Spaceflight-Induced Gene Expression Profiles in the Mouse Brain Are Attenuated by Treatment with the Antioxidant BuOE

Abstract

The demands of deep space pose a health risk to the central nervous system that has long been a concern when sending humans to space. While little is known about how spaceflight affects transcription spatially in the brain, a greater understanding of this process has the potential to aid strategies that mitigate the effects of spaceflight on the brain. Therefore, we performed GeoMx Digital Spatial Profiling of mouse brains subjected to either spaceflight or grounded controls. Four brain regions were selected: Cortex, Frontal Cortex, Corunu Ammonis I, and Dentate Gyrus. Antioxidants have emerged as a potential means of attenuating the effects of spaceflight, so we treated a subset of the mice with a superoxide dismutase mimic, MnTnBuOE-2-PyP 5+ (BuOE). Our analysis revealed hundreds of differentially expressed genes due to spaceflight in each of the four brain regions. Both common and region-specific transcriptomic responses were observed. Metabolic pathways and pathways sensitive to oxidative stress were enriched in the four brain regions due to spaceflight. These findings enhance our understanding of brain regional variation in susceptibility to spaceflight conditions. BuOE reduced the transcriptomic effects of spaceflight at a large number of genes, suggesting that this compound may attenuate oxidative stress-induced brain damage caused by the spaceflight environment.

Keywords: brain; digital spatial profiling; gene expression; regional difference; spaceflight.

Figure 1

DSP of the mouse brain under spaceflight and grounded control conditions. (A), A representative image (FLT_SAL_2|005, 006, 007, and 008) of the brain regions profiled by DSP in this study. (B) Principal components analysis of the SAL transcriptomic data from the indicated brain regions. Filled circles represent the GC data, while empty circles represent the FLT data.

Figure 2

Differentially expressed genes due to spaceflight conditions. (A–D), Volcano plots summarizing the differential gene expression analysis of the indicated region, comparing FLT-SAL versus GC-SAL. The number of DEGs is indicated for each brain region. Gene symbols are shown for the top 10 DEGs by the magnitude of the log₂ fold change (FC). (E), Heatmap of differential expression (DE) using log₂ FC values of the FLT-SAL versus GC-SAL DEGs from the indicated regions, along with normalized gene expression values of the indicated samples and regions. Genes are ordered by hierarchical clustering of the log₂ FC values.

Figure 3

Top spaceflight DEGs. (A–D), Barplots showing the normalized expression values of the top 5 DEGs (FLT-SAL versus GC-SAL) by magnitude of log₂ fold change.

Figure 4

Pathway analysis. Bar plots showing the p-value for the 7 most statistically significant pathways containing FLT-SAL versus GC-SAL DEGs in (A): CA, (B): DG, (C): FCT, (D): CT.

Figure 5

BuOE attenuates spaceflight-induced gene expression changes. (A), Principal components analysis of the indicated regions and treatment conditions. Each gene was averaged across replicates to obtain the PCA. Individual replicates are shown in the PCA in Supplementary File S1: Figure S3A. (B–E), Barplots comparing the number of spaceflight-induced DEGs (GC-SAL vs. FLT-SAL) that change in the opposite versus the same direction (dir) as BuOE-induced DEGs (FLT-SAL vs. FLT-BuOE). p-values were calculated by Fisher’s Exact test. *** p < 10⁻⁵; **** p < 10⁻¹⁰.

Figure 6

BuOE attenuation of spaceflight-induced gene expression changes of genes in oxidative stress–responsive pathways. (A–D), log2 fold change (FC) values of genes from the indicated comparisons, regions, and pathways. The top 20 genes by magnitude of log₂ FC from either of the two comparisons are shown. Genes are ordered by hierarchical clustering. GC vs. FLT (SAL) = GC-SAL versus FLT-SAL; SAL vs. BuOE (FLT) = FLT-SAL versus FLT-BuOE.