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

The dual roles of serotonin in antitumor immunity

Research has shown that a significant portion of cancer patients experience depressive symptoms, often accompanied by neuroendocrine hormone imbalances. Depression is frequently associated with decreased levels of serotonin with the alternate name 5-hydroxytryptamine (5-HT), leading to the common use of selective serotonin reuptake inhibitors (SSRIs) as antidepressants. However, the role of serotonin in tumor regulation remains unclear, with its expression levels displaying varied effects across different types of tumors. Tumor initiation and progression are closely intertwined with the immune function of the human body. Neuroimmunity, as an interdisciplinary subject, has played a unique role in the study of the relationship between psychosocial factors and tumors and their mechanisms in recent years. This article offers a comprehensive review of serotonin's regulatory roles in tumor onset and progression, as well as its impacts on immune cells in the tumor microenvironment. The aim is to stimulate further interdisciplinary research and discover novel targets for tumor treatment.

Serotonin signalling in cancer: Emerging mechanisms and therapeutic opportunities

BACKGROUND

Serotonin (5-hydroxytryptamine) is a multifunctional bioamine serving as a neurotransmitter, peripheral hormone and mitogen in the vertebrate system. It has pleiotropic activities in central nervous system and gastrointestinal function via an orchestrated action of serotonergic elements, particularly serotonin receptor-mediated signalling cascades. The mitogenic properties of serotonin have garnered recognition for years and have been exploited for repurposing serotonergic-targeted drugs in cancer therapy. However, emerging conflicting findings necessitate a more comprehensive elucidation of serotonin's role in cancer pathogenesis.

MAIN BODY AND CONCLUSION

Here, we provide an overview of the biosynthesis, metabolism and action modes of serotonin. We summarise our current knowledge regarding the effects of the peripheral serotonergic system on tumourigenesis, with a specific emphasis on its immunomodulatory activities in human cancers. We also discuss the dual roles of serotonin in tumour pathogenesis and elucidate the potential of serotonergic drugs, some of which display favourable safety profiles and impressive efficacy in clinical trials, as a promising avenue in cancer treatment.

KEY POINTS

Primary synthesis and metabolic routes of peripheral 5-hydroxytryptamine in the gastrointestinal tract. Advanced research has established a strong association between the serotonergic components and carcinogenic mechanisms. The interplay between serotonergic signalling and the immune system within the tumour microenvironment orchestrates antitumour immune responses. Serotonergic-targeted drugs offer valuable clinical options for cancer therapy.

Exploring the Role of Serotonin as an Immune Modulatory Component in Cardiovascular Diseases

Serotonin, also known as 5-hydroxytryptamine (5-HT) is a well-known neurotransmitter in the central nervous system (CNS), but also plays a significant role in peripheral tissues. There is a growing body of evidence suggesting that serotonin influences immune cell responses and contributes to the development of pathological injury in cardiovascular diseases, such as atherosclerosis, as well as other diseases which occur as a result of immune hyperactivity. In particular, high levels of serotonin are able to activate a multitude of 5-HT receptors found on the surface of immune cells, thereby influencing the process of atherosclerotic plaque formation in arteries. In this review, we will discuss the differences between serotonin production in the CNS and the periphery, and will give a brief outline of the function of serotonin in the periphery. In this context, we will particularly focus on the effects of serotonin on immune cells related to atherosclerosis and identify caveats that are important for future research.

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.

HIV Associated Neurocognitive Disorders Subsidence Through Citalopram Addition in Anti-retroviral Therapy (HANDS-CARE): A Concept Note

There is a pressing need to effectively manage HIV Associated Neurocognitive Disorders (HAND) in sub-Saharan Africa (SSA) where the burden is among the highest in the world. Contemporary approaches based on the use of Highly Active Antiretroviral Therapy (HAART) alone are inadequate interventions for HAND, especially in SSA where there is limited availability of the required combinations of HAART for effective central nervous system penetration and where many currently prescribed agents, including efavirenz, have neurotoxicity as a major drawback. This article reviews data supporting the rationale for additive citalopram in antiretroviral therapy as a latent approach to abate HAND. It proposes the conduct of a HIV Associated Neurocognitive Disorders Subsidence through Citalopram addition in Anti-Retroviral therapy (HANDS-CARE) pilot feasibility trial (RCT) to assess whether the adjunctive use of citalopram, a widely prescribed serotonergic antidepressant, will lead to a meaningful improvement in neurocognitive functioning and quality of life in patients with HAND who are receiving HAART. A preliminarily feasible and efficacy-suggesting HANDS-CARE trial could generate statistical, clinical and operational data necessary to design and conduct a future definitive RCT. If successful, this intervention will be applicable to resource-limited settings as well as developed countries. Effective management of HAND will improve the quality of life of HIV patients, and reduce the cost of managing the disease.

Effect of aprepitant on kynurenine to tryptophan ratio in cART treated and cART naïve adults living with HIV

Changes in tryptophan metabolism affect human physiology including the immune system, mood, and sleep and are associated with human immunodeficiency virus (HIV) pathogenesis. This study investigates whether the treatment of HIV-infected individuals with the neurokinin-1 receptor antagonist, aprepitant, alters tryptophan metabolism.This study utilized archival samples from 3 phase 1B clinical trials "Anti-HIV Neuroimmunomodulatory Therapy with Neurokinin-1 Antagonist Aprepitant"-2 double-blinded, placebo-controlled, and 1 open-label study. We tested samples from a total of 57 individuals: 26 combination antiretroviral therapy (cART) naïve individuals receiving aprepitant, 19 cART naïve individuals receiving placebo, and 12 individuals on a ritonavir-containing cART regimen receiving aprepitant. We evaluated the effect of aprepitant on tryptophan metabolism by measuring levels of kynurenine and tryptophan in archival plasma samples and calculating the kynurenine to tryptophan ratio.Aprepitant treatment affected tryptophan metabolism in both cART treated and cART naïve individuals with more profound effects in patients receiving cART. While aprepitant treatment affected tryptophan metabolism in all HIV-infected patients, it only significantly decreased kynurenine to tryptophan ratio in cART treated individuals. Aprepitant treatment offers an opportunity to target inflammation and mood disorders frequently co-existing in chronic HIV infection.

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.

A randomized trial of safety and pharmacodynamic interactions between a selective glucocorticoid receptor antagonist, PT150, and ethanol in healthy volunteers

PT150, a novel competitive glucocorticoid receptor (GR) antagonist, has proven safe in animal models, healthy volunteers, and people with depression. Our study is the first to investigate PT150’s safety with alcohol use. The primary objective of this study was to evaluate pharmacodynamic interactions between ethanol and PT150 in healthy subjects. This single-site, Phase I pilot trial consisted of community-recruited, healthy, alcohol-experienced participants aged 21–64 years. Of 32 participants screened, 11 were enrolled and randomized, one of which withdrew before intervention. PT150 (900 mg/day) was administered orally to all participants for five days. All participants received two beverage challenges on Day 1 (before PT150 administration) and Day 5 (after PT150 administration). On challenge days, they received both alcohol (16% ethanol) and placebo (1% ethanol) beverages in random order. Primary outcomes included breath alcohol level, blood pressure, heart rate, adverse events, and electrocardiogram changes. There were no statistically significant differences in vital signs or estimated blood alcohol concentrations between PT150 non-exposed and exposed groups during the ethanol challenge. There were no clinically significant abnormal electrocardiograms or serious adverse events. These data show that administration of PT150 with concurrent alcohol use is safe and well-tolerated. This study supports a future pharmacokinetic interaction study between PT150 and alcohol.

Trial Registration ClinicalTrials.gov Identifier: NCT03548714.

Role of serotonin receptor signaling in cancer cells and anti-tumor immunity

Serotonin or 5-hydroxytryptamine (5-HT) is a neurotransmitter known to affect emotion, behavior, and cognition, and its effects are mostly studied in neurological diseases. The crosstalk between the immune cells and the nervous system through serotonin and its receptors (5-HTRs) in the tumor microenvironment and the secondary lymphoid organs are known to affect cancer pathogenesis. However, the molecular mechanism of - alteration in the phenotype and function of - innate and adaptive immune cells by serotonin is not well explored. In this review, we discuss how serotonin and serotonin receptors modulate the phenotype and function of various immune cells, and how the 5-HT-5-HTR axis modulates antitumor immunity. Understanding how 5-HT and immune signaling are involved in tumor immunity could help improve therapeutic strategies to control cancer progression and metastasis.

Neurokinin receptors and their implications in various autoimmune diseases

Neurokinin receptors belong to the GPCRs family and are ubiquitously expressed throughout the nervous and immune systems. Neurokinin receptors in coordination with neurokinins playing an important role in many physiological processes, including smooth muscle contraction, secretion, proliferation, and nociception. They also contribute to various disease conditions such as inflammatory bowel disease, rheumatoid arthritis, multiple sclerosis, psoriasis, and cancer. Neurokinin receptors antagonist are potent and highly selective and showing success in treating chemotherapy-induced nausea and vomiting. In this review, discuss the various neurokinin receptor expression on immune cells and their importance in various inflammatory and autoimmune diseases and their therapeutic importance.

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The Neurokinin receptor is an important regulatory mechanism to control the neuronal and immune systems.

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Various neurokinin receptors (NK1R, NK2R, and NK3R) are expressed in neurons and cells of the immune system.

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Substance P (SP) controls the differentiation and function of immune cells.

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SP-NK1R receptor signaling shows substantial cross-talk between neuronal and immune systems in inflammation and autoimmunity.

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.

The relation between immunologic variables and symptom factors in patients with major depressive disorder

BACKGROUND

The associations between depression and immunity were investigated by measuring the scores of Hamilton Rating Scale for Depression (HRSD) and peripheral lymphocyte parameters in patients with major depressive disorder (MDD).

METHODS

Forty-nine patients with MDD were recruited and their clinical symptoms are evaluated with 17-item HRSD which was factorized using the confirmatory factor analysis (i.e., depression factor, insomnia factor, and anxiety factor). Basic immunologic variables such as CD4, CD8, and CD56-positive cell numbers were measured by flow cytometry. Natural killer cell activity (NKCA) was also assessed by ELISA method using K-562 cells as target cells. All patients were treated for 4 weeks with selective serotonin reuptake inhibitors. Immunologic and clinical variables were measured both at baseline and after medication.

RESULTS

CD8-positive cell number was increased (p < .05) and CD4/CD8 ratio was decreased (p < .01) after medication. NKCA showed a significant positive correlation with anxiety factor scores of HRSD (p < .05) at baseline. However, except NKCA, there was no correlation between other immunologic measures and symptom factors.

CONCLUSION

These results suggest that immunologic measure such as NKCA may be an important variable for symptom of MDD such as anxiety during acute depressive state.

Role of Substance P Neuropeptide in Inflammation, Wound Healing, and Tissue Homeostasis

Substance P (SP) is an undecapeptide present in the CNS and the peripheral nervous system. SP released from the peripheral nerves exerts its biological and immunological activity via high-affinity neurokinin 1 receptor (NK1R). SP is also produced by immune cells and acts as an autocrine or paracrine fashion to regulate the function of immune cells. In addition to its proinflammatory role, SP and its metabolites in combination with insulin-like growth factor-1 are shown to promote the corneal epithelial wound healing. Recently, we showed an altered ocular surface homeostasis in unmanipulated NK1R^-/- mice, suggesting the role of SP-NK1R signaling in ocular surface homeostasis under steady-state. This review summarizes the immunobiology of SP and its effect on immune cells and immunity to microbial infection. In addition, the effect of SP in inflammation, wound healing, and corneal epithelial homeostasis in the eye is discussed.

The neuropeptide galanin modulates natural killer cell function

Natural killer (NK) cells are part of the innate immune system and combat pathogens and tumors by secreting pro-inflammatory cytokines like interferon gamma (IFN-γ) and by their cytotoxic action. Galanin is a neuropeptide also expressed in peripheral tissue where it impacts several physiological functions, including inflammation. The effects of galanin are mediated via three receptors, GAL_1-3. Since other neuropeptides have been shown to regulate NK cell activity, we investigated the potential of galanin to modulate human NK cell function. NK cells were isolated from human peripheral blood mononuclear cells. mRNA expression was analyzed by qRT-PCR. The dynamic mass redistribution of NK cells upon regulatory peptide stimulation was determined by label-free biochip technology. IFN-γ producing NK cells were identified by flow cytometry analysis and IFN-γ secretion was measured by ELISA. NK cell cytotoxicity was analyzed by flow cytometry via CD107a mobilization. NK cells were found to express the receptor GAL₂ but not GAL₁, GAL₃ or galanin. Galanin per se did not affect the dynamic mass redistribution of NK cells, but significantly enhanced the response of NK cells to IL-18. Galanin significantly modulated the IFN-γ production of the CD56^bright NK cell population upon IL-12 and IL-18 stimulation. Furthermore, galanin significantly modulated the IL-12 and IL-18 stimulated IFN-γ secretion. NK cell cytotoxicity was not modulated by galanin treatment. Galanin can be classified as an immunomodulatory peptide as it is able to sensitize NK cells toward specific cytokines.

The Effects of Serotonin in Immune Cells

Serotonin [5-hydroxytryptamine (5-HT)] plays an important role in many organs as a peripheral hormone. Most of the body’s serotonin is circulating in the bloodstream, transported by blood platelets and is released upon activation. The functions of serotonin are mediated by members of the 7 known mammalian serotonin receptor subtype classes (15 known subtypes), the serotonin transporter (SERT), and by covalent binding of serotonin to different effector proteins. Almost all immune cells express at least one serotonin component. In recent years, a number of immunoregulatory functions have been ascribed to serotonin. In monocytes/macrophages, for example, serotonin modulates cytokine secretion. Serotonin can also suppress the release of tumor necrosis factor-α and interleukin-1β by activating serotonin receptors. Furthermore, neutrophil recruitment and T-cell activation can both be mediated by serotonin. These are only a few of the known immunomodulatory roles of serotonin that we will review here.

The Selective Serotonin Reuptake Inhibitor Citalopram Decreases Human Immunodeficiency Virus Receptor and Coreceptor Expression in Immune Cells

BACKGROUND

This study investigated whether the selective serotonin reuptake inhibitor (SSRI) citalopram downregulates the expression of the human immunodeficiency virus (HIV) receptor cluster of differentiation 4 (CD4) and coreceptors chemokine receptor type 5 and chemokine-related receptor type 4 (CCR5 and CXCR4) on peripheral blood mononuclear cells (PBMCs) and macrophages ex vivo as a potential mechanism of reducing susceptibility to HIV infection.

METHODS

The sample included 150 participants 18-58 years old (59% women, 65% African American, 61% with depression). Monocyte-depleted PBMCs were treated with phytohemagglutinin for 72 hours and then cultured in the presence of interleukin-2 with vehicle control or the SSRI (10(-6) mol/L) for 2 hours. To generate monocyte-derived macrophages, monocytes were cultured for 7 days, after which either vehicle control or SSRI (10(-6) mol/L) was added for 2 hours. RNA was collected from both cell types, and messenger RNA expression of CD4, CCR5, and CXCR4 was measured by real-time polymerase chain reaction.

RESULTS

In PBMCs, SSRI treatment decreased expression of CD4 (p = .009), CCR5 (p = .008), and CXCR4 (p < .0001). In monocyte-derived macrophages, SSRI treatment decreased expression of CD4 (p < .0001) and CXCR4 (p = .0003), but not CCR5 (p = .71). The suppressive effects of the SSRI on receptor expression did not differ as a function of depression diagnosis or depressive symptom severity.

CONCLUSIONS

Treatment with the SSRI at a physiologic dose decreased CD4, CCR5, and CXCR4 expression on PBMCs and macrophages ex vivo. These findings suggest that SSRI treatment, independent of depression status, downregulates HIV receptor and coreceptor expression and may reduce susceptibility of immune cells to HIV infection and decrease inflammation. If clinical trials confirm the present findings, ultimately there may be a role for using SSRI treatment adjunctively in HIV and acquired immunodeficiency syndrome.

Empirically Supported Use of Psychiatric Medications in Adolescents and Adults with IBD

BACKGROUND

The use of psychotropic medications, particularly antidepressants, is common in patients with inflammatory bowel disease (IBD) in spite of a lack of their robust efficacy in this population. This review provides an overview of the use trends of different classes of antidepressant and anti-anxiety medication and their effects on mood, nervous system function, gastrointestinal physiology and immunity drawing from the literature available in the general population, other medical conditions, and when available, patients with IBD. It also covers the evidence base for the actions, efficacy, and potential complications of antidepressants organized by different classes.

METHODS

We conducted a PubMed search of articles relating the different drug classes probed to the terms above in different populations of interest. All types of articles were accepted including case reports and series, open and randomized trials, reviews, and expert opinion. We also examined the reference lists of the publications found.

RESULTS

Selective serotonin reuptake inhibitors (SSRIs) and tricyclic antidepressants (TCAs) are the most commonly prescribed agents for anxiety and depression in patients with IBD, though their efficacy for these conditions in the general population are mild to moderate at best. SSRIs are generally well tolerated, though at higher doses, they, like most antidepressant classes, can be associated with activation, serotonergic syndrome, and increased suicidal ideation. TCAs have many more serious side effects but have some shown efficacy for functional GI symptoms. A newer class, the serotonin noradrenergic reuptake inhibitors (SNRIs), can be effective for refractory depression, anxiety and chronic pain syndromes with a side effect profile similar to both SSRIs and more mild manifestations of TCAs. Mirtazapine has moderate efficacy for depression if sedation and weight gain side effects are tolerated and some small support for use in nausea and vomiting. Bupropion targets dopamine and noradrenaline reuptake and has moderate efficacy for depression, and some small support for use in fatigue and smoking cessation. Buspirone has an indication for generalized anxiety disorder though studies show only a minimal benefit. It has some growing evidence for use in functional dyspepsia. Most of these agents have physiological effects on the brain, immune system, and gastrointestinal tract (with the exception of bupropion) hence their therapeutic and side effects manifested in these systems.

CONCLUSION

Antidepressant medications are frequently prescribed for depression, anxiety disorders, and chronic pain syndromes, but overall support for their efficacy is modest at best. Psychological interventions have growing support for having much more robust effects without the side effects of antidepressants and should be considered first-line treatment or at least an adjunct to psychotropic medications for these conditions.

Pharmacologic rationale for the NK1R antagonist, aprepitant as adjunctive therapy in HIV

BACKGROUND

Many HIV infected individuals with suppressed viral loads experience chronic immune activation frequently developing neurological impairment designated as HIV associated neurocognitive disorder (HAND). Adjunctive therapies may reduce HIV associated inflammation and therefore decrease the occurrence of HAND.

METHODS

We have conducted in vitro, animal and clinical studies of the neurokinin 1 receptor (NK1R) antagonist aprepitant in HIV/SIV infection.

RESULTS

Aprepitant inhibits HIV infection of human macrophages ex vivo with an ED50 ~ 5 µM. When administered at 125 mg once daily for 12 months to SIV-infected rhesus macaques, aprepitant reduced viral load by approximately tenfold and produced anti-anxiolytic effects. The anti-viral and anti-anxiolytic effects occur at approximately the third month of dosing; and the effects are sustained throughout the duration of drug administration. Protein binding experiments in culture media and animal and human plasma indicate that the free fraction of aprepitant is lower than previously reported supporting usage of higher doses in vivo. The analysis of blood samples from HIV positive individuals treated for 2 weeks with aprepitant at doses up to 375 mg demonstrated reduced levels of pro-inflammatory cytokines including G-CSF, IL-6, IL-8 and TNFα. Decreased pro-inflammatory cytokines may reduce HIV comorbidities associated with chronic inflammation.

CONCLUSIONS

Our results provide evidence for a unique combination of antiretroviral, anti-inflammatory and behavioral modulation properties of aprepitant in vitro and in vivo. These results provide robust support for a clinical exposure target above that recommended for chemotherapy-induced nausea and vomiting. Doses up to 375 mg once daily in HIV-infected patients still elicit sub-therapeutic exposure of aprepitant though effective plasma concentrations can be achievable by proper dose modulation.

Serotonin mediated immunoregulation and neural functions: Complicity in the aetiology of autism spectrum disorders

Serotonergic system has long been implicated in the aetiology of autism spectrum disorders (ASD), since platelet hyperserotonemia is consistently observed in a subset of autistic patients, who respond well to selective serotonin reuptake inhibitors. Apart from being a neurotransmitter, serotonin functions as a neurotrophic factor directing brain development and as an immunoregulator modulating immune responses. Serotonin transporter (SERT) regulates serotonin level in lymphoid tissues to ensure its proper functioning in innate and adaptive responses. Immunological molecules such as cytokines in turn regulate the transcription and activity of SERT. Dysregulation of serotonergic system could trigger signalling cascades that affect normal neural-immune interactions culminating in neurodevelopmental and neural connectivity defects precipitating behavioural abnormalities, or the disease phenotypes. Therefore, we suggest that a better understanding of the cross talk between serotonergic genes, immune systems and serotonergic neurotransmission will open wider avenues to develop pharmacological leads for addressing the core ASD behavioural deficits.

Immunomodulatory effects mediated by serotonin

Serotonin (5-HT) induces concentration-dependent metabolic effects in diverse cell types, including neurons, entherochromaffin cells, adipocytes, pancreatic beta-cells, fibroblasts, smooth muscle cells, epithelial cells, and leukocytes. Three classes of genes regulating 5-HT function are constitutively expressed or induced in these cells: (a) membrane proteins that regulate the response to 5-HT, such as SERT, 5HTR-GPCR, and the 5HT₃-ion channels; (b) downstream signaling transduction proteins; and (c) enzymes controlling 5-HT metabolism, such as IDO and MAO, which can generate biologically active catabolites, including melatonin, kynurenines, and kynurenamines. This review covers the clinical and experimental mechanisms involved in 5-HT-induced immunomodulation. These mechanisms are cell-specific and depend on the expression of serotonergic components in immune cells. Consequently, 5-HT can modulate several immunological events, such as chemotaxis, leukocyte activation, proliferation, cytokine secretion, anergy, and apoptosis. The effects of 5-HT on immune cells may be relevant in the clinical outcome of pathologies with an inflammatory component. Major depression, fibromyalgia, Alzheimer disease, psoriasis, arthritis, allergies, and asthma are all associated with changes in the serotonergic system associated with leukocytes. Thus, pharmacological regulation of the serotonergic system may modulate immune function and provide therapeutic alternatives for these diseases.

Serotonin modulation of macrophage polarization: inflammation and beyond

Macrophages display a ample plethora of effector functions whose acquisition is promoted by the surrounding cytokine and cellular environment. Depending on the stimulus, macrophages become specialized ("polarized") for either pathogen elimination, tissue repair and wound healing or immunosuppression. This "polarization" versatility allows macrophages to critically contribute to tissue homeostasis, as they promote initiation and resolution of inflammatory responses. As a consequence, deregulation of the tissue macrophage polarization balance is an etiological agent of chronic inflammation, autoimmune diseases, cancer and even obesity and insulin resistance. In the present review we describe current concepts on the molecular basis and the patho-physiological implications of macrophage polarization, and describe its modulation by serotonin (5-HT), a neurotransmitter that regulates inflammation and tissue repair via a large set of receptors (5-HTR1-7). 5-HT modulates the phenotypic and functional polarization of macrophages, and contributes to the maintenance of an anti-inflammatory state mainly via 5-HTR2B and 5-HTR7, whose activation has a great impact on macrophage gene expression profile. The identification of 5-HTR2B and 5-HTR7 as functionally-relevant polarization markers suggests their therapeutic value in inflammatory pathologies as well as their potential involvement in linking the immune and nervous systems.

Varicella zoster virus-specific immune responses to a herpes zoster vaccine in elderly recipients with major depression and the impact of antidepressant medications

BACKGROUND

The Depression Substudy of the Shingles Prevention Study (SPS) was designed to evaluate the association between major depression and immune responses to a high-titer live attenuated varicella zoster virus (VZV) vaccine (zoster vaccine), which boosts cell-mediated immunity (CMI) to VZV and decreases the incidence and severity of herpes zoster (HZ). The Depression Substudy was a 2-year longitudinal cohort study in 92 community-dwelling adults≥60 years of age who were enrolled in the SPS, a large, double-blind, placebo-controlled Veterans Affairs Cooperative zoster vaccine efficacy study.

METHODS

Forty subjects with major depressive disorder, stratified by use of antidepressant medications, and 52 age- and sex-matched controls with no history of depression or other mental illness had their VZV-CMI measured prior to vaccination with zoster vaccine or placebo and at 6 weeks, 1 year, and 2 years postvaccination.

RESULTS

Depressed subjects who were not treated with antidepressant medications had lower levels of VZV-CMI following administration of zoster vaccine than nondepressed controls or depressed subjects receiving antidepressants even when antidepressant medications failed to alter depressive symptom severity (P<.005). Similar results were obtained taking into account the time-varying status of depression and use of antidepressant medications, as well as changes in depressive symptoms, during the postvaccination period.

CONCLUSIONS

Depressed patients have diminished VZV-CMI responses to zoster vaccine, and treatment with antidepressant medication is associated with normalization of these responses. Because higher levels of VZV-CMI correlate with lower risk and severity of HZ, untreated depression may increase the risk and severity of HZ and reduce the efficacy of zoster vaccine.

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.

Natural killer cells promote immune tolerance by regulating inflammatory TH17 cells at the human maternal-fetal interface

Natural killer (NK) cells accumulate at the maternal-fetal interface in large numbers, but their exact roles in successful pregnancy remain poorly defined. Here, we provide evidence that T(H)17 cells and local inflammation can occur at the maternal-fetal interface during natural allogenic pregnancies. We found that decidual NK cells promote immune tolerance and successful pregnancy by dampening inflammatory T(H)17 cells via IFN-γ secreted by the CD56(bright)CD27(+) NK subset. This NK-cell-mediated regulatory response is lost in patients who experience recurrent spontaneous abortions, which results in a prominent T(H)17 response and extensive local inflammation. This local inflammatory response further affects the regulatory function of NK cells, leading to the eventual loss of maternal-fetal tolerance. Thus, our data identify NK cells as key regulatory cells at the maternal-fetal interface by suppressing T(H)17-mediated local inflammation.

Serotonin protects mouse liver from cholestatic injury by decreasing bile salt pool after bile duct ligation

Obstructive cholestasis induces liver injury, postoperative complications, and mortality after surgery. Adaptive control of cholestasis, including bile salt homeostasis, is necessary for recovery and survival. Peripheral serotonin is a cytoprotective neurotransmitter also associated with liver regeneration. The effect of serotonin on cholestatic liver injury is not known. Therefore, we tested whether serotonin affects the severity of cholestatic liver injury. We induced cholestasis by ligation of the bile duct (BDL) in either wild-type (WT) mice or mice lacking peripheral serotonin (Tph1(-/-) and immune thrombocytopenic [ITP] mice). Liver injury was assessed by the levels of plasma aspartate aminotransferase (AST), alanine aminotransferase (ALT) and tissue necrosis. Bile salt-regulating genes were measured by quantitative polymerase chain reaction and confirmed by western blotting and immunohistochemistry. Tph1(-/-) mice displayed higher levels of plasma AST, ALT, bile salts, and hepatic necrosis after 3 days of BDL than WT mice. Likewise, liver injury was disproportional in ITP mice. Moreover, severe cholestatic complications and mortality after prolonged BDL were increased in Tph1(-/-) mice. Despite the elevation in toxic bile salts, expression of genes involved in bile salt homeostasis and detoxification were not affected in Tph1(-/-) livers. In contrast, the bile salt reabsorption transporters Ostα and Ostβ were up-regulated in the kidneys of Tph1(-/-) mice, along with a decrease in urinary bile salt excretion. Serotonin reloading of Tph1(-/-) mice reversed this phenotype, resulting in a reduction of circulating bile salts and liver injury.

CONCLUSION

We propose a physiological function of serotonin is to ameliorate liver injury and stabilize the bile salt pool through adaptation of renal transporters in cholestasis.

Childhood trauma and health outcomes in HIV-infected patients: an exploration of causal pathways

OBJECTIVE

Traumatic life histories are highly prevalent in people living with HIV/AIDS and predict sexual risk behaviors, medication adherence, and all-cause mortality. Yet the causal pathways explaining these relationships remain poorly understood. We sought to quantify the association of trauma with negative behavioral and health outcomes and to assess whether those associations were explained by mediation through psychosocial characteristics.

METHODS

In 611 outpatient people living with HIV/AIDS, we tested whether trauma's influence on later health and behaviors was mediated by coping styles, self-efficacy, social support, trust in the medical system, recent stressful life events, mental health, and substance abuse.

RESULTS

In models adjusting only for sociodemographic and transmission category confounders (estimating total effects), pasttrauma exposure was associated with 7 behavioral and health outcomes including increased odds or hazard of recent unprotected sex [odds ratio (OR) = 1.17 per each additional type of trauma, 95% confidence interval = 1.07 to 1.29], medication nonadherence (OR = 1.13, 1.02 to 1.25), hospitalizations (hazard ratio = 1.12, 1.04 to 1.22), and HIV disease progression (hazard ratio = 1.10, 0.98 to 1.23). When all hypothesized mediators were included, the associations of trauma with health care utilization outcomes were reduced by about 50%, suggesting partial mediation (eg, OR for hospitalization changed from 1.12 to 1.07), whereas point estimates for behavioral and incident health outcomes remained largely unchanged, suggesting no mediation (eg, OR for unprotected sex changed from 1.17 to 1.18). Trauma remained associated with most outcomes even after adjusting for all hypothesized psychosocial mediators.

CONCLUSIONS

These data suggest that past trauma influences adult health and behaviors through pathways other than the psychosocial mediators considered in this model.

Diagnostic applications of Raman spectroscopy

Raman spectroscopy has been widely used in various fields of science. It has been successfully utilized to qualitatively and quantitatively determine the molecular compositions of solid, liquid, and gaseous samples. This review focuses on the diagnostic applications of Raman spectroscopy in the past 5 years, with specific emphasis on transplant allograft rejection and cancer detections. First we introduce the principle of Raman spectroscopy and associated surface enhancement techniques. Various recent biomedical and clinical applications of Raman spectroscopy are then reviewed in detail. Finally, we present the experimental and analytical techniques required to implement Raman spectroscopy in a laboratory.

FROM THE CLINICAL EDITOR

This review focuses on evolving diagnostic applications of Raman spectroscopy with special emphasis on transplant allograft rejection and cancer detection.

Safety considerations in drug treatment of depression in HIV-positive patients: an updated review

Major depressive disorder (MDD) is one of the most prevalent illnesses associated with HIV infection, and negatively affects medication adherence, disease progression and mortality in HIV disease. Co-morbid treatment of major depression in HIV disease is the optimal therapeutic approach, but discriminating MDD from normal fluctuations in mood state, personality or physiology is difficult. Definitive diagnosis of MDD is critical for drug safety and for avoiding unnecessary exposure to psychotropic medications. HIV patients respond to antidepressant treatment like the general population, and medication adverse effects and patient adherence are the best predictors of treatment outcome. This review attempts to assist the medical provider with the diagnosis and treatment of MDD in HIV patients. We outline the initial steps in screening and psychiatric referral, the antidepressants that are particularly useful in HIV-infected patients, and the adverse effects and pharmacological strategies for overcoming potential barriers to medication adherence. Potential interactions between the various classes of antidepressants and HIV/antiretroviral therapy, as well as management of HIV medication-related psychiatric adverse effects, are also discussed.

Regulation of NK92-MI cell cytotoxicity by substance P

The neuropeptide substance P (SP) can regulate a number of immunological functions in vitro and in vivo and may regulate natural killer (NK) cell activity. Here, we investigated whether SP has a role in regulating NK92-MI cell function in vitro, and how it influences NK cell activity. We found that SP dose dependently increased the cytotoxicity of NK92-MI cells and had a maximal effect at a concentration of 10(-12) and 10(-10) m. Furthermore, the expression of cytotoxic-associated molecules (perforin, granzyme) and activating receptor NKp46 [a member of natural cytotoxicity receptors (NCRs)] was observed to be upregulated by SP at optimal concentration, at which SP enhanced the cytotoxicity of NK92-MI cells. Neurokinin-1 receptor (NK-1R), a functional receptor of SP, was found on NK92-MI cells, and the observed effects of SP on NK92-MI cells could be more partially blocked by an NK-1R antagonist. Our data suggest that SP induces NK92-MI cell cytotoxicity by directly increasing the expression of cytotoxic granules and upregulates NK92-MI cell receptor-mediated functions indirectly. Thus, SP may regulate NK cell function mainly through NK-1R.

The metabolic advantage of tumor cells

1- Oncogenes express proteins of "Tyrosine kinase receptor pathways", a receptor family including insulin or IGF-Growth Hormone receptors. Other oncogenes alter the PP2A phosphatase brake over these kinases. 2- Experiments on pancreatectomized animals; treated with pure insulin or total pancreatic extracts, showed that choline in the extract, preserved them from hepatomas. Since choline is a methyle donor, and since methylation regulates PP2A, the choline protection may result from PP2A methylation, which then attenuates kinases. 3- Moreover, kinases activated by the boosted signaling pathway inactivate pyruvate kinase and pyruvate dehydrogenase. In addition, demethylated PP2A would no longer dephosphorylate these enzymes. A "bottleneck" between glycolysis and the oxidative-citrate cycle interrupts the glycolytic pyruvate supply now provided via proteolysis and alanine transamination. This pyruvate forms lactate (Warburg effect) and NAD+ for glycolysis. Lipolysis and fatty acids provide acetyl CoA; the citrate condensation increases, unusual oxaloacetate sources are available. ATP citrate lyase follows, supporting aberrant transaminations with glutaminolysis and tumor lipogenesis. Truncated urea cycles, increased polyamine synthesis, consume the methyl donor SAM favoring carcinogenesis. 4- The decrease of butyrate, a histone deacetylase inhibitor, elicits epigenic changes (PETEN, P53, IGFBP decrease; hexokinase, fetal-genes-M2, increase). 5- IGFBP stops binding the IGF - IGFR complex, it is perhaps no longer inherited by a single mitotic daughter cell; leading to two daughter cells with a mitotic capability. 6- An excess of IGF induces a decrease of the major histocompatibility complex MHC1, Natural killer lymphocytes should eliminate such cells that start the tumor, unless the fever prostaglandin PGE2 or inflammation, inhibit them...

Major depressive disorder and immunity to varicella-zoster virus in the elderly

Major depressive disorder has been associated with activation of inflammatory processes as well as with reductions in innate, adaptive and non-specific immune responses. The objective of this study was to evaluate the association between major depression and a disease-relevant immunologic response, namely varicella-zoster virus (VZV)-specific immunity, in elderly adults. A cross-sectional cohort study was conducted in 104 elderly community dwelling adults ≥ 60years of age who were enrolled in the depression substudy of the shingles prevention study, a double blind, placebo-controlled vaccine efficacy trial. Fifty-two subjects had a current major depressive disorder, and 52 age- and sex-matched controls had no history of depression or any mental illness. VZV-specific cell-mediated immunity (VZV-CMI) was measured by VZV responder cell frequency (VZV-RCF) and interferon-γ enzyme-linked immunospot (ELISPOT) assays, and antibody to VZV was measured by an enzyme-linked immunosorbent assay against affinity-purified VZV glycoproteins (gpELISA). VZV-CMI, measured by VZV-RCF, was significantly lower in the depressed group than in the controls (p<0.001), and VZV-RCF was inversely correlated with the severity of depressive symptoms in the depressed patients. In addition, an age-related reduction in VZV-RCF was observed in the depressed patients, but not in the controls. Furthermore, there was a trend for depressive symptom severity to be associated with lower ELISPOT counts. Finally, VZV-RCF was higher in depressed patients treated with antidepressant medications as compared to untreated depressed patients. Since lower levels of VZV-RCF appear to explain the increased risk and severity of herpes zoster observed in older adults, these findings suggest that, in addition to increasing age, depression may increase the risk and severity of herpes zoster.

5-HT and the immune system

The classical neurotransmitter, serotonin (5-HT), plays an important role outside of the central nervous system in immune signaling. Here I review recent studies describing 5-HT uptake in dendritic cells and B lymphocytes, 5-HT synthesis in T lymphocytes, and the role of specific 5-HT receptor subtypes in innate and adaptive immune cells. Furthermore, a recent paper describing the immune phenotype of 5-HT deficient mice is discussed.

Immune suppression and immune activation in depression

Depression has been characterized as a disorder of both immune suppression and immune activation. Markers of impaired cellular immunity (decreased natural killer cell cytotoxicity) and inflammation (elevated IL-6, TNFα, and CRP) have been associated with depression. These immunological markers have been associated with other medical illnesses, suggesting that immune dysregulation may be a central feature common to both depression and to its frequent medical comorbidities. Yet the significant associations of findings of both immune suppression and immune activation with depression raise questions concerning the relationship between these two classes of immunological observations. Depressed populations are heterogeneous groups, and there may be differences in the immune profiles of populations that are more narrowly defined in terms of symptom profile and/or demographic features. There have been few reports concurrently investigating markers of immune suppression and immune activation in the same depressed individuals. An emerging pre-clinical literature suggests that chronic inflammation may directly contribute to the pathophysiology of immune suppression in the context of illnesses such as cancer and rheumatoid arthritis. This literature provides us with specific immunoregulatory mechanisms mediating these relationships that could also explain differences in immune disturbances between subsets of depressed individuals We propose a research agenda emphasizing the assessment of these immunoregulatory mechanisms in large samples of depressed subjects as a means to define the relationships among immune findings (suppression and/or activation) within the same depressed individuals and to characterize subsets of depressed subjects based on shared immune profiles. Such a program of research, building on and integrating our knowledge of the psychoneuroimmunology of depression, could lead to innovation in the assessment and treatment of depression and its medical comorbidities.

Rescue of adult hippocampal neurogenesis in a mouse model of HIV neurologic disease

The prevalence of central nervous system (CNS) neurologic dysfunction associated with human immunodeficiency virus (HIV) infection continues to increase, despite the use of antiretroviral therapy. Previous work has focused on the deleterious effects of HIV on mature neurons and on development of neuroprotective strategies, which have consistently failed to show a meaningful clinical benefit. It is now well established that new neurons are continuously generated in discrete regions in the adult mammalian brain, and accumulating evidence supports important roles for these neurons in specific cognitive functions. In a transgenic mouse model of HIV neurologic disease with glial expression of the HIV envelope protein gp120, we demonstrate a significant reduction in proliferation of hippocampal neural progenitors in the dentate gyrus of adult animals, resulting in a dramatic decrease in the number of newborn neurons in the adult brain. We identify amplifying neural progenitor cells (ANPs) as the first class of progenitors affected by gp120, and we also demonstrate that newly generated neurons exhibit aberrant dendritic development. Furthermore, voluntary exercise and treatment with a selective serotonin reuptake inhibitor increase the ANP population and rescue the observed deficits in gp120 transgenic mice. Thus, during HIV infection, the envelope protein gp120 may potently inhibit adult hippocampal neurogenesis, and neurorestorative approaches may be effective in ameliorating these effects. Our study has significant implications for the development of novel therapeutic approaches for HIV-infected individuals with neurologic dysfunction and may be applicable to other neurodegenerative diseases in which hippocampal neurogenesis is impaired.

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.

Substance P inhibits natural killer cell cytotoxicity through the neurokinin-1 receptor

SP is a potent neuroimmunomodulator that functions through ligating members of the neurokinin receptor family, one of which, NK1R, is widely expressed in immune cells. As in humans, circulating SP levels are increased in pathologic states associated with impairment of NK cell functions, such as depression and HIV infection, we hypothesized that SP has a direct, inhibitory effect upon NK cells. We have studied a clonal human NK cell line (YTS) as well as ex vivo human NK cells and have determined that truncated and full-length NK1R isoforms are expressed in and SP bound by ex vivo NK cells and the YTS NK cell line. Incubation of YTS cells with 10⁻⁶ M SP and ex vivo NK cells with 10⁻⁵ M SP inhibited cytotoxic ability by ∼20% and reduced degranulation. This inhibitory effect upon cytotoxicity was partially prevented by the NK1R antagonist CP96,345. The treatment of YTS or ex vivo NK cells with SP neither down-modulated NCR expression nor affected triggering receptor-induced NF-κB activation. Preincubation of YTS cells with SP, however, did abbreviate the typically prolonged intracellular calcium increase induced by target cell engagement and reduced triggering receptor-induced pERK. Thus, SP has the potential to regulate NK cell functions and acts downstream from neurokinin receptors to modulate NK cell activation signaling. This mechanism may contribute to impairment of NK cell function in certain disease states associated with increased circulating SP. Antagonism of this system may present an opportunity to augment NK cell function therapeutically in selected human diseases.

Natural Killer cells: keepers of pregnancy in the turnstile of the environment

During early pregnancy, an orchestrated endocrine-immunological scenario of maternal adaptation toward tolerance of the semiallogeneic fetus is required. Mechanisms preventing fetal loss by protecting the immune privilege of the gravid uterus, i.e. Galectin-1 or regulatory T cells, have recently been identified. Further, the presence of a unique population of Natural Killer (NK) cells, in humans identified by their CD56(+++)Galectin (Gal)-1(+)CD16(-) phenotype in the uterine lining (decidua), has been proposed to be a pivotal aspect of maternal adaptation to pregnancy. Decidual NK (dNK) cells comprise the largest population of immune cells during the first trimester in human decidua and control trophoblast invasion and vascular remodeling through their ability to secrete an array of angiogenesis-regulating molecules, chemokines and cytokines. A wealth of environmental factors, such as smoking, altered nutrition, pollution or stress has been proposed to peril not only pregnancy, but also fetal development. Further, published evidence supports that NK cells act as sentinel cells and environmental challenges can change their phenotype, e.g. via epigenetic pathways. We here review the effect of environmental factors, largely stress perception, on NK cells and its implication for pregnancy, fetal development and general health. As NK cells may not only be passive responders to the environment, but can also be 'educated and licensed', we propose novel strategies aiming to take advantage of the versatility of NK cells in maintaining immunosurveillance and tissue homeostasis.

Genetic variations in the serotonin transporter gene-linked polymorphic region influence attraction for a favorite person and the associated interactions between the central nervous and immune systems

Limbic system activation that occurs when a person experiences several emotions is primarily represented by the amygdala output that influences autonomic brainstem nuclei that control autonomic nervous function, thus modulating the endocrine and immune systems. Amygdala activity is modulated by the serotonin transporter gene-linked polymorphic region (5HTTLPR); however, whether variations in 5HTTLPR influence central nervous and immune activities in response to positive stimuli remains unclear. Here, we found that seeing a favorite person induced significantly higher amygdala activity in individuals with the 5HTTLPR SS genotype than in others. This activity was positively correlated with changes in the NK cell proportion among peripheral lymphocytes. Thus, 5HTTLPR influences attraction and the associated interactions between the central nervous and immune systems in affectively positive situations.

Management of common psychiatric conditions in the HIV-positive population

Presentation and management of psychiatric illness in HIV-infected patients can pose a challenge for clinicians. Psychiatric illness can exist premorbidly or result from the progression and treatment of HIV infection, influencing the course of the illness both through behavior and putative biological factors. Mood disorders, anxiety, psychosis, delirium, dementia, and substance abuse disorders all factor heavily into the care of HIV-infected patients. Management, however, continues to draw on small and skewed datasets, and remains largely an extrapolation from seronegative patient experience. The following is a discussion of treatment considerations derived from recent literature, as well as a consideration of judgments that clinicians may make in the absence of available data. The use of antidepressants, stimulants, mood stabilizers, and antipsychotics is discussed, as are precautions that must be taken with the HIV population when using these medications, not only because of side effect vulnerability, but because of significant drug-drug interactions.

T-cell phenotypic and functional changes associated with social subordination and gene polymorphisms in the serotonin reuptake transporter in female rhesus monkeys

Increased vulnerability to psychosocial stressors likely predisposes individuals to decreased immune function and inability to control pathogens. While many factors influence the susceptibility to psychosocial stress, genetic polymorphisms may modify individual reactivity to environmental stressors. The present study evaluated how immune function was altered by the interaction of in polymorphisms in the gene that encodes the serotonin reuptake transporter (5HTT) and the psychosocial stress imposed by social subordination in adult female rhesus monkeys. Subjects were dominant and subordinate females that carried both alleles of the long promoter variant (l/l) of the 5HTT gene, and dominant and subordinate that had at least one allele for the short promoter length variant (l/s or s/s, s-variant). Plasma cortisol was higher in subordinate females in response to a social separation paradigm, confirming their increased reactivity to psychosocial stressors. Subordinate females exhibited increased T-cell activation and proliferation regardless of genotype. Despite these higher levels of T-cell proliferation and activation, subordinate females showed significantly lower frequency of T-cells. This latter finding may be due to an increased susceptibility to cell death, as indicated by higher levels of annexin-V+ CD4+ and CD8+ T-cells in s-variant subordinate compared to dominant females. These findings indicate that subordinate rhesus monkeys with the s-variant 5HTT genotype exhibit decreased T-cell numbers perhaps compromising their ability to mount an immune response to pathogens. These data underscore the importance for considering gene polymorphisms that influence emotional reactivity to better understand susceptibility to disease.

The impact of mental health and traumatic life experiences on antiretroviral treatment outcomes for people living with HIV/AIDS

Potent antiretroviral therapy (ART) has transformed HIV from a death sentence to a chronic illness. Accordingly, the goal of HIV care has shifted from delaying death to achieving optimal health outcomes through ART treatment. ART treatment success hinges on medication adherence. Extensive research has demonstrated that the primary barriers to ART adherence include mental illness, especially depression and substance abuse, as well as histories of traumatic experiences such as childhood sexual and physical abuse. These psychosocial factors are highly prevalent in people living with HIV/AIDS (PLWHA) and predict poor ART adherence, increased sexual risk behaviours, ART treatment failure, HIV disease progression and higher mortality rates. The efficacy of standard mental health interventions, such as antidepressant treatment and psychotherapy, has been well-defined, and a small but growing body of research demonstrates the potential for such interventions to improve ART adherence and reduce sexual risk behaviours. Despite this evidence, mental disorders in PLWHA frequently go undiagnosed and untreated. Challenges to the provision of mental healthcare for PLWHA in HIV clinical settings include time and resource constraints, lack of expertise in psychiatric diagnosis and treatment, and lack of available mental health referral services. Future research should prioritize the evaluation of mental health interventions that are cost-effective and feasible for widespread integration into HIV clinical care; the impact of such interventions on ART adherence and clinical outcomes; and interventions to identify individuals with histories of traumatic experiences and to elucidate the mechanisms through which such histories pose barriers to effective HIV treatment.

Serotonin decreases HIV-1 replication in primary cultures of human macrophages through 5-HT(1A) receptors

BACKGROUND AND PURPOSE

5-HT (serotonin) is known to be involved in neuroinflammation and immunoregulation. The human immunodeficiency virus (HIV) targets cells such as monocytes/macrophages, which colocalize with 5-HT-releasing cell types, mostly platelets. In this study, we investigated the effects of 5-HT on HIV-1-infected macrophages in vitro.

EXPERIMENTAL APPROACH

Human macrophages cultured in serum-free medium were treated over 7 days with 5-HT at three concentrations (0.01, 1 and 100 microM) with or without agonists and antagonists of 5-HT(1A) and 5-HT(2) receptors. After 7 days of treatment, macrophages were infected with HIV-1/Ba-L and virus replication was monitored over 16 days and expression of proviral HIV DNA was investigated by PCR after 24 h of infection. Cell surface expression of HIV-1/Ba-L receptor (CD4) and coreceptor (CCR5) was investigated by flow cytometry. The CCR5 ligand, macrophage inflammatory protein-1alpha (MIP-1alpha), was quantified by ELISA in cell culture supernatants and MIP-1alpha mRNA expression was assessed by reverse transcriptase-PCR.

KEY RESULTS

In vitro, 5-HT downregulated the membranous expression of CCR5 and led to a decrease of HIV-1 infection, probably through its action on 5-HT(1A) receptors. 5-HT (100 microM) was also able to induce overexpression of MIP-1alpha mRNA leading to an increase of MIP-1alpha secretion by human macrophages.

CONCLUSIONS AND IMPLICATIONS

The effects of 5-HT on HIV infection could be a consequence of the increase in MIP-1alpha concentrations and/or CCR5 receptor downregulation. These results suggest that 5-HT can inhibit the replication of HIV-1 in primary culture of human macrophages through its action on 5-HT(1A) receptors.