Metabolic and Transcriptomic Signatures of the Acute Psychological Stress Response in the Mouse Brain

Abstract

Acute stress response triggers various physiological responses such as energy mobilization to meet metabolic demands. However, the underlying molecular changes in the brain remain largely obscure. Here, we used a brief water avoidance stress (WAS) to elicit an acute stress response in mice. By employing RNA-sequencing and metabolomics profiling, we investigated the acute stress-induced molecular changes in the mouse whole brain. The aberrant expression of 60 genes was detected in the brain tissues of WAS-exposed mice. Functional analyses showed that the aberrantly expressed genes were enriched in various processes such as superoxide metabolism. In our global metabolomic profiling, a total of 43 brain metabolites were significantly altered by acute WAS. Metabolic pathways upregulated from WAS-exposed brain tissues relative to control samples included lipolysis, eicosanoid biosynthesis, and endocannabinoid synthesis. Acute WAS also elevated the levels of branched-chain amino acids, 5-aminovalerates, 4-hydroxy-nonenal-glutathione as well as mannose, suggesting complex metabolic changes in the brain. The observed molecular events in the present study provide a valuable resource that can help us better understand how acute psychological stress impacts neural functions.

Keywords: brain; metabolism; metabolomics; stress; transcriptomics.

Figure 1

Scheme of acute water avoidance stress (WAS) exposure; brain tissue samples were examined at 1 h after WAS by untargeted metabolomics (n = 6) and bulk RNA-sequencing analysis (n = 3).

Figure 2

Effects of acute WAS on the transcriptome of the mouse whole brain. (A) Volcano plot of the differentially expressed genes between the water-stressed group and control group. The green dots indicate genes that reduced 1.5-fold below, and the red dots indicate genes that increased 1.5-fold above. The vertical dotted lines showed 1.5-fold changes. The dotted black-line shows the p value cutoff (p = 0.050) with points above the line having p < 0.050 and points below the line having p > 0.050. (B,C) Gene Ontology (GO) enrichment analysis of the differentially expressed genes (DEGs) between the water-stressed and control groups. GO categories of the biological process are shown to the left of the charts. (B) Count of upregulated (red bars) and downregulated (green bars) genes were represented. The blue line of the graphs means −log₁₀(p value). (C) The x-axis represents the fold enrichment of the GO terms. The color and the size of the bubbles depend on the p value.

Figure 3

Overview on altered metabolites and directional changes. (A) Number of significantly altered biochemicals in the brain samples. (B) Box plot for corticosterone. The boxes outline the second and third quartile (middle 50%) of the data for each sample type. The error bars on the graph represent 1.5 × IQR (interquartile range for that metabolite within the sample type. * p < 0.05 (Welch’s two-tailed t-test).

Figure 4

Accumulation of long-chain fatty acids and polyunsaturated fatty acids by acute WAS. (A) Scheme of the PLA2-dependent lipolysis. Measurements of brain content of long-chain fatty acids (B), PUFAs (C), and lysolipids (D). Significantly different values determined by Welch’s two-tailed t-test (p < 0.05). Green color indicates significant difference (p ≤ 0.05) between the groups shown, metabolite ratio of < 1.00, Red indicates significant difference (p ≤ 0.05) between the groups shown; metabolite ratio of ≥ 1.00, Light Red indicates narrowly missed statistical cutoff for significance 0.05 < p < 0.10, metabolite ratio of ≥ 1.00. * Indicates compounds that have not been officially confirmed based on a standard, but identified by virtue of their recurrent chromatographic and spectral nature.

Figure 5

Effects of acute WAS on eicosanoids. (A) Eicosanoid metabolism. Measurements of brain content of PGF2alpha (B) and 15-HETE (C). * p < 0.05, ** p < 0.01 (Welch’s two-tailed t-test).

Figure 6

Effects of acute WAS on the endocannabinoid levels. (A) Endocannabinoid metabolism. Measurements of brain content of palmitoylethanolamide (B) and N-palmitoyl taurine long-chain fatty acids (C). * p < 0.05 (Welch’s two-tailed t-test).

Figure 7

Effects of acute WAS on branched amino acids and lysine metabolism. Measurements of the brain content of branched amino acids (A–C) and 5-aminovalerate (D). * p < 0.05, ** p < 0.01 (Welch’s two-tailed t-test).

Figure 8

Increased 4-hydroxy-nonenal-glutathione levels by acute WAS. (A) Scheme of 4-hydroxy-nonenal-glutathione synthesis. Measurements of brain content of 4-hydroxy-nonenal-glutathione (B). * p < 0.05 (Welch’s two-tailed t-test).

Figure 9

Effects of acute WAS on mannose levels. (A) Mannose metabolism. Measurements of brain content of mannose (B). * p < 0.05 (Welch’s two-tailed t-test).

Figure 10

Results of the joint-pathway analysis. (A) The pathways were shown as a scatter plot from integrating transcriptomics and targeted metabolomics data using MetaboAnalyst 5.0. Pathway impact scores, which summarize normalized topology measures of perturbed genes/metabolites in each pathway is shown on the x-axis. −log₁₀(p value) of the enrichment analysis results is shown on the y-axis. The sizes of the data points are correlated with pathway impact scores, and the color gradients correspond to the enrichment analysis results. Pathways were annotated by numbering when the p values calculated from the enrichment analysis were ≤0.05. (B–D) Annotated KEGG pathways. Genes: rectangles, compounds: circles, matching nodes are negative: green, positive: red, based on log(fold change).