Hydrogen inhalation: in vivo rat genotoxicity tests

Area of Science:

• Biomedical Science
• Toxicology
• Molecular Biology

Background:

• Molecular hydrogen (H2) exhibits antioxidant, anti-inflammatory, and anti-apoptotic properties.
• Existing literature provides safety data and acute toxicity information for H2 in various models.
• In vivo genotoxicity assessment is crucial for understanding the safety profile of H2.

Purpose of the Study:

• To evaluate the in vivo genotoxicity of molecular hydrogen (H2) in rats.
• To adhere to the International Council for Harmonization (ICH) S2 (R1) guidelines for genotoxicity testing.
• To assess potential DNA damage and related biomarkers following H2 exposure.

Main Methods:

• Wistar rats were divided into three groups: negative control, positive control (methyl methanesulfonate), and H2-treated (3.1% H2 gas mixture for 72 hours).
• Genotoxicity was assessed using the alkaline comet assay, formamidopyrimidine DNA glycosylase (Fpg)-modified comet assay, and bone marrow micronucleus assay.
• Analysis included comet-tail DNA intensity, "hedgehog" frequency, Fpg-sensitive sites, micronucleus formation, and immature to total erythrocyte ratio (IME%).

Main Results:

• H2 exposure did not increase comet-tail DNA intensity, indicating no DNA damage in blood, liver, lungs, or bronchoalveolar lavage fluid.
• No significant increase in "hedgehogs", Fpg-sensitive sites in lungs, or micronucleus formation was observed.
• The ratio of immature to total erythrocytes (IME%) remained balanced, showing no adverse effects on erythropoiesis.

Conclusions:

• The ICH S2 (R1) test battery revealed no evidence of in vivo genotoxicity in Wistar rats after 72 hours of exposure to a 3.1% H2 gas mixture.
• These findings support the safety of molecular hydrogen concerning genotoxicity.
• Further research into the therapeutic applications of H2 can proceed with a stronger safety foundation.