|Year : 2019 | Volume
| Issue : 3 | Page : 122-126
Inhalation of high-concentration hydrogen gas attenuates cognitive deficits in a rat model of asphyxia induced-cardiac arrest
Lei Huang1, Richard L Applegate II2, Patricia M Applegate3, Lei Gong4, Umut Ocak5, Warren Boling1, John H Zhang6
1 Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, CA, USA
2 Department of Anesthesiology and Pain Medicine, School of Medicine, University of California, Davis, Sacramento, CA, USA
3 Department of Cardiology, School of Medicine, University of California, Davis, Sacramento, CA, USA
4 Department of Pharmacy, 1st Affiliated Hospital to Zunyi Medical University, Zunyi, Guizhou Province, China
5 Department of Basic Sciences, Division of Physiology, School of Medicine, Loma Linda University, Loma Linda, CA, USA
6 Department of Anesthesiology, School of Medicine, Loma Linda University, Loma Linda, CA, USA
|Date of Submission||15-Apr-2019|
|Date of Decision||16-Apr-2019|
|Date of Acceptance||11-Jun-2019|
|Date of Web Publication||23-Sep-2019|
Department of Neurosurgery, School of Medicine, Loma Linda University, Loma Linda, CA
Source of Support: None, Conflict of Interest: None
Cognitive deficits are a devastating neurological outcome seen in survivors of cardiac arrest. We previously reported water electrolysis derived 67% hydrogen gas inhalation has some beneficial effects on short-term outcomes in a rat model of global brain hypoxia-ischemia induced by asphyxia cardiac arrest. In the present study, we further investigated its protective effects in long-term spatial learning memory function using the same animal model. Water electrolysis derived 67% hydrogen gas was either administered 1 hour prior to cardiac arrest for 1 hour and at 1-hour post-resuscitation for 1 hour (pre- & post-treatment) or at 1-hour post-resuscitation for 2 hours (post-treatment). T-maze and Morris water maze were used for hippocampal memory function evaluation at 7 and 14 days post-resuscitation, respectively. Neuronal degeneration within hippocampal Cornu Ammonis 1 (CA1) regions was examined by Fluoro-Jade staining ex vivo. Hippocampal deficits were detected at 7 and 18 days post-resuscitation, with increased neuronal degeneration within hippocampal CA1 regions. Both hydrogen gas treatment regimens significantly improved spatial learning function and attenuated neuronal degeneration within hippocampal CA1 regions at 18 days post-resuscitation. Our findings suggest that water electrolysis derived 67% hydrogen gas may be an effective therapeutic approach for improving cognitive outcomes associated with global brain hypoxia-ischemia following cardiac arrest. The study was approved by the Animal Health and Safety Committees of Loma Linda University, USA (approval number: IACUC #8170006) on March 2, 2017.
Keywords: high concentration hydrogen gas; cardiac arrest; global brain ischemia; brain resuscitation; cognitive deficit; water maze; neuron; rat
|How to cite this article:|
Huang L, Applegate II RL, Applegate PM, Gong L, Ocak U, Boling W, Zhang JH. Inhalation of high-concentration hydrogen gas attenuates cognitive deficits in a rat model of asphyxia induced-cardiac arrest. Med Gas Res 2019;9:122-6
|How to cite this URL:|
Huang L, Applegate II RL, Applegate PM, Gong L, Ocak U, Boling W, Zhang JH. Inhalation of high-concentration hydrogen gas attenuates cognitive deficits in a rat model of asphyxia induced-cardiac arrest. Med Gas Res [serial online] 2019 [cited 2019 Dec 8];9:122-6. Available from: http://www.medgasres.com/text.asp?2019/9/3/122/266986
| Introduction|| |
Cerebral hypoxia-ischemia injury is a significant source of morbidity and mortality in cardiac arrest survivors. Cardiac arrest disrupts global cerebral circulation, leading to neuronal damage in multiple brain regions including the hippocampus, cortex, cerebellum, thalamus, prefrontal cortex, and putamen., The Cornu Ammonis 1 (CA1) region of the hippocampus is particularly sensitive to cerebral ischemia and CA1 neuronal degeneration results in hippocampus dysfunction.,, Cardiac arrest survivors commonly experience cognitive deficits in memory and executive function.,,,
Emerging evidence has demonstrated that low concentration hydrogen gas (up to 3%) or hydrogen-rich saline attenuates hippocampal neuronal injury in animal models of global brain ischemia,, due to unique antioxidative and antiapoptotic properties. The safety of hydrogen gas therapy at this concentration was reported in several cases of patients with post-resuscitation syndromes. It may serves as a novel translational therapeutic approach in addition to neuroprotection strategies previously reported in the setting of experimental ischemic stroke.,,, Recently, water-electrolysis derived high concentration hydrogen gas has been shown in rats to provide similar neuroprotection against focal brain and retina ischemia-reperfusion injury without systemic adverse effects., We previously reported a tendency toward improvement in short-term neurological deficit scores provided by 67% hydrogen gas in a rat model of asphyxia-induced cardiac arrest (ACA). In the present study, we further investigated the efficacy of this 67% hydrogen gas in improving cognitive outcomes in global brain hypoxia-ischemia induced by ACA in rats.
| Materials and Methods|| |
All protocols were approved by the Animal Health and Safety Committees of Loma Linda University, USA (approval number: IACUC #8170006) on March 2, 2017) and were in compliance with Federal regulations.
Animal model and groups
A total of 44 male Sprague-Dawley rats (9 months old, body weight 450–550 g) were investigated in the following groups: sham (n = 6), ACA (n = 13), ACA + hydrogen post-treatment (n = 13), ACA + hydrogen pre- & post-treatment (n = 12) groups. ACA was induced as previously described.19 Briefly, rats were anesthetized with pentobarbital (45 mg/kg; Virbac AH, Inc., Fort Worth, TX, USA) and the trachea was orally intubated with a 14-gauge plastic catheter. For monitoring arterial pressure and administration of resuscitation drugs, two PE 50 catheters (Becton Dickinson, Franklin Lakes, NJ, USA) were inserted into the left femoral artery and vein until reaching the abdominal aorta and the inferior vena cava, respectively. Electrocardiogram (Lead II) was continually recorded. The animals were mechanically ventilated with room air at a rate of 100 breaths/min at a tidal volume of 0.55 mL/100 g for 15 minutes. Asphyxia resulted from intravenous injection of a chemical neuromuscular blockade (vecuronium 2 mg/kg intravenously injected, Mylan Institutional LLC., Rockford, IL, USA) followed by ventilator disconnection and endotracheal tube obstruction. After 9 minutes of asphyxia, precordial compression was started using a pneumatically driven mechanical chest compressor coincident mechanically ventilation (100% oxygen) at ratio of 2:1. At the start of precordial compression, a bolus dose of epinephrine (7.5 μg/kg, International medication system, LLC., South El Monte, CA, USA) with sodium bicarbonate (1 mEq/kg, Hospira, Lake Forest, IL, USA) was injected into the left femoral vein. Resuscitation or return of spontaneous circulation (ROSC) was defined as the return of supraventriclar rhythm with mean artery pressure over 60 mmHg (1 mmHg = 0.1333 kPa) for 5 minutes.
After resuscitation, mechanical ventilation support was continued, and then stopped 1 hour after ROSC. All catheters including endotracheal tube were removed. Animals were closely observed by the investigator for an additional 2 hours. Body temperature was monitored through a rectal temperature sensor (Model BAT-12, Physitemp instrument Inc., Clifton, NJ, USA) and maintained at 36.8 ± 0.2°C.
Lead II electrocardiogram, end-tidal carbon dioxide and arterial pressure were continuously recorded beginning 15 minutes before asphyxia induction and continuing to 1 hour after ROSC using a precordial compression-based data-acquisition system supported by WINDAQ software (DATAQ, Akron, OH, USA).
Hydrogen was delivered through a hydrogen treatment chamber with the inlet connected to a hydrogen nebulizer (AMS-H-01; Asclepius Meditec Co. Ltd., Shanghai, China) that produced a 67% hydrogen and 33% oxygen gas mixture. The hydrogen concentration was monitored by a hydrogen detector during the administration. Hydrogen was administered starting at 1 hour prior to cardiac arrest for 1 hour and then restarted at 1 hour post-resuscitation for 1 hour (pre- & post-treatment group) or starting at 1 hour post-resuscitation for 2 hours (post-treatment).
Cognitive function evaluation
Both T-maze and water maze are tests of cognitive function. The water-maze is a more comprehensive test of cognitive function but requires the rats to swim. At 7 days post-resuscitation, ACA rats did not have sufficient motor strength to swim, which would confound cognitive assessments. Thus at 7 days post-resuscitation, T-maze for spontaneous alternation was used to examine exploratory behavior and working memory of the hippocampus as previously described. Briefly, rats were placed in a T-shaped maze and allowed to freely explore the two arms of the maze throughout 10-trials. The spontaneous alternation rate was calculated as the percentage of the alternating choices out of 10 trials.
Starting on day 14 post-resuscitation, Morris water maze test was used to assess the learning and spatial memory function of rats as previously described. This four-day test consisted of both cued and hidden tests with test duration up to 60 seconds per trial. The activities and the swim paths of the rats were recorded by a video recording system. The total distance of swimming, latency, and swimming speed were measured by the Video Tracking System SMART-2000 (San Diego Instruments Inc., San Diego, CA, USA).
Fluoro-Jade C staining
ACA rats were sacrificed after completion of testing at either 7 days (n = 6/group) or 18 days post-resuscitation (n = 6/group), and sham rats (n = 6) were sacrificed on day 18 by deep anesthesia using 5% isoflurane followed by transcardial perfusion with 10% formaline. Brain frozen coronal slices (10 μm) at the level of the hippocampus were sectioned in a cryostat (CM3050S; Leica Microsystems, Buffalo Grove, IL, USA).
Neuronal degeneration was evaluated by Fluoro-Jade C staining kit (Millipore, Temecula, CA, USA) as previously described. Based on the manufacturer’s instructions, slices were incubated in 1% sodium hydroxide solution for 5 minutes, followed by 2-minute rinses with 70% ethanol then distilled water. Subsequently, the slices were incubated in 0.06% potassium permanganate solution for 10 minutes. Following 2-minute rinse in distilled water, the slices were incubated with 0.0001% solution of Fluoro-Jade C which was dissolved in 0.1% acetic acid. Then the slices were rinsed with distilled water 3 times for 1 minute each time. Slides were dried for 5 minutes, and then immersed in xylene for 1 minute, and then a cover slip with DPX (Sigma-Aldrich, St. Louis, MO, USA) was placed. The sections were reviewed using a Leica DMi8 fluorescence microscope (Leica Microsystems, Buffalo Grove, IL, USA). Image J software (ImageJ 1.5, NIH, Bethesda, MD, USA) was used to evaluate the numbers of Fluoro-Jade C positive neurons within CA1 regions (averaged from three fields of views for each rat).
Quantitative data were presented as the mean ± standard error of mean (SEM). SigmaPlot 11.0 (Systat Software, Inc., San Jose, CA, USA) was used for statistical analysis. One-way analysis of variance was applied for multiple comparisons followed by Student-Newman-Keuls post hoc test. A P value less than 0.05 was considered statistically significant.
| Results|| |
All animals survived the pre-ACA surgical procedure. One rat in ACA and one rat in ACA + hydrogen post-treatment groups could not be resuscitated.
Hydrogen treatment does not affect the hemodynamic parameters in rats with asphyxia induced-cardiac arrest
There were no significant differences in baseline and post-resuscitation values of heart rate, mean arterial pressure and end-tidal carbon dioxide among ACA, ACA + hydrogen post-treatment and ACA + hydrogen pre- & post-treatment groups (P > 0.05; data not shown).
Hydrogen treatment improves cognitive function of rats with asphyxia induced-cardiac arrest
At 7 days after resuscitation, the ACA rats had significantly worse performance in T-maze test than shams (P = 0.025). Although there was not statistical difference (hydrogen post-treatment + ACA vs. ACA: P = 0.345; hydrogen pre- & post-treatment +ACA vs. ACA: P = 0.295), both hydrogen gas treatment regimens tended to improve the percentage of spontaneous alternations, suggesting better exploratory behavior and working memory [Figure 1].
|Figure 1: Effect of hydrogen (H2) treatment on the T-maze test of rats with asphyxia induced-cardiac arrest (ACA) at 7 days post-resusciation.|
Note: Rats subjected to ACA had significantly lower rates of spontaneous alteration between the right and left arms than shams. There was a tendency toward improved T-maze performance in ACA rats that received hydrogen gas pre&post-treatment. Data were presented as the mean ± SEM (n = 6/group). *P < 0.05, vs. sham group (one-way analysis of variance followed by Student-Newman-Keuls post hoc test).
Click here to view
Morris water maze
Starting at 14 days after resuscitation, the Morris water maze test showed memory-learning deficits in ACA rats. On the 4th day of testing (18 days after resuscitation), ACA rats had significantly longer total swimming distances than shams (P = 0.012) before reaching the platform placed in the water. In the probe test in which the platform was removed from the southwest quadrant, ACA rats spent significantly lesser time in the southwest quadrant, suggesting spatial memory dysfunction (P = 0.005). Hydrogen treatments significantly shortened the total swimming distance in comparison to ACA rats (P = 0.025, ACA + hydrogen post-treatment vs. ACA; P = 0.01, ACA + hydrogen pre- & post-treatment vs. ACA; [Figure 2]. There was no significant difference in swimming speed among groups, suggesting the comparable motor function (data not shown).
|Figure 2: Effect of hydrogen (H2) treatment on the Morris water maze test of rats with asphyxia induced-cardiac arrest (ACA) starting at 14 days post-resuscitation.|
Note: (A) Swimming distance. There were signficant longer swimming distances in rats subjected to ACA at the 4th day of spatial learning testing. H2 treatment significantly shortened the total swimming distance. (B) Latency. Probe test showed that rats subjected to ACA spent significantly lesser time than shams in the quadrant where the platform was placed during spatial learning testing. This effect was diminished by H2 treatments. Data were presented as the mean ± SEM (n = 6/group). *P < 0.05, vs. sham group; #P < 0.05, vs. ACA group (one-way analysis of variance followed by Student-Newman-Keuls post hoc test).
Click here to view
Hydrogen treatment does increased the neuronal survival in the hippocampal CA1 region of rats with asphyxia
Correlating with the functional outcomes, Fluoro-Jade C staining showed: 1) elevated neuron death at day 7 (P = 0.016, vs. sham group) and day 18 (P = 0.013, vs. sham group) post-resuscitation within hippocampal CA1 regions in animals subjected to ACA; 2) hydrogen gas treatment improved neuronal survival at 7 days, reaching statistical significance at 18 days (P = 0.027, ACA + hydrogen post-treatment vs. ACA; P = 0.016, ACA + hydrogen pre- & post-treatment vs. ACA) after resuscitation [Figure 3].
|Figure 3: Effect of hydrogen (H2) treatment on the neuronal survival in the hippocampal CA1 region of rats with asphyxia induced-cardiac arrest (ACA) at 7 and 14 days (d) post-resusciation.|
Note: (A) In rats subjected to ACA, there were signifcantly greater number of Fluoro-Jade staining positive neurons, suggesting neuronal degeneration. H2 treatment improved neuron survival, which was significant at 14 d post-resuscitation. (B) Quantitative result of Fluoro-Jade staining positive neurons. Data were presented as the mean ± SEM (n = 6/group). *P < 0.05, vs. sham group; #P < 0.05, vs. ACA group (one-way analysis of variance followed by Student-Newman-Keuls post hoc test).
Click here to view
| Discussion|| |
Using a rat model of asphyxia induced-cardiac arrest, we demonstrated that 67% hydrogen gas administered either as pre- & post-treatment or post-treatment resulted in improved spatial learning function, which was associated with better neuronal survival within hippocampal CA1 regions.
Complex pathophysiologic mechanisms underlie global brain injury following cardiac arrest and cardiopulmonary-cerebral resuscitation, in which neuronal apoptosis is one of the important pathologic changes. The hippocampal CA1 region has been shown to be highly vulnerable to hypoxia-ischemia., In the present study, asphyxia induced-cardiac arrest resulted in global brain injury with significant degeneration of neurons within hippocampal CA1 regions at 7 and 18 days post-resuscitation. This neuronal damage was associated with hippocampal dysfunction as detected by T-maze and water maze test. The retired breeder rats used in this study were 8–12 months of age and our findings are consistent to previous report by Cohan et al. In their study, 9-month-old rats demonstrated significant spatial memory impairment and hippocampal CA1 neuron reduction following asphyxia cardiac arrest.
Oxidative stress causes lipid peroxidation and DNA oxidation, contributing to neuronal apoptosis in the setting of ischemia. Low concentration hydrogen gas inhalation at the start of CPR provided similar neuroprotection to therapeutic hypothermia and resulted in additive effects through its unique antioxidant features when applied with hypothermia in a rat model of ventricular fibrillation cardiac arrest., Hydrogen-rich saline also reduced the hippocampal tissue damage induced by global cerebral ischemia/reperfusion via protection of mitochondrial function. In 2016, Cui et al. demonstrated the neuroprotective efficacy of water electrolysis derived 67% hydrogen inhalation in a rat model of focal brain ischemia. Two hours of high concentration hydrogen treatment decreased brain reactive oxygen species levels, neuronal apoptosis and neuroinflammation within the cerebral cortex and hippocampus in the absence of systemic toxicity. In the present study, a modified T-maze used as a quick test of hippocampal function at 7 days after resuscitation showed water-electrolysis 67% hydrogen tended to improve exploratory behavior although this was not statistically significant. The improved functional outcome correlated with a tendency toward increased hippocampal CA1 neuron survival at 7 days post-resuscitation. Over 4 days beginning 14 days after resuscitation, rats treated with 67% hydrogen had significant improvement of hippocampal spatial learning memory as tested by water maze, a comprehensive behavioral test. Significantly less hippocampal CA1 neuron degeneration was associated with this cognitive improvement. Activation of the phosphoinositide 3-kinase/Akt pathway has been shown to play a role in the protective effects of 67% hydrogen gas in a rat model of liver ischemia-reperfusion. Because of the importance phosphoinositide 3-kinase/Akt signaling in neuronal survival, we speculate that a similar mechanism of protection would underlie the hippocampal neuron protection provided by high concentration hydrogen. Nevertheless, molecular hydrogen has been shown to activate a variety of signaling pathways contributing to its neuroprotection.
Human clinical studies of therapeutic hydrogen gas administration have been undertaken in Japan in 2017.,, The feasibility and safety of 2% hydrogen for patients with post cardiac arrest syndrome have been validated in a pilot clinical study. A multicenter randomized trial to confirm the efficacy of low concentration hydrogen gas inhalation on neurological outcomes in comatose survivors of out-of-hospital cardiac arrest is underway. Additionally, 3% hydrogen inhalation administered to patients 1 hour twice a day for 7 days following mild ischemic stroke significantly improved both MRI and neurological outcomes.
If the dose dependent effects of molecular hydrogen therapy that have been demonstrated in animal studies, translate to human neurological outcomes, then water electrolysis would be a safe way to generate high concentration hydrogen gas and would be feasible to use in clinical management of cardiac arrest survivors.
There are several limitations in the study. We only evaluated the cognitive benefits of hydrogen up to 18 days after ACA. Future study is necessary to confirm our finding at longer time points. In this study, we demonstrated cognitive benefits associated with the improved the neuron survival following hydrogen administration after resuscitation from ACA. However, mechanisms of neuroprotective effects potentially provided by high-concentration hydrogen need to be further elucidated.
In conclusion, our study suggests that high concentration hydrogen derived by water electrolysis could be a promising therapeutic strategy to decrease cognitive deficits in the setting of cardiac arrest.
Study performing, and references gathering: LH; study design: RLA, PMA, JHZ; data collection: LG, UO; manuscript conceiving and drafting: LH, JHZ; manuscript revising: RLA, PMA, WB. All authors approved the final version of manscript for publication.
Conflicts of interest
Institutional review board statement
The study was approved by the Animal Health and Safety Committees of Loma Linda University, USA (approval number: IACUC #8170006) on March 2, 2017.
Copyright license agreement
The Copyright License Agreement has been signed by all authors before publication.
Data sharing statement
Datasets analyzed during the current study are available from the corresponding author on reasonable request.
Checked twice by iThenticate.
Externally peer reviewed.
Open access statement
This is an open access journal, and articles are distributed under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike 4.0 License, which allows others to remix, tweak, and build upon the work non-commercially, as long as appropriate credit is given and the new creations are licensed under the identical terms.
| References|| |
Moulaert VR, Verbunt JA, van Heugten CM, Wade DT. Cognitive impairments in survivors of out-of-hospital cardiac arrest: a systematic review. Resuscitation
Horstmann A, Frisch S, Jentzsch RT, Müller K, Villringer A, Schroeter ML. Resuscitating the heart but losing the brain: brain atrophy in the aftermath of cardiac arrest. Neurology
Lim C, Alexander MP, LaFleche G, Schnyer DM, Verfaellie M. The neurological and cognitive sequelae of cardiac arrest. Neurology
Neigh GN, Glasper ER, Kofler J, et al. Cardiac arrest with cardiopulmonary resuscitation reduces dendritic spine density in CA1 pyramidal cells and selectively alters acquisition of spatial memory. Eur J Neurosci
Sugawara T, Kawase M, Lewen A, et al. Effect of hypotension severity on hippocampal CA1 neurons in a rat global ischemia model. Brain Res
Volpe BT, Davis HP, Towle A, Dunlap WP. Loss of hippocampal CA1 pyramidal neurons correlates with memory impairment in rats with ischemic or neurotoxin lesions. Behav Neurosci
Alexander MP, Lafleche G, Schnyer D, Lim C, Verfaellie M. Cognitive and functional outcome after out of hospital cardiac arrest. J Int Neuropsychol Soc
Roine RO, Kajaste S, Kaste M. Neuropsychological sequelae of cardiac arrest. JAMA
Ge P, Zhao J, Li S, Ding Y, Yang F, Luo Y. Inhalation of hydrogen gas attenuates cognitive impairment in transient cerebral ischemia via inhibition of oxidative stress. Neurol Res
Ji Q, Hui K, Zhang L, Sun X, Li W, Duan M. The effect of hydrogen-rich saline on the brain of rats with transient ischemia. J Surg Res
Nagatani K, Wada K, Takeuchi S, et al. Effect of hydrogen gas on the survival rate of mice following global cerebral ischemia. Shock
Tamura T, Hayashida K, Sano M, Onuki S, Suzuki M. Efficacy of inhaled hydrogen on neurological outcome following BRain Ischemia During post-cardiac arrest care (HYBRID II trial): study protocol for a randomized controlled trial. Trials
Bahjat FR, Alexander West G, Kohama SG, et al. Preclinical development of a prophylactic neuroprotective therapy for the preventive treatment of anticipated ischemia-reperfusion injury. Transl Stroke Res
Bell JD, Cho JE, Giffard RG. MicroRNA changes in preconditioning-induced neuroprotection. Transl Stroke Res
Schuhmann MK, Kraft P, Bieber M, et al. Influence of thrombolysis on the safety and efficacy of blocking platelet adhesion or secretory activity in acute ischemic stroke in mice. Transl Stroke Res
Tian J, Guo S, Chen H, et al. Combination of emricasan with ponatinib synergistically reduces ischemia/reperfusion injury in rat brain through simultaneous prevention of apoptosis and necroptosis. Transl Stroke Res
Cui J, Chen X, Zhai X, et al. Inhalation of water electrolysis-derived hydrogen ameliorates cerebral ischemia-reperfusion injury in rats - A possible new hydrogen resource for clinical use. Neuroscience
Wang R, Wu J, Chen Z, Xia F, Sun Q, Liu L. Postconditioning with inhaled hydrogen promotes survival of retinal ganglion cells in a rat model of retinal ischemia/reperfusion injury. Brain Res
Huang L, Applegate RL 2nd
, Applegate PM, Boling W, Zhang JH. Inhalation of high concentration hydrogen gas improves short-term outcomes in a rat model of asphyxia induced-cardiac arrest. Med Gas Res
Guo Z, Hu Q, Xu L, et al. Lipoxin A4 reduces inflammation through formyl peptide receptor 2/p38 MAPK signaling pathway in subarachnoid hemorrhage rats. Stroke
Xie Z, Huang L, Enkhjargal B, et al. Intranasal administration of recombinant Netrin-1 attenuates neuronal apoptosis by activating DCC/APPL-1/AKT signaling pathway after subarachnoid hemorrhage in rats. Neuropharmacology
Reis C, Akyol O, Araujo C, et al. Pathophysiology and the monitoring methods for cardiac arrest associated brain injury. Int J Mol Sci
Cohan CH, Neumann JT, Dave KR, et al. Effect of cardiac arrest on cognitive impairment and hippocampal plasticity in middle-aged rats. PLoS One
Chan PH. Reactive oxygen radicals in signaling and damage in the ischemic brain. J Cereb Blood Flow Metab
Hayashida K, Sano M, Kamimura N, et al. H(2) gas improves functional outcome after cardiac arrest to an extent comparable to therapeutic hypothermia in a rat model. J Am Heart Assoc
Hayashida K, Sano M, Kamimura N, et al. Hydrogen inhalation during normoxic resuscitation improves neurological outcome in a rat model of cardiac arrest independently of targeted temperature management. Circulation
Cui Y, Zhang H, Ji M, et al. Hydrogen-rich saline attenuates neuronal ischemia--reperfusion injury by protecting mitochondrial function in rats. J Surg Res
Li H, Chen O, Ye Z, et al. Inhalation of high concentrations of hydrogen ameliorates liver ischemia/reperfusion injury through A2A receptor mediated PI3K-Akt pathway. Biochem Pharmacol
Zhao H, Sapolsky RM, Steinberg GK. Phosphoinositide-3-kinase/akt survival signal pathways are implicated in neuronal survival after stroke. Mol Neurobiol
Huang L, Nakamura Y, Lo EH, Hayakawa K. Astrocyte signaling in the neurovascular unit after central nervous system injury. Int J Mol Sci
Katsumata Y, Sano F, Abe T, et al. The effects of hydrogen gas inhalation on adverse left ventricular remodeling after percutaneous coronary intervention for ST-elevated myocardial infarction- first pilot study in humans. Circ J
Ono H, Nishijima Y, Ohta S, et al. Hydrogen gas inhalation treatment in acute cerebral infarction: a randomized controlled clinical study on safety and neuroprotection. J Stroke Cerebrovasc Dis
Tamura T, Hayashida K, Sano M, et al. Feasibility and Safety of Hydrogen Gas Inhalation for Post-Cardiac Arrest Syndrome- First-in-Human Pilot Study. Circ J
Chen HG, Xie KL, Han HZ, et al. Heme oxygenase-1 mediates the anti-inflammatory effect of molecular hydrogen in LPS-stimulated RAW 264.7 macrophages. Int J Surg
Ohsawa I, Ishikawa M, Takahashi K, et al. Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med
[Figure 1], [Figure 2], [Figure 3]