H₂ Papers

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Postconditioning with inhaled hydrogen promotes survival of retinal ganglion cells in a rat model of retinal ischemia/reperfusion injury.

吸入水素によるポストコンディショニングがラット網膜虚血再灌流傷害モデルにおける網膜神経節細胞の生存を促進する

animal study inhalation positive 67%

Abstract

Using a rat model of retinal ischemia/reperfusion (I/R) injury, this study examined whether postconditioning with high-concentration inhaled hydrogen (67% H2 / 33% O2, 1 hour daily for 7 days beginning immediately after ischemia) could protect retinal ganglion cells (RGCs). RGC density assessed by hematoxylin-eosin staining and retrograde cholera toxin beta labeling was significantly greater in hydrogen-treated animals than in untreated I/R controls. Visual function measured by flash visual evoked potentials and pupillary light reflex was also better preserved in the hydrogen group. Oxidative stress marker 4-hydroxynonenal (4-HNE)-positive cell counts in the ganglion cell layer were reduced, and retinal overexpression of IL-1β and TNF-α induced by I/R was suppressed. These findings indicate that inhaled hydrogen postconditioning confers neuroprotection against retinal I/R injury through concurrent suppression of oxidative stress, inflammatory signaling, and apoptotic pathways.

Mechanism

Inhalation of 67% H2 reduces 4-hydroxynonenal accumulation and suppresses I/R-induced overexpression of IL-1β and TNF-α, thereby protecting retinal ganglion cells via coordinated inhibition of oxidative stress, inflammatory, and apoptotic pathways.

Bibliographic

Authors
Wang R, Wu J, Chen Z, Xia F, Sun Q, Liu L
Journal
Brain Res
Year
2016 (2016-02-01)
PMID
26705611
DOI
10.1016/j.brainres.2015.12.015

Tags

Disease:ischemia-reperfusion injury (107) retinal disease (27) Delivery:inhalation delivery (196) Mechanism:apoptosis regulation (280) anti-inflammatory (743) lipid peroxidation (238) oxidative stress (899) reactive oxygen species (774)

Delivery context

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

→ Evidence by delivery route

Safety notes

In air, molecular hydrogen is reported to be combustible across approximately **4% (LFL, lower flammability limit) to 75% (UFL, upper flammability limit)**. Among high-concentration hydrogen inhalers, 66% output sits inside this range, and even pure-hydrogen (100%) output forms a 4–75% concentration-gradient layer at the device–air boundary (the UFL 75% paradox). Engineering principle would therefore call for operation below LFL (the classical 4%); that figure, however, was measured under closed, pre-mixed, static conditions. For the open, dynamic inhalation environment, the empirical value reported in the literature is **10%**, which is the figure referenced in practice as the operating ceiling. The 66% / 100% output devices are recorded in the Japanese Consumer Affairs Agency accident-information database, and from these considerations are not recommended.

See also:

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