Oxytocin treatment improves dexamethasone‐induced depression‐like symptoms associated with enhancement of hippocampal CREB‐BDNF signaling in female mice

Protective potential of Bacillus subtilis (NMCC-path-14) against extraarticular manifestations during acute and sub-acute phase of arthritis using mice model

Extra-articular manifestations (EAM), which are associated with rheumatoid arthritis (RA), affect the quality of life of patients and are one of the critical causes of early mortality. This study was aimed at investigating whether Bacillus subtilis NMCC-path-14 (1 × 108 CFU/animal/day) could serve as a valuable therapeutic agent in managing EAM using complete Freund's adjuvant (CFA) induced arthritis during acute and sub-acute phases. Arthritis was induced using intra-dermal administration of CFA in the right hind paw of mice on day 1. Dexamethasone (Dexa) (5 mg/kg/day/animal) was used as a standard treatment. Animals in Dexa and Bacillus subtilis concurrent treatment (BS-CT) received treatments on day 1. The Bacillus subtilis pre-treatment (BS-PT) group received a probiotic dose 7 days before arthritis induction. Parameters like body weight, relative organ weight, colon length, hematology, serum biochemistry, antioxidant capacity, and histopathology of liver, kidney, spleen, colon, stress-related behavioral changes, and cortisol levels were evaluated on days 7 (acute) and 14 (sub-acute). Dexa failed to manage the EAM in arthritic mice and instead exacerbated them. On the other hand, B. subtilis NMCC-path-14 significantly declined EAM with no notable side effects, highlighting its safety and effectiveness. The current data show that B. subtilis NMCC-path-14 may be an alternative option for arthritis treatment that can reduce systemic symptoms associated with arthritis. More studies are required to comprehend the underlying mechanisms of mitigating the EAM by B. subtilis NMCC-path-14.

Moxie begets MOXI: The journey to a novel hypothesis about Mu-opioid and OXytocin system Interactions

This narrative review summarizes the early life of the author, Khalin E. Nisbett, and highlights the factors that led to her career in research and her development of two novel research hypotheses: the Mu-opioid and OXytocin system Interaction (MOXI) hypothesis and Mu-Opioid receptor antagonist and OXytocin receptor Agonist In Combination (MOXAIC) treatment hypothesis. Notably, Nisbett's career began in the era after countless studies demonstrated that oxytocin is not just a female neurotransmitter and not just a female reproductive hormone, an era in which researchers are exploring the role of oxytocin in emotion regulation, social interaction, and cognitive processing across both sexes. As such, the previously held perspective that oxytocin is "just a female hormone" did not impede Nisbett's ideas. Intrigued by science, emotion regulation, and social interaction, she began to explore the role of oxytocin and opioids in emotion regulation. On the heels of earlier theories, such as the Tend-and-Befriend theory and Opioid Theory of Social Attachment, she began to develop the MOXI hypothesis, which postulates that the μ-opioid receptor and oxytocin systems interact to mediate social interaction and emotion regulation. In this narrative review, Nisbett summarizes two studies that explored (i) the role of oxytocin in anxiety- and depression-like behavior and (ii) the effect of opioid receptor blockade on the anxiolytic-like effect of oxytocin, which led to a revision of the MOXI hypothesis and postulation of the Mu-Opioid receptor antagonist and OXytocin receptor Agonist In Combination (MOXAIC) treatment hypothesis. Nisbett also discusses several limitations of these hypotheses and her current research interests and aspirations.

Divergent effects of chronic continuous and intermittent social defeat stress on emotional behaviors: Impact on phosphorylated CREB and BDNF protein levels in the rat hippocampus

Chronic psychosocial stress stands as a significant heterogeneous risk factor for psychiatric disorders. The brain's physiological response to such stress varies based on the frequency and intensity of stress episodes. However, whether stress episodes divergently could affect hippocampal cyclic AMP response element-binding protein (CREB)-brain-derived neurotrophic factor (BDNF) signaling remains unclear, a key regulator of psychiatric symptoms. We aimed to assess how two distinct patterns of social defeat stress exposure impact anxiety- and depression-like behaviors, fear, and hippocampal CREB-BDNF signaling in adult male rats. To explore this, adult male Sprague-Dawley rats were subjected to psychosocial stress using a Resident/Intruder paradigm for ten consecutive days (continuous social defeat stress: [CS]) or ten social defeat stress over the course of 21 days (intermittent social defeat stress [IS]). Behavioral tests (including novelty-suppressed feeding test, forced swimming test, and contextually conditioned fear) were conducted. Protein expression levels of phosphorylated CREB and BDNF in the dorsal and ventral hippocampi were examined. CS led to heightened anxiety-like behavior, fear, and increased levels of phosphorylated CREB in both the dorsal and ventral hippocampi. Conversely, IS resulted in increased anxiety-like behavior and behavioral despair alongside decreased levels of phosphorylated CREB and BDNF, particularly in the dorsal hippocampus. These findings indicate that chronic psychosocial stress divergently affects hippocampal CREB-BDNF signaling and emotional regulation depending on the stress episode. Such insights could enhance our understanding of the molecular basis of the heterogeneity of psychiatric disorders and facilitate the development of innovative treatment approaches to patients with psychiatric disorders.

tiRNA-Gly-GCC-001 in major depressive disorder: Promising diagnostic and therapeutic biomarker

BACKGROUND AND PURPOSE

In major depressive disorder (MDD), exploration of biomarkers will be helpful in diagnosing the disorder as well as in choosing a treatment and predicting the treatment response. Currently, tRNA-derived small ribonucleic acids (tsRNAs) have been established as promising non-invasive biomarker candidates that may enable a more reliable diagnosis or monitoring of various diseases. Herein, we aimed to explore tsRNA expression together with functional activities in MDD development.

EXPERIMENTAL APPROACH

Serum samples were obtained from patients with MDD and healthy controls, and small RNA sequencing (RNA-Seq) was used to profile tsRNA expression. Dysregulated tsRNAs in MDD were validated by quantitative real-time polymerase chain reaction (qRT-PCR). The diagnostic utility of specific tsRNAs and the expression of these tsRNAs after antidepressant treatment were analysed.

KEY RESULTS

In total, 38 tsRNAs were significantly differentially expressed in MDD samples relative to healthy individuals (34 up-regulated and 4 down-regulated). qRT-PCR was used to validate the expression of six tsRNAs that were up-regulated in MDD (tiRNA-1:20-chrM.Ser-GCT, tiRNA-1:33-Gly-GCC-1, tRF-1:22-chrM.Ser-GCT, tRF-1:31-Ala-AGC-4-M6, tRF-1:31-Pro-TGG-2 and tRF-1:32-chrM.Gln-TTG). Interestingly, serum tiRNA-Gly-GCC-001 levels exhibited an area under the ROC curve of 0.844. Moreover, tiRNA-Gly-GCC-001 is predicted to suppress brain-derived neurotrophic factor (BDNF) expression. Furthermore, significant tiRNA-Gly-GCC-001 down-regulation was evident following an 8-week treatment course and served as a promising baseline predictor of patient response to antidepressant therapy.

CONCLUSION AND IMPLICATIONS

Our current work reports for the first time that tiRNA-Gly-GCC-001 is a promising MDD biomarker candidate that can predict patient responses to antidepressant therapy.

Association between RMTg Neuropeptide Genes and Negative Effect during Alcohol Withdrawal in Mice

Alcohol use disorders (AUDs) frequently co-occur with negative mood disorders, such as anxiety and depression, exacerbating relapse through dopaminergic dysfunction. Stress-related neuropeptides play a crucial role in AUD pathophysiology by modulating dopamine (DA) function. The rostromedial tegmental nucleus (RMTg), which inhibits midbrain dopamine neurons and signals aversion, has been shown to increase ethanol consumption and negative emotional states during abstinence. Despite some stress-related neuropeptides acting through the RMTg to affect addiction behaviors, their specific roles in alcohol-induced contexts remain underexplored. This study utilized an intermittent voluntary drinking model in mice to induce negative effect behavior 24 h into ethanol (EtOH) abstinence (post-EtOH). It examined changes in pro-stress (Pnoc, Oxt, Npy) and anti-stress (Crf, Pomc, Avp, Orx, Pdyn) neuropeptide-coding genes and analyzed their correlations with aversive behaviors. We observed that adult male C57BL/6J mice displayed evident anxiety, anhedonia, and depression-like symptoms at 24 h post-EtOH. The laser-capture microdissection technique, coupled with or without retrograde tracing, was used to harvest total ventral tegmental area (VTA)-projecting neurons or the intact RMTg area. The findings revealed that post-EtOH consistently reduced Pnoc and Orx levels while elevating Crf levels in these neuronal populations. Notably, RMTg Pnoc and Npy levels counteracted ethanol consumption and depression severity, while Crf levels were indicative of the mice's anxiety levels. Together, these results underscore the potential role of stress-related neuropeptides in the RMTg in regulating the negative emotions related to AUDs, offering novel insights for future research.

Efficacy of 1,5-anhydro-D-fructose on reducing mental stress: a randomized, double-blind, placebo-controlled trial-a pilot study

Brain-derived neurotrophic factor (BDNF) plays an important role in mental stress. We have previously reported that 1,5-anhydro-D-fructose (1,5-AF) increases brain BDNF in vivo. The present randomized, controlled, double-blind study aimed to clinically evaluate the effects of 1,5-AF oral intake on mental stress in terms of three parameters: sleep, mood, and bowel issues. Healthy volunteers aged between 22 and 71 years (n = 24) were randomly assigned to receive 5.5 g of 1,5-AF or placebo orally, once daily for 4 weeks. Pre- and post-intervention, the subjects completed the Oguri-Shirakawa-Azumi Sleep Inventory, Middle-Aged and Aged Version (OSA-MA); Profile of Mood States, Second Edition (POMS2); and Constipation Assessment Scale (CAS) questionnaires. In the OSA-MA, both "sleepiness on rising" and "sleep length" were significantly improved after treatment with 1,5-AF compared with before treatment. Furthermore, in the POMS2, there was a clear tendency toward reduced "Anger-Hostility" in the 1,5-AF group after treatment, and in the CAS, there was a clear tendency toward reduced "diarrhea or liquid stool" in the 1,5-AF group after treatment. Together, our findings indicate that 1,5-AF has some effects on reducing post-intervention mental stress levels.

Neonatal oxytocin treatment alters levels of precursor and mature BDNF forms and modifies the expression of neuronal markers in the male rat hippocampus

Neuropeptide oxytocin appears to be involved in the formation of hippocampal circuitry, underlying social memory and behaviour. Recent studies point to the role of oxytocin in regulating the levels of nerve growth factors that could influence neurogenesis and neuritogenesis during the early stages of brain development. Therefore, the aim of the present study was to evaluate the early developmental effect of oxytocin administration (P2 and P3 days, two doses, 5 μg/pup, s.c.) on the expression of 1) brain-derived neurotrophic factor (BDNF) isoforms and 2) GABAergic and glutamatergic markers in the male rat hippocampus. Furthermore, we evaluated the branching of dendrites of primary hippocampal GABAergic and glutamatergic neurons in response to incubation with oxytocin (1 μM). We found that after oxytocin administration, levels of proBDNF increased on P5 and mBDNF on P7 in the CA1 hippocampal region. We also observed a reduction in the expression of glutamatergic marker (VGluT2) on P7 compared to P5 in control and oxytocin treated rats. During the early developmental stages (P5, P7, P9) the expression of GABAergic markers (Gad65 and Gad67) decreased regardless of oxytocin treatment. Incubation in a presence of oxytocin reduced branching of glutamatergic hippocampal neurons and the opposite stimulatory effect of oxytocin was observed in GABAergic neurons. These findings suggest that oxytocin affects neurotrophin isoforms in the male rat hippocampus in the early stages of development, which could explain changes in glutamatergic neurons and their morphology.

The use of intranasal oxytocin in the treatment of eating disorders

Oxytocin (OXT) is a hypothalamic peptide that plays a number of roles in the body, being involved in labor and lactation, as well as cognitive-emotional processes and social behavior. In recent years, knowledge of the physiology of OXT has been repeatedly used to explore its potential role in the treatment of numerous diseases, identifying a significant role for OXT in appetite regulation, eating behavior, weight regulation, and food-related beliefs. In this review we provide an overview of publications on this topic, but due to the wealth of research, we have limited our focus to studies based on the use of intranasal OXT in psychiatric diseases, with a particular focus on the role of oxytocin in eating disorders and obesity. Accumulating evidence that OXT intranasal supplementation may provide some therapeutic benefit seems promising. In individuals with autistic spectrum disorders (ASD) and schizophrenia, OXT may affect core deficits, improving social cognition and reducing symptom severity in schizophrenia. Dysregulation of serum and CSF OXT levels, as well as polymorphisms of its genes, may affect emotion perception in patients with eating disorders and correlate with co-occurring depressive and anxiety disorders. Nevertheless, there are still many critical questions regarding the pharmacokinetics and pharmacodynamics of intranasal OXT that can only be answered in larger randomized controlled trials.

Involvement of brain-derived neurotrophic factor signaling in the pathogenesis of stress-related brain diseases

Neurotrophins including brain-derived neurotrophic factor, BDNF, have critical roles in neuronal differentiation, cell survival, and synaptic function in the peripheral and central nervous system. It is well known that a variety of intracellular signaling stimulated by TrkB, a high-affinity receptor for BDNF, is involved in the physiological and pathological neuronal aspects via affecting cell viability, synaptic function, neurogenesis, and cognitive function. As expected, an alteration of the BDNF/TrkB system is suspected to be one of the molecular mechanisms underlying cognitive decline in cognitive diseases and mental disorders. Recent evidence has also highlighted a possible link between the alteration of TrkB signaling and chronic stress. Furthermore, it has been demonstrated that downregulation of the BDNF/TrkB system and chronic stress have a role in the pathogenesis of Alzheimer's disease (AD) and mental disorders. In this review, we introduce current evidence showing a close relationship between the BDNF/TrkB system and the development of cognition impairment in stress-related disorders, and the possible contribution of the upregulation of the BDNF/TrkB system in a therapeutic approach against these brain diseases.

BDNF Unveiled: Exploring Its Role in Major Depression Disorder Serotonergic Imbalance and Associated Stress Conditions

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that plays a significant role in the survival and development of neurons, being involved in several diseases such as Alzheimer's disease and major depression disorder. The association between BDNF and major depressive disorder is the subject of extensive research. Indeed, numerous studies indicate that decreased levels of BDNF are linked to an increased occurrence of depressive symptoms, neuronal loss, and cortical atrophy. Moreover, it has been observed that antidepressive therapy can help restore BDNF levels. In this review, we will focus on the role of BDNF in major depression disorder serotonergic imbalance and associated stress conditions, particularly hypothalamic-pituitary-adrenal (HPA) axis dysregulation and oxidative stress. All of these features are highly connected to BDNF signaling pathways in the context of this disease, and exploring this topic will aim to advance our understanding of the disorder, improve diagnostic and treatment approaches, and potentially identify new therapeutic targets to alleviate the heavy burden of depression on society.

The role of the oxytocinergic system in the antidepressant-like effect of swimming training in male mice

Increasing evidence shows that higher physical activity such as running and swimming exercises is associated with decreased depression-related symptoms. However, underlying mechanisms are not fully understood. This study aimed to investigate whether oxytocinergic system can mediate the antidepressant effect of swimming exercises in mice. First, male NMRI mice were subjected to swimming training for eight weeks, then animals intraperitoneally received oxytocin antagonist (L-368899) 1hour before behavioral tests. We assessed anhedonia and social behavior and behavioral despair using the sucrose preference test, social interaction test, and tail suspension test. Oxytocin levels in the brain and serum were also measured. The results showed that swimming training decreased anhedonia and behavioral despair, whereas it increased social behavior and oxytocin levels in male mice. On the other hand, a subthreshold dose of oxytocin antagonist treatment in exercised mice prevented the antidepressant effect of swimming exercise via increased anhedonia and behavioral despair and decreased social behavior compared to the swimming training group. However, the blockade of oxytocin receptors did not affect oxytocin levels in exercised mice. Overall, these findings suggest that oxytocinergic system can play a role in mediating the antidepressant-like effect of swimming training in mice.

Upregulations of α1 adrenergic receptors and noradrenaline synthases in the medial prefrontal cortex are associated with emotional and cognitive dysregulation induced by post-weaning social isolation in male rats

Early-life social isolation induces emotional and cognitive dysregulation, such as increased aggression and anxiety, and decreases neuron excitability in the medial prefrontal cortex (mPFC). The noradrenergic system in the mPFC regulates emotion and cognitive function via α₁ or α_2A adrenergic receptors, depending on noradrenaline levels. However, social isolation-induced changes in the mPFC noradrenergic system have not been reported. Here, male Wistar rats received post-weaning social isolation for nine consecutive weeks and were administered behavioral tests (novel object recognition, elevated plus maze, aggression, and forced swimming, sequentially). Protein expression levels in the mPFC noradrenergic system (α₁ and α_2A adrenergic receptors, tyrosine hydroxylase, and dopamine-β-hydroxylase used as indices of noradrenaline synthesis and release) were examined through western blotting. Social isolation caused cognitive dysfunction, anxiety-like behavior, and aggression, but not behavioral despair. Socially-isolated rats exhibited increased protein levels of the α₁ adrenergic receptor, tyrosine hydroxylase, and dopamine-β-hydroxylase in the mPFC; there was no significant difference between the groups in the α_2A adrenergic receptor expression levels. Preferential activation of the α₁ adrenergic receptor caused by high noradrenaline concentration in the mPFC may be involved in social isolation-induced emotional and cognitive regulation impairments. Targeting the α₁ adrenergic receptor signaling pathway is a potential therapeutic strategy for psychiatric disorders with symptomatic features such as emotional and cognitive dysregulation.