Hydrogen-saturated saline protects intensive narrow band noise-induced hearing loss in guinea pigs through an antioxidant effect

A double-blinded, randomized controlled clinical trial of hydrogen inhalation therapy for idiopathic sudden sensorineural hearing loss

Background

Hydrogen (H₂) has been reported to be effective in reducing hearing loss due to several causes in animal studies. However, no study has examined the effectiveness of H₂ in treating hearing loss in humans. Thus, we investigated whether H₂ is effective for the treatment of idiopathic sudden sensorineural hearing loss (ISSNHL).

Materials and methods

We conducted a double-blind randomized controlled trial at six hospitals between June 2019 and March 2022. The study protocol and trial registration have been published in the Japan Registry of Clinical Trials (jRCT, No. jRCTs06119004). We randomly assigned patients with ISSNHL to receive either H₂ (H₂ group) or air as a placebo (control group) through inhalation combined with the administration of systemic glucocorticoids and prostaglandin E1. The primary outcome was the hearing threshold and changes in hearing threshold 3 months after therapy. In contrast, the secondary outcomes included the proportion of patients with a good prognosis (complete recovery or marked improvement).

Results

Sixty-five patients with ISSNHL (31 and 34 in the H₂ and control groups, respectively) were included in this study. The hearing threshold 3 months after treatment was not significantly different between the groups; 39.0 decibels (dB) (95% confidence interval [CI]: 28.7-49.3) and 49.5 dB (95% CI: 40.3-58.7) in the H₂ and control groups, respectively. In contrast, the changes in hearing threshold 3 months after treatment was 32.7 dB (95% CI: 24.2-41.3) and 24.2 dB (95% CI: 18.1-30.3) in the H₂ and control groups, respectively. Consequently, the changes in hearing threshold were significantly better in the H₂ group than in the control group (P = 0.048). However, no adverse effects due to the inhalation of H₂ gas have been reported.

Conclusion

This is the first study to investigate the efficacy of H₂ for the treatment of ISSNHL in humans. The results suggest that H₂ therapy may be effective for ISSNHL treatment.

Clinical trial registration

[https://jrct.niph.go.jp/re/reports/detail/10442], identifier [jRCTs06119004].

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.

Effect of Hydrogen Inhalation Therapy on Hearing Loss of Patients With Nasopharyngeal Carcinoma After Radiotherapy

Objective

To evaluate the clinical efficacy and safety of hydrogen inhalation in improving hearing loss in patients with long-term survival of nasopharyngeal carcinoma after radiotherapy.

Methods

The eustachian tube dysfunction score, pure tone air conduction threshold, bone conduction threshold, the score of tympanogram and otoscope were prospectively observed in patients with deafness after radiotherapy only or combined radiotherapy and chemotherapy for nasopharyngeal carcinoma. Paired t test and one-way analysis of variance were used to analyze the data before and after treatment.

Results

A total of 17 patients were observed. The median time from radiotherapy to now was 228 months, and the median time from the diagnose of deafness to now was 92 months. After 4 weeks of hydrogen inhalation, the score of eustachian tube dysfunction, air conduction and bone conduction hearing thresholds were significantly reduced, P values were 0.0293, 0.0027, 0.0404, respectively. The mean air-bone gap, the score of otoendoscopy and tympanogram were also decreased, but the differences were not significant (P = 0.2079, P = 0.0536, P = 0.1056). Patients with radiotherapy alone and concurrent chemo-radiotherapy had significantly lower air conduction hearing threshold after hydrogen absorption (P = 0.0142, P = 0.0495). The results of air and bone hearing thresholds before, 4 and 12 weeks after hydrogen inhalation showed a descending trend. The air and bone hearing thresholds before hydrogen inhalation were 74.69 ± 27.03 dB and 45.70 ± 21.58 dB, respectively. At the 12th week, the mean values of air and bone hearing thresholds were the lowest, which were 66.88 ± 20.88 dB and 40.94 ± 18.93 dB, respectively, but there was no significant difference in air and bone hearing thresholds among all groups (P = 0.6755, P = 0.7712). After hydrogen inhalation treatment, no adverse reactions such as nosebleed, chest pain, dyspnea, nausea, vomiting, dizziness, earache and allergic reaction were observed.

Conclusion

This is the first prospective study on the effect of hydrogen inhalation on hearing improvement in patients with deafness after radiotherapy/chemotherapy for nasopharyngeal carcinoma, suggesting that continuous hydrogen inhalation may be an alternative rehabilitation therapy for these patients.

Inhalation of Molecular Hydrogen, a Rescue Treatment for Noise-Induced Hearing Loss

Noise exposure is the most important external factor causing acquired hearing loss in humans, and it is strongly associated with the production of reactive oxygen species (ROS) in the cochlea. Several studies reported that the administration of various compounds with antioxidant effects can treat oxidative stress-induced hearing loss. However, traditional systemic drug administration to the human inner ear is problematic and has not been successful in a clinical setting. Thus, there is an urgent need to develop rescue treatment for patients with acute acoustic injuries. Hydrogen gas has antioxidant effects, rapid distribution, and distributes systemically after inhalation.The purpose of this study was to determine the protective efficacy of a single dose of molecular hydrogen (H₂) on cochlear structures. Guinea pigs were divided into six groups and sacrificed immediately after or at 1 or 2 weeks. The animals were exposed to broadband noise for 2 h directly followed by 1-h inhalation of 2% H₂ or room air. Electrophysiological hearing thresholds using frequency-specific auditory brainstem response (ABR) were measured prior to noise exposure and before sacrifice. ABR thresholds were significantly lower in H₂-treated animals at 2 weeks after exposure, with significant preservation of outer hair cells in the entire cochlea. Quantification of synaptophysin immunoreactivity revealed that H₂ inhalation protected the cochlear inner hair cell synaptic structures containing synaptophysin. The inflammatory response was greater in the stria vascularis, showing increased Iba1 due to H₂ inhalation.Repeated administration of H₂ inhalation may further improve the therapeutic effect. This animal model does not reproduce conditions in humans, highlighting the need for additional real-life studies in humans.

Use of the guinea pig in studies on the development and prevention of acquired sensorineural hearing loss, with an emphasis on noise

Guinea pigs have been used in diverse studies to better understand acquired hearing loss induced by noise and ototoxic drugs. The guinea pig has its best hearing at slightly higher frequencies relative to humans, but its hearing is more similar to humans than the rat or mouse. Like other rodents, it is more vulnerable to noise injury than the human or nonhuman primate models. There is a wealth of information on auditory function and vulnerability of the inner ear to diverse insults in the guinea pig. With respect to the assessment of potential otoprotective agents, guinea pigs are also docile animals that are relatively easy to dose via systemic injections or gavage. Of interest, the cochlea and the round window are easily accessible, notably for direct cochlear therapy, as in the chinchilla, making the guinea pig a most relevant and suitable model for hearing. This article reviews the use of the guinea pig in basic auditory research, provides detailed discussion of its use in studies on noise injury and other injuries leading to acquired sensorineural hearing loss, and lists some therapeutics assessed in these laboratory animal models to prevent acquired sensorineural hearing loss.

Molecular hydrogen: a preventive and therapeutic medical gas for various diseases

Since the 2007 discovery that molecular hydrogen (H2) has selective antioxidant properties, multiple studies have shown that H2 has beneficial effects in diverse animal models and human disease. This review discusses H2 biological effects and potential mechanisms of action in various diseases, including metabolic syndrome, organ injury, and cancer; describes effective H2 delivery approaches; and summarizes recent progress toward H2 applications in human medicine. We also discuss remaining questions in H2 therapy, and conclude with an appeal for a greater role for H2 in the prevention and treatment of human ailments that are currently major global health burdens. This review makes a case for supporting hydrogen medicine in human disease prevention and therapy.

Linking hydrogen-enhanced rice aluminum tolerance with the reestablishment of GA/ABA balance and miRNA-modulated gene expression: A case study on germination

Although previous results showed that exogenous hydrogen (H₂) alleviated aluminum (Al) toxicity, the detailed mechanism remains unclear. Here, we reported that the exposure of germinating rice seeds to Al triggered H₂ production, followed by a decrease of GA/ABA ratio and seed germination inhibition. Compared to inert gas (argon), H₂ pretreatment not only strengthened H₂ production and alleviated Al-induced germination inhibition, but also partially reestablished the balance between GA and ABA. By contrast, a GA biosynthesis inhibitor paclobutrazol (PAC) could block the H₂-alleviated germination inhibition. The expression of GA biosynthesis genes (GA20ox1 and GA20ox2) and ABA catabolism genes (ABA8ox1 and ABA8ox2), was also induced by H₂. Above results indicated that GA/ABA might be partially involved in H₂ responses. Subsequent results revealed that compared with Al alone, transcripts of miR398a and miR159a were decreased by H₂, and expression levels of their target genes OsSOD2 and OsGAMYB were up-regulated. Whereas, miR528 and miR160a transcripts were increased differentially, and contrasting tendencies were observed in the changes of their target genes (OsAO and OsARF10). The transcripts of Al-tolerant gene OsSTAR1/OsSTAR2 and OsFRDL4 were up-regulated. Above results were consistent with the anti-oxidant defense, decreased Al accumulation, and enhanced citrate efflux. Together, our results provided insight into the mechanism underlying H₂-triggered Al tolerance in plants.

Molecular mechanisms underlying the protective effects of hydrogen-saturated saline on noise-induced hearing loss

OBJECTIVES

This study aimed to explore the molecular mechanism of the protective effects of hydrogen-saturated saline on NIHL.

METHODS

Guinea pigs were divided into three groups: hydrogen-saturated saline; normal saline; and control. For saline administration, the guinea pigs were given daily abdominal injections 3 d before and 1 h before noise exposure. ABR were tested to examine cochlear physiology changes. The changes of 8-hydroxy-desoxyguanosine (8-HOdG), interleukin-1 (IL-1), interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor-α (TNF-α), intercellular cell adhesion molecule-1 (ICAM-1) and high mobility group box-1 protein (HMGB1) in the cochlea were also examined.

RESULTS

The results showed that pre-treatment with hydrogen-saturated saline could significantly attenuate noise-induced hearing loss. The concentration of 8-HOdG was also significantly decreased in the hydrogen-saturated saline group compared with the normal saline group. After noise exposure, the concentrations of IL-1, IL-6, TNF-α, and ICAM-1 in the cochlea of guinea pigs in the hydrogen-saturated saline group were dramatically reduced compared to those in the normal saline group. The concentrations of HMGB-1 and IL-10 in the hydrogen-saturated saline group were significantly higher than in those in the normal saline group immediately and at 7 d after noise exposure.

CONCLUSIONS

This study revealed for the first time the protective effects of hydrogen-saturated saline on noise-induced hearing loss (NIHL) are related to both the anti-oxidative activity and anti-inflammatory activity.

Protective effect of hydrogen-saturated saline on acute lung injury induced by oleic acid in rats

Background

The purpose of the study is to investigate the role and mechanisms of hydrogen-saturated saline (HSS) in the acute lung injury (ALI) induced by oleic acid (OA) in rats.

Methods

Rats were treated with OA (0.1 mL/kg) to induce ALI and then administered with HSS (5 mL/kg) by intravenous (iv) and intraperitoneal (ip) injection, respectively. Three hours after the injection with OA, the arterial oxygen partial pressure (PaO₂), arterial oxygen saturation (SaO₂), carbon dioxide partial pressure (PaCO₂), and bicarbonate (HCO₃⁻) levels were analyzed using blood gas analyzer. In addition, the levels of malondialdehyde (MDA), tumor necrosis factor-α (TNF-α), and interleukin 1β (IL-1β) and myeloperoxidase (MPO) activity were measured by commercial kits, and pathological changes of lung tissue were examined by HE staining. Finally, the correlations of MPO activity or MDA level with the levels of TNF-α or IL-1β were analyzed by Pearson’s correlation analysis.

Results

We found decreased PaO₂ levels and the pathological changes of lung tissue of ALI after OA injection. In addition, OA increased the levels of MDA, TNF-α, and IL-1β, as well as MPO activity in lung tissues (P < 0.05). However, after treatment with HSS, all of these changes were alleviated (P < 0.05), and these changes were mitigated when treated with HSS by ip then iv injection (P < 0.05). Furthermore, MDA level and MPO activity were positively correlated with TNF-α and IL-1β levels in the lung tissue, respectively (P < 0.01).

Conclusion

HSS attenuated ALI induced by OA in rats and might protect against ALI through selective resistance to oxidation and inhibiting inflammatory infiltration.

Hydrogen Inhalation Protects against Ototoxicity Induced by Intravenous Cisplatin in the Guinea Pig

Introduction: Permanent hearing loss and tinnitus as side-effects from treatment with the anticancer drug cisplatin is a clinical problem. Ototoxicity may be reduced by co-administration of an otoprotective agent, but the results in humans have so far been modest. Aim: The present preclinical in vivo study aimed to explore the protective efficacy of hydrogen (H₂) inhalation on ototoxicity induced by intravenous cisplatin. Materials and Methods: Albino guinea pigs were divided into four groups. The Cispt (n = 11) and Cispt+H₂ (n = 11) groups were given intravenous cisplatin (8 mg/kg b.w., injection rate 0.2 ml/min). Immediately after, the Cispt+H₂ group also received gaseous H₂ (2% in air, 60 min). The H₂ group (n = 5) received only H₂ and the Control group (n = 7) received neither cisplatin nor H₂. Ototoxicity was assessed by measuring frequency specific ABR thresholds before and 96 h after treatment, loss of inner (IHCs) and outer (OHCs) hair cells, and by performing densitometry-based immunohistochemistry analysis of cochlear synaptophysin, organic transporter 2 (OCT2), and copper transporter 1 (CTR1) at 12 and 7 mm from the round window. By utilizing metabolomics analysis of perilymph the change of metabolites in the perilymph was assessed. Results: Cisplatin induced electrophysiological threshold shifts, hair cell loss, and reduced synaptophysin immunoreactivity in the synapse area around the IHCs and OHCs. H₂ inhalation mitigated all these effects. Cisplatin also reduced the OCT2 intensity in the inner and outer pillar cells and in the stria vascularis as well as the CTR1 intensity in the synapse area around the IHCs, the Deiters' cells, and the stria vascularis. H₂ prevented the majority of these effects. Conclusion: H₂ inhalation can reduce cisplatin-induced ototoxicity on functional, cellular, and subcellular levels. It is proposed that synaptopathy may serve as a marker for cisplatin ototoxicity. The effect of H₂ on the antineoplastic activity of cisplatin needs to be further explored.

Noise exposure and oxidative balance in auditory and extra-auditory structures in adult and developing animals. Pharmacological approaches aimed to minimize its effects

Noise coming from urban traffic, household appliances or discotheques might be as hazardous to the health of exposed people as occupational noise, because may likewise cause hearing loss, changes in hormonal, cardiovascular and immune systems and behavioral alterations. Besides, noise can affect sleep, work performance and productivity as well as communication skills. Moreover, exposure to noise can trigger an oxidative imbalance between reactive oxygen species (ROS) and the activity of antioxidant enzymes in different structures, which can contribute to tissue damage. In this review we systematized the information from reports concerning noise effects on cell oxidative balance in different tissues, focusing on auditory and non-auditory structures. We paid specific attention to in vivo studies, including results obtained in adult and developing subjects. Finally, we discussed the pharmacological strategies tested by different authors aimed to minimize the damaging effects of noise on living beings.

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

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