cytometry. The expression of antioxidative enzymes (superoxide dismutase, glutathione peroxidase) was determined by real-time PCR analysis and enzymatic assay. The relative expression levels of Bcl-2 and Bax were analyzed by western blotting. The addition of AGEs increased the apoptosis of ECs in a concentration-dependent manner and HRM reduced the AGE (400 µg/ml)-induced apoptosis from 21.61±2.52 to 11.32±1.75%. HRM also significantly attenuated the AGE-induced intracellular ROS induction and decrease in the expression of antioxidative enzymes. In conclusion, hydrogen exhibits significant protective effects against AGE-induced EC injury possibly through reducing ROS generation, intracellular antioxidant enzyme system protection and elevation of the Bcl-2/Bax ratio.

Hydrogen-rich saline attenuates vascular smooth muscle cell proliferation and neointimal hyperplasia by inhibiting reactive oxygen species production and inactivating the Ras-ERK1/2-MEK1/2 and Akt pathways

Hydrogen-rich saline has been reported to prevent neointimal hyperplasia induced by carotid balloon injury. The purpose of the present study was to further investigate the molecular mechanisms underlying this phenomenon. Daily injection of a hydrogen-rich saline solution (HRSS) in rats was employed to study the effect of hydrogen on balloon injury-induced neointimal hyperplasia and the neointima/media ratio was assessed. HRSS significantly decreased the neointima area and neointima/media ratio in a dose-dependent manner. In vitro effects of hydrogen on fetal bovine serum (FBS)-induced vascular smooth muscle cell (VSMC) proliferation were also investigated. Hydrogen-rich medium (HRM) inhibited rat VSMC proliferation and migration induced by 10% FBS. FBS-induced reactive oxygen species (ROS) production and activation of intracellular Ras, MEK1/2, ERK1/2, proliferative cell nuclear antigen (PCNA), Akt were significantly inhibited by HRM. In addition, HRM blocked FBS-induced progression from the G0/G1 to the S-phase and increased the apoptosis rate of VSMCs. These results showed that hydrogen-rich saline was able to attenuate FBS-induced VSMC proliferation and neointimal hyperplasia by inhibiting ROS production and inactivating the Ras-ERK1/2-MEK1/2 and Akt pathways. Thus, HRSS may have potential therapeutic relevance for the prevention of human restenosis.

Effects of hydrogen-rich saline on rats with acute carbon monoxide poisoning

BACKGROUND

Studies have shown that inhalation of hydrogen gas, which acts as an antioxidant, can protect the brain against free radicals in rats with ischemia-reperfusion. The neuronal damage caused by acute carbon monoxide (CO) poisoning is partly free radical mediated. We hypothesize that hydrogen may prevent neurological damage from CO poisoning.

OBJECTIVES

This study is designed to test whether hydrogen (H(2))-rich saline will have a protective effect on rats with acute CO poisoning.

METHODS

Male Sprague-Dawley rats were subjected to CO poisoning. H(2)-rich saline was administered by peritoneal injection (6 mL/kg/24 h). We used the Morris water maze and the open field test to determine cognitive function. After cognitive function studies, rats were decapitated and the levels of trace elements copper (Cu), zinc (Zn), and iron (Fe) in serum and brain were assessed by flame atomic absorption spectrometry. Necrosis, apoptosis, and autophagy of neurons were assessed by H-E staining and immunohistochemical staining in another group of rats.

RESULTS

H(2)-rich saline treatment improved the cognitive deficits and reduced the degree of necrosis, apoptosis, and cell autophagy in rats. Additionally, H(2)-rich saline decreased the content of Fe in serum and brain in these rats, and increased the content of serum Cu related to free radical metabolism.

CONCLUSIONS

H(2)-rich saline may effectively protect the brain from injury after acute CO poisoning. The mechanism of this protection may be related to lessening oxidative damage by affecting trace elements in vivo.

Molecular hydrogen as an emerging therapeutic medical gas for neurodegenerative and other diseases

Effects of molecular hydrogen on various diseases have been documented for 63 disease models and human diseases in the past four and a half years. Most studies have been performed on rodents including two models of Parkinson's disease and three models of Alzheimer's disease. Prominent effects are observed especially in oxidative stress-mediated diseases including neonatal cerebral hypoxia; Parkinson's disease; ischemia/reperfusion of spinal cord, heart, lung, liver, kidney, and intestine; transplantation of lung, heart, kidney, and intestine. Six human diseases have been studied to date: diabetes mellitus type 2, metabolic syndrome, hemodialysis, inflammatory and mitochondrial myopathies, brain stem infarction, and radiation-induced adverse effects. Two enigmas, however, remain to be solved. First, no dose-response effect is observed. Rodents and humans are able to take a small amount of hydrogen by drinking hydrogen-rich water, but marked effects are observed. Second, intestinal bacteria in humans and rodents produce a large amount of hydrogen, but an addition of a small amount of hydrogen exhibits marked effects. Further studies are required to elucidate molecular bases of prominent hydrogen effects and to determine the optimal frequency, amount, and method of hydrogen administration for each human disease.