Yuanning Zeng

Background: Astrocytes play an important role in depression. However, their specific mechanisms, especially their subcellular mechanisms, remain unclear. Objective: We aimed to identify key genes associated with mitochondrial dynamics and astrocytes in Major Depressive Disorder (MDD), construct a diagnostic prediction model, and elucidate their regulatory mechanisms in neuroinflammation. Methods: Depression-related transcriptome datasets were retrieved from the GEO database. Overlapping differentially expressed genes between mitochondrial dynamics-related and astrocytes-associated genes were screened, followed by functional enrichment analysis. Machine learning algorithms were employed to establish a diagnostic model and identify hub genes. An LPS-induced mouse depression model was established, and depressive-like phenotypes were assessed through behavioral tests. Hub gene expression was validated by using quantitative real-time PCR and Western blotting. Results: A machine learning model with favorable diagnostic performance was constructed. LPS markedly upregulated hexokinase 2 (HK2) and ribosomal protein S7 (RPS7) expression in the prefrontal cortex and hippocampus, suggesting that glycolytic metabolism and ribosomal function contribute to LPS-induced neuropathological changes. Conclusions: HK2 and RPS7 were identified and validated as crucial hub genes responsive to neuroinflammation. The combined action of mitochondrial dynamics and astrocyte metabolic abnormalities may play a key role in depression’s pathogenesis, providing novel candidate biomarkers and theoretical support for the molecular diagnosis of MDD and anti-inflammatory targeted therapy.

Major depressive disorder is the most common mental illness. Mounting evidence indicates that astrocytes play a crucial role in the pathophysiology of depression; however, the underlying molecular mechanisms remain elusive. Compared with other neuronal cell types, astrocytes are enriched for arachidonic acid metabolism. Herein, we observed brain-region-specific alterations of epoxyeicosatrienoic acid (EET) signaling, which is an arachidonic acid metabolic pathway, in both a mouse model of depression and postmortem samples from patients with depression. The enzymatic activity of soluble epoxide hydrolase (sEH), the key enzyme in EET signaling, was selectively increased in the mPFC of susceptible mice after chronic social defeated stress and was negatively correlated with the social interaction ratio, which is an indicator of depressive-like behavior. The specific deletion of Ephx2 (encode sEH) in adult astrocytes induced resilience to stress, whereas the impaired EET signaling in the mPFC evoked depressive-like behaviors in response to stress. sEH was mainly expressed on lysosomes of astrocytes. Using pharmacological and genetic approaches performed on C57BL/6J background adult male mice, we found that EET signaling modulated astrocytic ATP release in vitro and in vivo. Moreover, astrocytic ATP release was required for the antidepressant-like effect of Ephx2 deletion in adult astrocytes. In addition, sEH inhibitors produced rapid antidepressant-like effects in multiple animal models of depression, including chronic social defeated stress and chronic mild stress. Together, our results highlight that EET signaling in astrocytes in the mPFC is essential for behavioral adaptation in response to psychiatric stress. SIGNIFICANCE STATEMENT Astrocytes, the most abundant glial cells of the brain, play a vital role in the pathophysiology of depression. Astrocytes secrete adenosine ATP, which modulates depressive-like behaviors. Notably, astrocytes are enriched for arachidonic acid metabolism. In the present study, we explored the hypothesis that epoxyeicosatrienoic acid signaling, an arachidonic acid metabolic pathway, modulates astrocytic ATP release and the expression of depressive-like behaviors. Our work demonstrated that epoxyeicosatrienoic acid signaling in astrocytes in the mPFC is essential for behavioral homeostatic adaptation in response to stress, and the extent of astrocyte functioning is greater than expected based on earlier reports.