Abstract
Major depressive disorder (MDD) is a complex condition with unclear pathophysiology. Molecular disruptions within limbic brain regions and the periphery contribute to depression symptomatology and a more complete understanding the diversity of molecular changes that occur in these tissues may guide the development of more efficacious antidepressant treatments. Here, we utilized a mouse chronic social stress model for the study of MDD and performed metabolomic, lipidomic, and proteomic profiling on serum plus several brain regions (ventral hippocampus, nucleus accumbens, and medial prefrontal cortex) of susceptible, resilient, and unstressed control mice. To identify how commonly used tricyclic antidepressants impact the molecular composition in these tissues, we treated stress-exposed mice with imipramine and repeated our multi-OMIC analyses. Proteomic analysis identified three serum proteins reduced in susceptible animals; lipidomic analysis detected differences in lipid species between resilient and susceptible animals in serum and brain; and metabolomic analysis revealed dysfunction of purine metabolism, beta oxidation, and antioxidants, which were differentially associated with stress susceptibility vs resilience by brain region. Antidepressant treatment ameliorated stress-induced behavioral abnormalities and affected key metabolites within outlined networks, most dramatically in the ventral hippocampus. This work presents a resource for chronic social stress-induced, tissue-specific changes in proteins, lipids, and metabolites and illuminates how molecular dysfunctions contribute to individual differences in stress sensitivity.
Highlights
Major depressive disorder (MDD) is a complex condition with unclear pathophysiology
To resolve the diverse molecular changes that occur within the brain and serum of mice in response to chronic social stress, we exposed C57BL/6J mice to ten days of chronic social defeat stress (CSDS), and 24 h after the final defeat we performed a social interaction (SI) test to identify susceptible or resilient mice (F2,117 = 32.82; ***p < 0.0001; one-way ANOVA followed by Bonferroni post-test) (Fig. 1A,B)
Lipidomic, and proteomic profiling in parallel on pooled samples of serum and of ventral hippocampus (vHipp), nucleus accumbens (NAc), and medial prefrontal cortex (mPFC) of susceptible, resilient, and undefeated control mice to capture the full spectrum of molecular changes in blood and brain that differentiate these populations (Fig. 1C,D)
Summary
Major depressive disorder (MDD) is a complex condition with unclear pathophysiology. Molecular disruptions within limbic brain regions and the periphery contribute to depression symptomatology and a more complete understanding the diversity of molecular changes that occur in these tissues may guide the development of more efficacious antidepressant treatments. We utilize an ethologically-validated mouse model for the study of depression called chronic social defeat stress (CSDS), where mice are exposed chronically to a social stress, which induces a range of MDD-like behavioral and molecular changes in a subset (~ 50%) of animals, referred to as s usceptible[2,3]. These defects are ameliorated by chronic antidepressant treatment[2,4,5].
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