Lactobacillus johnsonii HL79 mitigate plateau environment-induced hippocampal dysfunction in mice

Abstract

Plateau environment represents a common terrestrial characterized by multistress conditions including hypobaric hypoxia, low temperature, and intense radiation, yet sustain over 100 million permanent or transient inhabitants. While this extreme environment exerts profound impacts on cerebral architecture and gut microbiota homeostasis, precipitating cognitive deficits and microbiome-derived intestinal pathologies, the mechanistic interplay between plateau environment adaptation and microbial dynamics remains contentious. Here, we employ a microbiota-gut-brain axis framework to investigate whether probiotic intervention can ameliorate hippocampal impairments induced by simulated plateau environment exposure (3500-4000 m) in mice. Through simulated plateau environment exposure experiments, we revealed that extreme high-altitude conditions induced hippocampal memory dysfunction in mice, exacerbated oxidative stress damage in hippocampal tissues, and altered synaptic plasticity-related biomarkers including CREB transcription factor, BDNF protein levels, and electrophysiological power spectra. Administration of HL79 alleviated these burdens, including memory dysfunction and tissue damage, though complete reversal was not achieved. Combined hippocampal transcriptomic analyses suggested that HL79's beneficial effects primarily involved modulation of lipid-related gene expression in the hippocampus, consistent with prior reports of plateau environmental impacts on gene expression. Serum metabolomic results further reinforced this inference that differential metabolites regulated by HL79 are mainly enriched in bile secretion, taurine and hypotaurine metabolism, linoleic acid metabolism, and PPAR signaling pathways, though the precise regulatory mechanisms require further elucidation. This research provides a novel microbiota-gut-brain axis-based regulatory strategy for adaptation to extreme plateau environments and offers new evidence for understanding the relationship between gut microbiota and plateau environment adaptation at high elevations.

Keywords: Microbiota-gut-brain axis; Plateau environment; Probiotics; Spatial memory dysfunction.

Fig. 1

HL79 rescues plateau environment exposure-induced spatial memory deficits. A schematic of HL79 intervention in plateau-environment-exposed experimental design. B Schematic representation of the Morris water maze. C–I Escape latency across training days in different experimental groups. CON: Normoxic control. HA: Hypobaric hypoxia (simulated 3,500–4,000 m plateau). HAP: Hypoxia cohort supplemented with 1 × 101⁰ CFU/day HL79 via gastric gavage. Abbreviations maintained throughout subsequent analyses. Data are presented as mean ± standard deviation. One-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001 were considered significant, and ns means no significant difference

Fig. 2

Assessment of key oxidative stress biomarkers in hippocampus and serum. A Total antioxidant capacity (T-AOC). B Lipid peroxidation product malondialdehyde (MDA). C Glutathione peroxidase activity (GSH-Px). D Superoxide dismutase activity (SOD). Data are presented as mean ± standard deviation. One-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001 were considered significant, and ns means no significant difference

Fig. 3

Assessment of hippocampal synaptic plasticity-associated markers. A–C mRNA relative quantification of CREB, BDNF, and SYP genes in hippocampal tissue, normalized to CON group (set as 1). D–F Representative immunofluorescence images of CREB, BDNF, and SYP proteins in the hippocampus (scale bar: 50 μm). D Green represents CREB staining, blue represents DAPI staining. E Red represents BDNF staining, with DAPI. F Red represents SYP staining, and blue represents DAPI. Data are presented as mean ± standard deviation. One-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001 were considered significant, and ns means no significant difference

Fig. 4

Electrophysiological signal recording and analysis in the hippocampal CA1 subregion. A Position of the recording site in the left CA1 region. B, C The effects of high-altitude environment and HL79 on the power spectral density of LFP. D Schematic diagram of recording in the Schaffer collateral pathway-CA1 synapses of the left hippocampus, a stimulating electrode was positioned in the CA3 region and a recording electrode was located in the CA1 region. E Changes in paired-pulse index at different time intervals (top) and representation examples of evoked LFP responses of paired-pulse stimulation (down). F Representation examples of pre- and post-TBS traces (down), changes in LFP amplitude over recording (top left), and percentage change of LFP amplitude (top right). Data are presented as mean ± standard deviation. n = 6, one-way ANOVA. *P < 0.05, **P < 0.01, ***P < 0.001 were considered significant, and ns means no significant difference

Fig. 5

Effects of plateau environment exposure and HL79 gavage colonization on hippocampal gene transcription profiles. A Venn diagram illustrating differentially expressed genes (DEGs) among experimental groups, with the comparison between HA and CON groups designated as CON vs HA. Subsequent comparisons follow this nomenclature. B, C Volcano plots displaying DEGs for CON vs HA and HA vs HAP comparisons, respectively. Genes meeting the threshold criteria (P < 0.05 and|Log2FoldChange|> 1) are shown, with lipid metabolism-associated genes explicitly labeled. D, F Hierarchical clustering heatmap of DEG expression patterns and corresponding KEGG pathway enrichment analysis for the CON vs HA comparison. E, G Parallel analyses (gene expression clustering and pathway annotation) for the HA vs HAP comparison are presented correspondingly

Fig. 6

Impacts of plateau environment exposure and HL79 gavage colonization on serum metabolomic profiles. A Venn diagram of differential metabolites identified through pairwise comparisons across experimental groups. B, C Volcano plots visualizing differential metabolites in CON vs HA and HA vs HAP comparisons, respectively. Red dots denote metabolites meeting significance thresholds (P < 0.05 and|Log2FoldChange|> 1), with lipid-related metabolites text-labeled. D Pearson correlation matrix of differentially abundant metabolites in the HA vs HAP comparison. E KEGG pathway enrichment analysis of HA vs HAP differential metabolites. F Heatmap depicting Pearson correlations between lipid-associated hippocampal DEGs and the top 20 most significantly correlated differential metabolites from HA vs HAP serum profiles. G Abundance profiles of lipid metabolism-related metabolites among HA vs HAP differential serum metabolites. Data are presented as mean ± standard deviation. n = 6, Student's t test. *P < 0.05, **P < 0.01, ***P < 0.001 were considered significant, and ns means no significant difference