Lysosomal TFEB-TRPML1 Axis in Astrocytes Modulates Depressive-like Behaviors.

Lysosomes are important cellular structures for human health as centers for recycling, signaling, metabolism and stress adaptation. However, the potential role of lysosomes in stress-related emotions has long been overlooked. Here, it is found that lysosomal morphology in astrocytes is altered in the medial prefrontal cortex (mPFC) of susceptible mice after chronic social defeat stress. A screen of lysosome-related genes revealed that the expression of the mucolipin 1 gene (Mcoln1; protein: mucolipin TRP channel 1) is decreased in susceptible mice and depressed patients. Astrocyte-specific knockout of mucolipin TRP channel 1 (TRPML1) induced depressive-like behaviors by inhibiting lysosomal exocytosis-mediated adenosine 5'-triphosphate (ATP) release. Furthermore, this stress response of astrocytic lysosomes is mediated by the transcription factor EB (TFEB), and overexpression of TRPML1 rescued depressive-like behaviors induced by astrocyte-specific knockout of TFEB. Collectively, these findings reveal a lysosomal stress-sensing signaling pathway contributing to the development of depression and identify the lysosome as a potential target organelle for antidepressants.

Astrocytic ALKBH5 in stress response contributes to depressive-like behaviors in mice.

Epigenetic mechanisms bridge genetic and environmental factors that contribute to the pathogenesis of major depression disorder (MDD). However, the cellular specificity and sensitivity of environmental stress on brain epitranscriptomics and its impact on depression remain unclear. Here, we found that ALKBH5, an RNA demethylase of N6-methyladenosine (m6A), was increased in MDD patients' blood and depression models. ALKBH5 in astrocytes was more sensitive to stress than that in neurons and endothelial cells. Selective deletion of ALKBH5 in astrocytes, but not in neurons and endothelial cells, produced antidepressant-like behaviors. Astrocytic ALKBH5 in the mPFC regulated depression-related behaviors bidirectionally. Meanwhile, ALKBH5 modulated glutamate transporter-1 (GLT-1) m6A modification and increased the expression of GLT-1 in astrocytes. ALKBH5 astrocyte-specific knockout preserved stress-induced disruption of glutamatergic synaptic transmission, neuronal atrophy and defective Ca2+ activity. Moreover, enhanced m6A modification with S-adenosylmethionine (SAMe) produced antidepressant-like effects. Our findings indicate that astrocytic epitranscriptomics contribute to depressive-like behaviors and that astrocytic ALKBH5 may be a therapeutic target for depression.

P2X2 receptors in pyramidal neurons are critical for regulating vulnerability to chronic stress.

Rationale: Stress is a major risk factor for the development of depression. However, the underlying molecular mechanisms of stress vulnerability in depression are largely uncharacterized. Methods: P2X2 receptors (a major receptor for gliotransmitter-ATP) in the medial prefrontal cortex (mPFC) were identified by real-time qPCR, western blots and RNAscope in situ hybridization in chronic social defeat stress model (CSDS). We generated P2X2 conditional knockout mice and overexpressed AAV-P2X2 in CamkIIα-Cre mice. The depression-like behaviors were assessed via CSDS, subthreshold social defeat stress (SSDS), social interaction test (SI), forced interaction test (FIT), forced swimming test (FST), sucrose preference test (SPT), novel stressed feeding (NSF) and open field test (OFT). The neuronal activity and synapse function of P2X2 receptors in the mPFC were detected by in vivo fiber-photometry, patch-clamp techniques and neuronal morphometric analysis. Results: We identified that P2X2 receptors were increased in the mPFC of susceptible mice in CSDS. Conditional knockout of P2X2 receptors in pyramidal neurons promoted resilience of chronic stress-induced depressive-like behaviors, whereas pyramidal neurons - specific gain of P2X2 in the mPFC increased vulnerability to depressive-like behaviors. In vivo fiber-photometry, electrophysiology and neuronal morphometric analysis showed P2X2 receptors regulated neuronal activity and synapse function in the mPFC. Conclusions: Overall, our studies reveal a critical role of P2X2 in mediating vulnerability to chronic stress and identify P2X2 as a potential therapeutic target for treatment of stress-related mood disorders.

A Distinct Metabolically Defined Central Nucleus Circuit Bidirectionally Controls Anxiety-Related Behaviors.

Anxiety disorders are debilitating psychiatric diseases that affect ∼16% of the world's population. Although it has been proposed that the central nucleus of the amygdala (CeA) plays a role in anxiety, the molecular and circuit mechanisms through which CeA neurons modulate anxiety-related behaviors are largely uncharacterized. Soluble epoxide hydrolase (sEH) is a key enzyme in the metabolism of polyunsaturated fatty acids (PUFAs), and has been shown to play a role in psychiatric disorders. Here, we reported that sEH was enriched in neurons in the CeA and regulated anxiety-related behaviors in adult male mice. Deletion of sEH in CeA neurons but not astrocytes induced anxiety-like behaviors. Mechanistic studies indicated that sEH was required for maintaining the the excitability of sEH positive neurons (sEHCeA neurons) in the CeA. Using chemogenetic manipulations, we found that sEHCeA neurons bidirectionally regulated anxiety-related behaviors. Notably, we identified that sEHCeA neurons directly projected to the bed nucleus of the stria terminalis (BNST; sEHCeA-BNST). Optogenetic activation and inhibition of the sEHCeA-BNST pathway produced anxiolytic and anxiogenic effects, respectively. In summary, our studies reveal a set of molecular and circuit mechanisms of sEHCeA neurons underlying anxiety.SIGNIFICANCE STATEMENT Soluble epoxide hydrolase (sEH), a key enzyme that catalyzes the degradation of EETs, is shown to play a key role in mood disorders. It is well known that sEH is mostly localized in astrocytes in the prefrontal cortex and regulates depressive-like behaviors. Notably, sEH is also expressed in central nucleus of the amygdala (CeA) neurons. While the CeA has been studied for its role in the regulation of anxiety, the molecular and circuit mechanism is quite complex. In the present study, we explored a previously unknown cellular and circuitry mechanism that guides sEHCeA neurons response to anxiety. Our findings reveal a critical role of sEH in the CeA, sEHCeA neurons and CeA-bed nucleus of the stria terminalis (BNST) pathway in regulation of anxiety-related behaviors.