Molecular evidence for BDNF- and GABA-related dysfunctions in the amygdala of female subjects with major depression

LPS-induced inflammation reduces GABAergic interneuron markers and brain-derived neurotrophic factor in mouse prefrontal cortex and hippocampus

Inflammation, reduced gamma-aminobutyric acidergic (GABAergic) function and altered neuroplasticity are co-occurring pathophysiologies in major depressive disorder (MDD). However, the link between these biological changes remains unclear. We hypothesized that inflammation induces deficits in GABAergic interneuron markers and that this effect is mediated by brain-derived neurotrophic factor (BDNF). We report here that systemic inflammation induced by intraperitoneal injection of lipopolysaccharide (LPS) (0.125, 0.25, 0.5, 1, 2 mg/kg) in the first cohort of C57BL/6 mice (n = 72; 10-11 weeks; 50% female) resulted in increased interleukin 1-beta and interleukin-6 in prefrontal cortex (PFC) and hippocampus (HPC), as measured using enzyme-linked immunosorbent assay (ELISA). Quantitative real-time polymerase reaction (qPCR) was used to explore the effect of LPS on the expression of GABAergic interneuron markers. In the PFC of the second cohort (n = 39; 10-11 weeks; 50% female), 2 mg/kg of LPS decreased the expression of somatostatin (Sst) (p = 0.0014), parvalbumin (Pv) (p = 0.0257), cortistatin (Cort) (p = 0.0003), neuropeptide Y (Npy) (p = 0.0033) and cholecystokinin (Cck) (p = 0.0041), and did not affect corticotropin-releasing hormone (Crh) and vasoactive intestinal peptide (Vip) expression. In the HPC, 2 mg/kg of LPS decreased the expression of Sst (p = 0.0543), Cort (p = 0.0011), Npy (p = 0.0001), and Cck (p < 0.0001), and did not affect Crh, Pv, and Vip expression. LPS decreased the expression of Bdnf in the PFC (p < 0.0001) and HPC (p = 0.0003), which significantly correlated with affected markers (Sst, Pv, Cort, Cck, and Npy). Collectively, these results suggest that inflammation may causally contribute to cortical cell microcircuit GABAergic deficits observed in MDD.

Changes in neuroactive steroids, neurotrophins and immunological biomarkers after monotherapy 8-week rTMS treatment and their relationship with neurocognitive functions in depression

Repetitive transcranial magnetic stimulation (rTMS) has proven effective in the treatment of major depression. The underlying mechanisms of action are still poorly understood. We aimed to evaluate the changes in the levels of neuroactive steroids, neurotrophins and immunological biomarkers before and after rTMS treatment and assess the relationship of this change between clinical response and cognitive functions after monotherapy rTMS treatment. Twenty-three patients with major depressive disorder (MDD) and 25 matched healthy controls were included in the study. The Hamilton Depression Rating Scale (HDRS), Trail Making Test A and B forms and Digit Span Test were administered. Biomarkers (BDNF, TNF-α, IL-1ß, NAS) were run in the peripheral blood at the end of the first month that rTMS was administered daily and at the end of the 2nd month when that rTMS was administered once a week. Appropriate conditions were provided so that the relevant biomarkers were not affected by the biorhythm. After rTMS monotherapy, an increase in BDNF and allopregnanolone, a decrease in TNF-α, IL-1ß, DHEA, and DHEA-S levels was found to be statistically significant. The scores on cognitive tests increased with the treatment. Positive significant correlations was found between BDNF levels and cognitive tests at the end of the first and second months. Our findings suggest that the effects of rTMS treatment may be related to the neuroendocrine, neurotrophin, and immunological mechanisms. rTMS treatment is found to have positive effects on cognitive functions in the short term.

Unlocking new avenues for neuropsychiatric disease therapy: the emerging potential of Peroxisome proliferator-activated receptors as promising therapeutic targets

RATIONALE

Peroxisome proliferator-activated receptors (PPARs) are transcription factors that regulate various physiological processes such as inflammation, lipid metabolism, and glucose homeostasis. Recent studies suggest that targeting PPARs could be beneficial in treating neuropsychiatric disorders by modulating neuronal function and signaling pathways in the brain. PPAR-α, PPAR-δ, and PPAR-γ have been found to play important roles in cognitive function, neuroinflammation, and neuroprotection. Dysregulation of PPARs has been associated with neuropsychiatric disorders like bipolar disorder, schizophrenia, major depression disorder, and autism spectrum disorder. The limitations and side effects of current treatments have prompted research to target PPARs as a promising novel therapeutic strategy. Preclinical and clinical studies have shown the potential of PPAR agonists and antagonists to improve symptoms associated with these disorders.

OBJECTIVE

This review aims to provide an overview of the current understanding of PPARs in neuropsychiatric disorders, their potential as therapeutic targets, and the challenges and future directions for developing PPAR-based therapies.

METHODS

An extensive literature review of various search engines like PubMed, Medline, Bentham, Scopus, and EMBASE (Elsevier) databases was carried out with the keywords "PPAR, Neuropsychiatric disorders, Oxidative stress, Inflammation, Bipolar Disorder, Schizophrenia, Major depression disorder, Autism spectrum disorder, molecular pathway".

RESULT & CONCLUSION

Although PPARs present a hopeful direction for innovative therapeutic approaches in neuropsychiatric conditions, additional research is required to address obstacles and convert this potential into clinically viable and individualized treatments.

The relationship between BDNF and physical activity on depression

BACKGROUND/OBJECTIVE

Major depressive disorder (MDD) is one of the leading causes of disease burden and disability worldwide. Brain-derived neurotrophic factor (BDNF) seems to have an important role in the molecular mechanisms underlying MDD aetiology, given its implication in regulating neuronal plasticity. There is evidence that physical activity (PA) improves depressive symptoms, with a key role of BDNF in this effect. We aim to perform a systematic review examining the relationship between the BDNF Val66Met polymorphism and the BDNF protein, PA and MDD.

METHODS

Both observational and experimental design original articles or systematic reviews were selected, according to the PRISMA statement.

RESULTS

Six studies evaluated the Val66Met polymorphism, suggesting a greater impact of physical activity on depression depending on the Val66Met genotype. More discordant findings were observed among the 13 studies assessing BDNF levels with acute or chronic exercise interventions, mainly due to the high heterogeneity found among intervention designs, limited sample size, and potential bias.

CONCLUSIONS

Overall, there is cumulative evidence supporting the potential role of BDNF in the interaction between PA and MDD. However, this review highlights the need for further research with more homogeneous and standardised criteria, and pinpoints important confounding factors that must be considered in future studies to provide robust conclusions.

Leveraging interindividual variability in threat conditioning of inbred mice to model trait anxiety

Trait anxiety is a major risk factor for stress-induced and anxiety disorders in humans. However, animal models accounting for the interindividual variability in stress vulnerability are largely lacking. Moreover, the pervasive bias of using mostly male animals in preclinical studies poorly reflects the increased prevalence of psychiatric disorders in women. Using the threat imminence continuum theory, we designed and validated an auditory aversive conditioning-based pipeline in both female and male mice. We operationalised trait anxiety by harnessing the naturally occurring variability of defensive freezing responses combined with a model-based clustering strategy. While sustained freezing during prolonged retrieval sessions was identified as an anxiety-endophenotype behavioral marker in both sexes, females were consistently associated with an increased freezing response. RNA-sequencing of CeA, BLA, ACC, and BNST revealed massive differences in phasic and sustained responders' transcriptomes, correlating with transcriptomic signatures of psychiatric disorders, particularly post-traumatic stress disorder (PTSD). Moreover, we detected significant alterations in the excitation/inhibition balance of principal neurons in the lateral amygdala. These findings provide compelling evidence that trait anxiety in inbred mice can be leveraged to develop translationally relevant preclinical models to investigate mechanisms of stress susceptibility in a sex-specific manner.

Pathophysiology in cortico-amygdala circuits and excessive aversion processing: the role of oligodendrocytes and myelination

Stress-related psychiatric illnesses, such as major depressive disorder, anxiety and post-traumatic stress disorder, present with alterations in emotional processing, including excessive processing of negative/aversive stimuli and events. The bidirectional human/primate brain circuit comprising anterior cingulate cortex and amygdala is of fundamental importance in processing emotional stimuli, and in rodents the medial prefrontal cortex-amygdala circuit is to some extent analogous in structure and function. Here, we assess the comparative evidence for: (i) Anterior cingulate/medial prefrontal cortex<->amygdala bidirectional neural circuits as major contributors to aversive stimulus processing; (ii) Structural and functional changes in anterior cingulate cortex<->amygdala circuit associated with excessive aversion processing in stress-related neuropsychiatric disorders, and in medial prefrontal cortex<->amygdala circuit in rodent models of chronic stress-induced increased aversion reactivity; and (iii) Altered status of oligodendrocytes and their oligodendrocyte lineage cells and myelination in anterior cingulate/medial prefrontal cortex<->amygdala circuits in stress-related neuropsychiatric disorders and stress models. The comparative evidence from humans and rodents is that their respective anterior cingulate/medial prefrontal cortex<->amygdala circuits are integral to adaptive aversion processing. However, at the sub-regional level, the anterior cingulate/medial prefrontal cortex structure-function analogy is incomplete, and differences as well as similarities need to be taken into account. Structure-function imaging studies demonstrate that these neural circuits are altered in both human stress-related neuropsychiatric disorders and rodent models of stress-induced increased aversion processing. In both cases, the changes include altered white matter integrity, albeit the current evidence indicates that this is decreased in humans and increased in rodent models. At the cellular-molecular level, in both humans and rodents, the current evidence is that stress disorders do present with changes in oligodendrocyte lineage, oligodendrocytes and/or myelin in these neural circuits, but these changes are often discordant between and even within species. Nonetheless, by integrating the current comparative evidence, this review provides a timely insight into this field and should function to inform future studies-human, monkey and rodent-to ascertain whether or not the oligodendrocyte lineage and myelination are causally involved in the pathophysiology of stress-related neuropsychiatric disorders.

B cells and the stressed brain: emerging evidence of neuroimmune interactions in the context of psychosocial stress and major depression

The immune system has emerged as a key regulator of central nervous system (CNS) function in health and in disease. Importantly, improved understanding of immune contributions to mood disorders has provided novel opportunities for the treatment of debilitating stress-related mental health conditions such as major depressive disorder (MDD). Yet, the impact to, and involvement of, B lymphocytes in the response to stress is not well-understood, leaving a fundamental gap in our knowledge underlying the immune theory of depression. Several emerging clinical and preclinical findings highlight pronounced consequences for B cells in stress and MDD and may indicate key roles for B cells in modulating mood. This review will describe the clinical and foundational observations implicating B cell-psychological stress interactions, discuss potential mechanisms by which B cells may impact brain function in the context of stress and mood disorders, describe research tools that support the investigation of their neurobiological impacts, and highlight remaining research questions. The goal here is for this discussion to illuminate both the scope and limitations of our current understanding regarding the role of B cells, stress, mood, and depression.

Role of brain renin-angiotensin system in depression: A new perspective

Depression is a mood disorder characterized by abnormal thoughts. The pathophysiology of depression is related to the deficiency of serotonin (5HT), which is derived from tryptophan (Trp). Mitochondrial dysfunction, oxidative stress, and neuroinflammation are involved in the pathogenesis of depression. Notably, the renin-angiotensin system (RAS) is involved in the pathogenesis of depression, and different findings revealed that angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs) may be effective in depression. However, the underlying mechanism for the role of dysregulated brain RAS-induced depression remains speculative. Therefore, this review aimed to revise the conceivable role of ACEIs and ARBs and how these agents ameliorate the pathophysiology of depression. Dysregulation of brain RAS triggers the development and progression of depression through the reduction of brain 5HT and expression of brain-derived neurotrophic factor (BDNF) and the induction of mitochondrial dysfunction, oxidative stress, and neuroinflammation. Therefore, inhibition of central classical RAS by ARBS and ACEIs and activation of non-classical RAS prevent the development of depression by regulating 5HT, BDNF, mitochondrial dysfunction, oxidative stress, and neuroinflammation.

Interrogation of the human cortical peptidome uncovers cell-type specific signatures of cognitive resilience against Alzheimer's disease

Alzheimer's disease (AD) is characterised by age-related cognitive decline. Brain accumulation of amyloid-β plaques and tau tangles is required for a neuropathological AD diagnosis, yet up to one-third of AD-pathology positive community-dwelling elderly adults experience no symptoms of cognitive decline during life. Conversely, some exhibit chronic cognitive impairment in absence of measurable neuropathology, prompting interest into cognitive resilience-retained cognition despite significant neuropathology-and cognitive frailty-impaired cognition despite low neuropathology. Synapse loss is widespread within the AD-dementia, but not AD-resilient, brain. Recent evidence points towards critical roles for synaptic proteins, such as neurosecretory VGF, in cognitive resilience. However, VGF and related proteins often signal as peptide derivatives. Here, nontryptic peptidomic mass spectrometry was performed on 102 post-mortem cortical samples from individuals across cognitive and neuropathological spectra. Neuropeptide signalling proteoforms derived from VGF, somatostatin (SST) and protachykinin-1 (TAC1) showed higher abundance in AD-resilient than AD-dementia brain, whereas signalling proteoforms of cholecystokinin (CCK) and chromogranin (CHG) A/B and multiple cytoskeletal molecules were enriched in frail vs control brain. Integrating our data with publicly available single nuclear RNA sequencing (snRNA-seq) showed enrichment of cognition-related genes in defined cell-types with established links to cognitive resilience, including SST interneurons and excitatory intratelencephalic cells.

Neuroinflammation alters GABAergic neurotransmission in hyperammonemia and hepatic encephalopathy, leading to motor incoordination. Mechanisms and therapeutic implications

Enhanced GABAergic neurotransmission contributes to impairment of motor coordination and gait and of cognitive function in different pathologies, including hyperammonemia and hepatic encephalopathy. Neuroinflammation is a main contributor to enhancement of GABAergic neurotransmission through increased activation of different pathways. For example, enhanced activation of the TNFα-TNFR1-NF-κB-glutaminase-GAT3 pathway and the TNFα-TNFR1-S1PR2-CCL2-BDNF-TrkB pathway in cerebellum of hyperammonemic rats enhances GABAergic neurotransmission. This is mediated by mechanisms affecting GABA synthesizing enzymes GAD67 and GAD65, total and extracellular GABA levels, membrane expression of GABAA receptor subunits, of GABA transporters GAT1 and GAT three and of chloride co-transporters. Reducing neuroinflammation reverses these changes, normalizes GABAergic neurotransmission and restores motor coordination. There is an interplay between GABAergic neurotransmission and neuroinflammation, which modulate each other and altogether modulate motor coordination and cognitive function. In this way, neuroinflammation may be also reduced by reducing GABAergic neurotransmission, which may also improve cognitive and motor function in pathologies associated to neuroinflammation and enhanced GABAergic neurotransmission such as hyperammonemia, hepatic encephalopathy or Parkinson's disease. This provides therapeutic targets that may be modulated to improve cognitive and motor function and other alterations such as fatigue in a wide range of pathologies. As a proof of concept it has been shown that antagonists of GABAA receptors such as bicuculline reduces neuroinflammation and improves cognitive and motor function impairment in rat models of hyperammonemia and hepatic encephalopathy. Antagonists of GABAA receptors are not ideal therapeutic tools because they can induce secondary effects. As a more effective treatment to reduce GABAergic neurotransmission new compounds modulating it by other mechanisms are being developed. Golexanolone reduces GABAergic neurotransmission by reducing the potentiation of GABAA receptor activation by neurosteroids such as allopregnanolone. Golexanolone reduces neuroinflammation and GABAergic neurotransmission in animal models of hyperammonemia, hepatic encephalopathy and cholestasis and this is associated with improvement of fatigue, cognitive impairment and motor incoordination. This type of compounds may be useful therapeutic tools to improve cognitive and motor function in different pathologies associated with neuroinflammation and increased GABAergic neurotransmission.

Genetically encoded sensors for in vivo detection of neurochemicals relevant to depression

Depressive disorders are a common and debilitating form of mental illness with significant impacts on individuals and society. Despite the high prevalence, the underlying causes and mechanisms of depressive disorders are still poorly understood. Neurochemical systems, including serotonin, norepinephrine, and dopamine, have been implicated in the development and perpetuation of depressive symptoms. Current treatments for depression target these neuromodulator systems, but there is a need for a better understanding of their role in order to develop more effective treatments. Monitoring neurochemical dynamics during depressive symptoms is crucial for gaining a better a understanding of their involvement in depressive disorders. Genetically encoded sensors have emerged recently that offer high spatial-temporal resolution and the ability to monitor neurochemical dynamics in real time. This review explores the neurochemical systems involved in depression and discusses the applications and limitations of current monitoring tools for neurochemical dynamics. It also highlights the potential of genetically encoded sensors for better characterizing neurochemical dynamics in depression-related behaviors. Furthermore, potential improvements to current sensors are discussed in order to meet the requirements of depression research.

Investigating the Antidepressant Mechanisms of Polygonum sibiricum Polysaccharides via Microglial Polarization

Polygonum sibiricum, with its medicinal and edibility dual properties, has been widely recognized and utilized throughout Chinese history. As a kind of its effective component, Polygonum sibiricum polysaccharides (PSP) have been reported to be a promising novel antidepressant agent. Meanwhile, the precise mechanisms underlying its action remain elusive. The polarization state transition of microglia is intricately linked to neuroinflammation, indicating its crucial involvement in the pathophysiology of depression. Researchers are vigorously pursuing the exploration of this potential treatment strategy, aiming to comprehend its underlying mechanisms. Hence, the current study was designed to investigate the antidepressant mechanisms of PSP via Microglial M1/M2 Polarization, based on the lipopolysaccharide (LPS)-induced BV2 cell activation model. The results indicate that PSP significantly inhibited NO and LDH release and reduced ROS levels in LPS-induced BV2 cells. PSP could significantly reduce the protein expression level of Iba-1, decreased the mRNA levels of TNF-α, IL-1β, and IL-6, and increased the mRNA level of IL-10. PSP also significantly reduced the protein expression level of CD16/32 and increased that of CD206, reduced the mRNA level and fluorescence intensity of iNOS, and increased those of Arg-1. However, PSP pretreatment reversed the alterations of the BDNF/TrkB/CREB and Notch/Hes1 pathways in LPS-induced BV2 cells. These results suggested that PSP exerted the anti-inflammatory effects by inhibiting M1 phenotype polarization and promoting microglia polarization toward the M2 phenotype, and its regulation of microglia M1/M2 polarization may be associated with modulating the BDNF/TrkB/CREB and Notch/Hes1 pathways.

Behavioral as well as hippocampal transcriptomic and microglial responses differ across sexes in adult mouse offspring exposed to a dual genetic and environmental challenge

INTRODUCTION

A wide range of positive, negative, and cognitive symptoms compose the clinical presentation of schizophrenia. Schizophrenia is a multifactorial disorder in which genetic and environmental risk factors interact for a full emergence of the disorder. Infectious challenges during pregnancy are a well-known environmental risk factor for schizophrenia. Also, genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia. Translational animal models recapitulating these complex gene-environment associations have a great potential to untangle schizophrenia neurobiology and propose new therapeutic strategies.

METHODS

Given that genetic variants affecting the function of fractalkine signaling between neurons and microglia were linked to schizophrenia, we compared the outcomes of a well-characterized model of maternal immune activation induced using the viral mimetic polyinosinic:polycytidylic acid (Poly I:C) in wild-type versus fractalkine receptor knockout mice. Possible behavioral and immune alterations were assessed in male and female offspring during adulthood. Considering the role of the hippocampus in schizophrenia, microglial analyses and bulk RNA sequencing were performed within this region to assess the neuroimmune dynamics at play. Males and females were examined separately.

RESULTS

Offspring exposed to the dual challenge paradigm exhibited symptoms relevant to schizophrenia and unpredictably to mood disorders. Males displayed social and cognitive deficits related to schizophrenia, while females mainly presented anxiety-like behaviors related to mood disorders. Hippocampal microglia in females exposed to the dual challenge were hypertrophic, indicative of an increased surveillance, whereas those in males showed on the other end of the spectrum blunted morphologies with a reduced phagocytosis. Hippocampal bulk-RNA sequencing further revealed a downregulation in females of genes related to GABAergic transmission, which represents one of the main proposed causes of mood disorders.

CONCLUSIONS

Building on previous results, we identified in the current study distinctive behavioral phenotypes in female mice exposed to a dual genetic and environmental challenge, thus proposing a new model of neurodevelopmentally-associated mood and affective symptoms. This paves the way to future sex-specific investigations into the susceptibility to developmental challenges using animal models based on genetic and immune vulnerability as presented here.

Understanding the Biological Relationship between Migraine and Depression

Migraine is a highly prevalent neurological disorder. Among the risk factors identified, psychiatric comorbidities, such as depression, seem to play an important role in its onset and clinical course. Patients with migraine are 2.5 times more likely to develop a depressive disorder; this risk becomes even higher in patients suffering from chronic migraine or migraine with aura. This relationship is bidirectional, since depression also predicts an earlier/worse onset of migraine, increasing the risk of migraine chronicity and, consequently, requiring a higher healthcare expenditure compared to migraine alone. All these data suggest that migraine and depression may share overlapping biological mechanisms. Herein, this review explores this topic in further detail: firstly, by introducing the common epidemiological and risk factors for this comorbidity; secondly, by focusing on providing the cumulative evidence of common biological aspects, with a particular emphasis on the serotoninergic system, neuropeptides such as calcitonin-gene-related peptide (CGRP), pituitary adenylate cyclase-activating polypeptide (PACAP), substance P, neuropeptide Y and orexins, sexual hormones, and the immune system; lastly, by remarking on the future challenges required to elucidate the etiopathological mechanisms of migraine and depression and providing updated information regarding new key targets for the pharmacological treatment of these clinical entities.

Low-carbohydrate diet as a nutritional intervention in a major depression disorder: focus on relapse prevention

Objectives: Mood disorders are trending to be among the leading causes of years lived with disability. Despite multiple treatment options, around 30% patients with major depressive disorder (MDD) develop treatment resistant depression (TRD) and fail to respond to current pharmacological therapies. This study aimed to explore the potential benefits of nutritional treatment strategies, along with their molecular mechanisms of action, focusing especially on low-carbohydrate diet (LCHD), ketogenic diet (KD) and other strategies based on carbohydrates intake reduction.Methods: A comprehensive literature review was conducted to determine the impact of LCHD on alleviating depressive symptoms in patients with MDD, along with an explanation of its mode of action.Results: The study revealed significant impact of nutritional interventions based on restriction in carbohydrate intake such as LCHD, KD or sugar-sweetened beverages (SSB) exclusion on anxiety or depression symptoms reduction, mood improvement and lower risk of cognitive impairment or depression. The efficacy of these approaches is further substantiated by their underlying molecular mechanisms, mainly brain-derived neurotrophic factor (BDNF) which is a potential key target of sugar restriction diets in terms of neuroplasticity.Discussion: Healthcare professionals may consider implementing LCHD strategies for MDD and TRD patients to modify the disease process, maintain euthymia, and prevent depressive episode relapses. Ranging from the exclusion of SSB to the adherence to rigorous LCHD regimens, these nutritional approaches are safe, straightforward to implement, and may confer benefits for well-being and relapse prevention in this specific patient population.

Physical Exercise as an Intervention for Depression: Evidence for Efficacy and Mu-Opioid Receptors as a Mechanism of Action

Physical exercise is often cited as an important part of an intervention for depression, and there is empirical evidence to support this. However, the mechanism of action through which any potential antidepressant effects are produced is not widely understood. Recent evidence points toward the involvement of endogenous opioids, and especially the mu-opioid system, as a partial mediator of these effects. In this chapter, we discuss the current level of empirical support for physical exercise as either an adjunctive or standalone intervention for depression. We then review the extant evidence for involvement of endogenous opioids in the proposed antidepressant effects of exercise, with a focus specifically on evidence for mu-opioid system involvement.

The Role of Extrasynaptic GABA Receptors in Postpartum Depression

Postpartum depression is a serious disease with a high incidence and severe impact on pregnant women and infants, but its mechanism remains unclear. Recent studies have shown that GABA receptors, especially extrasynaptic receptors, are closely associated with postpartum depression. There are many different structures of GABA receptors, so different types of receptors have different functions, even though they transmit information primarily through GABA. In this review, we focus on the function of GABA receptors, especially extrasynaptic GABA receptors, and their association with postpartum depression. We have shown that the extrasynaptic GABA receptor has a significant impact on the activity and function of neurons through tonic inhibition. The extrasynaptic receptor and its ligands undergo drastic changes during pregnancy and childbirth. Abnormal changes or the body's inability to adjust and recover may be an important cause of postpartum depression. Finally, by reviewing the mechanisms of several novel antidepressants, we suggest that extrasynaptic receptors may be potential targets for the treatment of postpartum depression.

Behind the Mask: Parkinson's Disease and Depression

Parkinson's disease (PD) is a common, prevalent neurodegenerative disease. It is mainly characterized by motor symptoms such as rigidity, tremors, and bradykinesia, but it can also manifest with non-motor symptoms, of which depression is the most frequent. The latter can impair the quality of life, yet it gets overlooked and goes untreated because of the significant overlap in their clinical features, hence making the diagnosis difficult. Furthermore, there is limited data on the availability of appropriate criteria for making the diagnosis of depression in PD patients, as it can occur with varying expressions throughout the course of PD or it can also precede it. This review article has included a brief discussion on the diagnosis of depression in PD patients and their overlapped clinical manifestations. Understanding the mechanisms underlying the disease processes of PD and depression and the pathways interconnecting them gives better knowledge on devising treatment options for the patients. Only studies from Pubmed were included and all other databases were excluded. Studies from the last 50 years were included. Suitable references included in these studies were also extracted. Thus, depression in PD and PD in depression, along with their pharmacological and non-pharmacological treatment options, have been discussed.

[The relationship between the rs6265 polymorphism of the BDNF gene and the level of serum neurotrophic factor in patients with Parkinson's disease]

OBJECTIVE

To evaluate the clinical features and the level of serum brain-derived neurotrophic factor (BDNF) in groups of patients with Parkinson's disease (PD) differentiated by the genotypes of BDNF polymorphism (rs6265).

MATERIAL AND METHODS

The level of serum BDNF in the biomarkers' multiplex panel of neurodegenerative diseases (HNDG3MAG-36K) was assessed in 134 PD patients. Allele discrimination was carried out by real-time PCR using TaqMan probes for the analysis of BDNF rs6265 polymorphism in groups of patients and controls (n=192) matched for sex, age and ethnicity.

RESULTS

Comparing the distribution of rs6265 genotypes and alleles between groups of patients and controls no significant differences were found (p>0.05). Serum BDNF levels varied significantly by genotype (rs6265) among PD patients. Minimum mean serum BDNF level (320.1±164.6 pg/ml) was noted for individuals with the AA genotype, which significantly differs from the corresponding indicator among individuals with GA (2944.2±1590.6 pg/ml; p=0.0001) and GG genotypes (2949.4±1620.6 pg/ml; p=3.9×10-5). The concentration of BDNF significantly differed between patients with different forms of PD (p=0.0007) and increased as the stage of the disease progressed according to Hoehn and Yahr staging scale (p=1.0×10-6).

CONCLUSION

The BDNF rs6265 polymorphism was not associated with the development of PD in the studied population. The variability of the mean serum BDNF level was established depending on the genotype of the BDNF polymorphism in PD patients and a number of clinical features.

Bacopaside I alleviates depressive-like behaviors by modulating the gut microbiome and host metabolism in CUMS-induced mice

Bacopaside I (BSI) is a natural compound that is difficult to absorb orally but has been shown to have antidepressant effects. The microbiota-gut-brain axis is involved in the development of depression through the peripheral nervous system, endocrine system, and immune system and may be a key factor in the effect of BSI. Therefore, this study aimed to investigate the potential mechanism of BSI in the treatment of depression via the microbiota-gut-brain axis and to validate it in a fecal microbiota transplantation model. The antidepressant effect of BSI was established in CUMS-induced mice using behavioral tests and measurement of changes in hypothalamicpituitaryadrenal (HPA) axis-related hormones. The improvement of stress-induced gut-brain axis damage by BSI was observed by histopathological sections and enzyme-linked immunosorbent assay (ELISA). 16 S rDNA sequencing analysis indicated that BSI could modulate the abundance of gut microbiota and increase the abundance of probiotic bacteria. We also observed an increase in short-chain fatty acids, particularly acetic acid. In addition, BSI could modulate the disruption of lipid metabolism induced by CUMS. Fecal microbiota transplantation further confirmed that disruption of the microbiota-gut-brain axis is closely associated with the development of depression, and that the microbiota regulated by BSI exerts a partial antidepressant effect. In conclusion, BSI exerts antidepressant effects by remodeling gut microbiota, specifically through the Lactobacillus and Streptococcus-acetic acid-neurotrophin signaling pathways. Furthermore, BSI can repair damage to the gut-brain axis, regulate HPA axis dysfunction, and maintain immune homeostasis.

GABAA Receptor Availability in Relation to Cortical Excitability in Depressed and Healthy: A Positron Emission Tomography and Transcranial Magnetic Stimulation Study

INTRODUCTION

Gamma-aminobutyric acid (GABA) deficiency is suggested in depressive disorders, along with alterations in cortical excitability. However, whether these excitability changes are related to GABAA receptor availability is largely unknown. Our aim was to assess the correlation between these measures in depressed patients and healthy controls.

METHODS

Twenty-eight patients with a major depressive episode, measured before and after participating in a clinical trial with repetitive transcranial magnetic stimulation (TMS), and 15 controls underwent [11C]flumazenil positron emission tomography to assess GABAA receptor availability and paired pulse TMS (ppTMS) to evaluate cortical excitability. Both whole-brain voxel-wise GABAA receptor availability and mean values from left hand motor cortex and left paracentral lobule were correlated to the ppTMS outcomes: short-interval intracortical inhibition reflecting GABAA receptor activity, long-interval intracortical inhibition representing GABAB receptor activity, intracortical facilitation reflecting glutamate N-methyl-D-aspartate-receptor activity, as well as the resting motor threshold (rMT), considered a global measure of corticospinal excitability.

RESULTS

No significant differences in baseline GABAA receptor availability or cortical excitability were found between patients and controls. Additionally, no correlations were observed between baseline measurements of GABAA receptor availability and TMS outcomes. Changes in GABAA receptor availability in the hand motor cortex, between pre- and post-assessments, were inversely related to pre-post changes in hand rMT.

CONCLUSION

We found that a change in GABAA receptor availability was inversely related to a change in rMT, suggesting a link between GABA deficiency and increased rMT previously observed in depressive episodes. The results highlight the complex mechanisms governing cortical excitability measures and offer new insight into their properties during the depressive state.

Targeting BDNF with acupuncture: A novel integrated strategy for diabetes and depression comorbidity

Diabetes and depression are common comorbid conditions that impose a substantial health burden. Acupuncture may effectively improve symptoms in patients with diabetes and depression, but the underlying mechanism remains unclear. Brain-derived neurotrophic factor (BDNF) may play a vital role in the effects of acupuncture on diabetes and depression comorbidity. This review summarizes the potential role of BDNF in acupuncture for diabetes and depression comorbidity. BDNF appears to exert its effects via the BDNF-TrkB-ERK-CREB signaling pathway. BDNF levels are reduced in diabetes and depression, and acupuncture may increase BDNF expression, improving symptoms and glycemic control. High-quality research is needed to validate the efficacy of acupuncture for diabetes and depression comorbidity. Randomized controlled trials and mechanistic studies should investigate the BDNF pathway and other potential mechanisms. Improved understanding of the links between diabetes, depression and acupuncture may enable targeted and individualized patient care. Earlier diagnosis and management of diabetes and depression comorbidity should also be a priority.

Diagnostic Specificity and Association With Cognition of Molecular Alterations in Prefrontal Somatostatin Neurons in Schizophrenia

Importance

Individuals with schizophrenia (SZ) exhibit pronounced deficits in somatostatin (SST) messenger RNA (mRNA) levels in the dorsolateral prefrontal cortex (DLPFC). Molecularly distinct subtypes of SST neurons, located in the superficial and deep zones of the DLPFC, are thought to contribute to different functional processes of this region; understanding the specificity of SST alterations in SZ across these zones could inform the functional consequences of those alterations, including cognitive impairments characteristic of SZ.

Objective

To quantify mRNA levels of SST and related neuropeptides in the DLPFC in individuals with SZ, bipolar disorder (BPD), or major depressive disorder (MDD) and unaffected comparison individuals.

Design, Setting, and Participants

This case-control study, conducted from January 20, 2020, to March 30, 2022, used postmortem brain tissue specimens previously obtained from individuals with SZ, MDD, or BPD and unaffected individuals from a community population through 2 medical examiners' offices. Demographic, clinical, and educational information was ascertained through psychological autopsies.

Exposures

Diagnosis of SZ, BPD, or MDD.

Main Outcome and Measures

The main outcome was levels of SST and related neuropeptide mRNA in 2 DLPFC zones, examined using laser microdissection and quantitative polymerase chain reaction or fluorescent in situ hybridization (FISH). Findings were compared using educational attainment as a proxy measure of premorbid cognition.

Results

A total of 200 postmortem brain specimens were studied, including 65 from unaffected comparison individuals (42 [65%] male; mean [SD] age, 49.2 [14.1] years); 54 from individuals with SZ (37 [69%] male; mean [SD] age, 47.5 [13.3] years); 42 from individuals with MDD (24 [57%] male; mean [SD] age, 45.6 [12.1] years); and 39 from individuals with BPD (23 [59%] male; mean (SD) age, 46.2 [12.5] years). Compared with unaffected individuals, levels of SST mRNA were lower in both superficial (Cohen d, 0.68; 95% CI, 0.23-1.13; P = .004) and deep (Cohen d, 0.60; 95% CI, 0.16-1.04; P = .02) DLPFC zones in individuals with SZ; findings were confirmed using FISH. Levels of SST were lower only in the superficial zone in the group with MDD (Cohen d, 0.58; 95% CI, 0.14-1.02; P = .12), but the difference was not significant; SST levels were not lower in either zone in the BPD group. Levels of neuropeptide Y and tachykinin 1 showed similar patterns. Neuropeptide alterations in the superficial, but not deep, zone were associated with lower educational attainment only in the group with SZ (superficial: adjusted odds ratio, 1.71 [95% CI, 1.11-2.69]; P = .02; deep: adjusted odds ratio, 1.08 [95% CI, 0.64-1.84]; P = .77).

Conclusions and Relevance

The findings revealed diagnosis-specific patterns of molecular alterations in SST neurons in the DLPFC, suggesting that distinct disease processes are reflected in the differential vulnerability of SST neurons in individuals with SZ, MDD, and BPD. In SZ, alterations specifically in the superficial zone may be associated with cognitive dysfunction.

Somatostatin signaling modulates binge drinking behavior via the central nucleus of the amygdala

Somatostatin (SST) is a neuropeptide widely expressed in the central nervous system with dense expression in limbic regions such as the extended amygdala. It has recently gained attention for playing a role in modulating alcohol use disorders and co-morbid neuropsychiatric disorders. However, the role of SST in the central nucleus of the amygdala (CeA), a key region for neuropeptide regulation of alcohol and anxiety related behaviors, in alcohol consumption has not been assessed. In this work we perform an initial examination of the interaction between the CeA SST system and binge ethanol intake. Binge intake is a dangerous pattern of excessive ethanol consumption associated with health complications and the transition into alcohol dependence. We use the Drinking in the Dark (DID) model of binge intake in C57BL/6J male and female mice to examine: 1) the impact of 3 DID cycles on CeA SST expression; 2) the effect of intra-CeA SST injection on binge-like ethanol consumption; and 3) if the SST receptor 2 or 4 (SST2R or SST4R) mediate any effect on consumption. Our results show binge-like ethanol intake decreases SST expression in the CeA, but not neighboring basolateral amygdala. We further found intra-SST CeA administration reduces binge ethanol intake. This decrease was replicated by the administration of an SST4R agonist. These effects were not sex-dependent. Overall, this work lends further support for SST playing a role in alcohol related behaviors and as a potential therapeutic target.

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.

Maternal separation and its developmental consequences on anxiety and parvalbumin interneurons in the amygdala

The early postnatal period represents an exceptionally vulnerable phase for the development of neurobiological alterations, aberrant behavior, and psychiatric disorders. Altered GABAergic activity in the hippocampus and the amygdala have been identified in humans diagnosed with depression or anxiety disorders, as well as in respective animal models. Changes in GABAergic activity can be visualized by immunohistochemical staining of parvalbumin (PV) protein. Therewith, alterations in PV intensity as well as in the integrity of the perineural net surrounding PV positive (PV+) interneurons have been reported as consequences of early stress. In the current study, maternal separation (MS) was used to induce early life stress. Female and male Sprague-Dawley rats were subjected to MS over 4 h from postnatal days 2-20. Then, anxiety behavior and PV+ interneurons in the amygdala were analyzed using immunohistochemistry in adolescence or adulthood. MS induced increased anxiety behavior in the marble-burying test in adolescence as well as in the elevated plus maze in adulthood. No effect of sex was found. Concerning alterations of parvalbumin expression in the amygdala, a trend towards a lower number of parvalbumin-positive inhibitory interneurons was shown in the amygdala after MS in adolescence, with no differences in the total number of cells. The current study offers a developmental perspective, suggesting that the kind of anxiety behavior expressed by rats following MS changes over time from active to passive avoidance, indicating that effects of MS are highly dependent on developmental state. Moreover, a cell-type-specific effect of MS on the cellular composition of the amygdala is discussed. The presented study demonstrates the long-lasting consequences of early stress on behavior, offers a possible neurobiological correlate, and discusses possible mediators in the development of these alterations.

Brain-specific Pd1 deficiency leads to cortical neurogenesis defects and depressive-like behaviors in mice

Embryonic neurogenesis is tightly regulated by multiple factors to ensure the precise development of the cortex. Deficiency in neurogenesis may result in behavioral abnormalities. Pd1 is a well-known inhibitory immune molecule, but its function in brain development remains unknown. Here, we find brain specific deletion of Pd1 results in abnormal cortical neurogenesis, including enhanced proliferation of neural progenitors and reduced neuronal differentiation. In addition, neurons in Pd1 knockout mice exhibit abnormal morphology, both the total length and the number of primary dendrites were reduced. Moreover, Pd1cKO mice exhibit depressive-like behaviors, including immobility, despair, and anhedonia. Mechanistically, Pd1 regulates embryonic neurogenesis by targeting Pax3 through the β-catenin signaling pathway. The constitutive expression of Pax3 partly rescues the deficiency of neurogenesis in the Pd1 deleted embryonic brain. Besides, the administration of β-catenin inhibitor, XAV939, not only rescues abnormal brain development but also ameliorates depressive-like behaviors in Pd1cKO mice. Simultaneously, Pd1 plays a similar role in human neural progenitor cells (hNPCs) proliferation and differentiation. Taken together, our findings reveal the critical role and regulatory mechanism of Pd1 in embryonic neurogenesis and behavioral modulation, which could contribute to understanding immune molecules in brain development.

Borneol-modified PEGylated graphene oxide as a nanocarrier for brain-targeted delivery of ginsenoside Rg1 against depression

Depression is a chronic mental disorder which threatens human health and lives. However, the treatment of depression remains challenging largely due to blood brain barrier (BBB), which restricts drugs from entering the brain, resulting in a poor distribution of antidepressants in the brain. In this work, a novel brain-targeted drug delivery system was developed based on borneol-modified PEGylated graphene oxide (GO-PEG-BO). GO-PEG-BO was characterized and proved to possess excellent biocompatibility. By incorporating borneol, GO-PEG-BO could penetrate BBB efficiently by opening tight junctions and inhibiting the efflux system of BBB. The targeted distribution of GO-PEG-BO in the brain was observed by an in vivo biodistribution study. Moreover, GO-PEG-BO exhibited a neuroprotective effect, which is beneficial to the treatment of depression. Ginsenoside Rg1 (GRg1), which can relieve depressive symptoms but difficult to cross BBB, was loaded to GO-PEG-BO for the therapy of depression. In depressive rats, GRg1/GO-PEG-BO improved stress-induced anhedonia, despair and anxiety, and comprehensively relieved the depressive symptoms. In conclusion, GO-PEG-BO could serve as a promising nanocarrier for brain-targeted drug delivery, and provide a new strategy for the therapy of depression.

The effects of acupuncture on depression by regulating BDNF-related balance via lateral habenular nucleus BDNF/TrkB/CREB signaling pathway in rats

Depression is a major mental disease worldwide, causing dysfunction of Lateral Habenular (LHb). As a non-invasive alternative, acupuncture (AP) has been widely used to treat depression in clinic, yet few basic studies have been focused on the effects and mechanism of acupuncture on synaptic plasticity in LHb. Therefore, this study aimed to explore the potential mechanism of the antidepressant effect of acupuncture. Male Sprague-Dawley (SD) rats were randomly divided into control, chronic unpredictable mild stress (CUMS), AP, fluoxetine (FLX), acupoint catgut embedding (ACE), sham-ACE groups (n = 9/group). Rats were given a 28-day treatment at the Shangxing (GV23) and Fengfu (GV16) acupoints with acupuncture, ACE, sham-ACE or fluoxetine (2.1 mg/kg). The results showed that AP, FLX and ACE suppressed the behavioral deficits, increased the level of the 5-hydroxytryptamine and FNDC5/IRISIN in serum, also reduced the expression of pro-BDNF impacted by CUMS. Both AP and FLX ameliorated the %area of IBA-1, GFAP, BrdU and DCX in the LHb and increased the expression of BDNF/TrkB/CREB, with non-significant difference between the two groups These findings suggest that AP therapy relieves depression-related manifestations in depressed rats, suggesting a potential mechanism via the BDNF/TrkB/CREB pathway in LHb.

Brain-wide changes in excitation-inhibition balance of major depressive disorder: a systematic review of topographic patterns of GABA- and glutamatergic alterations

The excitation-inhibition (E/I) imbalance is an important molecular pathological feature of major depressive disorder (MDD) as altered GABA and glutamate levels have been found in multiple brain regions in patients. Healthy subjects show topographic organization of the E/I balance (EIB) across various brain regions. We here raise the question of whether such EIB topography is altered in MDD. Therefore, we systematically review the gene and protein expressions of inhibitory GABAergic and excitatory glutamatergic signaling-related molecules in postmortem MDD brain studies as proxies for EIB topography. Searches were conducted through PubMed and 45 research articles were finally included. We found: i) brain-wide GABA- and glutamatergic alterations; ii) attenuated GABAergic with enhanced glutamatergic signaling in the cortical-subcortical limbic system; iii) that GABAergic signaling is decreased in regions comprising the default mode network (DMN) while it is increased in lateral prefrontal cortex (LPFC). These together demonstrate abnormal GABA- and glutamatergic signaling-based EIB topographies in MDD. This enhances our pathophysiological understanding of MDD and carries important therapeutic implications for stimulation treatment.

Interventional Mental Health: A Transdisciplinary Approach to Novel Psychiatric Care Delivery

Mental health disorders are among the most common health conditions in the United States. Traditional clinical treatments rely on psychiatric counseling and, in many cases, prescription medications. We propose an innovative model, Interventional Mental Health, which employs a combination of modalities through a multifaceted approach to treat conditions that have exhibited limited responsiveness to traditional methods and individuals afflicted with multiple comorbidities simultaneously. We hypothesize that creating a unique treatment algorithm combining current therapeutic modalities such as Stellate Ganglion Blocks (SGB), Transcranial Magnetic Stimulation (TMS) therapy, and ketamine therapy, within a consolidated timeframe, will yield synergistic outcomes among patients presenting with comorbid post-traumatic stress disorder (PTSD), depression, and/or anxiety.

GABA-ergic Modulators: New Therapeutic Approaches to Premenstrual Dysphoric Disorder

Premenstrual dysphoric disorder (PMDD) is characterized by the predictable onset of mood and physical symptoms secondary to gonadal steroid fluctuation during the luteal phase of the menstrual cycle. Although menstrual-related affective dysfunction is responsible for considerable functional impairment and reduction in quality of life worldwide, currently approved treatments for PMDD are suboptimal in their effectiveness. Research over the past two decades has suggested that the interaction between allopregnanolone, a neurosteroid derivative of progesterone, and the gamma-aminobutyric acid (GABA) system represents an important relationship underlying symptom genesis in reproductive-related mood disorders, including PMDD. The objective of this narrative review is to discuss the plausible link between changes in GABAergic transmission secondary to the fluctuation of allopregnanolone during the luteal phase and mood impairment in susceptible individuals. As part of this discussion, we explore promising findings from early clinical trials of several compounds that stabilize allopregnanolone signaling during the luteal phase, including dutasteride, a 5-alpha reductase inhibitor; isoallopregnanolone, a GABA-A modulating steroid antagonist; and ulipristal acetate, a selective progesterone receptor modulator. We then reflect on the implications of these therapeutic advances, including how they may promote our knowledge of affective regulation more generally. We conclude that these and other studies of PMDD may yield critical insight into the etiopathogenesis of affective disorders, considering that (1) symptoms in PMDD have a predictable onset and offset, allowing for examination of affective state kinetics, and (2) GABAergic interventions in PMDD can be used to better understand the relationship between mood states, network regulation, and the balance between excitatory and inhibitory signaling in the brain.

Effects of astaxanthin on depressive and sleep symptoms: A narrative mini-review

Major depressive disorder (MDD) is a prevalent psychiatric condition that results in persistent feelings of sadness and loss of interest, imposing a significant economic burden on health systems and society. Impaired sleep is both a symptom and a risk factor for depression. Natural astaxanthin (AST), a carotenoid primarily derived from algae and aquatic animals, possesses multiple pharmacological properties such as anti-inflammatory, anti-apoptotic, and antioxidant stress effects. Prior research suggests that AST may have antidepressant properties. This mini-review highlights the potential mechanisms by which AST can prevent depression, providing novel insights into drug research for depression treatment. Specifically, this mechanism suggests that astaxanthin may improve sleep and thus potentially aid in the treatment of depression.

Towards Novel Potential Molecular Targets for Antidepressant and Antipsychotic Pharmacotherapies

Depression and schizophrenia are two highly prevalent and severely debilitating neuropsychiatric disorders. Both conventional antidepressant and antipsychotic pharmacotherapies are often inefficient clinically, causing multiple side effects and serious patient compliance problems. Collectively, this calls for the development of novel drug targets for treating depressed and schizophrenic patients. Here, we discuss recent translational advances, research tools and approaches, aiming to facilitate innovative drug discovery in this field. Providing a comprehensive overview of current antidepressants and antipsychotic drugs, we also outline potential novel molecular targets for treating depression and schizophrenia. We also critically evaluate multiple translational challenges and summarize various open questions, in order to foster further integrative cross-discipline research into antidepressant and antipsychotic drug development.

Absence of Depressive and Anxious Behavior with Genetic Dysregulation in Adult C57Bl/6J Mice after Prenatal Exposure to Ionizing Radiation

The exposure of ionizing radiation during early gestation often leads to deleterious and even lethal effects; however, few extensive studies have been conducted on late gestational exposures. This research examined the behavior al effects of C57Bl/6J mouse offspring exposed to low dose ionizing gamma irradiation during the equivalent third trimester. Pregnant dams were randomly assigned to sham or exposed groups to either low dose or sublethal dose radiation (50, 300, or 1000 mGy) at gestational day 15. Adult offspring underwent a behavioral and genetic analysis after being raised under normal murine housing conditions. Our results indicate very little change in the behavioral tasks measuring general anxiety, social anxiety, and stress-management in animals exposed prenatally across the low dose radiation conditions. Quantitative real-time polymerase chain reactions were conducted on the cerebral cortex, hippocampus, and cerebellum of each animal; results indicate some dysregulation in markers of DNA damage, synaptic activity, reactive oxygen species (ROS) regulation, and methylation pathways in the offspring. Together, our results provide evidence in the C57Bl/6J strain, that exposure to sublethal dose radiation (<1000 mGy) during the last period of gestation leads to no observable changes in behaviour when assessed as adults, although some changes in gene expression were observed for specific brain regions. These results indicate that the level of oxidative stress occurring during late gestation for this mouse strain is not sufficient for a change in the assessed behavioral phenotype, but results in some modest dysregulation of the genetic profile of the brain.

Mood disturbances in Parkinson's disease: From prodromal origins to application of animal models

Parkinson's disease (PD) is a complex illness with a constellation of environmental insults and genetic vulnerabilities being implicated. Strikingly, many studies only focus on the cardinal motor symptoms of the disease and fail to appreciate the major non-motor features which typically occur early in the disease process and are debilitating. Common comorbid psychiatric features, notably clinical depression, as well as anxiety and sleep disorders are thought to emerge before the onset of prominent motor deficits. In this review, we will delve into the prodromal stage of PD and how early neuropsychiatric pathology might unfold, followed by later motor disturbances. It is also of interest to discuss how animal models of PD capture the complexity of the illness, including depressive-like characteristics along with motor impairment. It remains to be determined how the underlying PD disease processes contributes to such comorbidity. But some of the environmental toxicants and microbial pathogens implicated in PD might instigate pro-inflammatory effects favoring α-synuclein accumulation and damage to brainstem neurons fueling the evolution of mood disturbances. We posit that comprehensive animal-based research approaches are needed to capture the complexity and time-dependent nature of the primary and co-morbid symptoms. This will allow for the possibility of early intervention with more novel and targeted treatments that fit with not only individual patient variability, but also with changes that occur over time with the evolution of the disease.

Neurotrophic basis to the pathogenesis of depression and phytotherapy

Depression is a major neuropsychiatric disease that considerably impacts individuals’ psychosocial function and life quality. Neurotrophic factors are now connected to the pathogenesis of depression, while the definitive neurotrophic basis remains elusive. Besides, phytotherapy is alternative to conventional antidepressants that may minimize undesirable adverse reactions. Thus, further research into the interaction between neurotrophic factors and depression and phytochemicals that repair neurotrophic factors deficit is highly required. This review highlighted the implication of neurotrophic factors in depression, with a focus on the brain-derived neurotrophic factor (BDNF), glial cell line-derived neurotrophic factor (GDNF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF), and detailed the antidepressant activities of various phytochemicals targeting neurotrophic factors. Additionally, we presented future opportunities for novel diagnostic and therapeutic strategies for depression and provided solutions to challenges in this area to accelerate the clinical translation of neurotrophic factors for the treatment of depression.

Young adult and aged female rats are vulnerable to amygdala-dependent, but not hippocampus-dependent, memory impairment following short-term high-fat diet

Global populations are increasingly consuming diets high in saturated fats and refined carbohydrates, and such diets have been well-associated with heightened inflammation and neurological dysfunction. Notably, older individuals are particularly vulnerable to the impact of unhealthy diet on cognition, even after a single meal, and pre-clinical rodent studies have demonstrated that short-term consumption of high-fat diet (HFD) induces marked increases in neuroinflammation and cognitive impairment. Unfortunately though, to date, most studies on the topic of nutrition and cognition, especially in aging, have been performed only in male rodents. This is especially concerning given that older females are more vulnerable to develop certain memory deficits and/or severe memory-related pathologies than males. Thus, the aim of the present study was to determine the extent to which short-term HFD consumption impacts memory function and neuroinflammation in female rats. Young adult (3 months) and aged (20-22 months) female rats were fed HFD for 3 days. Using contextual fear conditioning, we found that HFD had no effect on long-term contextual memory (hippocampus-dependent) at either age, but impaired long-term auditory-cued memory (amygdala-dependent) regardless of age. Gene expression of Il-1β was markedly dysregulated in the amygdala, but not hippocampus, of both young and aged rats after 3 days of HFD. Interestingly, modulation of IL-1 signaling via central administration of the IL-1 receptor antagonist (which we have previously demonstrated to be protective in males) had no impact on memory function following the HFD in females. Investigation of the memory-associated gene Pacap and its receptor Pac1r revealed differential effects of HFD on their expression in the hippocampus and amygdala. Specifically, HFD induced increased expression of Pacap and Pac1r in the hippocampus, whereas decreased Pacap was observed in the amygdala. Collectively, these data suggest that both young adult and aged female rats are vulnerable to amygdala-dependent (but not hippocampus-dependent) memory impairments following short-term HFD consumption, and identify potential mechanisms related to IL-1β and PACAP signaling in these differential effects. Notably, these findings are strikingly different than those previously reported in male rats using the same diet regimen and behavioral paradigms, and highlight the importance of examining potential sex differences in the context of neuroimmune-associated cognitive dysfunction.

Altered neurotransmission in stress-induced depressive disorders: The underlying role of the amygdala in depression

Depression is the second leading cause of disability in the world population, for which currently available pharmacological therapies either have poor efficacy or have some adverse effects. Accumulating evidence from clinical and preclinical studies demonstrates that the amygdala is critically implicated in depressive disorders, though the underlying pathogenesis mechanism needs further investigation. In this literature review, we overviewed depression and the key role of Gamma-aminobutyric acid (GABA) and Glutamate neurotransmission in depression. Notably, we discussed a new cholecystokinin-dependent plastic changes mechanism under stress and a possible antidepressant response of cholecystokinin B receptor (CCKBR) antagonist. Moreover, we discussed the fundamental role of the amygdala in depression, to discuss and understand the pathophysiology of depression and the inclusive role of the amygdala in this devastating disorder.

Boophone disticha attenuates five day repeated forced swim-induced stress and adult hippocampal neurogenesis impairment in male Balb/c mice

Depression is one of the most common neuropsychiatric disorders and is associated with dysfunction of the neuroendocrine system and alterations in specific brain proteins. Boophone disticha (BD) is an indigenous psychoactive bulb that belongs to the Amaryllidacae family, which is widely used in Southern Africa to treat depression, with scientific evidence of potent antidepressant-like effects. The present study examined the antidepressant effects of BD and its mechanisms of action by measuring some behavioural parameters in the elevated plus maze, brain content of corticosterone, brain derived neurotropic factor (BDNF), and neuroblast differentiation in the hippocampus of Balb/c mice exposed to the five day repeated forced swim stress (5d-RFSS). Male Balb/c mice were subjected to the 5d-RFSS protocol to induce depressive-like behaviour (decreased swimming, increased floating, decreased open arm entry, decreased time spent in the open arms and decreased head dips in the elevated plus maze test) and treated with distilled water, fluoxetine and BD. BD treatment (10 mg/kg/p.o for 3 weeks) significantly attenuated the 5d-RFSS-induced behavioural abnormalities and the elevated serum corticosterone levels observed in stressed mice. Additionally, 5d-RFSS exposure significantly decreased the number of neuroblasts in the hippocampus and BDNF levels in the brain of Balb/c mice, while fluoxetine and BD treatment attenuated these changes. The antidepressant effects of BD were comparable to those of fluoxetine, but unlike fluoxetine, BD did not show any anxiogenic effects, suggesting better pharmacological functions. In conclusion, our study shows that BD exerted antidepressant-like effects in 5d-RFSS mice, mediated in part by normalizing brain corticosterone and BDNF levels.

The role of GPR39 zinc receptor in the modulation of glutamatergic and GABAergic transmission

BACKGROUND

Despite our poor understanding of the pathophysiology of depression, a growing body of evidence indicates the role of both glutamate and gamma-aminobutyric acid (GABA) signaling behind the effects of rapid-acting antidepressants (RAADs). GPR39 is a zinc-sensing receptor whose activation leads to a prolonged antidepressant-like response in mice. Both GPR39 and zinc can modulate glutamatergic and GABAergic neurotransmission, however, exact molecular mechanisms are still elusive. In this study, we aimed to research the role of glutamatergic and GABAergic system activation in TC-G 1008 antidepressant-like effects and the disruptions in this effect caused by a low-zinc diet.

METHODS

In the first part of our study, we investigated the role of joint administration of the GPR39 agonist (TC-G 1008) and ligands of the glutamatergic or GABAergic systems, in antidepressant-like response. To evaluate animal behaviour we used the forced swim test in mice. In the second part of the study, we assessed the effectiveness of TC-G 1008-induced antidepressant-like response in conditions of decreased dietary zinc intake and its molecular underpinning by conducting a Western Blot analysis of selected proteins involved in glutamatergic and GABAergic neurotransmission.

RESULTS

The TC-G 1008-induced effect was blocked by the administration of NMDA or picrotoxin. The joint administration of TC-G 1008 along with muscimol or SCH50911 showed a trend toward decreased immobility time. Zinc-deficient diet resulted in dysregulation of GluN1, PSD95, and KCC2 protein expression.

CONCLUSIONS

Our findings indicate the important role of glutamate/GABA signaling in the antidepressant-like effect of TC-G 1008 and imply that GPR39 regulates the balance between excitatory and inhibitory activity in the brain. Thus, we suggest the zinc-sensing receptor be considered an interesting new target for the development of novel antidepressants.

Phytochemicals That Act on Synaptic Plasticity as Potential Prophylaxis against Stress-Induced Depressive Disorder

Depression is a neuropsychiatric disorder associated with persistent stress and disruption of neuronal function. Persistent stress causes neuronal atrophy, including loss of synapses and reduced size of the hippocampus and prefrontal cortex. These alterations are associated with neural dysfunction, including mood disturbances, cognitive impairment, and behavioral changes. Synaptic plasticity is the fundamental function of neural networks in response to various stimuli and acts by reorganizing neuronal structure, function, and connections from the molecular to the behavioral level. In this review, we describe the alterations in synaptic plasticity as underlying pathological mechanisms for depression in animal models and humans. We further elaborate on the significance of phytochemicals as bioactive agents that can positively modulate stress-induced, aberrant synaptic activity. Bioactive agents, including flavonoids, terpenes, saponins, and lignans, have been reported to upregulate brain-derived neurotrophic factor expression and release, suppress neuronal loss, and activate the relevant signaling pathways, including TrkB, ERK, Akt, and mTOR pathways, resulting in increased spine maturation and synaptic numbers in the neuronal cells and in the brains of stressed animals. In clinical trials, phytochemical usage is regarded as safe and well-tolerated for suppressing stress-related parameters in patients with depression. Thus, intake of phytochemicals with safe and active effects on synaptic plasticity may be a strategy for preventing neuronal damage and alleviating depression in a stressful life.

Identification of novel targets and pathways to distinguish suicide dependent or independent on depression diagnosis

In recent years, postmortem brain studies have revealed that some molecular, cellular, and circuit changes associated with suicide, have an independent or additive effect on depression. The aim of the present study is to identify potential phenotypic, tissue, and sex-specific novel targets and pathways to distinguish depression or suicide from major depressive disorder (MDD) comorbid with suicide. The mRNA expression profiling datasets from two previous independent postmortem brain studies of suicide and depression (GSE102556 and GSE101521) were retrieved from the GEO database. Machine learning analysis was used to differentiate three regrouped gene expression profiles, i.e., MDD with suicide, MDD without suicide, and suicide without depression. Weighted correlation network analysis (WGCNA) was further conducted to identify the key modules and hub genes significantly associated with each of these three sub-phenotypes. TissueEnrich approaches were used to find the essential brain tissues and the difference of tissue enriched genes between depression with or without suicide. Dysregulated gene expression cross two variables, including phenotypes and tissues, were determined by global analysis with Vegan. RRHO analysis was applied to examine the difference in global expression pattern between male and female groups. Using the optimized machine learning model, several ncRNAs and mRNAs with higher AUC and MeanDecreaseGini, including GCNT1P1 and AC092745.1, etc., were identified as potential molecular targets to distinguish suicide with, or without MDD and depression without suicide. WGCNA analysis identified some key modules significantly associated with these three phenotypes, and the gene biological functions of the key modules mainly relate to ncRNA and miRNA processing, as well as oxidoreductase and dehydrogenase activity. Hub genes such as RP11-349A22.5, C20orf196, MAPK8IP3 and RP11-697N18.2 were found in these key modules. TissueEnrich analysis showed that nucleus accumbens and subiculum were significantly changed among the 6 brain regions studied. Global analysis with Vegan and RRHO identified PRS26, ARNT and SYN3 as the most significantly differentially expressed genes across phenotype and tissues, and there was little overlap between the male and female groups. In this study, we have identified novel gene targets, as well as annotated functions of co-expression patterns and hub genes that are significantly distinctive between depression with suicide, depression without suicide, and suicide without depression. Moreover, global analysis across three phenotypes and tissues confirmed the evidence of sex difference in mood disorders.

Maternal anxiety, depression and stress affects offspring gut microbiome diversity and bifidobacterial abundances

Uncovering mechanisms underlying fetal programming during pregnancy is of critical importance. Atypical neurodevelopment during the pre- and immediate postnatal period has been associated with long-term adverse health outcomes, including mood disorders and aberrant cognitive ability in offspring. Maternal factors that have been implicated in anomalous offspring development include maternal inflammation and tress, anxiety, and depression. One potential mechanism through which these factors perturb normal offspring postnatal development is through microbiome disruption. The mother is a primary source of early postnatal microbiome seeding for the offspring, and the transference of a healthy microbiome is key in normal neurodevelopment. Since psychological stress, mood disorders, and inflammation have all been implicated in altering maternal microbiome community structure, passing on aberrant microbial communities to the offspring that may then affect developmental outcomes. Therefore, we examined how maternal stress, anxiety and depression assessed with standardized instruments, and maternal inflammatory cytokine levels in the pre- and postnatal period are associated with the offspring microbiome within the first 13 months of life, utilizing full length 16S sequencing on infant stool samples, that allowed for species-level resolution. Results revealed that infants of mothers who reported higher anxiety and perceived stress had reduced alpha diversity. Additionally, the relative taxonomic quantitative abundances of Bifidobacterium dentium and other species that have been associated with either modulation of the gut-brain axis, or other beneficial health outcomes, were reduced in the offspring of mothers with higher anxiety, perceived stress, and depression. We also found associations between bifidobacteria and prenatal maternal pro-inflammatory cytokines IL-6, IL-8, and IL-10. In summary, specific microbial taxa involved in maintaining proper brain and immune function are lower in offspring born to mothers with anxiety, depression, or stress, providing strong evidence for a mechanism by which maternal factors may affect offspring health through microbiota dysregulation.

Suicide and Neurotrophin Factors: A Systematic Review of the Correlation between BDNF and GDNF and Self-Killing

According to WHO data, suicide is a public health priority. In particular, suicide is the fourth-leading cause of death in young people. Many risk factors of suicide are described, including individual-, relationship-, community-, and societal-linked ones. The leading factor is the diagnosis of mental illness. Nevertheless, not all people who attempt suicide are psychiatric patients; these characteristics help define high-risk populations. There are currently no useful biomarkers to indicate the risk of suicide. In recent years, neurotrophic factors have increasingly become of scientific interest. This review aims to summarize the current scientific knowledge on the correlation between BDNF and GDNF and suicide, to theorize whether neurotrophins could be a reliable marker for an early diagnosis of suicidal risk. The authors conducted a systematic review following PRISMA criteria. They found eight research papers in agreement with the inclusion criteria. According to the results of these studies, there may be a connection between BDNF brain levels and complete suicide, although there are discrepancies. A lack of interest in GDNF may suggest less involvement in the suicidal dynamic. Further studies may provide helpful information to researchers.

BDNF receptor TrkB as the mediator of the antidepressant drug action

Brain-derived neurotrophic factor (BDNF) signaling through its receptor TrkB has for a long time been recognized as a critical mediator of the antidepressant drug action, but BDNF signaling has been considered to be activated indirectly through the action of typical and rapid-acting antidepressants through monoamine transporters and glutamate NMDA receptors, respectively. However, recent findings demonstrate that both typical and the fast-acting antidepressants directly bind to TrkB and thereby allosterically potentiate BDNF signaling, suggesting that TrkB is the direct target for antidepressant drugs. Increased TrkB signaling particularly in the parvalbumin-expressing interneurons orchestrates iPlasticity, a state of juvenile-like enhanced plasticity in the adult brain. iPlasticity sensitizes neuronal networks to environmental influences, enabling rewiring of networks miswired by adverse experiences. These findings have dramatically changed the position of TrkB in the antidepressant effects and they propose a new end-to-end model of the antidepressant drug action. This model emphasizes the enabling role of antidepressant treatment and the active participation of the patient in the process of recovery from mood disorders.

Participation of the Serotonergic System and Brain-Derived Neurotrophic Factor in the Antidepressant-like Effect of Flavonoids

Depressive disorders are among the most disabling diseases experienced around the world, and their incidence has significantly increased over the last few decades due to multiple environmental, social, and biological factors. The search for new pharmacological alternatives to treat depression is a global priority. In preclinical research, molecules obtained from plants, such as flavonoids, have shown promising antidepressant-like properties through several mechanisms of action that have not been fully elucidated, including crossing of the blood brain barrier (BBB). This review will focus on discussing the main findings related to the participation of the serotonergic system and brain-derived neurotrophic factor (BDNF) on the antidepressant-like effect of some flavonoids reported by behavioral, neurochemical, and molecular studies. In this sense, evidence shows that depressive individuals have low levels of serotonin and BDNF, while flavonoids can reverse it. Finally, the elucidation of the mechanism used by flavonoids to modulate serotonin and BDNF will contribute to our understanding of the neurobiological bases underlying the antidepressant-like effects produced by these natural compounds.

Decoding Shared Versus Divergent Transcriptomic Signatures Across Cortico-Amygdala Circuitry in PTSD and Depressive Disorders

OBJECTIVE

Posttraumatic stress disorder (PTSD) is a debilitating neuropsychiatric disease that is highly comorbid with major depressive disorder (MDD) and bipolar disorder. The overlap in symptoms is hypothesized to stem from partially shared genetics and underlying neurobiological mechanisms. To delineate conservation between transcriptional patterns across PTSD and MDD, the authors examined gene expression in the human cortex and amygdala in these disorders.

METHODS

RNA sequencing was performed in the postmortem brain of two prefrontal cortex regions and two amygdala regions from donors diagnosed with PTSD (N=107) or MDD (N=109) as well as from neurotypical donors (N=109).

RESULTS

The authors identified a limited number of differentially expressed genes (DEGs) specific to PTSD, with nearly all mapping to cortical versus amygdala regions. PTSD-specific DEGs were enriched in gene sets associated with downregulated immune-related pathways and microglia as well as with subpopulations of GABAergic inhibitory neurons. While a greater number of DEGs associated with MDD were identified, most overlapped with PTSD, and only a few were MDD specific. The authors used weighted gene coexpression network analysis as an orthogonal approach to confirm the observed cellular and molecular associations.

CONCLUSIONS

These findings provide supporting evidence for involvement of decreased immune signaling and neuroinflammation in MDD and PTSD pathophysiology, and extend evidence that GABAergic neurons have functional significance in PTSD.

The molecular pathophysiology of depression and the new therapeutics

Major depressive disorder (MDD) is a highly prevalent and disabling disorder. Despite the many hypotheses proposed to understand the molecular pathophysiology of depression, it is still unclear. Current treatments for depression are inadequate for many individuals, because of limited effectiveness, delayed efficacy (usually two weeks), and side effects. Consequently, novel drugs with increased speed of action and effectiveness are required. Ketamine has shown to have rapid, reliable, and long-lasting antidepressant effects in treatment-resistant MDD patients and represent a breakthrough therapy for patients with MDD; however, concerns regarding its efficacy, potential misuse, and side effects remain. In this review, we aimed to summarize molecular mechanisms and pharmacological treatments for depression. We focused on the fast antidepressant treatment and clarified the safety, tolerability, and efficacy of ketamine and its metabolites for the MDD treatment, along with a review of the potential pharmacological mechanisms, research challenges, and future clinical prospects.

Deletion of ghrelin alters tryptophan metabolism and exacerbates experimental ulcerative colitis in aged mice

A major component of aging is chronic, low-grade inflammation, attributable in part by impaired gut barrier function. We previously reported that deletion of ghrelin, a peptidergic hormone released mainly from the gut, exacerbates experimental muscle atrophy in aged mice. In addition, ghrelin has been shown to ameliorate colitis in experimental models of inflammatory bowel disease (IBD), although the role of endogenous ghrelin in host-microbe interactions is less clear. Here, we showed that 22-month-old global ghrelin knockout (Ghrl^-/-) mice exhibited significantly increased depressive-like behaviors, while anxiety levels and working memory were similar to littermate wild-type (WT) mice. Furthermore, old Ghrl^-/- mice showed significantly increased intestinal permeability to fluorescein isothiocyanate (FITC)-dextran, significantly higher colonic interleukin (IL-1β) levels, and trends for higher colonic IL-6 and tumor necrosis factor-α (TNF-α) compared to WT mice. Interestingly, young Ghrl^-/- and WT mice showed comparable depressive-like behavior and gut permeability, suggesting age-dependent exacerbation in gut barrier dysfunction in Ghrl^-/- mice. While fecal short-chain fatty acids levels were comparable between old Ghrl^-/- and WT mice, serum metabolome revealed alterations in metabolic cascades including tryptophan metabolism. Specifically, tryptophan and its microbial derivatives indole-3-acetic acid and indole-3-lactic acid were significantly reduced in old Ghrl^-/-mice. Furthermore, in an experimental model of dextran sulfate sodium (DSS)-induced colitis, Ghrl^-/- mice showed exacerbated disease symptoms, and higher levels of chemoattractant and pro-inflammatory cytokines in the colon. Overall, these data demonstrated that ghrelin deficiency is associated with gut barrier dysfunction, alterations in microbially derived tryptophan metabolites, and increased susceptibility to colitis. These data suggested that endogenous ghrelin contributes to maintaining a healthy host-microbe environment, ultimately impacting on brain function.