Memory impairment induced by exposure to simulated hypobaric hypoxia and phosphoproteomic analysis of hippocampus in mice

Abstract

Objective To observe the changes of protein phosphorylation levels in the hippocampus of mice with memory impairment caused by hypobaric hypoxia exposure, and to explore the key phosphorylated proteins and associated pathways involved in memory deficits. Methods Forty male C57BL/6 mice (7~8 weeks old, body weight 20±2 g) were randomly and equally divided into normoxic control group (Ctrl) and hypobaric hypoxic group (HH). The Ctrl group was housed under normoxic condition, while the HH group was fed for 7 d in a hypobaric chamber at simulated altitude of 6 000 m. Morris water maze (MWM) test was performed after hypoxia exposure, and the hippocampus tissues of mice were collected for phosphoproteomic analysis. Results MWM test showed that the escape latency of mice was significantly longer in the HH group than the Ctrl group (89.66±3.27 vs 38.61±4.83 s, P < 0.01), and the swimming distance was also remarkably increased in the HH group (959.21±99.61 vs 550.39±59.43 cm, P < 0.01). A total of 136 phosphopeptides with significant difference in expression between the 2 groups were detected by phosphoproteomic analysis, including 92 up-regulated phosphopeptides corresponding to 79 proteins and 44 down-regulated from 42 proteins. Gene Ontology (GO) enrichment analysis revealed that these differentially phosphorylated proteins were primarily distributed in postsynaptic density, asymmetric synapse and basal plasma membrane, and were mainly involved in biological processes such as cell junction assembly, synapse organization, vesicle-mediated transport in synapse, dendrite development and cognition. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that the differentially phosphorylated proteins were mainly enriched in pathways like insulin secretion, pancreatic secretion, glutamatergic synapse, endocytosis and long-term depression. Moreover, a protein-protein interaction (PPI) network with AGAP2, SYNGAP1, DRP2, DRP3 and PSD93 as the core proteins was formed. Conclusion Hypobaric hypoxia exposure can induce memory impairment in mice, which may be associated with the differential expression of phosphorylated proteins and changes of related pathways in the hippocampus of mice, and AGAP2, SYNGAP1, DRP2, DRP3 and PSD93 may be the key proteins during the process.

Keywords

• hypoxia
• hippocampus
• memory
• phosphoproteomics