Antidepressants augment natural killer cell activity: in vivo and in vitro

Role of Serotonergic System in Regulating Brain Tumor-Associated Neuroinflammatory Responses

Serotonin signaling regulates wide arrays of both neural and extra-neural functions. Serotonin is also found to affect cancer progression directly as well as indirectly by modulating the immune cells. In the brain, serotonin plays a key role in regulating various functions; disturbance of the normal activities of serotonin leads to various mental illnesses, including the neuroinflammatory response in the central nervous system (CNS). The neuroinflammatory response can be initiated in various psychological illnesses and brain cancer. Serotonergic signaling can impact the functions of both glial as well as the immune cells. It can also affect the tumor immune microenvironment and the inflammatory response associated with brain cancers. Apart from this, many drugs used for treatment of psychological illness are known to modulate serotonergic system and can cross the blood-brain barrier. Understanding the role of serotonergic pathways in regulating neuroinflammatory response and brain cancer will provide a new paradigm in modulating the serotonergic components in treating brain cancer and associated inflammation-induced brain damages.

The Relationship between Stress, Inflammation, and Depression

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

Selective serotonin reuptake inhibitor (SSRI) antidepressants reduce COVID-19 infection: prospects for use

Purpose

The absence of specific treatments for COVID-19 leads to an intense global effort in the search for new therapeutic interventions and better clinical outcomes for patients. This review aimed to present a selection of accepted studies that reported the activity of antidepressant drugs belonging to the selective serotonin receptor inhibitor (SSRI) class for treating the novel coronavirus.

Methods

A search was performed in PubMed and SciELO databases using the following search strategies: [(coronavirus) OR (COVID) OR (SARS-CoV-2) AND (antidepressant) OR (serotonin) OR (selective serotonin receptor inhibitors)]. In the end, eleven articles were included. We also covered information obtained from ClinicalTrials.gov in our research.

Results

Although several clinical trials are ongoing, only a few drugs have been officially approved to treat the infection. Remdesivir, an antiviral drug, despite favorable preliminary results, has restricted the use due to the risk of toxicity and methodological flaws. Antidepressant drugs were able to reduce the risk of intubation or death related to COVID-19, decrease the need for intensive medical care, and severely inhibit viral titers by up to 99%. Among the SSRIs studied so far, fluoxetine and fluvoxamine have shown to be the most promising against SARS-CoV-2.

Conclusion

If successful, these drugs can substantially reduce hospitalization and mortality rates, as well as allow for fully outpatient treatment for mild-to-moderate infections. Thus, repositioning SSRIs can provide benefits when faced with a rapidly evolving pandemic such as COVID-19.

Drug repurposing of selective serotonin reuptake inhibitors: Could these drugs help fight COVID-19 and save lives?

The current 2019 novel coronavirus disease (COVID-19), an emerging infectious disease, is undoubtedly the most challenging pandemic in the 21st century. A total of 92,977,768 confirmed cases of COVID-19 and 1,991,289 deaths were reported globally up to January 14, 2021. COVID-19 also affects people's mental health and quality of life. At present, there is no effective therapeutic strategy for the management of this disease. Therefore, in the absence of a specific vaccine or curative treatment, it is an urgent need to identify safe, effective and globally available drugs for reducing COVID-19 morbidity and fatalities. In this review, we focus on selective serotonin reuptake inhibitors (SSRIs: a class of antidepressant drugs with widespread availability and an optimal tolerability profile) that can potentially be repurposed for COVID-19 and are currently being tested in clinical trials. We also summarize the existing literature on what is known about the link between serotonin (5-HT) and the immune system. From the evidence reviewed here, we propose fluoxetine as an adjuvant therapeutic agent for COVID-19 based on its known immunomodulatory, anti-inflammatory and antiviral properties. Fluoxetine may potentially reduce pro-inflammatory chemokine/cytokines levels (such as CCL-2, IL-6, and TNF-α) in COVID-19 patients. Furthermore, fluoxetine may help to attenuate neurological complications of COVID-19.

Can selective serotonin reuptake inhibitors have a neuroprotective effect during COVID-19?

The absence of a specific treatment for SARS-CoV-2 infection led to an intense global effort in order to find new therapeutic interventions and improve patient outcomes. One important feature of COVID-19 pathophysiology is the activation of immune cells, with consequent massive production and release of inflammatory mediators that may cause impairment of several organ functions, including the brain. In addition to its classical role as a neurotransmitter, serotonin (5-hydroxytryptamine, 5-HT) has immunomodulatory properties, downregulating the inflammatory response by central and peripheral mechanisms. In this review, we describe the roles of 5-HT in the regulation of systemic inflammation and the potential benefits of the use of specific serotonin reuptake inhibitors as a coadjutant therapy to attenuate neurological complications of COVID-19.

Regulation of natural killer cell activity by glucocorticoids, serotonin, dopamine, and epinephrine

The immune system and the nervous system are highly complex organs composed of various different cells that must interact with each other for proper function of the system. This communication can be mediated by soluble factors. The factors released by the nervous system (neurotransmitters) differ from those released by the immune system (cytokines). Nevertheless, the nervous and immune systems can influence each other’s activity because immune cells express neurotransmitter receptors, and neurons express cytokine receptors. Moreover, immune cells can synthesize and release neurotransmitters themselves, thus using neurotransmitter-mediated pathways via autocrine and paracrine mechanisms. Natural killer (NK) cells are innate lymphocytes that are important for early and effective immune reactions against infections and cancer. Many studies have shown the strong influence of stress and the nervous system on NK cell activity. This phenomenon may be one reason why chronic stress leads to a higher incidence of infections and cancer. Here, we review the effects of neuroendocrine factors on the different activities of NK cells. Understanding the effects of neuroendocrine factors on NK cell activities during physiological and pathophysiological conditions may result in novel therapeutic strategies to enhance NK cell functions against tumors.

Direct potentiation of NK cell cytotoxicity by 8-azaguanine with potential antineoplastic activity

This study identified 8-azaguanine (8-AG) as a novel immunomodulatory drug (IMiD) through a high-throughput screen of the Preswick Chemical Library in a model of human NK cell cytotoxicity against blood cancer cells. 8-AG, originally developed as an antineoplastic agent, significantly increased the cytotoxicity of NK cells and was superior in this activity to previously known IMiDs, such as fluoxetine and amphotericin B, identified from the same library. IFN-γ expression was also slightly increased by 8-AG. Mechanistically, 8-AG increased conjugate formation between NK and target cells and subsequent cytolytic granule polarization, but not calcium mobilization, regulation of activating receptors, or expression of perforin or granzyme B. Thus, the antineoplastic activity of 8-AG should be re-evaluated in light of this novel potentiating effect on NK cells.

S100B suppression alters polarization of infiltrating myeloid-derived cells in gliomas and inhibits tumor growth

S100B, a member of the multigene family of Ca²⁺-binding proteins, is overexpressed by most malignant gliomas but its biological role in gliomagenesis is unclear. Recently, we demonstrated that low concentrations of S100B attenuated microglia activation through the induction of STAT3. Furthermore, S100B downregulation in a murine glioma model inhibited macrophage trafficking and tumor growth. Based on these observations, we hypothesized that S100B inhibitors may have antiglioma properties through modulation of tumor microenvironment.

To discover novel S100B inhibitors, we developed a high-throughput screening cell-based S100B promoter-driven luciferase reporter assay. Initial screening of 768 compounds in the NIH library identified 36 hits with >85% S100B inhibitory activity. Duloxetine (Dul, an SNRI) was selected for the initial proof-of-concept studies. At low concentrations (1–5 μM) Dul inhibited S100B and CCL2 production in mouse GL261 glioma cells, but had minimal cytotoxic activity in vitro. In vivo, however, Dul (30 mg/kg/14 days) inhibited S100B production, altered the polarization and trafficking of tumor-associated myeloid-derived cells, and inhibited the growth of intracranial GL261 gliomas. Dul therapeutic efficacy, however, was not observed in the K-Luc glioma model that expresses low levels of S100B. These findings affirm the role of S100B in gliomagenesis and justify the development of more potent S100B inhibitors for glioma therapy.

Modulatory Effects of Antidepressant Classes on the Innate and Adaptive Immune System in Depression

Current reviews exploring for unique immune-modulatory profiles of antidepressant classes are limited by focusing mainly on cytokine modulation only and neglecting other aspects of the innate and adaptive immune system. These reviews also do not include recent comparative clinical trials, immune-genetic studies and therapeutics with unique neurotransmitter profiles (e. g., agomelatine). This systematic review extends the established literature by comprehensively reviewing the effects of antidepressants classes on both the innate and adaptive immune system. Antidepressants appear, in general, to reduce pro-inflammatory factor levels, particularly C-reactive protein (CRP), tumour necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6. We caution against conclusions as to which antidepressant possesses the greater anti-inflammatory effect, given the methodological heterogeneity among studies and the small number of comparative studies. The effects of antidepressant classes on adaptive immune factors are complex and poorly understood, and few studies have been conducted. Methodological heterogeneity is high among these studies (e. g., length of study, cohort characteristics, dosage used and immune marker analysis). We recommend larger, comparative studies - in clinical and pre-clinical populations.

Gene expression in major depressive disorder

The search for genetic variants underlying major depressive disorder (MDD) has not yet provided firm leads to its underlying molecular biology. A complementary approach is to study gene expression in relation to MDD. We measured gene expression in peripheral blood from 1848 subjects from The Netherlands Study of Depression and Anxiety. Subjects were divided into current MDD (N=882), remitted MDD (N=635) and control (N=331) groups. MDD status and gene expression were measured again 2 years later in 414 subjects. The strongest gene expression differences were between the current MDD and control groups (129 genes at false-discovery rate, FDR<0.1). Gene expression differences across MDD status were largely unrelated to antidepressant use, inflammatory status and blood cell counts. Genes associated with MDD were enriched for interleukin-6 (IL-6)-signaling and natural killer (NK) cell pathways. We identified 13 gene expression clusters with specific clusters enriched for genes involved in NK cell activation (downregulated in current MDD, FDR=5.8 × 10(-5)) and IL-6 pathways (upregulated in current MDD, FDR=3.2 × 10(-3)). Longitudinal analyses largely confirmed results observed in the cross-sectional data. Comparisons of gene expression results to the Psychiatric Genomics Consortium (PGC) MDD genome-wide association study results revealed overlap with DVL3. In conclusion, multiple gene expression associations with MDD were identified and suggest a measurable impact of current MDD state on gene expression. Identified genes and gene clusters are enriched with immune pathways previously associated with the etiology of MDD, in line with the immune suppression and immune activation hypothesis of MDD.

Neuroimmunological mechanism of pruritus in atopic dermatitis focused on the role of serotonin

Although pruritus is the critical symptom of atopic dermatitis that profoundly affect the patients' quality of life, controlling and management of prurirtus still remains as unmet needs mainly due to the distinctive multifactorial pathogenesis of pruritus in atopic dermatitis. Based on the distinct feature of atopic dermatitis that psychological state of patients substantially influence on the intensity of pruritus, various psychotropic drugs have been used in clinic to relieve pruritus of atopic dermatitis patients. Only several psychotropic drugs were reported to show real antipruritic effects in atopic dermatitis patients including naltrexone, doxepin, trimipramine, bupropion, tandospirone, paroxetine and fluvoxamine. However, the precise mechanisms of antipruritic effect of these psychotropic drugs are still unclear. In human skin, serotonin receptors and serotonin transporter protein are expressed on skin cells such as keratinocytes, melanocytes, dermal fibroblasts, mast cells, T cells, natural killer cells, langerhans cells, and sensory nerve endings. It is noteworthy that serotonergic drugs, as well as serotonin itself, showed immune-modulating effect. Fenfluramine, fluoxetine and 2, 5-dimethoxy-4-iodoamphetamine significantly decreased lymphocyte proliferation. It is still questionable whether these serotonergic drugs exert the immunosuppressive effects via serotonin receptor or serotonin transporter. All these clinical and experimental reports suggest the possibility that antipruritic effects of selective serotonin reuptake inhibitors in atopic dermatitis patients might be at least partly due to their suppressive effect on T cells. Further studies should be conducted to elucidate the precise mechanism of neuroimmunological interaction in pruritus of atopic dermatitis.

Serotonergic chemosensory neurons modify the C. elegans immune response by regulating G-protein signaling in epithelial cells

The nervous and immune systems influence each other, allowing animals to rapidly protect themselves from changes in their internal and external environment. However, the complex nature of these systems in mammals makes it difficult to determine how neuronal signaling influences the immune response. Here we show that serotonin, synthesized in Caenorhabditis elegans chemosensory neurons, modulates the immune response. Serotonin released from these cells acts, directly or indirectly, to regulate G-protein signaling in epithelial cells. Signaling in these cells is required for the immune response to infection by the natural pathogen Microbacterium nematophilum. Here we show that serotonin signaling suppresses the innate immune response and limits the rate of pathogen clearance. We show that C. elegans uses classical neurotransmitters to alter the immune response. Serotonin released from sensory neurons may function to modify the immune system in response to changes in the animal's external environment such as the availability, or quality, of food.

NK cells in central nervous system disorders

NK cells are important players in immunity against pathogens and neoplasms. As a component of the innate immune system, they are one of the first effectors on sites of inflammation. Through their cytokine production capacities, NK cells participate in the development of a potent adaptive immune response. Furthermore, NK cells were found to have regulatory functions to limit and prevent autoimmunity via killing of autologous immune cells. These paradoxical functions of NK cells are reflected in CNS disorders. In this review, we discuss the phenotypes and functional features of peripheral and brain NK cells in brain tumors and infections, neurodegenerative diseases, acute vascular and traumatic damage, as well as mental disorders. We also discuss the implication of NK cells in neurotoxicity and neuroprotection following CNS pathology, as well as the crosstalk between NK cells and brain-resident immune cells.

Selective serotonin reuptake inhibitors inhibit human osteoclast and osteoblast formation and function

BACKGROUND

Selective serotonin reuptake inhibitors (SSRIs) are widely used antidepressants and one of the most commonly used medications. There is growing concern that SSRIs, which sequester in bone marrow at higher concentrations than brain or blood, increase bone fragility and fracture risk. However, their mechanism of action on human osteoclasts (OC) and osteoblasts (OB) differentiation remains unclear.

METHODS

Expression of serotonin receptors (5-HTR), transporter (5-HTT), and tryptophan hydroxylase 1 (TPH1) was assessed in human OC (precursors and mature) and OB (nonmineralizing and mineralizing) by polymerase chain reaction. OC formation and resorption was measured in the presence of 5 SSRIs. OBs cultured with SSRIs for 28 days were assessed for alkaline phosphatase (ALP) and bone mineralization. Cell viability and apoptosis were determined by annexin V flow cytometry.

RESULTS

OCs and OB expressed TPH1, 5-HTT, and 5-HTR1B. The 5-HTR2A was expressed only in OB, whereas 5-HTR2B expression increased from precursor to mature OC. All SSRIs (except citalopram) dose-dependently inhibited OC formation and resorption between 1 μmol/L and 10 μmol/L; order of potency: sertraline > fluoxetine > paroxetine > fluvoxamine > citalopram. Similarly, SSRIs (except citalopram) inhibited ALP and bone mineralization by OB but only at 30 μmol/L. Apoptosis was induced by SSRIs in OC and OB in an identical pattern to inhibitory effects. Serotonin treatment had no effect on either OC or OB parameters.

CONCLUSIONS

These data demonstrate that SSRIs differentially inhibit bone cell function via apoptosis. This may explain the mechanisms of bone loss with chronic use and aid clinical choices.

Antidepressants: influence on cancer and immunity?

Two decades ago, it was hypothesized that antidepressants could alter the course of neoplastic diseases. However, contradictory findings indicated that antidepressants could either have carcinogenic properties or improve the disease outcome. Intriguingly, controversial results were reported on the action of antidepressant drugs on immune function. Further hypotheses proposed that antidepressants could indirectly affect the cancer prognosis through the modulation of antitumor activity. Here we review the literature in order to elucidate the influence of antidepressants on cancer and immunity.

A dialogue between the immune system and brain, spoken in the language of serotonin

Neuropsychiatric disorders have long been linked to both immune system activation and alterations in serotonin (5-HT) signaling. In the CNS, the contributions of 5-HT modulate a broad range of targets, most notably, hypothalamic, limbic and cortical circuits linked to the control of mood and mood disorders. In the periphery, many are aware of the production and actions of 5-HT in the gut but are unaware that the molecule and its receptors are also present in the immune system where evidence suggests they contribute to the both innate and adaptive responses. In addition, there is clear evidence that the immune system communicates to the brain via both humoral and neuronal mechanisms, and that CNS 5-HT neurons are a direct or indirect target for these actions. Following a brief primer on the immune system, we describe our current understanding of the synthesis, release, and actions of 5-HT in modulating immune function, including the expression of 5-HT biosynthetic enzymes, receptors, and transporters that are typically studied with respect to the roles in the CNS. We then orient our presentation to recent findings that pro-inflammatory cytokines can modulate CNS 5-HT signaling, leading to a conceptualization that among the many roles of 5-HT in the body is an integrated physiological and behavioral response to inflammatory events and pathogens. From this perspective, altered 5-HT/immune conversations are likely to contribute to risk for neurobehavioral disorders historically linked to compromised 5-HT function or ameliorated by 5-HT targeted medications, including depression and anxiety disorders, obsessive-compulsive disorder (OCD), and autism. Our review raises the question as to whether genetic variation impacting 5-HT signaling genes may contribute to maladaptive behavior as much through perturbed immune system modulation as through altered brain mechanisms. Conversely, targeting the immune system for therapeutic development may provide an important opportunity to treat mental illness.

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

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

Selective serotonin reuptake inhibitor suppression of HIV infectivity and replication

OBJECTIVE

To test the hypothesis that the selective serotonin reuptake inhibitor (SSRI) citalopram would down-regulate human immunodeficiency virus (HIV) infectivity and that the greatest effects would be seen in people with depression. Depression is a risk factor for morbidity and mortality in HIV/acquired immune deficiency syndrome. Serotonin (5-HT) neurotransmission has been implicated in the pathobiology of depression, and pharmacologic therapies for depression target this system. The 5-HT transporter and 5-HT receptors are widely distributed throughout the central nervous and immune systems. Depression has been associated with suppression of natural killer cells and CD8(+) lymphocytes, key regulators of HIV infection.

METHODS

Ex vivo models for acute and chronic HIV infection were used to study the effects of citalopram on HIV viral infection and replication in 48 depressed and nondepressed women. For both the acute and chronic infection models, HIV reverse transcriptase activity was measured in the citalopram treatment condition and the control condition.

RESULTS

The SSRI significantly down-regulated the reverse transcriptase response in both the acute and chronic infection models. Specifically, citalopram significantly decreased the acute HIV infectivity of macrophages. Citalopram also significantly decreased HIV viral replication in the latently infected T-cell line and in the latently infected macrophage cell line. There was no difference in down-regulation by depression status.

CONCLUSIONS

These studies suggest that an SSRI enhances natural killer/CD8 noncytolytic HIV suppression in HIV/acquired immune deficiency syndrome and decreases HIV viral infectivity of macrophages, ex vivo, suggesting the need for in vivo studies to determine a potential role for agents targeting serotonin in the host defense against HIV.

Treatment-resistant depression prior to the diagnosis of cryptococcal meningitis: a case report

Comorbidity of chronic infectious disorders is one of the common causes of treatment-resistant depression. Depression may alter some aspects of immunity that can contribute to the development of infection. Here we describe an elderly male with treatment-resistant depression. Ten months after antidepressants were administered, he was found to have cryptococcal meningitis. After successful treatment of the central nervous system infection, his depressive symptoms improved apparently. A possible interaction between depression and cellular immunity was discussed. Physicians should be cautious about the risk of opportunistic infection in patients with depression, especially in immunocompromised condition.

Antidepressant pharmacotherapy: focus on sex differences in neuroimmunopharmacological crossroads

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

Immune function and health outcomes in women with depression

This research reports immune function and health outcomes in women with depression, as compared with a non-depressed control group. Using Psychoneuroimmunolgy theory and a descriptive comparison design, scores on the Beck Depression Inventory (BDI) were used to divide 40 non-hospitalized Caucasian women between the ages of 18 and 65 years into either the control or depression comparison group. Women with depression were found to report significantly more incidences of illness over the previous two months and they were found to have significantly more indicators of illness at the time of the exam as compared to the controls. However, contrary to what has been documented in some earlier studies of depression, women with depression were not found to have significantly different immune function measures as compared to the control group. There was also no significant correlation between scores on the BDI and natural killer cell cytotoxicity in this study. While these findings support a connection between depression and both increased self-report of illness and increased signs and symptoms of minor illness or inflammation on physical exam, this study was not able to document that these effects were related to decreased immune function, as measured by natural killer cell activity or white blood cell counts.

Psychopharmacology in HIV-infected patients

Neuropsychiatric disorders and syndromes may be underdiagnosed and inadequately treated in individuals infected with HIV. Depression in particular is among the most prevalent diagnoses, and data from controlled clinical studies have shown that antidepressant medications are efficacious and safe for treating depression in HIV-infected persons. A significant shortcoming of this literature is that most of the available data are from studies conducted before the advent of highly active antiretroviral therapy. In addition, apart from antidepressant medications, controlled studies systematically assessing efficacy and safety issues for other classes of psychotropic drugs (e.g., antipsychotic and anxiolytic medications) in HIV-infected persons are lacking. This review summarizes essential findings pertaining to the use of psychotropic medications to treat depression and other neuropsychiatric disorders in the context of HIV. It includes a discussion of clinically relevant treatment considerations (e.g., side effects, drug-drug interactions) derived from the existing literature as well as judgments that clinicians face in the absence of research data. Despite some shortcomings of the existing literature, overall there is compelling evidence that the appropriate use of psychotropic medications (coupled with behavioral therapy) can improve the quality of life of mentally ill HIV-infected individuals.

Selective serotonin reuptake inhibitor and substance P antagonist enhancement of natural killer cell innate immunity in human immunodeficiency virus/acquired immunodeficiency syndrome

BACKGROUND

Natural killer (NK) cells play an important role in innate immunity and are involved in the host defense against human immunodeficiency virus (HIV) infection. This study examines the potential role of three underlying regulatory systems that have been under investigation in central nervous system research as well as immune and viral research: serotonin, neurokinin, and glucocorticoid systems.

METHODS

Fifty-one HIV-seropositive subjects were recruited to achieve a representative sample of depressed and nondepressed women. The effects of a selective serotonin reuptake inhibitor (SSRI), a substance P (SP) antagonist, and a glucocorticoid antagonist on NK cell function were assessed in a series of ex vivo experiments of peripheral blood mononuclear cells from each HIV-seropositive subject.

RESULTS

Natural killer cell cytolytic activity was significantly increased by the SSRI citalopram and by the substance P antagonist CP-96345 relative to control conditions; the glucocorticoid antagonist, RU486, showed no effect on NK cytotoxicity. Our results suggest that the effects of the three agents did not differ as a function of depression.

CONCLUSIONS

Our findings provide evidence that NK cell function in HIV infection may be enhanced by serotonin reuptake inhibition and by substance P antagonism. It remains to be determined if HIV-related impairment in not only NK cytolytic activity but also NK noncytolytic activity can be improved by an SSRI or an SP antagonist. Clinical studies are warranted to address these questions and the potential roles of serotonergic agents and SP antagonists in improving NK cell immunity, delaying HIV disease progression, and extending survival with HIV infection.

Defeating cancer with antidepressants

Prostaglandins are ephemeral, infinitesimal signallers self-regulating every cell in the body, including those sub-serving mood and immunity. At first, they were perceived as a master switch, but now are believed to regulate every component of cellular micro-anatomy and physiology, including those of the organelles, cytoskeleton, proteins, enzymes, nucleic acids and mitochondria. Prostaglandins are responsible, paradoxically, for cell function and dysfunction. Excessive prostaglandin synthesis depresses immune function and may induce cancer. An ideal anti-cancer agent would inhibit prostaglandins in such a manner as to shut down the pathogenesis of cancer. In this paper, I will show that antidepressants have such properties.

Depressive disorders and immunity: 20 years of progress and discovery

Since the inception of Brain, Behavior and Immunity twenty years ago, many exciting developments have occurred regarding the relationship between depression and the immune system. These developments have increasingly put the field of psychoneuroimmunology into a clinical context with important translational implications. Initial studies focused on the impact of depression on relatively narrowly defined immunologic endpoints, which ultimately found their relevance in studies examining the effect of depression on immunologically-based diseases including infectious illnesses, autoimmune disorders, and cancer as well as more recently cardiovascular disease. Mechanistic studies have also greatly contributed to an understanding of those facets of depression, which might mediate these effects. More recently, the reciprocal influences of the immune system on the brain and behavior including depression have taken center stage. Increasing data now indicate that activated inflammatory processes can influence multiple aspects of CNS function including neurotransmitter metabolism, neuroendocrine function, and information processing leading to behavioral changes in humans that bespeak depression. These latter developments have intrigued scientists investigating the pathophysiology of depression and warrant consideration as some of the most exciting new developments in psychiatry in the past 20 years. What the future holds is a world of promise as multiple translational targets derived from the cytokine model of depression work their way into the clinical arena as drug targets for further development. Moreover, the work has served to instantiate brain-immune interactions as an essential component in psychiatric and medical co-morbidities and their impact on health and illness.

Lithium and antidepressants: Stimulating immune function and preventing and reversing infection

The ability to safely and economically stimulate immune function would transform the humanitarian and economic landscapes of nosocomial, surgical and antibiotic-resistant infections, as well as reduce the burden of epidemics, pandemics and bioterrorism. Such stimulation is widely held to be beyond our reach, an unfortunate misconception. As early as the mid 1980s sufficient evidence had accumulated to be able to state with conviction that lithium and antidepressants have these properties. Excessive production of prostaglandin E2 activates microorganisms and suppresses immune function, and lithium and antidepressants oppose prostaglandin E2. Immunostimulation is non-specific, possibly relevant to all infections, pertinent to one, two, or more concurrent infections, and highly cost/effective. In controlled studies an antidepressant would be relevant to that agent and only that agent, rendering such studies worthless. Over the past twenty years 22 drug companies have declined interest in developing antidepressants as antiinfectives. It would be unethical to deny the infected these well documented benefits.

Antidepressants, prostaglandins and the prevention and treatment of cancer

Among the putative mechanisms of carcinogenesis are up-regulation of cyclooxygenase, the synthesis and expression of oncogenes, viral activation, signal disruption, failed apoptosis, tumor initiation and promotion, angiogenesis, metastasis, immunosuppression, telomerase activity and autoimmunity. All are regulated by prostaglandins. Observable and radiographic regression of cancer has been documented in patients taking non-steroidal, anti-prostaglandin drugs such as indomethacin and ibuprofen. Antidepressants, too, have prostaglandin-inhibiting properties, and in vivo and in vitro evidence of their antineoplastic actions is emerging.

Ethanolic Extracts from Curcuma longa Attenuates Behavioral, Immune, and Neuroendocrine Alterations in a Rat Chronic Mild Stress Model

The ethanolic extracts from the rhizome of Curcuma longa L. (turmeric), possesses a wide variety of biological activities related to the treatment and prevention of affective disorders. To study their antidepressant effects, the impacts of chronic mild stress (CMS) and of the subsequent administration of ethanolic extracts of C. longa were investigated. Male Sprague-Dawley rats subjected to the CMS procedure demonstrated increased serum interleukin-6 and tumor necrosis factor-alpha levels, as well as a reduction of natural killer cell activity in splenocytes. In addition, CMS-treated rats exhibited elevated corticotropin-releasing factor in serum and medulla oblongata and cortisol levels in serum, with no significant change in serum adrenocorticotropin hormone levels. The preferential behavior of reduction in sucrose intake was also observed. These findings indicate that the alterations in immune and hypothalamic-pituitary-adrenal (HPA) axis systems could participate in the behavioral response to the CMS procedure in animals. Administration of ethanolic extracts of C. longa largely reversed the above effects. These results demonstrate the antidepressant-like activity of ethanolic extracts of C. longa in the rat CMS model of depression, at least in part by improving the abnormalities in immune and the HPA axis functions.

Initial conditions of psychotropic drug response: studies of serotonin transporter long promoter region (5-HTTLPR), serotonin transporter efficiency, cytokine and kinase gene expression relevant to depression and antidepressant outcome

The Hypothesis of Initial Conditions posits that differences in psychotropic drug response result from individual differences in receptor site kinetics, and differences in the sensitivity of downstream receptor-linked responses. This work examines data consistent with the hypothesis, specific to genetic and kinetic differences of the serotonin (5-HT) transporter (SERT), as they may be linked to divergent antidepressant response (ADR). The mechanisms for divergent ADR in association with different initial SERT function are considered within the context of SERT trafficking as sensitive to various different kinase and cytokine signals, some of which are dependent on the 5-HTTLPR polymorphism of the SERT gene. Pilot data suggest that human lymphocytes show kinase changes similar to those found in rat brain with ADT. These studies additionally suggest that ADT prompts a shift in cytokine gene expression toward a greater anti-inflammatory/inflammatory ratio. These latter findings are discussed within the context of a literature suggesting increased inflammatory cytokine levels in depression, and recent observations of increased temperature associated with depression. In sum, the data suggest the opportunity to identify response dependent protein (RDP) expression patterns that may differ with dichotomous ADR, and suggest new insights into understanding the mechanisms of psychotropic drug response through an understanding of initial differences in potential for psychotropic drug target regulation during therapy.

Effect of repeated administration of paroxetine and electroconvulsive shock on the proliferative response of lymphocytes and the synthesis of nitric oxide by macrophages in rats

OBJECTIVES

We sought to determine whether chronic administration of paroxetine and electroconvulsive shock (ECS), given separately or jointly, changes the proliferative response of T and B lymphocytes stimulated by mitogens and affect the production of nitric oxide (NO) by peritoneal macrophages.

METHODS

The experiment was conducted on male Wistar rats receiving treatment once daily for 12 consecutive days. Control animals were injected intraperitoneally (ip) with sterile distilled water (2 mL/kg) and were subjected to sham ECS. Paroxetine was administered ip in a dose of 10 mg/kg of body weight. ECS (150 mA, 50 Hz, 0.5 seconds) was delivered through ear clips. For combined treatment, paroxetine was given 30 minutes before ECS. The rats were killed 24 hours after the last treatment. Then, the proliferative response of splenocytes was induced by concanavalin A (Con A), lipopolysaccharide (LPS), or pokeweed mitogen and those of thymocytes by Con A and was later assessed by a standard [H]-thymidine incorporation assay. The spontaneous or induced (with LPS) NO synthesis in peritoneal macrophages was assessed as nitrite accumulation in 24-hour culture supernatants using the Griess reaction.

RESULTS

Only chronic treatment with ECS alone significantly increased the proliferative response of splenocytes to stimulation with Con A or LPS. The response of thymocytes was not changed in any group tested. Both the spontaneous NO synthesis and that induced with LPS in macrophages were significantly decreased only in rats receiving ECS.

CONCLUSIONS

We suggest that the ECS-induced suppression of NO synthesis by macrophages, resulting from the noradrenergic component of ECS action, may be responsible for the enhanced proliferative response of lymphocytes. Our data are in line with the results of other authors indicating that paroxetine and/or ECS modulate the immune system indirectly via the neuroendocrine system. The relatively high efficacy of ECS in the therapy for depression may be attributable to the ECS-evoked long-lasting changes in the immune system, which supports the macrophage theory of depression.

Effects of imipramine on T cell subsets in olfactory bulbectomized mice

To elucidate the immunological outcome in antidepressant therapy, the effects of acute or chronic imipramine (IMP) treatment on T cell subsets were examined in sham-operated (SO) and olfactory bulbectomized (OB) mice. Olfactory bulbectomy decreased the ratio of Lyt2-positive suppressor T cells to L3T4-positive T helper cells. Acute IMP treatment did not exert any effect on the ratio in SO nor in OB mice. Chronic IMP administration was found to significantly increase the ratio in SO and OB mice and, as a result, the ratio was significantly higher in SO mice compared with the control, while the ratio was normalized in OB mice. The present study may be suggestive of the immune activation in depression and of the immunosuppressive effects of antidepressants.

Depression and HIV infection: impact on immune function and disease progression

Can psychological factors, such as depression, affect human immunodeficiency virus progression? HIV infection is viewed as a chronic illness in which those infected often confront a number of emotional challenges and physical health and disease-related issues. Over the past 20 years, there has been increasing evidence that depression and other mood-related disturbances are commonly observed among HIV-positive individuals. There is also mounting data showing that depressive symptoms might further impact upon specific elements of immune system functioning and influence quality of life and health status. This paper will highlight studies examining the prevalence of depression during HIV infection and review some of the evidence examining the impact of depressive symptoms on immune function and HIV disease progression.

Psycho-neuro-immunological treatment of hepatocellular carcinoma with major depression--a single case report

A female patient, who was suffering major depression and advanced hepatocellular carcinoma (hepatoma), sought treatment in the Jozuka Mental Clinic. She was treated using a psycho-neuro-immunological approach. The treatments applied were psychotherapy, the antidepressant fluvoxamine, glycyrrhizinic acid and dehydroepiandrosterone (DHEA). Biochemical, endocrinological and immunological examinations were performed regularly. Improvement of liver function and reduction of alpha-fetoprotein were observed. The levels of DHEA, natural killer cell activity and cytokines (interleukines IL-2, IL-6, IL-12, interferon IFN-gamma) were normalised. Now, more than two and a half years after her admission, the patient is still well and symptom-free. While this may be a case of spontaneous regression, the results suggest that a psycho-neuro-immunological approach to treating the patient's depression and cancer was helpful for her recovery.

Comparison of immunological and endocrinological markers associated with major depression

Natural-killer-(NK)-cell activity and blood levels of interleukin 2 (IL-2), dehydro-epiandrosterone (DHEA), DHEA sulphate (DHEA-S) and cortisol were measured in 17 patients with major depression and 10 control subjects. Depression severity was evaluated using the Zung Self-rating Depression Scale. NK-cell activity and IL-2 levels were measured using a chromium-51 release test and an enzyme-linked immunosorbent assay, respectively. Radio-immunoassays were used to measure serum cortisol, DHEA and DHEA-S. As would be expected, patients with major depression had a higher score on the Zung Self-rating Depression Scale than healthy controls. Compared with controls, NK-cell activity and levels of cortisol and DHEA were reduced in patients with major depression, whereas IL-2 levels were increased. No difference was observed in DHEA-S levels between patients and controls. A reduction in NK-cell activity and DHEA levels, and an increase in IL-2 levels appear to be associated with major depression. Whether these changes are the cause or the consequence of the depression remains to be determined.

Focus on paroxetine

This review of paroxetine is based on Medline and PsycLit searches and a manual search of the available research literature. It aims to cover the pharmacology of this frequently prescribed SSRI antidepressant in terms of its indications, efficacy and adverse effects. Overall, paroxetine is a well-tolerated and safe first-line SSRI antidepressant with anxiolytic qualities. It has been found useful in depression, anxiety and other conditions such as obsessive compulsive disorder and post-traumatic stress disorder. The antidepressant has some advantages over earlier tricyclic medication in terms of a lack of cardiovascular side-effects and relative safety in overdose. Cessation of use, however, is associated with withdrawal or discontinuation symptoms and patients should be counselled as to how these might be avoided. A 3- or 4-week graded withdrawal regimen, perhaps with concomitant fluoxetine to cover serotonergic discontinuation symptoms, may be advisable.

Antidepressant treatment of cytokine-induced mood disorders

Significant evidence suggests that the immune system is capable of profoundly affecting central nervous system (CNS) functioning in ways that may contribute to the development and expression of neuropsychiatric disorders, including disorders of mood. This paper reviews evidence that the production of proinflammatory cytokines, whether in the context of therapeutic administration (e.g. interferon-α-2b for hepatitis C infection) or medical illness, induces a state of sickness behavior that closely resembles major depression. Antidepressants have been shown to abolish or attenuate cytokine-induced sickness behavior in laboratory animals and to protect against the development of major depression in the context of therapeutic cytokine administration in humans. Potential mechanisms by which antidepressants ameliorate depressive and/or sickness symptoms in the context of immune activation include direct effects on immune cell functioning, as well as modulatory effects on monoamine neurotransmitters, intracellular second messenger pathways and the neuroendocrine system, in particular the hypothalamic-pituitary-adrenal axis.

Lithium and antidepressants: inhibiting eicosanoids, stimulating immunity, and defeating microorganisms

Infection-emerging, reemerging, antibiotic-resistant, and bioengineered-increasingly threatens mankind. It is widely assumed that immunostimulating agents, were they to exist, would be ideal in battling microorganisms. Various investigators have established lithium and antidepressants as immunostimulants and antimicrobials and they have identified the mechanisms involved. Eicosanoids both depress immunity and activate microorganisms and lithium and antidepressants oppose eicosanoids. Such philosophers of science as Paul Feyerabend have argued that special interests invariably oppose revolutionary paradigms.

Age at onset of major depressive disorder predicts reductions in NK cell number and activity

BACKGROUND

Major depressive disorder (MDD) has been associated with altered immunologic parameters including reductions in natural killer cell activity (NKCA). It remains largely unknown, however, whether alterations in immune function characterize homogeneous sub-groups of MDD. The present study addressed the question of whether age at onset of index episode and/or duration of the present episode of MDD predicted alterations in NKCA and NK cell number.

METHODS

Participants met DSM-IV criteria for MDD. Age at onset of MDD, duration of the present episode, demographics, and comorbidity were obtained by SCID for all subjects (n = 36). Severity and symptom pattern of MDD was assessed by the Hamilton Depression Rating Scale. NKCA was measured using a standard chromium-release cytotoxicity assay and NK number assessed by flow cytometry.

RESULTS

Age at onset of MDD significantly predicted variance in NK cell number and NKCA. Consistent with previous studies, sleep disturbance and psychomotor retardation possessed significant explanatory power for variance in NK cell number and NKCA, respectively.

LIMITATIONS

Measures of age at onset of MDD and duration of the present episode were obtained by self-report and thus recall bias may attenuate the reliability of the present findings. The present study design also precludes conclusions regarding the temporal association between alterations in NK cells and MDD.

CONCLUSIONS

We propose that immunologic alterations, characterized by a suppression of NKCA and NK cell number concomitant with proinflammatory processes, may constitute an immunologic phenotype unique to early-age-onset depression and may be salient factors in the pathogenesis of depression.

Cell-mediated immune response in MDMA users after repeated dose administration: studies in controlled versus noncontrolled settings

Acute administration of 3,4-methylenedioxymethamphetamine (MDMA, "ecstasy") produces time-dependent immune dysfunction in humans. Recreational use of MDMA generally includes repeated drug consumption, often in association with other drugs, such as alcohol and cannabis. In the laboratory setting, repeated MDMA administration to healthy MDMA consumers produced a time-dependent immune dysfunction similar to that observed with the ingestion of a single dose, and the first of the two administrations paralleled the time-course of MDMA-induced cortisol stimulation kinetics and MDMA plasma concentrations. A significant decrease in CD4 T-helper cells with simultaneous increase in natural killer (NK) cell and a decrease in functional responsiveness of lymphocytes to mitogenic stimulation was observed. Response to the second dose was either long-lasting compared with the first dose or disproportionate and did not show any parallelism with cortisol and MDMA plasma concentrations. This circumstance extended the critical period during which immunocompetence is highly impaired as a result of MDMA use. Accumulation of MDMA in the body of a poor metabolizer induced higher immunomodulatory effects with statistically significant differences in NK cell function compared with extensive metabolizers. When basal values of lymphocyte subsets were examined in a population of recreational MDMA users participating in different clinical trials, alterations in several immunological parameters were observed. The absolute number of lymphocytes, in particular T lymphocytes and CD4 T-helper cell subsets, showed a trend toward reduced values, although cell counts were within normal limits. By contrast, NK cells in MDMA consumers were reduced to one-third of those from healthy persons. A statistically significant decrease in affected immune parameters was recorded during a 2-year observation period in a subgroup of recreational MDMA users. These permanent alterations in immunologic homeostasis may result in impairment of general health and subsequent increased susceptibility to infection and immune-related disorders.

Levels of monocyte reactive oxygen species are associated with reduced natural killer cell activity in major depressive disorder

Major depressive disorder (MDD) is associated with reductions in natural killer cell activity (NKCA), however the mechanism(s) mediating reduced NKCA in MDD has yet to be determined. In light of evidence that MDD is associated with an inflammatory immune response, we propose that reactive oxygen species (ROS), generated by inflammatory leukocytes (monocytes and/or neutrophils), may mediate the suppression of NKCA in MDD. Intracellular levels of monocyte ROS were significantly associated with reductions in NKCA in outpatients (n = 15) diagnosed with MDD. Sleep disturbance was also significantly correlated with reductions in NKCA. Elevated levels of ROS may be an additional characteristic of a subset of depressed patients in whom an inflammatory response persists and elevations in ROS may, in part, mediate the associations observed between MDD, cardiovascular disease, and cancer.

Effects of tramadol on T lymphocyte proliferation and natural killer cell activity in rats with sciatic constriction injury

We investigated the effects of acute and chronic tramadol treatment on T lymphocyte function and natural killer (NK) cell activity in rats receiving chronic constriction injury (CCI) of the sciatic nerve. T lymphocyte function was evaluated based on concanavalin-A (ConA)- and phytohemagglutinin (PHA)-induced splenocyte proliferation. NK cell activity was measured by lactic acid dehydrogenase release assay. The effects of tramadol on thermal hyperalgesia were also assessed by measuring paw withdrawal latency (PWL) in the rats. PWL was dose-dependently reversed by tramadol after acute treatment (single subcutaneous injection) with 10, 20, and 30 mg/kg, respectively. There was no significant change among acute treatment groups in NK cell activity, whereas splenocyte proliferation induced by ConA and PHA was significantly suppressed starting from a dose of 20 mg/kg. The reversal of the thermal hyperalgesia persisted throughout a period of chronic tramadol treatment of 40 and 80 mg/kg per day, respectively, with continuous subcutaneous infusion for 7 days at a uniform rate via osmotic minipumps. No modulation of NK cell activity was found in either dose group. However, the activity of splenocyte proliferation was decreased in the 80 mg/kg per day group when compared with the saline and 40 mg/kg per day groups. These data suggest that tramadol treatment has an immunological profile different from pure mu-opioid agonists like morphine, which is known to suppress both NK cell activity and T lymphocyte proliferation at a subanalgesic dose in CCI rats. Considering analgesic and immunosuppressive effects, tramadol treatment may be a better choice than morphine for treatment of chronic neuropathic pain, particularly in patients with compromised immunity.

The effects of St. John's Wort (Hypericum perforatum) on NK cell activity in vitro

St. John's Wort (Hypericum perforatum; H. perforatum) is a popular herbal supplement used to treat mild to moderate depression. H. perforatum possesses serotonergic properties such as inhibition of serotonin (5-hydroxytryptamine; 5-HT) reuptake. Serotonergic pharmacotherapy is associated with amelioration of depression as well as increases in natural killer (NK) cell activity (NKCA). Also, 5-HT and 5-HT analogs augment NKCA in vitro. Considering the serotonergic properties of H. perforatum, the effects of H. perforatum on NKCA were assessed in vitro. Mononuclear cells (MNCs) from normal donors were exposed in vitro to an extract of H. perforatum (LI160s) or established 5-HT stimulators of NKCA. After an overnight incubation, cells were washed and a standard 51Cr-release cytotoxicity assay performed to assess NKCA. LI160s at all concentrations failed to augment NKCA. However, in corroboration of previous studies, 5-HT, the selective serotonin reuptake inhibitors (SSRIs), paroxetine and norfluoxetine, and alpha-interferon augmented NKCA above control levels. Though an efficacious treatment for mild to moderate depression, H. perforatum differs from commonly prescribed serotonergic antidepressants insofar as H. perforatum fails to enhance NKCA in vitro. Therefore, the present results are consistent with pharmacologic studies indicating that H. perforatum possesses, at best, weak serotonergic activity.