Unpredictable chronic mild stress induces anxiety and depression-like behaviors and inactivates AMP-activated protein kinase in mice

SARM1 deficiency induced depressive-like behavior via AMPKα/p-eEF2 axis to synapse dysfunction

Sterile Alpha and TIR Motif Containing 1 (SARM1) are proteins implicated in various neurological processes; however, their role in depression remains unexplored. This study investigated the contribution of SARM1 to depressive-like behaviors in a chronic stress-induced depression model and SARM1 knockout (KO) mice. Depressive-like behaviors were assessed using a battery of behavioral tests, including the Open Field Test (OFT), the Forced Swim Test (FST), the Sucrose Preference Test (SPT), and the Tail Suspension Test (TST). Mitochondrial energy metabolism alteration, cytokine level changes, and other related molecular signaling protein expression were evaluated using ELISA and western blotting techniques to investigate the underlying mechanisms. Behavioral assessments (OFT, FST, SPT, TST) revealed depressive-like phenotypes in SARM1 KO mice, accompanied by altered mitochondrial energy metabolism (NAD+, ATP) in the cortex. Intriguingly, SARM1 depletion led to peripheral inflammation, as evidenced by elevated cytokine levels in plasma but not in brain regions (cortex). In addition, we found dysregulated energy metabolism, AMPK signaling, and synaptic plasticity in the cortex of SARM1 KO mice. Notably, AICAR (Acadesine), an AMPK activator, ameliorated depressive-like behaviors and synaptic dysfunction, while Compound C, an AMPK inhibitor, reversed these effects. Additionally, NH125, an eEF2 kinase inhibitor, improved depressive-like behaviors in SARM1 KO mice. These findings demonstrate that SARM1 is critical in regulating depressive-like behaviours through the AMPKα/p-eEF2 signaling pathway. Targeting AMPK signaling and synaptic function may offer novel therapeutic avenues for depression.

AMP-activated protein kinase in the amygdala and hippocampus contributes to enhanced fear memory in diabetic mice

BACKGROUND AND PURPOSE

Diabetic patients have an increased risk of psychiatric disorders. Because hyperglycaemia increases L-lactate in the brain and L-lactate inhibits AMP-activated protein kinase (AMPK), this study investigated the role of L-lactate and AMPK in strengthened fear memory, a model for human psychiatric disorders, in diabetic mice.

EXPERIMENTAL APPROACH

The diabetic model was mice injected with streptozotocin. Fear memory was measured using the conditioned fear test with low (0.45 mA) or high (0.50 mA) foot shock to cause low and high freezing, respectively. Protein levels of AMPK and phosphorylated AMPK (pAMPK) were measured by western blotting and immunohistochemistry.

KEY RESULTS

At 0.45 mA, the AMPK inhibitor dorsomorphin increased freezing, which was inhibited by the AMPK activator acadesine. In contrast, at 0.50 mA, acadesine decreased freezing, which was inhibited by dorsomorphin. In diabetic mice, pAMPK was decreased in the amygdala and hippocampus. Diabetic mice showed increased freezing at 0.45 mA, which was inhibited by acadesine. In the amygdala and hippocampus, L-lactate was increased in diabetic mice and injection of L-lactate into non-diabetic mice increased freezing at 0.45 mA. In addition, L-lactate decreased pAMPK in the hippocampus, but not the amygdala, and increase in freezing induced by L-lactate was inhibited by acadesine. Dorsomorphin-induced increase in freezing was inhibited by the AMPA receptor antagonist NBQX.

CONCLUSIONS AND INTERPRETATION

In diabetic mice, L-lactate is increased in the amygdala and hippocampus, possibly through hyperglycaemia, which strengthens fear memory through inhibition of AMPK and activation of glutamatergic function.

Single administration of a psychedelic [(R)-DOI] influences coping strategies to an escapable social stress

Psychedelic compounds have potentially rapid, long-lasting anxiolytic, antidepressive and anti-inflammatory effects. We investigated whether the psychedelic compound (R)-2,5-dimethoxy-4-iodoamphetamine [(R)-DOI], a selective 5-HT2A receptor partial agonist, decreases stress-related behavior in male mice exposed to repeated social aggression. Additionally, we explored the likelihood that these behavioral changes are related to anti-inflammatory properties of [(R)-DOI]. Animals were subjected to the Stress Alternatives Model (SAM), an escapable social stress paradigm in which animals develop reactive coping strategies - remaining in the SAM arena (Stay) with a social aggressor, or dynamically initiated stress coping strategies that involve utilizing the escape holes (Escape) to avoid aggression. Mice expressing these behavioral phenotypes display behaviors like those in other social aggression models that separate animals into stress-vulnerable (as for Stay) or stress-resilient (as for Escape) groups, which have been shown to have distinct inflammatory responses to social stress. These results show that Stay animals have heightened cytokine gene expression, and both Stay and Escape mice exhibit plasma and neural concentrations of the inflammatory cytokine tumor necrosis factor-α (TNFα) compared to unstressed control mice. Additionally, these results suggest that a single administration of (R)-DOI to Stay animals in low doses, can increase stress coping strategies such as increasing attention to the escape route, promoting escape behavior, and reducing freezing during socially aggressive interaction in the SAM. Lower single doses of (R)-DOI, in addition to shifting behavior to suggest anxiolytic effects, also concomitantly reduce plasma and limbic brain levels of the inflammatory cytokine TNFα.

Differential effect of chronic mild stress on anxiety and depressive-like behaviors in three strains of male and female laboratory mice

Major depressive disorder is the most common psychiatric disorder worldwide. To understand mechanisms and search for new approaches to treating depression, animal models are crucial. Chronic mild stress (CMS) is the most used animal model of depression. Although CMS is considered a robust model of depression, conflicting results have been reported for emotion-related behaviors, which the intrinsic characteristics of each rodent strain could explain. To further shed light on the impact of genetic background on the relevant parameters commonly addressed in depression, we examined the effect of 4-weeks CMS on anxiety and depression-related behaviors and body weight gain in three strain mice (BALB/c, C57BL/6, and CD1) of both sexes. CMS reduced body weight gain in C57BL/6NCrl and CD1 male mice. C57BL/6 animals exhibited a more pronounced anxious-like behavior than CD1 and BALB/c mice in the light-dark box (LDB) and the elevated plus maze (EPM) tests, whereas BALB/c animals exhibited the more robust depressive-like phenotype in the splash test (ST), tail suspension test (TST) and forced-swimming test (FST). Under CMS, exposure did not affect anxiety-related behaviors in any strain but induced depression-like behaviors strain-dependently. CMS C57BL/6 and CD1 mice of both sexes showed depression-like behaviors, and CMS BALB/c male mice exhibited reduced depressive behaviors in the FST. These results suggest a differential effect of stress, with the C57BL/6 strain being more vulnerable to stress than the CD1 and BALB/c strain mice. Furthermore, our findings emphasize the need for researchers to consider mouse strains and behavioral tests in their CMS experimental designs.

Contribution of changes in the orexin system and energy sensors in the brain in depressive disorder - a study in an animal model

BACKGROUND

Maternal elevated glucocorticoid levels during pregnancy can affect the developing fetus, permanently altering the structure and function of its brain throughout life. Excessive action of these hormones is known to contribute to psychiatric disorders, including depression.

MATERIALS

The study was performed in a rat model of depression based on prenatal administration of dexamethasone (DEX) in late pregnancy (0.1 mg/kg, days 14-21). We evaluated the effects of prenatal DEX treatment on the cognition and bioenergetic signaling pathways in the brain of adult male rats, in the frontal cortex and hippocampus, and in response to stress in adulthood, using behavioral and biochemical test batteries.

RESULTS

We revealed cognitive deficits in rats prenatally treated with DEX. At the molecular level, a decrease in the orexin A and orexin B levels and downregulation of the AMPK-SIRT1-PGC1α transduction pathway in the frontal cortex of these animals were observed. In the hippocampus, a decreased expression of orexin B was found and changes in the MR/GR ratio were demonstrated. Furthermore, an increase in HDAC5 level triggered by the prenatal DEX treatment in both brain structures and a decrease in MeCP2 level in the hippocampus were reported.

CONCLUSIONS

Our study demonstrated that prenatal DEX treatment is associated with cognitive dysfunction and alterations in various proteins leading to metabolic changes in the frontal cortex, while in the hippocampus adaptation mechanisms were activated. The presented results imply that different pathophysiological metabolic processes may be involved in depression development, which may be useful in the search for novel therapies.

Repetitive transcranial magnetic stimulation and fluoxetine attenuate astroglial activation and benefit behaviours in a chronic unpredictable mild stress mouse model of depression

Objectives: Repetitive transcranial magnetic stimulation (rTMS) has been considered as an effective antidepressant treatment; however, the mechanism of its antidepressant effect is still unclear. Fluoxetine, a selective serotonin reuptake inhibitor antidepressant, may be neuroprotective. The objective of the present study was to evaluate the effect and underlying possible neuroprotective mechanism of rTMS and fluoxetine on abnormal behaviours in a depressive mouse model induced by chronic unpredictable mild stress (CUMS).Methods: After 28 days of CUMS exposure, mice were chronically treated with rTMS (10 Hz for 5 s per train, total 20 trains per day) and (or) fluoxetine (5 mg/kg/day, intraperitoneally) for 28 days targeting on the frontal cortex. After the behavioural tests, the protein expressions of glial fibrillary acidic protein (GFAP), brain-derived neurotrophic factor (BDNF) and tyrosine kinase B (TrkB) were measured by immunohistochemistry and (or) Western Blot.Results: The results showed rTMS and (or) fluoxetine attenuated the locomotion decrease, anxiety and depressive like behaviours in the CUMS-exposed mice.Conclusion: Our results suggest that both rTMS and fluoxetine could benefit the CUMS-induced abnormal behaviours including depressive-like behaviours, and the beneficial effects of rTMS as well as fluoxetine on depression might be partly related to their neuroprotective effect on attenuating astroglial activation and BDNF decrease.

Differential targeting of lysophosphatidic acid LPA1, LPA2, and LPA3 receptor signalling by tricyclic and tetracyclic antidepressants

We previously reported that in different cell types antidepressant drugs activate lysophosphatidic acid (LPA) LPA1 receptor to induce proliferative and prosurvival responses. Here, we further characterize this unique action of antidepressants by examining their effects on two additional LPA receptor family members, LPA2 and LPA3. Human LPA1-3 receptors were stably expressed in HEK-293 cells (HEK-LPA1, -LPA2 and -LPA3 cells) and their functional activity was determined by Western blot and immunofluorescence. LPA effectively stimulated the phosphorylation of extracellular signal-regulated protein kinases 1 and 2 (ERK1/2) in HEK-LPA1, -LPA2, and -LPA3 cells. The tricyclic antidepressants amitriptyline, clomipramine, imipramine and desipramine increased phospho-ERK1/2 levels in HEK-LPA1 and -LPA3 cells but were relatively poor agonists in LPA2-expressing cells. The tetracyclic antidepressants mianserin and mirtazapine were active at all three LPA receptors. When combined with LPA, both amitriptyline and mianserin potentiated Gi/o-mediated phosphorylation of ERK1/2 induced by LPA in HEK-LPA1, -LPA2 and -LPA3 cells, CHO-K1 fibroblasts and HT22 hippocampal neuroblasts. This potentiation was associated with enhanced phosphorylation of CREB and S6 ribosomal protein, two molecular targets of activated ERK1/2. The antidepressants also potentiated LPA-induced Gq/11-mediated phosphorylation of AMP-activated protein kinase in HEK-LPA1 and -LPA3 cells. Conversely, amitriptyline and mianserin were found to inhibit LPA-induced Rho activation in HEK-LPA1 and LPA2 cells. These results indicate that tricyclic and tetracyclic antidepressants can act on LPA1, LPA2 and LPA3 receptor subtypes and exert differential effects on LPA signalling through these receptors.

The neural basis underlying female vulnerability to depressive disorders

Depressive disorders are more prevalent and severe in women; however, our knowledge of the underlying factors contributing to female vulnerability to depression remains limited. Additionally, females are notably underrepresented in studies seeking to understand the mechanisms of depression. Various animal models of depression have been devised, but only recently have females been included in research. In this comprehensive review, we aim to describe the sex differences in the prevalence, pathophysiology, and responses to drug treatment in patients with depression. Subsequently, we highlight animal models of depression in which both sexes have been studied, in the pursuit of identifying models that accurately reflect female vulnerability to depression. We also introduce explanations for the neural basis of sex differences in depression. Notably, the medial prefrontal cortex and the nucleus accumbens have exhibited sex differences in previous studies. Furthermore, other brain circuits involving the dopaminergic center (ventral tegmental area) and the serotonergic center (dorsal raphe nucleus), along with their respective projections, have shown sex differences in relation to depression. In conclusion, our review covers the critical aspects of sex differences in depression, with a specific focus on female vulnerability in humans and its representation in animal models, including the potential underlying mechanisms. Employing suitable animal models that effectively represent female vulnerability would benefit our understanding of the sex-dependent pathophysiology of depression.

Stress can affect mitochondrial energy metabolism and AMPK/SIRT1 signaling pathway in rats

OBJECTION

To investigate the potential link between aberrant mitochondrial energy metabolism mediated by the AMPK/SIRT1 pathway and the etiology of anxiety disorders.

METHODS

The anxiety rat model was established by uncertain empty water bottle（UEWB）stress. Rats were submitted behavioral tests on the seventh, fourteenth, and twenty-first days and had the prefrontal cortex and amygdala removed for biochemical tests. The morphological alterations of the mitochondria in the medial prefrontal cortex and amygdala were examined by using a transmission electron microscope. Expression levels of AMPK, SIRT1, PGC-1, NRF-1 and NRF-2 were tested by western-blot analysis. ATP, respiratory chain complex and caspase enzyme expressions were tested by neurochemical and biochemical assays.

RESULTS

Rats showed anxiety-like behavior after being exposed to the uncertain empty water bottle (UEWB) stress model. In model rats, mitochondrial structure is damaged, mitochondrial energy metabolism is decreased, and the expression of proteins associated with AMPK/SIRT1 pathway is significantly reduced in the brain.

CONCLUSION

The level of mitochondrial energy metabolism correlates with anxiety-like behavior. The main mechanism of anxiety disorder is a disturbance of mitochondrial energy metabolism, which might be related to AMPK/SIRT1 pathway.

AMPK and the Endocrine Control of Metabolism

Complex multicellular organisms require a coordinated response from multiple tissues to maintain whole-body homeostasis in the face of energetic stressors such as fasting, cold, and exercise. It is also essential that energy is stored efficiently with feeding and the chronic nutrient surplus that occurs with obesity. Mammals have adapted several endocrine signals that regulate metabolism in response to changes in nutrient availability and energy demand. These include hormones altered by fasting and refeeding including insulin, glucagon, glucagon-like peptide-1, catecholamines, ghrelin, and fibroblast growth factor 21; adipokines such as leptin and adiponectin; cell stress-induced cytokines like tumor necrosis factor alpha and growth differentiating factor 15, and lastly exerkines such as interleukin-6 and irisin. Over the last 2 decades, it has become apparent that many of these endocrine factors control metabolism by regulating the activity of the AMPK (adenosine monophosphate-activated protein kinase). AMPK is a master regulator of nutrient homeostasis, phosphorylating over 100 distinct substrates that are critical for controlling autophagy, carbohydrate, fatty acid, cholesterol, and protein metabolism. In this review, we discuss how AMPK integrates endocrine signals to maintain energy balance in response to diverse homeostatic challenges. We also present some considerations with respect to experimental design which should enhance reproducibility and the fidelity of the conclusions.

Anxiolytic effect of antidiabetic metformin is mediated by AMPK activation in mPFC inhibitory neurons

Diabetic patients receiving the antidiabetic drug metformin have been observed to exhibit a lower prevalence of anxiety disorders, yet the precise mechanism behind this phenomenon is unclear. In our study, we found that anxiety induces a region-specific reduction in AMPK activity in the medial prefrontal cortex (mPFC). Concurrently, transgenic mice with brain-specific AMPK knockout displayed abnormal anxiety-like behaviors. Treatment with metformin or the overexpression of AMPK restored normal AMPK activity in the mPFC and mitigated social stress-induced anxiety-like behaviors. Furthermore, the specific genetic deletion of AMPK in the mPFC not only instigated anxiety in mice but also nullified the anxiolytic effects of metformin. Brain slice recordings revealed that GABAergic excitation and the resulting inhibitory inputs to mPFC pyramidal neurons were selectively diminished in stressed mice. This reduction led to an excitation-inhibition imbalance, which was effectively reversed by metformin treatment or AMPK overexpression. Moreover, the genetic deletion of AMPK in the mPFC resulted in a similar defect in GABAergic inhibitory transmission and a consequent hypo-inhibition of mPFC pyramidal neurons. We also generated a mouse model with AMPK knockout specific to GABAergic neurons. The anxiety-like behaviors in this transgenic mouse demonstrated the unique role of AMPK in the GABAergic system in relation to anxiety. Therefore, our findings suggest that the activation of AMPK in mPFC inhibitory neurons underlies the anxiolytic effects of metformin, highlighting the potential of this primary antidiabetic drug as a therapeutic option for treating anxiety disorders.

Chronic Stress Impairs the Structure and Function of Astrocyte Networks in an Animal Model of Depression

Now astrocytes appear to be the key contributors to the pathophysiology of major depression. Evidence in rodents shows that chronic stress is associated with a decreased expression of astrocytic GFAP-immunoreactivity within the cortex in addition to changes in the complexity and length of astrocyte processes. Furthermore, postmortem brains of individuals with depression have revealed a decrease in astrocyte density. Notably, astrocytes are extensively coupled to one another through gap junctions to form a network, or syncytium, and we have previously demonstrated that syncytial isopotentiality is a mechanism by which astrocytes function as an efficient system with respect to brain homeostasis. Interestingly, the question of how astrocyte network function changes following chronic stress is yet to be elucidated. Here, we sought to examine the effects of chronic stress on network-level astrocyte (dys)function. Using a transgenic aldh1l1-eGFP astrocyte reporter mouse, a six-week unpredictable chronic mild stress (UCMS) paradigm as a rodent model of major depression, and immunohistochemical approaches, we show that the morphology of individual astrocytes is altered by chronic stress exposure. Additionally, in astrocyte syncytial isopotentiality measurement, we found that UCMS impairs the syncytial coupling strength of astrocytes within the hippocampus and prefrontal cortex-two brain regions that have been implicated in the regulation of mood. Together, these findings reveal that chronic stress leads to astrocyte atrophy and impaired gap junction coupling, raising the prospect that both individual and network-level astrocyte functionality are important in the etiology of major depression and other neuropsychiatric disorders.

Anterior cingulate cortex, but not amygdala, modulates the anxiogenesis induced by living with conspecifics subjected to chronic restraint stress in male mice

Cohabitation with a partner undergoing chronic restraint stress (CRE) induces anxiogenic-like behaviors through emotional contagion. We hypothesized that the anterior cingulate cortex (ACC) and the amygdala would be involved in the modulation of this emotional process. This study investigated the role of the ACC and amygdala in empathy-like behavior (e.g., anxiety-like responses) induced by living with a mouse subjected to CRE. Male Swiss mice were housed in pairs for 14 days and then allocated into two groups: cagemate stress (one animal of the pair was subjected to 14 days of restraint stress) and cagemate control (no animal experienced stress). Twenty-four hours after the last stress session, cagemates had their brains removed for recording FosB labeling in the ACC and amygdala (Exp.1). In experiments 2 and 3, 24 h after the last stress session, the cagemates received 0.1 μL of saline or cobalt chloride (CoCl₂ 1 mM) into the ACC or amygdala, and then exposed to the elevated plus-maze (EPM) for recording anxiety. Results showed a decrease of FosB labeling in the ACC without changing immunofluorescence in the amygdala of stress cagemate mice. Cohabitation with mice subjected to CRE provoked anxiogenic-like behaviors. Local inactivation of ACC (but not the amygdala) reversed the anxiogenic-like effects induced by cohabitation with a partner undergoing CRE. These results suggest the involvement of ACC, but not the amygdala, in anxiety induced by emotional contagion.

Anxiety-like behavior and GABAergic system in ovariectomized rats exposed to chronic mild stress

Stress or low level of estrogen could promote anxiety and depression; thus, it is of interest to investigate the combined effect of mild stress and the lack of estrogen on mental disorders by utilizing an animal model. This study was conducted to assess anxiety- and depressive- like behaviors in ovariectomized (Ovx) rats exposed to chronic mild stress (CMS) and determine the alteration in gamma-aminobutyric acid (GABA)-related transmission. Ovx rats were randomly assigned into four groups: (1) estrogen replacement (E2-NoCMS), (2) estrogen replacement and exposure to CMS (E2-CMS), (3) vehicle (VEH-NoCMS), and (4) vehicle and exposure to CMS (VEH-CMS). Following 4-week CMS, VEH groups (VEH-NoCMS and VEH-CMS) showed a similar level of anxiety-like behavior in elevated T-maze, whereas E2-CMS, VEH-NoCMS and VEH-CMS showed anxiety-like behavior in open field. The depressive-like behavior in the force swimming test tended to be affected by estrogen deprivation than CMS. The alteration of the GABAergic system as determined from the GABA level and mRNA expression of GABA-related transmission (i.e., glutamic acid decarboxylase, GABA transporter and GABA_A subunits) showed that the GABA level in the amygdala and frontal cortex was affected by CMS. For mRNA expression, the mRNA profile in the amygdala and hippocampus of VEH-NoCMS and E2-CMS was the same but different from those of VEH-NoCMS and E2-CMS. In addition, compared with E2-NoCMS, the mRNA profile in the frontal cortex was similar in VEH-NoCMS, E2-CMS, and VEH-CMS. These findings indicated that the underlying mechanism of the GABAergic system was differently modified, although VEH-NoCMS and VEH-CMS showed anxiety-like behavior. The findings of this study may provide a comprehensive understanding of the modulation of the GABAergic system during estrogen deprivation under CMS, as observed in menopausal women who were daily exposed to stress.

Handling method affects measures of anxiety, but not chronic stress in mice

Studies in mice have shown that less aversive handling methods (e.g. tunnel or cup handling) can reduce behavioural measures of anxiety in comparison to picking mice up by their tail. Despite such evidence, tail handling continues to be used routinely. Besides resistance to change accustomed procedures, this may also be due to the fact that current evidence in support of less aversive handling is mostly restricted to effects of extensive daily handling, which may not apply to routine husbandry practices. The aim of our study was to assess whether, and to what extent, different handling methods during routine husbandry induce differences in behavioural and physiological measures of stress in laboratory mice. To put the effects of handling method in perspective with chronic stress, we compared handling methods to a validated paradigm of unpredictable chronic mild stress (UCMS). We housed mice of two strains (Balb/c and C57BL/6) and both sexes either under standard laboratory conditions (CTRL) or under UCMS. Half of the animals from each housing condition were tail handled and half were tunnel handled twice per week, once during a cage change and once for a routine health check. We found strain dependent effects of handling method on behavioural measures of anxiety: tunnel handled Balb/c mice interacted with the handler more than tail handled conspecifics, and tunnel handled CTRL mice showed increased open arm exploration in the elevated plus-maze. Mice undergoing UCMS showed increased plasma corticosterone levels and reduced sucrose preference. However, we found no effect of handling method on these stress-associated measures. Our results therefore indicate that routine tail handling can affect behavioural measures of anxiety, but may not be a significant source of chronic husbandry stress. Our results also highlight strain dependent responses to handling methods.

Effects of cereblon on stress-activated redox proteins and core behavior

The mechanisms underlying the vulnerability and resilience of an individual to stress are only partly understood. Response to stress is determined by behavioral and biochemical changes in the brain. Chronic ultra-mild stress (CUMS) induces an anhedonic-like state in mice that resembles symptoms of human depression. This study reports the role of cereblon (CRBN) in regulating the metabolic and antioxidant status of neuronal tissues in the mouse model of CUMS. Intriguingly, Crbn^-/- (KO) mice showed resilient responsiveness, both at the behavioral and proteomic levels. Several core behaviors were also differentially altered by CUMS in KO mice. Liquid chromatography with tandem mass spectrometry (LC-MS/MS)-based proteome analysis of whole brain lysate (WBL) showed an enriched chaperonic, metabolic, and antioxidant status in the brains of KO subjects, including several members of DNAJ chaperones, creatine kinase, quinone oxidoreductase, superoxide dismutase (SOD1), glutathione S-transferase Mu (GSTM), peroxiredoxin-6 (PRDX6), and thioredoxin. Pathological phosphorylation as characterized by aggregation of tau and α-synuclein (α-syn) was significantly reduced in the neuronal tissues of KO mouse model of CUMS as compared to wild type (WT) mice. Furthermore, significantly increased SOD1 activity and reduced lipid peroxidation were observed in Crbn-KO systems. Integrated signaling pathways were also identified in CRBN-specific sub-networks constructed from protein-protein interaction analysis by STRING. The present study highlights the roles of CRBN in regulating the stress response (SR) and reshaping metabolic status in the brains of mice exposed to CUMS. A better understanding of the molecular mechanisms of depression and neurodegeneration can improve the development of novel treatments.

Boosting amygdaloid GABAergic and neurotrophic machinery via dapagliflozin-enhanced LKB1/AMPK signaling in anxious demented rats

Anxiety is a neuropsychiatric disturbance that is commonly manifested in various dementia forms involving Alzheimer's disease (AD). The mechanisms underlying AD-associated anxiety haven't clearly recognized the role of energy metabolism in anxiety represented by the amygdala's autophagic sensors; liver kinase B1 (LKB1)/adenosine monophosphate kinase (AMPK). Dapagliflozin (DAPA), a SGLT2 inhibitor, acts as an autophagic activator through LKB1 activation in several diseases including AD. Herein, the propitious yet undetected anxiolytic potential of DAPA as an autophagic enhancer was investigated in AD animal model with emphasis on amygdala's GABAergic neurotransmission and brain-derived neurotrophic factor (BDNF). Alzheimer's disease was induced by ovariectomy (OVX) along with seventy-days-D-galactose (D-Gal) administration (150 mg/kg/day, i.p). On the 43rd day of D-Gal injection, OVX/D-Gal-subjected rats received DAPA (1 mg/kg/day, p.o) alone or with dorsomorphin the AMPK inhibitor (DORSO, 25 μg/rat, i.v.). In the amygdala, LKB1/AMPK were activated by DAPA inducing GABA_B2 receptor stimulation; an effect that was abrogated by DORSO. Dapagliflozin also replenished the amygdala GABA, NE, and 5-HT levels along with glutamate suppression. Moreover, DAPA triggered BDNF production with consequent activation of its receptor, TrkB through activating GABA_B2-related downstream phospholipase C/diacylglycerol/protein kinase C (PLC/DAG/PKC) signaling. This may promote GABA_A expression, verifying the crosstalk between GABA_A and GABA_B2. The DAPA's anxiolytic effect was visualized by improved behavioral traits in elevated plus maze together with amendment of amygdala' histopathological abnormalities. Thus, the present study highlighted DAPA's anxiolytic effect which was attributed to GABA_B2 activation and its function to induce BDNF/TrkB and GABA_A expression through PLC/DAG/PKC pathway in AMPK-dependent manner.

The interplay of hypoxic and mental stress: Implications for anxiety and depressive disorders

Adequate oxygen supply is essential for the human brain to meet its high energy demands. Therefore, elaborate molecular and systemic mechanism are in place to enable adaptation to low oxygen availability. Anxiety and depressive disorders are characterized by alterations in brain oxygen metabolism and of its components, such as mitochondria or hypoxia inducible factor (HIF)-pathways. Conversely, sensitivity and tolerance to hypoxia may depend on parameters of mental stress and the severity of anxiety and depressive disorders. Here we discuss relevant mechanisms of adaptations to hypoxia, as well as their involvement in mental stress and the etiopathogenesis of anxiety and depressive disorders. We suggest that mechanisms of adaptations to hypoxia (including metabolic responses, inflammation, and the activation of chemosensitive brain regions) modulate and are modulated by stress-related pathways and associated psychiatric diseases. While severe chronic hypoxia or dysfunctional hypoxia adaptations can contribute to the pathogenesis of anxiety and depressive disorders, harnessing controlled responses to hypoxia to increase cellular and psychological resilience emerges as a novel treatment strategy for these diseases.

Treat more than heat-New therapeutic implications of Cimicifuga racemosa through AMPK-dependent metabolic effects

BACKGROUND

Cimicifuga racemosa extracts (CRE) have obtained a "well-established use status" in the treatment of postmenopausal (i.e., climacteric) complaints, which predominantly include vasomotor symptoms such as hot flushes and sweating, as well as nervousness, irritability, and metabolic changes. Although characteristic postmenopausal complaints are known for a very long time and the beneficial effects of CRE on climacteric symptoms are well accepted, both the pathophysiology of postmenopausal symptoms and the mechanism of action of CREs are not yet fully understood. In particular, current hypotheses suggest that changes in the α-adrenergic and serotonergic signaling pathways secondary to estrogen depletion are responsible for the development of hot flushes.

PURPOSE

Some of the symptoms associated with menopause cannot be explained by these hypotheses. Therefore, we attempted to extend our classic understanding of menopause by integrating of partly age-related metabolic impairments.

METHODS

A comprehensive literature survey was performed using the PubMed database for articles published through September 2021. The following search terms were used: (cimicifuga OR AMPK) AND (hot flush* OR hot flash* OR menopaus* OR osteoporos* OR cancer OR antioxida* OR cardiovasc*). No limits were set with respect to language, and the references cited in the articles retrieved were used to identify additional publications.

RESULTS

We found that menopause is a manifestation of the general aging process, with specific metabolic changes that aggravate menopausal symptoms, which are accelerated by estrogen depletion and associated neurotransmitter dysregulation. Cimicifuga extracts with their metabolic effects mitigate climacteric symptoms but may also modulate the aging process itself. Central to these effects are effects of CRE on the metabolic key regulator, the AMP-activated protein kinase (AMPK).

CONCLUSIONS

As an extension of this effect dimension, other off-label indications may appear attractive in the sense of repurposing of this herbal treatment.

Targeting NRF2 in Type 2 diabetes mellitus and depression: Efficacy of natural and synthetic compounds

Evidence supports a strong bidirectional association between depression and Type 2 diabetes mellitus (T2DM). The harmful impact of oxidative stress and chronic inflammation on the development of both disorders is widely accepted. Nuclear factor erythroid 2-related factor 2 (NRF2) is a pertinent target in disease management owing to its reputation as the master regulator of antioxidant responses. NRF2 influences the expression of various cytoprotective phase 2 antioxidant genes, which is hampered in both depression and T2DM. Through interaction and crosstalk with several signaling pathways, NRF2 endeavors to contain the widespread oxidative damage and persistent inflammation involved in the pathophysiology of depression and T2DM. NRF2 promotes the neuroprotective and insulin-sensitizing properties of its upstream and downstream targets, thereby interrupting and preventing disease advancement. Standard antidepressant and antidiabetic drugs may be powerful against these disorders, but unfortunately, they come bearing distressing side effects. Therefore, exploiting the therapeutic potential of NRF2 activators presents an exciting opportunity to manage such bidirectional and comorbid conditions.

Central Adiponectin Signaling – A Metabolic Regulator in Support of Brain Plasticity

Brain plasticity and metabolism are tightly connected by a constant influx of peripheral glucose to the central nervous system in order to meet the high metabolic demands imposed by neuronal activity. Metabolic disturbances highly affect neuronal plasticity, which underlies the prevalent comorbidity between metabolic disorders, cognitive impairment, and mood dysfunction. Effective pro-cognitive and neuropsychiatric interventions, therefore, should consider the metabolic aspect of brain plasticity to achieve high effectiveness. The adipocyte-secreted hormone, adiponectin, is a metabolic regulator that crosses the blood-brain barrier and modulates neuronal activity in several brain regions, where it exerts neurotrophic and neuroprotective properties. Moreover, adiponectin has been shown to improve neuronal metabolism in different animal models, including obesity, diabetes, and Alzheimer’s disease. Here, we aim at linking the adiponectin’s neurotrophic and neuroprotective properties with its main role as a metabolic regulator and to summarize the possible mechanisms of action on improving brain plasticity via its role in regulating the intracellular energetic activity. Such properties suggest adiponectin signaling as a potential target to counteract the central metabolic disturbances and impaired neuronal plasticity underlying many neuropsychiatric disorders.

Adenosine Monophosphate-activated Protein Kinase (AMPK) in serotonin neurons mediates select behaviors during protracted withdrawal from morphine in mice

Serotonin neurotransmission has been implicated in behavior deficits that occur during protracted withdrawal from opioids. In addition, studies have highlighted multiple pathways whereby serotonin (5-HT) modulates energy homeostasis, however the underlying metabolic effects of opioid withdrawal have not been investigated. A key metabolic regulator that senses the energy status of the cell and regulates fuel availability is Adenosine Monophosphate-activated Protein Kinase (AMPK). To investigate the interaction between cellular metabolism and serotonin in modulating protracted abstinence from morphine, we depleted AMPK in serotonin neurons. Morphine exposure via drinking water generates dependence in these mice, and both wildtype and serotonergic AMPK knockout mice consume similar amounts of morphine with no changes in body weight. Serotonergic AMPK contributes to baseline differences in open field and social interaction behaviors and blocks abstinence induced reductions in immobility following morphine withdrawal in the tail suspension test. Lastly, morphine locomotor sensitization is blunted in mice lacking AMPK in serotonin neurons. Taken together, our results suggest serotonergic AMPK mediates both baseline and protracted morphine withdrawal-induced behaviors.

High and fluctuating levels of ovarian hormones induce an anxiogenic effect, which can be modulated under stress conditions: Evidence from an assisted reproductive rodent model

Elevated levels of endogenous ovarian hormones are conditions commonly experienced by women undergoing assisted reproductive technologies (ART). Additionally, infertility-associated stress and treatment routines are factors that together may have a highly negative impact on female emotionality, which can be aggravated when several cycles of ART are needed to attempt pregnancy. This study aimed to investigate the effect of high and fluctuating levels of gonadal hormones induced by repeated ovarian stimulation on the stress response in rodents. To mimic the context of ART, female rats were exposed to an unpredictable chronic mild stress (UCMS) paradigm for four weeks. During this time, three cycles of ovarian stimulation (superovulation) (150 IU/Kg of PMSG and 75 IU/Kg of hCG) were applied, with intervals of two estrous cycles between them. The rats were distributed into four groups: Repeated Superovulation/UCMS; Repeated Superovulation/No Stress; Saline/UCMS; and Saline/No Stress. Anxiety-like and depressive-like behaviors were evaluated in a light-dark transition box and by splash test, respectively. Corticosterone, estradiol, progesterone, and biometric parameters were assessed. Data were analyzed using a two-way Generalized Linear Model (GzLM). Our results showed that repeated ovarian stimulation exerts by itself an expressive anxiogenic effect. Surprisingly, when high and fluctuating levels of ovarian hormones were combined with chronic stress, anxiety-like behavior was no longer observed, and a depressive-like state was not detected. Our findings suggest that females subjected to emotional overload induced by repeated ovarian stimulation and chronic stress seem to trigger the elaboration of adaptive coping strategies.

Virus-mediated decrease of LKB1 activity in the mPFC diminishes stress-induced depressive-like behaviors in mice

As a highly prevalent neuropsychiatric disorder worldwide, the pathophysiology of depression is not yet fully understood and based on multiple factors among which chronic stress is critical. Numerous previous studies have shown the role of central mammalian target of rapamycin complex 1 (mTORC1) signaling in depression. However, so far it remains elusive by which way chronic stress down-regulates the activity of central mTORC1. Liver kinase b1 (LKB1) has been demonstrated to regulate the activity of the mTORC1 signaling cascade by phosphorylating AMP activated protein kinase (AMPK). Here, this study aimed to explore whether LKB1 participates in depression by regulating the downstream AMPK-mTORC1 signaling, and various methods including mouse models of depression, western blotting and immunofluorescence were used together. Our results showed that chronic stress significantly enhanced the expression of both phosphorylated LKB1 and total LKB1 in the medial prefrontal cortex (mPFC) but not the hippocampus. Furthermore, genetic knockdown of LKB1 in the mPFC fully reversed not only the depressive-like behaviors induced by chronic stress in mice but also the effects of chronic stress on the activity of AMPK and the mTORC1 system. Taken together, this study preliminarily suggests that LKB1 in the mPFC could be a feasible target for antidepressants. This study also provides support for the potential use of LKB1 inhibition strategies against the chronic stress-related neuropsychiatric disorders.

Vorinostat (SAHA) May Exert Its Antidepressant-Like Effects Through the Modulation of Oxidative Stress Pathways

Suberoylanilide hydroxamic acid (SAHA/Vorinostat), a potent inhibitor of histone deacetylases (HDACs), is known to possess antidepressant properties. However, the exact mechanisms underlying this activity are unknown. In this study, we evaluated the effect of SAHA on the expression of GluN2A, GluN2B (NMDA receptor subunits), (p-)AMPK, and ΔFos proteins which are an integral part of the signal transduction pathways in the brain and also involved in the pathophysiology of depression as well as the mechanism of antidepressant action. We also measured the concentration of malondialdehyde (MDA - a product of lipid peroxidation). The study was carried out in the prefrontal cortex (PFC) and hippocampus (Hp), brain regions implicated in depression. Although SAHA induced changes in the expression of all the proteins and MDA concentration, the effects differed depending on the drug dose, time, and brain structure involved. SAHA reduced MDA concentration and significantly increased p-AMPK protein expression, indicating it may prevent oxidative stress. SAHA also increased the levels of HDAC3 and NMDA subunits (GluN2A and GluN2B), implying it is neuroprotective and may play a crucial role in synaptic plasticity. Moreover, ΔFosB and FosB levels were significantly elevated, suggesting that SAHA may modulate learning and memory processes. Overall, the data indicate that the Hp might play a pivotal role in the mechanism of action of SAHA, hinting at novel mechanisms it play in the antidepressant and neuroprotective effects of SAHA.

Naringenin improves depressive- and anxiety-like behaviors in mice exposed to repeated hypoxic stress through modulation of oxido-inflammatory mediators and NF-kB/BDNF expressions

Oxidative and inflammatory signaling pathways have been identified as important targets for mitigating hypoxic stress-induced neurological complications. Thus, the effects of naringenin, a potent antioxidant, anti-inflammatory and neuroprotective bioflavonoid on hypoxic stress-induced depressive-like and anxiety-related behaviors in mice, and the underlying molecular mechanisms were evaluated in this study. Thirty-five male Swiss mice were distributed into 5 groups (n = 7). Mice in group I (non-stress control) and group 2 (stress-control) both had vehicle (5 % DMSO), while groups 3-5 received naringenin (10, 25 and 50 mg/kg), intraperitonally. Thirty minutes later, mice in groups 2-5 were subjected to 15 min hypoxic stress, daily for 14 days. Locomotor activity, anxiety and depression were evaluated on day 15. The mice brains were processed for malondialdehyde, glutathione, superoxide-dismutase (SOD), catalase, tumor necrosis factor-alpha (TNF-α) and interleukin-1β assays. The serum corticosterone concentration and expressions of the brain immunopositive cells of inducible nitric oxide synthase (iNOS), nuclear factor kappa-B (NF-kB) and brain derived neurotrophic factor (BDNF) as well as histomorphological changes of the amygdala were also determined. Naringenin (25-50 mg/kg) ameliorated the hypolocomotion, depressive- and anxiety-like behaviors in hypoxic mice. The increased brain contents of malondialdehyde, TNF-α, interleukin-1β, and decreased antioxidant (glutathione and SOD) status were attenuated by naringenin. Naringenin (10 mg/kg) increases BDNF expression but did not significantly (p < 0.05) alter corticosterone and catalase contents. The increased expressions of iNOS and NF-kB as well as loss of amygdala neuronal cells were reduced by naringenin (10 mg/kg). Overall, these findings suggest that naringenin improves depressive- and anxiety-like behaviors in mice exposed to hypoxic stress by modulating oxido-inflammatory insults and NF-kB/BDNF expressions.

Increasing γ-Aminobutyric Acid Content in Vegetable Soybeans via High-Pressure Processing and Efficacy of Their Antidepressant-Like Activity in Mice

This study applied high-pressure processing (HPP) technology to enrich the gamma aminobutyric acid (GABA) content in vegetable soybeans and evaluated its antidepressant efficacy on mice, with depression induced by the unpredictable chronic mild stress (UCMS) model. The optimal conditions for HPP, storage time, and storage temperature, as well as antidepressant-like effects of vegetable soybeans, were evaluated and discussed. HPP could effectively and significantly increase GABA content in soybean, with optimum conditions at 200 MPa. The GABA content in the whole vegetable soybean was 436.05 mg/100 g. In mice animal tests, the tail suspension test (TST) showed that the immobility time of the GABA group was significantly shorter than that of the control group. The total travel distance in the open field test (OFT) showed that depressed mice fed with the GABA feed exhibited exploratory behavior. The GABA group showed a significantly higher degree of sucrose preference than the control group. Both results indicate that the GABA feed could effectively alleviate depressive symptomatology. Regarding biochemical parameters, the fecal and serum corticosterone (CORT) levels in the control group increased to 104.86 pg/mg after the onset of depression. In contrast, the fecal CORT level in the GABA group was significantly reduced to 23.98 pg/mg and was comparable to that in the control group (33.38 pg/mg). Reduced serum CORT level in the GABA group suggests an improvement in depressive symptomatology. The serotonin concentration was maintained in the GABA group after the induction of depression, suggesting its preventive activity. The HPP GABA-enriched soybeans exerted modulatory effects on the behaviors of depressed mice and displayed a potential for commercialization.

Chronic minocycline treatment exerts antidepressant effect, inhibits neuroinflammation, and modulates gut microbiota in mice

RATIONAL

Minocycline is a second-generation, semi-synthetic tetracycline, and has broad spectrum-antibacterial activity. Interestingly, many studies have demonstrated that minocycline is beneficial for depression, which may be due to its effects on neuroinflammation modulation. Recently, gut microbiota imbalance has been found in depression patient and animal models.

OBJECTIVES

Based on the fact of minocycline usually acting as an antibiotic and the relationship between depression, gut microbiota, and neuroinflammation, we designed this study to detect the effects of chronic minocycline treatment on antidepression, neuroinflammation, and gut microbiota modulation.

RESULTS

Our results showed that minocycline treatment for 4 weeks, not acute treatment, exerted antidepressant effect in mice exposed to unpredictable chronic mild stress (CUMS). Further results suggested that chronic minocycline treatment inhibited neuroinflammation of hippocampus and altered species abundance and metabolites of gut microbiota. Meantime, we found that chronic minocycline treatment ameliorated intestinal barrier disruption and reduced the bacteriological indexes, such as diamine oxidase, C-reaction protein, and endotoxin in peripheral blood of CUMS mice.

CONCLUSIONS

To sum up, our findings confirm that chronic minocycline treatment exerts the antidepressant effect, inhibits neuroinflammation, and modulates gut microbiota. All of these imply that the antidepressant mechanism of chronic minocycline treatment is maybe due to the combined action of neuroinflammation and gut microbiota modulation, which need further prospective studies.

Can social support during pregnancy affect maternal DNA methylation? Findings from a cohort of African-Americans

BACKGROUND

While stress and the absence of social support during pregnancy have been linked to poor health outcomes, the underlying biological mechanisms are unclear.

METHODS

We examined whether adverse experiences during pregnancy alter DNA methylation (DNAm) in maternal epigenomes. Analyses included 250 African-American mothers from the Boston Birth Cohort. Genome-wide DNAm profiling was performed in maternal blood collected after delivery, using the Infinium HumanMethylation450 Beadchip. Linear regression models, with adjustment of pertinent covariates, were applied.

RESULTS

While self-reported maternal psychosocial lifetime stress and stress during pregnancy was not associated with DNAm alterations, we found that absence of support from the baby's father was significantly associated with maternal DNAm changes in TOR3A, IQCB1, C7orf36, and MYH7B and that lack of support from family and friends was associated with maternal DNA hypermethylation on multiple genes, including PRDM16 and BANKL.

CONCLUSIONS

This study provides intriguing results suggesting biological embedding of social support during pregnancy on maternal DNAm, warranting additional investigation, and replication.

Aging increases vulnerability to stress-induced depression via upregulation of NADPH oxidase in mice

Brain aging proceeds with cellular and molecular changes in the limbic system. Aging-dependent changes might affect emotion and stress coping, yet the underlying mechanisms remain unclear. Here, we show aged (18-month-old) mice exhibit upregulation of NADPH oxidase and oxidative stress in the hippocampus, which mirrors the changes in young (2-month-old) mice subjected to chronic stress. Aged mice that lack p47phox, a key subunit of NADPH oxidase, do not show increased oxidative stress. Aged mice exhibit depression-like behavior following weak stress that does not produce depressive behavior in young mice. Aged mice have reduced expression of the epigenetic factor SUV39H1 and its upstream regulator p-AMPK, and increased expression of Ppp2ca in the hippocampus-changes that occur in young mice exposed to chronic stress. SUV39H1 mediates stress- and aging-induced sustained upregulation of p47phox and oxidative stress. These results suggest that aging increases susceptibility to stress by upregulating NADPH oxidase in the hippocampus.

Immunosuppressive effect and global dysregulation of blood transcriptome in response to psychosocial stress in vervet monkeys (Chlorocebus sabaeus)

Psychosocial stressors - life events that challenge social support and relationships - represent powerful risk factors for human disease; included amongst these events are relocation, isolation and displacement. To evaluate the impact of a controlled psychosocial stressor on physiology and underlying molecular pathways, we longitudinally studied the influence of a 28-day period of quarantine on biomarkers of immune signalling, microbial translocation, glycaemic health and blood transcriptome in the wild-born vervet monkey. This event caused a coordinated, mostly transient, reduction of circulating levels of nine immune signalling molecules. These were paralleled by a massive dysregulation of blood transcriptome, including genes implicated in chronic pathologies and immune functions. Immune and inflammatory functions were enriched among the genes downregulated in response to stress. An upregulation of genes involved in blood coagulation, platelet activation was characteristic of the rapid response to stress induction. Stress also decreased neutrophils and increased CD4 + T cell proportions in blood. This model of psychosocial stress, characterised by an immune dysregulation at the transcriptomic, molecular and cellular levels, creates opportunities to uncover the underlying mechanisms of stress-related diseases with an immune component, including cardiovascular diseases and susceptibility to infections.

Antidiabetic Drug Metformin Ameliorates Depressive-Like Behavior in Mice with Chronic Restraint Stress via Activation of AMP-Activated Protein Kinase

Depression is one of the most prevalent neuropsychiatric disorders in modern society. However, traditional drugs, such as monoaminergic agents, have defect showing lag response requiring several weeks to months. Additionally, these drugs have limited efficacy and high resistance rates in patients with depression. Thus, there is an urgent need to develop novel drugs or approaches for the treatment of depression. Here, using biochemical, pharmacological, genetic and behavioral methods, we demonstrate that metformin imparts a fast-acting antidepressant-like effect in naïve mice as well as stressed mice subjected to chronic restraint stress model. Moreover, inhibition of AMP-activated protein kinase (AMPK) activity by compound C or knock down of hippocampal AMPKα occluded the antidepressant-like effect induced by metformin. Our results suggest that metformin may be a viable therapeutic drug for the treatment of stress-induced depression via activation of AMPK.

Hypericin attenuates nonalcoholic fatty liver disease and abnormal lipid metabolism via the PKA-mediated AMPK signaling pathway in vitro and in vivo

Nonalcoholic fatty liver disease (NAFLD) is the most common liver disease worldwide and constitutes a major risk factor for progression to cirrhosis, liver failure and hepatocellular carcinoma (HCC). The occurrence of NAFLD is closely associated with abnormal lipid metabolism and implies a high risk of type 2 diabetes and cardiovascular disease. Therefore, specific and effective drugs for the prevention and treatment of NAFLD are necessary. Hypericin (HP) is one of the main active ingredients of Hypericum perforatum L., and we previously revealed its protective role in islet β-cells and its effects against type 2 diabetes. In this study, we aimed to explore the preventive and therapeutic effects of HP against NAFLD and the underlying mechanisms in vitro and in vivo. Here, we demonstrated that HP improved cell viability by reducing apoptosis and attenuated lipid accumulation in hepatocytes both in vitro and in vivovia attenuating oxidative stress, inhibiting lipogenesis and enhancing lipid oxidization. Thus, HP exhibited significant preventive and therapeutic effects against HFHS-induced NAFLD and dyslipidemia in mice. Furthermore, we demonstrated that HP directly bound to PKACα and activated PKA/AMPK signaling to elicit its effects against NAFLD, suggesting that PKACα is one of the drug targets of HP. In addition, the enhancing effect of HP on lipolysis in adipocytes through the activation of PKACα was also elucidated. Together, the conclusions indicated that HP, of which one of the targets is PKACα, has the potential to be used as a preventive or therapeutic drug against NAFLD or abnormal lipid metabolism in the future.

Celecoxib potentiates the antianxiety and anticompulsive-like activity of fluoxetine against chronic unpredictable mild stress in experimental animals

Obsessive-compulsive disorder (OCD) is considered a heterogeneous anxiety disorder that includes compulsions. Celecoxib is considered an adjuvant to fluoxetine in the management of OCD in a clinical study. However, the experimental evidence is yet to be established. Therefore, the antianxiety and anticompulsive-like activity of celecoxib (20 mg/kg, orally) was evaluated in the presence or absence of fluoxetine (20 mg/kg, orally) in mice who were exposed to chronic unpredictable mild stress (CUMS) for 14 consecutive days. Seven-day treatment of celecoxib significantly attenuated the CUMS-induced anxiety in open-field, hole-board, elevated plus maze tests, and compulsion in the marble-burying test. Celecoxib significantly reversed the CUMS-induced decrease and increase in the levels of serotonin (5-HT) and its metabolite (5-hydroxyindole acetic acid) in the prefrontal cortex, and attenuated the CUMS-induced increase in the levels of inflammatory markers such as interleukin-6 and tumor necrosis factor-α, and apoptosis marker caspase-3 in the prefrontal cortex. Celecoxib also potentiated the anxiolytic, anticompulsive, serotonergic, anti-inflammatory, and antiapoptotic activity of 7-day treatment with fluoxetine in CUMS-challenged animals compared with their monotherapy. Thus, it can be speculated that the combination of an anti-inflammatory agent with selective serotonin reuptake inhibitor could be a better therapeutic option in the management of stress-related disorders including selective serotonin reuptake inhibitor-resistant OCD.

Role of AMPK/SIRT1-SIRT3 signaling pathway in affective disorders in unpredictable chronic mild stress mice

OBJECTIVES

To explore the role of 5' adenosine monophosphate-activated protein kinase/sirtuin1-sirtuin3 (AMPK/SIRT1-SIRT3) signaling pathway in behavioral and neuroinflammation/oxidative stress alterations in unpredictable chronic mild stress (UCMS) model mice.

METHODS

Male ICR mice weighing 20-22 g were used in this study. Behavior performance was evaluated from the 14th day of drug treatment. Expression levels of AMPK, SIRT1, SIRT3, and NF-κBp65 were tested by immuno-blot analysis. Contents of tumor necrosis factor α (TNF-α), interleukin 1β (IL-1β) and interleukin 6 (IL-6) were detected by enzyme linked immunosorbent assay (ELISA). Reactive oxygen species (ROS), superoxide dismutase (SOD) and glutathione (GSH) expressions were tested by neurochemical and biochemical assays.

RESULTS

Behavioral disorders and decreases of AMPK, SIRT1 and SIRT3 induced by UCMS were all reversed by AICA Riboside (AICAR) treatment. These effects were correlated with alterations of oxidative stress (ROS, GSH, SOD) and inflammation (pNF-κBp65, TNF-α, IL-1β, IL-6) status. Co-treatment with SIRT3 inhibitor (3-TYP) in addition to AICAR abolished AICAR's effects on behavior and expression level of inflammation/oxidative stress-related factors of mice, without affecting the content of SIRT1. Contrarily, combining use of AICAR and SIRT1 inhibitor (Sirtinol or EX-527) increased SIRT3 level, which led to better alleviation of behavioral disorders, compared with single AICAR treatment. Interestingly, in normal or UCMS mice, up or down regulation of SIRT1 did not affect SIRT3 level.

CONCLUSION

Provided that AMPK is activated, SIRT1 inhibition could induce the increase of SIRT3, and SIRT3 exerts more beneficial function in alleviation of consequences of chronic stress than SIRT1.

d-Limonene protects PC12 cells against corticosterone-induced neurotoxicity by activating the AMPK pathway

The stress-induced hormone corticosterone initiates oxidative stress and inflammatory responses, culminating in cell apoptosis and neurological changes. We assessed the effects of d-Limonene on a PC12 cellular model of corticosterone-induced neurotoxicity, and whether these effects involved the AMP-activated protein kinase (AMPKα) pathway. PC12 cells were treated with corticosterone with or without d-limonene for 24 h. Western blots were performed to measure activation of AMPK pathway members [Silent mating type information regulation 2 homolog-1 (SIRT1), AMPKα, and nuclear factor (NFκB)], reactive oxygen species, inflammatory cytokines, and markers of apoptosis. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) was used to measure cell death after treatment. d-Limonene reversed the effects of corticosterone on PC12 cells: it decreased the levels of malondialdehyde (MDA) and nitric oxide (NO), activities of NADPH oxidase (p67-phox and p47-phox), expression of pro-inflammatory markers [inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), interleukin 6 (IL-6), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α)], and expression of pro-apoptotic proteins [Bcl2 associated with X protein (Bax) and cleaved caspase-3)]. d-Limonene also increased levels of the antioxidant enzymes superoxide dismutase 1 (SOD1) and heme oxygenase 1 (HO-1) and the anti-apoptotic protein Bcl-2 while decreasing the number of TUNEL-positive cells. d-limonene significantly activated AMPKα and suppressed NF-κB nuclear translocation through up-regulation of SIRT1. Addition of compound C, an AMPK inhibitor, severely weakened these neuroprotective effects of d-limonene. d-Limonene has a neuroprotective effect on corticosterone-induced PC12 cell injury induced by activating the AMPKα signaling pathway, and thereby inhibiting reactive oxygen species and inflammatory factors. These data suggest that d-limonene might protect against neuronal death to improve depressive symptoms.

Metformin exerts antidepressant effects by regulated DNA hydroxymethylation

Aim: We aim to study the antidepressant mechanism of metformin. Materials & methods: Tail suspension test and forced swimming test were used to detect the depression-like behavior; the expressions of target protein were examined by western blot; the levels of target genes were tested by quantitative PCR; the content of α-ketoglutarate and 5hmC were detected by ELISA kit. Results: We showed that metformin can improve the depression-like behavior in spatial restraint stress model; then we found that metformin through AMPK/Tet2 pathway increasing the expression of BDNF to antidepression. Conclusion: Our study provided evidences that metformin plays a role of antidepressant effects through the AMPK/Tet2/BDNF pathway.

Mice lacking Casp1, Ifngr and Nos2 genes exhibit altered depressive- and anxiety-like behaviour, and gut microbiome composition

Converging evidence supports the involvement of pro-inflammatory pathways and the gut microbiome in major depressive disorder (MDD). Pre-clinical and clinical studies suggest that decreasing pro-inflammatory signaling may provide clinical benefit in MDD. In this study, we used the chronic unpredictable stress (CUS) paradigm to assess whether mice lacking the pro-inflammatory caspase 1, interferon gamma-receptor, and nitric oxide synthase (Casp1, Ifngr, Nos2)-/- present altered depressive- and anxiety-like behaviour at baseline and in response to CUS. In comparison to wild-type (wt) mice, (Casp1, Ifngr, Nos2)-/- mice displayed decreased depressive- and anxiety-like behaviour, and increased hedonic-like behaviour and locomotor activity at baseline, and resistance to developing anhedonic-like behaviour and a heightened emotional state following stress. Plasma levels of ACTH and CORT did not differ between the triple knockout and wt mice following stress. The faecal microbiome of (Casp1, Ifngr, Nos2)-/- mice differed from that of wt mice at baseline and displayed reduced changes in response to chronic stress. Our results demonstrate that simultaneous deficit in multiple pro-inflammatory pathways has antidepressant-like effects at baseline, and confers resilience to stress-induced anhedonic-like behaviour. Moreover, accompanying changes in the gut microbiome composition suggest that CASP1, IFNGR and NOS2 play a role in maintaining microbiome homeostasis.

Lactobacillus plantarum DR7 alleviates stress and anxiety in adults: a randomised, double-blind, placebo-controlled study

Probiotics have been reported to exert beneficial effects along the gut-brain axis. This randomised, double-blind and placebo-controlled human study aimed to evaluate such properties of Lactobacillus plantarum DR7 and its accompanying mechanisms in stressed adults. One hundred and eleven (n=111; DR7 n=56, placebo n=55) stressed adults were recruited based on moderate stress levels using the PSS-10 questionnaire. The consumption of DR7 (1×109 cfu/day) for 12 weeks reduced symptoms of stress (P=0.024), anxiety (P=0.001), and total psychological scores (P=0.022) as early as 8 weeks among stressed adults compared to the placebo group as assessed by the DASS-42 questionnaire. Plasma cortisol level was reduced among DR7 subjects as compared to the placebo, accompanied by reduced plasma pro-inflammatory cytokines, such as interferon-γ and transforming growth factor-α and increased plasma anti-inflammatory cytokines, such as interleukin 10 (P<0.05). DR7 better improved cognitive and memory functions in normal adults (>30 years old), such as basic attention, emotional cognition, and associate learning (P<0.05), as compared to the placebo and young adults (<30 years old). The administration of DR7 enhanced the serotonin pathway, as observed by lowered expressions of plasma dopamine β-hydroxylase (DBH), tyrosine hydroxylase (TH), indoleamine 2,3-dioxygenase and tryptophan 2,3-dioxygenase accompanied by increased expressions of tryptophan hydroxylase-2 and 5-hydroxytryptamine receptor-6, while stabilising the dopamine pathway as observed via stabilised expressions of TH and DBH over 12 weeks as compared to the placebo (P<0.05). Our results indicated that DR7 fulfil the requirement of a probiotic strain as per recommendation of FAO/WHO and could be applicable as a natural strategy to improve psychological functions, cognitive health and memory in stressed adults.

Altered gut metabolome contributes to depression-like behaviors in rats exposed to chronic unpredictable mild stress

The gut microbiota has been increasingly correlated with depressive disorder. It was recently shown that the transplantation of the gut microbiota from depressed patients to animals can produce depressive-like behaviors, suggesting that the gut microbiota plays a causal role in the development of depression. In addition, metabolic disorder, which is strongly associated with depression, is exacerbated by changes in the composition of the gut microbiota and is alleviated by treatment with antidepressants. However, the key players and pathways that link the gut microbiota to the pathogenesis of depression remain largely unknown. To evaluate the relationships between depression and metabolic disorders in feces and plasma, we monitored changes in fecal and plasma metabolomes during the development of depressive-like behaviors in rats exposed to chronic unpredictable mild stress (CUMS). In these animals, the fecal metabolome was altered first and subjected to changes in the plasma metabolome. Changes in the abundance of fecal metabolites were associated with depressive-like behaviors and with altered levels of neurotransmitters in the hippocampus. Furthermore, the analysis of the fecal metabolome and the fecal microbiota in CUMS rats demonstrated consistent changes in the levels of several amino acids, including L-threonine, isoleucine, alanine, serine, tyrosine, and oxidized proline. Finally, we observed significant correlations between these amino acids and the altered fecal microbiota. The results of this study suggest that changes in amino acid metabolism by the gut microbiota contribute to changes in circulating amino acids and are associated with the behavior indices of depression.

Anti-Depressant-Like Effect of Sinomenine on Chronic Unpredictable Mild Stress-Induced Depression in a Mouse Model

BACKGROUND Sinomenine (SIN) is an extract of the Chinese medicinal herb Sinomenium acutum; it has various pharmacological properties, including immunosuppression and anti-inflammation. The present study aimed to investigate whether SIN has an anti-depressant-like effect in a mouse model of depression induced by chronic unpredictable mild stress (CUMS), and to explore the underlying molecular mechanisms. MATERIAL AND METHODS A mouse model of depression was established and treated with different concentrations of SIN (30, 100, or 300 mg/kg). Then, behavioral tests, including sucrose preference test (SPT), forced swimming test (FST), and the tail suspension test (TST), were performed. The levels of norepinephrine (NE), 5-hydroxytryptamine (5-HT), and proinflammatory cytokines (interleukin-1β [IL-1β] interleukin-6 [IL-6], and tumor necrosis factor-α [TNF-α]) in the hippocampus of mice were detected by ELISA assay. The levels of p-p38, p-p65, NLRP3, ASC, and caspase-1 were measured by Western blot or/and qRT-PCR. RESULTS The results showed that SIN significantly relieved CUMSinduced depressive-like behaviors. Compared with the model mice, SIN treatment significantly increased the sucrose preference of the mice, and the immobility time in the forced swimming and the tail suspension test were shortened. In addition, SIN decreased CUMS-induced reduction in the concentrations of NE and 5-HT in the hippocampus of mice. SIN reduced CUMS-induced increases in the levels of IL-1β, IL-6, and TNF-α in the hippocampus of mice. Furthermore, activation of the p38MAPK-NF-κB pathway and the nucleotide binding and oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome induced by CUMS were inhibited by SIN treatment. CONCLUSIONS In conclusion, our results indicate the antidepressantlike effects of SIN on chronic unpredictable mild stress-induced depression in a mouse model.

The ameliorating effect of exercise on long-term memory impairment and dendritic retraction via the mild activation of AMP-activated protein kinase in chronically stressed hippocampal CA1 neurons

[Purpose]

Chronic stress affects the neuronal architecture of hippocampal subfields including the Cornu Ammonis 1 (CA1) region, which governs long-term memory. Exercise exerts a beneficial effect on memory improvement via hippocampal AMP-activated protein kinase (AMPK) activation. However, the relationship between the two phenomena is poorly understood. This study used animal and cell culture experimental systems to investigate whether chronic stress-induced impairment of memory consolidation and maladaptation of the neuronal architecture in the hippocampal CA1 area is prevented by regular exercise through AMPK activation.

[Methods]

Mice underwent four weeks of treadmill running with or without a 6h/21d-restraint stress regimen, along with treatment with Compound C. Memory consolidation was assessed using the Morris Water Maze (MWM). Dendritic rearrangement of hippocampal CA1 neurons was evaluated using the Golgi-Cox stain and Sholl analysis. Additionally, the primary hippocampal culture system was adopted for in vitro experiments.

[Results]

Chronic stress-induced failure of memory retention and reduction in AMPK activation were ameliorated by the exercise regimen. Chronic stress-or repeated corticosterone (CORT)-provoked malformation of the neuronal architecture was also suppressed by both exercise and treatment with 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR).

[Conclusion]

Chronic stress causes dendritic retraction among dorsal hippocampal CA1 neurons via the downregulation of AMPK activation, thereby leading to failure of memory retention. In contrast, regular exercise protects against chronic stress-evoked defects in memory consolidation and changes in neuronal morphology in the dorsal hippocampal CA1 area via mild activation of AMPK.

Antidepressant and anxiolytic effects of the proprietary Chinese medicine Shexiang Baoxin pill in mice with chronic unpredictable mild stress

Depression and anxiety often co-occur with cardiac diseases. The Shexiang Baoxin pill (SBP) is a proprietary Chinese medicine initially used to treat cardiac conditions. This study explored whether SBP has antidepressant and anxiolytic effects in addition to hormonal and psychotropic mechanisms. Mice underwent 6 weeks of chronic unpredictable mild stress (CUMS) to induce depression- and anxiety-like behavior. During the 6-week experiment, mice received SBP at intragastric doses of 20.25 mg/kg or 40.5 mg/kg daily. Animals were then tested for depression in sucrose preference, forced-swimming, and tail suspension paradigms, and for anxiety in open field and elevated plus maze tests. Both SBP doses significantly reduced anhedonic behavior in the sucrose preference test; the high SBP dose also increased the number of entries into the central zone of the open field. SBP-treated mice had markedly lower blood levels of corticotrophin-releasing hormone (CRH) and adrenocorticotropic hormone (ACTH) than stressed mice treated with vehicle. Either low- or high-dose SBP reversed stress-induced reductions of norepinephrine (NE) and dopamine (DA) metabolites and the expression levels of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), and glial cell-derived neurotrophic factor (GDNF) in related brain regions. These results suggest that SBP could prevent and alleviate prolonged stress-induced anhedonia and anxiety in association with its suppression of the hypothalamic-pituitary-adrenal (HPA) axis hyperactivity, modulation of brain monoamine neurotransmitter metabolism and neurotrophins. SBP may be particularly suitable for the management of depressive and anxiety disorders in patients with cardiac conditions.

Activation of AMPK by metformin improves withdrawal signs precipitated by nicotine withdrawal

Cigarette smoking is the leading cause of preventable disease and death in the United States, with more persons dying from nicotine addiction than any other preventable cause of death. Even though smoking cessation incurs multiple health benefits, the abstinence rate remains low with current medications. Here we show that the AMP-activated protein kinase (AMPK) pathway in the hippocampus is activated following chronic nicotine use, an effect that is rapidly reversed by nicotine withdrawal. Increasing pAMPK levels and, consequently, downstream AMPK signaling pharmacologically attenuate anxiety-like behavior following nicotine withdrawal. We show that metformin, a known AMPK activator in the periphery, reduces withdrawal symptoms through a mechanism dependent on the presence of the AMPKα subunits within the hippocampus. This study provides evidence of a direct effect of AMPK modulation on nicotine withdrawal symptoms and suggests central AMPK activation as a therapeutic target for smoking cessation.