The cyclooxygenase-2 inhibitor celecoxib has therapeutic effects in major depression: results of a double-blind, randomized, placebo controlled, add-on pilot study to reboxetine

The inflammatory & neurodegenerative (I&ND) hypothesis of depression: leads for future research and new drug developments in depression

Despite extensive research, the current theories on serotonergic dysfunctions and cortisol hypersecretion do not provide sufficient explanations for the nature of depression. Rational treatments aimed at causal factors of depression are not available yet. With the currently available antidepressant drugs, which mainly target serotonin, less than two thirds of depressed patients achieve remission. There is now evidence that inflammatory and neurodegenerative (I&ND) processes play an important role in depression and that enhanced neurodegeneration in depression may-at least partly-be caused by inflammatory processes. Multiple inflammatory-cytokines, oxygen radical damage, tryptophan catabolites-and neurodegenerative biomarkers have been established in patients with depression and these findings are corroborated by animal models of depression. A number of vulnerability factors may predispose towards depression by enhancing inflammatory reactions, e.g. lower peptidase activities (dipeptidyl-peptidase IV, DPP IV), lower omega-3 polyunsaturated levels and an increased gut permeability (leaky gut). The cytokine hypothesis considers that external, e.g. psychosocial stressors, and internal stressors, e.g. organic inflammatory disorders or conditions, such as the postpartum period, may trigger depression via inflammatory processes. Most if not all antidepressants have specific anti-inflammatory effects, while restoration of decreased neurogenesis, which may be induced by inflammatory processes, may be related to the therapeutic efficacy of antidepressant treatments. Future research to disentangle the complex etiology of depression calls for a powerful paradigm shift, i.e. by means of a high throughput-high quality screening, including functional genetics and genotyping microarrays; established and novel animal and ex vivo-in vitro models for depression, such as new transgenic mouse models and endophenotype-based animal models, specific cell lines, in vivo and ex vivo electroporation, and organotypic brain slice culture models. This screening will allow to: 1) discover new I&ND biomarkers, both at the level of gene expression and the phenotype; and elucidate the underlying molecular I&ND pathways causing depression; and 2) identify new therapeutic targets in the I&ND pathways; develop new anti-I&ND drugs for these targets; select existing anti-I&ND drugs or substances that could augment the efficacy of antidepressants; and predict therapeutic response by genetic I&ND profiles.

A review of candidate pathways underlying the association between asthma and major depressive disorder

OBJECTIVE

To consider the mechanisms that may link asthma and major depressive disorder (MDD). Asthma and MDD co-occur at higher rates than expected, but whether this reflects shared underlying pathophysiological mechanisms is not known.

METHODS

A review of the epidemiological data linking asthma and MDD was conducted and the possible biological mechanisms that could account for the high rate of this comorbidity were reviewed.

RESULTS

MDD occurs in almost half of patients with asthma assessed in tertiary care centers. Dysregulation of the hypothalamic pituitary adrenal axis may predispose people to both MDD and asthma, and similar alterations in the immune, autonomic nervous, and other key systems are apparent and may contribute to this increased risk of co-occurrence.

CONCLUSIONS

High rates of MDD in asthma may result from the stress of chronic illness, the medications used to treat it, or a combination of the two. The high level of co-occurrence may also reflect dysregulation of certain stress-sensitive biological processes that contribute to the pathophysiology of both conditions.

Flow cytometric analysis of T cell subsets in paired samples of cerebrospinal fluid and peripheral blood from patients with neurological and psychiatric disorders

Recent studies suggest inflammatory mechanisms involved in the pathogenesis of major psychiatric disorders (MPD). T cells play a major role during inflammation, but little is known about T cell subpopulations in the cerebrospinal fluid (CSF). We investigated the frequency of cells positive for the surface markers CD4, CD8, CD25, CD45, CD69, and CD127 in 45 paired cerebrospinal fluid (CSF) and peripheral blood (PB) samples by multiparameter flow cytometry from patients with MPD of the schizophrenic and affective spectrum with normal CSF cell counts and compared them with those from patients with non-inflammatory (NIND), chronic inflammatory (CIND) neurological disorders, and meningitis (MEN). In MEN patients, CD4+ cell frequency in PB, but not in CSF, was significantly increased as compared to CIND and NIND. No difference between patient groups was observed for CD8+. CD4+CD45RO+ double positive cells in PB were significantly lower in CIND than in MEN or NIND. The frequency of CD4+CD25+ cells in PB was significantly higher in MEN than in MPD or CIND. For CSF, the percentage of CD4+CD127(dim) cells was significantly lower in MEN than in MPD. CD4+CD127(dim) in PB and CSF showed overlapping characteristic clusters between MPD and CIND and MEN patients. Overall, the hypothesis of low degree inflammation in a subgroup of MPD is supported. The analysis of lymphocyte subsets in PB and CSF constitutes a novel promising tool to understand underlying pathomechanisms in psychiatric and neurological disorders on an individual case level.

Bipolar disorder: candidate drug targets

Current pharmacotherapy for bipolar disorder is generally unsatisfactory for a large number of patients. Even with adequate modern bipolar pharmacological therapies, many afflicted individuals continue to have persistent mood episode relapses, residual symptoms, functional impairment, and psychosocial disability. Creating novel therapeutics for bipolar disorder is urgently needed. Promising drug targets and compounds for bipolar disorder worthy of further study include both systems and intracellular pathways and targets. Specifically, the purinergic system, the dynorphin opioid neuropeptide system, the cholinergic system (muscarinic and nicotinic systems), the melatonin and serotonin [5-hydroxytryptamine receptor 2C] system, the glutamatergic system, and the hypothalamic-pituitary adrenal axis have all been implicated. Intracellular pathways and targets worthy of further study include glycogen synthase kinase-3 protein, protein kinase C, and the arachidonic acid cascade.

Episode-specific differential gene expression of peripheral blood mononuclear cells in rapid cycling supports novel treatment approaches

Molecular mechanisms underlying bipolar affective disorders are unknown. Difficulties arise from genetic and phenotypic heterogeneity of patients and the lack of animal models. Thus, we focused on only one patient (n = 1) with an extreme form of rapid cycling. Ribonucleic acid (RNA) from peripheral blood mononuclear cells (PBMC) was analyzed in a three-tiered approach under widely standardized conditions. Firstly, RNA was extracted from PBMC of eight blood samples, obtained on two consecutive days within one particular episode, including two different consecutive depressive and two different consecutive manic episodes, and submitted to (1) screening by microarray hybridizations, followed by (2) detailed bioinformatic analysis, and (3) confirmation of episode-specific regulation of genes by quantitative real-time polymerase chain reaction (qRT-PCR).Secondly, results were validated in additional blood samples obtained one to two years later. Among gene transcripts elevated in depressed episodes were prostaglandin D synthetase (PTGDS) and prostaglandin D2 11-ketoreductase (AKR1C3), both involved in hibernation. We hypothesized them to account for some of the rapid cycling symptoms. A subsequent treatment approach over 5 months applying the cyclooxygenase inhibitor celecoxib (2 x 200 mg daily) resulted in reduced severity rating of both depressed and manic episodes. This case suggests that rapid cycling is a systemic disease, resembling hibernation, with prostaglandins playing a mediator role.

Is major depressive disorder a metabolic encephalopathy?

Metabolic encephalopathy is an acute disturbance in cellular metabolism in the brain evoked by conditions of hypoxia, hypoglycaemia, oxidative stress and/or inflammation. It usually develops acutely or subacutely and is reversible if the systemic disorder is treated. If left untreated, however, metabolic encephalopathy may result in secondary structural damage to the brain. Most encephalopathies are present with neuropsychiatric symptoms, one in particular being depression. However, mood disorders are often co-morbid with cardiovascular, liver, kidney and endocrine disorders, while increasing evidence concurs that depression involves inflammatory and neurodegenerative processes. This would suggest that metabolic disturbances resembling encephalopathy may underscore the basic neuropathology of depression at a far deeper level than currently realized. Viewing depression as a form of encephalopathy, and exploiting knowledge gleaned from our understanding of the neurochemistry and treatment of metabolic encephalopathy, may assist in our understanding of the neurobiology of depression, but also in realizing new ideas in the pharmacotherapy of mood disorders.

Mode of action of mood stabilizers: is the arachidonic acid cascade a common target?

Bipolar disorder is a major medical, social and economic burden worldwide. However, the mechanisms of action of effective antibipolar disorder drugs remain elusive. In this paper, we review studies using a neuropharmacological approach in unanesthetized rats, combined with kinetic, biochemical and molecular biology techniques, showing that chronic administration of three Food and Drug Administration-approved mood stabilizers (lithium, valproate and carbamazepine) at therapeutically relevant doses, selectively target the brain arachidonic acid (AA) cascade. Whereas chronic lithium and carbamazepine decrease the binding activity of activator protein-2 and in turn the transcription, translation and activity of its AA-selective calcium-dependent phospholipase A(2) gene product, valproate appears to be a non-competitive inhibitor of long-chain acyl-CoA synthetase. The net overlapping effects of the three drugs are decreased turnover of AA but not of docosahexaenoic acid in rat brain phospholipids, and decreased brain cyclooxygenase-2 and prostaglandin E(2). Although these observations support the hypothesis proposed by Rapoport and colleagues that the AA cascade is a common target of mood stabilizers, this hypothesis is not necessarily exclusive of other targets. Targeting the AA cascade with drugs or diet may be a useful therapeutic approach in bipolar disorder, and examining the AA cascade in patients might help in better understanding the disease.

Inflammation, glutamate, and glia in depression: a literature review

Multiple lines of evidence suggest that inflammation and glutamate dysfunction contribute to the pathophysiology of depression. In this review we provide an overview of how these two systems may interact. Excess levels of inflammatory mediators occur in a subgroup of depressed patients. Studies of acute experimental activation of the immune system with endotoxin and of chronic activation during interferon-alpha treatment show that inflammation can cause depression. Peripheral inflammation leads to microglial activation which could interfere with excitatory amino acid metabolism leading to inappropriate glutamate receptor activation. Loss of astroglia, a feature of depression, upsets the balance of anti- and pro-inflammatory mediators and further impairs the removal of excitatory amino acids. Microglia activated by excess inflammation, astroglial loss, and inappropriate glutamate receptor activation ultimately disrupt the delicate balance of neuroprotective versus neurotoxic effects in the brain, potentially leading to depression.

A psychoneuroimmunological perspective to Emil Kraepelins dichotomy: schizophrenia and major depression as inflammatory CNS disorders

The Kraepelinian classification of psychiatric disorders, in particular the dichotomy of dementia praecox and manic-depressive psychosis is under discussion since a long time. In recent years, not only new research in the fields of psychopathology and clinical outcome, but also findings of biological markers in the areas of neurophysiology, neuroendocrinology, psychoneuroimmunology, genetics, or psychopharmacology show a big overlap between both groups of disorders. This overlap of symptoms and markers of both disorders intensified the discussion and the proposals for new criteria for the classification of psychiatric disorders. By means of findings from the field of psychoneuroimmunology and inflammation it will be shown that different pathological mechanisms in depression and schizophrenia may lead to the same final common pathway of inflammation. These mechanisms include the immunological balance between type-1 and type-2 immune activation which influences the tryptophan-degradating enzyme indoleamine 2,3-dioxygenase (IDO) in the CNS in opposite ways, leading to an altered availability of tryptophan and serotonin, and a disturbance of the kynurenine metabolism with an imbalance in favor of the production of the NMDA-receptor agonist quinolinic acid in depression and of the NMDA-receptor antagonist kynurenic acid in schizophrenia. In both disorders, however, an increased production of prostaglandin E2 and increased expression of cyclo-oxygenase-2 reflect a slight inflammatory process taking place probably in different regions of the CNS. Albeit this common inflammatory pathway--inflammation is a general pathway of the body as answer to a lot of different noxae and pathogens--the Kraepelinian dichotomy is important with respect to pathological mechanisms and therapeutic approaches, not only for further research in understanding the exact pathological mechanisms but also for the development of preventive strategies in high risk individuals and in patients. Opposite pathways regarding the immune activation, the neurotoxic versus neuroprotective kynurenine metabolites and the agonistic versus antagonistic effects on the NMDA receptor and the glutamatergic neurotransmission show despite a possible therapeutic advantage of anti-inflammatory therapy in both disorders that the Kraepelinian dichotomy still has a significant value from a biologic-psychiatric point of view.

Lipopolysaccharide and a social stressor influence behaviour, corticosterone and cytokine levels: divergent actions in cyclooxygenase-2 deficient mice and wild type controls

Administration of the endotoxin, lipopolysaccharide (LPS) diminished motor activity and increased plasma corticosterone as well as circulating levels of interleukin-1beta (IL-1beta), IL-6, tumor necrosis-factor-alpha (TNF-alpha) and IL-10. Among cyclooxygenase-2 (COX-2) knockout mice the behavioural, corticosterone and cytokine variations promoted by LPS were moderately (home cage activity, corticosterone, TNF-alpha) or largely (IL-6) reduced. However, if mice were exposed to a psychosocial stressor (social disruption associated with grouping mice with novel cage-mates after a period of isolation) coupled with LPS treatment, then the effects of the COX-2 deletion were absent, or there was a synergistic or additive elevation apparent (e.g., in the case of TNF-alpha, IL-6 and corticosterone). Evidently, COX-2 deletion may have either pro- or anti-inflammatory actions, depending upon the psychosocial context in which immune activation occurs.

Can celecoxib affect P-glycoprotein-mediated drug efflux? A microPET study

INTRODUCTION

P-glycoprotein (Pgp) is an efflux pump that protects vital organs like the brain from toxic substances, but which is also associated with therapy resistance. The anti-inflammatory drug celecoxib potentiates the efficacy of several cytostatic and neurotropic drugs that are known Pgp substrates. To clarify whether Pgp is involved in the sensitizing effect of celecoxib, we investigated in vivo whether celecoxib is a substrate of Pgp and whether it can affect the efflux activity of the pump.

METHODS

In control rats and in rats treated with the Pgp modulator cyclosporin A (CsA), cerebral accumulation of radiolabeled [(11)C]celecoxib was investigated by ex vivo biodistribution and micro-positron emission tomography imaging. In addition, the effect of unlabeled celecoxib and CsA (positive control) on the cerebral uptake of the Pgp substrate [(11)C]verapamil was studied.

RESULTS

[(11)C]Celecoxib uptake in rat brain was relatively high and homogeneously distributed. Treatment of rats with CsA only marginally increased cerebral tracer uptake, which is most likely due to reduced tracer clearance from plasma. [(11)C]Verapamil brain uptake was more than 10-fold higher after treatment with CsA. In contrast, a high dose of celecoxib increased cerebral [(11)C]verapamil uptake only twofold, which was accompanied by a similar increase in tracer concentration in plasma.

CONCLUSIONS

This study shows that celecoxib is not a substrate of Pgp and does not substantially affect the Pgp-mediated efflux of [(11)C]verapamil. Therefore, celecoxib-induced augmentation of the efficacy of chemotherapeutic and neurotropic drugs must be due to another mechanism than modulation of Pgp-mediated drug efflux.

Effects of MK-886, a 5-lipoxygenase activating protein (FLAP) inhibitor, and 5-lipoxygenase deficiency on the forced swimming behavior of mice

A common biological pathway may contribute to the comorbidity of atherosclerosis and depression. Increased activity of the enzymatic 5-lipoxygenase (5-LOX, 5LO) pathway is a contributing factor in atherosclerosis and a 5-LOX inhibitor, MK-886, is beneficial in animal models of atherosclerosis. In the brain, MK-886 increases phosphorylation of the glutamate receptor subunit GluR1, and the increased phosphorylation of this receptor has been associated with antidepressant treatment. In this work, we evaluated the behavioral effects of MK-886 in an automated assay of mouse forced swimming, which identifies antidepressant activity as increased climbing behavior and/or decreased rest time. Whereas a single injection of MK-886 (3 and 10 mg/kg) did not affect forced swimming behaviors assayed 30 min later, six daily injections of 3 mg/kg MK-886 slightly increased climbing and significantly reduced rest time in wild-type mice but not in 5-LOX-deficient mice. A diet delivery of MK-886, 4 micro/(100 mg(body-weight)day), required 3 weeks to affect forced swimming; it increased climbing behavior. Climbing behavior was also increased in naive 5-LOX-deficient mice compared to naive wild-type controls. These results suggest that 5-LOX inhibition and deficiency may be associated with antidepressant activity. Increased climbing in a forced swimming assay is a typical outcome of antidepressants that increase noradrenergic and dopaminergic activity. Interestingly, 5-LOX deficiency and MK-886 treatment have been shown to be capable of increasing the behavioral effects of a noradrenaline/dopamine-potentiating drug, cocaine. Future research is needed to evaluate the clinical relevance of our findings.

Psychological factors in asthma

Asthma has long been considered a condition in which psychological factors have a role. As in many illnesses, psychological variables may affect outcome in asthma via their effects on treatment adherence and symptom reporting. Emerging evidence suggests that the relation between asthma and psychological factors may be more complex than that, however. Central cognitive processes may influence not only the interpretation of asthma symptoms but also the manifestation of measurable changes in immune and physiologic markers of asthma. Furthermore, asthma and major depressive disorder share several risk factors and have similar patterns of dysregulation in key biologic systems, including the neuroendocrine stress response, cytokines, and neuropeptides. Despite the evidence that depression is common in people with asthma and exerts a negative impact on outcome, few treatment studies have examined whether improving symptoms of depression do, in fact, result in better control of asthma symptoms or improved quality of life in patients with asthma.

The hygiene hypothesis and psychiatric disorders

The hygiene hypothesis proposes that several chronic inflammatory disorders (allergies, autoimmunity, inflammatory bowel disease) are increasing in prevalence in developed countries because a changing microbial environment has perturbed immunoregulatory circuits which normally terminate inflammatory responses. Some stress-related psychiatric disorders, particularly depression and anxiety, are associated with markers of ongoing inflammation, even without any accompanying inflammatory disorder. Moreover, pro-inflammatory cytokines can induce depression, which is commonly seen in patients treated with interleukin-2 or interferon-alpha. Therefore, some psychiatric disorders in developed countries might be attributable to failure of immunoregulatory circuits to terminate ongoing inflammatory responses. This is discussed in relation to the effects of the immune system on a specific group of brain serotonergic neurons involved in the pathophysiology of mood disorders.

Phenomic, convergent functional genomic, and biomarker studies in a stress-reactive genetic animal model of bipolar disorder and co-morbid alcoholism

We had previously identified the clock gene D-box binding protein (Dbp) as a potential candidate gene for bipolar disorder and for alcoholism, using a Convergent Functional Genomics (CFG) approach. Here we report that mice with a homozygous deletion of DBP have lower locomotor activity, blunted responses to stimulants, and gain less weight over time. In response to a chronic stress paradigm, these mice exhibit a diametric switch in these phenotypes. DBP knockout mice are also activated by sleep deprivation, similar to bipolar patients, and that activation is prevented by treatment with the mood stabilizer drug valproate. Moreover, these mice show increased alcohol intake following exposure to stress. Microarray studies of brain and blood reveal a pattern of gene expression changes that may explain the observed phenotypes. CFG analysis of the gene expression changes identified a series of novel candidate genes and blood biomarkers for bipolar disorder, alcoholism, and stress reactivity.

Celecoxib as an adjunct in the treatment of depressive or mixed episodes of bipolar disorder: a double-blind, randomized, placebo-controlled study

OBJECTIVE

To investigate whether the cox-2 inhibitor celecoxib has antidepressant effects in bipolar disorder (BD) patients during depressive or mixed phases.

METHODS

We studied 28 DSM-IV BD patients who were experiencing a depressive or mixed episode and were on a stable dose of a mood stabilizer or atypical antipsychotic medication. Subjects were randomized to receive 6 weeks of double-blind placebo or celecoxib (400 mg/day) treatment. Current mood stabilizer or antipsychotic medication remained at the same doses during the trial.

RESULTS

Intention-to-treat analysis showed that the patients receiving celecoxib had lower Hamilton Depression Rating Scale (HamD) scores after 1 week of treatment compared to the patients receiving placebo, but this difference was not statistically significant (p = 0.09). The improvement in the first week of treatment was statistically significant when the analysis included only the subjects who completed the full 6-week trial (p = 0.03). The two groups did not differ significantly on depressive or manic symptoms from the second week until the end of the trial. Celecoxib was well tolerated with the exception of two subjects who dropped out of the study due to rash.

CONCLUSIONS

Our findings suggest that adjunctive treatment with celecoxib may produce a rapid-onset antidepressant effect in BD patients experiencing depressive or mixed episodes.

From inflammation to sickness and depression: when the immune system subjugates the brain

In response to a peripheral infection, innate immune cells produce pro-inflammatory cytokines that act on the brain to cause sickness behaviour. When activation of the peripheral immune system continues unabated, such as during systemic infections, cancer or autoimmune diseases, the ensuing immune signalling to the brain can lead to an exacerbation of sickness and the development of symptoms of depression in vulnerable individuals. These phenomena might account for the increased prevalence of clinical depression in physically ill people. Inflammation is therefore an important biological event that might increase the risk of major depressive episodes, much like the more traditional psychosocial factors.

Evidence for an inhibitory immunomodulatory effect of selected antidepressants on rat splenocytes: possible relevance to depression and hyperactive-immune disorders

Antidepressants have been found to possess antiproliferative effect. In the immune system depression may activate pro-inflammatory cytokines. Therefore, the aim of this study was to assess the immunomodulatory activity of antidepressants in naïve rat. Rat splenocytes were activated with con A and treated with paroxetine, sertraline or clomipramine ex vivo. We found that the antidepressants inhibit cell viability and proliferation at IC50 of 5-8 microM of mitogen-stimulated rat splenocytes. This inhibitory effect was accompanied by cell cycle arrest and increase in apoptotic events as assayed by FACS. Moreover, antidepressants decrease the secretion of the TH1 factor--TNFalpha. In addition, the antidepressants reduced the expression of the enzyme cyclooxygenase2 which is involved in inflammation. On the cellular level we show the up-regulation of MAPK death signaling pathway and suppression of the anti-apoptotic factor--Bcl-2. These findings reveal the immunomodulatory effect of the selected antidepressants. These data suggest a novel use of antidepressants or their derivatives.

Identification and treatment of symptoms associated with inflammation in medically ill patients

Medically ill patients present with a high prevalence of non-specific comorbid symptoms including pain, sleep disorders, fatigue and cognitive and mood alterations that is a leading cause of disability. However, despite major advances in the understanding of the immune-to-brain communication pathways that underlie the pathophysiology of these symptoms in inflammatory conditions, little has been done to translate this newly acquired knowledge to the clinics and to identify appropriate therapies. In a multidisciplinary effort to address this problem, clinicians and basic scientists with expertise in areas of inflammation, psychiatry, neurosciences and psychoneuroimmunology were brought together in a specialized meeting organized in Bordeaux, France, on May 28-29, 2007. These experts considered key questions in the field, in particular those related to identification and quantification of the predominant symptoms associated with inflammation, definition of systemic and central markers of inflammation, possible domains of intervention for controlling inflammation-associated symptoms, and relevance of animal models of inflammation-associated symptoms. This resulted in a number of recommendations that should improve the recognition and management of inflammation-associated symptoms in medically ill patients.

Advanced glycation and lipoxidation end products--amplifiers of inflammation: the role of food

BACKGROUND

High levels of glycated and lipoxidated proteins and peptides in the body are repeatedly associated with chronic diseases. These molecules are strongly associated with activation of a specific receptor called RAGE and a long-lasting exaggerated level of inflammation in the body.

METHODS

PubMed reports over 5000 papers plus >13,500 articles about the related HbA(1c), most of them published in the past 5 years. Most of the available abstracts have been read and approximately 800 full papers have been studied.

RESULTS

RAGE, a member of the immunoglobulin superfamily of cell surface molecules and receptor for advanced glycation end products, known since 1992, functions as a master switch, induces sustained activation of nuclear factor kappaB (NFkappaB), suppresses a series of endogenous autoregulatory functions, and converts long-lasting proinflammatory signals into sustained cellular dysfunction and disease. Its activation is associated with high levels of dysfunctioning proteins in body fluids and tissues, and is strongly associated with a series of diseases from allergy and Alzheimers to rheumatoid arthritis and urogenital disorders. Heat treatment, irradiation, and ionization of foods increase the content of dysfunctioning molecules.

CONCLUSIONS

More than half of the studies are performed in diabetes and chronic renal diseases; there are few studies in other diseases. Most of our knowledge is based on animal studies and in vitro studies. These effects are worth further exploration both experimentally and clinically. An avoidance of foods rich in deranged proteins and peptides, and the consumption of antioxidants, especially polyphenols, seem to counteract such a development.

Immunomodulatory effect of selective serotonin reuptake inhibitors (SSRIs) on human T lymphocyte function and gene expression

Antidepressants have an antiproliferative effect in some cell lines. Depression may be associated with activation of some pro-inflammatory cytokines. Therefore, we evaluated the ex-vivo immunomodulatory effect of selective serotonin reuptake inhibitors (SSRIs) in T cells. We found that the SSRIs, paroxetine and sertraline decreased T-cell viability with IC50 around 10 microM. The inhibition obtained with exposure to the SSRIs was more pronounced than that achieved with dexamethasone. Moreover, these SSRIs inhibit the secretion of the TH1 factor-tumor necrosis factor(TNF)alpha from the cells. On the molecular level, the SSRIs suppressed signal transducer and activator of transcription 3 (Stat3) and cyclooxygenase(Cox)2 protein expression. The inhibitory effects were accompanied by alterations in gene expression as assessed in the gene array. These findings reveal an immunomodulatory effect of the SSRIs paroxetine and sertraline in human T cells. The clinical implications of our findings merit further investigation.

The immune-mediated alteration of serotonin and glutamate: towards an integrated view of depression

Beside the well-known deficiency in serotonergic neurotransmission as pathophysiological correlate of major depression (MD), recent evidence points to a pivotal role of increased glutamate receptor activation as well. However, cause and interaction of these neurotransmitter alterations are not understood. In this review, we present a hypothesis integrating current concepts of neurotransmission and hypothalamus-pituitary-adrenal (HPA) axis dysregulation with findings on immunological alterations and alterations in brain morphology in MD. An immune activation including increased production of proinflammatory cytokines has repeatedly been described in MD. Proinflammatory cytokines such as interleukin-2, interferon-gamma, or tumor necrosis factor-alpha activate the tryptophan- and serotonin-degrading enzyme indoleamine 2,3-dioxygenase (IDO). Depressive states during inflammatory somatic disorders are also associated with increased proinflammatory cytokines and increased consumption of tryptophan via activation of IDO. An enhanced consumption of serotonin and its precursor tryptophan through IDO activation could well explain the reduced availability of serotonergic neurotransmission in MD. An increased activation of IDO and its subsequent enzyme kynurenine monooxygenase by proinflammatory cytokines, moreover, leads to an enhanced production of quinolinic acid, a strong agonist of the glutamatergic N-methyl-D-aspartate receptor. In inflammatory states of the central nervous system, IDO is mainly activated in microglial cells, which preferentially metabolize tryptophan to the NMDA receptor agonist quinolinic acid, whereas astrocytes - counteracting this metabolism due to the lack of an enzyme of this metabolism - have been observed to be reduced in MD. Therefore the type 1/type 2 immune response imbalance, associated with an astrocyte/microglia imbalance, leads to serotonergic deficiency and glutamatergic overproduction. Astrocytes are further strongly involved in re-uptake and metabolic conversion of glutamate. The reduced number of astrocytes could contribute to both, a diminished counterregulation of IDO activity in microglia and an altered glutamatergic neurotransmission. Further search for antidepressant agents should take into account anti-inflammatory drugs, for example, cyclooxygenase-2 inhibitors, might exert antidepressant effects by acting on serotonergic deficiency, glutamatergic hyperfunction and antagonizing neurotoxic effects of quinolinic acid.

Neuropsychiatric manifestations of depression in multiple sclerosis: neuroinflammatory, neuroendocrine, and neurotrophic mechanisms in the pathogenesis of immune-mediated depression

Evidence suggests that depression in multiple sclerosis (MS) is largely biologically mediated by some of the same processes involved in the immunopathogenesis of this neurologic disease. In particular, the increase in proinflammatory cytokines, activation of the hypothalamic-pituitary-adrenal (HPA) axis, and reduction in neurotrophic factors that occur in MS may each account for the increased rate of depression seen in MS. The possible contributions of these neuroinflammatory, neuroendocrine, and neurotrophic mechanisms suggest a diverse array of novel treatment strategies for depression, both in the context of inflammatory conditions as well as in idiopathic depression. Furthermore, if such processes in MS play a causative role in the pathogenesis of depression, and depression in turn has affects on neurophysiological processes related to immune function, then treatment of depression might have a positive effect on MS disease progression. This makes treating MS depression a neuropsychiatric imperative.

Effects of estrogen against LPS-induced inflammation and toxicity in primary rat glial and neuronal cultures

Several lines of evidence link inflammation with neurodegenerative diseases, which are aggravated by the age-related decline in estrogen levels in postmenopausal women. Lipopolysaccharide (LPS) is used widely to stimulate glial cells to produce pro-inflammatory mediators such as NO, PGE(2), and TNF-alpha, and was found to be toxic in high doses. We examined the effects of a physiological dose of 17beta-estradiol (E2) against LPS-induced inflammation and toxicity (cell death) in rat primary glial and neuronal cultures. Cultures were treated with 0.1 nM E2 for 24 h and then exposed to LPS 0.5-200 microg/ml for another 24 h. Levels of NO, PGE(2), and TNF-alpha in the culture medium were determined by the Griess reaction assay, radio-immunoassay, and enzyme-linked immunoassay, respectively. Cell death was quantified by measuring the leakage of lactate dehydrogenase (LDH) into the medium from dead or dying cells using the non-radioactive cytotoxicity assay. E2 significantly reduced the LPS-induced increase in NO and TNF-alpha (but not PGE(2)) production in glial cells. PGE(2) and TNF-alpha were undetectable in neuronal cultures, while only basal levels of NO were detected, even after stimulation with LPS. Moreover, pretreatment with E2 significantly reduced LPS-induced cell death, as measured by the release of LDH, in both glial and neuronal cultures. These results suggest that the neuroprotective effects attributed to E2 are derived, at least in part, from its anti-inflammatory and cytoprotective effects in both glial and neuronal cells.

Chronic lamotrigine does not alter the turnover of arachidonic acid within brain phospholipids of the unanesthetized rat: implications for the treatment of bipolar disorder

RATIONALE

Drugs that are effective in treating the manic phase of bipolar disorder (lithium, carbamazepine, and valproate) upon chronic administration to rats decrease the turnover of arachidonic acid in their brain phospholipids. Lamotrigine may not be effective in the manic phase, but is effective in delaying the depressive phase and for treating rapid cycling bipolar disorder. Thus, lamotrigine provides a pharmacological tool to differentiate if downregulation of arachidonic acid turnover is specific to drugs effective in the manic phase of bipolar disorder.

MATERIALS AND METHODS

To test this hypothesis, rats were administered lamotrigine (10 mg kg(-1) day(-1)) or vehicle intragastrically once daily for 42 days. In the unanesthetized rat, [1-(14)C]arachidonic acid was infused intravenously and arterial blood plasma was sampled until the animal was killed at 5 min, and its microwaved brain was subjected to chemical and radiotracer analysis.

RESULTS

Using equations from our fatty acid model, we found that chronic lamotrigine compared with vehicle did not alter the net incorporation rate of plasma arachidonic acid into brain phospholipids, nor did it alter the turnover of arachidonic acid within brain phospholipids.

CONCLUSION

Chronic lamotrigine, which is effective in the depressive phase or rapid cycling bipolar disorder does not alter brain arachidonic acid turnover in the unanesthetized rat. These results are consistent with the hypothesis that drugs effective in treating the manic phase of bipolar disorder decrease brain arachidonic acid turnover.

Pharmacogenomics of neuroimmune interactions in human psychiatric disorders

There is bidirectional communication between the brain and the immune system. Overproduction of interleukin-1beta (IL-1beta) leads to systemic inflammatory response syndrome (SIRS). The crucial role of IL-1beta in inflammation has been highlighted by studies performed in caspase-1 knockout mice (casp1(-/-)), transgenic mice that lack mature IL-1beta and survive lethal doses of lypopolysaccharide (LPS). We have previously shown that IL-1beta, its receptor IL-1 receptor I (IL-1RI) and caspase-1 are expressed within the brain. Moreover, we documented that peripherally injected LPS triggers a specific spatiotemporal pattern of expression of IL-1beta mRNA within the brain, suggesting that IL-1beta could be a major regulator of the central inflammatory cascade. Therefore, we studied brain transcriptional patterns that occur during LPS-induced SIRS in wild-type and casp1(-/-) mice. We showed patterns of gene expression in wild-type and casp1(-/-) mice that included differential expression of several genes, such as those for cytokines, chemokines, nitric oxide synthase 2 and cyclo-oygenase 2. A key component of the neuroimmune-endocrine axis that is increased by IL-1beta is corticotrophin releasing hormone (CRH). We found increased response to antidepressants in patients homozygous for the GAG haplotype of CRH receptor-1. Our results support the hypotheses that the CRH receptor-1 gene and possibly other genes in stress-inflammatory pathways are involved in the response to antidepressant treatment. Since dysregulation of the neuroimmune-endocrine axis appears to be one of the fundamental biological mechanisms that underlie psychiatric disorders, our findings might contribute to increase the understanding of the molecular pathways that are altered in these diseases.

Caspase 1 deficiency reduces inflammation-induced brain transcription

The systemic inflammatory response syndrome (SIRS) is a life-threatening medical condition characterized by a severe and generalized inflammatory state that can lead to multiple organ failure and shock. The CNS regulates many features of SIRS such as fever, cardiovascular, and neuroendocrine responses. Central and systemic manifestations of SIRS can be induced by LPS or IL-1beta administration. The crucial role of IL-1beta in inflammation has been further highlighted by studies of mice lacking caspase 1 (casp1, also known as IL-1beta convertase), a protease that cleaves pro-IL-1beta into mature IL-1beta. Indeed, casp1 knockout (casp1(-/-)) mice survive lethal doses of LPS. The key role of IL-1beta in sickness behavior and its de novo expression in the CNS during inflammation led us to test the hypothesis that IL-1beta plays a major role modulating the brain transcriptome during SIRS. We show a gene-environment effect caused by LPS administration in casp1(-/-) mice. During SIRS, the expression of several genes, such as chemokines, GTPases, the metalloprotease ADAMTS1, IL-1RA, the inducible nitric oxide synthase, and cyclooxygenase-2, was differentially increased in casp1(-/-) mice. Our findings may contribute to the understanding of the molecular changes that take place within the CNS during sepsis and SIRS and the development of new therapies for these serious conditions. Our results indicate that those genes may also play a role in several neuropsychiatric conditions in which inflammation has been implicated and indicate that casp1 might be a potential therapeutic target for such disorders.

Cytokine-effects on glucocorticoid receptor function: relevance to glucocorticoid resistance and the pathophysiology and treatment of major depression

Glucocorticoids play an essential role in the response to environmental stressors, serving initially to mobilize bodily responses to challenge and ultimately serving to restrain neuroendocrine and immune reactions. A number of diseases including autoimmune, infectious and inflammatory disorders as well as certain neuropsychiatric disorders such as major depression have been associated with decreased responsiveness to glucocorticoids (glucocorticoid resistance), which is believed to be related in part to impaired functioning of the glucocorticoid receptor (GR). Glucocorticoid resistance, in turn, may contribute to excessive inflammation as well as hyperactivity of corticotropin releasing hormone and sympathetic nervous system pathways, which are known to contribute to a variety of diseases as well as behavioral alterations. Recent data indicate that glucocorticoid resistance may be a result of impaired GR function secondary to chronic exposure to inflammatory cytokines as may occur during chronic medical illness or chronic stress. Indeed, inflammatory cytokines and their signaling pathways including mitogen-activated protein kinases, nuclear factor-kappaB, signal transducers and activators of transcription, and cyclooxygenase have been found to inhibit GR function. Mechanisms include disruption of GR translocation and/or GR-DNA binding through protein-protein interactions of inflammatory mediators with the GR itself or relevant steroid receptor cofactors as well as alterations in GR phosphorylation status. Interestingly, cAMP signal transduction pathways can enhance GR function and inhibit cytokine signaling. Certain antidepressants have similar effects. Thus, further understanding the effects of cytokines on GR signaling and the mechanisms involved may reveal novel therapeutic targets for reversal of glucocorticoid resistance and restoration of glucocorticoid-mediated inhibition of relevant bodily/immune responses during stress and immune challenge.

Effect of the COX-2 inhibitor celecoxib on behavioural and immune changes in an olfactory bulbectomised rat model of depression

BACKGROUND

The olfactory bulbectomised (OBX) rat model is a chronic model of depression in which behavioural and neuroimmunoendocrine changes are reversed only after chronic antidepressant treatment. The cyclooxygenase 2 (COX-2) inhibitor celecoxib has been shown to improve the depressive symptoms in patients with major depression.

METHODS

The association between blood and brain immunological and behavioural changes in chronic treatment with COX-2 inhibitor was explored in the OBX rats and their sham-operated controls.

RESULTS

The OBX group showed significantly higher locomotor activity than the other groups in the first 5 min in the open field. In the home cage emergence test, the OBX group showed a significantly shorter latency period compared to the sham group (z = -3.192, p = 0.001) but there was no difference between the other three groups. In the hypothalamus, the OBX group had a significantly higher interleukin 1beta (IL-1beta) concentration than the OBX + celecoxib group (z = -1.89, p = 0.05) as well as a significantly higher IL-10 concentration (z = -1.995, p = 0.046). In the prefrontal cortex, the OBX group showed significantly higher concentrations of tumour necrosis factor alpha (z = -2.205, p = 0.028) and IL-1beta (z = -3.361, p = 0.001) than the OBX + celecoxib group, but a significantly lower concentration of IL-10 (p = -3.361, p = 0.001) than the OBX + celecoxib group.

CONCLUSIONS

The results of this study supported the potential therapeutic role of the COX-2 inhibitor celecoxib. It is possible that the behavioural changes following the chronic administration of celecoxib to the OBX rats are associated with an attenuation of the increase in the pro-inflammatory cytokines in the brain.

The etiology of poststroke depression: a review of the literature and a new hypothesis involving inflammatory cytokines

Although poststroke depression is unlikely to represent a single disorder and numerous etiologies for different kinds of poststroke depression will likely emerge as the result of future research, we believe that a number of poststroke depressive disorders are likely to be the result of specific changes in brain pathology and neurophysiology. Nevertheless, there are relatively few hypotheses about the pathophysiology of poststroke depression. This paper, therefore, proposes a new hypothesis for poststroke depression involving increased production of proinflammatory cytokines resulting from brain ischemia in cerebral areas linked to the pathogenesis of mood disorders. This paper reviews the evidence supporting the hypothesis that proinflammatory cytokines are involved in the occurrence of stroke as well as mood disorders linked to the brain damage. The increased production of proinflammatory cytokines such as IL-1beta, TNF-alpha or IL-18 resulting from stroke may lead to an amplification of the inflammatory process, particularly in limbic areas, and widespread activation of indoleamine 2,3-dioxygenase (IDO) and subsequently to depletion of serotonin in paralimbic regions such as the ventral lateral frontal cortex, polar temporal cortex and basal ganglia. The resultant physiological dysfunction may lead to poststroke depression. Future investigations may explore this hypothesis through more extensive studies on the role of proinflammatory cytokines, such as IL-1beta, TNF-alpha or even IL-18, in patients with poststroke depression.

Gene expression profiling of lymphoblastoid cell lines from monozygotic twins discordant in severity of autism reveals differential regulation of neurologically relevant genes

Background

The autism spectrum encompasses a set of complex multigenic developmental disorders that severely impact the development of language, non-verbal communication, and social skills, and are associated with odd, stereotyped, repetitive behavior and restricted interests. To date, diagnosis of these neurologically based disorders relies predominantly upon behavioral observations often prompted by delayed speech or aberrant behavior, and there are no known genes that can serve as definitive biomarkers for the disorders.

Results

Here we demonstrate, for the first time, that lymphoblastoid cell lines from monozygotic twins discordant with respect to severity of autism and/or language impairment exhibit differential gene expression patterns on DNA microarrays. Furthermore, we show that genes important to the development, structure, and/or function of the nervous system are among the most differentially expressed genes, and that many of these genes map closely in silico to chromosomal regions containing previously reported autism candidate genes or quantitative trait loci.

Conclusion

Our results provide evidence that novel candidate genes for autism may be differentially expressed in lymphoid cell lines from individuals with autism spectrum disorders. This finding further suggests the possibility of developing a molecular screen for autism based on expressed biomarkers in peripheral blood lymphocytes, an easily accessible tissue. In addition, gene networks are identified that may play a role in the pathophysiology of autism.