Engineering a novel intermittent hypoxia paradigm to induce rapid tolerance to severe hypoxia in rodents

: Background This study aimed to establish a novel, clinically translatable model of hypoxic preconditioning, termed intermittent hypoxic preconditioning (IHPC), to enhance acute hypoxic resistance in mouse hippocampal neurons. Methods Mice were allocated into three experimental groups: normoxic control, acute hypoxic exposure, and IHPC. The neuroprotective efficacy of IHPC was evaluated by neurological behavioral assessments, along with histological and molecular examinations of hippocampal neuronal viability and apoptosis. Results Behavioral analyses showed that while acute hypoxia significantly compromised cognitive function and neurological performance (both p < 0.05), IHPC pretreatment substantially ameliorated these deficits. At the molecular level, the IHPC group showed marked downregulation of the pro-apoptotic gene Bax and concomitant upregulation of the anti-apoptotic gene Bcl-2 compared with the acute hypoxia group. Consistently, compared with the acute hypoxia group, the IHPC group protein levels of cleaved caspase-3 , caspase-8 , and caspase-9 were significantly suppressed. TdT-mediated dUTP Nick-End Labeling (TUNEL) staining further corroborated these findings, compared with the acute hypoxia group, showing a substantial reduction in DNA fragmentation and staining intensity in the IHPC group, which indicated attenuated apoptotic activity. Conclusion This study shows that IHPC serves as an effective hypoxic preconditioning paradigm, conferring neuroprotection against an acute hypoxic insult by enhancing neuronal survival and suppressing apoptotic pathways in the hippocampal region.