H₂ Papers

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Inhalation of hydrogen gas suppresses hepatic injury caused by ischemia/reperfusion through reducing oxidative stress.

水素ガス吸入による虚血再灌流性肝障害への酸化ストレス軽減効果

animal study inhalation positive 1–4%

Abstract

Using a murine hepatic ischemia/reperfusion model, the portal triad supplying the left and left-middle liver lobes was fully occluded for 90 minutes, followed by 180 minutes of reperfusion. Administration of 1–4% H2 gas by inhalation during the final 190 minutes of this protocol resulted in marked reduction of hepatocyte death, along with decreased serum alanine aminotransferase levels and lower hepatic malondialdehyde concentrations, both indicators of oxidative tissue damage. Helium gas administered under identical conditions produced no comparable protection, confirming that the observed benefit is specific to molecular hydrogen. These findings suggest that H2 inhalation selectively neutralizes cytotoxic reactive oxygen species, particularly hydroxyl radicals, and may represent a broadly applicable approach for mitigating oxidative stress in organ injury contexts.

Mechanism

Inhaled molecular hydrogen selectively scavenges cytotoxic reactive oxygen species, including hydroxyl radicals, thereby reducing lipid peroxidation (malondialdehyde) and hepatocyte death during ischemia/reperfusion.

Bibliographic

Authors
Fukuda K, Asoh S, Ishikawa M, Yamamoto Y, Ohsawa I, Ohta S
Journal
Biochem Biophys Res Commun
Year
2007 (2007-09-28)
PMID
17673169
DOI
10.1016/j.bbrc.2007.07.088

Tags

Disease:ischemia-reperfusion injury (107) liver disease (56) Delivery:inhalation delivery (196) Mechanism:hydroxyl radical scavenging (352) 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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