Hydrogen gas reduces hyperoxic lung injury via the Nrf2 pathway in vivo
Kawamura T, Wakabayashi N, Shigemura N, Huang CS, Masutani K, Tanaka Y, Noda K, Peng X, Takahashi T, Billiar TR, Okumura M, Toyoda Y, Kensler TW, Nakao A. · American Journal of Physiology - Lung Cellular and Molecular Physiology. 2013;304(10):L646-L656.
Study at a glance
Preclinical
Male Lewis rats and male wild-type or Nrf2-deficient C57BL/6J mice exposed to continuous normoxia or 98% oxygen.
Continuous chamber exposure for 60 hours to 2% H₂ with either 98% O₂ or 98% balanced air; prolonged-survival rats remained exposed beyond 60 hours. · Total chamber flow was 2 L/min. H₂ flow was therefore 40 mL/min. In the hyperoxic mixture, O₂ flow was 1,960 mL/min. The exact O₂ fraction and flow within the separate 98%-balanced-air normoxic mixture are not stated and are not inferred.
Continuous 60-hour exposure for principal outcomes; prolonged hyperoxic survival assessed every eight hours until death.
H₂ improved several rat physiological, edema, inflammatory, apoptotic and survival measures and induced Nrf2-dependent genes. It did not significantly induce HO-1/activity under normoxia. In Nrf2-deficient mice H₂ did not improve oxygenation or gross/histological lung injury and did not induce HO-1/Nqo1/GSTA2, although MDA and 8-OHdG were reduced in both genotypes.
Continuous extreme-hyperoxia animal model, outcome-specific small groups, many surrogate/molecular endpoints and no human participants. The authors could not define how H₂ activates Nrf2. NIH and departmental/fellowship support was reported; no explicit conflict statement was identified, so absence is not inferred.
What kind of evidence is this?
Preclinical
Randomized four-gas-condition rat experiment with prolonged-survival cohort and wild-type/Nrf2-knockout mouse mechanistic replication
Respiratory health
Inhaled H₂
Information not yet classified
Some editorial classification fields are still pending. The source-reported outcomes and result are shown below; Hydrogenology does not infer a positive or negative signal from prose automatically.
Methods
Male Lewis rats and male wild-type or Nrf2-deficient C57BL/6J mice exposed to continuous normoxia or 98% oxygen.
Outcome-specific groups varied: commonly n=4-8 per condition in rats and n=4 per mouse condition; prolonged rat survival used n=5 per group. The article does not provide one overall animal total.
Continuous 60-hour exposure for principal outcomes; prolonged hyperoxic survival assessed every eight hours until death.
Continuous chamber exposure for 60 hours to 2% H₂ with either 98% O₂ or 98% balanced air; prolonged-survival rats remained exposed beyond 60 hours.
Inhaled premixed H₂ with oxygen or balanced air — not Brown's gas: H₂ was 2%, not approximately 66.7%.
Total chamber flow was 2 L/min. H₂ flow was therefore 40 mL/min. In the hyperoxic mixture, O₂ flow was 1,960 mL/min. The exact O₂ fraction and flow within the separate 98%-balanced-air normoxic mixture are not stated and are not inferred.
40 mL/min.
1,960 mL/min in the 98% O₂ hyperoxic mixture; not separately reportable for the balanced-air condition.
Matching 2% N₂ mixtures under hyperoxia and normoxia, plus Nrf2-wild-type versus Nrf2-deficient mice.
Outcomes and reported result
Blood oxygenation, weight, survival, edema/pleural effusion, lavage cells/protein, histology, cytokines, apoptosis, oxidative damage and Nrf2-dependent genes including HO-1.
H₂ improved several rat physiological, edema, inflammatory, apoptotic and survival measures and induced Nrf2-dependent genes. It did not significantly induce HO-1/activity under normoxia. In Nrf2-deficient mice H₂ did not improve oxygenation or gross/histological lung injury and did not induce HO-1/Nqo1/GSTA2, although MDA and 8-OHdG were reduced in both genotypes.
The complete free PMC article was checked for gas conditions, total flow, directly calculated H₂/O₂ flows, outcome-specific samples, positive and null genotype findings, limitations, funding and available disclosures.
A reported association, difference or mechanism is not automatically a clinical benefit.
Limitations and applicability
Continuous extreme-hyperoxia animal model, outcome-specific small groups, many surrogate/molecular endpoints and no human participants. The authors could not define how H₂ activates Nrf2. NIH and departmental/fellowship support was reported; no explicit conflict statement was identified, so absence is not inferred.
Experimental hyperoxic lung injury in rodents; it does not establish prevention or treatment of human oxygen toxicity, ALI or ARDS.
No single-study GRADE certainty rating is assigned. Read how records and evidence assessments are prepared.
Sources and record status
PMID: 23475767 · DOI: 10.1152/ajplung.00164.2012
Free full article in PubMed Central.
Complete PMC article and PubMed metadata; full-text extraction checked 9 August 2026.
10 August 2026
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