Fluoxetine suppresses calcium signaling in human T lymphocytes through depletion of intracellular calcium stores

[The influence of fluoxetine on neuroimmune interaction in multiple sclerosis]

OBJECTIVE

To study the effect of fluoxetine on Th17- and Th1-immune response, which plays an important role in the pathogenesis of multiple sclerosis (MS).

MATERIAL AND METHODS

Ten patients with relapsing-remitting MS and ten healthy subjects were examined. The functions of Th17- and Th1-immune responses were assessed by the production of cytokines interleukin-17 (IL-17) and interferon-gamma (IFN-γ) by CD4+ T cells stimulated with macrophages or microbeads coated with anti-CD3 and anti-CD28-antibodies. To assess the effect of fluoxetine on the macrophages-induced Th17- and Th1-immune response, macrophages were pre-incubated in the presence of fluoxetine and co-cultured with autologous CD4+ T-cells. In the case of stimulation of CD4+ T-cells with anti-CD3/CD28-microbeads, fluoxetine was added directly to the T-helper cells before adding of microbeads. In addition, we evaluated the effect of fluoxetine on the production of the factors of differentiation of Th17-cells cytokines IL-6 and IL-1β by macrophages. The levels of cytokines in the cell culture supernatants were measured by ELISA.

RESULTS

The production of IL-17 and IFN-γ by CD4+ T-cells stimulated with macrophages or anti-CD3/CD28-microbeads was comparable between the groups. Fluoxetine suppressed the production of IL-17 and IFN-γ by anti-CD/CD28-stimulated CD4+ T-cells in both groups. Fluoxetine also suppressed the production of IL-6 and IL-1β by macrophages as well as their ability to induce IL-17 and IFN-γ production by CD4+ T-cells in both groups.

CONCLUSIONS

Fluoxetine may have an anti-inflammatory effect in MS that could be mediated by suppression of Th17- and Th1-cells or macrophage-induced Th17- and Th1-immune response.

The glymphatic system and subarachnoid hemorrhage: disruption and recovery

The glymphatic system, or glial-lymphatic system, is a waste clearance system composed of perivascular channels formed by astrocytes that mediate the clearance of proteins and metabolites from the brain. These channels facilitate the movement of cerebrospinal fluid throughout brain parenchyma and are critical for homeostasis. Disruption of the glymphatic system leads to an accumulation of these waste products as well as increased interstitial fluid in the brain. These phenomena are also seen during and after subarachnoid hemorrhages (SAH), contributing to the brain damage seen after rupture of a major blood vessel. Herein this review provides an overview of the glymphatic system, its disruption during SAH, and its function in recovery following SAH. The review also outlines drugs which target the glymphatic system and may have therapeutic applications following SAH.

The role of 5-HT2B-receptors in fluoxetine-mediated modulation of Th17- and Th1-cells in multiple sclerosis

Fluoxetine is a selective serotonin reuptake inhibitor, which also has an immunomodulatory effect. We investigated the effects of fluoxetine and serotonin (5-HT) on the pro-inflammatory Th17- and Th1-cells in 30 patients with relapsing-remitting MS and 20 healthy subjects. Fluoxetine and 5-HT suppressed IL-17, IFN-γ and GM-CSF production by stimulated СD4⁺ T-cells in both groups. Blockade of 5-HT_2B-receptors decreased the inhibitory effect of fluoxetine on cytokine production in MS patients. Finally, 5-HT_2B-receptor activation inhibits IL-17, IFN-γ and GM-CSF production in both groups. These data suggest an anti-inflammatory role for fluoxetine in MS, which could be mediated by the activation of 5-HT_2B-receptors.

Potential Adverse Cardiovascular Effects of Treatment With Fluoxetine and Other Selective Serotonin Reuptake Inhibitors (SSRIs) in Patients With Geriatric Depression: Implications for Atherogenesis and Cerebromicrovascular Dysregulation

Late life depression is an important public health problem, which associates with increased risk of morbidity and mortality. Selective serotonin reuptake inhibitors (SSRIs), including fluoxetine, are often prescribed to treat geriatric depression. There is increasing evidence that fluoxetine and other SSRIs exert a wide range of cardiovascular side effects. Furthermore, there is evidence that aging may increase plasma level of SSRIs. In this overview, the potential role of side effects of treatment with fluoxetine and other SSRIs in the pathogenesis of age-related cardiovascular diseases, including atherogenesis, cardiac pathologies, and cerebromicrovascular impairment, is discussed.

Immunoregulatory natural compounds in stress-induced depression: An alternative or an adjunct to conventional antidepressant therapy?

The interplay of chronic stress, neuroinflammation and altered immune reactivity has been shown to be important for the pathophysiology of brain disorders such as schizophrenia, depressive disorders and post-traumatic stress disorder. This immuno-inflammatory theory has been extensively studied in the past three decades leading to the formation of the integrative discipline of psychoneuroimmunology. Targeting of the central nervous system by conventional pharmacotherapeutic methods is mainly through modulation of neuroendocrine systems such as the dopaminergic, GABA-ergic, adrenergic and serotoninergic systems. In recent years an increasing number of both experimental and clinical studies have shown that antidepressants can affect the immune system by reducing the production of pro-inflammatory cytokines such as IL-1β, IL-6 and TNF-α. However, due to the serious adverse effects accompanying the chronic administration of psychoactive drugs there is a continuous need to produce novel therapeutics that are both potent and safe. The present review aims to summarize the current knowledge in the field of psychoneuroimmunology and to delineate the main interactions between stress, inflammation, immunity and the brain. Additionally, this paper explores the use of plant-derived molecules that display a strong anti-stress effect and simultaneously modulate the immune response as an alternative or adjuvant to classical antidepressant drugs.

The antidepressant fluoxetine induces necrosis by energy depletion and mitochondrial calcium overload

Selective Serotonin Reuptake Inhibitor antidepressants, such as fluoxetine (Prozac), have been shown to induce cell death in cancer cells, paving the way for their potential use as cancer therapy. These compounds are able to increase cytosolic calcium concentration ([Ca2+]cyt), but the involved mechanisms and their physiological consequences are still not well understood. Here, we show that fluoxetine induces an increase in [Ca2+]cyt by emptying the endoplasmic reticulum (ER) through the translocon, an ER Ca2+ leakage structure. Our data also show that fluoxetine inhibits oxygen consumption and lowers mitochondrial ATP. This latter is essential for Ca2+ reuptake into the ER, and we postulated therefore that the fluoxetine-induced decrease in mitochondrial ATP production results in the emptying of the ER, leading to capacitative calcium entry. Furthermore, Ca2+ quickly accumulated in the mitochondria, leading to mitochondrial Ca2+ overload and cell death. We found that fluoxetine could induce an early necrosis in human peripheral blood lymphocytes and Jurkat cells, and could also induce late apoptosis, especially in the tumor cell line. These results shed light on fluoxetine-induced cell death and its potential use in cancer treatment.

Serotonin-reuptake inhibitors act centrally to cause bone loss in mice by counteracting a local anti-resorptive effect

The use of selective serotonin-reuptake inhibitors (SSRIs) has been associated with an increased risk of bone fracture, raising concerns about their increasingly broader usage. This deleterious effect is poorly understood, and thus strategies to avoid this side effect remain elusive. We show here that fluoxetine (Flx), one of the most-prescribed SSRIs, acts on bone remodeling through two distinct mechanisms. Peripherally, Flx has anti-resorptive properties, directly impairing osteoclast differentiation and function through a serotonin-reuptake-independent mechanism that is dependent on intracellular Ca2+ levels and the transcription factor Nfatc1. With time, however, Flx also triggers a brain-serotonin-dependent rise in sympathetic output that increases bone resorption sufficiently to counteract its local anti-resorptive effect, thus leading to a net effect of impaired bone formation and bone loss. Accordingly, neutralizing this second mode of action through co-treatment with the β-blocker propranolol, while leaving the peripheral effect intact, prevents Flx-induced bone loss in mice. Hence, this study identifies a dual mode of action of SSRIs on bone remodeling and suggests a therapeutic strategy to block the deleterious effect on bone homeostasis from their chronic use.

Fluoxetine Ameliorates Atopic Dermatitis-Like Skin Lesions in BALB/c Mice through Reducing Psychological Stress and Inflammatory Response

Atopic dermatitis (AD) is a common chronic inflammatory skin disorder, and patients with AD suffer from severe psychological stress, which markedly increases the prevalence rate of depression and anxiety disorders in later life. Fluoxetine, a selective serotonin reuptake inhibitor, has recently been reported to exert anti-inflammatory and immunosuppressive effects. However, it is unclear whether fluoxetine is effective in the treatment of AD through reducing psychological stress and inflammatory reaction. Here, we reported that a BALB/c mouse model of AD was induced by application of 2,4-dinitrochlorobenzene (DNCB) onto hairless dorsal skin. Chronic fluoxetine treatment (10 mg/kg per day, i.p.) significantly attenuated AD-like symptoms, as reflected by a dramatic decrease in scratching bouts, as well as a decrease in anxiety- and depressive-like behaviors. Furthermore, these behavioral changes were accompanied by a significant decrease in epidermal thickness, the number of mast cells in skin tissue, mRNA levels of interleukin-4 (IL-4) and IL-13 in the spleen, as well as serum immunoglobulin E (IgE) in the DNCB-treated mice by treatment with fluoxetine. Taken together, these results indicate that fluoxetine may suppress psychological stress and inflammatory response during AD development, and subsequently ameliorate AD symptoms, suggesting that fluoxetine may be a potential therapeutic agent against AD in clinic.

Calcium Signaling Pathway Is Associated with the Long-Term Clinical Response to Selective Serotonin Reuptake Inhibitors (SSRI) and SSRI with Antipsychotics in Patients with Obsessive-Compulsive Disorder

Background

Selective serotonin reuptake inhibitors (SSRI) are established first-line pharmacological treatments for obsessive-compulsive disorder (OCD), while antipsychotics are used as an augmentation strategy for SSRI in OCD patients who have either no response or a partial response to SSRI treatment. The goal of the present study was to identify genetic variants and pathways that are associated with the long-term clinical response of OCD patients to SSRI or SSRI with antipsychotics.

Methods

We first performed a genome-wide association study of 96 OCD patients to examine genetic variants contributing to the response to SSRI or SSRI with antipsychotics. Subsequently, we conducted pathway-based analyses by using Improved Gene Set Enrichment Analysis for Genome-wide Association Study (i-GSEA4GWAS) to examine the combined effects of genetic variants on the clinical response in OCD.

Results

While we failed to detect specific genetic variants associated with clinical responses to SSRI or to SSRI with an atypical antipsychotic at genome-wide levels of significance, we identified 8 enriched pathways for the SSRI treatment response and 5 enriched pathways for the treatment response to SSRI with an antipsychotic medication. Notably, the calcium signaling pathway was identified in both treatment responses.

Conclusions

Our results provide novel insight into the molecular mechanisms underlying the variability in clinical response to SSRI and SSRI with antipsychotics in OCD patients.

PTSD, a Disorder with an Immunological Component

Post-traumatic stress disorder (PTSD) has been associated with an inflammatory state. However, few studies have addressed the mechanisms underlying this immune imbalance that favors inflammation or how this imbalance contributes to PTSD. Whether the immune imbalance influences responsiveness or unresponsiveness of patients to PTSD treatments is currently not known. This review brings forward an immune emphasis to a mental health disorder that is unprecedented in its prevalence among combat Veterans of the ongoing conflicts in Iraq and Afghanistan and which also afflicts civilians who have undergone extreme traumatic experiences, such as following natural disasters, serious accidents, or assaults. Included is an overview of the correlative associations in human subjects between PTSD and inflammation and studies in animal models of PTSD, demonstrating causal contributions of inflammation and immune dysregulation to PTSD-like behavior following stress exposure.