Neuroimmune and neuroendocrine abnormalities in depression: two sides of the same coin

Biomarkers in the Diagnosis and Prediction of Medication Response in Depression and the Role of Nutraceuticals

Depression continues to be a significant and growing public health concern. In clinical practice, it involves a clinical diagnosis. There is currently no defined or agreed upon biomarker/s for depression that can be readily tested. A biomarker is defined as a biological indicator of normal physiological processes, pathogenic processes, or pharmacological responses to a therapeutic intervention that can be objectively measured and evaluated. Thus, as there is no such marker for depression, there is no objective measure of depression in clinical practice. The discovery of such a biomarker/s would greatly assist clinical practice and potentially lead to an earlier diagnosis of depression and therefore treatment. A biomarker for depression may also assist in determining response to medication. This is of particular importance as not all patients prescribed with medication will respond, which is referred to as medication resistance. The advent of pharmacogenomics in recent years holds promise to target treatment in depression, particularly in cases of medication resistance. The role of pharmacogenomics in routine depression management within clinical practice remains to be fully established. Equally so, the use of pharmaceutical grade nutrients known as nutraceuticals in the treatment of depression in the clinical practice setting is largely unknown, albeit frequently self-prescribed by patients. Whether nutraceuticals have a role in not only depression treatment but also in potentially modifying the biomarkers of depression has yet to be proven. The aim of this review is to highlight the potential biomarkers for the diagnosis, prediction, and medication response of depression.

Complement C5a Receptor Signaling Alters Stress Responsiveness and Modulates Microglia Following Chronic Stress Exposure

Background

Accumulating evidence underscores the pivotal role of heightened inflammation in the pathophysiology of stress-related diseases, but the underlying mechanisms remain elusive. The complement system, a key effector of the innate immune system, produces the C5-cleaved activation product C5a upon activation, initiating inflammatory responses through the canonical C5a receptor 1 (C5aR1). While C5aR1 is expressed in stress-responsive brain regions, its role in stress responsiveness remains unknown.

Methods

To investigate C5a-C5aR1 signaling in stress responses, mice underwent acute and chronic stress paradigms. Circulating C5a levels and messenger RNA expression of C5aR1 in the hippocampus and adrenal gland were measured. C5aR1-deficient mice were used to elucidate the effects of disrupted C5a-C5aR1 signaling across behavioral, hormonal, metabolic, and inflammation parameters.

Results

Chronic restraint stress elevated circulating C5a levels while reducing C5aR1 messenger RNA expression in the hippocampus and adrenal gland. Notably, the absence of C5aR1 signaling enhanced adrenal sensitivity to adrenocorticotropic hormone, concurrently reducing pituitary adrenocorticotropic hormone production and enhancing the response to acute stress. C5aR1-deficient mice exhibited attenuated reductions in locomotor activity and body weight under chronic stress. Additionally, these mice displayed increased glucocorticoid receptor sensitivity and disrupted glucose and insulin homeostasis. Chronic stress induced an increase in C5aR1-expressing microglia in the hippocampus, a response mitigated in C5aR1-deficient mice.

Conclusions

C5a-C5aR1 signaling emerges as a key metabolic regulator during stress, suggesting that complement activation and dysfunctional C5aR1 signaling may contribute to neuroinflammatory phenotypes in stress-related disorders. The results advocate for further exploration of complement C5aR1 as a potential therapeutic target for stress-related conditions.

The monoaminergic pathways are involved in the antidepressant-like effect of quercetin

Quercetin, a plant-derived flavonoid, is an antioxidant and has demonstrated antidepressant and anti-inflammatory activities in several animal models. However, there is scanty information on the underlying mechanisms of its antidepressant property. This present study aimed at assessing the involvement of monoaminergic systems in the antidepressant-like activity of quercetin in experimental animals. Mice received varying doses of quercetin (25, 50 &100 mg/kg daily) and were then subjected to open field test (OPF), despair tests, the reserpine test, and the yohimbine lethality test (YLT). In addition, monoaminergic involvement was investigated by combining quercetin (100 mg/kg) with dopaminergic antagonists (haloperidol and sulpiride), adrenergic blockers (prazosin, propranolol and yohimbine), and serotonergic blockers/inhibitors (metergoline). The results showed that quercetin produced significant anti-immobility effects in the forced swim test (FST) and tail suspension test (TST), suggesting antidepressant activity. In addition, the potentiation of yohimbine lethality by quercetin further indicates its antidepressant-like property. This antidepressant action demonstrated was, however, blocked when quercetin was co-administered with dopaminergic, adrenergic and serotonergic antagonists, suggesting involvement of the monoaminergic system in the antidepressant action of quercetin. Nevertheless, quercetin did not significantly alter the locomotor activity of mice, which implies lack of stimulant effect. Taken together, these outcomes suggest that monoaminergic systems are likely involved in the anti-depressant effect of quercetin in mice.

Quercetin reshapes gut microbiota homeostasis and modulates brain metabolic profile to regulate depression-like behaviors induced by CUMS in rats

Quercetin, an abundant flavonoid compound in plants, is considered a novel antidepressant; however, its mechanisms of action are poorly understood. This study aimed to investigate the therapeutic effects of quercetin on chronic unpredictable mild stress (CUMS)-induced depression-like behaviors in rats and explore the underlying mechanisms by combining untargeted metabolomics and 16S rRNA sequencing analysis of brain tissue metabolites and gut microbiota. Gut microbiota analysis revealed that at the phylum level, quercetin reduced Firmicutes and the Firmicutes/Bacteroidetes (F/B) ratio and enhanced Cyanobacteria. At the genus level, quercetin downregulated 6 and upregulated 14 bacterial species. Metabolomics analysis revealed that quercetin regulated multiple metabolic pathways, including glycolysis/gluconeogenesis, sphingolipid metabolism, the pentose phosphate pathway, and coenzyme A biosynthesis. This modulation leads to improvements in depression-like phenotypes, anxiety-like phenotypes, and cognitive function, highlighting the therapeutic potential of quercetin in treating depression.

Behavior, synaptic mitochondria, and microglia are differentially impacted by chronic adolescent stress and repeated endotoxin exposure in male and female rats

Early life adversity and chronic inflammation have both been associated with cognitive impairment and neural compromise. In this study, we investigated the interactions between a history of chronic adolescent stress (CAS) and repeated endotoxin exposure on behavior, synaptic mitochondria, and microglia in adult male and female Wistar rats. Adult rats from chronic stress and control conditions were exposed to either repeated endotoxin (lipopolysaccharide; LPS) or saline injections every 3 days for 9 weeks. In both sexes, repeated LPS, regardless of stress history, impaired working memory in the Y maze. Regarding spatial memory, LPS impaired function for females; whereas, CAS altered function in males. Although males had an increase in anxiety-like behavior shortly after CAS, there were no long-term effects on anxiety-like behavior or social interaction observed in males or females. Stress did not alter synaptic mitochondrial function in either sex. Repeated LPS altered synaptic mitochondrial function such that ATP production was increased in females only. There were no observed increases in IBA-1 positive cells within the hippocampus for either sex. However, LPS and CAS altered microglia morphology in females. Impact of repeated LPS was evident at the terminal endpoint with increased spleen weight in both sexes and decreased adrenal weight in males only. Circulating cytokines were not impacted by repeated LPS at the terminal endpoint, but evidence of CAS effects on cytokines in females were evident. These data suggest a long-term impact of chronic stress and an impact of repeated endotoxin challenge in adulthood; however, not all physiological and behavioral metrics examined were impacted by the paradigm employed in this study and the two environmental challenges rarely interacted.

Work-related causes of mental health conditions and interventions for their improvement in workplaces

Mental health problems and disorders are common among working people and are costly for the affected individuals, employers, and whole of society. This discussion paper provides an overview of the current state of knowledge on the relationship between work and mental health to inform research, policy, and practice. We synthesise available evidence, examining both the role of working conditions in the development of mental disorders, and what can be done to protect and promote mental health in the workplace. We show that exposure to some working conditions is associated with an increased risk of the onset of depressive disorders, the most studied mental disorders. The causality of the association, however, is still debated. Causal inference should be supported by more research with stronger linkage to theory, better exposure assessment, better understanding of biopsychosocial mechanisms, use of innovative analytical methods, a life-course perspective, and better understanding of the role of context, including the role of societal structures in the development of mental disorders. There is growing evidence for the effectiveness of interventions to protect and promote mental health and wellbeing in the workplace; however, there is a disproportionate focus on interventions directed towards individual workers and illnesses, compared with interventions for improving working conditions and enhancing mental health. Moreover, research on work and mental health is mainly done in high-income countries, and often does not address workers in lower socioeconomic positions. Flexible and innovative approaches tailored to local conditions are needed in implementation research on workplace mental health to complement experimental studies. Improvements in translating workplace mental health research to policy and practice, such as through workplace-oriented concrete guidance for interventions, and by national policies and programmes focusing on the people most in need, could capitalise on the growing interest in workplace mental health, possibly yielding important mental health gains in working populations.

Antidepressants and type 2 diabetes: highways to knowns and unknowns

Type 2 diabetes (T2D) is a metabolic disease caused by the development of insulin resistance (IR), relative insulin deficiency, and hyperglycemia. Hyperglycemia-induced neurochemical dysregulation activates the progression of depression in T2D patients. Therefore, management of depression by antidepressant agents improves glucose homeostasis and insulin sensitivity. However, prolong use of antidepressant drugs may increase the risk for the development of T2D. However, there is strong controversy concerning the use of antidepressant drugs in T2D. Therefore, this review try to elucidate the potential effects of antidepressant drugs in T2D regarding their detrimental and beneficial effects.

The impact of a stress management intervention including cultural components on stress biomarker levels and mental health indicators among indigenous women

We examined the effectiveness of a 26-week culture-inclusive intervention on reducing salivary stress biomarker levels, and perceived stress, depressive, and post-traumatic stress disorder (PTSD) symptoms measured using scales in 53 Indigenous women in Ontario, Canada. Statistical analyses compared the average biomarker levels, and the area under the curve (AUC) of biomarkers. Differences in biomarkers and mental health scale scores pre- and post-intervention were compared using mixed models with a random intercept. Interaction terms were included between the intervention and age, education, disability, and HIV status, individually, to test for sub-group differences. Cortisol AUC post-intervention was decreased compared to pre-intervention (β -1.29 µg/dL; 95%CI -2.35, -0.23). There was a slight decrease in perceived stress levels (aOR: -2.80; 95%CI -5.09, -0.50). The associations were stronger among women of younger age, higher education, and no disabilities. These interventions can be effective, but future interventions should target Indigenous population sub-groups to address individual needs.

Stressed Microglia: Neuroendocrine-Neuroimmune Interactions in the Stress Response

Stressful life experiences are associated with the development of neuropsychiatric disorders like depression. Emerging evidence indicates that microglia, the specialized resident macrophages of the brain, may be a key mediator of the relationship between psychosocial stressor exposure and adaptive or maladaptive responses at the level of synaptic, circuit, and neuroimmune alterations. Here, we review current literature regarding how psychosocial stressor exposure changes microglial structure and function, thereby altering behavioral and brain outcomes, with a particular focus on age- and sex-dependent effects. We argue that additional emphasis should be placed in future research on investigating sex differences and the impacts of stressor exposure during sensitive periods of development, as well as going beyond traditional morphological measurements to interrogate microglial function. The bidirectional relationship between microglia and the stress response, particularly the role of microglia in the neuroendocrine control of stress-related circuits, is also an important area for future investigation. Finally, we discuss emerging themes and future directions that point to the possibility of the development of novel therapeutics for stress-related neuropsychiatric disorders.

Chronic stress beginning in adolescence decreases spatial memory following an acute inflammatory challenge in adulthood

Prolonged stress beginning in adolescence can contribute to the dysregulation of the neuroendocrine system in adulthood. As the neuroendocrine and neuroimmune systems participate in bi-directional regulatory control, adolescent stress can prime the neuroimmune system to future inflammatory insults. Previous work from our group demonstrates that stress exaggerates the hippocampal response to inflammation, which can lead to deficits in learning and memory. In the current study, we sought to interrogate the interaction between an acute peripheral challenge of lipopolysaccharide (LPS) in male and female Wistar rats with a history of stress beginning in adolescence (CAS). Males from the CAS group were more vulnerable to the peripheral effects of LPS compared to non-stressed males including porphyrin staining and ruffled fur. In contrast, LPS generated similar peripheral effects in females regardless of adolescent stress history. Learning and memory were differentially impacted by LPS as a function of stress history and effects manifested differently when stratified by sex. Males with a history of adolescent stress exhibited deficits in initial learning. Females from the CAS group performed similar to controls during acquisition but exhibited a slight impairment during reversal learning. Males and females with a history of stress displayed memory impairment during the probe assessments as compared to their same-sex control group. We conclude that while stress beginning in adolescence enhanced the vulnerability of learning and memory to an inflammatory challenge, the phenotype of this effect manifested differently in males and females. These data demonstrate a sustained impact of adolescent stress on the neuroimmune system which is sufficient to influence cognitive performance in both sexes.

Understanding the Interplay between Air Pollution, Biological Variables, and Major Depressive Disorder: Rationale and Study Protocol of the DeprAir Study

Major depressive disorder (MDD) is a serious and disabling condition, whose etiological mechanisms are not fully understood. The aim of the DeprAir study is to verify the hypothesis that air pollution exposure may exacerbate neuroinflammation with consequent alterations in DNA methylation of genes involved in circadian rhythms and hormonal dysregulation, resulting in the worsening of depressive symptoms. The study population consists of 420 depressed patients accessing the psychiatry unit of the Policlinico Hospital (Milan, Italy), from September 2020 to December 2022. Data collection is still ongoing for about 100 subjects. For each participant demographic and lifestyle information, depression history and characteristics, as well as blood samples, were collected. MDD severity was assessed through five rating scales commonly used in clinical practice to assess the severity of affective symptoms. Exposure to particulate and gaseous air pollutants is assigned to each subject using both air pollution monitoring station measurements and estimates derived from a chemical transport model. DeprAir is the first study investigating in a comprehensive picture whether air pollution exposure could be an important modifiable environmental factor associated with MDD severity and which biological mechanisms mediate the negative effect of air pollution on mental health. Its results will represent an opportunity for preventive strategies, thus entailing a tremendous impact on public health.

Peripheral cytokine levels across psychiatric disorders: A systematic review and network meta-analysis

Immune dysregulated cytokine production is involved in mental diseases. However, the results are inconsistent and the pattern of cytokine alterations has not been compared across disorders. We performed a network impact analysis of cytokine levels for different psychiatric disorders including schizophrenia, major depressive disorder, bipolar disorder, panic disorder, post-traumatic stress disorder and obsessive compressive disorder to evaluate their clinical impact across conditions. Studies were identified by searching the electronic databases up to 31/05/2022. A total of eight cytokines, together with (high-sensitivity) C-reactive proteins (hsCRP/CRP) were included in the network meta-analysis. The levels of proinflammatory cytokines, hsCRP/CRP and interleukin 6 (IL-6) were significantly increased in patients with psychiatric disorders when compared to controls. IL-6 showed no significant difference among comparisons between disorders according to the network meta-analysis. Interleukin 10 (IL-10) is significantly increased in patients with bipolar disorder compared to major depressive disorder. Further, the level of interleukin-1 beta (IL-1β) was significantly increased in major depressive disorder as compared to bipolar disorder. The level of interleukin 8 (IL-8) varied among these psychiatric disorders based on the network meta-analysis result. Overall, abnormal cytokine levels were found in psychiatric disorders, and some of the cytokines displayed differential characteristics in these disorders, especially IL-8, pointing to a role as potential biomarkers for general and differential diagnosis.

Gray matter reduction is associated with cognitive dysfunction in depressed patients comorbid with subclinical hypothyroidism

Introduction

To explore the association between regional gray matter volume (GMV) and cognitive impairments and ascertain whether the regional brain alterations related to cognitive impairments occur in major depressive disorder (MDD) patients with comorbid subclinical hypothyroidism (SHypo).

Methods

We enrolled 32 MDD patients, 32 MDD patients with comorbid SHypo, and 32 normal controls and subjected them to thyroid function tests, neurocognitive tests, and magnetic resonance imaging (MRI). Using voxel-based morphometry (VBM) analysis, we examined the pattern of gray matter (GM) in these participants. We also used ANOVA to detect group differences and partial correlation to explore the potential association between GMV alterations and cognitive tests in comorbid patients.

Results

The comorbid patients exhibited significantly smaller GMV in the right middle frontal gyrus (MFG) than the non-comorbid group. Furthermore, the partial correlation analysis showed that GMV of the right MFG was associated with poor executive function (EF) performance in comorbid patients.

Conclusion

These findings provide valuable insight into the relationship between the alteration of GMV and cognitive dysfunction of MDD patients with comorbid SHypo.

[Morphofunctional cerebral changes associated with development of suicidal behavior]

THE AIM OF THE STUDY

Was to identify the cerebral areas, which demonstrate the most significant structural changes and damaged functional activity in patients with suicidal behavior. The original studies, presented in PubMed database, were used to analyze the literature. Additional literature in the form of atlases, review articles and publications, written in related spheres, was used to interpret the results. The study identified the 69 cerebral regions, demonstrating significant changes and the structures with the most significant deviations among them were selected. The regions of cerebral grey matter, in particular basal ganglia (structures of striatum and limbic system), as well as selected regions of cerebral cortex, specifically frontal, insularis, singulate and parietal mostly were included in the list. The decrease in grey matter volume, changes of neuronal and glial density, special patterns of activity and variations of functional association with other cerebral regions are described within mentioned structures. The literature review found that there was a lack of postmortem examinations in suicidal cases. Advanced study of the described structures is required in cases of completed suicide using new research methods.

The modulatory effects of alkaloid extracts of Cannabis sativa, Datura stramonium, Nicotiana tabacum and male Carica papaya on neurotransmitter, neurotrophic and neuroinflammatory systems linked to anxiety and depression

This study investigated the modulatory effects of alkaloid extracts of Cannabis sativa (CSAE), Datura stramonium (DSAE), Nicotiana tabacum (NTAE) and male Carica papaya (CMAE) on neurotransmitter, neurotrophic and neuro-inflammatory systems linked to anxiety and depression. Male Wistar rats were orally administered the alkaloid extracts in doses of 5, 50, 500, and 2000 mg/kg for 90 days. On day 91, neurobehavioural studies were evaluated, rats were sacrificed, brain hippocampus removed and tissue homogenate prepared. Biochemical, cytokine and neurotransmitter metabolisms were estimated in the hippocampus. Expressions of genes linked to anxiety and depression were evaluated by RT-qPCR. Results showed CSAE, NTAE and CMAE act as anxiolytic and antidepressant agents by depleting TNF-α, IL-1β and reactive oxygen species concentrations, and monoamine oxidase, angiotensin 1-converting enzyme and acetylcholinesterase activities while elevating IL-10 and dopamine concentrations and glutamate dehydrogenase activity at doses of 5, 50 and 500. Same doses of CSAE, NTAE and CMAE also depleted the gene expressions of GSK3β, JNK, NF-ĸB, and Nesfatin-1 while increasing expressions of CREB, BDNF, serotonin and Nrf2. However, administration of DSAE and 2000 mg/kg CSAE, NTAE and CMAE had adverse modulatory effects on the neurochemical concentrations and activities as well as the gene expressions of the evaluated neurotransmitter, neurotrophic and inflammatory systems. In conclusion, the study established the sub-chronic instrumentalization potential of CSAE, CMAE, and NTAE for anxiolytic and anti-depressive moods, though their use may be associated with dependence and addiction, which may result in more detrimental effects than any therapeutic potential they may proffer.

Galvanic Skin Response Features in Psychiatry and Mental Disorders: A Narrative Review

This narrative review is aimed at presenting the galvanic skin response (GSR) Biofeedback method and possibilities for its application in persons with mental disorders as a modern form of neurorehabilitation. In the treatment of mental disorders of various backgrounds and courses, attention is focused on methods that would combine pharmacological treatment with therapies improving functioning. Currently, the focus is on neuronal mechanisms which, being physiological markers, offer opportunities for correction of existing deficits. One such indicator is electrodermal activity (EDA), providing information about emotions, cognitive processes, and behavior, and thus, about the function of various brain regions. Measurement of the galvanic skin response (GSR), both skin conductance level (SCL) and skin conductance responses (SCR), is used in diagnostics and treatment of mental disorders, and the training method itself, based on GSR Biofeedback, allows for modulation of the emotional state depending on needs occurring. Summary: It is relatively probable that neurorehabilitation based on GSR-BF is a method worth noticing, which-in the future-can represent an interesting area of rehabilitation supplementing a comprehensive treatment for people with mental disorders.

Changes in regulators of lipid metabolism in the brain: a study of animal models of depression and hypothyroidism

Metabolic disturbances in the brain are assumed to be early changes involved in the pathogenesis of depression, and these alterations may be intensified by a deficiency of thyroid hormones. In contrast to glucose metabolism, the link between altered brain lipids and the pathogenesis of depression is poorly understood, therefore in the present study, we determine transcription factors and enzymes regulating cholesterol and fatty acid biosynthesis in the brain structures in an animal model of depression, hypothyroidism and the coexistence of these diseases.

In used model of depression, a decrease in the active form of the transcription factor SREBP-2 in the hippocampus was demonstrated, thus suggesting a reduction in cholesterol biosynthesis. In turn, in the hypothyroidism model, the reduction of cholesterol biosynthesis in the frontal cortex was demonstrated by both the reduction of mature SREBP-2 and the concentration of enzymes involved in cholesterol biosynthesis. The lower expression of LDL receptors in the frontal cortex indicates the restriction of cholesterol uptake into the cells in the model of coexistence of depression and hypothyroidism. Moreover, the identified changes in the levels of SNAP-25, GLP-1R and GLP-2R pointed to disturbances in synaptic plasticity and neuroprotection mechanisms in the examined brain structures.

In conclusion, a reduction in cholesterol synthesis in the hippocampus in the model of depression may be the reason for the reduction of synaptic plasticity, whereas a lower level of LDL-R occurring in the frontal cortex in rats from the model of depression and hypothyroidism coexistence could be the reason of anxiogenic and depression-like behaviors.

Spatiotemporal Dynamics of Stress-Induced Network Reconfigurations Reflect Negative Affectivity

BACKGROUND

Maladaptive stress responses are important risk factors in the etiology of mood and anxiety disorders, but exact pathomechanisms remain to be understood. Mapping individual differences of acute stress-induced neurophysiological changes, especially on the level of neural activation and functional connectivity (FC), could provide important insights in how variation in the individual stress response is linked to disease risk.

METHODS

Using an established psychosocial stress task flanked by two resting states, we measured subjective, physiological, and brain responses to acute stress and recovery in 217 participants with and without mood and anxiety disorders. To estimate blockwise changes in stress-induced activation and FC, we used hierarchical mixed-effects models based on denoised time series within predefined stress-related regions. We predicted inter- and intraindividual differences in stress phases (anticipation vs. stress vs. recovery) and transdiagnostic dimensions of stress reactivity using elastic net and support vector machines.

RESULTS

We identified four subnetworks showing distinct changes in FC over time. FC but not activation trajectories predicted the stress phase (accuracy = 70%, p_perm < .001) and increases in heart rate (R² = 0.075, p_perm < .001). Critically, individual spatiotemporal trajectories of changes across networks also predicted negative affectivity (ΔR² = 0.075, p_perm = .030) but not the presence or absence of a mood and anxiety disorder.

CONCLUSIONS

Spatiotemporal dynamics of brain network reconfiguration induced by stress reflect individual differences in the psychopathology dimension of negative affectivity. These results support the idea that vulnerability for mood and anxiety disorders can be conceptualized best at the level of network dynamics, which may pave the way for improved prediction of individual risk.

Alteration in the Expression of Genes Involved in Cerebral Glucose Metabolism as a Process of Adaptation to Stressful Conditions

Exposure to chronic stress leads to disturbances in glucose metabolism in the brain, and changes in the functioning of neurons coexisting with the development of depression. The detailed molecular mechanism and cerebral gluconeogenesis during depression are not conclusively established. The aim of the research was to assess the expression of selected genes involved in cerebral glucose metabolism of mice in the validated animal paradigm of chronic stress. To confirm the induction of depression-like disorders, we performed three behavioral tests: sucrose preference test (SPT), forced swim test (FST), and tail suspension test (TST). In order to study the cerebral glucose metabolism of the brain, mRNA levels of the following genes were determined in the prefrontal cortex of mice: Slc2a3, Gapdh, Ldha, Ldhb, and Pkfb3. It has been shown that exogenous, chronic administration of corticosterone developed a model of depression in behavioral tests. There were statistically significant changes in the mRNA level of the Slc2a3, Ldha, Gapdh, and Ldhb genes. The obtained results suggest changes in cerebral glucose metabolism as a process of adaptation to stressful conditions, and may provide the basis for introducing new therapeutic strategies for chronic stress-related depression.

Antidepressant Potential of Quercetin and its Glycoside Derivatives: A Comprehensive Review and Update

Depression is a global health problem with growing prevalence rates and serious impacts on the daily life of patients. However, the side effects of currently used antidepressants greatly reduce the compliance of patients. Quercetin is a flavonol present in fruits, vegetables, and Traditional Chinese medicine (TCM) that has been proved to have various pharmacological effects such as anti-depressant, anti-cancer, antibacterial, antioxidant, anti-inflammatory, and neuroprotective. This review summarizes the evidence for the pharmacological application of quercetin to treat depression. We clarified the mechanisms of quercetin regulating the levels of neurotransmitters, promoting the regeneration of hippocampal neurons, improving hypothalamic-pituitary-adrenal (HPA) axis dysfunction, and reducing inflammatory states and anti-oxidative stress. We also summarized the antidepressant effects of some quercetin glycoside derivatives to provide a reference for further research and clinical application.

Is there a relationship between morphological and functional platelet changes and depressive disorder?

BACKGROUND

Blood platelets, due to shared biochemical and functional properties with presynaptic serotonergic neurons, constituted, over the years, an attractive peripheral biomarker of neuronal activity. Therefore, the literature strongly focused on the investigation of eventual structural and functional platelet abnormalities in neuropsychiatric disorders, particularly in depressive disorder. Given their impact in biological psychiatry, the goal of the present paper was to review and critically analyze studies exploring platelet activity, functionality, and morpho-structure in subjects with depressive disorder.

METHODS

According to the PRISMA guidelines, we performed a systematic review through the PubMed database up to March 2020 with the search terms: (1) platelets in depression [Title/Abstract]"; (2) "(platelets[Title]) AND depressive disorder[Title/Abstract]"; (3) "(Platelet[Title]) AND major depressive disorder[Title]"; (4) (platelets[Title]) AND depressed[Title]"; (5) (platelets[Title]) AND depressive episode[Title]"; (6) (platelets[Title]) AND major depression[Title]"; (7) platelet activation in depression[All fields]"; and (8) platelet reactivity in depression[All fields]."

RESULTS

After a detailed screening analysis and the application of specific selection criteria, we included in our review a total of 106 for qualitative synthesis. The studies were classified into various subparagraphs according to platelet characteristics analyzed: serotonergic system (5-HT2A receptors, SERT activity, and 5-HT content), adrenergic system, MAO activity, biomarkers of activation, responsivity, morphological changes, and other molecular pathways.

CONCLUSIONS

Despite the large amount of the literature examined, nonunivocal and, occasionally, conflicting results emerged. However, the findings on structural and metabolic alterations, modifications in the expression of specific proteins, changes in the aggregability, or in the responsivity to different pro-activating stimuli, may be suggestive of potential platelet dysfunctions in depressed subjects, which would result in a kind of hyperreactive state. This condition could potentially lead to an increased cardiovascular risk. In line with this hypothesis, we speculated that antidepressant treatments would seem to reduce this hyperreactivity while representing a potential tool for reducing cardiovascular risk in depressed patients and, maybe, in other neuropsychiatric conditions. However, the problem of the specificity of platelet biomarkers is still at issue and would deserve to be deepened in future studies.

Influence of pro-obesogenic dietary habits on stress-induced cognitive alterations in healthy adult volunteers

Stress is a fundamental biological response that can be associated with alterations in cognitive processes. Unhealthy dietary habits are proposed to modulate this effect, notably through their pro-inflammatory potential. This cross-sectional study aimed to evaluate the influence of an obesogenic dietary pattern with inflammatory potential on stress-induced cognitive alterations in healthy volunteers. Fifty healthy adult participants were stratified into two diet groups: obesogenic vs. non-obesogenic, based on their self-reported consumption of fat, sugar, and salt, assessed by the French National Program for Nutrition and Health questionnaire and a food frequency questionnaire. Serum high-sensitive C-reactive protein (hsCRP) was measured as a marker of systemic inflammation using ELISA. Verbal memory and sustained attention were evaluated through the Verbal Recognition Memory (VRM) test and the Rapid Visual Information Processing (RVP) test respectively, from the Cambridge Neuropsychological Test Automated Battery. Assessments were performed before and after exposure to the psychological stressor Trier Social Stress Test (TSST). Stress response was evaluated by subjective stress perception, salivary cortisol, blood pressure, and heart rate. Twenty-two participants (44%) presented an obesogenic diet. Systemic inflammation was significantly higher in the obesogenic diet group (p=0.005). The TSST induced a significant stress response, regardless of dietary habits (Time effect p < 0.001). In the whole sample, exposure to TSST was associated with cognitive changes in the form of impaired performance on the VRM test and overall improved RVP scores. However, the obesogenic diet group exhibited an increased total number of false alarms (Time x Diet: p=0.014) on the RVP test after TSST exposure as well as a greater impairment in immediate verbal recognition on the VRM test (Time x Diet: p=0.002). This effect was not associated with the inflammatory component of the obesogenic diet. These results suggest that an obesogenic diet may sensitize healthy individuals to the detrimental effects of acute stress on cognitive performance.

A novel supplement with yeast β-glucan, prebiotic, minerals and Silybum marianum synergistically modulates metabolic and inflammatory pathways and improves steatosis in obese mice

OBJECTIVE

To evaluate the synergic effects of a novel oral supplement formulation, containing prebiotics, yeast β-glucans, minerals and silymarin (Silybum marianum), on lipid and glycidic metabolism, inflammatory and mitochondrial proteins of the liver, in control and high-fat diet-induced obese mice.

METHODS

After an acclimation period, 32 male C57BL/6 mice were divided into the following groups: nonfat diet (NFD) vehicle, NFD supplemented, high-fat diet (HFD) vehicle and HFD supplemented. The vehicle and experimental formulation were administered orally by gavage once a day during the last four weeks of the diet (28 consecutive days). We then evaluated energy homeostasis, inflammation, and mitochondrial protein expression in these groups of mice.

RESULTS

After four weeks of supplementation, study groups experienced reduced glycemia, dyslipidemia, fat, and hepatic fibrosis levels. Additionally, proliferator-activated receptor-α, AMP-activated protein kinase-1α, peroxisome proliferator-activated receptor γ co-activator-1α, and mitochondrial transcription factor A expression levels were augmented; however, levels of inhibitor of nuclear factor-κB kinase subunit α and p65 nuclear factor-κB expression, and oxidative markers were reduced. Notably, the cortisol/C-reactive protein ratio, a well-characterized marker of the hypothalamic-pituitary-adrenal axis immune interface status, was found to be modulated by the supplement.

CONCLUSION

We discovered that the novel supplement was able to modify different antioxidant, metabolic and inflammatory pathways, improving the energy homeostasis and inflammatory status, and consequently alleviated hepatic steatosis.

Gut microbiota diversity but not composition is related to saliva cortisol stress response at the age of 2.5 months

Human brain and intestinal microbes reportedly maintain a constant bidirectional connection through diverse neural, endocrine, immune, and metabolic pathways. Increasing evidence indicates that this communication system, referred to as microbiota-gut-brain axis, enables the gut microbes to influence several aspects of brain function and behavior, including hypothalamic-pituitary-adrenal (HPA) axis stress responses, and on the other hand, stress can affect gut microbiota. However, the role of gut microbiota in the HPA axis functioning in humans remains to be specified especially in early life. This study aimed at identifying the potential link between the cortisol stress response and the gut microbiota at the age of 2.5 months. Fecal microbiota profiles were acquired by 16S rRNA gene sequencing, while salivary cortisol responses after an exposure to a mild acute stressor represented the HPA axis reactivity. We observed that a blunted cortisol stress response was weakly associated with a diverse gut microbiota diversity at the age of 2.5 months. Gut microbiota composition was not associated with cortisol stress responsiveness, but rather with covariates, i.e. factors that influence gut microbiota composition and colonization.LAY SUMMARYThis exploratory study aimed at identifying possible links between cortisol stress responses and fecal microbiota composition in early infancy. In a well-characterized study population of 2.5-month-old infants, we observed that an attenuated cortisol stress responsiveness after a mild stressor was weakly associated with a diverse fecal microbiota. Our results suggest that the gut microbiota composition is associated with environmental factors, such as delivery mode and number of siblings, rather than with cortisol stress responsiveness, in this age group.

P2X7 Receptor as a Potential Target for Major Depressive Disorder

Major depressive disorder (MDD) is a common mental disorder. Although the genetic, biochemical, and psychological factors have been related to the development of MDD, it is generally believed that a series of pathological changes in the brain caused by chronic stress is the main cause of MDD. However, the specific mechanisms underlying chronic stress-induced MDD are largely undermined. Recent investigations have found that increased pro-inflammatory cytokines and changes in the inflammatory pathway in the microglia cells in the brain are the potential pathophysiological mechanism of MDD. P2X7 receptor (P2X7R) and its mediated signaling pathway play a key role in microglia activation. The present review aimed to present and discuss the accumulating data on the role of P2X7R in MDD. Firstly, we summarized the research progress in the correlation between P2X7R and MDD. Subsequently, we presented the P2X7R mediated microglia activation in MDD and the role of P2X7R in increased blood-brain barrier (BBB) permeability caused by chronic stress. Lastly, we also discussed the potential mechanism underlying-P2X7R expression changes after chronic stress. In conclusion, P2X7R is a key molecule regulating the activation of microglia. Chronic stress activates microglia in the hippocampus by secreting interleukin- 1β (IL-1β) and other inflammatory cytokines, and increasing the BBB permeability, thus promoting the occurrence and development of MDD, which indicated that P2X7R might be a promising therapeutic target for MDD.

Venlafaxine and L-Thyroxine Treatment Combination: Impact on Metabolic and Synaptic Plasticity Changes in an Animal Model of Coexisting Depression and Hypothyroidism

The clinical effectiveness of supportive therapy with thyroid hormones in drug-resistant depression is well-known; however, the mechanisms of action of these hormones in the adult brain have not been fully elucidated to date. We determined the effects of venlafaxine and/or L-thyroxine on metabolic parameters and markers involved in the regulation of synaptic plasticity and cell damage in an animal model of coexisting depression and hypothyroidism, namely, Wistar Kyoto rats treated with propylthiouracil. In this model, in relation to the depression model itself, the glycolysis process in the brain was weakened, and a reduction in pyruvate dehydrogenase in the frontal cortex was normalized only by the combined treatment with L-thyroxine and venlafaxine, whereas changes in pyruvate and lactate levels were affected by all applied therapies. None of the drugs improved the decrease in the expression of mitochondrial respiratory chain enzymes. No intensification of glucocorticoid action was shown, while an unfavorable change caused by the lack of thyroid hormones was an increase in the caspase-1 level, which was not reversed by venlafaxine alone. The results indicated that the combined administration of drugs was more effective in normalizing glycolysis and the transition to the Krebs cycle than the use of venlafaxine or L-thyroxine alone.

Hypothalamic-Pituitary-End-Organ Axes: Hormone Function in Female Patients with Major Depressive Disorder

Classic hypothalamic-pituitary-end-organ feedback loops - the hypothalamic-pituitary-adrenal axis (HPAA), hypothalamic-pituitary-thyroidal axis (HPTA), and hypothalamic-pituitary-gonadal axis (HPGA) - are associated with the neuroendocrine and immune systems in major depressive disorder (MDD). Female patients with MDD present with evident neuroendocrine and immunological changes. Glucocorticoid, thyroid hormone, and reproductive steroid levels fluctuate with menstrual cycles, which might lead to glucocorticoid receptor resistance, impairment of triiodothyronine conversion, and sex hormone secretion disorders. In this review, we summarize the independent and interactive functions of these three axes in female MDD patients. The similar molecular structure of steroids implies an interrelationship between the hypothalamic-pituitary-end-organ axes and the competitive inhibitory effects at the receptor level, especially when considering the HPAA and HPGA.

Dendritic Cells: Neglected Modulators of Peripheral Immune Responses and Neuroinflammation in Mood Disorders?

Affective disorders (AD) including major depressive disorder (MDD) and bipolar disorder (BD) are common mood disorders associated with increased disability and poor health outcomes. Altered immune responses characterized by increased serum levels of pro-inflammatory cytokines and neuroinflammation are common findings in patients with AD and in corresponding animal models. Dendritic cells (DCs) represent a heterogeneous population of myeloid cells that orchestrate innate and adaptive immune responses and self-tolerance. Upon sensing exogenous and endogenous danger signals, mature DCs secrete proinflammatory factors, acquire migratory and antigen presenting capacities and thus contribute to neuroinflammation in trauma, autoimmunity, and neurodegenerative diseases. However, little is known about the involvement of DCs in the pathogenesis of AD. In this review, we summarize the current knowledge on DCs in peripheral immune responses and neuroinflammation in MDD and BD. In addition, we consider the impact of DCs on neuroinflammation and behavior in animal models of AD. Finally, we will discuss therapeutic perspectives targeting DCs and their effector molecules in mood disorders.

Co-culture of monocytes and zona fasciculata adrenal cells: An in vitro model to study the immune-adrenal cross-talk

The hypothalamic-pituitary-adrenal axis is the primary neuroendocrine system activated to re-establish homeostasis during periods of stress, including critical illness and major surgery. During critical illness, evidence suggests that locally induced inflammation of the adrenal gland could facilitate immune-adrenal cross-talk and, in turn, modulate cortisol secretion. It has been hypothesized that immune cells are necessary to mediate the effect of inflammatory stimuli on the steroidogenic pathway that has been observed in vivo. To test this hypothesis, we developed and characterized a trans-well co-culture model of THP1 (human monocytic cell)-derived macrophages and ATC7 murine zona fasciculata adrenocortical cells. We found that co-culture of ATC7 and THP1 cells results in a significant increase in the basal levels of IL-6 mRNA in ATC7 cells, and this effect was potentiated by treatment with LPS. Addition of LPS to co-cultures of ATC7 and THP1 significantly decreased the expression of key adrenal steroidogenic enzymes (including StAR and DAX-1), and this was also found in ATC7 cells treated with pro-inflammatory cytokines. Moreover, 24-h treatment with the synthetic glucocorticoid dexamethasone prevented the effects of LPS stimulation on IL-6, StAR and DAX-1 mRNA in ATC7 cells co-cultured with THP1 cells. Our data suggest that the expression of IL-6 and steroidogenic genes in response to LPS depends on the activation of intra-adrenal immune cells. Moreover, we also show that the effects of LPS can be modulated by glucocorticoids in a time- and dose-dependent manner with potential implications for clinical practice.

Transcriptomic signaling pathways involved in a naturalistic model of inflammation-related depression and its remission

This study aimed at identifying molecular biomarkers of inflammation-related depression in order to improve diagnosis and treatment. For this, we performed whole-genome expression profiling from peripheral blood in a naturalistic model of inflammation-associated major depressive disorder (MDD) represented by comorbid depression in obese patients. We took advantage of the marked reduction of depressive symptoms and inflammation following bariatric surgery to test the robustness of the identified biomarkers. Depression was assessed during a clinical interview using Mini-International Neuropsychiatric Interview and the 10-item, clinician-administered, Montgomery-Asberg Depression Rating Scale. From a cohort of 100 massively obese patients, we selected 33 of them for transcriptomic analysis. Twenty-four of them were again analyzed 4-12 months after bariatric surgery. We conducted differential gene expression analyses before and after surgery in unmedicated MDD and non-depressed obese subjects. We found that TP53 (Tumor Protein 53), GR (Glucocorticoid Receptor), and NFκB (Nuclear Factor kappa B) pathways were the most discriminating pathways associated with inflammation-related MDD. These signaling pathways were processed in composite z-scores of gene expression that were used as biomarkers in regression analyses. Results showed that these transcriptomic biomarkers highly predicted depressive symptom intensity at baseline and their remission after bariatric surgery. While inflammation was present in all patients, GR signaling over-activation was found only in depressed ones where it may further increase inflammatory and apoptosis pathways. In conclusion, using an original model of inflammation-related depression and its remission without antidepressants, we provide molecular predictors of inflammation-related MDD and new insights in the molecular pathways involved.

Depression: Biological markers and treatment

Nowadays depression is considered as a systemic illness with different biological mechanisms involved in its etiology, including inflammatory response, hypothalamic-pituitary-adrenal (HPA) axis dysregulation and neurotransmitter and neurotrophic systems imbalance. Novel "omics" approaches, such as metabolomics and glycomics provide information about altered metabolic pathways and metabolites, as well as disturbances in glycosylation processes affected by or causing the development of depression. The clinical diagnosis of depression continues to be established based on the presence of the specific symptoms, but due to its heterogeneous underlying biological background, that differs according to the disease stage, there is an unmet need for treatment response biomarkers which would facilitate the process of appropriate treatment selection. This paper provides an overview of the role of major stress response system, the HPA axis, and its dysregulation in depression, possible involvement of neurotrophins, especially brain-derived neurotrophic factor, glial cell line-derived neurotrophic factor and insulin-like growth factor-1, in the development of depression. Article discusses how activated inflammation processes and increased cytokine levels, as well as disturbed neurotransmitter systems can contribute to different stages of depression and could specific metabolomic and glycomic species be considered as potential biomarkers of depression. The second part of the paper includes the most recent findings about available medical treatment of depression. The described biological factors impose an optimistic conclusion that they could represent easy obtainable biomarkers potentially predicting more personalized treatment and diagnostic options.

Biomarkers of Major Depressive Disorder: Knowing is Half the Battle

Major depressive disorder (MDD) is a heterogeneous disease which is why there are currently no specific methods to accurately test the severity, endophenotype or therapy response. This lack of progress is partly attributed to the com-plexity and variability of depression, in association with analytical variability of clinical literature and the wide number of theoretically complex biomarkers. The literature accessible, indicates that markers involved in inflammatory, neuro-trophic and metabolic processes and components of neurotransmitters and neuroendocrine systems are rather strong indicators to be considered clinically and can be measured through genetic and epigenetic, transcriptomic and proteomic, metabolomics and neuroimaging assessments. Promising biologic systems/markers found were i.e., growth biomarkers, endocrine markers, oxidant stress markers, proteomic and chronic inflammatory markers, are discussed in this review. Several lines of evidence suggest that a portion of MDD is a dopamine agonist-responsive subtype. This review analyzes concise reports on the pathophysiological biomarkers of MDD and therapeutic reactions via peripheral developmental factors, inflammative cytokines, endocrine factors and metabolic markers. Various literatures also support that endocrine and metabolism changes are associated with MDD. Accumulating evidence suggests that at least a portion of MDD patients show characteristics pathological changes regarding different clinical pathological biomarkers. By this review we sum up all the different biomarkers playing an important role in the detection or treatment of the different patients suffering from MDD. The review also gives an overview of different biomarker's playing a potential role in modulating effect of MDD.

On inflammatory hypothesis of depression: what is the role of IL-6 in the middle of the chaos?

Many patients with major depressive disorder (MDD) are reported to have higher levels of multiple inflammatory cytokines including interleukin 6 (IL-6). Recent studies both pre-clinical and clinical have advocated for the functional role of IL-6 in development of MDD and suggested a great potential for targeting this cytokine to open new avenues in pharmacotherapy of depression. The purpose of the present narrative review was to provide an integrated account of how IL-6 may contribute to development of depression. All peer-reviewed journal articles published before July 2020 for each area discussed were searched by WOS, PubMed, MEDLINE, Scopus, Google Scholar, for original research, review articles, and book chapters. Publications between 1980 and July 2020 were included. Alterations in IL-6 levels, both within the periphery and the brain, most probably contribute to depression symptomatology in numerous ways. As IL-6 acts on multiple differing target tissues throughout the body, dysregulation of this particular cytokine can precipitate a multitude of events relevant to depression and blocking its effects can prevent further escalation of inflammatory responses, and potentially pave the way for opening new avenues in diagnosis, treatment, and prevention of this debilitating disorder.

The Role of Inflammatory Proteins in Anti-Glucocorticoid Therapy for Treatment-Resistant Depression

BACKGROUND

Optimising treatments for patients with treatment-resistant depression (TRD) is key to reducing the burden of this severe illness. The anti-glucocorticoid medication metyrapone has mixed evidence supporting a role as a possible augmentation treatment in TRD. The degree of treatment resistance in depression has been associated prospectively and retrospectively with elevated inflammation, and inflammatory activity may influence responses to antidepressant treatments.

AIMS

To investigate whether levels of pro-inflammatory cytokines are associated with clinical outcomes to metyrapone or placebo.

METHODS

A double-blind RCT randomised patients with TRD to 3 weeks of placebo or metyrapone augmentation to ongoing serotonergic antidepressants. No benefit of metyrapone was reported in the primary analysis. The current study assessed levels of pro-inflammatory proteins interleukin-6 (IL-6), tumour necrosis factor (TNFα), c-reactive protein (CRP) and interleukin-10 (IL-10) before randomisation and after treatment as potential moderators and/or mediators of clinical outcomes.

RESULTS

The three pro-inflammatory proteins (but not IL-10) were elevated in this sample of patients with TRD compared to a non-affected control group. High pre-treatment IL-6 levels predicted a poorer response in the trial overall but did not moderate response to metyrapone versus placebo. Changes in IL-6 indirectly mediated depression outcome, with metyrapone increasing IL-6 levels and IL-6 increase associated with a poorer outcome on depression. Other inflammatory proteins did not mediate or moderate treatment outcomes.

INTERPRETATION

Metyrapone is hypothesised to have a therapeutic effect in depression on the basis of inhibiting the synthesis of cortisol. In this study, metyrapone did not reduce cortisol, possibly due to glucocorticoid system overcompensation). The mediation effect of IL-6 may support this and perhaps help to indicate why the treatment was not effective.

Childhood maltreatment history and attention bias variability in healthy adult women: role of inflammation and the BDNF Val66Met genotype

Childhood maltreatment has been associated with greater attention bias to emotional information, but the findings are controversial. Recently, a novel index of attention bias, i.e., attention bias variability (ABV), has been developed to better capture trauma-related attentional dysfunction. However, ABV in relation to childhood trauma has not been studied. Here, we examined the association of childhood maltreatment history with attention bias/ABV in 128 healthy adult women. Different types of childhood maltreatment were assessed with the Childhood Trauma Questionnaire. Attention bias/ABV was measured by the dot-probe task. Possible mechanisms whereby childhood maltreatment affects attention bias/ABV were also explored, focusing on blood proinflammatory markers and the BDNF Val66Met polymorphism. We observed a significant positive correlation between childhood emotional abuse and ABV (P = 0.002). Serum high-sensitivity tumor necrosis factor-α levels were significantly positively correlated with ABV (P < 0.001), but not with childhood maltreatment. Jonckheere-Terpstra trend test showed a significant tendency toward greater ABV with increasing numbers of the BDNF Met alleles (P = 0.021). A two-way analysis of variance further revealed that the genotype-by-emotional abuse interaction for ABV was significant (P = 0.022); individuals with the Val/Met and Met/Met genotypes exhibited even greater ABV when childhood emotional abuse was present. These results indicate that childhood emotional abuse can have a long-term negative impact on emotional attention control. Increased inflammation may be involved in the mechanism of ABV, possibly independently of childhood maltreatment. The BDNF Met allele may dose-dependently increase ABV by interacting with childhood emotional abuse.

Vortioxetine Prevents Lipopolysaccharide-Induced Memory Impairment Without Inhibiting the Initial Inflammatory Cascade

Vortioxetine is a novel multimodal antidepressant that modulates a wide range of neurotransmitters throughout the brain. Preclinical and clinical studies have shown that vortioxetine exerts positive effects on different cognitive domains and neuroprotective effects. Considering the key role of microglial cells in brain plasticity and cognition, we aimed at investigating the effects of pretreatment with vortioxetine in modulating behavioral and molecular effects induced by an immune challenge: peripheral injection of lipopolysaccharide (LPS). To this purpose, C57BL/6J male mice were first exposed to a 28-day standard diet or vortioxetine-enriched diet, which was followed by an acute immune challenge with LPS. Sickness symptoms and depressive-like behaviors (anhedonia and memory impairment) were tested 6 and 24 h after exposure to LPS, respectively. Moreover, the expressions of markers of immune activation and M1/M2 markers of microglia polarization were measured in the dorsal and ventral parts of the hippocampus. The pretreatment with vortioxetine did not affect both LPS-induced sickness behavior and anhedonia but prevented the deficit in the recognition memory induced by the immune challenge. At the transcriptional level, chronic exposure to vortioxetine did not prevent LPS-induced upregulation of proinflammatory cytokines 6 h after the immune challenge but rather seemed to potentiate the immune response to the challenge also by affecting the levels of expression of markers of microglia M1 phenotype, like cluster of differentiation (CD)14 and CD86, in an area-dependent manner. However, at the same time point, LPS injection significantly increased the expression of the M2 polarization inducer, interleukin 4, only in the hippocampus of animals chronically exposed to vortioxetine. These results demonstrate that a chronic administration of vortioxetine specifically prevents LPS-induced memory impairment, without affecting acute sickness behavior and anhedonia, and suggest that hippocampal microglia may represent a cellular target of this novel antidepressant medication. Moreover, we provide a useful model to further explore the molecular mechanisms specifically underlying cognitive impairments following an immune challenge.

HPA axis regulation and epigenetic programming of immune-related genes in chronically stressed and non-stressed mid-life women

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation has been associated with altered immune function, but the underlying molecular mechanisms are unclear. Epigenetic processes, including DNA methylation, respond to the glucocorticoid end-products of the HPA axis (cortisol in humans) and could be involved in this neuroendocrine-immune crosstalk. Here we examined the extent to which variations in HPA axis regulation are associated with peripheral blood DNA (CpG) methylation changes in 57 chronically stressed caregivers and 67 control women. DNA methylation was determined with the Illumina 450k array for a panel of genes involved in HPA axis and immune function. HPA axis feedback was assessed with the low-dose dexamethasone suppression test (DST), measuring the extent to which cortisol secretion is suppressed by the synthetic glucocorticoid dexamethasone. After multiple testing correction in the entire cohort, higher post-DST cortisol, reflecting blunted HPA axis negative feedback, but not baseline waking cortisol, was associated with lower DNA methylation at eight TNF and two FKBP5 CpG sites. Caregiver group status was associated with lower methylation at two IL6 CpG sites. Since associations were most robust with TNF methylation (32% of the 450k-covered sites), we further examined functionality of this epigenetic signature in cultured peripheral blood mononuclear cells in 33 participants; intriguingly, lower TNF methylation resulted in higher ex vivo TNF mRNA following immune stimulation. Taken together, our findings link chronic stress and HPA axis regulation with epigenetic signatures at immune-related genes, thereby providing novel insights into how aberrant HPA axis function may contribute to heightened inflammation and disease risk.

The Correlation Between Thyroid Function, Frontal Gray Matter, and Executive Function in Patients With Major Depressive Disorder

The present study was aimed to investigate the relationships between serum thyroid hormones (THs), frontal gray matter volume, and executive function in selected patients with major depressive disorder (MDD). One hundred and four MDD patients and seventy-five healthy controls (HCs) were subjected to thyroid-stimulating hormone (TSH), free Triiodothyronine (fT3), free Thyroxine (fT4), and executive function tests and underwent structural magnetic resonance imaging (MRI). Voxel-based morphometry (VBM) analysis was performed to compare group differences in the gray matter for the frontal lobe. Furthermore, mediation analysis was used to investigate whether gray matter volumes of the frontal gyrus mediated the relationship between serum THs and executive function in MDD patients. MDD patients exhibited significant gray matter volume reduction in several brain regions, including the left rectus, right middle frontal cortex, and left middle frontal cortex. Serum TSH levels are positively associated with altered regional gray matter volume patterns within MFG and executive function. Importantly, gray matter in the right MFG was a significant mediator between serum TSH levels and executive function. These findings expand our understanding of how thyroid function affects brain structure changes and executive function in MDD patients.

Removal of vasopressin cells from the paraventricular nucleus of the hypothalamus enhances lipopolysaccharide-induced sickness behaviour in mice

Vasopressin (AVP) cells in the paraventricular nucleus of the hypothalamus (PVN) are activated during sickness and project to multiple nuclei responsible for the anxiety, social and motivated behaviours affected during sickness, suggesting that these cells may play a role in sickness behaviours, typically expressed as reduced mobility, increased anxiety, anhedonia and social withdrawal. In the present study, we selectively ablated AVP neurones in the PVN of male and female mice (Mus musculus) and induced sickness behaviour via injection of bacterial lipopolysaccharide (LPS). We found that PVN AVP ablation increased the effects of LPS, specifically by further decreasing sucrose preference in males and females and decreasing the social preference of males, monitored within 24 hours of LPS injection. These results suggest that PVN AVP contributes to the change in motivated behaviours during sickness and may help promote recovery from infection..

Impaired Brain Energy Metabolism: Involvement in Depression and Hypothyroidism

Although hypothyroidism appears to be an important factor in the pathogenesis of depression, the impact of thyroid hormones on the bioenergetics of the adult brain is still poorly known. Since metabolic changes are reported to be a key player in the manifestation of depressive disorder, we investigated whether there are differences in selected metabolic markers in the frontal cortex and hippocampus of Wistar Kyoto rats (WKY; an animal model of depression) compared to those of control Wistar rats and whether the induction of hypothyroidism by propylthiouracil (PTU) elicits similar effects in these animals or intensifies some parameters in the WKY rats. In our study, we used WKY rats as a model of depression since this strain exhibits lower levels of monoamines in the brain than control rats and exhibits behavioral and hormonal alterations resembling those of depression, including increased reactivity to stress. The findings indicate a decrease in glycolysis intensity in both brain structures in the WKY rats as well as in both strains under hypothyroidism conditions. Furthermore, hypothyroidism disrupted the connection between glycolysis and the Krebs cycle in the frontal cortex and hippocampus in the depression model used in this study. Decreased thyroid hormone action was also shown to attenuate oxidative phosphorylation, and this change was greater in the WKY rats. Our results suggest that both the depression and hypothyroidism models are characterized by similar impairments in brain energy metabolism and mitochondrial function and, additionally, that the co-occurrence of hypothyroidism and depression may exacerbate some of the metabolic changes observed in depression.

Molecular insights into the therapeutic promise of targeting HMGB1 in depression

Depression is a common psychiatric disorder, the exact pathogenesis of which is still elusive. Studies have proposed that immunity disproportion and enhancement in proinflammatory cytokines might be linked with the development of depression. HMGB1 (High-mobility group box (1) protein has obtained more interest as an essential factor in inherent immune reactions and a regulating factor in various inflammation-related diseases. HMGB1 is a ubiquitous chromatin protein and is constitutively expressed in nucleated mammalian cells. HMGB1 is released by glial cells and neurons upon inflammasome activation and act as a pro-inflammatory cytokine. HMGB1 is a late mediator of inflammation and has been indicated as a major mediator in various neuroinflammatory diseases. Microglia, which is the brain immune cell, is stimulated by HMGB1 and released inflammatory mediators and induces chronic neurodegeneration in the CNS (central nervous system). In the current review, we aimed to investigate the role of HMGB1 in the pathogenesis of depression. The studies found that HMGB1 functions as proinflammatory cytokines primarily via binding receptors like RAGE (receptor for advanced glycation end product), TLR2 and TLR4 (Toll-like receptor 2 and 4). Further, HMGB1 added to the preparing impacts of stress-pretreatment and assumed a major function in neurodegenerative conditions through moderating neuroinflammation. Studies demonstrated that neuroinflammation played a major role in the development of depression. The patients of depression generally exhibited an elevated amount of proinflammatory cytokines in the serum, microglia activation and neuronal deficit in the CNS.

A Review of the Pharmacological Properties of Psoralen

Psoralen is the principal bioactive component in the dried fruits of Cullen corylifolium (L.) Medik (syn. Psoralea corylifolia L), termed "Buguzhi" in traditional Chinese medicine (TCM). Recent studies have demonstrated that psoralen displays multiple bioactive properties, beneficial for the treatment of osteoporosis, tumors, viruses, bacteria, and inflammation. The present review focuses on the research evidence relating to the properties of psoralen gathered over recent years. Firstly, multiple studies have demonstrated that psoralen exerts strong anti-osteoporotic effects via regulation of osteoblast/osteoclast/chondrocyte differentiation or activation due to the participation in multiple molecular mechanisms of the wnt/β-catenin, bone morphogenetic protein (BMP), inositol-requiring enzyme 1 (IRE1)/apoptosis signaling kinase 1 (ASK1)/c-jun N-terminal kinase (JNK) and the Protein Kinase B(AKT)/activator protein-1 (AP-1) axis, and the expression of miR-488, peroxisome proliferators-activated receptor-gamma (PPARγ), and matrix metalloproteinases (MMPs). In addition, the antitumor properties of psoralen are associated with the induction of ER stress-related cell death via enhancement of PERK: Pancreatic Endoplasmic Reticulum Kinase (PERK)/activating transcription factor (ATF), 78kD glucose-regulated protein (GRP78)/C/EBP homologous protein (CHOP), and 94kD glucose-regulated protein (GRP94)/CHOP signaling, and inhibition of P-glycoprotein (P-gp) or ATPase that overcomes multidrug resistance. Furthermore, multiple articles have shown that the antibacterial, anti-inflammatory and neuroprotective effects of psoralen are a result of its interaction with viral polymerase (Pol), destroying the formation of biofilm, and regulating the activation of tumor necrosis factor alpha (TNF-α), transforming growth factor beta (TGF-β), interleukin 4/5/6/8/12/13 (IL-4/5/6/8/12/13), GATA-3, acetylcholinesterase (AChE), and the hypothalamic-pituitary-adrenal (HPA) axis. Finally, the toxic effects and mechanisms of action of psoralen have also been reviewed.

Targeting Inflammatory-Mitochondrial Response in Major Depression: Current Evidence and Further Challenges

The prevalence of psychiatric disorders has increased in recent years. Among existing mental disorders, major depressive disorder (MDD) has emerged as one of the leading causes of disability worldwide, affecting individuals throughout their lives. Currently, MDD affects 15% of adults in the Americas. Over the past 50 years, pharmacotherapy, psychotherapy, and brain stimulation have been used to treat MDD. The most common approach is still pharmacotherapy; however, studies show that about 40% of patients are refractory to existing treatments. Although the monoamine hypothesis has been widely accepted as a molecular mechanism to explain the etiology of depression, its relationship with other biochemical phenomena remains only partially understood. This is the case of the link between MDD and inflammation, mitochondrial dysfunction, and oxidative stress. Studies have found that depressive patients usually exhibit altered inflammatory markers, mitochondrial membrane depolarization, oxidized mitochondrial DNA, and thus high levels of both central and peripheral reactive oxygen species (ROS). The effect of antidepressants on these events remains unclear. Nevertheless, the effects of ROS on the brain are well known, including lipid peroxidation of neuronal membranes, accumulation of peroxidation products in neurons, protein and DNA damage, reduced antioxidant defenses, apoptosis induction, and neuroinflammation. Antioxidants such as ascorbic acid, tocopherols, and coenzyme Q have shown promise in some depressive patients, but without consensus on their efficacy. Hence, this paper provides a review of MDD and its association with inflammation, mitochondrial dysfunction, and oxidative stress and is aimed at thoroughly discussing the putative links between these events, which may contribute to the design and development of new therapeutic approaches for patients.

Quercetin Alleviates LPS-Induced Depression-Like Behavior in Rats via Regulating BDNF-Related Imbalance of Copine 6 and TREM1/2 in the Hippocampus and PFC

Quercetin is a polyphenol with multiple biological activities, and results of our preliminary study showed that it could shorten the immobility time of mice in the forced swimming test and tail suspending test. The aim of this study was to investigate its effects on the behavioral performance of lipopolysaccharide (LPS)-challenged rats and explore the potential mechanism. The results showed that intragastrical administration of quercetin (40 mg/kg) could improve the bodyweight gain of LPS-challenged rats, increase the saccharin preference index in the saccharin preference test and the novel arm preference index in the Y-maze, and decrease the immobility time in the FST. However, it showed no significant effect on the performance of LPS-challenged rats in the Morris water maze and the plasma concentrations of nesfatin-1, C-reactive protein (CRP), and IL-6. Results of western blot showed that the expression levels of BDNF, Copine 6, p-TrkB, and the triggering receptors expressed on myeloid cells (TREM) 1 were decreased in both the hippocampus and the prefrontal cortex (PFC) of LPS-challenged rats, while the expression of TREM2 was increased. The protein expression of synapsin-1 was decreased in the hippocampus without significant changes in the PFC. These imbalance protein expressions could be balanced by treatment with quercetin. The results suggested that quercetin could alleviate LPS-induced depression-like behaviors and impairment of learning and memory in rats, the mechanism of which might be involved with regulating the BDNF-related imbalance expression of Copine 6 and TREM1/2 in the hippocampus and the PFC.

Zinc Deficiency During Pregnancy Leads to Altered Microbiome and Elevated Inflammatory Markers in Mice

Zinc is an essential trace metal for bacteria of the intestinal flora. Approximately 20% of dietary zinc – intake is used by intestinal bacteria. The microbiome has recently been described as an important factor for healthy brain function via so-called gut-brain interactions. Similarly, zinc deficiency has been associated with neurological problems such as depression, mental lethargy and cognitive impairments in humans and animal models. However, the underlying pathomechanisms are currently not well understood and a link between zinc deficiency and altered microbiota composition has not been studied. Especially during pregnancy, women may be prone to low zinc status. Thus, here, we investigate whether zinc deficiency alters gut-brain interaction in pregnant mice by triggering changes in the microbiome. To that end, pregnant mice were fed different diets being zinc-adequate, deficient in zinc, or adequate in zinc but high in zinc uptake antagonists for 8 weeks. Our results show that acute zinc-deficient pregnant mice and pregnant mice on a diet high in zinc uptake antagonists have an altered composition of gastro-intestinal (GI) microbiota. These changes were accompanied by alterations in markers for GI permeability. Within the brain, we found signs of neuroinflammation. Interestingly, microbiota composition, gut pathology, and inflammatory cytokine levels were partially rescued upon supplementation of mice with zinc amino-acid conjugates (ZnAA). We conclude that zinc deficiency may contribute to abnormal gut-brain signaling by altering gut physiology, microbiota composition and triggering an increase of inflammatory markers.

Adult neurogenesis in the mammalian dentate gyrus

Earlier observations in neuroscience suggested that no new neurons form in the mature central nervous system. Evidence now indicates that new neurons do form in the adult mammalian brain. Two regions of the mature mammalian brain generate new neurons: (a) the border of the lateral ventricles of the brain (subventricular zone) and (b) the subgranular zone (SGZ) of the dentate gyrus of the hippocampus. This review focuses only on new neuron formation in the dentate gyrus of the hippocampus. During normal prenatal and early postnatal development, neural stem cells (NSCs) give rise to differentiated neurons. NSCs persist in the dentate gyrus SGZ, undergoing cell division, with some daughter cells differentiating into functional neurons that participate in learning and memory and general cognition through integration into pre-existing neural networks. Axons, which emanate from neurons in the entorhinal cortex, synapse with dendrites of the granule cells (small neurons) of the dentate gyrus. Axons from granule cells synapse with pyramidal cells in the hippocampal CA3 region, which send axons to synapse with CA1 hippocampal pyramidal cells that send their axons out of the hippocampus proper. Adult neurogenesis includes proliferation, differentiation, migration, the death of some newly formed cells and final integration of surviving cells into neural networks. We summarise these processes in adult mammalian hippocampal neurogenesis and discuss the roles of major signalling molecules that influence neurogenesis, including neurotransmitters and some hormones. The recent controversy raised concerning whether or not adult neurogenesis occurs in humans also is discussed.

BDNF prevents central oxidative damage in a chronic unpredictable mild stress model: The possible role of PRDX-1 in anhedonic behavior

Prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis and sustained increase of glucocorticoids have been evidenced in major depression and are related to changes involving neurotrophins and markers of oxidative stress in response to inflammation. This study aimed to evaluate central measures of brain-derived neurotrophic factor (BDNF), oxidative damage and total antioxidant capacity in rats submitted to chronic unpredictable mild stress (CUMS), as well as to investigate the relationship between BDNF levels and differentially processes. For this purpose, male Wistar rats were submitted to CUMS for six weeks. Based on a sucrose preference test (SPT), the animals were divided into anhedonic or non-anhedonic clusters. Afterwards, forced swim test (FST) and open field test (OFT) were performed, and the animals were euthanized. Brain tissue was collected, followed by quantification of oxidative damage, total antioxidant capacity and BDNF levels. Anhedonic behavior was evidenced in stress-susceptible animals through decreased sucrose preference. No differences were found in FST or OFT results. We observed increased BDNF levels in the hippocampus (HPC) of animals exposed to the CUMS protocol, accompanied by decreased total antioxidant capacity, despite the absence of oxidative damage to lipids and proteins. Moreover, we used a bioinformatics approach to identify proteins involved in oxidative stress and inflammation pathways, which were differentially expressed in anhedonic animals from other studies with similar experimental protocol. expressed proteins (DEP) involved in oxidative stress and inflammatory biological Anhedonic behavior was associated with peroxiredoxin-1 (PRDX-1) up-regulation and down-regulation of proteins involved with apoptotic and inflammation signaling (RELA, ASK-1 and TAK-1) in the HPC. Taken together, these data suggest that BDNF and PRDX-1 might be involved in initial stress response, playing a compensatory role by preventing oxidative damage to lipids and proteins through the modulation of antioxidant defense after CUMS in anhedonic animals.

The Role of Inflammation in Depression and Fatigue

Depression and fatigue are conditions responsible for heavy global societal burden, especially in patients already suffering from chronic diseases. These symptoms have been identified by those affected as some of the most disabling symptoms which affect the quality of life and productivity of the individual. While many factors play a role in the development of depression and fatigue, both have been associated with increased inflammatory activation of the immune system affecting both the periphery and the central nervous system (CNS). This is further supported by the well-described association between diseases that involve immune activation and these symptoms in autoimmune disorders, such as multiple sclerosis and immune system activation in response to infections, like sepsis. Treatments for depression also support this immunopsychiatric link. Antidepressants have been shown to decrease inflammation, while higher levels of baseline inflammation predict lower treatment efficacy for most treatments. Those patients with higher initial immune activation may on the other hand be more responsive to treatments targeting immune pathways, which have been found to be effective in treating depression and fatigue in some cases. These results show strong support for the hypothesis that depression and fatigue are associated with an increased activation of the immune system which may serve as a valid target for treatment. Further studies should focus on the pathways involved in these symptoms and the development of treatments that target those pathways will help us to better understand these conditions and devise more targeted treatments.

Chronic Isolation Stress Affects Subsequent Crowding Stress-Induced Brain Nitric Oxide Synthase (NOS) Isoforms and Hypothalamic-Pituitary-Adrenal (HPA) Axis Responses

The nitric oxide (NO) pathway in the brain is involved in response to psychosocial stressors. The aim of this study was to elucidate the role of nNOS and iNOS in the prefrontal cortex (PFC), hippocampus (HIP), and hypothalamus (HYPO) during social isolation stress (IS), social crowding stress (CS), and a combined IS + CS. In the PFC, 3 days of CS increased iNOS but not nNOS protein level. In the HIP and HYPO, the levels of nNOS and iNOS significantly increased after 3 days of CS. In the PFC, IS alone (11 days) enhanced iNOS protein level following 3 days of CS and increased nNOS level in the HIP and HYPO after 14 days of CS. By contrast, in the HIP, IS abolished the subsequent CS-induced increase in nNOS in the HIP and strongly elevated iNOS level after 7 days of CS. In the HYPO, prior IS inhibited nNOS protein level induced by subsequent CS for 3 days, but increased nNOS protein level after longer exposure times to CS. Isolation stress strongly upregulated plasma interleukin-1β (IL-1β) and adrenocorticotropic hormone (ACTH) levels while corticosterone (CORT) level declined. We show that the modulatory action of the NO pathway and ACTH/CORT adaptation to chronic social isolation stress is dependent on the brain structure and nature and duration of the stressor. Our results indicate that isolation is a robust natural stressor in social animals; it enhances the NO pathway in the PFC and abolishes subsequent social CS-induced NOS responses in the HIP and HYPO.