Legumain knockout improves repeated corticosterone injection-induced depression-like emotional and cognitive deficits

A TrkB cleavage fragment in hippocampus promotes Depressive-Like behavior in mice

Decreased hippocampal tropomyosin receptor kinase B (TrkB) level is implicated in the pathophysiology of stress-induced mood disorder and cognitive decline. However, how TrkB is modified and mediates behavioral responses to chronic stress remains largely unknown. Here the effects and mechanisms of TrkB cleavage by asparagine endopeptidase (AEP) were examined on a preclinical murine model of chronic restraint stress (CRS)-induced depression. CRS activated IL-1β-C/EBPβ-AEP pathway in mice hippocampus, accompanied by elevated TrkB 1-486 fragment generated by AEP. Specifi.c overexpression or suppression of AEP-TrkB axis in hippocampal CaMKIIα-positive cells aggravated or relieved depressive-like behaviors, respectively. Mechanistically, in addition to facilitating AMPARs internalization, TrkB 1-486 interacted with peroxisome proliferator-activated receptor-δ (PPAR-δ) and sequestered it in cytoplasm, repressing PPAR-δ-mediated transactivation and mitochondrial function. Moreover, co-administration of 7,8-dihydroxyflavone and a peptide disrupting the binding of TrkB 1-486 with PPAR-δ attenuated depression-like symptoms not only in CRS animals, but also in Alzheimer's disease and aged mice. These findings reveal a novel role for TrkB cleavage in promoting depressive-like phenotype.

Repeated finasteride administration promotes synaptic plasticity and produces antidepressant- and anxiolytic-like effects in female rats

Finasteride is used in female-pattern hair loss, hirsutism, and polycystic ovarian syndrome. It inhibits 5α-reductase, which is an important enzyme in the biosynthesis of neurosteroids. The effects of finasteride treatment on mental health in female patients as well as the effects of repeated/chronic finasteride administration in female rodents are still unknown. Accordingly, in our study, we administered finasteride (10, 30, or 100 mg/Kg, s.c.) for 6 days in female rats and evaluated behavior, plasma steroid levels, and synaptic plasticity. Depression-like behavior was evaluated using forced swim test (FST) and splash test. Anxiety-like behavior was evaluated using novelty-suppressed feeding task (NSFT), elevated plus maze (EPM), open field test (OFT), and light-dark test (LDT). Plasma steroid levels were assessed using ELISA and synaptic plasticity by field potential recordings. We observed that finasteride decreased total immobility duration in FST, indicating antidepressant-like effect and decreased the latency to first bite in NSFT, showing anxiolytic-like effect. We also found a significant increase in plasma estradiol and a significant decrease in plasma corticosterone level. Furthermore, field potential recordings showed that finasteride increased hippocampal long-term potentiation. These results indicate that repeated finasteride administration in female rats may have antidepressant- and anxiolytic-like effect, which might be mediated by enhanced estradiol levels or decreased corticosterone levels. Further studies are required to validate the molecular mechanisms underlying the effects of finasteride in female rats. Understanding the mechanisms will help us in developing novel neurosteroid-based therapeutics in the treatment of neuropsychiatric disorders in women.

Sex differences in a corticosterone-induced depression model in mice: Behavioral, neurochemical, and molecular insights

Depression is characterized by a significant sex disparity, with higher rates observed in women compared to men. This study aimed to investigate the impact of sex on depressive behaviors and explore the underlying mechanisms using a corticosterone (CORT)-induced depression model in mice. Behavioral tests, Nissl staining, UPLC-MS/MS, and Western blot analysis were performed to assess behavioral changes, as well as neuronal alterations, neurotransmitter levels, and protein expressions in the hippocampus. The mice in the model group exhibited sex-specific anxiety- and depression-like behaviors. Nissl staining revealed structural abnormalities in the CA3 region of the hippocampus in females. Neurotransmitter analysis indicated decreased serotonin and norepinephrine levels in both sexes, while glutamate levels were elevated in females. Furthermore, female mice demonstrated elevated serum CORT levels. Western blot analysis revealed sex-specific alterations in specific protein expression. Female mice exhibited downregulated glucocorticoid receptor and brain-derived neurotrophic factor expression, whereas male mice showed minimal changes. Additionally, female mice displayed reduced phosphorylated AKT, phosphorylated PI3K, and phosphorylated mTOR levels. These findings enhance our understanding of sex-specific differences in the CORT-induced depression model and provide insights into the underlying mechanisms of depression. This research emphasizes sex in depression studies and supports tailored interventions.

Rosmarinic acid alleviate CORT-induced depressive-like behavior by promoting neurogenesis and regulating BDNF/TrkB/PI3K signaling axis

Rosmarinic acid (RA), a natural phenolic acid compound with a variety of bioactive properties. However, the antidepressant activity and mechanism of RA remain unclear. The aim of this study is to investigate the effects and potential mechanisms of RA on chronic CORT injection induced depression-like behavior in mice. Male C57BL/6 J mice were intraperitoneally injected with CORT (10 mg/kg) and were orally given RA daily (10 or 20 mg/kg) for 21 consecutive days. In vitro, the HT22 cells were exposed to CORT (200 μM) with RA (12.5, 25 or 50 μM) and LY294002 (a PI3K inhibitor) or ANA-12 (a TrkB inhibitor) treatment. The depression-like behavior and various neurobiological changes in the mice and cell injury and levels of target proteins in vitro were subsequently assessed. Here, RA treatment decreased the expression of p-GR/GR, HSP90, FKBP51, SGK-1 in mice hippocampi. Besides, RA increased the average optical density of Nissl bodies and number of dendritic spines in CA3 region, and enhanced Brdu and DCX expression and synaptic transduction in DG region, as well as up-regulated both the BDNF/TrkB/CREB and PI3K/Akt/mTOR signaling. Moreover, RA reduced structural damage and apoptosis in HT22 cells, increased the differentiation and maturation of them. More importantly, LY294002, but not ANA-12, reversed the effect of RA on GR nuclear translocation. Taken together, RA exerted antidepressant activities by modulating the hippocampal glucocorticoid signaling and hippocampal neurogenesis, which related to the BDNF/TrkB/PI3K signaling axis regulating GR nuclear translocation, provide evidence for the application of RA as a candidate for depression.

DFO treatment protects against depression-like behaviors and cognitive impairment in CUMS mice

Depression has several negative effects on emotion as well as learning and memory abilities. Previous studies showed that depression could exacerbate inflammation, which in turn further aggravated depression. Deferoxamine (DFO) is a chelating agent binding iron and aluminium, and is clinically applied to treat acute ion poisoning and hemochromatosis. Researches showed that it could reduce inflammation via increasing the expression of hypoxia-inducible factor-1alpha (HIF-1α). Here, we established a chronic unpredictable mild stress (CUMS) model to investigate whether DFO exerted a neuroprotective function in depression. The results demonstrated that CUMS (4 weeks) effectively induced depression-like behaviors in mice based on sucrose preference test (SPT), forced swim test (FST), tail suspension test (TST), open field test (OFT), and elevated plus-maze test (EPT). It also brought cognitive deficits based on Morris water maze (MWM) test and the impairment of synaptic plasticity based on in vivo electrophysiological recordings. Additionally, CUMS exposure significantly decreased the expression of hippocampal synapse related proteins and the spine density of neurons in the DG region, accompanied by increasing the expression of hippocampal inflammatory cytokines, and promoted the activation of microglia in the hippocampus. The expression of HIF-1α was down-regulated as expected. However, DFO distinctly reversed the CUMS-induced impairments. The mechanism is associated with the DFO inhibition of inflammation by upregulating HIF-1 expression, thereby alleviating a series of pathology changes. Together, these findings suggest that DFO likely plays a protective role in cognitive impairments and synaptic plasticity deficits resulting from depression.