Potential application of hydrogen in traumatic and surgical brain injury, stroke and neonatal hypoxia-ischemia
© Eckermann et al; licensee BioMed Central Ltd. 2012
Received: 3 January 2012
Accepted: 19 April 2012
Published: 19 April 2012
This article summarized findings of current preclinical studies that implemented hydrogen administration, either in the gas or liquid form, as treatment application for neurological disorders including traumatic brain injury (TBI), surgically induced brain injury (SBI), stroke, and neonatal hypoxic-ischemic brain insult (HI). Most reviewed studies demonstrated neuroprotective effects of hydrogen administration. Even though anti-oxidative potentials have been reported in several studies, further neuroprotective mechanisms of hydrogen therapy remain to be elucidated. Hydrogen may serve as an adjunct treatment for neurological disorders.
KeywordsHydrogen Neuroprotection Oxidative stress Reactive oxygen species
Traumatic brain injury (TBI) and cerebral vascular events can be devastating; yet there are few treatments proven to ameliorate the brain damage and overall outcome in patients. An ideal neuroprotectant would be non-toxic, easily administered, permeable at the blood-brain barrier (BBB), and offer protection at all stages of injury, including prophylaxis. Hydrogen sulfide (H2S) has shown some of these properties [1, 2]. Its mechanisms may be related to the attenuation of reactive oxygen species (ROS) , or to its role as a neuromodulator ; however, the use of H2S is controversial because of its toxicity  and gasotransmitter functions .
Hydrogen is the most abundant element in the universe . Room air concentrations of hydrogen gas higher than 4% (normal air content = 0.000055%) are explosive, and could cause asphyxiation . Therapeutically relevant dosages of hydrogen, as used in the following animal studies (range 2%-2.9%), appear to be well tolerated. Furthermore, 3% hydrogen gas has been safely and regularly used for human deep-sea divers without any adverse events .
Currently, to our knowledge, there are no FDA approved therapeutic regimens involving hydrogen gas or dissolved hydrogen. We sought to analyze recent available data regarding the use of hydrogen as a neuroprotectant.
Hydrogen therapy for traumatic brain injury and cerebral vascular events
Traumatic brain injury
Trauma is the leading cause of death in Americans younger than 45 years of age, and traumatic brain injury (TBI) accounts for over 50% of this mortality . Out of the 1.5 million Americans who sustain a TBI each year, 230,000 are hospitalized, 80,000 to 90,000 remain with long-term disabilities, 50,000 die, and the estimated annual cost exceeds $60 billion [11–13]. To investigate whether hydrogen (H2) exerts abilities to ameliorate the outcome after TBI, Ji et al. administered 2% H2 to rats, which were also subjected to experimental TBI . TBI-challenged rats, that did not inhale H2, presented with significantly greater brain edema, blood-brain barrier (BBB) permeability, lesion size, and neurological impairments, than those in the treatment group. Decreased levels of oxidative products such as malondialdehyde (MDA) and 8-iso-prostaglandin F2α (8-iso-PF2α), were decreased in brain tissues of treated animals, suggesting that H2 induces neuroprotection by reducing oxidative stress to the BBB.
Surgical brain injury
Each year, approximately 800,000 patients undergo neurosurgical procedures in the United States . This figure encompasses emergent as well as planned procedures. Neurosurgical operations have the potential to cause unavoidable damage to healthy brain tissue through application of pressure, tissue stretching, hemorrhage, and the use of electrocautery . This form of brain injury occurs regularly, despite of intraoperative adjunct treatments such as administration of steroids and mannitol in both emergent or scheduled procedures . Even standard microsurgical techniques have the ability to cause damage to the surrounding brain tissue, thus leading to early complications such as edema formation and local ischemia.
To determine the effects of hydrogen treatment following surgically-induced brain injury (SBI), Eckermann et al. utilized a novel rat model that involved a partial right frontal lobectomy . The following groups were compared: rats subjected to sham operation (craniotomy), SBI animals that received 2.9% hydrogen, which was administered concurrently with surgery for a period of 0.5 hours, and a control group (SBI + room air). Brain water content and neurological deficits were measured at 24 hours after SBI. The results demonstrated that hydrogen treatment significantly decreased the formation of cerebral edema, which resulted in improved neurobehavioral function; however, the treatment failed to reduce oxidative stress and cerebral inflammation (evaluated via Lipid Peroxidase and Myeloperoxidase assays, respectively) in rats subjected to SBI.
Stroke is a leading cause of death and long-term disability, particularly in the elderly population . It is associated with a 30-day mortality rate of approximately 20% . The prevalence of stroke is expected to increase significantly as the global population of men and women - older than 65 years of age - increases continuously by an estimated 9 million people per year . Consequently, it is most essential to investigate novel and potentially effective therapeutics to improve the neurofunctional outcome in patients. The effects of hydrogen treatment for ischemic stroke have been evaluated in an experimental rodent model of transient middle cerebral artery occlusion (tMCAO) . This model exerts its damaging effect through focal ischemia and reperfusion, which generates acute oxidative stress to the affected brain regions. Under general anesthesia the rat's left middle cerebral artery (MCA) was occluded using a nylon monofilament with a distal silicon rubber tip. The treatment group inhaled 2% hydrogen gas during the entire procedure. Treated and control animals underwent neurological testing, and were sacrificed at 12 hours, 24 hours, 3 days, and 7 days post-surgery. Brains were then sectioned and stained with 2,3,5-triphenyltetrazolium chloride (TTC) to label the infarcted brain area, followed by volumetric computation of the infarct volume. Observed protective effects of hydrogen therapy included: decreased infarct volume, maintenance of body weight after surgery, and improved neurological function when compared to control animals. Liu et al.  utilized the tMCAO model to evaluate neuroprotective effects of intraperitoneally administered hydrogen saline (1 ml/100 g body weight). The results showed that hydrogen saline significantly reduced infarct volume, brain edema, and neurological function when administered within a 6 hour time window after ischemia induction. Hydrogen saline reduced ROS, inflammation markers, as well as caspase 3 activity in the ischemic brain . Matchett et al. administered hydrogen gas (2.9%) to adult rats that were subjected to tMCAO . Hydrogen administration showed a tendency to reduce the infarction volume in the treatment group, when compared to control animals; however, neurological deficits were similar in both groups. Furthermore, Chen et al.  reported that hydrogen gas effectively reduced acute hyperglycemia-enhanced hemorrhagic transformation after focal ischemia in the rat. Potential mechanisms on how hydrogen gas ameliorates hemorrhagic transformation remain to be investigated.
Oshawa et al. demonstrated that hydrogen selectively reduced ROS in neuronal tissue cultures . The effects were demonstrated via electron spin resonance signals in cells subjected to oxygen glucose deprivation followed by oxygen glucose reperfusion, which models cerebral ischemia-reperfusion in vitro . After reperfusion, fluoroscopy demonstrated an immediate decrease in hydroxyl radicals (OH-), and an increase in neuronal survival at 24 hours, suggesting that hydrogen effectively protects neurons from oxidative stress-mediated cell death.
Hemorrhagic stroke is often more severe than ischemic stroke, and includes intracerebral hemorrhages (ICH) and subarachnoid hemorrhages (SAH). The mortality rates for ICH and SAH have been reported as 40% to 50%, and survivors are commonly affected by chronic morbidity . Furthermore, the aggregate lifetime cost of hemorrhagic stroke cases has been estimated as high as $5.6 to $6.0 billion per year . The effects of hydrogen administration in hemorrhagic stroke models have been previously reported. In a mouse model that implemented collagenase-induced ICH, hydrogen therapy was found to significantly reduce cerebral edema and neurological deficits at 24 hours after surgery; however, hydrogen post-treatment showed only a tendency to improve these outcomes at 72 hours after surgery . The authors conclude that hydrogen inhalation exerts an acute neuroprotective effect in mice subjected to experimental ICH. Similarly to these results, hydrogen treatment (2.9% for 2 hours) starting 1 hour after induction of experimental SAH (endovascular perforation method), ameliorated brain edema, reduced apoptosis, and improved neurological deficits at 24 hours, but not at 72 hours after surgery . The protective effects of hydrogen therapy were associated with the reduction of oxidative injury of lipids, proteins, and DNA.
Advances in perinatal care and neonatology led to increased survival of premature infants , yet the incidence of brain injury caused by neonatal hypoxia-ischemia (HI) remains high . Effective therapeutic modalities are limited for the treatment of HI. This form of CNS injury occurs at a very early stage in life. It is accompanied by a heavy toll on families and significant long-term healthcare demands. Since neonates have an immature free radical buffering system, they are believed to be more vulnerable to ROS damage.
Hydrogen treatment was associated with improved outcomes in a model of neonatal hypoxia/ischemia [31, 32]. Cai et al.  subjected seven-day old rat pups to left common carotid artery ligation followed by 90 minutes of hypoxia. Immediately after the HI injury the pups were placed in chambers containing 2% hydrogen for 30, 60, and 120 minutes. Twenty-four hours following hydrogen therapy, the animals were sacrificed and the brain damage was assessed with TTC and Nissl staining, TUNEL, and evaluation of caspase activity. Hydrogen therapy significantly reduced the number of TUNEL positive cells, and attenuated caspase activity, suggesting that hydrogen gas exerts neuroprotective effects by inhibiting cellular apoptosis after HI. However, in another study of HI, hydrogen treatment failed to show neuroprotective effects, possibly as a result of the severity of the injury . The authors concluded that hydrogen gas may have a neuroprotective effect against mild to moderate HI, but loses that effect in cases of severe HI injury.
Animal studies examining neuroprotection by hydrogen
Effects of H2
Ji et al. 
Brain edema↓, neurological deficits↓
H2 increased endogenous antioxidant enzymatic activities
Eckermann et al. 
Brain edema↓, neurological deficits↓
Ohsawa et al 
Brain infarction↓, neurological deficits↓
H2 selectively inhibited OH-
Matchett et al. 
Tendentially reduced brain infarction
Chen et al. 
H2 reduced hyperglycemia
Liu et al. 
Brain edema↓, infarction↓, neurological deficits↓
ROS↓, inflammation↓, apoptosis↓
Manaenko et al. 
Acute brain edema↓, neurological deficits↓
Zhan et al. 
Acute brain edema↓, neurological deficits↓
BBB permeability↓, ROS↓, apoptosis↓
Matchet et al. 
No beneficial effects
Cai et al. 
Brain infarction↓, apoptosis↓
H2 selectively inhibited caspase activity
A recent clinical study by Ono et al.  showed that acute treatment with OH- scavengers (Edaravone and hydrogen) improved MRI indices (accelerated normalization) in patients with brainstem infarction. In fact, intravenous injection of Edaravone combined with hydrogen saline showed significantly better results than administration of Edaravone alone. The effects of hydrogen have also been examined in a randomized, double-blinded, placebo-controlled crossover study implemented in patients with diabetes mellitus type 2 . Patients that received 900 ml/day of hydrogen-rich water for 8 weeks showed significant improvements of LDL cholesterol and urinary 8-isoprostanes. Further protective effects of hydrogen therapy were found in patients with mitochondrial myopathies, polymyositis and dermatomyositis .
Importantly, it needs to be determined if hydrogen treatment alters normal metabolism, since several agents classified as ROS, such as nitric oxide (NO), have important cell signaling functions and are regulators of physiologic responses . It is crucial that the administered antioxidant does not disturb these normal cell-signaling pathways. Hydrogen may also function by preventing break-down of the BBB. The most prominent and consistent effect is the reduction of cerebral edema and the improvement of neurological function post-injury. Hydrogen has several advantages as a potential antioxidant: it effectively reduces cytotoxic OH- in vivo, and demonstrates excellent penetration characteristics. Its ability to enter biomembranes and diffuse into mitochondria and cell nuclei render it highly effective as a powerful antioxidant .
Taken together, hydrogen appears to be a safe therapeutic with the ability to attenuate ROS production after diverse CNS injuries. Furthermore, hydrogen effectively reduced neuronal apoptosis and hemorrhagic transformation after ischemic brain injury. Its ease of use and availability will facilitate clinical transition in the near future; however, further mechanisms of neuroprotection need to be primarily investigated.
Blood brain barrier
Reactive oxygen species
Middle cerebral artery
Traumatic brain injury
Transient middle cerebral artery occlusion
- Tan BH, Wong PT, Bian JS: Hydrogen sulfide: a novel signaling molecule in the central nervous system. Neurochem Int. 2010, 56 (1): 3-10. 10.1016/j.neuint.2009.08.008.PubMed
- Qu K, et al: Hydrogen sulfide is a mediator of cerebral ischemic damage. Stroke. 2006, 37 (3): 889-893. 10.1161/01.STR.0000204184.34946.41.PubMed
- Lowicka E, Beltowski J: Hydrogen sulfide (H2S) - the third gas of interest for pharmacologists. Pharmacol Rep. 2007, 59 (1): 4-24.PubMed
- Kimura H: Hydrogen sulfide as a neuromodulator. Mol Neurobiol. 2002, 26 (1): 13-19. 10.1385/MN:26:1:013.PubMed
- Guidotti TL: Hydrogen sulfide: advances in understanding human toxicity. Int J Toxicol. 2010, 29 (6): 569-581. 10.1177/1091581810384882.PubMed
- Szabo C: Gaseotransmitters: new frontiers for translational science. Sci Transl Med. 2010, 2 (59): p. 59-ps54.
- Huang CS, et al: Recent advances in hydrogen research as a therapeutic medical gas. Free Radic Res. 2010, 44 (9): 971-982. 10.3109/10715762.2010.500328.PubMed
- Yang Z, et al: Extrinsic Fabry-Perot interferometric optical fiber hydrogen detection system. Appl Opt. 2010, 49 (15): 2736-2740. 10.1364/AO.49.002736.PubMed
- Gardette B, Delauze HG: Techniques of underwater intervention: means, methods, research and outlook. Bull Acad Natl Med. 1996, 180 (5): 975-983.PubMed
- Dutton RP, et al: Trauma mortality in mature trauma systems: are we doing better? An analysis of trauma mortality patterns, 1997-2008. J Trauma. 2010, 69 (3): 620-626. 10.1097/TA.0b013e3181bbfe2a.PubMed
- Thurman DJ, et al: Traumatic brain injury in the United States: A public health perspective. J Head Trauma Rehabil. 1999, 14 (6): 602-615. 10.1097/00001199-199912000-00009.PubMed
- Langlois JA, Rutland-Brown W, Wald MM: The epidemiology and impact of traumatic brain injury: a brief overview. J Head Trauma Rehabil. 2006, 21 (5): 375-378. 10.1097/00001199-200609000-00001.PubMed
- Langlois JA, et al: Traumatic brain injury-related hospital discharges. Results from a 14-state surveillance system, 1997. MMWR Surveill Summ. 2003, 52 (4): 1-20.PubMed
- Ji X, et al: Beneficial effects of hydrogen gas in a rat model of traumatic brain injury via reducing oxidative stress. Brain Res. 2010, 1354: 196-205.PubMed
- Etzioni DA, et al: The aging population and its impact on the surgery workforce. Ann Surg. 2003, 238 (2): 170-177.PubMed CentralPubMed
- Elliott-Lewis EW, Mason AM, Barrow DL: Evaluation of a new bipolar coagulation forceps in a thermal damage assessment. Neurosurgery. 2009, 65 (6): 1182-1187. 10.1227/01.NEU.0000356985.27936.93. discussion 1187PubMed
- Jadhav V, Zhang JH: Surgical brain injury: prevention is better than cure. Front Biosci. 2008, 13: 3793-3797.PubMed
- Eckermann JM, et al: Hydrogen is neuroprotective against surgically induced brain injury. Med Gas Res. 2011, 1 (1): 7-10.1186/2045-9912-1-7.PubMed CentralPubMed
- Tegos TJ, et al: Stroke: epidemiology, clinical picture, and risk factors-Part I of III. Angiology. 2000, 51 (10): 793-808. 10.1177/000331970005101001.PubMed
- Mukherjee D, Patil CG: Epidemiology and the global burden of stroke. World Neurosurg. 2011, 76 (6 Suppl): S85-S90.PubMed
- Ohsawa I, et al: Hydrogen acts as a therapeutic antioxidant by selectively reducing cytotoxic oxygen radicals. Nat Med. 2007, 13 (6): 688-694. 10.1038/nm1577.PubMed
- Liu Y, et al: Hydrogen saline offers neuroprotection by reducing oxidative stress in a focal cerebral ischemia-reperfusion rat model. Med Gas Res. 2011, 1 (1): 15-10.1186/2045-9912-1-15.PubMed CentralPubMed
- Matchett GA, et al: Hydrogen gas is ineffective in moderate and severe neonatal hypoxia-ischemia rat models. Brain Res. 2009, 1259: 90-97.PubMed
- Chen CH, et al: Hydrogen gas reduced acute hyperglycemia-enhanced hemorrhagic transformation in a focal ischemia rat model. Neuroscience. 2010, 169 (1): 402-414. 10.1016/j.neuroscience.2010.04.043.PubMed CentralPubMed
- Woo D, et al: Effect of untreated hypertension on hemorrhagic stroke. Stroke. 2004, 35 (7): 1703-1708. 10.1161/01.STR.0000130855.70683.c8.PubMed
- Taylor TN, et al: Lifetime cost of stroke in the United States. Stroke. 1996, 27 (9): 1459-1466. 10.1161/01.STR.27.9.1459.PubMed
- Manaenko A, et al: Hydrogen inhalation is neuroprotective and improves functional outcomes in mice after intracerebral hemorrhage. Acta neurochirurgica Supplement. 2011, 111: 179-183. 10.1007/978-3-7091-0693-8_30.PubMed CentralPubMed
- Zhan Y, et al: Hydrogen gas ameliorates oxidative stress in early brain injury after subarachnoid hemorrhage in rats. Crit Care Med. 2012, 40 (4): 1291-1296. 10.1097/CCM.0b013e31823da96d.PubMed CentralPubMed
- Smith LK, et al: Nature of socioeconomic inequalities in neonatal mortality: population based study. BMJ. 2010, 341: c6654-10.1136/bmj.c6654.PubMed CentralPubMed
- Lawrence RK, Inder TE: Anatomic changes and imaging in assessing brain injury in the term infant. Clin Perinatol. 2008, 35 (4): 679-693. 10.1016/j.clp.2008.07.013.PubMed CentralPubMed
- Cai J, et al: Hydrogen therapy reduces apoptosis in neonatal hypoxia-ischemia rat model. Neurosci Lett. 2008, 441 (2): 167-172. 10.1016/j.neulet.2008.05.077.PubMed
- Cai J, et al: Neuroprotective effects of hydrogen saline in neonatal hypoxia-ischemia rat model. Brain Res. 2009, 1256: 129-137.PubMed
- Laskowitz DT, Kolls BJ: Neuroprotection in subarachnoid hemorrhage. Stroke. 2010, 41 (10 Suppl): S79-S84.PubMed CentralPubMed
- Kellner CP, Connolly ES: Neuroprotective strategies for intracerebral hemorrhage: trials and translation. Stroke. 2010, 41 (10 Suppl): S99-S102.PubMed
- Ono H, et al: Improved brain MRI indices in the acute brain stem infarct sites treated with hydroxyl radical scavengers, Edaravone and hydrogen, as compared to Edaravone alone. A non-controlled study. Med Gas Res. 2011, 1 (1): 12-10.1186/2045-9912-1-12.PubMed CentralPubMed
- Kajiyama S, et al: Supplementation of hydrogen-rich water improves lipid and glucose metabolism in patients with type 2 diabetes or impaired glucose tolerance. Nutr Res. 2008, 28 (3): 137-143. 10.1016/j.nutres.2008.01.008.PubMed
- Ito M, et al: Open-label trial and randomized, double-blind, placebo-controlled, crossover trial of hydrogen-enriched water for mitochondrial and inflammatory myopathies. Med Gas Res. 2011, 1 (1): 24-10.1186/2045-9912-1-24.PubMed CentralPubMed
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