β-Catenin Role in the Vulnerability/Resilience to Stress-Related Disorders Is Associated to Changes in the Serotonergic System

Milnacipran and Vanillin Alleviate Fibromyalgia-Associated Depression in Reserpine-Induced Rat Model: Role of Wnt/β-Catenin Signaling

Fibromyalgia (FM) patients are highly susceptible to depression. Wnt/β-catenin signaling has shown a crucial role against depression in several studies. The FDA-approved FM drug, milnacipran (Miln), has shown antinociceptive potential against FM. Yet, no study has investigated its antidepressant potential in FM. Vanillin (Van), a well-known phytochemical often employed as flavoring agent, has been previously reported for its antidepressant and antinociceptive effects in several animal models, but has not been tested so far in FM. This study explored the antidepressant effect of Van and Miln in FM through investigating Wnt/β-catenin signaling. FM was induced in female Wistar rats by injecting reserpine (1 mg/kg/day s.c) for 3 days. Thereafter, animals received either Miln (30 mg/kg/day p.o) or Van (100 mg/kg/day p.o) for the subsequent 14 days. Results showed that both drugs demonstrated antidepressant effect in forced swimming test besides analgesic, and antiallodynic influences observed in Randall-Selitto, hot plate, cold allodynia, Von-Frey, and tail immersion tests. Biochemically, Miln and Van significantly enhanced serotonergic transmission in the hippocampus and upregulated the protein expression of the Wnt/GSK-3β/β-catenin signaling axis, including the downstream proteins, T cell factor, and dicer. This is followed by subsequent upregulation of the resilience micro ribonucleic acids (miRNAs) 124 and 135. Histopathological examinations corroborated the biochemical and molecular findings. Interestingly, these effects of Miln and Van were overturned via administration of the β-catenin inhibitor, XAV939 (0.1 mg/kg, i.p., daily). In conclusion, this study outlined the antidepressant aptitude of Miln and Van through activating Wnt/β-catenin signaling in the hippocampus in reserpine-induced FM.

Ameliorative Effect of Moringa oleifera Against CUMS-Induced Anxiety in Rats: β-Catenin and 5-HT1 A Crosstalk

Serotonin 1 A receptor (5-HT1 AR) signaling is pivotal for stress response, determining vulnerability or resilience to psychopathology. However, the precise pathological mechanisms underlying its role remain inconsistent. Moringa oleifera (MO), a plant with purported medicinal properties, has demonstrated potential efficacy against psychiatric disorders. However, no available information exists regarding its effects on 5-HT1 A signaling under normal and stressed conditions. This study is aimed at elucidating the effects of MO in conjunction with 5-HT1 A signaling. Rats were randomly assigned to four groups: normal (NRML), normal rats receiving MO orally at 200 mg/kg (MO), rats exposed to chronic unpredictable mild stress (CUMS) for 21 days (CUMS), and stressed rats administered MO from day 15 (CUMS + MO). Behavioral analysis was conducted using forced swimming and open field tests. Serotonergic markers, β-catenin, p-Erk, c-myc, and mTOR were assessed via ELISA, while miRNA clusters and individual miRNAs were analyzed using PCR. No significant differences were observed between the NRML and MO groups, both of which exhibited approximately normal biochemical activity, except for a decreased 5-HIAA/5-HT ratio in the MO group, which was reflected behaviorally. Rats subjected to CUMS displayed defective β-catenin signaling, potentially leading to compensatory activation of 5-HT1 A. Consistently, the CUMS + MO group exhibited normalized 5-HT1 A and 5-HT signaling, accompanied by reduced pThr183-Erk and its downstream targets, c-myc and miR- 203, to mitigate pathological anxiety. Additionally, mTOR and its downstream target, miR- 217, were reduced compared to stressed rats. MO exhibited a promising anxiolytic effect by modulating 5-HT1 A signaling, as evidenced by improved neurobehavioral outcomes and restoring biochemical balance in stressed rats. These findings highlight its potential therapeutic role in anxiety management.

Amelioration of gap junction dysfunction in a depression model by loganin: Involvement of GSK-3β/β-catenin signaling

ETHNOPHARMACOLOGICAL RELEVANCE

Cornus officinalis Sieb. et Zucc has significant neuroprotective activity and has been widely studied for its potential to improve cognitive function. Our team's previous research has found that loganin isolated from Cornus officinalis has an antidepressant effect. Depression is a mental disorder accompanied by dysfunction of Connexin43 (Cx43)-formed astrocytic gap junctions. However, the precise mechanisms of loganin involved remain uncertain.

AIM OF THE STUDY

We aimed to examine the mechanism by which loganin produces its antidepressant properties.

MATERIALS AND METHODS

Using a chronic unpredictable stress (CUS) model of depression in rats, the study evaluated the behavioral responses to treatment with loganin, fluoxetine, and their combination. Biochemical analyses were conducted to measure the expression and phosphorylation status of Cx43, β-catenin, GSK-3β in the brain. In vitro experiments were also performed how loganin protects the gap junctions in astrocytes that have been exposed to corticosterone.

RESULTS

After four weeks of loganin treatment, rats exposed to CUS showed a decrease in depressive-like behaviors. When combined with fluoxetine, the antidepressant-like effects were observed faster than with either treatment alone. Loganin significantly increased Cx43 expression in the prefrontal cortex and ventral hippocampus, reversed Cx43 mimetic peptide Gap26-induced depressive-like behaviors, decreased Cx43 phosphorylation at Ser368, increased β-catenin levels, and promoted GSK-3β phosphorylation at Ser9. In vitro, loganin prevented corticosterone-induced damage to gap junctions between astrocytes, an effect that was negated by XAV-939 (β-catenin inhibitor).

CONCLUSION

These results implied that loganin could exert antidepressant-like effects by improving the gap junctions of astrocytes in the prefrontal cortex and hippocampus, acting through the GSK-3β/β-catenin signaling pathway. The combination of loganin with fluoxetine may provide a faster onset of antidepressant action compared to either treatment alone, highlighting the potential of loganin as a natural adjunct therapy for depression.

The hippocampus in stress susceptibility and resilience: Reviewing molecular and functional markers

Understanding the individual variability that comes with the likelihood of developing stress-related psychopathologies is of paramount importance when addressing mechanisms of their neurobiology. This article focuses on the hippocampus as a region that is highly influenced by chronic stress exposure and that has strong ties to the development of related disorders, such as depression and post-traumatic stress disorder. We first outline three commonly used animal models that have been used to separate animals into susceptible and resilient cohorts. Next, we review molecular and functional hippocampal markers of susceptibility and resilience. We propose that the hippocampus plays a crucial role in the differences in the processing and storage of stress-related information in animals with different stress susceptibilities. These hippocampal markers not only help us attain a more comprehensive understanding of the various facets of stress-related pathophysiology, but also could be targeted for the development of new treatments.

Enhancing Endocannabinoid Signaling via β-Catenin in the Nucleus Accumbens Attenuates PTSD- and Depression-like Behavior of Male Rats

Inhibition of fatty acid amide hydrolase (FAAH), which increases anandamide levels, has been suggested as a potential treatment for stress-related conditions. We examined whether the stress-preventing effects of the FAAH inhibitor URB597 on behavior are mediated via β-catenin in the nucleus accumbens (NAc). Male rats were exposed to the shock and reminders model of PTSD and then treated with URB597 (0.4 mg/kg; i.p.). They were tested for anxiety- (freezing, startle response), depression-like behaviors (despair, social preference, anhedonia), and memory function (T-maze, social recognition). We also tested the involvement of the CB1 receptor (CB1r), β-catenin, and metabotropic glutamate receptor subtype 5 (mGluR5) proteins. URB597 prevented the shock- and reminders-induced increase in anxiety- and depressive-like behaviors, as well as the impaired memory via the CB1r-dependent mechanism. In the NAc, viral-mediated β-catenin overexpression restored the behavior of rats exposed to stress and normalized the alterations in protein levels in the NAc and the prefrontal cortex. Importantly, when NAc β-catenin levels were downregulated by viral-mediated gene transfer, the therapeutic-like effects of URB597 were blocked. We suggest a potentially novel mechanism for the therapeutic-like effects of FAAH inhibition that is dependent on β-catenin activation in the NAc in a PTSD rat model.

mTOR Knockdown in the Infralimbic Cortex Evokes A Depressive-like State in Mouse

Fast and sustained antidepressant effects of ketamine identified the mammalian target of rapamycin (mTOR) signaling pathway as the main modulator of its antidepressive effects. Thus, mTOR signaling has become integral for the preclinical evaluation of novel compounds to treat depression. However, causality between mTOR and depression has yet to be determined. To address this, we knocked down mTOR expression in mice using an acute intracerebral infusion of small interfering RNAs (siRNA) in the infralimbic (IL) or prelimbic (PrL) cortices of the medial prefrontal cortex (mPFC), and evaluated depressive- and anxious-like behaviors. mTOR knockdown in IL, but not PrL, cortex produced a robust depressive-like phenotype in mice, as assessed in the forced swimming test (FST) and the tail suspension test (TST). This phenotype was associated with significant reductions of mTOR mRNA and protein levels 48 h post-infusion. In parallel, decreased brain-derived neurotrophic factor (BDNF) expression was found bilaterally in both IL and PrL cortices along with a dysregulation of serotonin (5-HT) and glutamate (Glu) release in the dorsal raphe nucleus (DRN). Overall, our results demonstrate causality between mTOR expression in the IL cortex and depressive-like behaviors, but not in anxiety.

5-HT4 Receptors Are Not Involved in the Effects of Fluoxetine in the Corticosterone Model of Depression

Clinical and preclinical studies report the implication of 5-hydroxytryptamine 4 receptors (5-HT₄Rs) in depression and anxiety. Here, we tested whether the absence of 5-HT4Rs influences the response to the antidepressant fluoxetine in mice subjected to chronic corticosterone administration, an animal model of depression and anxiety. Therefore, the effects of chronic administration of fluoxetine in corticosterone-treated wild-type (WT) and 5-HT₄R knockout (KO) mice were evaluated in the open-field and novelty suppressed feeding tests. As 5-HT_1A receptor (5-HT_1AR) and brain-derived neurotrophic factor (BDNF) are critically involved in depression and anxiety, we further evaluated 5-HT_1A receptor functionality by [³⁵S]GTPγS autoradiography and BDNF mRNA expression by in situ hybridization techniques. We found that 5-HT₄R KO and WT mice displayed anxiety- and depressive-like behavior following chronic administration of corticosterone, as evidenced in the open-field and novelty suppressed feeding tests. In the open-field, a decreased central activity was observed in naïve and corticosterone-treated mice of both genotypes following chronic fluoxetine administration. In the novelty suppressed feeding test, a predictive paradigm of antidepressant activity, chronic treatment with fluoxetine reverted the latency to eat in both genotypes. The antidepressant also potentiated the corticosterone-induced desensitization of the 5-HT_1AR in the dorsal raphe nucleus. Further, chronic fluoxetine increased BDNF mRNA expression in the dentate gyrus of the hippocampus in corticosterone-treated mice of both genotypes. Therefore, our findings indicate that the behavioral effects of fluoxetine in the corticosterone model of depression and anxiety appear not to be dependent on 5-HT₄Rs.