Anti-Inflammatory effects of antidepressants through suppression of the interferon-gamma/interleukin-10 production ratio

A magic pill? A qualitative analysis of patients' views on the role of antidepressant therapy in inflammatory bowel disease (IBD)

Background

Studies with healthy volunteers have demonstrated that antidepressants can improve immunoregulatory activity and thus they may have a potential to positively impact the disease course in inflammatory bowel disease (IBD), a chronic and incurable condition. However, patients’ views on the role of antidepressants in the management of their IBD are unknown. Thus, this study aimed to explore patients’ experiences and opinions regarding the effect of antidepressants on IBD course before possibly undertaking future treatment trials with antidepressants.

Methods

Semi-structured in-depth interviews with open-ended questions were conducted with a randomly selected sample of IBD patients recruited at the Australian public hospital IBD clinic and currently receiving antidepressants. A qualitative content analysis was undertaken to summarise patients’ responses. A Visual Analogue Scale was used to provide a quantitative assessment of patients’ experiences with antidepressants.

Results

Overall, 15 IBD sufferers currently on antidepressants (nine females, six males) were interviewed. All 15 reported a positive response to antidepressants reporting they improved their quality of life, with minimal side-effects. Five patients (33.3%) felt the antidepressant had specifically improved their IBD course. Three patients noted how they believed the reduction in feelings of stress mediated the positive influence of the antidepressant on IBD course. Ten patients (66.7%) felt the antidepressants had not specifically influenced their IBD. Nine patients (60.0%) had a generally positive attitude towards antidepressants, four patients (26.7%) were ambivalent, and two patients (13.3%) held a negative view towards antidepressants. Twelve patients (80.0%) stated that they would be willing to participate in clinical trials.

Conclusions

Antidepressants seem to be well tolerated by IBD patients. One third of patients reported an observable improvement of their IBD under the influence of this treatment. The positive attitude towards antidepressants in these participants may make the conduct of clinical trials to further assess for any specific role on IBD course feasible. However, due to a small sample size, a qualitative nature of this study and in light of the results of studies on other populations indicating reluctance to taking antidepressants at least in some patients, these results should be interpreted with caution until confirmed in quantitative studies.

Early pospartum alexithymia and risk for depression: relationship with serum thyrotropin, free thyroid hormones and thyroid autoantibodies

Most psychometric evaluations in the postpartum (PP) target depression (PPD) and show an association with thyroid autoantibodies (TAb), not with thyroid function. Three studies evaluated PP alexithymia, but none its relationship with thyroid indices. We tested 74 women aged 31.8±4.64 years, on day 3 PP, by the Edinburgh Postnatal Depression Scale (EPDS), the Montgomery and Asberg Depression Rating Scale (MADRS), and the Toronto Alexithymia Scale (TAS). Concurrently, we measured serum thyrotropin (TSH), free T3 (FT3), free T4 (FT4), thyroperoxidase and thyroglobulin antibodies (TPOAb, TgAb). Using cut-off scores of ≥12 (EPDS), ≥15 (MADRS) and ≥61 (TAS), rates of women with abnormal EPDS and MADRS scores were similar (31%, 30% and 28.4%, respectively). TAS scores were higher and proportions of alexithymics were greater in the abnormal EPDS group or in the abnormal MADRS group than in the normal EPDS or MADRS group. EPDS correlated significantly with TAS. Compared to nonalexithymics, alexythimics had lower FT4, higher FT3, lower FT4:FT3 ratio, and insignificantly higher TPOAb or TgAb levels. Only TPOAb and TgAb were significantly higher in women at risk for PPD compared to women not at risk for PPD, but solely at EPDS cut-off values of ≥13 or ≥14. TAS correlated directly with TPOAb and FT3, and inversely with FT4:FT3 ratio, while EPDS correlated only with TPOAb. Comparing women at risk for depression but nonalexithymics or women alexithymics but not at risk for depression vs. women normal on all scales, the former had lower FT3 and higher FT4:FT3 ratio while the latter had lower both FT4 and FT4:FT3 ratio. We conclude that PPD risk and alexithymia (i) are partly comorbid and directly associated with thyroid autoimmunity; (ii) their association with serum free thyroid hormones and with FT4:FT3 ratio goes in opposite directions.

The possible role of the kynurenine pathway in anhedonia in adolescents

To address the heterogeneous nature of adolescent major depression (MDD), we investigated anhedonia, a core symptom of MDD. We recently reported activation of the kynurenine pathway (KP), a central neuroimmunological pathway which metabolizes tryptophan (TRP) into kynurenine (KYN) en route to several neurotoxins, in a group of highly anhedonic MDD adolescents. In this study, we aimed to extend our prior work and examine the relationship between KP activity and anhedonia, measured quantitatively, in a group of MDD adolescents and in a combined group of MDD and healthy control adolescents. Thirty-six adolescents with MDD (22 medication-free) and 20 controls were included in the analysis. Anhedonia scores were generated based on clinician- and subject-rated assessments and a semi-structured clinician interview. Blood KP metabolites, collected in the AM after an overnight fast, were measured using high-performance liquid chromatography. The rate-limiting enzyme of the KP, indoleamine 2,3-dioxygenase (IDO), was estimated by the ratio of KYN/TRP. Pearson correlation tests were used to assess correlations between anhedonia scores and KP measures while controlling for MDD severity. IDO activity and anhedonia scores were positively correlated in the group psychotropic medication-free adolescents with MDD (r = 0.42, P = 0.05) and in a combined group of MDD subjects and healthy controls (including medicated patients: r = 0.30, P = 0.02; excluding medicated patients: r = 0.44, P = 0.004). In conclusions, our findings provide further support for the role for the KP, particularly IDO, in anhedonia in adolescent MDD. These results emphasize the importance of dimensional approaches in the investigation of psychiatric disorders.

No evidence for an anti-inflammatory effect of escitalopram intervention in healthy individuals with a family history of depression

Inflammation may contribute to the pathogenesis of depression and antidepressants are hypothesised to have an anti-inflammatory effect. In this randomised double-blinded trial we investigated the cytokine levels in supernatants of stimulated whole blood samples from first degree relatives to patients with depression randomised to a single daily dose of either 10mg escitalopram or placebo for four weeks. No significant differences were found in any of the cytokine levels between the participants treated with escitalopram (n=21) or placebo (n=23). Our data does thus not support the hypothesis of a global anti-inflammatory effect of escitalopram on cytokines in healthy subjects.

Cytokine changes in the pathophysiology of poststroke depression

OBJECTIVE

Poststroke depression (PSD) is a frequent psychiatric sequela after stroke, and its influence is detrimental. However, the etiology of PSD is still not clear. Although many studies have indicated that immune dysregulation plays an important role in the pathophysiology of depression, it is still unknown if PSD involves the same mechanism. Thus, the current study objectives were to evaluate whether there were cytokine changes when patients with ischemic stroke suffered from PSD.

METHOD

We included ischemic stroke patients without depression when the stroke occurred and followed them for 1 year. The Hamilton Depression Rating Scale score and cytokines were assessed at baseline and at the 1st, 3rd, 6th, 9th and 12th months after stroke.

RESULTS

One hundred four patients with ischemic stroke participated and completed the study, and 12 suffered from PSD during the 1-year study period. There were significant increases in the cytokines interleukin-6 (IL-6), interleukin-10 (IL-10), tumor necrosis factor α (TNF-α) and interferon-γ, and the ratios of IL-6/IL-10 and TNF-α/IL-10 were also elevated. Interleukin-1β was too low to show any difference.

CONCLUSION

Our study suggested that immune imbalance plays a possible role in the pathophysiology of PSD and that IL-6 and TNF-α are key cytokines.

Neuroimmune endocrine effects of antidepressants

Antidepressant pharmacotherapy is to date the most often used treatment for depression, but the exact mechanism of action underlying its therapeutic effect is still unclear. Many theories have been put forward to account for depression, as well as antidepressant activity, but none of them is exhaustive. Neuroimmune endocrine impairment is found in depressed patients; high levels of circulating corticosteroids along with hyperactivation of the immune system, high levels of proinflammatory cytokines, low levels of melatonin in plasma and urine, and disentrainment of circadian rhythms have been demonstrated. Moreover, antidepressant treatment seems to correct or at least to interfere with these alterations. In this review, we summarize the complex neuroimmune endocrine and chronobiological alterations found in patients with depression and how these systems interact with each other. We also explain how antidepressant therapy can modify these systems, along with some possible mechanisms of action shown in animal and human models.

A neuroimmunological perspective on anxiety disorders

OBJECTIVE

Research into psychoneuroimmunology has led to substantial advances in our understanding of the reciprocal interactions between the central nervous system and the immune system in neuropsychiatric disorders. To date, the presence of inflammatory responses and the crucial role of cytokines in major depression have been addressed in numerous studies. However, neuroinflammatory hypotheses in anxiety disorders have been studied less extensively than in major depression. There is a high research need for better understanding of both the heterogeneous role of specific cytokines in the control of anxious states and in different anxiety disorders and of the immunomodulating effects of antidepressants on anxiety.

METHODS

Relevant literature was identified through a search of MEDLINE via PubMed. We discuss recent research on neuroimmunology in anxiety and make methodological recommendations for future investigation of neuroinflammatory hypotheses in anxiety disorders.

RESULTS

Some accumulating evidence has indicated modulatory effects of cytokines on neuronal communication and anxiety; however, research has not revealed consistent reproducible findings.

CONCLUSIONS

The availability of inflammatory biomarkers may provide an opportunity to identify patients via specific pathophysiological processes and to monitor therapeutic responses within relevant pathways. Further understanding of the neuroimmunological mechanisms to untangle the reciprocal associations between inflammation and anxiety is warranted.

Mechanistic explanations how cell-mediated immune activation, inflammation and oxidative and nitrosative stress pathways and their sequels and concomitants play a role in the pathophysiology of unipolar depression

This paper reviews that cell-mediated-immune (CMI) activation and inflammation contribute to depressive symptoms, including anhedonia; anxiety-like behaviors; fatigue and somatic symptoms, e.g. illness behavior or malaise; and mild cognitive impairment (MCI). These effects are in part mediated by increased levels of pro-inflammatory cytokines (PICs), e.g. interleukin-1 (IL-1), IL-6 and tumor necrosis factor (TNF)α, and Th-1-derived cytokines, such as IL-2 and interferon (IFN)γ. Moreover, new pathways, i.e. concomitants and sequels of CMI activation and inflammation, were detected in depression: (1) Induction of indoleamine 2,3-dioxygenase (IDO) by IFNγ and some PICs is associated with depleted plasma tryptophan, which may interfere with brain 5-HT synthesis, and increased production of anxiogenic and depressogenic tryptophan catabolites. (2) Increased bacterial translocation may cause depression-like behaviors by activating the cytokine network, oxidative and nitrosative stress (O&NS) pathways and IDO. (3) Induction of O&NS causes damage to membrane ω3 PUFAs, functional proteins, DNA and mitochondria, and autoimmune responses directed against intracellular molecules that may cause dysfunctions in intracellular signaling. (4) Decreased levels of ω3 PUFAs and antioxidants, such as coenzyme Q10, glutathione peroxidase or zinc, are associated with an increased inflammatory potential; more oxidative damage; the onset of specific symptoms; and changes in the expression or functions of brain 5-HT and N-methyl-d-aspartate receptors. (5) All abovementioned factors cause neuroprogression, that is a combination of neurodegeneration, neuronal apoptosis, and lowered neurogenesis and neuroplasticity. It is concluded that depression may be the consequence of a complex interplay between CMI activation and inflammation and their sequels/concomitants which all together cause neuroprogression that further shapes the depression phenotype. Future research should employ high throughput technologies to collect genetic and gene expression and protein data from patients with depression and analyze these data by means of systems biology methods to define the dynamic interactions between the different cell signaling networks and O&NS pathways that cause depression.

Role of vitamin D in multiple sclerosis: implications for disease management

SUMMARY This review discusses the evidence on the role of vitamin D in multiple sclerosis (MS) and whether vitamin D supplementation is effective for the management of MS. People with MS are at high risk of vitamin D deficiency, osteoporosis and fractures. Observational data suggest that higher vitamin D levels are associated with lower relapse risk and there is promising evidence on its effect on MRI measures, disability progression, mental health and fatigue. However, there is currently insufficient randomized controlled trial evidence to recommend vitamin D supplementation with the aim to improve those outcomes. There is sufficient evidence to justify assessing and correcting vitamin D and calcium levels to optimize bone health in people with MS at high absolute risk of fracture.

Antidepressants for pain management in rheumatoid arthritis

BACKGROUND

Pain management is a high priority for patients with rheumatoid arthritis (RA). Antidepressants are sometimes used as adjuvant agents to enhance pain relief, help with sleep and reduce depression. Such antidepressants include tricyclic antidepressants (TCAs), monoamine oxidase inhibitors (MAOIs), selective serotonin reuptake inhibitors (SSRIs), selective serotonin noradrenaline reuptake inhibitors (SNRIs) and norepinephrine reuptake inhibitors (NRIs). However, the prescription of antidepressants in this population remains controversial because of conflicting scientific evidence.

OBJECTIVES

The aim of this review was to determine the efficacy and safety of antidepressants in pain management in patients with RA.

SEARCH METHODS

We performed a computer assisted search of the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010, 4th quarter); MEDLINE (1950 to November Week 1, 2010); EMBASE (2010 Week 44); and PsycINFO (1806 to November Week 2, 2010). We also searched the 2008-2009 American College of Rheumatology (ACR) and European League Against Rheumatism (EULAR) abstracts and performed a handsearch of reference lists of articles.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) which compared an antidepressant therapy to another therapy (active or placebo, including non-pharmacological therapies) in adult patients with RA who had at least one clinically relevant outcome measure. Outcomes of interest were pain, adverse effects, function, sleep, depression and quality of life.

DATA COLLECTION AND ANALYSIS

Two blinded review authors independently extracted data and assessed the risk of bias in the trials. We conducted meta-analyses to examine the efficacy of antidepressants on pain, depression and function, as well as their safety.

MAIN RESULTS

We included eight RCTs (652 participants) in this review. All trials evaluated TCAs and two trials evaluated a SSRI as a comparator. Seven of the eight trials had high risk of bias. There was insufficient data for a number needed to treat for an additional beneficial outcome (NNTB) to be calculated for the primary outcome measure of pain. The qualitative analyses found no evidence of an effect of antidepressants on pain intensity or depression in the short-term (less than one week), and conflicting evidence of a medium- (one to six weeks) or long-term (more than six weeks) benefit. There were significantly more minor adverse events in patients receiving TCAs compared with those receiving a placebo (risk ratio (RR) 2.27, 95% confidence interval (CI) 1.17 to 4.42), but there was no significant increase in withdrawals due to an adverse event (RR 1.09, 95% CI 0.49 to 2.42).

AUTHORS' CONCLUSIONS

There is currently insufficient evidence to support the routine prescription of antidepressants as analgesics in patients with RA as no reliable conclusions about their efficacy can be drawn from eight placebo RCTs. The use of these agents may be associated with adverse events which are generally mild and do not lead to cessation of treatment. More high quality trials are needed in this area.

Vitamin D status in patients with MS is negatively correlated with depression, but not with fatigue

BACKGROUND

Depressive symptoms and fatigue are frequent and disabling symptoms of multiple sclerosis (MS). Depression and fatigue have been associated with a poor vitamin D status, and a poor vitamin D status is often found in MS.

AIM

Assess whether vitamin D status contributes to depressive symptoms and fatigue in MS.

METHODS

Patients with MS that participated in previous studies in which depression and fatigue were assessed and of whom serum 25-hydroxyvitamin D (25(OH)D) levels were available within a timeframe of less than one half-life of 25(OH)D were included. Depression and fatigue were assessed with the Hospital Anxiety and Depression Scale and the Multidimensional Fatigue Inventory.

RESULTS

  Fifty-nine patients were included. Mean scores of fatigue and depression were 14.6 (SD 4.2) and 6.2 (SD 4.4), respectively. The mean vitamin D status was 62.3 nm (SD 27.8). Vitamin D status correlated negatively with depression (r=-0.326, P=0.006). No significant correlation was found between vitamin D status and fatigue. In a multiple regression model, vitamin D status was not a significant contributor to depression, after controlling for age Expanded Disability Status Scale score and fatigue (P=0.078). Alternatively, depression and fatigue did not contribute to vitamin D status.

DISCUSSION

This study shows a negative correlation between vitamin D status and depressive symptoms in patients with MS. Although multiple confounders exist, we observed an indication that vitamin D status might contribute to the presence of depressive symptoms in MS. Therefore, further studies on vitamin D in MS should include depressive symptoms as outcome measures to confirm these findings.

Altered expression of genes involved in inflammation and apoptosis in frontal cortex in major depression

The etiology of major depression (MDD), a common and complex disorder, remains obscure. Gene expression profiling was conducted on post-mortem brain tissue samples from Brodmann Area 10 (BA10) in the prefrontal cortex from psychotropic drug-free persons with a history of MDD and age, gender, and post-mortem interval-matched normal controls (n=14 pairs of subjects). Microarray analysis was conducted using the Affymetrix Exon 1.0 ST arrays. A set of differential expression changes was determined by dual-fold change-probability criteria (∣average log ratios∣>0.585 [equivalent to a 1.5-fold difference in either direction], P<0.01), whereas molecular pathways of interest were evaluated using Gene Set Enrichment Analysis software. The results strongly implicate increased apoptotic stress in the samples from the MDD group. Three anti-apoptotic factors, Y-box-binding protein 1, caspase-1 dominant-negative inhibitor pseudo-ICE, and the putative apoptosis inhibitor FKGS2, were over-expressed. Gene set analysis suggested up-regulation of a variety of pro- and anti-inflammatory cytokines, including interleukin 1α (IL-1α), IL-2, IL-3, IL-5, IL-8, IL-9, IL-10, IL-12A, IL-13, IL-15, IL-18, interferon gamma (IFNγ), and lymphotoxin α (TNF superfamily member 1). The genes showing reduced expression included metallothionein 1M (MT1M), a zinc-binding protein with a significant function in the modulation of oxidative stress. The results of this study indicate that post-mortem brain tissue samples from BA10, a region that is involved in reward-related behavior, show evidence of local inflammatory, apoptotic, and oxidative stress in MDD.

Fluoxetine inhibits NF-κB signaling in intestinal epithelial cells and ameliorates experimental colitis and colitis-associated colon cancer in mice

Although fluoxetine, a selective serotonin reuptake inhibitor, is known to demonstrate anti-inflammatory activity, little information is available on the effect of fluoxetine regarding intestinal inflammation. This study investigates the role of fluoxetine in the attenuation of acute murine colitis by suppression of the NF-κB pathway in intestinal epithelial cells (IEC). Fluoxetine significantly inhibited activated NF-κB signals and the upregulated expression of interleukin-8 (IL-8) in COLO 205 colon epithelial cells stimulated with tumor necrosis factor-α (TNF-α). Pretreatment with fluoxetine attenuated the increased IκB kinase (IKK) and IκBα phosphorylation induced by TNF-α. In a murine model, administration of fluoxetine significantly reduced the severity of dextran sulfate sodium (DSS)-induced colitis, as assessed by the disease activity index, colon length, and histology. In addition, the DSS-induced phospho-IKK activation, myeloperoxidase activity, a parameter of neutrophil accumulation, and the secretion of macrophage-inflammatory protein-2, a mouse homolog of IL-8, were significantly decreased in fluoxetine-pretreated mice. Moreover, fluoxetine significantly attenuated the development of colon cancer in mice inoculated with azoxymethane and DSS. These results indicate that fluoxetine inhibits NF-κB activation in IEC and that it ameliorates DSS-induced acute murine colitis and colitis-associated tumorigenesis, suggesting that fluoxetine is a potential therapeutic agent for the treatment of inflammatory bowel disease.

Selective serotonin reuptake inhibitors attenuate the antigen presentation from dendritic cells to effector T lymphocytes

Fluoxetine, one of the selective serotonin reuptake inhibitors (SSRIs), has been found to possess immune modulation effects, in addition to its antidepressant effects. However, it remains unclear whether SSRIs can suppress the antigen-presenting function of dendritic cells (DCs). Therefore, Fluoxetine was applied to a co-culture of Aggregatibacter actinomycetemcomitans (Aa)-reactive T cells (×Aa-T) isolated from Aa-immunized mice and DCs. This resulted in the suppressed proliferation of ×Aa-T stimulated with Aa-antigen presentation by DCs. Specifically, Fluoxetine increased the extracellular 5-hydroxytryptamine (5-HT) in the ×Aa-T/DC co-culture, whereas exogenously applied 5-HT promoted T-cell proliferation in the ×Aa-T/DC co-culture, indicating that Fluoxetine-mediated suppression of ×Aa-T/DC responses cannot be attributed to extracellular 5-HT. Instead, Fluoxetine remarkably suppressed the expression of costimulatory molecule ICOS-L on DCs. Fluoxetine also promoted a greater proportion of CD86(Low) immature DCs than CD86(High) mature DCs, while maintaining the expression levels of CD80, MHC-class-II and PD-L1. These results suggested that Fluoxetine suppressed the ability of DCs to present bacterial antigens to T cells, and the resulting T-cell proliferation, in a SERT/5-HT-independent manner and that diminished expression of ICOS-L on DCs and increase of CD86(Low) immature DCs caused by Fluoxetine might be partially associated with Fluoxetine-mediated suppression of DC/T-cell responses.

An Evolutionary Hypothesis of Suicide: Why it Could be Biologically Adaptive and is so Prevalent in Certain Occupations

From an evolutionary perspective, suicide is a puzzle, because it has serious adverse effects, yet is remarkably common and heritable. An hypothesis is proposed to explain this puzzle, by explaining how suicide could be adaptive through reducing risk that individuals will transmit infections to kin. Empirical evidence supports four predictions from the hypothesis. There are well-established mechanisms by which infections and immune factors increase risk for mental disorders that contribute to suicide. Suicide is more prevalent in occupations with greater exposure to infection and immune-compromising factors and at higher latitudes, where key environmental factors increase vulnerability to infection. In several other highly social species, suicide-like behaviors have evolved to reduce transmission of infections. If the hypothesis is correct, detection and treatment of underlying infections and immune dysfunction should help predict and prevent suicidal behavior, while also combating spread of infectious diseases.

Inflammation in depression: is adiposity a cause?

Mounting evidence indicates that inflammation may play a significant role in the development of depression. Patients with depression exhibit increased inflammatory markers, and administration of cytokines and other inflammatory stimuli can induce depressive symptoms. Mechanisms by which cytokines access the brain and influence neurotransmitter systems relevant to depression have also been described, as have preliminary findings indicating that antagonizing inflammatory pathways may improve depressive symptoms. One primary source of inflammation in depression appears to be adiposity. Adipose tissue is a rich source of inflammatory factors including adipokines, chemokines, and cytokines, and a bidirectional relationship between adiposity and depression has been revealed. Adiposity is associated with the development of depression, and depression is associated with adiposity, reflecting a potentional vicious cycle between these two conditions which appears to center around inflammation. Treatments targeting this vicious cycle may be especially relevant for the treatment and prevention of depression as well as its multiple comorbid disorders such as cardiovascular disease, diabetes, and cancer, all of which have also been associated with both depression and inflammation.

Depression is an inflammatory disease, but cell-mediated immune activation is the key component of depression

The first findings that depression is characterized by cell-mediated immune activation and inflammation were published between 1990-1993 (Maes et al.). Recently, it was reported that--based on meta-analysis results--depression is an inflammatory disorder because the plasma levels of two cytokines are increased, i.e. interleukin-(IL)-6 and tumor necrosis factor-α (TNFα). The same meta-analysis found that plasma IL-2 and interferon-(IFN)γ levels are not altered in depression, suggesting that there is no T cell activation in that illness. The present paper reviews the body of evidence that depression is accompanied by cell-mediated immune activation. The findings include: increased serum levels of the soluble IL-2 receptor (sIL-2R) and the sCD8 molecule; increased numbers and percentages of T cells bearing T cell activation markers, such as CD2+CD25+, CD3+CD25+, and HLA-DR+; increased stimulated production of IFNγ; higher neopterin and sTNFR-1 or sTNFR-2 levels; induction of indoleamine 2,3-dioxygenase (IDO) with lowered levels of plasma tryptophan and increased levels of tryptophan catabolites along the IDO pathway (TRYCATs); and glucocorticoid resistance in immune cells. Interferon-α (IFNα)-based immunotherapy shows that baseline and IFNα-induced activation of T cells, IDO activity and TRYCAT formation are related to the development of IFNα-induced depressive symptoms. Animal models of depression show that a cell-mediated immune response is related to the development of depression-like behavior. Antidepressants and mood stabilizers suppress different aspects of cell-mediated immunity and rather specifically target IFNγ production. This review shows that inflammation and cell-mediated immune activation are key factors in depression.

In animal models, psychosocial stress-induced (neuro)inflammation, apoptosis and reduced neurogenesis are associated to the onset of depression

Recently, the inflammatory and neurodegenerative (I&ND) hypothesis of depression was formulated (Maes et al., 2009), i.e. the neurodegeneration and reduced neurogenesis that characterize depression are caused by inflammation, cell-mediated immune activation and their long-term sequels. The aim of this paper is to review the body of evidence that external stressors may induce (neuro)inflammation, neurodegeneration and reduced neurogenesis; and that antidepressive treatments may impact on these pathways. The chronic mild stress (CMS) and learned helplessness (LH) models show that depression-like behaviors are accompanied by peripheral and central inflammation, neuronal cell damage, decreased neurogenesis and apoptosis in the hippocampus. External stress-induced depression-like behaviors are associated with a) increased interleukin-(IL)1β, tumor necrosis factor-α, IL-6, nuclear factor κB, cyclooxygenase-2, expression of Toll-like receptors and lipid peroxidation; b) antineurogenic effects and reduced brain-derived neurotrophic factor (BDNF) levels; and c) apoptosis with reduced levels of Bcl-2 and BAG1 (Bcl-2 associated athanogene 1), and increased levels of caspase-3. Stress-induced inflammation, e.g. increased IL-1β, but not reduced neurogenesis, is sufficient to cause depression. Antidepressants a) reduce peripheral and central inflammatory pathways by decreasing IL-1β, TNFα and IL-6 levels; b) stimulate neuronal differentiation, synaptic plasticity, axonal growth and regeneration through stimulatory effects on the expression of different neurotrophic factors, e.g. trkB, the receptor for brain-derived neurotrophic factor; and c) attenuate apoptotic pathways by activating Bcl-2 and Bcl-xl proteins, and suppressing caspase-3. It is concluded that external stressors may provoke depression-like behaviors through activation of inflammatory, oxidative, apoptotic and antineurogenic mechanisms. The clinical efficacity of antidepressants may be ascribed to their ability to reverse these different pathways.

Pro-inflammatory cytokines and depression in myocardial infarction

Aim. To assess the associations between inflammatory factors and anxiety (A) and depression (D) levels in patients with myocardial infarction (MI). Material and methods. The study included 100 MI patients, hospitalised with a diagnosis of Q-wave MI (mean age 62,0±1,3 years). The methods of psychosocial status assessment included Zung depression scale and SpielbergerKhanin personal and reactive anxiety scales. The inflammatory markers of interest included interleukins (IL) 1-beta, IL-6, IL-8, IL-10, and C-reactive protein (CRP). Results. D and A symptoms in the early post-MI stage were associated with higher risk of cardiovascular events in the following year. Among MI patients with comparable MI severity, D and A symptoms were linked to higher levels of pro-inflammatory cytokines IL-1-beta, IL-8, IL-8, and INF-gamma. Conclusion. In MI patients with D and A symptoms, one of the mechanisms of poor prognosis is an activation of subclinical inflammation.

Toward an anti-inflammatory strategy for depression

It has become clear that the inflammatory immune system is altered during the course of clinical depression. In particular, studies on human patients have found depression to be associated with disturbances in the trafficking of cells of the adaptive immune system, coupled with elevations of innate immune messengers and pro-inflammatory cytokines. Paralleling these findings, stressor-based animal models of depression have implicated several cytokines, most notably interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α. Elevations of these cytokines and general inflammatory indicators, such as C-reactive protein, together with reductions of specific immune cells (e.g., T lymphocytes) might serve as useful biomarkers of depression or at least, certain subtypes of the disorder. Recent reports also suggest the possibility that anti-inflammatory agents could have therapeutic value in acting as adjunct treatments with traditional anti-depressants. Along these lines, we presently discuss the evidence for pro-inflammatory cytokine involvement in depression, as well as the possibility that anti-inflammatory agents and trophic cytokines themselves might have important anti-depressant properties.

Oral administration of fluoxetine alters the proliferation/apoptosis balance of lymphoma cells and up-regulates T cell immunity in tumor-bearing mice

Antidepressants have a controversial role with regard to their influence on cancer and immunity. Recently, we showed that fluoxetine administration induces an enhancement of the T-cell mediated immunity in naïve mice, resulting in the inhibition of tumor growth. Here we studied the effects of fluoxetine on lymphoma proliferation/apoptosis and immunity in tumor bearing-mice. We found an increase of apoptotic cells (active Caspase-3(+)) and a decrease of proliferative cells (PCNA(+)) in tumors growing in fluoxetine-treated animals. In addition, differential gene expressions of cell cycle and death markers were observed. Cyclins D3, E and B were reduced in tumors from animals treated with fluoxetine, whereas the tumor suppressor p53 and the cell cycle inhibitors p15/INK4B, p16/INK4A and p27/Kip1 were increased. Besides, the expression of the antiapoptotic factor Bcl-2 and the proapoptotic factor Bad were lower and higher respectively in these animals. These changes were accompanied by increased IFN-γ and TNF-α levels as well as augmented circulating CD8(+) T lymphocytes in tumor-bearing mice treated with the antidepressant. Therefore, we propose that the up-regulation of T-cell mediated antitumor immunity may be contributing to the alterations of tumor cell proliferation and apoptosis thus resulting in the inhibition of tumor progression.

Fluoxetine inhibited extracellular matrix of pulmonary artery and inflammation of lungs in monocrotaline-treated rats

AIM

To investigate the effects of the selective serotonin reuptake inhibitor (SSRI) fluoxetine on extracellular matrix (ECM) remodeling of the pulmonary artery and inflammation of the lungs in pulmonary arterial hypertension (PAH) induced by monocrotaline in rats.

METHODS

MCT-induced chronic PAH was established in Wistar rats. After treatment with fluoxetine for 3 weeks, pulmonary hemodynamic measurement and morphological investigation of lung tissues were undertaken. The main components of the ECM, elastin and collagen, were detected using Van Gieson stain and Orcein stain, respectively, or using Victoria-ponceau's double stain. The ECM proteolytic enzymes matrix metalloproteinase (MMP)-2 and MMP-9, and the tissue inhibitors of metalloproteinase (TIMP)-1 and TIMP-2, were detected by Western blot. Inflammation of lung tissue was assayed using lung morphology and inflammatory cytokine expression.

RESULTS

Fluoxetine (2 and 10 mg/kg) significantly inhibited MCT-induced PAH, attenuated pulmonary arterial muscularization and ECM remodeling, and decreased MMP/TIMP expression. Fluoxetine also suppressed inflammatory responses in lung tissue and inhibited the expression of the inflammatory cytokines interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), monocyte chemotactic protein (MCP-1) and intercellular adhesion molecule-1 (ICAM-1).

CONCLUSION

Fluoxetine inhibited MCT-induced ECM remodeling of the pulmonary artery and inflammation of lung tissue. These effects were related to its inhibition on MMPs/TIMPs and cytokine productions.

Depression: a repair response to stress-induced neuronal microdamage that can grade into a chronic neuroinflammatory condition?

Depression is a major contributor to the global burden of disease and disability, yet it is poorly understood. Here we review data supporting a novel theoretical model for the biology of depression. In this model, a stressful life event leads to microdamage in the brain. This damage triggers an injury repair response consisting of a neuroinflammatory phase to clear cellular debris and a spontaneous tissue regeneration phase involving neurotrophins and neurogenesis. During healing, released inflammatory mediators trigger sickness behavior and psychological pain via mechanisms similar to those that produce physical pain during wound healing. The depression remits if the neuronal injury repair process resolves successfully. Importantly, however, the acute psychological pain and neuroinflammation often transition to chronicity and develop into pathological depressive states. This hypothesis for depression explains substantially more data than alternative models, including why emerging data show that analgesic, anti-inflammatory, pro-neurogenic and pro-neurotrophic treatments have antidepressant effects. Thus, an acute depressive episode can be conceptualized as a normally self-limiting but highly error-prone process of recuperation from stress-triggered neuronal microdamage.

A biological pathway linking inflammation and depression: activation of indoleamine 2,3-dioxygenase

This article highlights the evidence linking depression to increased inflammatory drive and explores putative mechanisms for the association by reviewing both preclinical and clinical literature. The enzyme indoleamine 2,3-dioxygenase is induced by proinflammatory cytokines and may form a link between immune functioning and altered neurotransmission, which results in depression. Increased indoleamine 2,3-dioxygenase activity may cause both tryptophan depletion and increased neurotoxic metabolites of the kynurenine pathway, two alterations which have been hypothesized to cause depression. The tryptophan-kynurenine pathway is comprehensively described with a focus on the evidence linking metabolite alterations to depression. The use of immune-activated groups at high risk of depression have been used to explore these hypotheses; we focus on the studies involving chronic hepatitis C patients receiving interferon-alpha, an immune activating cytokine. Findings from this work have led to novel strategies for the future development of antidepressants including inhibition of indoleamine 2,3-dioxygenase, moderating the cytokines which activate it, or addressing other targets in the kynurenine pathway.

Increase in IL-6 levels among major depressive disorder patients after a 6-week treatment with duloxetine 60 mg/day: a preliminary observation

BACKGROUND

Immune modifications, including changes in interleukin (IL)-6 levels, have often been observed in major depressive disorder (MDD) during treatment with selective serotonin reuptake inhibitors (SSRIs) or the serotonin norepinephrine reuptake inhibitor (SNRI) venlafaxine. Nevertheless, no equivalent observation for the SNRI duloxetine has been made to date.

METHOD

Sixteen patients diagnosed with MDD and an actual major depressive episode according to DSM-IV criteria and 16 healthy controls entered a 6-week trial with duloxetine 60 mg/day. All subjects (n = 32) were assessed using the Hamilton Depression Rating Scale (HAM-D), the Young Mania Rating Scale (YMRS), and were monitored for IL-6 levels both at baseline and at week 6. Blood samples for IL-6 levels were evaluated by ELISA.

RESULTS

After 6 weeks of treatment, the mean total scores for HAM-D declined both in the depressed and control groups, while IL-6 modification showed an opposite trend both in depressed (12.38 ± 19.80 to 19.73 ± 18.94 pg/mL) and control subjects (12.25 ± 21.12 to 17.63 ± 20.44 pg/mL), as did YMRS (ns), although none of the subjects switched to (hypo)mania. Of note, IL-6 levels increased significantly only in the responders subgroup (n = 9; P = 0.012).

CONCLUSION

The small sample size and weak design of this study limit the validity of our results, which should be regarded as preliminary only. Nonetheless, the trend of increasing IL-6 levels observed in responder patients treated with duloxetine should prompt further controlled, extended studies with larger samples, with the specific aim of better assessing a putative differential role of norepinephrinergic antidepressant stimulation of serotonergic reuptake inhibition in determining modifications in IL-6 levels. Ideally, more accurate replication studies may contribute to further understanding of the complex interaction of mood, antidepressant response, and the immune system.

Regulatory T cells increased while IL-1β decreased during antidepressant therapy

BACKGROUND

Regulatory T cells (Tregs, CD4(+)CD25(hi)) are specialized in steering the immune response and cytokine release to maintain tolerance to self-antigens. As cytokines such as interleukin (IL)-1β, IL-6 and interferon (IFN)-α have been shown to be involved in the pathophysiology of depression and cytokine levels have been shown to change during successful antidepressant treatment, we tested the involvement CD4(+)CD25(hi) Tregs in these immunological processes during antidepressant therapy.

METHODS

16 patients suffering from a depressive episode were included into the study and treated with antidepressants according to their doctor's choice. Blood samples were collected during the first week after admission and after 6 weeks of treatment. Therein, we determined plasma levels of IL-1β, and measured IL-1β, IL-6 and IFN-α levels in the stimulated blood by performing a whole blood assay. We distinguished lymphocytes and identified CD4(+)CD25(hi) Tregs by multiparameter flow cytometry. The psychopathological status was assessed using the Hamilton Depression Rating Scale (HAMD-21).

RESULTS

HAMD-21 score, IL-1β serum levels as well as LPS-stimulated IL-1β and IL-6 production had decreased significantly at the end of treatment. In contrast, the amount of CD4(+)CD25(hi) cells increased significantly from 2.74% ± 0.88 (mean value ± standard deviation) to 3.54% ± 1.21; p = 0.007. No significant changes in virus-induced IFN-α production was observed.

CONCLUSIONS

The increase in CD4(+)CD25(hi) Tregs during antidepressant therapy may be the reason for the decrease in cytokine production and the recovery from depression.

The effect of newer serotonin-noradrenalin antidepressants on cytokine production: a review of the current literature

Cytokines may influence brain activities especially during stressful conditions, and elevated levels of IL-6 and C-reactive protein have been pointed out in subjects with Major Depression. If pro-inflammatory cytokines play a causative role in major depressive disorders, one would expect that antidepressants may down-regulate these cytokines or interfere with their actions, leading to improvement of depressive symptoms. Accumulating evidence has been published that antidepressants modulate cytokine production and this is particularly true for Tricyclics and Selective serotonin reuptake inhibitors (SSRIs), but the influence of newer antidepressants acting on both serotonin (5-HT) and norepinephrine (NE) such as venlafaxine, duloxetine and mirtazapine on cytokine levels has not been extensively studied. However, both pre-clinical and clinical studies examined in this review have demonstrated that newer serotonin-noradrenalin antidepressants can inhibit the production and/or release of pro-inflammatory cytokines and stimulate the production of anti-inflammatory cytokines, suggesting that reductions in inflammation might contribute to treatment response. Moreover, the results of the present review support the notion that the serotonin-noradrenalin antidepressants venlafaxine and mirtazapine may influence cytokine secretion in patients affected by MD, restoring the equilibrium between their physiological and pathological levels and leading to recovery. To date, no studies have evaluated the effect of duloxetine, the newest serotonin-noradrenalin antidepressant, on cytokine levels and therefore this should be evaluated in future studies.

The immunobiology of Tourette's disorder, pediatric autoimmune neuropsychiatric disorders associated with Streptococcus, and related disorders: a way forward

Obsessive-compulsive disorder (OCD) and related conditions including Tourette's disorder (TD) are chronic, relapsing disorders of unknown etiology associated with marked impairment and disability. Associated immune dysfunction has been reported and debated in the literature since the late 80s. The immunologic culprit receiving the most interest has been Group A Streptococcus (GAS), which began to receive attention as a potential cause of neuropsychiatric symptoms, following the investigation of the symptoms reported in Sydenham's chorea (SC) and rheumatic fever, such as motor tics, vocal tics, and both obsessive-compulsive and attention deficit/hyperactivity symptoms. Young children have been described as having a sudden onset of these neuropsychiatric symptoms temporally associated with GAS, but without supporting evidence of rheumatic fever. This presentation of OCD and tics has been termed pediatric autoimmune neuropsychiatric disorders associated with Streptococcus (PANDAS). Of note, SC, OCD, and TD often begin in early childhood and share common anatomic areas--the basal ganglia of the brain and the related cortical and thalamic sites--adding support to the possibility that these disorders might share a common immunologic and/or genetic vulnerability. Relevant manuscripts were identified through searches of the PsycINFO and MedLine databases using the following keywords: OCD, immune, PANDAS, Sydenham chorea, Tourette's disorder Group A Streptococcus. Articles were also identified through reference lists from research articles and other materials on childhood OCD, PANDAS, and TD between 1966 and December 2010. Considering the overlap of clinical and neuroanatomic findings among these disorders, this review explores evidence regarding the immunobiology as well as the relevant clinical and therapeutic aspects of TD, OCD, and PANDAS.

Eating ourselves to death (and despair): the contribution of adiposity and inflammation to depression

Obesity and related metabolic conditions are of epidemic proportions in most of the world, affecting both adults and children. The accumulation of lipids in the body in the form of white adipose tissue in the abdomen is now known to activate innate immune mechanisms. Lipid accumulation causes adipocytes to directly secrete the cytokines interleukin (IL) 6 and tumor necrosis factor alpha (TNFalpha), but also monocyte chemoattractant protein 1 (MCP-1), which results in the accumulation of leukocytes in fat tissue. This sets up a chronic inflammatory state which is known to mediate the association between obesity and conditions such as cardiovascular disease, type 2 diabetes, and cancer. There is also a substantial literature linking inflammation with risk for depression. This includes the observations that: (1) people with inflammatory diseases such as multiple sclerosis, cardiovascular disease, and psoriasis have elevated rates of depression; (2) many people administered inflammatory cytokines such as interferon alpha develop depression that is indistinguishable from depression in non-medically ill populations; (3) a significant proportion of depressed persons show upregulation of inflammatory factors such as IL-6, C-reactive protein, and TNFalpha; (4) inflammatory cytokines can interact with virtually every pathophysiologic domain relevant to depression, including neurotransmitter metabolism, neuroendocrine function, and synaptic plasticity. While many factors may contribute to the association between inflammatory mediators and depression, we hypothesize that increased adiposity may be one causal pathway. Mediational analysis suggests a bi-directional association between adiposity and depression, with inflammation possibly playing an intermediary role.

Altered expression of CD4(+)CD25(+) regulatory T cells and its 5-HT(1a) receptor in patients with major depression disorder

BACKGROUND

There is growing interest in immune imbalance observed in major depression, but the mechanism of this imbalance is still not well understood. CD4(+)CD25(+) regulatory T (Treg) cells are known to play an important role in immune regulation. However, their role in major depression has rarely been explored. The aims of this study are to determine the immune imbalance status in patients when first diagnosed with major depression, and to explore possible indications of Treg cell involvement in immune imbalance of major depression.

METHODS

27 patients with major depression and 27 healthy individuals were recruited in the study. The immune imbalance was observed by the analysis of Th cell cytokines and CD4(+)CD25(+) Treg cell level. The 5-HT in peripheral serum was measured with HPLC, and changes of Foxp3 and 5-HT(1a) receptor were observed by RT-PCR and double-immunofluorescence.

RESULTS

Despite the similar total lymphocyte count between patients and healthy individuals, the Th1/Th2 ratio increased and the CD4(+)CD25(+) Treg cells decreased in patients' peripheral blood. Moreover, we found that the level of 5-HT was decreased in peripheral serum, and the expression of 5-HT(1a) receptor was also decreased in peripheral lymphocytes of major depression patients, notably in the CD4(+)CD25(+) Treg cells rather than CD4(+)CD25(-) T cells.

LIMITATIONS

The details of interaction between 5-HT(1a) receptors and Treg cells in major depression need further exploration.

CONCLUSION

CD4(+)CD25(+) Treg cells may contribute to the immune imbalance in patients with major depression, which could involve its interaction with 5-HT system.

Antidepressant pharmacotherapy: focus on sex differences in neuroimmunopharmacological crossroads

Major depression is a stress-related disorder that shows a clear female preponderance. Sex differences in antidepressant response have been documented in both the clinical and experimental settings. It is of interest that antidepressant drugs exert critical immunotropic influences, mediated by direct and/or compensatory routes; these effects are not completely understood but comprise a matter of intensive investigation. Even though human studies have found only a few sex-related differences in the immunotropic effects of antidepressants, recent experimental evidence in the chronic mild stress model of depression points towards a sexually dimorphic neuroimmune playground in view of chronic antidepressant treatment. Herein, we provide a concise review regarding the effects of antidepressant pharmacotherapy on neuroimmune manifestations by concentrating on intriguing sex differences.

Effect of venlafaxine on bone loss associated with ligature-induced periodontitis in Wistar rats

Background

The present study investigated the effects of venlafaxine, an antidepressant drug with immunoregulatory properties on the inflammatory response and bone loss associated with experimental periodontal disease (EPD).

Materials and Methods

Wistar rats were subjected to a ligature placement around the second upper left molar. The treated groups received orally venlafaxine (10 or 50 mg/kg) one hour before the experimental periodontal disease induction and daily for 10 days. Vehicle-treated experimental periodontal disease and a sham-operated (SO) controls were included. Bone loss was analyzed morphometrically and histopathological analysis was based on cell influx, alveolar bone, and cementum integrity. Lipid peroxidation quantification and immunohistochemistry to TNF-α and iNOS were performed.

Results

Experimental periodontal disease rats showed an intense bone loss compared to SO ones (SO = 1.61 ± 1.36; EPD = 4.47 ± 1.98 mm, p < 0.001) and evidenced increased cellular infiltration and immunoreactivity for TNF-α and iNOS. Venlafaxine treatment while at low dose (10 mg/kg) afforded no significant protection against bone loss (3.25 ± 1.26 mm), a high dose (50 mg/kg) caused significantly enhanced bone loss (6.81 ± 3.31 mm, p < 0.05). Venlafaxine effectively decreased the lipid peroxidation but showed no significant change in TNF-α or iNOS immunoreactivity.

Conclusion

The increased bone loss associated with high dose venlafaxine may possibly be a result of synaptic inhibition of serotonin uptake.

Fluoxetine and citalopram exhibit potent antiinflammatory activity in human and murine models of rheumatoid arthritis and inhibit toll-like receptors

OBJECTIVE

Selective serotonin reuptake inhibitors (SSRIs), in addition to their antidepressant effects, have been reported to have antiinflammatory effects. The aim of this study was to assess the antiarthritic potential of 2 SSRIs, fluoxetine and citalopram, in murine collagen-induced arthritis (CIA) and in a human ex vivo disease model of rheumatoid arthritis (RA).

METHODS

Following therapeutic administration of SSRIs, paw swelling was assessed and clinical scores were determined daily in DBA/1 mice with CIA. Joint architecture was examined histologically at the end of the treatment period. Cultures of human RA synovial membranes were treated with SSRIs, and cytokine production was measured. Toll-like receptor (TLR) function was examined in murine and human macrophages, human B cells, and human fibroblast-like synovial cells treated with SSRIs.

RESULTS

Both SSRIs significantly inhibited disease progression in mice with CIA, with fluoxetine showing the greatest degree of efficacy at the clinical and histologic levels. In addition, both drugs significantly inhibited the spontaneous production of tumor necrosis factor, interleukin-6, and interferon-gamma-inducible protein 10 in human RA synovial membrane cultures. Fluoxetine and citalopram treatment also inhibited the signaling of TLRs 3, 7, 8, and 9, providing a potential mechanism for their antiinflammatory action.

CONCLUSION

Fluoxetine and citalopram treatment selectively inhibit endosomal TLR signaling, ameliorate disease in CIA, and suppress inflammatory cytokine production in human RA tissue. These data highlight the antiarthritic potential of the SSRI drug family and provide further evidence of the involvement of TLRs in the pathogenesis of RA. The SSRIs may provide a template for potential antiarthritic drug development.

A psychoneuroimmunological review on cytokines involved in antidepressant treatment response

OBJECTIVES

The literature exploring the role that cytokine functioning plays in the pathogenesis and treatment of depressive illness is reviewed. The review focuses on the influence of antidepressants on cytokines, and on how treatment response might be affected by genetic variants of cytokines.

METHOD

The authors systematically reviewed the scientific literature on the subject over the last 20 years, searching PubMed, PsychInfo, and Cochrane databases.

RESULTS

Antidepressants modulate cytokine functioning, and these mechanisms appear to directly influence treatment outcome in depression. Antidepressants appear to normalize serum levels of major inflammatory cytokines, including interleukin (IL)-1beta, IL-6, tumor necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma). Antidepressants are postulated to modulate cytokine functioning through their effects on intracellular cyclic adenosyl monophosphate (cAMP), serotonin metabolism, the hypothalamo-pituitary-adrenocortical (HPA) axis or through a direct action on neurogenesis. Preliminary research shows that cytokine genotypes and functioning may be able to help predict antidepressant treatment response.

CONCLUSIONS

Current literature demonstrates an association between antidepressant action and cytokine functioning in major depression. Improved understanding of the specific pharmacologic and pharmacogenetic mechanisms is needed. Such knowledge may serve to enhance our understanding of depression, leading to promising new directions in the pathology, nosology, and treatment of depression.

Effect of co-administration of fluoxetine and amantadine on immunoendocrine parameters in rats subjected to a forced swimming test

Considerable attention has been paid to a possible role of immunological dysregulation in the pathogenesis of depression. It has been reported that combined administration of antidepressant drugs and the non-competitive NMDA receptor antagonist amantadine reduces immobility time in the forced swimming test (FST). Moreover, preliminary clinical data show that such a combination of drugs has a beneficial effect on treatment-resistant depressed patients. Since immune activation and a pro-inflammatory response are clearly evident in treatment-resistant depression, the aim of the present study was to examine the effect of a combination of the antidepressant fluoxetine and amantadine on immunoendocrine parameters in rats subjected to the forced swimming test. The obtained results revealed synergistic antidepressant effects of the combined administration of fluoxetine (10 mg/kg) and amantadine (10 mg/kg) - drugs otherwise ineffective when given separately in the above doses. Antidepressant activity was accompanied with a significant decrease in the capacity of splenocytes to proliferate in response to concanavalin A. Moerover, fluoxetine and the combination of amantadine and fluoxetine reduced relative spleen weight in rats subjected to the FST, compared to rats treated with the vehicle. The combination of amantadine and fluoxetine enhanced the production of the negative immunoregulator interleukin-10 (but not interferon-gamma) in rats subjected to the FST. The exposure to the FST produced an increase in plasma corticosterone levels, which was significantly attenuated by pretreatment with fluoxetine and amantadine. In summary, the antidepressive efficacy of a combination of fluoxetine and amantadine given in suboptimal doses may be related to the negative immunoendocrine effects of these drugs.

Concomitant administration of fluoxetine and amantadine modulates the activity of peritoneal macrophages of rats subjected to a forced swimming test

Recent studies show that administration of a non-competitive NMDA receptor antagonist, amantadine (AMA), potentiates the action of antidepressant drugs. Since antidepressants may modulate functioning of the immune system and activation of a pro-inflammatory response in depressive disorders is frequently reported, the aim of the present study was to examine whether a combined administration of AMA and the antidepressant, fluoxetine (FLU), to rats subsequently subjected to a forced swimming test (FST) modifies the parameters of macrophage activity, directly related to their immunomodulatory functions, i.e., arginase (ARG) activity and synthesis of nitric oxide (NO). We found that 10 mg/kg AMA and 10 mg/kg FLU, ineffective in FST for antidepressant-like activity when administered alone, increased the ARG/NO ratio in macrophages when administered concomitantly. This effect was accompanied by a decrease of cellular adherence. Concurrently, the basal metabolic activity of the cells measured with reduction of resazurin, and intracellular host defense as assessed by a synthesis of superoxide anion, were not affected by such antidepressive treatment. Our data indicate that co-administration of AMA and FLU decreases the pro-inflammatory properties of macrophages and causes a redirection of immune response toward anti-inflammatory activity, as one can anticipate in the case of an effective antidepressive treatment.

Interferon-gamma deficiency modifies the effects of a chronic stressor in mice: Implications for psychological pathology

Pro-inflammatory cytokines promote behavioral and neurochemical variations similar to those evident following stressor exposure, and have been implicated in promoting depressive illness. Indeed, immunotherapeutic application of the cytokine, interferon-alpha, promoted depressive illness in cancer and hepatitis C patients. We assessed the possibility that another interferon cytokine family member, interferon-gamma (IFN-gamma), might contribute to the behavioral and biochemical alterations provoked by a chronic stressor regimen that has been used to model neuropsychiatric pathology in rodents. As predicted, IFN-gamma-deficient mice displayed basal differences in behavior (e.g., reduced open field exploration) and altered neurochemical activity (e.g., increased noradrenergic and serotonergic activity within the central amygdala), relative to their wild-type counterparts. Moreover, stressor-induced elevations of corticosterone and the pro-inflammatory cytokine, tumor necrosis factor-alpha, were attenuated in IFN-gamma-deficient mice. Similarly, the IFN-gamma null mice were refractory to the chronic stressor-induced alterations of dopamine metabolism (within the prefrontal cortex, paraventricular nucleus of the hypothalamus and central amygdala) evident in wild-type mice. Yet, the chronic stressor provoked signs of anxiety (e.g., reduced open field exploration) and depression-like behavior (e.g., increased forced swim immobility, reduced consumption of a palatable solution) among both wild-type and IFN-gamma knockout mice alike, suggesting a dissociation of behavioral functioning from the stressor-induced alterations of immunological, hormonal and dopaminergic activity. Together, these data suggest a complex neurobehavioral phenotype, wherein IFN-gamma deletion engenders a state of heightened basal emotionality coupled with increased monoaminergic activity in the amygdala. At the same time, however, IFN-gamma deficiency appears to blunt some of the neurochemical, corticoid and cytokine alterations ordinarily associated with chronic stressor exposure.

A meta-analysis of cytokines in major depression

BACKGROUND

Major depression occurs in 4.4% to 20% of the general population. Studies suggest that major depression is accompanied by immune dysregulation and activation of the inflammatory response system (IRS). Our objective was to quantitatively summarize the data on concentrations of specific cytokines in patients diagnosed with a major depressive episode and controls.

METHODS

We performed a meta-analysis of studies measuring cytokine concentration in patients with major depression, with a database search of the English literature (to August 2009) and a manual search of references.

RESULTS

Twenty-four studies involving unstimulated measurements of cytokines in patients meeting DSM criteria for major depression were included in the meta-analysis; 13 for tumor necrosis factor (TNF)-alpha, 9 for interleukin (IL)-1beta, 16 for IL-6, 5 for IL-4, 5 for IL-2, 4 for IL-8, 6 for IL-10, and 4 for interferon (IFN)-gamma. There were significantly higher concentrations of TNF-alpha (p < .00001), weighted mean difference (WMD) (95% confidence interval) 3.97 pg/mL (2.24 to 5.71), in depressed subjects compared with control subjects (438 depressed/350 nondepressed). Also, IL-6 concentrations were significantly higher (p < .00001) in depressed subjects compared with control subjects (492 depressed/400 nondepressed) with an overall WMD of 1.78 pg/mL (1.23 to 2.33). There were no significant differences among depressed and nondepressed subjects for the other cytokines studied.

CONCLUSIONS

This meta-analysis reports significantly higher concentrations of the proinflammatory cytokines TNF-alpha and IL-6 in depressed subjects compared with control subjects. While both positive and negative results have been reported in individual studies, this meta-analytic result strengthens evidence that depression is accompanied by activation of the IRS.

Pro-inflammatory biomakers in depression: treatment with venlafaxine

High levels of pro-inflammatory biomarkers have been reported in depression. In the present study, five pro-inflammatory biomarkers were measured in the blood of patients with major depressive disorder (MDD). Biomarker levels were compared to age- and sex-matched healthy subjects. Patients with MDD had significantly higher baseline levels of tumour necrosis factor-alpha (TNFalpha, P=0.04), interleukin-1beta (IL1beta, P=0.03), and monocyte chemotactic protein-1 (MCP-1; P=0.02) compared to controls. There were no differences between groups in levels of cell determinant-40 ligand (CD40L) and C-reactive protein (CRP). A subset of the MDD patients consented to undergo treatment with venlafaxine (an SNRI: at lower doses a selective serotonin reuptake inhibitor; at higher doses also a norepinephrine reuptake inhibitor) for 8 weeks. By week 8, all treatment completers had responded therapeutically. However, levels of TNFalpha, IL1beta, and MCP-1 remained elevated. A concave quadratic equation described the associations between plasma venlafaxine concentrations and IL1beta (P=0.03), TNFalpha (P=0.09), and MCP-1 (P=0.02), suggesting that these biomarkers may have become selectively lowered in the serotonergic dose range of venlafaxine. This is the first report of venlafaxine's possible effect on pro-inflammatory biomarkers.

Effects of venlafaxine and fluoxetine on lymphocyte subsets in patients with major depressive disorder: a flow cytometric analysis

BACKGROUND

Studies have yielded conflicting results concerning flow cytometric lymphocyte analyses in patients with depression. Data about the effect of antidepressants on lymphocyte subsets are also contradictory. The aim of this study was to determine effects of venlafaxine versus fluoxetine on lymphocyte subsets in depressive patients.

METHODS

Sixty-nine patients diagnosed with major depressive disorder (MDD) according to DSM-IV and 36 healthy controls are included in the study. Sixty-nine patients were randomized to take fluoxetine (FLX) (n=33) or venlafaxine (VEN) (n=36). Serum lymphocyte subsets included CD3, CD4, CD8, CD16/56, CD19, CD45, Anti-HLA-DR which were measured by flow cytometric analyses at baseline and 6 weeks after the start of treatment. The severity of depression was evaluated with Hamilton rating scale for depression.

RESULTS

At baseline, patients with MDD had significantly lower CD16/56 ratio and higher CD45 ratio compared to the controls. Although numerically higher in the VEN treated patients, treatment response rates between the FLX (53%) and the VEN (75%) groups were not different statistically. CD45 values decreased significantly in the VEN group at the end of the 6 week treatment period whereas no difference was observed in the FLX group. By the 6th week, treatment responders showed a significantly higher CD16/56 ratio than non-responders. Baseline severity of depression and anxiety was positively correlated with baseline CD45 ratio and negatively correlated with baseline CD16/56 ratio. We did not observe consistent changes in the absolute number of circulating B or T cells, nor in the helper/inducer (CD4) or suppressor/cytotoxic (CD8) subsets.

CONCLUSIONS

CD16/56 was lower in patients with MDD and increased in treatment responders at 6th week. CD45 ratio was higher in patients with MDD than healthy subjects; it decreased with antidepressant treatment and was positively correlated with the severity of depression. Antidepressant treatment contributes to immune regulation in patients with major depressive disorder.

Effects of bupropion augmentation on pro-inflammatory cytokines in escitalopram-resistant patients with major depressive disorder

Studies so far have provided contradictory results on immune system markers during use of antidepressants. There are no data on changes in immune parameters after treatment augmentation. The present study aimed to clarify whether the addition of bupropion in escitalopram-resistant patients with major depression causes changes in the immune system and whether treatment response could be predicted by baseline levels of cytokines. We recruited 28 depressive patients (11 men and 17 women) who did not respond to 12-week treatment with escitalopram (20 mg/d) for an augmentation trial with bupropion (150-300 mg/day). The levels of soluble interleukin-2 receptor, interleukin-8 (IL-8) and tumor-necrosis factor-alpha were measured before and 6 weeks after addition of bupropion. For a control group, we recruited 45 healthy volunteers (19 men and 26 women). The results indicated that the baseline levels of studied cytokines did not predict treatment response to bupropion augmentation. Concentration of IL-8 increased during the treatment similarly in both responder and non-responder groups. Although bupropion augmentation had increased the response rate in escitalopram-resistant patients, this clinical improvement was not accompanied by specific changes in studied cytokine levels.

Interleukin-10: a key cytokine in depression?

An increasing body of evidence implicates proinflammatory cytokines in psychiatric disorders, namely, in depression. Of notice, recent studies showed that anti-inflammatory cytokines, such as IL-10, also modulate depressive-like behavior. In this article, we propose that the anti-inflammatory cytokine IL-10 is a putative link between two of the most widely reported phenomenon observed in depressed patients: the disruption of the hypothalamic-pituitary-adrenal axis and the imbalanced production of cytokines. If so, IL-10 might represent a novel target for antidepressant therapy.

Low serum IL-10 concentrations and loss of regulatory association between IL-6 and IL-10 in adults with major depression

Elevated circulating pro-inflammatory cytokines are associated with symptoms of depression, and disorders involving chronic inflammation are often co-morbid with major depression. Since healthy immune regulation is accomplished through counter-balancing effects of pro- and anti-inflammatory cytokines, we hypothesized that depressed subjects (compared to controls) would express lower concentrations of the anti-inflammatory/immunoregulatory cytokine interleukin (IL)-10, and a higher IL-6/IL-10 ratio. We also examined the possibility that depressed subjects may exhibit a deficiency in the regulatory loop involving IL-6 induced secretion of IL-10. Therefore, we hypothesized that circulating IL-6 and IL-10 would be positively correlated in controls, while the correlation would be weaker in depressed subjects. Resting state serum cytokine concentrations were quantified in 12 unmedicated depressed subjects, and 11 age, gender, and ethnicity-matched controls. Depressed subjects showed significantly lower IL-10 (p=0.03, Cohen's d=-0.96), non-significantly higher IL-6, and significantly higher IL-6/IL-10 ratios (p=0.05, Cohen's d=0.50). Across all participants, higher scores on the self-rated Inventory of Depressive Symptoms were associated with lower IL-10 (r(21)=-0.57, p=0.005) and non-significantly higher IL-6/IL-10 ratios (r(21)=0.38, p=0.07), but not related to IL-6 concentrations. As hypothesized, IL-6 and IL-10 concentrations were strongly and positively correlated in controls (r(9)=0.81, p=0.003), but were completely dissociated in depressed subjects (r(10)=0.01, p=0.98). These results suggest that lower IL-10 levels, a higher IL-6/IL-10 ratio, and the apparent absence of a counter-balancing, immunoregulatory increase in IL-10 in response to elevated IL-6 concentrations contribute to the pro-inflammatory physiological milieu that is known to be associated with major depression. Therefore, reduced induction/availability of IL-10, that would normally inhibit pro-inflammatory cytokine actions and resolve inflammation, may contribute to the depressogenic as well as the inflammatory disease-promoting effects of chronic, low-level elevations in pro-inflammatory cytokines.

Interleukin-1 receptor antagonist and incident depressive symptoms over 6 years in older persons: the InCHIANTI study

BACKGROUND

We test the hypothesis that in older persons higher plasma levels of inflammatory markers predict the development of depressive symptoms during a 6-year follow-up.

METHOD

This study is part of the InCHIANTI (Invecchiare in Chianti, aging in the Chianti area) study, a prospective population-based study of older persons. The sample consisted of 991 participants, ages 65 years and older. Serum levels of C-reactive protein, interleukin (IL)-1beta, IL-1 receptor antagonist (ra), tumor necrosis factor-alpha, IL-6, IL-6 receptor, and IL-18 were measured. Depressive symptoms were assessed at baseline and at the 3- and 6-year follow-ups with the Center for Epidemiological Studies-Depression Scale (CES-D). Depressed mood was defined as CES-D > 20. Potential confounders were baseline variables related to sociodemographic, somatic health, and functional status.

RESULTS

At baseline, IL-1ra levels were significantly higher (p = .004) in depressed compared with nondepressed participants. After adjustment for confounders, among subjects free of depression at baseline, those in the third and fourth IL-1ra quartiles compared with those in the lowest quartile had, respectively, a 2.32-fold (95% confidence interval: 1.21-4.42, p = .01) and 2.78-fold (95% confidence interval: 1.47-5.26, p = .002) higher risk of developing depressed mood during a 6-year follow-up.

CONCLUSIONS

In old age, persons with high plasma levels of IL1-ra had a higher risk of developing depressive symptoms over time. These findings suggest a potential causal role for inflammation in the development of depressive symptoms in older persons.

Changes in circulating cytokine levels in midlife women with psychological symptoms with selective serotonin reuptake inhibitor and Japanese traditional medicine

OBJECTIVE

The aim of the present study was to compare the effects on serum cytokine concentrations of paroxetine, a selective serotonin re-uptake inhibitor, and kamishoyosan, a Japanese traditional medicine, in midlife women with psychological symptoms.

METHODS

Seventy-six women with psychological symptoms such as anxiety and mild depression as menopausal symptoms were enrolled in this study. Thirty-eight women received oral administration of 10mg paroxetine every day, and 38 women received oral administration of kamshoyosan every day for 6 months. Overall climacteric symptoms were assessed using Greene's climacteric scale. Serum levels of cytokines were measured using a multiplexed human cytokine assay.

RESULTS

Greene's total scores in both women treated with paroxetine and in women treated with kamishoyosan decreased significantly. Percentage decreases in Greene's total, psychological and vasomotor scores during the 6-month period in the paroxetine group were significantly greater than those in the kamishoyosan group. Serum IL-6 concentration in women treated with paroxetine decreased significantly. Serum concentrations of IL-8, IL-10, macrophage inflammatory protein (MIP)-1beta and monocyte chemoattractant protein-1 in women treated with paroxetine decreased significantly. On the other hand, serum IL-6 concentration in women treated with kamishoyosan decreased significantly, but other serum concentrations did not change significantly.

CONCLUSION

Decrease in IL-6 concentration may be involved in the mechanism of the actions of both paroxetine and kamishoyosan in women with psychological symptoms, and IL-6 may therefore be useful as a marker of treatment. The action of paroxetine may also be associated with decreases in IL-8, IL-10, MIP-1beta.