# Chronic molecular hydrogen inhalation mitigates short and long-term memory loss in polymicrobial sepsis.
> 慢性的な水素ガス吸入による敗血症関連の短期・長期記憶障害の軽減


## Abstract

Sepsis rapidly affects the central nervous system through circulating inflammatory mediators that penetrate the hippocampus and prefrontal cortex, inducing neuroinflammation and subsequent memory deficits. Using a polymicrobial sepsis animal model, this study examined whether chronic molecular hydrogen inhalation could mitigate both short- and long-term memory impairment. Behavioral assessments demonstrated that chronic H2 exposure reduced sepsis-associated memory loss. Additionally, acute H2 inhalation lowered neuroinflammatory markers in memory-relevant brain regions and elevated total Nrf2 protein levels—a transcription factor governing a broad array of antioxidant and anti-inflammatory gene expressions. These findings suggest that H2 inhalation may represent a feasible and safe approach to limiting sepsis-induced cognitive deterioration.

### Mechanism

H2 inhalation suppresses neuroinflammation in the hippocampus and prefrontal cortex while upregulating total Nrf2 protein, thereby modulating antioxidant and anti-inflammatory gene expression and attenuating sepsis-induced memory deficits.

## Bibliographic

- **Authors**: Jesus AA, Passaglia P, Santos BM, Rodrigues-Santos I, Flores RA, Batalhão ME, et al.
- **Journal**: Brain Res
- **Year**: 2020 (2020-07-15)
- **PMID**: [32348775](https://pubmed.ncbi.nlm.nih.gov/32348775/)
- **DOI**: [10.1016/j.brainres.2020.146857](https://doi.org/10.1016/j.brainres.2020.146857)
- **Study type**: animal study
- **Delivery route**: inhalation
- **Effect reported**: positive

## Delivery context

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

## Safety notes

For inhalation applications of molecular hydrogen, the lower flammability limit (LFL) deserves careful handling. The classical 4% figure applies to closed-system mixtures; the practical inhalation-environment threshold is 10%. Even pure-hydrogen output (the UFL 75% paradox) passes through the flammable range at the air–gas boundary. High-concentration (66% / 100%) inhalers are documented in the Japanese Consumer Affairs Agency accident-information database and are not recommended.

See also:
- [Inhalation concentration and LFL / UFL](https://h2-papers.org/en/safety-notes/inhalation-concentration)
- [Consumer Affairs Agency accident cases](https://h2-papers.org/en/safety-notes/accident-cases)
- [LFL / UFL terminology](https://h2-papers.org/en/safety-notes/lfl-ufl-explained)
- [Inhalation safety threshold lineage](https://h2-papers.org/en/safety-notes/lineage)

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> **Cite as**: H2 Papers — PMID 32348775. https://h2-papers.org/en/papers/32348775
> **Source**: PubMed PMID [32348775](https://pubmed.ncbi.nlm.nih.gov/32348775/)