Hippocampal BMP signaling as a common pathway for antidepressant action

Vilazodone Alleviates Neurogenesis-Induced Anxiety in the Chronic Unpredictable Mild Stress Female Rat Model: Role of Wnt/β-Catenin Signaling

Defective β-catenin signaling is accompanied with compensatory neurogenesis process that may pave to anxiety. β-Catenin has a distinct role in alleviating anxiety in adolescence; however, it undergoes degradation by the degradation complex Axin and APC. Vilazodone (VZ) is a fast, effective antidepressant with SSRI activity and 5-HT1A partial agonism that amends somatic and/or psychic symptoms of anxiety. Yet, there is no data about anxiolytic effect of VZ on anxiety-related neurogenesis provoked by stress-reduced β-catenin signaling. Furthermore, females have specific susceptibility toward psychopathology. The aim of the present study is to uncover the molecular mechanism of VZ relative to Wnt/β-catenin signaling in female rats. Stress-induced anxiety was conducted by subjecting the rats to different stressful stimuli for 21 days. On the 15th day, stressed rats were treated with VZ(10 mg/kg, p.o.) alone or concomitant with the Wnt inhibitor: XAV939 (0.1 mg/kg, i.p.). Anxious rats showed low β-catenin level turned over by Axin-1 with unanticipated reduction of APC pursued with elevated protein levels of neurogenesis-stimulating proteins: c-Myc and pThr183-Erk likewise gene expressions of miR-17-5p and miR-18. Two weeks of VZ treatment showed anxiolytic effect figured by alleviation of hippocampal histological examination. VZ protected β-catenin signal via reduction in Axin-1 and elevation of APC conjugated with modulation of β-catenin downstream targets. The cytoplasmic β-catenin turnover by Axin-1 was restored by XAV939. Herein, VZ showed anti-anxiety effect, which may be in part through regaining the balance of the reduced β-catenin and its subsequent exaggerated response of p-Erk, c-Myc, Dicer-1, miR-17-5p, and miR-18.

BMP Antagonist Gremlin 2 Regulates Hippocampal Neurogenesis and Is Associated with Seizure Susceptibility and Anxiety

The Bone Morphogenetic Protein (BMP) signaling pathway is vital in neural progenitor cell proliferation, specification, and differentiation. The BMP signaling antagonist Gremlin 2 (Grem2) is the most potent natural inhibitor of BMP expressed in the adult brain; however its function remains unknown. To address this knowledge gap, we have analyzed mice lacking Grem2 via homologous recombination (Grem2-/- ). Histological analysis of brain sections revealed significant scattering of CA3 pyramidal cells within the dentate hilus in the hippocampus of Grem2-/- mice. Furthermore, the number of proliferating neural stem cells and neuroblasts was significantly decreased in the subgranular zone of Grem2-/- mice compared with that of wild-type (WT) controls. Due to the role of hippocampal neurogenesis in neurological disorders, we tested mice on a battery of neurobehavioral tests. Grem2-/- mice exhibited increased anxiety on the elevated zero maze in response to acute and chronic stress. Specifically, male Grem2-/- mice showed increased anxiogenesis following chronic stress, and this was correlated with higher levels of BMP signaling and decreased proliferation in the dentate gyrus. Additionally, when chemically challenged with kainic acid, Grem2-/- mice displayed a higher susceptibility to and increased severity of seizures compared with WTs. Together, our data indicate that Grem2 regulates BMP signaling and is vital in maintaining homeostasis in adult hippocampal neurogenesis and structure. Furthermore, the lack of Grem2 contributes to the development and progression of neurogenesis-related disorders such as anxiety and epilepsy.

Major depressive disorder elevates the risk of dentofacial deformity: a bidirectional two-sample Mendelian randomization study

Background

The association between psychiatric disorders and dentofacial deformities has attracted widespread attention. However, their relationship is currently unclear and controversial.

Methods

A two-sample bidirectional MR analysis was performed to study the causal relationship between dentofacial deformity and eight psychiatric disorders, including major depressive disorder, panic disorder, schizophrenia, bipolar disorder, attention deficit hyperactivity disorder, Alzheimer's disease, autism spectrum disorder, and neuroticism. Inverse variance weighted, weighted median, MR-Egger regression, weighted mode four methods, and further sensitivity analyses were conducted.

Results

The major depressive disorder affected dentofacial deformity, with an OR = 1.387 (95% CI = 1.181-1.629, P = 6.77×10-5). No other psychiatric disorders were found to be associated with dentofacial deformity. In turn, dentofacial deformity were associated with neuroticism, with an OR = 1.050 (95% CI = 1.008-1.093, P = 0.018). And there was no evidence that dentofacial deformity would increase the risk of other psychiatric disorders.

Conclusions

Major depressive disorder might elevate the risk of dentofacial deformities, and dentofacial deformity conditions would increase the risk of the incidence of neuroticism.

MuSK-BMP signaling in adult muscle stem cells maintains quiescence and regulates myofiber size

A central question in adult stem cell biology is elucidating the signaling pathways regulating their dynamics and function in diverse physiological and age-related contexts. Muscle stem cells in adults (Satellite Cells; SCs) are generally quiescent but can activate and contribute to muscle repair and growth. Here we tested the role of the MuSK-BMP pathway in regulating adult SC quiescence by deletion of the BMP-binding MuSK Ig3 domain ('ΔIg3-MuSK'). At 3 months of age SC and myonuclei numbers and myofiber size were comparable to WT. However, at 5 months of age SC density was decreased while myofiber size, myonuclear number and grip strength were increased - indicating that SCs had activated and productively fused into the myofibers over this interval. Transcriptomic analysis showed that SCs from uninjured ΔIg3-MuSK mice exhibit signatures of activation. Regeneration experiments showed that ΔIg3-MuSK SCs maintain full stem cell function. Expression of ΔIg3-MuSK in adult SCs was sufficient to break quiescence and increase myofiber size. We conclude that the MuSK-BMP pathway regulates SC quiescence and myofiber size in a cell autonomous, age-dependent manner. Targeting MuSK-BMP signaling in muscle stem cells thus emerges a therapeutic strategy for promoting muscle growth and function in the settings of injury, disease, and aging.

Highlights

MuSK, in its role as a BMP co-receptor, regulates adult muscle stem cell quiescenceThe MuSK-BMP pathway acts cell autonomouslyIncreased muscle size and function with preservation of myonuclear density and stemness in mice with attenuated MuSK-BMP signaling.

The multifaceted effects of fluoxetine treatment on cognitive functions

Fluoxetine, the prototypical selective serotonin reuptake inhibitor (SSRI), is widely used to treat major depressive disorder (MDD) and a variety of other central nervous system conditions, primarily due to its established clinical safety profile. Although its efficacy in treating depression is well-recognized, the impact of fluoxetine on cognitive functions remains inconsistent and elusive. In this review, we first examine the well-substantiated biological mechanisms underlying fluoxetine's antidepressant effects, which include serotonin reuptake inhibition and activation of TrkB receptors-key to brain-derived neurotrophic factor (BDNF) signaling. Subsequently, we delve into the cognitive side effects observed in both preclinical and clinical studies, affecting domains such as memory, attention, and executive functions. While certain studies indicate cognitive improvements in patients with underlying disorders, there is also evidence of negative effects, influenced by variables like gender, duration of treatment, age, disease pathology, and the specifics of cognitive testing. Significantly, the negative cognitive outcomes reported in preclinical research often involve healthy, non-diseased animals. This review underscores the necessity for heightened caution in fluoxetine prescription and further investigation into its potentially detrimental cognitive effects, even when used prophylactically.

Ketamine's rapid and sustained antidepressant effects are driven by distinct mechanisms

Administration of multiple subanesthetic doses of ketamine increases the duration of antidepressant effects relative to a single ketamine dose, but the mechanisms mediating this sustained effect are unclear. Here, we demonstrate that ketamine's rapid and sustained effects on affective behavior are mediated by separate and temporally distinct mechanisms. The rapid effects of a single dose of ketamine result from increased activity of immature neurons in the hippocampal dentate gyrus without an increase in neurogenesis. Treatment with six doses of ketamine over two weeks doubled the duration of behavioral effects after the final ketamine injection. However, unlike ketamine's rapid effects, this more sustained behavioral effect did not correlate with increased immature neuron activity but instead correlated with increased numbers of calretinin-positive and doublecortin-positive immature neurons. This increase in neurogenesis was associated with a decrease in bone morphogenetic protein (BMP) signaling, a known inhibitor of neurogenesis. Injection of a BMP4-expressing lentivirus into the dentate gyrus maintained BMP signaling in the niche and blocked the sustained - but not the rapid - behavioral effects of ketamine, indicating that decreased BMP signaling is necessary for ketamine's sustained effects. Thus, although the rapid effects of ketamine result from increased activity of immature neurons in the dentate gyrus without requiring an increase in neurogenesis, ketamine's sustained effects require a decrease in BMP signaling and increased neurogenesis along with increased neuron activity. Understanding ketamine's dual mechanisms of action should help with the development of new rapid-acting therapies that also have safe, reliable, and sustained effects.

Retrospective Multicenter Study on Outcome Measurement for Dyskinesia Improvement in Parkinson's Disease Patients with Pallidal and Subthalamic Nucleus Deep Brain Stimulation

Deep brain stimulation (DBS) is an effective treatment for dyskinesia in patients with Parkinson’s disease (PD), among which the therapeutic targets commonly used include the subthalamic nucleus (STN) and the globus pallidus internus (GPi). Levodopa-induced dyskinesia (LID) is one of the common motor complications arising in PD patients on chronic treatment with levodopa. In this article, we retrospectively evaluated the outcomes of LID with the Unified Dyskinesia Rating Scale (UDysRS) in patients who underwent DBS in multiple centers with a GPi or an STN target. Meanwhile, the Med off MDS-Unified Parkinson’s Disease Rating Scale (MDS-UPDRS-Ⅲ) and the levodopa equivalent daily dose (LEDD) were also observed as secondary indicators. PD patients with a GPi target showed a more significant improvement in the UDysRS compared with an STN target (92.9 ± 16.7% vs. 66.0 ± 33.6%, p < 0.0001). Both the GPi and the STN showed similar improvement in Med off UPDRS-III scores (49.8 ± 22.6% vs. 52.3 ± 29.5%, p = 0.5458). However, the LEDD was obviously reduced with the STN target compared with the GPi target (44.6 ± 28.1% vs. 12.2 ± 45.8%, p = 0.006).