Clinical trial of adjunctive celecoxib treatment in patients with major depression: a double blind and placebo controlled trial

COX-2 Inhibitors, Aspirin, and Other Potential Anti-Inflammatory Treatments for Psychiatric Disorders

Inflammatory processes associated with persistent (chronic) infection have long been discussed as etiological factors in psychiatric disorders. Studies have found that people with major depression have higher levels of pro-inflammatory cytokines, for example, IL-1, IL-6, and tumor necrosis factor-alpha, and C-reactive protein. In schizophrenia, many reports have described raised levels of cytokines, for example, IL-6; and meta-analyses have confirmed these findings. Microglia cells are important in inflammatory processes, and positron emission tomography studies have shown microglia activation in both depression and schizophrenia.As a consequence of the above findings, immunomodulation is widely discussed as a potential treatment approach in both major depression and schizophrenia. The COX-2 inhibitor celecoxib was found to have a significant positive effect on major depression, not only in single studies but also in meta-analyses. Celecoxib has also been studied in schizophrenia and has shown efficacy, in particular, in early disease stages. The mixed COX inhibitor aspirin (acetylsalicylic acid) seems to have both protective and therapeutic effects on schizophrenia.This paper discusses the hypothesized role of inflammation in major depression and schizophrenia, including markers of inflammation; pertinent studies on celecoxib and aspirin; and additional immunomodulatory therapeutic strategies.

Impact, Diagnosis, Phenomenology, and Biology

This section provides summaries of the epidemiology, phenomenology, nosology, and the suspected biological substrates of the depressive disorders. It particularly emphasizes the historical evolution of the pertinent diagnostic constructs and the prognostic import both of the various diagnostic groupings and of the individual symptoms and symptom clusters.

Neurobiology and Therapeutic Potential of Cyclooxygenase-2 (COX-2) Inhibitors for Inflammation in Neuropsychiatric Disorders

Neuropsychiatric disorders, such as depression, bipolar disorder, schizophrenia, obsessive-compulsive disorder, and neurodevelopmental disorders such as autism spectrum disorder, are associated with significant illness burden. Accumulating evidence supports an association between these disorders and inflammation. Consequently, anti-inflammatory agents, such as the cyclooxygenase-2 inhibitors, represent a novel avenue to prevent and treat neuropsychiatric illness. In this paper, we first review the role of inflammation in psychiatric pathophysiology including inflammatory cytokines' influence on neurotransmitters, the hypothalamic-pituitary-adrenal axis, and microglial mechanisms. We then discuss how cyclooxygenase-2-inhibitors influence these pathways with potential therapeutic benefit, with a focus on celecoxib, due to its superior safety profile. A search was conducted in PubMed, Embase, and PsychINFO databases, in addition to Clinicaltrials.gov and the Stanley Medical Research Institute trial registries. The results were presented as a narrative review. Currently available outcomes for randomized controlled trials up to November 2017 are also discussed. The evidence reviewed here suggests cyclooxygenase-2 inhibitors, and in particular celecoxib, may indeed assist in treating the symptoms of neuropsychiatric disorders; however, further studies are required to assess appropriate illness stage-related indication.

Principles of inflammasome priming and inhibition: Implications for psychiatric disorders

The production of inflammatory proteins by the innate immune system is a tightly orchestrated procedure that allows the body to efficiently respond to exogenous and endogenous threats. Recently, accumulating evidence has indicated that disturbances in the inflammatory response system not only provoke autoimmune disorders, but also can have deleterious effects on neuronal function and mental health. As inflammation in the brain is primarily mediated by microglia, there has been an expanding focus on the mechanisms through which these cells initiate and propagate neuroinflammation. Microglia can enter persistently active states upon their initial recognition of an environmental stressor and are thereafter prone to elicit amplified and persistent inflammatory responses following subsequent exposures to stressors. A recent focus on why primed microglia cells are susceptible to environmental insults has been the NLRP3 inflammasome. Its function within the innate immune system is regulated in such a manner that supports a role for the complex in gating neuroinflammatory responses. The activation of NLRP3 inflammasome in microglia results in the cleavage of zymogen inflammatory interleukins into functional forms that elicit a number of consequential effects in the local neuronal environment. There is evidence to support the principle that within primed neuroimmune systems a lowered threshold for NLRP3 activation can cause persistent neuroinflammation or the amplified production of inflammatory cytokines, such as IL-1β and IL-18. Over the course of an individual's lifetime, persistent neuroinflammation can subsequently lead to the pathophysiological signatures that define psychological disorders. Therefore, targeting the NLRP3 inflammasome complex may represent an innovative and consequential approach to limit neuroinflammatory states in psychiatric disorders, such as major depressive disorder.

Sub-chronic celecoxib prevents soluble beta amyloid-induced depressive-like behaviour in rats

BACKGROUND

Depression and Alzheimer's disease (AD) are co-morbid conditions. Neuropsychiatric symptoms have been reported as prodromal symptoms of AD-like dementia and soluble forms of beta amyloid peptide (Aβ), the main constituent of insoluble plaques typical of AD brains, have been implicated in such an effect. We have previously shown that intracerebral injection of Aβ can evoke a depressive-like state in rats, accompanied by neurochemical and neuroendocrine alterations reminiscent of depressive symptoms in humans. AD and depression are crucially linked by neuroinflammation and cyclooxygenase II (COX-2) enzyme involvement is an intriguing field of research. Indeed, its pharmacological inhibition has shown both antidepressant and Aβ modulating effects.

METHODS

Male rats were exposed to sub-chronic celecoxib (15 mg/kg/day sc for 8 days), a selective COX-2 inhibitor or vehicle (saline), starting from the day before central intracerebroventricular injection of Aβ peptide (5µL of 4 µM solution or vehicle for sham). Animals were tested for depressive-like behaviour by using the forced swimming test paradigm and prefrontal serotonin (5-HT) content and plasma Aβ levels were further evaluated.

RESULTS

We found that celecoxib treatment prevented the pro-depressive effects induced by Aβ. Moreover, it also prevented the reduction in 5-HT content in prefrontal cortex of Aβ-treated rats and decreased their plasma Aβ levels.

CONCLUSIONS

Taken together, our data indicate that celecoxib could be a suitable pharmaceutical tool for the treatment of depressive state related to increased Aβ levels.

Anti-inflammatory treatment of depression: study protocol for a randomised controlled trial of vortioxetine augmented with celecoxib or placebo

Background

In patients with major depressive disorder (MDD), antidepressant response and remission rates are low, highlighting the need for new treatment approaches. Recently, the abundant literature linking inflammatory processes and depressive symptoms have led to the hypothesis that selecting treatment for MDD based on the patient’s inflammatory status could be a promising strategy to improve outcomes in patients suffering from MDD. The aim of the randomised control trial we propose is to investigate the antidepressant efficacy of the combined treatment of MDD with antidepressant medication plus anti-inflammatory medication in individuals with raised inflammation levels. For the first time, this study will prospectively test the efficacy of an antidepressant plus anti-inflammatory augmentation based on baseline inflammatory maker levels in MDD using a randomised controlled trial design.

Methods

This study proposes to measure blood C-reactive protein (CRP) levels before the initiation of treatment in 200 participants with MDD. Study participants are then assigned into one of two study strata: either into the ‘Depression with inflammation’ stratum (CRP levels > 3 mg/L); or into the ‘Depression without inflammation’ stratum (CRP levels ≤ 3 mg/L). Within each of the two study strata, participants randomly receive either antidepressant medication alone (vortioxetine) plus anti-inflammatory medication (celecoxib) or vortioxetine plus placebo for six weeks. At the end of the treatment period, participants have the opportunity to continue vortioxetine alone for a six-month post-trial period. Clinical outcomes are measured at baseline, fortnightly during the treatment period and at the three-month and six-month post-trial visits. The primary outcome is change in MADRS score, with a primary endpoint of a score reduction by 50% from baseline to six weeks (end of augmentation treatment with celecoxib). Secondary clinical outcomes are changes in the cognitive dimensions of depression (cognitive function, emotion processing and social cognition). Biological outcome measures (levels of CRP and other inflammatory markers) are measured at baseline, after six weeks of treatment and at the six-month post-trial visit.

Discussion

The current study will generate novel evidence for biomarker-based personalised antidepressant treatment selection based on patient inflammatory status before treatment.

Trial registration

Australian New Zealand Clinical Trials Registry (ANZCTR), ACTRN12617000527369p. Registered on 11 April 2017.

Electronic supplementary material

The online version of this article (10.1186/s13063-018-2829-7) contains supplementary material, which is available to authorized users.

Genome-wide analysis of LPS-induced inflammatory response in the rat ventral hippocampus: Modulatory activity of the antidepressant agomelatine

OBJECTIVES

Several studies reported that antidepressant drugs have immune-regulatory effects by acting on specific inflammatory mediators. However, considering the highly complex nature of the inflammatory response, we have adopted an unbiased genome-wide strategy to investigate the immune-regulatory activity of the antidepressant agomelatine in modulating the response to an acute inflammatory challenge.

METHODS

Microarray analysis was used to identify genes modulated in the ventral hippocampus of adult rats chronically treated with agomelatine (40 mg/kg, os) before being challenged with a single injection of lipopolysaccharide (LPS; 250 μg/kg, i.p.).

RESULTS

The administration of LPS induced the transcription of 284 genes mainly associated with pathways related to the immune/inflammatory system. Agomelatine modulated pathways not only connected to its antidepressant activity, but was also able to prevent the activation of genes induced by LPS. Further comparisons between gene lists of the diverse experimental groups led to the identification of a few transcripts modulated by LPS on which agomelatine has the larger effect of normalisation. Among them, we found the pro-inflammatory cytokine Il-1β and, interestingly, the metabotropic glutamatergic transporter Grm2.

CONCLUSIONS

These results are useful to better characterise the association between depression and inflammation, revealing new potential targets for pharmacological intervention for depression associated to inflammation.

Immune and Neuroprotective Effects of Physical Activity on the Brain in Depression

Physical activity-a lifestyle factor that is associated with immune function, neuroprotection, and energy metabolism-modulates the cellular and molecular processes in the brain that are vital for emotional and cognitive health, collective mechanisms that can go awry in depression. Physical activity optimizes the stress response, neurotransmitter level and function (e.g., serotonergic, noradrenergic, dopaminergic, and glutamatergic), myokine production (e.g., interleukin-6), transcription factor levels and correlates [e.g., peroxisome proliferator-activated receptor C coactivator-1α [PGC-1α], mitochondrial density, nitric oxide pathway activity, Ca2+ signaling, reactive oxygen specie production, and AMP-activated protein kinase [AMPK] activity], kynurenine metabolites, glucose regulation, astrocytic health, and growth factors (e.g., brain-derived neurotrophic factor). Dysregulation of these interrelated processes can effectuate depression, a chronic mental illness that affects millions of individuals worldwide. Although the biogenic amine model has provided some clinical utility in understanding chronic depression, a need remains to better understand the interrelated mechanisms that contribute to immune dysfunction and the means by which various therapeutics mitigate them. Fortunately, convergent evidence suggests that physical activity improves emotional and cognitive function in persons with depression, particularly in those with comorbid inflammation. Accordingly, the aims of this review are to (1) underscore the link between inflammatory correlates and depression, (2) explicate immuno-neuroendocrine foundations, (3) elucidate evidence of neurotransmitter and cytokine crosstalk in depressive pathobiology, (4) determine the immunomodulatory effects of physical activity in depression, (5) examine protocols used to effectuate the positive effects of physical activity in depression, and (6) highlight implications for clinicians and scientists. It is our contention that a deeper understanding of the mechanisms by which inflammation contributes to the pathobiology of depression will translate to novel and more effective treatments, particularly by identifying relevant patient populations that can benefit from immune-based therapies within the context of personalized medicine.

Brain Kynurenine and BH4 Pathways: Relevance to the Pathophysiology and Treatment of Inflammation-Driven Depressive Symptoms

The prevalence of depressive disorders is growing worldwide, notably due to stagnation in the development of drugs with greater antidepressant efficacy, the continuous large proportion of patients who do not respond to conventional antidepressants, and the increasing rate of chronic medical conditions associated with an increased vulnerability to depressive comorbidities. Accordingly, better knowledge on the pathophysiology of depression and mechanisms underlying depressive comorbidities in chronic medical conditions appears urgently needed, in order to help in the development of targeted therapeutic strategies. In this review, we present evidence pointing to inflammatory processes as key players in the pathophysiology and treatment of depressive symptoms. In particular, we report preclinical and clinical findings showing that inflammation-driven alterations in specific metabolic pathways, namely kynurenine and tetrahydrobiopterin (BH4) pathways, leads to substantial alterations in the metabolism of serotonin, glutamate and dopamine that are likely to contribute to the development of key depressive symptom dimensions. Accordingly, anti-inflammatory interventions targeting kynurenine and BH4 pathways may be effective as novel treatment or as adjuvants of conventional medications rather directed to monoamines, notably when depressive symptomatology and inflammation are comorbid in treated patients. This notion is discussed in the light of recent findings illustrating the tight interactions between known antidepressant drugs and inflammatory processes, as well as their therapeutic implications. Altogether, this review provides valuable findings for moving toward more adapted and personalized therapeutic strategies to treat inflammation-related depressive symptoms.

Immune system and obsessive-compulsive disorder

BACKGROUND

Recently, much attention has been devoted to the possible alterations of the immune system in obsessive-compulsive disorder (OCD). Therefore, the aim of this paper was to review the current literature on the relationships between OCD and immune system.

METHODS

A PubMed and Google Scholar search was performed with specific keywords.

RESULTS

In the childhood, much emphasis has been given to the relationship between group A Streptococcus (GAS) infection and the development of a group of clinical syndromes characterized by neuropsychiatric symptoms known as "pediatric autoimmune neuropsychiatric disorders associated with streptococcus" (PANDAS). However, more recently, PANDAS has been reconsidered and evolved towards pediatric acute-onset neuropsychiatric syndrome (PANS) and/or Childhood Acute Neuropsychiatric Syndrome (CANS) all characterized by the presence of typical of OCD symptoms and tics. In adult OCD patients, different immunological parameters have been described to differ from those of healthy control subjects, although a few numbers of studies were carred out and most of them performed in small samples.

CONCLUSIONS

Although the exact relationships between OCD and immune processes are still unclear, available literature supports their role in the pathophysiology of OCD, while providing a fascinating hint for possible immunotherapeutic treatments in OCD.

Plasma C-reactive protein levels in bipolar depression during cyclooxygenase-2 inhibitor combination treatment

Immune system activation and neuroinflammation appear to play a key role in the pathophysiology and treatment of bipolar depression (BDD). This study is the first to analyze blood levels of the pro-inflammatory biomarker C-reactive protein (CRP) in bipolar disorder patients treated with the cyclooxygenase-2 inhibitor, celecoxib (CBX). In this double-blind study, 47 consenting patients with BDD were randomized to receive either escitalopram (10 mg twice/day) + CBX (200 mg twice/day), or escitalopram (10 mg twice/day) + placebo (twice/day). Plasma CRP levels were measured in both patient groups at baseline, week 4, and week 8, and in a healthy control (HC) group of subjects (N = 35) once. Symptoms were rated using the 17-item Hamilton Depression Scale (HAMD-17). The CBX group had significantly lower HAMD-17 scores vs. placebo at week 4 (P = 0.026) and week 8 (P = 0.002). Therefore, SSRI + CBX is more effective than SSRI + placebo in reversing treatment resistance and augmenting antidepressant response in BDD. Baseline CRP levels were significantly increased amongst BDD patients versus HC subjects, indicating that CRP may be a useful biomarker for BDD (P = 0.044). No significant differences in CRP levels were measured between CBX and placebo groups at baseline (P = 0.156), but by week 8 CRP was significantly decreased in the CBX group vs. placebo (P = 0.003). This indicates reduced inflammation in CBX-treated patients, and that CRP may be a useful biomarker for monitoring treatment response in BDD patients during SSRI + CBX combination treatment. CRP and IL-6 levels were positively correlated in the CBX group, and CRP levels were positively correlated with BMI.

Anti-inflammatory treatment and risk of depression in 91,842 patients with acute coronary syndrome and 91,860 individuals without acute coronary syndrome in Denmark

BACKGROUND

We examined if treatment with acetylsalicylic acid (ASA), non-steroid anti-inflammatory drugs (NSAID), or statins after acute coronary syndrome (ACS) are associated with decreased risk of depression.

METHOD

This register-based cohort study included all individuals with a first-time hospital admissions with an ACS diagnosis registered between January 2001 to December 2009 (N=91,842) and a comparable reference population without ACS (N=91,860). Information of ASA, NSAID, and statin use were retrieved from a national prescription register. The study population was followed for hospitalization with depression or receiving prescription of antidepressant medication for up to one year after ACS or study entry (early depression) or one to twelve years after ACS or study entry (late depression).

RESULTS

ASA use after ACS was associated with decreased risk of early depression with hazard ratios (HR) of 0.89 (95% confidence interval 0.85-0.93) but not with late depression 0.96 (0.90-1.01). The corresponding HRs for statin were 0.90 (0.86-0.94) and 0.86 (0.82-0.90). In the non-ACS population, statin use was not associated with neither early nor late depression (HRs 1.04 (0.96-1.12) and 1.00 (0.95-1.06)), while ASA was associated with increased risk of late (HR 1.09 (1.04-1.14)) but not early depression (HR 1.03 (0.97-1.09)). In both populations, NSAID use was associated with increased risk of late but not early depression.

CONCLUSION

Use of ASA or statins were associated with decreased risk of depression in ACS patients but not in individuals without ACS, while use of NSAID was associated with increased risk of late depression in both populations.

Low tumor necrosis factor-α levels predict symptom reduction during electroconvulsive therapy in major depressive disorder

OBJECTIVE

Changes in the tumor necrosis factor-α (TNFα) have been associated with major depressive disorder (MDD). Findings concerning the effects of electroconvulsive therapy (ECT) on the TNFα level have been contradictory. The aim was to examine the immediate and long-term changes in the TNFα level and their associations with symptom reduction in patients with MDD during ECT.

METHOD

The study included 30 patients with MDD. Their TNFα levels were measured at baseline and 2 and 4 hr after the first, fifth and last ECT session. Depressive symptoms were assessed with the Montgomery-Asberg Depression Rating Scale (MADRS).

RESULTS

The TNFα level decreased from baseline to the 2- and 4-hr measurements. There was a correlation between the first ECT session TNFα levels and the relative symptom reduction according to the MADRS score after the ECT series. Both the first (baseline) ECT and 4-hr TNFα levels were lower in responders than in nonresponders.

CONCLUSION

ECT consistently induced a decrease in the TNFα level after each studied session. A low TNFα level at the first ECT appeared to predict a symptom reduction. These findings suggest that TNFα might have a role in the pathogenesis in MDD and in the mechanism of action of ECT.

Therapeutic Strategies for Treatment of Inflammation-related Depression

BACKGROUND

Mounting evidence demonstrates enhanced systemic levels of inflammatory mediators in depression, indicating that inflammation may play a role in the etiology and course of mood disorders. Indeed, proinflammatory cytokines induce a behavioral state of conservation- withdrawal resembling human depression, characterized by negative mood, fatigue, anhedonia, psychomotor retardation, loss of appetite, and cognitive deficits. Neuroinflammation also contributes to non-responsiveness to current antidepressant (AD) therapies. Namely, response to conventional AD medications is associated with a decrease in inflammatory biomarkers, whereas resistance to treatment is accompanied by increased inflammation.

METHODS

In this review, we will discuss the utility and shortcomings of pharmacologic AD treatment strategies focused on inflammatory pathways, applied alone or as an adjuvant component to current AD therapies.

RESULTS

Mechanisms of cytokine actions on behavior involve activation of inflammatory pathways in the brain, resulting in changes of neurotransmitter metabolism, neuroendocrine function, and neuronal plasticity. Selective serotonin reuptake inhibitors exhibit the most beneficial effects in restraining the inflammation markers in depression. Different anti-inflammatory agents exhibit AD effects via modulating neurotransmitter systems, neuroplasticity markers and glucocorticoid receptor signaling. Anti-inflammatory add-on therapy in depression highlights such treatment as a candidate for enhancement strategy in patients with moderate-to-severe depression.

CONCLUSION

The interactions between the immune system and CNS are not only involved in shaping behavior, but also in responding to therapeutics. Even though, substantial evidence from animal and human research support a beneficial effect of anti-inflammatory add-on therapy in depression, further research with special attention on safety, particularly during prolonged periods of antiinflammatory co-treatments, is required.

IDO chronic immune activation and tryptophan metabolic pathway: A potential pathophysiological link between depression and obesity

Obesity and depression are among the most pressing health problems in the contemporary world. Obesity and depression share a bidirectional relationship, whereby each condition increases the risk of the other. By inference, shared pathways may underpin the comorbidity between obesity and depression. Activation of cell-mediated immunity (CMI) is a key factor in the pathophysiology of depression. CMI cytokines, including IFN-γ, TNFα and IL-1β, induce the catabolism of tryptophan (TRY) by stimulating indoleamine 2,3-dioxygenase (IDO) resulting in the synthesis of kynurenine (KYN) and other tryptophan catabolites (TRYCATs). In the CNS, TRYCATs have been related to oxidative damage, inflammation, mitochondrial dysfunction, cytotoxicity, excitotoxicity, neurotoxicity and lowered neuroplasticity. The pathophysiology of obesity is also associated with a state of aberrant inflammation that activates aryl hydrocarbon receptor (AHR), a pathway involved in the detection of intracellular or environmental changes as well as with increases in the production of TRYCATs, being KYN an agonists of AHR. Both AHR and TRYCATS are involved in obesity and related metabolic disorders. These changes in the TRYCAT pathway may contribute to the onset of neuropsychiatric symptoms in obesity. This paper reviews the role of immune activation, IDO stimulation and increased TRYCAT production in the pathophysiology of depression and obesity. Here we suggest that increased synthesis of detrimental TRYCATs is implicated in comorbid obesity and depression and is a new drug target to treat both diseases.

Immune-based strategies for mood disorders: facts and challenges

INTRODUCTION

Inflammation seems to play a role in the pathophysiology of mood disorders, including major depressive disorder (MDD) and bipolar disorder (BD). In the last years several studies have shown increased levels of inflammatory and/or immune markers in patients with mood disorders. Accordingly, the immune system has become a target of interest for the development of biomarkers and therapeutics for mood disorders. Areas covered: Here, we review the evidence showing low-grade inflammation in mood disorders and the studies evaluating immune-based strategies for the treatment of these conditions. Expert commentary: Clinical trials with non-steroidal anti-inflammatory drugs, polyunsaturated acids, N-acetylcysteine, anti-cytokines, physical activity and probiotics have provided promising results in terms of antidepressant efficacy in patients with MDD and BD. Regarding stem cells, only studies with animal models have been performed so far with interesting pre-clinical results. Due to the preliminary nature of the results, most of the clinical studies need to be replicated and/or confirmed in larger clinical settings, embracing the highly heterogeneous pathophysiology of mood disorders.

Proteomics profiling reveals inflammatory biomarkers of antidepressant treatment response: Findings from the CO-MED trial

Animal and human studies suggest an association between depression and aberrant immune response. Further, common inflammatory markers may change during the course of antidepressant treatment in patients. The objective of this study was to evaluate changes in inflammatory markers and clinical outcomes from subjects enrolled in the Combining Medications to Enhance Depression Outcome (CO-MED) trial. At baseline and week 12 (treatment completion), plasma samples of 102 participants were analyzed via a multiplex assay comprised of inflammatory markers using a 27-plex standard assay panel plus a 4-plex human acute phase xMAP technology based platform. We carried out analyses in two steps. First, t-tests were used to identify inflammatory marker levels that changed between baseline and week 12. For markers that were altered, logistic regression models were then conducted to look for associated changes in remission at week 12. Among the 31 inflammatory markers analyzed, several cytokines (IL-5, IFN-γ, IL-13), two chemokines (Eotaxin-1/CCL11, RANTES) and an acute-phase reactant (serum amyloid P component) showed change from baseline to week 12. However, only two indicated differential remission responses. Interestingly, increased levels of Eotaxin-1/CCL11 correlated with remission at week 12, whereas decreased levels of IFN-γ correlated with non-remission at week 12. Results suggest that these inflammatory proteins may serve as predictors of treatment response.

Immunological aspects of the treatment of depression and schizophrenia

Schizophrenia and major depression (MD) have been associated with immune system dysfunction. One example of this is the altered level of cytokines—important inflammatory mediators—in blood, and a proinflammatory immune state has been described in some subgroups of patients. A knock to the immune system in early life might trigger a life-long increased immune reactivity, and infections and autoimmune disorders are now known to be risk factors for development of schizophrenia and MD. Pro- and anti-inflammatory cytokines mediate indoleamine 2,3-dioxygenase activity; this enzyme drives metabolism of tryptophan and kynurenin in the central nervous system and degrades serotonin. Alterations of serotonergic, noradrenergic, and glutamatergic neurotransmission have been associated with low-level neuroinflammation, and anti-inflammatory compounds have a therapeutic benefit in MD and schizophrenia, as shown in meta-analyses. Moreover, antidepressants and antipsychotics have intrinsic immunomodulatory effects. With evidence pointing to the role inflammatory processes play in the pathogenesis of major psychiatric disorders, this review will look at various immunological aspects of treatment of such disorders.

Efficacy and safety of celecoxib monotherapy for mild to moderate depression in patients with colorectal cancer: A randomized double-blind, placebo controlled trial

Cancer-related inflammation is an essential process in malignancies. Celecoxib, a nonsteroidal anti-inflammatory drug that acts via the selective inhibition of cyclooxygenase (COX)-2, has shown favorable effects in several psychiatric disorders. The present study aimed to assess the safety and efficacy of celecoxib single therapy on depressive symptoms of patients with colorectal cancer who underwent chemotherapy. The study was conducted as a 6-week, parallel-group, randomized, double-blind, placebo-controlled trial. Forty participants randomly received either 400mg/day celecoxib or placebo. Treatment effect was assessed using the Hamilton Depression Rating Scale (HDRS) and Visual Analogue Scale (VAS) score at baseline and at week 2, 4 and 6 of the trial. Over 6 weeks, patients who received celecoxib showed significant improvement in scores of the Hamilton Depression rating Scale (P=0.003). When comparing the Mean Difference (95% CI) between the two groups of therapy, the celecoxib group demonstrated greater reduction in HDRS score during the study period at weeks 4 (1.95, 95% CI 0.27-3.63, P value =0.024) and 6 (2.60, 95% CI 0.96-4.23, P=0.003). This study indicates celecoxib as a potential monotherapy treatment strategy for mild to moderate depression in patients with colorectal cancer who underwent chemotherapy.

Anti-inflammatory treatment for major depressive disorder: implications for patients with an elevated immune profile and non-responders to standard antidepressant therapy

Major depressive disorder (MDD) is a prevalent and disabling psychiatric disease with rates of non-responsiveness to antidepressants ranging from 30-50%. Historically, the monoamine depletion hypothesis has dominated the view on the pathophysiology of depression. However, the lack of responsiveness to antidepressants and treatment resistance suggests that additional mechanisms might play a role. Evidence has shown that a subgroup of depressive patients may have an underlying immune deregulation that could explain the lack of therapeutic benefit from antidepressants. Stimuli like inflammation and infection can trigger the activation of microglia to release pro-inflammatory cytokines, acting on two main pathways: (1) activation of the hypothalamic-pituitary adrenal axis, generating an imbalance in the serotonergic and noradrenergic circuits; (2) increased activity of the enzyme indoleamine-2,3-dioxygenase, resulting in depletion of serotonin levels and the production of quinolinic acid. If this hypothesis is proven true, the subgroup of MDD patients with increased levels of pro-inflammatory cytokines, mainly IL-6, TNF-α and IL-1β, might benefit from an anti-inflammatory intervention. Here, we discuss the pre-clinical and clinical studies that have provided support for treatment with non-steroidal anti-inflammatory drugs in depressed patients with inflammatory comorbidities or an elevated immune profile, as well as evidences for anti-inflammatory properties of standard antidepressants.

Anti-inflammatory treatments for mood disorders: Systematic review and meta-analysis

BACKGROUND

Recent studies suggest that anti-inflammatory medication may play a role in the treatment of mood disorders.

AIMS

The purpose of this study was to determine the efficacy of anti-inflammatory drugs in patients with major depressive disorder and bipolar disorder.

METHOD

The Cochrane Central Register of Controlled Trials, PubMed, EMBASE, PsychINFO and Clinicaltrials.gov were searched from inception until 15 April 2017 for completed and on-going randomized controlled trials of anti-inflammatory agents for major depressive disorder and bipolar disorder. Data from randomized controlled trials assessing the antidepressant and anti-manic effect of adjunctive mechanistically diverse anti-inflammatory agents were pooled to determine standard mean differences (SMDs) compared with placebo and/or treatment as usual.

RESULTS

Patients receiving anti-inflammatory agents showed lower post-treatment depressive symptom scores compared with those receiving placebo with a standard mean difference of -0.71 (six randomized controlled trials, n=214, 95% CI -1.24 to -0.17, p=0.009). Anti-inflammatory treatment was found to reduce post-treatment manic symptom scores with a standard mean difference of -0.72 (three randomized controlled trials, n=96, 95% CI -1.31 to -0.13, p=0.02). Anti-inflammatories did not show a statistically significant improvement in the secondary outcome measure (change in symptom scores from baseline to outcome).

CONCLUSIONS

Further high quality trials are needed before making recommendations for the routine clinical use of anti-inflammatories in the treatment of mood disorders.

Cyclooxygenase Inhibition: Pain, Inflammation, and the Cardiovascular System

Inhibitors of the cyclooxygenases (COXs), the nonsteroidal antiinflammatory drugs (NSAIDs), relieve inflammatory pain, but are associated with gastrointestinal and cardiovascular complications. Given the widespread use of NSAIDs, there has been a longstanding interest in optimizing their risk-benefit ratio, for example by reducing their gastrointestinal risk. More recently, the focus has shifted toward the cardiovascular complications of NSAIDs and very large prospective studies have been performed to compare cardiovascular risk across distinct NSAIDs. Surprisingly, much less attention has been paid to the efficacy side of the risk-benefit ratio. There is marked variability in the degree of pain relief by NSAIDs due to the complex interplay of molecular mechanisms contributing to the pain sensation, variability in the disposition of NSAIDs, and imprecision in the quantification of human pain. Here we discuss how NSAIDs relieve pain, how molecular mechanisms relate to clinical efficacy, and how this may inform our interpretation of clinical trials.

A Randomized, Double-Blind Placebo-Controlled Trial on Effectiveness and Safety of Celecoxib Adjunctive Therapy in Adolescents with Acute Bipolar Mania

OBJECTIVE

Recent studies have focused on the role of inflammatory cascades as one of the possible etiologic factors of bipolar disorder. We hypothesize that celecoxib, through its anti-inflammatory properties, may have a therapeutic role in acute bipolar mania.

PATIENTS AND METHODS

Forty-two adolescent inpatients with the diagnosis of acute bipolar mania participated in a parallel, randomized, double-blind controlled trial, and 40 patients underwent an 8-week treatment with either celecoxib (100 mg twice daily) or placebo as an adjunctive treatment to lithium and risperidone. Patients were evaluated using Young Mania Rating Scale (YMRS) at baseline and weeks 2, 4, and 8. The primary outcome measure was to assess the efficacy of celecoxib compared with placebo in improving mania symptoms.

RESULT

General linear model repeated measures showed significant effect for time × treatment interaction on YMRS scores [F (2.54, 96.56) = 3.21, p = 0.03]. Significantly greater improvement was observed in YMRS scores in the celecoxib group compared with the placebo group from baseline YMRS score at week 8 (p = 0.04). Although a 35% greater response to treatment (considering a Clinical Global Impressions-Improvement score of ≤2, very much/much improved) was observed in the celecoxib group compared with the placebo group, the difference did not reach the statistical significance level (p = 0.09). No serious adverse event was reported.

CONCLUSIONS

Celecoxib may be an effective adjuvant therapy in treatment of manic episodes (without psychotic features) of adolescents with bipolar mood disorder. The mood-stabilizing role of this drug might be mediated through its action on inflammatory cascades.

Evidence for Inflammation-Associated Depression

This chapter explores the evidence supporting inflammation-associated depression. Data to date suggest a bidirectional relationship between inflammation and depression wherein one process can drive the other. A wealth of animal and clinical studies have demonstrated an association between concentrations of pro-inflammatory cytokines - specifically interleukin (IL)-1β, IL-6, and tumor necrosis factor-α - and depressive symptoms. There is also evidence that this pro-inflammatory state is accompanied by aberrant inflammation-related processes including platelet activation factor hyperactivity, oxidative and nitrosative stress, and damage to mitochondria. These complex and interrelated mechanisms can collectively contribute to negative neurobiological outcomes that may, in part, underlie the etiopathology of depression. Mounting evidence has shown a concomitant reduction in both depressive symptoms and pro-inflammatory cytokine concentrations following treatment with pharmacological anti-inflammatory interventions. Taken together, the reviewed preclinical and clinical findings may suggest the existence of a distinct inflammatory subtype of depression in which these patients exhibit unique biochemical and clinical features and may potentially experience improved clinical outcomes with inflammation-targeted pharmacotherapy.

Pharmacotherapy in Generalized Anxiety Disorder: Novel Experimental Medicine Models and Emerging Drug Targets

Many pharmacological and psychological approaches have been found efficacious in patients with generalized anxiety disorder (GAD), but many treatment-seeking patients will not respond and others will relapse despite continuing with interventions that initially had beneficial effects. Other patients will respond but then stop treatment early because of untoward effects such as sexual dysfunction, drowsiness, and weight gain. There is much scope for the development of novel approaches that could have greater overall effectiveness or acceptability than currently available interventions or that have particular effectiveness in specific clinical subgroups. 'Experimental medicine' studies in healthy volunteers model disease states and represent a proof-of-concept approach for the development of novel therapeutic interventions: they determine whether to proceed to pivotal efficacy studies and so can reduce delays in translating innovations into clinical practice. Investigations in healthy volunteers challenged with the inhalation of air 'enriched' with 7.5% carbon dioxide (CO₂) indicate this technique provides a validated and robust experimental medicine model, mirroring the subjective, autonomic, and cognitive features of GAD. The anxiety response during CO₂ challenge probably involves both central noradrenergic neurotransmission and effects on acid-base sensitive receptors and so may stimulate development of novel agents targeted at central chemosensors. Increasing awareness of the potential role of altered cytokine balance in anxiety and the interplay of cytokines with monoaminergic mechanisms may also encourage the investigation of novel agents with modulating effects on immunological profiles. Although seemingly disparate, these two approaches to treatment development may pivot on a shared mechanism in exerting anxiolytic-like effects through pharmacological effects on acid-sensing ion channels.

Interleukin-4 is a participant in the regulation of depressive-like behavior

Inflammatory immune activation has been frequently associated with the development of major depression. Microglia might serve as an important interface in this immune system-to-brain communication. Interleukin-4, the major Th2 type cytokine, might be protective against depression due to its ability to counter-regulate inflammation and to inhibit serotonin transporter activity. By using an Interferon-α mouse model, we show that a decreased IL-4 responsiveness of microglia was specifically related to the development of depressive-like behavior. IL-4 deficient mice in a BALB/cJ background showed a considerable increase of depressive-like behavior in the forced swim (FST) and tail suspension test (TST) and reduced avoidance behavior in an active avoidance task. Prior conditioning with unescapable foot shocks further decreased avoidance behavior (learned helplessness) but to a similar level as in the wild type strain. IFN-α treatment was not able to further enhance the already increased level of depressive-like behavior in the FST and TST. Thus, IL-4 seems to be a critical participant in the regulation of depressive-like behavior in an untreated baseline condition. Increase of depressive-like behavior during inflammation in wild-type mice might be mediated to some extent by a reduction of IL-4 signaling.

Inflammation in Depression and the Potential for Anti-Inflammatory Treatment

Accumulating evidence supports an association between depression and inflammatory processes, a connection that seems to be bidirectional. Clinical trials have indicated antidepressant treatment effects for anti-inflammatory agents, both as add-on treatment and as monotherapy. In particular, nonsteroidal anti-inflammatory drugs (NSAIDs) and cytokine-inhibitors have shown antidepressant treatment effects compared to placebo, but also statins, poly-unsaturated fatty acids, pioglitazone, minocycline, modafinil, and corticosteroids may yield antidepressant treatment effects. However, the complexity of the inflammatory cascade, limited clinical evidence, and the risk for side effects stress cautiousness before clinical application. Thus, despite proof-of-concept studies of anti-inflammatory treatment effects in depression, important challenges remain to be investigated. Within this paper, we review the association between inflammation and depression together with the current evidence on use of anti-inflammatory treatment in depression. Based on this, we address the questions and challenges that seem most important and relevant to future studies, such as timing, most effective treatment lengths and identification of subgroups of patients potentially responding better to different anti-inflammatory treatment regimens.

Mood Therapeutics: Novel Pharmacological Approaches for Treating Depression

INTRODUCTION

Real-world effectiveness trials suggest that antidepressant efficacy is limited in many patients with mood disorders, underscoring the urgent need for novel therapeutics to treat these disorders. Areas covered: Here, we review the clinical evidence supporting the use of novel modulators for the treatment of mood disorders, including specific glutamate modulators such as: 1) high-trapping glutamatergic modulators; 2) subunit (NR2B)-specific N-methyl-D-aspartate (NMDA) receptor antagonists; 3) NMDA receptor glycine-site partial agonists; and 4) metabotropic glutamate receptor (mGluR) modulators. We also discuss other promising, non-glutamatergic targets for potential rapid antidepressant effects in mood disorders, including the cholinergic system, the glucocorticoid system, and the inflammation pathway, as well as several additional targets of interest. Clinical evidence is emphasized, and non-pharmacological somatic treatments are not reviewed. In general, this paper only explores agents available in the United States. Expert commentary: Of these novel targets, the most promising - and the ones for whom the most evidence exists - appear to be the ionotropic glutamate receptors. However, moving forward will require us to fully embrace the goal of personalized medicine and will require health professionals to pre-emptively identify potential responders.

Propentofylline Prevents Sickness Behavior and Depressive-Like Behavior Induced by Lipopolysaccharide in Rats via Neuroinflammatory Pathway

Recent studies have demonstrated the intimate relationship between depression and immune disturbances. Aware of the efficacy limits of existing antidepressant drugs and the potential anti-inflammatory properties of propentofylline, we sought to evaluate the use of propentofylline as a depression treatment. We used a rat model of depression induced by repetitive lipopolysaccharide (LPS) administrations. We have studied sickness behavior, by assessing daily body weight, open field behavior, and TNF-α plasmatic levels. Anxiety-like behavior (light-dark test), depressive-like behavior (forced swim test), plasmatic levels of the brain-derived neurotrophic factor (BDNF, depression biomarker), and central glial fibrillary acidic protein (GFAP) expression (an astrocyte biomarker) were also evaluated. LPS induced body weight loss, open field behavior impairments (decreased locomotion and rearing, and increased immobility), and increased TNF-α levels in rats, compared with control group. Thus, LPS induced sickness behavior. LPS also increased the immobility and reduced climbing in the forced swim test, when compared with the control group, i.e., LPS induced depressive-like behavior in rats. Propentofylline prevented sickness behavior after four days of consecutive treatment, as well as prevented the depressive-like behavior after five days of consecutive treatments. Propentofylline also prevented the increase in GFAP expression induced by LPS. Neither LPS nor propentofylline has influenced the anxiety and BDNF levels of rats. In conclusion, repetitive LPS administrations induced sickness behavior and depressive-like behavior in rats. Propentofylline prevented both sickness behavior and depressive-like behavior via neuroinflammatory pathway. The present findings may contribute to a better understanding and treatment of depression and associated diseases.

High Kynurenine (a Tryptophan Metabolite) Predicts Remission in Patients with Major Depression to Add-on Treatment with Celecoxib

BACKGROUND

Signs of an inflammatory process have been described in major depression.

METHODS

In a double-blind, randomized study of celecoxib or placebo add-on to reboxetine in 40 depressed patients, celecoxib treatment has beneficial effects. In order to evaluate the tryptophan/kynurenine metabolism and to identify predictors for remission, tryptophan (TRP), kynurenine (KYN), kynurenic acid (KYNA), and quinolinic acid (QUIN) were estimated in the serum of 32 patients before and after treatment and in a group of 20 healthy controls.

RESULTS

KYN levels were significantly lower in patients (p = 0.008), and the QUIN/KYN ratios were significantly higher (p = 0.028). At baseline, the higher KYN/TRP ratio was predictive for remission during celecoxib add-on treatment (p = 0.04) as well as for remission in the overall patient group (p = 0.01). In the placebo group, remitters showed a higher KYNA/QUIN ratio (p = 0.032). In the overall group, remitters showed lower KYNA/KYN (p = 0.035) and QUIN/KYN (p = 0.011) ratios. The lower the formation of downstream metabolites, especially QUIN, the better the treatment outcome.

CONCLUSION

The high KYN/TRP ratio predicted remission after treatment with celecoxib in this small sample of depressed patients. Eventually, the KYN/TRP ratio might be a marker for those patients, which benefit from an additional anti-inflammatory treatment.

Therapeutic Implications of Brain-Immune Interactions: Treatment in Translation

A wealth of data has been amassed that details a complex, yet accessible, series of pathways by which the immune system, notably inflammation, can influence the brain and behavior. These data have opened the window to a diverse array of novel targets whose potential efficacy is tied to specific neurotransmitters and neurocircuits as well as specific behaviors. What is clear is that the impact of inflammation on the brain cuts across psychiatric disorders and engages dopaminergic and glutamatergic pathways that regulate motivation and motor activity as well as the sensitivity to threat. Given the ability to identify patient populations with increased inflammation, the precision of interventions can be further tuned, in conjunction with the ability to establish target engagement in the brain through the use of multiple neuroimaging strategies. After a brief overview of the mechanisms by which inflammation affects the brain and behavior, this review examines the extant literature on the efficacy of anti-inflammatory treatments, while forging guidelines for future intelligent clinical trial design. An examination of the most promising therapeutic strategies is also provided, along with some of the most exciting clinical trials that are currently being planned or underway.

Inflammation-Associated Co-morbidity Between Depression and Cardiovascular Disease

Morbidity and mortality of cardiovascular disease (CVD) is exceedingly high worldwide. Depressive illness is a serious psychiatric illness that afflicts a significant portion of the world population. Epidemiological studies have confirmed the high co-morbidity between these two disease entities. The co-morbidity is bidirectional and the mechanisms responsible for it are complex and multifaceted. In addition to genetic, biological systems, psychosocial, and behavioral factors that are involved include the central and autonomic nervous systems, the neuroendocrine, immune, and the vascular and hematologic systems. Specific pathophysiologic factors across these systems include homeostatic imbalance between the sympathetic and the parasympathetic systems with loss of heart rate variability (HRV) in depression, sympathoadrenal activation, hypothalamic-pituitary-adrenal (HPA) axis activation, immune system dysregulation resulting in a pro-inflammatory status, platelet activation, and endothelial dysfunction. These abnormalities have been demonstrated in most individuals diagnosed with major depressive disorder (MDD), bipolar disorder (BPD), and probably in other psychiatric disorders. A likely common instigator underlying the co-morbidity between cardiovascular pathology and depression is mental stress. Chronic stress shifts the homeostatic balance in the autonomic nervous system with sustained sympathetic overdrive and diminished vagal tone. Diminished vagal tone contributes to a pro-inflammatory status with associated sequelae. Stress hormones and certain pro-inflammatory substances released by macrophages and microglia upregulate the rate-limiting enzymes in the metabolic pathway of tryptophan (TRP). This enzymatic upregulation stimulates the kynurenine (KYN) pathway resulting in the formation of neurotoxic metabolites. Inflammation occurs in cardiac, cardiovascular, and cerebrovascular pathology independent of the presence or absence of depression. Inflammation is closely associated with endothelial dysfunction, a preamble to atherosclerosis and atherothrombosis. Endothelial dysfunction has been detected in depression and may prove to be a trait marker for this illness. Thus understanding vascular biology in conjunction with psychiatric co-morbidity will be of critical importance. Antidepressant drug therapy is of definite benefit to patients with medical and psychiatric co-morbidity and may reverse the pro-inflammatory status associated with depression. There is, however, an urgent need to develop novel pharmacotherapeutic approaches to benefit a much larger proportion of patients suffering from these disease entities.

Inflammation Effects on Brain Glutamate in Depression: Mechanistic Considerations and Treatment Implications

There has been increasing interest in the role of glutamate in mood disorders, especially given the profound effect of the glutamate receptor antagonist ketamine in improving depressive symptoms in patients with treatment-resistant depression. One pathway by which glutamate alterations may occur in mood disorders involves inflammation. Increased inflammation has been observed in a significant subgroup of patients with mood disorders, and inflammatory cytokines have been shown to influence glutamate metabolism through effects on astrocytes and microglia. In addition, the administration of the inflammatory cytokine interferon-alpha has been shown to increase brain glutamate in the basal ganglia and dorsal anterior cingulate cortex as measured by magnetic resonance spectroscopy (MRS). Moreover, MRS studies in patients with major depressive disorder have revealed that increased markers of inflammation including C-reactive protein correlate with increased basal ganglia glutamate, which in turn was associated with anhedonia and psychomotor retardation. Finally, human and laboratory animal studies have shown that the response to glutamate antagonists such as ketamine is predicted by increased inflammatory cytokines. Taken together, these data make a strong case that inflammation may influence glutamate metabolism to alter behavior, leading to depressive symptoms including anhedonia and psychomotor slowing.

Fluoxetine treatment affects the inflammatory response and microglial function according to the quality of the living environment

It has been hypothesized that selective serotonin reuptake inhibitors (SSRIs), the most common treatment for major depression, affect mood through changes in immune function. However, the effects of SSRIs on inflammatory response are contradictory since these act either as anti- or pro-inflammatory drugs. Previous experimental and clinical studies showed that the quality of the living environment moderates the outcome of antidepressant treatment. Therefore, we hypothesized that the interplay between SSRIs and the environment may, at least partially, explain the apparent incongruence regarding the effects of SSRI treatment on the inflammatory response. In order to investigate such interplay, we exposed C57BL/6 mice to chronic stress to induce a depression-like phenotype and, subsequently, to fluoxetine treatment or vehicle (21days) while being exposed to either an enriched or a stressful condition. At the end of treatment, we measured the expression levels of several anti- and pro-inflammatory cytokines and inflammatory mediators in the whole hippocampus and in isolated microglia. We also determined microglial density, distribution, and morphology to investigate their surveillance state. Results show that the effects of fluoxetine treatment on inflammation and microglial function, as compared to vehicle, were dependent on the quality of the living environment. In particular, fluoxetine administered in the enriched condition increased the expression of pro-inflammatory markers compared to vehicle, while treatment in a stressful condition produced anti-inflammatory effects. These findings provide new insights regarding the effects of SSRIs on inflammation, which may be crucial to devise pharmacological strategies aimed at enhancing antidepressant efficacy by means of controlling environmental conditions.

Serum Cytokine Levels in Major Depressive Disorder and Its Role in Antidepressant Response

OBJECTIVE

Cytokines have been reported to have key roles in major depressive disorder (MDD). However, much less is known about cytokines in MDD and antidepressant treatment due to the diversity of cytokines and the heterogeneity of depression. We investigated the levels of cytokines in patients with MDD compared with healthy subjects and their associations with antidepressant response.

METHODS

We investigated the changes of several cytokines (eotaxin, sCD40L, IL-8, MCP-1alpha, TNF-alpha, INF-gamma and MIP-1alpha) by Luminex assay in 66 patients with MDD and 22 healthy controls. The antidepressant response was assessed by 17-item Hamilton Rating Scale for Depression.

RESULTS

We found the levels of sCD40L (p=0.001), IL-8 (p=0.004) and MCP-1 (p=0.03) of healthy controls were significantly higher than those of depressive patients. However, the level of eotaxin and TNF-alpha were not associated with MDD. In addition, we found the level of MCP-1 was significantly changed after antidepressant treatment (p=0.01).

CONCLUSION

These findings suggest the roles of cytokines in MDD are complex, and could vary according to the individual characteristics of each patient. Further studies regarding the relationship between cytokines and MDD will be required.

Side effect profile similarities shared between antidepressants and immune-modulators reveal potential novel targets for treating major depressive disorders

Background

Side effects, or the adverse effects of drugs, contain important clinical phenotypic information that may be useful in predicting novel or unknown targets of a drug. It has been suggested that drugs with similar side-effect profiles may share common targets. The diagnostic class, Major Depressive Disorder, is increasingly viewed as being comprised of multiple depression subtypes with different biological root causes. One ‘type’ of depression generating substantial interest today focuses on patients with high levels of inflammatory burden, indicated by elevated levels of C-reactive proteins (CRP) and pro-inflammatory cytokines such as interleukin 6 (IL-6). It has been suggested that drugs targeting the immune system may have beneficial effect on this subtype of depressed patients, and several studies are underway to test this hypothesis directly. However, patients have been treated with both anti-inflammatory and antidepressant compounds for decades. It may be possible to exploit similarities in clinical readouts to better understand the antidepressant effects of immune-related drugs.

Methods

Here we explore the space of approved drugs by comparing the drug side effect profiles of known antidepressants and drugs targeting the immune system, and further examine the findings by comparing the human cell line expression profiles induced by them with those induced by antidepressants.

Results

We found 7 immune-modulators and 14 anti-inflammatory drugs sharing significant side effect profile similarities with antidepressants. Five of the 7 immune modulators share most similar side effect profiles with antidepressants that modulate dopamine release and/or uptake. In addition, the immunosuppressant rapamycin and the glucocorticoid alclometasone induces transcriptional changes similar to multiple antidepressants.

Conclusions

These findings suggest that some antidepressants and some immune-related drugs may affect common molecular pathways. Our findings support the idea that certain medications aimed at the immune system may be helpful in relieving depressive symptoms, and suggest that it may be of value to test immune-modulators for antidepressant-like activity in future proof-of-concept studies.

Pharmacogenomics of Drug Metabolizing Enzymes and Transporters: Relevance to Precision Medicine

The interindividual genetic variations in drug metabolizing enzymes and transporters influence the efficacy and toxicity of numerous drugs. As a fundamental element in precision medicine, pharmacogenomics, the study of responses of individuals to medication based on their genomic information, enables the evaluation of some specific genetic variants responsible for an individual’s particular drug response. In this article, we review the contributions of genetic polymorphisms to major individual variations in drug pharmacotherapy, focusing specifically on the pharmacogenomics of phase-I drug metabolizing enzymes and transporters. Substantial frequency differences in key variants of drug metabolizing enzymes and transporters, as well as their possible functional consequences, have also been discussed across geographic regions. The current effort illustrates the common presence of variability in drug responses among individuals and across all geographic regions. This information will aid health-care professionals in prescribing the most appropriate treatment aimed at achieving the best possible beneficial outcomes while avoiding unwanted effects for a particular patient.

Celecoxib attenuates depressive-like behavior associated with immunological liver injury in C57BL/6 mice through TNF-α and NF-κb dependent mechanisms

AIM

Depression associating patients with chronic liver diseases is a major treatment goal. This study aimed to evaluate the potential hepatoprotective and antidepressant effects of celecoxib in a model of experimental autoimmune hepatitis (EAH) and depressive-like behavior in C57BL/6 mice.

MAIN METHODS

EAH was induced by immunization with S-100 liver antigen emulsified in complete Freund's adjuvant (CFA). Mice were randomly allocated to 5 groups; control phosphate buffered saline group; control CFA group; EAH group, and 2 groups of EAH plus celecoxib (7.5 or 15mg/kg/d respectively). Mice were assessed behaviorally by novelty-suppressed test, tail suspension test, locomotor assessment and forced swimming tests. Serum liver enzymes and hepatic hydroxyproline content were biochemically analyzed. Histopathological analysis for liver and brain sections and immunohistochemical studies for hepatic and hippocampal tumor necrosis factor (TNF-α), nuclear factor Kappa-B (NF-κB) and caspase-3 were performed.

KEY FINDINGS

EAH group exhibited significant depressive-like changes, increase in liver enzymes and hepatic hydroxyproline content. Signs of autoimmune hepatitis and structural changes in hippocampus were confirmed by histopathological studies. Immunohistochemical examination revealed overexpression of hepatic and hippocampal TNF-α, NF-κB and caspase-3 positive cells. Celecoxib (7.5mg/kg/d) significantly ameliorated hepatic biochemical changes, hepatic and hippocampal histopathological and immunohistochemical changes induced in EAH group. Celecoxib (15mg/kg/d) significantly ameliorated the behavioral changes, histopathological and immunohistochemical changes in hippocampus, with non-significant change in hepatic biochemical profile, histopathological and immunohistochemical changes induced in EAH group.

SIGNIFICANCE

The celecoxib (7.5mg/kg/d) through its anti-inflammatory effect may represent a new therapeutic approach to treat autoimmune hepatitis associated with depressive symptoms.

Are the emergence of affective disturbances in neuropathic pain states contingent on supraspinal neuroinflammation?

Neuro-immune interactions contribute to the pathogenesis of neuropathic pain due to peripheral nerve injury. A large body of preclinical evidence supports the idea that the immune system acts to modulate the sensory symptoms of neuropathy at both peripheral and central nervous system sites. The potential involvement of neuro-immune interactions in the highly debilitating affective disturbances of neuropathic pain, such as depression, anhedonia, impaired cognition and reduced motivation has received little attention. This is surprising given the widely accepted view that sickness behaviour, depression, cognitive impairment and other neuropsychiatric conditions can arise from inflammatory mechanisms. Moreover, there is a set of well-described immune-to-brain transmission mechanisms that explain how peripheral inflammation can lead to supraspinal neuroinflammation. In the last 5years increasing evidence has emerged that peripheral nerve injury induces supraspinal changes in cytokine or chemokine expression and alters glial cell activity. In this systematic review, based on strong preclinical evidence, we advance the argument that the emergence of affective disturbances in neuropathic pain states are contingent on pro-inflammatory mediators in the interconnected hippocampal-medial prefrontal circuitry that subserve affective behaviours. We explore how dysregulation of inflammatory mediators in these networks may result in affective disturbances through a wide variety of neuromodulatory mechanisms. There are also promising results from clinical trials showing that anti-inflammatory agents have efficacy in the treatment of a variety of neuropsychiatric conditions including depression and appear suited to sub-groups of patients with elevated pro-inflammatory profiles. Thus, although further research is required, aggressively targeting supraspinal pro-inflammatory mediators at critical time-points in appropriate clinical populations is likely to be a novel avenue to treat debilitating affective disturbances in neuropathic conditions.

Microglial dysfunction connects depression and Alzheimer's disease

Alzheimer's disease (AD) and major depressive disorder (MDD) are highly prevalent neuropsychiatric conditions with intriguing epidemiological overlaps. Depressed patients are at increased risk of developing late-onset AD, and around one in four AD patients are co-diagnosed with MDD. Microglia are the main cellular effectors of innate immunity in the brain, and their activation is central to neuroinflammation - a ubiquitous process in brain pathology, thought to be a causal factor of both AD and MDD. Microglia serve several physiological functions, including roles in synaptic plasticity and neurogenesis, which may be disrupted in neuroinflammation. Following early work on the 'sickness behavior' of humans and other animals, microglia-derived inflammatory cytokines have been shown to produce depressive-like symptoms when administered exogenously or released in response to infection. MDD patients consistently show increased circulating levels of pro-inflammatory cytokines, and anti-inflammatory drugs show promise for treating depression. Activated microglia are abundant in the AD brain, and concentrate around senile plaques, hallmark lesions composed of aggregated amyloid-β peptide (Aβ). The Aβ burden in affected brains is regulated largely by microglial clearance, and the complex activation state of microglia may be crucial for AD progression. Intriguingly, recent reports have linked soluble Aβ oligomers, toxins that accumulate in AD brains and are thought to cause memory impairment, to increased brain cytokine production and depressive-like behavior in mice. Here, we review recent findings supporting the inflammatory hypotheses of AD and MDD, focusing on microglia as a common player and therapeutic target linking these devastating disorders.

Microglia activation is associated with IFN-α induced depressive-like behavior

Inflammatory immune activation has been frequently associated with the development of major depression. This association was confirmed in patients receiving long-term treatment with pro-inflammatory interferon-α (IFN-α). Microglia, the resident immune cells in the brain, might serve as an important interface in this immune system-to-brain communication. The aim of the present study was to investigate the role of microglia in an IFN-α mouse model of immune-mediated depression. Male BALB/c mice were treated with daily injections of IFN-α for two weeks. Depressive-like behavior was analyzed in the forced swim and tail suspension test. Activation of microglia was measured by flow cytometry. Pro-inflammatory M1 type (MHC-II, CD40, CD54, CD80, CD86, CCR7), anti-inflammatory M2 type (CD206, CD200R), and maturation markers (CD11c, CCR7) were tested, as well as the chemokine receptor CCR2. IFN-α led to a significant increase in depressive-like behavior and expression of the pro-inflammatory surface markers MHC-II, CD86, and CD54, indicating M1 polarization. Because IFN-α-treated mice showed great individual variance in the behavioral response to IFN-α, they were further divided into vulnerable and non-vulnerable subgroups. Only IFN-α vulnerable mice (characterized by their development of depressive-like behavior in response to IFN-α) showed an increased expression of MHC-II and CD86, while CD54 was similarly enhanced in both subgroups. Thus, IFN-α-induced activation of microglia was specifically associated with depressive-like behavior.

Integrating neuroimmune systems in the neurobiology of depression

Data from clinical and preclinical studies indicate that immune dysregulation, specifically of inflammatory processes, is associated with symptoms of major depressive disorder (MDD). In particular, increased levels of circulating pro-inflammatory cytokines and concomitant activation of brain-resident microglia can lead to depressive behavioural symptoms. Repeated exposure to psychological stress has a profound impact on peripheral immune responses and perturbs the function of brain microglia, which may contribute to neurobiological changes underlying MDD. Here, we review these findings and discuss ongoing studies examining neuroimmune mechanisms that influence neuronal activity as well as synaptic plasticity. Interventions targeting immune-related cellular and molecular pathways may benefit subsets of MDD patients with immune dysregulation.

Cyclooxygenase-2 inhibition reduces stress-induced affective pathology

Mood and anxiety disorders are the most prevalent psychiatric conditions and are exacerbated by stress. Recent studies have suggested cyclooxygenase-2 (COX-2) inhibition could represent a novel treatment approach or augmentation strategy for affective disorders including anxiety disorders and major depression. We show that traditional COX-2 inhibitors and a newly developed substrate-selective COX-2 inhibitor (SSCI) reduce a variety of stress-induced behavioral pathologies in mice. We found that these behavioral effects were associated with a dampening of neuronal excitability in the basolateral amygdala (BLA) ex vivo and in vivo, and were mediated by small-conductance calcium-activated potassium (SK) channel and CB1 cannabinoid receptor activation. Taken together, these data provide further support for the potential utility of SSCIs, as well as traditional COX-2 inhibitors, as novel treatment approaches for stress-related psychiatric disorders.

Mapping inflammation onto mood: Inflammatory mediators of anhedonia

Evidence supports inflammatory involvement in mood and cognitive symptoms across psychiatric, neurological and medical disorders; however, inflammation is not a sensitive or specific characteristic of these diagnoses. The National Institute of Mental Health Research Domain Criteria (RDoC) ask for a shift away from symptom-based diagnoses toward a transdiagnostic neurobiological focus in the study of brain illnesses. The RDoC matrix may provide a useful framework for integrating the effects of inflammation on brain function. Based on preclinical and clinical findings, relevant relationships span negative and positive valence systems, cognitive systems, systems for social processes and arousal/regulatory systems. As an exemplar, we consider the psychopathological domain of anhedonia, conceptualizing the relevance of inflammation (e.g., cellular immunity) and downstream processes (e.g., indoleamine 2,3-dioxygenase activation and oxidative inactivation of tetrahydrobiopterin) across RDoC units of analysis (e.g., catecholamine neurotransmitter molecules, nucleus accumbens medium spiny neuronal cells, dopaminergic mesolimbic and mesocortical reward circuits, animal paradigms, etc.). We discuss implications across illnesses affecting the brain, including infection, major depressive disorder, stroke, Alzheimer's disease and type 2 diabetes.

Microglial Cells as a Link between Cannabinoids and the Immune Hypothesis of Psychiatric Disorders

Psychiatric disorders are one of the leading causes of disability worldwide. Although several therapeutic options are available, the exact mechanisms responsible for the genesis of these disorders remain to be fully elucidated. In the last decade, a body of evidence has supported the involvement of the immune system in the pathophysiology of these conditions. Microglial cells play a significant role in maintaining brain homeostasis and surveillance. Dysregulation of microglial functions has been associated with several psychiatric conditions. Cannabinoids regulate the brain–immune axis and inhibit microglial cell activation. Here, we summarized evidence supporting the hypothesis that microglial cells could be a target for cannabinoid influence on psychiatric disorders, such as anxiety, depression, schizophrenia, and stress-related disorders.