Tricyclic antidepressants inhibit IL-6, IL-1 beta and TNF-alpha release in human blood monocytes and IL-2 and interferon-gamma in T cells

The olfactory bulbectomised rat as a model of depression

Bilateral olfactory bulbectomy results in changes in behavior, and in the endocrine, immune and neurotransmitter systems, that simulates many of those seen in patients with major depression. The olfactory system in the rat forms a part of the limbic region in which the amygdala and hippocampus contribute to the emotional and memory components of behavior. However, the loss of olfaction alone, which results from bulbectomy, is not the major factor that contributes to the behavioral abnormalities as peripherally induced anosmia does not cause the same behavioral changes. Thus it would appear that bulbectomy causes a major dysfunction of the cortical-hippocampal-amygdala circuit that underlies the behavioral and other changes. These neuroanatomical areas also seem to be dysfunctional in the patient with major depression. Chronic, but not acute, administration of antidepressants largely corrects most the behavioral, endocrine, immune and neurotransmitter changes that occur following bulbectomy. Thus the olfactory bulbectomized rat is not only a model for detecting antidepressant activity but also one for exploring the inter-relationships between these systems that are also dysfunctional in patients with major depression.

Treatment of Depression and Effect of Antidepression Treatment on Nutritional Status in Chronic Hemodialysis Patients

BACKGROUND

Depression, which is the most common psychological complication in patients with end-stage renal disease (ESRD), has an impact on the clinical outcome and is associated with malnutrition in chronic hemodialysis patients. This study evaluated the effect of antidepression treatment on nutritional status in depressed chronic hemodialysis patients.

METHODS

Sixty-two ESRD patients who underwent dialysis for more than 6 months were interviewed and completed a Beck Depression Inventory assessment. Thirty-four patients who had scores greater than 18 on the Beck Depression Inventory score and met Diagnostic and Statistical Manual of Mental Disorders, 4th Edition criteria for major depressive disorder were selected to receive paroxetine 10 mg/day and psychotherapy for 8 weeks. The remaining 28 patients were assigned to the control group. Change in the severity of depressive symptoms was ascertained by administering the Hamilton Depression Rating Scale. Nutritional status was evaluated by normalized protein catabolic rate, serum albumin and blood urea nitrogen level.

RESULTS

All patients successfully completed 8 weeks of antidepression treatment. Antidepression treatment decreased the severity of depressive symptoms (Hamilton Depression Rating Scale score: 16.6 +/- 7.0 versus 15.1 +/- 6.6, P < 0.01) and increased normalized protein catabolic rate (1.04 +/- 0.24 versus 1.17 +/- 0.29 g/kg/day, P < 0.05), serum albumin (37.3 +/- 2.0 versus 38.7 +/- 3.2 g/l, P < 0.005), and prehemodialysis blood urea nitrogen level (24.3 +/- 5.6 versus 30.2 +/- 7.9 mmol/L, P < 0.001). In the control group, no change was noted during the study period.

CONCLUSION

This study suggests that antidepressant medication with supportive psychotherapy can successfully treat depression and improve nutritional status in chronic hemodialysis patients with depression.

Chronic administration of tianeptine balances lipopolysaccharide-induced expression of cytokines in the spleen and hypothalamus of rats

The antidepressant tianeptine has been shown to protect the hippocampus against the deleterious consequences of stress and to attenuate the behavioral and neuroendocrine effects of the cytokine inducer lipopolysaccharide (LPS). Since sickness symptoms are linked to peripheral and brain production of cytokines and pro-inflammatory cytokines can promote neurotoxicity, the present study was undertaken to test the possibility that tianeptine attenuates production of pro-inflammatory cytokines. This hypothesis has been tested by studying the effects of a chronic intraperitoneal (i.p.) administration of tianeptine (10 mg/kg twice a day for 21 days) to rats on the induction by LPS (250 microg/kg, i.p.) of the production of pro- and anti-inflammatory cytokines, at the periphery (spleen, pituitary) and in the brain (hypothalamus, hippocampus). The expression of mRNAs coding for IL-1 beta, TNF-alpha, IL-6 or IL-10 (RT-PCR) and plasma levels of IL-1 beta, TNF-alpha and IL-10 (ELISA) were measured at various time intervals following LPS. Chronic tianeptine treatment attenuated LPS-induced expression of TNF-alpha in the spleen as well as plasma levels of this cytokine and altered the central balance between pro- and anti-inflammatory cytokines (IL-1 beta/IL-10). These results open new vistas in the pharmacological activity of tianeptine and provide further insights on the possible mechanisms of action involved in its neuroprotective properties.

ATF2, a member of the CREB/ATF family of transcription factors, in chronic stress and consequent to antidepressant treatment: animal models and human post-mortem brains

The regulation of gene expression has been implicated in the etiology and treatment of depression. Transcription factors serve as the intermediates between intracellular cascades and gene expression, and may therefore be involved in the pathophysiology and pharmacotherapy of depression. We and others have previously reported an increase in the phosphorylation of the transcription factor cAMP response element binding protein (CREB) by antidepressants, alongside brain region-specific alterations in pCREB by stress. In the present study, we examined the expression of another member of the CREB/ATF family of transcription factors, ATF2, in the brains of rats chronically treated with two different antidepressants, and in rats 4 months after their exposure to prolonged stress. ATF2 phosphorylation was decreased by antidepressants and increased at the aftermath of prolonged stress, specifically in the frontal cortex. We also examined ATF2 expression in the ventral parieto-occipital region of post-mortem human brains of normal controls, depressed, bipolar, and schizophrenic patients, obtained from the Stanley Foundation Brain Consortium. No alterations were observed in the levels of ATF2. However, in the depressed group, the pATF2 levels were higher in unmedicated compared to medicated patients, suggesting an antidepressant-induced reduction in pATF2. We discuss the possible role of ATF2 in depression, and propose that an interplay between ATF2 and CREB, and possibly other transcription factors, determines the final gene expression pattern in the etiology and treatment of depression.

Stimulatory effect of antidepressants on the production of IL-6

A body of evidence indicates that the therapeutic activity of antidepressants is connected with their modulatory effect on the inflammatory response system and cell-mediated immunity. The present study was carried out to examine the effects of antidepressant agents, such as imipramne, venlafaxine, l-5-hydroxytryptophan, fluoxetine and a combination of l-5-hydroxytryptophan and fluoxetine, on the production of the pleotrophic cytokines TNF-alpha and IL-6. Diluted whole blood from fluoxetine-treated patients with treatment-resistant depression (TRD) (mean age: 50.6+/-3.9 years), age-matched healthy controls (mean age: 51.6+/-1.7 years) and younger healthy volunteers (mean age: 35.4+/-1.7 years) was stimulated with phytohemagglutinin (PHA) and lipopolysaccharide (LPS) for 48 h with or without incubation with the antidepressants at 10(-6) and 10(-5) M. The major findings of this study are: (1). imipramine and venlafaxine (at the higher concentration), 5-HTP (at lower and higher concentrations) and a combination of 5-HTP and fluoxetine (both at the lower concentration) increased the production of IL-6; (2). all drugs used did not affect TNF-alpha production. IL-6 production was significantly higher in depressed patients than in age-matched volunteers, whereas TNF-alpha production was significantly higher in older volunteers than in younger ones. We speculate that the therapeutic activity of these antidepressants is at least partly connected with their effect on the cytokine network and IL-6 production.

Behavioral and biochemical studies on chronic mild stress models in rats treated with a Chinese traditional prescription Banxia-houpu decoction

There is increasing evidence that psychological stress and depression trigger changes in various biochemical parameters in animals and in human subjects. In order to study these effects, the impact of chronic mild stress (CMS) on rats, and of the subsequent administration of Banxia-houpu decoction and fluoxetine, were studied regarding their effects on the following biochemical parameters: 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) levels in various brain regions, natural killer (NK) cell and lymphokine-activated killer (LAK) cell activities in spleen, serum lipid profiles including total cholesterol (TC), high density lipoprotein cholesterol (HDLc), low density lipoprotein cholesterol (LDLc) and triglyceride (TG), liver superoxide dismutase (SOD) and nitric oxide synthase (NOS) activities, serum malondialdehyde (MDA), and interleukin-2 (IL-2) levels. The effects of drug administration on preference behavior for consumption of sucrose solution were also assessed. Rats subjected to CMS exhibited a reduction in sucrose intake, 5-HT, 5-HIAA, IL-2, TC, HDLc and LDLc levels, as well as, diminished NK cell and LAK cell activities. Conversely, liver SOD and NOS activities and serum TG and MDA levels were increased following CMS exposures. Administration of Banxia-houpu decoction and fluoxetine produced beneficial effects on the stressed rats by improving sucrose consumption. This behavioral change was accompanied by amelioration of numbers CMS-induced biochemical changes. Banxia-houpu decoction is a traditional Chinese prescription containing pinellia tuber, magnolia bark, hoelen, perilla herb and ginger rhizome, and has been used for centuries in China to treat mental diseases including depression and schizophrenia. However, the pharmacological profile of the decoction is different from that of fluoxetine. These findings suggest that the therapeutic actions of Banxia-houpu decoction are due to a combination of multiple biochemical effects, and may help to elucidate the mechanisms through which distinct biochemical parameters play a role in the etiology of depression.

Differential effects of antidepressants on glucocorticoid receptors in human primary blood cells and human monocytic U-937 cells

A number of data support the assumption that antidepressants (ADs) normalize the altered function of the hypothalamic-pituitary-adrenocortical (HPA) system involved in the pathophysiology of depressive disorder via direct effects on glucocorticoid receptors (GRs). In the present study, we examined the tricyclic ADs desipramine (DESI) and imipramine (IMI), the noradrenaline reuptake inhibitor maprotiline (MAPRO), and the noradrenergic and specific serotonergic AD (NaSSA) mirtazapine (MIR) for their effects on GR expression in primary human leukocytes and in monocytic U-937 cells. Semiquantitative RT-PCR indicated that the ADs exert differential effects on GR-mRNA levels in both primary human leukocytes and U-937 cells: whereas MAPRO and IMI did not induce pronounced changes in GR-mRNA levels, DESI and MIR significantly decreased the amounts of GR-mRNA in both cell systems. Further characterization of the effects of MIR revealed a time dependency of the regulation with an initial increase of GR-mRNA levels above control levels after 2.5 h of treatment and a decrease after 4, 24, and 48 h of incubation. A dose-response analysis demonstrated maximal effects of MIR at a concentration of 10(-7) M. Immunohistochemical studies showed that MIR increased the GR protein levels in a time-dependent manner and that this upregulation appeared earlier by additional treatment with dexamethasone (DEX). A translocation of the GR protein from the cytoplasm to the nucleus was induced between 24 and 48 h of treatment with MIR and MIR/DEX, respectively. Taken together, our data further support the assumption that ADs influence the neuroendocrine and immune system via effects on cellular GRs.

Cytokines in depression and heart failure

OBJECTIVE

There is a convincing body of evidence linking depression, cardiovascular disease, and mortality. There is also growing evidence that depression is a risk factor for congestive heart failure (CHF) and that CHF patients with major depression have higher rates of mortality and repeat hospitalizations. Currently there are no proposed neurobiological or neuroimmune mechanisms for the comorbidity of heart failure and depression.

METHODS

This review focuses on the recent literature about the role of cytokines in CHF and depression as separate conditions. This review also attempts to identify the overlapping immunological mechanisms that have a potential for future research in the pathophysiology of comorbid depression and CHF.

RESULTS

Results of current studies suggest that cytokines exert deleterious effects on the heart and that soluble tumor necrosis factor (TNF) receptor 2 leads to reversal of the cardiotoxic effects of TNF, although the clinical significance of this is unclear. Major depression has been associated with alteration of various aspects of the innate immune system, including cellular components (such as microphages, neutrophils, and natural killer cells) and soluble mediators (such as acute-phase reaction proteins and cytokines). It is inconclusive whether antidepressants have immunoregulatory effects.

CONCLUSIONS

The literature has not yet addressed the role of cytokines in comorbid depression and CHF. But cytokines may provide a new avenue in understanding brain-body interaction in depression and heart failure.

Chronic treatment with the antidepressant tianeptine attenuates lipopolysaccharide-induced Fos expression in the rat paraventricular nucleus and HPA axis activation

The antidepressant tianeptine has been shown to decrease the response of the hypothalamic-pituitary-adrenal (HPA) axis to stress and to attenuate the behavioral effects of the cytokine inducer, lipopolysaccharide (LPS). Since LPS also activates the HPA axis, the objective of this study was to assess the effects of tianeptine on the HPA axis activation and Fos expression induced by intraperitoneal (i.p.) administration of LPS (30 and 250 microg/kg respectively). Chronic, but not acute, tianeptine treatment (10 mg/kg twice a day for 15 days, i.p.) attenuated LPS-induced increase of plasma ACTH and corticosterone in rats bearing an indwelling catheter in the jugular vein and Fos immunoreactivity in the paraventricular nucleus (PVN). These results open new vistas on the pharmacological activity of tianeptine and provide further insights on the action mechanisms of antidepressants in clinics.

Influence of antidepressants on intracellular levels of cyclic adenosine monophosphate in human peripheral blood mononuclear cells

This study examines the effects of paroxetine and imipramine on intracellular concentrations of cyclic adenosine monophosphate (cAMP) in human peripheral blood mononuclear cells. It was found that imipramine and paroxetine had no effect on basal cAMP-levels. Stimulation with lipopolysaccharides and phytohaemagglutinin increased intracellular cAMP concentrations. However, pre-incubation with imipramine or paroxetine, did not influence this increase. These data do not support the hypothesis that cAMP may be related to the in vitro anti-inflammatory effects of antidepressants.

Lack of effects by tricyclic antidepressant and serotonin inhibitors on anorexia in MCG 101 tumor-bearing mice with eicosanoid-related cachexia

OBJECTIVES

Anorexia is a major clinical problem in large number of patients with advanced cancer disease. Serotonergic mechanisms are assumed to play a role in the process of feeding behavior during normal and pathologic circumstances, which may also involve cancer anorexia according to previous experimental and clinical studies.

METHODS

In the present study, we evaluated the effect of the tricyclic antidepressants desipramine (7.5 mg x kg(-1) x d(-1), intraperitoneal) and imipramine (2 to 5 mg. kg(-1) x d(-1), intraperitoneal) the serotonin synthesis inhibitor para-chlorophenylalanine (300 mg x kg(-1) x d(-1), intraperitoneal), the serotonin receptor 5-HT(2C) antagonist cyproheptadine (5 mg x kg(-1) x d(-1), intraperitoneal) and the selective serotonin reuptake inhibitor citalopram (20 mg x kg(-1) x d(-1), intraperitoneal) on anorexia in MCG-101 tumor-bearing mice, a model with significant anorexia and cachexia sensitive to cyclooxygenase inhibition. Also, MCG 101-bearing mice develop well-recognized alterations in brain tryptophan/serotonin metabolism as increased Trp, 5-HPT, and 5-HIAA during tumor progression.

RESULTS

Daily provision of desipramine, imipramine, para-chloropheylalanine, cyproheptadine, and citalopram at doses that cause behavioral and metabolic alterations in normal mice did not alter food intake or body weight in tumor-bearing and healthy control mice. Also, the treatments did not decrease elevated plasma concentrations of interleukin-6 and prostaglandin E(2) in the tumor-bearing mice.

CONCLUSIONS

Thus, our results do not support previous observations that serotonin metabolism itself is a major factor behind anorexia in tumor-bearing animals in general. Rather, other mechanisms, such as eicosanoid and nitric oxide-dependent pathways, seem to be more important for induction of anorexia along tumor progression in the present model.

Antidepressant drugs and cytokines in mood disorders

This article reviews recent developments in cytokine research that pertain to pharmacological treatment of mood disorders such as antidepressants and lithium. We review the possible involvement of cytokines in mood disorders and their role in the therapeutic effects of antidepressant drugs. Growing evidence suggests that specific cytokines signal the brain to generate neurochemical, neuroimmune, neuroendocrine and behavior changes. An imbalance of cytokines within the central nervous system (CNS), or even systemically, may play a role in the pathophysiology of mood disorders. Modulation of these cytokines by chronic antidepressant treatment may result in restored balance. However, the effect of antidepressants on cytokines is still unclear both in clinical and preclinical research due to limited data. Further research is needed to clarify the involvement of cytokines in mood disorders. Understanding this relationship may lead to rational, therapeutic improvements in antidepressant and mood stabilizing drugs.

Depression and adipose essential polyunsaturated fatty acids

The objective of the present study was to investigate the relation between adipose tissue polyunsaturated fatty acids, an index of long-term or habitual fatty acid dietary intake, and depression. The sample consisted of 247 healthy adults (146 males, 101 females) from the island of Crete. The number of subjects with complete data on all variables studied was 139. Subjects were examined at the Preventive Medicine and Nutrition Clinic of the University of Crete. Depression was assessed through the use of the Zung Self-rating Depression Scale. Mildly depressed subjects had significantly reduced (-34.6%) adipose tissue docosahexaenoic acid (DHA) levels than non-depressed subjects. Multiple linear regression analysis indicated that depression related negatively to adipose tissue DHA levels. In line with the findings of other studies, the observed negative relation between adipose tissue DHA and depression, in the present study, appears to indicate increasing long-term dietary DHA intakes with decreasing depression. This is the first literature report of a relation between adipose tissue DHA and depression. Depression has been reported to be associated with increased cytokine production, such as IL-1, IL-2, IL-6, INF-gamma and INF-alpha. On the other hand, fish oil and omega-3 fatty acids have been reported to inhibit cytokine synthesis. The observed negative relation between adipose DHA and depression, therefore, may stem from the inhibiting effect of DHA on cytokine synthesis.

Suppressive effect of TRH and antidepressants on human interferon-γ production in vitro

BACKGROUND

It has been established that thyrotropin-releasing hormone (TRH) affects several aspects of immunoreactivity, e.g. production of proinflammatory cytokines. It has been shown that TRH enhances the therapeutic efficiency of classical tricyclic antidepressants. Proinflammatory cytokines may play a role in the etiology of depression, whereas the therapeutic efficacy of antidepressants may be related to their negative immunoregulatory effects.

OBJECTIVE

In order to verify the hypothesis that TRH-induced increase of therapeutic efficiency of classical tricyclic antidepressants results from synergistic inhibitory effects of these agents on the secretion of proinflammatory cytokines, we determine the effect of imipramine or fluoxetine with and without TRH on the production of interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α) and interleukin-10 (IL-10) by stimulated human whole blood cells.

METHODS

Diluted whole blood of 17 volunteers was incubated with imipramine or fluoxetine (both in doses of 10-5 M) with or without TRH (in a dose of 10-5 M). The supernatants were collected 24 h later for the assay of TNF-α and after 72 h for the assays of IFN-γ and IL-10. The three cytokines were assayed by ELISA methods.

RESULTS

A significant decrease in production of IFN-γ was observed in cells stimulated with mitogens and co-incubated with imipramine or fluoxetine and TRH. Under the same conditions, TRH alone did not change the production of these cytokines, whereas imipramine alone significantly decreases IFN-γ production, and fluoxetine alone significantly decreases IFN-γ and TNF-α production.

CONCLUSION

Although a significant decrease in IFN-γ production was observed after joint application of TRH and antidepressants, our data did not support the above-mentioned hypothesis. Indeed, we did not observe synergistic inhibitory effects of these agents on the secretion of proinflammatory cytokines.

Interleukine-6 serum levels correlate with response to antidepressant sleep deprivation and sleep phase advance

Unstimulated production of interleukine-6 (IL-6) is known to be enhanced in patients affected by a major depressive episode. Recent studies supported a role for basal IL-6 levels in predicting response to antidepressant drug treatments. In a sample of 10 consecutively admitted drug-free bipolar depressed inpatients, we investigated the possible correlation between unstimulated pretreatment production of IL-6 and antidepressant response to a night of total sleep deprivation (TSD) followed by a night of sleep phase advance (SPA), a nonpharmacologic treatment which is known to rapidly improve depressive symptomatology. Changes in perceived mood during treatment were recorded with self-administered Visual Analogue Scales (VAS). We observed a significant inverse correlation between IL-6 serum levels and VAS scores after treatment, meaning that higher IL-6 values before treatment were associated with worse response. This finding is in agreement with previous studies about amitriptyline and lithium antidepressant treatments. Our preliminary finding confirms the clinical value of IL-6 baseline concentration as a predictor of response to antidepressant treatment.

Effects of serotonin and catecholamine depletion on interleukin-6 activation and mood in human volunteers

There is increasing evidence that depression and related neurotic illnesses are associated with alterations in immune function that may contribute to their pathogenesis. For example, clinical and experimental studies have shown that abnormal HPA-axis activation and monoamine neurotransmission may be related to an increased release of proinflammatory cytokines from stimulated lymphocytes in the periphery and brain. In the present investigation, the effects of tryptophan depletion (TD) on unstimulated plasma interleukin-6 (IL-6) concentrations were investigated in order to determine whether acute changes in serotonin (5-HT) neurotransmission would induce a proinflammatory response in healthy individuals. The effects of TD were compared with the analogous procedure of tyrosine depletion (TPD), which reduces catecholamine metabolism in humans. Thirteen female participants completed three experimental sessions: TD, TPD and a balanced-control condition (B). Mood-ratings and blood sampling were performed at baseline and 5 h after the administration of the mixtures. Analyses revealed that TD and TPD markedly reduced tryptophan and tyrosine/phenylalanine levels, respectively. No changes in plasma IL-6 production or ratings of lowered mood were observed, however, subjects did report feeling more fatigued after TD. These findings indicate that a transient disruption in global monoamine function does not stimulate a proinflammatory response of IL-6 in normal volunteers.

Drug-induced phospholipidosis: are there functional consequences?

Phospholipidosis induced by drugs with a cationic amphiphilic structure is a generalized condition in humans and animals that is characterized by an intracellular accumulation of phospholipids and the concurrent development of concentric lamellar bodies. The primary mechanism responsible for the development of phospholipidosis is an inhibition of lysosomal phospholipase activity by the drugs. While the biochemical and ultrastructural features of the condition have been well characterized, much less effort has been directed toward understanding whether the condition has adverse effects on the organism. While there are a few cationic amphiphilic drugs that have been reported to cause phospholipidosis in humans, the principal concern with this condition is in the pharmaceutical industry during preclinical testing. While this class of drugs should technically be referred to as cationic lipophilic, the term cationic amphiphilic is widely used and recognized in this field, and for this reason, the terminology cationic amphiphilic drugs (CADs) will be employed in this Minireview. The aim of this Minireview is to provide an evaluation of the state of knowledge on the functional consequences of CAD-induced phospholipidosis.

Differences in interleukins' patterns between dysthymia and major depression

We assessed whether cytokine production-interleukin (IL)-1beta, IL-6 and tumour necrosis factor-alpha (TNFalpha)-is affected in depressed patients, dysthymia (Dt) and major depression (MD), and its association with various parameters of severity and clinical course. We found a possible different pattern of interleukin production between Dt and MD.

Changes in the immune system in depression and dementia: causal or co-incidental effects?

It is now widely accepted that psychological stress and psychiatric illness can compromise immune function. Furthermore the mechanisms whereby such changes occur are probably associated with the activities of the cytokines and other inflammatory mediators of the immune system which are known to initiate changes in behaviour. This review aims to summarise the experimental and clinical evidence that implicates the pro-inflammatory cytokines in the pathological changes seen in major depression and in Alzheimer's disease (AD). In major depression, evidence is provided to show that both activation (e.g., macrophage activity, acute phase proteins) and inhibition (e.g., natural killer cell activity) of the immune system occur. Many of the behavioural changes seen in depression are simulated by three pro-inflammatory cytokines (IL-1, IL-6 and TNF-alpha), which may produce their impact on the brain by activating cyclooxygenase, nitric acid synthase and corticotrophin releasing factor. Effective antidepressant treatments largely attenuate the immune changes thereby raising the possibility that the normalisation of central biogenic amine function that are conventionally implicated in the cause of depression may be secondary to those of the pro-inflammatory cytokines. With respect to AD, while the cause(s) are unknown, there is both experimental and clinical evidence to suggest that inflammatory processes in the brain caused in particular by TNF-alpha together with the subsequent rise in free radicals, are instrumental in causing the pathological changes which underlie the disease. Evidence in favour of the inflammatory hypothesis is supported by the finding that nonsteroidal anti-inflammatory drugs slow down the progression of the disease.Although, more research is needed into the inter-relationships between the various pro-inflammatory cytokines and the behavioural changes invoked in major depression and AD, the immunological hypothesis has been important in stimulating new concepts regarding the causes of the pathological changes in these diseases and how effective drug treatments may attenuate them.

The immune system, depression and the action of antidepressants

It is well established that the hypothalamic-pituitary-adrenal axis (HPA) is activated by both external and internal stressors which result in the hypersecretion of adrenal glucocorticoids. In major depression the prolonged elevation of the glucocorticoid concentration leads to a desensitisation of the central glucocorticoid receptors and probably those receptors located on macrophages. These changes may account for the observation that many aspects of cellular immunity are activated in depression (for example, the increased release of pro-inflammatory cytokines from activated macrophages in the periphery and brain, and the increased release of acute phase proteins from the liver) even though other aspects of immunity (for example, natural killer cell activity and T-cell replication) are depressed. It is also known that some of the pro-inflammatory cytokines are potent activators of the HPA axis. Evidence is provided that the consequences of the hypersecretion of glucocorticoids and pro-inflammatory cytokines result in the malfunctioning of noradrenergic and serotonergic neurotransmission in the brain, changes which are reflected in the major symptoms of depression. Support for this view is provided by observations of the effects of some of these cytokines in non-depressed individuals being treated with pro-inflammatory and related cytokines for cancer. This has led to the hypothesis that depression is a form of sickness behaviour which forms the basis of the macrophage theory of depression. The review concludes with a discussion of the role of antidepressants in attenuating the adverse effects of glucocorticoids and pro-inflammatory cytokines on central neurotransmission. Although the precise mechanisms whereby antidepressants these changes is uncertain, there is evidence that they reduce the release of pro-inflammatory cytokines from activated macrophages and thereby facilitate the feedback inhibition of the HPA axis; this results in a reduction in the release of glucocorticoids from the adrenal glands. In addition, many antidepressants have been shown to increase the release of endogenous cytokine antagonists such as interleukin-1 receptor antagonist and interleukin-10. Evidence is also presented to show that different classes of antidepressants act as cyclooxygenase inhibitors which, by lowering the concentration of inflammatory prostaglandins in the brain, reduce the detrimental impact of the inflammatory changes on neurotransmitter function. An advantage of the macrophage hypothesis is that it extends the biogenic amine hypothesis of depression to take account of changes in the endocrine and immune systems which also play a crucial role in the aetiology of depression. In addition, the macrophage hypothesis may broaden the basis of understanding the mechanism of action of antidepressants.

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

There is some evidence that major depression--in particular, treatment-resistant depression (TRD)--is accompanied by activation of the inflammatory response system and that proinflammatory cytokines may play a role in the etiology of depression. This study was carried out to examine the effects of antidepressive agents, i.e., imipramine, venlafaxine, L-5-hydroxytryptophan, and fluoxetine on the production of interferon-gamma (IFN-gamma), a proinflammatory cytokine, and interleukin-10 (IL-10), a negative immunoregulatory cytokine. Diluted whole blood of fluoxetine-treated patients with TRD (mean age, 50.6+/-3.9 years) and age-matched healthy controls (mean age, 51.6+/-1.7 years) and younger healthy volunteers (mean age, 35.4+/-9.6 years) was stimulated with phytohemagglutinin (1 microg/mL) and lipopolysaccharide (5 microg/mL) for 48 hours with and without incubation with the antidepressants at 10-6 M and 10(-5) M. IFN-gamma and IL-10 were quantified by means of enzyme-linked immunoassays. The ratio of IFN-gamma to IL-10 production by immunocytes was computed because this ratio is of critical importance in determining the capacity of immunocytes to activate or inhibit monocytic and T-lymphocytic functions. All four antidepressive drugs significantly increased the production of IL-10. Fluoxetine significantly decreased the production of IFN-gamma. All four antidepressants significantly reduced the IFN-gamma/IL-10 ratio. There were no significant differences in the antidepressant-induced changes in IFN-gamma or IL-10 between younger and older healthy volunteers and TRD patients. Tricyclic antidepressants, selective serotonin reuptake inhibitors, and serotonin-noradrenaline reuptake inhibitors, as well as the immediate precursor of serotonin, have a common, negative immunoregulatory effect by suppressing the IFN-gamma/IL-10 production ratio. It is suggested that the therapeutic efficacy of antidepressants may be related to their negative immunoregulatory effects.

Prolonged desipramine treatment increases the production of interleukin-10, an anti-inflammatory cytokine, in C57BL/6 mice subjected to the chronic mild stress model of depression

BACKGROUND

Depression is associated with activation of the inflammatory response system (IRS). In humans, antidepressants significantly increase the production of interleukin-10 (IL-10), a negative immunoregulatory cytokine. The aims of the present study were to examine the effects of desipramine, a tricyclic antidepressant, on the IRS in C57BL/6 mice with and without exposure to chronic mild stress (CMS).

METHODS

We examined the effects of desipramine on the cytotoxic activity of natural killer (NK) cells, the proliferative responses of lymphocytes after stimulation with IL-1, IL-2, lipopolysaccharide (LPS), concanavaline-A (Con-A), phytohaemagglutinin-P (PHA), pokeweed mitogen (PWM), and anti-CD3 monoclonal antibodies, the production of IL-2, IL-4, IL-10 and interferon-gamma (IFNgamma) by T lymphocytes and the ability of B cells to proliferate after stimulation by lipopolysaccharide (LPS).

RESULTS

Prolonged treatment of C57BL/6 mice subjected to CMS with desipramine increases the ability of T cells to produce IL-10 and the ability of B cells to proliferate after stimulation with LPS; and significantly decreases the cytotoxic activity of NK cells and the proliferative responses of lymphocytes after stimulation with Con-A, PHA and anti-CD3 monoclonal antibodies. Repeated administration of desipramine to non-stressed mice increases the activity of T lymphocytes, lowers that of B lymphocytes, increases the production of IL-10 by T cells and has no significant effect on the activity of NK cells.

CONCLUSION

Prolonged desipramine treatment of stressed and non-stressed C57BL/6 mice induces an increase in the production of IL-10, an anti-inflammatory cytokine.

Plasma inflammatory cytokine response to surgical trauma in chronic depressed patients

We investigated inflammatory cytokine response in chronic depressed patients during abdominal surgery. Twenty-five major depressed patients (Group D) and twenty-five patients (Group C) as the control were studied. Plasma interleukin 6 (IL-6), interleukin 8 (IL-8) and tumour necrosis factor-alpha (TNF-alpha) concentrations were measured before and at 15 min after induction of anesthesia, the end of surgery, 24 h and 3 days after the operation. Plasma IL-6 concentrations in Group D at the end of the operation and 24 h after surgery were significantly lower than those of Group C. The plasma IL-6 concentration (87.1+/-55.3 pg/ml) of patients scoring more than 18 points in the Hamilton depression-rating score at the end of the operation was significantly higher than 57.5+/-76.7 pg/ml of patients scoring less than 18 points. Plasma IL-8 concentration (6.1+/-3.2 pg/ml) in Group D at the end of the operation was significantly lower than 8.7+/-4.2 pg/ml of Group C. We conclude that plasma IL-6 and IL-8 response to surgical trauma is inhibited in chronic depressed patients. The IL-6 response to surgical trauma is depending on the clinical state of depression.

The immunoregulatory effects of antidepressants

There is some evidence that major depression is accompanied by activation of the inflammatory-response system (IRS). It has been hypothesized that increased production of proinflammatory cytokines may play a role in the etiology of major depression. If increased production of proinflammatory cytokines is at all involved in the etiology of depression, one would expect antidepressive treatments to have negative immunoregulatory effects. This paper reviews the effects of antidepressants, such as tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), heterocyclic antidepressants (HCAs), serotonin-noradrenaline reuptake inhibitors (SNRIs), lithium, l-5-hydroxytroptophan (L-5-HTP), reversible inhibitors of MAO-A (RIMA) on the production of proinflammatory cytokines, e.g. interferon-gamma (IFNgamma), and negative immunoregulatory cytokines and agents, e.g. interleukin-10 (IL-10). In depressed patients, prolonged treatment with antidepressants and mood stabilizers normalizes signs of activation of the IRS, such as increased serum IL-6 and acute phase protein concentrations. In vitro, it has been shown that various types of antidepressive drugs, including TCAs (imipramine; clomipramine); SSRIs (citalopram, fluoxetine, sertraline); lithium; SNRIs (venlafaxine); HCAs (trazodone); RIMAs (moclobemide) and L-5-HTP significantly suppress the ratio of IFNgamma/IL-10 production by peripheral blood immunocytes. These antidepressant drugs appear to have a common effect on the IRS, i.e. in vitro they increase the production of IL-10 by peripheral blood leukocytes. Thus, the results suggest that antidepressants have negative immunoregulatory effects. It may be speculated that antidepressants exert some of their antidepressant effects through their negative immunoregulatory capacities. Copyright 2001 John Wiley & Sons, Ltd.

Effects of repeated fluoxetine and citalopram administration on cytokine release in C57BL/6 mice

This study examines the effects of repeated administration of the selective serotonin reuptake inhibitors (SSRIs), fluoxetine and citalopram (10 mg/kg, i.p.), on immunoreactivity in C57BL/6 mice. Immune functions were evaluated by the ability of splenocytes to reduce a tetrazolium salt to formazan (MTT test), to proliferate, and to produce cytokines, including interleukin (IL)-1, IL-2, IL-4, IL-6, IL-10 and interferon gamma (IFN gamma). Citalopram administered for 1, 2 and 4 weeks stimulates the proliferative activity of splenocytes and suppresses their ability to secrete the anti-inflammatory cytokine IL-4. Fluoxetine administration for 1 and 2 weeks, but not 4 weeks, stimulates the proliferative activity of splenocytes, whereas a 4-week administration of fluoxetine suppresses the secretion of IL-4. Four weeks of prolonged administration of citalopram and fluoxetine induces a significant increase in the production of IL-6 and IL-10, a cytokine with immunosuppressive and anti-inflammatory activities. The results show that, in C57BL/6 mice, the immunomodulatory effects of SSRIs depend on the SSRI used and the duration of administration.

The effect of repeated amitriptyline and desipramine administration on cytokine release in C57BL/6 mice

This study examines the effects of repeated amitriptyline and desipramine administration (10 mg/kg, IP) on the immunoreactivity of saline-injected C57BL/6 mice, as evaluated by the ability of splenocytes to reduce a tetrazolium salt to formazan (MTT test), to proliferate, and to produce cytokines, such as interleukin (IL)-1, IL-2, IL-4, IL-6, IL-10 and interferon gamma (IFN-gamma). Desipramine and amitriptyline administered for one or two weeks enhance the biochemical (estimated by MTT test) and proliferative activities of splenocytes. One and two weeks administration of desipramine significantly reduces the secretion of IL-4, an anti-inflammatory cytokine. Amitriptyline administration for four weeks stimulates the proliferative activity of splenocytes and enhances IL-2 bioactivity, whereas four weeks desipramine aministration does not change these parameters in comparison to saline treated control mice. Prolonged desipramine administration (seven and 28 days) significantly increased the bioactivity of IL-1. Four weeks of prolonged administration of amitriptyline and desipramine induces a significant increase in the secretion of IL-10, a cytokine with immunosuppressive and anti-inflammatory activities. The results show that the immunoregulatory effects of tricyclic antidepressants in C57BL/6 mice depend on the drugs used and on the duration of administration.

Antidepressant-induced lipidosis with special reference to tricyclic compounds

Cationic amphiphilic drugs, in general, induce phospholipid disturbances. Tricyclic, as well as other antidepressants belong to this group. In experimental animals, antidepressants induce lipid storage disorders in cells of most organs, a so-called generalized phospholipidosis. This disorder is conveniently detected by electron microscopic examination revealing myelin figures. Myelin figures or myeloid bodies are subcellular organelles containing unicentric lamellar layers. The lipidotic induction potency during in vivo is related to the apolarity of the compound. Metabolism of phospholipids takes place within the cell continuously. Several underlying mechanisms may be responsible for the induction of the phospholipid disturbance. For instance, it has been suggested that the compounds bind to phospholipids and such binding may alter the phospholipid's suitability as a substrate for phospholipases. Free TCA or metabolites thereof may also inhibit phospholipases directly, as has been demonstrated for sphingomyelinase in glioma and neuroblastoma cells. Both these mechanisms might result in phospholipidosis. Interaction between drug and phospholipid bilayer has been investigated by nuclear magnetic resonance technique. There seems to be large differences in the sensitivities amongst different organs. Steroid-producing cells of the adrenal cortex, testis and ovaries are in particular susceptible to drug-induced lipidosis. The so-called foam cells are lung macrophages located in the interstitium which become densely packed with myelin figures during TCA exposure. It requires about 3-6 weeks of treatment to develop this converted cell. In cell cultures however, phospholipidosis is demonstrated already after 24 h only. It appears that the cells that undergo TCA-induced lipidosis may recover after withdrawal of the drug. The time required to achieve complete recovery ranges from 3-4 weeks to several months, depending on the organ affected. Little is known about the functional significance of lipidosis. Even if TCA and other antidepressants show other effects, it has not been possible to exclusively relate it to phospholipidosis. However, few attempts have been made to correlate the physiological effects of TCAs in experimental animals to the morphological changes associated with phospholipidosis. There is an increasing evidence however, that cationic amphiphilic drugs may have effects on immune function, signal transduction and receptor-mediated events, effects that to some extent might be related to disturbances in phospholipid metabolism.

The in vitro immunosuppressive effects of moclobemide in healthy volunteers

BACKGROUND

Many studies have demonstrated that major depression is related to an activation of the inflammatory response system (IRS) with an increased production of proinflammatory cytokines. It has been shown that tricyclic antidepressants and serotonin reuptake inhibitors suppress the activation of the IRS in depression and have negative immunoregulatory effects in vitro. Little is known on the immune effects of moclobemide, a reversible monoamine oxidase A inhibitor.

METHODS

We examined, in nine normal volunteers, the in vitro effects of moclobemide on the production of interleukin-6 (IL-6), IL-8, tumor necrosis factor-alpha (TNFalpha), interferon-gamma (IFNgamma), IL-10 and the IL-1 receptor antagonist (IL-1RA) by diluted whole blood stimulated or not with lipopolysaccharide (LPS)+phytohemagglutinin (PHA).

RESULTS

Moclobemide 10(-3) and 10(-5) M significantly suppressed the unstimulated production of TNFalpha and IL-8, and significantly enhanced the stimulated-production of IL-10. The production of IL-6, IL-1RA and IFNgamma was not significantly affected either in the unstimulated or stimulated conditions.

CONCLUSIONS

Moclobemide has negative immunoregulatory capacities through inhibition of the production of proinflammatory cytokines, i.e. TNFalpha and IL-8, and through enhancement of the production of IL-10, an anti-inflammatory cytokine.

The malaise theory of depression: major depressive disorder is sickness behavior and antidepressants are analgesic

The malaise theory of depression constitutes a re-conceptualization and re-definition of major depressive disorder (MDD). It is proposed that the state or emotion of malaise should be considered the core symptom of depression, rather than sadness of mood. The syndrome of MDD is identified as a consequence of inappropriate sickness behavior mediated by immune activation including abnormalities in cytokines. Antidepressants are suggested to exert their specifically beneficial effects through an analgesic effect on the core dysphoric symptoms of malaise. These ideas are consistent with a substantial body of published literature and lead to a wide range of testable predictions.

Stress, depression and the activation of the immune system

Both stress and depression have been associated with impaired immune function and increased susceptibility of the patient to infectious diseases and cancer. While it was initially thought that the hypercorticosolaemia caused a suppression of immune function, it is now apparent that adaptive changes result from chronic stress and depression that lead to a hypoactivity of the glucocorticoid receptors on immune cells and in limbic regions of the brain. Thus depression is now thought to be associated with activation of some aspects of cellular immunity resulting in the hypersecretion of proinflammatory cytokines and the hyperactivity of the hypothalamic-pituitary-adrenal axis. There is also experimental evidence to show that such immune activation induces "stress-like" behavioural and neurochemical changes in rodents which supports the hypothesis that the hypersecretion of proinflammatory cytokines are involved in the pathology of depression. This review attempts to show how the immune, endocrine and neurotransmitter systems are integrated and how the result of such integration may be causally involved in the aetiology of depression.

Differential effect of chronic antidepressant treatments on lipopolysaccharide-induced depressive-like behavioural symptoms in the rat

In the present study we observed that lipopolysaccharide (LPS) administration provoked a characteristic reduction in body weight gain, food consumption, saccharin (but not water) consumption and nocturnal locomotor activity. It has been previously suggested that the ability of LPS to suppress the consumption of, and preference for, a palatable solution such as saccharin without altering water consumption, may represent an anhedonic response. The results of the present study demonstrate that chronic treatment with the tricyclic antidepressant (TCA) desipramine (7.5 mg/kg; i.p.) prevented LPS-induced anorexia, loss of body weight, the antidipsogenic effect and hypoactivity. In contrast, chronic treatment with the antidepressants paroxetine (7.5 mg/kg; i.p.) and venlafaxine (10 mg/kg; i.p.) failed to alter any of the LPS-induced behavioural responses. Furthermore, chronic treatment with desipramine (and to a lesser extent paroxetine) reduced the consumption of, and preference for, saccharin suggesting that these antidepressant treatments induce an "anhedonic" response in their own right. In conclusion, chronic desipramine treatment attenuated LPS-induced depressive-like behavioural symptoms in the rat. However, chronic treatment with paroxetine and venlafaxine did not significantly alter LPS-induced behavioural responses. The results of the present study support the hypothesis that TCA's may exert part of their anti-depressive efficacy through their effects on the immune system. However, this property does not appear to be shared by newer antidepressants which possess a better side effect profile than the TCA's. The suppressive effect of TCA's on proinflammatory cytokine secretion is discussed as a mechanism by which these agents alter LPS-induced behavioural responses.

Differential effect of a single high dose of the tricyclic antidepressant imipramine on interleukin-1beta and tumor necrosis factor-alpha secretion following an in vivo lipopolysaccharide challenge in rats

Tricyclic antidepressants (TCAs) of which imipramine is one, are commonly used in the treatment of depressive disorders and other forms of psychiatric illness. There have been many reports regarding the suppressive effects of TCAs on immune function. However, information is still limited regarding the effects of TCAs on the immune system, as many of the studies conducted to date have concentrated on in vitro exposure to such drugs, or ex vivo measures of immunity following drug administration. Thus in the present investigation, an in vivo challenge with bacterial lipopolysaccharide (LPS) (100 microg/kg; i.p.) was used to assess immunocompetence following administration of a single high dose of the TCA, imipramine (100 mg/kg, p.o.). The results demonstrated that imipramine pretreatment inhibits LPS-induced increases in serum concentrations of the proinflammatory cytokine, tumor necrosis factor (TNF)-alpha both 3 and 6 h, following administration. However, LPS-induced interleukin (IL)-1beta secretion was not significantly altered following imipramine treatment at either of the timepoints examined. In addition, serum concentrations of corticosterone and the antiinflammatory cytokine IL-10 were measured, and imipramine treatment failed to alter either basal, or LPS-induced increases in these immunosuppressive agents. In conclusion, although IL-1beta and TNF-alpha are both macrophage-derived proinflammatory cytokines, the present study demonstrates a differential sensitivity of these cytokines to the suppressive effects of the TCA imipramine. Furthermore, the suppressive effects of imipramine on LPS-induced TNF-alpha secretion could not be attributed to either increased glucocorticoid levels, or increased secretion of the antiinflammatory cytokine IL-10. The relevance of these findings to antidepressant-induced immunotoxicity are discussed.

Effects of chronic mild stress (CMS) and imipramine administration, on spleen mononuclear cell proliferative response, serum corticosterone level and brain norepinephrine content in male mice

There is increasing evidence that stress and emotional reactions produce changes in various immune processes. These changes may be due to alterations of the stress responses endocrine and for autonomic mediating mechanisms. In order to study such effects, the impact of chronic mild stress (CMS) application, and of subsequent imipramine administration were studied on the spleen mononuclear cell proliferative response period. OFI strain male mice were subjected to 4 or 7 weeks of CMS. The effects of these treatments on serum corticosterone levels and hypothalamic and hippocampal norepinephrine (NE) contents were also assessed. Subjects submitted to CMS had a higher spleen mononuclear cell proliferative response after either treatment duration. Imipramine treatment diminished this response enhancement in CMS exposed animals, but did not alter the proliferative responses of control subjects. Serum corticosterone levels, as well as hypothalamic and hippocampal nonrepinephrine contents did not significantly vary between groups. Taken together, these results suggest that CMSs effects on immune reactivity are not related to serum glucocorticoids or NE changes in these locations associated with the hypothalamic-pituitary- adrenocortical (HPA) axis.

Characterisation of serotonin transport mechanisms in rainbow trout peripheral blood lymphocytes: role in PHA-induced lymphoproliferation

In this study, we investigated the serotonin transport mechanisms in rainbow trout (Oncorhynchus mykiss) peripheral blood Lymphocytes. We have observed that the transport of serotonin is a membrane transport process that have the properties of a secondary active transport system. The binding isotherm of [3H]-paroxetine, a serotonin transport blocker, demonstrated a high-affinity binding site with a positive type of cooperativity, Hill coefficient being higher than unity. Known specific inhibitors of the mammalian serotonin transporter significantly inhibited the uptake process in fish lymphocytes. In order to demonstrate the physiological relevance of the serotonin transporter in T-cell activation, we conducted experiments on lymphocytes activated or not by phytohemagglutinin (PHA), a T-cell mitogen. We have observed that addition of PHA for 24hrs, increased the Vmax but not the Km of this transporter. Serotonin uptake inhibitors diminished the PHA-activated proliferation of fish lymphocytes. The intracellular concentrations of cAMP were found to regulate the serotonin uptake and the PHA-stimulated proliferation as the agents known to augment cAMP stimulated serotonin uptake, and inhibited the lymphoproliferation. Inhibitory effects of increased cAMP on the proliferation were reversed by the addition of the nanomolar concentrations of 8-OH-DPAT, a 5-HT1A receptor agonist which is known to diminish the intracellular cAMP concentrations, suggesting that serotonin also regulates PHA-induced proliferation via 5-HT1A membrane receptors in an autocrine manner. These results all together demonstrate that fish lymphocytes possess an active serotonin transporter that is implicated in the proliferation of these immunocompetent cells.

Depression, stress and immunological activation: the role of cytokines in depressive disorders

Traditionally, both stress and depression have been associated with impaired immune function and increased susceptibility to infectious and neoplastic disease. However over the last number of years a large body of evidence suggests that major depression is associated with signs of immunological activation. Moreover it has been suggested that cytokine hypersecretion may be involved in the aetiology of depressive disorders. The present article reviews the evidence from both clinical and experimental studies which implicates immunological activation and particularly hypersecretion of cytokines in the onset and maintenance of depressive illness. Both clinical and experimental studies indicate that stress and depression are associated with increased circulating concentrations of cytokines such as IL-1beta, IL-6 and gamma-IFN and positive acute phase proteins, and hyperactivity of the HPA-axis. In addition, it has been reported that immunological activation induces "stress-like" behavioural and neurochemical changes in laboratory animals. Although for many years it has been suggested that stress acts a predisposing factor to depressive illness, the precise mechanisms by which stress-induced depressive symptoms occur are not fully understood. Nevertheless, behavioural changes due to stress have often been explained in terms of changes in neurotransmitter function in the brain. In the present article increased cytokine secretion is implicated as a mechanism whereby stress can induce depression.

Tricyclic antidepressants induce apoptosis in human T lymphocytes

Apoptosis is a form of programmed cell death that is involved in cell turnover. In the present study we show that the tricyclic antidepressants (TCAS) imipramine, clomipramine and citalopram induce apoptosis in human peripheral lymphocytes. Lymphocytes were incubated with these three drugs for up to 48 h. Apoptosis was characterized by typical nucleosomal DNA fragmentation on agarose gel, as well as quantitated using 4'-6-diamidino-2-phenylindole (DAPI) staining and 3'-OH end-labeling of fragmented DNA at the single cell level. Apoptosis induced by TCAs was shown to be dose-dependent and could be detected after a 24 h incubation. The optimal concentrations of the three TCAs found to induce apoptosis were 50 microM imipramine, 20 microM clomipramine and 180 microM citalopram. Furthermore, immunofluorescence and three-color flow cytometry were used to identify the phenotype of apoptotic cells. TCA-induced apoptosis was shown to involve exclusively T-lymphocytes. Cytotoxic T-lymphocytes were more prone to undergo apoptosis than were T-helper cells. In conclusion, the present investigation clearly demonstrates that TCAs exert cell biological effects upon human T-lymphocytes. Further studies are required to determine the possible clinical relevance of these findings.