Hydrogen gas promotes neuroprotection and upregulates ATF5 expression in neonatal hypoxic-ischemic brain injury

Neonatal brain injury, typically caused by hypoxia-ischemia (HI), results in irreversible cortical and white matter damage, leading to severe neurological sequelae. Therapeutic hypothermia, the only available clinical intervention, has limited effectiveness and is not suitable for all patients. Molecular hydrogen gas exerts neuroprotective effects due to its antioxidant properties and is gaining attention as a potential therapeutic strategy. However, its cellular and molecular effects in the injured neonatal brain are poorly understood. Using a robust HI brain injury model in neonatal piglets, whose brain structure and development closely resemble those of human neonates, we investigated the cell type-specific impact of hydrogen gas following neonatal HI injury and examined the potential molecular mediators underlying its neuroprotective effects. Hydrogen gas treatment significantly attenuated HI-induced apoptosis in both cortical neurons and white matter oligodendrocytes, thereby preserving their cell densities to levels comparable to uninjured controls. These neuroprotective effects were accompanied by reduced microglial activation, astrocyte expansion and myelin loss. RNAscope analyses revealed that hydrogen gas upregulated the expression of the anti-apoptotic factor activating transcription factor 5 (ATF5) in both neurons and mature oligodendrocytes, suggesting a cell-specific protective mechanism. These findings demonstrate that hydrogen gas exerts robust neuroprotection for cortical neurons and white matter oligodendrocytes following neonatal HI injury, and ATF5 is a potential mediator of its anti-apoptotic effects. Our study highlights the clinical feasibility of hydrogen gas as a novel therapeutic strategy for neonatal brain injury.