Comparison of the Antidepressant-Like Effects of Estradiol and That of Selective Serotonin Reuptake Inhibitors in Middle-Aged Ovariectomized Rats

Molecular signatures of premature aging in Major Depression and Substance Use Disorders

Major depressive disorder (MDD) and substance-use disorders (SUDs) often lead to premature aging, increasing vulnerability to cognitive decline and other forms of dementia. This study utilized advanced systems bioinformatics to identify aging "signatures" in MDD and SUDs and evaluated the potential for known lifespan-extending drugs to target and reverse these signatures. The results suggest that inhibiting the transcriptional activation of FOS gene family members holds promise in mitigating premature aging in MDD and SUDs. Conversely, antidepressant drugs activating the PI3K/Akt/mTOR pathway, a common mechanism in rapid-acting antidepressants, may accelerate aging in MDD patients, making them unsuitable for those with comorbid aging-related conditions like dementia and Alzheimer's disease. Additionally, this innovative approach identifies potential anti-aging interventions for MDD patients, such as Deferoxamine, Resveratrol, Estradiol valerate, and natural compounds like zinc acetate, genistein, and ascorbic acid, regardless of comorbid anxiety disorders. These findings illuminate the premature aging effects of MDD and SUDs and offer insights into treatment strategies for patients with comorbid aging-related conditions, including dementia and Alzheimer's disease.

Investigating the Role of 17β-Estradiol on the Serotonergic System, Targeting Soy Isoflavones as a Strategy to Reduce Menopausal Depression: A Mechanistic Review

Low serotonin is one factor implicated in the development of depression. 17β-estradiol (E2) has been shown to modulate gene expression regulating the neurotransmission of serotonin. Sex hormone levels fluctuate dramatically during the menopausal transition, coinciding with a 14-fold increased risk of depression. This review aimed to examine the effect of soy isoflavones to support decreased and variable E2 levels before and after menopause, linked to an investigation of the pathophysiological mechanisms underlying the protective influence of E2 on the serotonin pathway. The overall aim of this review is to assess the potential of soy isoflavones to reduce depression in middle-aged women. A systematic literature search was performed in three stages. 1,421 papers were screened for relevance to the research aims and objectives. 63 papers were selected based on pre-defined inclusion/exclusion criteria (13 reviews, 24 mechanistic and 26 intervention studies) and critically appraised. Available research supported the hypotheses that E2 increases serotonin synthesis and availability through stimulation of tryptophan hydroxylase-2 (TPH-2) and decreased degradation by monoamine oxidase-A (MAO-A). There was less scientific agreement on the effects of E2 on serotonin transporter (SERT) and serotonin receptors 1 A and 2 A. Studies varied widely on the effectiveness of soy isoflavones in reducing depressive symptoms in (peri)menopausal women. Animal and human studies acknowledge women's increased risk of depression linked to fluctuating E2 rather than absolute levels. However, mechanisms linking E2 variability with depression remain an underrepresented area of research. Study limitations and heterogeneity may contribute to varying results for soy isoflavones and some effects of E2 on the serotonin pathway.

Estradiol reduced 5-HT reuptake by Downregulating the Gene Expression of Plasma Membrane Monoamine Transporter (PMAT, Slc29a4) through estrogen receptor β and the MAPK/ERK signaling pathway

Estrogen deficiency-induced female depression is closely related to 5-hydroxytriptamine (5-HT) deficiency. Estradiol (17β-estradiol, E₂) regulates the monoamine transporters and acts as an antidepressant by affecting 5-HT clearance through estrogen receptors and related signaling pathways at the genome level, although the specific mechanisms require further exploration. The brain expresses higher levels of plasma membrane monoamine transporter (PMAT, involved in 5-HT reuptake of the uptake 2 system) than other uptake transporters. In this study, we found that estrogen-deficient ovariectomized (OVX) rats had high PMAT mRNA and protein expression levels in the hippocampus and estradiol significantly reduced these levels. Furthermore, estradiol inhibits PMAT expression and reduced 5-HT reuptake in neurons and astrocytes and estradiol regulated the PMAT expression mainly by affecting estrogen receptor β (ERβ) at the genomic level in astrocytes. Further cell and animal experiments showed that estradiol also regulated PMAT expression through the MAPK/ERK signaling pathway and not through the PI3K/AKT signaling pathway. In conclusion, estradiol inhibits 5-HT reuptake by regulating PMAT expression at the genomic level through ERβ and the MAPK/ERK signaling pathway, highlighting the importance of PMAT in the antidepressant effects of estradiol through 5-HT clearance reduction.

Neurotransmitter Release of Reprogrammed Cells Using Electrochemical Detection Methods

The detection of neurotransmitter release from reprogrammed human cell is an important demonstration of their functionality. Electrochemistry has the distinct advantages over alternative methods that it allows for the measuring of the analyte of interest at a high temporal resolution. This is necessary for fast events, such as neurotransmitter release and reuptake, which happen in the order of milliseconds to seconds. The precise description of these kinetic events can lead to insights into the function of cells in health and disease and allows for the exploration of events that might be missed using methods that look at absolute concentration values or methods that have a slower sampling rate. In the present chapter, we describe the use of constant potential amperometry and enzyme-coated multielectrode arrays for the detection of glutamate in vitro. These biosensors have the distinct advantage of "self-referencing," a method providing high selectivity while retaining outstanding temporal resolution. Here, we provide a step-by-step user guide for a commercially available system and its application for in vitro systems such as reprogrammed cells.

Effects of ketamine and other rapidly acting antidepressants on hippocampal excitatory and inhibitory transmission

A single sub-anesthetic intravascular dose of the use-dependent NMDAR antagonist, ketamine, improves mood in patients with treatment resistant depression within hours that can last for days, creating an entirely new treatment strategy for the most seriously ill patients. However, the psychomimetic effects and abuse potential of ketamine require that new therapies be developed that maintain the rapid antidepressant effects of ketamine without the unwanted side effects. This necessitates a detailed understanding of what cellular and synaptic mechanisms are immediately activated once ketamine reaches the brain that triggers the needed changes to elicit the improved behavior. Intense research has centered on the effects of ketamine, and the other rapidly acting antidepressants, on excitatory and inhibitory circuits in hippocampus and medial prefrontal cortex to determine common mechanisms, including key modifications in synaptic transmission and the precise location of the NMDARs that mediate the rapid and sustained antidepressant response. We review data comparing the effects of ketamine with other NMDAR receptor modulators and the muscarinic M1 acetylcholine receptor antagonist, scopolamine, together with evidence supporting the disinhibition hypothesis and the direct inhibition hypothesis of ketamine's mechanism of action on synaptic circuits using preclinical models.

Ovariectomy-induced depressive-like behavior and brain glucose metabolism changes in female rats are not affected by chronic mild stress

The increased incidence of depression in women going through peri-menopause suggests that fluctuations in estrogen levels may increase the risk of developing depression. Nonetheless, this psychiatric disorder is likely to be multifactorial and consequently an additional trigger may be needed to induce depression in this population. Stress could be such a trigger. We therefore investigated the effect of ovarian estrogen depletion and chronic mild stress (CMS) on depressive-like behavior and brain metabolism in female rats. Approximately 2 and 9 weeks after estrogen depletion by ovariectomy, behavioral changes were assessed in the open-field test and the forced swim test, and brain metabolism was measured with [¹⁸F]FDG PET imaging. A subset of animals was subjected to a 6-weeks CMS protocol starting 17 days after ovariectomy. Short-term estrogen depletion had a significant effect on brain metabolism in subcortical areas, but not on behavior. Differences in depressive-like behavior were only found after prolonged estrogen depletion, leading to an increased immobility time in the forced swim test. Prolonged estrogen depletion also resulted in an increase in glucose metabolism in frontal cortical areas and hippocampus, whereas a decrease glucose metabolism was found in temporal cortical areas, hypothalamus and brainstem. Neither short-term nor prolonged estrogen depletion caused anxiety-like behavior. Changes in body weight, behavior and brain glucose metabolism were not significantly affected by CMS. In conclusion, ovarian estrogen depletion resulted in changes in brain metabolism and depressive-like behavior, but these changes were not enhanced by CMS.

Venlafaxine Mitigates Depressive-Like Behavior in Ovariectomized Rats by Activating the EPO/EPOR/JAK2 Signaling Pathway and Increasing the Serum Estradiol Level

Reduced estradiol levels are associated with depression in women during the transition to and after menopause. A considerable number of studies focusing on the theme of treating depression through the activation of erythropoietin (EPO)-induced signaling pathways have been published. Venlafaxine is an approved antidepressant drug that inhibits both serotonin and norepinephrine transporters. The aim of the present study was to investigate the effects of venlafaxine on the depressive-like behaviors and serum estradiol levels in female rats following ovariectomy (OVX) and the possible roles of EPO-induced signaling pathways. Venlafaxine (10 mg/kg/day) was orally administered to OVX rats over a period of 4 weeks using two different treatment regimens: either starting 24 h or 2 weeks after OVX. Venlafaxine showed a superior efficacy in inducing antidepressant-like effects after an acute treatment (24 h post-OVX) than after the delayed treatment (2 weeks post-OVX) and was characterized by a decreased immobility time in the forced swimming test. In parallel, venlafaxine induced EPO and EPO receptor mRNA expression and increased levels of phospho-Janus kinase 2 (p-JAK2), phospho-signal transducer and activator of transcription 5, and phospho-extracellular signal-regulated kinase 1/2 in the hippocampus of OVX rats. Meanwhile, rats exhibited a marked reduction in the hippocampal Bax/Bcl2 ratio, caspase-3 activity, and tumor necrosis factor alpha levels after venlafaxine treatment. Venlafaxine also increased the hippocampal brain-derived neurotrophic factor and serum estradiol levels. Based on these findings, venlafaxine exerts a neuroprotective effect on OVX rats that is at least partially attributed to the activation of EPO/EPOR/JAK2 signaling pathways, anti-apoptotic activities, anti-inflammatory activities, and neurotrophic activities, as well as an increase in serum estradiol level. Graphical Abstract ᅟ.

ERβ agonist alters RNA splicing factor expression and has a longer window of antidepressant effectiveness than estradiol after long-term ovariectomy

BACKGROUND

Estrogen therapy (ET), an effective treatment for perimenopausal depression, often fails to ameliorate symptoms when initiated late after the onset of menopause. Our previous work has suggested that alternative splicing of RNA might mediate these differential effects of ET.

METHODS

Female Sprague–Dawley rats were treated with estradiol (E2) or vehicle 6 days (early ET) or 180 days (late ET) after ovariectomy (OVX). We investigated the differential expression of RNA splicing factors and tryptophan hydroxylase 2 (TPH2) protein using a customized RT2 Profiler PCR Array, reverse-transcription polymerase chain reaction, immunoprecipitation and behaviour changes in clinically relevant early and late ET.

RESULTS

Early ET, but not late ET, prolonged swimming time in the forced swim test and reduced anxiety-like behaviours in the elevated plus maze. It reversed OVX-increased (SFRS7 and SFRS16) or OVX-decreased (ZRSR2 and CTNNB1) mRNA levels of splicing factors and ERβ splicing changes in the brains of OVX rats. Early ET, but not late ET, also increased the expression of TPH2 and decreased monoamine oxidase A levels in the dorsal raphe in the brains of OVX rats. In late ET, only diarylpropionitrile (an ERβ-specific agonist) achieved similar results — not E2 (an ERα and ERβ agonist) or propylpyrazoletriol (an ERα-specific agonist).

LIMITATIONS

Our experimental paradigm mimicked early and late ET in the clinical setting, but the contribution of age and OVX might be difficult to distinguish.

CONCLUSION

These findings suggest that ERβ alternative splicing and altered responses in the regulatory system for serotonin may mediate the antidepressant efficacy of ET associated with the timing of therapy initiation. It is likely that ERβ-specific ligands would be effective estrogen-based antidepressants late after the onset of menopause.

Paroxetine blunts the corticosterone response to swim-induced stress and increases depressive-like behavior in a rat model of postpartum depression

Perinatal depression (PND) affects 15% of women. During the perinatal period both stress- and gonadal hormones fluctuate widely. Putatively, these fluctuations are involved in PND disease mechanisms. The serotonin system is sensitive to such hormone fluctuations, and serotonin reuptake inhibitors (SSRIs) are used to treat PND, although treatment is suboptimal and it is not known at which peripartum time-point SSRI treatment may be most efficacious. In this study, we investigate the effect of the SSRI paroxetine (5mg/kgs.c.) on swim stress-induced corticosterone in a rat model of postpartum depression. In the rat model corticosterone (CORT; 40mg/kgs.c.) was administered in Sprague Dawley rats across postpartum day (PD)2 to PD14. Stress response was measured during the first exposure to the forced swim test (FST1), and depressive-like behavior was measured in both FST1 and FST2. We found that paroxetine completely blunted the swim stress-induced CORT response and increased depressive-like behavior in both FST1 and FST2. Our findings suggest that in the postpartum context, SSRIs compromise stress axis dynamics, which are needed for a healthy stress response. This is likely unfavorable for reversing depressive-like behavior and may provide a rationale for augmentation strategies beyond SSRIs alone to optimize the clinical management of PND.

Long-Term Administration of Queen Bee Acid (QBA) to Rodents Reduces Anxiety-Like Behavior, Promotes Neuronal Health and Improves Body Composition

Background: Queen bee acid (QBA; 10-hydroxy-2-decenoic acid) is the predominant fatty acid in royal jelly (RJ) and has activity at estrogen receptors, which affect brain function and body composition. However, few, long-term studies have assessed QBA effects in brain health and body composition. Methods: Primary hippocampal neurons were treated with QBA (0–30 µM) and challenged with glutamate or hypoxia. QBA was fed to aged, male Sprague-Dawley rats (12–24 mg/kg/day) and to adult male and female Balb/C mice (30–60 mg/kg/day) for ≥3.5 months. Rats were evaluated in a behavioral test battery of brain function. Mice were measured for fat and muscle composition, as well as bone density. Results: QBA increased neuron growth and protected against glutamate challenge and hypoxia challenge. Rats receiving QBA had reduced anxiety-like behavior, increased body weight, and better maintenance of body weight with age. Mice receiving QBA exhibited increased body weight, muscle mass, and adiposity in males, and increased bone density, but decreased adiposity, in females. Conclusions: QBA is an active component of RJ that promotes the growth and protection of neurons, reduces anxiety-like phenotypes, and benefits bone, muscle and adipose tissues in a sex-dependent manner, which further implicates estrogen receptors in the effects of QBA.

Early maternal separation promotes apoptosis in dentate gyrus and alters neurological behaviors in adolescent rats

Adverse early-life experience such as maternal separation (MS) affects the behavior of adult, and may also aggravate the outcome of neurological insults. In this study, we aimed to investigate the effects of early MS on hippocampus-related behaviors, and to assess the mechanisms. Newborn rats were randomly divided into normal control and MS groups. Our data showed that MS (P3-P21) impaired learning ability as well as memory retrieval, and caused depression-like activity, but decreased anxiety-like activity. Glutamate receptor 1 (GluR1) expression in the dentate gyrus (DG) region was significantly reduced in the adults (P60). Mechanically, MS promoted apoptosis, and reduced protein kinase B (AKT) phosphorylation in the DG region in the early phase (P21). By contrast, MS did not affect ERK phosphorylation. Our data implicate that the inactivation of AKT pathway and apoptosis of DG cells might contribute to MS-induced behavioral changes. This study would provide useful evidence implicating the pathological changes for MS.