Daily inhalation of hydrogen gas has a blood pressure-lowering effect in a rat model of hypertension

Degradation products of magnesium implant synergistically enhance bone regeneration: Unraveling the roles of hydrogen gas and alkaline environment

Biodegradable magnesium (Mg) implant generally provides temporary fracture fixation and facilitates bone regeneration. However, the exact effects of generated Mg ions (Mg2+), hydrogen gas (H2), and hydroxide ions (OH-) by Mg degradation on enhancing fracture healing are not fully understood. Here we investigate the in vivo degradation of Mg intramedullary nail (Mg-IMN), revealing the generation of these degradation products around the fracture site during early stages. Bulk-RNA seq indicates that H2 and alkaline pH increase periosteal cell proliferation, while Mg2+ may mainly enhance extracellular matrix formation and cell adhesion in the femur ex vivo. In vivo studies further reveal that H2, Mg2+ and alkaline pH individually generate comparable effects to the enhanced bone regeneration in the Mg-IMN group. Mechanistically, the degradation products elevate sensory calcitonin gene-related peptide (CGRP) and simultaneously suppress adrenergic factors in newly formed bone. H2 and Mg2+, instead of alkaline pH, increase CGRP synthesis and inhibit adrenergic receptors. Our findings, for the first time, elucidate that Mg2+, H2, and alkaline pH environment generated by Mg-IMN act distinctly and synergistically mediated by the skeletal interoceptive regulation to accelerate bone regeneration. These findings may advance the understanding on biological functions of Mg-IMN in fracture repair and even other bone disorders.

Effectiveness and safety of hydrogen inhalation therapy as an additional treatment for hypertension in real-world practice: a retrospective, observational study in China

Aim

To evaluate the real-life effectiveness and safety of hydrogen inhalation (HI) therapy as an additional treatment in Chinese adults with hypertension.

Methods

This observational, retrospective clinical study included hypertensive patients receiving routine antihypertensives with or without HI initiation from 2018 to 2023. Participants were assigned to the HI group or non-HI group (control group) after propensity score matching. The changes in mean systolic blood pressure (SBP) level during the 24-week follow-up period in different groups were examined primarily. The secondary outcome was the changes in diastolic blood pressure (DBP) and blood pressure (BP) control rate during the study. Several subgroup and sensitivity analyses were performed to confirm the robustness of our main findings. Adverse event (AE) was also assessed in patients of both groups.

Results

In total, we selected 2,364 patients into the analysis. Both mean SBP and DBP levels significantly decreased in the HI group compared to control group at each follow-up visit with the between group difference of -4.63 mm Hg (95% CI, -6.51 to -2.74) at week 8, -6.69 mm Hg (95% CI, -8.54 to -4.85) at week 16, -7.81 mm Hg (95% CI, -9.57 to -6.04) at week 24 for SBP, and -1.83 mm Hg (95% CI, -3.21 to -0.45) at week 8, -2.57 mm Hg (95% CI, -3.97 to -1.17) at week 16, -2.89 mm Hg (95% CI, -4.24 to -1.54) at week 24 for DBP. Patients in the HI group were more likely to attain controlled BP at the follow-up period with odds ratio of 1.44 (95% CI, 1.21-1.72) at week 8, 1.90 (95% CI, 1.59-2.27) at week 16, and 2.24 (95% CI, 1.87-2.68) at the end. The trends of subgroup and sensitivity analyses were mostly consistent with the main analysis. The incidences of AEs were similar between the HI group and control group with all p-value >0.05.

Conclusion

The HI therapy is related to significant amelioration in BP levels with acceptable safety profile in Chinese hypertensive adults after 24 weeks of treatment, building a clinical ground for further research to evaluate the antihypertensive effect of HI therapy.

Combination of Hydrogen Inhalation and Hypothermic Temperature Control After Out-of-Hospital Cardiac Arrest: A Post hoc Analysis of the Efficacy of Inhaled Hydrogen on Neurologic Outcome Following Brain Ischemia During PostCardiac Arrest Care II Trial

OBJECTIVE

The Efficacy of Inhaled Hydrogen on Neurologic Outcome Following Brain Ischemia During Post-Cardiac Arrest Care (HYBRID) II trial (jRCTs031180352) suggested that hydrogen inhalation may reduce post-cardiac arrest brain injury (PCABI). However, the combination of hypothermic target temperature management (TTM) and hydrogen inhalation on outcomes is unclear. The aim of this study was to investigate the combined effect of hydrogen inhalation and hypothermic TTM on outcomes after out-of-hospital cardiac arrest (OHCA).

DESIGN

Post hoc analysis of a multicenter, randomized, controlled trial.

SETTING

Fifteen Japanese ICUs.

PATIENTS

Cardiogenic OHCA enrolled in the HYBRID II trial.

INTERVENTIONS

Hydrogen mixed oxygen (hydrogen group) versus oxygen alone (control group).

MEASUREMENTS AND MAIN RESULTS

TTM was performed at a target temperature of 32-34°C (TTM32-TTM34) or 35-36°C (TTM35-TTM36) per the institutional protocol. The association between hydrogen + TTM32-TTM34 and 90-day good neurologic outcomes was analyzed using generalized estimating equations. The 90-day survival was compared between the hydrogen and control groups under TTM32-TTM34 and TTM35-TTM36, respectively. The analysis included 72 patients (hydrogen [ n = 39] and control [ n = 33] groups) with outcome data. TTM32-TTM34 was implemented in 25 (64%) and 24 (73%) patients in the hydrogen and control groups, respectively ( p = 0.46). Under TTM32-TTM34, 17 (68%) and 9 (38%) patients achieved good neurologic outcomes in the hydrogen and control groups, respectively (relative risk: 1.81 [95% CI, 1.05-3.66], p < 0.05). Hydrogen + TTM32-TTM34 was independently associated with good neurologic outcomes (adjusted odds ratio 16.10 [95% CI, 1.88-138.17], p = 0.01). However, hydrogen + TTM32-TTM34 did not improve survival compared with TTM32-TTM34 alone (adjusted hazard ratio: 0.22 [95% CI, 0.05-1.06], p = 0.06).

CONCLUSIONS

Hydrogen + TTM32-TTM34 was associated with improved neurologic outcomes after cardiogenic OHCA compared with TTM32-TTM34 monotherapy. Hydrogen inhalation is a promising treatment option for reducing PCABI when combined with TTM32-TTM34.

Using oral molecular hydrogen supplements to combat microinflammation in humans: a pilot observational study

Background: Persistent inflammation over time can cause gradual harm to the body. Molecular hydrogen has the potential to specifically counteract reactive oxygen species (ROS), reduce disease severity, and enhance overall health. Investigations of the anti-inflammatory and antioxidant properties of oral solid hydrogen capsules (OSHCs) are currently limited, prompting our examination of the beneficial effects of OSHCs. Subsequently, we conducted a clinical study to assess the impact of OSHCs supplementation on individuals with chronic inflammation. Materials and methods: Initially, we evaluated the oxidative reduction potential (ORP) properties of the OSHCs solution by comparing it to hydrogen-rich water (HRW) and calcium hydride (CaH2) treated water. In our outpatient department, stable patients with chronic illnesses who were treated with varying doses of OSHCs were randomized into low-, medium-, and high-dose groups for 4 weeks. Primary outcomes included changes in the serum erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) concentrations after four weeks of OSHCs consumption. Secondary outcomes included changes in the Brief Fatigue Inventory-Taiwan (BFI-T) fatigue scale, Control Status Scale for Diabetes (CSSD70) scores, and Disease Activity Score 28 (DAS28). Results: Compared to HRW and CaH2, OSHCs demonstrated a prolonged reduction in ORP for 60 minutes in vitro and enabled a regulated release of hydrogen over 24 hours. A total of 30 participants, with 10 in each dosage (low/medium/high) group, completed the study. The average ESR120 significantly decreased from the first week to the fourth week, with a noticeable dose effect (low-dose group, p = 0.494; high-dose group, p = 0.016). Overall, the average CRP concentration showed a distinct decreasing trend after four weeks of OSHCs administration (w0 vs. w4, p = 0.077). The average DAS28 score demonstrated a significant decrease following OSHCs treatment. Furthermore, there were improvements in the BFI-T and CSSD70 scores. Conclusion: OSHCs supplementation may exert anti-inflammatory and antioxidant effects on individuals with chronic inflammation. However, further clinical studies could be investigated to explore the potential therapeutic effects of OSHCs.

Protective Effects of Hydrogen Gas Inhalation for Hindlimb Ischaemia-Reperfusion Injury in a Mouse Model

OBJECTIVE

Ischaemia-reperfusion (I/R) injury is a severe post-operative complication that triggers an inflammatory response and causes severe damage. Hydrogen gas has anti-oxidant and anti-apoptotic properties and has been shown to be safe in humans. The study aimed to investigate whether hydrogen gas protects against skeletal muscle I/R injury.

METHODS

Experimental basic research using mice. A total of 160 eight to 10 week old albino laboratory bred strain of house mice (25.8 ± 0.68 g) were used in this study. The mice were cable tied to the hindlimb under anaesthesia and then placed in an anaesthesia box filled with air and 2% isoflurane (control group); 80 mice were additionally subjected to 1.3% hydrogen gas in this mix (hydrogen group). After two hours, the cable ties were removed to initiate reperfusion, and hydrogen inhalation lasted for six hours in the hydrogen group. After six hours, the mice were taken out of the box and kept in cages under standard conditions until time for observation at 16 different time points after reperfusion: zero, two, four, six, eight, and 10 hours and one, two, three, four, five, six, seven, 14, 21, and 28 days. Five mice were sacrificed using excess anaesthesia at each time point, and the bilateral hindlimb tissues were harvested. The inflammatory effects of the I/R injury were assessed by evaluating serum interleukin-6 concentrations using enzyme linked immunosorbent assay, as well as histological and immunohistochemical analyses. Untreated mice with I/R injury were used as controls.

RESULTS

Hydrogen gas showed protective effects associated with a reduction in inflammatory cell infiltration (neutrophils, macrophages, and lymphocytes), a reduced area of damaged muscle, maintenance of normal muscle cells, and replacement of damaged muscle cells with neoplastic myocytes.

CONCLUSION

Inhalation of hydrogen gas had a protective effect against hindlimb I/R injury in mice, in part by reducing inflammatory cell infiltration and in part by preserving normal muscle cells.

Establishment and application of a new 4/6 infarct nephrectomy rat model for moderate chronic kidney disease

PURPOSE

To develop a new 4/6 infarct nephrectomy (INx) model rat mimicking moderate chronic kidney disease (CKD) and to evaluate its application.

METHODS

We modified the conventional 5/6 INx rat model to create the 4/6 INx model by ligating the renal artery branch to induce infarction of one-third of the left kidney after right kidney removal and compared biochemically and histologically both models. To demonstrate the application of the 4/6 INx model, the effects of a supplementary compound containing calcium carbonate, chitosan, palm shell activated charcoal etc., that is effective for both CKD and its complications, were compared between both models.

RESULTS

Impairment of renal function in the 4/6 INx group was significantly more moderate than in the 5/6 INx group (P < 0.05). The 4/6 INx group showed less histological damage in kidney than in the 5/6 INx group. The supplementary compound did not improve CKD in the 5/6 INx group, but ameliorated elevation of blood urea nitrogen in the 4/6 INx group.

CONCLUSIONS

We developed the 4/6 INx model, which is more moderate than the conventional 5/6 INx model. This model could potentially demonstrate the effectiveness of drugs and supplements intended to prevent CKD and its progression.

Application of Electrolyzed Hydrogen Water for Management of Chronic Kidney Disease and Dialysis Treatment-Perspective View

Chronic kidney disease (CKD), which is globally on the rise, has become an urgent challenge from the perspective of public health, given its risk factors such as end-stage renal failure, cardiovascular diseases, and infections. The pathophysiology of CKD, including dialysis patients, is deeply associated with enhanced oxidative stress in both the kidneys and the entire body. Therefore, the introduction of a safe and widely applicable antioxidant therapy is expected as a measure against CKD. Electrolyzed hydrogen water (EHW) generated through the electrolysis of water has been confirmed to possess chemical antioxidant capabilities. In Japan, devices producing this water have become popular for household drinking water. In CKD model experiments conducted to date, drinking EHW has been shown to suppress the progression of kidney damage related to hypertension. Furthermore, clinical studies have reported that systemic oxidative stress in patients undergoing dialysis treatment using EHW is suppressed, leading to a reduction in the incidence of cardiovascular complications. In the future, considering EHW as one of the comprehensive measures against CKD holds significant importance. The medical utility of EHW is believed to be substantial, and further investigation is warranted.

Evaluation of the safety and potential lipid-lowering effects of oral hydrogen-rich coral calcium (HRCC) capsules in patients with metabolic syndrome: a prospective case series study

Background

Metabolic syndrome is characterized by a cluster-like occurrence of conditions such as hypertension, hyperglycaemia, elevated low-density lipoprotein (LDL) cholesterol or triglycerides (TG) and high visceral fat. Metabolic syndrome is linked to the build-up of plaque within the artery, which leads to disorders of the circulatory, nervous and immune systems. A variety of treatments target the regulation of these conditions; nevertheless, they remain dominant risk factors for the development of type 2 diabetes (T2DM) and cardiovascular disease (CVD), which affect 26.9% of the US population. Management and intervention strategies for improving cholesterol and/or TG are worthwhile, and recent studies on hydrogen treatment are promising, particularly as molecular hydrogen is easily ingested. This study aimed to investigate the lipid-lowering effects and quality of life (QOL) improvement of hydrogen-rich coral calcium (HRCC) in patients with metabolic syndrome.

Methods

The patients, all Taiwanese, were randomly assigned to 3 different doses (low, medium, and high) of HRCC capsules. The primary outcome was the adverse effects/symptoms during this 4-week use of HRCC capsules. The secondary outcome was lipid profile changes. Complete blood count, inflammatory biomarkers, and QOL were also measured before and after the course of HRCC.

Results

Sixteen patients with metabolic syndrome completed this study (7 males, 9 females; mean age: 62 years; range: 32-80). No obvious adverse effects were recorded. Only changes in blood TG reached significance. The baseline TG value was 193.19 μL (SD = 107.44), which decreased to 151.75 μL (SD = 45.27) after 4 weeks of HRCC (p = 0.04). QOL showed no significant changes.

Conclusion

This study is the first human clinical trial evaluating HRCC capsules in patients with metabolic syndrome. Based on the safety and potential TG-lowering effects of short-term HRCC, further long-term investigations of HRCC are warranted.

Clinical trial registration

[ClinicalTrials.gov], identifier [NCT05196295].

Diverse Possibilities of Si-Based Agent, a Unique New Antioxidant

Antioxidant therapy is an effective approach for treating diseases in which oxidative stress is involved in the onset of symptoms. This approach aims to rapidly replenish the antioxidant substances in the body when they are depleted due to excess oxidative stress. Importantly, a supplemented antioxidant must specifically eliminate harmful reactive oxygen species (ROS) without reacting with physiologically beneficial ROS, which are important to the body. In this regard, typically used antioxidant therapies can be effective, but may cause adverse effects due to their lack of specificity. We believe that Si-based agents are epoch-making drugs that can overcome these problems associated with current antioxidative therapy. These agents alleviate the symptoms of oxidative-stress-associated diseases by generating large amounts of the antioxidant hydrogen in the body. Moreover, Si-based agents are expected to be highly effective therapeutic drug candidates because they have anti-inflammatory, anti-apoptotic, and antioxidant effects. In this review, we discuss Si-based agents and their potential future applications in antioxidant therapy. There have been several reports of hydrogen generation from silicon nanoparticles, but unfortunately, none have been approved as pharmaceutical agents. Therefore, we believe that our research into medical applications using Si-based agents is a breakthrough in this research field. The knowledge obtained thus far from animal models of pathology may greatly contribute to the improvement of existing treatment methods and the development of new treatment methods. We hope that this review will further revitalize the research field of antioxidants and lead to the commercialization of Si-based agents.

Pharmacokinetics of hydrogen administered intraperitoneally as hydrogen-rich saline and its effect on ischemic neuronal cell death in the brain in gerbils

Intraperitoneal administration of hydrogen (H2)-containing saline inhibited neuronal cell death in ischemic stroke in a number of animal models, but it is unknown whether H2 is absorbed from the abdominal cavity into the blood and reaches the brain. In this study, we investigated whether intraperitoneal administration of saline containing H2 inhibits neuronal cell death caused by cerebral ischemia and measured the concentration of H2 in the carotid artery and inferior vena cava (IVC). Gerbils were subjected to transient unilateral cerebral ischemia twice, and saline or H2-rich saline was administered intraperitoneally three or seven times every 12 hours. We evaluated the number of apoptotic cells in the hippocampus and cerebral cortex on day 3 and the number of viable neurons in the hippocampus and cerebral cortex on day 7. In addition, a single dose of saline or H2-rich saline was administered intraperitoneally, and blood H2 levels in the carotid artery and IVC were measured. On day 3 of ischemia/reperfusion, the number of neurons undergoing apoptosis in the cortex was significantly lower in the H2-rich saline group than in the saline group, and on day 7, the number of viable neurons in the hippocampus and cerebral cortex was significantly higher in the H2-rich saline group. Intraperitoneal administration of H2-rich saline resulted in large increases in H2 concentration in the IVC ranging from 0.00183 mg/L (0.114%) to 0.00725 mg/L (0.453%). In contrast, carotid H2 concentrations remained in the range of 0.00008 mg/L (0.0049%) to 0.00023 (0.0146%). On average, H2 concentrations in carotid artery were 0.04 times lower than in IVC. These results indicate that intraperitoneal administration of H2-rich saline significantly suppresses neuronal cell death after cerebral ischemia, even though H2 hardly reaches the brain.

Impact of hemodialysis solutions containing different levels of molecular hydrogen (H2) on the patient-reported outcome of fatigue

Background

Reportedly, dialysis solutions containing molecular hydrogen (H2) might ameliorate patient-reported fatigue in hemodialysis (HD) patients. However, it is unknown whether its impact might differ with different H2 levels.

Method

This single-arm, prospective observational study examined 105 patients on chronic HD (62 males; mean age, 66 years; mean HD duration, 117 months). All patients were originally treated with an HD solution with 47 ppb (mean) H2 for more than 12 months, followed by an HD solution with 154 ppb (mean) H2 for 8 weeks. Baseline and changes in subjective fatigue status rated on a numerical rating scale (NRS) were assessed before the start of the study (baseline) and 8th week of the study.

Results

Patients were classified into three groups according to the presence of subjective fatigue at baseline: Group A (15.2%), presence of fatigue on both HD and HD-free days; Group B (28.6%), fatigue only on HD days; and Group C (56.2%), freedom from fatigue. In Group A, NRS scores during the 8-week period were significantly decreased as compared with 0 week, at the 4th and 8th week on HD days, and at the 8th week on HD-free day, respectively. While no consistent changes were found in other groups. At the 8th week, 64 patients (61%) presented absence of or decrease in the NRS score of fatigue, while the rest of patients did not present the decrease in NRS (the non-improved: 39%). Regarding the factors related to the non-improved, prescription of antihypertensive agents was a significant independent risk factor by multivariate analysis, indicating the possible involvement of excess fall in blood pressure (BP) in those patients.

Conclusion

Amelioration of the patient-reported outcome of fatigue might be influenced by H2 levels in the HD solution, and the optimal H2 level in the dialysate needs to be elucidated in consideration of clinical type of fatigue and BP control status.

Hydrogen-Rich Water Mitigates LPS-Induced Chronic Intestinal Inflammatory Response in Rats via Nrf-2 and NF-κB Signaling Pathways

Long-term exposure to low-dose lipopolysaccharide can impair intestinal barriers, causing intestinal inflammation and leading to systemic inflammation. Hydrogen-rich water possesses antioxidant and anti-inflammatory functions and exerts inhibitory effects on various inflammatory diseases. In this study, we investigated whether oral hydrogen-rich water could prevent lipopolysaccharide-induced chronic intestinal inflammation. An experimental model was established by feeding hydrogen-rich water, followed by the injection of lipopolysaccharide (200 μg/kg) in the tail vein of rats after seven months. ELISA, Western blot, immunohistochemistry, and other methods were used to detect related cytokines, proteins related to the NF-κB and Nrf-2 signaling pathways, and tight-junction proteins to study the anti-inflammatory and antioxidant effects of hydrogen-rich water. The obtained results show that hydrogen-rich water significantly increased the levels of superoxide dismutase and structural proteins; activated the Nrf-2 signaling pathway; downregulated the expression of inflammatory factors cyclooxygenase-2, myeloperoxidase, and ROS; and decreased the activation of the NF-κB signaling pathway. These results suggest that hydrogen-rich water could protect against chronic intestinal inflammation in rats caused by lipopolysaccharide-induced activation of the NF-κB signaling pathway by regulating the Nrf-2 signaling pathway.

The effect of a low dose hydrogen-oxygen mixture inhalation in midlife/older adults with hypertension: A randomized, placebo-controlled trial

Objective: To explore the effect of a low-dose hydrogen-oxygen (H2-O2) mixture inhalation in midlife/older adults with hypertension. Methods: This randomized, placebo-controlled trial included 60 participants with hypertension aged 50-70 years who were randomly divided into Air group (inhaled placebo air) or H2-O2 group [inhaled H2-O2 mixture (66% H2/33% O2)]. Participants in both groups were treated 4 h per day for 2 weeks. Four-limb blood pressure and 24-h ambulatory blood pressure were monitored before and after the intervention, and levels of plasma hormones related to hypertension were determined. Results: A total of 56 patients completed the study (27 in the Air group and 29 in the H2-O2 group). The right and left arm systolic blood pressure (SBP) were significantly decreased in H2-O2 group compared with the baseline levels (151.9 ± 12.7 mmHg to 147.1 ± 12.0 mmHg, and 150.7 ± 13.3 mmHg to 145.7 ± 13.0 mmHg, respectively; all p < 0.05). Meanwhile, the H2-O2 intervention significantly decreased diastolic nighttime ambulatory blood pressure by 2.7 ± 6.5 mmHg (p < 0.05). All blood pressures were unaffected in placebo group (all p > 0.05). When stratified by age (aged 50-59 years versus aged 60-70 years), participants in the older H2-O2 group showed a larger reduction in right arm SBP compared with that in the younger group (p < 0.05). In addition, the angiotensin II, aldosterone, and cortisol levels as well as the aldosterone-to-renin ratio in plasma were significantly lower in H2-O2 group compared with baseline (p < 0.05). No significant differences were observed in the Air group before and after the intervention. Conclusion: Inhalation of a low-dose H2-O2 mixture exerts a favorable effect on blood pressure, and reduces the plasma levels of hormones associated with hypertension on renin-angiotensin-aldosterone system and stress in midlife/older adults with hypertension.

Hydrogen Gas Inhalation Attenuates Acute Impulse Noise Trauma: A Preclinical In Vivo Study

OBJECTIVE

Molecular hydrogen (H₂) has shown therapeutic potential in several oxidative stress-related conditions in humans, is well-tolerated, and is easily administered via inhalation.The aim of this preclinical in vivo study was to investigate whether impulse noise trauma can be prevented by H₂ when inhaled immediately after impulse noise exposure.

METHODS

Guinea pigs (n = 26) were subjected to impulse noise (n = 400; 156 dB SPL; 0.33/s; n = 11; the Noise group), to impulse noise immediately followed by H₂ inhalation (2 mol%; 500 ml/min; 1 hour; n = 10; the Noise + H₂ group), or to H₂ inhalation (n = 5; the H₂ group). The acoustically evoked ABR threshold at 3.15, 6.30, 12.5, 20.0, and 30.0 kHz was assessed before and 4 days after impulse noise and/or H₂ exposure. The cochleae were harvested after the final ABR assessment for quantification of hair cells.

RESULTS

Noise exposure caused ABR threshold elevations at all frequencies (median 35, 35, 30, 35, and 35 dB SPL, the Noise group; 20, 25, 10, 13, and 20 dB SPL, the Noise + H₂ group; P < .05) but significantly less so in the Noise + H₂ group (P < .05). Outer hair cell (OHC) loss was in the apical, mid, and basal regions 8.8%, 53%, and 14% in the Noise group and 3.5%, 22%, and 1.2% in the Noise + H₂ group. The corresponding inner hair cell (IHC) loss was 0.1%, 14%, and 3.5% in the Noise group and 0%, 2.8%, and 0% in the Noise + H₂ group. The difference between the groups was significant in the basal region for OHCs (P = .003) and apical (P = .033) and basal (P = .048) regions for IHCs.

CONCLUSIONS

Acute acoustic trauma can be reduced by H₂ when inhaled immediately after impulse noise exposure.

Neutrophils and Neutrophil Extracellular Traps in Cardiovascular Disease: An Overview and Potential Therapeutic Approaches

Recent advances in pharmacotherapy have markedly improved the prognosis of cardiovascular disease (CVD) but have not completely conquered it. Therapies targeting the NOD-like receptor family pyrin domain containing 3 inflammasome and its downstream cytokines have proven effective in the secondary prevention of cardiovascular events, suggesting that inflammation is a target for treating residual risk in CVD. Neutrophil-induced inflammation has long been recognized as important in the pathogenesis of CVD. Circadian rhythm-related and disease-specific microenvironment changes give rise to neutrophil diversity. Neutrophils are primed by various stimuli, such as chemokines, cytokines, and damage-related molecular patterns, and the activated neutrophils contribute to the inflammatory response in CVD through degranulation, phagocytosis, reactive oxygen species generation, and the release of neutrophil extracellular traps (NETs). In particular, NETs promote immunothrombosis through the interaction with vascular endothelial cells and platelets and are implicated in the development of various types of CVD, such as acute coronary syndrome, deep vein thrombosis, and heart failure. NETs are promising candidates for anti-inflammatory therapy in CVD, and their efficacy has already been demonstrated in various animal models of the disease; however, they have yet to be clinically applied in humans. This narrative review discusses the diversity and complexity of neutrophils in the trajectory of CVD, the therapeutic potential of targeting NETs, and the related clinical issues.

H2 Inhibits the Formation of Neutrophil Extracellular Traps

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NETs have been implicated as therapeutic targets to address inflammation and thrombotic tissue damage in conditions such as sepsis, acute respiratory disease syndrome, COVID-19, and CVDs.

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H₂ has been clinically and experimentally proven to ameliorate inflammation; however, the underlying molecular mechanisms remain elusive.

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Compared with control neutrophils, PMA-stimulated human neutrophils exposed to H₂ exhibited reduced citrullination of histones and release of NET components; mechanistically, H₂-mediated neutralization of HOCl produced during oxidative bursts suppresses DNA damage.

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Inhalation of H₂ inhibited the formation and release of NET components in the blood and BAL of the LPS-induced sepsis in mice and aged mini pigs.

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H₂ therapy is potentially a new therapeutic strategy for inflammatory diseases involving NETs associated with excessive neutrophil activation.

Neutrophil extracellular traps (NETs) contribute to inflammatory pathogenesis in numerous conditions, including infectious and cardiovascular diseases, and have attracted attention as potential therapeutic targets. H₂ acts as an antioxidant and has been clinically and experimentally proven to ameliorate inflammation. This study was performed to investigate whether H₂ could inhibit NET formation and excessive neutrophil activation. Neutrophils isolated from the blood of healthy volunteers were stimulated with phorbol-12-myristate-13-acetate (PMA) or the calcium ionophore A23187 in H₂-exposed or control media. Compared with control neutrophils, PMA- or A23187-stimulated human neutrophils exposed to H₂ exhibited reduced neutrophil aggregation, citrullination of histones, membrane disruption by chromatin complexes, and release of NET components. CXCR4^high neutrophils are highly prone to NETs, and H₂ suppressed Ser-139 phosphorylation in H2AX, a marker of DNA damage, thereby suppressing the induction of CXCR4 expression. H₂ suppressed both myeloperoxidase chlorination activity and production of reactive oxygen species to the same degree as N-acetylcysteine and ascorbic acid, while showing a more potent ability to inhibit NET formation than these antioxidants do in PMA-stimulated neutrophils. Although A23187 formed NETs in a reactive oxygen species–independent manner, H₂ inhibited A23187-induced NET formation, probably via direct inhibition of peptidyl arginine deiminase 4-mediated histone citrullination. Inhalation of H₂ inhibited the formation and release of NET components in the blood and bronchoalveolar lavage fluid in animal models of lipopolysaccharide-induced sepsis (mice and aged mini pigs). Thus, H₂ therapy can be a novel therapeutic strategy for NETs associated with excessive neutrophil activation.