Hydrogen gas inhalation improves delayed brain injury by alleviating early brain injury after experimental subarachnoid hemorrhage.
水素ガス吸入によるくも膜下出血後の早期脳損傷軽減を介した遅発性脳損傷の改善：ラットモデルを用いた検討
Abstract
Using a rat SAH combined with unilateral common carotid artery occlusion (UCCAO) model, this study examined whether 1.3% H2 gas inhalation (mixed with 30% oxygen and balanced nitrogen) could reduce both early brain injury (EBI) and delayed brain injury (DBI). Inhalation was administered for 2 hours on day 0 and 30 minutes on day 1 from anesthesia induction. EBI was evaluated via brain edema, S100B expression, and JNK phosphorylation on day 2, with neurological deficits assessed on day 3. Reactive astrogliosis and cerebral vasospasm (CV) severity were measured on days 3 and 7, while DBI was assessed by neurological deficits and neuronal cell death on day 7. Compared with controls, the H2 group showed significant improvements in EBI, reactive astrogliosis, and DBI. CV severity did not differ significantly between groups. These findings indicate that H2 inhalation suppresses DBI by mitigating EBI independently of any effect on cerebral vasospasm.
Mechanism
H2 is proposed to scavenge reactive oxygen species, thereby suppressing JNK phosphorylation, S100B expression, and brain edema as markers of early brain injury, which in turn reduces reactive astrogliosis and delayed neuronal cell death without altering cerebral vasospasm.
Bibliographic
- Authors
- Kumagai K, Toyooka T, Takeuchi S, Otani N, Wada K, Tomiyama A, et al.
- Journal
- Sci Rep
- Year
- 2020 (2020-07-23)
- PMID
- 32704088
- DOI
- 10.1038/s41598-020-69028-5
- PMC
- PMC7378202
Tags
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.
Safety notes
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