International Union of Basic and Clinical Pharmacology CIV: The Neurobiology of Treatment-resistant Depression: From Antidepressant Classifications to Novel Pharmacological Targets

From Stress to Synapse: The Neuronal Atrophy Pathway to Mood Dysregulation

Mood disorders, including major depressive disorder and bipolar disorder, are among the most prevalent mental health conditions globally, yet their underlying mechanisms remain incompletely understood. This review critically examines the neuronal atrophy hypothesis, which posits that chronic stress and associated neurobiological changes lead to structural and functional deficits in critical brain regions, contributing to mood disorder pathogenesis. Key mechanisms explored include dysregulation of neurotrophic factors such as brain-derived neurotrophic factor (BDNF), elevated glucocorticoids from stress responses, neuroinflammation mediated by cytokines, and mitochondrial dysfunction disrupting neuronal energy metabolism. These processes collectively impair synaptic plasticity, exacerbate structural atrophy, and perpetuate mood dysregulation. Emerging evidence from neuroimaging, genetic, and epigenetic studies underscores the complexity of these interactions and highlights the role of environmental factors such as early-life stress and urbanization. Furthermore, therapeutic strategies targeting neuroplasticity, including novel pharmacological agents, lifestyle interventions, and anti-inflammatory treatments, are discussed as promising avenues for improving patient outcomes. Advancing our understanding of the neuronal atrophy hypothesis could lead to more effective, sustainable interventions for managing mood disorders and mitigating their global health burden.

Can dextromethorphan-bupropion reduce mental pain in depressed individuals? A generating hypothesis overview perspective

Globally, major depressive disorder, or MDD, is a leading cause of disability. It negatively impacts social interactions and significantly limits daily functioning, ultimately reducing life satisfaction. The prevalence rate is about twice as high in women as in males. It is believed that the genesis of major depressive disorder is complicated and includes biological, genetic, environmental, and psychological factors. Mental pain, although distinguishable, constitutes a crucial framework in major depressive disorder (MDD) as the pair may precipitate suicide risk. Mental pain, as conceptualized in Panksepp's emotional theory, is especially relevant when considering the key role of the opioid system, which can influence feelings tied to grief and separation. There has been a renewed interest in targeting the opioid system for antidepressant treatment in MDD and to soothe mental pain. Antidepressant drugs endowed with partial mu-opioid receptor (MOR) agonism and kappa-opioid receptor (KOR) antagonism might represent novel pharmacological tools to address unmet needs in MDD patients. The combination of dextromethorphan and bupropion is a well-tolerated, rapid-acting treatment option for adults affected by MDD. We hypothesized that dextromethorphan-bupropion could impact the reduction of mental pain in MDD patients by targeting the opioid system, as supported by Panksepp's theory. The combination of dextromethorphan with bupropion might deal with various aspects of mental pain, possibly improving treatment results.

Points regarding neuroscience-based nomenclature: evaluating its impact on psychiatric residency training

This study evaluates the impact of neuroscience-based nomenclature (NbN) training on psychiatric residents in Flanders, Belgium. Addressing Zemach et al.'s findings on NbN's potential, we investigated its application in clinical practice. We assessed changes in knowledge, prescribing habits, and communication skills through focus groups and a longitudinal survey. Our results indicated no statistically significant shifts post-training, highlighting the complexity of integrating NbN into clinical practice. These findings underscore the critical need for psychopharmacological nomenclature and psychopathology to evolve in tandem, ensuring that advancements in understanding mental disorders align with pharmacological education.

A Scoping Review of Eosinophilic Pneumonia and Antidepressants: An Association Not to Be Overlooked

Background: Eosinophilic pneumonias denote a rare condition, wherein infiltrating eosinophilic granulocytes accumulate within the lung parenchyma. Although eosinophilic pneumonias may be idiopathic, they are also associated with secondary causes. More than 110 medications have been linked to eosinophilic pneumonia, including several antidepressants. This review presents an analysis of case reports of eosinophilic pneumonia correlated to antidepressants. Objectives: The objectives of this study are to provide a contemporary overview of the literature delineating eosinophilic pneumonia as a potential sequela of antidepressant medication treatment, and to discuss possible pathogenetic mechanisms linking antidepressants to eosinophilic pneumonia. Methods and Data Selection: A literature search was performed in PubMed and Scopus databases from 1963 to October 2024. The search strategy used the terms "eosinophilic pneumonia AND antidepressants". Sources included in this review were screened for relevance, focusing on references discussing eosinophilic pneumonia associated with any class of antidepressants. Case reports meeting the diagnostic criteria for acute eosinophilic pneumonia (AEP) or chronic eosinophilic pneumonia (CEP) were included in the review. Clinical, epidemiological, laboratory, radiology and bronchoscopy data, implicated antidepressant and dosage, and therapeutic interventions were reported. Results: This study found that various types of antidepressants are associated with AEP and CEP. The clinical presentation ranges from mild symptoms to respiratory failure and intubation. Outcomes were favorable in most cases, with complete remission achieved after discontinuation of the causative drug and, in severe cases, a short course of corticosteroids. Conclusions: Although a rare cause, antidepressants may lead to eosinophilic pneumonia, and should be considered in the differential diagnosis of unexplained pulmonary infiltrates. Clinical suspicion must be aroused, as early recognition would prevent unnecessary work-up and navigation of the diagnosis.

Treatment-resistant depression: molecular mechanisms and management

Due to the heterogeneous nature of depression, the underlying etiological mechanisms greatly differ among individuals, and there are no known subtype-specific biomarkers to serve as precise targets for therapeutic efficacy. The extensive research efforts over the past decades have not yielded much success, and the currently used first-line conventional antidepressants are still ineffective for close to 66% of patients. Most clinicians use trial-and-error treatment approaches, which seem beneficial to only a fraction of patients, with some eventually developing treatment resistance. Here, we review evidence from both preclinical and clinical studies on the pathogenesis of depression and antidepressant treatment response. We also discuss the efficacy of the currently used pharmacological and non-pharmacological approaches, as well as the novel emerging therapies. The review reveals that the underlying mechanisms in the pathogenesis of depression and antidepressant response, are not specific, but rather involve an interplay between various neurotransmitter systems, inflammatory mediators, stress, HPA axis dysregulation, genetics, and other psycho-neurophysiological factors. None of the current depression hypotheses sufficiently accounts for the interactional mechanisms involved in both its etiology and treatment response, which could partly explain the limited success in discovering efficacious antidepressant treatment. Effective management of treatment-resistant depression (TRD) requires targeting several interactional mechanisms, using subtype-specific and/or personalized therapeutic modalities, which could, for example, include multi-target pharmacotherapies in augmentation with psychotherapy and/or other non-pharmacological approaches. Future research guided by interaction mechanisms hypotheses could provide more insights into potential etiologies of TRD, precision biomarker targets, and efficacious therapeutic modalities.

Function and mechanism of lysine crotonylation in health and disease

Lysine crotonylation is a newly identified posttranslational modification that is different from the widely studied lysine acetylation in structure and function. In the last dozen years, great progress has been made in lysine crotonylation-related studies, and lysine crotonylation is involved in reproduction, development and disease. In this review, we highlight the similarities and differences between lysine crotonylation and lysine acetylation. We also summarize the methods and tools for the detection and prediction of lysine crotonylation. At the same time, we outline the recent advances in understanding the mechanisms of enzymatic and metabolic regulation of lysine crotonylation, as well as the regulating factors that selectively recognize this modification. Particularly, we discussed how dynamic changes in crotonylation status maintain physiological health and result in the development of disease. This review not only points out the new functions of lysine crotonylation but also provides new insights and exciting opportunities for managing various diseases.

Major challenges in youth psychopathology: treatment-resistant depression. A narrative review

Major depressive disorder (MDD) represents a major health issue in adolescents and young adults, leading to high levels of disability and profoundly impacting overall functioning. The clinical presentation of MDD in this vulnerable age group may slightly differ from what can be observed in adult populations, and psychopharmacological strategies do not always lead to optimal response. Resistance to antidepressant treatment has a prevalence estimated around 40% in youths suffering from MDD and is associated with higher comorbidity rates and suicidality. Several factors, encompassing biological, environmental, and clinical features, may contribute to the emergence of treatment-resistant depression (TRD) in adolescents and young adults. Furthermore, TRD may underpin the presence of an unrecognized bipolar diathesis, increasing the overall complexity of the clinical picture and posing major differential diagnosis challenges in the clinical practice. After summarizing current evidence on epidemiological and clinical correlates of TRD in adolescents and young adults, the present review also provides an overview of possible treatment strategies, including novel fast-acting antidepressants. Despite these pharmacological agents are promising in this population, their usage is expected to rely on risk-benefit ratio and to be considered in the context of integrated models of care.

Sildenafil, alone and in combination with imipramine or escitalopram, display antidepressant-like effects in an adrenocorticotropic hormone-induced (ACTH) rodent model of treatment-resistant depression

BACKGROUND

Major depressive disorder (MDD) represents a challenge with high prevalence and limited effectiveness of existing treatments, particularly in cases of treatment-resistant depression (TRD). Innovative strategies and alternative drug targets are therefore necessary. Sildenafil, a selective phosphodiesterase type 5 (PDE5) inhibitor, is known to exert neuroplastic, anti-inflammatory, and antioxidant properties, and is a promising antidepressant drug candidate.

AIM

To investigate whether sildenafil monotherapy or in combination with a known antidepressant, can elicit antidepressant-like effects in an adrenocorticotropic hormone (ACTH)-induced rodent model of TRD.

METHODS

ACTH-naïve and ACTH-treated male Sprague-Dawley (SD) rats received various sub-acute drug treatments, followed by behavioural tests and biochemical analyses conversant with antidepressant actions.

RESULTS

Sub-chronic ACTH treatment induced significant depressive-like behaviour in rats, evidenced by increased immobility during the forced swim test (FST). Sub-acute sildenafil (10 mg/kg) (SIL-10) (but not SIL-3), and combinations of imipramine (15 mg/kg) (IMI-15) and sildenafil (3 mg/kg) (SIL-3) or escitalopram (15 mg/kg) (ESC-15) and SIL-3, exhibited significant antidepressant-like effects. ACTH treatment significantly elevated hippocampal levels of brain-derived neurotrophic factor (BDNF), serotonin, norepinephrine, kynurenic acid (KYNUA), quinolinic acid (QUINA), and glutathione. The various mono- and combined treatments significantly reversed some of these changes, whereas IMI-15 + SIL-10 significantly increased glutathione disulfide levels. ESC-15 + SIL-3 significantly reduced plasma corticosterone levels.

CONCLUSION

This study suggests that sildenafil shows promise as a treatment for TRD, either as a stand-alone therapy or in combination with a traditional antidepressant. The neurobiological mechanism underlying the antidepressant-like effects of the different sildenafil mono- and combination therapies reflects a multimodal action and cannot be explained in full by changes in the individually measured biomarker levels.

Repetitive Transcranial Magnetic Stimulation With and Without Text4Support for the Treatment of Resistant Depression: Protocol for a Patient-Centered Multicenter Randomized Controlled Pilot Trial

BACKGROUND

Treatment-resistant depression (TRD) is the inability of a patient with major depressive disorder (MDD) to accomplish or achieve remission after an adequate trial of antidepressant treatments. Several combinations and augmentation treatment strategies for TRD exist, including the use of repetitive transcranial magnetic stimulation (rTMS), and new therapeutic options are being introduced. Text4Support, a text message-based form of cognitive behavioral therapy that allows patients with MDD to receive daily supportive text messages for correcting or altering negative thought patterns through positive reinforcement, may be a useful augmentation treatment strategy for patients with TRD. It is however currently unknown if adding the Text4Support intervention will enhance the response of patients with TRD to rTMS treatment.

OBJECTIVE

This study aims to assess the initial comparative clinical effectiveness of rTMS with and without the Text4Support program as an innovative patient-centered intervention for the management of patients diagnosed with TRD.

METHODS

This study is a multicenter, prospective, parallel-design, 2-arm, rater-blinded randomized controlled pilot trial. The recruitment process is scheduled to last 12 months. It will involve active treatment for 6 weeks, observation, and a follow-up period of 6 months for participants in the study arms. In total, 200 participants diagnosed with TRD at rTMS care clinics in Edmonton, Alberta, and rTMS clinics in Halifax, Nova Scotia will be randomized to 1 of 2 treatment arms (rTMS sessions alone or rTMS sessions plus Text4Support intervention). Participants in each group will be made to complete evaluation measures at baseline, and 1, 3, and 6 months. The primary outcome measure will be the mean change in the scores of the Patient Health Questionnaire-9 (PHQ-9). The secondary outcome measures will involve the scores of the 7-item Generalized Anxiety Disorders Scale (GAD-7), Columbia-Suicide Severity Rating Scale (CSSRS), and World Health Organization-Five Well-Being Index (WHO-5). Patient data will be analyzed with descriptive statistics, repeated measures, and correlational analyses. Qualitative data will be analyzed using the thematic analysis framework.

RESULTS

The results of the study are expected to be available 18 months from the start of recruitment. We hypothesize that participants enrolled in the rTMS plus Text4Support intervention treatment arm of the study will achieve superior outcomes compared with the outcomes of participants enrolled in the rTMS alone arm.

CONCLUSIONS

The application of the combination of rTMS and Text4Support has not been investigated previously. Therefore, we hope that this study will provide a concrete base of data to evaluate the practical application and efficacy of using the novel combination of these 2 treatment modalities.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

PRR1-10.2196/46830.

Review on Surface-Modified Electrodes for the Enhanced Electrochemical Detection of Selective Serotonin Reuptake Inhibitors (SSRIs)

Selective serotonin re-uptake inhibitors (SSRIs) are one of the most commonly prescribed classes of antidepressants used for the treatment of moderate to severe depressive disorder, personality disorders and various phobias. This class of antidepressants was created with improved margins of safety. However, genetic polymorphism may be responsible for the high variability in patients' responses to treatment, ranging from failure to delayed therapeutic responses to severe adverse effects of treatment. It is crucial that the appropriate amount of SSRI drugs is administered to ensure the optimum therapeutic efficacy and intervention to minimise severe and toxic effects in patients, which may be the result of accidental and deliberate cases of poisoning. Determining SSRI concentration in human fluids and the environment with high sensitivity, specificity and reproducibility, and at a low cost and real-time monitoring, is imperative. Electrochemical sensors with advanced functional materials have drawn the attention of researchers as a result of these advantages over conventional techniques. This review article aims to present functional materials such as polymers, carbon nanomaterials, metal nanomaterials as well as composites for surface modification of electrodes for sensitive detection and quantification of SSRIs, including fluoxetine, citalopram, paroxetine, fluvoxamine and sertraline. Sensor fabrication, sensor/analyte interactions, design rationale and properties of functional material and the electrocatalytic effect of the modified electrode on SSRI detection are discussed.

Residual insomnia in major depressive disorder: a systematic review

Introduction

The ultimate goal in major depressive disorder (MDD) treatment is recovery. A proportion of MDD patients with formal remission experience persistent difficulties, which impair their daily functioning. Residual insomnia is one of the most common residual symptoms. Patients with residual insomnia experience relapse significantly earlier and have a poor prognosis. Little is known about possible ways of treatment and what subtype of insomnia is mostly reported.

Methods

A systematic literature review was carried out in PubMed and Web of Science to synthesize the current status of knowledge about effective treatment methods and insomnia subtypes in residual insomnia in MDD.

Results

A few non-pharmacological treatment methods e.g., Cognitive Behavioral Therapy for Insomnia (CBT-I), Mindfulness-Based Cognitive Therapy (MBCT), behavioral activation (BA) and pharmacological methods (gabapentin, clonazepam) have proven to mitigate residual insomnia. Cognitive Behavioral Therapy for Depression (CBT-D) ameliorates insomnia complaints to a limited extent. Mid-nocturnal insomnia is the most common residual insomnia subtype in MDD patients.

Conclusion

Residual insomnia is a very common complaint and most often appears as mid-nocturnal insomnia. Scarce data points out the benefits from pharmacotherapy, psychotherapy, and BA. More research is needed.

Effect of Ketamine on Sleep in Treatment-Resistant Depression: A Systematic Review

BACKGROUND

Depression is a debilitating disease with a high socioeconomic burden. Regular antidepressants usually require several weeks to ameliorate symptoms; however, numerous patients do not achieve remission. What is more, sleep disturbances are one of the most common residual symptoms. Ketamine is a novel antidepressant with rapid onset of action with a proven antisuicidal effect. Little is known about its impact on sleep-wake and circadian rhythm alterations. The aim of this systematic review is to research the impact ketamine has on sleep disturbances in depression.

METHODS

PubMed, Web of Science, and APA PsycINFO were searched for relevant studies on ketamine's impact on sleep disturbances in depression. Preferred Reporting Items for Systematic Reviews and Meta-Analyses PRISMA2020 methodology was applied. The systematic review protocol was registered in the PROSPERO Registry (CRD42023387897).

RESULTS

Five studies were included in this review. Two studies reported significant improvement in sleep measured by MADRS (Montgomery-Åsberg Depression Rating Scale) and QIDS-SR16 (Quick Inventory of Depressive Symptomatology Self-Report (16-item)) scales after intravenous ketamine and intranasal esketamine administration. One case report showed mitigation of symptoms in PSQI (Pittsburgh Sleep Quality Index) and ISI (Insomnia Severity Index) during 3-month treatment with esketamine. In two studies, sleep was objectively measured by nocturnal EEG (electroencephalography) and showed a decrease in nocturnal wakefulness accompanied by an increase in slow wave (SWS) and rapid eye movement (REM) sleep.

CONCLUSION

Ketamine reduces the severity of sleep insomnia in depression. Robust data are lacking. More research is needed.

Antidepressant discontinuation syndrome: A state-of-the-art clinical review

Antidepressant drugs are prescribed to patients with depressive, anxiety disorders, and other conditions. Evidence about antidepressant discontinuation syndrome (ADS) and related outcomes is sparse, although potentially burdensome in some patients. The present state-of-the-art review aims to appraise the most current evidence about ADS critically. ADS has been documented for most antidepressant drugs, although most literature focuses on selective serotonin reuptake inhibitors prescribed for depression. While down-titration cannot exclude the chance of ADS, it is nonetheless warranted in the clinical setting, especially for short half-life and sedative compounds such as paroxetine. Integrative management with concurrent pharmacotherapy and psychotherapy may minimize the eventual unpleasant effects arising within the discontinuation process. In addition, patient-tailored interventions and education should be part of the discontinuation strategy. Future research must rely on broadly accepted definitions for ADS and related phenomena such as antidepressant withdrawal and shed further light on the underpinning neurobiology. Discriminating between ADS-related phenomena and relapse of depression is likewise warranted, along with a neuroscience-based nomenclature instead of a class one.

Prenatal stress induces a depressive-like phenotype in adolescent rats: The key role of TGF-β1 pathway

Stressful experiences early in life, especially in the prenatal period, can increase the risk to develop depression during adolescence. However, there may be important qualitative and quantitative differences in outcome of prenatal stress (PNS), where some individuals exposed to PNS are vulnerable and develop a depressive-like phenotype, while others appear to be resilient. PNS exposure, a well-established rat model of early life stress, is known to increase vulnerability to depression and a recent study demonstrated a strong interaction between transforming growth factor-β1 (TGF-β1) gene and PNS in the pathogenesis of depression. Moreover, it is well-known that the exposure to early life stress experiences induces brain oxidative damage by increasing nitric oxide levels and decreasing antioxidant factors. In the present work, we examined the role of TGF-β1 pathway in an animal model of adolescent depression induced by PNS obtained by exposing pregnant females to a stressful condition during the last week of gestation. We performed behavioral tests to identify vulnerable or resilient subjects in the obtained litters (postnatal day, PND > 35) and we carried out molecular analyses on hippocampus, a brain area with a key role in the pathogenesis of depression. We found that female, but not male, PNS adolescent rats exhibited a depressive-like behavior in forced swim test (FST), whereas both male and female PNS rats showed a deficit of recognition memory as assessed by novel object recognition test (NOR). Interestingly, we found an increased expression of type 2 TGF-β1 receptor (TGFβ-R2) in the hippocampus of both male and female resilient PNS rats, with higher plasma TGF-β1 levels in male, but not in female, PNS rats. Furthermore, PNS induced the activation of oxidative stress pathways by increasing inducible nitric oxide synthase (iNOS), NADPH oxidase 1 (NOX1) and NOX2 levels in the hippocampus of both male and female PNS adolescent rats. Our data suggest that high levels of TGF-β1 and its receptor TGFβ-R2 can significantly increase the resiliency of adolescent rats to PNS, suggesting that TGF-β1 pathway might represent a novel pharmacological target to prevent adolescent depression in rats.

Possible Use of Minocycline in Adjunction to Intranasal Esketamine for the Management of Difficult to Treat Depression following Extensive Pharmacogenomic Testing: Two Case Reports

The advent of intra-nasal esketamine (ESK), one of the first so called fast-acting antidepressant, promises to revolutionize the management of treatment resistant depression (TRD). This NMDA receptor antagonist has proven to be rapidly effective in the short- and medium-term course of the illness, revealing its potential in targeting response in TRD. Although many TRD ESK responders are able to achieve remission, a considerable portion of them undergo a metamorphosis of their depression into different clinical presentations, characterized by instable responses and high recurrence rates that can be considered closer to the concept of Difficult to Treat Depression (DTD) than to TRD. The management of these DTD patients usually requires a further complex multidisciplinary approach and can benefit from the valuable contribution of new personalized medicine tools such as therapeutic drug monitoring and pharmacogenetics. Despite this, these patients usually come with long and complex previous treatments history and, often, advanced and sophisticated ongoing pharmacological schemes that can make the finding of new alternative options to face the current recurrences extremely challenging. In this paper, we describe two DTD patients—already receiving intranasal ESK but showing an instable course—who were clinically stabilized by the association with minocycline, a semisynthetic second-generation tetracycline with known and promising antidepressant properties.

Epidemiology of treatment resistant depression among major depressive disorder patients in Israel

INTRODUCTION

Major depressive disorder (MDD) is one of the most common mental disorders worldwide, estimated to affect 10-15% of the population per year. Treatment resistant depression (TRD) is estimated to affect a third of these patients who show difficulties in social and occupational function, decline of physical health, suicidal thoughts and increased health care utilization. We describe the prevalence of MDD, TRD and associated healthcare resource utilization in Maccabi Healthcare Services (MHS), a 2.5 million-member state-mandated health service in Israel.

METHODS

All MHS members with an MDD diagnosis were identified within the years 2017-2018 and prevalence assessed by age, sex and TRD. To assess the incidence of MDD, members aged 18-65 years at the start of any MDD episode were identified between 1^st January 2016 and 31^st May 2018 with at least one systemic first-line antidepressant treatment within three months before or after the initial episode. Treatment patterns, time on first-line treatment, and healthcare resource utilization were compared by TRD.

RESULTS

A total of 4960 eligible MDD patients were identified (median age = 51 years, 65% female), representing a period prevalence of 0.218%, and of those, a high proportion of patients received drug treatment (92%). Among incident MDD cases (n = 2553), 24.4% had TRD. Factors associated with TRD included increasing age and personality disorder. Median time on treatment was 3.7 months (longer for those without TRD than those with) and 81.9% of patients purchased more than one month's supply of therapy. In the year after index, patients with TRD had a significant increased number of visits to primary care physicians, psychiatrists, emergency room visits, general hospitalizations, and psychiatric hospitalizations.

CONCLUSION

Our study shows that prevalence of MDD in Israel is low compared to other countries, however once diagnosed, patients' are likely to receive drug treatment. Among patients diagnosed with MDD, the proportion of TRD is similar to other countries, increases with age and is associated with increased healthcare utilization, therefore should be a focus of continued research for finding effective long term treatment options.

Genetic and epigenetic factors associated with depression: An updated overview

Depression is a complex psychiatric disturbance involving many environmental, genetic, and epigenetic factors. Until now, genetic, and non-genetic studies are still on the way to understanding the complex mechanism of this disease, and there are still many questions that have not yet been answered. Depression includes a large spectrum of heterogeneous symptoms correlated to the deficit of a range of psychological, cognitive, and emotional processes, and it affects various age groups. It is classified into several types according to the severity of symptoms, time of occurrence, and time. Following the World Health Organization (WHO), depression attacks near 350 million persons globally. Several factors overlap in causing depression, including genetic and epigenetic factors, environmental conditions, various stresses, lack of some nutrients to which people are exposed, and excessive stress and abuse in childhood. This study included conducting surveys on depression and new treatment trends based on epigenetic factors associated with the occurrence of the disease. Epigenetic factors provide a completely novel dimension to therapeutic approaches as most diseases are not monogenic, and it is likely that the environment has a significant contribution. Epigenetic inheritance is included in many mental and psychiatric disorders such as depression. In general, epigenetic modifications could be summarized in 3 major points: DNA methylation, histone modification, and non-mediated regulation of RNA (ncRNA). This study also describes some genes associated with one of the depressive disorders using bioinformatics tools and gene bank and had the genes: SLC6A4, COMT, TPH2, FKBP5, MDD1, HTR2A, and MDD2. As in this study, the awareness of Saudi society about depression and its genetic and non-genetic causes was estimated. The results showed that an encouraging percentage of more than half of the research sample possessed correct information about this disorder.

Vitamin D Deficiency in Patients Receiving Antidepressant Medications

Тhis study aimed at exploring vitamin D levels in treated depressive patients in comparison to healthy individuals. The cross-sectional study included 20 ambulatory and inpatients with depressive episodes taking antidepressants and 30 healthy individuals. The serum concentration of 25(OH)D from collected blood samples was determined using biochemical analyzers. Serum 25(OH)D levels (ng/mL) in patients were significantly lower (the mean 13.1, standard deviation 7.3, median 11.4, minimal 3.8, maximal 35.9) then in control subjects (19.4, 9.1, 15.8, 7.6, 43.6) (p=0.004). Additional targeted research is needed because some lifestyle and dietary habits which are known to influence vitamin D status may confound observed effects.

New Insights Into the Pivotal Role of CREB-Regulated Transcription Coactivator 1 in Depression and Comorbid Obesity

Depression and obesity are major public health concerns, and there is mounting evidence that they share etiopathophysiological mechanisms. The neurobiological pathways involved in both mood and energy balance regulation are complex, multifactorial and still incompletely understood. As a coactivator of the pleiotropic transcription factor cAMP response element-binding protein (CREB), CREB-regulated transcription coactivator 1 (CRTC1) has recently emerged as a novel regulator of neuronal plasticity and brain functions, while CRTC1 dysfunction has been associated with neurodegenerative and psychiatric diseases. This review focuses on recent evidence emphasizing the critical role of CRTC1 in the neurobiology of depression and comorbid obesity. We discuss the role of CRTC1 downregulation in mediating chronic stress-induced depressive-like behaviors, and antidepressant response in the light of the previously characterized Crtc1 knockout mouse model of depression. The putative role of CRTC1 in the alteration of brain energy homeostasis observed in depression is also discussed. Finally, we highlight rodent and human studies supporting the critical involvement of CRTC1 in depression-associated obesity.

Treatment-Resistant Depression in Poland—Epidemiology and Treatment

(1) Background: Major depressive disorder (MDD) is one of the most prevalent psychiatric disorders worldwide. Although several antidepressant drugs have been developed, up to 30% of patients fail to achieve remission, and acute remission rates decrease with the number of treatment steps required. The aim of the current project was to estimate and describe the population of treatment-resistant depression (TRD) patients in outpatient clinics in Poland. (2) Methods: The project involved a representative sample of psychiatrists working in outpatient clinics, chosen through a process of quota random sampling. The doctors completed two questionnaires on a consecutive series of patients with MDD, which captured the patients’ demographics, comorbidities, and medical histories. TRD was defined as no improvement seen after a minimum of two different antidepressant drug therapies applied in sufficient doses for a minimum of 4 weeks each. The data were weighted and extrapolated to the population of TRD outpatients in Poland. (3) Results: A total of 76 psychiatrists described 1781 MDD patients, out of which 396 fulfilled the criteria of TRD. The TRD patients constituted 25.2% of all MDD patients, which led to the number of TRD outpatients in Poland being estimated at 34,800. The demographics, comorbidities, medical histories, and histories of treatment of Polish TRD patients were described. In our sample of the TRD population (mean age: 45.6 ± 13.1 years; female: 64%), the patients had experienced 2.1 ± 1.6 depressive episodes (including the current one), and the mean duration of the current episode was 4.8 ± 4.4 months. In terms of treatment strategies, most patients (around 70%) received monotherapy during the first three therapies, while combination antidepressant drugs (ADs) were applied more often from the fourth line of treatment. The use of additional medications and augmentation was reported in only up to one third of the TRD patients. During all of the treatment steps, patients most often received a selective serotonin reuptake inhibitor (SSRI) and a serotonin norepinephrine reuptake inhibitor (SNRI). (4) Conclusions: TRD is a serious problem, affecting approximately one fourth of all depressive patients and nearly 35,000 Poles.

Antioxidant Activity of Fluoxetine and Vortioxetine in a Non-Transgenic Animal Model of Alzheimer's Disease

Depression is a risk factor for the development of Alzheimer’s disease (AD). A neurobiological and clinical continuum exists between AD and depression, with neuroinflammation and oxidative stress being involved in both diseases. Second-generation antidepressants, in particular selective serotonin reuptake inhibitors (SSRIs), are currently investigated as neuroprotective drugs in AD. By employing a non-transgenic AD model, obtained by intracerebroventricular (i.c.v.) injection of amyloid-β (Aβ) oligomers in 2-month-old C57BL/6 mice, we recently demonstrated that the SSRI fluoxetine (FLX) and the multimodal antidepressant vortioxetine (VTX) reversed the depressive-like phenotype and memory deficits induced by Aβ oligomers rescuing the levels of transforming growth factor-β1 (TGF-β1). Aim of our study was to test FLX and VTX for their ability to prevent oxidative stress in the hippocampus of Aβ-injected mice, a brain area strongly affected in both depression and AD. The long-term intraperitoneal (i.p.) administration of FLX (10 mg/kg) or VTX (5 and 10 mg/kg) for 24 days, starting 7 days before Aβ injection, was able to prevent the over-expression of inducible nitric oxide synthase (iNOS) and NADPH oxidase 2 (Nox2) induced by Aβ oligomers. Antidepressant pre-treatment was also able to rescue the mRNA expression of glutathione peroxidase 1 (Gpx1) antioxidant enzyme. FLX and VTX also prevented Aβ-induced neurodegeneration in mixed neuronal cultures treated with Aβ oligomers. Our data represent the first evidence that the long-term treatment with the antidepressants FLX or VTX can prevent the oxidative stress phenomena related to the cognitive deficits and depressive-like phenotype observed in a non-transgenic animal model of AD.

Pregabalin augmentation of antidepressants in major depression - results from a European multicenter study

BACKGROUND

We aimed to investigate the prescription pattern of pregabalin augmentation of antidepressants in major depressive disorder (MDD) and to explore variables associated with add-on pregabalin treatment.

METHODS

1410 MDD patients participated in this naturalistic European multicenter study with retrospective assessment of treatment response. Analyses of covariance, chi-squared tests, and binary logistic regressions were accomplished to determine differences in socio-demographic and clinical characteristics between MDD patients with and without pregabalin augmentation.

RESULTS

Add-on pregabalin was established in 102 (7.23%) MDD patients. Compared to those without receiving pregabalin, pregabalin-treated patients were characterized by a significantly higher likelihood for older age (mean: 54.74 ± 13.08 vs 49.93 ± 14.13 years), unemployment (78.43% vs 51.23%), melancholic features (83.33% vs 58.94%), inpatient treatment (72.55% vs 31.65%), previous psychiatric hospitalizations (13.52 ± 24.82 vs 4.96 ± 19.93 weeks), any somatic comorbidity (68.63% vs 44.57%), comorbid hypertension (37.25% vs 17.51%), more severe depressive symptom severity at the onset of the current episode (mean MADRS: 37.55 ± 9.00 vs 33.79 ± 7.52), receiving augmentation/combination treatment strategies in general (mean number of psychotropic drugs: 3.64 ± 0.92 vs 2.07 ± 1.17), and with antidepressants (50.00% vs 27.91%) and antipsychotics (46.08% vs 24.08%) in particular.

LIMITATIONS

Due to its observational cross-sectional study design, our patient sample might not be fully representative for MDD patients in primary care settings.

CONCLUSIONS

Our findings suggest that add-on pregabalin is particularly administered in more severe/difficult-to-treat MDD conditions, whereas no association between the prescription of adjunctive pregabalin and comorbid anxiety symptoms could be determined.

Novel drug developmental strategies for treatment-resistant depression

Major depressive disorder is a leading cause of disability worldwide. Because conventional therapies are ineffective in many patients, novel strategies are needed to overcome treatment‐resistant depression (TRD). Limiting factors of successful drug development in the last decades were the lack of (1) knowledge of pathophysiology, (2) translational animal models and (3) objective diagnostic biomarkers. Here, we review novel drug targets and drug candidates currently investigated in Phase I–III clinical trials. The most promising approaches are inhibition of glutamatergic neurotransmission by NMDA and mGlu₅ receptor antagonists, modulation of the opioidergic system by κ receptor antagonists, and hallucinogenic tryptamine derivates. The only registered drug for TRD is the NMDA receptor antagonist, S‐ketamine, but add‐on therapies with second‐generation antipsychotics, certain nutritive, anti‐inflammatory and neuroprotective agents seem to be effective. Currently, there is an intense research focus on large‐scale, high‐throughput omics and neuroimaging studies. These results might provide new insights into molecular mechanisms and potential novel therapeutic strategies.

Melancholic features in major depression - a European multicenter study

There is still a debate, if melancholic symptoms can be seen rather as a more severe subtype of major depressive disorder (MDD) or as a separate diagnostic entity. The present European multicenter study comprising altogether 1410 MDD in- and outpatients sought to investigate the influence of the presence of melancholic features in MDD patients. Analyses of covariance, chi-squared tests, and binary logistic regression analyses were accomplished to determine differences in socio-demographic and clinical variables between MDD patients with and without melancholia. We found a prevalence rate of 60.71% for melancholic features in MDD. Compared to non-melancholic MDD patients, they were characterized by a significantly higher likelihood for higher weight, unemployment, psychotic features, suicide risk, inpatient treatment, severe depressive symptoms, receiving add-on medication strategies in general, and adjunctive treatment with antidepressants, antipsychotics, benzodiazepine (BZD)/BZD-like drugs, low-potency antipsychotics, and pregabalin in particular. With regard to the antidepressant pharmacotherapy, we found a less frequent prescription of selective serotonin reuptake inhibitors (SSRIs) in melancholic MDD. No significant between-group differences were found for treatment response, non-response, and resistance. In summary, we explored primarily variables to be associated with melancholia which can be regarded as parameters for the presence of severe/difficult-to treat MDD conditions. Even if there is no evidence to realize any specific treatment strategy in melancholic MDD patients, their prescribed medication strategies were different from those for patients without melancholia.

Experimental Therapeutics in Treatment-Resistant Major Depressive Disorder

Treatment-Resistant Depression (TRD) patients remain a challenging sub-division of patients with Major Depressive Disorder (MDD) in day to day clinical practice. As with any diagnostic condition, comprehensive evaluation, exclusion of other psychiatric conditions, assessment of co-morbid medical and psychiatric illnesses and psychosocial stressors are the keys to appropriate diagnosis and subsequent management. There are various management options available for the treatment of MDD, however, about 30% of the patients fail to achieve full remission of symptoms despite multiple trials and belong to this sub-category of MDD. This article brings forth discussion of other non-conventional medication and non-medication treatment alternatives that merit exploration of their efficacy in TRD. Many of the proposed novel medications and other treatment modalities such as Deep Brain Stimulation, exercise, yoga are already used for other medical and psychiatric disorders and have some evidence suggesting their potential benefits in TRD in conjunction with conventional medications or even as monotherapy. Nevertheless, more research is needed in this direction to establish effectiveness.

New agents and perspectives in the pharmacological treatment of major depressive disorder

Despite the important advances in the understanding of the pathophysiology of MDD, a large proportion of depressed patients do not respond well to currently available pharmacological agents. The present review focuses on new targets and future directions in the pharmacological treatment of MDD. Novel agents and their efficacy in the treatment of depression are discussed, with a focus on the respectively target pathophysiological pathways and the level of available evidence. Although it is expected that classic antidepressants will remain the cornerstone of MDD treatment, at least for the near future, a large number of novel compounds is currently under investigation as for their efficacy in the treatment of MDD, many of which with promising results.

Drug repositioning for treatment-resistant depression: Hypotheses from a pharmacogenomic study

About 20-30% of patients with major depressive disorder (MDD) develop treatment-resistant depression (TRD) and finding new effective treatments for TRD has been a challenge. This study aimed to identify new possible pharmacological options for TRD. Genes in pathways included in predictive models of TRD in a previous whole exome sequence study were compared with those coding for targets of drugs in any phase of development, nutraceuticals, proteins and peptides from Drug repurposing Hub, Drug-Gene Interaction database and DrugBank database. We tested if known gene targets were enriched in TRD-associated genes by a hypergeometric test. Compounds enriched in TRD-associated genes after false-discovery rate (FDR) correction were annotated and compared with those showing enrichment in genes associated with MDD in the last Psychiatric Genomics Consortium genome-wide association study. Among a total of 15,475 compounds, 542 were enriched in TRD-associated genes (FDR p < .05). Significant results included drugs which are currently used in TRD (e.g. lithium and ketamine), confirming the rationale of this approach. Interesting molecules included modulators of inflammation, renin-angiotensin system, proliferator-activated receptor agonists, glycogen synthase kinase 3 beta inhibitors and the rho associated kinase inhibitor fasudil. Nutraceuticals, mostly antioxidant polyphenols, were also identified. Drugs showing enrichment for TRD-associated genes had a higher probability of enrichment for MDD-associated genes compared to those having no TRD-genes enrichment (p = 6.21e-55). This study suggested new potential treatments for TRD using a in silico approach. These analyses are exploratory only but can contribute to the identification of drugs to study in future clinical trials.

Lycium barbarum polysaccharide-glycoprotein preventative treatment ameliorates aversive

Previous studies have shown that Lycium barbarum polysaccharide, the main active component of Lycium barbarum, exhibits anti-inflammatory and antioxidant effects in treating neurological diseases. However, the therapeutic action of Lycium barbarum polysaccharide on depression has not been studied. In this investigation, we established mouse models of depression using aversive stimuli including exposure to fox urine, air puff and foot shock and physical restraint. Concurrently, we administered 5 mg/kg per day Lycium barbarum polysaccharide-glycoprotein to each mouse intragastrically for the 28 days. Our results showed that long-term exposure to aversive stimuli significantly enhanced depressive-like behavior evaluated by the sucrose preference test and the forced swimming test and increased anxiety-like behaviors evaluated using the open field test. In addition, aversive stimuli-induced depressed mice exhibited aberrant neuronal activity in the lateral habenula. Importantly, concurrent Lycium barbarum polysaccharide-glycoprotein treatment significantly reduced these changes. These findings suggest that Lycium barbarum polysaccharide-glycoprotein is a potential preventative intervention for depression and may act by preventing aberrant neuronal activity and microglial activation in the lateral habenula. The study was approved by the Jinan University Institutional Animal Care and Use Committee (approval No. 20170301003) on March 1, 2017.

Post-weaning Social Isolated Flinders Sensitive Line Rats Display Bio-Behavioural Manifestations Resistant to Fluoxetine: A Model of Treatment-Resistant Depression

Treatment-resistant depression (TRD) complicates the management of major depression (MD). The underlying biology of TRD involves interplay between genetic propensity and chronic and/or early life adversity. By combining a genetic animal model of MD and post-weaning social isolation rearing (SIR), we sought to produce an animal that displays more severe depressive- and social anxiety-like manifestations resistant to standard antidepressant treatment. Flinders Sensitive Line (FSL) pups were social or isolation reared from weaning [postnatal day (PND) 21], receiving fluoxetine (FLX) from PND 63 (10 mg/kg × 14 days), and compared to Sprague Dawley (SD) controls. Depressive-, anxiety-like, and social behaviour were assessed from PND 72 in the forced swim test (FST) and social interaction test (SIT). Post-mortem cortico-hippocampal norepinephrine (NE), serotonin (5-HT), and dopamine (DA), as well as plasma interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-α), corticosterone (CORT), and dopamine-beta-hydroxylase (DBH) levels were assayed. FSL rats displayed significant cortico-hippocampal monoamine disturbances, and depressive- and social anxiety-like behaviour, the latter two reversed by FLX. SIR-exposed FSL rats exhibited significant immobility in the FST and social impairment which were, respectively, worsened by or resistant to FLX. In SIR-exposed FSL rats, FLX significantly raised depleted NE and 5-HT, significantly decreased DBH and caused a large effect size increase in DA and decrease in CORT and TNF-α. Concluding, SIR-exposed FSL rats display depressive- and social anxiety-like symptoms that are resistant to, or worsened by, FLX, with reduced plasma DBH and suppressed cortico-hippocampal 5-HT, NE and DA, all variably altered by FLX. Exposure of a genetic animal model of MD to post-weaning SIR results in a more intractable depressive-like phenotype as well as changes in TRD-related biomarkers, that are resistant to traditional antidepressant treatment. Given the relative absence of validated animal models of TRD, these findings are especially promising and warrant study, especially further predictive validation.

Protective effects of Colomast®, A New Formulation of Adelmidrol and Sodium Hyaluronate, in A Mouse Model of Acute Restraint Stress

Stress is generally defined as a homeostatic disruption from actual or implied threats and alters the homeostatic balance of different body organs, such as gastrointestinal function and the hypothalamic-pituitary-adrenal axis (HPA), inducing the release of glucocorticoid hormones. Stress is also known to be a risk factor for the development of depression and anxiety. However, until today there are no suitable therapies for treating of stress. The aim of this study was to explore the protective effect of Colomast®, a new preparation containing Adelmidrol, an enhancer of physiological of palmitoylethanolamide (PEA), and sodium hyaluronate in an animal model of immobilization stress. Acute restraint stress (ARS) was induced in mice by fixation for 2 h of the four extremities with an adhesive tape and Colomast® (20 mg/kg) was administered by oral gavage 30 min before the immobilization. Colomast® pre-treatment was able to decrease histopathological changes in the gastrointestinal tract, cytokines expression, neutrophil infiltration, mast cell activation, oxidative stress, as well as modulate nuclear factor NF-kB and apoptosis pathways after ARS induction. Moreover, Colomast® was able to restore tight junction in both ileum and hippocampus and cortex. Additionally, we demonstrated that Colomast® ameliorated depression and anxiety-related behaviours, and modulate inflammatory and apoptosis pathways also in brain after ARS induction. In conclusion, our results suggest Colomast® to be a potential approach to ARS.

Rislenemdaz treatment in the lateral habenula improves despair-like behavior in mice

The specific GluN2B antagonist rislenemdaz (Ris; a.k.a. MK-0657 and CERC-301) is in phase II clinical trial as an antidepressive drug, but the working mechanism for its antidepressant effects is not clearly understood. Given the important role of the lateral habenula (LHb) in the pathogenesis of depression and the fact that GluN2B-containing N-methyl-D-aspartate receptors and brain-derived neurotrophic factor (BDNF) are expressed in the LHb, we conducted a study to examine whether the LHb mediates Ris' antidepressant effects in a chronic restraint stress (CRS)-induced depressive-like mouse model. In this study, Ris was administered systemically or locally into the LHb. Short hairpin RNAs were used to knockdown BDNF in the LHb. Depressive-like behaviors were assessed with the open field test, forced swimming test, tail suspension test, and sucrose preference test. Expression of GluN2B, BDNF, and c-Fos in the LHb were analyzed with western blotting and immunohistochemistry under condition with Ris administered systemically or with BDNF knockdown in the LHb. We found that both systemic and intra-LHb administration of Ris alleviated CRS-induced despair-like behavior and that systemic Ris reduced LHb expression of GluN2B, BDNF, and c-Fos (a neuronal activity marker). Specific knockdown of BDNF in the LHb prevented CRS-induced despair-like behavior, while preventing CRS-induced increases in BDNF and c-Fos expression in the LHb. Together these results suggest that Ris may exert its antidepressant effects through affecting the LHb such as downregulating BDNF expression in the LHb.

Could ketamine be the answer to treating treatment-resistant major depressive disorder?

Major depressive disorder (MDD) is a common, serious, debilitating condition affecting 350 million people worldwide, which remains to be unsatisfactorily treated with 53% of patients still complaining of symptoms after completing their courses with the correct dosage. Ketamine, which was approved by the Food and Drug Administration in 2019, is a potential treatment option for those recalcitrant cases. The mechanism of ketamine is not fully understood, but as type it is classified as an N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, and can be given intravenously, intranasally and orally. It is used to treat treatment-resistant depression, depression associated with suicidal ideation, mood and anxiety disorders and depressions associated with either type of bipolar disorder. Although ketamine is considered relatively safe, several side effects have been reported with the major ones being psychiatric in the form of worsening mood, anxiety and agitation; psychotomimetic in the form of dissociation, perceptual disturbance and abnormal sensations; cardiovascular in the form of increased blood pressure and increased heart rate; and neurological in the form of headache and dizziness. Ketamine is still not approved worldwide for usage in patients with treatment-resistant MDD, but if it is approved sometime in the future with relatively fewer side effects, it is expected to significantly save millions of dollars spent yearly on patients with treatment-resistant depression and that will lift this major burden off the shoulders of healthcare professionals. This study was designed to measure the effects of ketamine, an NMDA receptor antagonist, on patients with treatment-resistant MDD and to analyse the concept that makes it different and relatively safer than other major antidepressants like selective serotonin reuptake inhibitors, monoamine oxidase inhibitors and TCAs (tricyclic antidepressants).

Inflammation as the Common Biological Link Between Depression and Cardiovascular Diseases: Can Carnosine Exert a Protective Role?

Several epidemiological studies have clearly shown the high co-morbidity between depression and Cardiovascular Diseases (CVD). Different studies have been conducted to identify the common pathophysiological events of these diseases such as the overactivation of the hypothalamic- pituitary-adrenal axis and, most importantly, the dysregulation of immune system which causes a chronic pro-inflammatory status. The biological link between depression, inflammation, and CVD can be related to high levels of pro-inflammatory cytokines, such as IL-1β, TNF-α, and IL-6, released by macrophages which play a central role in the pathophysiology of both depression and CVD. Pro-inflammatory cytokines interfere with many of the pathophysiological mechanisms relevant to depression by upregulating the rate-limiting enzymes in the metabolic pathway of tryptophan and altering serotonin metabolism. These cytokines also increase the risk to develop CVD, because activation of macrophages under this pro-inflammatory status is closely associated with endothelial dysfunction and oxidative stress, a preamble to atherosclerosis and atherothrombosis. Carnosine (β-alanyl-L-histidine) is an endogenous dipeptide which exerts a strong antiinflammatory activity on macrophages by suppressing reactive species and pro-inflammatory cytokines production and altering pro-inflammatory/anti-inflammatory macrophage polarization. This dipeptide exhibits antioxidant properties scavenging reactive species and preventing oxidative stress-induced pathologies such as CVD. In the present review we will discuss the role of oxidative stress and chronic inflammation as common pathophysiological events both in depression and CVD and the preclinical and clinical evidence on the protective effect of carnosine in both diseases as well as the therapeutic potential of this dipeptide in depressed patients with a high co-morbidity of cardiovascular diseases.

Is cognitive dysfunction involved in difficult-to-treat depression? Characterizing resistance from a cognitive perspective

BACKGROUND

This study aimed to identify clinical and cognitive factors associated with increased risk for difficult-to-treat depression (DTD) or treatment-resistant depression (TRD).

METHODS

A total of 229 adult outpatients with major depression were recruited from the mental health unit at a public hospital. Participants were subdivided into resistant and nonresistant groups according to their Maudsley Staging Model score. Sociodemographic, clinical, and cognitive (objective and subjective measures) variables were compared between groups, and a logistic regression model was used to identify the factors most associated with TRD risk.

RESULTS

TRD group patients present higher verbal memory impairment than the nonresistant group irrespective of pharmacological treatment or depressive symptom severity. Logistic regression analysis showed that low verbal memory scores (odds ratio [OR]: 2.02; 95% confidence interval [CI]: 1.38-2.95) together with high depressive symptom severity (OR: 1.29; CI95%: 1.01-1.65) were associated with TRD risk.

CONCLUSIONS

Our findings align with neuroprogression models of depression, in which more severe patients, defined by greater verbal memory impairment and depressive symptoms, develop a more resistant profile as a result of increasingly detrimental neuronal changes. Moreover, our results support a more comprehensive approach in the evaluation and treatment of DTD in order to improve illness course. Longitudinal studies are warranted to confirm the predictive value of verbal memory and depression severity in the development of TRD.

Antidepressant Drugs and Physical Activity: A Possible Synergism in the Treatment of Major Depression?

Major depressive disorder (MDD) is a severe mental illness that affects 5–20% of the general population. Current antidepressant drugs exert only a partial clinical efficacy because approximately 30% of depressed patients failed to respond to these drugs and antidepressants produce remission only in 30% of patients. This can be explained by the fact that the complex pathophysiology of depression has not been completely elucidated, and treatments have been mainly developed following the “monoaminergic hypothesis” of depression without considering the key role of other factors involved in the pathogenesis of MDD, such as the role of chronic stress and neuroinflammation. Chronic stress acts as a risk factor for the development of MDD through the impairment of neurotrophins signaling such as brain-derived neurotrophic factor (BDNF) and transforming-growth-factor-β1 (TGF-β1). Stress-induced depressive pathology contributes to altered BDNF level and function in MDD patients and, thereby, an impairment of neuroplasticity at the regional and circuit level. Recent studies demonstrate that aerobic exercise strongly increases BDNF production and it may contribute as a non-pharmacological strategy to improve the treatment of cognitive and affective symptoms in MDD. Here we will provide a general overview on the possible synergism between physical activity and antidepressants in MDD. Physical activity can synergize with antidepressant treatment by rescuing neurotrophins signaling in MDD patients, promoting neuronal health and recovery of function in MDD-related circuits, finally enhancing pharmacotherapeutic response. This synergism might be particularly relevant in elderly patients with late-life depression, a clinical subgroup with an increased risk to develop dementia.

Vagus nerve stimulation and Neurotrophins: a biological psychiatric perspective

Since 2004, vagus nerve stimulation (VNS) has been used in treatment-resistant or treatment-intolerant depressive episodes. Today, VNS is suggested as possible therapy for a larger spectrum of psychiatric disorders, including schizophrenia, obsessive compulsive disorders, and panic disorders. Despite a large body of literature supports the application of VNS in patients' treatment, the exact mechanism of action of VNS remains not fully understood. In the present study, the major knowledges on the brain areas and neuronal pathways regulating neuroimmune and autonomic response subserving VNS effects are reviewed. Furthermore, the involvement of the neurotrophins (NTs) Nerve Growth Factor (NGF) and Brain Derived Neurotrophic Factor (BDNF) in vagus nerve (VN) physiology and stimulation is revised. The data on brain NGF/BDNF synthesis and in turn on the activity-dependent plasticity, connectivity rearrangement and neurogenesis, are presented and discussed as potential biomarkers for optimizing stimulatory parameters for VNS. A vagus nerve-neurotrophin interaction model in the brain is finally proposed as a working hypothesis for future studies addressed to understand pathophysiology of psychiatric disturbance.

Predictors of Treatment Resistance Across Different Clinical Subtypes of Depression: Comparison of Unipolar vs. Bipolar Cases

OBJECTIVE

Treatment-resistant depression (TRD) and treatment-resistant bipolar depression (TRBD) poses a significant clinical and societal burden, relying on different operational definitions and treatment approaches. The detection of clinical predictors of resistance is elusive, soliciting clinical subtyping of the depressive episodes, which represents the goal of the present study.

METHODS

A hundred and thirty-one depressed outpatients underwent psychopathological evaluation using major rating tools, including the Hamilton Rating Scale for Depression, which served for subsequent principal component analysis, followed-up by cluster analysis, with the ultimate goal to fetch different clinical subtypes of depression.

RESULTS

The cluster analysis identified two clinically interpretable, yet distinctive, groups among 53 bipolar (resistant cases = 15, or 28.3%) and 78 unipolar (resistant cases = 20, or 25.6%) patients. Among the MDD patients, cluster "1" included the following components: "Psychic symptoms, depressed mood, suicide, guilty, insomnia" and "genitourinary, gastrointestinal, weight loss, insight". Altogether, with broadly defined "mixed features," this latter cluster correctly predicted treatment outcome in 80.8% cases of MDD. The same "broadly-defined" mixed features of depression (namely, the standard Diagnostic and Statistical Manual for Mental Disorders, Fifth Edition-DSM-5-specifier plus increased energy, psychomotor activity, irritability) correctly classified 71.7% of BD cases, either as TRBD or not.

LIMITATIONS

Small sample size and high rate of comorbidity.

CONCLUSIONS

Although relying on different operational criteria and treatment history, TRD and TRBD seem to be consistently predicted by broadly defined mixed features among different clinical subtypes of depression, either unipolar or bipolar cases. If replicated by upcoming studies to encompass also biological and neuropsychological measures, the present study may aid in precision medicine and informed pharmacotherapy.

Human induced pluripotent stem cells technology in treatment resistant depression: novel strategies and opportunities to unravel ketamine's fast-acting antidepressant mechanisms

Approximately 30% of Major Depressive Disorder (MDD) patients develop treatment-resistant depression (TRD). Among the different causes that make TRD so challenging in both clinical and research contexts, major roles are played by the inadequate understanding of MDD pathophysiology and the limitations of current pharmacological treatments. Nevertheless, the field of psychiatry is facing exciting times. Combined with recent advances in genome editing techniques, human induced pluripotent stem cell (hiPSC) technology is offering novel and unique opportunities in both disease modelling and drug discovery. This technology has allowed innovative disease-relevant patient-specific in vitro models to be set up for many psychiatric disorders. Such models hold great potential in enhancing our understanding of MDD pathophysiology and overcoming many of the well-known practical limitations inherent to animal and post-mortem models. Moreover, the field is approaching the advent of (es)ketamine, a glutamate N-methyl-d-aspartate (NMDA) receptor antagonist, claimed as one of the first and exemplary agents with rapid (in hours) antidepressant effects, even in TRD patients. Although ketamine seems poised to transform the treatment of depression, its exact mechanisms of action are still unclear but greatly demanded, as the resulting knowledge may provide a model to understand the mechanisms behind rapid-acting antidepressants, which may lead to the discovery of novel compounds for the treatment of depression. After reviewing insights into ketamine's mechanisms of action (derived from preclinical animal studies) and depicting the current state of the art of hiPSC technology below, we will consider the implementation of an hiPSC technology-based TRD model for the study of ketamine's fast acting antidepressant mechanisms of action.

In-vitro and in situ assessment of the efflux of five antidepressants by breast cancer resistance protein

Objectives

Antidepressants need to penetrate the blood–brain barrier (BBB) to exert their functions in the central nervous system. Breast cancer resistance protein (BCRP), an efflux transporter abundantly expressed in the BBB, prevents the accumulation of many drugs in the brain. This study aimed to identify whether five commonly used antidepressants (sertraline, duloxetine, fluoxetine, amitriptyline and mirtazapine) are BCRP substrates.

Methods

A combination of bidirectional transport and intracellular accumulation experiments was conducted on BCRP-overexpressing MDCKII and wild-type (WT) cells, and in situ brain perfusion was conducted in rats.

Key findings

The bidirectional transport study revealed that the net efflux ratio (NER) of sertraline reached 2.08 but decreased to 1.06 when co-incubated with Ko143, a selective BCRP inhibitor. Conversely, the other four antidepressants did not appear to be BCRP substrates, due to their low NER values (&lt;1.5). The accumulation of sertraline in MDCKII-BCRP cells was significantly lower than that in MDCKII-WT cells. The presence of Ko143 significantly increased the sertraline accumulation in MDCKII-BCRP cells but not in MDCKII-WT cells. Brain perfusion showed that the permeability of 1 and 5 μm sertraline was significantly higher in the presence of Ko143.

Conclusions

Taken together, BCRP is involved in sertraline efflux.

Subtypes of treatment-resistant depression determined by a latent class analysis in a Chinese clinical population

BACKGROUND

This study aimed to explore subtypes of treatment-resistant depression (TRD).

METHODS

Latent class analysis (LCA) was performed on clinical and demographic data collected from 375 patients with TRD. Clinical variables were compared across subtypes. Treatment outcomes across subtypes of TRD were compared separately for those within each subtype with anxiety (those with a HRSD-17 anxiety/somatization factor score ≥ 7) and those without anxiety. LCA subtypes were compared using Cochran's and Mantel-Haenszel χ² test, respectively. Unordered multinomial logistic regression was used to assess clinical correlates of TRD subtypes.

RESULTS

Three categories were detected: severe depression (66%), moderate depression with anxiety (9%) and mild depression with anxiety/somatization (25%). Gender, age, age at first onset, family monthly income, number of hospitalizations, HRSD-17 and clinical global impression-severity (CGI) scores were significantly different across the three groups. Remission rates were significantly different among anxious cases with severe (43.75%), moderate (22.73%) and mild (26.25%) depression subtypes. Compared to cases in the mild depression group, those in the severe depression group had a greater likelihood of being male, having a later age of first onset, higher numbers of hospitalization, higher HRSD-17 and CGI total scores, and lower family income. Those in the moderate depression group were more likely to be male and have lower family income than those in the mild depression group.

LIMITATIONS

Representative bias, relatively small sample size, unbalanced group size and incomplete indicator variables might have a negative effect on the validity and generalization of the findings.

CONCLUSIONS

Depression severity could be a basis for subtype classification of patients with TRD. The classification of latent class of TRD observed in our study was similar to the structure found in MDD. Longitudinal research into the stability of the latent structure of TRD across illness course is merited as is research into treatment outcomes for TRD subtypes.