Hydrogen inhibits microglial activation and regulates microglial phenotype in a mouse middle cerebral artery occlusion model

Molecular Hydrogen: Emerging Treatment for Stroke Management

Ischemic stroke is a major cause of death and disability worldwide. However, only intravenous thrombolysis using mechanical thrombectomy or tissue plasminogen activator is considered an effective and approved treatment. Molecular hydrogen is an emerging therapeutic agent and has recently become a research focus. Molecular hydrogen is involved in antioxidative, anti-inflammatory, and antiapoptotic functions in normal physical processes and may play an important role in stroke management; it has been evaluated in numerous preclinical and clinical studies in several administration formats, including inhalation of hydrogen gas, intravenous or intraperitoneal injection of hydrogen-enriched solution, or drinking of hydrogen-enriched water. In addition to investigation of the underlying mechanisms, the safety and efficacy of using molecular hydrogen have been carefully evaluated, and favorable outcomes have been achieved. All available evidence indicates that molecular hydrogen may be a promising treatment option for stroke management in the future. This review aimed to provide an overview of the role of molecular hydrogen in the management of stroke and possible further modifications of treatment conditions and procedures in terms of dose, duration, and administration route.

Molecular Hydrogen: an Emerging Therapeutic Medical Gas for Brain Disorders

Oxidative stress and neuroinflammation are the main physiopathological changes involved in the initiation and progression of various neurodegenerative disorders or brain injuries. Since the landmark finding reported in 2007 found that hydrogen reduced the levels of peroxynitrite anions and hydroxyl free radicals in ischemic stroke, molecular hydrogen's antioxidative and anti-inflammatory effects have aroused widespread interest. Due to its excellent antioxidant and anti-inflammatory properties, hydrogen therapy via different routes of administration exhibits great therapeutic potential for a wide range of brain disorders, including Alzheimer's disease, neonatal hypoxic-ischemic encephalopathy, depression, anxiety, traumatic brain injury, ischemic stroke, Parkinson's disease, and multiple sclerosis. This paper reviews the routes for hydrogen administration, the effects of hydrogen on the previously mentioned brain disorders, and the primary mechanism underlying hydrogen's neuroprotection. Finally, we discuss hydrogen therapy's remaining issues and challenges in brain disorders. We conclude that understanding the exact molecular target, finding novel routes, and determining the optimal dosage for hydrogen administration is critical for future studies and applications.

Drinking hydrogen water improves photoreceptor structure and function in retinal degeneration 6 mice

Retinitis pigmentosa (RP) is a genetically heterogeneous group of inherited retinal disorders involving the progressive dysfunction of photoreceptors and the retinal pigment epithelium, for which there is currently no treatment. The rd6 mouse is a natural model of autosomal recessive retinal degeneration. Given the known contributions of oxidative stress caused by reactive oxygen species (ROS) and selective inhibition of potent ROS peroxynitrite and OH·by H₂ gas we have previously demonstrated, we hypothesized that ingestion of H₂ water may delay the progression of photoreceptor death in rd6 mice. H₂ mice showed significantly higher retinal thickness as compared to controls on optical coherence tomography. Histopathological and morphometric analyses revealed higher thickness of the outer nuclear layer for H₂ mice than controls, as well as higher counts of opsin red/green-positive cells. RNA sequencing (RNA-seq) analysis of differentially expressed genes in the H₂ group versus control group revealed 1996 genes with significantly different expressions. Gene and pathway ontology analysis showed substantial upregulation of genes responsible for phototransduction in H₂ mice. Our results show that drinking water high in H₂ (1.2-1.6 ppm) had neuroprotective effects and inhibited photoreceptor death in mice, and suggest the potential of H₂ for the treatment of RP.

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

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

Perioperative stroke: A perspective on challenges and opportunities for experimental treatment and diagnostic strategies

Perioperative stroke is an ischemic or hemorrhagic cerebral event during or up to 30 days after surgery. It is a feared condition due to a relatively high incidence, difficulties in timely detection, and unfavorable outcome compared to spontaneously occurring stroke. Recent preclinical data suggest that specific pathophysiological mechanisms such as aggravated neuroinflammation contribute to the detrimental impact of perioperative stroke. Conventional treatment options are limited in the perioperative setting due to difficult diagnosis and medications affecting coagulation in may cases. On the contrary, the chance to anticipate cerebrovascular events at the time of surgery may pave the way for prevention strategies. This review provides an overview on perioperative stroke incidence, related problems, and underlying pathophysiological mechanisms. Based on this analysis, we assess experimental stroke treatments including neuroprotective approaches, cell therapies, and conditioning medicine strategies regarding their potential use in perioperative stroke. Interestingly, the specific aspects of perioperative stroke might enable a more effective application of experimental treatment strategies such as classical neuroprotection whereas others including cell therapies may be of limited use. We also discuss experimental diagnostic options for perioperative stroke augmenting classical clinical and imaging stroke diagnosis. While some experimental stroke treatments may have specific advantages in perioperative stroke, the paucity of established guidelines or multicenter clinical research initiatives currently limits their thorough investigation.

Safety of Prolonged Inhalation of Hydrogen Gas in Air in Healthy Adults

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Ischemia-reperfusion injury is common in critically ill patients, and directed therapies are lacking. Inhaled hydrogen gas diminishes ischemia-reperfusion injury in models of shock, stroke, and cardiac arrest. The purpose of this study was to investigate the safety of inhaled hydrogen gas at doses required for a clinical efficacy study.

Xiao-Xu-Ming decoction prevented hemorrhagic transformation induced by acute hyperglycemia through inhibiting AGE-RAGE-mediated neuroinflammation

Stroke is one of the leading causes of death worldwide. Hemorrhagic transformation (HT) is a common serious complication of ischemic stroke (IS) and is related to poor prognosis. Hyperglycemia after stroke is associated with the occurrence of HT and seriously affects the clinical treatment of stroke. Our previous experiments demonstrated that the Xiao-Xu-Ming decoction effective components group (XXMD), which is a Chinese medicine formula reconstituted by active ingredients, has multiple pharmacological effects in the treatment of IS. However, the effects of XXMD on HT after IS remain unclear. Thus, we investigated the preventive effects of XXMD on hyperglycemia-induced HT and further explored the underlying mechanism. Acute hyperglycemia combined with the electrocoagulation cerebral ischemia model was used to establish the HT model. XXMD (37.5, 75, 150 mg/kg/d) was given by gavage for 5 days. Network pharmacology was used to predict potential targets and pathways of XXMD in HT occurrence, and further studies confirmed the related targets. The results showed that hyperglycemia aggravated neurological deficits and blood-brain barrier (BBB) disruption, leading to intracerebral hemorrhage. Pretreatment with XXMD improved neurological function and BBB integrity and inhibited HT occurrence. Network pharmacology revealed that AGE-RAGE-mediated neuroinflammation may be associated with hyperglycemia-induced HT. Further studies confirmed that hyperglycemia activated the AGE-RAGE signaling pathway, increased the expression of HMGB1, TLR4 and p-p65, and induced the release of inflammatory factors and neutrophil infiltration, leading to HT. XXMD could inhibit AGE-RAGE-mediated neuroinflammation. These findings indicated that pretreatment with XXMD alleviated hyperglycemia-induced HT, which may be associated with the inhibition of AGE-RAGE-mediated neuroinflammation. Therefore, XXMD may be a potential therapeutic drug for HT.

Molecular Hydrogen Application in Stroke: Bench to Bedside

Stroke is a major cause of mortality and morbidity worldwide. Effective treatments are limited. Molecular hydrogen is emerging as a novel medical gas with therapeutic potential for various neurological diseases, including stroke. We reviewed the experimental and clinical findings of the effects of molecular hydrogen therapy in stroke patients and models. The underlying neuroprotective mechanisms against stroke pathology were also discussed.

Neuroprotective Effects of Molecular Hydrogen: A Critical Review

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