Neuroimmunomodulation in Major Depressive Disorder: Focus on Caspase 1, Inducible Nitric Oxide Synthase, and Interferon-Gamma

T cell-mediated skin-brain axis: Bridging the gap between psoriasis and psychiatric comorbidities

Psoriasis, a chronic inflammatory skin condition, is often accompanied by psychiatric comorbidities such as anxiety, depression, suicidal ideation, and other mental disorders. Psychological disorders may also play a role in the development and progression of psoriasis. The intricate interplay between the skin diseases and the psychiatric comorbidities is mediated by the 'skin-brain axis'. Understanding the mechanisms underlying psoriasis and psychiatric comorbidities can help improve the efficacy of treatment by breaking the vicious cycle of diseases. T cells and related cytokines play a key role in the pathogenesis of psoriasis and psychiatric diseases, and are crucial components of the 'skin-brain axis'. Apart from damaging the blood-brain barrier (BBB) directly, T cells and secreted cytokines could interact with the hypothalamic-pituitary-adrenal axis (HPA axis) and the sympathetic nervous system (SNS) to exacerbate skin diseases or mental disorders. However, few reviews have systematically summarized the roles and mechanisms of T cells in the interaction between psoriasis and psychiatric comorbidities. In this review, we discussed several key T cells and their roles in the 'skin-brain axis', with a focus on the mechanisms underlying the interplay between psoriasis and mental commodities, to provide data that might help develop effective strategies for the treatment of both psoriasis and psychiatric comorbidities.

The effect of Vortioxetine on the NLRP3 pathway and microglial activity in the prefrontal cortex in an experimental model of depression

BACKGROUND

Increasing evidence suggests that early life stress (ELS) and neuroinflammation are associated with the pathophysiology of depression. The purpose of this study was to determine the effects of Vortioxetine (VOR), a novel antidepressant, on ELS-induced behavioral changes and neuroinflammation.

METHOD

Wistar Albino 4-week-old male rats were divided into four groups: control; chronic unpredictable stress (CUMS), VOR, CUMS + VOR. Neurobehavioral assessment was performed on the first, 21st, and 42nd days. RT-PCR was used to detect the expression of P2X7, NLRP3, IL1β, IL18 in the prefrontal cortex. To assess the microglial activities of the prefrontal cortex, immunohistochemically stained CD68, and leukocyte common antigen (LCA) preparations were scanned with Manual WSI software, Basler camera, and scored.

RESULT AND DISCUSSION

Exposure to CUMS was associated with depression and anxiety-like behaviors, and administration of VOR led to improvement in these behaviors. NLRP3, IL-1β, and IL-18 were shown to be upregulated in the prefrontal cortex of CUMS rats, while their high expression was inhibited by VOR treatment. CD68 and LCA expressions were significantly higher in the CUMS group compared to the other groups.

CONCLUSION

According to these results, it may be considered that NLRP3 inflammasome-associated neuroinflammatory response and microglial activation may play a role in the etiopathogenesis of ELS.

Blood RNA-sequencing analysis in acrylamide-induced neurotoxicity and depressive symptoms in rats

Acrylamide (ACR) is a by-product of the Maillard reaction, which occurs when food reacts at high temperatures. Occupational exposure is a risk factor for chronic ACR toxicity. ACR may cause neurotoxicity and depressive symptoms with high concentration in the blood; however, the underlying mechanism remains unknown. We showed the rats developed neurotoxic symptoms after being fed with ACR for 28 days, such as reduced activity and hind limb muscle weakness. We investigated whether ACR exposure causes gene expression differences by blood RNA sequencing and analyzed the differential expression of depressive symptoms-associated genes. The result indicated that IFN-γ the key regulator of neurotoxicity and depressive symptoms was induced by ACR. ACR induced the ubiquitin-mediated proteolysis pathway and JAK/STAT pathways gene expression. ACR upregulated the expression of IFN-γ, inducing neuroinflammation and neurotoxicity. ACR also upregulated the expression of JAK2, STAT1, PI3K, AKT, IκBα, UBE2D4, NF-κB, TNF-α, and iNOS in rat brain tissues and Neuro-2a cells. Thus, IFN-γ induction by ACR may induce depressive symptoms, and the ubiquitin-mediated proteolysis pathway and JAK/STAT pathways may involve in ACR neurotoxicity and depressive symptoms.

The antidepressant-like effect of doxycycline is associated with decreased nitric oxide metabolite levels in the prefrontal cortex

Doxycycline is an antibiotic that has shown neuroprotective, anti-inflammatory, and antidepressant-like effects. Low doses of doxycycline revert the behavioral and neuroinflammatory responses induced by lipopolysaccharide treatment in a mice model of depression. However, the molecular mechanisms involved in the antidepressant action of doxycycline are not yet understood. Doxycycline inhibits the synthesis of nitric oxide (NO), which increases after stress exposure. Inducible NO synthase (iNOS) inhibition also causes antidepressant-like effects in animal models sensitive to antidepressant-like effects such as the forced swimming test (FST). However, no direct study has yet investigated if the antidepressant-like effects of doxycycline could involve changes in NO-mediated neurotransmission. Therefore, this study aimed at investigating: i) the behavioral effects induced by doxycycline alone or in association with ineffective doses of a NO donor (sodium nitroprusside, SNP) or an iNOS inhibitor (1400 W) in mice subjected to the FST; and ii) doxycycline effects in NO metabolite levels in the prefrontal cortex and hippocampus these animals. Male mice (8 weeks) received i.p. injection of saline or doxycycline (10, 30, and 50 mg/kg), alone or combined with SNP (0.1, 0.5, and 1 mg/kg) or 1400 W (1, 3, and 10 µg/kg), and 30 min later were submitted to the FST. Animals were sacrificed immediately after, and NO metabolites nitrate/nitrite (NOx) were measured in the prefrontal cortex and hippocampus. Doxycycline (50 mg/kg) reduced both the immobility time in the FST and NOx levels in the prefrontal cortex of mice compared to the saline group. The antidepressant-like effect of doxycycline in the FST was prevented by SNP (1 mg/kg) pretreatment. Additionally, sub-effective doses of doxycycline (30 mg/kg) associated with 1400 W (1 µg/kg) induced an antidepressant-like effect in the FST. Altogether, our data suggest that the reducing NO levels in the prefrontal cortex through inhibition of iNOS could be related to acute doxycycline treatment resulting in rapid antidepressant-like effects in mice.

Progress of plant polyphenol extracts in treating depression by anti-neuroinflammatory mechanism: A review

There is a growing body of evidence supporting the involvement of central nervous system inflammation in the pathophysiology of depression. Polyphenols are a diverse group of compounds known for their antioxidative and anti-inflammatory properties. They offer a promising and effective supplementary approach to alleviating neuropsychiatric symptoms associated with inflammation-induced depression. This paper provides a summary of the potential anti-neuroinflammatory mechanisms of plant polyphenol extracts against depression. This includes direct interference with inflammatory regulators and inhibition of the expression of pro-inflammatory cytokines. Additionally, it covers downregulating the expression of pro-inflammatory cytokines by altering protein kinases or affecting the activity of the signaling pathways that they activate. These pathways interfere with the conduction of signaling molecules, resulting in the destruction and reduced synthesis of all inflammatory mediators and cytokines. This reduces the apoptosis of neurons and plays a neuroprotective role. This paper provides a theoretical basis for the clinical application of plant polyphenols.

Exploring the role of inflammation in major depressive disorder: beyond the monoamine hypothesis

Major depressive disorder affects approximately 8.4% of the United States population. The World Health Organization estimates that 280 million adults worldwide are suffering from depression. They have estimated that by 2030 it will be the second most serious condition. Current treatment relies on the monoamine hypothesis, however, one-third of patients with MDD do not respond to monoamine-based antidepressants. For years, it was hypothesized that the primary pathway of MDD involved serotonin as the main neurotransmitter. The monoamine hypothesis, a widely accepted theory, sought to explain the biological basis of MDD as being caused by the depletion of monoamine neurotransmitters, namely norepinephrine and serotonin. This hypothesis regarding monoamines as the pathophysiological basis of MDD led to the design and widespread use of selective serotonin reuptake inhibitors. However, given that only one-third of patients improve with SSRI it is reasonable to infer that the pathway involved is more complex than once hypothesized and there are more neurotransmitters, receptors, and molecules involved. The monoamine hypothesis does not explain why there is a delay in the onset of effect and action of SSRIs. Several studies have demonstrated that chronic stress is a risk factor for the development of MDD. Thus the monoamine hypothesis alone is not enough to fully account for the pathophysiology of MDD highlighting the need for further research involving the pathways of MDD. In this paper, we review the role of inflammation and cytokines on MDD and discuss other pathways involved in the development and persistence of depressive symptoms.

In silico evaluation of the role of lisdexamfetamine on attention-deficit/hyperactivity disorder common psychiatric comorbidities: mechanistic insights on binge eating disorder and depression

Attention-deficit/hyperactivity disorder (ADHD) is a psychiatric condition well recognized in the pediatric population that can persist into adulthood. The vast majority of patients with ADHD present psychiatric comorbidities that have been suggested to share, to some extent, the pathophysiological mechanism of ADHD. Lisdexamfetamine (LDX) is a stimulant prodrug approved for treating ADHD and, in the US, also for binge eating disorder (BED). Herein, we evaluated, through a systems biology-based in silico method, the efficacy of a virtual model of LDX (vLDX) as ADHD treatment to improve five common ADHD psychiatric comorbidities in adults and children, and we explored the molecular mechanisms behind LDX's predicted efficacy. After the molecular characterization of vLDX and the comorbidities (anxiety, BED, bipolar disorder, depression, and tics disorder), we created a protein-protein interaction human network to which we applied artificial neural networks (ANN) algorithms. We also generated virtual populations of adults and children-adolescents totaling 2,600 individuals and obtained the predicted protein activity from Therapeutic Performance Mapping System models. The latter showed that ADHD molecular description shared 53% of its protein effectors with at least one studied psychiatric comorbidity. According to the ANN analysis, proteins targeted by vLDX are predicted to have a high probability of being related to BED and depression. In BED, vLDX was modeled to act upon neurotransmission and neuroplasticity regulators, and, in depression, vLDX regulated the hypothalamic-pituitary-adrenal axis, neuroinflammation, oxidative stress, and glutamatergic excitotoxicity. In conclusion, our modeling results, despite their limitations and although requiring in vitro or in vivo validation, could supplement the design of preclinical and potentially clinical studies that investigate treatment for patients with ADHD with psychiatric comorbidities, especially from a molecular point of view.

Caspase-1 affects chronic restraint stress-induced depression-like behaviors by modifying GABAergic dysfunction in the hippocampus

Major depression disorder (MDD) is one of the most common psychiatric disorders and one of the leading causes of disability in worldwide. Both inflammation and GABAergic dysfunction have been implicated in the pathophysiology of MDD. Caspase-1, a classic inflammatory caspase, regulates AMPARs-mediated glutamatergic neurotransmission. However, the role of caspase-1 in chronic stress-induced GABAergic dysfunction remains largely unknown. In this study, we found that serum and hippocampal caspase-1-IL-1β levels increased significantly in chronic restraint stress (CRS) mice, and a significant negative correlation occurred between levels of caspase-1 and depression-like behaviors. Furthermore, CRS significantly decreased GAD67 mRNA levels and GABAergic neurotransmission accompanied by the reduction of GABA concentration, reduced the amplitude and frequency of mIPSCs inhibitory postsynaptic currents (mIPSCs) and the decreased surface expression of GABA_ARs γ2 subunit in the hippocampus. Genetic deficiency of caspase-1 not only blocked CRS-induced depression-like behaviors, but also alleviated CRS-induced impairments in GABAergic neurotransmission. Finally, reexpression of caspase-1 in the hippocampus of Caspase-1^-/- mice increased susceptibility to stress-induced anxiety- and depression-like behaviors through inhibiting GAD67 expression and GABA_ARs-mediated synaptic transmission. Our study suggests that CRS dysregulates GABAergic neurotransmission via increasing the levels of caspase-1-mediated neuroinflammation in the hippocampus, ultimately leading to depression-like behaviors. This work illustrates that targeting caspase-1 may provide potential therapeutic benefits to stress-related GABAergic dysfunction in the pathogenesis of MDD.

From the immune system to mood disorders especially induced by Toxoplasma gondii: CD4+ T cell as a bridge

Toxoplasma gondii (T. gondii), a ubiquitous and obligatory intracellular protozoa, not only alters peripheral immune status, but crosses the blood-brain barrier to trigger brain parenchymal injury and central neuroinflammation to establish latent cerebral infection in humans and other vertebrates. Recent findings underscore the strong correlation between alterations in the peripheral and central immune environment and mood disorders. Th17 and Th1 cells are important pro-inflammatory cells that can drive the pathology of mood disorders by promoting neuroinflammation. As opposed to Th17 and Th1, regulatory T cells have inhibitory inflammatory and neuroprotective functions that can ameliorate mood disorders. T. gondii induces neuroinflammation, which can be mediated by CD4+ T cells (such as Tregs, Th17, Th1, and Th2). Though the pathophysiology and treatment of mood disorder have been currently studied, emerging evidence points to unique role of CD4+ T cells in mood disorder, especially those caused by T. gondii infection. In this review, we explore some recent studies that extend our understanding of the relationship between mood disorders and T. gondii.

Effects of repeated lysergic acid diethylamide (LSD) on the mouse brain endocannabinoidome and gut microbiome

BACKGROUND AND PURPOSE

Psychedelics elicit prosocial, antidepressant and anxiolytic effects via neuroplasticity, neurotransmission and neuro-immunomodulatory mechanisms. Whether psychedelics affect the brain endocannabinoid system and its extended version, the endocannabinoidome (eCBome) or the gut microbiome, remains unknown.

EXPERIMENTAL APPROACH

Adult C57BL/6N male mice were administered lysergic acid diethylamide (LSD) or saline for 7 days. Sociability was assessed in the direct social interaction and three chambers tests. Prefrontal cortex and hippocampal endocannabinoids, endocannabinoid-like mediators and metabolites were quantified via high-pressure liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Neurotransmitter levels were assessed via HPLC-UV/fluorescence. Gut microbiome changes were investigated by 16S ribosomal DNA sequencing.

KEY RESULTS

LSD increased social preference and novelty and decreased hippocampal levels of the N-acylethanolamines N-linoleoylethanolamine (LEA), anandamide (N-arachidonoylethanolamine) and N-docosahexaenoylethanolamine (DHEA); the monoacylglycerol 1/2-docosahexaenoylglycerol (1/2-DHG); the prostaglandins D₂ (PGD₂ ) and F2α (PGF_2α ); thromboxane 2 and kynurenine. Prefrontal eCBome mediator and metabolite levels were less affected by the treatment. LSD decreased Shannon alpha diversity of the gut microbiota, prevented the decrease in the Firmicutes:Bacteroidetes ratio observed in saline-treated mice and altered the relative abundance of the bacterial taxa Bifidobacterium, Ileibacterium, Dubosiella and Rikenellaceae RC9.

CONCLUSIONS AND IMPLICATIONS

The prosocial effects elicited by repeated LSD administration are accompanied by alterations of hippocampal eCBome and kynurenine levels, and the composition of the gut microbiota. Modulation of the hippocampal eCBome and kynurenine pathway might represent a mechanism by which psychedelic compounds elicit prosocial effects and affect the gut microbiome.

Effect of botulinum toxin type A on non-motor symptoms and quality of life in Meige syndrome

Background

It has been shown in previous studies that botulinum toxin type A (BTX-A) can effectively relieve the motor symptoms of Meige syndrome. However, its effect on non-motor symptoms (NMS) and quality of life (QoL) has not been comprehensively studied. This study aimed to explore the effects of BTX-A on NMS and QoL and to clarify the relationship between changes in motor symptoms, NMS, and QoL after BTX-A.

Methods

Seventy-five patients were recruited for the study. All patients were assessed by a series of clinical assessments before, one, and 3 months after BTX-A treatment. Dystonic symptoms, psychiatric disturbances, sleep disorders, and QoL were evaluated.

Results

After 1 and 3 months of BTX-A treatment, the scores of motor symptoms, anxiety, and depression were significantly decreased (P < 0.05). Except for general health, the scores of the other 36-item short-form health survey QoL subitems were significantly improved after BTX-A (P < 0.05). After 1 month of treatment, the changes in anxiety and depression were not correlated with changes in motor symptoms (P > 0.05). Still, they were negatively correlated with changes in physical functioning, role-physical and mental component summary QoL (P < 0.05).

Conclusions

BTX-A effectively improved motor symptoms, anxiety, depression, and QoL. Anxiety and depression improvement did not correlate with motor symptom changes after BTX-A, and QoL improvements were strongly associated with psychiatric disturbances.

Anti-Inflammatory, Antioxidant, and Neuroprotective Effects of Polyphenols-Polyphenols as an Element of Diet Therapy in Depressive Disorders

Depressive disorders can affect up to 350 million people worldwide, and in developed countries, the percentage of patients with depressive disorders may be as high as 10%. During depression, activation of pro-inflammatory pathways, mitochondrial dysfunction, increased markers of oxidative stress, and a reduction in the antioxidant effectiveness of the body are observed. It is estimated that approximately 30% of depressed patients do not respond to traditional pharmacological treatments. However, more and more attention is being paid to the influence of active ingredients in food on the course and risk of neurological disorders, including depression. The possibility of using foods containing polyphenols as an element of diet therapy in depression was analyzed in the review. The possibility of whether the consumption of products such as polyphenols could alleviate the course of depression or prevent the progression of it was also considered. Results from preclinical studies demonstrate the potential of phenolic compounds have the potential to reduce depressive behaviors by regulating factors related to oxidative stress, neuroinflammation, and modulation of the intestinal microbiota.

Possible role of the NLRP3 inflammasome and the gut-brain axis in multiple sclerosis-related depression

Multiple sclerosis (MS) is an autoimmune and demyelinating disease of the central nervous system that results from complex interactions between genetic and environmental determinants. Patients with MS exhibit a high risk of depression, however, the exact pathomechanisms remain largely unknown. It is becoming widely accepted that the gut-brain axis (GBA) disorders may exert an influence on neuroinflammation and psychiatric symptoms, including so-called MS-related depression. The element suggested as a bridge between intestinal disorders, depression, and MS is an inflammatory response with the central role of the NLR family pyrin domain containing 3 (NLRP3) inflammasome. The pro-inflammatory activity of effector cytokines of the NLRP3 inflammasome forms the hypothesis that it is actively involved in the development of inflammatory and autoimmune diseases. Despite extensive reviews considering the possible origins of MS-related depression, its complex pathophysiology prevents any easy determination of its underlying mechanisms. This paper aims to discuss molecular mechanisms related to the GBA axis that can mediate dysbiosis, intestinal barrier dysfunction, disruption of blood-brain barrier integrity, neuroinflammation, and subsequent manifestation of MS-related major depressive disorder.

How Oxidative Stress Induces Depression?

Depression increasingly affects a wide range and a large number of people worldwide, both physically and psychologically, which makes it a social problem requiring prompt attention and management. Accumulating clinical and animal studies have provided us with substantial insights of disease pathogenesis, especially central monoamine deficiency, which considerably promotes antidepressant research and clinical treatment. The first-line antidepressants mainly target the monoamine system, whose drawbacks mainly include slow action and treatment resistant. The novel antidepressant esketamine, targeting on central glutamatergic system, rapidly and robustly alleviates depression (including treatment-resistant depression), whose efficiency is shadowed by potential addictive and psychotomimetic side effects. Thus, exploring novel depression pathogenesis is necessary, for seeking more safe and effective therapeutic methods. Emerging evidence has revealed vital involvement of oxidative stress (OS) in depression, which inspires us to pursue antioxidant pathway for depression prevention and treatment. Fully uncovering the underlying mechanisms of OS-induced depression is the first step towards the avenue, thus we summarize and expound possible downstream pathways of OS, including mitochondrial impairment and related ATP deficiency, neuroinflammation, central glutamate excitotoxicity, brain-derived neurotrophic factor/tyrosine receptor kinase B dysfunction and serotonin deficiency, the microbiota-gut-brain axis disturbance and hypothalamic-pituitary-adrenocortical axis dysregulation. We also elaborate on the intricate interactions between the multiple aspects, and molecular mechanisms mediating the interplay. Through reviewing the related research progress in the field, we hope to depict an integral overview of how OS induces depression, in order to provide fresh ideas and novel targets for the final goal of efficient treatment of the disease.

Interferon γ: a master cytokine in microglia-mediated neural network dysfunction and neurodegeneration

Traditionally, lymphocytic interferon γ (IFN-γ) was considered to be a simple 'booster' of proinflammatory responses by microglia (brain-resident macrophages) during bacterial or viral infection. Recent slice culture (in situ) and in vivo studies suggest, however, that IFN-γ has a unique role in microglial activation. Priming by IFN-γ results in proliferation (microgliosis), enhanced synapse elimination, and moderate nitric oxide release sufficient to impair synaptic transmission, gamma rhythm activity, and cognitive functions. Moreover, IFN-γ is pivotal for driving Toll-like receptor (TLR)-activated microglia into neurotoxic phenotypes that induce energetic and oxidative stress, severe network dysfunction, and neuronal death. Pharmacological targeting of activated microglia could be beneficial during elevated IFN-γ levels, blood-brain barrier leakage, and parenchymal T lymphocyte infiltration associated with, for instance, encephalitis, multiple sclerosis, and Alzheimer's disease.

Depression in patients with inflammatory bowel disease is associated with increased risk of dementia and Parkinson's disease: A nationwide, population-based study

Background

Inflammatory bowel disease (IBD) may be associated with depression which is considered an important cause of dementia and Parkinson's disease (PD). In the present study, the effects of depression on the development of dementia and/or PD in patients with IBD were evaluated.

Materials and methods

A nationwide population-based cohort study was conducted using claims data from the Health Insurance Review and Assessment Service in Korea. The incidence of dementia and PD were analyzed based on the presence of depression in patients with IBD.

Results

During a mean follow-up of 8 years, IBD patients with depression experienced dementia (6.7 vs. 2.0%; p < 0.001) and PD (1.1 vs. 0.3%; p < 0.001) significantly more than IBD patients without depression. Compared with IBD patients without depression, the risk of developing dementia was significantly higher in IBD patients with depression [adjusted hazard ratio (aHR) for IBD, Crohn's disease (CD), and ulcerative colitis (UC), 2.03, p < 0.001; 1.68, p = 0.033; 2.13, p < 0.001, respectively]. Compared with IBD patients without depression, the risk of developing PD was significantly higher in IBD patients with depression (aHR for IBD, CD, and UC, 2.54, p < 0.001; 1.93, p = 0.470; 2.75, p < 0.001, respectively). The cumulative incidence of dementia and PD in IBD patients with depression was significantly higher than in IBD patients without depression and showed a steady increase after a diagnosis of depression.

Conclusion

The risk of dementia and/or PD increased after a diagnosis of depression in patients with IBD.

Effects of Two Distinct Psychoactive Microbes, Lacticaseibacillus rhamnosus JB-1 and Limosilactobacillus reuteri 6475, on Circulating and Hippocampal mRNA in Male Mice

Discovery of the microbiota-gut–brain axis has led to proposed microbe-based therapeutic strategies in mental health, including the use of mood-altering bacterial species, termed psychobiotics. However, we still have limited understanding of the key signaling pathways engaged by specific organisms in modulating brain function, and evidence suggests that bacteria with broadly similar neuroactive and immunomodulatory actions can drive different behavioral outcomes. We sought to identify pathways distinguishing two psychoactive bacterial strains that seemingly engage similar gut–brain signaling pathways but have distinct effects on behaviour. We used RNAseq to identify mRNAs differentially expressed in the blood and hippocampus of mice following Lacticaseibacillus rhamnosus JB-1, and Limosilactobacillus reuteri 6475 treatment and performed Gene Set Enrichment Analysis (GSEA) to identify enrichment in pathway activity. L. rhamnosus, but not L. reuteri treatment altered several pathways in the blood and hippocampus, and the rhamnosus could be clearly distinguished based on mRNA profile. In particular, L. rhamnosus treatment modulated the activity of interferon signaling, JAK/STAT, and TNF-alpha via NF-KB pathways. Our results highlight that psychobiotics can induce complex changes in host gene expression, andin understanding these changes, we may help fine-tune selection of psychobiotics for treating mood disorders.

The Relationship between Stress, Inflammation, and Depression

A narrative review about the relationship between stress, inflammation, and depression is made as follows: Chronic stress leads to various stress-related diseases such as depression. Although most human diseases are related to stress exposure, the common pathways between stress and pathophysiological processes of different disorders are still debatable. Chronic inflammation is a crucial component of chronic diseases, including depression. Both experimental and clinical studies have demonstrated that an increase in the levels of pro-inflammatory cytokines and stress hormones, such as glucocorticoids, substantially contributes to the behavioral alterations associated with depression. Evidence suggests that inflammation plays a key role in the pathology of stress-related diseases; however, this link has not yet been completely explored. In this study, we aimed to determine the role of inflammation in stress-induced diseases and whether a common pathway for depression exists. Recent studies support pharmacological and non-pharmacological treatment approaches significantly associated with ameliorating depression-related inflammation. In addition, major depression can be associated with an activated immune system, whereas antidepressants can exert immunomodulatory effects. Moreover, non-pharmacological treatments for major depression (i.e., exercise) may be mediated by anti-inflammatory actions. This narrative review highlights the mechanisms underlying inflammation and provides new insights into the prevention and treatment of stress-related diseases, particularly depression.

Brain-Derived Neurotrophic Factor and Extracellular Vesicle-Derived miRNAs in an Italian Cohort of Individuals With Obesity: A Key to Explain the Link Between Depression and Atherothrombosis

Background

Obesity and depression are intertwined diseases often associated with an increased risk of cardiovascular (CV) complications. Brain-Derived Neurotrophic Factor (BDNF), altered in the brain both of subjects with depression and obesity, provides a potential link between depression and thrombosis. Since the relationship among peripheral BDNF, depression and obesity is not well-defined, the aim of the present report has been to address this issue taking advantage of the contribution played by extracellular vesicle (EV)-derived miRNAs.

Research Process

Associations among circulating BDNF, depression and EV-derived miRNAs related to atherothrombosis have been evaluated in a large Italian cohort of obese individuals (n = 743), characterized by the Beck Depression Inventory (BDI-II) score.

Results

BDI-II was negatively associated with BDNF levels without a significant impact of the rs6265 BDNF polymorphism; this association was modified by raised levels of IFN-γ. BDNF levels were linked to an increase of 80 EV-derived miRNAs and a decrease of 59 miRNAs related to atherosclerosis and thrombosis. Network analysis identified at least 18 genes targeted by these miRNAs, 7 of which involved in depression and CV risk. The observation of a possible link among BDNF, depression, and miRNAs related to atherothrombosis and depression in obesity is novel and may lead to a wider use of BDNF as a CV risk biomarker in this specific subject group.

Diagnosis of Neural Activity among Abnormal Brain Regions in Patients with Major Depressive Disorder by Magnetic Resonance Imaging Features

In order to explore the diagnostic value of magnetic resonance imaging (MRI) for neural activity among abnormal brain regions in patients with major depressive disorder (MDD), thirty patients with MDD (observation group) were selected for comparison with 30 healthy people without MDD (control group). The included subjects were examined by MRI to compare the MRI features and were analyzed for regional homogeneity (ReHo) and amplitude low-frequency fluctuations (ALFF). The results showed that compared with the control group, the brain regions with increased ReHo and ALFF in the observation group were medial frontal gyrus (right), middle temporal lobe (left), inferior parietal lobe (left), and posterior cerebellar lobe (right); the brain region with increased ReHo and ALFF in the observation group was the middle temporal gyrus (right). Compared with the control group, there were significant differences in ReHo and ALFF in the observation group. It was found that the brain function of patients with MDD was abnormal compared with that of the normal subjects, and the brain network activity was also abnormal. MRI features can be used to explore abnormal brain regions in patients with MDD and have positive guiding value.

In Vitro Effects of Cannabidiol on Activated Immune–Inflammatory Pathways in Major Depressive Patients and Healthy Controls

Major depressive disorder and major depressive episodes (MDD/MDE) are characterized by the activation of the immune–inflammatory response system (IRS) and the compensatory immune–regulatory system (CIRS). Cannabidiol (CBD) is a phytocannabinoid isolated from the cannabis plant, which is reported to have antidepressant-like and anti-inflammatory effects. The aim of the present study is to examine the effects of CBD on IRS, CIRS, M1, T helper (Th)-1, Th-2, Th-17, T regulatory (Treg) profiles, and growth factors in depression and healthy controls. Culture supernatant of stimulated (5 μg/mL of PHA and 25 μg/mL of LPS) whole blood of 30 depressed patients and 20 controls was assayed for cytokines using the LUMINEX assay. The effects of three CBD concentrations (0.1 µg/mL, 1 µg/mL, and 10 µg/mL) were examined. Depression was characterized by significantly increased PHA + LPS-stimulated Th-1, Th-2, Th-17, Treg, IRS, CIRS, and neurotoxicity profiles. CBD 0.1 µg/mL did not have any immune effects. CBD 1.0 µg/mL decreased CIRS activities but increased growth factor production, while CBD 10.0 µg/mL suppressed Th-1, Th-17, IRS, CIRS, and a neurotoxicity profile and enhanced T cell growth and growth factor production. CBD 1.0 to 10.0 µg/mL dose-dependently decreased sIL-1RA, IL-8, IL-9, IL-10, IL-13, CCL11, G-CSF, IFN-γ, CCL2, CCL4, and CCL5, and increased IL-1β, IL-4, IL-15, IL-17, GM-CSF, TNF-α, FGF, and VEGF. In summary, in this experiment, there was no beneficial effect of CBD on the activated immune profile of depression and higher CBD concentrations can worsen inflammatory processes.

Uncovering associations between mental illness diagnosis, nitric oxide synthase gene variation, and peripheral nitric oxide concentration

Nitric oxide (NO) signalling has been implicated in the pathogenesis of several mental illnesses; however, its specific contribution remains unclear. We investigated whether peripheral NO concentration is associated with specific diagnoses, and whether there is a correlation with genetic variation in NO synthase (NOS) genes. We included 185 participants in the study; 52 healthy controls, 43 major depressive disorder (MDD) patients, 41 bipolar disorder (BPD) patients, and 49 schizophrenia (SCZ) patients. Clinical, genetic, and biochemical data were collected at admission to a psychiatric hospital and at discharge. Serum was used to quantify concentration of the stable NO metabolites nitrite and nitrate. Individuals were genotyped for the NOS1 exon 1f variable number of tandem repeats 1 (VNTR1) polymorphism, and single nucleotide polymorphisms (SNPs) in the NOS1, NOS1AP and NOS3 genes. At admission, SCZ patients were found to have significantly higher peripheral NO metabolite (NO_x-) concentrations compared to healthy controls, MDD and BPD patients. NOS1 exon 1f VNTR1 short allele carriers were found to have significantly increased NO_x- concentration. Moreover, this result was still significant in patients even at discharge. The data also revealed that patients who did not remit in their depressive symptoms had significantly increased NO_x- concentration compared to remitters at discharge, supported by the finding of a significant positive correlation between depression symptom severity and NO_x- concentration. Taken together, it is possible that elevated peripheral NO_x- concentration is associated with increased severity of psychopathology, potentially due to NOS1 exon1f VNTR1 genotype. Our results further implicate NO signalling in mental illness pathogenesis, supporting its possible use as a peripheral biomarker, and imply that NOS genotype may play a significant role in regulating peripheral NO_x- concentration.

Interferon-γ enhances neocortical synaptic inhibition by promoting membrane association and phosphorylation of GABAA receptors in a protein kinase C-dependent manner

Interferon-γ (IFN-γ), an important mediator of the antiviral immune response, can also act as a neuromodulator. CNS IFN-γ levels rise acutely in response to infection and therapeutically applied IFN-γ provokes CNS related side effects. Moreover, IFN-γ plays a key role in neurophysiological processes and a variety of chronic neurological and neuropsychiatric conditions. To close the gap between basic research, behavioral implications and clinical applicability, knowledge of the mechanism behind IFN-γ related changes in brain function is crucial. Here, we studied the underlying mechanism of acutely augmented neocortical inhibition by IFN-γ (1.000 IU ml^-1) in layer 5 pyramidal neurons of male Wistar rats. We demonstrate postsynaptic mediation of IFN-γ augmented inhibition by pressure application of GABA and analysis of paired pulse ratios. IFN-γ increases membrane presence of GABA_AR γ₂, as quantified by cell surface biotinylation and functional synaptic GABA_AR number, as determined by peak-scaled non-stationary noise analysis. The increase in functional receptor number was comparable to the increase in underlying miniature inhibitory postsynaptic current (mIPSC) amplitudes. Blockage of putative intracellular mediators, namely phosphoinositide 3-kinase and protein kinase C (PKC) by Wortmannin and Calphostin C, respectively, revealed PKC-dependency of the pro-inhibitory IFN-γ effect. This was corroborated by increased serine phosphorylation of P-serine PKC motifs on GABA_AR γ₂ upon IFN-γ application. GABA_AR single channel conductance, intracellular chloride levels and GABA_AR driving force are unlikely to contribute to the effect, as shown by single channel recordings and chloride imaging. The effect of IFN-γ on mIPSC amplitudes was similar in female and male rats, suggesting a gender-independent mechanism of action. Collectively, these results indicate a novel mechanism for the regulation of inhibition by IFN-γ, which could impact on neocortical function and therewith behavior.

Differential Diagnosis Findings Between Alzheimer's Disease and Major Depressive Disorder: A Review

Background

Differentiating diagnosis between Alzheimer's disease and major depressive disorder in the elderly is a great clinical challenge. This study aimed to identify the establishment of differential diagnosis protocols between Alzheimer's disease and major depressive disorder.

Methods

We searched studies in the Ovid MEDLINE, EMBASE, PsycINFO, and Web of Science databases between 2009 and 2019. A total of 155 references were found for searching relevant articles using Boolean search. After exclusion of redundancies and assessing of title, abstract, and full text for eligibility, 11 articles were selected. The total sample size was 1077 distributed in 8 different countries.

Results

Significant results were found for differential diagnosis between Alzheimer's disease and major depressive disorder, such as overall mental status, episodic memory, visuospatial construction, delayed recognition task, semantic verbal fluency, visual task in short-term memory, atrophy of the hippocampus, cortical activation in specific tasks, and cerebrospinal fluid biomarkers.

Conclusion

These findings are good pathways for discriminating Alzheimer's disease from major depression in the elderly.

A pilot exploration of multi-omics research of gut microbiome in major depressive disorders

The pathophysiology of major depressive disorder (MDD) remains obscure. Recently, the microbiota-gut-brain (MGB) axis's role in MDD has an increasing attention. However, the specific mechanism of the multi-level effects of gut microbiota on host metabolism, immunity, and brain structure is unclear. Multi-omics approaches based on the analysis of different body fluids and tissues using a variety of analytical platforms have the potential to provide a deeper understanding of MGB axis disorders. Therefore, the data of metagenomics, metabolomic, inflammatory factors, and MRI scanning are collected from the two groups including 24 drug-naïve MDD patients and 26 healthy controls (HCs). Then, the correlation analysis is performed in all omics. The results confirmed that there are many markedly altered differences, such as elevated Actinobacteria abundance, plasma IL-1β concentration, lipid, vitamin, and carbohydrate metabolism disorder, and diminished grey matter volume (GMV) of inferior frontal gyrus (IFG) in the MDD patients. Notably, three kinds of discriminative bacteria, Ruminococcus bromii, Lactococcus chungangensis, and Streptococcus gallolyticus have an extensive correlation with metabolome, immunology, GMV, and clinical symptoms. All three microbiota are closely related to IL-1β and lipids (as an example, phosphoethanolamine (PEA)). Besides, Lactococcus chungangensis is negatively related to the GMV of left IFG. Overall, this study demonstrate that the effects of gut microbiome exert in MDD is multifactorial.

Microglial Inflammatory-Metabolic Pathways and Their Potential Therapeutic Implication in Major Depressive Disorder

Increasing evidence supports the notion that neuroinflammation plays a critical role in the etiology of major depressive disorder (MDD), at least in a subset of patients. By virtue of their capacity to transform into reactive states in response to inflammatory insults, microglia, the brain's resident immune cells, play a pivotal role in the induction of neuroinflammation. Experimental studies have demonstrated the ability of microglia to recognize pathogens or damaged cells, leading to the activation of a cytotoxic response that exacerbates damage to brain cells. However, microglia display a wide range of responses to injury and may also promote resolution stages of inflammation and tissue regeneration. MDD has been associated with chronic priming of microglia. Recent studies suggest that altered microglial morphology and function, caused either by intense inflammatory activation or by senescence, may contribute to depression and associated impairments in neuroplasticity. In this context, modifying microglia phenotype by tuning inflammatory pathways might have important translational relevance to harness neuroinflammation in MDD. Interestingly, it was recently shown that different microglial phenotypes are associated with distinct metabolic pathways and analysis of the underlying molecular mechanisms points to an instrumental role for energy metabolism in shaping microglial functions. Here, we review various canonical pro-inflammatory, anti-inflammatory and metabolic pathways in microglia that may provide new therapeutic opportunities to control neuroinflammation in brain disorders, with a strong focus on MDD.

Biological, Psychological, and Social Determinants of Depression: A Review of Recent Literature

Depression is one of the leading causes of disability, and, if left unmanaged, it can increase the risk for suicide. The evidence base on the determinants of depression is fragmented, which makes the interpretation of the results across studies difficult. The objective of this study is to conduct a thorough synthesis of the literature assessing the biological, psychological, and social determinants of depression in order to piece together the puzzle of the key factors that are related to this condition. Titles and abstracts published between 2017 and 2020 were identified in PubMed, as well as Medline, Scopus, and PsycInfo. Key words relating to biological, social, and psychological determinants as well as depression were applied to the databases, and the screening and data charting of the documents took place. We included 470 documents in this literature review. The findings showed that there are a plethora of risk and protective factors (relating to biological, psychological, and social determinants) that are related to depression; these determinants are interlinked and influence depression outcomes through a web of causation. In this paper, we describe and present the vast, fragmented, and complex literature related to this topic. This review may be used to guide practice, public health efforts, policy, and research related to mental health and, specifically, depression.

Young Plasma Induces Antidepressant-Like Effects in Aged Rats Subjected to Chronic Mild Stress by Suppressing Indoleamine 2,3-Dioxygenase Enzyme and Kynurenine Pathway in the Prefrontal Cortex

Pathophysiology of depression in elderlies is linked to aging-associated increase in indoleamine 2,3-dioxygenase (IDO) levels and activity and kynurenine (Kyn) metabolites. Moreover, these aging-induced changes may alter the brain's responses to stress. Growing evidence suggested that young plasma can positively affect brain dysfunctions in old age. The present study aimed to investigate whether the antidepressant effects of young plasma administration in aged rats subjected to chronic unpredictable mild stress (CUMS) and underlying mechanisms, focusing on the prefrontal cortex (PFC). Young (3 months old) and aged (22 months old) male rats were divided into five groups; young control, aged control, aged rats subjected to CUMS (A + CUMS), aged rats subjected to CUMS and treated with young plasma (A + CUMS + YP), and aged rats subjected to CUMS and treated with old plasma (A + CUMS + OP). Plasma was injected (1 ml, intravenously) three times per week for four weeks. Young plasma significantly improved CUMS-induced depressive-like behaviors, evidenced by the increased sucrose consumption ratio in the sucrose preference test and the reduced immobility time in the forced swimming test. Furthermore, young plasma markedly reduced the levels of interferon-gamma (IFN-γ), IDO, Kyn, and Kyn to tryptophan (Kyn/Trp) ratio in PFC tissue. Expression levels of the serotonin transporter and growth-associated protein (GAP)-43 were also significantly increased after chronic administration of young plasma. These findings provide evidence for the antidepressant effect of young plasma in old age; however, whether it improves depressive behaviors or faster recovery from stress-induced deficits is required to be elucidated.

T helper cells in depression: central role of Th17 cells

Depression is one of the most common neuropsychiatric disorders in the world. While conventional pharmaceutical therapy targets monoaminergic pathway dysfunction, it has not been totally successful in terms of positive outcomes, remission, and preventing relapses. There is an increasing amount of evidence that neuroinflammation may play a significant part in the pathophysiology of depression. Among the key components of the neuroinflammatory pathways already known to be active are the T helper (Th) cells, especially Th17 cells. While various preclinical and clinical studies have reported increased levels of Th17 cells in both serum and brain tissue of laboratory model animals, contradictory results have argued against a pertinent role of Th17 cells in depression. Recent studies have also revealed a role for more pathogenic and inflammatory subsets of Th17 in depression, as well as IL-17A and Th17 cells in non-responsiveness to conventional antidepressant therapy. Despite recent advances, there is still a significant knowledge gap concerning the exact mechanism by which Th17 cells influence neuroinflammation in depression. This review first provides a short introduction to the major findings that led to the discovery of the role of Th cells in depression. The major subsets of Th cells known to be involved in neuroimmunology of depression, such as Th1, Th17, and T regulatory cells, are subsequently described, with an in-depth discussion on current knowledge about Th17 cells in depression.

The change of gut microbiota in MDD patients under SSRIs treatment

The alterations in the gut microbiota have been reported to be correlated with the development of depression. The purpose of this study was to investigate the changes of intestinal microbiota in depressed patients after antidepressant treatment. We recruited 30 MDD patients (MDD group) and 30 healthy controls (control group). The MDD group received individualized treatment with escitalopram at a maximum dose of 20 mg/day. After depressive symptoms improved to a HAMD scale score > 50%, a fecal sample was collected again and used as the follow-up group. The differences of gut microbiota between patients and controls, the characteristics of gut microbiota under treatment and the potential differences in metabolic functions were thus investigated. The Firmicutes/Bacteroidetes ratio was significantly different within three groups, and the ratio of follow-up group was significantly lower than those of the other two groups. Alpha diversity was significantly higher in MDD group than those of the other groups, and the alpha diversity was not significantly different between control and follow-up groups. The beta diversity of some patients resembled participants in the control group. The metabolic function of gut microbiota after treatment was still different from that of the control group. This study suggests that the intestinal flora of depressed patients has a tendency to return to normal under escitalopram treatment.

Study on caspase-1 and partial cognitive impairment in the comorbidity of type 2 diabetes and MDD

BACKGROUND

Major depressive disorder (MDD) is a major mood disorder characterized by chronic low mood with cognitive impairment. Diabetes mellitus is a group of chronic metabolic diseases, Type 2 diabetes (T2DM) will obviously increase the risk of dementia. People with the the comorbidity of T2DM and MDD have a higher risk of dementia. In this study, we aim to investigate partial cognitive impairment in the comorbidity of T2DM and MDD, and to determine the relationship between changes in caspase-1 expression and cognitive impairment. To further explore the role of caspase-1 in the partial cognitive impairment in the comorbidity of T2DM and MDD.

METHODS

A total of 162 people were enrolled, there were 49 patients in the comorbidity of T2DM and MDD group, 54 patients in the MDD group, and 45 patients in the T2DM group. Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) was used to assess the cognitive function of these three groups. Serum level of caspase-1 was determined by ELISA, and the level of caspase-1, as well as partial cognitive function, was compared in the three groups.

RESULTS

The cognitive impairment of patients of the comorbidity of T2DM and MDD group was worse than the MDD group and the T2DM group, and the immediate memory, attention, and delayed memory in the comorbidity of T2DM and MDD group were lower than those in the other two groups, and the caspase-1 of the comorbidity of T2DM and MDD is higher than the caspase-1 of the MDD group, all the difference was statistically significant (P < 0.05). Caspase-1 protein was negatively correlated with immediate memory, attention, and delayed memory (r=-0.332, r=-0.182, r=-0.313, P<0.05).

CONCLUSION

The cognitive impairment of patients of the comorbidity of T2DM and MDD group was worse than the MDD group and the T2DM group, and the immediate memory, attention, and delayed memory in the comorbidity of T2DM and MDD group were lower than those in the other two groups. The differences of the caspase-1 in the comorbidity of T2DM and MDD group, the MDD group and the T2DM group were significant, the level of the caspase-1 is higher than the other two groups, the cognitive impairment of three groups is associated with caspase-1, suggesting caspase-1 protein may be involved in the cognitive impairment aggravation mechanism of the comorbidity of T2DM and MDD group.

Effects of Antidepressant Treatment on Peripheral Biomarkers in Patients with Major Depressive Disorder (MDD)

Major depressive disorder (MDD) is one of the most prevalent mental illness and a leading cause of disability worldwide. Despite a range of effective treatments, more than 30% of patients do not achieve remission as a result of conventional therapy. In these circumstances the identification of novel drug targets and pathogenic factors becomes essential for selecting more efficacious and personalized treatment. Increasing evidence has implicated the role of inflammation in the pathophysiology of depression, revealing potential new pathways and treatment options. Moreover, convergent evidence indicates that MDD is related to disturbed neurogenesis and suggests a possible role of neurotrophic factors in recovery of function in patients. Although the influence of antidepressants on inflammatory cytokines balance was widely reported in various studies, the exact correlation between drugs used and specific cytokines and neurotrophins serum levels often remains inconsistent. Available data suggest anti-inflammatory properties of selective serotonin reuptake inhibitors (SSRIs), selective serotonin and noradrenaline inhibitors (SNRIs), and tricyclic antidepressants (TCAs) as a possible additional mechanism of reduction of depressive symptoms. In this review, we outline emerging data regarding the influence of different antidepressant drugs on a wide array of peripheral biomarkers such as interleukin (IL)-1ß, IL-2, IL-5, IL-6, IL-8, IL-10, C-reactive protein (CRP), or interferon (IFN)-γ. Presented results indicate anti-inflammatory effect for selected drugs or lack of such effect. Research in this field is insufficient to define the role of inflammatory markers as a predictor of treatment response in MDD.

Depression in patients with chronic hepatitis-C treated with direct-acting antivirals: A real-world prospective observational study

BACKGROUND

Direct-acting antiviral (DAAs) therapy showed high safety and efficacy profile in patients with chronic hepatitis C (CHC) particularly those with previous or current psychiatric illness. The aim of this study was to evaluate the incidence and potential risk factors of depression and psychological distress following DAAs therapy in CHC euthymic Egyptian patients with no previous or current diagnosis of any psychiatric disorders.

METHODS

This is a prospective study that included 126 patients diagnosed with chronic hepatitis C virus genotype-4. Patients were candidate for DAAs therapy and were recruited consecutively (convenient sample) from the viral hepatitis center, Department of Endemic medicine, Kasr Al-Ainy Hospitals, Cairo University. Symptom Checklist 90-R, Beck Depression Inventory (BDI) and Structured Clinical Interview for DSM-IV (SCID IV) were performed at baseline and at 12 weeks post-treatment with DAAs.

RESULTS

Forty-seven patients were included in the final analysis. Depression severity increased after treatment as BDI scores increased significantly than baseline scores (p= < 0.001). About one third of patients (32%) had moderate to severe depression. All Symptom Checklist-90 scores showed significant increase after treatment.

LIMITATIONS

Dropout rate of patients for the 12 weeks post-treatment assessment was 33.8%.

CONCLUSION

Depression and psychological distress can occur with DAAs treatments. Close psychosocial assessment and patient monitoring are still needed.

Identification of major depressive disorder disease-related genes and functional pathways based on system dynamic changes of network connectivity

Background

Major depressive disorder (MDD) is a leading psychiatric disorder that involves complex abnormal biological functions and neural networks. This study aimed to compare the changes in the network connectivity of different brain tissues under different pathological conditions, analyzed the biological pathways and genes that are significantly related to disease progression, and further predicted the potential therapeutic drug targets.

Methods

Expression of differentially expressed genes (DEGs) were analyzed with postmortem cingulate cortex (ACC) and prefrontal cortex (PFC) mRNA expression profile datasets downloaded from the Gene Expression Omnibus (GEO) database, including 76 MDD patients and 76 healthy subjects in ACC and 63 MDD patients and 63 healthy subjects in PFC. The co-expression network construction was based on system network analysis. The function of the genes was annotated by Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis. Human Protein Reference Database (HPRD, http://www.hprd.org/) was used for gene interaction relationship mapping.

Results

We filtered 586 DEGs in ACC and 616 DEGs in PFC for further analysis. By constructing the co-expression network, we found that the gene connectivity was significantly reduced under disease conditions (P = 0.04 in PFC and P = 1.227e−09 in ACC). Crosstalk analysis showed that CD19, PTDSS2 and NDST2 were significantly differentially expressed in ACC and PFC of MDD patients. Among them, CD19 and PTDSS2 have been targeted by several drugs in the Drugbank database. KEGG pathway analysis demonstrated that the function of CD19 and PTDSS2 were enriched with the pathway of Glycerophospholipid metabolism and T cell receptor signaling pathway.

Conclusion

Co-expression network and tissue comparing analysis can identify signaling pathways and cross talk genes related to MDD, which may provide novel insight for understanding the molecular mechanisms of MDD.

Inflammatory Depression-Mechanisms and Non-Pharmacological Interventions

Treatment of depression is hampered by the failure to identify distinct symptom profiles with distinct pathophysiologies that differentially respond to distinct treatments. We posit that inflammatory depression is a meaningful depression subtype associated with specific symptoms and biological abnormalities. We review several upstream, potentially causative, mechanisms driving low-grade inflammation in this subtype of depression. We also discuss downstream mechanisms mediating the link between inflammation and symptoms of depression, including alterations in dopaminergic neurotransmission and tryptophan metabolism. Finally, we review evidence for several non-pharmacological interventions for inflammatory depression, including probiotics, omega-3 fatty acids, and physical exercise interventions. While some evidence suggests that these interventions may be efficacious in inflammatory depression, future clinical trials should consider enriching patient populations for inflammatory markers, or stratify patients by inflammatory status, to confirm or refute this hypothesis.

Antioxidant-Rich Woodfordia fruticosa Leaf Extract Alleviates Depressive-Like Behaviors and Impede Hyperglycemia

Dhaiphul (Woodfordia fruticosa) is a frequently demanded plant in South-East Asian regions for its diverse medicinal values. This study was proposed to examine antioxidant, antidiabetic, and antidepressant potentials of methanol extract of W. fruticosa leaves (MEWF) and its derived n-hexane (NHFMEWF) and ethyl acetate (EAFMEWF) fractions through in vitro, in vivo, and computational models. Among test samples, MEWF and EAFMEWF contained the highest phenolic content and showed maximal antioxidant activity in DPPH radical scavenging and ferric reducing power assays. In comparison, NHFMEWF possessed maximum flavonoid content and a significantly potent α-amylase inhibitory profile comparable with positive control acarbose. In animal models of depression (forced swimming and tail suspension test), EAFMEWF and NHFMEWF demonstrated a dose-dependent antidepressant-like effect; explicitly, the depressive-like behaviors significantly declined in EAFMEWF-treated dosing groups in contrast to the control group. In the computational analysis, previously isolated flavonoid compounds from Dhaiphul leaves manifested potent binding affinity against several key therapeutic target proteins of diabetes and depressive disorders including α-amylase, serotonin transporter, dopamine transporter, and neuronal nitric oxide synthase with varying pharmacokinetics and toxicity profiles. This research's outcomes may provide potential dietary supplements for mitigating hyperglycemia, cellular toxicity, and depressive disorder.

Botulinum Neurotoxin Therapy for Depression: Therapeutic Mechanisms and Future Perspective

Depression is one of the most common mental disorders, which causes global burden. Antidepressants and psychotherapies are the mainstay of treatment for depression, which have limited efficacy. Thus, alternative approaches for preventing and treating depression are urgently required. Recent clinical trials and preclinical researches have clarified that peripheral facial injection of botulinum neurotoxin type A (BoNT/A) is a rapid, effective and relative safe therapy for improving some symptoms of depression. Despite its safety and efficacy, the underlying therapeutic mechanisms of BoNT/A for depression remains largely unclear. In the present review, we updated and summarized the clinical and preclinical evidence supporting BoNT/A therapy for the treatment of depression. We further discussed the potential mechanisms underlying therapeutic effects of BoNT/A on depression. Notably, we recently identified that the anti-depressant effects of BoNT/A associated with up-regulation of 5-HT levels and brain-derived neurotrophic factor (BDNF) expression in the hippocampus in a preclinical mouse model. In summary, these studies suggest that BoNT/A therapy is a potential effective and safe intervention for the management of depression. However, fundamental questions remain regarding the future prospects of BoNT/A therapy, including safety, efficacy, dose-response relationships, identification of potential predictors of response, and the precise mechanisms underlying BoNT/A therapy.

Metformin improves depressive-like symptoms in mice via inhibition of peripheral and central NF-κB-NLRP3 inflammation activation

Emerging evidence indicates that NLRP3 inflammasome-induced inflammation plays a crucial role in the pathogenesis of depression. Thus, inhibition of NLRP3 inflammasome activation may offer a therapeutic benefit in the treatment of depression. Metformin has been shown to have potential anti-inflammatory activity, but the underlying mechanisms remain obscure. We used a chronic mild stress model of depression and cultured primary macrophage to investigate the effects of metformin on depression and its underlying mechanisms. We demonstrated that metformin alleviated depressive-like behaviors in the chronic mild stress-induced anhedonia model of depression. We further found that metformin significantly suppressed NLRP3 inflammasome activation, subsequent caspase-1 cleavage, and interleukin-1β secretion in both peripheral macrophages and central hippocampus. Our findings reveal that metformin confers an antidepressant effect partly through inhibition of peripheral and central NLRP3 inflammasome activation. In light of metformin favorable properties, it should be evaluated in the treatment of depression and related neurologic disorders characterized by NLRP3 inflammasome activation.

Asiaticoside produces an antidepressant‑like effect in a chronic unpredictable mild stress model of depression in mice, involving reversion of inflammation and the PKA/pCREB/BDNF signaling pathway

Asiaticoside is one of the triterpenoid components found in Centella asiatica that has promising neuroprotective properties. The present study aimed to evaluate the antidepressant‑like properties of asiaticoside and to investigate the possible mechanisms underlying its mode of action using a mouse model of chronic unpredictable mild stress (CMS). Behavioral tests, including sucrose preference test, forced swimming test and tail suspension test, were performed to evaluate symptoms of depression. The expression levels of neurotransmitters, 5‑hydroxytryptamine (5‑HT) and norepinephrine (NE), in the hippocampus were measured by high‑performance liquid chromatography. ELISA and western blotting were used to detect protein expression. It was demonstrated that asiaticoside treatment (20 and 40 mg/kg; intragastric) significantly reversed the decrease in sucrose consumption, and reduced the immobility time in tail suspension tests and forced swimming tests in CMS mice. Furthermore, asiaticoside treatment upregulated the expression of 5‑HT and NE in the CMS mouse model. Asiaticoside administration also downregulated the levels of interleukin (IL)‑1β, IL‑6 and tumor necrosis factor‑α in the hippocampus, and reduced the phosphorylation of nuclear factor (NF)‑κBp65 and the expression of nod‑like receptor protein 3 (NLRP3), thus decreasing the expression of mature caspase‑1. Furthermore, asiaticoside significantly increased the levels of cAMP and protein kinase A (PKA), and enhanced phosphorylation of the cAMP‑related specific marker vasodilator‑stimulated phosphoprotein at serine 157. Therefore, asiaticoside may activate the cAMP/PKA signaling pathway to inhibit NF‑κB‑ and NLRP3‑related inflammation. Moreover, phosphorylation of the cAMP‑responsive element‑binding protein at serine 133 and the expression of brain‑derived neurotrophic factor were increased after asiaticoside administration. Collectively, the present results suggested that asiaticoside may play a vital role as an antidepressant and anti‑inflammatory agent in the CMS mouse model by regulating the cAMP/PKA signaling pathway.

Zinc, but not paracetamol, prevents depressive-like behavior and sickness behavior, and inhibits interferon-gamma and astrogliosis in rats

Considering all mental and addictive disorders, depression is the most responsible for years of life lost due to premature mortality and disability. Antidepressant drugs have limited effectiveness. Depression can be triggered by immune/inflammatory factors. Zinc and paracetamol interfere with immune system and have demonstrated beneficial effects on depression treatment when administered concomitant with antidepressant drugs. The objective of this study was to test zinc and/or paracetamol as treatments of depressive-like behavior, sickness behavior, and anxiety in rats, as well as to understand the central and peripheral mechanisms involved. Sickness behavior and depressive-like behavior were induced in rats with repetitive lipopolysaccharide (LPS, 1 mg/kg for two consecutive days) administrations. Rats received zinc and/or paracetamol for three consecutive days. Sickness behavior (daily body weight and open field general activity); anxiety (light-dark test); depressive-like/antidepressant behavior (forced swim test); plasma corticosterone and interferon (IFN)-gamma levels; and glial fibrillary acidic protein (GFAP) and tyrosine hydroxylase (TH) brain expression were evaluated. LPS induced sickness behavior and depressive-like behavior, as well as elevated IFN-gamma levels and increased GFAP expression. Zinc prevented both behavioral and biochemical impairments. Paracetamol and zinc + paracetamol association induced only slight beneficial effects. Anxiety, corticosterone, and TH do not seem be related with depression and the other behavioral and neuroimmune changes. In conclusion, zinc treatment was beneficial for sickness behavior and depressive-like behavior without concomitant administration of antidepressants. IFN-gamma and GFAP were linked with the expression of sickness behavior and depressive-like behavior and were also involved with the antidepressant effects. Therefore, zinc, IFN-gamma, and GFAP pathways should be considered for depression treatment.

A Fatal Alliance between Microglia, Inflammasomes, and Central Pain

Microglia are the resident immune cells in the CNS, which survey the brain parenchyma for pathogens, initiate inflammatory responses, secrete inflammatory mediators, and phagocyte debris. Besides, they play a role in the regulation of brain ion homeostasis and in pruning synaptic contacts and thereby modulating neural networks. More recent work shows that microglia are embedded in brain response related to stress phenomena, the development of major depressive disorders, and pain-associated neural processing. The microglia phenotype varies between activated-toxic-neuroinflammatory to non-activated-protective-tissue remodeling, depending on the challenges and regulatory signals. Increased inflammatory reactions result from brain damage, such as stroke, encephalitis, as well as chronic dysfunctions, including stress and pain. The dimension of damage/toxic stimuli defines the amplitude of inflammation, ranging from an on-off event to low but continuous simmering to uncontrollable. Pain, either acute or chronic, involves inflammasome activation at the point of origin, the different relay stations, and the sensory and processing cortical areas. This short review aimed at identifying a sinister role of the microglia-inflammasome platform for the development and perpetuation of acute and chronic central pain and its association with changes in CNS physiology.

Dihydrolipoic acid protects against lipopolysaccharide-induced behavioral deficits and neuroinflammation via regulation of Nrf2/HO-1/NLRP3 signaling in rat

Background

Recently, depression has been identified as a prevalent and severe mental disorder. However, the mechanisms underlying the depression risk remain elusive. The neuroinflammation and NLRP3 inflammasome activation are known to be involved in the pathology of depression. Dihydrolipoic acid (DHLA) has been reported as a strong antioxidant and exhibits anti-inflammatory properties in various diseases, albeit the direct relevance between DHLA and depression is yet unknown. The present study aimed to investigate the preventive effect and potential mechanism of DHLA in the lipopolysaccharide (LPS)-induced sickness behavior in rats.

Methods

Adult male Sprague–Dawley rats were utilized. LPS and DHLA were injected intraperitoneally every 2 days and daily, respectively. Fluoxetine (Flu) was injected intraperitoneally daily. PD98059, an inhibitor of ERK, was injected intraperitoneally 1 h before DHLA injection daily. Small interfering ribonucleic acid (siRNA) for nuclear factor erythroid 2-like (Nrf2) was injected into the bilateral hippocampus 14 days before the DHLA injection. Depression-like behavior tests were performed. Western blot and immunofluorescence staining detected the ERK/Nrf2/HO-1/ROS/NLRP3 pathway-related proteins.

Results

The DHLA and fluoxetine treatment exerted preventive effects in LPS-induced sickness behavior rats. The DHLA treatment increased the expression of ERK, Nrf2, and HO-1 but decreased the ROS generation levels and reduced the expression of NLRP3, caspase-1, and IL-1β in LPS-induced sickness behavior rats. PD98059 abolished the effects of DHLA on preventive effect as well as the levels of Nrf2 and HO-1 proteins. Similarly, Nrf2 siRNA reversed the preventive effect of DHLA administration via the decreased expression of HO-1.

Conclusions

These findings suggested that DHLA exerted a preventive effect via ERK/Nrf2/HO-1/ROS/NLRP3 pathway in LPS-induced sickness behavior rats. Thus, DHLA may serve as a potential therapeutic strategy for depression.

Antidepressants of different classes cause distinct behavioral and brain pro- and anti-inflammatory changes in mice submitted to an inflammatory model of depression

BACKGROUND

Depressed patients present increased plasma levels of lipopolysaccharide (LPS) and neuroinflammatory alterations. Here, we determined the neuroimmune effects of different classes of ADs by using the LPS inflammatory model of depression.

METHODS

Male rats received amitriptyline (AMI) a tricyclic, S-citalopram (ESC) a selective serotonin reuptake inhibitor, tranylcypromine (TCP) a monoamine oxidase inhibitor, vortioxetine (VORT) a multimodal AD or saline for ten days. One-hour after the last AD administration, rats were exposed to LPS 0.83 mg/kg or saline and 24 h later were tested for depressive-like behavior. Plasma corticosterone, brain levels of nitrite, pro- and anti-inflammatory cytokines, phospho-cAMP Response Element-Binding Protein (CREB) and nuclear factor (NF)-kB p 65 were determined.

RESULTS

LPS induced despair-like, impaired motivation/self-care behavior and caused anhedonia. All ADs prevented LPS-induced despair-like behavior, but only VORT rescued impaired self-care behavior. All ADs prevented LPS-induced increase in brain pro-inflammatory cytokines [interleukin (IL)-1β and IL-6] and T-helper 1 cytokines [tumor necrosis factor (TNF)-α and interferon-γ]. VORT increased striatal and hypothalamic IL-4 levels. All ADs prevented LPS-induced neuroendocrine alterations represented by increased levels of hypothalamic nitrite and plasma corticosterone response. VORT and ESC prevented LPS-induced increase in NF-kBp65 hippocampal expression, while ESC, TCP and VORT, but not IMI, prevented the alterations in phospho-CREB expression.

LIMITATIONS

LPS model helps to understand depression in a subset of depressed patients with immune activation. The levels of neurotransmitters were not determined.

CONCLUSION

This study provides new evidence for the immunomodulatory effects of ADs, and shows a possible superior anti-inflammatory profile of TCP and VORT.

NLRP1-Mediated Antidepressant Effect of Ketamine in Chronic Unpredictable Mild Stress Model in Rats

OBJECTIVE

NOD-like receptor protein 1 (NLRP1) inflammasome complex has been recently associated with chronic unpredictable mild stress (CUMS) model of depression. Our aim was to investigate whether ketamine-induced antidepressant effect is associated with suppression of NLRP1.

METHODS

Wistar albino rats were divided into control, CUMS, CUMS+acute ketamine (a single 10 mg/kg dose) and CUMS+chronic ketamine (daily 10 mg/kg injections for 3 weeks) groups (n=10 for each group). Sucrose preference test and forced swimming test were performed to assess anhedonia and immobility time respectively for the severety of depression symptoms. Brain tissues were dissected and prefrontal cortex and hippocampus regions were used for real-time polymerase chain reaction (PCR) and immunohistochemical analysis.

RESULTS

CUMS procedure significantly induced depressive-like symptoms whereas both acute and chronic ketamine treatment ameliorated them. mRNA expression levels of NLRP1, caspase 1, apoptosis-associated speck-like protein containing a CARD (ASC), NF-κB, endothelial nitric oxide synthase, IL-1β, IL-6, toll-like receptor 4 (TLR-4) and purinergic 2×7 receptor (P2X7R) and numbers of Iba- 1+and GFAP+glial cells were reduced by acute and/or chronic ketamine treatment.

CONCLUSION

In the present study for the first time upstream and downstream elements of the NLRP1 inflammasome complex are shown to be suppressed by ketamine thus reinforcing the involvement of NLRP1 in the physiopathology of depression.

The cytokine network in the pathogenesis of major depressive disorder. Close to translation?

Major depressive disorder (MDD) is a common condition that afflicts the general population across a broad spectrum of ages and social backgrounds. MDD has been identified by the World Health Organization as a leading cause of disability worldwide. Approximately 30% of patients are poor responsive to standard of care (SOC) treatment and novel therapeutic approaches are warranted. Since chronic inflammation, as it is often observed in certain cancers, type 2 diabetes, psoriasis and chronic arthritis, are accompanied by depression, it has been suggested that immunoinflammatory processes may be involved in the pathogenesis of MDD. Cytokines are a group of glycoproteins secreted from lymphoid and non-lymphoid cells that orchestrate immune responses. It has been suggested that a dysregulated production of cytokines may be implicated in the pathogenesis and maintenance of MDD. On the basis of their functions, cytokines can be subdivided in pro-inflammatory and anti-inflammatory cytokines. Since abnormal blood and cerebrospinal fluid of both pro and anti-inflammatory cytokines are altered in MDD, it has been suggested that abnormal cytokine homeostasis may be implicated in the pathogenesis of MDD and possibly to induction of therapeutic resistance. We review current data that indicate that cytokines may represent a useful tool to identify MDD patients that may benefit from tailored immunotherapeutic approaches and may represent a potential tailored therapeutic target.

Gene expression signature of antidepressant treatment response/non-response in Flinders Sensitive Line rats subjected to maternal separation

Neurobiological underpinnings of treatment-resistant depression, a debilitating condition associated with significant functional impairment, have not been elucidated. Consequently, the aim of this study was to use animal models of response and resistance to antidepressant treatment, in an attempt to identify differences in associated transcriptional responses. Flinders Sensitive Line rats were subjected to maternal separation (MS) and chronically treated with Escitalopram or Nortriptyline. Antidepressants reduced immobility time in the forced swim test in non-MS rats, while lack of antidepressant behavioural response was observed in MS animals. We developed a novel bioinformatic algorithm that enabled identification of transcriptional signatures in hippocampus and pre-frontal cortex that discriminate vehicle- and antidepressant-treated subjects in both MS and non-MS rats. Functional annotation analysis showed that in antidepressant-responder rats the most enriched pathways included IQGAPs activation, toll-like receptor trafficking, energy metabolism, and regulation of endopeptidase activity. The analysis of interacting proteins implicated synaptic vesicles and neurotransmitter release, ubiquitin regulation, cytoskeleton organisation and carbohydrate metabolism. In contrast, in treatment-resistant MS rats, main expression changes were revealed in ribosomal proteins, inflammatory responses, transcriptional/epigenetic regulation, and small GTPases. Susceptibility signature shared Rtn1, Zdhhc5, Igsf6, and Sim1 genes with the latest depression GWAS meta-analysis, while antidepressant resistance signature shared Ctnnd1, Rbms3, Atp1a3, and Pla2r1 genes. In conclusion, this study demonstrated that distinct transcriptional signatures are associated with behavioural response or non-response to antidepressant treatment. The identification of genes involved in antidepressant response will increase the comprehension of the neurobiological underpinnings of treatment-resistant depression, thus contributing to identification of novel therapeutic targets.

Increased interleukin 18 activity in adolescents with early-onset psychosis is associated with cortisol and depressive symptoms

OBJECTIVE

Evidence indicates that the pathophysiology of adult psychosis involves immune dysregulation, but its associations with stress are often not considered. The inflammatory cytokine interleukin (IL)-18, which is elevated in adult schizophrenia, is suggested to be sensitive to stress. We compared the associations of IL-18 with cortisol and clinical variables in adolescents with early-onset psychosis (EOP) aged 12-18 years and age-matched healthy controls (HC).

METHOD

We measured serum IL-18, IL-18 binding protein (IL-18BP), IL-18 receptor accessory protein (IL-18RAP), IL-18 receptor 1 (IL-18R1) and cortisol, and calculated the IL-18/IL-18BP ratio in patients (n = 31) and HC (n = 60). Psychotic symptoms were assessed using the Positive and Negative Syndrome Scale and depressive symptoms by the Mood and Feelings Questionnaire-Child version (MFQ-C). Bivariate correlation analysis was used to explore relationships between IL-18/IL-18BP ratio and cortisol, depression and other clinical characteristics. Hierarchical multiple linear regression analysis was used to assess their individual contributions to the variance of the IL-18/IL-18BP ratio.

RESULTS

Patients had significantly higher IL-18 levels and IL-18/IL-18BP ratios than HC, but similar IL-18BP, IL-18RAP and IL-18R1. Both cortisol (R² change = 0.05) and the MFQ-C score (R² change = 0.09) contributed significantly to the variance in IL-18/IL-18BP ratios after controlling for confounders.

CONCLUSION

We found increased IL-18 system activity in adolescents with EOP. Cortisol and depressive symptoms each contributed to the variance in the IL-18/IL-18BP ratio. Our findings support activation of inflammatory pathways in adolescent psychosis and suggest interactions between stress, inflammation and depressive symptoms in EOP.

Nitric oxide: Antidepressant mechanisms and inflammation

Millions of individuals worldwide suffers from mood disorders, especially major depressive disorder (MDD), which has a high rate of disease burden in society. Although targeting the biogenic amines including serotonin, and norepinephrine have provided invaluable links with the pharmacological treatment of MDD over the last four decades, a growing body of evidence suggest that other biologic systems could contribute to the pathophysiology and treatment of MDD. In this chapter, we highlight the potential role of nitric oxide (NO) signaling in the pathophysiology and thereby treatment of MDD. This has been investigated over the last four decades by showing that (i) levels of NO are altered in patients with major depression; (ii) modulators of NO signaling exert antidepressant effects in patients with MDD or in the animal studies; (iii) NO signaling could be targeted by a variety of antidepressants in animal models of depression; and (iv) NO signaling can potentially modulate the inflammatory pathways that underlie the pathophysiology of MDD. These findings, which hypothesize an NO involvement in MDD, can provide a new insight into novel therapeutic approaches for patients with MDD in the future.